Actin-interacting Protein 1 Promotes Disassembly of Actin-depolymerizing Factor/Cofilin-bound Actin Filaments in a pH-dependent Manner.

Science.gov (United States)

Nomura, Kazumi; Hayakawa, Kimihide; Tatsumi, Hitoshi; Ono, Shoichiro

2016-03-04

Actin-interacting protein 1 (AIP1) is a conserved WD repeat protein that promotes disassembly of actin filaments when actin-depolymerizing factor (ADF)/cofilin is present. Although AIP1 is known to be essential for a number of cellular events involving dynamic rearrangement of the actin cytoskeleton, the regulatory mechanism of the function of AIP1 is unknown. In this study, we report that two AIP1 isoforms from the nematode Caenorhabditis elegans, known as UNC-78 and AIPL-1, are pH-sensitive in enhancement of actin filament disassembly. Both AIP1 isoforms only weakly enhance disassembly of ADF/cofilin-bound actin filaments at an acidic pH but show stronger disassembly activity at neutral and basic pH values. However, a severing-defective mutant of UNC-78 shows pH-insensitive binding to ADF/cofilin-decorated actin filaments, suggesting that the process of filament severing or disassembly, but not filament binding, is pH-dependent. His-60 of AIP1 is located near the predicted binding surface for the ADF/cofilin-actin complex, and an H60K mutation of AIP1 partially impairs its pH sensitivity, suggesting that His-60 is involved in the pH sensor for AIP1. These biochemical results suggest that pH-dependent changes in AIP1 activity might be a novel regulatory mechanism of actin filament dynamics. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

The actinome of Dictyostelium discoideum in comparison to actins and actin-related proteins from other organisms.

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Jayabalan M Joseph

Full Text Available Actin belongs to the most abundant proteins in eukaryotic cells which harbor usually many conventional actin isoforms as well as actin-related proteins (Arps. To get an overview over the sometimes confusing multitude of actins and Arps, we analyzed the Dictyostelium discoideum actinome in detail and compared it with the genomes from other model organisms. The D. discoideum actinome comprises 41 actins and actin-related proteins. The genome contains 17 actin genes which most likely arose from consecutive gene duplications, are all active, in some cases developmentally regulated and coding for identical proteins (Act8-group. According to published data, the actin fraction in a D. discoideum cell consists of more than 95% of these Act8-type proteins. The other 16 actin isoforms contain a conventional actin motif profile as well but differ in their protein sequences. Seven actin genes are potential pseudogenes. A homology search of the human genome using the most typical D. discoideum actin (Act8 as query sequence finds the major actin isoforms such as cytoplasmic beta-actin as best hit. This suggests that the Act8-group represents a nearly perfect actin throughout evolution. Interestingly, limited data from D. fasciculatum, a more ancient member among the social amoebae, show different relationships between conventional actins. The Act8-type isoform is most conserved throughout evolution. Modeling of the putative structures suggests that the majority of the actin-related proteins is functionally unrelated to canonical actin. The data suggest that the other actin variants are not necessary for the cytoskeleton itself but rather regulators of its dynamical features or subunits in larger protein complexes.

Separation of actin-dependent and actin-independent lipid rafts

NARCIS (Netherlands)

Klappe, Karin; Hummel, Ina; Kok, Jan Willem

2013-01-01

Lipid rafts have been isolated on the basis of their resistance to various detergents and more recently by using detergent-free procedures. The actin cytoskeleton is now recognized as a dynamic regulator of lipid raft stability. We carefully analyzed the effects of the cortical actin-disrupting

Computational Study of the Binding Mechanism of Actin-Depolymerizing Factor 1 with Actin in Arabidopsis thaliana.

Directory of Open Access Journals (Sweden)

Juan Du

Full Text Available Actin is a highly conserved protein. It plays important roles in cellular function and exists either in the monomeric (G-actin or polymeric form (F-actin. Members of the actin-depolymerizing factor (ADF/cofilin protein family bind to both G-actin and F-actin and play vital roles in actin dynamics by manipulating the rates of filament polymerization and depolymerization. It has been reported that the S6D and R98A/K100A mutants of actin-depolymerizing factor 1 (ADF1 in Arabidopsis thaliana decreased the binding affinity of ADF for the actin monomer. To investigate the binding mechanism and dynamic behavior of the ADF1-actin complex, we constructed a homology model of the AtADF1-actin complex based on the crystal structure of AtADF1 and the twinfilin C-terminal ADF-H domain in a complex with a mouse actin monomer. The model was then refined for subsequent molecular dynamics simulations. Increased binding energy of the mutated system was observed using the Molecular Mechanics Generalized Born Surface Area and Poisson-Boltzmann Surface Area (MM-GB/PBSA methods. To determine the residues that make decisive contributions to the ADF1 actin-binding affinity, per-residue decomposition and computational alanine scanning analyses were performed, which provided more detailed information on the binding mechanism. Root-mean-square fluctuation and principal component analyses confirmed that the S6D and R98A/K100A mutants induced an increased conformational flexibility. The comprehensive molecular insight gained from this study is of great importance for understanding the binding mechanism of ADF1 and G-actin.

Effects of F/G-actin ratio and actin turn-over rate on NADPH oxidase activity in microglia

DEFF Research Database (Denmark)

Rasmussen, Izabela; Pedersen, Line Hjortshøj; Byg, Luise

2010-01-01

Most in vivo studies that have addressed the role of actin dynamics in NADPH oxidase function in phagocytes have used toxins to modulate the polymerization state of actin and mostly effects on actin has been evaluated by end point measurements of filamentous actin, which says little about actin d...... dynamics, and without consideration for the subcellular distribution of the perturbed actin cytoskeleton....

A new F-actin structure in fungi: actin ring formation around the cell nucleus of Cryptococcus neoformans.

Science.gov (United States)

Kopecká, Marie; Kawamoto, Susumu; Yamaguchi, Masashi

2013-04-01

The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as 'funicular cabin' for the cell nucleus, and actin cables as intracellular 'funicular' suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.

Superficial chemical peeling with salicylic acid in facial dermatoses

International Nuclear Information System (INIS)

Bari, A.U.; Iqbal, Z.; Rahman, S.B.

2007-01-01

To determine the effectiveness of salicylic acid chemical peeling in common dermatological conditions affecting face in people with predominant Fitzpatrick skin type IV and V. A total of 167 patients of either gender, aged between 13 to 60 years, having some facial dermatoses (melasma, acne vulgaris, postinflammatory hyperpigmentations, freckles, fine lines and wrinkles, post-inflammatory scars, actinic keratoses, and plane facial warts) were included. A series of eight weekly hospital based peeling sessions was conducted in all patients under standardized conditions with 30% salicylic acid. Clinical improvement in different disorders was evaluated by change in MASI score, decrease in the size of affected area and % reduction in lesions count. McNemar test was applied for data analysis. Majority of the patients showed moderate to excellent response. There was 35% to 63% improvement (p< 0.05) in all dermatoses. Significant side effects, as feared in Asian skins were not observed. Chemical peeling with salicylic acid is an effective and safe treatment modality in many superficial facial dermatoses. (author)

Disease: H01404 [KEGG MEDICUS

Lifescience Database Archive (English)

Full Text Available H01404 Punctate palmoplantar keratoderma (PPKP), including: Brauer-Buschke-Fischer disease; Porokeratosis...ypes; PPKP1 (Brauer-Buschke-Fischer disease), PPKP2 (porokeratosis punctata palmaris et plantaris), and PPKP

Actin filaments as tension sensors.

