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Sample records for biological membranes regulating

  1. From biological membranes to biomimetic model membranes

    Directory of Open Access Journals (Sweden)

    Eeman, M.

    2010-01-01

    Full Text Available Biological membranes play an essential role in the cellular protection as well as in the control and the transport of nutrients. Many mechanisms such as molecular recognition, enzymatic catalysis, cellular adhesion and membrane fusion take place into the biological membranes. In 1972, Singer et al. provided a membrane model, called fluid mosaic model, in which each leaflet of the bilayer is formed by a homogeneous environment of lipids in a fluid state including globular assembling of proteins and glycoproteins. Since its conception in 1972, many developments were brought to this model in terms of composition and molecular organization. The main development of the fluid mosaic model was made by Simons et al. (1997 and Brown et al. (1997 who suggested that membrane lipids are organized into lateral microdomains (or lipid rafts with a specific composition and a molecular dynamic that are different to the composition and the dynamic of the surrounding liquid crystalline phase. The discovery of a phase separation in the plane of the membrane has induced an explosion in the research efforts related to the biology of cell membranes but also in the development of new technologies for the study of these biological systems. Due to the high complexity of biological membranes and in order to investigate the biological processes that occur on the membrane surface or within the membrane lipid bilayer, a large number of studies are performed using biomimicking model membranes. This paper aims at revisiting the fundamental properties of biological membranes in terms of membrane composition, membrane dynamic and molecular organization, as well as at describing the most common biomimicking models that are frequently used for investigating biological processes such as membrane fusion, membrane trafficking, pore formation as well as membrane interactions at a molecular level.

  2. Fusion of biological membranes

    Indian Academy of Sciences (India)

    K Katsov; M Müller; M Schick

    2005-06-01

    The process of membrane fusion has been examined by Monte Carlo simulation, and is found to be very different than the conventional picture. The differences in mechanism lead to several predictions, in particular that fusion is accompanied by transient leakage. This prediction has recently been verified. Self-consistent field theory is applied to examine the free energy barriers in the different scenarios.

  3. Ubiquitination of the bacterial inositol phosphatase, SopB, regulates its biological activity at the plasma membrane.

    LENUS (Irish Health Repository)

    Knodler, Leigh A

    2009-11-01

    The Salmonella type III effector, SopB, is an inositol polyphosphate phosphatase that modulates host cell phospholipids at the plasma membrane and the nascent Salmonella-containing vacuole (SCV). Translocated SopB persists for many hours after infection and is ubiquitinated but the significance of this covalent modification has not been investigated. Here we identify by mass spectrometry six lysine residues of SopB that are mono-ubiquitinated. Substitution of these six lysine residues with arginine, SopB-K(6)R, almost completely eliminated SopB ubiquitination. We found that ubiquitination does not affect SopB stability or membrane association, or SopB-dependent events in SCV biogenesis. However, two spatially and temporally distinct events are dependent on ubiquitination, downregulation of SopB activity at the plasma membrane and prolonged retention of SopB on the SCV. Activation of the mammalian pro-survival kinase Akt\\/PKB, a downstream target of SopB, was intensified and prolonged after infection with the SopB-K(6)R mutant. At later times, fewer SCV were decorated with SopB-K(6)R compared with SopB. Instead SopB-K(6)R was present as discrete vesicles spread diffusely throughout the cell. Altogether, our data show that ubiquitination of SopB is not related to its intracellular stability but rather regulates its enzymatic activity at the plasma membrane and intracellular localization.

  4. Ninth International Workshop on Plant Membrane Biology

    Energy Technology Data Exchange (ETDEWEB)

    1993-12-31

    This report is a compilation of abstracts from papers which were discussed at a workshop on plant membrane biology. Topics include: plasma membrane ATP-ases; plant-environment interactions, membrane receptors; signal transduction; ion channel physiology; biophysics and molecular biology; vaculor H+ pumps; sugar carriers; membrane transport; and cellular structure and function.

  5. FDA 101: Regulating Biological Products

    Science.gov (United States)

    ... Products For Consumers Home For Consumers Consumer Updates FDA 101: Regulating Biological Products Share Tweet Linkedin Pin ... field. back to top What biological products does FDA regulate? The Center for Biologics Evaluation and Research ( ...

  6. Polyunsaturated Lipids Regulate Membrane Domain Stability by Tuning Membrane Order.

    Science.gov (United States)

    Levental, Kandice R; Lorent, Joseph H; Lin, Xubo; Skinkle, Allison D; Surma, Michal A; Stockenbojer, Emily A; Gorfe, Alemayehu A; Levental, Ilya

    2016-04-26

    The plasma membrane (PM) serves as the functional interface between a cell and its environment, hosting extracellular signal transduction and nutrient transport among a variety of other processes. To support this extensive functionality, PMs are organized into lateral domains, including ordered, lipid-driven assemblies termed lipid rafts. Although the general requirements for ordered domain formation are well established, how these domains are regulated by cell-endogenous mechanisms or exogenous perturbations has not been widely addressed. In this context, an intriguing possibility is that dietary fats can incorporate into membrane lipids to regulate the properties and physiology of raft domains. Here, we investigate the effects of polyunsaturated fats on the organization of membrane domains across a spectrum of membrane models, including computer simulations, synthetic lipid membranes, and intact PMs isolated from mammalian cells. We observe that the ω-3 polyunsaturated fatty acid docosahexaenoic acid is robustly incorporated into membrane lipids, and this incorporation leads to significant remodeling of the PM lipidome. Across model systems, docosahexaenoic acid-containing lipids enhance the stability of ordered raft domains by increasing the order difference between them and coexisting nonraft domains. The relationship between interdomain order disparity and the stability of phase separation holds for a spectrum of different perturbations, including manipulation of cholesterol levels and high concentrations of exogenous amphiphiles, suggesting it as a general feature of the organization of biological membranes. These results demonstrate that polyunsaturated fats affect the composition and organization of biological membranes, suggesting a potential mechanism for the extensive effects of dietary fat on health and disease.

  7. Membrane biology: fission behind BARs.

    Science.gov (United States)

    Haucke, Volker

    2012-06-05

    Membrane bending is accomplished in part by amphipathic helix insertion into the bilayer and the assembly of BAR domain scaffolds preparing the membrane for fission. Two recent studies highlight the roles of amphipathic helices and BAR scaffolds in membrane fission and establish the structural basis of membrane bending by the N-BAR protein endophilin.

  8. Synthetic membranes and membrane processes with counterparts in biological systems

    Science.gov (United States)

    Matson, Stephen L.

    1996-02-01

    Conventional synthetic membranes, fashioned for the most part from rather unremarkable polymeric materials, are essentially passive structures that achieve various industrial and biomedical separations through simple and selective membrane permeation processes. Indeed, simplicity of membrane material, structure, and function has long been perceived as a virtue of membranes relative to other separation processes with which they compete. The passive membrane separation processes -- exemplified by micro- and ultrafiltration, dialysis, reverse osmosis, and gas permeation -- differ from one another primarily in terms of membrane morphology or structure (e.g., porous, gel-type, and nonporous) and the permeant transport mechanism and driving force (e.g., diffusion, convection, and 'solution/diffusion'). The passive membrane separation processes have in common the fact that interaction between permeant and membrane material is typically weak and physicochemical in nature; indeed, it is frequently an objective of membrane materials design to minimize interaction between permeant and membrane polymer, since such strategies can minimize membrane fouling. As a consequence, conventional membrane processes often provide only modest separation factors or permselectivities; that is, they are more useful in performing 'group separations' (i.e., the separation of different classes of material) than they are in fractionating species within a given class. It has long been recognized within the community of membrane technologists that biological membrane structures and their components are extraordinarily sophisticated and powerful as compared to their synthetic counterparts. Moreover, biomembranes and related biological systems have been 'designed' according to a very different paradigm -- one that frequently maximizes and capitalizes on extraordinarily strong and biochemically specific interactions between components of the membrane and species interacting with them. Thus, in recent

  9. Biological Fuel Cells and Membranes.

    Science.gov (United States)

    Ghassemi, Zahra; Slaughter, Gymama

    2017-01-17

    Biofuel cells have been widely used to generate bioelectricity. Early biofuel cells employ a semi-permeable membrane to separate the anodic and cathodic compartments. The impact of different membrane materials and compositions has also been explored. Some membrane materials are employed strictly as membrane separators, while some have gained significant attention in the immobilization of enzymes or microorganisms within or behind the membrane at the electrode surface. The membrane material affects the transfer rate of the chemical species (e.g., fuel, oxygen molecules, and products) involved in the chemical reaction, which in turn has an impact on the performance of the biofuel cell. For enzymatic biofuel cells, Nafion, modified Nafion, and chitosan membranes have been used widely and continue to hold great promise in the long-term stability of enzymes and microorganisms encapsulated within them. This article provides a review of the most widely used membrane materials in the development of enzymatic and microbial biofuel cells.

  10. CHARMM-GUI Membrane Builder toward realistic biological membrane simulations.

    Science.gov (United States)

    Wu, Emilia L; Cheng, Xi; Jo, Sunhwan; Rui, Huan; Song, Kevin C; Dávila-Contreras, Eder M; Qi, Yifei; Lee, Jumin; Monje-Galvan, Viviana; Venable, Richard M; Klauda, Jeffery B; Im, Wonpil

    2014-10-15

    CHARMM-GUI Membrane Builder, http://www.charmm-gui.org/input/membrane, is a web-based user interface designed to interactively build all-atom protein/membrane or membrane-only systems for molecular dynamics simulations through an automated optimized process. In this work, we describe the new features and major improvements in Membrane Builder that allow users to robustly build realistic biological membrane systems, including (1) addition of new lipid types, such as phosphoinositides, cardiolipin (CL), sphingolipids, bacterial lipids, and ergosterol, yielding more than 180 lipid types, (2) enhanced building procedure for lipid packing around protein, (3) reliable algorithm to detect lipid tail penetration to ring structures and protein surface, (4) distance-based algorithm for faster initial ion displacement, (5) CHARMM inputs for P21 image transformation, and (6) NAMD equilibration and production inputs. The robustness of these new features is illustrated by building and simulating a membrane model of the polar and septal regions of E. coli membrane, which contains five lipid types: CL lipids with two types of acyl chains and phosphatidylethanolamine lipids with three types of acyl chains. It is our hope that CHARMM-GUI Membrane Builder becomes a useful tool for simulation studies to better understand the structure and dynamics of proteins and lipids in realistic biological membrane environments.

  11. The nature and biology of basement membranes.

    Science.gov (United States)

    Pozzi, Ambra; Yurchenco, Peter D; Iozzo, Renato V

    2017-01-01

    Basement membranes are delicate, nanoscale and pliable sheets of extracellular matrices that often act as linings or partitions in organisms. Previously considered as passive scaffolds segregating polarized cells, such as epithelial or endothelial cells, from the underlying mesenchyme, basement membranes have now reached the center stage of biology. They play a multitude of roles from blood filtration to muscle homeostasis, from storing growth factors and cytokines to controlling angiogenesis and tumor growth, from maintaining skin integrity and neuromuscular structure to affecting adipogenesis and fibrosis. Here, we will address developmental, structural and biochemical aspects of basement membranes and discuss some of the pathogenetic mechanisms causing diseases linked to abnormal basement membranes.

  12. Measuring shape fluctuations in biological membranes

    Science.gov (United States)

    Monzel, C.; Sengupta, K.

    2016-06-01

    Shape fluctuations of lipid membranes have intrigued cell biologists and physicists alike. In the cellular context, their origin—thermal or active—and their physiological significance are open questions. These small incessant displacements, also called membrane undulations, have mostly been studied in model membranes and membranes of simple cells like erythrocytes. Thermal fluctuations of such membranes have been very well described both theoretically and experimentally; active fluctuations are a topic of current interest. Experimentally, membrane fluctuations are not easy to measure, the main challenge being to develop techniques which are capable of measuring very small displacements at very high speed, and preferably over a large area and long time. Scattering techniques have given access to fluctuations in membrane stacks and a variety of optical microscopy based techniques have been devised to study membrane fluctuations of unilamellar vesicles, erythrocytes and other cells. Among them are flicker spectroscopy, dynamic light scattering, diffraction phase microscopy and reflection interference contrast microscopy. Each of these techniques has its advantages and limitations. Here we review the basic principles of the major experimental techniques used to measure bending or shape fluctuations of biomembranes. We report seminal results obtained with each technique and highlight how these studies furthered our understanding of physical properties of membranes and their interactions. We also discuss suggested role of membrane fluctuations in different biological processes.

  13. Mesoscopic models of biological membranes

    DEFF Research Database (Denmark)

    Venturoli, M.; Sperotto, Maria Maddalena; Kranenburg, M.;

    2006-01-01

    , as model systems to understand the fundamental properties of biomembranes. The properties of lipid bilayers can be studied at different time and length scales. For some properties it is sufficient to envision a membrane as an elastic sheet, while for others it is important to take into account the details...... of the individual atoms. In this review, we focus on an intermediate level, where groups of atoms are lumped into pseudo-particles to arrive at a coarse-grained, or mesoscopic, description of a bilayer, which is subsequently studied using molecular simulation. The aim of this review is to compare various strategies...

  14. Biological Membrane Ion Channels Dynamics, Structure, and Applications

    CERN Document Server

    Chung, Shin-Ho; Krishnamurthy, Vikram

    2007-01-01

    Ion channels are biological nanotubes that are formed by membrane proteins. Because ion channels regulate all electrical activities in living cells, understanding their mechanisms at a molecular level is a fundamental problem in biology. This book deals with recent breakthroughs in ion-channel research that have been brought about by the combined effort of experimental biophysicists and computational physicists, who together are beginning to unravel the story of these exquisitely designed biomolecules. With chapters by leading experts, the book is aimed at researchers in nanodevices and biosensors, as well as advanced undergraduate and graduate students in biology and the physical sciences. Key Features Presents the latest information on the molecular mechanisms of ion permeation through membrane ion channels Uses schematic diagrams to illustrate important concepts in biophysics Written by leading researchers in the area of ion channel investigations

  15. Nanocrack-regulated self-humidifying membranes

    Science.gov (United States)

    Park, Chi Hoon; Lee, So Young; Hwang, Doo Sung; Shin, Dong Won; Cho, Doo Hee; Lee, Kang Hyuck; Kim, Tae-Woo; Kim, Tae-Wuk; Lee, Mokwon; Kim, Deok-Soo; Doherty, Cara M.; Thornton, Aaron W.; Hill, Anita J.; Guiver, Michael D.; Lee, Young Moo

    2016-04-01

    The regulation of water content in polymeric membranes is important in a number of applications, such as reverse electrodialysis and proton-exchange fuel-cell membranes. External thermal and water management systems add both mass and size to systems, and so intrinsic mechanisms of retaining water and maintaining ionic transport in such membranes are particularly important for applications where small system size is important. For example, in proton-exchange membrane fuel cells, where water retention in the membrane is crucial for efficient transport of hydrated ions, by operating the cells at higher temperatures without external humidification, the membrane is self-humidified with water generated by electrochemical reactions. Here we report an alternative solution that does not rely on external regulation of water supply or high temperatures. Water content in hydrocarbon polymer membranes is regulated through nanometre-scale cracks (‘nanocracks’) in a hydrophobic surface coating. These cracks work as nanoscale valves to retard water desorption and to maintain ion conductivity in the membrane on dehumidification. Hydrocarbon fuel-cell membranes with surface nanocrack coatings operated at intermediate temperatures show improved electrochemical performance, and coated reverse-electrodialysis membranes show enhanced ionic selectivity with low bulk resistance.

  16. Structure Biology of Membrane Bound Enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Dax [Johns Hopkins Univ., Baltimore, MD (United States). School of Medicine. Dept. of Physiology

    2016-11-30

    The overall goal of the proposed research is to understand the membrane-associated active processes catalyzed by an alkane $\\square$-hydroxylase (AlkB) from eubacterium Pseudomonase oleovorans. AlkB performs oxygenation of unactivated hydrocarbons found in crude oils. The enzymatic reaction involves energy-demanding steps in the membrane with the uses of structurally unknown metal active sites featuring a diiron [FeFe] center. At present, a critical barrier to understanding the membrane-associated reaction mechanism is the lack of structural information. The structural biology efforts have been challenged by technical difficulties commonly encountered in crystallization and structural determination of membrane proteins. The specific aims of the current budget cycle are to crystalize AlkB and initiate X-ray analysis to set the stage for structural determination. The long-term goals of our structural biology efforts are to provide an atomic description of AlkB structure, and to uncover the mechanisms of selective modification of hydrocarbons. The structural information will help elucidating how the unactivated C-H bonds of saturated hydrocarbons are oxidized to initiate biodegradation and biotransformation processes. The knowledge gained will be fundamental to biotechnological applications to biofuel transformation of non-edible oil feedstock. Renewable biodiesel is a promising energy carry that can be used to reduce fossil fuel dependency. The proposed research capitalizes on prior BES-supported efforts on over-expression and purification of AlkB to explore the inner workings of a bioenergy-relevant membrane-bound enzyme.

  17. Plasma membrane regulates Ras signaling networks.

    Science.gov (United States)

    Chavan, Tanmay Sanjeev; Muratcioglu, Serena; Marszalek, Richard; Jang, Hyunbum; Keskin, Ozlem; Gursoy, Attila; Nussinov, Ruth; Gaponenko, Vadim

    2015-01-01

    Ras GTPases activate more than 20 signaling pathways, regulating such essential cellular functions as proliferation, survival, and migration. How Ras proteins control their signaling diversity is still a mystery. Several pieces of evidence suggest that the plasma membrane plays a critical role. Among these are: (1) selective recruitment of Ras and its effectors to particular localities allowing access to Ras regulators and effectors; (2) specific membrane-induced conformational changes promoting Ras functional diversity; and (3) oligomerization of membrane-anchored Ras to recruit and activate Raf. Taken together, the membrane does not only attract and retain Ras but also is a key regulator of Ras signaling. This can already be gleaned from the large variability in the sequences of Ras membrane targeting domains, suggesting that localization, environment and orientation are important factors in optimizing the function of Ras isoforms.

  18. Ion channels regulating mast cell biology.

    Science.gov (United States)

    Ashmole, I; Bradding, P

    2013-05-01

    Mast cells play a central role in the pathophysiology of asthma and related allergic conditions. Mast cell activation leads to the degranulation of preformed mediators such as histamine and the secretion of newly synthesised proinflammatory mediators such as leukotrienes and cytokines. Excess release of these mediators contributes to allergic disease states. An influx of extracellular Ca2+ is essential for mast cell mediator release. From the Ca2+ channels that mediate this influx, to the K+ , Cl- and transient receptor potential channels that set the cell membrane potential and regulate Ca2+ influx, ion channels play a critical role in mast cell biology. In this review we provide an overview of our current knowledge of ion channel expression and function in mast cells with an emphasis on how channels interact to regulate Ca2+ signalling.

  19. Biological hydrogen production using a membrane bioreactor.

    Science.gov (United States)

    Oh, Sang-Eun; Iyer, Prabha; Bruns, Mary Ann; Logan, Bruce E

    2004-07-01

    A cross-flow membrane was coupled to a chemostat to create an anaerobic membrane bioreactor (MBR) for biological hydrogen production. The reactor was fed glucose (10,000 mg/L) and inoculated with a soil inoculum heat-treated to kill non-spore-forming methanogens. Hydrogen gas was consistently produced at a concentration of 57-60% in the headspace under all conditions. When operated in chemostat mode (no flow through the membrane) at a hydraulic retention time (HRT) of 3.3 h, 90% of the glucose was removed, producing 2200 mg/L of cells and 500 mL/h of biogas. When operated in MBR mode, the solids retention time (SRT) was increased to SRT = 12 h producing a solids concentration in the reactor of 5800 mg/L. This SRT increased the overall glucose utilization (98%), the biogas production rate (640 mL/h), and the conversion efficiency of glucose-to-hydrogen from 22% (no MBR) to 25% (based on a maximum of 4 mol-H(2)/mol-glucose). When the SRT was increased from 5 h to 48 h, glucose utilization (99%) and biomass concentrations (8,800 +/- 600 mg/L) both increased. However, the biogas production decreased (310 +/- 40 mL/h) and the glucose-to-hydrogen conversion efficiency decreased from 37 +/- 4% to 18 +/- 3%. Sustained permeate flows through the membrane were in the range of 57 to 60 L/m(2) h for three different membrane pore sizes (0.3, 0.5, and 0.8 microm). Most (93.7% to 99.3%) of the membrane resistance was due to internal fouling and the reversible cake resistance, and not the membrane itself. Regular backpulsing was essential for maintaining permeate flux through the membrane. Analysis of DNA sequences using ribosomal intergenic spacer analysis indicated bacteria were most closely related to members of Clostridiaceae and Flexibacteraceae, including Clostridium acidisoli CAC237756 (97%), Linmingia china AF481148 (97%), and Cytophaga sp. MDA2507 AF238333 (99%). No PCR amplification of 16s rRNA genes was obtained when archaea-specific primers were used.

  20. Formation and Regulation of Mitochondrial Membranes

    Directory of Open Access Journals (Sweden)

    Laila Cigana Schenkel

    2014-01-01

    Full Text Available Mitochondrial membrane phospholipids are essential for the mitochondrial architecture, the activity of respiratory proteins, and the transport of proteins into the mitochondria. The accumulation of phospholipids within mitochondria depends on a coordinate synthesis, degradation, and trafficking of phospholipids between the endoplasmic reticulum (ER and mitochondria as well as intramitochondrial lipid trafficking. Several studies highlight the contribution of dietary fatty acids to the remodeling of phospholipids and mitochondrial membrane homeostasis. Understanding the role of phospholipids in the mitochondrial membrane and their metabolism will shed light on the molecular mechanisms involved in the regulation of mitochondrial function and in the mitochondrial-related diseases.

  1. Regulation of Plasma Membrane Recycling by CFTR

    Science.gov (United States)

    Bradbury, Neil A.; Jilling, Tamas; Berta, Gabor; Sorscher, Eric J.; Bridges, Robert J.; Kirk, Kevin L.

    1992-04-01

    The gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) is defective in patients with cystic fibrosis. Although the protein product of the CFTR gene has been proposed to function as a chloride ion channel, certain aspects of its function remain unclear. The role of CFTR in the adenosine 3',5'-monophosphate (cAMP)-dependent regulation of plasma membrane recycling was examined. Adenosine 3',5'-monophosphate is known to regulate endocytosis and exocytosis in chloride-secreting epithelial cells that express CFTR. However, mutant epithelial cells derived from a patient with cystic fibrosis exhibited no cAMP-dependent regulation of endocytosis and exocytosis until they were transfected with complementary DNA encoding wild-type CFTR. Thus, CFTR is critical for cAMP-dependent regulation of membrane recycling in epithelial tissues, and this function of CFTR could explain in part the pleiotropic nature of cystic fibrosis.

  2. Towards Systems Biology of Mycotoxin Regulation

    OpenAIRE

    Christof Rampitsch; Rajagopal Subramaniam

    2013-01-01

    Systems biology is a scientific approach that integrates many scientific disciplines to develop a comprehensive understanding of biological phenomena, thus allowing the prediction and accurate simulation of complex biological behaviors. It may be presumptuous to write about toxin regulation at the level of systems biology, but the last decade of research is leading us closer than ever to this approach. Past research has delineated multiple levels of regulation in the pathways leading to the b...

  3. Budded membrane microdomains as regulators for cellular tension

    OpenAIRE

    Sens, Pierre; Turner, Matthew S.

    2005-01-01

    We propose a mechanism for mechanical regulation at the membrane of living cells, based on the exchange of membrane area between the cell membrane and a membrane reservoir. The reservoir is composed of invaginated membrane microdomains which are liable to flatten upon increase of membrane strain, effectively controlling membrane tension. We show that the domain shape transition is first order, allowing for coexistence between flat and invaginated domains. During coexistence, the membrane tens...

  4. Metric dynamics for membrane transformation through regulated cell proliferation

    OpenAIRE

    Ito, Hiroshi C.

    2016-01-01

    This study develops an equation for describing three-dimensional membrane transformation through proliferation of its component cells regulated by morphogen density distributions on the membrane. The equation is developed in a two-dimensional coordinate system mapped on the membrane, referred to as the membrane coordinates. When the membrane expands, the membrane coordinates expand in the same manner so that the membrane is invariant in the coordinates. In the membrane coordinate system, the ...

  5. Effect of Antimicrobial Peptide-Amide: Indolicidin on Biological Membranes

    Directory of Open Access Journals (Sweden)

    Attila Gergely Végh

    2011-01-01

    Full Text Available Indolicidin, a cationic antimicrobial tridecapeptide amide, is rich in proline and tryptophan residues. Its biological activity is intensively studied, but the details how indolicidin interacts with membranes are not fully understood yet. We report here an in situ atomic force microscopic study describing the effect of indolicidin on an artificial supported planar bilayer membrane of dipalmitoyl phosphatidylcholine (DPPC and on purple membrane of Halobacterium salinarum. Concentration dependent interaction of the peptide and membranes was found in case of DPPC resulting the destruction of the membrane. Purple membrane was much more resistant against indolicidin, probably due to its high protein content. Indolicidin preferred the border of membrane disks, where the lipids are more accessible. These data suggest that the atomic force microscope is a powerful tool in the study of indolicidin-membrane interaction.

  6. Membrane curvature in cell biology: An integration of molecular mechanisms.

    Science.gov (United States)

    Jarsch, Iris K; Daste, Frederic; Gallop, Jennifer L

    2016-08-15

    Curving biological membranes establishes the complex architecture of the cell and mediates membrane traffic to control flux through subcellular compartments. Common molecular mechanisms for bending membranes are evident in different cell biological contexts across eukaryotic phyla. These mechanisms can be intrinsic to the membrane bilayer (either the lipid or protein components) or can be brought about by extrinsic factors, including the cytoskeleton. Here, we review examples of membrane curvature generation in animals, fungi, and plants. We showcase the molecular mechanisms involved and how they collaborate and go on to highlight contexts of curvature that are exciting areas of future research. Lessons from how membranes are bent in yeast and mammals give hints as to the molecular mechanisms we expect to see used by plants and protists.

  7. System biology of gene regulation.

    Science.gov (United States)

    Baitaluk, Michael

    2009-01-01

    A famous joke story that exhibits the traditionally awkward alliance between theory and experiment and showing the differences between experimental biologists and theoretical modelers is when a University sends a biologist, a mathematician, a physicist, and a computer scientist to a walking trip in an attempt to stimulate interdisciplinary research. During a break, they watch a cow in a field nearby and the leader of the group asks, "I wonder how one could decide on the size of a cow?" Since a cow is a biological object, the biologist responded first: "I have seen many cows in this area and know it is a big cow." The mathematician argued, "The true volume is determined by integrating the mathematical function that describes the outer surface of the cow's body." The physicist suggested: "Let's assume the cow is a sphere...." Finally the computer scientist became nervous and said that he didn't bring his computer because there is no Internet connection up there on the hill. In this humorous but explanatory story suggestions proposed by theorists can be taken to reflect the view of many experimental biologists that computer scientists and theorists are too far removed from biological reality and therefore their theories and approaches are not of much immediate usefulness. Conversely, the statement of the biologist mirrors the view of many traditional theoretical and computational scientists that biological experiments are for the most part simply descriptive, lack rigor, and that much of the resulting biological data are of questionable functional relevance. One of the goals of current biology as a multidisciplinary science is to bring people from different scientific areas together on the same "hill" and teach them to speak the same "language." In fact, of course, when presenting their data, most experimentalist biologists do provide an interpretation and explanation for the results, and many theorists/computer scientists aim to answer (or at least to fully describe

  8. Testing of Synthetic Biological Membranes for Forward Osmosis Applications

    Science.gov (United States)

    Parodi, Jurek; Mangado, Jaione Romero; Stefanson, Ofir; Flynn, Michael; Mancinelli, Rocco; Kawashima, Brian; Trieu, Serena; Brozell, Adrian; Rosenberg, Kevan

    2016-01-01

    Commercially available forward osmosis membranes have been extensively tested for human space flight wastewater treatment. Despite the improvements achieved in the last decades, there is still a challenge to produce reliable membranes with anti-fouling properties, chemical resistance, and high flux and selectivity. Synthetic biological membranes that mimic the ones present in nature, which underwent millions of years of evolution, represent a potential solution for further development and progress in membrane technology. Biomimetic forward osmosis membranes based on a polymeric support filter and coated with surfactant multilayers have been engineered to investigate how different manufacturing processes impact the performance and structure of the membrane. However, initial results of the first generation prototype membranes tests reveal a high scatter in the data, due to the current testing apparatus set up. The testing apparatus has been upgraded to improve data collection, reduce errors, and to allow higher control of the testing process.

  9. Tethered bilayer lipid membranes (tBLMs): interest and applications for biological membrane investigations.

    Science.gov (United States)

    Rebaud, Samuel; Maniti, Ofelia; Girard-Egrot, Agnès P

    2014-12-01

    Biological membranes play a central role in the biology of the cell. They are not only the hydrophobic barrier allowing separation between two water soluble compartments but also a supra-molecular entity that has vital structural functions. Notably, they are involved in many exchange processes between the outside and inside cellular spaces. Accounting for the complexity of cell membranes, reliable models are needed to acquire current knowledge of the molecular processes occurring in membranes. To simplify the investigation of lipid/protein interactions, the use of biomimetic membranes is an approach that allows manipulation of the lipid composition of specific domains and/or the protein composition, and the evaluation of the reciprocal effects. Since the middle of the 80's, lipid bilayer membranes have been constantly developed as models of biological membranes with the ultimate goal to reincorporate membrane proteins for their functional investigation. In this review, after a brief description of the planar lipid bilayers as biomimetic membrane models, we will focus on the construction of the tethered Bilayer Lipid Membranes, the most promising model for efficient membrane protein reconstitution and investigation of molecular processes occurring in cell membranes.

  10. Homeoviscous adaptation and the regulation of membrane lipids

    DEFF Research Database (Denmark)

    Ernst, Robert; Ejsing, Christer S; Antonny, Bruno

    2016-01-01

    Biological membranes are complex and dynamic assemblies of lipids and proteins. Poikilothermic organisms including bacteria, fungi, reptiles, and fish do not control their body temperature and must adapt their membrane lipid composition in order to maintain membrane fluidity in the cold. This ada......Biological membranes are complex and dynamic assemblies of lipids and proteins. Poikilothermic organisms including bacteria, fungi, reptiles, and fish do not control their body temperature and must adapt their membrane lipid composition in order to maintain membrane fluidity in the cold...

  11. Lipophilic drug transfer between liposomal and biological membranes

    DEFF Research Database (Denmark)

    Fahr, Alfred; van Hoogevest, Peter; Kuntsche, Judith;

    2006-01-01

    is described as solubility of a drug in phospholipid membranes and the kinetics of transfer of a lipophilic drug between membranes. Finally, the consequences of these two factors on the design of lipid-based carriers for oral, as well as parenteral use, for lipophilic drugs and lead selection of oral...... lipophilic drugs is described. Since liposomes serve as model-membranes for natural membranes, the assessment of lipid solubility and transfer kinetics of lipophilic drug using liposome formulations may additionally have predictive value for bioavailability and biodistribution and the pharmacokinetics......This review presents the current knowledge on the interaction of lipophilic, poorly water soluble drugs with liposomal and biological membranes. The center of attention will be on drugs having the potential to dissolve in a lipid membrane without perturbing them too much. The degree of interaction...

  12. Importance of the hexagonal lipid phase in biological membrane organisation

    Directory of Open Access Journals (Sweden)

    Juliette eJouhet

    2013-12-01

    Full Text Available Abstract:Domains are present in every natural membrane. They are characterised by a distinctive protein and/or lipid composition. Their size is highly variable from the nano- to the micrometer scale. The domains confer specific properties to the membrane leading to original structure and function. The determinants leading to domain organisation are therefore important but remain obscure. This review presents how the ability of lipids to organize into hexagonal II or lamellar phases can promote particular local structures within membranes. Since biological membranes are composed of a mixture of lipids, each with distinctive biophysical properties, lateral and transversal sorting of lipids can promote creation of domains inside the membrane through local modulation of the lipid phase. Lipid biophysical properties have been characterized for long based on in vitro analyses using non-natural lipid molecules; their re-examinations using natural lipids might open interesting perspectives on membrane architecture occurring in vivo in various cellular and physiological contexts.

  13. Introduction to fluorescence probing of biological membranes.

    Science.gov (United States)

    Demchenko, Alexander P; Duportail, Guy; Oncul, Sule; Klymchenko, Andrey S; Mély, Yves

    2015-01-01

    Fluorescence is one of the most powerful and commonly used tools in biophysical studies of biomembrane structure and dynamics that can be applied on different levels, from lipid monolayers and bilayers to living cells, tissues, and whole animals. Successful application of this method relies on proper design of fluorescence probes with optimized photophysical properties. These probes are efficient for studying the microscopic analogs of viscosity, polarity, and hydration, as well as the molecular order, environment relaxation, and electrostatic potentials at the sites of their location. Being smaller than the membrane width they can sense the gradients of these parameters across the membrane. We present examples of novel dyes that achieve increased spatial resolution and information content of the probe responses. In this respect, multiparametric environment-sensitive probes feature considerable promise.

  14. Investigating Membranes: Using Artificial Membranes to Convey Chemistry and Biology Concepts

    Science.gov (United States)

    Zrelak, Yoshi; McCallister, Gary

    2009-01-01

    While not organic in nature, quick-"growing" artificial membranes can be a profound visual aid when teaching students about cellular processes and the chemical nature of membranes. Students are often intrigued when they see biological and chemical concepts come to life before their eyes. In this article, the authors share their approach to growing…

  15. Ultrafast spectroscopy of model biological membranes

    NARCIS (Netherlands)

    Ghosh, Avishek

    2009-01-01

    In this PhD thesis, I have described the novel time-resolved sum-frequency generation (TR-SFG) spectroscopic technique that I developed during the course of my PhD research and used it study the ultrafast vibrational, structural and orientational dynamics of water molecules at model biological membr

  16. Applications of membrane computing in systems and synthetic biology

    CERN Document Server

    Gheorghe, Marian; Pérez-Jiménez, Mario

    2014-01-01

    Membrane Computing was introduced as a computational paradigm in Natural Computing. The models introduced, called Membrane (or P) Systems, provide a coherent platform to describe and study living cells as computational systems. Membrane Systems have been investigated for their computational aspects and employed to model problems in other fields, like: Computer Science, Linguistics, Biology, Economy, Computer Graphics, Robotics, etc. Their inherent parallelism, heterogeneity and intrinsic versatility allow them to model a broad range of processes and phenomena, being also an efficient means to solve and analyze problems in a novel way. Membrane Computing has been used to model biological systems, becoming with time a thorough modeling paradigm comparable, in its modeling and predicting capabilities, to more established models in this area. This book is the result of the need to collect, in an organic way, different facets of this paradigm. The chapters of this book, together with the web pages accompanying th...

  17. Nanodomain stabilization dynamics in plasma membranes of biological cells

    Science.gov (United States)

    Das, Tamal; Maiti, Tapas K.; Chakraborty, Suman

    2011-02-01

    We discover that a synergistically amplifying role of stabilizing membrane proteins and continuous lipid recycling can explain the physics governing the stability, polydispersity, and dynamics of lipid raft domains in plasma membranes of biological cells. We establish the conjecture using a generalized order parameter based on theoretical formalism, endorsed by detailed scaling arguments and domain mapping. Quantitative agreements with morphological distributions of raft complexes, as obtained from Förster resonance energy transfer based visualization, support the present theoretical conjecture.

  18. Molecular probes for nonlinear optical imaging of biological membranes

    Science.gov (United States)

    Blanchard-Desce, Mireille H.; Ventelon, Lionel; Charier, Sandrine; Moreaux, Laurent; Mertz, Jerome

    2001-12-01

    Second-harmonic generation (SHG) and two-photon excited fluorescence (TPEF) are nonlinear optical (NLO) phenomena that scale with excitation intensity squared, and hence give rise to an intrinsic 3-dimensional resolution when used in microscopic imaging. TPEF microscopy has gained widespread popularity in the biology community whereas SHG microscopy promises to be a powerful tool because of its sensitivity to local asymmetry. We have implemented an approach toward the design of NLO-probes specifically adapted for SHG and/or TPEF imaging of biological membranes. Our strategy is based on the design of nanoscale amphiphilic NLO-phores. We have prepared symmetrical bolaamphiphilic fluorophores combining very high two-photon absorption (TPA) cross-sections in the visible red region and affinity for cellular membranes. Their incorporation and orientation in lipid membranes can be monitored via TPEF anisotropy. We have also prepared amphiphilic push-pull chromophores exhibiting both large TPA cross-sections and very large first hyperpolarizabilities in the near-IR region. These NLO-probes have proved to be particularly useful for imaging of biological membranes by simultaneous SHG and TPEF microscopy and offer attractive prospects for real-time imaging of fundamental biological processes such as adhesion, fusion or reporting of membrane potentials.

  19. Low threshold random lasing actions in natural biological membranes

    Science.gov (United States)

    Huang, Dengfeng; Xu, Min; Liu, Xiyun; Yang, Ming; Yi, Tao; Wang, Chuanke; Li, Tingshuai; Liu, Shenye

    2016-06-01

    We report random lasing actions stemming from natural biological membranes doped with Rhodamine 6G (Rh6G) laser dye which were then stimulated by a pulsed laser. The membranes have concave-convex structures and are expected to form resonators for weak light scatterings. The laser emission varies with the type of membrane and is also closely related to the dye concentration and pump energy. The threshold for the laser generation obviously rises when the concentration of doped laser dye is increased. The simulation results show lasing distributions are localized, indicating that the laser modes are very sensitive to the indicant angles of pump light.

  20. Regulation of transport processes across the tonoplast membrane

    Directory of Open Access Journals (Sweden)

    Oliver eTrentmann

    2014-09-01

    Full Text Available In plants, the vacuole builds up the cellular turgor and represents an important component in cellular responses to diverse stress stimuli. Rapid volume changes of cells, particularly of motor cells, like guard cells, are caused by variation of osmolytes and consequently of the water contents in the vacuole. Moreover, directed solute uptake into or release out of the large central vacuole allows adaptation of cytosolic metabolite levels according to the current physiological requirements and specific cellular demands. Therefore, solute passage across the vacuolar membrane, the tonoplast, has to be tightly regulated. Important principles in vacuolar transport regulation are changes of tonoplast transport protein abundances by differential expression of genes or changes of their activities, e.g. due to post-translational modification or by interacting proteins. Because vacuolar transport is in most cases driven by an electro-chemical gradient altered activities of tonoplast proton pumps significantly influence vacuolar transport capacities. Intense studies on individual tonoplast proteins but also unbiased system biological approaches have provided important insights into the regulation of vacuolar transport. This short review refers to selected examples of tonoplast proteins and their regulation, with special focus on protein phosphorylation.

  1. CFD Simulation of Fouling by Biological materials in Membrane Bioreactor

    Directory of Open Access Journals (Sweden)

    Raziye, Ahmadi

    2016-06-01

    Full Text Available In recent years membrane bioreactors filtration is increasingly used in wastewater treatment to enhance the quality of wastewater. The main problem in preventing the widespread use of membrane bioreactor is its congestion which has a severe impact on output flux to time ratio. If solid suspensions with high concentrations exist in the wastewater, this influence will be even more severe. In addition to the suspended solids in the liquid mixture, Extracellular polymeric materials (EPS and soluble microbial products (SMP are also known as basic microbial products that cause membrane fouling. EPS can be calculated within and on the membrane which increases the viscosity of suspended solids in the liquid mixture and increases filtration resistance. SMPs cannot penetrate the pores of the ultra filtration membrane due to the limited size of the pores which would cause fouling in membrane processes. According to the above issues, providing a model that indicates the properties and conditions of formation and destruction of SMP and EPS at the same time seems necessary. In this paper, CFD simulation of biological fouling in membrane bioreactor is provided using Fluent software.

  2. Biological Membranes in Extreme Conditions: Simulations of Anionic Archaeal Tetraether Lipid Membranes.

    Directory of Open Access Journals (Sweden)

    Luis Felipe Pineda De Castro

    Full Text Available In contrast to the majority of organisms that have cells bound by di-ester phospholipids, archaeal membranes consist of di- and tetraether phospholipids. Originating from organisms that withstand harsh conditions (e.g., low pH and a wide range of temperatures such membranes have physical properties that make them attractive materials for biological research and biotechnological applications. We developed force-field parameters based on the widely used Generalized Amber Force Field (GAFF to enable the study of anionic tetraether membranes of the model archaean Sulfolobus acidocaldarius by computer simulations. The simulations reveal that the physical properties of these unique membranes depend on the number of cyclopentane rings included in each lipid unit, and on the size of cations that are used to ensure charge neutrality. This suggests that the biophysical properties of Sulfolobus acidocaldarius cells depend not only on the compositions of their membranes but also on the media in which they grow.

  3. Biological Membranes in Extreme Conditions: Simulations of Anionic Archaeal Tetraether Lipid Membranes

    Science.gov (United States)

    Pineda De Castro, Luis Felipe; Dopson, Mark

    2016-01-01

    In contrast to the majority of organisms that have cells bound by di-ester phospholipids, archaeal membranes consist of di- and tetraether phospholipids. Originating from organisms that withstand harsh conditions (e.g., low pH and a wide range of temperatures) such membranes have physical properties that make them attractive materials for biological research and biotechnological applications. We developed force-field parameters based on the widely used Generalized Amber Force Field (GAFF) to enable the study of anionic tetraether membranes of the model archaean Sulfolobus acidocaldarius by computer simulations. The simulations reveal that the physical properties of these unique membranes depend on the number of cyclopentane rings included in each lipid unit, and on the size of cations that are used to ensure charge neutrality. This suggests that the biophysical properties of Sulfolobus acidocaldarius cells depend not only on the compositions of their membranes but also on the media in which they grow. PMID:27167213

  4. Did the last common ancestor have a biological membrane?

    Directory of Open Access Journals (Sweden)

    Jékely Gáspár

    2006-11-01

    Full Text Available Abstract All theories about the origin and evolution of membrane bound cells necessarily have to cope with the nature of the last common ancestor of cellular life. One of the most important aspect of this ancestor, whether it had a closed biological membrane or not, has recently been intensely debated. Having a consensus about it would be an important step towards an eventual (though probably still remote synthesis of the best elements of the current multitude of cell evolution models. Here I analyse the structural and functional conservation of the few universally distributed proteins that were undoubtedly present in the last common ancestor and that carry out membrane-associated functions. These include the SecY subunit of the protein-conducting channel, the signal recognition particle, the signal recognition particle receptor, the signal peptidase, and the proton ATPase. The conserved structural and functional aspects of these proteins indicate that the last common ancestor was associated with a hydrophobic layer with two hydrophilic sides (an inside and an outside that had a full-fledged and asymmetric protein insertion and translocation machinery and served as a permeability barrier for protons and other small molecules. It is difficult to escape the conclusion that the last common ancestor had a closed biological membrane from which all cellular membranes evolved.

  5. Continuous Modeling of Calcium Transport Through Biological Membranes

    Science.gov (United States)

    Jasielec, J. J.; Filipek, R.; Szyszkiewicz, K.; Sokalski, T.; Lewenstam, A.

    2016-08-01

    In this work an approach to the modeling of the biological membranes where a membrane is treated as a continuous medium is presented. The Nernst-Planck-Poisson model including Poisson equation for electric potential is used to describe transport of ions in the mitochondrial membrane—the interface which joins mitochondrial matrix with cellular cytosis. The transport of calcium ions is considered. Concentration of calcium inside the mitochondrion is not known accurately because different analytical methods give dramatically different results. We explain mathematically these differences assuming the complexing reaction inside mitochondrion and the existence of the calcium set-point (concentration of calcium in cytosis below which calcium stops entering the mitochondrion).

  6. Modifications of the Dielectric Properties of Biological Membranes by Heating

    CERN Document Server

    Savescu, S B

    2004-01-01

    Biological cell suspensions are known to show dielectric dispersions due to the Maxwell-Wagner mechanism. Many examples are summarized in a number of papers by Schwan [7, 9, 10]. By the application of an appropriate analysis to the dielectric dispersion, it is possible to estimate electrical phase parameters related to protoplasm and cell membrane. A dielectric theory of interfacial polarization for a suspension of conducting particles (protoplasm) covered with poorly conducting shells (plasma membrane) was developed by Pauly and Schwan [7], and was satisfactory applied for low volume fractions of suspended particles (less than about 0.2). The purpose of this paper is to examine the change in yeast plasma membrane permittivity after heating treatment, by using the Pauly and Schwan's theory.

  7. Lipids: architects and regulators of membrane dynamics and trafficking.

    Science.gov (United States)

    Moreau, Patrick

    2007-05-01

    We have recently shown that an inhibition of sterol synthesis by fenpropimorph leads to an accumulation of sterol precursors, hydroxypalmitic acid-containing glucosylceramides and detergent resistant membranes in the Golgi bodies instead of the plasma membrane, suggesting that the individual molecules or the microdomains were blocked in the Golgi. These results and others from several eukaryotic models link lipid metabolism with membrane morphodynamics that are involved in membrane trafficking. Focus has been expanded to other lipid families, and numerous evidences are given showing lipids and lipid-modifying enzymes as key regulators of membrane homeostasis which can strongly regulate membrane morphodynamics and therefore trafficking. Beside protein-based machineries, lipid-based machineries are also shown as crucial regulatory forces involved in protein transport and sorting.

  8. Ion transport through biological membranes an integrated theoretical approach

    CERN Document Server

    Mackey, Michael C

    1975-01-01

    This book illustrates some of the ways physics and mathematics have been, and are being, used to elucidate the underlying mechan­ isms of passive ion movement through biological membranes in general, and the membranes of excltable cells in particular. I have made no effort to be comprehensive in my introduction of biological material and the reader interested in a brief account of single cell electro­ physlology from a physically-oriented biologists viewpoint will find the chapters by Woodbury (1965) an excellent introduction. Part I is introductory in nature, exploring the basic electrical properties of inexcitable and excitable cell plasma membranes. Cable theory is utilized to illustrate the function of the non-decrementing action potential as a signaling mechanism for the long range trans­ mission of information in the nervous system, and to gain some in­ sight into the gross behaviour of neurons. The detailed analysis of Hodgkin and Huxley on the squid giant axon membrane ionic conductance properties...

  9. Hybrid Adsorption-Membrane Biological Reactors for Improved Performance and Reliability of Perchlorate Removal Processes

    Science.gov (United States)

    2008-12-01

    carbon supply for the autotrophic perchlorate reducing bacteria. The membrane used in the reactor is a hollow-fiber microfiltration membrane made from...1 HYBRID ADSORPTION- MEMBRANE BIOLOGICAL REACTORS FOR IMPROVED PERFORMANCE AND RELIABILITY OF PERCHLORATE REMOVAL PROCESSES L.C. Schideman...Center Champaign, IL 61826, USA ABSTRACT This study introduces the novel HAMBgR process (Hybrid Adsorption Membrane Biological Reactor) and

  10. Autophagic regulation of smooth muscle cell biology

    Science.gov (United States)

    Salabei, Joshua K.; Hill, Bradford G.

    2014-01-01

    Autophagy regulates the metabolism, survival, and function of numerous cell types, including those comprising the cardiovascular system. In the vasculature, changes in autophagy have been documented in atherosclerotic and restenotic lesions and in hypertensive vessels. The biology of vascular smooth muscle cells appears particularly sensitive to changes in the autophagic program. Recent evidence indicates that stimuli or stressors evoked during the course of vascular disease can regulate autophagic activity, resulting in modulation of VSMC phenotype and viability. In particular, certain growth factors and cytokines, oxygen tension, and pharmacological drugs have been shown to trigger autophagy in smooth muscle cells. Importantly, each of these stimuli has a redox component, typically associated with changes in the abundance of reactive oxygen, nitrogen, or lipid species. Collective findings support the hypothesis that autophagy plays a critical role in vascular remodeling by regulating smooth muscle cell phenotype transitions and by influencing the cellular response to stress. In this graphical review, we summarize current knowledge on the role of autophagy in the biology of the smooth muscle cell in (patho)physiology. PMID:25544597

  11. Autophagic regulation of smooth muscle cell biology

    Directory of Open Access Journals (Sweden)

    Joshua K. Salabei

    2015-04-01

    Full Text Available Autophagy regulates the metabolism, survival, and function of numerous cell types, including those comprising the cardiovascular system. In the vasculature, changes in autophagy have been documented in atherosclerotic and restenotic lesions and in hypertensive vessels. The biology of vascular smooth muscle cells appears particularly sensitive to changes in the autophagic program. Recent evidence indicates that stimuli or stressors evoked during the course of vascular disease can regulate autophagic activity, resulting in modulation of VSMC phenotype and viability. In particular, certain growth factors and cytokines, oxygen tension, and pharmacological drugs have been shown to trigger autophagy in smooth muscle cells. Importantly, each of these stimuli has a redox component, typically associated with changes in the abundance of reactive oxygen, nitrogen, or lipid species. Collective findings support the hypothesis that autophagy plays a critical role in vascular remodeling by regulating smooth muscle cell phenotype transitions and by influencing the cellular response to stress. In this graphical review, we summarize current knowledge on the role of autophagy in the biology of the smooth muscle cell in (pathophysiology.

  12. Type IV Collagens and Basement Membrane Diseases: Cell Biology and Pathogenic Mechanisms.

    Science.gov (United States)

    Mao, Mao; Alavi, Marcel V; Labelle-Dumais, Cassandre; Gould, Douglas B

    2015-01-01

    Basement membranes are highly specialized extracellular matrices. Once considered inert scaffolds, basement membranes are now viewed as dynamic and versatile environments that modulate cellular behaviors to regulate tissue development, function, and repair. Increasing evidence suggests that, in addition to providing structural support to neighboring cells, basement membranes serve as reservoirs of growth factors that direct and fine-tune cellular functions. Type IV collagens are a major component of all basement membranes. They evolved along with the earliest multicellular organisms and have been integrated into diverse fundamental biological processes as time and evolution shaped the animal kingdom. The roles of basement membranes in humans are as complex and diverse as their distributions and molecular composition. As a result, basement membrane defects result in multisystem disorders with ambiguous and overlapping boundaries that likely reflect the simultaneous interplay and integration of multiple cellular pathways and processes. Consequently, there will be no single treatment for basement membrane disorders, and therapies are likely to be as varied as the phenotypes. Understanding tissue-specific pathology and the underlying molecular mechanism is the present challenge; personalized medicine will rely upon understanding how a given mutation impacts diverse cellular functions.

  13. Allosteric Regulation by a Critical Membrane

    CERN Document Server

    Kimchi, Ofer; Machta, Benjamin B

    2016-01-01

    Many of the processes that underly neural computation are carried out by ion channels embedded in the plasma membrane, a two-dimensional liquid that surrounds all cells. Recent experiments have demonstrated that this membrane is poised close to a liquid-liquid critical point in the Ising universality class. Here we use both exact and stochastic techniques on the lattice Ising model to explore the ramifications of proximity to criticality for proteins that are allosterically coupled to Ising composition modes. Owing to diverging generalized susceptibilities, such a protein's activity becomes strongly influenced by perturbations that influence the two relevant parameters of the critical point, especially the critical temperature. In addition, the protein's kinetics acquire a range of time scales from its surrounding membrane, naturally leading to non-Markovian dynamics.

  14. Biological control of biofilms on membranes by metazoans.

    Science.gov (United States)

    Klein, Theresa; Zihlmann, David; Derlon, Nicolas; Isaacson, Carl; Szivak, Ilona; Weissbrodt, David G; Pronk, Wouter

    2016-01-01

    Traditionally, chemical and physical methods have been used to control biofouling on membranes by inactivating and removing the biofouling layer. Alternatively, the permeability can be increased using biological methods while accepting the presence of the biofouling layer. We have investigated two different types of metazoans for this purpose, the oligochaete Aelosoma hemprichi and the nematode Plectus aquatilis. The addition of these grazing metazoans in biofilm-controlled membrane systems resulted in a flux increase of 50% in presence of the oligochaetes (Aelosoma hemprichi), and a flux increase of 119-164% in presence of the nematodes (Plectus aquatilis) in comparison to the control system operated without metazoans. The change in flux resulted from (1) a change in the biofilm structure, from a homogeneous, cake-like biofilm to a more heterogeneous, porous structure and (2) a significant reduction in the thickness of the basal layer. Pyrosequencing data showed that due to the addition of the predators, also the community composition of the biofilm in terms of protists and bacteria was strongly affected. The results have implications for a range of membrane processes, including ultrafiltration for potable water production, membrane bioreactors and reverse osmosis.

  15. Effect of choline carboxylate ionic liquids on biological membranes.

    Science.gov (United States)

    Rengstl, Doris; Kraus, Birgit; Van Vorst, Matthew; Elliott, Gloria D; Kunz, Werner

    2014-11-01

    Choline carboxylates, ChCm, with m=2-10 and choline oleate are known as biocompatible substances, yet their influence on biological membranes is not well-known, and the effect on human skin has not previously been investigated. The short chain choline carboxylates ChCm with m=2, 4, 6 act as hydrotropes, solubilizing hydrophobic compounds in aqueous solution, while the longer chain choline carboxylates ChCm with m=8, 10 and oleate are able to form micelles. In the present study, the cytotoxicity of choline carboxylates was tested using HeLa and SK-MEL-28 cells. The influence of these substances on liposomes prepared from dipalmitoylphosphatidylcholine (DPPC) was also evaluated to provide insights on membrane interactions. It was observed that the choline carboxylates with a chain length of m>8 distinctly influence the bilayer, while the shorter ones had minimal interaction with the liposomes.

  16. Hydrodynamic collective effects of active proteins in biological membranes

    CERN Document Server

    Koyano, Yuki; Mikhailov, Alexander S

    2016-01-01

    Lipid bilayers forming biological membranes are known to behave as viscous 2D fluids on submicrometer scales; usually they contain a large number of active protein inclusions. Recently, it has been shown [Proc. Nat. Acad. Sci. USA 112, E3639 (2015)] that such active proteins should in- duce non-thermal fluctuating lipid flows leading to diffusion enhancement and chemotaxis-like drift for passive inclusions in biomembranes. Here, a detailed analytical and numerical investigation of such effects is performed. The attention is focused on the situations when proteins are concentrated within lipid rafts. We demonstrate that passive particles tend to become attracted by active rafts and are accumulated inside them.

  17. Molecular dynamics simulations of biological membranes and membrane proteins using enhanced conformational sampling algorithms.

    Science.gov (United States)

    Mori, Takaharu; Miyashita, Naoyuki; Im, Wonpil; Feig, Michael; Sugita, Yuji

    2016-07-01

    This paper reviews various enhanced conformational sampling methods and explicit/implicit solvent/membrane models, as well as their recent applications to the exploration of the structure and dynamics of membranes and membrane proteins. Molecular dynamics simulations have become an essential tool to investigate biological problems, and their success relies on proper molecular models together with efficient conformational sampling methods. The implicit representation of solvent/membrane environments is reasonable approximation to the explicit all-atom models, considering the balance between computational cost and simulation accuracy. Implicit models can be easily combined with replica-exchange molecular dynamics methods to explore a wider conformational space of a protein. Other molecular models and enhanced conformational sampling methods are also briefly discussed. As application examples, we introduce recent simulation studies of glycophorin A, phospholamban, amyloid precursor protein, and mixed lipid bilayers and discuss the accuracy and efficiency of each simulation model and method. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.

  18. Mechanism of long-range proton translocation along biological membranes.

    Science.gov (United States)

    Medvedev, Emile S; Stuchebrukhov, Alexei A

    2013-02-14

    Recent experiments suggest that protons can travel along biological membranes up to tens of micrometers, but the mechanism of transport is unknown. To explain such a long-range proton translocation we describe a model that takes into account the coupled bulk diffusion that accompanies the migration of protons on the surface. We show that protons diffusing at or near the surface before equilibrating with the bulk desorb and re-adsorb at the surface thousands of times, giving rise to a power-law desorption kinetics. As a result, the decay of the surface protons occurs very slowly, allowing for establishing local gradient and local exchange, as was envisioned in the early local models of biological energy transduction.

  19. Translocation of a phycoerythrin alpha subunit across five biological membranes.

    Science.gov (United States)

    Gould, Sven B; Fan, Enguo; Hempel, Franziska; Maier, Uwe-G; Klösgen, Ralf Bernd

    2007-10-12

    Cryptophytes, unicellular algae, evolved by secondary endosymbiosis and contain plastids surrounded by four membranes. In contrast to cyanobacteria and red algae, their phycobiliproteins do not assemble into phycobilisomes and are located within the thylakoid lumen instead of the stroma. We identified two gene families encoding phycoerythrin alpha and light-harvesting complex proteins from an expressed sequence tag library of the cryptophyte Guillardia theta. The proteins bear a bipartite topogenic signal responsible for the transport of nuclear encoded proteins via the ER into the plastid. Analysis of the phycoerythrin alpha sequences revealed that more than half of them carry an additional, third topogenic signal comprising a twin arginine motif, which is indicative of Tat (twin arginine transport)-specific targeting signals. We performed import studies with several derivatives of one member using a diatom transformation system, as well as intact chloroplasts and thylakoid vesicles isolated from pea. We demonstrated the different targeting properties of each individual part of the tripartite leader and show that phycoerythrin alpha is transported across the thylakoid membrane into the thylakoid lumen and protease-protected. Furthermore, we showed that thylakoid transport of phycoerythrin alpha takes place by the Tat pathway even if the 36 amino acid long bipartite topogenic signal precedes the actual twin arginine signal. This is the first experimental evidence of a protein being targeted across five biological membranes.

  20. Behavior in Electric Fields of Simple Biological Membranes

    Science.gov (United States)

    Honciuc, Maria; Slavnicu, Elena

    The latest studies in biophysics and biochemistry have revealed the major role that liquid crystals (LC) and related phenomena play in biological processes. To account for a number of membrane mechanisms in view of the theoretical model developed by S. J. Singer, studies were carried out on mixtures of fatty acids (arachidic, lauric, butyric) and cholesterol in different weight percentages. Such mixtures may help one understand some mechanisms on which the operation of biological membranes relies. To this end, the way these mixtures behave in an electric field was studied. Electric measurements were conducted from which the average time of electric relaxation (τ) and average electric permittivity (ɛr) were determined. Depending on cholesterol percentage, changes by more than one order of magnitude were found to occur in the electric relaxation time. The ratio between the various fatty acid components did not influence the average time τ in any significant manner. By contrast, the relative electric permittivity ɛr was seen to decrease by at least one order of magnitude with raising the cholesterol percentage. The electric properties of such systems essentially depend on changing the amount of cholesterol in the system.

  1. Hydrodynamic collective effects of active proteins in biological membranes

    Science.gov (United States)

    Koyano, Yuki; Kitahata, Hiroyuki; Mikhailov, Alexander S.

    2016-08-01

    Lipid bilayers forming biological membranes are known to behave as viscous two-dimensional fluids on submicrometer scales; usually they contain a large number of active protein inclusions. Recently, it was shown [A. S. Mikhailov and R. Kapral, Proc. Natl. Acad. Sci. USA 112, E3639 (2015), 10.1073/pnas.1506825112] that such active proteins should induce nonthermal fluctuating lipid flows leading to diffusion enhancement and chemotaxislike drift for passive inclusions in biomembranes. Here, a detailed analytical and numerical investigation of such effects is performed. The attention is focused on the situations when proteins are concentrated within lipid rafts. We demonstrate that passive particles tend to become attracted by active rafts and are accumulated inside them.

  2. FDA Regulation of Follow-On Biologics

    Science.gov (United States)

    2009-02-24

    biologic is similar to the brand-name (innovator) product made by the pharmaceutical or biotechnology industry . In contrast to a biologic, most commonly used drugs are synthesized via a chemical process.

  3. Intravacuolar Membranes Regulate CD8 T Cell Recognition of Membrane-Bound Toxoplasma gondii Protective Antigen

    Directory of Open Access Journals (Sweden)

    Jodie Lopez

    2015-12-01

    Full Text Available Apicomplexa parasites such as Toxoplasma gondii target effectors to and across the boundary of their parasitophorous vacuole (PV, resulting in host cell subversion and potential presentation by MHC class I molecules for CD8 T cell recognition. The host-parasite interface comprises the PV limiting membrane and a highly curved, membranous intravacuolar network (IVN of uncertain function. Here, using a cell-free minimal system, we dissect how membrane tubules are shaped by the parasite effectors GRA2 and GRA6. We show that membrane association regulates access of the GRA6 protective antigen to the MHC I pathway in infected cells. Although insertion of GRA6 in the PV membrane is key for immunogenicity, association of GRA6 with the IVN limits presentation and curtails GRA6-specific CD8 responses in mice. Thus, membrane deformations of the PV regulate access of antigens to the MHC class I pathway, and the IVN may play a role in immune modulation.

  4. Model Checking the Biological Model of Membrane Computing with Probabilistic Symbolic Model Checker by Using Two Biological Systems

    Directory of Open Access Journals (Sweden)

    Ravie c. Muniyandi

    2010-01-01

    Full Text Available Problem statement: Membrane computing formalism has provided better modeling capabilities for biological systems in comparison to conventional mathematical models. Model checking could be used to reason about the biological system in detail and with precision by verifying formally whether membrane computing model meets the properties of the system. Approach: This study was carried to investigate the preservation of properties of two biological systems that had been modeled and simulated in membrane computing by a method of model checking using PRISM. The two biological systems were prey-predator population and signal processing in the legend-receptor networks of protein TGF-ß. Results: The model checking of membrane computing model of the biological systems with five different properties showed that the properties of the biological systems could be preserved in the membrane computing model. Conclusion: Membrane computing model not only provides a better approach in representing and simulating a biological system but also able to sustain the basic properties of the system.

  5. Physics of the Chemical Asymmetry of the Cell Membrane: Implications in Gene Regulation and Pharmacology

    Directory of Open Access Journals (Sweden)

    Ziad Omran

    2015-09-01

    Full Text Available Signalling proteins are key regulators of basic cell physiology and tissues morphogenesis. Whilst signalling proteins are paramount for the cell to function optimally, their down regulation or inhibition is also central to tune the cell and its environment. One process involved in this tuning mechanism is membrane budding, otherwise known as endocytosis. The origin of the physical force driving the budding process and endocytosis has been the subject of much controversy. After two decades the budding process is now well described and it is acknowledged that fundamental principles from soft matter physics are at play. This opens a new window for understanding gene regulations, pharmacokinetic and multi drug resistance in cancer. This review recalls the first steps that have led to a better understanding of cell biology through the use of physics and; how the use of physics has shed light in areas of cell biology, cancer and pharmacology. It is, therefore, not a review of the many enzymes involved in membrane vesiculation and membrane curvature; it is more of an historical account.

  6. Nuclear translocation of EGF receptor regulated by Epstein-Barr virus encoded latent membrane protein 1

    Institute of Scientific and Technical Information of China (English)

    TAO; Yongguang; SONG; Xin; TAN; Yunnian; LIN; Xiaofeng; ZH

    2004-01-01

    Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is considered to be the major oncogenic protein of EBV encoded proteins, and also it has always been the core of the oncogenic mechanism of EBV. Traditional receptor theory demonstrates that cell surface receptors exert biological functions on the membrane, which neither enter into the nucleus nor directly affect the transcription of the target genes. But, advanced studies on nuclear translocation of the epidermal growth factor receptor (EGFR) family have greatly developed our knowledge of the biological function of cell surface receptors. In this study, we used Tet-on LMP1 HNE2 cell line as a cell model, which is a dual-stable LMP1 integrated NPC cell line and the expression of LMP1 in which could be regulated by Tet system. We found that LMP1 could regulate the nuclear translocation of EGFR in a dose-dependent manner from both quantitative and qualitative levels through the Western blot analysis and the immunofluorescent analysis with a laser scanning confocal microscope. We further demonstrated that the nuclear localization sequence of EGFR played some roles in the location of the protein within the nucleus under LMP1 regulation, and the nuclear accumulation of EGFR regulated by LMP1 was in a ligand-independent manner. These findings provide a novel view that the regulation of LMP1 on the nuclear translocation of EGFR is critical for the process of nasopharyngeal carcinoma.

  7. A model of plasma membrane flow and cytosis regulation in growing pollen tubes.

    Science.gov (United States)

    Chavarría-Krauser, Andrés; Yejie, Du

    2011-09-21

    A model of cytosis regulation in growing pollen tubes is developed and simulations presented. The authors address the question on the minimal assumptions needed to describe the pattern of exocytosis and endocytosis reported recently by experimental biologists. Biological implications of the model are also treated. Concepts of flow and conservation of membrane material are used to pose an equation system, which describes the movement of plasma membrane in the tip of growing pollen tubes. After obtaining the central equations, relations describing the rates of endocytosis and exocytosis are proposed. Two cytosis receptors (for exocytosis and endocytosis), which have different recycling rates and activation times, suffice to describe a stable growing tube. Simulations show a very good spatial separation between endocytosis and exocytosis, in which separation is shown to depend strongly on exocytic vesicle delivery. In accordance to measurements, most vesicles in the clear zone are predicted to be endocytic. Membrane flow is essential to maintain cell polarity, and bi-directional flow seems to be a natural consequence of the proposed mechanism. For the first time, a model addressing plasma membrane flow and cytosis regulation were posed. Therefore, it represents a missing piece in an integrative model of pollen tube growth, in which cell wall mechanics, hydrodynamic fluxes and regulation mechanisms are combined.

  8. An Ion Switch Regulates Fusion of Charged Membranes

    Science.gov (United States)

    Siepi, Evgenios; Lutz, Silke; Meyer, Sylke; Panzner, Steffen

    2011-01-01

    Here we identify the recruitment of solvent ions to lipid membranes as the dominant regulator of lipid phase behavior. Our data demonstrate that binding of counterions to charged lipids promotes the formation of lamellar membranes, whereas their absence can induce fusion. The mechanism applies to anionic and cationic liposomes, as well as the recently introduced amphoteric liposomes. In the latter, an additional pH-dependent lipid salt formation between anionic and cationic lipids must occur, as indicated by the depletion of membrane-bound ions in a zone around pH 5. Amphoteric liposomes fuse under these conditions but form lamellar structures at both lower and higher pH values. The integration of these observations into the classic lipid shape theory yielded a quantitative link between lipid and solvent composition and the physical state of the lipid assembly. The key parameter of the new model, κ(pH), describes the membrane phase behavior of charged membranes in response to their ion loading in a quantitative way. PMID:21575575

  9. Rigid proteins and softening of biological membranes-with application to HIV-induced cell membrane softening.

    Science.gov (United States)

    Agrawal, Himani; Zelisko, Matthew; Liu, Liping; Sharma, Pradeep

    2016-05-06

    A key step in the HIV-infection process is the fusion of the virion membrane with the target cell membrane and the concomitant transfer of the viral RNA. Experimental evidence suggests that the fusion is preceded by considerable elastic softening of the cell membranes due to the insertion of fusion peptide in the membrane. What are the mechanisms underpinning the elastic softening of the membrane upon peptide insertion? A broader question may be posed: insertion of rigid proteins in soft membranes ought to stiffen the membranes not soften them. However, experimental observations perplexingly appear to show that rigid proteins may either soften or harden membranes even though conventional wisdom only suggests stiffening. In this work, we argue that regarding proteins as merely non-specific rigid inclusions is flawed, and each protein has a unique mechanical signature dictated by its specific interfacial coupling to the surrounding membrane. Predicated on this hypothesis, we have carried out atomistic simulations to investigate peptide-membrane interactions. Together with a continuum model, we reconcile contrasting experimental data in the literature including the case of HIV-fusion peptide induced softening. We conclude that the structural rearrangements of the lipids around the inclusions cause the softening or stiffening of the biological membranes.

  10. Proceedings Fourth Workshop on Membrane Computing and Biologically Inspired Process Calculi 2010

    CERN Document Server

    Ciobanu, Gabriel; 10.4204/EPTCS.40

    2010-01-01

    The 4th Workshop on Membrane Computing and Biologically Inspired Process Calculi (MeCBIC 2010) is organized in Jena as a satellite event of the Eleventh International Conference on Membrane Computing (CMC11). Biological membranes play a fundamental role in the complex reactions which take place in cells of living organisms. The importance of this role has been considered in two different types of formalisms introduced recently. Membrane systems were introduced as a class of distributed parallel computing devices inspired by the observation that any biological system is a complex hierarchical structure, with a flow of biochemical substances and information that underlies their functioning. The modeling and analysis of biological systems has also attracted considerable interest of the process algebra research community. Thus the notions of membranes and compartments have been explicitly represented in a family of calculi, such as ambients and brane calculi. A cross fertilization of these two research areas has ...

  11. Regulation of the basement membrane by epithelia generated forces

    Science.gov (United States)

    Tanner, Kandice

    2012-12-01

    Tumor metastasis involves a progressive loss of tissue architecture and dissolution of structural boundaries between the epithelium and connective tissue. The basement membrane (BM), a specialized network of extracellular matrix proteins forms a barrier that physically restricts pre-invasive lesions such that they remain as local insults. The BM is not a static structure, but one that is constantly regenerated and remodeled in the adult organism. Matrix organization also regulates cell function. Thus alterations in the balance of synthesis, remodeling and proteolytic degradation of the extracellular matrix proteins may contribute to a loss of structural integrity. However, the de novo assembly and maintenance of the complex structural properties of in vivo basement membranes remain elusive. Here, this paper highlights the current understanding on the structural properties and the establishment of the BM, and discusses the potential role of self-generated forces in adult tissue remodeling and the maintenance of the BM as a malignancy suppressor.

  12. Regulation of multispanning membrane protein topology via post-translational annealing.

    Science.gov (United States)

    Van Lehn, Reid C; Zhang, Bin; Miller, Thomas F

    2015-09-26

    The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis.

  13. Spatial Structures and Regulation in Biological Systems

    DEFF Research Database (Denmark)

    Yde, Pernille

    model of the tissue and show how coupled cells are able to function as an excitable medium and propagate waves of high cytokine concentration through the tissue. If the internal regulation in the cells is over-productive, the model predicts a continuous amplification of cytokines, which spans the entire...... inflammation and over-production of the cytokine IL-1β are characteristic features of islets in patients with type II diabetes. We expand the model of Chapter 4 in order to study the inflammatory response in islets of Langerhans, with a special focus on the influence imposed by the spatial conditions - namely...

  14. Salmonella enterotoxin (Stn regulates membrane composition and integrity

    Directory of Open Access Journals (Sweden)

    Masayuki Nakano

    2012-07-01

    The mechanism of action of Salmonella enterotoxin (Stn as a virulence factor in disease is controversial. Studies of Stn have indicated both positive and negative effects on Salmonella virulence. In this study, we attempted to evaluate Stn function and its effects on Salmonella virulence. To investigate Stn function, we first performed in vitro and in vivo analysis using mammalian cells and a murine ileal loop model. In these systems, we did not observe differences in virulence phenotypes between wild-type Salmonella and an stn gene-deleted mutant. We next characterized the phenotypes and molecular properties of the mutant strain under various in vitro conditions. The proteomic profiles of the total cell membrane protein fraction differed between wild type and mutant in that there was an absence of a protein in the mutant strain, which was identified as OmpA. By far-western blotting, OmpA was found to interact directly with Stn. To verify this result, the morphology of Salmonella was examined by transmission electron microscopy, with OmpA localization being analyzed by immunogold labeling. Compared with wild-type Salmonella, the mutant strain had a different pole structure and a thin periplasmic space; OmpA was not seen in the mutant. These results indicate that Stn, via regulation of OmpA membrane localization, functions in the maintenance of membrane composition and integrity.

  15. Plasma membrane calcium pump regulation by metabolic stress

    Institute of Scientific and Technical Information of China (English)

    Jason; IE; Bruce

    2010-01-01

    The plasma membrane Ca2+-ATPase(PMCA)is an ATPdriven pump that is critical for the maintenance of low resting[Ca2+]i in all eukaryotic cells.Metabolic stress, either due to inhibition of mitochondrial or glycolytic metabolism,has the capacity to cause ATP depletion and thus inhibit PMCA activity.This has potentially fatal consequences,particularly for non-excitable cells in which the PMCA is the major Ca2+efflux pathway.This is because inhibition of the PMCA inevitably leads to cytosolic Ca2+ overload and the consequent cell death.However,the relationship between metabolic stress,ATP depletion and inhibition of the PMCA is not as simple as one would have originally predicted.There is increasing evidence that metabolic stress can lead to the inhibition of PMCA activity independent of ATP or prior to substantial ATP depletion.In particular,there is evidence that the PMCA has its own glycolytic ATP supply that can fuel the PMCA in the face of impaired mitochondrial function.Moreover, membrane phospholipids,mitochondrial membrane potential,caspase/calpain cleavage and oxidative stress have all been implicated in metabolic stress-induced inhibition of the PMCA.The major focus of this review is to challenge the conventional view of ATP-dependent regulation of the PMCA and bring together some of the alternative or additional mechanisms by which metabolic stress impairs PMCA activity resulting in cytosolic Ca2+ overload and cytotoxicity.

  16. [THE ROLE OF BIOLOGICAL MEMBRANES IN DIFFERENTIAL DIAGNOSTICS OF SALMONELLA AND ACUTE ALCOHOL GASTROENTERITIS].

    Science.gov (United States)

    Makarov, V K; Makarov, P V

    2015-01-01

    We evaluated the influence of Salmonella infection and alcohol on biological membranes from the content of serum phospholipid fraction known to be a component ofenterocyte membranes. Any change of membrane phospholipid content leads to a change of their blood level. The study included 50 patients with acute alcohol gastroenteritis, 50 ones with salmonella gastroenteritis, and 50 healthy subjects. Both salmonellosis and alcohol caused differently directed changes in biological membranes. The mechanism of diarrhea in patients with salmonella and acute alcohol gastroenteritis is different. Diarrhea associated with alcohol gastroenteritis is due to enhanced viscosity of biomembranes that decreases in salmonella gastroenteritis. It suggests different approaches to the treatment of these conditions. The membrane destruction coefficient below 2 is an additional proof of alcoholic etiology of gastroenteritis whereas its value above 3 confirms the involvement of salmonellosis in pathogenesis of gastroenteritis.