Science.gov (United States)

Galkin, Vitold E; Orlova, Albina; Egelman, Edward H

2012-02-07

The field of mechanobiology has witnessed an explosive growth over the past several years as interest has greatly increased in understanding how mechanical forces are transduced by cells and how cells migrate, adhere and generate traction. Actin, a highly abundant and anomalously conserved protein, plays a large role in forming the dynamic cytoskeleton that is so essential for cell form, motility and mechanosensitivity. While the actin filament (F-actin) has been viewed as dynamic in terms of polymerization and depolymerization, new results suggest that F-actin itself may function as a highly dynamic tension sensor. This property may help explain the unusual conservation of actin's sequence, as well as shed further light on actin's essential role in structures from sarcomeres to stress fibers. Copyright © 2012 Elsevier Ltd. All rights reserved.

Actinic keratosis

DEFF Research Database (Denmark)

Erlendsson, Andrés M; Egekvist, Henrik; Lorentzen, Henrik F.

2016-01-01

Objectives: The incidence of actinic keratosis (AK) is increasing, and several treatment options are available. The aim of this study was to describe clinical characteristics and treatment patterns in patients with AK treated by Danish dermatologists. Methods: A multicenter, non-interventional, c......Objectives: The incidence of actinic keratosis (AK) is increasing, and several treatment options are available. The aim of this study was to describe clinical characteristics and treatment patterns in patients with AK treated by Danish dermatologists. Methods: A multicenter, non...... and currently suspected in 9.4% of AK-affected anatomical regions. Lesions of AK were located primarily on the face (38.6%), scalp (12.8%), and hands (11.2%). Actinic keratosis commonly presented with multiple AK lesions (38.6%) and field cancerization (38.5%). The treatments used most frequently were...

Polycation induced actin bundles

OpenAIRE

Muhlrad, Andras; Grintsevich, Elena E.; Reisler, Emil

2011-01-01

Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations an...

Geometrical Determinants of Neuronal Actin Waves.

Science.gov (United States)

Tomba, Caterina; Braïni, Céline; Bugnicourt, Ghislain; Cohen, Floriane; Friedrich, Benjamin M; Gov, Nir S; Villard, Catherine

2017-01-01

Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time between the production of consecutive actin waves, or mean inter-wave interval (IWI), was identified. It scales with the neurite width, and more precisely with the width of the proximal segment close to the soma. In addition, the IWI is independent of the total number of neurites. These two results suggest a mechanistic model of actin wave production, by which the material conveyed by actin waves is assembled in the soma until it reaches the threshold leading to the initiation and propagation of a new actin wave. Based on these observations, we formulate a predictive theoretical description of actin wave-driven neuronal growth and polarization, which consistently accounts for different sets of experiments.

Tailor-made ezrin actin binding domain to probe its interaction with actin in-vitro.

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Rohini Shrivastava

Full Text Available Ezrin, a member of the ERM (Ezrin/Radixin/Moesin protein family, is an Actin-plasma membrane linker protein mediating cellular integrity and function. In-vivo study of such interactions is a complex task due to the presence of a large number of endogenous binding partners for both Ezrin and Actin. Further, C-terminal actin binding capacity of the full length Ezrin is naturally shielded by its N-terminal, and only rendered active in the presence of Phosphatidylinositol bisphosphate (PIP2 or phosphorylation at the C-terminal threonine. Here, we demonstrate a strategy for the design, expression and purification of constructs, combining the Ezrin C-terminal actin binding domain, with functional elements such as fusion tags and fluorescence tags to facilitate purification and fluorescence microscopy based studies. For the first time, internal His tag was employed for purification of Ezrin actin binding domain based on in-silico modeling. The functionality (Ezrin-actin interaction of these constructs was successfully demonstrated by using Total Internal Reflection Fluorescence Microscopy. This design can be extended to other members of the ERM family as well.

Adhesive F-actin Waves: A Novel Integrin-Mediated Adhesion Complex Coupled to Ventral Actin Polymerization

OpenAIRE

Case, Lindsay B.; Waterman, Clare M.

2011-01-01

At the leading lamellipodium of migrating cells, protrusion of an Arp2/3-nucleated actin network is coupled to formation of integrin-based adhesions, suggesting that Arp2/3-mediated actin polymerization and integrin-dependent adhesion may be mechanistically linked. Arp2/3 also mediates actin polymerization in structures distinct from the lamellipodium, in "ventral F-actin waves" that propagate as spots and wavefronts along the ventral plasma membrane. Here we show that integrins engage the ex...

Actinic keratosis among seafarers.

Science.gov (United States)

Oldenburg, M; Kuechmeister, B; Ohnemus, U; Baur, X; Moll, I

2013-11-01

The aim of this study was to assess the prevalence of UV-induced actinic keratosis and further skin lesions. A newly developed questionnaire about lifetime UV radiation exposure was completed by 514 seafarers. An experienced dermatologist inspected the whole-body skin status of all participants. The questionnaire revealed a pre-employment UV radiation exposure in 104 seafarers, sunbed use in 26 subjects and a median work-related UV radiation exposure at sea of 20 years. The diagnosis of actinic keratoses was made in 94 seafarers and the clinical diagnosis of skin cancers in 48 seafarers (28 basal cell carcinoma, 11 squamous cell carcinoma, 9 malignant melanoma). After age standardisation according to a European reference population, the male European seafarers in this study had a 1.80-fold increased risk of actinic keratosis. Actinic keratoses [OR 1.03 (1.01-1.05)] and squamous cell carcinoma [OR 1.07 (1.01-1.13)] were related to the duration of seafaring time in years. A significant association was also found between actinic keratosis/squamous cell carcinoma and sunlight exposure during home leave [OR 1.67 (1.03-2.81) and OR 6.19 (1.18-32.40)]. Furthermore, the engine room personnel-especially the technical officers-were at higher risk of developing actinic keratosis. Due to the high prevalence of actinic keratosis especially among older seafarers with fair skin, with longer duration of seafaring employment at sea and with higher UV exposure during home leave, more intensive advice should be given on sun protection both at sea and ashore.

Green fluorescent protein-mtalin causes defects in actin organization and cell expansion in Arabidopsis and inhibits actin depolymerizing factor's actin depolymerizing activity in vitro

NARCIS (Netherlands)

Ketelaar, T.; Anthony, R.G.; Hussey, P.J.

2004-01-01

Expression of green fluorescent protein (GFP) linked to an actin binding domain is a commonly used method for live cell imaging of the actin cytoskeleton. One of these chimeric proteins is GFP-mTalin (GFP fused to the actin binding domain of mouse talin). Although it has been demonstrated that

Bacterial Actins.

Science.gov (United States)

Izoré, Thierry; van den Ent, Fusinita

2017-01-01

A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell. FtsA is widespread across bacteria and it is one of the earliest components of the divisome to arrive at midcell, where it anchors the cell division machinery to the membrane. FtsA binds directly to FtsZ filaments and to the membrane through its C-terminus. FtsA shows altered domain architecture when compared to the canonical actin fold. FtsA's subdomain 1C replaces subdomain 1B of other members of the actin family and is located on the opposite side of the molecule. Nevertheless, when FtsA assembles into protofilaments, the protofilament structure is preserved, as subdomain 1C replaces subdomain IB of the following subunit in a canonical actin filament. MreB has an essential role in shape-maintenance of most rod-shaped bacteria. Unusually, MreB filaments assemble from two protofilaments in a flat and antiparallel arrangement. This non-polar architecture implies that both MreB filament ends are structurally identical. MreB filaments bind directly to membranes where they interact with both cytosolic and membrane proteins, thereby forming a key component of the elongasome. MreB filaments in cells are short and dynamic, moving around the long axis of rod-shaped cells, sensing curvature of the membrane and being implicated in peptidoglycan synthesis.