  17. Ice Formation in Model Biological Membranes in the Presence of Cryoprotectors

    CERN Document Server

    Kiselev, M A; Kisselev, A M; Ollivon, M

    2000-01-01

    Ice formation in model biological membranes is studied by SAXS and WAXS in the presence of cryoprotectors: dimethyl sulfoxide and glycerol. Three types of phospholipid membranes: DPPC, DMPC, DSPC are chosen for the investigation as well-studied model biological membranes. A special cryostat is used for sample cooling from 14.1C to -55.4C. The ice formation is only detected by WAXS in binary phospholipid/water and ternary phospholipid/cryoprotector/water systems in the condition of excess solvent. Ice formation in a binary phospholipid/water system creates an abrupt decrease of the membrane repeat distance by delta-d, so-called ice-induced dehydration of intermembrane space. The value of delta-d decreases as the cryoprotector concentration increases. The formation of ice does not influence the membrane structure (delta-d = 0) for cryoprotector mole fractions higher than 0.05.

  18. Controlled light field concentration through turbid biological membrane for phototherapy.

    Science.gov (United States)

    Wang, Fujuan; He, Hexiang; Zhuang, Huichang; Xie, Xiangsheng; Yang, Zhenchong; Cai, Zhigang; Gu, Huaiyu; Zhou, Jianying

    2015-06-01

    Laser propagation through a turbid rat dura mater membrane is shown to be controllable with a wavefront modulation technique. The scattered light field can be refocused into a target area behind the rat dura mater membrane with a 110 times intensity enhancement using a spatial light modulator. The efficient laser intensity concentration system is demonstrated to imitate the phototherapy for human brain tumors. The power density in the target area is enhanced more than 200 times compared with the input power density on the dura mater membrane, thus allowing continued irradiation concentration to the deep lesion without damage to the dura mater. Multibeam inputs along different directions, or at different positions, can be guided to focus to the same spot behind the membrane, hence providing a similar gamma knife function in optical spectral range. Moreover, both the polarization and the phase of the input field can be recovered in the target area, allowing coherent field superposition in comparison with the linear intensity superposition for the gamma knife.

  19. Organelle acidification negatively regulates vacuole membrane fusion in vivo

    Science.gov (United States)

    Desfougères, Yann; Vavassori, Stefano; Rompf, Maria; Gerasimaite, Ruta; Mayer, Andreas

    2016-01-01

    The V-ATPase is a proton pump consisting of a membrane-integral V0 sector and a peripheral V1 sector, which carries the ATPase activity. In vitro studies of yeast vacuole fusion and evidence from worms, flies, zebrafish and mice suggested that V0 interacts with the SNARE machinery for membrane fusion, that it promotes the induction of hemifusion and that this activity requires physical presence of V0 rather than its proton pump activity. A recent in vivo study in yeast has challenged these interpretations, concluding that fusion required solely lumenal acidification but not the V0 sector itself. Here, we identify the reasons for this discrepancy and reconcile it. We find that acute pharmacological or physiological inhibition of V-ATPase pump activity de-acidifies the vacuole lumen in living yeast cells within minutes. Time-lapse microscopy revealed that de-acidification induces vacuole fusion rather than inhibiting it. Cells expressing mutated V0 subunits that maintain vacuolar acidity were blocked in this fusion. Thus, proton pump activity of the V-ATPase negatively regulates vacuole fusion in vivo. Vacuole fusion in vivo does, however, require physical presence of a fusion-competent V0 sector. PMID:27363625

  20. Flavonoid-membrane interactions: possible consequences for biological effects of some polyphenolic compounds

    Institute of Scientific and Technical Information of China (English)

    Andrzej B HENDRICH

    2006-01-01

    Flavonoids are found ubiquitously in higher plants and constitute an important component of the majority of peoples' daily diets. The biological activities of flavonoids cover a very broad spectrum, from anticancer and antibacterial activities through to inhibition of bone resorption. In the present paper, the interactions between flavonoids and lipid bilayers as well as biological membranes and their components are reviewed, with special emphasis on the structure-activity relationships and mechanisms underlying the biological activity of flavonoids.

  1. Membrane Domains and Their Relevance to the Organization of Biological Membranes

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2012-01-01

    The aim of this chapter is to provide a succinct update about research focused on membrane domains, particularly summarizing new information obtained using imaging techniques. This is presented and discussed in the context of the vast information previously reported using classical biophysical...... of lateral heterogeneity in lipid bilayers are discussed, including a synopsis of classical biophysical techniques used to study membrane lateral structure. Later in the chapter the focus shifts to giant vesicles and planar membranes recapitulating information on lipid domains obtained using imaging...

  2. Membrane materials for storing biological samples intended for comparative nanotoxicological testing

    Science.gov (United States)

    Metelkin, A.; Kuznetsov, D.; Kolesnikov, E.; Chuprunov, K.; Kondakov, S.; Osipov, A.; Samsonova, J.

    2015-11-01

    The study is aimed at identifying the samples of most promising membrane materials for storing dry specimens of biological fluids (Dried Blood Spots, DBS technology). Existing sampling systems using cellulose fiber filter paper have a number of drawbacks such as uneven distribution of the sample spot, dependence of the spot spreading area on the individual biosample properties, incomplete washing-off of the sample due to partially inconvertible sorption of blood components on cellulose fibers, etc. Samples of membrane materials based on cellulose, polymers and glass fiber with applied biosamples were studied using methods of scanning electron microscopy, FT-IR spectroscopy and surface-wetting measurement. It was discovered that cellulose-based membrane materials sorb components of biological fluids inside their structure, while membranes based on glass fiber display almost no interaction with the samples and biological fluid components dry to films in the membrane pores between the structural fibers. This characteristic, together with the fact that membrane materials based on glass fiber possess sufficient strength, high wetting properties and good storage capacity, attests them as promising material for dry samples of biological fluids storage systems.

  3. Crystalline polymorphism induced by charge regulation in ionic membranes.

    Science.gov (United States)

    Leung, Cheuk-Yui; Palmer, Liam C; Kewalramani, Sumit; Qiao, Baofu; Stupp, Samuel I; Olvera de la Cruz, Monica; Bedzyk, Michael J

    2013-10-08

    The crystallization of molecules with polar and hydrophobic groups, such as ionic amphiphiles and proteins, is of paramount importance in biology and biotechnology. By coassembling dilysine (+2) and carboxylate (-1) amphiphiles of various tail lengths into bilayer membranes at different pH values, we show that the 2D crystallization process in amphiphile membranes can be controlled by modifying the competition of long-range and short-range interactions among the polar and the hydrophobic groups. The pH and the hydrophobic tail length modify the intermolecular packing and the symmetry of their crystalline phase. For hydrophobic tail lengths of 14 carbons (C14), we observe the coassembly into crystalline bilayers with hexagonal molecular ordering via in situ small- and wide-angle X-ray scattering. As the tail length increases, the hexagonal lattice spacing decreases due to an increase in van der Waals interactions, as demonstrated by atomistic molecular dynamics simulations. For C16 and C18 we observe a reentrant crystalline phase transition sequence, hexagonal-rectangular-C-rectangular-P-rectangular-C-hexagonal, as the solution pH is increased from 3 to 10.5. The stability of the rectangular phases, which maximize tail packing, increases with increasing tail length. As a result, for very long tails (C22), the possibility of observing packing symmetries other than rectangular-C phases diminishes. Our work demonstrates that it is possible to systematically exchange chemical and mechanical energy by changing the solution pH value within a range of physiological conditions at room temperature in bilayers of molecules with ionizable groups.

  4. Kinetic modelling of coupled transport across biological membranes.

    Science.gov (United States)

    Korla, Kalyani; Mitra, Chanchal K

    2014-04-01

    In this report, we have modelled a secondary active co-transporter (symport and antiport), based on the classical kinetics model. Michaelis-Menten model of enzyme kinetics for a single substrate, single intermediate enzyme catalyzed reaction was proposed more than a hundred years ago. However, no single model for the kinetics of co-transport of molecules across a membrane is available in the literature We have made several simplifying assumptions and have followed the basic Michaelis-Menten approach. The results have been simulated using GNU Octave. The results will be useful in general kinetic simulations and modelling.

  5. Study of the benzocaine transfer from aqueous solution to the interior of a biological membrane.

    Science.gov (United States)

    Porasso, Rodolfo D; Bennett, W F Drew; Oliveira-Costa, S D; López Cascales, J J

    2009-07-23

    The precise molecular mechanism of general anesthetics remains unknown. It is therefore important to understand where molecules with anesthetic properties localize within biological membranes. We have determined the free energy profile of a benzocaine molecule (BZC) across a biological membrane using molecular dynamics simulation. We use an asymmetric phospholipid bilayer with DPPS in one leaflet of a DPPC bilayer (Lopez Cascales et al. J. Phys. Chem. B 2006, 110, 2358-2363) to model a biological bilayer. From the free energy profile, we predict the zone of actuation of a benzocaine is located in the hydrocarbon region or at the end of the lipid head, depending of the presence of charged lipids (DPPS) in the leaflet. We observe a moderate increase in the disorder of the membrane and in particular an increase in the disorder of DPPS. Static and dynamic physicochemical properties of the benzocaine, such as its dipole orientation, translational diffusion coefficient, and rotational relaxation time were measured.

  6. Contribution of assimilable organic carbon to biological fouling in seawater reverse osmosis membrane treatment.

    Science.gov (United States)

    Weinrich, Lauren; LeChevallier, Mark; Haas, Charles N

    2016-09-15

    Biological fouling occurs on RO membranes when bacteria and nutrients are present in conditions that are conducive to growth and proliferation of the bacteria. Controlling microbial growth on the membranes is typically limited to biocide application (i.e., disinfectants) in seawater RO plants. However, biological growth and subsequent fouling has not been well-managed. Pretreatment has not been focused on nutrient limitation. This project used a biological assay, the assimilable organic carbon (AOC) test to evaluate pretreatment effects on the nutrient supply. The AOC test provided a useful surrogate measurement for the biodegradability or biofouling potential of RO feed water. Biofouling observed in controlled conditions at the bench- and pilot-scale resulted in statistically significant correlations between AOC and the operational effects caused by biofouling. Membrane fouling rates are observed through operational changes over time such as increased differential pressure between the membrane feed and concentrate locations and decreased permeate flux through the membrane. In full scale plants there were strong correlations when AOC was used as a predictor variable for increased differential pressure (0.28-0.55 bar from September-December 2012) and decreased specific flux (1.40 L per hour/(m(2) · bar)). Increased differential pressure was associated with RO membrane biological fouling when the median AOC was 50 μg/L during pilot testing. Conditions were also evaluated at the bench-scale using a flat sheet RO membrane. In a comparison test using 30 and 1000 μg/L AOC, fouling was detected on more portions of the membrane when AOC was higher. Biofilm and bacterial deposits were apparent from scanning electron microscope imaging and biomass measurements using ATP.

  7. Lipid-lipid and lipid-drug interactions in biological membranes

    Science.gov (United States)

    Martynowycz, Michael W.

    Interactions between lipids and drug molecules in biological membranes help govern proper biological function in organisms. The mechanisms responsible for hydrophobic drug permeation remain elusive. Many small molecule drugs are hydrophobic. These drugs inhibit proteins in the cellular interior. The rise of antibiotic resistance in bacteria is thought to be caused by mutations in protein structure, changing drug kinetics to favor growth. However, small molecule drugs have been shown to have different mechanisms depending in the structure of the lipid membrane of the target cell. Biological membranes are investigated using Langmuir monolayers at the air-liquid interface. These offer the highest level of control in the mimetic system and allow them to be investigated using complementary techniques. Langmuir isotherms and insertion assays are used to determine the area occupied by each lipid in the membrane and the change in area caused by the introduction of a drug molecule, respectively. Specular X-ray reflectivity is used to determine the electron density of the monolayer, and grazing incidence X-ray diffraction is used to determine the in-plane order of the monolayer. These methods determine the affinity of the drug and the mechanism of action. Studies are presented on hydrophobic drugs with mammalian membrane mimics using warfarin along with modified analogues, called superwarfarins. Data shows that toxicity of these modified drugs are modulated by the membrane cholesterol content in cells; explaining several previously unexplained effects of the drugs. Membrane mimics of bacteria are investigated along with their interactions with a hydrophobic antibiotic, novobiocin. Data suggests that permeation of the drug is mediated by modifications to the membrane lipids, and completely ceases translocation under certain circumstances. Circumventing deficiencies in small, hydrophobic drugs is approached by using biologically mimetic oligomers. Peptoids, mimetic of host

  8. Electrochemically deposited and etched membranes with precisely sized micropores for biological fluids microfiltration

    Science.gov (United States)

    Hamzah, A. A.; Zainal Abidin, H. E.; Yeop Majlis, B.; Mohd Nor, M.; Ismardi, A.; Sugandi, G.; Tiong, T. Y.; Dee, C. F.; Yunas, J.

    2013-07-01

    This paper presents simple and economical, yet reliable techniques to fabricate a micro-fluidic filter for MEMS lab-on-chip (LoC) applications. The microporous filter is a crucial component in a MEMS LoC system. Microsized components and contaminants in biological fluids are selectively filtered using copper and silicon membranes with precisely controlled microsized pores. Two techniques were explored in microporous membrane fabrication, namely copper electroplating and electrochemical etching (ECE) of silicon. In the first technique, a copper membrane with evenly distributed micropores was fabricated by electroplating the copper layer on the silicon nitride membrane, which was later removed to leave the freestanding microporous membrane structure. The second approach involves the thinning of bulk silicon down to a few micrometers thick using KOH and etching the resulting silicon membrane in 5% HF by ECE to create micropores. Upon testing with nanoparticles of various sizes, it was observed that electroplated copper membrane passes nanoparticles up to 200 nm wide, while porous silicon membrane passes nanoparticles up to 380 nm in size. Due to process compatibility, simplicity, and low-cost fabrication, electroplated copper and porous silicon membranes enable synchronized microfilter fabrication and integration into the MEMS LoC system.

  9. On the effect of prestrain and residual stress in thin biological membranes.

    Science.gov (United States)

    Rausch, Manuel K; Kuhl, Ellen

    2013-09-01

    Understanding the difference between ex vivo and in vivo measurements is critical to interpret the load carrying mechanisms of living biological systems. For the past four decades, the ex vivo stiffness of thin biological membranes has been characterized using uniaxial and biaxial tests with remarkably consistent stiffness parameters, even across different species. Recently, the in vivo stiffness was characterized using combined imaging techniques and inverse finite element analyses. Surprisingly, ex vivo and in vivo stiffness values differed by up to three orders of magnitude. Here, for the first time, we explain this tremendous discrepancy using the concept of prestrain. We illustrate the mathematical modeling of prestrain in nonlinear continuum mechanics through the multiplicative decomposition of the total elastic deformation into prestrain-induced and load-induced parts. Using in vivo measured membrane kinematics and associated pressure recordings, we perform an inverse finite element analysis for different prestrain levels and show that the resulting membrane stiffness may indeed differ by four orders of magnitude depending on the prestrain level. Our study motivates the hypothesis that prestrain is important to position thin biological membranes in vivo into their optimal operating range, right at the transition point of the stiffening regime. Understanding the effect of prestrain has direct clinical implications in regenerative medicine, medical device design, and and tissue engineering of replacement constructs for thin biological membranes.

  10. New insights into the regulation of cholesterol efflux from the sperm membrane

    OpenAIRE

    Tamara Leahy; Bart M Gadella

    2015-01-01

    Cholesterol is an essential component of the mammalian plasma membrane because it promotes membrane stability without comprising membrane fluidity. Given this important cellular role, cholesterol levels are tightly controlled at multiple levels. It has been clearly shown that cholesterol redistribution and depletion from the sperm membrane is a key part of the spermatozoon's preparation for fertilization. Some factors that regulate these events are described (e.g., bicarbonate, calcium) but t...

  11. Membrane lipid rafts, master regulators of hematopoietic stem cell retention in bone marrow and their trafficking.

    Science.gov (United States)

    Ratajczak, M Z; Adamiak, M

    2015-07-01

    Cell outer membranes contain glycosphingolipids and protein receptors, which are integrated into glycoprotein microdomains, known as lipid rafts, which float freely in the membrane bilayer. These structures have an important role in assembling signaling molecules (e.g., Rac-1, RhoH and Lyn) together with surface receptors, such as the CXCR4 receptor for α-chemokine stromal-derived factor-1, the α4β1-integrin receptor (VLA-4) for vascular cell adhesion molecule-1 and the c-kit receptor for stem cell factor, which together regulate several aspects of hematopoietic stem/progenitor cell (HSPC) biology. Here, we discuss the role of lipid raft integrity in the retention and quiescence of normal HSPCs in bone marrow niches as well as in regulating HSPC mobilization and homing. We will also discuss the pathological consequences of the defect in lipid raft integrity seen in paroxysmal nocturnal hemoglobinuria and the emerging evidence for the involvement of lipid rafts in hematological malignancies.

  12. Integration of biological method and membrane technology in treating palm oil mill effluent.

    Science.gov (United States)

    Zhang, Yejian; Yan, Li; Qiao, Xiangli; Chi, Lina; Niu, Xiangjun; Mei, Zhijian; Zhang, Zhenjia

    2008-01-01

    Palm oil industry is the most important agro-industry in Malaysia, but its by-product-palm oil mill effluent (POME), posed a great threat to water environment. In the past decades, several treatment and disposal methods have been proposed and investigated to solve this problem. A two-stage pilot-scale plant was designed and constructed for POME treatment. Anaerobic digestion and aerobic biodegradation constituted the first biological stage, while ultrafiltration (UF) and reverse osmosis (RO) membrane units were combined as the second membrane separation stage. In the anaerobic expanded granular sludge bed (EGSB) reactor, about 43% organic matter in POME was converted into biogas, and COD reduction efficiency reached 93% and 22% in EGSB and the following aerobic reactor, respectively. With the treatment in the first biological stage, suspended solids and oil also decreased to a low degree. All these alleviated the membrane fouling and prolonged the membrane life. In the membrane process unit, almost all the suspended solids were captured by UF membranes, while RO membrane excluded most of the dissolved solids or inorganic salts from RO permeate. After the whole treatment processes, organic matter in POME expressed by BOD and COD was removed almost thoroughly. Suspended solids and color were not detectable in RO permeate any more, and mineral elements only existed in trace amount (except for K and Na). The high-quality effluent was crystal clear and could be used as the boiler feed water.

  13. Integration of biological method and membrane technology in treating palm oil mill effluent

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yejian; YAN Li; QIAO Xiangli; CHI Lina; NIU Xiangjun; MEI Zhijian; ZHANG Zhenjia

    2008-01-01

    Palm oil industry is the most important agro-industry in Malaysia, but its by-product-palm oil mill effluent (POME), posed a great threat to water environment. In the past decades, several treatment and disposal methods have been proposed and investigated to solve this problem. A two-stage pilot-scale plant was designed and constructed for POME treatment. Anaerobic digestion and aerobic biodegradation constituted the first biological stage, while ultrafiltration (UF) and reverse osmosis (RO) membrane units were combined as the second membrane separation stage. In the anaerobic expanded granular sludge bed (EGSB) reactor, about 43% organic matter in POME was converted into biogas, and COD reduction efficiency reached 93% and 22% in EGSB and the following aerobic reactor, respectively. With the treatment in the first biological stage, suspended solids and oil also decreased to a low degree. All these alleviated the membrane fouling and prolonged the membrane life. In the membrane process unit, almost all the suspended solids were captured by UF membranes, while RO membrane excluded most of the dissolved solids or inorganic salts from RO permeate. After the whole treatment processes, organic matter in POME expressed by BOD and COD was removed almost thoroughly. Suspended solids and color were not detectable in RO permeate any more, and mineral elements only existed in trace amount (except for K and Na). The high-quality effluent was crystal clear and could be used as the boiler feed water.

  14. On the dielectric relaxation of biological cell suspensions: the effect of the membrane electrical conductivity.

    Science.gov (United States)

    Di Biasio, A; Cametti, C

    2011-06-01

    Due to the mismatch of the electrical parameters (the permittivity ϵ' and the electrical conductivity σ) of the membrane of a biological cell with the ones of the cytosol and the extracellular medium, biological cell suspensions are the site, under the influence of an external electric field, of large dielectric relaxations in the radiowave frequency range. However, a point still remains controversial, i.e., whether or not the value of membrane conductivity σ(s) might be extracted from the de-convolution of the dielectric spectra or otherwise if it would be more reasonable to assign to the membrane conductivity a value equal to zero. This point is not to be considered with superficiality since it concerns an a priori choice which ultimately influences the values of the electrical parameters deduced from this technique. As far as this point is concerned, the opinion of the researchers in this field diverges. We believe that, at least within certain limits, the membrane conductivity can be deduced from the shape of the relaxation spectra. We substantiate this thesis with two different examples concerning the first a suspension of human normal erythrocyte cells and the second a suspension of human lymphocyte cells. In both cases, by means of an accurate fitting procedure based on the Levenberg-Marquardt method for complex functions, we can evaluate the membrane conductivity σ(s) with its associated uncertainty. The knowledge of the membrane electrical conductivity will favor the investigation of different ion transport mechanisms across the cell membrane.

  15. Salmonellae PhoPQ regulation of the outer membrane to resist innate immunity.

    Science.gov (United States)

    Dalebroux, Zachary D; Miller, Samuel I

    2014-02-01

    Salmonellae sense host cues to regulate properties important for bacterial survival and replication within host tissues. The PhoPQ two-component regulatory system senses phagosome acidification and cationic antimicrobial peptides (CAMP) to regulate the protein and lipid contents of the bacterial envelope that comprises an inner and outer membrane. PhoPQ-regulated lipid components of the outer membrane include lipopolysaccharides and glycerophospholipids. Envelope proteins regulated by PhoPQ, include: components of virulence associated secretion systems, the flagellar apparatus, membrane transport systems, and proteins that are likely structural components of the outer membrane. PhoPQ alteration of the bacterial surface results in increased bacterial resistance to CAMP and decreased detection by the innate immune system. This review details the molecular complexity of the bacterial cell envelope and highlights the outer membrane lipid bilayer as an environmentally regulated bacterial organelle.

  16. A Trade Study of Two Membrane-Aerated Biological Water Processors

    Science.gov (United States)

    Allada, Ram; Lange, Kevin; Vega. Leticia; Roberts, Michael S.; Jackson, Andrew; Anderson, Molly; Pickering, Karen

    2011-01-01

    Biologically based systems are under evaluation as primary water processors for next generation life support systems due to their low power requirements and their inherent regenerative nature. This paper will summarize the results of two recent studies involving membrane aerated biological water processors and present results of a trade study comparing the two systems with regards to waste stream composition, nutrient loading and system design. Results of optimal configurations will be presented.

  17. The force generated by biological membranes on a polymer rod and its response: Statics and dynamics

    Science.gov (United States)

    Daniels, D. R.; Turner, M. S.

    2004-10-01

    We propose a theory for the force exerted by a fluctuating membrane on a polymer rod tip. Using statistical mechanical methods, the expression for the generated force is written in terms of the distance of the rod tip from the membrane "frame." We apply the theory in calculating the stall force and membrane displacement required to cease the growth of a growing fiber induced by membrane fluctuations, as well as the membrane force and membrane displacement required for rod/fiber buckling. We also consider the dynamics of a growing fiber tip under the influence of a fluctuation-induced membrane force. We discuss the importance of our results in various biological contexts. Finally, we present a method to simultaneously extract both the rigidity of the semiflexible rod and the force applied by, e.g., the membrane from the measurements of the bending fluctuations of the rod. Such a measurement of the force would give information about the thermodynamics of the rod polymerization that involves the usual Brownian ratchet mechanism.

  18. Fluorescence response of hypocrellin B to the environmental changes in a mimic biological membrane--liposome

    Institute of Scientific and Technical Information of China (English)

    JIN Xuanye; ZHAO Yuewei; XIE Jie; ZHAO Jingquan

    2004-01-01

    Liposome is well known as not only a drug-delivery system but also a simple model for biological membranes. It was reported that fluorescence properties of hypocrellins were changeable over some extreme pH values. In the current work, the effects of the microenvironments on the fluorescence properties of HB in liposome, including approximately physiological range of pH values pH = 6.0-8.0, concentration of cholesterols and ionic strength of the solution, were studied. It was found that the fluorescence intensity of HB was sensitive to and also regulated by the microenvironments. When concentration of cholesterols and ionic strength keep invariable in PBS solution, there exists the maximum for the fluorescence of HB-liposome at pH 7.4 while the minimum for that of HB at pH 7.0. In addition, when pH value keeps constant (7.2), there exists the maximum at the ionic strength of 0.12 mol/kg while that at the concentration of 6x10-4 mol/L for cholesterols. On the other hand, in PBS solution, the lower the ionic strength is, the higher the fluorescence intensity is. The environment-sensitive fluorescence may be potentially applicable to probe some specific environmental features in cells or tissues.

  19. Application of integrated ozone biological aerated filters and membrane filtration in water reuse of textile effluents.

    Science.gov (United States)

    He, Yaozhong; Wang, Xiaojun; Xu, Jinling; Yan, Jinli; Ge, Qilong; Gu, Xiaoyang; Jian, Lei

    2013-04-01

    A combined process including integrated ozone-BAFs (ozone biological aerated filters) and membrane filtration was first applied for recycling textile effluents in a cotton textile mill with capacity of 5000 m(3)/d. Influent COD (chemical oxygen demand) in the range of 82-120 mg/L, BOD5 (5-day biochemical oxygen demand) of 12.6-23.1 mg/L, suspended solids (SSs) of 38-52 mg/L and color of 32-64° were observed during operation. Outflows with COD≤45 mg/L, BOD5≤7.6 mg/L, SS≤15 mg/L, color≤8° were obtained after being decontaminated by ozone-BAF with ozone dosage of 20-25 mg/L. Besides, the average removal rates of PVA (polyvinyl alcohol) and UV254 were 100% and 73.4% respectively. Permeate water produced by RO (reverse osmosis) could be reused in dyeing and finishing processes, while the RO concentrates could be discharged directly under local regulations with COD≤100 mg/L, BOD5≤21 mg/L, SS≤52 mg/L, color≤32°. Results showed that the combined process could guarantee water reuse with high quality, and solve the problem of RO concentrate disposal.

  20. A role for the membrane in regulating Chlamydomonas flagellar length.

    Directory of Open Access Journals (Sweden)

    William Dentler

    Full Text Available Flagellar assembly requires coordination between the assembly of axonemal proteins and the assembly of the flagellar membrane and membrane proteins. Fully grown steady-state Chlamydomonas flagella release flagellar vesicles from their tips and failure to resupply membrane should affect flagellar length. To study vesicle release, plasma and flagellar membrane surface proteins were vectorially pulse-labeled and flagella and vesicles were analyzed for biotinylated proteins. Based on the quantity of biotinylated proteins in purified vesicles, steady-state flagella appeared to shed a minimum of 16% of their surface membrane per hour, equivalent to a complete flagellar membrane being released every 6 hrs or less. Brefeldin-A destroyed Chlamydomonas Golgi, inhibited the secretory pathway, inhibited flagellar regeneration, and induced full-length flagella to disassemble within 6 hrs, consistent with flagellar disassembly being induced by a failure to resupply membrane. In contrast to membrane lipids, a pool of biotinylatable membrane proteins was identified that was sufficient to resupply flagella as they released vesicles for 6 hrs in the absence of protein synthesis and to support one and nearly two regenerations of flagella following amputation. These studies reveal the importance of the secretory pathway to assemble and maintain full-length flagella.

  1. Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

    Directory of Open Access Journals (Sweden)

    Alfred Blume

    2007-10-01

    Full Text Available The two main steps of the membranolytic activity of detergents: 1 the partitioning of detergent molecules in the membrane and 2 the solubilisation of the membrane are systematically investigated. The interactions of two bile salt molecules, sodium cholate (NaC and sodium deoxycholate (NaDC with biological phospholipid model membranes are considered. The membranolytic activity is analysed as a function of the hydrophobicity of the bile salt, ionic strength, temperature, membrane phase properties, membrane surface charge and composition of the acyl chains of the lipids. The results are derived from calorimetric measurements (ITC, isothermal titration calorimetry. A thermodynamic model is described, taking into consideration electrostatic interactions, which is used for the calculation of the partition coefficient as well as to derive the complete thermodynamic parameters describing the interaction of detergents with biological membranes (change in enthalpy, change in free energy, change in entropy etc. The solubilisation properties are described in a so-called vesicle-to-micelle phase transition diagram. The obtained results are supplemented and confirmed by data obtained from other biophysical techniques (DSC differential scanning calorimetry, DLS dynamic light scattering, SANS small angle neutron scattering.

  2. Regulation of cytokinesis by membrane trafficking involving small GTPases and the ESCRT machinery.

    Science.gov (United States)

    Nakayama, Kazuhisa

    2016-01-01

    During cell division, cells undergo membrane remodeling to achieve changes in their size and shape. In addition, cell division entails local delivery and retrieval of membranes and specific proteins as well as remodeling of cytoskeletons, in particular, upon cytokinetic abscission. Accumulating lines of evidence highlight that endocytic membrane removal from and subsequent membrane delivery to the plasma membrane are crucial for the changes in cell size and shape, and that trafficking of vesicles carrying specific proteins to the abscission site participate in local remodeling of membranes and cytoskeletons. Furthermore, the endosomal sorting complex required for transport (ESCRT) machinery has been shown to play crucial roles in cytokinetic abscission. Here, the author briefly overviews membrane-trafficking events early in cell division, and subsequently focus on regulation and functional significance of membrane trafficking involving Rab11 and Arf6 small GTPases in late cytokinesis phases and assembly of the ESCRT machinery in cytokinetic abscission.

  3. Autoinhibitory Regulation of Plasma Membrane H+-ATPases

    DEFF Research Database (Denmark)

    Pedersen, Jesper Torbøl

    Electrochemical gradients across cell membranes are essential for nutrient uptake. In plant and fungal cells the electrochemical gradient across the plasma membrane (PM) can build much higher than in mammalian cells. The protein responsible for this gradient is the essential PM H+-ATPase that uses...

  4. Regulation of the Plasma Membrane H+-ATPase

    DEFF Research Database (Denmark)

    Falhof, Janus

    The plasma membrane (PM) H+-ATPase is responsible for generating the electrochemical gradientthat drives the secondary transport of nutrients across the cellular membrane. It belongs to a familyof cation and lipid transporters that are vital to many organisms. PM H+-ATPases are Type P3AATPases...

  5. Controlling potassium selectivity and proton blocking in a hybrid biological/solid-state polymer nanoporous membrane.

    Science.gov (United States)

    Balme, Sébastien; Picaud, Fabien; Kraszewski, Sebastian; Déjardin, Philippe; Janot, Jean Marc; Lepoitevin, Mathilde; Capomanes, Jhon; Ramseyer, Christophe; Henn, François

    2013-05-01

    Specific separations of protons and cations are usually performed by electromembrane processes, which require external electric energy. An easier process would be using a membrane able to separate both entities by passive diffusion. Presently, such synthetic nanoporous membranes do not exist. Here, we report the production of a robust hybrid biological/artificial solid-state membrane, which allows selective permeation of alkali metal cations without competing or concurrent permeation of protons. This membrane is simple to prepare and is based on the hydrophobic nature of the polymeric pore walls, and the confined gramicidin A molecules within. This work opens a new route for separation in the domain of nanobiofiltration, especially for tunable nanodevices based on differential ion conduction, with a fundamental understanding of the confinement mechanism.

  6. Cytosol-dependent membrane fusion in ER, nuclear envelope and nuclear pore assembly: biological implications.

    Science.gov (United States)

    Rafikova, Elvira R; Melikov, Kamran; Chernomordik, Leonid V

    2010-01-01

    Endoplasmic reticulum and nuclear envelope rearrangements after mitosis are often studied in the reconstitution system based on Xenopus egg extract. In our recent work we partially replaced the membrane vesicles in the reconstitution mix with protein-free liposomes to explore the relative contributions of cytosolic and transmembrane proteins. Here we discuss our finding that cytosolic proteins mediate fusion between membranes lacking functional transmembrane proteins and the role of membrane fusion in endoplasmic reticulum and nuclear envelope reorganization. Cytosol-dependent liposome fusion has allowed us to restore, without adding transmembrane nucleoporins, functionality of nuclear pores, their spatial distribution and chromatin decondensation in nuclei formed at insufficient amounts of membrane material and characterized by only partial decondensation of chromatin and lack of nuclear transport. Both the mechanisms and the biological implications of the discovered coupling between spatial distribution of nuclear pores, chromatin decondensation and nuclear transport are discussed.

  7. Towards integrated operation of membrane bioreactors: effects of aeration on biological and filtration performance.

    Science.gov (United States)

    Dalmau, M; Monclús, H; Gabarrón, S; Rodriguez-Roda, I; Comas, J

    2014-11-01

    Two experimental studies evaluated the effect of aerobic and membrane aeration changes on sludge properties, biological nutrient removal and filtration processes in a pilot plant membrane bioreactor. The optimal operating conditions were found at an aerobic dissolved oxygen set-point (DO) of 0.5 mg O2 L(-1) and a membrane specific aeration demand (SADm) of 1 m h(-1), where membrane aeration can be used for nitrification. Under these conditions, a total flow reduction of 42% was achieved (75% energy reduction) without compromising nutrient removal efficiencies, maintaining sludge characteristics and controlled filtration. Below these optimal operating conditions, the nutrient removal efficiency was reduced, increasing 20% for soluble microbial products, 14% for capillarity suction time and reducing a 15% for filterability. Below this DO set-point, fouling increased with a transmembrane pressure 75% higher. SADm below 1 m h(-1) doubled the values of transmembrane pressure, without recovery after achieving the initial conditions.

  8. Lateral organization, bilayer asymmetry, and inter-leaflet coupling of biological membranes.

    Science.gov (United States)

    Nickels, Jonathan D; Smith, Jeremy C; Cheng, Xiaolin

    2015-11-01

    Understanding of cell membrane organization has evolved significantly from the classic fluid mosaic model. It is now recognized that biological membranes are highly organized structures, with differences in lipid compositions between inner and outer leaflets and in lateral structures within the bilayer plane, known as lipid rafts. These organizing principles are important for protein localization and function as well as cellular signaling. However, the mechanisms and biophysical basis of lipid raft formation, structure, dynamics and function are not clearly understood. One key question, which we focus on in this review, is how lateral organization and leaflet compositional asymmetry are coupled. Detailed information elucidating this question has been sparse because of the small size and transient nature of rafts and the experimental challenges in constructing asymmetric bilayers. Resolving this mystery will require advances in both experimentation and modeling. We discuss here the preparation of model systems along with experimental and computational approaches that have been applied in efforts to address this key question in membrane biology. We seek to place recent and future advances in experimental and computational techniques in context, providing insight into in-plane and transverse organization of biological membranes.

  9. Impact of membrane solid-liquid separation on design of biological nutrient removal activated sludge systems.

    Science.gov (United States)

    Ramphao, M; Wentzel, M C; Merritt, R; Ekama, G A; Young, T; Buckley, C A

    2005-03-20

    Installing membranes for solid-liquid separation into biological nutrient removal (BNR) activated sludge (AS) systems makes a profound difference not only in the design of the BNR system itself, but also in the design approach for the whole wastewater treatment plant (WWTP). In multizone BNR systems with membranes in the aerobic reactor and fixed volumes for the anaerobic, anoxic, and aerobic zones (i.e., fixed volume fractions), the mass fractions can be controlled (within a range) with the interreactor recycle ratios. This zone mass fraction flexibility is a significant advantage in membrane BNR systems over conventional BNR systems with SSTs, because it allows for changing of the mass fractions to optimize biological N and P removal in conformity with influent wastewater characteristics and the effluent N and P concentrations required. For PWWF/ADWF ratios in the upper range (f(q) approximately 2.0), aerobic mass fractions in the lower range (f(maer) secondary settling tanks is not as large (40% to 60%), the cost of the membranes can be offset against sludge thickening and stabilization costs. Moving from a flow-unbalanced raw wastewater system to a flow-balanced (f(q) = 1), low (usually settled) wastewater strength system can double the ADWF capacity of the biological reactor, but the design approach of the WWTP changes from extended aeration to include primary sludge stabilization. The cost of primary sludge treatment then has to be paid from the savings from the increased WWTP capacity.

  10. The formation of endosymbiotic membrane compartments: membrane identity markers and the regulation of vesicle trafficking

    NARCIS (Netherlands)

    Ivanov, S.

    2012-01-01

    In symbiosis of plants and arbuscular mycorrhizal fungi as well as in rhizobium-legume symbiosis the microbes are hosted intracellularly, inside specialized membrane compartments of the host. These membrane compartments are morphologically different but similar in function, since they control the ex

  11. tRNAs as regulators of biological processes

    Directory of Open Access Journals (Sweden)

    Medha eRaina

    2014-06-01

    Full Text Available Transfer RNAs (tRNA are best known for their role as adaptors during translation of the genetic code. Beyond their canonical role during protein biosynthesis, tRNAs also perform additional functions in both prokaryotes and eukaryotes for example in regulating gene expression. Aminoacylated tRNAs have also been implicated as substrates for non-ribosomal peptide bond formation, post-translational protein labeling, modification of phospholipids in the cell membrane and antibiotic biosyntheses. Most recently tRNA fragments, or tRFs, have also been recognized to play regulatory roles. Here we examine in more details some of the new functions emerging for tRNA in a variety of cellular processes outside of protein synthesis.

  12. Evaluation and biological characterization of bilayer gelatin/chondroitin-6-sulphate/hyaluronic acid membrane.

    Science.gov (United States)

    Wang, Tzu-Wei; Sun, Jui-Sheng; Wu, Hsi-Chin; Huang, Yi-Chau; Lin, Feng-Huei

    2007-08-01

    A biodegradable polymer scaffold was developed using gelatin, chondroitin-6-sulphate, and hyaluronic acid in the form of bilayer network. The bilayer porous structure of gelatin-chondroitin-6-sulphate-hyaluronic acid (G-C6S-HA) membrane was fabricated using different freezing temperatures followed by lyophilization. 1-Ethyl-3(3-dimethylaminopropyl) carbodiimide was used as crosslinking agent to improve the biological stability of the scaffold. The morphology, physical-chemical properties, and biocompatibility of bilayer G-C6S-HA membrane were evaluated in this study. The functional groups change in crosslinked G-C6S-HA scaffold was characterized by fourier transform infrared spectroscopy. The retention of glycosaminoglycan contents and matrix degradation rate were also examined by p-dimethylamino benzaldehyde and 2,4,6-trinitrobenzene sulphonic acid, respectively. Water absorption capacity was carried out to study G-C6S-HA membrane water containing characteristics. The morphology of the bilayer G-C6S-HA membrane was investigated under scanning electron microscope and light microscopy. In vitro biocompatibility was conducted with MTT test, LDH assay, as well as histological analysis. The results showed that the morphology of bilayer G-C6S-HA membrane was well reserved. The physical-chemical properties were also adequate. With good biocompatibility, this bilayer G-C6S-HA membrane would be suitable as a matrix in the application of tissue engineering.

  13. Fusion Pore Diameter Regulation by Cations Modulating Local Membrane Anisotropy

    Directory of Open Access Journals (Sweden)

    Doron Kabaso

    2012-01-01

    Full Text Available The fusion pore is an aqueous channel that is formed upon the fusion of the vesicle membrane with the plasma membrane. Once the pore is open, it may close again (transient fusion or widen completely (full fusion to permit vesicle cargo discharge. While repetitive transient fusion pore openings of the vesicle with the plasma membrane have been observed in the absence of stimulation, their frequency can be further increased using a cAMP-increasing agent that drives the opening of nonspecific cation channels. Our model hypothesis is that the openings and closings of the fusion pore are driven by changes in the local concentration of cations in the connected vesicle. The proposed mechanism of fusion pore dynamics is considered as follows: when the fusion pore is closed or is extremely narrow, the accumulation of cations in the vesicle (increased cation concentration likely leads to lipid demixing at the fusion pore. This process may affect local membrane anisotropy, which reduces the spontaneous curvature and thus leads to the opening of the fusion pore. Based on the theory of membrane elasticity, we used a continuum model to explain the rhythmic opening and closing of the fusion pore.

  14. Membrane mechanisms and intracellular signalling in cell volume regulation

    DEFF Research Database (Denmark)

    Hoffmann, Else Kay; Dunham, Philip B.

    1995-01-01

    Volume regulation, Signal transduction, Calcium-calmodulin, Stretch-activated channels, Eicosanoids, Macromolecular crowding, Cytoskeleton, Protein phosphorylation, dephosphorylation.......Volume regulation, Signal transduction, Calcium-calmodulin, Stretch-activated channels, Eicosanoids, Macromolecular crowding, Cytoskeleton, Protein phosphorylation, dephosphorylation....

  15. Combined ion conductance and fluorescence confocal microscopy for biological cell membrane transport studies

    Science.gov (United States)

    Shevchuk, A. I.; Novak, P.; Velazquez, M. A.; Fleming, T. P.; Korchev, Y. E.

    2013-09-01

    Optical visualization of nanoscale morphological changes taking place in living biological cells during such important processes as endo- and exocytosis is challenging due to the low refractive index of lipid membranes. In this paper we summarize and discuss advances in the powerful combination of two complementary live imaging techniques, ion conductance and fluorescence confocal microscopy, that allows cell membrane topography to be related with molecular-specific fluorescence at high spatial and temporal resolution. We demonstrate the feasibility of the use of ion conductance microscopy to image apical plasma membrane of mouse embryo trophoblast outgrowth cells at a resolution sufficient to depict single endocytic pits. This opens the possibility to study individual endocytic events in embryo trophoblast outgrowth cells where endocytosis plays a crucial role during early stages of embryo development.

  16. Induction, regulation, degradation, and biological significance of mammalian metallothioneins.

    Science.gov (United States)

    Miles, A T; Hawksworth, G M; Beattie, J H; Rodilla, V

    2000-01-01

    MTs are small cysteine-rich metal-binding proteins found in many species and, although there are differences between them, it is of note that they have a great deal of sequence and structural homology. Mammalian MTs are 61 or 62 amino acid polypeptides containing 20 conserved cysteine residues that underpin the binding of metals. The existence of MT across species is indicative of its biological demand, while the conservation of cysteines indicates that these are undoubtedly central to the function of this protein. Four MT isoforms have been found so far, MT-1, MT-2, MT-3, and MT-4, but these also have subtypes with 17 MT genes identified in man, of which 10 are known to be functional. Different cells express different MT isoforms with varying levels of expression perhaps as a result of the different function of each isoform. Even different metals induce and bind to MTs to different extents. Over 40 years of research into MT have yielded much information on this protein, but have failed to assign to it a definitive biological role. The fact that multiple MT isoforms exist, and the great variety of substances and agents that act as inducers, further complicates the search for the biological role of MTs. This article reviews the current knowledge on the biochemistry, induction, regulation, and degradation of this protein in mammals, with a particular emphasis on human MTs. It also considers the possible biological roles of this protein, which include participation in cell proliferation and apoptosis, homeostasis of essential metals, cellular free radical scavenging, and metal detoxification.

  17. Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Collingwood, S.A.; Ingolfsson, H.I.;

    2010-01-01

    Membrane protein function is regulated by the host lipid bilayer composition. This regulation may depend on specific chemical interactions between proteins and individual molecules in the bilayer, as well as on non-specific interactions between proteins and the bilayer behaving as a physical entity...... with collective physical properties (e.g. thickness, intrinsic monolayer curvature or elastic moduli). Studies in physico-chemical model systems have demonstrated that changes in bilayer physical properties can regulate membrane protein function by altering the energetic cost of the bilayer deformation associated...... physical properties. This advance is because of the introduction of new tools for studying lipid bilayer regulation of protein function. The present review provides an introduction to the regulation of membrane protein function by the bilayer physical properties. We further describe the use of gramicidin...

  18. Function and regulation of lipid biology in Caenorhabditis elegans aging

    Directory of Open Access Journals (Sweden)

    Nicole Shangming Hou

    2012-05-01

    Full Text Available Rapidly expanding aging populations and a concomitant increase in the prevalence of age-related diseases are global health problems today. Over the past three decades, a large body of work has led to the identification of genes and regulatory networks that affect longevity and health span, often benefitting from the tremendous power of genetics in vertebrate and invertebrate model organisms. Interestingly, many of these factors appear linked to lipids, important molecules that participate in cellular signaling, energy metabolism, and structural compartmentalization. Despite the putative link between lipids and longevity, the role of lipids in aging remains poorly understood. Emerging data from the model organism Caenorhabditis elegans suggest that lipid composition may change during aging, as several pathways that influence aging also regulate lipid metabolism enzymes; moreover, some of these enzymes apparently play key roles in the pathways that affect the rate of aging. By understanding how lipid biology is regulated during C. elegans aging, and how it impacts molecular, cellular and organismal function, we may gain insight into novel ways to delay aging using genetic or pharmacological interventions. In the present review we discuss recent insights into the roles of lipids in C. elegans aging, including regulatory roles played by lipids themselves, the regulation of lipid metabolic enzymes, and the roles of lipid metabolism genes in the pathways that affect aging.

  19. Function and Regulation of Lipid Biology in Caenorhabditis elegans Aging

    Science.gov (United States)

    Hou, Nicole Shangming; Taubert, Stefan

    2012-01-01

    Rapidly expanding aging populations and a concomitant increase in the prevalence of age-related diseases are global health problems today. Over the past three decades, a large body of work has led to the identification of genes and regulatory networks that affect longevity and health span, often benefiting from the tremendous power of genetics in vertebrate and invertebrate model organisms. Interestingly, many of these factors appear linked to lipids, important molecules that participate in cellular signaling, energy metabolism, and structural compartmentalization. Despite the putative link between lipids and longevity, the role of lipids in aging remains poorly understood. Emerging data from the model organism Caenorhabditis elegans suggest that lipid composition may change during aging, as several pathways that influence aging also regulate lipid metabolism enzymes; moreover, some of these enzymes apparently play key roles in the pathways that affect the rate of aging. By understanding how lipid biology is regulated during C. elegans aging, and how it impacts molecular, cellular, and organismal function, we may gain insight into novel ways to delay aging using genetic or pharmacological interventions. In the present review we discuss recent insights into the roles of lipids in C. elegans aging, including regulatory roles played by lipids themselves, the regulation of lipid metabolic enzymes, and the roles of lipid metabolism genes in the pathways that affect aging. PMID:22629250

  20. Biomineralization studies on cellulose membrane exposed to biological fluids of Anodonta cygnea.

    Science.gov (United States)

    Lopes, Anabela; Lopes-Lima, Manuel; Ferreira, Jorge; Araújo, Sandra; Hinzmann, Mariana; Oliveira, José; Rocha, António; Domingues, Bernardo; Bobos, Iulius; Machado, Jorge

    2014-06-01

    The present work proposes to analyse the results obtained under in vitro conditions where cellulose artificial membranes were incubated with biological fluids from the freshwater bivalve Anodonta cygnea. The membranes were mounted between two half 'Ussing chambers' with different composition solutions in order to simulate epithelial surfaces separating organic fluid compartments. The membrane surfaces were submitted to two synthetic calcium and phosphate solutions on opposite sides, at pH 6.0, 7.0 or 9.0 during a period of 6 hours. Additional assays were accomplished mixing these solutions with haemolymph or extrapallial fluid from A. cygnea, only on the calcium side. A selective ion movement, mainly dependent on the membrane pore size and/or cationic affinity, occurred with higher permeability for calcium ions to the opposite phosphate chamber supported by calcium diffusion forces across the cellulose membrane. In general, this promoted a more intense mineral precipitation on the phosphate membrane surface. A strong deposition of calcium phosphate mineral was observed at pH 9.0 as a primary layer with a homogeneous microstructure, being totally absent at pH 6.0. The membrane showed an additional crystal phase at pH 7.0 exhibiting a very particular hexagonal or cuttlebone shape, mainly on the phosphate surface. When organic fluids of A. cygnea were included, these crystal forms presented a high tendency to aggregate under rosaceous shapes, also predominantly in the phosphate side. The cellulose membrane was permeable to small organic molecules that diffused from the calcium towards the phosphate side. In the calcium side, very few similar crystals were observed. The presence of organic matrix from A. cygnea fluids induced a preliminary apatite-brushite crystal polymorphism. So, the present results suggest that cellulose membranes can be used as surrogates of biological epithelia with preferential ionic diffusion from the calcium to the phosphate side where the main

  1. Regulation of Vascular Growth in the Chorioallantoic Membrane of Japanese Quail Eggs

    Science.gov (United States)

    Montague, Idoreyin P.

    2004-01-01

    The Microgravity Research Program is part of NASA's Office of Biological and Physical Research (OBPR). The mission of the Microgravity Fluid Physics research program is to facilitate and conduct the best possible fluid physics research using the space environment and make this knowledge available to the scientific community and the public at large. During the summer of 2004, I worked in this division with Dr. Patricia Parsons-Wingerter. Dr. Parsons was working on several projects that used the chorioallantoic membrane (CAM) of Japanese quail eggs. The CAM develops in the eggs of birds and reptiles and is a very vascular fetal membrane composed of the fused chorion and adjacent wall of the allantois. The CAM is formed on day 4 of incubation and its primary job is to mediate gas exchanges with the extra embryonic environment. The CAM of our Japanese quail eggs is easily identifiable to us because it is transparent and it sits on top of the yolk with the embryo in the center. The CAM is of interest because of its many applications in the field of medicine as it relates to vascular remodeling and angiogenesis. Angiogenesis is simply the growth or formation of new blood vessels and anti-angiogenesis is the inhibition of said vessels. Angiogenesis occurs naturally in a healthy body for healing wounds and for restoring blood flow to tissues after injury and in females during the monthly reproductive cycle. In many serious diseases, like several types of cancer and those that affect the heart and cardiovascular system, the body loses control over angiogenesis. These diseases, which are dependent on angiogenesis, result when new blood vessels either grow excessively or insufficiently. The chorioallantoic membrane of our Japanese quail eggs gives a good model of angiogenesis. We used angiogenic regulators to inhibit or stimulate vascular growth in the CAM in a healthy manner and they induced distinct vascular patterns in vivo. Certain dominant regulators can be recognized by

  2. MicroRNA-regulated networks: the perfect storm for classical molecular biology, the ideal scenario for systems biology.

    Science.gov (United States)

    Vera, Julio; Lai, Xin; Schmitz, Ulf; Wolkenhauer, Olaf

    2013-01-01

    MicroRNAs (miRNAs) are involved in many regulatory pathways some of which are complex networks enriched in regulatory motifs like positive or negative feedback loops or coherent and incoherent feedforward loops. Their complexity makes the understanding of their regulation difficult and the interpretation of experimental data cumbersome. In this book chapter we claim that systems biology is the appropriate approach to investigate the regulation of these miRNA-regulated networks. Systems biology is an interdisciplinary approach by which biomedical questions on biochemical networks are addressed by integrating experiments with mathematical modelling and simulation. We here introduce the foundations of the systems biology approach, the basic theoretical and computational tools used to perform model-based analyses of miRNA-regulated networks and review the scientific literature in systems biology of miRNA regulation, with a focus on cancer.

  3. Importin beta negatively regulates nuclear membrane fusion and nuclear pore complex assembly.

    Science.gov (United States)

    Harel, Amnon; Chan, Rene C; Lachish-Zalait, Aurelie; Zimmerman, Ella; Elbaum, Michael; Forbes, Douglass J

    2003-11-01

    Assembly of a eukaryotic nucleus involves three distinct events: membrane recruitment, fusion to form a double nuclear membrane, and nuclear pore complex (NPC) assembly. We report that importin beta negatively regulates two of these events, membrane fusion and NPC assembly. When excess importin beta is added to a full Xenopus nuclear reconstitution reaction, vesicles are recruited to chromatin but their fusion is blocked. The importin beta down-regulation of membrane fusion is Ran-GTP reversible. Indeed, excess RanGTP (RanQ69L) alone stimulates excessive membrane fusion, leading to intranuclear membrane tubules and cytoplasmic annulate lamellae-like structures. We propose that a precise balance of importin beta to Ran is required to create a correct double nuclear membrane and simultaneously to repress undesirable fusion events. Interestingly, truncated importin beta 45-462 allows membrane fusion but produces nuclei lacking any NPCs. This reveals distinct importin beta-regulation of NPC assembly. Excess full-length importin beta and beta 45-462 act similarly when added to prefused nuclear intermediates, i.e., both block NPC assembly. The importin beta NPC block, which maps downstream of GTPgammaS and BAPTA-sensitive steps in NPC assembly, is reversible by cytosol. Remarkably, it is not reversible by 25 microM RanGTP, a concentration that easily reverses fusion inhibition. This report, using a full reconstitution system and natural chromatin substrates, significantly expands the repertoire of importin beta. Its roles now encompass negative regulation of two of the major events of nuclear assembly: membrane fusion and NPC assembly.

  4. Immunization to regulate fertility: biological and cultural frameworks.

    Science.gov (United States)

    Schrater, A F

    1995-09-01

    Deliberate immunization to control fertility differs from that to control disease. Those differences can be discussed within various frameworks, e.g., intent, recipient population, biological bases, and immunological targets. Others include differing perspectives of developers, providers and users, and rights of the state to impose programs of control. Almost all of the differences are grounded in the social, economic, and gendered aspects of societies. The intent of providing a fertility-regulating vaccine is to prevent pregnancy. In theory, men as well as women could receive such vaccines; in reality, most are designed for women. Traditional vaccines are intended to prevent disease and are generally given to susceptible individuals whether male or female, child or adult. The biological bases of contraceptive vaccines are molecules specific to reproduction. The immune response generated by most anti-fertility vaccines is directed toward 'self', one's own cells and molecules. In contrast, the bases of traditional vaccines are materials derived from non-self, disease-causing microorganisms; the immunological targets are those microorganisms or their toxic products. From a developer perspective vaccines that regulate fertility differ little from those that control disease; both prevent a particular condition. Developers cite these advantages to contraceptive vaccines: non-invasive, no serious side-effects, easy to use, reduced patient failure, and long-lasting but naturally reversible. Because anti-fertility vaccines have been tested only in small-scale clinical trials, information on user reactions and experiences is limited. Not surprisingly, the perspectives of women's health advocates and of potential users (mostly women) often differ markedly from those of developers. Women cite as disadvantages the cryptic nature of immunity which leaves one without an obvious signal for the beginning of protection (against pregnancy) and its decline, and the inability to 'turn

  5. Specificity and mechanism of action of alpha-helical membrane-active peptides interacting with model and biological membranes by single-molecule force spectroscopy.

    Science.gov (United States)

    Sun, Shiyu; Zhao, Guangxu; Huang, Yibing; Cai, Mingjun; Shan, Yuping; Wang, Hongda; Chen, Yuxin

    2016-07-01

    In this study, to systematically investigate the targeting specificity of membrane-active peptides on different types of cell membranes, we evaluated the effects of peptides on different large unilamellar vesicles mimicking prokaryotic, normal eukaryotic, and cancer cell membranes by single-molecule force spectroscopy and spectrum technology. We revealed that cationic membrane-active peptides can exclusively target negatively charged prokaryotic and cancer cell model membranes rather than normal eukaryotic cell model membranes. Using Acholeplasma laidlawii, 3T3-L1, and HeLa cells to represent prokaryotic cells, normal eukaryotic cells, and cancer cells in atomic force microscopy experiments, respectively, we further studied that the single-molecule targeting interaction between peptides and biological membranes. Antimicrobial and anticancer activities of peptides exhibited strong correlations with the interaction probability determined by single-molecule force spectroscopy, which illustrates strong correlations of peptide biological activities and peptide hydrophobicity and charge. Peptide specificity significantly depends on the lipid compositions of different cell membranes, which validates the de novo design of peptide therapeutics against bacteria and cancers.

  6. Liquid membrane extraction techniques for trace metal analysis and speciation in environmental and biological matrices

    Energy Technology Data Exchange (ETDEWEB)

    Ndungu, Kuria

    1999-04-01

    In this thesis, liquid-membrane-based methods for the analysis of trace metal species in samples of environmental and biological origin were developed. By incorporating extracting reagents in the membrane liquid, trace metal ions were selectively separated from humic-rich natural waters and urine samples, prior to their determination using various instrumental techniques. The extractions were performed in closed flow systems thus allowing easy automation of both the sample clean-up and enrichment. An acidic organophosphorus reagent (DEHPA) and a basic tetraalkylammonium reagent (Aliquat-336) were used as extractants in the membrane liquid to selectively extract and enrich cationic and anionic metal species respectively. A speciation method for chromium species was developed that allowed the determination of cationic Cr(III) species and anionic CR(VI) species in natural water samples without the need of a chromatographic separation step prior to their detection. SLM was also coupled on-line to potentiometric stripping analysis providing a fast and sensitive method for analysis of Pb in urine samples. A microporous membrane liquid-liquid extraction (MMLLE) method was developed for the determination of organotin compounds in natural waters that reduced the number of manual steps involved in the LLE of organotin compounds prior to their CC separation. Clean extracts obtained after running unfiltered humic-rich river water samples through the MMLLE flow system allowed selective determination of all the organotin compounds in a single run using GC-MS in the selected ion monitoring mode (SIM) 171 refs, 9 figs, 4 tabs

  7. Membrane protein structural biology using X-ray free electron lasers.

    Science.gov (United States)

    Neutze, Richard; Brändén, Gisela; Schertler, Gebhard F X

    2015-08-01

    Membrane protein structural biology has benefitted tremendously from access to micro-focus crystallography at synchrotron radiation sources. X-ray free electron lasers (XFELs) are linear accelerator driven X-ray sources that deliver a jump in peak X-ray brilliance of nine orders of magnitude and represent a disruptive technology with potential to dramatically change the field. Membrane proteins were amongst the first macromolecules to be studied with XFEL radiation and include proof-of-principle demonstrations of serial femtosecond crystallography (SFX), the observation that XFEL data can deliver damage free crystallographic structures, initial experiments towards recording structural information from 2D arrays of membrane proteins, and time-resolved SFX, time-resolved wide angle X-ray scattering and time-resolved X-ray emission spectroscopy studies. Conversely, serial crystallography methods are now being applied using synchrotron radiation. We believe that a context dependent choice of synchrotron or XFEL radiation will accelerate progress towards novel insights in understanding membrane protein structure and dynamics.

  8. Differential regulation of two types of monogalactosyldiacylglylcerol synthase in membrane lipid remodeling under phosphate-limited conditions in sesame plants

    Directory of Open Access Journals (Sweden)

    Mie eShimojima

    2013-11-01

    Full Text Available Phosphate (Pi limitation causes drastic lipid remodeling in plant membranes. Glycolipids substitute for the phospholipids that are degraded, thereby supplying Pi needed for essential biological processes. Two major types of remodeling of membrane lipids occur in higher plants: whereas one involves an increase in the concentration of sulfoquinovosyldiacylglycerol in plastids to compensate for a decreased concentration of phosphatidylglycerol, the other involves digalactosyldiacylglycerol (DGDG synthesis in plastids and the export of DGDG to extraplastidial membranes to compensate for reduced abundances of phospholipids. Lipid remodeling depends on an adequate supply of monogalactosyldiacylglycerol (MGDG, which is a substrate that supports the elevated rate of DGDG synthesis that is induced by low Pi availability. Regulation of MGDG synthesis has been analyzed most extensively using the model plant Arabidopsis thaliana, although orthologous genes that encode putative MGDG synthases exist in photosynthetic organisms from bacteria to higher plants. We recently hypothesized that two types of MGDG synthase diverged after the appearance of seed plants. This divergence might have both enabled plants to adapt to a wide range of Pi availability in soils and contributed to the diversity of seed plants. In the work presented here, we found that membrane lipid remodeling also takes place in sesame, which is one of the most common traditional crops grown in Asia. We identified two types of MGDG synthase from sesame (encoded by SeMGD1 and SeMGD2 and analyzed their enzymatic properties. Our results show that both genes correspond to the Arabidopsis type-A and -B isoforms of MGDG synthase. Notably, whereas Pi limitation up-regulates only the gene encoding the type-B isoform of Arabidopsis, low Pi availability up-regulates the expression of both SeMGD1 and SeMGD2. We discuss the significance of the different responses to low Pi availability in sesame and

  9. Regulation of Ras signaling and function by plasma membrane microdomains.

    Science.gov (United States)

    Goldfinger, Lawrence E; Michael, James V

    2017-02-07

    Together H-, N- and KRAS mutations are major contributors to ~30% of all human cancers. Thus, Ras inhibition remains an important anti-cancer strategy. The molecular mechanisms of isotypic Ras oncogenesis are still not completely understood. Monopharmacological therapeutics have not been successful in the clinic. These disappointing outcomes have led to attempts to target elements downstream of Ras, mainly targeting either the Phosphatidylinositol 3-Kinase (PI3K) or Mitogen-Activated Protein Kinase (MAPK) pathways. While several such approaches are moderately effective, recent efforts have focused on preclinical evaluation of combination therapies to improve efficacies. This review will detail current understanding of the contributions of plasma membrane microdomain targeting of Ras to mitogenic and tumorigenic signaling and tumor progression. Moreover, this review will outline novel approaches to target Ras in cancers, including targeting schemes for new drug development, as well as putative re-purposing of drugs in current use to take advantage of blunting Ras signaling by interfering with Ras plasma membrane microdomain targeting and retention.

  10. Crystal structure of a membrane-bound metalloenzyme that catalyses the biological oxidation of methane

    Energy Technology Data Exchange (ETDEWEB)

    Lieberman, R.L.; Rosenzweig, A.C. (NWU)

    2010-03-08

    Particulate methane monooxygenase (pMMO) is an integral membrane metalloenzyme that catalyses the conversion of methane to methanol. Knowledge of how pMMO performs this extremely challenging chemistry may have an impact on the use of methane as an alternative energy source by facilitating the development of new synthetic catalysts. We have determined the structure of pMMO from the methanotroph Methylococcus capsulatus (Bath) to a resolution of 2.8 {angstrom}. The enzyme is a trimer with an {alpha}{sub 3}{beta}{sub 3}{gamma}{sub 3} polypeptide arrangement. Two metal centres, modelled as mononuclear copper and dinuclear copper, are located in soluble regions of each pmoB subunit, which resembles cytochrome c oxidase subunit II. A third metal centre, occupied by zinc in the crystal, is located within the membrane. The structure provides new insight into the molecular details of biological methane oxidation.

  11. Temperature-dependent phase transitions in zeptoliter volumes of a complex biological membrane

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, Maxim P; Jesse, Stephen; Kalinin, Sergei V [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Hohlbauch, Sophia; Proksch, Roger [Asylum Research, Santa Barbara, CA 93117 (United States); King, William P [Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801 (United States); Voitchovsky, Kislon [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Contera, Sonia Antoranz [Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, Oxford (United Kingdom)

    2011-02-04

    Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50-60 deg. C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 {+-} 5 deg. C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.

  12. Temperature-dependent phase transitions of a complex biological membrane in zeptoliter volumes

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, Maxim [ORNL; Hohlbauch, Sophia [Asylum Research, Santa Barbara, CA; King, William P [University of Illinois, Urbana-Champaign; Voitchovsky, K [Massachusetts Institute of Technology (MIT); Contera, S Antoranz [University of Oxford; Jesse, Stephen [ORNL; Kalinin, Sergei V [ORNL; Proksch, Roger [Asylum Research, Santa Barbara, CA

    2011-01-01

    Phase transitions in purple membrane have been a topic of debate for the past two decades. In this work we present studies of a reversible transition of purple membrane in the 50 60 C range in zeptoliter volumes under different heating regimes (global heating and local heating). The temperature of the reversible phase transition is 52 5 C for both local and global heating, supporting the hypothesis that this transition is mainly due to a structural rearrangement of bR molecules and trimers. To achieve high resolution measurements of temperature-dependent phase transitions, a new scanning probe microscopy-based method was developed. We believe that our new technique can be extended to other biological systems and can contribute to the understanding of inhomogeneous phase transitions in complex systems.

  13. Depression, osteoporosis, serotonin and cell membrane viscosity between biology and philosophical anthropology

    Directory of Open Access Journals (Sweden)

    Gabrielli Fabio

    2011-03-01

    Full Text Available Abstract Due to the relationship between biology and culture, we believe that depression, understood as a cultural and existential phenomenon, has clear markers in molecular biology. We begin from an existential analysis of depression constituting the human condition and then shift to analysis of biological data confirming, according to our judgment, its original (ontological structure. In this way philosophy is involved at the anthropological level, in as much as it detects the underlying meanings of depression in the original biological-cultural horizon of human life. Considering the integration of knowledge it is the task of molecular biology to identify the aforementioned markers, to which the existential aspects of depression are linked to. In particular, recent works show the existence of a link between serotonin and osteoporosis as a result of a modified expression of the low-density lipoprotein receptor-related protein 5 gene. Moreover, it is believed that the hereditary or acquired involvement of tryptophan hydroxylase 2 (Tph2 or 5-hydroxytryptamine transporter (5-HTT is responsible for the reduced concentration of serotonin in the central nervous system, causing depression and affective disorders. This work studies the depression-osteoporosis relationship, with the aim of focusing on depressive disorders that concern the quantitative dynamic of platelet membrane viscosity and interactome cytoskeleton modifications (in particular Tubulin and Gsα protein as a possible condition of the involvement of the serotonin axis (gut, brain and platelet, not only in depression but also in connection with osteoporosis.

  14. Selective regulation of maize plasma membrane aquaporin trafficking and activity by the SNARE SYP121.

    Science.gov (United States)

    Besserer, Arnaud; Burnotte, Emeline; Bienert, Gerd Patrick; Chevalier, Adrien S; Errachid, Abdelmounaim; Grefen, Christopher; Blatt, Michael R; Chaumont, François

    2012-08-01

    Plasma membrane intrinsic proteins (PIPs) are aquaporins facilitating the diffusion of water through the cell membrane. We previously showed that the traffic of the maize (Zea mays) PIP2;5 to the plasma membrane is dependent on the endoplasmic reticulum diacidic export motif. Here, we report that the post-Golgi traffic and water channel activity of PIP2;5 are regulated by the SNARE (for soluble N-ethylmaleimide-sensitive factor protein attachment protein receptor) SYP121, a plasma membrane resident syntaxin involved in vesicle traffic, signaling, and regulation of K(+) channels. We demonstrate that the expression of the dominant-negative SYP121-Sp2 fragment in maize mesophyll protoplasts or epidermal cells leads to a decrease in the delivery of PIP2;5 to the plasma membrane. Protoplast and oocyte swelling assays showed that PIP2;5 water channel activity is negatively affected by SYP121-Sp2. A combination of in vitro (copurification assays) and in vivo (bimolecular fluorescence complementation, Förster resonance energy transfer, and yeast split-ubiquitin) approaches allowed us to demonstrate that SYP121 and PIP2;5 physically interact. Together with previous data demonstrating the role of SYP121 in regulating K(+) channel trafficking and activity, these results suggest that SYP121 SNARE contributes to the regulation of the cell osmotic homeostasis.

  15. Selective Regulation of Maize Plasma Membrane Aquaporin Trafficking and Activity by the SNARE SYP121[W

    Science.gov (United States)

    Besserer, Arnaud; Burnotte, Emeline; Bienert, Gerd Patrick; Chevalier, Adrien S.; Errachid, Abdelmounaim; Grefen, Christopher; Blatt, Michael R.; Chaumont, François

    2012-01-01

    Plasma membrane intrinsic proteins (PIPs) are aquaporins facilitating the diffusion of water through the cell membrane. We previously showed that the traffic of the maize (Zea mays) PIP2;5 to the plasma membrane is dependent on the endoplasmic reticulum diacidic export motif. Here, we report that the post-Golgi traffic and water channel activity of PIP2;5 are regulated by the SNARE (for soluble N-ethylmaleimide-sensitive factor protein attachment protein receptor) SYP121, a plasma membrane resident syntaxin involved in vesicle traffic, signaling, and regulation of K+ channels. We demonstrate that the expression of the dominant-negative SYP121-Sp2 fragment in maize mesophyll protoplasts or epidermal cells leads to a decrease in the delivery of PIP2;5 to the plasma membrane. Protoplast and oocyte swelling assays showed that PIP2;5 water channel activity is negatively affected by SYP121-Sp2. A combination of in vitro (copurification assays) and in vivo (bimolecular fluorescence complementation, Förster resonance energy transfer, and yeast split-ubiquitin) approaches allowed us to demonstrate that SYP121 and PIP2;5 physically interact. Together with previous data demonstrating the role of SYP121 in regulating K+ channel trafficking and activity, these results suggest that SYP121 SNARE contributes to the regulation of the cell osmotic homeostasis. PMID:22942383

  16. Pattern formation in biological fluids II: cell deformation in shear fields evidences convective membrane organisation

    CERN Document Server

    Lofthouse, J

    2004-01-01

    The mechanical behaviour and symmetry-breaking shape deformation of red blood cells subjected to shear flows is used to demonstrate that far from being random fluids, both the membrane and cytoplasm of every biological cell undergo spatially organised convective and shear driven flows when the cell maintains a Near Equilibrium state through continuousmetabolic activity. The model demonstrates that fluid bifurcation events drive cell shape changes, rather than a Meccano like cytoskeletal structure, and represents a significant Gestalt shift in models of cell mechanics.

  17. Regulation of plant plasma membrane H+- and Ca2+-ATPases by terminal domains

    DEFF Research Database (Denmark)

    Bækgaard, Lone; Fuglsang, Anja Thoe; Palmgren, Michael Gjedde

    2005-01-01

    In the last few years, major progress has been made to elucidate the structure, function, and regulation of P-type plasma membrane H(+)-and Ca(2+)-ATPases. Even though a number of regulatory proteins have been identified, many pieces are still lacking in order to understand the complete regulator...... mechanisms of these pumps. In plant plasma membrane H(+)- and Ca(2+)-ATPases, autoinhibitory domains are situated in the C- and N-terminal domains, respectively. A model for a common mechanism of autoinhibition is discussed....

  18. Shell and membrane theories in mechanics and biology from macro- to nanoscale structures

    CERN Document Server

    Mikhasev, Gennadi

    2015-01-01

    This book presents the latest results related to shells  characterize and design shells, plates, membranes and other thin-walled structures, a multidisciplinary approach from macro- to nanoscale is required which involves the classical disciplines of mechanical/civil/materials engineering (design, analysis, and properties) and physics/biology/medicine among others. The book contains contributions of a meeting of specialists (mechanical engineers, mathematicians, physicists and others) in such areas as classical and non-classical shell theories. New trends with respect to applications in mechanical, civil and aero-space engineering, as well as in new branches like medicine and biology are presented which demand improvements of the theoretical foundations of these theories and a deeper understanding of the material behavior used in such structures.

  19. Exosomes as therapeutic drug carriers and delivery vehicles across biological membranes: current perspectives and future challenges.

    Science.gov (United States)

    Ha, Dinh; Yang, Ningning; Nadithe, Venkatareddy

    2016-07-01

    Exosomes are small intracellular membrane-based vesicles with different compositions that are involved in several biological and pathological processes. The exploitation of exosomes as drug delivery vehicles offers important advantages compared to other nanoparticulate drug delivery systems such as liposomes and polymeric nanoparticles; exosomes are non-immunogenic in nature due to similar composition as body׳s own cells. In this article, the origin and structure of exosomes as well as their biological functions are outlined. We will then focus on specific applications of exosomes as drug delivery systems in pharmaceutical drug development. An overview of the advantages and challenges faced when using exosomes as a pharmaceutical drug delivery vehicles will also be discussed.

  20. Vacuolar H+-ATPase in the nuclear membranes regulates nucleo-cytosolic proton gradients.

    Science.gov (United States)

    Santos, Julianna Maria; Martínez-Zaguilán, Raul; Facanha, Arnoldo Rocha; Hussain, Fazle; Sennoune, Souad R

    2016-10-01

    The regulation of the luminal pH of each organelle is crucial for its function and must be controlled tightly. Nevertheless, it has been assumed that the nuclear pH is regulated by the cytoplasmic proton transporters via the diffusion of H(+) across the nuclear pores because of their large diameter. However, it has been demonstrated that ion gradients exist between cytosol and nucleus, suggesting that the permeability of ions across the nuclear pores is restricted. Vacuolar H(+)-ATPase (V-H(+)-ATPase) is responsible for the creation and maintenance of trans-membrane electrochemical gradient. We hypothesize that V-H(+)-ATPase located in the nuclear membranes functions as the primary mechanism to regulate nuclear pH and generate H(+) gradients across the nuclear envelope. We studied the subcellular heterogeneity of H(+) concentration in the nucleus and cytosol using ratio imaging microscopy and SNARF-1, a pH indicator, in prostate cells. Our results indicate that there are proton gradients across the nuclear membranes that are generated by V-H(+)-ATPase located in the outer and inner nuclear membranes. We demonstrated that these gradients are mostly dissipated by inhibiting V-H(+)-ATPase. Immunoblots and V-H(+)-ATPase activity corroborated the existence of V-H(+)-ATPase in the nuclear membranes. This study demonstrates that V-H(+)-ATPase is functionally expressed in nuclear membranes and is responsible for nuclear H(+) gradients that may promote not only the coupled transport of substrates, but also most electrochemically driven events across the nuclear membranes. This study represents a paradigm shift that the nucleus can regulate its own pH microenvironment, providing new insights into nuclear ion homeostasis and signaling.