Dendritic Actin Cytoskeleton: Structure, Functions, and Regulations

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Anja Konietzny

2017-05-01

Full Text Available Actin is a versatile and ubiquitous cytoskeletal protein that plays a major role in both the establishment and the maintenance of neuronal polarity. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin that can be readily visualized using electron- and fluorescence microscopy. With the development of super-resolution microscopy in the past few years, previously unknown structures of the actin cytoskeleton have been uncovered: a periodic lattice consisting of actin and spectrin seems to pervade not only the whole axon, but also dendrites and even the necks of dendritic spines. Apart from that striking feature, patches of F-actin and deep actin filament bundles have been described along the lengths of neurites. So far, research has been focused on the specific roles of actin in the axon, while it is becoming more and more apparent that in the dendrite, actin is not only confined to dendritic spines, but serves many additional and important functions. In this review, we focus on recent developments regarding the role of actin in dendrite morphology, the regulation of actin dynamics by internal and external factors, and the role of F-actin in dendritic protein trafficking.

Superficial basal cell carcinoma: A comparison of superficial only subtype with superficial combined with other subtypes by age, sex and anatomic site in 3150 cases.

Science.gov (United States)

Pyne, John H; Myint, Esther; Barr, Elizabeth M; Clark, Simon P; David, Michael; Na, Renua; Hou, Ruihang

2017-08-01

Basal cell carcinoma (BCC) may present as superficial subtype alone (sBCC) or superficial combined with other subtypes. The objective of this study was to compare sBCC without or with other BCC subtypes by age, sex and anatomic site. We retrospectively collected superficial BCC with the above characteristics from an Australian center during 2009 to 2014. We recorded 1528 sBCC and 1622 superficial BCC combined with other BCC subtype cases. Males numbered 2007 and females 1140. On males, head sites (forehead, cheek, nose and ear combined) compared to limb plus trunk sites displayed a higher incidence of superficial BCC combined with either nodular and or aggressive BCC subtypes (OR 13.15 CI 95% 8.9-19.5 P < .0001). On females a similar comparison also found a higher incidence of superficial BCC combined with solid subtype BCC on head sites compared to trunk and limb sites (OR 9.66 CI 95% 5.8-16.1 P < .0001). Superficial BCC alone is more likely on younger females on trunk and limb sites. Small partial biopsies reported as sBCC may miss other BCC subtypes present with higher risk on facial sites for males and females. Males had smaller proportions of superficial only subtype BCC on facial and ear sites compared to females. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Superficial skin ulcers

International Nuclear Information System (INIS)

Samaila, Modupeola O.; Rafindadi, Abdulmumini H.; Oluwole, Olabode P.; Adewuyi, Sunday A.

2007-01-01

Objective was to determine the underlying cause of superficial skin ulcers over a 15-year period. A retrospective histopathological analysis of 670 cases of superficial skin ulcers diagnosed in the Dept. of Pathology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria from January 1991 to December 2005. A total of 670 superficial skin ulcers were analyzed. The mail to female gender ratio was 409:261(1.5:1.0) and a peakage frequency of 44.3 %( 297) in the 5th and 6th decades. Spectrum of lesions encountered was categorized into inflammatory, infections, benign and malignant diseases. The malignant lesions were 309 (46.1%), non-specific inflammation 302 (45.1%), granulation tissue 25 (3.7%) and pseudoepitheliomatous hyperplasia 14 (2.1%). A total of 18(2.7%) specific infections were encountered, which included bacterial, fungal and viral infection. Benign lesions were 2(0.3%), comprising of neurofibroma and Bowen's disease. The most common malignant lesion was squamous cell carcinoma 203 (30.3%) with a male to female ratio of 128:75 (1.7:1.0). Of these 161 were well differentiated tumors. The lower limb was the prevalent site distribution of all the ulcers. Superficial ulcers may be harbinger of malignant diseases. Squamous cell carcinoma remains the most common malignant lesion arising from chronic superficial ulcers from our setting. Adequate tissue biopsy and early diagnosis may reduce the attendant morbidity of these ulcers. (author)

Cytoskeletal actin dynamics shape a ramifying actin network underpinning immunological synapse formation

DEFF Research Database (Denmark)

Fritzsche, Marco; Fernandes, Ricardo A.; Chang, Veronica T.

2017-01-01

optical microscopes to analyze resting and activated T cells, we show that, following contact formation with activating surfaces, these cells sequentially rearrange their cortical actin across the entire cell, creating a previously unreported ramifying actin network above the immunological synapse...

Mesoscopic model of actin-based propulsion.

Directory of Open Access Journals (Sweden)

Jie Zhu

Full Text Available Two theoretical models dominate current understanding of actin-based propulsion: microscopic polymerization ratchet model predicts that growing and writhing actin filaments generate forces and movements, while macroscopic elastic propulsion model suggests that deformation and stress of growing actin gel are responsible for the propulsion. We examine both experimentally and computationally the 2D movement of ellipsoidal beads propelled by actin tails and show that neither of the two models can explain the observed bistability of the orientation of the beads. To explain the data, we develop a 2D hybrid mesoscopic model by reconciling these two models such that individual actin filaments undergoing nucleation, elongation, attachment, detachment and capping are embedded into the boundary of a node-spring viscoelastic network representing the macroscopic actin gel. Stochastic simulations of this 'in silico' actin network show that the combined effects of the macroscopic elastic deformation and microscopic ratchets can explain the observed bistable orientation of the actin-propelled ellipsoidal beads. To test the theory further, we analyze observed distribution of the curvatures of the trajectories and show that the hybrid model's predictions fit the data. Finally, we demonstrate that the model can explain both concave-up and concave-down force-velocity relations for growing actin networks depending on the characteristic time scale and network recoil. To summarize, we propose that both microscopic polymerization ratchets and macroscopic stresses of the deformable actin network are responsible for the force and movement generation.

Polycation induced actin bundles.

Science.gov (United States)

Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

2011-04-01

Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder. Copyright © 2011 Elsevier B.V. All rights reserved.