  1. A membrane-specific tyrosinase chelate: the mitotic regulator?

    Science.gov (United States)

    Kharasch, J A

    1987-06-01

    Cancer's random, reversible, unstable transitions to "normal" structures imply their functional relation. Similar random, continuous, reversible oncogene "mutational transformation" also lacks a consistent hybrid. Positing cancer's "mutationally altered genotype" leads to medically foreign causes, qualities, inducers, suppressors, immune proteins, and viruses. Its random variation, however, opposes the functionally discrete, ordered, stable, irreversible hybrid variation and single-valued transforms of molecular genetics. There, "causal mutational operators" remain unspecified; only consistent single-valued DNA base and amino acid change, as "transform operand", are made explicit. A mitotically "blocked" (normal) and "unblocked" (malignant) stem cell "phenotype", operationally constructed from microscopic data, is therefore viewed within the homeostatic context of open-system enzyme-regulatory equilibrium. This functional, stochastic field distribution between "structurally bound" and "freely dividing" stem cell number discloses their putative regulatory mitotic-blocking factor. A tyrosinase complex, interacting by Cu2+-Fe2+ chelation with a proline hydroxylase divisional enzyme near stem cell ribosomes, maintains steady-state mitotic equilibrium. Based upon familiar medical, biochemical, and energy principles this confronts cancer's pigmentary-depigmentary signs, glycolytic metabolism, elevated serum tyrosinase, defective collagen production, exposed membrane binding sites, and tyrosine's recent growth control role.

  2. Rigid proteins and softening of biological membranes—with application to HIV-induced cell membrane softening

    Science.gov (United States)

    Agrawal, Himani; Zelisko, Matthew; Liu, Liping; Sharma, Pradeep

    2016-05-01

    A key step in the HIV-infection process is the fusion of the virion membrane with the target cell membrane and the concomitant transfer of the viral RNA. Experimental evidence suggests that the fusion is preceded by considerable elastic softening of the cell membranes due to the insertion of fusion peptide in the membrane. What are the mechanisms underpinning the elastic softening of the membrane upon peptide insertion? A broader question may be posed: insertion of rigid proteins in soft membranes ought to stiffen the membranes not soften them. However, experimental observations perplexingly appear to show that rigid proteins may either soften or harden membranes even though conventional wisdom only suggests stiffening. In this work, we argue that regarding proteins as merely non-specific rigid inclusions is flawed, and each protein has a unique mechanical signature dictated by its specific interfacial coupling to the surrounding membrane. Predicated on this hypothesis, we have carried out atomistic simulations to investigate peptide-membrane interactions. Together with a continuum model, we reconcile contrasting experimental data in the literature including the case of HIV-fusion peptide induced softening. We conclude that the structural rearrangements of the lipids around the inclusions cause the softening or stiffening of the biological membranes.

  3. Elmo2 Is a Regulator of Insulin-dependent Glut4 Membrane Translocation.

    Science.gov (United States)

    Sun, Yingmin; Côté, Jean-François; Du, Keyong

    2016-07-29

    Elmo2, a member of the Elmo protein family, has been implicated in the regulation of Rac1 and Akt activation. Recently, we found that Elmo2 specifically interacts with ClipR-59. Because Akt and Rac1 have been implicated in insulin dependent Glut4 membrane translocation, we hypothesize here that Elmo2 may play a role in insulin-dependent Glut4 membrane translocation. Accordingly, we found that overexpression of Elmo2 enhanced, whereas its knockdown suppressed, insulin-dependent Glut4 membrane translocation in both 3T3-L1 adipocytes and L6 skeletal muscle cells. We also examined whether Elmo2 contributes to the insulin-mediated activation of Rac1 and Akt. We found that Elmo2 is required for insulin-induced Rac1 GTP loading, but not AKT activation, in L6 cells induced by insulin. Instead, Elmo2 is required to promote the insulin-induced membrane association of Akt. Together, our studies demonstrate that Elmo2 is a new regulator of insulin-dependent Glut4 membrane translocation through modulating Rac1 activity and Akt membrane compartmentalization.

  4. Regulation of developmental and environmental signaling by interaction between microtubules and membranes in plant cells

    Directory of Open Access Journals (Sweden)

    Qun Zhang

    2015-12-01

    Full Text Available ABSTRACT Cell division and expansion require the ordered arrangement of microtubules, which are subject to spatial and temporal modifications by developmental and environmental factors. Understanding how signals translate to changes in cortical microtubule organization is of fundamental importance. A defining feature of the cortical microtubule array is its association with the plasma membrane; modules of the plasma membrane are thought to play important roles in the mediation of microtubule organization. In this review, we highlight advances in research on the regulation of cortical microtubule organization by membrane-associated and membrane-tethered proteins and lipids in response to phytohormones and stress. The transmembrane kinase receptor Rho-like guanosine triphosphatase, phospholipase D, phosphatidic acid, and phosphoinositides are discussed with a focus on their roles in microtubule organization.

  5. Pressuromodulation at the cell membrane as the basis for small molecule hormone and peptide regulation of cellular and nuclear function.

    Science.gov (United States)

    Sarin, Hemant

    2015-11-26

    Building on recent knowledge that the specificity of the biological interactions of small molecule hydrophiles and lipophiles across microvascular and epithelial barriers, and with cells, can be predicted on the basis of their conserved biophysical properties, and the knowledge that biological peptides are cell membrane impermeant, it has been further discussed herein that cellular, and thus, nuclear function, are primarily regulated by small molecule hormone and peptide/factor interactions at the cell membrane (CM) receptors. The means of regulating cellular, and thus, nuclear function, are the various forms of CM Pressuromodulation that exist, which include Direct CM Receptor-Mediated Stabilizing Pressuromodulation, sub-classified as Direct CM Receptor-Mediated Stabilizing Shift Pressuromodulation (Single, Dual or Tri) or Direct CM Receptor-Mediated Stabilizing Shift Pressuromodulation (Single, Dual or Tri) cum External Cationomodulation (≥3+ → 1+); which are with respect to acute CM receptor-stabilizing effects of small biomolecule hormones, growth factors or cytokines, and also include Indirect CM- or CM Receptor-Mediated Pressuromodulation, sub-classified as Indirect 1ary CM-Mediated Shift Pressuromodulation (Perturbomodulation), Indirect 2ary CM Receptor-Mediated Shift Pressuromodulation (Tri or Quad Receptor Internal Pseudo-Cationomodulation: SS 1+), Indirect 3ary CM Receptor-Mediated Shift Pressuromodulation (Single or Dual Receptor Endocytic External Cationomodulation: 2+) or Indirect (Pseudo) 3ary CM Receptor-Mediated Shift Pressuromodulation (Receptor Endocytic Hydroxylocarbonyloetheroylomodulation: 0), which are with respect to sub-acute CM receptor-stabilizing effects of small biomolecules, growth factors or cytokines. As a generalization, all forms of CM pressuromodulation decrease CM and nuclear membrane (NM) compliance (whole cell compliance), due to pressuromodulation of the intracellular microtubule network and increases the exocytosis of pre

  6. Membraner

    DEFF Research Database (Denmark)

    Bach, Finn

    2009-01-01

    Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner......Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner...

  7. Thermal Regulation of Membrane Lipid Fluidity by a Two-Component System in "Bacillus Subtilis"

    Science.gov (United States)

    Bredeston, L. M.; Marciano, D.; Albanesi, D.; De Mendoza, D.; Delfino, J. M.

    2011-01-01

    This article describes a simple and robust laboratory exercise on the regulation of membrane unsaturated fatty acid composition in bacteria by a decrease in growth temperature. We take advantage of the well characterized Des pathway of "Bacillus subtilis", composed of a [delta]5-desaturase (encoded by the "des" gene) and the canonical…

  8. Polarized membrane traffic and cell polarity development is dependent on dihydroceramide synthase-regulated sphinganine turnover

    NARCIS (Netherlands)

    van Ijzendoorn, SCD; van der Wouden, JM; Liebisch, G; Schmitz, G; Hoekstra, D

    2004-01-01

    Sphingoid bases have been implicated in various cellular processes including cell growth, apoptosis and cell differentiation. Here, we show that the regulated turnover of sphingoid bases is crucial for cell polarity development, i.e., the biogenesis of apical plasma membrane domains, in well-differe

  9. Proteomic analysis identifies interleukin 11 regulated plasma membrane proteins in human endometrial epithelial cells in vitro

    Directory of Open Access Journals (Sweden)

    Stanton Peter G

    2011-05-01

    Full Text Available Abstract Background During the peri-implantation period, the embryo adheres to an adequately prepared or receptive endometrial surface epithelium. Abnormal embryo adhesion to the endometrium results in embryo implantation failure and infertility. Endometrial epithelial cell plasma membrane proteins critical in regulating adhesion may potentially be infertility biomarkers or targets for treating infertility. Interleukin (IL 11 regulates human endometrial epithelial cells (hEEC adhesion. Its production is abnormal in women with infertility. The objective of the study was to identify IL11 regulated plasma membrane proteins in hEEC in vitro using a proteomic approach. Methods Using a 2D-differential in-gel electrophoresis (DIGE electrophoresis combined with LCMS/MS mass spectrometry approach, we identified 20 unique plasma membrane proteins differentially regulated by IL11 in ECC-1 cells, a hEEC derived cell line. Two IL11 regulated proteins with known roles in cell adhesion, annexin A2 (ANXA2 and flotillin-1 (FLOT1, were validated by Western blot and immunocytochemistry in hEEC lines (ECC-1 and an additional cell line, Ishikawa and primary hEEC. Flotilin-1 was further validated by immunohistochemistry in human endometrium throughout the menstrual cycle (n = 6-8/cycle. Results 2D-DIGE analysis identified 4 spots that were significantly different between control and IL11 treated group. Of these 4 spots, there were 20 proteins that were identified with LCMS/MS. Two proteins; ANXA2 and FLOT1 were chosen for further analyses and have found to be significantly up-regulated following IL11 treatment. Western blot analysis showed a 2-fold and a 2.5-fold increase of ANXA2 in hEEC membrane fraction of ECC-1 and Ishikawa cells respectively. Similarly, a 1.8-fold and a 2.3/2.4-fold increase was also observed for FLOT1 in hEEC membrane fraction of ECC-1 and Ishikawa cells respectively. In vitro, IL11 induced stronger ANXA2 expression on cell surface of primary h

  10. Biophysical and biological characterization of intraoral multilayer membranes as potential carriers: A new drug delivery system for dentistry.

    Science.gov (United States)

    Silva, Mariana Dos Santos; Neto, Natalino Lourenço; da Costa, Silgia Aparecida; da Costa, Sirlene Maria; Oliveira, Thais Marchini; Oliveira, Rodrigo Cardoso de; Machado, Maria Aparecida Andrade Moreira

    2017-02-01

    The current study developed through layer-by-layer deposition a multilayer membrane for intraoral drug delivery and analyzed the biochemical, functional, and biological properties of this membrane. For that purpose, we designed a three-layer chlorhexidine-incorporated membrane composed by pure chitosan and alginate. The biochemical, functional, and biological properties were analyzed by the following tests: degradation in saliva medium; controlled drug release; water absorption, mass loss; pH analysis; and biocompatibility through fibroblast cell viability by MTT assay. All tests were conducted at three different periods (24, 48 and 72hours). The results demonstrated that hybrid membranes composed by alginate and chitosan with glycerol had greater water absorption and mass loss in buffer solution and in artificial saliva. The controlled drug release test revealed that the hybrid membrane exhibited greater drug release (0.075%). All chlorhexidine-incorporated membranes reduced the cell viability, and chitosan membranes with and without glycerol did not interfere with fibroblast viability. The biochemical and biophysical characteristics of the designed membranes and the findings of cell viability tests indicate great potential for application in Dentistry.

  11. Modelling the biological performance of a side-stream membrane bioreactor using ASM1

    Institute of Scientific and Technical Information of China (English)

    TIAN Ke-jun; LIU Xin-ai; JIANG Tao; M.D. Kennedy; J.C. Schippers; P.A. Vanrolleghem

    2004-01-01

    Membrane bioreactors(MBRs) are attracting global interest but the mathematical modeling of the biological performance of MBRs remains very limited. This study focuses on the modelling of a side-stream MBR system using Activated Sludge Model No.1(ASM1), and comparing the results with the modelling of traditional activated sludge processes. ASM1 parameters relevant for the long-term biological behaviour in MBR systems were calibrated(i.e. YH=0.72gCOD/gCOD, YA=0.25gCOD/gN, bH=0.25 d-1, bA=0.080 d-1 and fP=0.06), and generally agreed with the parameters in traditional activated sludge processes, with the exception that a higher autotrophic biomass decay rate was observed in the MBR. A sensitivity analysis for steady state operation and DO dynamics suggested that the biological performance of the MBR system(the sludge concentration, effluent quality and the DO dynamics) are very sensitive to the parameters(i.e. YH, YA, bH, bA, (maxH and (maxA), and influent wastewater components(XI, Ss, Xs, SNH).

  12. Mitochondrial glutathione transferases involving a new function for membrane permeability transition pore regulation.

    Science.gov (United States)

    Aniya, Yoko; Imaizumi, Naoki

    2011-05-01

    The mitochondria in mammalian cells are a predominant resource of reactive oxygen species (ROS), which are produced during respiration-coupled oxidative metabolism or various chemical stresses. End-products from membrane-lipid peroxidation caused by ROS are highly toxic, thereby their elimination/scavenging are protective of mitochondria and cells against oxidative damages. In mitochondria, soluble (kappa, alpha, mu, pi, zeta) and membrane-bound glutathione transferases (GSTs) (MGST1) are distributed. Mitochondrial GSTs display both glutathione transferase and peroxidase activities that detoxify such harmful products through glutathione (GSH) conjugation or GSH-mediated peroxide reduction. Some GST isoenzymes are induced by oxidative stress, an adaptation mechanism for the protection of cells from oxidative stress. Membrane-bound MGST1 is activated through the thiol modification in oxidative conditions. Protective action of MGST1 against oxidative stress has been confirmed using MCF7 cells highly expressed of MGST1. In recent years, mitochondria have been recognized as a regulator of cell death via both apoptosis and necrosis, where oxidative stress-induced alteration of the membrane permeability is an important step. Recent studies have shown that MGST1 in the inner mitochondrial membrane could interact with the mitochondrial permeability transition (MPT) regulator proteins, such as adenine nucleotide translocator (ANT) and/or cyclophilin D, and could contribute to oxidant-induced MPT pores. Interaction of GST alpha with ANT has also been shown. In this review, functions of the mitochondrial GSTs, including a new role for mitochondria-mediated cell death, are described.

  13. Proceedings First Workshop on Applications of Membrane computing, Concurrency and Agent-based modelling in POPulation biology

    CERN Document Server

    Milazzo, Paolo; 10.4204/EPTCS.33

    2010-01-01

    This volume contains the papers presented at the first International Workshop on Applications of Membrane Computing, Concurrency and Agent-based Modelling in Population Biology (AMCA-POP 2010) held in Jena, Germany on August 25th, 2010 as a satellite event of the 11th Conference on Membrane Computing (CMC11). The aim of the workshop is to investigate whether formal modelling and analysis techniques could be applied with profit to systems of interest for population biology and ecology. The considered modelling notations include membrane systems, Petri nets, agent-based notations, process calculi, automata-based notations, rewriting systems and cellular automata. Such notations enable the application of analysis techniques such as simulation, model checking, abstract interpretation and type systems to study systems of interest in disciplines such as population biology, ecosystem science, epidemiology, genetics, sustainability science, evolution and other disciplines in which population dynamics and interactions...

  14. New insights into the regulation of cholesterol efflux from the sperm membrane.

    Science.gov (United States)

    Leahy, Tamara; Gadella, Bart M

    2015-01-01

    Cholesterol is an essential component of the mammalian plasma membrane because it promotes membrane stability without comprising membrane fluidity. Given this important cellular role, cholesterol levels are tightly controlled at multiple levels. It has been clearly shown that cholesterol redistribution and depletion from the sperm membrane is a key part of the spermatozoon's preparation for fertilization. Some factors that regulate these events are described (e.g., bicarbonate, calcium) but the mechanisms underlying cholesterol export are poorly understood. How does a hydrophobic cholesterol molecule inserted in the sperm plasma membrane enter the energetically unfavorable aqueous surroundings? This review will provide an overview of knowledge in this area and highlight our gaps in understanding. The overall aim is to better understand cholesterol redistribution in the sperm plasma membrane, its relation to the possible activation of a cholesterol transporter and the role of cholesterol acceptors. Armed with such knowledge, sperm handling techniques can be adapted to better prepare spermatozoa for in vitro and in vivo fertilization.

  15. Na/K pump regulation of cardiac repolarization: insights from a systems biology approach

    KAUST Repository

    Bueno-Orovio, Alfonso

    2013-05-15

    The sodium-potassium pump is widely recognized as the principal mechanism for active ion transport across the cellular membrane of cardiac tissue, being responsible for the creation and maintenance of the transarcolemmal sodium and potassium gradients, crucial for cardiac cell electrophysiology. Importantly, sodium-potassium pump activity is impaired in a number of major diseased conditions, including ischemia and heart failure. However, its subtle ways of action on cardiac electrophysiology, both directly through its electrogenic nature and indirectly via the regulation of cell homeostasis, make it hard to predict the electrophysiological consequences of reduced sodium-potassium pump activity in cardiac repolarization. In this review, we discuss how recent studies adopting the systems biology approach, through the integration of experimental and modeling methodologies, have identified the sodium-potassium pump as one of the most important ionic mechanisms in regulating key properties of cardiac repolarization and its rate dependence, from subcellular to whole organ levels. These include the role of the pump in the biphasic modulation of cellular repolarization and refractoriness, the rate control of intracellular sodium and calcium dynamics and therefore of the adaptation of repolarization to changes in heart rate, as well as its importance in regulating pro-arrhythmic substrates through modulation of dispersion of repolarization and restitution. Theoretical findings are consistent across a variety of cell types and species including human, and widely in agreement with experimental findings. The novel insights and hypotheses on the role of the pump in cardiac electrophysiology obtained through this integrative approach could eventually lead to novel therapeutic and diagnostic strategies. © 2013 Springer-Verlag Berlin Heidelberg.

  16. Glycosylation of Sodium/Iodide Symporter (NIS) Regulates Its Membrane Translocation and Radioiodine Uptake

    OpenAIRE

    Taemoon Chung; Hyewon Youn; Chan Joo Yeom; Keon Wook Kang; June-Key Chung

    2015-01-01

    Purpose Human sodium/iodide symporter (hNIS) protein is a membrane glycoprotein that transports iodide ions into thyroid cells. The function of this membrane protein is closely regulated by post-translational glycosylation. In this study, we measured glycosylation-mediated changes in subcellular location of hNIS and its function of iodine uptake. Methods HeLa cells were stably transfected with hNIS/tdTomato fusion gene in order to monitor the expression of hNIS. Cellular localization of hNIS ...

  17. The Balance of Fluid and Osmotic Pressures across Active Biological Membranes with Application to the Corneal Endothelium.

    Directory of Open Access Journals (Sweden)

    Xi Cheng

    Full Text Available The movement of fluid and solutes across biological membranes facilitates the transport of nutrients for living organisms and maintains the fluid and osmotic pressures in biological systems. Understanding the pressure balances across membranes is crucial for studying fluid and electrolyte homeostasis in living systems, and is an area of active research. In this study, a set of enhanced Kedem-Katchalsky (KK equations is proposed to describe fluxes of water and solutes across biological membranes, and is applied to analyze the relationship between fluid and osmotic pressures, accounting for active transport mechanisms that propel substances against their concentration gradients and for fixed charges that alter ionic distributions in separated environments. The equilibrium analysis demonstrates that the proposed theory recovers the Donnan osmotic pressure and can predict the correct fluid pressure difference across membranes, a result which cannot be achieved by existing KK theories due to the neglect of fixed charges. The steady-state analysis on active membranes suggests a new pressure mechanism which balances the fluid pressure together with the osmotic pressure. The source of this pressure arises from active ionic fluxes and from interactions between solvent and solutes in membrane transport. We apply the proposed theory to study the transendothelial fluid pressure in the in vivo cornea, which is a crucial factor maintaining the hydration and transparency of the tissue. The results show the importance of the proposed pressure mechanism in mediating stromal fluid pressure and provide a new interpretation of the pressure modulation mechanism in the in vivo cornea.

  18. Outer membrane vesicles mediate transport of biologically active Vibrio cholerae cytolysin (VCC from V. cholerae strains.

    Directory of Open Access Journals (Sweden)

    Sridhar Elluri

    Full Text Available Outer membrane vesicles (OMVs released from Gram-negative bacteria can serve as vehicles for the translocation of virulence factors. Vibrio cholerae produce OMVs but their putative role in translocation of effectors involved in pathogenesis has not been well elucidated. The V. cholerae cytolysin (VCC, is a pore-forming toxin that lyses target eukaryotic cells by forming transmembrane oligomeric β-barrel channels. It is considered a potent toxin that contributes to V. cholerae pathogenesis. The mechanisms involved in the secretion and delivery of the VCC have not been extensively studied.OMVs from V. cholerae strains were isolated and purified using a differential centrifugation procedure and Optiprep centrifugation. The ultrastructure and the contents of OMVs were examined under the electron microscope and by immunoblot analyses respectively. We demonstrated that VCC from V. cholerae strain V:5/04 was secreted in association with OMVs and the release of VCC via OMVs is a common feature among V. cholerae strains. The biological activity of OMV-associated VCC was investigated using contact hemolytic assay and epithelial cell cytotoxicity test. It showed toxic activity on both red blood cells and epithelial cells. Our results indicate that the OMVs architecture might play a role in stability of VCC and thereby can enhance its biological activities in comparison with the free secreted VCC. Furthermore, we tested the role of OMV-associated VCC in host cell autophagy signalling using confocal microscopy and immunoblot analysis. We observed that OMV-associated VCC triggered an autophagy response in the target cell and our findings demonstrated for the first time that autophagy may operate as a cellular defence mechanism against an OMV-associated bacterial virulence factor.Biological assays of OMVs from the V. cholerae strain V:5/04 demonstrated that OMV-associated VCC is indeed biologically active and induces toxicity on mammalian cells and

  19. A novel membrane distillation-thermophilic bioreactor system: biological stability and trace organic compound removal.

    Science.gov (United States)

    Wijekoon, Kaushalya C; Hai, Faisal I; Kang, Jinguo; Price, William E; Guo, Wenshan; Ngo, Hao H; Cath, Tzahi Y; Nghiem, Long D

    2014-05-01

    The removal of trace organic compounds (TrOCs) by a novel membrane distillation-thermophilic bioreactor (MDBR) system was examined. Salinity build-up and the thermophilic conditions to some extent adversely impacted the performance of the bioreactor, particularly the removal of total nitrogen and recalcitrant TrOCs. While most TrOCs were well removed by the thermophilic bioreactor, compounds containing electron withdrawing functional groups in their molecular structure were recalcitrant to biological treatment and their removal efficiency by the thermophilic bioreactor was low (0-53%). However, the overall performance of the novel MDBR system with respect to the removal of total organic carbon, total nitrogen, and TrOCs was high and was not significantly affected by the conditions of the bioreactor. All TrOCs investigated here were highly removed (>95%) by the MDBR system. Biodegradation, sludge adsorption, and rejection by MD contribute to the removal of TrOCs by MDBR treatment.

  20. Nonenzymatic Reactions above Phospholipid Surfaces of Biological Membranes: Reactivity of Phospholipids and Their Oxidation Derivatives.

    Science.gov (United States)

    Solís-Calero, Christian; Ortega-Castro, Joaquín; Frau, Juan; Muñoz, Francisco

    2015-01-01

    Phospholipids play multiple and essential roles in cells, as components of biological membranes. Although phospholipid bilayers provide the supporting matrix and surface for many enzymatic reactions, their inherent reactivity and possible catalytic role have not been highlighted. As other biomolecules, phospholipids are frequent targets of nonenzymatic modifications by reactive substances including oxidants and glycating agents which conduct to the formation of advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs). There are some theoretical studies about the mechanisms of reactions related to these processes on phosphatidylethanolamine surfaces, which hypothesize that cell membrane phospholipids surface environment could enhance some reactions through a catalyst effect. On the other hand, the phospholipid bilayers are susceptible to oxidative damage by oxidant agents as reactive oxygen species (ROS). Molecular dynamics simulations performed on phospholipid bilayers models, which include modified phospholipids by these reactions and subsequent reactions that conduct to formation of ALEs and AGEs, have revealed changes in the molecular interactions and biophysical properties of these bilayers as consequence of these reactions. Then, more studies are desirable which could correlate the biophysics of modified phospholipids with metabolism in processes such as aging and diseases such as diabetes, atherosclerosis, and Alzheimer's disease.

  1. Innovative hybrid biological reactors using membranes; Reactores biologico hibrido innovadores utilizando membranas

    Energy Technology Data Exchange (ETDEWEB)

    Diez, R.; Esteban-Garcia, A. L.; Florio, L. de; Rodriguez-Hernandez, L.; Tejero, I.

    2011-07-01

    In this paper we present two lines of research on hybrid reactors including the use of membranes, although with different functions: RBPM, biofilm reactors and membranes filtration RBSOM, supported biofilm reactors and oxygen membranes. (Author) 14 refs.

  2. In situ single molecule imaging of cell membranes: linking basic nanotechniques to cell biology, immunology and medicine.

    Science.gov (United States)

    Pi, Jiang; Jin, Hua; Yang, Fen; Chen, Zheng W; Cai, Jiye

    2014-11-01

    The cell membrane, which consists of a viscous phospholipid bilayer, different kinds of proteins and various nano/micrometer-sized domains, plays a very important role in ensuring the stability of the intracellular environment and the order of cellular signal transductions. Exploring the precise cell membrane structure and detailed functions of the biomolecules in a cell membrane would be helpful to understand the underlying mechanisms involved in cell membrane signal transductions, which could further benefit research into cell biology, immunology and medicine. The detection of membrane biomolecules at the single molecule level can provide some subtle information about the molecular structure and the functions of the cell membrane. In particular, information obtained about the molecular mechanisms and other information at the single molecule level are significantly different from that detected from a large amount of biomolecules at the large-scale through traditional techniques, and can thus provide a novel perspective for the study of cell membrane structures and functions. However, the precise investigations of membrane biomolecules prompts researchers to explore cell membranes at the single molecule level by the use of in situ imaging methods, as the exact conformation and functions of biomolecules are highly controlled by the native cellular environment. Recently, the in situ single molecule imaging of cell membranes has attracted increasing attention from cell biologists and immunologists. The size of biomolecules and their clusters on the cell surface are set at the nanoscale, which makes it mandatory to use high- and super-resolution imaging techniques to realize the in situ single molecule imaging of cell membranes. In the past few decades, some amazing imaging techniques and instruments with super resolution have been widely developed for molecule imaging, which can also be further employed for the in situ single molecule imaging of cell membranes. In

  3. The Plasma Membrane Ca2+ ATPase and the Plasma Membrane Sodium Calcium Exchanger Cooperate in the Regulation of Cell Calcium

    Science.gov (United States)

    Brini, Marisa; Carafoli, Ernesto

    2011-01-01

    Calcium is an ambivalent signal: it is essential for the correct functioning of cell life, but may also become dangerous to it. The plasma membrane Ca2+ ATPase (PMCA) and the plasma membrane Na+/Ca2+ exchanger (NCX) are the two mechanisms responsible for Ca2+ extrusion. The NCX has low Ca2+ affinity but high capacity for Ca2+ transport, whereas the PMCA has a high Ca2+ affinity but low transport capacity for it. Thus, traditionally, the PMCA pump has been attributed a housekeeping role in maintaining cytosolic Ca2+, and the NCX the dynamic role of counteracting large cytosolic Ca2+ variations (especially in excitable cells). This view of the roles of the two Ca2+ extrusion systems has been recently revised, as the specific functional properties of the numerous PMCA isoforms and splicing variants suggests that they may have evolved to cover both the basal Ca2+ regulation (in the 100 nM range) and the Ca2+ transients generated by cell stimulation (in the μM range). PMID:21421919

  4. Report on the 53rd Annual Meeting of the Canadian Society of Biochemistry, Molecular and Cellular Biology: "Membrane Proteins in Health and Disease".

    Science.gov (United States)

    Reithmeier, Reinhart A F; Casey, Joseph R

    2011-04-01

    The meeting "Membrane Proteins in Health and Disease" featured 6 sessions and 2 satellite meetings. At the opening session, Gunnar von Heijne delivered a plenary lecture entitled Insertion of Membrane Proteins into the Endoplasmic Reticulum. The following session topics were Membrane Protein Trafficking and Folding, Regulation of Membrane Proteins, Membrane Protein Structure, Membrane Proteins in Diverse Species, and Membrane Proteins and Diseases. The satellite meetings discussed bicarbonate transporters and Na+/H+ exchangers. Together the 21 lectures and 106 posters presented at the meeting spanned the full spectrum of current research into membrane protein structure and function.

  5. Membrane plasmalogen composition and cellular cholesterol regulation: a structure activity study

    Directory of Open Access Journals (Sweden)

    Su-Myat Khine K

    2010-06-01

    Full Text Available Abstract Background Disrupted cholesterol regulation leading to increased circulating and membrane cholesterol levels is implicated in many age-related chronic diseases such as cardiovascular disease (CVD, Alzheimer's disease (AD, and cancer. In vitro and ex vivo cellular plasmalogen deficiency models have been shown to exhibit impaired intra- and extra-cellular processing of cholesterol. Furthermore, depleted brain plasmalogens have been implicated in AD and serum plasmalogen deficiencies have been linked to AD, CVD, and cancer. Results Using plasmalogen deficient (NRel-4 and plasmalogen sufficient (HEK293 cells we investigated the effect of species-dependent plasmalogen restoration/augmentation on membrane cholesterol processing. The results of these studies indicate that the esterification of cholesterol is dependent upon the amount of polyunsaturated fatty acid (PUFA-containing ethanolamine plasmalogen (PlsEtn present in the membrane. We further elucidate that the concentration-dependent increase in esterified cholesterol observed with PUFA-PlsEtn was due to a concentration-dependent increase in sterol-O-acyltransferase-1 (SOAT1 levels, an observation not reproduced by 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA reductase inhibition. Conclusion The present study describes a novel mechanism of cholesterol regulation that is consistent with clinical and epidemiological studies of cholesterol, aging and disease. Specifically, the present study describes how selective membrane PUFA-PlsEtn enhancement can be achieved using 1-alkyl-2-PUFA glycerols and through this action reduce levels of total and free cholesterol in cells.

  6. Appoptosin interacts with mitochondrial outer-membrane fusion proteins and regulates mitochondrial morphology.

    Science.gov (United States)

    Zhang, Cuilin; Shi, Zhun; Zhang, Lingzhi; Zhou, Zehua; Zheng, Xiaoyuan; Liu, Guiying; Bu, Guojun; Fraser, Paul E; Xu, Huaxi; Zhang, Yun-Wu

    2016-03-01

    Mitochondrial morphology is regulated by fusion and fission machinery. Impaired mitochondria dynamics cause various diseases, including Alzheimer's disease. Appoptosin (encoded by SLC25A38) is a mitochondrial carrier protein that is located in the mitochondrial inner membrane. Appoptosin overexpression causes overproduction of reactive oxygen species (ROS) and caspase-dependent apoptosis, whereas appoptosin downregulation abolishes β-amyloid-induced mitochondrial fragmentation and neuronal death during Alzheimer's disease. Herein, we found that overexpression of appoptosin resulted in mitochondrial fragmentation in a manner independent of its carrier function, ROS production or caspase activation. Although appoptosin did not affect levels of mitochondrial outer-membrane fusion (MFN1 and MFN2), inner-membrane fusion (OPA1) and fission [DRP1 (also known as DNM1L) and FIS1] proteins, appoptosin interacted with MFN1 and MFN2, as well as with the mitochondrial ubiquitin ligase MITOL (also known as MARCH5) but not OPA1, FIS1 or DRP1. Appoptosin overexpression impaired the interaction between MFN1 and MFN2, and mitochondrial fusion. By contrast, co-expression of MFN1, MITOL and a dominant-negative form of DRP1, DRP1(K38A), partially rescued appoptosin-induced mitochondrial fragmentation and apoptosis, whereas co-expression of FIS1 aggravated appoptosin-induced apoptosis. Together, our results demonstrate that appoptosin can interact with mitochondrial outer-membrane fusion proteins and regulates mitochondrial morphology.

  7. Acid sphingomyelinase activity is regulated by membrane lipids and facilitates cholesterol transfer by NPC2.

    Science.gov (United States)

    Oninla, Vincent O; Breiden, Bernadette; Babalola, Jonathan O; Sandhoff, Konrad

    2014-12-01

    During endocytosis, membrane components move to intraluminal vesicles of the endolysosomal compartment for digestion. At the late endosomes, cholesterol is sorted out mainly by two sterol-binding proteins, Niemann-Pick protein type C (NPC)1 and NPC2. To study the NPC2-mediated intervesicular cholesterol transfer, we developed a liposomal assay system. (Abdul-Hammed, M., B. Breiden, M. A. Adebayo, J. O. Babalola, G. Schwarzmann, and K. Sandhoff. 2010. Role of endosomal membrane lipids and NPC2 in cholesterol transfer and membrane fusion. J. Lipid Res. 51: 1747-1760.) Anionic lipids stimulate cholesterol transfer between liposomes while SM inhibits it, even in the presence of anionic bis(monoacylglycero)phosphate (BMP). Preincubation of vesicles containing SM with acid sphingomyelinase (ASM) (SM phosphodiesterase, EC 3.1.4.12) results in hydrolysis of SM to ceramide (Cer), which enhances cholesterol transfer. Besides SM, ASM also cleaves liposomal phosphatidylcholine. Anionic phospholipids derived from the plasma membrane (phosphatidylglycerol and phosphatidic acid) stimulate SM and phosphatidylcholine hydrolysis by ASM more effectively than BMP, which is generated during endocytosis. ASM-mediated hydrolysis of liposomal SM was also stimulated by incorporation of diacylglycerol (DAG), Cer, and free fatty acids into the liposomal membranes. Conversely, phosphatidylcholine hydrolysis was inhibited by incorporation of cholesterol, Cer, DAG, monoacylglycerol, and fatty acids. Our data suggest that SM degradation by ASM is required for physiological secretion of cholesterol from the late endosomal compartment, and is a key regulator of endolysosomal lipid digestion.

  8. HIV-1 matrix dependent membrane targeting is regulated by Gag mRNA trafficking.

    Directory of Open Access Journals (Sweden)

    Jing Jin

    Full Text Available Retroviral Gag polyproteins are necessary and sufficient for virus budding. Productive HIV-1 Gag assembly takes place at the plasma membrane. However, little is known about the mechanisms by which thousands of Gag molecules are targeted to the plasma membrane. Using a bimolecular fluorescence complementation (BiFC assay, we recently reported that the cellular sites and efficiency of HIV-1 Gag assembly depend on the precise pathway of Gag mRNA export from the nucleus, known to be mediated by Rev. Here we describe an assembly deficiency in human cells for HIV Gag whose expression depends on hepatitis B virus (HBV post-transcriptional regulatory element (PRE mediated-mRNA nuclear export. PRE-dependent HIV Gag expressed well in human cells, but assembled with slower kinetics, accumulated intracellularly, and failed to associate with a lipid raft compartment where the wild-type Rev-dependent HIV-1 Gag efficiently assembles. Surprisingly, assembly and budding of PRE-dependent HIV Gag in human cells could be rescued in trans by co-expression of Rev-dependent Gag that provides correct membrane targeting signals, or in cis by replacing HIV matrix (MA with other membrane targeting domains. Taken together, our results demonstrate deficient membrane targeting of PRE-dependent HIV-1 Gag and suggest that HIV MA function is regulated by the trafficking pathway of the encoding mRNA.

  9. Urothelial endocytic vesicle recycling and lysosomal degradative pathway regulated by lipid membrane composition.

    Science.gov (United States)

    Grasso, E J; Calderón, R O

    2013-02-01

    lipid composition on sorting of the endocytosed material. This suggests that changes in the membrane organization can be one of the underlying mechanisms for regulating the endocytosis/exocytosis processes and membrane intracellular trafficking.

  10. Retaining activity of enzymes after capture and extraction within a single-drop of biological fluid using immunoaffinity membranes.

    Science.gov (United States)

    Shimazaki, Youji; Sato, Yuki

    2016-05-15

    The purpose of this study was the measurement of enzyme activity within a single-drop of biological fluid after micropurification. Esterase and lactate dehydrogenase (LDH) retained their enzymatic activities after being captured by membrane-immobilized antibodies, which were prepared by non-denaturing two-dimensional electrophoresis, transferred to polyvinylidene difluoride and then stained by Ponceau S. The activities of both enzymes were also measured after being captured by antibodies and biotinylated antibodies bound to membrane-immobilized protein A or avidin, respectively. After esterase and LDH were captured from biological samples by membrane-immobilized protein A or avidin, their activities were semi-quantitatively measured on the surface of the membrane using fluorescence determination. More than 51% of enzyme activities were retained even after the enzymes were captured by biotinylated antibody bound to membrane-immobilized avidin and eluted by rinsing with 5μL of 1% Triton X-100, compared with the activities of the enzyme on the immunoaffinity membrane.

  11. Construction of membrane-bound artificial cells using microfluidics: a new frontier in bottom-up synthetic biology.

    Science.gov (United States)

    Elani, Yuval

    2016-06-15

    The quest to construct artificial cells from the bottom-up using simple building blocks has received much attention over recent decades and is one of the grand challenges in synthetic biology. Cell mimics that are encapsulated by lipid membranes are a particularly powerful class of artificial cells due to their biocompatibility and the ability to reconstitute biological machinery within them. One of the key obstacles in the field centres on the following: how can membrane-based artificial cells be generated in a controlled way and in high-throughput? In particular, how can they be constructed to have precisely defined parameters including size, biomolecular composition and spatial organization? Microfluidic generation strategies have proved instrumental in addressing these questions. This article will outline some of the major principles underpinning membrane-based artificial cells and their construction using microfluidics, and will detail some recent landmarks that have been achieved.

  12. Enhancement in biological response of Ag-nano composite polymer membranes using plasma treatment for fabrication of efficient bio materials

    Science.gov (United States)

    Agrawal, Narendra Kumar; Sharma, Tamanna Kumari; Chauhan, Manish; Agarwal, Ravi; Vijay, Y. K.; Swami, K. C.

    2016-05-01

    Biomaterials are nonviable material used in medical devices, intended to interact with biological systems, which are becoming necessary for the development of artificial material for biological systems such as artificial skin diaphragm, valves for heart and kidney, lenses for eye etc. Polymers having novel properties like antibacterial, antimicrobial, high adhesion, blood compatibility and wettability are most suitable for synthesis of biomaterial, but all of these properties does not exist in any natural or artificial polymeric material. Nano particles and plasma treatment can offer these properties to the polymers. Hence a new nano-biomaterial has been developed by modifying the surface and chemical properties of Ag nanocomposite polymer membranes (NCPM) by Argon ion plasma treatment. These membranes were characterized using different techniques for surface and chemical modifications occurred. Bacterial adhesion and wettability were also tested for these membranes, to show direct use of this new class of nano-biomaterial for biomedical applications.

  13. Synthetic biology: regulating industry uses of new biotechnologies.

    Science.gov (United States)

    Erickson, Brent; Singh, Rina; Winters, Paul

    2011-09-02

    In our view, synthetic biology is an extension of the continuum of genetic science that has been used safely for more than 40 years by the biotechnology industry in the development of commercial products. Examples of synthetic biology use by biotechnology companies illustrate the potential to substantially reduce research and development time and to increase speed to market. Improvements in the speed and cost of DNA synthesis are enabling scientists to design modified bacterial chromosomes that can be used in the production of renewable chemicals, biofuels, bioproducts, renewable specialty chemicals, pharmaceutical intermediates, fine chemicals, food ingredients, and health care products. Regulatory options should support innovation and commercial development of new products while protecting the public from potential harms.

  14. Regulation of the membrane insertion and conductance activity of the metamorphic chloride intracellular channel protein CLIC1 by cholesterol.

    Directory of Open Access Journals (Sweden)

    Stella M Valenzuela

    Full Text Available The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer.

  15. Regulation of the membrane insertion and conductance activity of the metamorphic chloride intracellular channel protein CLIC1 by cholesterol.

    Science.gov (United States)

    Valenzuela, Stella M; Alkhamici, Heba; Brown, Louise J; Almond, Oscar C; Goodchild, Sophia C; Carne, Sonia; Curmi, Paul M G; Holt, Stephen A; Cornell, Bruce A

    2013-01-01

    The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer.

  16. Regulation of membrane excitability: a convergence on voltage-gated sodium conductance.

    Science.gov (United States)

    Lin, Wei-Hsiang; Baines, Richard A

    2015-02-01

    The voltage-gated sodium channel (Nav) plays a key role in regulation of neuronal excitability. Aberrant regulation of Nav expression and/or function can result in an imbalance in neuronal activity which can progress to epilepsy. Regulation of Nav activity is achieved by coordination of a multitude of mechanisms including RNA alternative splicing and translational repression. Understanding of these regulatory mechanisms is complicated by extensive genetic redundancy: the mammalian genome encodes ten Navs. By contrast, the genome of the fruitfly, Drosophila melanogaster, contains just one Nav homologue, encoded by paralytic (DmNa v ). Analysis of splicing in DmNa v shows variants exhibit distinct gating properties including varying magnitudes of persistent sodium current (INaP). Splicing by Pasilla, an identified RNA splicing factor, alters INaP magnitude as part of an activity-dependent mechanism. Enhanced INaP promotes membrane hyperexcitability that is associated with seizure-like behaviour in Drosophila. Nova-2, a mammalian Pasilla homologue, has also been linked to splicing of Navs and, moreover, mouse gene knockouts display seizure-like behaviour.Expression level of Navs is also regulated through a mechanism of translational repression in both flies and mammals. The translational repressor Pumilio (Pum) can bind to Na v transcripts and repress the normal process of translation, thus regulating sodium current (INa) density in neurons. Pum2-deficient mice exhibit spontaneous EEG abnormalities. Taken together, aberrant regulation of Nav function and/or expression is often epileptogenic. As such, a better understanding of regulation of membrane excitability through RNA alternative splicing and translational repression of Navs should provide new leads to treat epilepsy.

  17. Tuning Liposome Membrane Permeability by Competitive Peptide Dimerization and Partitioning-Folding Interactions Regulated by Proteolytic Activity.

    Science.gov (United States)

    Lim, Seng Koon; Sandén, Camilla; Selegård, Robert; Liedberg, Bo; Aili, Daniel

    2016-01-01

    Membrane active peptides are of large interest for development of drug delivery vehicles and therapeutics for treatment of multiple drug resistant infections. Lack of specificity can be detrimental and finding routes to tune specificity and activity of membrane active peptides is vital for improving their therapeutic efficacy and minimize harmful side effects. We describe a de novo designed membrane active peptide that partition into lipid membranes only when specifically and covalently anchored to the membrane, resulting in pore-formation. Dimerization with a complementary peptide efficiently inhibits formation of pores. The effect can be regulated by proteolytic digestion of the inhibitory peptide by the matrix metalloproteinase MMP-7, an enzyme upregulated in many malignant tumors. This system thus provides a precise and specific route for tuning the permeability of lipid membranes and a novel strategy for development of recognition based membrane active peptides and indirect enzymatically controlled release of liposomal cargo.

  18. Tuning Liposome Membrane Permeability by Competitive Peptide Dimerization and Partitioning-Folding Interactions Regulated by Proteolytic Activity

    Science.gov (United States)

    Lim, Seng Koon; Sandén, Camilla; Selegård, Robert; Liedberg, Bo; Aili, Daniel

    2016-02-01

    Membrane active peptides are of large interest for development of drug delivery vehicles and therapeutics for treatment of multiple drug resistant infections. Lack of specificity can be detrimental and finding routes to tune specificity and activity of membrane active peptides is vital for improving their therapeutic efficacy and minimize harmful side effects. We describe a de novo designed membrane active peptide that partition into lipid membranes only when specifically and covalently anchored to the membrane, resulting in pore-formation. Dimerization with a complementary peptide efficiently inhibits formation of pores. The effect can be regulated by proteolytic digestion of the inhibitory peptide by the matrix metalloproteinase MMP-7, an enzyme upregulated in many malignant tumors. This system thus provides a precise and specific route for tuning the permeability of lipid membranes and a novel strategy for development of recognition based membrane active peptides and indirect enzymatically controlled release of liposomal cargo.

  19. "Do as I say!" : parenting and the biology of child self-regulation

    NARCIS (Netherlands)

    Kok, Rianne

    2013-01-01

    The development of self-regulation is one of the major challenges of a child’s healthy development. In the current thesis, the contribution and interplay of parental and biological factors in the development of self-regulation in preschoolers are studied in a large population-based cohort, the Gener

  20. Receptor dimer stabilization by hierarchical plasma membrane microcompartments regulates cytokine signaling.

    Science.gov (United States)

    You, Changjiang; Marquez-Lago, Tatiana T; Richter, Christian Paolo; Wilmes, Stephan; Moraga, Ignacio; Garcia, K Christopher; Leier, André; Piehler, Jacob

    2016-12-01

    The interaction dynamics of signaling complexes is emerging as a key determinant that regulates the specificity of cellular responses. We present a combined experimental and computational study that quantifies the consequences of plasma membrane microcompartmentalization for the dynamics of type I interferon receptor complexes. By using long-term dual-color quantum dot (QD) tracking, we found that the lifetime of individual ligand-induced receptor heterodimers depends on the integrity of the membrane skeleton (MSK), which also proved important for efficient downstream signaling. By pair correlation tracking and localization microscopy as well as by fast QD tracking, we identified a secondary confinement within ~300-nm-sized zones. A quantitative spatial stochastic diffusion-reaction model, entirely parameterized on the basis of experimental data, predicts that transient receptor confinement by the MSK meshwork allows for rapid reassociation of dissociated receptor dimers. Moreover, the experimentally observed apparent stabilization of receptor dimers in the plasma membrane was reproduced by simulations of a refined, hierarchical compartment model. Our simulations further revealed that the two-dimensional association rate constant is a key parameter for controlling the extent of MSK-mediated stabilization of protein complexes, thus ensuring the specificity of this effect. Together, experimental evidence and simulations support the hypothesis that passive receptor confinement by MSK-based microcompartmentalization promotes maintenance of signaling complexes in the plasma membrane.

  1. Deacylation on the matrix side of the mitochondrial inner membrane regulates cardiolipin remodeling.

    Science.gov (United States)

    Baile, Matthew G; Whited, Kevin; Claypool, Steven M

    2013-06-01

    The mitochondrial-specific lipid cardiolipin (CL) is required for numerous processes therein. After its synthesis on the matrix-facing leaflet of the inner membrane (IM), CL undergoes acyl chain remodeling to achieve its final form. In yeast, this process is completed by the transacylase tafazzin, which associates with intermembrane space (IMS)-facing membrane leaflets. Mutations in TAZ1 result in the X-linked cardiomyopathy Barth syndrome. Amazingly, despite this clear pathophysiological association, the physiological importance of CL remodeling is unresolved. In this paper, we show that the lipase initiating CL remodeling, Cld1p, is associated with the matrix-facing leaflet of the mitochondrial IM. Thus monolysocardiolipin generated by Cld1p must be transported to IMS-facing membrane leaflets to gain access to tafazzin, identifying a previously unknown step required for CL remodeling. Additionally, we show that Cld1p is the major site of regulation in CL remodeling; and that, like CL biosynthesis, CL remodeling is augmented in growth conditions requiring mitochondrially produced energy. However, unlike CL biosynthesis, dissipation of the mitochondrial membrane potential stimulates CL remodeling, identifying a novel feedback mechanism linking CL remodeling to oxidative phosphorylation capacity.

  2. Quantitative analysis of membrane trafficking in regulation of Cdc42 polarity.

    Science.gov (United States)

    Watson, Leah J; Rossi, Guendalina; Brennwald, Patrick

    2014-12-01

    Vesicle delivery of Cdc42 has been proposed as an important mechanism for generating and maintaining Cdc42 polarity at the plasma membrane. This mechanism requires the density of Cdc42 on secretory vesicles to be equal to or higher than the plasma membrane polarity cap. Using a novel method to estimate Cdc42 levels on post-Golgi secretory vesicles in intact yeast cells, we: (1) determined that endocytosis plays an important role in Cdc42's association with secretory vesicles (2) found that a GFP-tag placed on the N-terminus of Cdc42 negatively impacts this vesicle association and (3) quantified the surface densities of Cdc42 on post-Golgi vesicles which revealed that the vesicle density of Cdc42 is three times more dilute than that at the polarity cap. This work suggests that the immediate consequence of secretory vesicle fusion with the plasma membrane polarity cap is to dilute the local Cdc42 surface density. This provides strong support for the model in which vesicle trafficking acts to negatively regulate Cdc42 polarity on the cell surface while also providing a means to recycle Cdc42 between the cell surface and internal membrane locations.

  3. Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag

    Directory of Open Access Journals (Sweden)

    Melanie Friedrich

    2016-04-01

    Full Text Available The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (l- domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane.

  4. Glutamic Acid Residues in HIV-1 p6 Regulate Virus Budding and Membrane Association of Gag.

    Science.gov (United States)

    Friedrich, Melanie; Setz, Christian; Hahn, Friedrich; Matthaei, Alina; Fraedrich, Kirsten; Rauch, Pia; Henklein, Petra; Traxdorf, Maximilian; Fossen, Torgils; Schubert, Ulrich

    2016-04-25

    The HIV-1 Gag p6 protein regulates the final abscission step of nascent virions from the cell membrane by the action of its two late (L-) domains, which recruit Tsg101 and ALIX, components of the ESCRT system. Even though p6 consists of only 52 amino acids, it is encoded by one of the most polymorphic regions of the HIV-1 gag gene and undergoes various posttranslational modifications including sumoylation, ubiquitination, and phosphorylation. In addition, it mediates the incorporation of the HIV-1 accessory protein Vpr into budding virions. Despite its small size, p6 exhibits an unusually high charge density. In this study, we show that mutation of the conserved glutamic acids within p6 increases the membrane association of Pr55 Gag followed by enhanced polyubiquitination and MHC-I antigen presentation of Gag-derived epitopes, possibly due to prolonged exposure to membrane bound E3 ligases. The replication capacity of the total glutamic acid mutant E0A was almost completely impaired, which was accompanied by defective virus release that could not be rescued by ALIX overexpression. Altogether, our data indicate that the glutamic acids within p6 contribute to the late steps of viral replication and may contribute to the interaction of Gag with the plasma membrane.

  5. Alternative routes to the cell surface underpin insulin-regulated membrane trafficking of GLUT4.

    Science.gov (United States)

    Kioumourtzoglou, Dimitrios; Pryor, Paul R; Gould, Gwyn W; Bryant, Nia J

    2015-07-15

    Insulin-stimulated delivery of glucose transporters (GLUT4, also known as SLC2A4) from specialized intracellular GLUT4 storage vesicles (GSVs) to the surface of fat and muscle cells is central to whole-body glucose regulation. This translocation and subsequent internalization of GLUT4 back into intracellular stores transits through numerous small membrane-bound compartments (internal GLUT4-containing vesicles; IGVs) including GSVs, but the function of these different compartments is not clear. Cellugyrin (also known as synaptogyrin-2) and sortilin define distinct populations of IGV; sortilin-positive IGVs represent GSVs, but the function of cellugyrin-containing IGVs is unknown. Here, we demonstrate a role for cellugyrin in intracellular sequestration of GLUT4 in HeLa cells and have used a proximity ligation assay to follow changes in pairwise associations between cellugyrin, sortilin, GLUT4 and membrane trafficking machinery following insulin-stimulation of 3T3-L1 adipoctyes. Our data suggest that insulin stimulates traffic from cellugyrin-containing to sortilin-containing membranes, and that cellugyrin-containing IGVs provide an insulin-sensitive reservoir to replenish GSVs following insulin-stimulated exocytosis of GLUT4. Furthermore, our data support the existence of a pathway from cellugyrin-containing membranes to the surface of 3T3-L1 adipocytes that bypasses GSVs under basal conditions, and that insulin diverts traffic away from this into GSVs.

  6. Independent regulation of reovirus membrane penetration and apoptosis by the mu1 phi domain.

    Directory of Open Access Journals (Sweden)

    Pranav Danthi

    2008-12-01

    Full Text Available Apoptosis plays an important role in the pathogenesis of reovirus encephalitis. Reovirus outer-capsid protein mu1, which functions to penetrate host cell membranes during viral entry, is the primary regulator of apoptosis following reovirus infection. Ectopic expression of full-length and truncated forms of mu1 indicates that the mu1 phi domain is sufficient to elicit a cell death response. To evaluate the contribution of the mu1 phi domain to the induction of apoptosis following reovirus infection, phi mutant viruses were generated by reverse genetics and analyzed for the capacity to penetrate cell membranes and elicit apoptosis. We found that mutations in phi diminish reovirus membrane penetration efficiency by preventing conformational changes that lead to generation of key reovirus entry intermediates. Independent of effects on membrane penetration, amino acid substitutions in phi affect the apoptotic potential of reovirus, suggesting that phi initiates apoptosis subsequent to cytosolic delivery. In comparison to wild-type virus, apoptosis-defective phi mutant viruses display diminished neurovirulence following intracranial inoculation of newborn mice. These results indicate that the phi domain of mu1 plays an important regulatory role in reovirus-induced apoptosis and disease.

  7. ACKR2: An Atypical Chemokine Receptor Regulating Lymphatic Biology

    Science.gov (United States)

    Bonavita, Ornella; Mollica Poeta, Valeria; Setten, Elisa; Massara, Matteo; Bonecchi, Raffaella

    2017-01-01

    The lymphatic system plays an important role in the induction of the immune response by transporting antigens, inflammatory mediators, and leukocytes from peripheral tissues to draining lymph nodes. It is emerging that lymphatic endothelial cells (LECs) are playing an active role in this context via the expression of chemokines, inflammatory mediators promoting cell migration, and chemokine receptors. Particularly, LECs express atypical chemokine receptors (ACKRs), which are unable to promote conventional signaling and cell migration while they are involved in the regulation of chemokine availability. Here, we provide a summary of the data on the role of ACKR2 expressed by lymphatics, indicating an essential role for this ACKRs in the regulation of the inflammation and the immune response in different pathological conditions, including infection, allergy, and cancer. PMID:28123388

  8. Src regulates membrane trafficking of the Kv3.1b channel.

    Science.gov (United States)

    Bae, Seong Han; Kim, Dong Hyun; Shin, Seok Kyo; Choi, Jin Sung; Park, Kang-Sik

    2014-01-03

    The Kv3.1 channel plays a crucial role in regulating the high-frequency firing properties of neurons. Here, we determined whether Src regulates the subcellular distributions of the Kv3.1b channel. Co-expression of active Src induced a dramatic redistribution of Kv3.1b to the endoplasmic reticulum. Furthermore, co-expression of the Kv3.1b channel with active Src induced a remarkable decrease in the pool of Kv3.1b at the cell surface. Moreover, the co-expression of active Src results in a significant decrease in the peak current densities of the Kv3.1b channel, and a substantial alteration in the voltage dependence of its steady-state inactivation. Taken together, these results indicate that Src kinase may play an important role in regulating membrane trafficking of Kv3.1b channels.

  9. Isolation, Characterization and Biological Properties of Membrane Vesicles Produced by the Swine Pathogen Streptococcus suis.

    Directory of Open Access Journals (Sweden)

    Bruno Haas

    Full Text Available Streptococcus suis, more particularly serotype 2, is a major swine pathogen and an emerging zoonotic agent worldwide that mainly causes meningitis, septicemia, endocarditis, and pneumonia. Although several potential virulence factors produced by S. suis have been identified in the last decade, the pathogenesis of S. suis infections is still not fully understood. In the present study, we showed that S. suis produces membrane vesicles (MVs that range in diameter from 13 to 130 nm and that appear to be coated by capsular material. A proteomic analysis of the MVs revealed that they contain 46 proteins, 9 of which are considered as proven or suspected virulence factors. Biological assays confirmed that S. suis MVs possess active subtilisin-like protease (SspA and DNase (SsnA. S. suis MVs degraded neutrophil extracellular traps, a property that may contribute to the ability of the bacterium to escape the host defense response. MVs also activated the nuclear factor-kappa B (NF-κB signaling pathway in both monocytes and macrophages, inducing the secretion of pro-inflammatory cytokines, which may in turn contribute to increase the permeability of the blood brain barrier. The present study brought evidence that S. suis MVs may play a role as a virulence factor in the pathogenesis of S. suis infections, and given their composition be an excellent candidate for vaccine development.

  10. Degradation of pharmaceuticals from membrane biological reactor sludge with Trametes versicolor.

    Science.gov (United States)

    Llorens-Blanch, Guillem; Badia-Fabregat, Marina; Lucas, Daniel; Rodriguez-Mozaz, Sara; Barceló, Damià; Pennanen, Taina; Caminal, Gloria; Blánquez, Paqui

    2015-02-01

    Emerging contaminants are a wide group of chemical products that are found at low concentrations in the environment. These contaminants can be either natural, e.g., estrogens, or synthetics, such as pesticides and pharmaceuticals, which can enter the environment through the water and sludge from wastewater treatment plants (WWTP). The growth of Trametes versicolor on membrane biological reactor (MBR) sludge in bioslurry systems at the Erlenmeyer scale was assessed and its capacity for removing pharmaceutical and personal care products (PPCPs) was evaluated. The ability of the fungus to remove hydrochlorothiazide (HZT) from liquid media cultures was initially assessed. Consequently, different bioslurry media (complete nutrient, glucose and no-nutrient addition) and conditions (sterile and non-sterile) were tested, and the removal of spiked HZT was monitored under each condition. The highest spiked HZT removal was assessed under non-sterile conditions without nutrient addition (93.2%). Finally, the removal assessment of a broad set of pharmaceuticals was performed in non-spiked bioslurry. Under non-sterile conditions, the fungus was able to completely degrade 12 out of the 28 drugs initially detected in the MBR sludge, achieving an overall degradation of 66.9%. Subsequent microbial analysis showed that the microbial diversity increased after 15 days of treatment, but there was still some T. versicolor in the bioslurry. Results showed that T. versicolor can be used to remove PPCPs in bioslurry systems under non-sterile conditions, without extra nutrients in the media, and in matrices as complex as an MBR sludge.

  11. Function of Membrane-Associated Proteoglycans in the Regulation of Satellite Cell Growth.

    Science.gov (United States)

    Song, Yan

    2016-01-01

    Muscle growth can be divided into embryonic and postnatal periods. During the embryonic period, mesenchymal stem cells proliferate and differentiate to form muscle fibers. Postnatal muscle growth (hypertrophy) is characterized by the enlargement of existing muscle fiber size. Satellite cells (also known as adult myoblasts) are responsible for hypertrophy. The activity of satellite cells can be regulated by their extracellular matrix (ECM). The ECM is composed of collagens, proteoglycans, non-collagenous glycoproteins, cytokines and growth factors. Proteoglycans contain a central core protein with covalently attached glycosaminoglycans (GAGs: chondroitin sulfate, keratan sulfate, dermatan sulfate, and heparan sulfate) and N- or O-linked glycosylation chains. Membrane-associated proteoglycans attach to the cell membrane either through a glycosylphosphatidylinositol anchor or transmembrane domain. The GAGs can bind proteins including cytokines and growth factors. Both cytokines and growth factors play important roles in regulating satellite cell growth and development. Cytokines are generally associated with immune cells. However, cytokines can also affect muscle cell development. For instance, interleukin-6, tumor necrosis factor-α, and leukemia inhibitory factor have been reported to affect the proliferation and differentiation of satellite cells and myoblasts. Growth factors are potent stimulators or inhibitors of satellite cell proliferation and differentiation. The proper function of some cytokines and growth factors requires an interaction with the cell membrane-associated proteoglycans to enhance the affinity to bind to their primary receptors to initiate downstream signal transduction. This chapter is focused on the interaction of membrane-associated proteoglycans with cytokines and growth factors, and their role in satellite cell growth and development.

  12. Interaction of Clostridium perfringens epsilon-toxin with biological and model membranes: A putative protein receptor in cells.

    Science.gov (United States)

    Manni, Marco M; Sot, Jesús; Goñi, Félix M

    2015-03-01

    Epsilon-toxin (ETX) is a powerful toxin produced by some strains of Clostridium perfringens (classified as types B and D) that is responsible for enterotoxemia in animals. ETX forms pores through the plasma membrane of eukaryotic cells, consisting of a β-barrel of 14 amphipathic β-strands. ETX shows a high specificity for certain cell lines, of which Madin-Darby canine kidney (MDCK) is the first sensitive cell line identified and the most studied one. The aim of this study was to establish the role of lipids in the toxicity caused by ETX and the correlation of its activity in model and biological membranes. In MDCK cells, using cell counting and confocal microscopy, we have observed that the toxin causes cell death mediated by toxin binding to plasma membrane. Moreover, ETX binds and permeabilizes the membranes of giant plasma membrane vesicles (GPMV). However, little effect is observed on protein-free vesicles. The data suggest the essential role of a protein receptor for the toxin in cell membranes.

  13. Biological treatment of mixtures of toluene and n-hexane vapours in a hollow fibre membrane bioreactor.

    Science.gov (United States)

    Zhao, Kang; Xiu, Guangli; Xu, Lihang; Zhang, Danian; Zhang, Xiaofeng; Deshusses, Marc A

    2011-04-01

    Membrane bioreactors are gaining interest for the control of contaminated air streams. In this study, the removal of toluene and n-hexane vapours in a hollow fibre membrane bioreactor (HFMB) was investigated. The focus was on quantifying the possible interactions occurring during the simultaneous biotreatment of the two volatile pollutants. Two lab-scale units fitted with microporous polypropylene hollow fibre membranes were connected in series and inoculated with activated sludge. Contaminated air was passed through the lumen at gas residence times ranging from 2.3 to 9.4 s while a pollutant-degrading biofilm developed on the shell side of the fibres. When toluene was treated alone, very high elimination capacities (up to 750 g m(-3) h(-1) based on lumen volume, or 1.25 g m(-2) h(-1) when normalized by the hollow fibre membrane area) were reached. When toluene and hexane were treated simultaneously, toluene biodegradation was partially inhibited by n-hexane, resulting in lower toluene removal rates. On the other hand, hexane removal was only marginally affected by the presence of toluene and was degraded at very high rates (upwards of 440 g m(-3) h(-1) or 0.73 g m(-2) h(-1) without breakthrough). Overall, this study demonstrates that mixtures of toluene and n-hexane vapours can be effectively removed in hollow fibre membrane bioreactors and that complex biological interactions may affect one or more of the pollutants undergoing treatment in gas-phase membrane bioreactors.

  14. Membrane and integrative nuclear fibroblastic growth factor receptor (FGFR) regulation of FGF-23.

    Science.gov (United States)

    Han, Xiaobin; Xiao, Zhousheng; Quarles, L Darryl

    2015-04-17

    Fibroblastic growth factor receptor 1 (FGFR1) signaling pathways are implicated in the regulation of FGF-23 gene transcription, but the molecular pathways remain poorly defined. We used low molecular weight (LMW, 18 kDa) FGF-2 and high molecular weight (HMW) FGF-2 isoforms, which, respectively, activate cell surface FGF receptors and intranuclear FGFR1, to determine the roles of membrane FGFRs and integrative nuclear FGFR1 signaling (INFS) in the regulation of FGF-23 gene transcription in osteoblasts. We found that LMW-FGF-2 induced NFAT and Ets1 binding to conserved cis-elements in the proximal FGF-23 promoter and stimulated FGF-23 promoter activity through PLCγ/calcineurin/NFAT and MAPK pathways in SaOS-2 and MC3T3-E1 osteoblasts. In contrast, HMW-FGF-2 stimulated FGF-23 promoter activity in osteoblasts through a cAMP-dependent binding of FGFR1 and cAMP-response element-binding protein (CREB) to a conserved cAMP response element (CRE) contiguous with the NFAT binding site in the FGF-23 promoter. Mutagenesis of the NFAT and CRE binding sites, respectively, inhibited the effects of LMW-FGF-2 and HMW-FGF-23 to stimulate FGF-23 promoter activity. FGF-2 activation of both membrane FGFRs and INFS-dependent FGFR1 pathways may provide a means to integrate systemic and local regulation of FGF-23 transcription under diverse physiological and pathological conditions.

  15. DHHC7 Palmitoylates Glucose Transporter 4 (Glut4) and Regulates Glut4 Membrane Translocation.

    Science.gov (United States)

    Du, Keyong; Murakami, Shoko; Sun, Yingmin; Kilpatrick, Casey L; Luscher, Bernhard

    2017-02-17

    Insulin-dependent translocation of glucose transporter 4 (Glut4) to the plasma membrane plays a key role in the dynamic regulation of glucose homeostasis. We recently showed that this process is critically dependent on palmitoylation of Glut4 at Cys-223. To gain further insights into the regulation of Glut4 palmitoylation, we set out to identify the palmitoyl acyltransferase (PAT) involved. Here we report that among 23 mammalian DHHC proteins, DHHC7 is the major Glut4 PAT, based on evidence that ectopic expression of DHHC7 increased Glut4 palmitoylation, whereas DHHC7 knockdown in 3T3-L1 adipocytes and DHHC7 KO in adipose tissue and muscle decreased Glut4 palmitoylation. Moreover, inactivation of DHHC7 suppressed insulin-dependent Glut4 membrane translocation in both 3T3-L1 adipocytes and primary adipocytes. Finally, DHHC7 KO mice developed hyperglycemia and glucose intolerance, thereby confirming that DHHC7 represents the principal PAT for Glut4 and that this mechanism is essential for insulin-regulated glucose homeostasis.

  16. [The aspects of adenylate cyclase activity regulation in myocardium cell membranes during hypokinesia].

    Science.gov (United States)

    Bulanova, K Ia; Komar, E S; Lobanok, L M

    1999-01-01

    Nonstimulated and isoproterenol, GTF, GITF, NaF stimulated activities of the adenylate cyclase in sarcolemma in white rats' myocardium was studied after two weeks of hypokinesia. As was established, in restrained animals the sensitivity of adenylate cyclase to the specified agents was increased and transition to the bimodal GTF regulation took place. It is hypothesised that involvement of membrane-bound Gi-proteins in the adrenergic effects on cardiomyocytes is one of mechanisms of the cardiotropic effects of restraint and heart distresses.

  17. Preparation, characterization, biological activity, and transport study of polystyrene based calcium–barium phosphate composite membrane

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Mohammad Mujahid Ali; Rafiuddin,, E-mail: rafi_amu@rediffmail.com

    2013-10-15

    Calcium–barium phosphate (CBP) composite membrane with 25% polystyrene was prepared by co-precipitation method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and Thermogravimetric analysis (TGA) were used to characterize the membrane. The membrane was found to be crystalline in nature with consistent arrangement of particles and no indication of visible cracks. The electrical potentials measured across the composite membrane in contact with univalent electrolytes (KCl, NaCl and LiCl), have been found to increase with decrease in concentrations. Thus the membrane was found to be cation-selective. Transport properties of developed membranes may be utilized for the efficient desalination of saline water and more importantly demineralization process. The antibacterial study of this composite membrane shows good results for killing the disease causing bacteria along with waste water treatment. Highlights: • Transport properties of composite membrane are evaluated. • The composite membrane was found to be stable in all media. • TMS method is used for electrochemical characterization. • The membrane was found to be cation selective. • The order of surface charge density was found to be LiCl < NaCl < KCl.

  18. Ultrafiltration of biologically treated domestic wastewater: How membrane properties influence performance

    KAUST Repository

    Filloux, Emmanuelle

    2014-09-01

    In this study, the impact of membrane properties on membrane fouling and permeate water quality was investigated. Short- and long-term laboratory scale experiments using four commercially available hollow fiber UF membranes were performed to study the impact of membrane properties on reversible and irreversible fouling. No significant differences in terms of permeate quality (i.e. biopolymer rejection) were observed over the four tested membranes. It was found that membrane characteristics including pore size, pore distribution and especially materials had a strong impact on the filtration performances in terms of both reversible and irreversible fouling. The short-term filtration tests showed that due to its specific hydrodynamic condition only the inside-out mode UF membrane was subjected to irreversible fouling. These data demonstrate the importance of membrane selection with appropriate operating conditions for optimum performances. The added value of membrane characterization to lab-scale filtration tests for membrane performance was discussed. © 2014 Elsevier B.V. All rights reserved.

  19. The supramolecular architecture, function, and regulation of thylakoid membranes in red algae: an overview.

    Science.gov (United States)

    Su, Hai-Nan; Xie, Bin-Bin; Zhang, Xi-Ying; Zhou, Bai-Cheng; Zhang, Yu-Zhong

    2010-11-01

    Red algae are a group of eukaryotic photosynthetic organisms. Phycobilisomes (PBSs), which are composed of various types of phycobiliproteins and linker polypeptides, are the main light-harvesting antennae in red algae, as in cyanobacteria. Two morphological types of PBSs, hemispherical- and hemidiscoidal-shaped, are found in different red algae species. PBSs harvest solar energy and efficiently transfer it to photosystem II (PS II) and finally to photosystem I (PS I). The PS I of red algae uses light-harvesting complex of PS I (LHC I) as a light-harvesting antennae, which is phylogenetically related to the LHC I found in higher plants. PBSs, PS II, and PS I are all distributed throughout the entire thylakoid membrane, a pattern that is different from the one found in higher plants. Photosynthesis processes, especially those of the light reactions, are carried out by the supramolecular complexes located in/on the thylakoid membranes. Here, the supramolecular architecture, function and regulation of thylakoid membranes in red algal are reviewed.

  20. Monoclonal antibodies against the iron regulated outer membrane Proteins of Acinetobacter baumannii are bactericidal

    Directory of Open Access Journals (Sweden)

    Goel Vikas

    2001-08-01

    Full Text Available Abstract Background Iron is an important nutrient required by all forms of life.In the case of human hosts,the free iron availability is 10-18M,which is far less than what is needed for the survival of the invading bacterial pathogen.To survive in such conditions, bacteria express new proteins in their outer membrane and also secrete iron chelators called siderophores. Results/ Discussion Acinetobacter baumannii ATCC 19606, a nosocomial pathogen which grows under iron restricted conditions, expresses four new outer membrane proteins,with molecular weight ranging from 77 kDa to 88 kDa, that are called Iron Regulated Outer Membrane Proteins (IROMPs. We studied the functional and immunological properties of IROMPs expressed by A.baumanii ATCC 19606.The bands corresponding to IROMPs were eluted from SDS-PAGE and were used to immunize BALB/c mice for the production of monoclonal antibodies. Hybridomas secreting specific antibodies against these IROMPs were selected after screening by ELISA and their reactivity was confirmed by Western Blot. The antibodies then generated belonged to IgM isotype and showed bactericidical and opsonising activities against A.baumanii in vitro.These antibodies also blocked siderophore mediated iron uptake via IROMPs in bacteria. Conclusion This proves that iron uptake via IROMPs,which is mediated through siderophores,may have an important role in the survival of A.baumanii inside the host,and helps establishing the infection.

  1. α-Synuclein Membrane Association Is Regulated by the Rab3a Recycling Machinery and Presynaptic Activity*♦

    Science.gov (United States)

    Chen, Robert H. C.; Wislet-Gendebien, Sabine; Samuel, Filsy; Visanji, Naomi P.; Zhang, Gang; Marsilio, Diana; Langman, Tammy; Fraser, Paul E.; Tandon, Anurag

    2013-01-01

    α-Synuclein is an abundant presynaptic protein and a primary component of Lewy bodies in Parkinson disease. Although its pathogenic role remains unclear, in healthy nerve terminals α-synuclein undergoes a cycle of membrane binding and dissociation. An α-synuclein binding assay was used to screen for vesicle proteins involved in α-synuclein membrane interactions and showed that antibodies directed to the Ras-related GTPase Rab3a and its chaperone RabGDI abrogated α-synuclein membrane binding. Biochemical analyses, including density gradient sedimentation and co-immunoprecipitation, suggested that α-synuclein interacts with membrane-associated GTP-bound Rab3a but not to cytosolic GDP-Rab3a. Accumulation of membrane-bound α-synuclein was induced by the expression of a GTPase-deficient Rab3a mutant, by a dominant-negative GDP dissociation inhibitor mutant unable to recycle Rab3a off membranes, and by Hsp90 inhibitors, radicicol and geldanamycin, which are known to inhibit Rab3a dissociation from membranes. Thus, all treatments that inhibited Rab3a recycling also increased α-synuclein sequestration on intracellular membranes. Our results suggest that membrane-bound GTP-Rab3a stabilizes α-synuclein on synaptic vesicles and that the GDP dissociation inhibitor·Hsp90 complex that controls Rab3a membrane dissociation also regulates α-synuclein dissociation during synaptic activity. PMID:23344955

  2. Crz1p regulates pH homeostasis in Candida glabrata by altering membrane lipid composition.

    Science.gov (United States)

    Yan, Dongni; Lin, Xiaobao; Qi, Yanli; Liu, Hui; Chen, Xiulai; Liu, Liming; Chen, Jian

    2016-09-23

    The asexual facultative aerobic haploid yeast Candida glabrata is widely used in the industrial production of various organic acids. To elucidate the physiological function of the transcription factor CgCrz1p and its role in tolerance to acid stress we deleted or overexpressed the corresponding gene CgCRZ1 Deletion of CgCRZ1 resulted in a 60% decrease in dry cell weight (DCW) and a 50% drop in cell viability compared to the wild type at pH 2.0. Expression of lipid metabolism-associated genes was also significantly down-regulated. Consequently, the proportion of C18:1 fatty acids, ratio of unsaturated to saturated fatty acids, and ergosterol content decreased by 30%, 46%, and 30%, respectively. Additionally, membrane integrity, fluidity, and H(+)-ATPase activity were reduced by 45%, 9%, and 50%, respectively. In contrast, overexpression of CgCrz1p increased C18:1 and ergosterol content by 16% and 40%, respectively. Overexpression also enhanced membrane integrity, fluidity, and H(+)-ATPase activity by 31%, 6%, and 20%, respectively. Moreover, in the absence of pH buffering, DCW and pyruvate titer increased by 48% and 60%, respectively, compared to the wild type. Together, these results suggest that CgCrz1p regulates tolerance to acidic conditions by altering membrane lipid composition in C. glabrata IMPORTANCE: The present study provides an insight into the metabolism of Candida glabrata under acidic conditions, such as those encountered during industrial production of organic acids. We found that overexpression of the transcription factor CgCrz1p improved viability, biomass, and pyruvate yields at low pH. Analysis of plasma membrane lipid composition indicated that CgCrz1p might play an important role in its integrity and fluidity, and enhanced the pumping of protons in acidic environments. We propose that altering the structure of the cell membrane may provide a successful strategy for increasing C glabrata productivity at low pH.