The actin multigene family of Paramecium tetraurelia

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Wagner Erika

2007-03-01

Full Text Available Abstract Background A Paramecium tetraurelia pilot genome project, the subsequent sequencing of a Megabase chromosome as well as the Paramecium genome project aimed at gaining insight into the genome of Paramecium. These cells display a most elaborate membrane trafficking system, with distinct, predictable pathways in which actin could participate. Previously we had localized actin in Paramecium; however, none of the efforts so far could proof the occurrence of actin in the cleavage furrow of a dividing cell, despite the fact that actin is unequivocally involved in cell division. This gave a first hint that Paramecium may possess actin isoforms with unusual characteristics. The genome project gave us the chance to search the whole Paramecium genome, and, thus, to identify and characterize probably all actin isoforms in Paramecium. Results The ciliated protozoan, P. tetraurelia, contains an actin multigene family with at least 30 members encoding actin, actin-related and actin-like proteins. They group into twelve subfamilies; a large subfamily with 10 genes, seven pairs and one trio with > 82% amino acid identity, as well as three single genes. The different subfamilies are very distinct from each other. In comparison to actins in other organisms, P. tetraurelia actins are highly divergent, with identities topping 80% and falling to 30%. We analyzed their structure on nucleotide level regarding the number and position of introns. On amino acid level, we scanned the sequences for the presence of actin consensus regions, for amino acids of the intermonomer interface in filaments, for residues contributing to ATP binding, and for known binding sites for myosin and actin-specific drugs. Several of those characteristics are lacking in several subfamilies. The divergence of P. tetraurelia actins and actin-related proteins between different P. tetraurelia subfamilies as well as with sequences of other organisms is well represented in a phylogenetic

Diclofenac Topical (actinic keratosis)

Science.gov (United States)

... topical gel (Solaraze) is used to treat actinic keratosis (flat, scaly growths on the skin caused by ... The way diclofenac gel works to treat actinic keratosis is not known.Diclofenac is also available as ...

Non-Straub type actin from molluscan catch muscle

Energy Technology Data Exchange (ETDEWEB)

Shelud' ko, Nikolay S., E-mail: sheludko@stl.ru; Girich, Ulyana V.; Lazarev, Stanislav S.; Vyatchin, Ilya G.

2016-05-27

We have developed a method of obtaining natural actin from smooth muscles of the bivalves on the example of the Crenomytilus grayanus catch muscle. The muscles were previously rigorized to prevent a loss of thin filaments during homogenization and washings. Thin filaments were isolated with a low ionic strength solution in the presence of ATP and sodium pyrophosphate. Surface proteins of thin filaments-tropomyosin, troponin, calponin and some minor actin-binding proteins-were dissociated from actin filaments by increasing the ionic strength to 0.6 M KCL. Natural fibrillar actin obtained in that way depolymerizes easily in low ionic strength solutions commonly used for the extraction of Straub-type actin from acetone powder. Purification of natural actin was carried out by the polymerization–depolymerization cycle. The content of inactivated actin remaining in the supernatant is much less than at a similar purification of Straub-type actin. A comparative investigation was performed between the natural mussel actin and the Straub-type rabbit skeletal actin in terms of the key properties of actin: polymerization, activation of Mg-ATPase activity of myosin, and the electron-microscopic structure of actin polymers. -- Highlights: •We developed method of repolymerizable invertebrate smooth muscle actin obtaining. •Our method does not involve use of denaturating agents, which could modify proteins. •Viscosity and polymerization rate of actin, gained that way, is similar to Straub one. •Electron microscopy showed that repolymerized mussel actin is similar to Straub one. •Repolymerized mussel actin has greater ATPase activating capacity, than Straub actin.

Geometrical Determinants of Neuronal Actin Waves

OpenAIRE

Tomba, Caterina; Bra?ni, C?line; Bugnicourt, Ghislain; Cohen, Floriane; Friedrich, Benjamin M.; Gov, Nir S.; Villard, Catherine

2017-01-01

Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time betwe...

Stochastic Severing of Actin Filaments by Actin Depolymerizing Factor/Cofilin Controls the Emergence of a Steady Dynamical Regime

Science.gov (United States)

Roland, Jeremy; Berro, Julien; Michelot, Alphée; Blanchoin, Laurent; Martiel, Jean-Louis

2008-01-01

Actin dynamics (i.e., polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned to explain the rapid actin filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin filament dynamics in the presence of actin depolymerizing factor (ADF)/cofilin. We limited the molecular mechanism to 1), the spontaneous growth of filaments by polymerization of actin monomers, 2), the ageing of actin subunits in filaments, 3), the cooperative binding of ADF/cofilin to actin filament subunits, and 4), filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we found that the average filament length, 〈L〉, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: −2/3). We also showed that the average subunit residence time inside the filament, 〈T〉, depends on the actin monomer (power law: −1/6) and ADF/cofilin (power law: −2/3) concentrations. In addition, filament length fluctuations are ∼20% of the average filament length. Moreover, ADF/cofilin fragmentation while modulating filament length keeps filaments in a high molar ratio of ATP- or ADP-Pi versus ADP-bound subunits. This latter property has a protective effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin filaments. Our analysis shows that ADF/cofilin regulation maintains actin filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo. PMID:18065447

Cytoplasmic Actin: Purification and Single Molecule Assembly Assays

Science.gov (United States)

Hansen, Scott D.; Zuchero, J. Bradley; Mullins, R. Dyche

2014-01-01

The actin cytoskeleton is essential to all eukaryotic cells. In addition to playing important structural roles, assembly of actin into filaments powers diverse cellular processes, including cell motility, cytokinesis, and endocytosis. Actin polymerization is tightly regulated by its numerous cofactors, which control spatial and temporal assembly of actin as well as the physical properties of these filaments. Development of an in vitro model of actin polymerization from purified components has allowed for great advances in determining the effects of these proteins on the actin cytoskeleton. Here we describe how to use the pyrene actin assembly assay to determine the effect of a protein on the kinetics of actin assembly, either directly or as mediated by proteins such as nucleation or capping factors. Secondly, we show how fluorescently labeled phalloidin can be used to visualize the filaments that are created in vitro to give insight into how proteins regulate actin filament structure. Finally, we describe a method for visualizing dynamic assembly and disassembly of single actin filaments and fluorescently labeled actin binding proteins using total internal reflection fluorescence (TIRF) microscopy. PMID:23868587

Unconventional actin conformations localize on intermediate filaments in mitosis

International Nuclear Information System (INIS)

Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan

2011-01-01

Research highlights: → Unconventional actin conformations colocalize with vimentin on a cage-like structure in metaphase HEK 293T cells. → These conformations are detected with the anti-actin antibodies 1C7 ('lower dimer') and 2G2 ('nuclear actin'), but not C4 (monomeric actin). → Mitotic unconventional actin cables are independent of filamentous actin or microtubules. → Unconventional actin colocalizes with vimentin on a nocodazole-induced perinuclear dense mass of cables. -- Abstract: Different structural conformations of actin have been identified in cells and shown to reside in distinct subcellular locations of cells. In this report, we describe the localization of actin on a cage-like structure in metaphase HEK 293T cells. Actin was detected with the anti-actin antibodies 1C7 and 2G2, but not with the anti-actin antibody C4. Actin contained in this structure is independent of microtubules and actin filaments, and colocalizes with vimentin. Taking advantage of intermediate filament collapse into a perinuclear dense mass of cables when microtubules are depolymerized, we were able to relocalize actin to such structures. We hypothesize that phosphorylation of intermediate filaments at mitosis entry triggers the recruitment of different actin conformations to mitotic intermediate filaments. Storage and partition of the nuclear actin and antiparallel 'lower dimer' actin conformations between daughter cells possibly contribute to gene transcription and transient actin filament dynamics at G1 entry.