  3. Hemorrhagic shock impairs myocardial cell volume regulation and membrane integrity in dogs

    Energy Technology Data Exchange (ETDEWEB)

    Horton, J.W.

    1987-06-01

    An in vitro myocardial slice technique was used to quantitate alterations in cell volume regulation and membrane integrity after 2 h or hemorrhagic shock. After in vitro incubation in Krebs-Ringer-phosphate medium containing trace (/sup 14/C)inulin, values (ml H/sub 2/O/g dry wt) for control nonshocked myocardial slices were 4.03 /plus minus/ 0.11 (SE) for total water, 2.16 /plus minus/ 0.07 for inulin impermeable space, and 1.76 /plus minus/ 0.15 for inulin diffusible space. Shocked myocardial slices showed impaired response to cold incubation. After 2 h of in vivo shock, total tissue water, inulin diffusible space, and inulin impermeable space increased significantly for subendocardium, whereas changes in subepicardium parameters were minimal. Shock-induced cellular swelling was accompanied by an increased total tissue sodium, but no change in tissue potassium. Calcium entry blockade in vivo significantly reduced subendocardial total tissue water as compared with shock-untreated dogs. In addition, calcium entry blockade reduced shock-induced increases in inulin diffusible space. In vitro myocardial slice studies confirm alterations in subendocardial membrane integrity after 2 h of in vivo hemorrhagic shock. Shock-induced abnormalities in myocardial cell volume regulation are reduced by calcium entry blockade in vivo.

  4. The cell biology of inflammasomes: Mechanisms of inflammasome activation and regulation.

    Science.gov (United States)

    Sharma, Deepika; Kanneganti, Thirumala-Devi

    2016-06-20

    Over the past decade, numerous advances have been made in the role and regulation of inflammasomes during pathogenic and sterile insults. An inflammasome complex comprises a sensor, an adaptor, and a zymogen procaspase-1. The functional output of inflammasome activation includes secretion of cytokines, IL-1β and IL-18, and induction of an inflammatory form of cell death called pyroptosis. Recent studies have highlighted the intersection of this inflammatory response with fundamental cellular processes. Novel modulators and functions of inflammasome activation conventionally associated with the maintenance of homeostatic biological functions have been uncovered. In this review, we discuss the biological processes involved in the activation and regulation of the inflammasome.

  5. Constant change: dynamic regulation of membrane transport by calcium signalling networks keeps plants in tune with their environment.

    Science.gov (United States)

    Kleist, Thomas J; Luan, Sheng

    2016-03-01

    Despite substantial variation and irregularities in their environment, plants must conform to spatiotemporal demands on the molecular composition of their cytosol. Cell membranes are the major interface between organisms and their environment and the basis for controlling the contents and intracellular organization of the cell. Membrane transport proteins (MTPs) govern the flow of molecules across membranes, and their activities are closely monitored and regulated by cell signalling networks. By continuously adjusting MTP activities, plants can mitigate the effects of environmental perturbations, but effective implementation of this strategy is reliant on precise coordination among transport systems that reside in distinct cell types and membranes. Here, we examine the role of calcium signalling in the coordination of membrane transport, with an emphasis on potassium transport. Potassium is an exceptionally abundant and mobile ion in plants, and plant potassium transport has been intensively studied for decades. Classic and recent studies have underscored the importance of calcium in plant environmental responses and membrane transport regulation. In reviewing recent advances in our understanding of the coding and decoding of calcium signals, we highlight established and emerging roles of calcium signalling in coordinating membrane transport among multiple subcellular locations and distinct transport systems in plants, drawing examples from the CBL-CIPK signalling network. By synthesizing classical studies and recent findings, we aim to provide timely insights on the role of calcium signalling networks in the modulation of membrane transport and its importance in plant environmental responses.

  6. Molecular aspects of GAPR-1 interactions with biological and model membranes

    NARCIS (Netherlands)

    van Galen, J.

    2008-01-01

    Golgi-Associated Plant Pathogenesis-Related protein 1 (GAPR-1) is a mammalian protein that belongs to the superfamily of plant pathogenesis related proteins group 1 (PR-1). It is a peripheral membrane protein that strongly associates with the cytosolic leaflet of Golgi membranes and is enriched in l

  7. Synthetic Biology Tools for the Membrane – Targeted Localisation and Elucidation of Protein Interactions

    DEFF Research Database (Denmark)

    Wendel, Sofie; Seppala, Susanna; Nørholm, Morten

    2014-01-01

    (SMA) for isolation of membrane proteins. SMA is a polymer which spontaneously digs into a lipid membrane and carves out a disc containing protein and native lipids (2). By elucidating protein interactions we will be able to tune and optimise heterologous pathway expression in our E. coli cell...

  8. Protein kinase A regulates 3-phosphatidylinositide dynamics during platelet-derived growth factor-induced membrane ruffling and chemotaxis.

    Science.gov (United States)

    Deming, Paula B; Campbell, Shirley L; Baldor, Linda C; Howe, Alan K

    2008-12-12

    Spatial regulation of the cAMP-dependent protein kinase (PKA) is required for chemotaxis in fibroblasts; however, the mechanism(s) by which PKA regulates the cell migration machinery remain largely unknown. Here we report that one function of PKA during platelet-derived growth factor (PDGF)-induced chemotaxis was to promote membrane ruffling by regulating phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) dynamics. Inhibition of PKA activity dramatically altered membrane dynamics and attenuated formation of peripheral membrane ruffles in response to PDGF. PKA inhibition also significantly decreased the number and size of PIP(3)-rich membrane ruffles in response to uniform stimulation and to gradients of PDGF. This ruffling defect was quantified using a newly developed method, based on computer vision edge-detection algorithms. PKA inhibition caused a marked attenuation in the bulk accumulation of PIP(3) following PDGF stimulation, without effects on PI3-kinase (PI3K) activity. The deficits in PIP(3) dynamics correlated with a significant inhibition of growth factor-induced membrane recruitment of endogenous Akt and Rac activation in PKA-inhibited cells. Simultaneous inhibition of PKA and Rac had an additive inhibitory effect on growth factor-induced ruffling dynamics. Conversely, the expression of a constitutively active Rac allele was able to rescue the defect in membrane ruffling and restore the localization of a fluorescent PIP(3) marker to membrane ruffles in PKA-inhibited cells, even in the absence of PI3K activity. These data demonstrate that, like Rac, PKA contributes to PIP(3) and membrane dynamics independently of direct regulation of PI3K activity and suggest that modulation of PIP(3)/3-phosphatidylinositol (3-PI) lipids represents a major target for PKA in the regulation of PDGF-induced chemotactic events.

  9. Defining central themes in breast cancer biology by differential proteomics: conserved regulation of cell spreading and focal adhesion kinase.

    Science.gov (United States)

    Bateman, Nicholas W; Sun, Mai; Hood, Brian L; Flint, Melanie S; Conrads, Thomas P

    2010-10-01

    Breast cancer is a highly heterogeneous disease, an observation that underscores the importance of elucidating conserved molecular characteristics, such as gene and protein expression, across breast cancer cell types toward providing a greater understanding of context-specific features central to this disease. Motivated by the goal of defining central biological themes across breast cancer cell subtypes, we conducted a global proteomic analysis of three breast cancer cell lines, MCF7, SK-BR-3, and MDA-MB-231, and compared these to a model of nontransformed mammary cells (MCF10A). Our results demonstrate modulation of proteins localized to the extracellular matrix, plasma membrane, and nucleus, along with coordinate decreases in proteins that regulate "cell spreading," a cellular event previously shown to be dysregulated in transformed cells. Protein interaction network analysis revealed the clustering of focal adhesion kinase (FAK), a fundamental regulator of cell spreading, with several proteins identified as mutually, differentially abundant across breast cancer cell lines that impact expression and activity of FAK, such as neprilysin and keratin 19. These analyses provide insights into conservation of protein expression across breast cancer cell subtypes, a subset of which warrants further investigation for their roles in the regulation of cell spreading and FAK in breast cancer.

  10. Fluorescence response of hypocrellin B to the environmental changes in a mimic biological membrane--liposome

    Institute of Scientific and Technical Information of China (English)

    JIN; Xuanye; ZHAO; Yuewei; XIE; Jie; ZHAO; Jingquan

    2004-01-01

    , Photochem.Photobiol., 2001, 73 (5): 482-488.[13]Mang, T. S., Dougherty, T. J., Potter, W. R. et al., Photobleaching of porphyrins used in photodynamic therapy and implications for therapy, Photochem. Photobiol., 1987, 45: 501-506.[14]Shoko, Y., Tadahiro, T., Masahiko, A., Preparation of ganglioside GM3 liposomes and their membrane properties, Colloid Surface B, 2002, 27: 181-187.[15]Murakami, S., Packer, L., The role of cations in the organization of chloroplast membranes, Arch. Biochem. Biophys., 1971, 146:337-347.[16]Angeli, N. G., Lagorio, M. G., San Román, E. et al., Meso-substituted cationic porphyrins of biological interest, Photophysical and physicochemical properties in solution and bound to liposomes,Photochem. Photobiol., 2000, 72(1 ): 49-56.

  11. Quantitative Modeling of Membrane Transport and Anisogamy by Small Groups Within a Large-Enrollment Organismal Biology Course

    Directory of Open Access Journals (Sweden)

    Eric S. Haag

    2016-12-01

    Full Text Available Quantitative modeling is not a standard part of undergraduate biology education, yet is routine in the physical sciences. Because of the obvious biophysical aspects, classes in anatomy and physiology offer an opportunity to introduce modeling approaches to the introductory curriculum. Here, we describe two in-class exercises for small groups working within a large-enrollment introductory course in organismal biology. Both build and derive biological insights from quantitative models, implemented using spreadsheets. One exercise models the evolution of anisogamy (i.e., small sperm and large eggs from an initial state of isogamy. Groups of four students work on Excel spreadsheets (from one to four laptops per group. The other exercise uses an online simulator to generate data related to membrane transport of a solute, and a cloud-based spreadsheet to analyze them. We provide tips for implementing these exercises gleaned from two years of experience.

  12. ATF2, a paradigm of the multifaceted regulation of transcription factors in biology and disease.

    Science.gov (United States)

    Watson, Gregory; Ronai, Ze'ev; Lau, Eric

    2017-02-15

    Stringent transcriptional regulation is crucial for normal cellular biology and organismal development. Perturbations in the proper regulation of transcription factors can result in numerous pathologies, including cancer. Thus, understanding how transcription factors are regulated and how they are dysregulated in disease states is key to the therapeutic targeting of these factors and/or the pathways that they regulate. Activating transcription factor 2 (ATF2) has been studied in a number of developmental and pathological conditions. Recent findings have shed light on the transcriptional, post-transcriptional, and post-translational regulatory mechanisms that influence ATF2 function, and thus, the transcriptional programs coordinated by ATF2. Given our current knowledge of its multiple levels of regulation and function, ATF2 represents a paradigm for the mechanistic complexity that can regulate transcription factor function. Thus, increasing our understanding of the regulation and function of ATF2 will provide insights into fundamental regulatory mechanisms that influence how cells integrate extracellular and intracellular signals into a genomic response through transcription factors. Characterization of ATF2 dysfunction in the context of pathological conditions, particularly in cancer biology and response to therapy, will be important in understanding how pathways controlled by ATF2 or other transcription factors might be therapeutically exploited. In this review, we provide an overview of the currently known upstream regulators and downstream targets of ATF2.

  13. Wrapping of a deformable nanoparticle by the cell membrane: Insights into the flexibility-regulated nanoparticle-membrane interaction

    Science.gov (United States)

    Tang, Huayuan; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-09-01

    Although many researches have been conducted on the interaction of the cell membrane with the rigid nanoparticle (NP), relatively little is known about the interaction of the membrane with the deformable NP, which is a promising kind of drug delivery carrier. In this paper, we investigate the wrapping of a deformable NP by the membrane, with particular attention paid to the location of the NP. Phase diagrams with respect to the normalized NP-membrane adhesion strength and the bending stiffness ratio between the NP and membrane are presented. The results show that the NP is easier to be fully wrapped but harder to be shallowly wrapped when the NP locates outside than inside the vesicle. For the system with an outside NP, there are three distinct stages separated by two critical bending stiffness ratios as the NP becomes softer. Moreover, the critical normalized adhesion strength required for a deformable NP to be fully wrapped is the same as that for a rigid NP when the bending stiffness ratio is higher than a critical value, which is different from the wrapping behavior by an initially flat membrane. In addition, a larger vesicle size facilitates the full wrapping configuration when the NP is inside, whereas it prohibits it when the NP is outside. These results are consistent with the previous research and can provide guidelines for the design of drug delivery systems based on the flexibility-tunable NPs.

  14. Circadian- and Light-Dependent Regulation of Resting Membrane Potential and Spontaneous Action Potential Firing of Drosophila Circadian Pacemaker Neurons

    OpenAIRE

    Sheeba, Vasu; Gu, Huaiyu; Sharma, Vijay K.; O'Dowd, Diane K.; Holmes, Todd C

    2007-01-01

    The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly ...

  15. Membrane fusion

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    At Stanford University, Boxer lab, I worked on membrane fusion of small unilamellar lipid vesicles to flat membranes tethered to glass surfaces. This geometry closely resembles biological systems in which liposomes fuse to plasma membranes. The fusion mechanism was studied using DNA zippering...... between complementary strands linked to the two apposing membranes closely mimicking the zippering mechanism of SNARE fusion complexes....

  16. Vimentin is involved in regulation of mitochondrial motility and membrane potential by Rac1

    Directory of Open Access Journals (Sweden)

    Elena A. Matveeva

    2015-10-01

    Full Text Available In this study we show that binding of mitochondria to vimentin intermediate filaments (VIF is regulated by GTPase Rac1. The activation of Rac1 leads to a redoubling of mitochondrial motility in murine fibroblasts. Using double-mutants Rac1(G12V, F37L and Rac1(G12V, Y40H that are capable to activate different effectors of Rac1, we show that mitochondrial movements are regulated through PAK1 kinase. The involvement of PAK1 kinase is also confirmed by the fact that expression of its auto inhibitory domain (PID blocks the effect of activated Rac1 on mitochondrial motility. The observed effect of Rac1 and PAK1 kinase on mitochondria depends on phosphorylation of the Ser-55 of vimentin. Besides the effect on motility Rac1 activation also decreases the mitochondrial membrane potential (MMP which is detected by ∼20% drop of the fluorescence intensity of mitochondria stained with the potential sensitive dye TMRM. One of important consequences of the discovered regulation of MMP by Rac1 and PAK1 is a spatial differentiation of mitochondria in polarized fibroblasts: at the front of the cell they are less energized (by ∼25% than at the rear part.

  17. Plasma membrane calcium ATPase proteins as novel regulators of signal transduction pathways

    Institute of Scientific and Technical Information of China (English)

    Mary; Louisa; Holton; Michael; Emerson; Ludwig; Neyses; Angel; L; Armesilla

    2010-01-01

    Emerging evidence suggests that plasma membrane calcium ATPases (PMCAs) play a key role as regulators of calcium-triggered signal transduction pathways via interaction with partner proteins. PMCAs regulate these pathways by targeting specific proteins to cellular sub-domains where the levels of intracellular freecalcium are kept low by the calcium ejection properties of PMCAs. According to this model, PMCAs have been shown to interact functionally with the calcium-sensitive proteins neuronal nitric oxide synthase, calmodulindependent serine protein kinase, calcineurin and endothelial nitric oxidase synthase. Transgenic animals with altered expression of PMCAs are being used to evaluate the physiological significance of these interactions. To date, PMCA interactions with calcium-dependent partner proteins have been demonstrated to play a crucial role in the pathophysiology of the cardiovascular system via regulation of the nitric oxide and calcineurin/nuclear factor of activated T cells pathways. This new evidence suggests that PMCAs play a more sophisticated role than the mere ejection of calcium from the cells, by acting as modulators of signaling transduction pathways.

  18. Stress regulated members of the plant organic cation transporter family are localized to the vacuolar membrane

    Directory of Open Access Journals (Sweden)

    Koch Wolfgang

    2008-07-01

    Full Text Available Abstract Background In Arabidopsis six genes group into the gene family of the organic cation transporters (OCTs. In animals the members of the OCT-family are mostly characterized as polyspecific transporters involved in the homeostasis of solutes, the transport of monoamine neurotransmitters and the transport of choline and carnitine. In plants little is known about function, localisation and regulation of this gene family. Only one protein has been characterized as a carnitine transporter at the plasma membrane so far. Findings We localized the five uncharacterized members of the Arabidopsis OCT family, designated OCT2-OCT6, via GFP fusions and protoplast transformation to the tonoplast. Expression analysis with RNA Gel Blots showed a distinct, organ-specific expression pattern of the individual genes. With reporter gene fusion of four members we analyzed the tissue specific distribution of OCT2, 3, 4, and 6. In experiments with salt, drought and cold stress, we could show that AtOCT4, 5 and 6 are up-regulated during drought stress, AtOCT3 and 5 during cold stress and AtOCT 5 and 6 during salt stress treatments. Conclusion Localisation of the proteins at the tonoplast and regulation of the gene expression under stress conditions suggests a specific role for the transporters in plant adaptation to environmental stress.

  19. Cross-membrane signal transduction of receptor tyrosine kinases (RTKs): from systems biology to systems pharmacology.

    Science.gov (United States)

    Benson, Neil; van der Graaf, Piet H; Peletier, Lambertus A

    2013-03-01

    Receptor tyrosine kinases are high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. They straddle the cell wall and play an important role in cross-membrane signalling. We present a two-component systems pharmacology model based on the local physiology and identify characteristic features of its dynamics. We thus present a transparent tool for studying the effects of drug intervention and ways of administration on cross-membrane signalling through these receptors.

  20. The biological basis of autism spectrum disorders: evaluation of oxidative stress and erytrocyte membrane alterations

    OpenAIRE

    Ghezzo, Alessandro

    2015-01-01

    This case-control study involved a total of 29 autistic children (Au) aged 6 to 12 years, and 28 gender and age-matched typically developing children (TD). We evaluated a high number of peripheral oxidative stress parameters, erythrocyte and lymphocyte membrane functional features and membrane lipid composition of erythrocyte. Erythrocyte TBARS, Peroxiredoxin II, Protein Carbonyl Groups and urinary HEL and isoprostane levels were elevated in AU (confirming an imbalance of the redox status of...

  1. The human Na(+)/H(+) exchanger 1 is a membrane scaffold protein for extracellular signal-regulated kinase 2

    DEFF Research Database (Denmark)

    Hendus-Altenburger, Ruth; Pedraz-Cuesta, Elena; Olesen, Christina W;

    2016-01-01

    BACKGROUND: Extracellular signal-regulated kinase 2 (ERK2) is an S/T kinase with more than 200 known substrates, and with critical roles in regulation of cell growth and differentiation and currently no membrane proteins have been linked to ERK2 scaffolding. METHODS AND RESULTS: Here, we identify...... the human Na(+)/H(+) exchanger 1 (hNHE1) as a membrane scaffold protein for ERK2 and show direct hNHE1-ERK1/2 interaction in cellular contexts. Using nuclear magnetic resonance (NMR) spectroscopy and immunofluorescence analysis we demonstrate that ERK2 scaffolding by hNHE1 occurs by one of three D...... and ERK2, and provides a molecular mechanism for the important ERK2 scaffolding function of the membrane protein hNHE1, which regulates the phosphorylation of both hNHE1 and ERK2....

  2. Differences in metacognitive regulation in introductory biology students: when prompts are not enough.

    Science.gov (United States)

    Stanton, Julie Dangremond; Neider, Xyanthe N; Gallegos, Isaura J; Clark, Nicole C

    2015-01-01

    Strong metacognition skills are associated with learning outcomes and student performance. Metacognition includes metacognitive knowledge-our awareness of our thinking-and metacognitive regulation-how we control our thinking to facilitate learning. In this study, we targeted metacognitive regulation by guiding students through self-evaluation assignments following the first and second exams in a large introductory biology course (n = 245). We coded these assignments for evidence of three key metacognitive-regulation skills: monitoring, evaluating, and planning. We found that nearly all students were willing to take a different approach to studying but showed varying abilities to monitor, evaluate, and plan their learning strategies. Although many students were able to outline a study plan for the second exam that could effectively address issues they identified in preparing for the first exam, only half reported that they followed their plans. Our data suggest that prompting students to use metacognitive-regulation skills is effective for some students, but others need help with metacognitive knowledge to execute the learning strategies they select. Using these results, we propose a continuum of metacognitive regulation in introductory biology students. By refining this model through further study, we aim to more effectively target metacognitive development in undergraduate biology students.

  3. A computer simulation approach to quantify the true area and true area compressibility modulus of biological membranes

    Energy Technology Data Exchange (ETDEWEB)

    Chacón, Enrique, E-mail: echacon@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid, Spain and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Tarazona, Pedro, E-mail: pedro.tarazona@uam.es [Departamento de Física Teórica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC), and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, Madrid 28049 (Spain); Bresme, Fernando, E-mail: f.bresme@imperial.ac.uk [Department of Chemistry, Imperial College London, SW7 2AZ London (United Kingdom)

    2015-07-21

    We present a new computational approach to quantify the area per lipid and the area compressibility modulus of biological membranes. Our method relies on the analysis of the membrane fluctuations using our recently introduced coupled undulatory (CU) mode [Tarazona et al., J. Chem. Phys. 139, 094902 (2013)], which provides excellent estimates of the bending modulus of model membranes. Unlike the projected area, widely used in computer simulations of membranes, the CU area is thermodynamically consistent. This new area definition makes it possible to accurately estimate the area of the undulating bilayer, and the area per lipid, by excluding any contributions related to the phospholipid protrusions. We find that the area per phospholipid and the area compressibility modulus features a negligible dependence with system size, making possible their computation using truly small bilayers, involving a few hundred lipids. The area compressibility modulus obtained from the analysis of the CU area fluctuations is fully consistent with the Hooke’s law route. Unlike existing methods, our approach relies on a single simulation, and no a priori knowledge of the bending modulus is required. We illustrate our method by analyzing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers using the coarse grained MARTINI force-field. The area per lipid and area compressibility modulus obtained with our method and the MARTINI forcefield are consistent with previous studies of these bilayers.

  4. Negative regulation of syntaxin4/SNAP-23/VAMP2-mediated membrane fusion by Munc18c in vitro.

    Directory of Open Access Journals (Sweden)

    Fiona M Brandie

    Full Text Available BACKGROUND: Translocation of the facilitative glucose transporter GLUT4 from an intracellular store to the plasma membrane is responsible for the increased rate of glucose transport into fat and muscle cells in response to insulin. This represents a specialised form of regulated membrane trafficking. Intracellular membrane traffic is subject to multiple levels of regulation by conserved families of proteins in all eukaryotic cells. Notably, all intracellular fusion events require SNARE proteins and Sec1p/Munc18 family members. Fusion of GLUT4-containing vesicles with the plasma membrane of insulin-sensitive cells involves the SM protein Munc18c, and is regulated by the formation of syntaxin 4/SNAP23/VAMP2 SNARE complexes. METHODOLOGY/PRINCIPAL FINDINGS: Here we have used biochemical approaches to characterise the interaction(s of Munc18c with its cognate SNARE proteins and to examine the role of Munc18c in regulating liposome fusion catalysed by syntaxin 4/SNAP23/VAMP2 SNARE complex formation. We demonstrate that Munc18c makes contacts with both t- and v-SNARE proteins of this complex, and directly inhibits bilayer fusion mediated by the syntaxin 4/SNAP23/VAMP2 SNARE complex. CONCLUSION/SIGNIFICANCE: Our reductionist approach has enabled us to ascertain a direct inhibitory role for Munc18c in regulating membrane fusion mediated by syntaxin 4/SNAP23/VAMP2 SNARE complex formation. It is important to note that two different SM proteins have recently been shown to stimulate liposome fusion mediated by their cognate SNARE complexes. Given the structural similarities between SM proteins, it seems unlikely that different members of this family perform opposing regulatory functions. Hence, our findings indicate that Munc18c requires a further level of regulation in order to stimulate SNARE-mediated membrane fusion.

  5. Dynamin regulates metaphase furrow formation and plasma membrane compartmentalization in the syncytial Drosophila embryo

    Science.gov (United States)

    Rikhy, Richa; Mavrakis, Manos; Lippincott-Schwartz, Jennifer

    2015-01-01

    ABSTRACT The successive nuclear division cycles in the syncytial Drosophila embryo are accompanied by ingression and regression of plasma membrane furrows, which surround individual nuclei at the embryo periphery, playing a central role in embryo compartmentalization prior to cellularization. Here, we demonstrate that cell cycle changes in dynamin localization and activity at the plasma membrane (PM) regulate metaphase furrow formation and PM organization in the syncytial embryo. Dynamin was localized on short PM furrows during interphase, mediating endocytosis of PM components. Dynamin redistributed off ingressed PM furrows in metaphase, correlating with stabilized PM components and the associated actin regulatory machinery on long furrows. Acute inhibition of dynamin in the temperature sensitive shibire mutant embryo resulted in morphogenetic consequences in the syncytial division cycle. These included inhibition of metaphase furrow ingression, randomization of proteins normally polarized to intercap PM and disruption of the diffusion barrier separating PM domains above nuclei. Based on these findings, we propose that cell cycle changes in dynamin orchestrate recruitment of actin regulatory machinery for PM furrow dynamics during the early mitotic cycles in the Drosophila embryo. PMID:25661871

  6. Rab, Arf, and Arl-Regulated Membrane Traffic in Cortical Neuron Migration.

    Science.gov (United States)

    Tang, Bor Luen

    2016-07-01

    The migration of projection neurons from its birthplace in the subventricular zone to their final destination in the cortical plate is a complex process that requires a series of highly coordinated cellular events. Amongst the key factors involved in the processes are modulators of cytoskeletal dynamics, as well as cellular membrane traffic. Members of the small GTPases family responsible for the latter process, the Rabs and Arfs, have been recently implicated in cortical neuron migration. Rab5 and Rab11, which are key modulators of endocytosis and endocytic recycling respectively, ensure proper surface expression and distribution of N-cadherin, a key adhesion protein that tethers migrating neurons to the radial glia fiber tracts during pia-directed migration. Rab7, which is associated with lysosomal biogenesis and function, is important for the final step of terminal translocation when N-cadherin is downregulated by lysosomal degradation. Arf6 activity, which is known to be important in neuronal processes outgrowth, may negatively impact the multipolar-bipolar transition of cortical neurons undergoing radial migration, but the downstream effector of Arf6 in this regard is not yet known. In addition to the above, members of the Arl family which have been recently shown to be important in radial glia scaffold formation, would also be important for cortical neuron migration. In this short review, we discuss recent advances in our understanding of the importance of membrane traffic regulated by the Rab, Arf, and Arl family members in cortical neuron migration.

  7. The role of membrane fatty-acid transporters in regulating skeletal muscle substrate use during exercise.

    Science.gov (United States)

    Pelsers, Maurice M A L; Stellingwerff, Trent; van Loon, Luc J C

    2008-01-01

    While endogenous carbohydrates form the main substrate source during high-intensity exercise, long-chain fatty acids (LCFA) represent the main substrate source during more prolonged low- to moderate-intensity exercise. Adipose tissue lipolysis is responsible for the supply of LCFA to the contracting muscle. Once taken up by skeletal muscle tissue, LCFA can either serve as a substrate for oxidative phosphorylation or can be directed towards esterification into triacylglycerol. Myocellular uptake of LCFA comprises a complex and incompletely understood process. Although LCFA can enter the cell via passive diffusion, more recent reports indicate that LCFA uptake is tightly regulated by plasma membrane-located transport proteins (fatty acid translocase [FAT/CD36], plasmalemmal-located fatty acid binding protein [FABPpm] and fatty acid transport protein [FATP]). Depending on cardiac and skeletal muscle energy demands, some of these LCFA transporters can translocate rapidly from intracellular pools to the plasma membrane to allow greater LCFA uptake. This translocation process can be induced by insulin and/or muscle contraction. However, the precise signalling pathways responsible for activating the translocation machinery remain to be elucidated. This article will provide an overview on the effects of diet, acute exercise and exercise training on the expression and/or translocation of the various LCFA transporters in skeletal muscle tissue (FAT/CD36, FABPpm, FATP).

  8. Dynamin regulates metaphase furrow formation and plasma membrane compartmentalization in the syncytial Drosophila embryo

    Directory of Open Access Journals (Sweden)

    Richa Rikhy

    2015-02-01

    Full Text Available The successive nuclear division cycles in the syncytial Drosophila embryo are accompanied by ingression and regression of plasma membrane furrows, which surround individual nuclei at the embryo periphery, playing a central role in embryo compartmentalization prior to cellularization. Here, we demonstrate that cell cycle changes in dynamin localization and activity at the plasma membrane (PM regulate metaphase furrow formation and PM organization in the syncytial embryo. Dynamin was localized on short PM furrows during interphase, mediating endocytosis of PM components. Dynamin redistributed off ingressed PM furrows in metaphase, correlating with stabilized PM components and the associated actin regulatory machinery on long furrows. Acute inhibition of dynamin in the temperature sensitive shibire mutant embryo resulted in morphogenetic consequences in the syncytial division cycle. These included inhibition of metaphase furrow ingression, randomization of proteins normally polarized to intercap PM and disruption of the diffusion barrier separating PM domains above nuclei. Based on these findings, we propose that cell cycle changes in dynamin orchestrate recruitment of actin regulatory machinery for PM furrow dynamics during the early mitotic cycles in the Drosophila embryo.

  9. Cryobehavior of the plasma membrane in protoplasts isolated from cold-acclimated Arabidopsis leaves is related to surface area regulation.

    Science.gov (United States)

    Yamazaki, Tomokazu; Kawamura, Yukio; Uemura, Matsuo

    2008-06-01

    Extracellular freezing in plants results in dehydration and mechanical stresses upon the plasma membrane. Plants that acquire enhanced freezing tolerance after cold acclimation can withstand these two physical stresses. To understand the tolerance to freeze-induced physical stresses, the cryobehavior of the plasma membrane was observed using protoplasts isolated from cold-acclimated Arabidopsis thaliana leaves with the combination of a lipophilic fluorescent dye FM 1-43 and cryomicroscopy. We found that many vesicular structures appeared in the cytoplasmic region near the plasma membrane just after extracellular freezing occurred. These structures, referred to as freeze-induced vesicular structures (FIVs), then developed horizontally near the plasma membrane during freezing. There was a strong correlation between the increase in individual FIV size and the decrease in the surface area of the protoplasts during freezing. Some FIVs fused with their neighbors as the temperature decreased. Occasionally, FIVs fused with the plasma membrane, which may be necessary to relax the stress upon the plasma membrane during freezing. Vesicular structures resembling FIVs were also induced when protoplasts were mechanically pressed between a coverslip and slide glass. Fewer FIVs formed when protoplasts were subjected to hyperosmotic solution, suggesting that FIV formation is associated with mechanical stress rather than dehydration. Collectively, these results suggest that cold-acclimated plant cells may balance membrane tension in the plasma membrane by regulating the surface area. This enables plant cells to withstand the direct mechanical stress imposed by extracellular freezing.

  10. Insulin-regulated Glut4 translocation: membrane protein trafficking with six distinctive steps.

    Science.gov (United States)

    Brewer, Paul Duffield; Habtemichael, Estifanos N; Romenskaia, Irina; Mastick, Cynthia Corley; Coster, Adelle C F

    2014-06-20

    The trafficking kinetics of Glut4, the transferrin (Tf) receptor, and LRP1 were quantified in adipocytes and undifferentiated fibroblasts. Six steps were identified that determine steady state cell surface Glut4: (i) endocytosis, (ii) degradation, (iii) sorting, (iv) sequestration, (v) release, and (vi) tethering/docking/fusion. Endocytosis of Glut4 is 3 times slower than the Tf receptor in fibroblasts (ken = 0.2 min(-1) versus 0.6 min(-1)). Differentiation decreases Glut4 ken 40% (ken = 0.12 min(-1)). Differentiation also decreases Glut4 degradation, increasing total and cell surface Glut4 3-fold. In fibroblasts, Glut4 is recycled from endosomes through a slow constitutive pathway (kex = 0.025-0.038 min(-1)), not through the fast Tf receptor pathway (kex = 0.2 min(-1)). The kex measured in adipocytes after insulin stimulation is similar (kex = 0.027 min(-1)). Differentiation decreases the rate constant for sorting into the Glut4 recycling pathway (ksort) 3-fold. In adipocytes, Glut4 is also sorted from endosomes into a second exocytic pathway through Glut4 storage vesicles (GSVs). Surprisingly, transfer from endosomes into GSVs is highly regulated; insulin increases the rate constant for sequestration (kseq) 8-fold. Release from sequestration in GSVs is rate-limiting for Glut4 exocytosis in basal adipocytes. AS160 regulates this step. Tethering/docking/fusion of GSVs to the plasma membrane is regulated through an AS160-independent process. Insulin increases the rate of release and fusion of GSVs (kfuseG) 40-fold. LRP1 cycles with the Tf receptor and Glut4 in fibroblasts but predominantly with Glut4 after differentiation. Surprisingly, AS160 knockdown accelerated LRP1 exocytosis in basal and insulin-stimulated adipocytes. These data indicate that AS160 may regulate trafficking into as well as release from GSVs.

  11. Thermodynamic competition between membrane protein oligomeric states

    Science.gov (United States)

    Kahraman, Osman; Haselwandter, Christoph A.

    2016-10-01

    Self-assembly of protein monomers into distinct membrane protein oligomers provides a general mechanism for diversity in the molecular architectures, and resulting biological functions, of membrane proteins. We develop a general physical framework describing the thermodynamic competition between different oligomeric states of membrane proteins. Using the mechanosensitive channel of large conductance as a model system, we show how the dominant oligomeric states of membrane proteins emerge from the interplay of protein concentration in the cell membrane, protein-induced lipid bilayer deformations, and direct monomer-monomer interactions. Our results suggest general physical mechanisms and principles underlying regulation of protein function via control of membrane protein oligomeric state.

  12. Thermodynamic competition between membrane protein oligomeric states

    CERN Document Server

    Kahraman, Osman

    2016-01-01

    Self-assembly of protein monomers into distinct membrane protein oligomers provides a general mechanism for diversity in the molecular architectures, and resulting biological functions, of membrane proteins. We develop a general physical framework describing the thermodynamic competition between different oligomeric states of membrane proteins. Using the mechanosensitive channel of large conductance as a model system, we show how the dominant oligomeric states of membrane proteins emerge from the interplay of protein concentration in the cell membrane, protein-induced lipid bilayer deformations, and direct monomer-monomer interactions. Our results suggest general physical mechanisms and principles underlying regulation of protein function via control of membrane protein oligomeric state.

  13. Recruitment of SH-containing peptides to lipid and biological membranes through the use of a palmitic acid functionalized with a maleimide group.

    Science.gov (United States)

    Haralampiev, Ivan; Mertens, Monique; Schwarzer, Roland; Herrmann, Andreas; Volkmer, Rudolf; Wessig, Pablo; Müller, Peter

    2015-01-02

    This study presents a novel and easily applicable approach to recruit sulfhydryl-containing biomolecules to membranes by using a palmitic acid which is functionalized with a maleimide group. Notably, this strategy can also be employed with preformed (biological) membranes. The applicability of the assay is demonstrated by characterizing the binding of a Rhodamine-labeled peptide to lipid and cellular membranes using methods of fluorescence spectroscopy, lifetime measurement, and microscopy. Our approach offers new possibilities for preparing biologically active liposomes and manipulating living cells.

  14. The dynamics of the biological membrane surrounding the buffalo milk fat globule investigated as a function of temperature.

    Science.gov (United States)

    Nguyen, Hanh T H; Madec, Marie-Noëlle; Ong, Lydia; Kentish, Sandra E; Gras, Sally L; Lopez, Christelle

    2016-08-01

    The biological membrane surrounding fat globules in milk (the MFGM) is poorly understood, despite its importance in digestion and in determining the properties of fat globules. In this study, in situ structural investigations of buffalo MFGM were performed as a function of temperature (4-60°C), using confocal microscopy. We demonstrate that temperature and rate of temperature change affected the lipid domains formed in the MFGM with the lateral segregation (i) of high Tm lipids and cholesterol in a Lo phase for both TTm and (ii) of high Tm lipids in a gel phase for Tfat globules during processing and digestion.

  15. Membrane-localized β-subunits alter the PIP2 regulation of high-voltage activated Ca2+ channels.

    Science.gov (United States)

    Suh, Byung-Chang; Kim, Dong-Il; Falkenburger, Björn H; Hille, Bertil

    2012-02-21

    The β-subunits of voltage-gated Ca(2+) (Ca(V)) channels regulate the functional expression and several biophysical properties of high-voltage-activated Ca(V) channels. We find that Ca(V) β-subunits also determine channel regulation by the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)). When Ca(V)1.3, -2.1, or -2.2 channels are cotransfected with the β3-subunit, a cytosolic protein, they can be inhibited by activating a voltage-sensitive lipid phosphatase to deplete PIP(2). When these channels are coexpressed with a β2a-subunit, a palmitoylated peripheral membrane protein, the inhibition is much smaller. PIP(2) sensitivity could be increased by disabling the two palmitoylation sites in the β2a-subunit. To further test effects of membrane targeting of Ca(V) β-subunits on PIP(2) regulation, the N terminus of Lyn was ligated onto the cytosolic β3-subunit to confer lipidation. This chimera, like the Ca(V) β2a-subunit, displayed plasma membrane localization, slowed the inactivation of Ca(V)2.2 channels, and increased the current density. In addition, the Lyn-β3 subunit significantly decreased Ca(V) channel inhibition by PIP(2) depletion. Evidently lipidation and membrane anchoring of Ca(V) β-subunits compete with the PIP(2) regulation of high-voltage-activated Ca(V) channels. Compared with expression with Ca(V) β3-subunits alone, inhibition of Ca(V)2.2 channels by PIP(2) depletion could be significantly attenuated when β2a was coexpressed with β3. Our data suggest that the Ca(V) currents in neurons would be regulated by membrane PIP(2) to a degree that depends on their endogenous β-subunit combinations.

  16. A Sucrose Solution Application to the Study of Model Biological Membranes

    CERN Document Server

    Kiselev, M A; Kisselev, A M; Lombardo, D; Killany, M; Lesieur, S; Ollivon, M

    2001-01-01

    The small-angle X-ray and neutron scattering, time resolved X-ray small-angle and wide-angle diffraction coupled with differential scanning calorimetry have been applied to the investigation of unilamellar and multilamellar dimyristoylphosphatidylcholine (DMPC) vesicles in sucrose buffers with sucrose concentrations from 0 to 60%. Sucrose buffer decreased vesicle size and polydispersity and increased an X-ray contrast between phospholipid membrane and bulk solvent sufficiently. No influence of sucrose on the membrane thickness or mutual packing of hydrocarbon chains has been detected. The region of sucrose concentrations 30%-40% created the best experimental conditions for X-ray small-angle experiments with phospholipid vesicles.

  17. Membrane cholesterol regulates lysosome-plasma membrane fusion events and modulates Trypanosoma cruzi invasion of host cells.

    Directory of Open Access Journals (Sweden)

    Bárbara Hissa

    Full Text Available BACKGROUND: Trypomastigotes of Trypanosoma cruzi are able to invade several types of non-phagocytic cells through a lysosomal dependent mechanism. It has been shown that, during invasion, parasites trigger host cell lysosome exocytosis, which initially occurs at the parasite-host contact site. Acid sphingomyelinase released from lysosomes then induces endocytosis and parasite internalization. Lysosomes continue to fuse with the newly formed parasitophorous vacuole until the parasite is completely enclosed by lysosomal membrane, a process indispensable for a stable infection. Previous work has shown that host membrane cholesterol is also important for the T. cruzi invasion process in both professional (macrophages and non-professional (epithelial phagocytic cells. However, the mechanism by which cholesterol-enriched microdomains participate in this process has remained unclear. METHODOLOGY/PRINCIPAL FINDING: In the present work we show that cardiomyocytes treated with MβCD, a drug able to sequester cholesterol from cell membranes, leads to a 50% reduction in invasion by T. cruzi trypomastigotes, as well as a decrease in the number of recently internalized parasites co-localizing with lysosomal markers. Cholesterol depletion from host membranes was accompanied by a decrease in the labeling of host membrane lipid rafts, as well as excessive lysosome exocytic events during the earlier stages of treatment. Precocious lysosomal exocytosis in MβCD treated cells led to a change in lysosomal distribution, with a reduction in the number of these organelles at the cell periphery, and probably compromises the intracellular pool of lysosomes necessary for T. cruzi invasion. CONCLUSION/SIGNIFICANCE: Based on these results, we propose that cholesterol depletion leads to unregulated exocytic events, reducing lysosome availability at the cell cortex and consequently compromise T. cruzi entry into host cells. The results also suggest that two different pools of

  18. Contribution of a Membrane Estrogen Receptor to the Estrogenic Regulation of Body Temperature and Energy Homeostasis

    Science.gov (United States)

    Roepke, Troy A.; Bosch, Martha A.; Rick, Elizabeth A.; Lee, Benjamin; Wagner, Edward J.; Seidlova-Wuttke, Dana; Wuttke, Wolfgang; Scanlan, Thomas S.; Rønnekleiv, Oline K.; Kelly, Martin J.

    2010-01-01

    The hypothalamus is a key region of the central nervous system involved in the control of homeostasis, including energy and core body temperature (Tc). 17β-Estradiol (E2) regulates Tc, in part, via actions in the basal hypothalamus and preoptic area. E2 primarily controls hypothalamic functions via the nuclear steroid receptors, estrogen receptor α/β. However, we have previously described an E2-responsive, Gq-coupled membrane receptor that reduces the postsynaptic inhibitory γ-aminobutyric acid-ergic tone and attenuates postovariectomy body weight gain in female guinea pigs through the administration of a selective Gq-mER ligand, STX. To determine the role of Gq-mER in regulating Tc, energy and bone homeostasis, ovariectomized female guinea pigs, implanted ip with temperature probes, were treated with STX or E2 for 7–8 wk. Tc was recorded for 4 wk, whereas food intake and body weight were monitored daily. Bone density and fat accumulation were determined postmortem. Both E2 and STX significantly reduced Tc in the females compared with controls. STX, similar to E2, reduced food intake and fat accumulation and increased tibial bone density. Therefore, a Gq-mER-coupled signaling pathway appears to be involved in maintaining homeostatic functions and may constitute a novel therapeutic target for treatment of hypoestrogenic symptoms. PMID:20685867

  19. Geranylgeranyl-regulated transport of the prenyltransferase UBIAD1 between membranes of the ER and Golgi.

    Science.gov (United States)

    Schumacher, Marc M; Jun, Dong-Jae; Jo, Youngah; Seemann, Joachim; DeBose-Boyd, Russell A

    2016-07-01

    UbiA prenyltransferase domain-containing protein-1 (UBIAD1) utilizes geranylgeranyl pyrophosphate (GGpp) to synthesize the vitamin K2 subtype menaquinone-4. Previously, we found that sterols trigger binding of UBIAD1 to endoplasmic reticulum (ER)-localized HMG-CoA reductase, the rate-limiting enzyme in synthesis of cholesterol and nonsterol isoprenoids, including GGpp. This binding inhibits sterol-accelerated degradation of reductase, which contributes to feedback regulation of the enzyme. The addition to cells of geranylgeraniol (GGOH), which can become converted to GGpp, triggers release of UBIAD1 from reductase, allowing for its maximal degradation and permitting ER-to-Golgi transport of UBIAD1. Here, we further characterize geranylgeranyl-regulated transport of UBIAD1. Results of this characterization support a model in which UBIAD1 continuously cycles between the ER and medial-trans Golgi of isoprenoid-replete cells. Upon sensing a decline of GGpp in ER membranes, UBIAD1 becomes trapped in the organelle where it inhibits reductase degradation. Mutant forms of UBIAD1 associated with Schnyder corneal dystrophy (SCD), a human eye disease characterized by corneal accumulation of cholesterol, are sequestered in the ER and block reductase degradation. Collectively, these findings disclose a novel sensing mechanism that allows for stringent metabolic control of intracellular trafficking of UBIAD1, which directly modulates reductase degradation and becomes disrupted in SCD.

  20. Chitosan facilitates structure formation of the salivary gland by regulating the basement membrane components.

    Science.gov (United States)

    Yang, Tsung-Lin; Hsiao, Ya-Chuan

    2015-10-01

    Tissue structure is important for inherent physiological function and should be recapitulated during tissue engineering for regenerative purposes. The salivary gland is a branched organ that is responsible for saliva secretion and regulation. The salivary glands develop from epithelial-mesenchymal interactions, and depend on the support of the basement membrane (BM). Chitosan-based biomaterials have been demonstrated to be competent in facilitating the formation of salivary gland tissue structure. However, the underlying mechanisms have remained elusive. In the developing submandibular gland (SMG), the chitosan effect was found to diminish when collagen and laminin were removed from cultured SMG explants. Chitosan increased the expression of BM components including collagen, laminin, and heparan sulfate proteoglycan, and also facilitated BM components and the corresponding receptors to be expressed in tissue-specific patterns beneficial for SMG branching. The chitosan effect decreased when either laminin components or receptors were inhibited, as well when the downstream signaling was blocked. Our results revealed that chitosan promotes salivary glands branching through the BM. By regulating BM components and receptors, chitosan efficiently stimulated downstream signaling to facilitate salivary gland branching. The present study revealed the underlying mechanism of the chitosan effect in engineering SMG structure formation.

  1. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  2. Regulation of Spatiotemporal Patterns by Biological Variability: General Principles and Applications to Dictyostelium discoideum.

    Directory of Open Access Journals (Sweden)

    Miriam Grace

    2015-11-01

    Full Text Available Spatiotemporal patterns often emerge from local interactions in a self-organizing fashion. In biology, the resulting patterns are also subject to the influence of the systematic differences between the system's constituents (biological variability. This regulation of spatiotemporal patterns by biological variability is the topic of our review. We discuss several examples of correlations between cell properties and the self-organized spatiotemporal patterns, together with their relevance for biology. Our guiding, illustrative example will be spiral waves of cAMP in a colony of Dictyostelium discoideum cells. Analogous processes take place in diverse situations (such as cardiac tissue, where spiral waves occur in potentially fatal ventricular fibrillation so a deeper understanding of this additional layer of self-organized pattern formation would be beneficial to a wide range of applications. One of the most striking differences between pattern-forming systems in physics or chemistry and those in biology is the potential importance of variability. In the former, system components are essentially identical with random fluctuations determining the details of the self-organization process and the resulting patterns. In biology, due to variability, the properties of potentially very few cells can have a driving influence on the resulting asymptotic collective state of the colony. Variability is one means of implementing a few-element control on the collective mode. Regulatory architectures, parameters of signaling cascades, and properties of structure formation processes can be "reverse-engineered" from observed spatiotemporal patterns, as different types of regulation and forms of interactions between the constituents can lead to markedly different correlations. The power of this biology-inspired view of pattern formation lies in building a bridge between two scales: the patterns as a collective state of a very large number of cells on the one hand

  3. Posttranscriptional Regulation of Splicing Factor SRSF1 and Its Role in Cancer Cell Biology

    Directory of Open Access Journals (Sweden)

    Vânia Gonçalves

    2015-01-01

    Full Text Available Over the past decade, alternative splicing has been progressively recognized as a major mechanism regulating gene expression patterns in different tissues and disease states through the generation of multiple mRNAs from the same gene transcript. This process requires the joining of selected exons or usage of different pairs of splice sites and is regulated by gene-specific combinations of RNA-binding proteins. One archetypical splicing regulator is SRSF1, for which we review the molecular mechanisms and posttranscriptional modifications involved in its life cycle. These include alternative splicing of SRSF1 itself, regulatory protein phosphorylation events, and the role of nuclear versus cytoplasmic SRSF1 localization. In addition, we resume current knowledge on deregulated SRSF1 expression in tumors and describe SRSF1-regulated alternative transcripts with functional consequences for cancer cell biology at different stages of tumor development.

  4. Identification of a novel role for dematin in regulating red cell membrane function by modulating spectrin-actin interaction.

    Science.gov (United States)

    Koshino, Ichiro; Mohandas, Narla; Takakuwa, Yuichi

    2012-10-12

    The membrane skeleton plays a central role in maintaining the elasticity and stability of the erythrocyte membrane, two biophysical features critical for optimal functioning and survival of red cells. Many constituent proteins of the membrane skeleton are phosphorylated by various kinases, and phosphorylation of β-spectrin by casein kinase and of protein 4.1R by PKC has been documented to modulate erythrocyte membrane mechanical stability. In this study, we show that activation of endogenous PKA by cAMP decreases membrane mechanical stability and that this effect is mediated primarily by phosphorylation of dematin. Co-sedimentation assay showed that dematin facilitated interaction between spectrin and F-actin, and phosphorylation of dematin by PKA markedly diminished this activity. Quartz crystal microbalance measurement revealed that purified dematin specifically bound the tail region of the spectrin dimer in a saturable manner with a submicromolar affinity. Pulldown assay using recombinant spectrin fragments showed that dematin, but not phospho-dematin, bound to the tail region of the spectrin dimer. These findings imply that dematin contributes to the maintenance of erythrocyte membrane mechanical stability by facilitating spectrin-actin interaction and that phosphorylation of dematin by PKA can modulate these effects. In this study, we have uncovered a novel functional role for dematin in regulating erythrocyte membrane function.

  5. Location and activity of ubiquinone 10 and ubiquinone analogues in model and biological membranes

    Energy Technology Data Exchange (ETDEWEB)

    Cornell, B.A.; Keniry, M.A.; Post, A.; Roberston, R.N.; Weir, L.E.; Westerman, P.W.

    1987-12-01

    Deuteriated analogues of ubiquinone 10 (Q/sup 10/) have been dispersed with plasma membranes of Escherichia coli and with the inner membranes of beetroot mitochondria. Orientational order at various deuteriated sites was measured by solid-state deuterium nuclear magnetic resonance (/sup 2/H NMR). Similar measurements were made, using the compounds dispersed in dimyristoylphosphatidylcholine (DMPC) and egg yolk lecithin and dispersions prepared from the lipid extracts of beetroot mitochondria. In all cases only a single unresolved /sup 2/H NMR spectrum (typically 1000-Hz full width at half-height) was observed at concentrations down to 0.02 mol % Q/sub 10/ per membrane lipid. This result shows that most Q/sub 10/ is in a mobile environment which is physically separate from the orientational constraints of the bilayer lipid chains. In contrast, a short-chain analog of Q/sub 10/, in which the 10 isoprene groups have been replaced by a perdeuteriated tridecyl chain, showed /sup 2/H NMR spectra with quadrupolar splittings typical of an ordered lipid that is intercalated into the bilayer. The NADH oxidase activity and O/sub 2/ uptake in Escherichia coli and in mitochondria were independent of which analog was incorporated into the membrane. Thus, despite the major difference in their physical association with membranes, or their lipid extracts, the electron transport function of the long- and short-chain ubiquinones is similar, suggesting that the bulk of the long-chain ubiquinone does not have a direct function in electron transporting activity. The physiologically active Q/sub 10/ may only be a small fraction of the total ubiquinone, a fraction that is below the level of detection of the present NMR equipment. However, our results do not support any model of Q/sub 10/ electron transport action that includes intercalation of the long isoprenoid chain in lipid.

  6. Biological principles of microRNA-mediated regulation: shared themes amid diversity.

    Science.gov (United States)

    Flynt, Alex S; Lai, Eric C

    2008-11-01

    Regulation of gene activity by microRNAs is critical to myriad aspects of eukaryotic development and physiology. Amidst an extensive regulatory web that is predicted to involve thousands of transcripts, emergent themes are now beginning to illustrate how microRNAs have been incorporated into diverse settings. These include potent inhibition of individual key targets, fine-tuning of target activity, the coordinated regulation of target batteries, and the reversibility of some aspects of microRNA-mediated repression. Such themes may reflect some of the inherent advantages of exploiting microRNA control in biological circuits, and provide insight into the consequences of microRNA dysfunction in disease.

  7. The role of putrescine in the regulation of proteins and fatty acids of thylakoid membranes under salt stress.

    Science.gov (United States)

    Shu, Sheng; Yuan, Yinghui; Chen, Jie; Sun, Jin; Zhang, Wenhua; Tang, Yuanyuan; Zhong, Min; Guo, Shirong

    2015-10-05

    Polyamines can alleviate the inhibitory effects of salinity on plant growth by regulating photosynthetic efficiency. However, little information is available to explain the specific mechanisms underlying the contribution of polyamines to salt tolerance of the photosynthetic apparatus. Here, we investigated the role of putrescine (Put) on the photosynthetic apparatus of cucumber seedlings under salt stress. We found that NaCl stress resulted in severe ion toxicity and oxidative stress in cucumber chloroplasts. In addition, salinity caused a significant increase in the saturated fatty acid contents of thylakoid membranes. Put altered unsaturated fatty acid content, thereby alleviating the disintegration of thylakoid grana lamellae and reducing the number of plastoglobuli in thylakoid membranes. BN-PAGE revealed Put up-regulated the expression of ATP synthase, CP47, D1, Qb, and psbA proteins and down-regulated CP24, D2, and LHCII type III in NaCl-stressed thylakoid membranes. qRT-PCR analysis of gene expression was used to compare transcript and protein accumulation among 10 candidate proteins. For five of these proteins, induced transcript accumulation was consistent with the pattern of induced protein accumulation. Our results suggest that Put regulates protein expression at transcriptional and translational levels by increasing endogenous polyamines levels in thylakoid membranes, which may stabilise photosynthetic apparatus under salt stress.

  8. Regulation by the quorum sensor from Vibrio indicates a receptor function for the membrane anchors of adenylate cyclases.

    Science.gov (United States)

    Beltz, Stephanie; Bassler, Jens; Schultz, Joachim E

    2016-02-27

    Adenylate cyclases convert intra- and extracellular stimuli into a second messenger cAMP signal. Many bacterial and most eukaryotic ACs possess membrane anchors with six transmembrane spans. We replaced the anchor of the AC Rv1625c by the quorum-sensing receptor from Vibrio harveyi which has an identical 6TM design and obtained an active, membrane-anchored AC. We show that a canonical class III AC is ligand-regulated in vitro and in vivo. At 10 µM, the cholera-autoinducer CAI-1 stimulates activity 4.8-fold. A sequence based clustering of membrane domains of class III ACs and quorum-sensing receptors established six groups of potential structural and functional similarities. The data support the notion that 6TM AC membrane domains may operate as receptors which directly regulate AC activity as opposed and in addition to the indirect regulation by GPCRs in eukaryotic congeners. This adds a completely novel dimension of potential AC regulation in bacteria and vertebrates.

  9. Structure and ultrastructure of fresh and preserved biological membranes of Santa Inês sheep (Ovis aries, L., 1758

    Directory of Open Access Journals (Sweden)

    Roméria Rodrigues Barbosa

    2012-06-01

    Full Text Available The use of biological implants, of animal or synthetic origin, is recommended for the reconstruction of tissue defects. Therefore, the objective of this study was to analyze the morphological structure and ultrastructure of the parietal peritoneum, parietal pericardium, tunica vaginalis and fascia lata of 15 Santa Inês sheep, which were adult males from Estância Santa Barbara, in the city of Poloni – SP. The membranes were collected immediately after the animals were slaughtered, individually identified and separated into two parts. The first part was stored in saline solution, and called the fresh sample. The other portion was stored in 98% glycerol for 15, 30, 60 and 90 days. All samples were subjected to standard histological techniques. Fresh samples and those preserved in glycerin for 30 days were also preparated and analyzed using scanning electron microscopy. We concluded that the fresh and preserved membranes, parietal peritoneum, parietal pericardium, tunica vaginalis and fascia lata, of the adult male Santa Inês sheep had a single type of tissue, which was unmodeled, dense connective tissue. The 98% glycerin used as a preservation medium was effective in maintaining the structural integrity of the tissue membranes.

  10. Priority of TCM in Regulating Gene Function as a Whole Through Development of Modern Biology

    Institute of Scientific and Technical Information of China (English)

    Hu zuo-wei; zhou yan-ping; Shen zi-yin

    2004-01-01

    Molecular Biology based on the DNA Double-helix structure has made great progress in 20 century.After Human Genome Project (HGP) completed, Molecular Biology is faced upon more and more challenges, andtake changes from protion concept to integration concept, from linear thinking to complicated thinking. so post-genomics, including functional genomics, proteomics, is gradually established. Among them, System Biology is themost prominent. It is becoming to tend to integration, and infiltrate to each other for the two thinking of genomeand TCM in studying life science, which reflect the inevitablility and importance of integration of TCM and West-ern Medicine. The priority of TCM in treatment as a whole, and regulating functional gene and functional networkmay take greater achievement in post - genomic time.

  11. Understanding the role of ETS-mediated gene regulation in complex biological processes.

    Science.gov (United States)

    Findlay, Victoria J; LaRue, Amanda C; Turner, David P; Watson, Patricia M; Watson, Dennis K

    2013-01-01

    Ets factors are members of one of the largest families of evolutionarily conserved transcription factors, regulating critical functions in normal cell homeostasis, which when perturbed contribute to tumor progression. The well-documented alterations in ETS factor expression and function during cancer progression result in pleiotropic effects manifested by the downstream effect on their target genes. Multiple ETS factors bind to the same regulatory sites present on target genes, suggesting redundant or competitive functions. The anti- and prometastatic signatures obtained by examining specific ETS regulatory networks will significantly improve our ability to accurately predict tumor progression and advance our understanding of gene regulation in cancer. Coordination of multiple ETS gene functions also mediates interactions between tumor and stromal cells and thus contributes to the cancer phenotype. As such, these new insights may provide a novel view of the ETS gene family as well as a focal point for studying the complex biological control involved in tumor progression. One of the goals of molecular biology is to elucidate the mechanisms that contribute to the development and progression of cancer. Such an understanding of the molecular basis of cancer will provide new possibilities for: (1) earlier detection, as well as better diagnosis and staging of disease; (2) detection of minimal residual disease recurrences and evaluation of response to therapy; (3) prevention; and (4) novel treatment strategies. Increased understanding of ETS-regulated biological pathways will directly impact these areas.

  12. Regulation of leptin expression by 17beta-estradiol in human placental cells involves membrane associated estrogen receptor alpha.

    Science.gov (United States)

    Gambino, Yésica P; Pérez Pérez, Antonio; Dueñas, José L; Calvo, Juan Carlos; Sánchez-Margalet, Víctor; Varone, Cecilia L

    2012-04-01

    The placenta produces a wide number of molecules that play essential roles in the establishment and maintenance of pregnancy. In this context, leptin has emerged as an important player in reproduction. The synthesis of leptin in normal trophoblastic cells is regulated by different endogenous biochemical agents, but the regulation of placental leptin expression is still poorly understood. We have previously reported that 17β-estradiol (E(2)) up-regulates placental leptin expression. To improve the understanding of estrogen receptor mechanisms in regulating leptin gene expression, in the current study we examined the effect of membrane-constrained E(2) conjugate, E-BSA, on leptin expression in human placental cells. We have found that leptin expression was induced by E-BSA both in BeWo cells and human placental explants, suggesting that E(2) also exerts its effects through membrane receptors. Moreover E-BSA rapidly activated different MAPKs and AKT pathways, and these pathways were involved in E(2) induced placental leptin expression. On the other hand we demonstrated the presence of ERα associated to the plasma membrane of BeWo cells. We showed that E(2) genomic and nongenomic actions could be mediated by ERα. Supporting this idea, the downregulation of ERα level through a specific siRNA, decreased E-BSA effects on leptin expression. Taken together, these results provide new evidence of the mechanisms whereby E(2) regulates leptin expression in placenta and support the importance of leptin in placental physiology.

  13. Detailed search for protein kinase(s) involved in plasma membrane H+-ATPase activity regulation of yeast cells.

    Science.gov (United States)

    Pereira, Renata R; Castanheira, Diogo; Teixeira, Janaina A; Bouillet, Leoneide E M; Ribeiro, Erica M C; Trópia, Maria M J; Alvarez, Florencia; Correa, Lygia F M; Mota, Bruno E F; Conceição, Luis Eduardo F R; Castro, Ieso M; Brandão, Rogelio L

    2015-03-01

    This study displays a screening using yeast strains deficient in protein kinases known to exist in Saccharomyces cerevisiae. From 95 viable single mutants, 20 mutants appear to be affected in the glucose-induced extracellular acidification. The mutants that are unaffected in calcium signaling were tested for their sensitivity to hygromycin B. Furthermore, we verified whether the remaining mutants produced enzymes that are appropriately incorporated at plasma membrane. Finally, we measure the kinetic properties of the enzyme in purified plasma membranes from glucose-starved as well as glucose-fermenting cells. We confirmed the kinase Ptk2 involvement in H(+)-ATPase regulation (increase of affinity for ATP). However, the identification of the kinase(s) responsible for phosphorylation that leads to an increase in Vmax appears to be more complex. Complementary experiments were performed to check how those protein kinases could be related to the control of the plasma membrane H(+)-ATPase and/or the potential membrane. In summary, our results did not permit us to identify the protein kinase(s) involved in regulating the catalytic efficiency of the plasma membrane H(+)-ATPase. Therefore, our results indicate that the current regulatory model based on the phosphorylation of two different sites located in the C-terminus tail of the enzyme could be inappropriate.

  14. Preparation, regulation and biological application of a Schiff base fluorescence probe

    Science.gov (United States)

    Yin, Ninghua; Diao, Haipeng; Liu, Wen; Wang, Jingru; Feng, Liheng

    2016-01-01

    A facile fluorescence switch with Schiff base units was designed and achieved by nucleophilic addition and dehydration reaction. The fluorescence of the probe can be regulated by metal ions (Al3 + and Cu2 +). The whole process shows that the weak fluorescence of the probe enhances with the addition of Al3 +, and then the strong fluorescence of the probe/Al3 + ensemble reduces by introducing Cu2 +. Meanwhile, the solution color changes of the probe with metal ions can be observed under 365 nm UV-vis light from weak light, pale green, green, pale green to weak light. Noticeably, the photo regulation processes of the probe by metal ions can be realized in the biological system and applied in cells imaging. The work provides a new strategy for designing facile regulation probe and develops a new application for Schiff base derivatives.

  15. Metabolic regulation of neutrophil spreading, membrane tubulovesicular extensions (cytonemes) formation and intracellular pH upon adhesion to fibronectin.

    Science.gov (United States)

    Galkina, Svetlana I; Sud'ina, Galina F; Klein, Thomas

    2006-08-01

    Circulating leukocytes have a round cell shape and roll along vessel walls. However, metabolic disorders can lead them to adhere to the endothelium and spread (flatten). We studied the metabolic regulation of adhesion, spreading and intracellular pH (pHi) of neutrophils (polymorphonuclear leukocytes) upon adhesion to fibronectin-coated substrata. Resting neutrophils adhered and spread on fibronectin. An increase in pHi accompanied neutrophil spreading. Inhibition of oxidative phosphorylation or inhibition of P- and F-type ATPases affected neither neutrophil spreading nor pHi. Inhibition of glucose metabolism or V-ATPase impaired neutrophil spreading, blocked the increase in the pHi and induced extrusion of membrane tubulovesicular extensions (cytonemes), anchoring cells to substrata. Omission of extracellular Na(+) and inhibition of chloride channels caused a similar effect. We propose that these tubulovesicular extensions represent protrusions of exocytotic trafficking, supplying the plasma membrane of neutrophils with ion exchange mechanisms and additional membrane for spreading. Glucose metabolism and V-type ATPase could affect fusion of exocytotic trafficking with the plasma membrane, thus controlling neutrophil adhesive state and pHi. Cl(-) efflux through chloride channels and Na(+) influx seem to be involved in the regulation of the V-ATPase by carrying out charge compensation for the proton-pumping activity and through V-ATPase in regulation of neutrophil spreading and pHi.

  16. Regulation of B cell differentiation by intracellular membrane associated proteins and microRNAs: role in the antibody response

    Directory of Open Access Journals (Sweden)

    Zheng eLou

    2015-10-01

    Full Text Available B cells are central to adaptive immunity and their functions in antibody responses are exquisitely regulated. As suggested by recent findings, B cell differentiation is mediated by intracellular membrane structures (including endosomes, lysosomes and autophagosomes and protein factors specifically associated with these membranes, including Rab7, Atg5 and Atg7. These factors participate in vesicle formation/trafficking, signal transduction and induction of gene expression to promote antigen presentation, CSR/SHM, and generation/maintenance of plasma cells and memory B cells. Their expression is induced in B cells activated to differentiate and further fine-tuned by immune-modulating microRNAs, which coordinates CSR/SHM, plasma cell differentiation and memory B cell differentiation. These short non-coding RNAs would individually target multiple factors associated with the same intracellular membrane compartments and collaboratively target a single factor in addition to regulate AID and Blimp-1. These, together with regulation of microRNA biogenesis and activities by endosomes and autophagosomes, show that intracellular membranes and microRNAs, two broadly relevant cell constituents, play important roles in balancing gene expression to specify B cell differentiation processes for optimal antibody responses.

  17. Ferlins: regulators of vesicle fusion for auditory neurotransmission, receptor trafficking and membrane repair.

    Science.gov (United States)

    Lek, Angela; Evesson, Frances J; Sutton, R Bryan; North, Kathryn N; Cooper, Sandra T

    2012-02-01

    Ferlins are a family of multiple C2 domain proteins with emerging roles in vesicle fusion and membrane trafficking. Ferlin mutations are associated with muscular dystrophy (dysferlin) and deafness (otoferlin) in humans, and infertility in Caenorhabditis elegans (Fer-1) and Drosophila (misfire), demonstrating their importance for normal cellular functioning. Ferlins show ancient origins in eukaryotic evolution and are detected in all eukaryotic kingdoms, including unicellular eukaryotes and apicomplexian protists, suggesting origins in a common ancestor predating eukaryotic evolutionary branching. The characteristic feature of the ferlin family is their multiple tandem cytosolic C2 domains (five to seven C2 domains), the most of any protein family, and an extremely rare feature amongst eukaryotic proteins. Ferlins also bear a unique nested DysF domain and small conserved 60-70 residue ferlin-specific sequences (Fer domains). Ferlins segregate into two subtypes based on the presence (type I ferlin) or absence (type II ferlin) of the DysF and FerA domains. Ferlins have diverse tissue-specific and developmental expression patterns, with ferlin animal models united by pathologies arising from defects in vesicle fusion. Consistent with their proposed role in vesicle trafficking, ferlin interaction partners include cytoskeletal motors, other vesicle-associated trafficking proteins and transmembrane receptors or channels. Herein we summarize the research history of the ferlins, an intriguing family of structurally conserved proteins with a preserved ancestral function as regulators of vesicle fusion and receptor trafficking.

  18. On active disturbance rejection in temperature regulation of the proton exchange membrane fuel cells

    Science.gov (United States)

    Li, Dazi; Li, Chong; Gao, Zhiqiang; Jin, Qibing

    2015-06-01

    Operating a Proton Exchange Membrane fuel cell (PEMFC) system to maintain the stack temperature stable is one of the key issues in PEMFC's normal electrochemical reaction process. Its temperature characteristic is easily affected by inlet gas humidity, external disturbances, and electrical load changes and so on. Because of the complexity and nonlinearity of the reaction process, it is hard to build a model totally consistent with the real characteristic of the process. If model uncertainty, external disturbances, parameters changes can be regarded as "total disturbance", which is then estimated and compensated, the accurate model is no longer required and the control design can be greatly simplified to meet the practical needs. Based on this idea, an active disturbance rejection control (ADRC) with a switching law is proposed for the problem of precise temperature regulation in PEMFC. Results of the work show that the proposed control system allows the PEMFC to operate successfully at the temperature of 343 K point in the presence of two different disturbances.

  19. Role of the basement membrane in regulation of cardiac electrical properties.

    Science.gov (United States)

    Yang, Huaxiao; Borg, Thomas K; Wang, Zhonghai; Ma, Zhen; Gao, Bruce Z

    2014-06-01

    In the heart muscle, each adult cardiomyocyte is enclosed by a basement membrane (BM). This innermost extracellular matrix is a layered assembly of laminin, collagen IV, glycoproteins, and proteoglycans. In this study, the role of the BM network in regulation of the electrical properties of neonatal cardiomyocytes (NCMs) cultured on an aligned collagen I gel was investigated using a multielectrode array (MEA). A laminin antibody was added to the culture medium for 48-120 h to conjugate newly secreted laminin. Then, morphology of the NCMs on an MEA was monitored using a phase contrast microscope, and the BM network that was immunocytostained for laminin was imaged using a fluorescence microscope. When the BM laminin was absent in this culture model, dramatic changes in NCM morphology were observed. Simultaneously, the MEA-recorded cardiac field potential showed changes compared to that from the control groups: The period of contraction shortened to 1/2 of that from the control groups, and the waveform of the calcium influx shifted from a flat plateau to a peak-like waveform, indicating that the electrical properties of the NCMs were closely related to the components and distribution of the BM network.

  20. Insulin regulates Glut4 confinement in plasma membrane clusters in adipose cells.

    Science.gov (United States)

    Lizunov, Vladimir A; Stenkula, Karin; Troy, Aaron; Cushman, Samuel W; Zimmerberg, Joshua

    2013-01-01

    Insulin-stimulated delivery of glucose transporter-4 (GLUT4) to the plasma membrane (PM) is the hallmark of glucose metabolism. In this study we examined insulin's effects on GLUT4 organization in PM of adipose cells by direct microscopic observation of single monomers tagged with photoswitchable fluorescent protein. In the basal state, after exocytotic delivery only a fraction of GLUT4 is dispersed into the PM as monomers, while most of the GLUT4 stays at the site of fusion and forms elongated clusters (60-240 nm). GLUT4 monomers outside clusters diffuse freely and do not aggregate with other monomers. In contrast, GLUT4 molecule collision with an existing cluster can lead to immediate confinement and association with that cluster. Insulin has three effects: it shifts the fraction of dispersed GLUT4 upon delivery, it augments the dissociation of GLUT4 monomers from clusters ∼3-fold and it decreases the rate of endocytic uptake. All together these three effects of insulin shift most of the PM GLUT4 from clustered to dispersed states. GLUT4 confinement in clusters represents a novel kinetic mechanism for insulin regulation of glucose homeostasis.

  1. The Fluid-Mosaic Model of Membrane Structure: still relevant to understanding the structure, function and dynamics of biological membranes after more than 40 years.

    Science.gov (United States)

    Nicolson, Garth L

    2014-06-01

    In 1972 the Fluid-Mosaic Membrane Model of membrane structure was proposed based on thermodynamic principals of organization of membrane lipids and proteins and available evidence of asymmetry and lateral mobility within the membrane matrix [S. J. Singer and G. L. Nicolson, Science 175 (1972) 720-731]. After over 40years, this basic model of the cell membrane remains relevant for describing the basic nano-structures of a variety of intracellular and cellular membranes of plant and animal cells and lower forms of life. In the intervening years, however, new information has documented the importance and roles of specialized membrane domains, such as lipid rafts and protein/glycoprotein complexes, in describing the macrostructure, dynamics and functions of cellular membranes as well as the roles of membrane-associated cytoskeletal fences and extracellular matrix structures in limiting the lateral diffusion and range of motion of membrane components. These newer data build on the foundation of the original model and add new layers of complexity and hierarchy, but the concepts described in the original model are still applicable today. In updated versions of the model more emphasis has been placed on the mosaic nature of the macrostructure of cellular membranes where many protein and lipid components are limited in their rotational and lateral motilities in the membrane plane, especially in their natural states where lipid-lipid, protein-protein and lipid-protein interactions as well as cell-matrix, cell-cell and intracellular membrane-associated protein and cytoskeletal interactions are important in restraining the lateral motility and range of motion of particular membrane components. The formation of specialized membrane domains and the presence of tightly packed integral membrane protein complexes due to membrane-associated fences, fenceposts and other structures are considered very important in describing membrane dynamics and architecture. These structures along

  2. Membrane Biophysics

    CERN Document Server

    Ashrafuzzaman, Mohammad

    2013-01-01

    Physics, mathematics and chemistry all play a vital role in understanding the true nature and functioning of biological membranes, key elements of living processes. Besides simple spectroscopic observations and electrical measurements of membranes we address in this book the phenomena of coexistence and independent existence of different membrane components using various theoretical approaches. This treatment will be helpful for readers who want to understand biological processes by applying both simple observations and fundamental scientific analysis. It provides a deep understanding of the causes and effects of processes inside membranes, and will thus eventually open new doors for high-level pharmaceutical approaches towards fighting membrane- and cell-related diseases.