Boolean gates on actin filaments

International Nuclear Information System (INIS)

Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

2016-01-01

Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

Boolean gates on actin filaments

Energy Technology Data Exchange (ETDEWEB)

Siccardi, Stefano, E-mail: ssiccardi@2ssas.it [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom); Tuszynski, Jack A., E-mail: jackt@ualberta.ca [Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Adamatzky, Andrew, E-mail: andrew.adamatzky@uwe.ac.uk [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom)

2016-01-08

Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

Bulkiness or aromatic nature of tyrosine-143 of actin is important for the weak binding between F-actin and myosin-ADP-phosphate

Energy Technology Data Exchange (ETDEWEB)

Gomibuchi, Yuki [Graduate School of Science and Engineering, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan); Uyeda, Taro Q.P. [Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Wakabayashi, Takeyuki, E-mail: tw007@nasu.bio.teikyo-u.ac.jp [Graduate School of Science and Engineering, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan); Department of Judo Therapy, Faculty of Medical Technology, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan)

2013-11-29

Highlights: •The effect of mutation of Tyr143 that becomes more exposed on assembly was examined. •Mutation of tyrosine-143 of Dictyostelium actin changed actin polymerizability. •The bulkiness or aromatic nature of Tyr143 is important for the weak binding. •The weak interaction between myosin and actin strengthened by Tyr143Trp mutation. -- Abstract: Actin filaments (F-actin) interact with myosin and activate its ATPase to support force generation. By comparing crystal structures of G-actin and the quasi-atomic model of F-actin based on high-resolution cryo-electron microscopy, the tyrosine-143 was found to be exposed more than 60 Å{sup 2} to the solvent in F-actin. Because tyrosine-143 flanks the hydrophobic cleft near the hydrophobic helix that binds to myosin, the mutant actins, of which the tyrosine-143 was replaced with tryptophan, phenylalanine, or isoleucine, were generated using the Dictyostelium expression system. It polymerized significantly poorly when induced by NaCl, but almost normally by KCl. In the presence of phalloidin and KCl, the extents of the polymerization of all the mutant actins were comparable to that of the wild-type actin so that the actin-activated myosin ATPase activity could be reliably compared. The affinity of skeletal heavy meromyosin to F-actin and the maximum ATPase activity (V{sub max}) were estimated by a double reciprocal plot. The Tyr143Trp-actin showed the higher affinity (smaller K{sub app}) than that of the wild-type actin, with the V{sub max} being almost unchanged. The K{sub app} and V{sub max} of the Tyr143Phe-actin were similar to those of the wild-type actin. However, the activation by Tyr143Ile-actin was much smaller than the wild-type actin and the accurate determination of K{sub app} was difficult. Comparison of the myosin ATPase activated by the various mutant actins at the same concentration of F-actin showed that the extent of activation correlates well with the solvent-accessible surface areas (ASA

Actin expression in some Platyhelminthe species.

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Fagotti, A; Panara, F; Di Rosa, I; Simoncelli, F; Gabbiani, G; Pascolini, R

1994-10-01

Actin expression in some Platyhelminthe species was demonstrated by western-blotting and immunocytochemical analysis using two distinct anti-actin antibodies: the anti-total actin that reacts against all actin isoforms of higher vertebrates and the anti-alpha SM-1 that recognizes the alpha-smooth muscle (alpha SM) isotype of endothermic vertebrates (Skalli et al., 1986). Western-blotting experiments showed that all species tested, including some free-living Platyhelminthes (Tricladida and Rhabdocoela) and the parasitic Fasciola hepatica, were stained by anti-total actin antibody while only Dugesidae and Dendrocoelidae showed a positive immunoreactivity against anti-alpha SM-1. These results were confirmed by cytochemical immunolocalization using both avidin biotin conjugated peroxidase reaction on paraffin sections, and immunogold staining on Lowicryl 4KM embedded specimens. Our findings may contribute to the understanding of Platyhelminthes phylogeny.

Actin dynamics and the elasticity of cytoskeletal networks

Directory of Open Access Journals (Sweden)

2009-09-01

Full Text Available The structural integrity of a cell depends on its cytoskeleton, which includes an actin network. This network is transient and depends upon the continual polymerization and depolymerization of actin. The degradation of an actin network, and a corresponding reduction in cell stiffness, can indicate the presence of disease. Numerical simulations will be invaluable for understanding the physics of these systems and the correlation between actin dynamics and elasticity. Here we develop a model that is capable of generating actin network structures. In particular, we develop a model of actin dynamics which considers the polymerization, depolymerization, nucleation, severing, and capping of actin filaments. The structures obtained are then fed directly into a mechanical model. This allows us to qualitatively assess the effects of changing various parameters associated with actin dynamics on the elasticity of the material.

The nature of the globular- to fibrous-actin transition.

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Oda, Toshiro; Iwasa, Mitsusada; Aihara, Tomoki; Maéda, Yuichiro; Narita, Akihiro

2009-01-22

Actin plays crucial parts in cell motility through a dynamic process driven by polymerization and depolymerization, that is, the globular (G) to fibrous (F) actin transition. Although our knowledge about the actin-based cellular functions and the molecules that regulate the G- to F-actin transition is growing, the structural aspects of the transition remain enigmatic. We created a model of F-actin using X-ray fibre diffraction intensities obtained from well oriented sols of rabbit skeletal muscle F-actin to 3.3 A in the radial direction and 5.6 A along the equator. Here we show that the G- to F-actin conformational transition is a simple relative rotation of the two major domains by about 20 degrees. As a result of the domain rotation, the actin molecule in the filament is flat. The flat form is essential for the formation of stable, helical F-actin. Our F-actin structure model provides the basis for understanding actin polymerization as well as its molecular interactions with actin-binding proteins.

Recruitment Kinetics of Tropomyosin Tpm3.1 to Actin Filament Bundles in the Cytoskeleton Is Independent of Actin Filament Kinetics.

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Appaduray, Mark A; Masedunskas, Andrius; Bryce, Nicole S; Lucas, Christine A; Warren, Sean C; Timpson, Paul; Stear, Jeffrey H; Gunning, Peter W; Hardeman, Edna C

2016-01-01

The actin cytoskeleton is a dynamic network of filaments that is involved in virtually every cellular process. Most actin filaments in metazoa exist as a co-polymer of actin and tropomyosin (Tpm) and the function of an actin filament is primarily defined by the specific Tpm isoform associated with it. However, there is little information on the interdependence of these co-polymers during filament assembly and disassembly. We addressed this by investigating the recovery kinetics of fluorescently tagged isoform Tpm3.1 into actin filament bundles using FRAP analysis in cell culture and in vivo in rats using intracellular intravital microscopy, in the presence or absence of the actin-targeting drug jasplakinolide. The mobile fraction of Tpm3.1 is between 50% and 70% depending on whether the tag is at the C- or N-terminus and whether the analysis is in vivo or in cultured cells. We find that the continuous dynamic exchange of Tpm3.1 is not significantly impacted by jasplakinolide, unlike tagged actin. We conclude that tagged Tpm3.1 may be able to undergo exchange in actin filament bundles largely independent of the assembly and turnover of actin.

Wnt Signalling Promotes Actin Dynamics during Axon Remodelling through the Actin-Binding Protein Eps8.

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Eleanna Stamatakou

Full Text Available Upon arrival at their synaptic targets, axons slow down their growth and extensively remodel before the assembly of presynaptic boutons. Wnt proteins are target-derived secreted factors that promote axonal remodelling and synaptic assembly. In the developing spinal cord, Wnts secreted by motor neurons promote axonal remodelling of NT-3 responsive dorsal root ganglia neurons. Axon remodelling induced by Wnts is characterised by growth cone pausing and enlargement, processes that depend on the re-organisation of microtubules. However, the contribution of the actin cytoskeleton has remained unexplored. Here, we demonstrate that Wnt3a regulates the actin cytoskeleton by rapidly inducing F-actin accumulation in growth cones from rodent DRG neurons through the scaffold protein Dishevelled-1 (Dvl1 and the serine-threonine kinase Gsk3β. Importantly, these changes in actin cytoskeleton occurs before enlargement of the growth cones is evident. Time-lapse imaging shows that Wnt3a increases lamellar protrusion and filopodia velocity. In addition, pharmacological inhibition of actin assembly demonstrates that Wnt3a increases actin dynamics. Through a yeast-two hybrid screen, we identified the actin-binding protein Eps8 as a direct interactor of Dvl1, a scaffold protein crucial for the Wnt signalling pathway. Gain of function of Eps8 mimics Wnt-mediated axon remodelling, whereas Eps8 silencing blocks the axon remodelling activity of Wnt3a. Importantly, blockade of the Dvl1-Eps8 interaction completely abolishes Wnt3a-mediated axonal remodelling. These findings demonstrate a novel role for Wnt-Dvl1 signalling through Eps8 in the regulation of axonal remodeling.

Fibroblast-mediated contraction in actinically exposed and actinically protected aging skin

International Nuclear Information System (INIS)

Marks, M.W.; Morykwas, M.J.; Wheatley, M.J.

1990-01-01

The changes in skin morphology over time are a consequence of both chronologic aging and the accumulation of environmental exposure. Through observation, we know that actinic radiation intensifies the apparent aging of skin. We have investigated the effects of aging and actinic radiation on the ability of fibroblasts to contract collagen-fibroblast lattices. Preauricular and postauricular skin samples were obtained from eight patients aged 49 to 74 undergoing rhytidectomy. The samples were kept separate, and the fibroblasts were grown in culture. Lattices constructed with preauricular fibroblasts consistently contracted more than lattices containing postauricular fibroblasts. The difference in amount of contraction in 7 days between sites was greatest for the younger patients and decreased linearly as donor age increased (r = -0.96). This difference may be due to preauricular fibroblasts losing their ability to contract a lattice as aging skin is exposed to more actinic radiation

Managing actinic keratosis in primary care.

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Salmon, Nicola; Tidman, Michael J

2016-10-01

Actinic, or solar, keratosis is caused by chronic ultraviolet-induced damage to the epidermis. In the UK, 15-23% of individuals have actinic keratosis lesions. Risk factors include: advanced age; male gender; cumulative sun exposure or phototherapy; Fitzpatrick skin phototypes I-II; long-term immuno-suppression and genetic syndromes e.g. xeroderma pigmentosum and albinism. Actinic keratoses are regarded by some authorities as premalignant lesions that may transform into invasive squamous cell carcinoma (SCC) and by others as in situ SCC that may progress to an invasive stage. The risk of malignant change appears low; up to 0.5% per lesion per year. Up to 20-30% of lesions may spontaneously regress but in the absence of any reliable prognostic clinical indicators regarding malignant potential active treatment is considered appropriate. Actinic keratosis lesions may present as discrete hyperkeratotic papules, cutaneous horns, or more subtle flat lesions on sun-exposed areas of skin. The single most helpful diagnostic sign is an irregularly roughened surface texture: a sandpaper-like feel almost always indicates actinic damage. Dermatoscopy can be helpful in excluding signs of basal cell carcinoma when actinic keratosis is non-keratotic. It is always important to consider the possibility of SCC. The principal indication for referral to secondary care is the possibility of cutaneous malignancy. However, widespread and severe actinic damage in patients who are immunosuppressed is also a reason for referral.

Bioinformatics study of the mangrove actin genes

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Basyuni, M.; Wasilah, M.; Sumardi

2017-01-01

This study describes the bioinformatics methods to analyze eight actin genes from mangrove plants on DDBJ/EMBL/GenBank as well as predicted the structure, composition, subcellular localization, similarity, and phylogenetic. The physical and chemical properties of eight mangroves showed variation among the genes. The percentage of the secondary structure of eight mangrove actin genes followed the order of a helix > random coil > extended chain structure for BgActl, KcActl, RsActl, and A. corniculatum Act. In contrast to this observation, the remaining actin genes were random coil > extended chain structure > a helix. This study, therefore, shown the prediction of secondary structure was performed for necessary structural information. The values of chloroplast or signal peptide or mitochondrial target were too small, indicated that no chloroplast or mitochondrial transit peptide or signal peptide of secretion pathway in mangrove actin genes. These results suggested the importance of understanding the diversity and functional of properties of the different amino acids in mangrove actin genes. To clarify the relationship among the mangrove actin gene, a phylogenetic tree was constructed. Three groups of mangrove actin genes were formed, the first group contains B. gymnorrhiza BgAct and R. stylosa RsActl. The second cluster which consists of 5 actin genes the largest group, and the last branch consist of one gene, B. sexagula Act. The present study, therefore, supported the previous results that plant actin genes form distinct clusters in the tree.

Apatite-mediated actin dynamics in resorbing osteoclasts.

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Saltel, Frédéric; Destaing, Olivier; Bard, Frédéric; Eichert, Diane; Jurdic, Pierre

2004-12-01

The actin cytoskeleton is essential for osteoclasts main function, bone resorption. Two different organizations of actin have been described in osteoclasts, the podosomes belt corresponding to numerous F-actin columns arranged at the cell periphery, and the sealing zone defined as a unique large band of actin. To compare the role of these two different actin organizations, we imaged osteoclasts on various substrata: glass, dentin, and apatite. Using primary osteoclasts expressing GFP-actin, we found that podosome belts and sealing zones, both very dynamic actin structures, were present in mature osteoclasts; podosome belts were observed only in spread osteoclasts adhering onto glass, whereas sealing zone were seen in apico-basal polarized osteoclasts adherent on mineralized matrix. Dynamic observations of several resorption cycles of osteoclasts seeded on apatite revealed that 1) podosomes do not fuse together to form the sealing zone; 2) osteoclasts alternate successive stationary polarized resorption phases with a sealing zone and migration, nonresorption phases without any specific actin structure; and 3) apatite itself promotes sealing zone formation though c-src and Rho signaling. Finally, our work suggests that apatite-mediated sealing zone formation is dependent on both c-src and Rho whereas apico-basal polarization requires only Rho.

Bundling Actin Filaments From Membranes: Some Novel Players

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Clément eThomas

2012-08-01

Full Text Available Progress in live-cell imaging of the cytoskeleton has significantly extended our knowledge about the organization and dynamics of actin filaments near the plasma membrane of plant cells. Noticeably, two populations of filamentous structures can be distinguished. On the one hand, fine actin filaments which exhibit an extremely dynamic behavior basically characterized by fast polymerization and prolific severing events, a process referred to as actin stochastic dynamics. On the other hand, thick actin bundles which are composed of several filaments and which are comparatively more stable although they constantly remodel as well. There is evidence that the actin cytoskeleton plays critical roles in trafficking and signaling at both the cell cortex and organelle periphery but the exact contribution of actin bundles remains unclear. A common view is that actin bundles provide the long-distance tracks used by myosin motors to deliver their cargo to growing regions and accordingly play a particularly important role in cell polarization. However, several studies support that actin bundles are more than simple passive highways and display multiple and dynamic roles in the regulation of many processes, such as cell elongation, polar auxin transport, stomatal and chloroplast movement, and defense against pathogens. The list of identified plant actin-bundling proteins is ever expanding, supporting that plant cells shape structurally and functionally different actin bundles. Here I review the most recently characterized actin-bundling proteins, with a particular focus on those potentially relevant to membrane trafficking and/or signaling.