  3. Applications of Amniotic Membrane and Fluid in Stem Cell Biology and Regenerative Medicine

    Directory of Open Access Journals (Sweden)

    Kerry Rennie

    2012-01-01

    Full Text Available The amniotic membrane (AM and amniotic fluid (AF have a long history of use in surgical and prenatal diagnostic applications, respectively. In addition, the discovery of cell populations in AM and AF which are widely accessible, nontumorigenic and capable of differentiating into a variety of cell types has stimulated a flurry of research aimed at characterizing the cells and evaluating their potential utility in regenerative medicine. While a major focus of research has been the use of amniotic membrane and fluid in tissue engineering and cell replacement, AM- and AF-derived cells may also have capabilities in protecting and stimulating the repair of injured tissues via paracrine actions, and acting as vectors for biodelivery of exogenous factors to treat injury and diseases. Much progress has been made since the discovery of AM and AF cells with stem cell characteristics nearly a decade ago, but there remain a number of problematic issues stemming from the inherent heterogeneity of these cells as well as inconsistencies in isolation and culturing methods which must be addressed to advance the field towards the development of cell-based therapies. Here, we provide an overview of the recent progress and future perspectives in the use of AM- and AF-derived cells for therapeutic applications.

  4. Water transport across biological membranes: Overton, water channels, and peritoneal dialysis.

    Science.gov (United States)

    Devuyst, O

    2010-01-01

    Peritoneal dialysis involves diffusive and convective transports and osmosis through the highly vascularized peritoneal membrane. Several lines of evidence have demonstrated that the water channel aquaporin-1 (AQP1) corresponds to the ultrasmall pore predicted by the modelization of peritoneal transport. Proof-of-principle studies have shown that upregulation of the expression of AQP1 in peritoneal capillaries is reflected by increased water permeability and ultrafiltration, without affecting the osmotic gradient and the permeability for small solutes. Inversely, studies in Aqp1 mice have shown that haplo-insufficiency in AQP1 is reflected by significant attenuation of water transport. Recent studies have identified lead compounds that could act as agonists of aquaporins, as well as putative binding sites and potential mechanisms of gating the water channel. By modulating water transport, these pharmacological agents could have clinically relevant effects in targeting specific tissues or disease states. These studies on the peritoneal membrane also provide an experimental framework to investigate the role of water channels in the endothelium and various cell types.

  5. A phosphatidylinositol transfer protein integrates phosphoinositide signaling with lipid droplet metabolism to regulate a developmental program of nutrient stress-induced membrane biogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jihui; Lin, Coney Pei-Chen; Pathak, Manish C.; Temple, Brenda R.S.; Nile, Aaron H.; Mousley, Carl J.; Duncan, Mara C.; Eckert, Debra M.; Leiker, Thomas J.; Ivanova, Pavlina T.; Myers, David S.; Murphy, Robert C.; Brown, H. Alex; Verdaasdonk, Jolien; Bloom, Kerry S.; Ortlund, Eric A.; Neiman, Aaron M.; Bankaitis, Vytas A. (Emory-MED); (UNCSM); (UNC); (UCHSC); (TAM); (Vanderbilt-MED); (SBU); (Utah)

    2016-07-06

    Lipid droplet (LD) utilization is an important cellular activity that regulates energy balance and release of lipid second messengers. Because fatty acids exhibit both beneficial and toxic properties, their release from LDs must be controlled. Here we demonstrate that yeast Sfh3, an unusual Sec14-like phosphatidylinositol transfer protein, is an LD-associated protein that inhibits lipid mobilization from these particles. We further document a complex biochemical diversification of LDs during sporulation in which Sfh3 and select other LD proteins redistribute into discrete LD subpopulations. The data show that Sfh3 modulates the efficiency with which a neutral lipid hydrolase-rich LD subclass is consumed during biogenesis of specialized membrane envelopes that package replicated haploid meiotic genomes. These results present novel insights into the interface between phosphoinositide signaling and developmental regulation of LD metabolism and unveil meiosis-specific aspects of Sfh3 (and phosphoinositide) biology that are invisible to contemporary haploid-centric cell biological, proteomic, and functional genomics approaches.

  6. A phosphatidylinositol transfer protein integrates phosphoinositide signaling with lipid droplet metabolism to regulate a developmental program of nutrient stress-induced membrane biogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jihui; Lin, Coney Pei-Chen; Pathak, Manish C.; Temple, Brenda R.S.; Nile, Aaron H.; Mousley, Carl J.; Duncan, Mara C.; Eckert, Debra M.; Leiker, Thomas J.; Ivanova, Pavlina T.; Myers, David S.; Murphy, Robert C.; Brown, H. Alex; Verdaasdonk, Jolien; Bloom, Kerry S.; Ortlund, Eric A.; Neiman, Aaron M.; Bankaitis, Vytas A. [Emory-MED; (SBU); (TAM); (UNC); (Vanderbilt-MED); (Utah); (UCHSC)

    2014-07-11

    Lipid droplet (LD) utilization is an important cellular activity that regulates energy balance and release of lipid second messengers. Because fatty acids exhibit both beneficial and toxic properties, their release from LDs must be controlled. Here we demonstrate that yeast Sfh3, an unusual Sec14-like phosphatidylinositol transfer protein, is an LD-associated protein that inhibits lipid mobilization from these particles. We further document a complex biochemical diversification of LDs during sporulation in which Sfh3 and select other LD proteins redistribute into discrete LD subpopulations. The data show that Sfh3 modulates the efficiency with which a neutral lipid hydrolase-rich LD subclass is consumed during biogenesis of specialized membrane envelopes that package replicated haploid meiotic genomes. These results present novel insights into the interface between phosphoinositide signaling and developmental regulation of LD metabolism and unveil meiosis-specific aspects of Sfh3 (and phosphoinositide) biology that are invisible to contemporary haploid-centric cell biological, proteomic, and functional genomics approaches.

  7. The amphiphilic nature of saponins and their effects on artificial and biological membranes and potential consequences for red blood and cancer cells.

    Science.gov (United States)

    Lorent, Joseph H; Quetin-Leclercq, Joëlle; Mingeot-Leclercq, Marie-Paule

    2014-11-28

    Saponins, amphiphiles of natural origin with numerous biological activities, are widely used in the cosmetic and pharmaceutical industry. Some saponins exhibit relatively selective cytotoxic effects on cancer cells but the tendency of saponins to induce hemolysis limits their anticancer potential. This review focused on the effects of saponin activity on membranes and consequent implications for red blood and cancer cells. This activity seems to be strongly related to the amphiphilic character of saponins that gives them the ability to self-aggregate and interact with membrane components such as cholesterol and phospholipids. Membrane interactions of saponins with artificial membrane models, red blood and cancer cells are reviewed with respect to their molecular structures. The review considered the mechanisms of these membrane interactions and their consequences including the modulation of membrane dynamics, interaction with membrane rafts, and membrane lysis. We summarized current knowledge concerning the mechanisms involved in the interactions of saponins with membrane lipids and examined the structure activity relationship of saponins regarding hemolysis and cancer cell death. A critical analysis of these findings speculates on their potential to further develop new anticancer compounds.

  8. Advanced treatment of biologically pretreated coal gasification wastewater by a novel integration of catalytic ultrasound oxidation and membrane bioreactor.

    Science.gov (United States)

    Jia, Shengyong; Han, Hongjun; Zhuang, Haifeng; Xu, Peng; Hou, Baolin

    2015-01-01

    Laboratorial scale experiments were conducted to investigate a novel system integrating catalytic ultrasound oxidation (CUO) with membrane bioreactor (CUO-MBR) on advanced treatment of biologically pretreated coal gasification wastewater. Results indicated that CUO with catalyst of FeOx/SBAC (sewage sludge based activated carbon (SBAC) which loaded Fe oxides) represented high efficiencies in eliminating TOC as well as improving the biodegradability. The integrated CUO-MBR system with low energy intensity and high frequency was more effective in eliminating COD, BOD5, TOC and reducing transmembrane pressure than either conventional MBR or ultrasound oxidation integrated MBR. The enhanced hydroxyl radical oxidation, facilitation of substrate diffusion and improvement of cell enzyme secretion were the mechanisms for CUO-MBR performance. Therefore, the integrated CUO-MBR was the promising technology for advanced treatment in engineering applications.

  9. Human mammary microenvironment better regulates the biology of human breast cancer in humanized mouse model.

    Science.gov (United States)

    Zheng, Ming-Jie; Wang, Jue; Xu, Lu; Zha, Xiao-Ming; Zhao, Yi; Ling, Li-Jun; Wang, Shui

    2015-02-01

    During the past decades, many efforts have been made in mimicking the clinical progress of human cancer in mouse models. Previously, we developed a human breast tissue-derived (HB) mouse model. Theoretically, it may mimic the interactions between "species-specific" mammary microenvironment of human origin and human breast cancer cells. However, detailed evidences are absent. The present study (in vivo, cellular, and molecular experiments) was designed to explore the regulatory role of human mammary microenvironment in the progress of human breast cancer cells. Subcutaneous (SUB), mammary fat pad (MFP), and HB mouse models were developed for in vivo comparisons. Then, the orthotopic tumor masses from three different mouse models were collected for primary culture. Finally, the biology of primary cultured human breast cancer cells was compared by cellular and molecular experiments. Results of in vivo mouse models indicated that human breast cancer cells grew better in human mammary microenvironment. Cellular and molecular experiments confirmed that primary cultured human breast cancer cells from HB mouse model showed a better proliferative and anti-apoptotic biology than those from SUB to MFP mouse models. Meanwhile, primary cultured human breast cancer cells from HB mouse model also obtained the migratory and invasive biology for "species-specific" tissue metastasis to human tissues. Comprehensive analyses suggest that "species-specific" mammary microenvironment of human origin better regulates the biology of human breast cancer cells in our humanized mouse model of breast cancer, which is more consistent with the clinical progress of human breast cancer.

  10. Identification of Extracellular Matrix Components and Biological Factors in Micronized Dehydrated Human Amnion/Chorion Membrane

    Science.gov (United States)

    Lei, Jennifer; Priddy, Lauren B.; Lim, Jeremy J.; Massee, Michelle; Koob, Thomas J.

    2017-01-01

    Objective: The use of bioactive extracellular matrix (ECM) grafts such as amniotic membranes is an attractive treatment option for enhancing wound repair. In this study, the concentrations, activity, and distribution of matrix components, growth factors, proteases, and inhibitors were evaluated in PURION® Processed, micronized, dehydrated human amnion/chorion membrane (dHACM; MiMedx Group, Inc.). Approach: ECM components in dHACM tissue were assessed by using immunohistochemical staining, and growth factors, cytokines, proteases, and inhibitors were quantified by using single and multiplex ELISAs. The activities of proteases that were native to the tissue were determined via gelatin zymography and EnzChek® activity assay. Results: dHACM tissue contained the ECM components collagens I and IV, hyaluronic acid, heparin sulfate proteoglycans, fibronectin, and laminin. In addition, numerous growth factors, cytokines, chemokines, proteases, and protease inhibitors that are known to play a role in the wound-healing process were quantified in dHACM. Though matrix metalloproteinases (MMPs) were present in dHACM tissues, inhibitors of MMPs overwhelmingly outnumbered the MMP enzymes by an overall molar ratio of 28:1. Protease activity assays revealed that the MMPs in the tissue existed primarily either in their latent form or complexed with inhibitors. Innovation: This is the first study to characterize components that function in wound healing, including inhibitor and protease content and activity, in micronized dHACM. Conclusion: A variety of matrix components and growth factors, as well as proteases and their inhibitors, were identified in micronized dHACM, providing a better understanding of how micronized dHACM tissue can be used to effectively promote wound repair. PMID:28224047

  11. The inner nuclear membrane protein Src1 associates with subtelomeric genes and alters their regulated gene expression.

    Science.gov (United States)

    Grund, Stefanie E; Fischer, Tamás; Cabal, Ghislain G; Antúnez, Oreto; Pérez-Ortín, José E; Hurt, Ed

    2008-09-08

    Inner nuclear membrane proteins containing a LEM (LAP2, emerin, and MAN1) domain participate in different processes, including chromatin organization, gene expression, and nuclear envelope biogenesis. In this study, we identify a robust genetic interaction between transcription export (TREX) factors and yeast Src1, an integral inner nuclear membrane protein that is homologous to vertebrate LEM2. DNA macroarray analysis revealed that the expression of the phosphate-regulated genes PHO11, PHO12, and PHO84 is up-regulated in src1Delta cells. Notably, these PHO genes are located in subtelomeric regions of chromatin and exhibit a perinuclear location in vivo. Src1 spans the nuclear membrane twice and exposes its N and C domains with putative DNA-binding motifs to the nucleoplasm. Genome-wide chromatin immunoprecipitation-on-chip analyses indicated that Src1 is highly enriched at telomeres and subtelomeric regions of the yeast chromosomes. Our data show that the inner nuclear membrane protein Src1 functions at the interface between subtelomeric gene expression and TREX-dependent messenger RNA export through the nuclear pore complexes.

  12. The human Na+/H+ exchanger 1 is a membrane scaffold protein for extracellular signal-regulated kinase 2

    DEFF Research Database (Denmark)

    Hendus-Altenburger, Ruth; Pedraz Cuesta, Elena; Olesen, Christina Wilkens

    2016-01-01

    BACKGROUND: Extracellular signal-regulated kinase 2 (ERK2) is an S/T kinase with more than 200 known substrates, and with critical roles in regulation of cell growth and differentiation and currently no membrane proteins have been linked to ERK2 scaffolding. METHODS AND RESULTS: Here, we identify...... the human Na(+)/H(+) exchanger 1 (hNHE1) as a membrane scaffold protein for ERK2 and show direct hNHE1-ERK1/2 interaction in cellular contexts. Using nuclear magnetic resonance (NMR) spectroscopy and immunofluorescence analysis we demonstrate that ERK2 scaffolding by hNHE1 occurs by one of three D...... in vitro, in a distinct temporal order, with the phosphorylation rates at the individual sites being modulated by the docking sites in a distant dependent manner. CONCLUSIONS: This work characterizes a new type of scaffolding complex, which we term a "shuffle complex", between the disordered hNHE1-tail...

  13. Modes and regulation of endocytic membrane retrieval in mouse auditory hair cells.

    Science.gov (United States)

    Neef, Jakob; Jung, Sangyong; Wong, Aaron B; Reuter, Kirsten; Pangrsic, Tina; Chakrabarti, Rituparna; Kügler, Sebastian; Lenz, Christine; Nouvian, Régis; Boumil, Rebecca M; Frankel, Wayne N; Wichmann, Carolin; Moser, Tobias

    2014-01-15

    Synaptic vesicle recycling sustains high rates of neurotransmission at the ribbon-type active zones (AZs) of mouse auditory inner hair cells (IHCs), but its modes and molecular regulation are poorly understood. Electron microscopy indicated the presence of clathrin-mediated endocytosis (CME) and bulk endocytosis. The endocytic proteins dynamin, clathrin, and amphiphysin are expressed and broadly distributed in IHCs. We used confocal vglut1-pHluorin imaging and membrane capacitance (Cm) measurements to study the spatial organization and dynamics of IHC exocytosis and endocytosis. Viral gene transfer expressed vglut1-pHluorin in IHCs and targeted it to synaptic vesicles. The intravesicular pH was ∼6.5, supporting only a modest increase of vglut1-pHluorin fluorescence during exocytosis and pH neutralization. Ca(2+) influx triggered an exocytic increase of vglut1-pHluorin fluorescence at the AZs, around which it remained for several seconds. The endocytic Cm decline proceeded with constant rate (linear component) after exocytosis of the readily releasable pool (RRP). When exocytosis exceeded three to four RRP equivalents, IHCs additionally recruited a faster Cm decline (exponential component) that increased with the amount of preceding exocytosis and likely reflects bulk endocytosis. The dynamin inhibitor Dyngo-4a and the clathrin blocker pitstop 2 selectively impaired the linear component of endocytic Cm decline. A missense mutation of dynamin 1 (fitful) inhibited endocytosis to a similar extent as Dyngo-4a. We propose that IHCs use dynamin-dependent endocytosis via CME to support vesicle cycling during mild stimulation but recruit bulk endocytosis to balance massive exocytosis.

  14. Regulation of membrane cholecystokinin-2 receptor by agonists enables classification of partial agonists as biased agonists.

    Science.gov (United States)

    Magnan, Rémi; Masri, Bernard; Escrieut, Chantal; Foucaud, Magali; Cordelier, Pierre; Fourmy, Daniel

    2011-02-25

    Given the importance of G-protein-coupled receptors as pharmacological targets in medicine, efforts directed at understanding the molecular mechanism by which pharmacological compounds regulate their presence at the cell surface is of paramount importance. In this context, using confocal microscopy and bioluminescence resonance energy transfer, we have investigated internalization and intracellular trafficking of the cholecystokinin-2 receptor (CCK2R) in response to both natural and synthetic ligands with different pharmacological features. We found that CCK and gastrin, which are full agonists on CCK2R-induced inositol phosphate production, rapidly and abundantly stimulate internalization. Internalized CCK2R did not rapidly recycle to plasma membrane but instead was directed to late endosomes/lysosomes. CCK2R endocytosis involves clathrin-coated pits and dynamin and high affinity and prolonged binding of β-arrestin1 or -2. Partial agonists and antagonists on CCK2R-induced inositol phosphate formation and ERK1/2 phosphorylation did not stimulate CCK2R internalization or β-arrestin recruitment to the CCK2R but blocked full agonist-induced internalization and β-arrestin recruitment. The extreme C-terminal region of the CCK2R (and more precisely phosphorylatable residues Ser(437)-Xaa(438)-Thr(439)-Thr(440)-Xaa(441)-Ser(442)-Thr(443)) were critical for β-arrestin recruitment. However, this region and β-arrestins were dispensable for CCK2R internalization. In conclusion, this study allowed us to classify the human CCK2R as a member of class B G-protein-coupled receptors with regard to its endocytosis features and identified biased agonists of the CCK2R. These new important insights will allow us to investigate the role of internalized CCK2R·β-arrestin complexes in cancers expressing this receptor and to develop new diagnosis and therapeutic strategies targeting this receptor.

  15. Reciprocal regulation of pyoluteorin production with membrane transporter gene expression in Pseudomonas fluorescens Pf-5.

    Science.gov (United States)

    Brodhagen, Marion; Paulsen, Ian; Loper, Joyce E

    2005-11-01

    Pyoluteorin is a chlorinated polyketide antibiotic secreted by the rhizosphere bacterium Pseudomonas fluorescens Pf-5. Genes encoding enzymes and transcriptional regulators involved in pyoluteorin production are clustered in the genome of Pf-5. Sequence analysis of genes adjacent to the known pyoluteorin biosynthetic gene cluster revealed the presence of an ABC transporter system. We disrupted two putative ABC transporter genes by inserting transcriptional fusions to an ice nucleation reporter gene. Mutations in pltI and pltJ, which are predicted to encode a membrane fusion protein and an ATP-binding cassette of the ABC transporter, respectively, greatly reduced pyoluteorin production by Pf-5. During the transition from exponential growth to stationary phase, populations of a pltI mutant were lower than those of a pltI+ strain in a culture medium containing pyoluteorin, suggesting a role for the transport system in efflux and the resistance of Pf-5 to the antibiotic. Although pltI or pltJ mutant strains displayed low pyoluteorin production, they did not accumulate proportionately more of the antibiotic intracellularly, indicating that pltI and pltJ do not encode an exclusive exporter for pyoluteorin. Transcription of the putative pyoluteorin efflux genes pltI and pltJ was enhanced by exogenous pyoluteorin. These new observations parallel an earlier finding that pyoluteorin enhances the transcription of pyoluteorin biosynthesis genes and pyoluteorin production in Pf-5. This report provides evidence of a coordination of pyoluteorin production and the transcription of genes encoding a linked transport apparatus, wherein each requires the other for optimal expression.

  16. Reduced plasma membrane surface expression of GLAST mediates decreased glutamate regulation in the aged striatum.

    Science.gov (United States)

    Nickell, Justin; Salvatore, Michael F; Pomerleau, Francois; Apparsundaram, Subbu; Gerhardt, Greg A

    2007-11-01

    Extracellular L-glutamate poses a severe excitotoxic threat to neurons and glia when unregulated, therefore low synaptic levels of this neurotransmitter must be maintained via a rapid and robust transport system. A recent study from our laboratory showed a reduced glutamate uptake rate in the striatum of the aged Fischer 344 (F344) rat, yet the mechanism underlying this phenomenon is unknown. The current study utilized in vivo electrochemical recordings, immunoblotting and biotinylation in young (6 months), late-middle aged (18 months) and aged (24 months) F344 rats to elucidate the potential role that glutamate transporters (GLT-1, GLAST, and EAAC1) may play in this mechanism. Here we show that the time necessary to clear glutamate from the late-middle aged and aged striatum is significantly prolonged in comparison to the young striatum. In addition, an analysis of various sub-regions of the striatum revealed a marked dorsoventral gradient in terms of glutamate clearance times in the aged striatum, a phenomenon which was not present in the striatum of the animals of the remaining age groups. We also found that the decreased glutamate clearance time observed in the late-middle aged and aged rats is not due to a decrease in the production of total transporter protein among these three transporters. Rather, a significant reduction in the amount of GLAST expressed on the plasma membrane surface in the aged animals (approximately 55% when compared to young rats) may contribute to this phenomenon. These age-related alterations in extracellular l-glutamate regulation may be key contributors to the increased susceptibility of the aged brain to excitotoxic insults such as stroke and hypoxia.

  17. MAL Is a Regulator of the Recruitment of Myelin Protein PLP to Membrane Microdomains

    NARCIS (Netherlands)

    Bijlard, Marjolein; de Jonge, Jenny C.; Klunder, Bert; Nomden, Anita; Hoekstra, Dick; Baron, Wia

    2016-01-01

    In oligodendrocytes (OLGs), an indirect, transcytotic pathway is mediating transport of de novo synthesized PLP, a major myelin specific protein, from the apical-like plasma membrane to the specialized basolateral-like myelin membrane to prevent its premature compaction. MAL is a well-known regulato

  18. Key factors regulating the mass delivery of macromolecules to model cell membranes

    DEFF Research Database (Denmark)

    Campbell, Richard A.; Watkins, Erik B.; Jagalski, Vivien;

    2014-01-01

    diffusion and continuous delivery. Neutron reflectometry measurements were carried out on supported lipid bilayers of varying charge and on hydrophilic silica surfaces. Translocation of the macromolecule across the membrane and adsorption of the lamellar aggregates occur only when the membrane (1...

  19. Line tension at lipid phase boundaries regulates formation of membrane vesicles in living cells

    DEFF Research Database (Denmark)

    Vind-Kezunovic, D.; Nielsen, C.H.; Wojewodzka, U.;

    2008-01-01

    fluorescein-labeled cholera toxin B subunit which labels ganglioside GM(1) enriched plasma membrane rafts. Cholesterol depletion with methyl-beta-cyclodextrin enhanced DiI vesiculation, GM(1)/DiI domain separation and was accompanied by a detachment of the subcortical cytoskeleton from the plasma membrane...

  20. Line tension at lipid phase boundaries regulates formation of membrane vesicles in living cells

    DEFF Research Database (Denmark)

    Vind-Kezunovic, Dina; Helix Nielsen, Claus; Wojewodzka, Urszula;

    2008-01-01

    -labeled cholera toxin B subunit which labels ganglioside GM(1) enriched plasma membrane rafts. Cholesterol depletion with methyl-beta-cyclodextrin enhanced DiI vesiculation, GM(1)/DiI domain separation and was accompanied by a detachment of the subcortical cytoskeleton from the plasma membrane. Based...

  1. Variations in criteria regulating treatment with reimbursed biologic DMARDs across European countries. Are differences related to country's wealth?

    DEFF Research Database (Denmark)

    Putrik, Polina; Ramiro, Sofia; Kvien, Tore K;

    2014-01-01

    To explore criteria regulating treatment with reimbursed biologic disease-modifying antirheumatic drugs (bDMARDs) in patients with rheumatoid arthritis (RA) across Europe and to relate criteria to indicators of national socioeconomic welfare.......To explore criteria regulating treatment with reimbursed biologic disease-modifying antirheumatic drugs (bDMARDs) in patients with rheumatoid arthritis (RA) across Europe and to relate criteria to indicators of national socioeconomic welfare....

  2. Synapse-associated protein 97 regulates the membrane properties of fast-spiking parvalbumin interneurons in the visual cortex.

    Science.gov (United States)

    Akgul, Gulcan; Wollmuth, Lonnie P

    2013-07-31

    Fast-spiking parvalbumin (PV)-positive interneurons in layers 2/3 of the visual cortex regulate gain control and tuning of visual processing. Synapse-associated protein 97 (SAP97) belongs to a family of proteins that have been implicated in regulating glutamatergic synaptic transmission at pyramidal-to-pyramidal connections in the nervous system. For PV interneurons in mouse visual cortex, the expression of SAP97 is developmentally regulated, being expressed in almost all juvenile but only a fraction, ~40%, of adult PV interneurons. Using whole-cell patch-clamping, single-cell RT-PCR to assay endogenous expression of SAP97 and exogenous expression of SAP97, we investigated the functional significance of SAP97 in PV interneurons in layers 2/3 of the visual cortex. PV interneurons expressing SAP97, either endogenously or via exogenous expression, showed distinct membrane properties from those not expressing SAP97. This included an overall decrease in membrane excitability, as indexed by a decrease in membrane resistance and an increase in the stimulus threshold for the first action potential firing. Additionally, SAP97-expressing PV interneurons fired action potentials more frequently and, at moderate stimulus intensities, showed irregular or stuttering firing patterns. Furthermore, SAP97-expressing PV interneurons showed increased glutamatergic input and more extensive dendritic branching when compared with non-expressing PV interneurons. These differences in membrane and synaptic properties would significantly alter how PV interneurons expressing SAP97 compared with those not expressing SAP97 would function in local networks. Thus, our results indicate that the scaffolding protein SAP97 is a critical molecular factor regulating the input-output relationships of cortical PV interneurons.

  3. Victimization and Biological Stress Responses in Urban Adolescents: Emotion Regulation as a Moderator.

    Science.gov (United States)

    Kliewer, Wendy

    2016-09-01

    Associations between urban adolescents' victimization experiences and biological stress responses were examined, as well as emotion regulation as a moderator of these associations. Data from a 4-wave longitudinal study with a low-income, community-based sample (n = 242; 91 % African American; 57 % female; M = 11.98, SD = 1.56 years at baseline) revealed that victimization, assessed over 3 study waves, was associated with an attenuated cortisol response to a stress interview at the final study wave, indicating that responses of the Hypothalamus-Pituitary-Adrenal (HPA) axis were dysregulated. Cortisol responses were moderated by caregiver-reported adolescent emotion regulation, suggesting that this modifiable protective factor that is taught in many school-based prevention programs could help reduce harm associated with HPA axis dysregulation linked to victimization.

  4. Membrane-initiated Actions of Estradiol that Regulate Reproduction, Energy Balance and Body Temperature

    Science.gov (United States)

    Kelly, Martin J.; Rønnekleiv, Oline K.

    2012-01-01

    It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. However, there now exists compelling evidence for membrane estrogen receptors in hypothalamic and other brain neurons. But, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell signaling. Therefore, this review will consider our current knowledge of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how they contribute to homeostatic functions. PMID:22871514

  5. Regulation of the V-ATPase along the endocytic pathway occurs through reversible subunit association and membrane localization.

    Directory of Open Access Journals (Sweden)

    Céline Lafourcade

    Full Text Available The lumen of endosomal organelles becomes increasingly acidic when going from the cell surface to lysosomes. Luminal pH thereby regulates important processes such as the release of internalized ligands from their receptor or the activation of lysosomal enzymes. The main player in endosomal acidification is the vacuolar ATPase (V-ATPase, a multi-subunit transmembrane complex that pumps protons from the cytoplasm to the lumen of organelles, or to the outside of the cell. The active V-ATPase is composed of two multi-subunit domains, the transmembrane V(0 and the cytoplasmic V(1. Here we found that the ratio of membrane associated V(1/Vo varies along the endocytic pathway, the relative abundance of V(1 being higher on late endosomes than on early endosomes, providing an explanation for the higher acidity of late endosomes. We also found that all membrane-bound V-ATPase subunits were associated with detergent resistant membranes (DRM isolated from late endosomes, raising the possibility that association with lipid-raft like domains also plays a role in regulating the activity of the proton pump. In support of this, we found that treatment of cells with U18666A, a drug that leads to the accumulation of cholesterol in late endosomes, affected acidification of late endosome. Altogether our findings indicate that the activity of the vATPase in the endocytic pathway is regulated both by reversible association/dissociation and the interaction with specific lipid environments.

  6. The dimer interface of the membrane type 1 matrix metalloproteinase hemopexin domain: crystal structure and biological functions.

    Science.gov (United States)

    Tochowicz, Anna; Goettig, Peter; Evans, Richard; Visse, Robert; Shitomi, Yasuyuki; Palmisano, Ralf; Ito, Noriko; Richter, Klaus; Maskos, Klaus; Franke, Daniel; Svergun, Dmitri; Nagase, Hideaki; Bode, Wolfram; Itoh, Yoshifumi

    2011-03-04

    Homodimerization is an essential step for membrane type 1 matrix metalloproteinase (MT1-MMP) to activate proMMP-2 and to degrade collagen on the cell surface. To uncover the molecular basis of the hemopexin (Hpx) domain-driven dimerization of MT1-MMP, a crystal structure of the Hpx domain was solved at 1.7 Å resolution. Two interactions were identified as potential biological dimer interfaces in the crystal structure, and mutagenesis studies revealed that the biological dimer possesses a symmetrical interaction where blades II and III of molecule A interact with blades III and II of molecule B. The mutations of amino acids involved in the interaction weakened the dimer interaction of Hpx domains in solution, and incorporation of these mutations into the full-length enzyme significantly inhibited dimer-dependent functions on the cell surface, including proMMP-2 activation, collagen degradation, and invasion into the three-dimensional collagen matrix, whereas dimer-independent functions, including gelatin film degradation and two-dimensional cell migration, were not affected. These results shed light on the structural basis of MT1-MMP dimerization that is crucial to promote cellular invasion.

  7. Cruciform structures are a common DNA feature important for regulating biological processes

    Directory of Open Access Journals (Sweden)

    Arrowsmith Cheryl

    2011-08-01

    Full Text Available Abstract DNA cruciforms play an important role in the regulation of natural processes involving DNA. These structures are formed by inverted repeats, and their stability is enhanced by DNA supercoiling. Cruciform structures are fundamentally important for a wide range of biological processes, including replication, regulation of gene expression, nucleosome structure and recombination. They also have been implicated in the evolution and development of diseases including cancer, Werner's syndrome and others. Cruciform structures are targets for many architectural and regulatory proteins, such as histones H1 and H5, topoisomerase IIβ, HMG proteins, HU, p53, the proto-oncogene protein DEK and others. A number of DNA-binding proteins, such as the HMGB-box family members, Rad54, BRCA1 protein, as well as PARP-1 polymerase, possess weak sequence specific DNA binding yet bind preferentially to cruciform structures. Some of these proteins are, in fact, capable of inducing the formation of cruciform structures upon DNA binding. In this article, we review the protein families that are involved in interacting with and regulating cruciform structures, including (a the junction-resolving enzymes, (b DNA repair proteins and transcription factors, (c proteins involved in replication and (d chromatin-associated proteins. The prevalence of cruciform structures and their roles in protein interactions, epigenetic regulation and the maintenance of cell homeostasis are also discussed.

  8. Outcomes of a 2-year investigation on enhanced biological nutrients removal and trace organics elimination in membrane bioreactor (MBR).

    Science.gov (United States)

    Lesjean, B; Gnirss, R; Buisson, H; Keller, S; Tazi-Pain, A; Luck, F

    2005-01-01

    Two configurations of membrane bioreactors were identified to achieve enhanced biological phosphorus and nitrogen removal, and assessed over more than two years with two parallel pilot plants of 2m3 each. Both configurations included an anaerobic zone ahead of the biological reactor, and differed by the position of the anoxic zone: standard pre-denitrification, or post-denitrification without dosing of carbon source. Both configurations achieved improved phosphorus removal. The goal of 50 microgP/L in the effluent could be consistently achieved with two types of municipal wastewater, the second site requiring a low dose of ferric salt ferric salt eliminated for 10 mg BOD5 in the influent. The post-denitrification configuration enabled a very good elimination of nitrogen. Daily nitrate concentration as low as 1 mgN/L could be monitored in the effluent in some periods. The denitrification rates, greater than those expected for endogenous denitrification, could be accounted for by the use of the glycogene pool, internally stored by the denitrifying microorganisms in the anaerobic zone. Pharmaceuticals residues and steroids were regularly monitored on the two parallel MBR pilot plants during the length of the trials, and compared with the performance of the Berlin-Ruhleben WWTP. Although some compounds such as carbamazepine were persistent through all the systems, most of the compounds could be better removed by the MBR plants. The influence of temperature, sludge age and compound concentration could be shown, as well as the significance of biological mechanisms in the removal of trace organic compounds.

  9. Regulation of glycolytic oscillations by mitochondrial and plasma membrane H+-ATPases

    DEFF Research Database (Denmark)

    Olsen, Lars Folke; Andersen, Ann Zahle; Lunding, Anita

    2009-01-01

    We investigated the coupling between glycolytic and mitochondrial membrane potential oscillations in Saccharomyces cerevisiae under semianaerobic conditions. Glycolysis was measured as NADH autofluorescence, and mitochondrial membrane potential was measured using the fluorescent dye 3,3'-diethylo......We investigated the coupling between glycolytic and mitochondrial membrane potential oscillations in Saccharomyces cerevisiae under semianaerobic conditions. Glycolysis was measured as NADH autofluorescence, and mitochondrial membrane potential was measured using the fluorescent dye 3......,3'-diethyloxacarbocyanine iodide. The responses of glycolytic and membrane potential oscillations to a number of inhibitors of glycolysis, mitochondrial electron flow, and mitochondrial and plasma membrane H(+)-ATPase were investigated. Furthermore, the glycolytic flux was determined as the rate of production of ethanol...... in a number of different situations (changing pH or the presence and absence of inhibitors). Finally, the intracellular pH was determined and shown to oscillate. The results support earlier work suggesting that the coupling between glycolysis and mitochondrial membrane potential is mediated by the ADP...

  10. Novel, energy-optimized membrane design for biological waste water treatment systems; Ein neuentwickeltes Niedrig-Energie-Membransystem fuer Membran-Biologien

    Energy Technology Data Exchange (ETDEWEB)

    Luebbecke, S. [Preussag Wassertechnik GmbH, Bremen (Germany)

    1999-07-01

    In industrial waste water treatment, circular movement of waste water, scarcity of space for erecting waste water treatment plants, and economy are factors of eminent importance, calling for innovative, efficient process techniques. Up to now, separation of activated sludge from cleaned waste water has been done almost exclusively by means of sedimentation. But because of the slight difference in density between water and biomass, large final sedimentation tanks are indispensable, and attainable biomass concentrations in an activated sludge tank (or bioreactor) are low (3-4g/l). Given that cleaning performance is directly proportional to biomass concentration, achieving higher biomass concentrations spells substantially enhanced efficiency per unit of space of biological systems, thus saving reaction volume. For this task, membrane techniques are suitable, which, contrary to sedimentation, permit random-selection, operationally stable retention and concentration of biomass with a definitely smaller space requirement. (orig.) [German] Bei der industriellen Abwasserbehandlung stehen die Kreislauffuehrung des Abwassers, beengte Platzverhaeltnisse fuer die Errichtung von Abwasserbehandlungsanlagen und die Wirtschaftlichkeit im Vordergrund, so dass dort innovative, effiziente Verfahrenstechniken gefragt sind. Zur Abtrennung des Belebtschlammes vom gereinigten Abwasser wird bisher fast ausschliesslich die Sedimentation eingesetzt. Der geringe Dichteunterschied zwischen Wasser und Biomasse macht jedoch grosse Nachklaerbecken notwendig und die erreichbaren Biomassekonzentrationen im Belebungsbecken (bzw. Bioreaktor) sind gering (3-4 g/l). Da die Reinigungsleistung der Biomassekonzentration direkt proportional ist, kann mit der Einstellung hoeherer Biomassekonzentrationen die Raumumsatzleistung biologischer Systeme erheblich gesteigert und somit Reaktionsvolumen eingespart werden. Fuer diese Aufgabe koennen Membranverfahren eingesetzt werden, die im Gegensatz zur

  11. Cancer metabolism meets systems biology: Pyruvate kinase isoform PKM2 is a metabolic master regulator

    Directory of Open Access Journals (Sweden)

    Fabian V Filipp

    2013-01-01

    Full Text Available Pyruvate kinase activity is controlled by a tightly woven regulatory network. The oncofetal isoform of pyruvate kinase (PKM2 is a master regulator of cancer metabolism. PKM2 engages in parallel, feed-forward, positive and negative feedback control contributing to cancer progression. Besides its metabolic role, non-metabolic functions of PKM2 as protein kinase and transcriptional coactivator for c-MYC and hypoxia-inducible factor 1-alpha are essential for epidermal growth factor receptor activation-induced tumorigenesis. These biochemical activities are controlled by a shift in the oligomeric state of PKM2 that includes acetylation, oxidation, phosphorylation, prolyl hydroxylation and sumoylation. Metabolically active PKM2 tetramer is allosterically regulated and responds to nutritional and stress signals. Metabolically inactive PKM2 dimer is imported into the nucleus and can function as protein kinase stimulating transcription. A systems biology approach to PKM2 at the genome, transcriptome, proteome, metabolome and fluxome level reveals how differences in biomolecular structure translate into a global rewiring of cancer metabolism. Cancer systems biology takes us beyond the Warburg effect, opening unprecedented therapeutic opportunities.

  12. The biology of cancer testis antigens: putative function, regulation and therapeutic potential.

    Science.gov (United States)

    Fratta, Elisabetta; Coral, Sandra; Covre, Alessia; Parisi, Giulia; Colizzi, Francesca; Danielli, Riccardo; Nicolay, Hugues Jean Marie; Sigalotti, Luca; Maio, Michele

    2011-04-01

    Cancer testis antigens (CTA) are a large family of tumor-associated antigens expressed in human tumors of different histological origin, but not in normal tissues except for testis and placenta. This tumor-restricted pattern of expression, together with their strong in vivo immunogenicity, identified CTA as ideal targets for tumor-specific immunotherapeutic approaches, and prompted the development of several clinical trials of CTA-based vaccine therapy. Driven by this practical clinical interest, a more detailed characterization of CTA biology has been recently undertaken. So far, at least 70 families of CTA, globally accounting for about 140 members, have been identified. Most of these CTA are expressed during spermatogenesis, but their function is still largely unknown. Epigenetic events, particularly DNA methylation, appear to be the primary mechanism regulating CTA expression in both normal and transformed cells, as well as in cancer stem cells. In view of the growing interest in CTA biology, the aim of this review is to provide the most recent information on their expression, regulation and function, together with a brief summary of the major clinical trials involving CTA as therapeutic agents. The pharmacologic modulation of CTA expression profiles on neoplastic cells by DNA hypomethylating drugs will also be discussed as a feasible approach to design new combination therapies potentially able to improve the clinical efficacy of currently adopted CTA-based immunotherapeutic regimens in cancer patients.

  13. Regulation of high-voltage-activated Ca(2+) channel function, trafficking, and membrane stability by auxiliary subunits.

    Science.gov (United States)

    Felix, Ricardo; Calderón-Rivera, Aida; Andrade, Arturo

    2013-09-01

    Voltage-gated Ca(2+) (CaV) channels mediate Ca(2+) ions influx into cells in response to depolarization of the plasma membrane. They are responsible for initiation of excitation-contraction and excitation-secretion coupling, and the Ca(2+) that enters cells through this pathway is also important in the regulation of protein phosphorylation, gene transcription, and many other intracellular events. Initial electrophysiological studies divided CaV channels into low-voltage-activated (LVA) and high-voltage-activated (HVA) channels. The HVA CaV channels were further subdivided into L, N, P/Q, and R-types which are oligomeric protein complexes composed of an ion-conducting CaVα1 subunit and auxiliary CaVα2δ, CaVβ, and CaVγ subunits. The functional consequences of the auxiliary subunits include altered functional and pharmacological properties of the channels as well as increased current densities. The latter observation suggests an important role of the auxiliary subunits in membrane trafficking of the CaVα1 subunit. This includes the mechanisms by which CaV channels are targeted to the plasma membrane and to appropriate regions within a given cell. Likewise, the auxiliary subunits seem to participate in the mechanisms that remove CaV channels from the plasma membrane for recycling and/or degradation. Diverse studies have provided important clues to the molecular mechanisms involved in the regulation of CaV channels by the auxiliary subunits, and the roles that these proteins could possibly play in channel targeting and membrane Stabilization.

  14. Municipal Sewage Treated by a Pilot-Scale Membrane Biological Reactor%膜生物反应器处理市政污水中试研究

    Institute of Scientific and Technical Information of China (English)

    李天成; 马将军; 朱慎林; 陈萃仙

    2005-01-01

    It is obviously advantageous for membrane biological reactor to treat municipal sewage over traditional active sludge process. Multi-species microbes in active sludge retained completely by submerged hollow fiber curtain-like micro-filtration membrane module with pore-size of 0.5 mm in an integrated pilot-scale membrane biological reactor self-designed. Meanwhile, the pilot plant comprised an anoxic zone to enable denitrification. In this experiment, two kinds of practical municipal sewage were continuously treated by using this membrane biological reactor in order to evaluate the properties of membrane module, such as the relationship between vacuum degree in membrane module and water flux of membrane, relationship between operational time and water flux of membrane and the way to prevent membrane pollution. Further, all sorts of water quality indexes for inlets and effluents, such as COD, turbidity, NH3-N and apparent colourity were measured in time. And the experimental results showed that there were so excellent water qualities for outlet water as to meet the water-quality standards for urban miscellaneous consumption water. Moreover, the change of sludge concentrations (MLSS) was also monitored on every day. In conclusion, it is instructive for the designing and operational data to commercial applications in the future, which are obtained from this pilot-scale membrane biological reactor.%相对于传统活性污泥法,膜生物反应器处理生活污水具有显著的优势.通过在自行设计、加工的浸没式中空纤维微滤膜生物反应器中试装置上连续处理两种生活污水,旨在研究中空纤维微滤膜组件的性能及其影响因素,膜水通量随膜组件内真空度的变化,膜水通量随运行时间的变化和膜污染产生的原因及防治措施.了解膜生物反应器对生活污水的净化效果,出水COD、NH3-N、表色色度和浊度随运行时间的变化,膜生物反应器内污泥浓度随运行时间的变

  15. Profilin as a regulator of the membrane-actin cytoskeleton interface in plant cells

    Directory of Open Access Journals (Sweden)

    Tiantian eSun

    2013-12-01

    Full Text Available Membrane structures and cytoskeleton dynamics are intimately inter-connected in the eukaryotic cell. Recently, the molecular mechanisms operating at this interface have been progressively addressed. Many experiments have revealed that the actin cytoskeleton can interact with membranes through various discrete membrane domains. The actin-binding protein, profilin has been proven to inhibit actin polymerization and to promote F-actin elongation. This is dependent on many factors, such as the profilin/G-actin ratio and the ionic environment of the cell. Additionally, profilin has specific domains that interact with phosphoinositides and poly-L-proline rich proteins; theoretically, this gives profilin the opportunity to interact with membranes, and a large number of experiments have confirmed this possibility. In this article, we summarize recent findings in plant cells, and discuss the evidence of the connections among actin cytoskeleton, profilin and biomembranes through direct or indirect relationships.

  16. Molecular insights into amyloid regulation by membrane cholesterol and sphingolipids: common mechanisms in neurodegenerative diseases

    OpenAIRE

    Fantini, Jacques; Yahi, Nouara

    2010-01-01

    Alzheimer, Parkinson and other neurodegenerative diseases involve a series of brain proteins, referred to as ‘amyloidogenic proteins’, with exceptional conformational plasticity and a high propensity for self-aggregation. Although the mechanisms by which amyloidogenic proteins kill neural cells are not fully understood, a common feature is the concentration of unstructured amyloidogenic monomers on bidimensional membrane lattices. Membrane-bound monomers undergo a series of lipid-dependent co...

  17. A membrane-tethered transcription factor ANAC089 negatively regulates floral initiation in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The plant-specific NAC (NAM, ATAF1/2,and CUC2) transcription factors have a regulatory function in developmental processes and stress responses. Notably a group of NAC members named NTLs (NTM1-Like) are membrane-tethered, ensuring plants rapidly respond to developmental changes and environmental stimuli. Our results indicated that ANAC089 was a membrane-tethered transcription factor and its truncated form was responsible for the physiological function in flowering time control.

  18. Macoilin, a conserved nervous system-specific ER membrane protein that regulates neuronal excitability.

    Directory of Open Access Journals (Sweden)

    Fausto Arellano-Carbajal

    2011-03-01

    Full Text Available Genome sequence comparisons have highlighted many novel gene families that are conserved across animal phyla but whose biological function is unknown. Here, we functionally characterize a member of one such family, the macoilins. Macoilins are characterized by several highly conserved predicted transmembrane domains towards the N-terminus and by coiled-coil regions C-terminally. They are found throughout Eumetazoa but not in other organisms. Mutants for the single Caenorhabditis elegans macoilin, maco-1, exhibit a constellation of behavioral phenotypes, including defects in aggregation, O₂ responses, and swimming. MACO-1 protein is expressed broadly and specifically in the nervous system and localizes to the rough endoplasmic reticulum; it is excluded from dendrites and axons. Apart from subtle synapse defects, nervous system development appears wild-type in maco-1 mutants. However, maco-1 animals are resistant to the cholinesterase inhibitor aldicarb and sensitive to levamisole, suggesting pre-synaptic defects. Using in vivo imaging, we show that macoilin is required to evoke Ca²(+ transients, at least in some neurons: in maco-1 mutants the O₂-sensing neuron PQR is unable to generate a Ca²(+ response to a rise in O₂. By genetically disrupting neurotransmission, we show that pre-synaptic input is not necessary for PQR to respond to O₂, indicating that the response is mediated by cell-intrinsic sensory transduction and amplification. Disrupting the sodium leak channels NCA-1/NCA-2, or the N-,P/Q,R-type voltage-gated Ca²(+ channels, also fails to disrupt Ca²(+ responses in the PQR cell body to O₂ stimuli. By contrast, mutations in egl-19, which encodes the only Caenorhabditis elegans L-type voltage-gated Ca²(+ channel α1 subunit, recapitulate the Ca²(+ response defect we see in maco-1 mutants, although we do not see defects in localization of EGL-19. Together, our data suggest that macoilin acts in the ER to regulate assembly or

  19. MYC function and regulation in flies: how Drosophila has enlightened MYC cancer biology

    Directory of Open Access Journals (Sweden)

    Jue Er Amanda Lee

    2014-12-01

    Full Text Available Progress in our understanding of the complex signaling events driving human cancer would have been unimaginably slow without discoveries from Drosophila genetic studies. Significantly, many of the signaling pathways now synonymous with cancer biology were first identified as a result of elegant screens for genes fundamental to metazoan development. Indeed the name given to many core cancer-signaling cascades tells of their history as developmental patterning regulators in flies—e.g. Wingless (Wnt, Notch and Hippo. Moreover, astonishing insight has been gained into these complex signaling networks, and many other classic oncogenic signaling networks (e.g. EGFR/RAS/RAF/ERK, InR/PI3K/AKT/TOR, using sophisticated fly genetics. Of course if we are to understand how these signaling pathways drive cancer, we must determine the downstream program(s of gene expression activated to promote the cell and tissue over growth fundamental to cancer. Here we discuss one commonality between each of these pathways: they are all implicated as upstream activators of the highly conserved MYC oncogene and transcription factor. MYC can drive all aspects of cell growth and cell cycle progression during animal development. MYC is estimated to be dysregulated in over 50% of all cancers, underscoring the importance of elucidating the signals activating MYC. We also discuss the FUBP1/FIR/FUSE system, which acts as a ‘cruise control’ on the MYC promoter to control RNA Polymerase II pausing and, therefore, MYC transcription in response to the developmental signaling environment. Importantly, the striking conservation between humans and flies within these major axes of MYC regulation has made Drosophila an extremely valuable model organism for cancer research. We therefore discuss how Drosophila studies have helped determine the validity of signaling pathways regulating MYC in vivo using sophisticated genetics, and continue to provide novel insight into cancer biology.

  20. Voltage-sensing phosphatase reveals temporal regulation of TRPC3/C6/C7 channels by membrane phosphoinositides.

    Science.gov (United States)

    Itsuki, Kyohei; Imai, Yuko; Okamura, Yasushi; Abe, Kihachiro; Inoue, Ryuji; Mori, Masayuki X

    2012-01-01

    TRPC3/C6/C7 channels, a subgroup of classical/canonical TRP channels, are activated by diacylglycerol produced via activation of phospholipase C (PLC)-coupled receptors. Recognition of the physiological importance of these channels has been steadily growing, but the mechanism by which they are regulated remains largely unknown. We recently used a membrane-resident danio rerio voltage-sensing phosphatase (DrVSP) to study TRPC3/C6/C7 regulation and found that the channel activity was controlled by PtdIns(4,5)P(2)-DAG signaling in a self-limiting manner (Imai Y et al., the Journal of Physiology, 2012). In this addendum, we present the advantages of using DrVSP as a molecular tool to study PtdIns(4,5)P(2) regulation. DrVSP should be readily applicable for studying phosphoinositide metabolism-linked channel regulation as well as lipid dynamics. Furthermore, in comparison to other modes of self-limiting ion channel regulation, the regulation of TRPC3/C6/C7 channels seems highly susceptible to activation signal strength, which could potentially affect both open duration and the time to peak activation and inactivation. Dysfunction of such self-limiting regulation may contribute to the pathology of the cardiovascular system, gastrointestinal tract and brain, as these channels are broadly distributed and affected by numerous neurohormonal agonists.

  1. Ion channel regulation of the dynamical instability of the resting membrane potential in saccular hair cells of the green frog (Rana esculenta)

    NARCIS (Netherlands)

    Jorgensen, F; Kroese, ABA

    2005-01-01

    Aims: We investigated the ion channel regulation of the resting membrane potential of hair cells with the aim to determine if the resting membrane potential is poised close to instability and thereby a potential cause of the spontaneous afferent spike activity. Methods: The ionic mechanism and the d

  2. Redox regulation and antioxidative defence in Arabidopsis leaves viewed from a systems biology perspective.

    Science.gov (United States)

    Wormuth, Dennis; Heiber, Isabelle; Shaikali, Jehad; Kandlbinder, Andrea; Baier, Margarete; Dietz, Karl-Josef

    2007-04-30

    Redox regulation is a central control element in cell metabolism. It is employed to adjust photosynthesis and the antioxidant defence system of leaves to the prevailing environment. During recent years progress has been made in describing the redox-dependent alterations in metabolism, the thiol/disulfide proteome, the redox-dependent and cross-talking signalling pathways and the target genes of redox regulation. Some transcription factors have been identified as proteins that perform thiol/disulfide transitions linked to the redox-regulation of specific plant promoters. In addition first mathematical models have been designed to simulate antioxidant defence and predict its response. Taken together, a profound experimental data set has been generated which allows to approach a systems biology type of understanding of antioxidant defence in photosynthesising cells in the near future. Since oxidative stress is likely to limit plant growth under stress, such a systematic understanding of antioxidant defence will help to define novel targets for breeding stress-tolerant plants.

  3. Super-resolution microscopy reveals the insulin-resistance-regulated reorganization of GLUT4 on plasma membranes.

    Science.gov (United States)

    Gao, Lan; Chen, Junling; Gao, Jing; Wang, Hongda; Xiong, Wenyong

    2017-01-15

    GLUT4 (also known as SLC2A4) is essential for glucose uptake in skeletal muscles and adipocytes, which play central roles in whole-body glucose metabolism. Here, using direct stochastic optical reconstruction microscopy (dSTORM) to investigate the characteristics of plasma-membrane-fused GLUT4 at the single-molecule level, we have demonstrated that insulin and insulin resistance regulate the spatial organization of GLUT4 in adipocytes. Stimulation with insulin shifted the balance of GLUT4 on the plasma membrane toward a more dispersed configuration. In contrast, insulin resistance induced a more clustered distribution of GLUT4 and increased the mean number of molecules per cluster. Furthermore, our data demonstrate that the F(5)QQI motif and lipid rafts mediate the maintenance of GLUT4 clusters on the plasma membrane. Mutation of F(5)QQI (F(5)QQA-GLUT4) induced a more clustered distribution of GLUT4; moreover, destruction of lipid rafts in adipocytes expressing F(5)QQA-GLUT4 dramatically decreased the percentage of large clusters and the mean number of molecules per cluster. In conclusion, our data clarify the effects of insulin stimulation or insulin resistance on GLUT4 reorganization on the plasma membrane and reveal new pathogenic mechanisms of insulin resistance.

  4. The ATP-binding cassette transporter-2 (ABCA2) regulates esterification of plasma membrane cholesterol by modulation of sphingolipid metabolism.

    Science.gov (United States)

    Davis, Warren

    2014-01-01

    The ATP-binding cassette transporters are a large family (~48 genes divided into seven families A-G) of proteins that utilize the energy of ATP-hydrolysis to pump substrates across lipid bilayers against a concentration gradient. The ABC "A" subfamily is comprised of 13 members and transport sterols, phospholipids and bile acids. ABCA2 is the most abundant ABC transporter in human and rodent brain with highest expression in oligodendrocytes, although it is also expressed in neurons. Several groups have studied a possible connection between ABCA2 and Alzheimer's disease as well as early atherosclerosis. ABCA2 expression levels have been associated with changes in cholesterol and sphingolipid metabolism. In this paper, we hypothesized that ABCA2 expression level may regulate esterification of plasma membrane-derived cholesterol by modulation of sphingolipid metabolism. ABCA2 overexpression in N2a neuroblastoma cells was associated with an altered bilayer distribution of the sphingolipid ceramide that inhibited acylCoA:cholesterol acyltransferase (ACAT) activity and cholesterol esterification. In contrast, depletion of endogenous ABCA2 in the rat schwannoma cell line D6P2T increased esterification of plasma membrane cholesterol following treatment with exogenous bacterial sphingomyelinase. These findings suggest that control of ABCA2 expression level may be a key locus of regulation for esterification of plasma membrane-derived cholesterol through modulation of sphingolipid metabolism.

  5. Regulation of anionic lipids in binary membrane upon the adsorption of polyelectrolyte: A Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Xiaozheng Duan

    2013-06-01

    Full Text Available We employ Monte Carlo simulations to investigate the interaction between an adsorbing linear flexible cationic polyelectrolyte and a binary fluid membrane. The membrane contains neutral phosphatidyl–choline, PC and multivalent anionic (phosphatidylinositol, PIP2 lipids. We systematically study the influences of the solution ionic strength, the chain length and the bead charge density of the polyelectrolyte on the lateral rearrangement and the restricted mobility of the multivalent anionic lipids in the membrane. Our findings show that, the cooperativity effect and the electrostatic interaction of the polyelectrolyte beads can significantly affect the segregation extent and the concentration gradients of the PIP2 molecules, and further cooperate to induce the complicated hierarchical mobility behaviors of PIP2 molecules. In addition, when the polyelectrolyte brings a large amount of charges, it can form a robust electrostatic well to trap all PIP2 and results in local overcharge of the membrane. This work presents a mechanism to explain the membrane heterogeneity formation induced by the adsorption of charged macromolecule.

  6. Noninvasive microelectrode ion flux estimation technique (MIFE) for the study of the regulation of root membrane transport by cyclic nucleotides

    KAUST Repository

    Ordoñez, Natalia Maria

    2013-09-03

    Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular. © Springer Science+Business Media New York 2013.

  7. Cholesterol metabolism: A review of how ageing disrupts the biological mechanisms responsible for its regulation.

    Science.gov (United States)

    Morgan, A E; Mooney, K M; Wilkinson, S J; Pickles, N A; Mc Auley, M T

    2016-05-01

    Cholesterol plays a vital role in the human body as a precursor of steroid hormones and bile acids, in addition to providing structure to cell membranes. Whole body cholesterol metabolism is maintained by a highly coordinated balancing act between cholesterol ingestion, synthesis, absorption, and excretion. The aim of this review is to discuss how ageing interacts with these processes. Firstly, we will present an overview of cholesterol metabolism. Following this, we discuss how the biological mechanisms which underpin cholesterol metabolism are effected by ageing. Included in this discussion are lipoprotein dynamics, cholesterol absorption/synthesis and the enterohepatic circulation/synthesis of bile acids. Moreover, we discuss the role of oxidative stress in the pathological progression of atherosclerosis and also discuss how cholesterol biosynthesis is effected by both the mammalian target of rapamycin and sirtuin pathways. Next, we examine how diet and alterations to the gut microbiome can be used to mitigate the impact ageing has on cholesterol metabolism. We conclude by discussing how mathematical models of cholesterol metabolism can be used to identify therapeutic interventions.

  8. Assaying the proton transport and regulation of UCP1 using solid supported membranes.

    Science.gov (United States)

    Blesneac, Iulia; Ravaud, Stéphanie; Machillot, Paul; Zoonens, Manuela; Masscheylen, Sandrine; Miroux, Bruno; Vivaudou, Michel; Pebay-Peyroula, Eva

    2012-08-01

    The uncoupling protein 1 (UCP1) is a mitochondrial protein that carries protons across the inner mitochondrial membrane. It has an important role in non-shivering thermogenesis, and recent evidence suggests its role in human adult metabolism. Using rapid solution exchange on solid supported membranes, we succeeded in measuring electrical currents generated by the transport activity of UCP1. The protein was purified from mouse brown adipose tissue, reconstituted in liposomes and absorbed on solid supported membranes. A fast pH jump activated the ion transport, and electrical signals could be recorded. The currents were characterized by a fast rise and a slow decay, were stable over time, inhibited by purine nucleotides and activated by fatty acids. This new assay permits direct observation of UCP1 activity in controlled cell-free conditions, and opens up new possibilities for UCP1 functional characterization and drug screening because of its robustness and its potential for automation.

  9. Ubiquitination regulates the plasma membrane expression of renal UT-A urea transporters.

    Science.gov (United States)

    Stewart, Gavin S; O'Brien, Jennifer H; Smith, Craig P

    2008-07-01

    The renal UT-A urea transporters UT-A1, UT-A2, and UT-A3 are known to play an important role in the urinary concentrating mechanism. The control of the cellular localization of UT-A transporters is therefore vital to overall renal function. In the present study, we have investigated the effect of ubiquitination on UT-A plasma membrane expression in Madin-Darby canine kidney (MDCK) cell lines expressing each of the three renal UT-A transporters. Inhibition of the ubiquitin-proteasome pathway caused an increase in basal transepithelial urea flux across MDCK-rat (r)UT-A1 and MDCK-mouse (m)UT-A2 monolayers (P UT-A transporter expression in the plasma membrane (P UT-A3 expression in the plasma membrane (P UT-A urea transporters, but that this is not the mechanism primarily used by vasopressin to produce its physiological effects.

  10. Melatonin as a promising agent of regulating stem cell biology and its application in disease therapy.

    Science.gov (United States)

    Zhang, Shuo; Chen, Simon; Li, Yuan; Liu, Yu

    2017-03-01

    Stem cells have emerged as an important approach to repair and regenerate damaged tissues or organs and show great therapeutic potential in a variety of diseases. However, the low survival of engrafted stem cells still remains a major challenge for stem cell therapy. As a major hormone from the pineal gland, melatonin has been shown to play an important role in regulating the physiological and pathological functions of stem cells, such as promoting proliferation, migration and differentiation. Thus, melatonin combined with stem cell transplantation displayed promising application potential in neurodegenerative diseases, liver cirrhosis, wound healing, myocardial infarction, kidney ischemia injury, osteoporosis, etc. It exerts its physiological and pathological functions through its anti-oxidant, anti-inflammatory, anti-apoptosis and anti-ageing properties. Here, we summarize recent advances on exploring the biological role of melatonin in stem cells, and discuss its potential applications in stem cell-based therapy.

  11. Chemical biology tools for regulating RAS signaling complexity in space and time.

    Science.gov (United States)

    van Hattum, Hilde; Waldmann, Herbert

    2014-09-18

    Rat sarcoma (RAS) family members are small GTPases that control a number of signaling pathways important for normal cellular proliferation. Therefore, it is no surprise that a significant portion of human tumors express constitutively active mutated RAS proteins, which leads to deregulation of RAS signaling pathways, resulting in pathological perturbations of cell growth and death. Although the molecular details of RAS signaling cascades are well understood, there is still a largely unmet need for small molecule probes to control RAS signaling in space and time. More broadly, given the prevalence of mutated RAS in cancer, the need to translate the insights obtained from using small molecule probes into clinically useful drugs is also significant. In this review, we introduce RAS proteins and the signaling pathways they are involved in, and discuss some of the innovative chemical biology approaches to regulate RAS signaling, which include the exploitation of newly identified binding pockets, covalent inhibitors for mutated RAS, and RAS localization impairment.

  12. Support for the revocation of general safety test regulations in biologics license applications.

    Science.gov (United States)

    Evans, Dana M; Thorn, Jennifer M; Arch-Douglas, Katherine; Sperry, Justin B; Thompson, Bruce; Davis, Heather L; McCluskie, Michael J

    2016-05-01

    The United States Food and Drug Administration recently removed the requirement for a General Safety Test (GST) for biologics in the Code of Federal Regulations (21 CFR 610.11). The GST, as well as abnormal toxicity (European Pharmacopeia) and innocuity tests (World Health Organization), were designed to test for extraneous toxic contaminants on each product lot intended for human use. Tests require one-week observations for general health and weight following injection of specified volumes of product batches into guinea pigs and mice. At the volumes specified, dose-related toxicity may result when the product is pharmacologically active in rodents. With vaccines, required doses may be > 3 logs higher than intended human dose on a weight-adjusted basis and if an immune modulatory adjuvant is included, systemic immune hyperactivation may cause toxicity. Herein, using the CpG/alum adjuvant combination we evaluated the different test protocols and showed their unsuitability for this adjuvant combination.

  13. Osmotically regulated floating asymmetric membrane capsule for controlled site-specific delivery of ranitidine hydrochloride: optimization by central composite design.

    Science.gov (United States)

    Chauhan, Manvendra S; Kumar, Anil; Pathak, Kamla

    2012-12-01

    A nondisintegrating, floating asymmetric membrane capsule (FAMC) was developed to achieve site-specific osmotic flow of a highly water-soluble drug, ranitidine hydrochloride (RHCl), in a controlled manner. Solubility suppression of RHCl was achieved by the common ion effect, using optimized coated sodium chloride as a formulation component. The capsular wall of FAMC was prepared by the phase inversion process wherein the polymeric membrane was precipitated on glass pins by dipping them in a solution of cellulose acetate followed by quenching. Central composite design was utilized to investigate the influence of independent variables, namely, level(s) of membrane former, pore former, and osmogen, on percent cumulative drug release (response). The release mechanism of RHCl through FAMC was confirmed as osmotic pumping. The asymmetry of the membrane was characterized by scanning electron microscopy that revealed a dense nonporous outer region of membrane supported by an inner porous region. Differential scanning calorimetry indicated no incompatibility between the drug and excipients. In vitro drug release in three biorelevant media, pH 2.5 (low fed), pH 4.5 (intermediate fed), and pH 6.5 (high fed), demonstrated pH-independent release of RHCl (P > 0.05). Floating ability for 12 h of the optimized FAMC9 was visually examined during the in vitro release studies that showed maximal drug release with zero-order kinetics (r (2) = 0.9991). Thus, a novel osmotically regulated floating capsular system was developed for site-specific delivery of RHCl.

  14. m-calpain Activation Is Regulated by Its Membrane Localization and by Its Binding to Phosphatidylinositol 4,5-Bisphosphate*

    Science.gov (United States)

    Leloup, Ludovic; Shao, Hanshuang; Bae, Yong Ho; Deasy, Bridget; Stolz, Donna; Roy, Partha; Wells, Alan

    2010-01-01

    m-calpain plays a critical role in cell migration enabling rear de-adhesion of adherent cells by cleaving structural components of the adhesion plaques. Growth factors and chemokines regulate keratinocyte, fibroblast, and endothelial cell migration by modulating m-calpain activity. Growth factor receptors activate m-calpain secondary to phosphorylation on serine 50 by ERK. Concurrently, activated m-calpain is localized to its inner membrane milieu by binding to phosphatidylinositol 4,5-bisphosphate (PIP2). Opposing this, CXCR3 ligands inhibit cell migration by blocking m-calpain activity secondary to a PKA-mediated phosphorylation in the C2-like domain. The failure of m-calpain activation in the absence of PIP2 points to a key regulatory role, although whether this PIP2-mediated membrane localization is regulatory for m-calpain activity or merely serves as a docking site for ERK phosphorylation is uncertain. Herein, we report the effects of two CXCR3 ligands, CXCL11/IP-9/I-TAC and CXCL10/IP-10, on the EGF- and VEGF-induced redistribution of m-calpain in human fibroblasts and endothelial cells. The two chemokines block the tail retraction and, thus, the migration within minutes, preventing and reverting growth factor-induced relocalization of m-calpain to the plasma membrane of the cells. PKA phosphorylation of m-calpain blocks the binding of the protease to PIP2. Unexpectedly, we found that this was due to membrane anchorage itself and not merely serine 50 phosphorylation, as the farnesylation-induced anchorage of m-calpain triggers a strong activation of this protease, leading notably to an increased cell death. Moreover, the ERK and PKA phosphorylations have no effect on this membrane-anchored m-calpain. However, the presence of PIP2 is still required for the activation of the anchored m-calpain. In conclusion, we describe a novel mechanism of m-calpain activation by interaction with the plasma membrane and PIP2 specifically, this phosphoinositide acting as a

  15. A Novel Role for Progesterone Receptor Membrane Component 1 (PGRMC1): A Partner and Regulator of Ferrochelatase.

    Science.gov (United States)

    Piel, Robert B; Shiferaw, Mesafint T; Vashisht, Ajay A; Marcero, Jason R; Praissman, Jeremy L; Phillips, John D; Wohlschlegel, James A; Medlock, Amy E

    2016-09-20

    Heme is an iron-containing cofactor essential for multiple cellular processes and fundamental activities such as oxygen transport. To better understand the means by which heme synthesis is regulated during erythropoiesis, affinity purification coupled with mass spectrometry (MS) was performed to identify putative protein partners interacting with ferrochelatase (FECH), the terminal enzyme in the heme biosynthetic pathway. Both progesterone receptor membrane component 1 (PGRMC1) and progesterone receptor membrane component 2 (PGRMC2) were identified in these experiments. These interactions were validated by reciprocal affinity purification followed by MS analysis and immunoblotting. The interaction between PGRMC1 and FECH was confirmed in vitro and in HEK 293T cells, a non-erythroid cell line. When cells that are recognized models for erythroid differentiation were treated with a small molecule inhibitor of PGRMC1, AG-205, there was an observed decrease in the level of hemoglobinization relative to that of untreated cells. In vitro heme transfer experiments showed that purified PGRMC1 was able to donate heme to apo-cytochrome b5. In the presence of PGRMC1, in vitro measured FECH activity decreased in a dose-dependent manner. Interactions between FECH and PGRMC1 were strongest for the conformation of FECH associated with product release, suggesting that PGRMC1 may regulate FECH activity by controlling heme release. Overall, the data illustrate a role for PGRMC1 in regulating heme synthesis via interactions with FECH and suggest that PGRMC1 may be a heme chaperone or sensor.

  16. Phosphatase-dependent regulation of epithelial mitogen-activated protein kinase responses to toxin-induced membrane pores.

    Directory of Open Access Journals (Sweden)

    Jorge L Aguilar

    Full Text Available Diverse bacterial species produce pore-forming toxins (PFT that can puncture eukaryotic cell membranes. Host cells respond to sublytic concentrations of PFT through conserved intracellular signaling pathways, including activation of mitogen-activated protein kinases (MAPK, which are critical to cell survival. Here we demonstrate that in respiratory epithelial cells p38 and JNK MAPK were phosphorylated within 30 min of exposure to pneumolysin, the PFT from Streptococcus pneumoniae. This activation was tightly regulated, and dephosphorylation of both MAPK occurred within 60 min following exposure. Pretreatment of epithelial cells with inhibitors of cellular phosphatases, including sodium orthovanadate, calyculin A, and okadaic acid, prolonged and intensified MAPK activation. Specific inhibition of MAPK phosphatase-1 did not affect the kinetics of MAPK activation in PFT-exposed epithelial cells, but siRNA-mediated knockdown of serine/threonine phosphatases PP1 and PP2A were potent inhibitors of MAPK dephosphorylation. These results indicate an important role for PP1 and PP2A in termination of epithelial responses to PFT and only a minor contribution of dual-specificity phosphatases, such as MAPK phosphatase-1, which are the major regulators of MAPK signals in other cell types. Epithelial regulation of MAPK signaling in response to membrane disruption involves distinct pathways and may require different strategies for therapeutic interventions.

  17. Transient receptor potential vanilloid-1 signaling as a regulator of human sebocyte biology.

    Science.gov (United States)

    Tóth, Balázs I; Géczy, Tamás; Griger, Zoltán; Dózsa, Anikó; Seltmann, Holger; Kovács, László; Nagy, László; Zouboulis, Christos C; Paus, Ralf; Bíró, Tamás

    2009-02-01

    Transient receptor potential vanilloid-1 (TRPV1), originally described as a central integrator of nociception, is expressed on human epidermal and hair follicle keratinocytes and is involved in regulation of cell growth and death. In human pilosebaceous units, we had shown that TRPV1 stimulation inhibits hair shaft elongation and matrix keratinocyte proliferation, and induces premature hair follicle regression and keratinocyte apoptosis. In the current study, we have explored the role of TRPV1-mediated signaling in sebaceous gland (SG) biology, using a human sebocyte cell culture model (SZ95 sebocytes). Demonstrating that human skin SG in situ and SZ95 sebocytes in vitro express TRPV1, we show that the prototypic TRPV1 agonist, capsaicin, selectively inhibits basal and arachidonic acid-induced lipid synthesis in a dose-, time-, and extracellular calcium-dependent and a TRPV1-specific manner. Low-dose capsaicin stimulates cellular proliferation via TRPV1, whereas higher concentrations inhibit sebocyte growth and induce cell death independent of TRPV1. Moreover, capsaicin suppresses the expression of genes involved in lipid homeostasis and of selected proinflammatory cytokines. Collectively, these findings support the concept that TRPV1 signaling is a significant, previously unreported player in human sebocyte biology and identify TRPV1 as a promising target in the clinical management of inflammatory SG disorders (for example, acne vulgaris).

  18. Inositol phospholipids regulate the guanine-nucleotide-exchange factor Tiam1 by facilitating its binding to the plasma membrane and regulating GDP/GTP exchange on Rac1.

    Science.gov (United States)

    Fleming, Ian N; Batty, Ian H; Prescott, Alan R; Gray, Alex; Kular, Gursant S; Stewart, Hazel; Downes, C Peter

    2004-09-15

    Binding of the Rac1-specific guanine-nucleotide-exchange factor, Tiam1, to the plasma membrane requires the N-terminal pleckstrin homology domain. In the present study, we show that membrane-association is mediated by binding of PtdIns(4,5)P(2) to the pleckstrin homology domain. Moreover, in 1321N1 astrocytoma cells, translocation of Tiam1 to the cytosol, following receptor-mediated stimulation of PtdIns(4,5)P(2) breakdown, correlates with decreased Rac1-GTP levels, indicating that membrane-association is required for GDP/GTP exchange on Rac1. In addition, we show that platelet-derived growth factor activates Rac1 in vivo by increasing PtdIns(3,4,5)P(3) concentrations, rather than the closely related lipid, PtdIns(3,4)P(2). Finally, the data demonstrate that PtdIns(4,5)P(2) and PtdIns(3,4,5)P(3) bind to the same pleckstrin homology domain in Tiam1 and that soluble inositol phosphates appear to compete with lipids for this binding. Together, these novel observations provide strong evidence that distinct phosphoinositides regulate different functions of this enzyme, indicating that local concentrations of signalling lipids and the levels of cytosolic inositol phosphates will play crucial roles in determining its activity in vivo.

  19. Biological processes in prevention and intervention: the promotion of self-regulation as a means of preventing school failure.

    Science.gov (United States)

    Blair, Clancy; Diamond, Adele

    2008-01-01

    This paper examines interrelations between biological and social influences on the development of self-regulation in young children and considers implications of these interrelations for the promotion of self-regulation and positive adaptation to school. Emotional development and processes of emotion regulation are seen as influencing and being influenced by the development of executive cognitive functions, including working memory, inhibitory control, and mental flexibility important for the effortful regulation of attention and behavior. Developing self-regulation is further understood to reflect an emerging balance between processes of emotional arousal and cognitive regulation. Early childhood educational programs that effectively link emotional and motivational arousal with activities designed to exercise and promote executive functions can be effective in enhancing self-regulation, school readiness, and school success.

  20. Drosophila laminins act as key regulators of basement membrane assembly and morphogenesis.

    Science.gov (United States)

    Urbano, Jose M; Torgler, Catherine N; Molnar, Cristina; Tepass, Ulrich; López-Varea, Ana; Brown, Nicholas H; de Celis, Jose F; Martín-Bermudo, Maria D

    2009-12-01

    Laminins are heterotrimeric molecules found in all basement membranes. In mammals, they have been involved in diverse developmental processes, from gastrulation to tissue maintenance. The Drosophila genome encodes two laminin alpha chains, one beta and one Gamma, which form two distinct laminin trimers. So far, only mutations affecting one or other trimer have been analysed. In order to study embryonic development in the complete absence of laminins, we mutated the gene encoding the sole laminin beta chain in Drosophila, LanB1, so that no trimers can be made. We show that LanB1 mutant embryos develop until the end of embryogenesis. Electron microscopy analysis of mutant embryos reveals that the basement membranes are absent and the remaining extracellular material appears disorganised and diffuse. Accordingly, abnormal accumulation of major basement membrane components, such as Collagen IV and Perlecan, is observed in mutant tissues. In addition, we show that elimination of LanB1 prevents the normal morphogenesis of most organs and tissues, including the gut, trachea, muscles and nervous system. In spite of the above structural roles for laminins, our results unravel novel functions in cell adhesion, migration and rearrangement. We propose that while an early function of laminins in gastrulation is not conserved in Drosophila and mammals, their function in basement membrane assembly and organogenesis seems to be maintained throughout evolution.