Probing friction in actin-based motility

International Nuclear Information System (INIS)

Marcy, Yann; Joanny, Jean-Francois; Prost, Jacques; Sykes, Cecile

2007-01-01

Actin dynamics are responsible for cell protrusion and certain intracellular movements. The transient attachment of the actin filaments to a moving surface generates a friction force that resists the movement. We probe here the dynamics of these attachments by inducing a stick-slip behavior via micromanipulation of a growing actin comet. We show that general principles of adhesion and friction can explain our observations

Dynamic Regulation of Sarcomeric Actin Filaments in Striated Muscle

OpenAIRE

Ono, Shoichiro

2010-01-01

In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin sub...

Actin filaments – a target for redox regulation

Science.gov (United States)

Wilson, Carlos; Terman, Jonathan R.; González-Billault, Christian; Ahmed, Giasuddin

2016-01-01

Actin and its ability to polymerize into dynamic filaments is critical for the form and function of cells throughout the body. While multiple proteins have been characterized as affecting actin dynamics through non-covalent means, actin and its protein regulators are also susceptible to covalent modifications of their amino acid residues. In this regard, oxidation-reduction (Redox) intermediates have emerged as key modulators of the actin cytoskeleton with multiple different effects on cellular form and function. Here, we review work implicating Redox intermediates in post-translationally altering actin and discuss what is known regarding how these alterations affect the properties of actin. We also focus on two of the best characterized enzymatic sources of these Redox intermediates – the NADPH oxidase NOX and the flavoprotein monooxygenase MICAL – and detail how they have both been identified as altering actin, but share little similarity and employ different means to regulate actin dynamics. Finally, we discuss the role of these enzymes and redox signaling in regulating the actin cytoskeleton in vivo and highlight their importance for neuronal form and function in health and disease. PMID:27309342

Comparative histochemical study of Bowen’s disease and actinic keratosis: preserved normal basal cells in Bowen’s disease

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H Ishida

2009-12-01

Full Text Available The degree of DNA-instability as revealed by immunohistochemical staining with anti-cytidine antibody after acid hydrolysis (DNA-instability test has been recently used as a marker of malignancy. This technique was applied to examine 17 skin tissue samples of Bowen’s disease, 47 of actinic keratosis, 15 of squamous cell carcinoma, 5 of seborrheic keratosis, and 10 of normal skin. All benign neoplastic cells of seborrheic keratosis and normal epidermal cells were negative. On the other hand, all cancer cells were positive with the DNA-instability test, indicating their malignancy, but all basal cells in Bowen’s disease were completely negative. Compatible with this result, the basal cells in Bowen’s disease were characteristically normal as evident in other histochemical examinations. Thus, they were negative with p53 immunohistochemistry, with normal signals of chromosome 17 in situ hybridisation and argyrophilic nucleolar organiser region, and showed slightly enhanced proliferative activity as revealed by proliferating cell nuclear antigen immunohistochemistry. Immunohistochemical staining with 34 ß E12 (monoclonal antibody against cytokeratins 1, 5, 10, and 14, which stains all normal epidermal keratinocytes including basal cells, showed that only the basal cells of Bowen’s disease stained strongly and homogeneously, while all cancer cells in the upper layers of Bowen’s disease and all layers of actinic keratosis were only sporadically or weakly stained. Staining with 34 ß B4 (monoclonal antibody against cytokeratin 1, which recognises the whole epidermis except for the basal layer in the normal epidermis, showed that the basal cells in the Bowen’s disease were completely negative, and lower layer cells in the actinic keratosis and upper layer cells in Bowen’s disease were only sporadically stained positive, although the superficial layer cells in actinic keratosis stained strongly and homogeneously. Our findings clearly

Characterizing interaction forces between actin and proteins of the tropomodulin family reveals the presence of the N-terminal actin-binding site in leiomodin.

Science.gov (United States)

Arslan, Baran; Colpan, Mert; Gray, Kevin T; Abu-Lail, Nehal I; Kostyukova, Alla S

2018-01-15

Tropomodulin family of proteins includes several isoforms of tropomodulins (Tmod) and leiomodins (Lmod). These proteins can sequester actin monomers or nucleate actin polymerization. Although it is known that their actin-binding properties are isoform-dependent, knowledge on how they vary in strengths of interactions with G-actin is missing. While it is confirmed in many studies that Tmods have two actin-binding sites, information on number and location of actin-binding sites in Lmod2 is controversial. We used atomic force microscopy to study interactions between G-actin and proteins of the tropomodulin family. Unbinding forces between G-actin and Tmod1, Tmod2, Tmod3, or Lmod2 were quantified. Our results indicated that Tmod1 and Tmod3 had unimodal force distributions, Tmod2 had a bimodal distribution and Lmod2 had a trimodal distribution. The number of force distributions correlates with the proteins' abilities to sequester actin or to nucleate actin polymerization. We assigned specific unbinding forces to the individual actin-binding sites of Tmod2 and Lmod2 using mutations that destroy actin-binding sites of Tmod2 and truncated Lmod2. Our results confirm the existence of the N-terminal actin-binding site in Lmod2. Altogether, our data demonstrate how the differences between the number and the strength of actin-binding sites of Tmod or Lmod translate to their functional abilities. Copyright © 2017 Elsevier Inc. All rights reserved.

Plasmin enzymatic activity in the presence of actin

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Yusova E. I.

2015-10-01

Full Text Available Aim. To study the changes in the plasmin activity towards substrates with high and low molecular mass in the presence of actin. Methods. The proteins used for this investigation were obtained by affinity chromatography and gel-filtration. The plasmin enzymatic activity was determined by a turbidimetric assay and a chromogenic substrate-based assay. The enzyme linked immunosorbent assay and biotin-avidin-phosphatase system were used to study the interaction of plasminogen and its fragments with actin. Results. It was shown that G-actin causes 1.5-fold decrease in the rate of polymeric fibrin hydrolysis by plasmin and Glu-plasminogen activated by the tissue plasminogen activator. However, actin did not impede plasmin autolysis and had no influence on its amidase activity. We have studied an interaction of biotinylated Glu-plasminogen and its fragments (kringle 1-3, kringle 4 and mini-plasminogen with immobilized G-actin. Glu-plasminogen and kringle 4 had a high affinity towards actin (C50 is 113 and 117 nM correspondingly. Mini-plasminogen and kringe 4 did not bind to actin. A similar affinity of Glu-plasminogen and kringle 1-3 towards actin proves the involvement of the kringle 1-3 lysine-binding sites of the native plasminogen form in the actin interaction. Conclusions. Actin can modulate plasmin specificity towards high molecular mass substrates through its interaction with lysine-binding sites of the enzyme kringle domains. Actin inhibition of the fibrinolytic activity of plasmin is due to its competition with fibrin for thelysine binding sites of plasminogen/plasmin.

Xenopus egg cytoplasm with intact actin.