  1. Palmitoylation regulates plasma membrane–nuclear shuttling of R7BP, a novel membrane anchor for the RGS7 family

    OpenAIRE

    2005-01-01

    The RGS7 (R7) family of RGS proteins bound to the divergent Gβ subunit Gβ5 is a crucial regulator of G protein–coupled receptor (GPCR) signaling in the visual and nervous systems. Here, we identify R7BP, a novel neuronally expressed protein that binds R7–Gβ5 complexes and shuttles them between the plasma membrane and nucleus. Regional expression of R7BP, Gβ5, and R7 isoforms in brain is highly coincident. R7BP is palmitoylated near its COOH terminus, which targets the protein to the plasma me...

  2. Biologic

    CERN Document Server

    Kauffman, L H

    2002-01-01

    In this paper we explore the boundary between biology and the study of formal systems (logic). In the end, we arrive at a summary formalism, a chapter in "boundary mathematics" where there are not only containers but also extainers ><, entities open to interaction and distinguishing the space that they are not. The boundary algebra of containers and extainers is to biologic what boolean algebra is to classical logic. We show how this formalism encompasses significant parts of the logic of DNA replication, the Dirac formalism for quantum mechanics, formalisms for protein folding and the basic structure of the Temperley Lieb algebra at the foundations of topological invariants of knots and links.

  3. Voltage-gated K+ currents in mouse articular chondrocytes regulate membrane potential.

    Science.gov (United States)

    Clark, Robert B; Hatano, Noriyuki; Kondo, Colleen; Belke, Darrell D; Brown, Barry S; Kumar, Sanjay; Votta, Bartholomew J; Giles, Wayne R

    2010-01-01

    Membrane currents and resting potential of isolated primary mouse articular chondrocytes maintained in monolayer cell culture for 1-9 days were recorded using patch clamp methods. Quantitative RT-PCR showed that the most abundantly expressed transcript of voltage-gated K(+) channels was for K(V)1.6, and immunological methods confirmed the expression of K(V)1.6 α-subunit proteins. These chondrocytes expressed a large time- and potential-dependent, Ca(2+)-independent 'delayed rectifier' K(+) current. Steady-state activation was well-fit by a Boltzmann function with a threshold near -50 mV, and a half-activation potential of -34.5 mV. The current was 50% blocked by 1.48 mM tetraethylammonium, 0.66 mM 4-aminopyridine and 20.6 nM α-dendrotoxin. The current inactivated very slowly at membrane potentials in the range of the resting potential of the chondrocytes. Resting membrane potential of the chondrocytes at room temperature (19-21°C) and in 5 mM external K(+) was -46.4 ± 1.3 mV (mean ± s.e.m; n = 23), near the 'foot' of the activation curve of this K(+) current. Resting potential was depolarized by an average of 4.2 ± 0.8 mV by 25 mM TEA, which blocked about 95% of the K(+) current. At a membrane potential of -50 mV, the apparent time constant of inactivation (tau(in)) was 37.9 s, and the 'steady-state' current level was 19% of that at a holding potential of -90 mV; at -40 mV, tau(in) was 20.3 s, and 'steady-state' current was 5% of that at -90 mV. These results demonstrate that in these primary cultured, mouse articular chondrocytes steady-state activation of a voltage-gated K(+) current contributes to resting membrane potential. However, this current is also likely to have a significant physiological role in repolarizing the chondrocyte following depolarizing stimuli that might occur in conditions of membrane stretch. For example, activation of TRP('transient receptor potential') non-specific cation channels in these cells during cyclic loading and unloading

  4. Biological stress regulation in female adolescents: a key role for confiding.

    Science.gov (United States)

    Oskis, Andrea; Clow, Angela; Loveday, Catherine; Hucklebridge, Frank; Sbarra, David A

    2015-05-01

    Attachment behaviors play a critical role in regulating emotion within the context of close relationships, and attachment theory is currently used to inform evidence-based practice in the areas of adolescent health and social care. This study investigated the association between female adolescents' interview-based attachment behaviors and two markers of hypothalamic-pituitary-adrenal axis activity: cortisol and dehydroepiandrosterone (DHEA). Unlike the classic stress hormone cortisol, there is very limited investigation of DHEA-a quintessential developmental hormone-in relation to attachment, especially in adolescents. Fifty-five healthy females mean age 14.36 (±2.41) years participated in the attachment style interview. A smaller cortisol awakening response was related to anxious attachment attitudes, including more fear of rejection, whereas greater morning basal DHEA secretion was only predicted by lower levels of reported confiding in one's mother. These attachment-hormone relationships may be developmental markers in females, as they were independent of menarche status. These findings highlight that the normative shifts occurring in attachment to caregivers around adolescence are reflected in adolescents' biological stress regulation. We discuss how studying these shifts can be informed by evolutionary-developmental theory.

  5. Molecular systems biology of Sic1 in yeast cell cycle regulation through multiscale modeling.

    Science.gov (United States)

    Barberis, Matteo

    2012-01-01

    Cell cycle control is highly regulated to guarantee the precise timing of events essential for cell growth, i.e., DNA replication onset and cell division. Failure of this control plays a role in cancer and molecules called cyclin-dependent kinase (Cdk) inhibitors (Ckis) exploit a critical function in cell cycle timing. Here we present a multiscale modeling where experimental and computational studies have been employed to investigate structure, function and temporal dynamics of the Cki Sic1 that regulates cell cycle progression in Saccharomyces cerevisiae. Structural analyses reveal molecular details of the interaction between Sic1 and Cdk/cyclin complexes, and biochemical investigation reveals Sic1 function in analogy to its human counterpart p27(Kip1), whose deregulation leads to failure in timing of kinase activation and, therefore, to cancer. Following these findings, a bottom-up systems biology approach has been developed to characterize modular networks addressing Sic1 regulatory function. Through complementary experimentation and modeling, we suggest a mechanism that underlies Sic1 function in controlling temporal waves of cyclins to ensure correct timing of the phase-specific Cdk activities.

  6. Nutritional regulation of division of labor in honey bees: toward a systems biology perspective.

    Science.gov (United States)

    Ament, Seth A; Wang, Ying; Robinson, Gene E

    2010-01-01

    Organisms adapt their behavior and physiology to environmental conditions through processes of phenotypic plasticity. In one well-studied example, the division of labor among worker honey bees involves a stereotyped yet plastic pattern of behavioral and physiological maturation. Early in life, workers perform brood care and other in-hive tasks and have large internal nutrient stores; later in life, they forage for nectar and pollen outside the hive and have small nutrient stores. The pace of maturation depends on colony conditions, and the environmental, physiological, and genomic mechanisms by which this occurs are being actively investigated. Here we review current knowledge of the mechanisms by which a key environmental variable, nutritional status, influences worker honey bee division of labor. These studies demonstrate that changes in individual nutritional status and conserved food-related molecular and hormonal pathways regulate the age at which individual bees begin to forage. We then outline ways in which systems biology approaches, enabled by the sequencing of the honey bee genome, will allow researchers to gain deeper insight into nutritional regulation of honey bee behavior, and phenotypic plasticity in general.

  7. The virulence protein SopD2 regulates membrane dynamics of Salmonella-containing vacuoles.

    Directory of Open Access Journals (Sweden)

    Nina Schroeder

    Full Text Available Salmonella enterica serovar Typhimurium is a Gram-negative bacterial pathogen causing gastroenteritis in humans and a systemic typhoid-like illness in mice. The capacity of Salmonella to cause diseases relies on the establishment of its intracellular replication niche, a membrane-bound compartment named the Salmonella-containing vacuole (SCV. This requires the translocation of bacterial effector proteins into the host cell by type three secretion systems. Among these effectors, SifA is required for the SCV stability, the formation of Salmonella-induced filaments (SIFs and plays an important role in the virulence of Salmonella. Here we show that the effector SopD2 is responsible for the SCV instability that triggers the cytoplasmic release of a sifA(- mutant. Deletion of sopD2 also rescued intra-macrophagic replication and increased virulence of sifA(- mutants in mice. Membrane tubular structures that extend from the SCV are the hallmark of Salmonella-infected cells. Until now, these unique structures have not been observed in the absence of SifA. The deletion of sopD2 in a sifA(- mutant strain re-established membrane trafficking from the SCV and led to the formation of new membrane tubular structures, the formation of which is dependent on other Salmonella effector(s. Taken together, our data demonstrate that SopD2 inhibits the vesicular transport and the formation of tubules that extend outward from the SCV and thereby contributes to the sifA(- associated phenotypes. These results also highlight the antagonistic roles played by SopD2 and SifA in the membrane dynamics of the vacuole, and the complex actions of SopD2, SifA, PipB2 and other unidentified effector(s in the biogenesis and maintenance of the Salmonella replicative niche.

  8. The Interaction of Polyglutamine Peptides with Lipid Membranes Is Regulated by Flanking Sequences Associated with Huntingtin*

    Science.gov (United States)

    Burke, Kathleen A.; Kauffman, Karlina J.; Umbaugh, C. Samuel; Frey, Shelli L.; Legleiter, Justin

    2013-01-01

    Huntington disease (HD) is caused by an expanded polyglutamine (poly(Q)) repeat near the N terminus of the huntingtin (htt) protein. Expanded poly(Q) facilitates formation of htt aggregates, eventually leading to deposition of cytoplasmic and intranuclear inclusion bodies containing htt. Flanking sequences directly adjacent to the poly(Q) domain, such as the first 17 amino acids on the N terminus (Nt17) and the polyproline (poly(P)) domain on the C-terminal side of the poly(Q) domain, heavily influence aggregation. Additionally, htt interacts with a variety of membraneous structures within the cell, and Nt17 is implicated in lipid binding. To investigate the interaction between htt exon1 and lipid membranes, a combination of in situ atomic force microscopy, Langmuir trough techniques, and vesicle permeability assays were used to directly monitor the interaction of a variety of synthetic poly(Q) peptides with different combinations of flanking sequences (KK-Q35-KK, KK-Q35-P10-KK, Nt17-Q35-KK, and Nt17-Q35-P10-KK) on model membranes and surfaces. Each peptide aggregated on mica, predominately forming extended, fibrillar aggregates. In contrast, poly(Q) peptides that lacked the Nt17 domain did not appreciably aggregate on or insert into lipid membranes. Nt17 facilitated the interaction of peptides with lipid surfaces, whereas the poly(P) region enhanced this interaction. The aggregation of Nt17-Q35-P10-KK on the lipid bilayer closely resembled that of a htt exon1 construct containing 35 repeat glutamines. Collectively, this data suggests that the Nt17 domain plays a critical role in htt binding and aggregation on lipid membranes, and this lipid/htt interaction can be further modulated by the presence of the poly(P) domain. PMID:23572526

  9. Regulation of membrane protein function by lipid bilayer elasticity—a single molecule technology to measure the bilayer properties experienced by an embedded protein

    DEFF Research Database (Denmark)

    Lundbæk, Jens August

    2008-01-01

    , in the general regulation of membrane protein function, is unclear. This is to a large extent due to lack of a generally accepted framework in which to understand the many observations. The present review summarizes studies which have demonstrated that the hydrophobic interactions between a membrane protein...... and the host lipid bilayer provide an energetic coupling, whereby protein function can be regulated by the bilayer elasticity. The feasibility of this ‘hydrophobic coupling mechanism’ has been demonstrated using the gramicidin channel, a model membrane protein, in planar lipid bilayers. Using voltage...... properties experienced by an embedded protein has been developed. A theoretical and technological framework, to study the regulation of membrane protein function by lipid bilayer elasticity, has been established....

  10. On the emergence of biology from chemistry: a discontinuist perspective from the point of view of stability and regulation.

    Science.gov (United States)

    Bich, Leonardo; Damiano, Luisa

    2012-10-01

    In this paper we argue that molecular evolution, and the evolution of prebiotic and early biological systems are qualitatively different processes, in which a crucial role is played respectively by structural stability and by dynamical mechanisms of regulation and integration. These different features entail also distinct modalities of interaction between system and environment that need to be taken into consideration when discussing molecular and biological evolution and selection.

  11. Regulation of Ca2+ channels by SNAP-25 via recruitment of syntaxin-1 from plasma membrane clusters

    DEFF Research Database (Denmark)

    Toft-Bertelsen, Trine Lisberg; Ziomkiewicz, Iwona; Houy, Sébastien;

    2016-01-01

    SNAP-25 regulates Ca(2+) channels, with potentially important consequences for diseases involving an aberrant SNAP-25 expression level. How this regulation is executed mechanistically remains unknown. We investigated this question in mouse adrenal chromaffin cells and found that SNAP-25 inhibits Ca......(2+) currents, with the B-isoform being more potent than the A-isoform, but not when syntaxin-1 is cleaved by botulinum neurotoxin C. In contrast, syntaxin-1 inhibits Ca(2+) currents independently of SNAP-25. Further experiments using immunostaining showed that endogenous or exogenous SNAP-25...... expression recruits syntaxin-1 from clusters on the plasma membrane, thereby increasing the immunoavailability of syntaxin-1 and leading indirectly to Ca(2+) current inhibition. Expression of Munc18-1, which recruits syntaxin-1 within the exocytotic pathway, does not modulate Ca(2+) channels, whereas...

  12. MapA, an iron-regulated, cytoplasmic membrane protein in the cyanobacterium Synechococcus sp. strain PCC7942.

    Science.gov (United States)

    Webb, R; Troyan, T; Sherman, D; Sherman, L A

    1994-08-01

    Growth of Synechococcus sp. strain PCC 7942 in iron-deficient media leads to the accumulation of an approximately 34-kDa protein. The gene encoding this protein, mapA (membrane-associated protein A), has been cloned and sequenced (GenBank accession number, L01621). The mapA transcript is not detectable in normally grown cultures but is stably accumulated by cells grown in iron-deficient media. However, the promoter sequence for this gene does not resemble other bacterial iron-regulated promoters described to date. The carboxyl-terminal region of the derived amino acid sequence of MapA resembles bacterial proteins involved in iron acquisition, whereas the amino-terminal end of MapA has a high degree of amino acid identity with the abundant, chloroplast envelope protein E37. An approach employing improved cellular fractionation techniques as well as electron microscopy and immunocytochemistry was essential in localizing MapA protein to the cytoplasmic membrane of Synechococcus sp. strain PCC 7942. When these cells were grown under iron-deficient conditions, a significant fraction of MapA could also be localized to the thylakoid membranes.

  13. A systems biology approach to identify the signalling network regulated by Rho-GDI-γ during neural stem cell differentiation.

    Science.gov (United States)

    Wang, Jiao; Hu, Fuyan; Cheng, Hua; Zhao, Xing-Ming; Wen, Tieqiao

    2012-11-01

    Understanding the molecular mechanism that underlies the differentiation of neural stem cells (NSCs) is vital to develop regenerative medicines for neurological disorders. In our previous work, Rho-GDI-γ was found to be able to prompt neuronal differentiation when it was down regulated. However, it is unclear how Rho-GDI-γ regulates this differentiation process. Therefore, a novel systems biology approach is presented here to identify putative signalling pathways regulated by Rho-GDI-γ during NSC differentiation, and these pathways can provide insights into the NSC differentiation mechanisms. In particular, our proposed approach combines the predictive power of computational biology and molecular experiments. With different biological experiments, the genes in the computationally identified signalling network were validated to be indeed regulated by Rho-GDI-γ during the differentiation of NSCs. In particular, one randomly selected pathway involving Vcp, Mapk8, Ywhae and Ywhah was experimentally verified to be regulated by Rho-GDI-γ. These promising results demonstrate the effectiveness of our proposed systems biology approach, indicating the potential predictive power of integrating computational and experimental approaches.

  14. Oxidation of Membrane Curvature-Regulating Phosphatidylethanolamine Lipid Results in Formation of Bilayer and Cubic Structures.

    Science.gov (United States)

    Sankhagowit, Shalene; Lee, Ernest Y; Wong, Gerard C L; Malmstadt, Noah

    2016-03-15

    Oxidation is associated with conditions related to chronic inflammations and aging. Cubic structures have been observed in the smooth endoplasmic reticulum and mitochondrial membranes of cells under oxidative stress (e.g., tumor cells and virus-infected cells). It has been previously suspected that oxidation can result in the rearrangement of lipids from a fluid lamellar phase to a cubic structure in organelles containing membranes enriched with amphiphiles that have nonzero intrinsic curvature, such as phosphatidylethanolamine (PE) and cardiolipin. This study focuses on the oxidation of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), a lipid that natively forms an inverted hexagonal phase at physiological conditions. The oxidized samples contain an approximately 3:2 molar ratio of nonoxidized to oxidized DOPE. Optical microscopy images collected during the hydration of this mixture from a dried film suggest that the system evolves into a coexistence of a stable fluid lamellar phase and transient square lattice structures with unit cell sizes of 500-600 nm. Small-angle X-ray scattering of the same lipid mixture yielded a body-centered Im3m cubic phase with the lattice parameter of 14.04 nm. On average, the effective packing parameter of the oxidized DOPE species was estimated to be 0.657 ± 0.069 (standard deviation). This suggests that the oxidation of PE leads to a group of species with inverted molecular intrinsic curvature. Oxidation can create amphiphilic subpopulations that potently impact the integrity of the membrane, since negative Gaussian curvature intrinsic to cubic phases can enable membrane destabilization processes.

  15. Membrane lipids regulate ganglioside GM2 catabolism and GM2 activator protein activity.

    Science.gov (United States)

    Anheuser, Susi; Breiden, Bernadette; Schwarzmann, Günter; Sandhoff, Konrad

    2015-09-01

    Ganglioside GM2 is the major lysosomal storage compound of Tay-Sachs disease. It also accumulates in Niemann-Pick disease types A and B with primary storage of SM and with cholesterol in type C. Reconstitution of GM2 catabolism with β-hexosaminidase A and GM2 activator protein (GM2AP) at uncharged liposomal surfaces carrying GM2 as substrate generated only a physiologically irrelevant catabolic rate, even at pH 4.2. However, incorporation of anionic phospholipids into the GM2 carrying liposomes stimulated GM2 hydrolysis more than 10-fold, while the incorporation of plasma membrane stabilizing lipids (SM and cholesterol) generated a strong inhibition of GM2 hydrolysis, even in the presence of anionic phospholipids. Mobilization of membrane lipids by GM2AP was also inhibited in the presence of cholesterol or SM, as revealed by surface plasmon resonance studies. These lipids also reduced the interliposomal transfer rate of 2-NBD-GM1 by GM2AP, as observed in assays using Förster resonance energy transfer. Our data raise major concerns about the usage of recombinant His-tagged GM2AP compared with untagged protein. The former binds more strongly to anionic GM2-carrying liposomal surfaces, increases GM2 hydrolysis, and accelerates intermembrane transfer of 2-NBD-GM1, but does not mobilize membrane lipids.

  16. Membrane lipids regulate ganglioside GM2 catabolism and GM2 activator protein activity[S

    Science.gov (United States)

    Anheuser, Susi; Breiden, Bernadette; Schwarzmann, Günter; Sandhoff, Konrad

    2015-01-01

    Ganglioside GM2 is the major lysosomal storage compound of Tay-Sachs disease. It also accumulates in Niemann-Pick disease types A and B with primary storage of SM and with cholesterol in type C. Reconstitution of GM2 catabolism with β-hexosaminidase A and GM2 activator protein (GM2AP) at uncharged liposomal surfaces carrying GM2 as substrate generated only a physiologically irrelevant catabolic rate, even at pH 4.2. However, incorporation of anionic phospholipids into the GM2 carrying liposomes stimulated GM2 hydrolysis more than 10-fold, while the incorporation of plasma membrane stabilizing lipids (SM and cholesterol) generated a strong inhibition of GM2 hydrolysis, even in the presence of anionic phospholipids. Mobilization of membrane lipids by GM2AP was also inhibited in the presence of cholesterol or SM, as revealed by surface plasmon resonance studies. These lipids also reduced the interliposomal transfer rate of 2-NBD-GM1 by GM2AP, as observed in assays using Förster resonance energy transfer. Our data raise major concerns about the usage of recombinant His-tagged GM2AP compared with untagged protein. The former binds more strongly to anionic GM2-carrying liposomal surfaces, increases GM2 hydrolysis, and accelerates intermembrane transfer of 2-NBD-GM1, but does not mobilize membrane lipids. PMID:26175473

  17. Supported Lipid Bilayer Platform To Test Inhibitors of the Membrane Attack Complex: Insights into Biomacromolecular Assembly and Regulation.

    Science.gov (United States)

    Yorulmaz, Saziye; Jackman, Joshua A; Hunziker, Walter; Cho, Nam-Joon

    2015-11-01

    Complement activation plays an important role in innate immune defense by triggering formation of the membrane attack complex (MAC), which is a biomacromolecular assembly that exhibits membrane-lytic activity against foreign invaders including various pathogens and biomaterials. Understanding the details of MAC structure and function has been the subject of extensive work involving bulk liposome and erythrocyte assays. However, it is difficult to characterize the mechanism of action of MAC inhibitor drug candidates using the conventional assays. To address this issue, we employ a biomimetic supported lipid bilayer platform to investigate how two MAC inhibitors, vitronectin and clusterin, interfere with MAC assembly in a sequential addition format, as monitored by the quartz crystal microbalance-dissipation (QCM-D) technique. Two experimental strategies based on modular assembly were selected, precincubation of inhibitor and C5b-7 complex before addition to the lipid bilayer or initial addition of inhibitor followed by the C5b-7 complex. The findings indicate that vitronectin inhibits membrane association of C5b-7 via a direct interaction with C5b-7 and via competitive membrane association onto the supported lipid bilayer. On the other hand, clusterin directly interacts with C5b-7 such that C5b-7 is still able to bind to the lipid bilayer, and clusterin affects the subsequent binding of other complement proteins involved in the MAC assembly. Taken together, the findings in this study outline a biomimetic approach based on supported lipid bilayers to explore the interactions between complement proteins and inhibitors, thereby offering insight into MAC assembly and regulation.

  18. Complexin 2 modulates vesicle-associated membrane protein (VAMP) 2-regulated zymogen granule exocytosis in pancreatic acini.

    Science.gov (United States)

    Falkowski, Michelle A; Thomas, Diana D H; Groblewski, Guy E

    2010-11-12

    Complexins are soluble proteins that regulate the activity of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes necessary for vesicle fusion. Neuronal specific complexin 1 has inhibitory and stimulatory effects on exocytosis by clamping trans-SNARE complexes in a prefusion state and promoting conformational changes to facilitate membrane fusion following cell stimulation. Complexins are unable to bind to monomeric SNARE proteins but bind with high affinity to ternary SNARE complexes and with lower affinity to target SNARE complexes. Far less is understood about complexin function outside the nervous system. Pancreatic acini express the complexin 2 isoform by RT-PCR and immunoblotting. Immunofluorescence microscopy revealed complexin 2 localized along the apical plasma membrane consistent with a role in secretion. Accordingly, complexin 2 was found to interact with vesicle-associated membrane protein (VAMP) 2, syntaxins 3 and 4, but not with VAMP 8 or syntaxin 2. Introduction of recombinant complexin 2 into permeabilized acini inhibited Ca(2+)-stimulated secretion in a concentration-dependent manner with a maximal inhibition of nearly 50%. Mutations of the central α-helical domain reduced complexin 2 SNARE binding and concurrently abolished its inhibitory activity. Surprisingly, mutation of arginine 59 to histidine within the central α-helical domain did not alter SNARE binding and moreover, augmented Ca(2+)-stimulated secretion by 130% of control. Consistent with biochemical studies, complexin 2 colocalized with VAMP 2 along the apical plasma membrane following cholecystokinin-8 stimulation. These data demonstrate a functional role for complexin 2 outside the nervous system and indicate that it participates in the Ca(2+)-sensitive regulatory pathway for zymogen granule exocytosis.

  19. Complexin 2 Modulates Vesicle-associated Membrane Protein (VAMP) 2-regulated Zymogen Granule Exocytosis in Pancreatic Acini*

    Science.gov (United States)

    Falkowski, Michelle A.; Thomas, Diana D. H.; Groblewski, Guy E.

    2010-01-01

    Complexins are soluble proteins that regulate the activity of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes necessary for vesicle fusion. Neuronal specific complexin 1 has inhibitory and stimulatory effects on exocytosis by clamping trans-SNARE complexes in a prefusion state and promoting conformational changes to facilitate membrane fusion following cell stimulation. Complexins are unable to bind to monomeric SNARE proteins but bind with high affinity to ternary SNARE complexes and with lower affinity to target SNARE complexes. Far less is understood about complexin function outside the nervous system. Pancreatic acini express the complexin 2 isoform by RT-PCR and immunoblotting. Immunofluorescence microscopy revealed complexin 2 localized along the apical plasma membrane consistent with a role in secretion. Accordingly, complexin 2 was found to interact with vesicle-associated membrane protein (VAMP) 2, syntaxins 3 and 4, but not with VAMP 8 or syntaxin 2. Introduction of recombinant complexin 2 into permeabilized acini inhibited Ca2+-stimulated secretion in a concentration-dependent manner with a maximal inhibition of nearly 50%. Mutations of the central α-helical domain reduced complexin 2 SNARE binding and concurrently abolished its inhibitory activity. Surprisingly, mutation of arginine 59 to histidine within the central α-helical domain did not alter SNARE binding and moreover, augmented Ca2+-stimulated secretion by 130% of control. Consistent with biochemical studies, complexin 2 colocalized with VAMP 2 along the apical plasma membrane following cholecystokinin-8 stimulation. These data demonstrate a functional role for complexin 2 outside the nervous system and indicate that it participates in the Ca2+-sensitive regulatory pathway for zymogen granule exocytosis. PMID:20829354

  20. Arabidopsis thaliana AUCSIA-1 regulates auxin biology and physically interacts with a kinesin-related protein.

    Directory of Open Access Journals (Sweden)

    Barbara Molesini

    Full Text Available Aucsia is a green plant gene family encoding 44-54 amino acids long miniproteins. The sequenced genomes of most land plants contain two Aucsia genes. RNA interference of both tomato (Solanum lycopersicum Aucsia genes (SlAucsia-1 and SlAucsia-2 altered auxin sensitivity, auxin transport and distribution; it caused parthenocarpic development of the fruit and other auxin-related morphological changes. Here we present data showing that the Aucsia-1 gene of Arabidopsis thaliana alters, by itself, root auxin biology and that the AtAUCSIA-1 miniprotein physically interacts with a kinesin-related protein. The AtAucsia-1 gene is ubiquitously expressed, although its expression is higher in roots and inflorescences in comparison to stems and leaves. Two allelic mutants for AtAucsia-1 gene did not display visible root morphological alterations; however both basipetal and acropetal indole-3-acetic acid (IAA root transport was reduced as compared with wild-type plants. The transcript steady state levels of the auxin efflux transporters ATP BINDING CASSETTE subfamily B (ABCB ABCB1, ABCB4 and ABCB19 were reduced in ataucsia-1 plants. In ataucsia-1 mutant, lateral root growth showed an altered response to i exogenous auxin, ii an inhibitor of polar auxin transport and iii ethylene. Overexpression of AtAucsia-1 inhibited primary root growth. In vitro and in vivo protein-protein interaction experiments showed that AtAUCSIA-1 interacts with a 185 amino acids long fragment belonging to a 2712 amino acids long protein of unknown function (At4g31570. Bioinformatics analysis indicates that the AtAUCSIA-1 interacting protein (AtAUCSIA-1IP clusters with a group of CENP-E kinesin-related proteins. Gene ontology predictions for the two proteins are consistent with the hypothesis that the AtAUCSIA-1/AtAUCSIA-1IP complex is involved in the regulation of the cytoskeleton dynamics underlying auxin biology.

  1. Study on Biologic Activity for Membrane of Normal Bone Marrow Cells with Infection of Epidemic Hemorrhagic Fever Virus

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using DPH fluorescence probe, the membrane of normal bone marrow cells with infection of epidemic hemorrhagic fever virus (EHFV) was labeled. The membrane lipid fluidity was obviously decreased from the membrane lipid fluorescence polarization. The membrane lipid fluidity of lymphocyte, monocyte and neutrophilic granulocyte was dynamically observed. After culturing the cells for 1, 6, 24 and 72 h, it was found that all the membrane lipid fluidity of the infected cells was decreased obviously with the longer the culturing time, the more obvious it. Compared with the normal control groups, there was a significant difference statistically (P<0. 05-0. 01). It was suggested that the decrease of the membrane lipid fluidity of normal bone marrow cell with infection of EHFV had correlation with the degree of virus invading and cellfunction injury.

  2. Biological evaluation of PLLA membranes, with different pore diameters, to stimulate cell adhesion and growth in vitro

    Science.gov (United States)

    Montesanto, S.; Fucarino, A.; Bucchieri, F.; La Carrubba, V.; Brucato, V.

    2015-12-01

    Polymeric membranes prepared via DIPS (Diffusion Induced Phase Separation) are widely studied and utilized as scaffolds for the regeneration of tissue. In this work, poly (L)-lactide membrane are prepared through a DIPS protocol starting from a ternary solution made of polymer, dioxane (solvent) and water (non-solvent). A three-dimensional, porous and mechanically stable membrane is desirable for ingrowth of human bronchial epithelial cells.

  3. Protein Kinase A Regulates 3-Phosphatidylinositide Dynamics during Platelet-derived Growth Factor-induced Membrane Ruffling and Chemotaxis*S⃞

    Science.gov (United States)

    Deming, Paula B.; Campbell, Shirley L.; Baldor, Linda C.; Howe, Alan K.

    2008-01-01

    Spatial regulation of the cAMP-dependent protein kinase (PKA) is required for chemotaxis in fibroblasts; however, the mechanism(s) by which PKA regulates the cell migration machinery remain largely unknown. Here we report that one function of PKA during platelet-derived growth factor (PDGF)-induced chemotaxis was to promote membrane ruffling by regulating phosphatidylinositol 3,4,5-trisphosphate (PIP3) dynamics. Inhibition of PKA activity dramatically altered membrane dynamics and attenuated formation of peripheral membrane ruffles in response to PDGF. PKA inhibition also significantly decreased the number and size of PIP3-rich membrane ruffles in response to uniform stimulation and to gradients of PDGF. This ruffling defect was quantified using a newly developed method, based on computer vision edge-detection algorithms. PKA inhibition caused a marked attenuation in the bulk accumulation of PIP3 following PDGF stimulation, without effects on PI3-kinase (PI3K) activity. The deficits in PIP3 dynamics correlated with a significant inhibition of growth factor-induced membrane recruitment of endogenous Akt and Rac activation in PKA-inhibited cells. Simultaneous inhibition of PKA and Rac had an additive inhibitory effect on growth factor-induced ruffling dynamics. Conversely, the expression of a constitutively active Rac allele was able to rescue the defect in membrane ruffling and restore the localization of a fluorescent PIP3 marker to membrane ruffles in PKA-inhibited cells, even in the absence of PI3K activity. These data demonstrate that, like Rac, PKA contributes to PIP3 and membrane dynamics independently of direct regulation of PI3K activity and suggest that modulation of PIP3/3-phosphatidylinositol (3-PI) lipids represents a major target for PKA in the regulation of PDGF-induced chemotactic events. PMID:18936099

  4. A theoretical lens on a biology intensive orientation program: A study of self-efficacy and self-regulation of freshman biology majors

    Science.gov (United States)

    Wheeler, Erin R.

    There is a national effort to increase the number of undergraduate students graduating in science, math, engineering, and technology (STEM) (National Science Foundation, 2007). The majority of students initially populating these STEM majors ultimately switch to and graduate from non-STEM majors (Seymour & Hewitt, 2000; Seymour, 2002). The source of attrition from STEM fields lies within the difficulty of concepts presented in freshman STEM introductory courses (Jensen & Moore, 2007, 2008, 2009; Seymour & Hewitt, 2000). These gateway courses are considered high-risk because nearly half of students enrolled in these courses receive either a "D" or "F" or completely withdraw from the course (Labov, 2004). Research shows that students who have uncalibrated self-efficacy and an attenuated self-regulated learning are unsuccessful in high-risk courses (Kitsantas et al., 2008; Ross, Green, Salisbury-Glennon, & Tollefson, 2006; Zimmerman, 2002). Traditional academic assistance, such as tutoring, learning to learn courses, and supplemental instruction, does not explicitly develop an undergraduate's self-efficacy and self-regulated learning as it specifically relates to the STEM domains (Cao & Nietfeld, 2007; Dembo & Seli, 2006; Ross et al., 2006; Simpson, Hind, Nist, Burrell, 1997). Some STEM departments have created academic interventions, such as one-credit seminars, orientation programs, and bridge programs, to directly address the needs of STEM majors (Belzer, 2003; Bonner, 2009; Chevalier, Chrisman, & Kelsey, 2001; Hutchison-Green, Follman, & Bodner, 2008; D. J. Minchella, Yazvac, C. W., Fodrea, R. A., Ball G., 2007; Reyes, Anderson-Rowland, & McCartney, 1998). This study focused on the effect of a biology-intensive orientation program on biology majors' self-efficacy and self-regulated learning. The study utilized approximately 300 undergraduate biology majors participating in a biology-intensive orientation that occurred on August 7-12, 2011, at a public state

  5. Regulation of Early Steps of GPVI Signal Transduction by Phosphatases: A Systems Biology Approach.

    Directory of Open Access Journals (Sweden)

    Joanne L Dunster

    2015-11-01

    Full Text Available We present a data-driven mathematical model of a key initiating step in platelet activation, a central process in the prevention of bleeding following Injury. In vascular disease, this process is activated inappropriately and causes thrombosis, heart attacks and stroke. The collagen receptor GPVI is the primary trigger for platelet activation at sites of injury. Understanding the complex molecular mechanisms initiated by this receptor is important for development of more effective antithrombotic medicines. In this work we developed a series of nonlinear ordinary differential equation models that are direct representations of biological hypotheses surrounding the initial steps in GPVI-stimulated signal transduction. At each stage model simulations were compared to our own quantitative, high-temporal experimental data that guides further experimental design, data collection and model refinement. Much is known about the linear forward reactions within platelet signalling pathways but knowledge of the roles of putative reverse reactions are poorly understood. An initial model, that includes a simple constitutively active phosphatase, was unable to explain experimental data. Model revisions, incorporating a complex pathway of interactions (and specifically the phosphatase TULA-2, provided a good description of the experimental data both based on observations of phosphorylation in samples from one donor and in those of a wider population. Our model was used to investigate the levels of proteins involved in regulating the pathway and the effect of low GPVI levels that have been associated with disease. Results indicate a clear separation in healthy and GPVI deficient states in respect of the signalling cascade dynamics associated with Syk tyrosine phosphorylation and activation. Our approach reveals the central importance of this negative feedback pathway that results in the temporal regulation of a specific class of protein tyrosine phosphatases in

  6. Plasma Membrane CFTR Regulates RANTES Expression via Its C-Terminal PDZ-Interacting Motif

    OpenAIRE

    Estell, Kim; Braunstein, Gavin; Tucker, Torry; Varga, Karoly; Collawn, James F.; Schwiebert, Lisa M.

    2003-01-01

    Despite the identification of 1,000 mutations in the cystic fibrosis gene product CFTR, there remains discordance between CFTR genotype and lung disease phenotype. The study of CFTR, therefore, has expanded beyond its chloride channel activity into other possible functions, such as its role as a regulator of gene expression. Findings indicate that CFTR plays a role in the expression of RANTES in airway epithelia. RANTES is a chemokine that has been implicated in the regulation of mucosal immu...

  7. Topology mapping of insulin-regulated glucose transporter GLUT4 using computational biology.

    Science.gov (United States)

    Chakraborty, Chiranjib; Bandyopadhyay, Sanghamitra; Maulik, Ujjwal; Agoramoorthy, Govindasamy

    2013-01-01

    The type 2 diabetes is increasing rapidly around the globe. The primary cause for this is insulin resistance due to the disruption of the insulin signal transduction mechanism. Insulin signal transduction stimulates glucose transport through the glucose transporter GLUT4, by promoting the exocytosis process. Understanding the structural topology of GLUT4 mechanism will increase our understanding of the dynamic activities about glucose transport and its regulation in the membrane environment. However, little is known about the topology of GLUT4. In this article, we have determined the amino acid composition, disulfide topology, structure conformation pattern of GLUT4. The amino acid composition portrays that leucine composition is the highest contributing to 15.5% among all other amino acids. Three cysteine residues such as Cys223, Cys361, and Cys363 were observed and the last two were associated with one disulfide bond formation. We have generated surface cavities to know the clefts/pockets on the surface of this protein that showed few irregular cavities placed mostly in the transmembrane-helical part. Besides, topology mapping of 12 transmembrane-helixes was done to predict N- and O-glycosylation sites and to show the highly glycosylated GLUT4 that includes both N- and O-glycosylation sites. Furthermore, hydrophobic segment and molecular charge distribution were analyzed. This article shows that bioinformatics tools can provide a rapid methodology to predict the topology of GLUT4. It also provides insights into the structural details and structural functioning relationships in the human GLUT4. The results can be of great help to advance future drug development research using GLUT4 as a target protein.

  8. Is the fluid mosaic (and the accompanying raft hypothesis a suitable model to describe fundamental features of biological membranes? What may be missing?

    Directory of Open Access Journals (Sweden)

    Luis Alberto Bagatolli

    2013-11-01

    Full Text Available The structure, dynamics, and stability of lipid bilayers are controlled by thermodynamic forces, leading to overall tensionless membranes with a distinct lateral organization and a conspicuous lateral pressure profile. Bilayers are also subject to built-in curvature-stress instabilities that may be released locally or globally in terms of morphological changes leading to the formation of non-lamellar and curved structures. A key controller of the bilayer’s propensity to form curved structures is the average molecular shape of the different lipid molecules. Via the curvature stress, molecular shape mediates a coupling to membrane-protein function and provides a set of physical mechanisms for formation of lipid domains and laterally differentiated regions in the plane of the membrane. Unfortunately, these relevant physical features of membranes are often ignored in the most popular models for biological membranes. Results from a number of experimental and theoretical studies emphasize the significance of these fundamental physical properties and call for a refinement of the fluid mosaic model (and the accompanying raft hypothesis.

  9. Asymmetric PDLLA membranes containing Bioglass(R) for guided tissue regeneration: characterization and in vitro biological behavior

    NARCIS (Netherlands)

    Leal, A.I.; Caridade, S.G.; Ma, J.; Yu, N.; Gomes, M.E.R.; Reis, R.L.; Jansen, J.A.; Walboomers, X.F.; Mano, J.F.

    2013-01-01

    OBJECTIVE: In the treatment of periodontal defects, composite membranes might be applied to protect the injured area and simultaneously stimulate tissue regeneration. This work describes the development and characterization of poly(d,l-lactic acid)/Bioglass(R) (PDLLA/BG) composite membranes with asy

  10. A-RAF kinase functions in ARF6 regulated endocytic membrane traffic.

    Directory of Open Access Journals (Sweden)

    Elena Nekhoroshkova

    Full Text Available BACKGROUND: RAF kinases direct ERK MAPK signaling to distinct subcellular compartments in response to growth factor stimulation. METHODOLOGY/PRINCIPAL FINDINGS: Of the three mammalian isoforms A-RAF is special in that one of its two lipid binding domains mediates a unique pattern of membrane localization. Specific membrane binding is retained by an N-terminal fragment (AR149 that corresponds to a naturally occurring splice variant termed DA-RAF2. AR149 colocalizes with ARF6 on tubular endosomes and has a dominant negative effect on endocytic trafficking. Moreover actin polymerization of yeast and mammalian cells is abolished. AR149/DA-RAF2 does not affect the internalization step of endocytosis, but trafficking to the recycling compartment. CONCLUSIONS/SIGNIFICANCE: A-RAF induced ERK activation is required for this step by activating ARF6, as A-RAF depletion or inhibition of the A-RAF controlled MEK-ERK cascade blocks recycling. These data led to a new model for A-RAF function in endocytic trafficking.

  11. The IFT-A complex regulates Shh signaling through cilia structure and membrane protein trafficking.

    Science.gov (United States)

    Liem, Karel F; Ashe, Alyson; He, Mu; Satir, Peter; Moran, Jennifer; Beier, David; Wicking, Carol; Anderson, Kathryn V

    2012-06-11

    Two intraflagellar transport (IFT) complexes, IFT-A and IFT-B, build and maintain primary cilia and are required for activity of the Sonic hedgehog (Shh) pathway. A weak allele of the IFT-A gene, Ift144, caused subtle defects in cilia structure and ectopic activation of the Shh pathway. In contrast, strong loss of IFT-A, caused by either absence of Ift144 or mutations in two IFT-A genes, blocked normal ciliogenesis and decreased Shh signaling. In strong IFT-A mutants, the Shh pathway proteins Gli2, Sufu, and Kif7 localized correctly to cilia tips, suggesting that these pathway components were trafficked by IFT-B. In contrast, the membrane proteins Arl13b, ACIII, and Smo failed to localize to primary cilia in the absence of IFT-A. We propose that the increased Shh activity seen in partial loss-of-function IFT-A mutants may be a result of decreased ciliary ACIII and that the loss of Shh activity in the absence of IFT-A is a result of severe disruptions of cilia structure and membrane protein trafficking.

  12. [Effects of biological regulated measures on active organic carbon and erosion-resistance in the Three Gorges Reservoir region soil].

    Science.gov (United States)

    Huang, Ru; Huang, Lin; He, Bing-Hui; Zhou, Li-Jiang; Yu, Chuan; Wang, Feng

    2013-07-01

    To gain a better knowledge of characteristics of soils and provide a scientific basis for soil erosion control in the Three Gorges Reservoir Area, contents of aggregates and total soil organic carbon (SOC), as well as soil active organic carbon fractions including particulate organic carbon (POC), readily oxidized organic carbon (ROC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) in the 0-30 cm soil layer under seven different biological regulated measures were studied by the field investigation combined with the laboratory analysis. Results showed that the content of the SOC and active organic carbon fractions decreased with the increasing soil depth; the content of the SOC and active organic carbon fractions in 0-10 cm was significantly higher than that in 20-30 cm. The stability of soil aggregates were also significantly influenced by biological regulated measures, the content of > 0.25 mm water-stable aggregates in seven types of biological regulated measures was in the order of Koelreuteria bipinnata + Cassia suffruticasa > hedgerows > closed forest > natural restoration > economic forest > traditional planting > control plot, moreover, the content of 0.25 mm water-stable aggregates correlated positively with the content of SOC. Soils under different biological regulated measures all demonstrated fractal features, and soil under the measure of Koelreuteria bipinnata + Cassia suffruticasa was found to have the lowest value of fractal dimension and soil erodiable K, indicating a relatively strong structure stability and erosion-resistant capacity. Negative correlation was observed when compared the content of active organic carbon fractions with the soil erodiable K. It can be concluded that properties of soil can be managed through biological regulated measures; thence had an influence on the soil erosion-resistant capacity.

  13. A comparative study of the safety and efficacy effect of 5-fluorouracil or mitomycin C mounted biological delivery membranes in a rabbit model of glaucoma filtration surgery

    Directory of Open Access Journals (Sweden)

    Wu ZH

    2013-03-01

    Full Text Available Zhihong Wu,1 Shuning Li,2 Ningli Wang,2 Wanshun Liu,3 Wen Liu3 1General Hospital of Armed Police Forces, Beijing, People’s Republic of China; 2Beijing Tongren Eye Center, Capital Medical University, Beijing, People’s Republic of China 3Ocean University of China, Qingdao, People’s Republic of China Purpose: To investigate the potential usage of biological delivery membranes containing mitomycin C (MMC or 5-fluorouracil (5-FU in the construction of glaucoma-filtering blebs, and to evaluate their safety and efficacy. Methods: Chitosan was selected as the biological membrane carrier to prepare sustained-released membranes. Twelve micrograms of 5-FU or MMC was covalently conjugated onto the membranes by solvent volatilization. Rabbits underwent glaucoma filtration surgery and were randomly allocated into one of the four treatment regimens: glaucoma filtration operation with no implantation of chitosan membrane group (as control, drug-free chitosan membrane implantation group (blank/placebo group, membrane containing 5-FU treatment group (5-FU group, and membrane containing MMC treatment group (MMC group. Each group consisted of 12 rabbits. Intraocular pressure (IOP was measured and evaluated over a 28-day period follow-up preoperatively, then after surgery on days 1, 3, 5, 7, 14, 21, and 28 by Tono-Pen. The aqueous humor was analyzed in each experimental and control groups at days 4, 6, 8, 10, 12, 14, 16, and 20 after operation. Bleb survival and anterior segment were examined with a slit lamp microscope and photographed simultaneously. Two rabbits from each group were killed on day 28 and eight eye samples obtained for histopathological study. Corneas and lenses were examined by transmission and scanning electron microscopy. Results: Both 5-FU and MMC significantly prolonged bleb survival compared with control groups. The filtering bleb’s survival period was significantly more prolonged in the MMC and 5-FU groups (maintained 14 days than the

  14. Decidual-secreted factors alter invasive trophoblast membrane and secreted proteins implying a role for decidual cell regulation of placentation.

    Directory of Open Access Journals (Sweden)

    Ellen Melaleuca Menkhorst

    Full Text Available Inadequate or inappropriate implantation and placentation during the establishment of human pregnancy is thought to lead to first trimester miscarriage, placental insufficiency and other obstetric complications. To create the placental blood supply, specialized cells, the 'extravillous trophoblast' (EVT invade through the differentiated uterine endometrium (the decidua to engraft and remodel uterine spiral arteries. We hypothesized that decidual factors would regulate EVT function by altering the production of EVT membrane and secreted factors. We used a proteomics approach to identify EVT membrane and secreted proteins regulated by decidual cell factors. Human endometrial stromal cells were decidualized in vitro by treatment with estradiol (10(-8 M, medroxyprogesterone acetate (10(-7 M and cAMP (0.5 mM for 14 days. Conditioned media (CM was collected on day 2 (non-decidualized CM and 14 (decidualized CM of treatment. Isolated primary EVT cultured on Matrigel™ were treated with media control, non-decidualized or decidualized CM for 16 h. EVT CM was fractionated for proteins <30 kDa using size-exclusion affinity nanoparticles (SEAN before trypsin digestion and HPLC-MS/MS. 43 proteins produced by EVT were identified; 14 not previously known to be expressed in the placenta and 12 which had previously been associated with diseases of pregnancy including preeclampsia. Profilin 1, lysosome associated membrane glycoprotein 1 (LAMP1, dipeptidyl peptidase 1 (DPP1/cathepsin C and annexin A2 expression by interstitial EVT in vivo was validated by immunhistochemistry. Decidual CM regulation in vitro was validated by western blotting: decidualized CM upregulated profilin 1 in EVT CM and non-decidualized CM upregulated annexin A2 in EVT CM and pro-DPP1 in EVT cell lysate. Here, non-decidualized factors induced protease expression by EVT suggesting that non-decidualized factors may induce a pro-inflammatory cascade. Preeclampsia is a pro

  15. Low intensity ultrasound induces apoptosis via MPT channel on mitochondrial membrane: Target for regulating cancer therapy or not?

    Science.gov (United States)

    Feng, Yi; Wan, Mingxi

    2017-03-01

    To discuss how the mitochondrion is involved in low intensity ultrasound induced apoptosis, HepG2 cells were irradiated by low intensity focused ultrasound (ISPTA = 3W/cm2, 1 min) and then cultured from 3-12 h post irradiation in the study. The morphological alteration was examined by light and fluorescent microscopy respectively. Cell viability and apoptosis were examined by trypan blue staining and flow cytometry with double staining of FITC-labelled Annexin-V/PI. Key proteins responded to irradiation were screened out by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and shotgun proteomic methods with Agilent 1100 HPLC-Chip-MS technology. Representative apoptotic morphological characteristics and increased percentage of apoptotic cells were achieved. Six important proteins (4 up-regulated and 2 down-regulated) were selected and analyzed. It revealed low intensity focused ultrasound could induce apoptosis in HepG2 cells and the US-induced apoptosis was mitochondria-dependent and caspases-dependent. Moreover, mitochondrial membrane permeability transition (MPT) is related to ultrasound induced apoptosis, but VDAC may be not the main MPT channel. Understanding it could help to assist the cancer therapy by regulating the MPT as the target.

  16. Transport proteins regulate the flux of metabolites and cofactors across the membrane of plants peroxisomes

    Directory of Open Access Journals (Sweden)

    Nicole eLinka

    2012-01-01

    Full Text Available In land plants, peroxisomes play key roles in various metabolic pathways, including the most prominent examples lipid mobilization and photorespiration. Given the large number of substrates that are exchanged across the peroxisomal membrane, a wide spectrum of metabolite and cofactor transporters is required and need to be efficiently coordinated. These peroxisomal transport proteins are a perquisite for metabolic reactions inside plant peroxisomes and the entire peroxisomal permeome is closely linked to the adaption of photosynthetic organisms during land plant evolution to fulfill and optimize their new metabolic demands in cells, tissues, and organs. This review assesses for the first time the distribution of these peroxisomal transporters within the algal and plant species underlining their evolutionary relevance. Despite the importance of peroxisomal transporters, the majority of these proteins, however, are still unknown at the molecular level in plants as well as in other eukaryotic organisms. Up to date, four transport proteins have been recently identified and functionally characterized in Arabidopsis so far: One transporter for the import of fatty acids and three carrier proteins for the uptake of the cofactors ATP and NAD into plant peroxisomes. The transport of the three substrates across the peroxisomal membrane is essential for the degradation of fatty acids and fatty acids-related compounds via β-oxidation. This metabolic pathway plays multiple functions for growth and development in plants that has been crucial for during land plant evolution. Here, we describe the current state of their physiological roles in Arabidopsis and discuss novel features in their putative transport mechanisms.

  17. Dynamic membrane depolarization is an early regulator of ependymoglial cell response to spinal cord injury in axolotl.

    Science.gov (United States)

    Sabin, Keith; Santos-Ferreira, Tiago; Essig, Jaclyn; Rudasill, Sarah; Echeverri, Karen

    2015-12-01

    Salamanders, such as the Mexican axolotl, are some of the few vertebrates fortunate in their ability to regenerate diverse structures after injury. Unlike mammals they are able to regenerate a fully functional spinal cord after injury. However, the molecular circuitry required to initiate a pro-regenerative response after spinal cord injury is not well understood. To address this question we developed a spinal cord injury model in axolotls and used in vivo imaging of labeled ependymoglial cells to characterize the response of these cells to injury. Using in vivo imaging of ion sensitive dyes we identified that spinal cord injury induces a rapid and dynamic change in the resting membrane potential of ependymoglial cells. Prolonged depolarization of ependymoglial cells after injury inhibits ependymoglial cell proliferation and subsequent axon regeneration. Using transcriptional profiling we identified c-Fos as a key voltage sensitive early response gene that is expressed specifically in the ependymoglial cells after injury. This data establishes that dynamic changes in the membrane potential after injury are essential for regulating the specific spatiotemporal expression of c-Fos that is critical for promoting faithful spinal cord regeneration in axolotl.

  18. Global transcriptional regulation by H-NS and its biological influence on the virulence of Enterohemorrhagic Escherichia coli.

    Science.gov (United States)

    Wan, Baoshan; Zhang, Qiufen; Tao, Jing; Zhou, Aiping; Yao, Yu-Feng; Ni, Jinjing

    2016-08-22

    As a global transcriptional regulator, H-NS, the histone-like nucleoid-associated DNA-binding and bridging protein, plays a wide range of biological roles in bacteria. In order to determine the role of H-NS in regulating gene transcription and further find out the biological significance of this protein in Enterohemorrhagic Escherichia coli (EHEC), we conducted transcriptome analysis of hns mutant by RNA sequencing. A total of 983 genes were identified to be regulated by H-NS in EHEC. 213 and 770 genes were down-regulated and up-regulated in the deletion mutant of hns, respectively. Interestingly, 34 of 97 genes on virulence plasmid pO157 were down-regulated by H-NS. Although the deletion mutant of hns showed a decreased survival rate in macrophage compared with the wild type strain, it exhibited the higher ability to colonize mice gut and became more virulent to BALB/c mice. The BALB/c mice infected with the deletion mutant of hns showed a lower survival rate, and a higher bacterial burden in the gut, compared with those infected with wild type strain, especially when the gut microbiota was not disturbed by antibiotic administration. These findings suggest that H-NS plays an important role in virulence of EHEC by interacting with host gut microbiota.

  19. Application of the principles of systems biology and Wiener's cybernetics for analysis of regulation of energy fluxes in muscle cells in vivo.

    Science.gov (United States)

    Guzun, Rita; Saks, Valdur

    2010-03-08

    The mechanisms of regulation of respiration and energy fluxes in the cells are analyzed based on the concepts of systems biology, non-equilibrium steady state kinetics and applications of Wiener's cybernetic principles of feedback regulation. Under physiological conditions cardiac function is governed by the Frank-Starling law and the main metabolic characteristic of cardiac muscle cells is metabolic homeostasis, when both workload and respiration rate can be changed manifold at constant intracellular level of phosphocreatine and ATP in the cells. This is not observed in skeletal muscles. Controversies in theoretical explanations of these observations are analyzed. Experimental studies of permeabilized fibers from human skeletal muscle vastus lateralis and adult rat cardiomyocytes showed that the respiration rate is always an apparent hyperbolic but not a sigmoid function of ADP concentration. It is our conclusion that realistic explanations of regulation of energy fluxes in muscle cells require systemic approaches including application of the feedback theory of Wiener's cybernetics in combination with detailed experimental research. Such an analysis reveals the importance of limited permeability of mitochondrial outer membrane for ADP due to interactions of mitochondria with cytoskeleton resulting in quasi-linear dependence of respiration rate on amplitude of cyclic changes in cytoplasmic ADP concentrations. The system of compartmentalized creatine kinase (CK) isoenzymes functionally coupled to ANT and ATPases, and mitochondrial-cytoskeletal interactions separate energy fluxes (mass and energy transfer) from signalling (information transfer) within dissipative metabolic structures - intracellular energetic units (ICEU). Due to the non-equilibrium state of CK reactions, intracellular ATP utilization and mitochondrial ATP regeneration are interconnected by the PCr flux from mitochondria. The feedback regulation of respiration occurring via cyclic fluctuations of

  20. Effects of Lycium barbarum. polysaccharide on type 2 diabetes mellitus rats by regulating biological rhythms

    Science.gov (United States)

    Zhao, Rui; Gao, Xu; Zhang, Tao; Li, Xing

    2016-01-01

    Objective(s): Type 2 diabetes mellitus (T2DM) is associated with circadian disruption. Our previous experimental results have showed that dietary Lycium barbarum. polysaccharide (LBP-4a) exhibited hypoglycemic and improving insulin resistance (IR) activities. This study was to explore the mechanisms of LBP-4a for improving hyperglycemia and IR by regulating biological rhythms in T2DM rats. Materials and Methods: The rats of T2DM were prepared by the high-sucrose-fat diets and injection of streptozotocin (STZ). The levels of insulin, leptin and melatonin were measured by enzyme linked immunosorbent assay (ELISA). The effect of LBP-4a on mRNA expression of melatonin receptors (MT2) in epididymal adipose tissue was evaluated by RT-PCR. The expression of CLOCK and BMAL1 in pancreatic islet cells was detected by Western blotting. Results: Our data indicated that the 24-hr rhythm of blood glucose appeared to have consistent with normal rats after gavaged administration of LBP-4a for each day of the 4 weeks, and the effects of hypoglycemia and improving hyperinsulinemia in T2DM rats treated at high dose were much better than that at low dose. The mechanisms were related to increasing MT2 level in epididymal adipose tissue and affecting circadian clocks gene expression of CLOCK and BMAL1 in pancreatic islet cells. Conclusion: LBP-4a administration could treat T2DM rats. These observations provided the background for the further development of LBP-4a as a potential dietary therapeutic agent in the treatment of T2DM. PMID:27803791

  1. Investigating Flipped Learning: Student Self-Regulated Learning, Perceptions, and Achievement in an Introductory Biology Course

    Science.gov (United States)

    Sletten, Sarah Rae

    2017-01-01

    In flipped classrooms, lectures, which are normally delivered in-class, are assigned as homework in the form of videos, and assignments that were traditionally assigned as homework, are done as learning activities in class. It was hypothesized that the effectiveness of the flipped model hinges on a student's desire and ability to adopt a self-directed learning style. The purpose of this study was twofold; it aimed at examining the relationship between two variables—students' perceptions of the flipped model and their self-regulated learning (SRL) behaviors—and the impact that these variables have on achievement in a flipped class. For the study, 76 participants from a flipped introductory biology course were asked about their SRL strategy use and perceptions of the flipped model. SRL strategy use was measured using a modified version of the Motivated Strategies for Learning Questionnaire (MSLQ; Wolters et al. 2005), while the flipped perceptions survey was newly derived. Student letter grades were collected as a measure of achievement. Through regression analysis, it was found that students' perceptions of the flipped model positively predict students' use of several types of SRL strategies. However, the data did not indicate a relationship between student perceptions and achievement, neither directly nor indirectly, through SRL strategy use. Results suggest that flipped classrooms demonstrate their successes in the active learning sessions through constructivist teaching methods. Video lectures hold an important role in flipped classes, however, students may need to practice SRL skills to become more self-directed and effectively learn from them.

  2. Reciprocal Regulation of Pyoluteorin Production with Membrane Transporter Gene Expression in Pseudomonas fluorescens Pf-5

    OpenAIRE

    2005-01-01

    Pyoluteorin is a chlorinated polyketide antibiotic secreted by the rhizosphere bacterium Pseudomonas fluorescens Pf-5. Genes encoding enzymes and transcriptional regulators involved in pyoluteorin production are clustered in the genome of Pf-5. Sequence analysis of genes adjacent to the known pyoluteorin biosynthetic gene cluster revealed the presence of an ABC transporter system. We disrupted two putative ABC transporter genes by inserting transcriptional fusions to an ice nucleation reporte...

  3. A membrane fusion protein αSNAP is a novel regulator of epithelial apical junctions.

    Directory of Open Access Journals (Sweden)

    Nayden G Naydenov

    Full Text Available Tight junctions (TJs and adherens junctions (AJs are key determinants of the structure and permeability of epithelial barriers. Although exocytic delivery to the cell surface is crucial for junctional assembly, little is known about the mechanisms controlling TJ and AJ exocytosis. This study was aimed at investigating whether a key mediator of exocytosis, soluble N-ethylmaleimide sensitive factor (NSF attachment protein alpha (αSNAP, regulates epithelial junctions. αSNAP was enriched at apical junctions in SK-CO15 and T84 colonic epithelial cells and in normal human intestinal mucosa. siRNA-mediated knockdown of αSNAP inhibited AJ/TJ assembly and establishment of the paracellular barrier in SK-CO15 cells, which was accompanied by a significant down-regulation of p120-catenin and E-cadherin expression. A selective depletion of p120 catenin effectively disrupted AJ and TJ structure and compromised the epithelial barrier. However, overexpression of p120 catenin did not rescue the defects of junctional structure and permeability caused by αSNAP knockdown thereby suggesting the involvement of additional mechanisms. Such mechanisms did not depend on NSF functions or induction of cell death, but were associated with disruption of the Golgi complex and down-regulation of a Golgi-associated guanidine nucleotide exchange factor, GBF1. These findings suggest novel roles for αSNAP in promoting the formation of epithelial AJs and TJs by controlling Golgi-dependent expression and trafficking of junctional proteins.

  4. The plant plasma membrane H+-ATPase

    DEFF Research Database (Denmark)

    Ekberg, Kira

      The very high mobility of protons in aqueous solutions demands special features of membrane proton transporters to sustain efficient yet regulated proton transport across biological membranes. By the use of the chemical energy of ATP, plasma-membrane-embedded H+-ATPases extrude protons from cells...... of plants and fungi to generate electrochemical proton gradients. A recently published crystal structure of a plasma membrane H(+)-ATPase contributes to our knowledge about the mechanism of these essential enzymes. Together with biochemical and structural data presented in this thesis we are now able...... to describe the basic molecular components that allow the plasma membrane proton H+-ATPase to carry out proton transport against large membrane potentials. Moreover, a completely new paradigm for post-translational activation of these proteins is presented. The talk will focus on the following themes...

  5. Bioelectrochemistry II membrane phenomena

    CERN Document Server

    Blank, M

    1987-01-01

    This book contains the lectures of the second course devoted to bioelectro­ chemistry, held within the framework of the International School of Biophysics. In this course another very large field of bioelectrochemistry, i. e. the field of Membrane Phenomena, was considered, which itself consists of several different, but yet related subfields. Here again, it can be easily stated that it is impossible to give a complete and detailed picture of all membrane phenomena of biological interest in a short course of about one and half week. Therefore the same philosophy, as the one of the first course, was followed, to select a series of lectures at postgraduate level, giving a synthesis of several membrane phenomena chosen among the most'important ones. These lectures should show the large variety of membrane-regulated events occurring in living bodies, and serve as sound interdisciplinary basis to start a special­ ized study of biological phenomena, for which the investigation using the dual approach, physico-che...

  6. ADP-ribosylation of dinitrogenase reductase in Azospirillum brasilense is regulated by AmtB-dependent membrane sequestration of DraG.

    Science.gov (United States)

    Huergo, Luciano F; Souza, Emanuel M; Araujo, Mariana S; Pedrosa, Fábio O; Chubatsu, Leda S; Steffens, Maria B R; Merrick, Mike

    2006-01-01

    Nitrogen fixation in some diazotrophic bacteria is regulated by mono-ADP-ribosylation of dinitrogenase reductase (NifH) that occurs in response to addition of ammonium to the extracellular medium. This process is mediated by dinitrogenase reductase ADP-ribosyltransferase (DraT) and reversed by dinitrogenase reductase glycohydrolase (DraG), but the means by which the activities of these enzymes are regulated are unknown. We have investigated the role of the P(II) proteins (GlnB and GlnZ), the ammonia channel protein AmtB and the cellular localization of DraG in the regulation of the NifH-modification process in Azospirillum brasilense. GlnB, GlnZ and DraG were all membrane-associated after an ammonium shock, and both this membrane sequestration and ADP-ribosylation of NifH were defective in an amtB mutant. We now propose a model in which membrane association of DraG after an ammonium shock creates a physical separation from its cytoplasmic substrate NifH thereby inhibiting ADP-ribosyl-removal. Our observations identify a novel role for an ammonia channel (Amt) protein in the regulation of bacterial nitrogen metabolism by mediating membrane sequestration of a protein other than a P(II) family member. They also suggest a model for control of ADP-ribosylation that is likely to be applicable to all diazotrophs that exhibit such post-translational regulation of nitrogenase.

  7. RIN4 functions with plasma membrane H+-ATPases to regulate stomatal apertures during pathogen attack

    DEFF Research Database (Denmark)

    Liu, Jun; Elmore, James M.; Fuglsang, Anja Thoe;

    2009-01-01

    exhibit differential PM H+-ATPase activity. PM H+-ATPase activation induces stomatal opening, enabling bacteria to gain entry into the plant leaf; inactivation induces stomatal closure thus restricting bacterial invasion. The rin4 knockout line exhibited reduced PM H+-ATPase activity and, importantly, its...... stomata could not be re-opened by virulent Pseudomonas syringae. We also demonstrate that RIN4 is expressed in guard cells, highlighting the importance of this cell type in innate immunity. These results indicate that the Arabidopsis protein RIN4 functions with the PM H+-ATPase to regulate stomatal...

  8. High-throughput analysis of drugs in biological fluids by desorption electrospray ionization mass spectrometry coupled with thin liquid membrane extraction

    DEFF Research Database (Denmark)

    Rosting, Cecilie; Pedersen-Bjergaard, Stig; Hansen, Steen Honore'

    2013-01-01

    -30%. A reliability test was performed on 20 samples with methadone, amitriptyline, nortriptyline and pethidine in urine, showing that none of the samples having concentrations above the LOD were missed and no false positives were found. Diphenhydramine and one of its metabolites were detected in authentic samples...... of urine and saliva, and methadone was detected from a whole-blood sample spiked to a concentration of 100 ng mL(-1). The method has several advantages, such as extremely low price in consumables, the possibility of fast analysis of very crude biofluids such as whole blood and the potential for a very high......Biological fluids such as urine, saliva and whole blood were analyzed for contents of drugs by a new combination of desorption electrospray ionization mass spectrometry (DESI-MS) and thin liquid membrane extraction (TLME). Analytes from the sample were extracted into a thin liquid membrane...

  9. Comparison of regulated passive membrane conductance in action potential-firing fast- and slow-twitch muscle.

    Science.gov (United States)

    Pedersen, Thomas Holm; Macdonald, William Alexander; de Paoli, Frank Vincenzo; de Paoli, Frank Vinzenco; Gurung, Iman Singh; Nielsen, Ole Baekgaard

    2009-10-01

    In several pathological and experimental conditions, the passive membrane conductance of muscle fibers (G(m)) and their excitability are inversely related. Despite this capacity of G(m) to determine muscle excitability, its regulation in active muscle fibers is largely unexplored. In this issue, our previous study (Pedersen et al. 2009. J. Gen. Physiol. doi:10.1085/jgp.200910291) established a technique with which biphasic regulation of G(m) in action potential (AP)-firing fast-twitch fibers of rat extensor digitorum longus muscles was identified and characterized with temporal resolution of seconds. This showed that AP firing initially reduced G(m) via ClC-1 channel inhibition but after approximately 1,800 APs, G(m) rose substantially, causing AP excitation failure. This late increase of G(m) reflected activation of ClC-1 and K(ATP) channels. The present study has explored regulation of G(m) in AP-firing slow-twitch fibers of soleus muscle and compared it to G(m) dynamics in fast-twitch fibers. It further explored aspects of the cellular signaling that conveyed regulation of G(m) in AP-firing fibers. Thus, in both fiber types, AP firing first triggered protein kinase C (PKC)-dependent ClC-1 channel inhibition that reduced G(m) by approximately 50%. Experiments with dantrolene showed that AP-triggered SR Ca(2+) release activated this PKC-mediated ClC-1 channel inhibition that was associated with reduced rheobase current and improved function of depolarized muscles, indicating that the reduced G(m) enhanced muscle fiber excitability. In fast-twitch fibers, the late rise in G(m) was accelerated by glucose-free conditions, whereas it was postponed when intermittent resting periods were introduced during AP firing. Remarkably, elevation of G(m) was never encountered in AP-firing slow-twitch fibers, even after 15,000 APs. These observations implicate metabolic depression in the elevation of G(m) in AP-firing fast-twitch fibers. It is concluded that regulation of G(m) is

  10. Bax and Bak function as the outer membrane component of the mitochondrial permeability pore in regulating necrotic cell death in mice.

    Science.gov (United States)

    Karch, Jason; Kwong, Jennifer Q; Burr, Adam R; Sargent, Michelle A; Elrod, John W; Peixoto, Pablo M; Martinez-Caballero, Sonia; Osinska, Hanna; Cheng, Emily H-Y; Robbins, Jeffrey; Kinnally, Kathleen W; Molkentin, Jeffery D

    2013-08-27

    A critical event in ischemia-based cell death is the opening of the mitochondrial permeability transition pore (MPTP). However, the molecular identity of the components of the MPTP remains unknown. Here, we determined that the Bcl-2 family members Bax and Bak, which are central regulators of apoptotic cell death, are also required for mitochondrial pore-dependent necrotic cell death by facilitating outer membrane permeability of the MPTP. Loss of Bax/Bak reduced outer mitochondrial membrane permeability and conductance without altering inner membrane MPTP function, resulting in resistance to mitochondrial calcium overload and necrotic cell death. Reconstitution with mutants of Bax that cannot oligomerize and form apoptotic pores, but still enhance outer membrane permeability, permitted MPTP-dependent mitochondrial swelling and restored necrotic cell death. Our data predict that the MPTP is an inner membrane regulated process, although in the absence of Bax/Bak the outer membrane resists swelling and prevents organelle rupture to prevent cell death. DOI:http://dx.doi.org/10.7554/eLife.00772.001.

  11. Ribosomal protein S6 kinase1 coordinates with TOR-Raptor2 to regulate thylakoid membrane biosynthesis in rice.

    Science.gov (United States)

    Sun, Linxiao; Yu, Yonghua; Hu, Weiqin; Min, Qiming; Kang, Huiling; Li, Yilu; Hong, Yue; Wang, Xuemin; Hong, Yueyun

    2016-07-01

    Ribosomal protein S6 kinase (S6K) functions as a key component in the target of rapamycin (TOR) pathway involved in multiple processes in eukaryotes. The role and regulation of TOR-S6K in lipid metabolism remained unknown in plants. Here we provide genetic and pharmacological evidence that TOR-Raptor2-S6K1 is important for thylakoid galactolipid biosynthesis and thylakoid grana modeling in rice (Oryza sativa L.). Genetic suppression of S6K1 caused pale yellow-green leaves, defective thylakoid grana architecture. S6K1 directly interacts with Raptor2, a core component in TOR signaling, and S6K1 activity is regulated by Raptor2 and TOR. Plants with suppressed Raptor2 expression or reduced TOR activity by inhibitors mimicked the S6K1-deficient phenotype. A significant reduction in galactolipid content was found in the s6k1, raptor2 mutant or TOR-inhibited plants, which was accompanied by decreased transcript levels of the set of genes such as lipid phosphate phosphatase α5 (LPPα5), MGDG synthase 1 (MGD1), and DGDG synthase 1 (DGD1) involved in galactolipid synthesis, compared to the control plants. Moreover, loss of LPPα5 exhibited a similar phenotype with pale yellow-green leaves. These results suggest that TOR-Raptor2-S6K1 is important for modulating thylakoid membrane lipid biosynthesis, homeostasis, thus enhancing thylakoid grana architecture and normal photosynthesis ability in rice.

  12. Photoperiodic regulation of melatonin membrane receptor (MT1R) expression and steroidogenesis in testis of adult golden hamster, Mesocricetus auratus.

    Science.gov (United States)

    Mukherjee, Arun; Haldar, Chandana

    2014-11-01

    Photoperiodic modulation of melatonin membrane receptor (MT1R) expression in testis has never been reported for any seasonal breeder. Thus, the aim of the present study was to investigate the expression dynamics of MT1R in testis and its interaction with testicular steroidogenesis in a long-day breeder, Mesocricetus auratus. Hamsters were exposed to different photoperiodic conditions i.e. critical- (CP; 12.5L:11.5D); short-day- (SD; 8L:16D) and long-day- (LD; 16L:8D) for 10 weeks wherein testicular steroidogenesis, local melatonin synthesis and the expression of MT1R were analyzed. SD induced melatonin suppressed testicular steroidogenesis as evident from regressed testicular histoarchitecture, decreased expression of AR, StAR, LH-R, P₄₅₀SCC and enzyme activities of 3β- and 17β-HSD. Differential photoperiodic regulation of MT1R expression in testis suggests its involvement in photoperiodic signal transduction for seasonal adjustment of reproduction. Increased S-NAT (Serotonin N-acetyl transferase) activity and local testicular melatonin under SD condition suggest an inhibitory effect of the local melatonergic system on testicular steroidogenesis. Completely opposite responses were recorded for all the parameters analyzed when hamsters were exposed to CP or LD conditions. In conclusion, we may suggest that photoperiod via regulating circulatory and local melatonin level as well as MT1R expression in testes fine tunes the steroidogenesis and thereby, the reproductive status of male golden hamster.

  13. Transcriptional regulation of cytosol and membrane alanyl-aminopeptidase in human T cell subsets.

    Science.gov (United States)

    Bukowska, Alicja; Tadje, Janine; Arndt, Marco; Wolke, Carmen; Kähne, Thilo; Bartsch, Jaqueline; Faust, Jürgen; Neubert, Klaus; Hashimoto, Yuichi; Lendeckel, Uwe

    2003-04-01

    Aminopeptidase inhibitors strongly affect the proliferation and function of immune cells in man and animals and are promising agents for the pharmacological treatment of inflammatory or autoimmune diseases. Membrane alanyl-aminopeptidase (mAAP) has been considered as the major target of these anti-inflammatory aminopeptidase inhibitors. Recent evidence also points to a role of the cytosol alanyl-aminopeptidase (cAAP) in the immune response. In this study we used quantitative RT-PCR to determine the mRNA expression of both cAAP and mAAP in resting and activated peripheral T cells and also in CD4+, CD8+, Th1, Th2 and Treg (CD4+ CD25+) subpopulations. Both mAAP and cAAP mRNAs were expressed in all cell types investigated, and in response to activation their expression appeared to be upregulated in CD8+ cells, but downregulated in Treg cells. In CD4+ cells, mAAP and cAAP mRNAs were affected in opposite ways in response to activation. The cAAP-specific inhibitor, PAQ-22, did not affect either cAAP or mAAP expression in activated CD4+ or CD8+ cells, whereas in activated Treg cells it markedly upregulated the mRNA levels of both aminopeptidases. The non-discriminatory inhibitor, phebestin, significantly increased the amount of mAAP and cAAP mRNA in CD4+ and that of cAAP in Treg cells.

  14. The solution structure of ChaB, a putative membrane ion antiporter regulator from Escherichia coli

    Directory of Open Access Journals (Sweden)

    Iannuzzi Pietro

    2004-08-01

    Full Text Available Abstract Background ChaB is a putative regulator of ChaA, a Na+/H+ antiporter that also has Ca+/H+ activity in E. coli. ChaB contains a conserved 60-residue region of unknown function found in other bacteria, archaeabacteria and a series of baculoviral proteins. As part of a structural genomics project, the structure of ChaB was elucidated by NMR spectroscopy. Results The structure of ChaB is composed of 3 α-helices and a small sheet that pack tightly to form a fold that is found in the cyclin-box family of proteins. Conclusion ChaB is distinguished from its putative DNA binding sequence homologues by a highly charged flexible loop region that has weak affinity to Mg2+ and Ca2+ divalent metal ions.

  15. The machinery at endoplasmic reticulum-plasma membrane contact sites contributes to spatial regulation of multiple Legionella effector proteins.

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    Andree Hubber

    2014-07-01

    Full Text Available The Dot/Icm system of the intracellular pathogen Legionella pneumophila has the capacity to deliver over 270 effector proteins into host cells during infection. Important questions remain as to spatial and temporal mechanisms used to regulate such a large array of virulence determinants after they have been delivered into host cells. Here we investigated several L. pneumophila effector proteins that contain a conserved phosphatidylinositol-4-phosphate (PI4P-binding domain first described in the effector DrrA (SidM. This PI4P binding domain was essential for the localization of effectors to the early L. pneumophila-containing vacuole (LCV, and DrrA-mediated recruitment of Rab1 to the LCV required PI4P-binding activity. It was found that the host cell machinery that regulates sites of contact between the plasma membrane (PM and the endoplasmic reticulum (ER modulates PI4P dynamics on the LCV to control localization of these effectors. Specifically, phosphatidylinositol-4-kinase IIIα (PI4KIIIα was important for generating a PI4P signature that enabled L. pneumophila effectors to localize to the PM-derived vacuole, and the ER-associated phosphatase Sac1 was involved in metabolizing the PI4P on the vacuole to promote the dissociation of effectors. A defect in L. pneumophila replication in macrophages deficient in PI4KIIIα was observed, highlighting that a PM-derived PI4P signature is critical for biogenesis of a vacuole that supports intracellular multiplication of L. pneumophila. These data indicate that PI4P metabolism by enzymes controlling PM-ER contact sites regulate the association of L. pneumophila effectors to coordinate early stages of vacuole biogenesis.

  16. Activity-dependent regulation of the K/Cl transporter KCC2 membrane diffusion, clustering, and function in hippocampal neurons.

    Science.gov (United States)

    Chamma, Ingrid; Heubl, Martin; Chevy, Quentin; Renner, Marianne; Moutkine, Imane; Eugène, Emmanuel; Poncer, Jean Christophe; Lévi, Sabine

    2013-09-25

    The neuronal K/Cl transporter KCC2 exports chloride ions and thereby influences the efficacy and polarity of GABA signaling in the brain. KCC2 is also critical for dendritic spine morphogenesis and the maintenance of glutamatergic transmission in cortical neurons. Because KCC2 plays a pivotal role in the function of central synapses, it is of particular importance to understand the cellular and molecular mechanisms underlying its regulation. Here, we studied the impact of membrane diffusion and clustering on KCC2 function. KCC2 forms clusters in the vicinity of both excitatory and inhibitory synapses. Using quantum-dot-based single-particle tracking on rat primary hippocampal neurons, we show that KCC2 is slowed down and confined at excitatory and inhibitory synapses compared with extrasynaptic regions. However, KCC2 escapes inhibitory synapses faster than excitatory synapses, reflecting stronger molecular constraints at the latter. Interfering with KCC2-actin interactions or inhibiting F-actin polymerization releases diffusion constraints on KCC2 at excitatory but not inhibitory synapses. Thus, F-actin constrains KCC2 diffusion at excitatory synapses, whereas KCC2 is confined at inhibitory synapses by a distinct mechanism. Finally, increased neuronal activity rapidly increases the diffusion coefficient and decreases the dwell time of KCC2 at excitatory synapses. This effect involves NMDAR activation, Ca(2+) influx, KCC2 S940 dephosphorylation and calpain protease cleavage of KCC2 and is accompanied by reduced KCC2 clustering and ion transport function. Thus, activity-dependent regulation of KCC2 lateral diffusion and clustering allows for a rapid regulation of chloride homeostasis in neurons.

  17. CONSTRUCTION OF DIDACTIC MODEL OF MEMBRANE AND EXTRACELLULAR MATRIX TO FACILITATE THE TEACHING/LEARNING BY BIOLOGICAL SCIENCES STUDENTS AT UFRN

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    M. V.S. Medeiros et al

    2015-08-01

    Full Text Available This work was developed in the course of MOLECULAR DIVERSITY, required curricular component for the courses of Biological Sciences at UFRN. This course intends to encourage the study of the chemical structure and function of biomolecules using lectures and practical classes. Looking at the evaluations from previous semesters, it became evident that the subjects of the membrane and extracellular matrix were not being learned in a meaningful way. We also noticed lack of motivation from students due to difficulties in understanding molecules, weakening the teaching/learning process. Given this situation, our work aimed to encourage students to construct the constituent molecules of the membrane and extracellular matrix and assemble these structures, in order to understand molecular interactions, improve understanding of the subject and facilitate the learning process. This was accomplished through a monitoring project with the help of monitors. The proposed methodology consisted of separating the class into groups, where each would be responsible for making and exposing the other students to one of the molecules (Membrane Lipids, integrins, fibronectin, collagen, elastin, laminin, hyaluronic acid, and then discussing these molecules’ structural characteristics and interactions. The students could use various types of materials like cardboard, colored pens and polystyrene. The molecules were presented to the class, and the groups had set up the membrane and the matrix indicating the location of molecules and their possible interactions. All groups created their molecules according to given specifications. They created didactic and colorful molecules and positively interacted with all other groups during the assembly of the membrane and extracellular matrix; they also discussed molecules functions and interactions. We noticed during presentations and evaluation a strong performance in the subjects in question, as well as the construction of a

  18. Novel secreted isoform of adhesion molecule ICAM-4: Potential regulator of membrane-associated ICAM-4 interactions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gloria; Spring, Frances A.; Parons, Stephen F.; Mankelow, Tosti J.; Peters, Luanne L.; Koury, Mark J.; Mohandas, Narla; Anstee, David J.; Chasis, Joel Anne

    2003-02-18

    ICAM-4, a newly characterized adhesion molecule, is expressed early in human erythropoiesis and functions as a ligand for binding a4b1 and aV integrin-expressing cells. Within the bone marrow, erythroblasts surround central macrophages forming erythroblastic islands. Evidence suggests that these islands are highly specialized subcompartments where cell adhesion events, in concert with cytokines, play critical roles in regulating erythropoiesis and apoptosis. Since erythroblasts express a4b1 and ICAM-4 and macrophages exhibit aV, ICAM-4 is an attractive candidate for mediating cellular interactions within erythroblastic islands. To determine whether ICAM-4 binding properties are conserved across species, we first cloned and sequenced the murine homologue. The translated amino acid sequence showed 68 percent overall identity with human ICAM-4. Using recombinant murine ICAM-4 extracellular domains, we discovered that hematopoietic a4b1-expressing HEL cells and non-hematopoietic aV-expressing FLY cells adhered to mouse ICAM-4. Cell adhesion studies showed that FLY and HEL cells bound to mouse and human proteins with similar avidity. These data strongly suggest conservation of integrin-binding properties across species. Importantly, we characterized a novel second splice cDNA that would be predicted to encode an ICAM-4 isoform, lacking the membrane-spanning domain. Erythroblasts express both isoforms of ICAM-4. COS-7 cells transfected with GFP constructs of prototypic or novel ICAM-4 cDNA showed different cellular localization patterns. Moreover, analysis of tissue culture medium revealed that the novel ICAM-4 cDNA encodes a secreted protein. We postulate that secretion of this newly described isoform, ICAM-4S, may modulate binding of membrane-associated ICAM-4 and could thus play a critical regulatory role in erythroblast molecular attachments.

  19. Membrane-initiated actions of estradiol (E2 in the regulation of LH secretion in ovariectomized (OVX ewes

    Directory of Open Access Journals (Sweden)

    Oakley Amy E

    2010-05-01

    Full Text Available Abstract Background We demonstrated that E2 conjugated to BSA (E2BSA induces a rapid membrane-initiated inhibition of LH secretion followed hours later by a slight increase in LH secretion. Whether these actions of E2BSA are restricted to the pituitary gland and whether the membrane-initiated pathway of E2BSA contributes to the up-regulation of the number of GnRH receptors during the positive feedback effect of E2 were evaluated here. We have shown that the suppression of LH secretion induced by E2 and E2BSA is the result of a decreased responsiveness of the pituitary gland to GnRH. In this study we further tested the ability of E2BSA to decrease the responsiveness of the pituitary gland to GnRH under the paradigm of the preovulatory surge of LH induced by E2. Methods For the first experiment GnRH and LH secretions were determined in samples of pituitary portal and jugular blood, respectively, in ewes treated with 12 mg E2BSA. In the second experiment, the number of GnRH receptors was quantified in ewes 12 h after administration of 25 micrograms E2 (the expected time for the increase in the number of GnRH receptors and the positive feedback effect of E2 in LH secretion or 12 mg E2BSA. In the third experiment, the preovulatory-like surge of LH was characterized in ewes injected with 25 micrograms E2 alone or followed 8 h later (before the beginning of the LH surge with 60 mg E2BSA. Results a the decrease in LH secretion induced by E2BSA was not accompanied by changes in the pulsatile pattern of GnRH, b E2BSA increased the number of GnRH receptors, and c the presence of E2BSA in E2-treated ewes delayed the onset, reduced the length, and decreased the amount of LH released during the preovulatory surge of LH. Conclusions a the rapid suppression of LH secretion induced by E2BSA is mediated only via a direct action on the pituitary gland, b E2 acting via a membrane-initiated pathway contributes to increase the number of GnRH receptors and, c

  20. Leptospira interrogans endostatin-like outer membrane proteins bind host fibronectin, laminin and regulators of complement.

    Directory of Open Access Journals (Sweden)

    Brian Stevenson

    Full Text Available The pathogenic spirochete Leptospira interrogans disseminates throughout its hosts via the bloodstream, then invades and colonizes a variety of host tissues. Infectious leptospires are resistant to killing by their hosts' alternative pathway of complement-mediated killing, and interact with various host extracellular matrix (ECM components. The LenA outer surface protein (formerly called LfhA and Lsa24 was previously shown to bind the host ECM component laminin and the complement regulators factor H and factor H-related protein-1. We now demonstrate that infectious L. interrogans contain five additional paralogs of lenA, which we designated lenB, lenC, lenD, lenE and lenF. All six genes encode domains predicted to bear structural and functional similarities with mammalian endostatins. Sequence analyses of genes from seven infectious L. interrogans serovars indicated development of sequence diversity through recombination and intragenic duplication. LenB was found to bind human factor H, and all of the newly-described Len proteins bound laminin. In addition, LenB, LenC, LenD, LenE and LenF all exhibited affinities for fibronectin, a distinct host extracellular matrix protein. These characteristics suggest that Len proteins together facilitate invasion and colonization of host tissues, and protect against host immune responses during mammalian infection.

  1. An ER-resident membrane protein complex regulates nicotinic acetylcholine receptor subunit composition at the synapse

    Science.gov (United States)

    Almedom, Ruta B; Liewald, Jana F; Hernando, Guillermina; Schultheis, Christian; Rayes, Diego; Pan, Jie; Schedletzky, Thorsten; Hutter, Harald; Bouzat, Cecilia; Gottschalk, Alexander

    2009-01-01

    Nicotinic acetylcholine receptors (nAChRs) are homo- or heteropentameric ligand-gated ion channels mediating excitatory neurotransmission and muscle activation. Regulation of nAChR subunit assembly and transfer of correctly assembled pentamers to the cell surface is only partially understood. Here, we characterize an ER transmembrane (TM) protein complex that influences nAChR cell-surface expression and functional properties in Caenorhabditis elegans muscle. Loss of either type I TM protein, NRA-2 or NRA-4 (nicotinic receptor associated), affects two different types of muscle nAChRs and causes in vivo resistance to cholinergic agonists. Sensitivity to subtype-specific agonists of these nAChRs is altered differently, as demonstrated by whole-cell voltage-clamp of dissected adult muscle, when applying exogenous agonists or after photo-evoked, channelrhodopsin-2 (ChR2) mediated acetylcholine (ACh) release, as well as in single-channel recordings in cultured embryonic muscle. These data suggest that nAChRs desensitize faster in nra-2 mutants. Cell-surface expression of different subunits of the ‘levamisole-sensitive' nAChR (L-AChR) is differentially affected in the absence of NRA-2 or NRA-4, suggesting that they control nAChR subunit composition or allow only certain receptor assemblies to leave the ER. PMID:19609303

  2. Investigating how the attributes of self-associated drug complexes influence the passive transport of molecules through biological membranes.

    Science.gov (United States)

    Inacio, R; Barlow, D; Kong, X; Keeble, J; Jones, S A

    2016-05-01

    Relatively little is known about how drug self-association influences absorption into the human body. This study presented two hydrophobic membranes with a series of solutions containing different types of tetracaine aggregates with the aim of understanding how the attributes of supramolecular aggregate formation influenced passive membrane transport. The data showed that aqueous solutions of the unprotonated form of tetracaine displayed a significantly higher (ptransport compared to solutions with mixtures of the unprotonated and protonated drug microspecies (e.g. transport through the skin was 0.96±0.31μgcm(-2)min(-1) and 1.59±0.26μgcm(-2)min(-1) respectively). However, despite an enhanced rate of drug transport and a better membrane partitioning the unionised molecules showed a significantly longer (ptransport studies showed that larger tetracaine aggregates with smaller surface charge gave rise to the longer lag times. These large aggregates demonstrated more extensive intermolecular bonding and therefore, it was suggest that it was the enhanced propensity of the unionised species to form tightly bound drug aggregates that caused the delay in the membrane penetration.

  3. A chemical biology approach to interrogate quorum-sensing regulated behaviors at the molecular and cellular level.

    Science.gov (United States)

    Lowery, Colin A; Matamouros, Susana; Niessen, Sherry; Zhu, Jie; Scolnick, Jonathan; Lively, Jenny M; Cravatt, Benjamin F; Miller, Samuel I; Kaufmann, Gunnar F; Janda, Kim D

    2013-07-25

    Small molecule probes have been used extensively to explore biologic systems and elucidate cellular signaling pathways. In this study, we use an inhibitor of bacterial communication to monitor changes in the proteome of Salmonella enterica serovar Typhimurium with the aim of discovering unrecognized processes regulated by AI-2-based quorum-sensing (QS), a mechanism of bacterial intercellular communication that allows for the coordination of gene expression in a cell density-dependent manner. In S. typhimurium, this system regulates the uptake and catabolism of intercellular signals and has been implicated in pathogenesis, including the invasion of host epithelial cells. We demonstrate that our QS antagonist is capable of selectively inhibiting the expression of known QS-regulated proteins in S. typhimurium, thus attesting that QS inhibitors may be used to confirm proposed and elucidate previously unidentified QS pathways without relying on genetic manipulation.

  4. Cholesterol as a factor regulating the influence of natural (PAF and lysoPAF) vs synthetic (ED) ether lipids on model lipid membranes.

    Science.gov (United States)

    Flasiński, Michał; Wydro, Paweł; Hąc-Wydro, Katarzyna; Dynarowicz-Łątka, Patrycja

    2013-11-01

    In this work we have performed a comparative study on the effect of antineoplastic ether lipid-edelfosine (ED), its natural analogs - Platelet Activating Factor (PAF) and its precursor (lyso-PAF), both lacking anticancer properties, on cholesterol/phosphatidylcholine (Chol/PC) monolayers, serving as model membranes. Since all the above ether lipids are membrane active, it can be expected that their effect on membranes may differentiate their biological activity. Our investigations were aimed at studying potential relationship of the effect of ED, PAF and lyso-PAF on model membranes, differing in condensation. We have modified molecular packing of Chol/PC model systems either by increasing the level of sterol in the system or changing the structure of PC, while keeping the same sterol content. Additionally, we have performed a detailed comparison of the miscibility of ED, PAF and lyso-PAF with various membrane lipids. The collected data evidenced that all the investigated ether lipids influence Chol/PC films in the same way; however, in a different magnitude. Moreover, the interactions of ED, PAF and lyso-PAF with model membranes were the strongest at the highest level of sterol in the system. A thorough analysis of the obtained results has proved that the effect of the investigated ether lipids on membranes is not dependent on the condensation of the system, but it is strongly determined by the concentration of cholesterol. Since ED was found to interact with model membranes stronger than PAF and lyso-PAF, we have suggested that this fact may contribute to differences in cytotoxicity of these compounds.

  5. Regulation of Trafficking, Membrane Retention and Turnover of the Na+, HCO3- Co-Transporter NBCn1 in Epithelial Cells

    DEFF Research Database (Denmark)

    Olesen, Christina Wilkens

    and mechanisms of NBCn1 sorting, targeting, membrane retention, and degradation, providing a broader understanding of how NBCn1 is regulated in epithelial cells. These findings may guide future investigations into the regulation and roles of NBCn1 in normal and diseased epithelial tissues.......- transporters in cancer, and to increase the understanding of the regulation and roles of NBCn1 in normal and cancerous epithelial cells, (ii) by determining the mechanisms through which expression of p95HER2 and NCBn1 impacts on cisplatin chemotherapy-induced cell death and (iii) by elucidating the kinetics...... and mechanisms of NBCn1 trafficking, membrane retention and degradation in MCF-7 cells and other epithelial cell types. In Paper-I we review existing evidence regarding the possible roles of the SLC4 and SLC26 families of HCO3 - transporters in breast, colon and lung cancer. Bioinformatic analysis of publicly...

  6. Type IV Collagen Controls the Axogenesis of Cerebellar Granule Cells by Regulating Basement Membrane Integrity in Zebrafish.

    Science.gov (United States)

    Takeuchi, Miki; Yamaguchi, Shingo; Yonemura, Shigenobu; Kakiguchi, Kisa; Sato, Yoshikatsu; Higashiyama, Tetsuya; Shimizu, Takashi; Hibi, Masahiko

    2015-10-01

    Granule cells (GCs) are the major glutamatergic neurons in the cerebellum, and GC axon formation is an initial step in establishing functional cerebellar circuits. In the zebrafish cerebellum, GCs can be classified into rostromedial and caudolateral groups, according to the locations of their somata in the corresponding cerebellar lobes. The axons of the GCs in the caudolateral lobes terminate on crest cells in the dorsal hindbrain, as well as forming en passant synapses with Purkinje cells in the cerebellum. In the zebrafish mutant shiomaneki, the caudolateral GCs extend aberrant axons. Positional cloning revealed that the shiomaneki (sio) gene locus encodes Col4a6, a subunit of type IV collagen, which, in a complex with Col4a5, is a basement membrane (BM) component. Both col4a5 and col4a6 mutants displayed similar abnormalities in the axogenesis of GCs and retinal ganglion cells (RGCs). Although type IV collagen is reported to control axon targeting by regulating the concentration gradient of an axonal guidance molecule Slit, Slit overexpression did not affect the GC axons. The structure of the BM surrounding the tectum and dorsal hindbrain was disorganized in the col4a5 and col4a6 mutants. Moreover, the abnormal axogenesis of the caudolateral GCs and the RGCs was coupled with aberrant BM structures in the type IV collagen mutants. The regrowth of GC axons after experimental ablation revealed that the original and newly formed axons displayed similar branching and extension abnormalities in the col4a6 mutants. These results collectively suggest that type IV collagen controls GC axon formation by regulating the integrity of the BM, which provides axons with the correct path to their targets.

  7. Type IV Collagen Controls the Axogenesis of Cerebellar Granule Cells by Regulating Basement Membrane Integrity in Zebrafish.

    Directory of Open Access Journals (Sweden)

    Miki Takeuchi

    2015-10-01

    Full Text Available Granule cells (GCs are the major glutamatergic neurons in the cerebellum, and GC axon formation is an initial step in establishing functional cerebellar circuits. In the zebrafish cerebellum, GCs can be classified into rostromedial and caudolateral groups, according to the locations of their somata in the corresponding cerebellar lobes. The axons of the GCs in the caudolateral lobes terminate on crest cells in the dorsal hindbrain, as well as forming en passant synapses with Purkinje cells in the cerebellum. In the zebrafish mutant shiomaneki, the caudolateral GCs extend aberrant axons. Positional cloning revealed that the shiomaneki (sio gene locus encodes Col4a6, a subunit of type IV collagen, which, in a complex with Col4a5, is a basement membrane (BM component. Both col4a5 and col4a6 mutants displayed similar abnormalities in the axogenesis of GCs and retinal ganglion cells (RGCs. Although type IV collagen is reported to control axon targeting by regulating the concentration gradient of an axonal guidance molecule Slit, Slit overexpression did not affect the GC axons. The structure of the BM surrounding the tectum and dorsal hindbrain was disorganized in the col4a5 and col4a6 mutants. Moreover, the abnormal axogenesis of the caudolateral GCs and the RGCs was coupled with aberrant BM structures in the type IV collagen mutants. The regrowth of GC axons after experimental ablation revealed that the original and newly formed axons displayed similar branching and extension abnormalities in the col4a6 mutants. These results collectively suggest that type IV collagen controls GC axon formation by regulating the integrity of the BM, which provides axons with the correct path to their targets.

  8. Protein kinase C (PKC phosphorylates the system N glutamine transporter SN1 (slc38a3 and regulates its membrane trafficking and degradation

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    Lise Sofie H. Nissen-Meyer

    2013-10-01

    Full Text Available The system N transporter SN1 (also known as SNAT3 is enriched on perisynaptic astroglial cell membranes. SN1 mediates electroneutral and bidirectional glutamine transport, and regulates the intracellular as well as the extracellular concentrations of glutamine. We hypothesize that SN1 participates in the glutamate/GABA-glutamine cycle and regulates the amount of glutamine supplied to the nerve terminals for replenishment of the neurotransmitter pools of glutamate and GABA. We also hypothesize that its activity on the plasma membrane is regulated by PKC-mediated phosphorylation and that SN1 activity has an impact on synaptic plasticity. This review discusses inconcistencies reported in the regulation of SN1 by PKC and presents a consolidated model for regulation and degradation of SN1 and the subsequent functional implications. As SN1 function is likely also regulated by PKC-mediated phosphorylation in peripheral organs, the same mechanisms may, thus, have impact on e.g. pH regulation in the kidney, urea formation in the liver and insulin secretion in the pancreas.

  9. Assessing two-dimensional crystallization trials of small membrane proteins for structural biology studies by electron crystallography.

    Science.gov (United States)

    Johnson, Matthew C; Rudolph, Frederik; Dreaden, Tina M; Zhao, Gengxiang; Barry, Bridgette A; Schmidt-Krey, Ingeborg

    2010-10-29

    Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray crystallography to study structure-function questions of membrane proteins, as well as soluble proteins. Screening for two-dimensional (2D) crystals by transmission electron microscopy (EM) is the critical step in finding, optimizing, and selecting samples for high-resolution data collection by cryo-EM. Here we describe the fundamental steps in identifying both large and ordered, as well as small 2D arrays, that can potentially supply critical information for optimization of crystallization conditions. By working with different magnifications at the EM, data on a range of critical parameters is obtained. Lower magnification supplies valuable data on the morphology and membrane size. At higher magnifications, possible order and 2D crystal dimensions are determined. In this context, it is described how CCD cameras and online-Fourier Transforms are used at higher magnifications to assess proteoliposomes for order and size. While 2D crystals of membrane proteins are most commonly grown by reconstitution by dialysis, the screening technique is equally applicable for crystals produced with the help of monolayers, native 2D crystals, and ordered arrays of soluble proteins. In addition, the methods described here are applicable to the screening for 2D crystals of even smaller as well as larger membrane proteins, where smaller proteins require the same amount of care in identification as our examples and the lattice of larger proteins might be more easily identifiable at earlier stages of the screening.

  10. Estimation of PSD Shifts for High-Resolution Metrology of Thickness Micro-Changes with Possible Applications in Vessel Walls and Biological Membrane Characterization

    Science.gov (United States)

    Ramos, Antonio; Bazán, Ivonne; Negreira, Carlos; Brum, Javier; Gómez, Tomás; Calás, Héctor; Ruiz, Abelardo; de la Rosa, José Manuel

    2012-01-01

    Achieving accurate measurements of inflammation levels in tissues or thickness changes in biological membranes (e.g., amniotic sac, parietal pleura) and thin biological walls (e.g., blood vessels) from outside the human body, is a promising research line in the medical area. It would provide a technical basis to study the options for early diagnosis of some serious diseases such as hypertension, atherosclerosis or tuberculosis. Nevertheless, achieving the aim of non-invasive measurement of those scarcely-accessible parameters on patient internal tissues, currently presents many difficulties. The use of high-frequency ultrasonic transducer systems appears to offer a possible solution. Previous studies using conventional ultrasonic imaging have shown this, but the spatial resolution was not sufficient so as to permit a thickness evaluation with clinical significance, which requires an accuracy of a few microns. In this paper a broadband ultrasonic technique, that was recently developed by the authors to address other non-invasive medical detection problems (by integrating a piezoelectric transducer into a spectral measuring system), is extended to our new objective; the aim is its application to the thickness measurement of sub-millimeter membranes or layers made of materials similar to some biological tissues (phantoms). The modeling and design rules of such a transducer system are described, and various methods of estimating overtones location in the power spectral density (PSD) are quantitatively assessed with transducer signals acquired using piezoelectric systems and also generated from a multi-echo model. Their effects on the potential resolution of the proposed thickness measuring tool, and their capability to provide accuracies around the micron are studied in detail. Comparisons are made with typical tools for extracting spatial parameters in laminar samples from echo-waveforms acquired with ultrasonic transducers. Results of this advanced measurement

  11. Estimation of PSD Shifts for High-Resolution Metrology of Thickness Micro-Changes with Possible Applications in Vessel Walls and Biological Membrane Characterization

    Directory of Open Access Journals (Sweden)

    Abelardo Ruiz

    2012-11-01

    Full Text Available Achieving accurate measurements of inflammation levels in tissues or thickness changes in biological membranes (e.g., amniotic sac, parietal pleura and thin biological walls (e.g., blood vessels from outside the human body, is a promising research line in the medical area. It would provide a technical basis to study the options for early diagnosis of some serious diseases such as hypertension, atherosclerosis or tuberculosis. Nevertheless, achieving the aim of non-invasive measurement of those scarcely-accessible parameters on patient internal tissues, currently presents many difficulties. The use of high-frequency ultrasonic transducer systems appears to offer a possible solution. Previous studies using conventional ultrasonic imaging have shown this, but the spatial resolution was not sufficient so as to permit a thickness evaluation with clinical significance, which requires an accuracy of a few microns. In this paper a broadband ultrasonic technique, that was recently developed by the authors to address other non-invasive medical detection problems (by integrating a piezoelectric transducer into a spectral measuring system, is extended to our new objective; the aim is its application to the thickness measurement of sub-millimeter membranes or layers made of materials similar to some biological tissues (phantoms. The modeling and design rules of such a transducer system are described, and various methods of estimating overtones location in the power spectral density (PSD are quantitatively assessed with transducer signals acquired using piezoelectric systems and also generated from a multi-echo model. Their effects on the potential resolution of the proposed thickness measuring tool, and their capability to provide accuracies around the micron are studied in detail. Comparisons are made with typical tools for extracting spatial parameters in laminar samples from echo-waveforms acquired with ultrasonic transducers. Results of this advanced

  12. 75 FR 6401 - Medical Devices Regulated by the Center for Biologics Evaluation and Research; Availability of...

    Science.gov (United States)

    2010-02-09

    ... Evaluation and Research; Availability of Summaries of Safety and Effectiveness Data for Premarket Approval... safety and effectiveness data to the Division of Dockets Management (HFA-305), Food and Drug... the Center for Biologics Evaluation and Research (CBER). This list is intended to inform the public...

  13. Governing synthetic biology in the light of the Access and Benefit Sharing regulation (ABS).

    Science.gov (United States)

    Augusto, Carlos; Gutiérrez, Conde

    2014-01-01

    Synthetic biology is a change of paradigm, i.e. from the exploitation of natural and genetic resources to lab production of biological entities. This transitional shift represents a great challenge for developing countries, particularly those which host biodiversity, and users of genetic resources, since the latter might not be longer required to access to actual genetic resources (tangible genetic resources) but rather genetic resources' information (intangible genetic resources) in order to replicate those resources in labs. This could mean that users of genetic resource would not have to comply with the Convention on Biological Diversity (CBD) and its complementary treaty, the Nagoya Protocol, known also as the Access and Benefit Sharing regime (ABS). Both international instrument demands that States create legal mechanisms to secure access and benefit sharing, i.e., users of genetic resources are required to obtain prior informed consent (PIC) from host countries of biodiversity and reach mutual agreed terms (MATs), in which users and countries agree how to share the benefits arise from the utilization of genetic resources. The ABS regime is particularly relevant since its implementation at national and regional level has created tensions between users of genetic resources and developing countries. This situation could lead to users removing interest in the exploitation of genetic resources, subsequently, meaning that their focus would move towards technologies that rely less on tangible genetic resources, including synthetic biology. This papers aim to discuss the scope of the CBD and the Nagoya Protocol in the light of synthetic biology and the implications for developing countries.

  14. Caveolin-1 directly interacts with UT-A1 urea transporter: the role of caveolae/lipid rafts in UT-A1 regulation at the cell membrane.

    Science.gov (United States)

    Feng, Xiuyan; Huang, Haidong; Yang, Yuan; Fröhlich, Otto; Klein, Janet D; Sands, Jeff M; Chen, Guangping

    2009-06-01

    The cell plasma membrane contains specialized microdomains called lipid rafts which contain high amounts of sphingolipids and cholesterol. Lipid rafts are involved in a number of membrane protein functions. The urea transporter UT-A1, located in the kidney inner medullary collecting duct (IMCD), is important for urine concentrating ability. In this study, we investigated the possible role of lipid rafts in UT-A1 membrane regulation. Using sucrose gradient cell fractionation, we demonstrated that UT-A1 is concentrated in the caveolae-rich fraction both in stably expressing UT-A1 HEK293 cells and in freshly isolated kidney IMCD suspensions. In these gradients, UT-A1 at the cell plasma membrane is codistributed with caveolin-1, a major component of caveolae. The colocalization of UT-A1 in lipid rafts/caveolae was further confirmed in isolated caveolae from UT-A1-HEK293 cells. The direct association of UT-A1 and caveolin-1 was identified by immunoprecipitation and GST pull-down assay. Examination of internalized UT-A1 in pEGFP-UT-A1 transfected HEK293 cells fluorescent overlap with labeled cholera toxin subunit B, a marker of the caveolae-mediated endocytosis pathway. Disruption of lipid rafts by methyl-beta-cyclodextrin or knocking down caveolin-1 by small-interference RNA resulted in UT-A1 cell membrane accumulation. Functionally, overexpression of caveolin-1 in oocytes decreased UT-A1 urea transport activity and UT-A1 cell surface expression. Our results indicate that lipid rafts/caveolae participate in UT-A1 membrane regulation and this effect is mediated via a direct interaction of caveolin-1 with UT-A1.

  15. Regulation of mutagenesis by exogenous biological factors in the eukaryotic cell systems

    Directory of Open Access Journals (Sweden)

    Lukash L. L.

    2013-07-01

    Full Text Available The representations of the mutations and the nature of spontaneous mutation process and mutagenesis induced by exogenous oncoviruses, DNAs and proteins-mitogens are analysed. Exogenous biological factors induce DNA damages in regulatory-informational way, acting on the cellular systems for maintenance of genetical stability. Molecular mechanisms are the same as at spontaneous mutagenesis but they are realized with the participation of alien genetical material. Among biological mutagens, the oncoviruses and mobile genetic elements (MGEs are distinguished as the strongest destabilizing factors which direct tumor transformation of somatic mammalian cells. Genetical reprogramming or changing the programs of gene expression at the differentiation of stem and progenitor cells under growth factors and citokines is probably followed by mutations and recombinations as well.

  16. Membrane-anchored MucR mediates nitrate-dependent regulation of alginate production in Pseudomonas aeruginosa

    KAUST Repository

    Wang, Yajie

    2015-04-29

    Alginates exhibit unique material properties suitable for medical and industrial applications. However, if produced by Pseudomonas aeruginosa, it is an important virulence factor in infection of cystic fibrosis patients. The alginate biosynthesis machinery is activated by c-di-GMP imparted by the inner membrane protein, MucR. Here, it was shown that MucR impairs alginate production in response to nitrate in P. aeruginosa. Subsequent site-specific mutagenesis of MucR revealed that the second MHYT sensor motif (MHYT II, amino acids 121–124) of MucR sensor domain was involved in nitrate sensing. We also showed that both c-di-GMP synthesizing and degrading active sites of MucR were important for alginate production. Although nitrate and deletion of MucR impaired alginate promoter activity and global c-di-GMP levels, alginate yields were not directly correlated with alginate promoter activity or c-di-GMP levels, suggesting that nitrate and MucR modulate alginate production at a post-translational level through a localized pool of c-di-GMP. Nitrate increased pel promoter activity in the mucR mutant while in the same mutant the psl promoter activity was independent of nitrate. Nitrate and deletion of mucR did not impact on swarming motility but impaired attachment to solid surfaces. Nitrate and deletion of mucR promoted the formation of biofilms with increased thickness, cell density, and survival. Overall, this study provided insight into the functional role of MucR with respect to nitrate-mediated regulation of alginate biosynthesis. © 2015 Springer-Verlag Berlin Heidelberg

  17. VX-809 corrects folding defects in cystic fibrosis transmembrane conductance regulator protein through action on membrane-spanning domain 1.

    Science.gov (United States)

    Ren, Hong Yu; Grove, Diane E; De La Rosa, Oxana; Houck, Scott A; Sopha, Pattarawut; Van Goor, Fredrick; Hoffman, Beth J; Cyr, Douglas M

    2013-10-01

    Cystic fibrosis (CF) is a fatal genetic disorder associated with defective hydration of lung airways due to the loss of chloride transport through the CF transmembrane conductance regulator protein (CFTR). CFTR contains two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs), and a regulatory domain, and its channel assembly requires multiple interdomain contacts. The most common CF-causing mutation, F508del, occurs in NBD1 and results in misfolding and premature degradation of F508del-CFTR. VX-809 is an investigational CFTR corrector that partially restores CFTR function in people who are homozygous for F508del-CFTR. To identify the folding defect(s) in F508del-CFTR that must be repaired to treat CF, we explored the mechanism of VX-809 action. VX-809 stabilized an N-terminal domain in CFTR that contains only MSD1 and efficaciously restored function to CFTR forms that have missense mutations in MSD1. The action of VX-809 on MSD1 appears to suppress folding defects in F508del-CFTR by enhancing interactions among the NBD1, MSD1, and MSD2 domains. The ability of VX-809 to correct F508del-CFTR is enhanced when combined with mutations that improve F508del-NBD1 interaction with MSD2. These data suggest that the use of VX-809 in combination with an additional CFTR corrector that suppresses folding defects downstream of MSD1 may further enhance CFTR function in people with F508del-CFTR.

  18. [Special considerations for the regulation of biological medicinal products in individualised medicine. More than stratified medicine].

    Science.gov (United States)

    Müller-Berghaus, J; Volkers, P; Scherer, J; Cichutek, K

    2013-11-01

    The term individualised medicine, also called personalised medicine, is commonly used as an equivalent to stratified medicine. However, this is erroneous since quite often it is forgotten that especially biological medicinal products have other aspects of individualization that go beyond mere stratification. The principles of stratified medicine have been applied for biological medicinal products for many years. A historical example is diphtheria antitoxin made from horse serum, while current examples are transfusion of red blood cells and the administration of factor VIII in haemophilia A. The stratifying aspects of these medicinal products are given by the following considerations: diphtheria antitoxin is only administered after a diagnosis of diphtheria and not in other forms of tonsillitis, red blood cells should only be transfused once blood group compatibility as been established and factor VIII replacement is only administered in haemophilia A as opposed to other acquired or hereditary disease of the coagulation system. The peculiarities of biological medicinal products, in particular the inherent variability of the drug, are especially important for autologous cellular medicinal products. In addition to the expected variability of the biological source material there is interindividual variability of patients as cell donors, which make definition of specifications and determination of criteria for pharmaceutical quality and potency tests difficult. Therapy with modified autologous cells, a common and important application of advanced therapy medicinal products, is exemplary for the special considerations that must be made when evaluating pharmaceutical quality, mode of action and toxicological properties of the biological medicine. The clinical investigation of advanced therapy medicinal products with the intent of demonstrating safety and efficacy is particularly challenging because of the complexity of therapy, which often involves invasive interventions

  19. Neutrons reveal how nature uses structural themes and variation in biological regulation

    Energy Technology Data Exchange (ETDEWEB)

    Trewhella, Jill [School of Molecular and Microbial Biosciences, University of Sydney, Sydney 2006 (Australia)]. E-mail: jtrewhella@usyd.edu.au

    2006-11-15

    Healthy cellular function requires tight regulation of a multitude of bio-molecular interactions and processes, often in response to external stimuli. In achieving this regulation, nature uses a number of 'second messengers' that are released inside cells in response to first messengers, such as hormones that bind to the cell surface. Divalent calcium and cyclic nucleotides, like cAMP, are among nature's second messengers that bind to receptor proteins inside cells order to regulate the activities of various targets, including many protein kinases. Kinases are enzymes that catalyze the attachment of phosphate groups to proteins in order to modulate their functions. We have been using neutron contrast variation and small-angle solution scattering to study the interactions of the second messenger receptor proteins and their regulatory targets in order to understand the structural basis for these complex processes that use a number of common structural motifs to accomplish highly regulated function. Our most recent work has focused on the different isoforms of the cAMP-dependent protein kinase and the muscle regulatory complex troponin.

  20. Model cell membranes

    DEFF Research Database (Denmark)

    Günther-Pomorski, Thomas; Nylander, Tommy; Cardenas Gomez, Marite

    2014-01-01

    The high complexity of biological membranes has motivated the development and application of a wide range of model membrane systems to study biochemical and biophysical aspects of membranes in situ under well defined conditions. The aim is to provide fundamental understanding of processes control...

  1. Advanced treatment of biologically pretreated coal gasification wastewater by a novel integration of three-dimensional catalytic electro-Fenton and membrane bioreactor.

    Science.gov (United States)

    Jia, Shengyong; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng

    2015-12-01

    Laboratorial scale experiments were conducted to investigate a novel system three-dimensional catalytic electro-Fenton (3DCEF, catalyst of sewage sludge based activated carbon which loaded Fe3O4) integrating with membrane bioreactor (3DCEF-MBR) on advanced treatment of biologically pretreated coal gasification wastewater. The results indicated that 3DCEF-MBR represented high efficiencies in eliminating COD and total organic carbon, giving the maximum removal efficiencies of 80% and 75%, respectively. The integrated 3DCEF-MBR system significantly reduced the transmembrane pressure, giving 35% lower than conventional MBR after 30 days operation. The enhanced hydroxyl radical oxidation and bacteria self repair function were the mechanisms for 3DCEF-MBR performance. Therefore, the integrated 3DCEF-MBR was expected to be the promising technology for advanced treatment in engineering applications.

  2. Application of chemical, biological and membrane separation processes in textile industry with recourse to zero effluent discharge--a case study.

    Science.gov (United States)

    Nandy, T; Dhodapkar, R S; Pophali, G R; Kaul, S N; Devotta, S

    2005-09-01

    Environmental concerns associated with textile processing had placed the textile sector in a Southern State of India under serious threat of survival. The textile industries were closed under the orders of the Statutory Board for reason of inadequate compliance to environmental discharge norms of the State for the protection of the drinking water source of the State capital. In compliance with the direction of the Board for zero effluent discharge, advanced treatment process have been implemented for recovery of boiler feed quality water with recourse to effluent recycling/reuse. The paper describes to a case study on the adequacy assessment of the full scale effluent treatment plant comprising chemical, biological and filtration processes in a small scale textile industry. In addition, implementation of measures for discernable improvement in the performance of the existing units through effective operation & maintenance, and application of membrane separation processes leading to zero effluent discharge is also highlighted.

  3. Optimization of the biological process using flat membrane bioreactors. Maximum treatment performance with minimum reactor volume; Optimizacion del proceso biologico con BRM de membrana plana. Maximo rendimiento de depuracion con minimo volumen de reactor

    Energy Technology Data Exchange (ETDEWEB)

    Lluch Vallmithana, S.; Lopez Gavin, A.

    2006-07-01

    In a conventional activated sludge process, the membranes are inside the biological reactor where they drain the water through suction or a water column. This system can be operated with heavy loads and sludge of 12-14 g/l or more, and is not affected by problems of bulking or foaming. This makes it suitable for treating difficult industrial waste waters, providing treated water that is free of bacteria and viruses. Micro filtration membranes are flat without any rubbing between them. The membranes require infrequent chemical cleaning and do not need back washing. As no final sedimented is needed, the waste water treatment plant occupies less space. (Author)

  4. Effect of sludge retention time on the biological performance of anaerobic membrane bioreactors treating corn-to-ethanol thin stillage with high lipid content.

    Science.gov (United States)

    Dereli, Recep Kaan; van der Zee, Frank P; Heffernan, Barry; Grelot, Aurelie; van Lier, Jules B

    2014-02-01

    The potential of anaerobic membrane bioreactors (AnMBRs) for the treatment of lipid rich corn-to-ethanol thin stillage was investigated at three different sludge retention times (SRT), i.e. 20, 30 and 50 days. The membrane assisted biomass retention in AnMBRs provided an excellent solution to sludge washout problems reported for the treatment of lipid rich wastewaters by granular sludge bed reactors. The AnMBRs achieved high COD removal efficiencies up to 99% and excellent effluent quality. Although higher organic loading rates (OLRs) up to 8.0 kg COD m(-3) d(-1) could be applied to the reactors operated at shorter SRTs, better biological degradation efficiencies, i.e. up to 83%, was achieved at increased SRTs. Severe long chain fatty acid (LCFA) inhibition was observed at 50 days SRT, possibly caused by the extensive dissolution of LCFA in the reactor broth, inhibiting the methanogenic biomass. Physicochemical mechanisms such as precipitation with divalent cations and adsorption on the sludge played an important role in the occurrence of LCFA removal, conversion, and inhibition.

  5. The radioinduced membranes injuries as biological dose indicators: mechanisms of studies and practical applications; Les dommages membranaires radio-induits comme bio-indicateurs de dose: etudes des mecanismes et applications pratiques

    Energy Technology Data Exchange (ETDEWEB)

    Vincent-Genod, Lucie

    2001-10-15

    After an accidental overexposure, the assessment of the received dose in biological dosimetry is performed by a method based on the effects of irradiation on the DNA molecule. But this technique shows some limitations; therefore we tried to find new bio-sensors of radiation exposure. We have pointed out that membrane is a critical target of ionising radiation after an in vitro and in vivo overexposure. In vitro, these modifications were involved in the radio-induced apoptotic pathway. The measure of membrane fluidity allowed us to obtain an overall view of cellular membrane. Moreover, in vivo, by changing the lipid nutritional status of animals, our results displayed the important role played by membrane lipid composition in radio-induced membrane alterations. Besides, membrane effects were adjusted by the extracellular physiological control, and in particular by the damages on membrane fatty acid pattern. Finally, we have tested the use of membrane fluidity index as a bio-sensor of radiation exposure on in vivo models and blood samples from medical total body irradiated patients. The results achieved on animal models suggested that the membrane fluidity index was a bio-sensor of radiation exposure. Nevertheless, the observations realised on patients highlight that the effect of the first dose fraction of the radiotherapy treatment had some difficulties to be noticed. Indeed, the combined treatment: chemotherapy and radiotherapy disturbed the membrane fluidity index measures. To conclude, whereas this parameter was not a bio-sensor of irradiation exposure usable in biological dosimetry, it may allow us to assess the radio-induced damages and their cellular but also tissue impacts. (author)

  6. Epithelial SCAP/INSIG/SREBP signaling regulates multiple biological processes during perinatal lung maturation.

    Directory of Open Access Journals (Sweden)

    James P Bridges

    Full Text Available Pulmonary surfactant is required for lung function at birth and throughout postnatal life. Defects in the surfactant system are associated with common pulmonary disorders including neonatal respiratory distress syndrome and acute respiratory distress syndrome in children and adults. Lipogenesis is essential for the synthesis of pulmonary surfactant by type II epithelial cells lining the alveoli. This study sought to identify the role of pulmonary epithelial SREBP, a transcriptional regulator of cellular lipid homeostasis, during a critical time period of perinatal lung maturation in the mouse. Genome wide mRNA expression profiling of lung tissue from transgenic mice with epithelial-specific deletions of Scap (Scap(Δ/Δ, resulting in inactivation of SREBP signaling or Insig1 and Insig2 (Insig1/2(Δ/Δ, resulting in activation of SREBP signaling was assessed. Differentially expressed genes responding to SREBP perturbations were identified and subjected to functional enrichment analysis, pathway mapping and literature mining to predict upstream regulators and transcriptional networks regulating surfactant lipid homeostasis. Through comprehensive data analysis and integration, time dependent effects of epithelial SCAP/INSIG/SREBP deletion and defined SCAP/INSIG/SREBP-associated genes, bioprocesses and downstream pathways were identified. SREBP signaling influences epithelial development, cell death and cell proliferation at E17.5, while primarily influencing surfactant physiology, lipid/sterol synthesis, and phospholipid transport after birth. SREBP signaling integrated with the Wnt/β-catenin and glucocorticoid receptor signaling pathways during perinatal lung maturation. SREBP regulates perinatal lung lipogenesis and maturation through multiple mechanisms by interactions with distinct sets of regulatory partners.

  7. Novel nanometer scaffolds regulate the biological behaviors of neural stem cells

    Institute of Scientific and Technical Information of China (English)

    Jihui Zhou; Zhiqiang Liu; Fuge Sui; Meng Yao; Yansong Wang; Yugang Liu; Feipeng Tian; Qiang Li; He Xiaofeng; Lin Shao

    2013-01-01

    Ideal tissue-engineered scaffold materials regulate proliferation, apoptosis and differentiation of cells seeded on them by regulating gene expression. In this study, aligned and randomly oriented collagen nanofiber scaffolds were prepared using electronic spinning technology. Their diameters and appearance reached the standards of tissue-engineered nanometer scaffolds. The nanofiber scaffolds were characterized by a high swelling ratio, high porosity and good mechanical properties. The proliferation of spinal cord-derived neural stem cells on novel nanofiber scaffolds was obviously enhanced. The proportions of cells in the S and G2/M phases noticeably increased. Moreover, the proliferation rate of neural stem cells on the aligned collagen nanofiber scaffolds was high. The expression levels of cyclin D1 and cyclin-dependent kinase 2 were increased. Bcl-2 expression was significantly increased, but Bax and caspase-3 gene expressions were obviously decreased. There was no significant difference in the differentiation of neural stem cells into neurons on aligned and randomly oriented collagen nanofiber scaffolds. These results indicate that novel nanofiber scaffolds could promote the proliferation of spinal cord-derived neural stem cells and inhibit apoptosis without inducing differentiation. Nanofiber scaffolds regulate apoptosis and proliferation in neural stem cells by altering gene expression.

  8. IGF-IEc expression, regulation and biological function in different tissues.

    Science.gov (United States)

    Dai, Zhongquan; Wu, Feng; Yeung, Ella W; Li, Yinghui

    2010-08-01

    Insulin-like growth factor I (IGF-I) is an important growth factor for embryonic development, postnatal growth, tissue repair and maintenance of homeostasis. IGF-I functions and regulations are complex and tissue-specific. IGF-I mediates growth hormone signaling to target tissues during growth, but many IGF-I variants have been discovered, resulting in complex models to describe IGF-I function and regulation. Mechano-growth factor (MGF) is an alternative splicing variant of IGF-I and serves as a local tissue repair factor that responds to changes in physiological conditions or environmental stimuli. MGF expression is significantly increased in muscle, bone and tendon following damage resulting from mechanical stimuli and in the brain and heart following ischemia. MGF has been shown to activate satellite cells in muscle resulting in hypertrophy or regeneration, and functions as a neuroprotectant in brain ischemia. Both expression and processing of this IGF-I variant are tissue specific, but the functional mechanism is poorly understood. MGF and its short derivative have been examined as a potential therapy for muscular dystrophy and cerebral hypoxia-ischemia using experimental animals. Although the unique mode of action of MGF has been identified, the details remain elusive. Here we review the expression and regulation of MGF and the function of this IGF-I isoform in tissue protection.

  9. Computational Systems Biology Approach Predicts Regulators and Targets of microRNAs and Their Genomic Hotspots in Apoptosis Process.

    Science.gov (United States)

    Alanazi, Ibrahim O; Ebrahimie, Esmaeil

    2016-07-01

    Novel computational systems biology tools such as common targets analysis, common regulators analysis, pathway discovery, and transcriptomic-based hotspot discovery provide new opportunities in understanding of apoptosis molecular mechanisms. In this study, after measuring the global contribution of microRNAs in the course of apoptosis by Affymetrix platform, systems biology tools were utilized to obtain a comprehensive view on the role of microRNAs in apoptosis process. Network analysis and pathway discovery highlighted the crosstalk between transcription factors and microRNAs in apoptosis. Within the transcription factors, PRDM1 showed the highest upregulation during the course of apoptosis, with more than 9-fold expression increase compared to non-apoptotic condition. Within the microRNAs, MIR1208 showed the highest expression in non-apoptotic condition and downregulated by more than 6 fold during apoptosis. Common regulators algorithm showed that TNF receptor is the key upstream regulator with a high number of regulatory interactions with the differentially expressed microRNAs. BCL2 and AKT1 were the key downstream targets of differentially expressed microRNAs. Enrichment analysis of the genomic locations of differentially expressed microRNAs led us to the discovery of chromosome bands which were highly enriched (p < 0.01) with the apoptosis-related microRNAs, such as 13q31.3, 19p13.13, and Xq27.3 This study opens a new avenue in understanding regulatory mechanisms and downstream functions in the course of apoptosis as well as distinguishing genomic-enriched hotspots for apoptosis process.

  10. Considerations for the use of human participants in vector biology research: a tool for investigators and regulators.

    Science.gov (United States)

    Achee, Nicole L; Youngblood, Laura; Bangs, Michael J; Lavery, James V; James, Stephanie

    2015-02-01

    A thorough search of the existing literature has revealed that there are currently no published recommendations or guidelines for the interpretation of US regulations on the use of human participants in vector biology research (VBR). An informal survey of vector biologists has indicated that issues related to human participation in vector research have been largely debated by academic, national, and local Institutional Review Boards (IRBs) in the countries where the research is being conducted, and that interpretations and subsequent requirements made by these IRBs have varied widely. This document is intended to provide investigators and corresponding scientific and ethical review committee members an introduction to VBR methods involving human participation and the legal and ethical framework in which such studies are conducted with a focus on US Federal Regulations. It is also intended to provide a common perspective for guiding researchers, IRB members, and other interested parties (i.e., public health officials conducting routine entomological surveillance) in the interpretation of human subjects regulations pertaining to VBR.

  11. Development of a Univariate Membrane-Based Mid-Infrared Method for Protein Quantitation and Total Lipid Content Analysis of Biological Samples

    Directory of Open Access Journals (Sweden)

    Ivona Strug

    2014-01-01

    Full Text Available Biological samples present a range of complexities from homogeneous purified protein to multicomponent mixtures. Accurate qualification of such samples is paramount to downstream applications. We describe the development of an MIR spectroscopy-based analytical method offering simultaneous protein quantitation (0.25–5 mg/mL and analysis of total lipid or detergent species, as well as the identification of other biomolecules present in biological samples. The method utilizes a hydrophilic PTFE membrane engineered for presentation of aqueous samples in a dried format compatible with fast infrared analysis. Unlike classical quantification techniques, the reported method is amino acid sequence independent and thus applicable to complex samples of unknown composition. By comparison to existing platforms, this MIR-based method enables direct quantification using minimal sample volume (2 µL; it is well-suited where repeat access and limited sample size are critical parameters. Further, accurate results can be derived without specialized training or knowledge of IR spectroscopy. Overall, the simplified application and analysis system provides a more cost-effective alternative to high-throughput IR systems for research laboratories with minimal throughput demands. In summary, the MIR-based system provides a viable alternative to current protein quantitation methods; it also uniquely offers simultaneous qualification of other components, notably lipids and detergents.

  12. The experimental power of FR900359 to study Gq-regulated biological processes

    Science.gov (United States)

    Schrage, Ramona; Schmitz, Anna-Lena; Gaffal, Evelyn; Annala, Suvi; Kehraus, Stefan; Wenzel, Daniela; Büllesbach, Katrin M.; Bald, Tobias; Inoue, Asuka; Shinjo, Yuji; Galandrin, Ségolène; Shridhar, Naveen; Hesse, Michael; Grundmann, Manuel; Merten, Nicole; Charpentier, Thomas H.; Martz, Matthew; Butcher, Adrian J.; Slodczyk, Tanja; Armando, Sylvain; Effern, Maike; Namkung, Yoon; Jenkins, Laura; Horn, Velten; Stößel, Anne; Dargatz, Harald; Tietze, Daniel; Imhof, Diana; Galés, Céline; Drewke, Christel; Müller, Christa E.; Hölzel, Michael; Milligan, Graeme; Tobin, Andrew B.; Gomeza, Jesús; Dohlman, Henrik G.; Sondek, John; Harden, T. Kendall; Bouvier, Michel; Laporte, Stéphane A.; Aoki, Junken; Fleischmann, Bernd K.; Mohr, Klaus; König, Gabriele M.; Tüting, Thomas; Kostenis, Evi

    2015-01-01

    Despite the discovery of heterotrimeric αβγ G proteins ∼25 years ago, their selective perturbation by cell-permeable inhibitors remains a fundamental challenge. Here we report that the plant-derived depsipeptide FR900359 (FR) is ideally suited to this task. Using a multifaceted approach we systematically characterize FR as a selective inhibitor of Gq/11/14 over all other mammalian Gα isoforms and elaborate its molecular mechanism of action. We also use FR to investigate whether inhibition of Gq proteins is an effective post-receptor strategy to target oncogenic signalling, using melanoma as a model system. FR suppresses many of the hallmark features that are central to the malignancy of melanoma cells, thereby providing new opportunities for therapeutic intervention. Just as pertussis toxin is used extensively to probe and inhibit the signalling of Gi/o proteins, we anticipate that FR will at least be its equivalent for investigating the biological relevance of Gq. PMID:26658454

  13. Biologically inspired highly durable iron phthalocyanine catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells.

    Science.gov (United States)

    Li, Wenmu; Yu, Aiping; Higgins, Drew C; Llanos, Bernard G; Chen, Zhongwei

    2010-12-08

    In the present work, we have designed and synthesized a new highly durable iron phtalocyanine based nonprecious oxygen reduction reaction (ORR) catalyst (Fe-SPc) for polymer electrolyte membrane fuel cells (PEMFCs). The Fe-SPc, with a novel structure inspired by that of naturally occurring oxygen activation catalysts, is prepared by a nonpyrolyzing method, allowing adequate control of the atomic structure and surface properties of the material. Significantly improved ORR stability of the Fe-SPc is observed compared with the commercial Fe-Pc catalysts. The Fe-SPc has similar activity to that of the commercial Fe-Pc initially, while the Fe-SPc displays 4.6 times higher current density than that of the commercial Fe-Pc after 10 sweep potential cycles, and a current density that is 7.4 times higher after 100 cycles. This has been attributed to the incorporation of electron-donating functional groups, along with a high degree of steric hindrance maintaining active site isolation. Nonprecious Fe-SPc is promising as a potential alternative ORR electrocatalyst for PEMFCs.

  14. A systems biology approach identifies the biochemical mechanisms regulating monoterpenoid essential oil composition in peppermint

    Science.gov (United States)

    Rios-Estepa, Rigoberto; Turner, Glenn W.; Lee, James M.; Croteau, Rodney B.; Lange, B. Markus

    2008-01-01

    The integration of mathematical modeling and experimental testing is emerging as a powerful approach for improving our understanding of the regulation of metabolic pathways. In this study, we report on the development of a kinetic mathematical model that accurately simulates the developmental patterns of monoterpenoid essential oil accumulation in peppermint (Mentha × piperita). This model was then used to evaluate the biochemical processes underlying experimentally determined changes in the monoterpene pathway under low ambient-light intensities, which led to an accumulation of the branchpoint intermediate (+)-pulegone and the side product (+)-menthofuran. Our simulations indicated that the environmentally regulated changes in monoterpene profiles could only be explained when, in addition to effects on biosynthetic enzyme activities, as yet unidentified inhibitory effects of (+)-menthofuran on the branchpoint enzyme pulegone reductase (PR) were assumed. Subsequent in vitro analyses with recombinant protein confirmed that (+)-menthofuran acts as a weak competitive inhibitor of PR (Ki = 300 μM). To evaluate whether the intracellular concentration of (+)-menthofuran was high enough for PR inhibition in vivo, we isolated essential oil-synthesizing secretory cells from peppermint leaves and subjected them to steam distillations. When peppermint plants were grown under low-light conditions, (+)-menthofuran was selectively retained in secretory cells and accumulated to very high levels (up to 20 mM), whereas under regular growth conditions, (+)-menthofuran levels remained very low (<400 μM). These results illustrate the utility of iterative cycles of mathematical modeling and experimental testing to elucidate the mechanisms controlling flux through metabolic pathways. PMID:18287058

  15. Biological clocks in the duodenum and the diurnal regulation of duodenal and plasma serotonin.

    Directory of Open Access Journals (Sweden)

    Elizabeth Ebert-Zavos

    Full Text Available Serotonin in blood plasma is primarily synthesized in the duodenum, as brain derived serotonin does not cross the blood-brain barrier. Because serotonin in the brain and retina is synthesized under the control of a circadian clock, we sought to determine if a circadian clock in the duodenum regulates serotonin synthesis and release in blood. We examined gene expression in the duodenum of chickens at different times of the day and found that the duodenum rhythmically expresses molecular circadian clock genes and genes controlling serotonin biosynthesis, specifically tryptophan hydroxylase, in a light dark cycle (LD. Analysis of the duodenum and blood plasma showed that the amount of serotonin in the duodenum varies across the day and that serotonin profiles in blood plasma are also rhythmic in LD, but were not rhythmic in constant darkness. Because serotonin in the gut affects duodenal nutrient absorption and gut motility, the control of serotonin production in the duodenum by LD cycles could provide an additional mechanism by which the external environment controls nutrient uptake and digestive function. The diurnal regulation of plasma serotonin may also serve as an additional biochemical signal in the blood encoding time and could be used by target tissues to indicate the status of nutrient absorption.

  16. Phactr3/scapinin, a member of protein phosphatase 1 and actin regulator (phactr family, interacts with the plasma membrane via basic and hydrophobic residues in the N-terminus.

    Directory of Open Access Journals (Sweden)

    Akihiro Itoh

    Full Text Available Proteins that belong to the protein phosphatase 1 and actin regulator (phactr family are involved in cell motility and morphogenesis. However, the mechanisms that regulate the actin cytoskeleton are poorly understood. We have previously shown that phactr3, also known as scapinin, localizes to the plasma membrane, including lamellipodia and membrane ruffles. In the present study, experiments using deletion and point mutants showed that the basic and hydrophobic residues in the N-terminus play crucial roles in the localization to the plasma membrane. A BH analysis (http://helixweb.nih.gov/bhsearch is a program developed to identify membrane-binding domains that comprise basic and hydrophobic residues in membrane proteins. We applied this program to phactr3. The results of the BH plot analysis agreed with the experimentally determined region that is responsible for the localization of phactr3 to the plasma membrane. In vitro experiments showed that the N-terminal itself binds to liposomes and acidic phospholipids. In addition, we showed that the interaction with the plasma membrane via the N-terminal membrane-binding sequence is required for phactr3-induced morphological changes in Cos7 cells. The membrane-binding sequence in the N-terminus is highly conserved in all members of the phactr family. Our findings may provide a molecular basis for understanding the mechanisms that allow phactr proteins to regulate cell morphogenesis.

  17. Efficacy of Regulated 12-Session Matrix Model on restraining methamphetamine-dependence: Biological evidence and self-reports

    Directory of Open Access Journals (Sweden)

    Zahra Amiri

    2016-09-01

    Full Text Available Introduction: Substance abuse is accompanied by a wide range of psychological, social, and economic adverse outcomes and damages. Methamphetamine (abuse is dangerous because of its wide range adverse outcomes and hazardous sustaining side effects. Moreover, Methamphetamine-dependence is usually treatment-resistant. This study evaluated the Regulated 12-Session Matrix Model in treatment of outpatient ethamphetamine-dependent individuals. Method: 24 individuals were chosen according to inclusion/exclusion criteria of the study and randomly assigned to equal experimental (age range 19-41; mean age: 46.9 and control groups (age range: 21-42; mean age: 27.8. Experimental group members partook Regulated 12-Session Matrix Model once a week in 12 consecutive weeks, while control group members remained at waitlist. Results:Independent t-test in 12th week showed that experimental group had lower methamphetamine use, comparing to control group (p<.05.Phillai’s Trace, Wilk’sLambda,Hotelling-Lawley's trace, and Roy's largest root showed that there are significant association between experimental and control groups in reduction of methamphetamine-use lapse (p<.05.Within-subject F ratio revealed that “methamphetamine use” was significantly reduced in experimental group after clinical intervention (p<.001. Urine test showed significant difference in results of negative responses by the end of intervention (p<.05 in experimental group, compared to control group, which was also significant from the results of both groups in pre-test (p<.001. Discussion and conclusion: Efficacy of Regulated 12-Session Matrix Model in craving control and reduction of lapse and substance (abuse in methamphetamine-dependent patients was approved with self-reports and biological indicators. Regulated 12-Session Matrix Model has been proved to be beneficial in methamphetaminedependencetreatment in Iran and other alike cultural and social atmospheres. Limitations and future

  18. Computational biology of genome expression and regulation--a review of microarray bioinformatics.

    Science.gov (United States)

    Wang, Junbai

    2008-01-01

    Microarray technology is being used widely in various biomedical research areas; the corresponding microarray data analysis is an essential step toward the best utilizing of array technologies. Here we review two components of the microarray data analysis: a low level of microarray data analysis that emphasizes the designing, the quality control, and the preprocessing of microarray experiments, then a high level of microarray data analysis that focuses on the domain-specific microarray applications such as tumor classification, biomarker prediction, analyzing array CGH experiments, and reverse engineering of gene expression networks. Additionally, we will review the recent development of building a predictive model in genome expression and regulation studies. This review may help biologists grasp a basic knowledge of microarray bioinformatics as well as its potential impact on the future evolvement of biomedical research fields.

  19. The Role of the p53 Protein in Stem-Cell Biology and Epigenetic Regulation.

    Science.gov (United States)

    Levine, Arnold J; Puzio-Kuter, Anna M; Chan, Chang S; Hainaut, Pierre

    2016-09-01

    The p53 protein plays a passive and an active role in stem cells. The transcriptional activities of p53 for cell-cycle arrest and DNA repair are largely turned off in stem cells, but there is some indication that long-term stem-cell viability may require other p53-regulated functions. When p53 is activated in stem cells, it stops cell division and promotes the commitment to a differentiation pathway and the formation of progenitor cells. In the absence of any p53 activity, stem-cell replication continues and mistakes in the normal epigenetic pathway occur at a higher probability. In the presence of a functionally active p53 protein, epigenetic stability is enforced and stem-cell replication is regulated by commitment to differentiation. Over a lifetime of an organism, stem-cell clones compete in a tissue niche for Darwinian replicative advantages and in doing so accumulate mutations that permit stem-cell replication. Mutations in the p53 gene give stem cells this advantage, increase the clonal stem-cell population, and lower the age at which cancers can occur. Li-Fraumeni patients that inherit p53 mutations develop tumors in a tissue-type-specific fashion at younger ages. Throughout the life of a Li-Fraumeni patient, the tumor types that arise occur in tissues where stem cells are active and cell division is most rapid. Thus, p53 mutations that are inherited or occur during developmental life act in stem cells of the mesenchymal and epithelial lineages, whereas p53 mutations that occur in progenitor or differentiated (somatic) cells later in life function in tissues of endodermal origins, indicating that p53 may function differently in different developmental lineages.

  20. Does dissolved organic carbon regulate biological methane oxidation in semiarid soils?

    Science.gov (United States)

    Sullivan, Benjamin W; Selmants, Paul C; Hart, Stephen C

    2013-07-01

    In humid ecosystems, the rate of methane (CH4 ) oxidation by soil-dwelling methane-oxidizing bacteria (MOB) is controlled by soil texture and soil water holding capacity, both of which limit the diffusion of atmospheric CH4 into the soil. However, it remains unclear whether these same mechanisms control CH4 oxidation in more arid soils. This study was designed to measure the proximate controls of potential CH4 oxidation in semiarid soils during different seasons. Using a unique and well-constrained 3-million-year-old semiarid substrate age gradient, we were able to hold state factors constant while exploring the relationship between seasonal potential CH4 oxidation rates and soil texture, soil water holding capacity, and dissolved organic carbon (DOC). We measured unexpectedly higher rates of potential CH4 oxidation in the wet season than the dry season. Although other studies have attributed low CH4 oxidation rates in dry soils to desiccation of MOB, we present several lines of evidence that this may be inaccurate. We found that soil DOC concentration explained CH4 oxidation rates better than soil physical factors that regulate the diffusion of CH4 from the atmosphere into the soil. We show evidence that MOB facultatively incorporated isotopically labeled glucose into their cells, and MOB utilized glucose in a pattern among our study sites that was similar to wet-season CH4 oxidation rates. This evidence suggests that DOC, which is utilized by MOB in other environments with varying effects on CH4 oxidation rates, may be an important regulator of CH4 oxidation rates in semiarid soils. Our collective understanding of the facultative use of DOC by MOB is still in its infancy, but our results suggest it may be an important factor controlling CH4 oxidation in soils from dry ecosystems.

  1. Endocannabinoid system as a regulator of tumor cell malignancy – biological pathways and clinical significance

    Science.gov (United States)

    Pyszniak, Maria; Tabarkiewicz, Jacek; Łuszczki, Jarogniew J

    2016-01-01

    The endocannabinoid system (ECS) comprises cannabinoid receptors (CBs), endogenous cannabinoids, and enzymes responsible for their synthesis, transport, and degradation of (endo)cannabinoids. To date, two CBs, CB1 and CB2, have been characterized; however, orphan G-protein-coupled receptor GPR55 has been suggested to be the third putative CB. Several different types of cancer present abnormal expression of CBs, as well as other components of ECS, and this has been shown to correlate with the clinical outcome. Although most effects of (endo)cannabinoids are mediated through stimulation of classical CBs, they also interact with several molecules, either prosurvival or proapoptotic molecules. It should be noted that the mode of action of exogenous cannabinoids differs significantly from that of endocannabinoid and results from the studies on their activity both in vivo and in vitro could not be easily compared. This review highlights the main signaling pathways involved in the antitumor activity of cannabinoids and the influence of their activation on cancer cell biology. We also discuss changes in the expression pattern of the ECS in various cancer types that have an impact on disease progression and patient survival. A growing amount of experimental data imply possible exploitation of cannabinoids in cancer therapy. PMID:27486335

  2. Hoc protein regulates the biological effects of T4 phage in mammals.

    Science.gov (United States)

    Dabrowska, Krystyna; Zembala, Maria; Boratynski, Janusz; Switala-Jelen, Kinga; Wietrzyk, Joanna; Opolski, Adam; Szczaurska, Katarzyna; Kujawa, Marek; Godlewska, Joanna; Gorski, Andrzej

    2007-06-01

    We previously investigated the biological, non-antibacterial effects of bacteriophage T4 in mammals (binding to cancer cells in vitro and attenuating tumour growth and metastases in vivo); we selected the phage mutant HAP1 that was significantly more effective than T4. In this study we describe a non-sense mutation in the hoc gene that differentiates bacteriophage HAP1 and its parental strain T4. We found no substantial effects of the mutation on the mutant morphology, and its effects on electrophoretic mobility and hydrodynamic size were moderate. Only the high ionic strength of the environment resulted in a size difference of about 10 nm between T4 and HAP1. We compared the antimetastatic activity of the T2 phage, which does not express protein Hoc, with those of T4 and HAP1 (B16 melanoma lung colonies). We found that HAP1 and T2 decreased metastases with equal effect, more strongly than did T4. We also investigated concentrations of T4 and HAP1 in the murine blood, tumour (B16), spleen, liver, or muscle. We found that HAP1 was rapidly cleared from the organism, most probably by the liver. Although HAP1 was previously defined to bind cancer cells more effectively (than T4), its rapid elimination precluded its higher concentration in tumours.

  3. Interaction of chemical species with biological regulation of the metabolism of essential trace elements

    Energy Technology Data Exchange (ETDEWEB)

    Windisch, W. [Center of Life and Food Sciences, Technische Univ. Muenchen, Freising (Germany)

    2002-02-01

    Variations in the chemical speciation of dietary trace elements can result in the provision of different amounts of these micronutrients to the organism and might thus induce interactions with trace-element metabolism. The chemical species of Zn, Fe, Cu, and Mn can interact with other components of the diet even before reaching the site of absorption, e.g. by formation of poorly soluble complexes with phytic acid. This might considerably modify the amount of metabolically available trace elements; differences between absorptive capacity per se toward dietary species seems to be less important. Homeostasis usually limits the quantities of Zn, Fe, Cu, and Mn transported from the gut into the organism, and differences between dietary species are largely eliminated at this step. There is no homeostatic control of absorption of Se and I, and organisms seem to be passively exposed to influx of these micronutrients irrespective of dietary speciation. Inside the organism the trace elements are usually converted into a metabolically recognizable form, channeled into their biological functions, or submitted to homeostatically controlled excretion. Some dietary species can, however, be absorbed as intact compounds. As long as the respective quantities of trace elements are not released from their carriers, they are not recognized properly by trace element metabolism and might induce tissue accumulation, irrespective of homeostatic control. (orig.)

  4. Generation of a tightly regulated doxycycline-inducible model for studying mouse intestinal biology.

    Science.gov (United States)

    Roth, Sabrina; Franken, Patrick; van Veelen, Wendy; Blonden, Lau; Raghoebir, Lalini; Beverloo, Berna; van Drunen, Ellen; Kuipers, Ernst J; Rottier, Robbert; Fodde, Riccardo; Smits, Ron

    2009-01-01

    To develop a sensitive and inducible system to study intestinal biology, we generated a transgenic mouse model expressing the reverse tetracycline transactivator rtTA2-M2 under control of the 12.4 kb murine Villin promoter. The newly generated Villin-rtTA2-M2 mice were then bred with the previously developed tetO-HIST1H2BJ/GFP model to assess inducibility and tissue-specificity. Expression of the histone H2B-GFP fusion protein was observed exclusively upon doxycycline induction and was uniformly distributed throughout the intestinal epithelium. The Villin-rtTA2-M2 was also found to drive transgene expression in the developing mouse intestine. Furthermore, we could detect transgene expression in the proximal tubules of the kidney and in a population of alleged gastric progenitor cells. By administering different concentrations of doxycycline, we show that the Villin-rtTA2-M2 system drives transgene expression in a dosage-dependent fashion. Thus, we have generated a novel doxycycline-inducible mouse model, providing a valuable tool to study the effect of different gene dosages on intestinal physiology and pathology.

  5. Different sets of ER-resident J-proteins regulate distinct polar nuclear-membrane fusion events in Arabidopsis thaliana.

    Science.gov (United States)

    Maruyama, Daisuke; Yamamoto, Masaya; Endo, Toshiya; Nishikawa, Shuh-ichi

    2014-11-01

    Angiosperm female gametophytes contain a central cell with two polar nuclei. In many species, including Arabidopsis thaliana, the polar nuclei fuse during female gametogenesis. We previously showed that BiP, an Hsp70 in the endoplasmic reticulum (ER), was essential for membrane fusion during female gametogenesis. Hsp70 function requires partner proteins for full activity. J-domain containing proteins (J-proteins) are the major Hsp70 functional partners. A. thaliana ER contains three soluble J-proteins, AtERdj3A, AtERdj3B, and AtP58(IPK). Here, we analyzed mutants of these proteins and determined that double-mutant ovules lacking AtP58(IPK) and AtERdj3A or AtERdj3B were defective in polar nuclear fusion. Electron microscopy analysis identified that polar nuclei were in close contact, but no membrane fusion occurred in mutant ovules lacking AtP58(IPK) and AtERdj3A. The polar nuclear outer membrane appeared to be connected via the ER remaining at the inner unfused membrane in mutant ovules lacking AtP58(IPK) and AtERdj3B. These results indicate that ER-resident J-proteins, AtP58(IPK)/AtERdj3A and AtP58(IPK)/AtERdj3B, function at distinct steps of polar nuclear-membrane fusion. Similar to the bip1 bip2 double mutant female gametophytes, the aterdj3a atp58(ipk) double mutant female gametophytes defective in fusion of the outer polar nuclear membrane displayed aberrant endosperm proliferation after fertilization with wild-type pollen. However, endosperm proliferated normally after fertilization of the aterdj3b atp58(ipk) double mutant female gametophytes defective in fusion of the inner membrane. Our results indicate that the polar nuclear fusion defect itself does not cause an endosperm proliferation defect.

  6. The N-terminal region of organic anion transporting polypeptide 1B3 (OATP1B3) plays an essential role in regulating its plasma membrane trafficking.

    Science.gov (United States)

    Chun, Se-Eun; Thakkar, Nilay; Oh, Yunseok; Park, Ji Eun; Han, Songhee; Ryoo, Gongmi; Hahn, Hyunggu; Maeng, Sang Hyun; Lim, Young-Ran; Han, Byung Woo; Lee, Wooin

    2017-05-01

    Organic anion transporting polypeptide 1B3 (OATP1B3) is a major influx transporter mediating the hepatic uptake of various endogenous substrates as well as clinically important drugs such as statins and anticancer drugs. However, molecular mechanisms controlling the membrane trafficking of OATP1B3 have been largely unknown. Several reports recently indicated the presence of a distinct, cancer-type OATP1B3 variant lacking the N-terminal 28 amino acids compared to OATP1B3 expressed in non-malignant hepatocytes. Interestingly, the cancer-type OATP1B3 variant is located predominantly in the cytoplasm, implicating the involvement of the N-terminal region of OATP1B3 in its membrane trafficking. In the current study, we set out to experimentally validate the importance of the N-terminal region of OATP1B3 and to identify responsible sequence motif(s) in that region. A number of truncation or point mutants of OATP1B3 were transiently expressed in HEK293T, HCT-8 or MDCK II cells and their expression in cytoplasmic and surface membrane fractions were analyzed by immunoblotting. Our results indicated that the N-terminal sequence of OATP1B3, in particular, at the amino acid positions between 12 and 28, may be indispensable in its membrane trafficking. Moreover, our results using a fusion construct indicated that the first 50 amino acids of OATP1B3 are sufficient for its membrane localization. The importance of the N-terminal region in membranous localization was shared among the other OATP1B subfamily members, OATP1B1 and rat Oatp1b2. Our efforts to identify the responsible amino acid(s) or structure motif(s) in the N-terminal region did not pinpoint individual amino acids or motifs with putative secondary structures. Our current findings however demonstrate that the N-terminal region is important for the membrane localization of the OATP1B subfamily members and should facilitate future investigations of the mechanisms involved in the regulation and membrane trafficking of

  7. Mobility in geometrically confined membranes.

    Science.gov (United States)

    Domanov, Yegor A; Aimon, Sophie; Toombes, Gilman E S; Renner, Marianne; Quemeneur, François; Triller, Antoine; Turner, Matthew S; Bassereau, Patricia

    2011-08-02

    Lipid and protein lateral mobility is essential for biological function. Our theoretical understanding of this mobility can be traced to the seminal work of Saffman and Delbrück, who predicted a logarithmic dependence of the protein diffusion coefficient (i) on the inverse of the size of the protein and (ii) on the "membrane size" for membranes of finite size [Saffman P, Delbrück M (1975) Proc Natl Acad Sci USA 72:3111-3113]. Although the experimental proof of the first prediction is a matter of debate, the second has not previously been thought to be experimentally accessible. Here, we construct just such a geometrically confined membrane by forming lipid bilayer nanotubes of controlled radii connected to giant liposomes. We followed the diffusion of individual molecules in the tubular membrane using single particle tracking of quantum dots coupled to lipids or voltage-gated potassium channels KvAP, while changing the membrane tube radius from approximately 250 to 10 nm. We found that both lipid and protein diffusion was slower in tubular membranes with smaller radii. The protein diffusion coefficient decreased as much as 5-fold compared to diffusion on the effectively flat membrane of the giant liposomes. Both lipid and protein diffusion data are consistent with the predictions of a hydrodynamic theory that extends the work of Saffman and Delbrück to cylindrical geometries. This study therefore provides strong experimental support for the ubiquitous Saffman-Delbrück theory and elucidates the role of membrane geometry and size in regulating lateral diffusion.

  8. Partitioning of Lipids at Domain Boundaries in Model Membranes

    NARCIS (Netherlands)

    Schafer, Lars V.; Marrink, Siewert J.

    2010-01-01

    Line-active molecules ("linactants") that bind to the boundary interface between different fluid lipid domains in membranes have a strong potential as regulators of the lateral heterogeneity that is important for many biological processes. Here, we use molecular dynamics simulations in combination w

  9. Experimental measurements and mathematical modeling of biological noise arising from transcriptional and translational regulation of basic synthetic gene circuits.

    Science.gov (United States)

    Bandiera, Lucia; Pasini, Alice; Pasotti, Lorenzo; Zucca, Susanna; Mazzini, Giuliano; Magni, Paolo; Giordano, Emanuele; Furini, Simone

    2016-04-21

    The small number of molecules, unevenly distributed within an isogenic cell population, makes gene expression a noisy process, and strategies have evolved to deal with this variability in protein concentration and to limit its impact on cellular behaviors. As translational efficiency has a major impact on biological noise, a possible strategy to control noise is to regulate gene expression processes at the post-transcriptional level. In this study, fluctuations in the concentration of a green fluorescent protein were compared, at the single cell level, upon transformation of an isogenic bacterial cell population with synthetic gene circuits implementing either a transcriptional or a post-transcriptional control of gene expression. Experimental measurements showed that protein variability is lower under post-transcriptional control, when the same average protein concentrations are compared. This effect is well reproduced by stochastic simulations, supporting the hypothesis that noise reduction is due to the control mechanism acting on the efficiency of translation. Similar strategies are likely to play a role in noise reduction in natural systems and to be useful for controlling noise in synthetic biology applications.

  10. Networks and their applications to biological systems: From ecological dynamics to gene regulation

    Science.gov (United States)

    Sevim, Volkan

    In this dissertation, we study three biological applications of networks. The first one is a biological coevolution model, in which a species is defined by a genome in the form of a finite bitstring and the interactions between species are given by a fixed matrix with randomly distributed elements. Here we study a version of the model, in which the matrix elements are correlated to a controllable degree by means of an averaging scheme. This method allows creation of mutants resembling their ancestors (wildtype). We compare long kinetic Monte Carlo simulations of models with uncorrelated and correlated interactions. We find that while there are quantitative differences, most qualitative features, such as 1/f behavior in power spectral densities for the diversity indices and the power-law distribution of species lifetimes, are not significantly affected by the correlations in the interaction matrix. The second application is the growth of a directed network, in which the growth is constrained by the cost of adding links to the existing nodes. This is a new preferential-attachment scheme, in which a new node attaches to an existing node i with probability pi(k i, k'i ) ∝ ( k'i /ki)gamma, where ki and k'i are the number of outgoing and incoming links at i, respectively, and gamma is a constant. First, we calculate the degree distribution for the outgoing links for a simplified form of this function, pi( ki) ∝ k-1i , both analytically and by Monte Carlo simulations. The distribution decays like kmuk/Gamma(k) for large k, where mu is a constant. We relate this mechanism to simple food-web models by implementing it in the cascade model. We also study the generalized case, pi(ki, k'i ) ∝ ( k'i /ki)gamma, by simulations. The third application is the evolution of robustness to mutations and noise in gene regulatory networks. It has been shown that robustness to mutations and noise can evolve through stabilizing selection for optimal phenotypes in model gene regulatory

  11. Endocannabinoid system as a regulator of tumor cell malignancy – biological pathways and clinical significance

    Directory of Open Access Journals (Sweden)

    Pyszniak M

    2016-07-01

    Full Text Available Maria Pyszniak,1–3 Jacek Tabarkiewicz,1,2 Jarogniew J Łuszczki4,5 1Centre for Innovative Research in Medical and Natural Sciences, Faculty of Medicine, 2Department of Immunology, Faculty of Medicine, University of Rzeszów, Rzeszów, 3Postgraduate School of Molecular Medicine, Medical University of Warsaw, Warszawa, 4Department of Pathophysiology, Medical University of Lublin, 5Isobolographic Analysis Laboratory, Institute of Agricultural Medicine, Lublin, Poland Abstract: The endocannabinoid system (ECS comprises cannabinoid receptors (CBs, endogenous cannabinoids, and enzymes responsible for their synthesis, transport, and degradation of (endocannabinoids. To date, two CBs, CB1 and CB2, have been characterized; however, orphan G-protein-coupled receptor GPR55 has been suggested to be the third putative CB. Several different types of cancer present abnormal expression of CBs, as well as other components of ECS, and this has been shown to correlate with the clinical outcome. Although most effects of (endocannabinoids are mediated through stimulation of classical CBs, they also interact with several molecules, either prosurvival or proapoptotic molecules. It should be noted that the mode of action of exogenous cannabinoids differs significantly from that of endocannabinoid and results from the studies on their activity both in vivo and in vitro could not be easily compared. This review highlights the main signaling pathways involved in the antitumor activity of cannabinoids and the influence of their activation on cancer cell biology. We also discuss changes in the expression pattern of the ECS in various cancer types that have an impact on disease progression and patient survival. A growing amount of experimental data imply possible exploitation of cannabinoids in cancer therapy. Keywords: cannabinoids, cancer, cell signaling, cannabinoid receptor, delta-9-tetrahy­drocannabinol

  12. Biological clocks and regulation of seasonal reproduction and migration in birds.

    Science.gov (United States)

    Kumar, Vinod; Wingfield, John C; Dawson, Alistair; Ramenofsky, Marilyn; Rani, Sangeeta; Bartell, Paul

    2010-01-01

    Timekeeping is important at two levels: to time changes in physiology and behavior within each day and within each year. For the former, birds have a system of at least three independent circadian clocks present in the retina of the eyes, the pineal gland, and the hypothalamus. This differs from the situation in mammals in which the input, pacemaker, and output are localized in different structures. Each bird clock interacts with at least one other clock, and together, they appear to form a centralized clock system that keeps daily time. These clocks have a powerful endogenous component, and the daily light-dark cycle entrains them to 24 h. The timing and duration of life history stages that make up annual cycle of an individual must also be controlled by some form of timekeeping. However, evidence for the existence of an equivalent endogenous circannual clock is less clear. Environmental cues, particularly photoperiod, appear to have a more direct role than simply entraining the clock to calendar time. For example, the timing of migration is probably greatly influenced by photoperiod, but its manifestation each day, as Zugunruhe, appears to be under circadian control. Migration involves marked changes in physiology to cope with the energetic demands. There is still much that we do not know about how organisms' timekeeping systems respond to their natural environment, particularly how salient signals from the environment are perceived and then transduced into appropriately timed biological functions. However, given that changes in environmental input affects the clock, increasing human disturbance of the environment is likely to adversely affect these systems.

  13. Bile acids modulate signaling by functional perturbation of plasma membrane domains.

    Science.gov (United States)

    Zhou, Yong; Maxwell, Kelsey N; Sezgin, Erdinc; Lu, Maryia; Liang, Hong; Hancock, John F; Dial, Elizabeth J; Lichtenberger, Lenard M; Levental, Ilya

    2013-12-13

    Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.

  14. Soil nematode assemblages indicate the potential for biological regulation of pest species

    Science.gov (United States)

    Steel, Hanne; Ferris, Howard

    2016-05-01

    In concept, regulation or suppression of target nematode pest species should be enhanced when an abundance of predator species is supported by ample availability of bacterial- fungal- and non-damaging plant-feeding prey species. We selected soils from natural and managed environments that represented different levels of resource availability and disturbance. In microcosm chambers of each soil, in its natural state or after heat defaunation, we introduced test prey species not already resident in the soils (Meloidogyne incognita and Steinernema feltiae). Survival of the test prey was determined after a 5-day bioassay exposure. Across the soils tested, predator abundance and biomass were greater in undisturbed soils with plentiful resources and lower in soils from agricultural sites. Suppressiveness to the two introduced species increased with both numerical abundance and metabolic footprint of the predator assemblages. The magnitude of the increase in suppressiveness was greater at low numbers of predators then dampened to an asymptotic level at greater predator abundance, possibly determined by temporal and spatial aspects of the bioassay system and/or satiation of the predators. The more resource-limited the predators were and the higher the metabolic predator footprint, the greater the suppressiveness. The applied implications of this study are that soil suppressiveness to pest species may be enhanced by increasing resources to predators, removing chemical and physical constraints to their survival and increase, and altering management practices so that predators and target prey are co-located in time and space.

  15. Insights into the translational regulation of biologically active open reading frames of Pelargonium line pattern virus.

    Science.gov (United States)

    Castaño, Aurora; Ruiz, Leticia; Hernández, Carmen

    2009-04-10

    Pelargonium line pattern virus (PLPV), a proposed member of a prospective genus (Pelarspovirus) within family Tombusviridae, has a positive-sense, single-stranded genomic RNA. According to previous predictions, it contains six open reading frames (ORFs) potentially encoding proteins of 27 (p27), 13 (p13), 87 (p87), 7 (p7), 6 (p6), and 37 kDa (p37). Using a variety of techniques we demonstrate that all predicted ORFs are functional, with the exception of (p13) and (p6). We also characterize a previously unidentified ORF which encodes a 9.7 kDa protein (p9.7) that is essential for viral movement. Furthermore, we present evidence that the single subgenomic RNA (sgRNA) produced by the virus directs synthesis of p7, p9.7 and p37. Remarkably, the translation of these totally unrelated proteins is coordinated via leaky-scanning. This mechanism seems to be favoured by the poor translation context of the start codon of ORF(p7), the non-AUG weak initiation codon of ORF(p9.7) and the lack of additional AUG codons in any reading frame preceding ORF(p37). The results also suggest that precise regulation of protein production from the sgRNA is critical for virus viability. Altogether, the data supports the notion that PLPV belongs to a new genus of plant viruses.

  16. Arf and RhoA regulate both the cytosolic and the membrane-bound phospholipase D from human placenta

    DEFF Research Database (Denmark)

    Vinggaard, Anne Marie; Hansen, Harald S.; Provost, J.J.;

    1997-01-01

    proteins 1 µM mArf3 (2-fold) and 0.37 nM RhoA (2-fold). This is the first report to show RhoA activation of a cytosolic PLD. The activation by mArf3 was maintained after partial purification on DEAE Sepharose of the enzyme. We have previously reported the existence of a membrane-bound PLD from human...... for the inhibitory effect. Furthermore, placental membrane PLD was activated by 30 µM GTP¿S (4-fold) and by mArf3 (1 µM) and RhoA (0.37 nM) by a factor of 3 and 2, respectively. The solubilized membrane phospholipase D was partially purified to a basal specific activity of 25-37 nmol/min/mg. This preparation...

  17. [Study of pretreatment on microfiltration of huanglian jiedu decoction with ceramic membranes based on solution environment regulation theory].

    Science.gov (United States)

    Li, Bo; Zhang, Lian-Jun; Guo, Li-Wei; Fu, Ting-Ming; Zhu, Hua-Xu

    2014-01-01

    To optimize the pretreatment of Huanglian Jiedu decoction before ceramic membranes and verify the effect of different pretreatments in multiple model system existed in Chinese herb aqueous extract. The solution environment of Huanglian Jiedu decoction was adjusted by different pretreatments. The flux of microfiltration, transmittance of the ingredients and removal rate of common polymers were as indicators to study the effect of different solution environment It was found that flocculation had higher stable permeate flux, followed by vacuuming filtration and adjusting pH to 9. The removal rate of common polymers was comparatively high. The removal rate of protein was slightly lower than the simulated solution. The transmittance of index components were higher when adjust pH and flocculation. Membrane blocking resistance was the major factor in membrane fouling. Based on the above indicators, the effect of flocculation was comparatively significant, followed by adjusting pH to 9.

  18. Up-regulation of NG2 proteoglycan and interferon-induced transmembrane proteins 1 and 3 in mouse astrocytoma: a membrane proteomics approach.

    Science.gov (United States)

    Seyfried, Nicholas T; Huysentruyt, Leanne C; Atwood, James A; Xia, Qiangwei; Seyfried, Thomas N; Orlando, Ron

    2008-05-18

    Although brain tumors are classified as if their lineage were well understood, the relationship between the molecular events that specify neural cell lineage and brain tumors remains enigmatic. Traditionally, cell surface membrane antigens have served as biomarkers that distinguish brain tumor origin and malignancy. In this study, membrane proteins were identified from a terminally differentiated mouse astrocyte (AC) and CT-2A astrocytoma (CT-2A) cell line using liquid-chromatography coupled with tandem mass spectrometry (LC-MS/MS). A total of 321 and 297 protein groups with at least one unique peptide were identified in the AC and CT-2A cells. Using a label-free quantitative MS approach, 25 plasma membrane proteins in CT-2A were found significantly up- or down-regulated compared with those in AC. Three of the up-regulated proteins, chondroitin sulfate proteoglycan-4 (Cspg4), interferon-induced transmembrane protein-2 (IFITM2) and -3 (IFITM3) were further validated by semi-quantitative RT-PCR analysis. In addition, a third member of the IFITM family, interferon-induced transmembrane protein-1 (IFITM1) was also analyzed. Expression of Cspg4, IFITM1 and IFITM3 was significantly greater in the CT-2A cells than that in the AC cells. Interestingly, Cspg4, also known as neuronal/glial 2 (NG2) proteoglycan in human, is an oligodendrocyte progenitor marker. Therefore, our data suggest that the CT-2A tumor may be derived from NG2 glia rather than from fully differentiated astrocytes. Moreover, the CT-2A cells also express a series of interferon-induced signature proteins that may be specific to this tumor. These data highlight the utility of LC-MS/MS for the identification of brain tumor membrane biomarkers.

  19. The biological clock is regulated by adrenergic signaling in brown fat but is dispensable for cold-induced thermogenesis.

    Directory of Open Access Journals (Sweden)

    Siming Li

    Full Text Available The biological clock plays an important role in integrating nutrient and energy metabolism with other cellular processes. Previous studies have demonstrated that core clock genes are rhythmically expressed in peripheral tissues, including the liver, skeletal muscle, pancreatic islets, and white and brown adipose tissues. These peripheral clocks are entrained by physiological cues, thereby aligning the circadian pacemaker to tissue functions. The mechanisms that regulate brown adipose tissue clock in response to physiological signals remain poorly understood. Here we found that the expression of core clock genes is highly responsive to cold exposure in brown fat, but not in white fat. This cold-inducible regulation of the clock network is mediated by adrenergic receptor activation and the transcriptional coactivator PGC-1α. Brown adipocytes in mice lacking a functional clock contain large lipid droplets accompanied by dysregulation of genes involved in lipid metabolism and adaptive thermogenesis. Paradoxically, the "clockless" mice were competent in maintaining core body temperature during cold exposure. These studies elucidated the presence of adrenergic receptor/clock crosstalk that appears to be required for normal thermogenic gene expression in brown fat.

  20. Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds.

    Science.gov (United States)

    Jaganathan, Ganesh K; Han, Yingying; Li, Weijie; Song, Danping; Song, Xiaoyan; Shen, Mengqi; Zhou, Qiang; Zhang, Chenxue; Liu, Baolin

    2017-03-13

    The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h(-1)) suffered significantly higher membrane damage at temperature between -20 °C and -10 °C than slow cooled (3 °Ch(-1)) seeds (P  0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to -20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes.

  1. Biological preconcentrator

    Science.gov (United States)

    Manginell, Ronald P.; Bunker, Bruce C.; Huber, Dale L.

    2008-09-09

    A biological preconcentrator comprises a stimulus-responsive active film on a stimulus-producing microfabricated platform. The active film can comprise a thermally switchable polymer film that can be used to selectively absorb and desorb proteins from a protein mixture. The biological microfabricated platform can comprise a thin membrane suspended on a substrate with an integral resistive heater and/or thermoelectric cooler for thermal switching of the active polymer film disposed on the membrane. The active polymer film can comprise hydrogel-like polymers, such as poly(ethylene oxide) or poly(n-isopropylacrylamide), that are tethered to the membrane. The biological preconcentrator can be fabricated with semiconductor materials and technologies.

  2. Basement membrane reconstruction in human skin equivalents is regulated by fibroblasts and/or exogenously activated keratinocytes

    NARCIS (Netherlands)

    El Ghalbzouri, A; Jonkman, MF; Dijkman, R; Ponec, M

    2005-01-01

    This study was undertaken to examine the role fibroblasts play in the formation of the basement membrane (BM) in human skin equivalents. For this purpose, keratinocytes were seeded on top of fibroblast-free or fibroblast-populated collagen matrix or de-epidermized dermis and cultured in the absence

  3. Membrane targeting of cGMP-dependent protein kinase is required for cystic fibrosis transmembrane conductance regulator Cl- channel activation

    NARCIS (Netherlands)

    A.B. Vaandrager (Arie); A. Smolenski; B.C. Tilly (Bernard); A.B. Houtsmuller (Adriaan); E.M.E. Ehlert (Ehrich); A.G. Bot (Alice); M.J. Edixhoven (Marcel); W.E. Boomaars (Wendy); S.M. Lohmann (Suzanne); H.R. de Jonge (Hugo)

    1998-01-01

    textabstractA recently cloned isoform of cGMP-dependent protein kinase (cGK), designated type II, was implicated as the mediator of cGMP-provoked intestinal Cl- secretion based on its localization in the apical membrane of enterocytes and on its capacity to activate cys

  4. CHX14 is a plasma membrane K-efflux transporter that regulates K+ redistribution in "Arabidopsis thaliana"

    Science.gov (United States)

    Potassium (K(+)) is essential for plant growth and development, yet the molecular identity of many K(+) transporters remains elusive. Here we characterized cation/H(+) exchanger (CHX) 14 as a plasma membrane K(+) transporter. "CHX14" expression was induced by elevated K(+) and histochemical analysis...

  5. Reciprocal interactions between Beta1-integrin and epidermal growth factor in three-dimensional basement membrane breast cultures: A different perspective in epithelial biology

    Energy Technology Data Exchange (ETDEWEB)

    Wang, F.; Weaver, V.M.; Petersen, O.W.; Larabell, C.A.; Dedhar, S.; Briand, P.; Lupu, R.; Bissell, M.J.

    1998-09-30

    Anchorage and growth factor independence are cardinal features of the transformed phenotype. Although it is logical that the two pathways must be coregulated in normal tissues to maintain homeostasis, this has not been demonstrated directly. We showed previously that down-modulation of {beta}1-integrin signaling reverted the malignant behavior of a human breast tumor cell line (T4-2) derived from phenotypically normal cells (HMT-3522) and led to growth arrest in a threedimensional (3D) basement membrane assay in which the cells formed tissue-like acini (14). Here, we show that there is a bidirectional cross-modulation of {beta}1-integrin and epidermal growth factor receptor (EGFR) signaling via the mitogenactivated protein kinase (MAPK) pathway. The reciprocal modulation does not occur in monolayer (2D) cultures. Antibodymediated inhibition of either of these receptors in the tumor cells, or inhibition of MAPK kinase, induced a concomitant downregulation of both receptors, followed by growth-arrest and restoration of normal breast tissue morphogenesis. Crossmodulation and tissue morphogenesis were associated with attenuation of EGF-induced transient MAPK activation. To specifically test EGFR and {beta}1-integrin interdependency, EGFR was overexpressed in nonmalignant cells, leading to disruption of morphogenesis and a compensatory up-regulation of {beta}1-integrin expression, again only in 3D. Our results indicate that when breast cells are spatially organized as a result of contact with basement membrane, the signaling pathways become coupled and bidirectional. They further explain why breast cells fail to differentiate in monolayer cultures in which these events are mostly uncoupled. Moreover, in a subset of tumor cells in which these pathways are misregulated but functional, the cells could be 'normalized' by manipulating either pathway.

  6. The effects of different preservation processes on the total protein and growth factor content in a new biological product developed from human amniotic membrane.

    Science.gov (United States)

    Russo, Alessandra; Bonci, Paola; Bonci, Paolo

    2012-06-01

    The aim of this work is to quantify the total protein and growth factors content in a tissue-suspension obtained from processed human amniotic membrane (hAM). hAM was collected, frozen, freeze dried, powdered and sterilized by γ-irradiation. At each step of the process, samples were characterized for the total protein amounts by a Bradford protein assay and for the growth factor concentrations by ELISA test of the tissue suspensions. Frozen-hAM samples show higher release of total proteins and specific growth factors in the tissue suspension in comparison with freeze-dried hAM. We observed that even if the protein extraction is hindered once the tissue is dried, the powdering process allows a greater release in the tissue suspension of total proteins and growth factors after tissue re-solubilization in comparison with only the freeze-drying process (+91 ± 13% for EGF, +16 ± 4% for HGF, +11 ± 5% for FGF, +16 ± 9% for TGF-β1), and a greater release of EGF (85 ± 10%) in comparison with only the freezing process, because proteins become much readily solubilized in the solution. According with these results, we describe a protocol to obtain a new sterile biological product from hAM tissue, with well-known effects of thermal, mechanical and physical processes on the total protein and grow factors contents.

  7. Evidence for functional interaction of plasma membrane electron transport, voltage-dependent anion channel and volume-regulated anion channel in frog aorta

    Indian Academy of Sciences (India)

    Rashmi P Rao; J Prakasa Rao

    2010-12-01

    Frog aortic tissue exhibits plasma membrane electron transport (PMET) owing to its ability to reduce ferricyanide even in the presence of mitochondrial poisons, such as cyanide and azide. Exposure to hypotonic solution (108 mOsmol/kg H2O) enhanced the reduction of ferricyanide in excised aortic tissue of frog. Increment in ferricyanide reductase activity was also brought about by the presence of homocysteine (100 M dissolved in isotonic frog Ringer solution), a redox active compound and a potent modulator of PMET. Two plasma-membrane-bound channels, the volume regulated anion channel (VRAC) and the voltage-dependent anion channel (VDAC), are involved in the response to hypotonic stress. The presence of VRAC and VDAC antagonists–tamoxifen, glibenclamide, fluoxetine and verapamil, and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), respectively–inhibited this enhanced activity brought about by either hypotonic stress or homocysteine. The blockers do not affect the ferricyanide reductase activity under isotonic conditions. Taken together, these findings indicate a functional interaction of the three plasma membrane proteins, namely, ferricyanide reductase (PMET), VDAC and VRAC.

  8. The Role of Soil Biological Function in Regulating Agroecosystem Services and Sustainability in the Quesungual Agroforestry System

    Science.gov (United States)

    Fonte, S.; Pauli, N.; Rousseau, L.; SIX, J. W. U. A.; Barrios, E.

    2014-12-01

    The Quesungual agroforestry system from western Honduras has been increasingly promoted as a promising alternative to traditional slash-and-burn agriculture in tropical dry forest regions of the Americas. Improved residue management and the lack of burning in this system can greatly impact soil biological functioning and a number of key soil-based ecosystem services, yet our understanding of these processes has not been thoroughly integrated to understand system functionality as a whole that can guide improved management. To address this gap, we present a synthesis of various field studies conducted in Central America aimed at: 1) quantifying the influence of the Quesungual agroforestry practices on soil macrofauna abundance and diversity, and 2) understanding how these organisms influence key soil-based ecosystem services that ultimately drive the success of this system. A first set of studies examined the impact of agroecosystem management on soil macrofauna populations, soil fertility and key soil processes. Results suggest that residue inputs (derived from tree biomass pruning), a lack of burning, and high tree densities, lead to conditions that support abundant, diverse soil macrofauna communities under agroforestry, with soil organic carbon content comparable to adjacent forest. Additionally, there is great potential in working with farmers to develop refined soil quality indicators for improved land management. A second line of research explored interactions between residue management and earthworms in the regulation of soil-based ecosystem services. Earthworms are the most prominent ecosystem engineers in these soils. We found that earthworms are key drivers of soil structure maintenance and the stabilization of soil organic matter within soil aggregates, and also had notable impacts on soil nutrient dynamics. However, the impact of earthworms appears to depend on residue management practices, thus indicating the need for an integrated approach for

  9. T3 Regulates a Human Macrophage-Derived TSH-β Splice Variant: Implications for Human Bone Biology.

    Science.gov (United States)

    Baliram, R; Latif, R; Morshed, S A; Zaidi, M; Davies, T F

    2016-09-01

    TSH and thyroid hormones (T3 and T4) are intimately involved in bone biology. We have previously reported the presence of a murine TSH-β splice variant (TSH-βv) expressed specifically in bone marrow-derived macrophages and that exerted an osteoprotective effect by inducing osteoblastogenesis. To extend this observation and its relevance to human bone biology, we set out to identify and characterize a TSH-β variant in human macrophages. Real-time PCR analyses using human TSH-β-specific primers identified a 364-bp product in macrophages, bone marrow, and peripheral blood mononuclear cells that was sequence verified and was homologous to a human TSH-βv previously reported. We then examined TSH-βv regulation using the THP-1 human monocyte cell line matured into macrophages. After 4 days, 46.1% of the THP-1 cells expressed the macrophage markers CD-14 and macrophage colony-stimulating factor and exhibited typical morphological characteristics of macrophages. Real-time PCR analyses of these cells treated in a dose-dependent manner with T3 showed a 14-fold induction of human TSH-βv mRNA and variant protein. Furthermore, these human TSH-βv-positive cells, induced by T3 exposure, had categorized into both M1 and M2 macrophage phenotypes as evidenced by the expression of macrophage colony-stimulating factor for M1 and CCL-22 for M2. These data indicate that in hyperthyroidism, bone marrow resident macrophages have the potential to exert enhanced osteoprotective effects by oversecreting human TSH-βv, which may exert its local osteoprotective role via osteoblast and osteoclast TSH receptors.

  10. Regulation of mitogen-activated protein kinase pathways by the plasma membrane Na+/H+ exchanger, NHE1

    DEFF Research Database (Denmark)

    Pedersen, Stine Helene Falsig; Darborg, Barbara Vasek; Rentsch, Maria Louise;

    2006-01-01

    The mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK, play a major role in the regulation of pivotal cellular processes such as cell death/survival balance, cell cycle progression, and cell migration. MAP...

  11. Role of the Na+/K+-ATPase in regulating the membrane potential in rat peritoneal mast cells.

    Science.gov (United States)

    Friis, U G; Praetorius, H A; Knudsen, T; Johansen, T

    1997-10-01

    1. The aim of this study was to investigate the effect of the Na+/K+-ATPase on the membrane potential of peritoneal mast cells isolated from male Sprague-Dawley SPF-rats. 2. Experiments were performed at 22-26 degrees C in the tight-seal whole-cell configuration of the patch-clamp technique by use of Sylgard-coated patch pipettes (3-6 M[omega]). High-resolution membrane currents were recorded with an EPC-9 patch-clamp amplifier controlled by the 'E9SCREEN' software. In addition, a charting programme on another computer synchronously recorded at low resolution (2 Hz) membrane potential and holding current (low-pass filtered at 500 Hz). 3. Na+/K+-ATPase activity was measured as the ouabain-sensitive change in the zero-current potential. The zero-current potential in rat peritoneal mast cells measured 2 min after obtaining whole-cell configuration amounted to 1.7 +/- 2.5 mV (n = 21). Ouabain (5 mM), a Na+/K+-ATPase-inhibitor, had only a very minor effect upon the membrane potential under resting conditions (n = 3). 4. When mast cells were superfused with nominal calcium-free external solution, the cells hyperpolarized (delta mV: 20.2 +/- 3.8 mV (n = 5)). In addition, when the mast cells were preincubated in nominal calcium-free external solution for 12 +/- 1.6 min before whole-cell configuration, the membrane potential amounted to -53.7 +/- 9.8 mV (n = 8). A subsequent superfusion with ouabain (5 mM) depolarized the membrane potential (ouabain-sensitive hyperpolarization (delta mV): 23.0 +/- 8.4 mV (n = 8)). 5. A high intracellular concentration of Na+ ([Na+]i) (26.6 mM) also resulted in hyperpolarization (delta mV: 20.2 +/- 9.1 mV (n = 7)), but only when ATP was present. A subsequent superfusion with ouabain (5 mM) repolarized these cells to -1.2 +/- 14 mV (ouabain-sensitive hyperpolarization (delta mV): 19.7 +/- 7.7 mV (n = 7)). 6. The size of the [Na+]i-dependent hyperpolarization was dose-dependent. Low [Na+]i (1 mM) had no effect on membrane potential and these

  12. Membrane phospholipid fatty acid composition regulates cardiac SERCA activity in a hibernator, the Syrian hamster (Mesocricetus auratus.

    Directory of Open Access Journals (Sweden)

    Sylvain Giroud

    Full Text Available Polyunsaturated fatty acids (PUFA have strong effects on hibernation and daily torpor. Increased dietary uptake of PUFA of the n-6 class, particularly of Linoleic acid (LA, C18:2 n-6 lengthens torpor bout duration and enables animals to reach lower body temperatures (T(b and metabolic rates. As previously hypothesized, this well-known influence of PUFA may be mediated via effects of the membrane fatty acid composition on sarcoplasmic reticulum (SR Ca(2+-ATPase 2a (SERCA in the heart of hibernators. We tested the hypotheses that high proportions of n-6 PUFA in general, or specifically high proportions of LA (C18:2 n-6 in SR phospholipids (PL should be associated with increased cardiac SERCA activity, and should allow animals to reach lower minimum T(b in torpor. We measured activity of SERCA from hearts of hibernating and non-hibernating Syrian hamsters (Mesocricetus auratus in vitro at 35 °C. Further, we determined the PL fatty acid composition of the SR membrane of these hearts. We found that SERCA activity strongly increased as the proportion of LA in SR PL increased but was negatively affected by the content of Docosahexaenoic acid (DHA; C22:6 n-3. SR PL from hibernating hamsters were characterized by high proportions of LA and low proportions of DHA. As a result, SERCA activity was significantly higher during entrance into torpor and in torpor compared to inter-bout arousal. Also, animals with increased SERCA activity reached lower T(b during torpor. Interestingly, a subgroup of hamsters which never entered torpor but remained euthermic throughout winter displayed a phenotype similar to animals in summer. This was characterized by lower proportions of LA and increased proportions of DHA in SR membranes, which is apparently incompatible with torpor. We conclude that the PUFA composition of SR membranes affects cardiac function via modulating SERCA activity, and hence determines the minimum T(b tolerated by hibernators.

  13. Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

    Institute of Scientific and Technical Information of China (English)

    LI Yan-feng; ZHUO Ye-hong; BI Wei-na; BAI Yu-jing; LI Yan-na; WANG Zhi-jian

    2008-01-01

    Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance.Ion channels play an important role in these processes.The main aim of this study was to determine whether the well-characterized members of the Kvl family (Kv1.3) contribute to the Kv currents in ciliary epithelium.Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle.Ciliary epithelium samples were isolated from the rabbits.We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium.Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium,however it seemed to express more in the apical membrane of the nonpigmented epithelial cells.One nmol/L margatoxin,a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential.The cytosotic calcium increased after NPE cell depolarization,this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine.These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.Conclusion Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

  14. Insights into the localization and function of the membrane trafficking regulator GNOM ARF-GEF at the Golgi apparatus in Arabidopsis.

    Science.gov (United States)

    Naramoto, Satoshi; Otegui, Marisa S; Kutsuna, Natsumaro; de Rycke, Riet; Dainobu, Tomoko; Karampelias, Michael; Fujimoto, Masaru; Feraru, Elena; Miki, Daisuke; Fukuda, Hiroo; Nakano, Akihiko; Friml, Jiří

    2014-07-01

    GNOM is one of the most characterized membrane trafficking regulators in plants, with crucial roles in development. GNOM encodes an ARF-guanine nucleotide exchange factor (ARF-GEF) that activates small GTPases of the ARF (ADP ribosylation factor) class to mediate vesicle budding at endomembranes. The crucial role of GNOM in recycling of PIN auxin transporters and other proteins to the plasma membrane was identified in studies using the ARF-GEF inhibitor brefeldin A (BFA). GNOM, the most prominent regulator of recycling in plants, has been proposed to act and localize at so far elusive recycling endosomes. Here, we report the GNOM localization in context of its cellular function in Arabidopsis thaliana. State-of-the-art imaging, pharmacological interference, and ultrastructure analysis show that GNOM predominantly localizes to Golgi apparatus. Super-resolution confocal live imaging microscopy identified GNOM and its closest homolog GNOM-like 1 at distinct subdomains on Golgi cisternae. Short-term BFA treatment stabilizes GNOM at the Golgi apparatus, whereas prolonged exposures results in GNOM translocation to trans-Golgi network (TGN)/early endosomes (EEs). Malformed TGN/EE in gnom mutants suggests a role for GNOM in maintaining TGN/EE function. Our results redefine the subcellular action of GNOM and reevaluate the identity and function of recycling endosomes in plants.

  15. Evidence that the Essential Response Regulator YycF in Streptococcus pneumoniae Modulates Expression of Fatty Acid Biosynthesis Genes and Alters Membrane Composition†

    Science.gov (United States)

    Mohedano, M. Luz; Overweg, Karin; de la Fuente, Alicia; Reuter, Mark; Altabe, Silvia; Mulholland, Francis; de Mendoza, Diego; López, Paloma; Wells, Jerry M.

    2005-01-01

    The YycFG two-component system, originally identified in Bacillus subtilis, is highly conserved among gram-positive bacteria with low G+C contents. In Streptococcus pneumoniae, the YycF response regulator has been reported to be essential for cell growth, but the signal to which it responds and the gene members of the regulon remain unclear. In order to investigate the role of YycFG in S. pneumoniae, we increased the expression of yycF by using a maltose-inducible vector and analyzed the genome-wide effects on transcription and protein expression during the course of yycF expression. The induction of yycF expression increased histidine kinase yycG transcript levels, suggesting an autoregulation of the yycFG operon. Evidence from both proteomic and microarray transcriptome studies as well as analyses of membrane fatty acid composition indicated that YycFG is involved in the regulation of fatty acid biosynthesis pathways and in determining fatty acid chain lengths in membrane lipids. In agreement with recent transcriptome data on pneumococcal cells depleted of YycFG, we also identified several other potential members of the YycFG regulon that are required for virulence and cell wall biosynthesis and metabolism. PMID:15774879

  16. The cytoplasmic domain of the gamete membrane fusion protein HAP2 targets the protein to the fusion site in Chlamydomonas and regulates the fusion reaction

    Science.gov (United States)

    Liu, Yanjie; Pei, Jimin; Grishin, Nick; Snell, William J.

    2015-01-01

    Cell-cell fusion between gametes is a defining step during development of eukaryotes, yet we know little about the cellular and molecular mechanisms of the gamete membrane fusion reaction. HAP2 is the sole gamete-specific protein in any system that is broadly conserved and shown by gene disruption to be essential for gamete fusion. The wide evolutionary distribution of HAP2 (also known as GCS1) indicates it was present in the last eukaryotic common ancestor and, therefore, dissecting its molecular properties should provide new insights into fundamental features of fertilization. HAP2 acts at a step after membrane adhesion, presumably directly in the merger of the lipid bilayers. Here, we use the unicellular alga Chlamydomonas to characterize contributions of key regions of HAP2 to protein location and function. We report that mutation of three strongly conserved residues in the ectodomain has no effect on targeting or fusion, although short deletions that include those residues block surface expression and fusion. Furthermore, HAP2 lacking a 237-residue segment of the cytoplasmic region is expressed at the cell surface, but fails to localize at the apical membrane patch specialized for fusion and fails to rescue fusion. Finally, we provide evidence that the ancient HAP2 contained a juxta-membrane, multi-cysteine motif in its cytoplasmic region, and that mutation of a cysteine dyad in this motif preserves protein localization, but substantially impairs HAP2 fusion activity. Thus, the ectodomain of HAP2 is essential for its surface expression, and the cytoplasmic region targets HAP2 to the site of fusion and regulates the fusion reaction. PMID:25655701

  17. Association with the Plasma Membrane Is Sufficient for Potentiating Catalytic Activity of Regulators of G Protein Signaling (RGS) Proteins of the R7 Subfamily.

    Science.gov (United States)

    Muntean, Brian S; Martemyanov, Kirill A

    2016-03-25

    Regulators of G protein Signaling (RGS) promote deactivation of heterotrimeric G proteins thus controlling the magnitude and kinetics of responses mediated by G protein-coupled receptors (GPCR). In the nervous system, RGS7 and RGS9-2 play essential role in vision, reward processing, and movement control. Both RGS7 and RGS9-2 belong to the R7 subfamily of RGS proteins that form macromolecular complexes with R7-binding protein (R7BP). R7BP targets RGS proteins to the plasma membrane and augments their GTPase-accelerating protein (GAP) activity, ultimately accelerating deactivation of G protein signaling. However, it remains unclear if R7BP serves exclusively as a membrane anchoring subunit or further modulates RGS proteins to increase their GAP activity. To directly answer this question, we utilized a rapidly reversible chemically induced protein dimerization system that enabled us to control RGS localization independent from R7BP in living cells. To monitor kinetics of Gα deactivation, we coupled this strategy with measuring changes in the GAP activity by bioluminescence resonance energy transfer-based assay in a cellular system containing μ-opioid receptor. This approach was used to correlate changes in RGS localization and activity in the presence or absence of R7BP. Strikingly, we observed that RGS activity is augmented by membrane recruitment, in an orientation independent manner with no additional contributions provided by R7BP. These findings argue that the association of R7 RGS proteins with the membrane environment provides a major direct contribution to modulation of their GAP activity.

  18. Surface glycosylation of polymeric membranes

    Institute of Scientific and Technical Information of China (English)

    DAI ZhengWei; WAN LingShu; XU ZhiKang

    2008-01-01

    Surface glycosylation of polymeric membranes has been inspired by the structure of natural biomembranes. It refers to that glycosyl groups are introduced onto the membrane surface by various strategies, which combine the separation function of the membrane with the biological function of the saccharides in one system. In this review, progress in the surface glycosylation of polymeric membranes is highlighted in two aspects, i.e. the glycosylation methods and the potential applications of the surface-glycosylated membranes.

  19. Hydrostatic pressure decreases membrane fluidity and lipid desaturase expression in chondrocyte progenitor cells.

    Science.gov (United States)

    Montagne, Kevin; Uchiyama, Hiroki; Furukawa, Katsuko S; Ushida, Takashi

    2014-01-22

    Membrane biomechanical properties are critical in modulating nutrient and metabolite exchange as well as signal transduction. Biological membranes are predominantly composed of lipids, cholesterol and proteins, and their fluidity is tightly regulated by cholesterol and lipid desaturases. To determine whether such membrane fluidity regulation occurred in mammalian cells under pressure, we investigated the effects of pressure on membrane lipid order of mouse chondrogenic ATDC5 cells and desaturase gene expression. Hydrostatic pressure linearly increased membrane lipid packing and simultaneously repressed lipid desaturase gene expression. We also showed that cholesterol mimicked and cholesterol depletion reversed those effects, suggesting that desaturase gene expression was controlled by the membrane physical state itself. This study demonstrates a new effect of hydrostatic pressure on mammalian cells and may help to identify the molecular mechanisms involved in hydrostatic pressure sensing in chondrocytes.

  20. Suspension membrane reactor for biological elimination of non-degradable materials from mixed effluents. Final report; Suspensionsmembranreaktor zur biologischen Eliminierung schwer abbaubarer Stoffe aus Abwassergemischen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Raebiger, N.; Schierenbeck, A.

    2002-07-01

    An earlier research project had shown that a combined process involving membrane filtration and a bioreactor ensure substrate-specific times of residue inside the reactor, i.e. high selective conversation at low discharge rates. The second project aimed at higher flexibility. For this purpose, a two-stage suspension membrane reactor was developed in which the filtration stage and the bioreactor were decoupled. The liquid effluents are concentrated first in a nanofiltration stage, and the permeate, which should be free of non-degradable materials, is discharged. The concentrate is treated in the biological reaction stage and recirculated into the nanofiltration stage in order to ensure complete degradation during a substrate-specific time of residue. An intermediate microfiltration stage serves to retain biomass and prevent the growth of a biofilm in the nanofiltration stage. The method was tested with the practically relevant model pollutant 4-chlorophenol and a real industrial effluent from the antifelting stage of a Bremen woollen mill (Bremer Wollkaemmerei), with a high AOX concentration. [German] Im vorhergehenden Teil des Forschungsvorhabens konnte gezeigt werden, dass durch eine kombinierte Anwendung der Membranfiltration mit einem Bioreaktor eine substratspezifische Verweilzeitverteilung im Reaktor und damit eine hohe selektive Umsatzleistung bei gleichzeitig niedrigen Ablaufwerten realisierbar ist. Um eine groessere Flexibilitaet bei dem Einsatz verschiedener Membranmodule zu realisieren, wurde in dem zweiten Abschnitt des Forschungsvorhabens eine zweistufige Anlage vom Typ des Suspensions-Membranreaktors entwickelt, bei der Filtration und Bioreaktor entkoppelt werden. Das zu reinigende Abwasser wird zunaechst in einer Nanofiltrationsstufe aufkonzentriert, das moeglichst an schwer abbaubaren Stoffen freie Permeat bildet den Ablauf der Anlage. Der Konzentratstrom wird in der nachfolgenden Reaktionsstufe biologisch behandelt und in die Nanofiltrationsstufe

  1. Functional Genomic and Advanced Genetic Studies Reveal Novel Insights into the Metabolism, Regulation, and Biology of Haloferax volcanii

    Directory of Open Access Journals (Sweden)

    Jörg Soppa

    2011-01-01

    Full Text Available The genome sequence of Haloferax volcanii is available and several comparative genomic in silico studies were performed that yielded novel insight for example into protein export, RNA modifications, small non-coding RNAs, and ubiquitin-like Small Archaeal Modifier Proteins. The full range of functional genomic methods has been established and results from transcriptomic, proteomic and metabolomic studies are discussed. Notably, Hfx. volcanii is together with Halobacterium salinarum the only prokaryotic species for which a translatome analysis has been performed. The results revealed that the fraction of translationally-regulated genes in haloarchaea is as high as in eukaryotes. A highly efficient genetic system has been established that enables the application of libraries as well as the parallel generation of genomic deletion mutants. Facile mutant generation is complemented by the possibility to culture Hfx. volcanii in microtiter plates, allowing the phenotyping of mutant collections. Genetic approaches are currently used to study diverse biological questions–from replication to posttranslational modification—and selected results are discussed. Taken together, the wealth of functional genomic and genetic tools make Hfx. volcanii a bona fide archaeal model species, which has enabled the generation of important results in recent years and will most likely generate further breakthroughs in the future.

  2. Antioxidant pathways are up-regulated during biological nitrogen fixation to prevent ROS-induced nitrogenase inhibition in Gluconacetobacter diazotrophicus.

    Science.gov (United States)

    Alquéres, Sylvia M C; Oliveira, Jose Henrique M; Nogueira, Eduardo M; Guedes, Helma V; Oliveira, Pedro L; Câmara, Fernando; Baldani, Jose I; Martins, Orlando B

    2010-10-01

    Gluconacetobacter diazotrophicus, an endophyte isolated from sugarcane, is a strict aerobe that fixates N(2). This process is catalyzed by nitrogenase and requires copious amounts of ATP. Nitrogenase activity is extremely sensitive to inhibition by oxygen and reactive oxygen species (ROS). However, the elevated oxidative metabolic rates required to sustain biological nitrogen fixation (BNF) may favor an increased production of ROS. Here, we explored this paradox and observed that ROS levels are, in fact, decreased in nitrogen-fixing cells due to the up-regulation of transcript levels of six ROS-detoxifying genes. A cluster analyses based on common expression patterns revealed the existence of a stable cluster with 99.8% similarity made up of the genes encoding the α-subunit of nitrogenase Mo-Fe protein (nifD), superoxide dismutase (sodA) and catalase type E (katE). Finally, nitrogenase activity was inhibited in a dose-dependent manner by paraquat, a redox cycler that increases cellular ROS levels. Our data revealed that ROS can strongly inhibit nitrogenase activity, and G. diazotrophicus alters its redox metabolism during BNF by increasing antioxidant transcript levels resulting in a lower ROS generation. We suggest that careful controlled ROS production during this critical phase is an adaptive mechanism to allow nitrogen fixation.

  3. Biological Evaluation (In Vitro and In Vivo) of Bilayered Collagenous Coated (Nano Electrospun and Solid Wall) Chitosan Membrane for Periodontal Guided Bone Regeneration.

    Science.gov (United States)

    Lotfi, Ghogha; Shokrgozar, Mohammad Ali; Mofid, Rasoul; Abbas, Fatemeh Mashhadi; Ghanavati, Farzin; Baghban, Alireza Akbarzadeh; Yavari, Seyedeh Kimia; Pajoumshariati, Seyedramin

    2016-07-01

    The application of barrier membranes in guided bone regeneration (GBR) has become a commonly used surgical technique in periodontal research. The objectives of this study were to evaluate the in vitro biocompatibility and osteogenic differentiation of mesenchymal stem cells (MSCs) on two different collagenous coatings (nano electrospun fibrous vs. solid wall) of bilayered collagen/chitosan membrane and their histological evaluation on bone regeneration in rabbit calvarial defects. It was found that chitosan-nano electrospun collagen (CNC) membranes had higher proliferation/metabolic activity compared to the chitosan-collagen (CC) and pristine chitosan membranes. The qRT-PCR analysis demonstrated the CNC membranes induced significant expression of osteogenic genes (Osteocalcin, RUNX2 and Col-α1) in MSCs. Moreover, higher calcium content and alkaline phosphatase activity of MSCs were observed compared to the other groups. Histologic and histomorphometric evaluations were performed on the uncovered (negative control) as well as covered calvarial defects of ten adult white rabbits with different membranes (CNC, CC, BioGide (BG, positive control)) at 1 and 2 months after surgery. More bone formation was detected in the defects covered with CNC and BG membranes than those covered by CC and the negative control. No inflammation and residual biomaterial particles were observed on the membrane surface or in the surrounding tissues in the surgical areas. These results suggest that bilayer CNC membrane can have the potential for use as a GBR membrane material facilitating bone formation.

  4. Plasma membrane ATPases

    DEFF Research Database (Denmark)

    Palmgren, Michael Broberg; Bækgaard, Lone; Lopez Marques, Rosa Laura

    2011-01-01

    The plasma membrane separates the cellular contents from the surrounding environment. Nutrients must enter through the plasma membrane in order to reach the cell interior, and toxic metabolites and several ions leave the cell by traveling across the same barrier. Biological pumps in the plasma me...

  5. Agp2p, the plasma membrane transregulator of polyamine uptake, regulates the antifungal activities of the plant defensin NaD1 and other cationic peptides.

    Science.gov (United States)

    Bleackley, Mark R; Wiltshire, Jennifer L; Perrine-Walker, Francine; Vasa, Shaily; Burns, Rhiannon L; van der Weerden, Nicole L; Anderson, Marilyn A

    2014-05-01

    Cationic antifungal peptides (AFPs) act through a variety of mechanisms but share the common feature of interacting with the fungal cell surface. NaD1, a defensin from Nicotiana alata, has potent antifungal activity against a variety of fungi of both hyphal and yeast morphologies. The mechanism of action of NaD1 occurs via three steps: binding to the fungal cell surface, permeabilization of the plasma membrane, and internalization and interaction with intracellular targets to induce fungal cell death. The targets at each of these three stages have yet to be defined. In this study, the screening of a Saccharomyces cerevisiae deletion collection led to the identification of Agp2p as a regulator of the potency of NaD1. Agp2p is a plasma membrane protein that regulates the transport of polyamines and other molecules, many of which carry a positive charge. Cells lacking the agp2 gene were more resistant to NaD1, and this resistance was accompanied by a decreased uptake of defensin. Agp2p senses and regulates the uptake of the polyamine spermidine, and competitive inhibition of the antifungal activity of NaD1 by spermidine was observed in both S. cerevisiae and the plant pathogen Fusarium oxysporum. The resistance of agp2Δ cells to other cationic antifungal peptides and decreased binding of the cationic protein cytochrome c to agp2Δ cells compared to that of wild-type cells have led to a proposed mechanism of resistance whereby the deletion of agp2 leads to an increase in positively charged molecules at the cell surface that repels cationic antifungal peptides.

  6. Lithium transport across biological membranes

    DEFF Research Database (Denmark)

    Holstein-Rathlou, N H

    1990-01-01

    Li+ is actively transported out of cells, and across different epithelia of both mammalian and amphibian origin. Due to the low affinity of the Na+/K(+)-ATPase for Li+, the transport is most likely energized by exchange and/or cotransport processes. The detailed mechanism by which Li+ is reabsorb...

  7. Role of the Na+/K+-ATPase in regulating the membrane potential in rat peritoneal mast cells

    DEFF Research Database (Denmark)

    Friis, U G; Praetorius, Birger Hans; Knudsen, T;

    1997-01-01

    1. The aim of this study was to investigate the effect of the Na+/K+-ATPase on the membrane potential of peritoneal mast cells isolated from male Sprague-Dawley SPF-rats. 2. Experiments were performed at 22-26 degrees C in the tight-seal whole-cell configuration of the patch-clamp technique by use...... current (low-pass filtered at 500 Hz). 3. Na+/K+-ATPase activity was measured as the ouabain-sensitive change in the zero-current potential. The zero-current potential in rat peritoneal mast cells measured 2 min after obtaining whole-cell configuration amounted to 1.7 +/- 2.5 mV (n = 21). Ouabain (5 m......M), a Na+/K+-ATPase-inhibitor, had only a very minor effect upon the membrane potential under resting conditions (n = 3). 4. When mast cells were superfused with nominal calcium-free external solution, the cells hyperpolarized (delta mV: 20.2 +/- 3.8 mV (n = 5)). In addition, when the mast cells were...

  8. Membrane steroid-binding protein 1 (MSBP1) negatively regulates brassinosteroid signaling by enhancing the endocytosis of BAK1

    Institute of Scientific and Technical Information of China (English)

    Li Song; Qiu-Ming Shi; Xiao-Hua Yang; Zhi-Hong Xu; Hong-Wei Xue

    2009-01-01

    Brassinosteroids (BRs) are perceived by transmembrane receptors and play vital roles in plant growth and devel-opment, as well as cell in responses to environmental stimuli. The transmembrane receptor BRI1 can directly bind to brassinolide (BL), and BAK1 interacts with BRI1 to enhance the BRll-mediated BR signaling. Our previous studies indicated that a membrane steroid-binding protein 1 (MSBP1) could bind to BL in vitro and is negatively involved in BR signaling. To further elucidate the underlying mechanism, we here show that MSBP1 specifically interacts with the extracellular domain of BAKI in vivo in a BL-independent manner. Suppressed cell expansion and BR responses by increased expression of MSBPI can be recovered by overexpressing BAKI or its intracellular kinase domain, sug-gesting that MSBPI may suppress BR signaling through interacting with BAK1. Subcellular localization studies re-vealed that both MSBPI and BAKI are localized to plasma membrane and endocytic vesicles and MSBPI accelerates BAKI endocytosis, which results in suppressed BR signaling by shifting the equilibrium of BAKI toward endosomes. Indeed, enhanced MSBPI expression reduces the interaction between BRI1 and BAK1 in vivo, demonstrating that MSBPI acts as a negative factor at an early step of the BR signaling pathway.

  9. Regulation of Smoothened Phosphorylation and High-Level Hedgehog Signaling Activity by a Plasma Membrane Associated Kinase.

    Directory of Open Access Journals (Sweden)

    Shuangxi Li

    2016-06-01

    Full Text Available Hedgehog (Hh signaling controls embryonic development and adult tissue homeostasis through the G protein coupled receptor (GPCR-family protein Smoothened (Smo. Upon stimulation, Smo accumulates on the cell surface in Drosophila or primary cilia in vertebrates, which is thought to be essential for its activation and function, but the underlying mechanisms remain poorly understood. Here we show that Hh stimulates the binding of Smo to a plasma membrane-associated kinase Gilgamesh (Gish/CK1γ and that Gish fine-tunes Hh pathway activity by phosphorylating a Ser/Thr cluster (CL-II in the juxtamembrane region of Smo carboxyl-terminal intracellular tail (C-tail. We find that CL-II phosphorylation is promoted by protein kinase A (PKA-mediated phosphorylation of Smo C-tail and depends on cell surface localization of both Gish and Smo. Consistent with CL-II being critical for high-threshold Hh target gene expression, its phosphorylation appears to require higher levels of Hh or longer exposure to the same level of Hh than PKA-site phosphorylation on Smo. Furthermore, we find that vertebrate CK1γ is localized at the primary cilium to promote Smo phosphorylation and Sonic hedgehog (Shh pathway activation. Our study reveals a conserved mechanism whereby Hh induces a change in Smo subcellular localization to promote its association with and activation by a plasma membrane localized kinase, and provides new insight into how Hh morphogen progressively activates Smo.

  10. Regulation of Smoothened Phosphorylation and High-Level Hedgehog Signaling Activity by a Plasma Membrane Associated Kinase.

    Science.gov (United States)

    Li, Shuangxi; Li, Shuang; Han, Yuhong; Tong, Chao; Wang, Bing; Chen, Yongbin; Jiang, Jin

    2016-06-01

    Hedgehog (Hh) signaling controls embryonic development and adult tissue homeostasis through the G protein coupled receptor (GPCR)-family protein Smoothened (Smo). Upon stimulation, Smo accumulates on the cell surface in Drosophila or primary cilia in vertebrates, which is thought to be essential for its activation and function, but the underlying mechanisms remain poorly understood. Here we show that Hh stimulates the binding of Smo to a plasma membrane-associated kinase Gilgamesh (Gish)/CK1γ and that Gish fine-tunes Hh pathway activity by phosphorylating a Ser/Thr cluster (CL-II) in the juxtamembrane region of Smo carboxyl-terminal intracellular tail (C-tail). We find that CL-II phosphorylation is promoted by protein kinase A (PKA)-mediated phosphorylation of Smo C-tail and depends on cell surface localization of both Gish and Smo. Consistent with CL-II being critical for high-threshold Hh target gene expression, its phosphorylation appears to require higher levels of Hh or longer exposure to the same level of Hh than PKA-site phosphorylation on Smo. Furthermore, we find that vertebrate CK1γ is localized at the primary cilium to promote Smo phosphorylation and Sonic hedgehog (Shh) pathway activation. Our study reveals a conserved mechanism whereby Hh induces a change in Smo subcellular localization to promote its association with and activation by a plasma membrane localized kinase, and provides new insight into how Hh morphogen progressively activates Smo.

  11. [The inversion of concepts about biological role of system rennin-angiotensin II- aldosterone and functions of arterial tension as a metabolism regulator].

    Science.gov (United States)

    Titov, V N

    2015-02-01

    The phylogenetic theory of general pathology postulates that in physiology and pathology the concepts of biological role of arterial tension had been subjected to inversion. The activation by nephron of synthesis of components rennin-angiotensin II and increasing of aldosterone secretion are directed not to increase arterial tension but to preserve volume of piece of third world ocean privatized by each entity as pool of intercellular medium where all cells continue to live as billions years before. In phylogenetic sense, early organs can't regulate effect of physical factor of regulation of metabolism the late one in phylogenesis of arterial tension. The cause of increasing of arterial tension is the vasomotor center but not the kidneys. The vasomotor center increases arterial tension in the proximal section and further hydrodynamic tension in the distal section of arterial stream and tends to resuscitate function of nephrons, biological function of endoecology and biological reaction of excretion. The arterial tension, besides the main role in biological function of locomotion, is a physical factor of compensation of disorders of biological functions of homeostasis, trophology, endoecology and adaptation. In phylogenesis, three levels of metabolism regulation has been developed The specific regulation of biochemical reactions occurs on autocrine level. In paracrin regulated cell cenosises, at distal section of arterial stream, metabolism is regulated by billions of local peristaltic pumps through compensation of biological reaction of endothelium-depended vasodilatation, micro-circulation, effect of humoral mediators and hormonal principles. In vivo, from the level of vasomotor center, metabolism non-specifically and systemic regulates physical factor-arterial tension through sympathetic activation of heart. The arterial tension in proximal section of arterial stream overcomes resistance and physically "forces through" arterioles with disordered micro

  12. Inverting Notions of the Biological Role of the Renin → Angiotensin-II → Aldosterone System and the Function of Arterial Pressure as a Metabolism Regulator

    Directory of Open Access Journals (Sweden)

    Vladimir N. Titov

    2014-09-01

    Full Text Available The phylogenetic theory of general pathology postulates that notions of the biological role of arterial pressure (AP in physiology and pathology have been subjected to inversion. The nephron’s activation of the synthesis of the components renin → angiotensin-II (A-II and the augmentation of aldosterone secretion are directed not at an increase in AP but at preserving the volume of the piece of the third world ocean, privatized by each species, - the pool of the intercellular milieu in which, just like millions of years before, there continue to live all cells. Phylogenetically earlier organs cannot regulate the action of a later one in AP phylogenesis – a physical factor in metabolism regulation. It is not the kidneys that increase AP but the vasomotor center, which, increasing AP in the proximal segment and further hydrodynamic pressure in the distal segment of the arterial bed, seeks to reanimate the function of nephrons, the biological function of endoecology and the biological reaction of excretion. In addition to playing a major role in the biological function of locomotion, AP is a physical factor in compensating for impairments in the biological functions of homeostasis, trophology, endoecology, and adaptation. There have formed sequentially three levels of metabolic regulation in phylogenesis. At an autocrine level, there occurs a specific regulation of biochemical reactions. Within paracrinally regulated communities of cells, in the distal segment of the arterial bed, metabolism is regulated by millions of local peristaltic pumps through compensating for the biological reaction of endothelium-dependent vasodilation, microcirculation, and the action of humoral mediators and hormonal principles. In vivo from the level of the vasomotor center metabolism is non-specifically, systemically regulated by the physical factor – AP – through sympathetic activation of the heart; in the proximal segment of the arterial bed and the distal

  13. Voltage-dependent regulation of CaV2.2 channels by Gq-coupled receptor is facilitated by membrane-localized β subunit.

    Science.gov (United States)

    Keum, Dongil; Baek, Christina; Kim, Dong-Il; Kweon, Hae-Jin; Suh, Byung-Chang

    2014-10-01

    G protein-coupled receptors (GPCRs) signal through molecular messengers, such as Gβγ, Ca(2+), and phosphatidylinositol 4,5-bisphosphate (PIP2), to modulate N-type voltage-gated Ca(2+) (CaV2.2) channels, playing a crucial role in regulating synaptic transmission. However, the cellular pathways through which GqPCRs inhibit CaV2.2 channel current are not completely understood. Here, we report that the location of CaV β subunits is key to determining the voltage dependence of CaV2.2 channel modulation by GqPCRs. Application of the muscarinic agonist oxotremorine-M to tsA-201 cells expressing M1 receptors, together with CaV N-type α1B, α2δ1, and membrane-localized β2a subunits, shifted the current-voltage relationship for CaV2.2 activation 5 mV to the right and slowed current activation. Muscarinic suppression of CaV2.2 activity was relieved by strong depolarizing prepulses. Moreover, when the C terminus of β-adrenergic receptor kinase (which binds Gβγ) was coexpressed with N-type channels, inhibition of CaV2.2 current after M1 receptor activation was markedly reduced and delayed, whereas the delay between PIP2 hydrolysis and inhibition of CaV2.2 current was decreased. When the Gβγ-insensitive CaV2.2 α1C-1B chimera was expressed, voltage-dependent inhibition of calcium current was virtually abolished, suggesting that M1 receptors act through Gβγ to inhibit CaV2.2 channels bearing membrane-localized CaV β2a subunits. Expression of cytosolic β subunits such as β2b and β3, as well as the palmitoylation-negative mutant β2a(C3,4S), reduced the voltage dependence of M1 muscarinic inhibition of CaV2.2 channels, whereas it increased inhibition mediated by PIP2 depletion. Together, our results indicate that, with membrane-localized CaV β subunits, CaV2.2 channels are subject to Gβγ-mediated voltage-dependent inhibition, whereas cytosol-localized β subunits confer more effective PIP2-mediated voltage-independent regulation. Thus, the voltage dependence of

  14. 嗅球结构及其对生物节律的调控%Structure and regulation of biological rhythms of olfactory bulb

    Institute of Scientific and Technical Information of China (English)

    徐兴远; 王毅群

    2011-01-01

    Olfactory bulb is a key component of olfaction. Recent researches have found that olfactory bulb regulates the biological rhythms, and it expresses regulatory genes relatively independent of suprachiasmatic nucleus. Based on the research of the structure and regulation of biological rhythms of olfactory bulb, it has become a new focus in basic and clinical medicineto study some nervous system diseases and biological rhythms such as sleep. This article summarizes the structure and the effect on regulating biological rhythms of olfactory bulb.%嗅球是人体控制嗅觉的关键部位.近年来研究发现,嗅球还参与了生物节律的调控,其相对独立于视交叉上核表达节律调控基因.基于嗅球与脑内的神经联系以及其对生物节律调控的作用,深入研究一些神经系统疾病和睡眠等人体自身节律可能会成为基础和临床医学研究的新热点.本文将介绍嗅球的结构,并对其参与调控生物节律的功能进行分析总结.

  15. Assessing the nature of lipid raft membranes.

    Directory of Open Access Journals (Sweden)

    Perttu S Niemelä

    2007-02-01

    Full Text Available The paradigm of biological membranes has recently gone through a major update. Instead of being fluid and homogeneous, recent studies suggest that membranes are characterized by transient domains with varying fluidity. In particular, a number of experimental studies have revealed the existence of highly ordered lateral domains rich in sphingomyelin and cholesterol (CHOL. These domains, called functional lipid rafts, have been suggested to take part in a variety of dynamic cellular processes such as membrane trafficking, signal transduction, and regulation of the activity of membrane proteins. However, despite the proposed importance of these domains, their properties, and even the precise nature of the lipid phases, have remained open issues mainly because the associated short time and length scales have posed a major challenge to experiments. In this work, we employ extensive atom-scale simulations to elucidate the properties of ternary raft mixtures with CHOL, palmitoylsphingomyelin (PSM, and palmitoyloleoylphosphatidylcholine. We simulate two bilayers of 1,024 lipids for 100 ns in the liquid-ordered phase and one system of the same size in the liquid-disordered phase. The studies provide evidence that the presence of PSM and CHOL in raft-like membranes leads to strongly packed and rigid bilayers. We also find that the simulated raft bilayers are characterized by nanoscale lateral heterogeneity, though the slow lateral diffusion renders the interpretation of the observed lateral heterogeneity more difficult. The findings reveal aspects of the role of favored (specific lipid-lipid interactions within rafts and clarify the prominent role of CHOL in altering the properties of the membrane locally in its neighborhood. Also, we show that the presence of PSM and CHOL in rafts leads to intriguing lateral pressure profiles that are distinctly different from corresponding profiles in nonraft-like membranes. The results propose that the functioning of

  16. Spatiotemporal Organization of Spin-Coated Supported Model Membranes

    Science.gov (United States)

    Simonsen, Adam Cohen

    biomembranes is randomly organized to facilitate membrane function. However, during the last 10-20 years it has become increasingly clear that the components of biomembranes are not randomly organized but that the lateral distribution is heterogeneous and time dependent. A picture is emerging where the interactions among membrane components and between membranes and external structures give rise to dynamically maintained domains with distinct sizes and compositions. Such domains are coupled to membrane function through their regulation of membrane-bound proteins. Experimentally, the investigation of domain structures in artificial and natural membranes have been enhanced by the proposition of the so-called raft hypothesis [5-7]. According to this hypothesis, rafts are nanoscale regions of biological membranes that are linked to important cellular processes and signaling pathways [8,9]. Rafts originated as insoluble membrane fragments upon treatment of cellular membranes with cold detergent [10].

  17. [Participation of proteinkinase CK2 in regulation of human erythrocytes plasma membrane redox system activity: relative contribution of ca(2+)-dependent and ca(2+)-independent mechanisms of its activation].

    Science.gov (United States)

    Iakovenko, I N; Zhirnov, V V; Kozachenko, O P; Shablykin, O V; Brovarets', V S

    2012-01-01

    Involvement of protein kinase CK2 (2.7.11.1) in modulation of live cells trans-plasma membrane electron transport was first discovered. Using human erythrocytes a decrease of plasma membrane redox system (PMRS) activity is shown under the action of specific protein kinase CK2 inhibitors. Using inhibitory analysis the activity regulation of human erythrocytes PMRS by Ca(2+)-dependent and Ca(2+)-independent mechanisms were investigated. It was shown that functional Ca(2+)-antagonists (nitrendipine and calmidazolium) significantly increased, and functional Ca(2+)-agonists to some extent reduced or did not affect the trans-plasma membrane electron transport in these cells.

  18. Coronavirus membrane-associated papain-like proteases induce autophagy through interacting with Beclin1 to negatively regulate antiviral innate immunity.

    Science.gov (United States)

    Chen, Xiaojuan; Wang, Kai; Xing, Yaling; Tu, Jian; Yang, Xingxing; Zhao, Qian; Li, Kui; Chen, Zhongbin

    2014-12-01

    Autophagy plays important roles in modulating viral replication and antiviral immune response. Coronavirus infection is associated with the autophagic process, however, little is known about the mechanisms of autophagy induction and its contribution to coronavirus regulation of host innate responses. Here, we show that the membrane-associated papain-like protease PLP2 (PLP2-TM) of coronaviruses acts as a novel autophagy-inducing protein. Intriguingly, PLP2-TM induces incomplete autophagy process by increasing the accumulation of autophagosomes but blocking the fusion of autophagosomes with lysosomes. Furthermore, PLP2-TM interacts with the key autophagy regulators, LC3 and Beclin1, and promotes Beclin1 interaction with STING, the key regulator for antiviral IFN signaling. Finally, knockdown of Beclin1 partially reverses PLP2-TM's inhibitory effect on innate immunity which resulting in decreased coronavirus replication. These results suggested that coronavirus papain-like protease induces incomplete autophagy by interacting with Beclin1, which in turn modulates coronavirus replication and antiviral innate immunity.

  19. A Bioinformatics Analysis Reveals a Group of MocR Bacterial Transcriptional Regulators Linked to a Family of Genes Coding for Membrane Proteins

    Directory of Open Access Journals (Sweden)

    Teresa Milano

    2016-01-01

    Full Text Available The MocR bacterial transcriptional regulators are characterized by an N-terminal domain, 60 residues long on average, possessing the winged-helix-turn-helix (wHTH architecture responsible for DNA recognition and binding, linked to a large C-terminal domain (350 residues on average that is homologous to fold type-I pyridoxal 5′-phosphate (PLP dependent enzymes like aspartate aminotransferase (AAT. These regulators are involved in the expression of genes taking part in several metabolic pathways directly or indirectly connected to PLP chemistry, many of which are still uncharacterized. A bioinformatics analysis is here reported that studied the features of a distinct group of MocR regulators predicted to be functionally linked to a family of homologous genes coding for integral membrane proteins of unknown function. This group occurs mainly in the Actinobacteria and Gammaproteobacteria phyla. An analysis of the multiple sequence alignments of their wHTH and AAT domains suggested the presence of specificity-determining positions (SDPs. Mapping of SDPs onto a homology model of the AAT domain hinted at possible structural/functional roles in effector recognition. Likewise, SDPs in wHTH domain suggested the basis of specificity of Transcription Factor Binding Site recognition. The results reported represent a framework for rational design of experiments and for bioinformatics analysis of other MocR subgroups.

  20. A Bioinformatics Analysis Reveals a Group of MocR Bacterial Transcriptional Regulators Linked to a Family of Genes Coding for Membrane Proteins

    Science.gov (United States)

    Milano, Teresa

    2016-01-01

    The MocR bacterial transcriptional regulators are characterized by an N-terminal domain, 60 residues long on average, possessing the winged-helix-turn-helix (wHTH) architecture responsible for DNA recognition and binding, linked to a large C-terminal domain (350 residues on average) that is homologous to fold type-I pyridoxal 5′-phosphate (PLP) dependent enzymes like aspartate aminotransferase (AAT). These regulators are involved in the expression of genes taking part in several metabolic pathways directly or indirectly connected to PLP chemistry, many of which are still uncharacterized. A bioinformatics analysis is here reported that studied the features of a distinct group of MocR regulators predicted to be functionally linked to a family of homologous genes coding for integral membrane proteins of unknown function. This group occurs mainly in the Actinobacteria and Gammaproteobacteria phyla. An analysis of the multiple sequence alignments of their wHTH and AAT domains suggested the presence of specificity-determining positions (SDPs). Mapping of SDPs onto a homology model of the AAT domain hinted at possible structural/functional roles in effector recognition. Likewise, SDPs in wHTH domain suggested the basis of specificity of Transcription Factor Binding Site recognition. The results reported represent a framework for rational design of experiments and for bioinformatics analysis of other MocR subgroups. PMID:27446613

  1. A system biology approach highlights a hormonal enhancer effect on regulation of genes in a nitrate responsive "biomodule"

    Directory of Open Access Journals (Sweden)

    Nero Damion

    2009-06-01

    Full Text Available Abstract Background Nitrate-induced reprogramming of the transcriptome has recently been shown to be highly context dependent. Herein, a systems biology approach was developed to identify the components and role of cross-talk between nitrate and hormone signals, likely to be involved in the conditional response of NO3- signaling. Results Biclustering was used to identify a set of genes that are N-responsive across a range of Nitrogen (N-treatment backgrounds (i.e. nitrogen treatments under different growth conditions using a meta-dataset of 76 Affymetrix ATH1 chips from 5 different laboratories. Twenty-one biclusters were found to be N-responsive across subsets of this meta-dataset. N-bicluster 9 (126 genes was selected for further analysis, as it was shown to be reproducibly responsive to NO3- as a signal, across a wide-variety of background conditions and datasets. N-bicluster 9 genes were then used as "seed" to identify putative cross-talk mechanisms between nitrate and hormone signaling. For this, the 126 nitrate-regulated genes in N-bicluster 9 were biclustered over a meta-dataset of 278 ATH1 chips spanning a variety of hormone treatments. This analysis divided the bicluster 9 genes into two classes: i genes controlled by NO3- only vs. ii genes controlled by both NO3- and hormones. The genes in the latter group showed a NO3- response that is significantly enhanced, compared to the former. In silico analysis identified two Cis-Regulatory Elements candidates (CRE (E2F, HSE potentially involved the interplay between NO3- and hormonal signals. Conclusion This systems analysis enabled us to derive a hypothesis in which hormone signals are proposed to enhance the nitrate response, providing a potential mechanistic explanation for the link between nitrate signaling and the control of plant development.

  2. Microcompartments within the yeast plasma membrane.

    Science.gov (United States)

    Merzendorfer, Hans; Heinisch, Jürgen J