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Field, Christine M; Nguyen, Phuong A; Ishihara, Keisuke; Groen, Aaron C; Mitchison, Timothy J

2014-01-01

We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we term "actin-intact egg extract." These are undiluted egg cytoplasm that contains abundant organelles, and glycogen which supplies energy, and represents the least perturbed cell-free cytoplasm preparation we know of. We used this system to probe cell cycle regulation of actin and myosin-II dynamics (Field et al., 2011), and to reconstitute the large, interphase asters that organize early Xenopus embryos (Mitchison et al., 2012; Wühr, Tan, Parker, Detrich, & Mitchison, 2010). Actin-intact Xenopus egg extracts are useful for analysis of actin dynamics, and interaction of actin with other cytoplasmic systems, in a cell-free system that closely mimics egg physiology, and more generally for probing the biochemistry and biophysics of the egg, zygote, and early embryo. Detailed protocols are provided along with assays used to check cell cycle state and tips for handling and storing undiluted egg extracts. © 2014 Elsevier Inc. All rights reserved.

Mechanics model for actin-based motility.

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Lin, Yuan

2009-02-01

We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

Titin-Actin Interaction: PEVK-Actin-Based Viscosity in a Large Animal

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Charles S. Chung

2011-01-01

Full Text Available Titin exhibits an interaction between its PEVK segment and the actin filament resulting in viscosity, a speed dependent resistive force, which significantly influences diastolic filling in mice. While diastolic disease is clinically pervasive, humans express a more compliant titin (N2BA:N2B ratio ~0.5–1.0 than mice (N2BA:N2B ratio ~0.2. To examine PEVK-actin based viscosity in compliant titin-tissues, we used pig cardiac tissue that expresses titin isoforms similar to that in humans. Stretch-hold experiments were performed at speeds from 0.1 to 10 lengths/s from slack sarcomere lengths (SL to SL of 2.15 μm. Viscosity was calculated from the slope of stress-relaxation vs stretch speed. Recombinant PEVK was added to compete off native interactions and this found to reduce the slope by 35%, suggesting that PEVK-actin interactions are a strong contributor of viscosity. Frequency sweeps were performed at frequencies of 0.1–400 Hz and recombinant protein reduced viscous moduli by 40% at 2.15 μm and by 50% at 2.25 μm, suggesting a SL-dependent nature of viscosity that might prevent SL ``overshoot’’ at long diastolic SLs. This study is the first to show that viscosity is present at physiologic speeds in the pig and supports the physiologic relevance of PEVK-actin interactions in humans in both health and disease.

Electrostatics Control Actin Filament Nucleation and Elongation Kinetics*

Science.gov (United States)

Crevenna, Alvaro H.; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L.; Lamb, Don C.; Wedlich-Söldner, Roland

2013-01-01

The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment. PMID:23486468

Electrostatics control actin filament nucleation and elongation kinetics.

Science.gov (United States)

Crevenna, Alvaro H; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L; Lamb, Don C; Wedlich-Söldner, Roland

2013-04-26

The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment.

Distinct functional interactions between actin isoforms and nonsarcomeric myosins.

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Mirco Müller

Full Text Available Despite their near sequence identity, actin isoforms cannot completely replace each other in vivo and show marked differences in their tissue-specific and subcellular localization. Little is known about isoform-specific differences in their interactions with myosin motors and other actin-binding proteins. Mammalian cytoplasmic β- and γ-actin interact with nonsarcomeric conventional myosins such as the members of the nonmuscle myosin-2 family and myosin-7A. These interactions support a wide range of cellular processes including cytokinesis, maintenance of cell polarity, cell adhesion, migration, and mechano-electrical transduction. To elucidate differences in the ability of isoactins to bind and stimulate the enzymatic activity of individual myosin isoforms, we characterized the interactions of human skeletal muscle α-actin, cytoplasmic β-actin, and cytoplasmic γ-actin with human myosin-7A and nonmuscle myosins-2A, -2B and -2C1. In the case of nonmuscle myosins-2A and -2B, the interaction with either cytoplasmic actin isoform results in 4-fold greater stimulation of myosin ATPase activity than was observed in the presence of α-skeletal muscle actin. Nonmuscle myosin-2C1 is most potently activated by β-actin and myosin-7A by γ-actin. Our results indicate that β- and γ-actin isoforms contribute to the modulation of nonmuscle myosin-2 and myosin-7A activity and thereby to the spatial and temporal regulation of cytoskeletal dynamics. FRET-based analyses show efficient copolymerization abilities for the actin isoforms in vitro. Experiments with hybrid actin filaments show that the extent of actomyosin coupling efficiency can be regulated by the isoform composition of actin filaments.

Incorporation of mammalian actin into microfilaments in plant cell nucleus

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Paves Heiti

2004-04-01

Full Text Available Abstract Background Actin is an ancient molecule that shows more than 90% amino acid homology between mammalian and plant actins. The regions of the actin molecule that are involved in F-actin assembly are largely conserved, and it is likely that mammalian actin is able to incorporate into microfilaments in plant cells but there is no experimental evidence until now. Results Visualization of microfilaments in onion bulb scale epidermis cells by different techniques revealed that rhodamine-phalloidin stained F-actin besides cytoplasm also in the nuclei whereas GFP-mouse talin hybrid protein did not enter the nuclei. Microinjection of fluorescently labeled actin was applied to study the presence of nuclear microfilaments in plant cells. Ratio imaging of injected fluorescent rabbit skeletal muscle actin and phalloidin staining of the microinjected cells showed that mammalian actin was able to incorporate into plant F-actin. The incorporation occurred preferentially in the nucleus and in the perinuclear region of plant cells whereas part of plant microfilaments, mostly in the periphery of cytoplasm, did not incorporate mammalian actin. Conclusions Microinjected mammalian actin is able to enter plant cell's nucleus, whereas incorporation of mammalian actin into plant F-actin occurs preferentially in the nucleus and perinuclear area.

The Bacterial Actin MamK

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Ozyamak, Ertan; Kollman, Justin; Agard, David A.; Komeili, Arash

2013-01-01

It is now recognized that actin-like proteins are widespread in bacteria and, in contrast to eukaryotic actins, are highly diverse in sequence and function. The bacterial actin, MamK, represents a clade, primarily found in magnetotactic bacteria, that is involved in the proper organization of subcellular organelles, termed magnetosomes. We have previously shown that MamK from Magnetospirillum magneticum AMB-1 (AMB-1) forms dynamic filaments in vivo. To gain further insights into the molecular mechanisms that underlie MamK dynamics and function, we have now studied the in vitro properties of MamK. We demonstrate that MamK is an ATPase that, in the presence of ATP, assembles rapidly into filaments that disassemble once ATP is depleted. The mutation of a conserved active site residue (E143A) abolishes ATPase activity of MamK but not its ability to form filaments. Filament disassembly depends on both ATPase activity and potassium levels, the latter of which results in the organization of MamK filaments into bundles. These data are consistent with observations indicating that accessory factors are required to promote filament disassembly and for spatial organization of filaments in vivo. We also used cryo-electron microscopy to obtain a high resolution structure of MamK filaments. MamK adopts a two-stranded helical filament architecture, but unlike eukaryotic actin and other actin-like filaments, subunits in MamK strands are unstaggered giving rise to a unique filament architecture. Beyond extending our knowledge of the properties and function of MamK in magnetotactic bacteria, this study emphasizes the functional and structural diversity of bacterial actins in general. PMID:23204522

HIGH ORIGIN OF SUPERFICIAL ULNAR ARTERY- A CASE REPORT

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Anjana Jayakumaran Nair

2017-03-01

Full Text Available BACKGROUND High origin and superficially placed ulnar artery is a rare anatomical variant that usually arises either in the axilla or arm and runs a superficial course in the forearm, enters the hand and participates in the formation of superficial palmar arch. During routine dissection of cadavers in our department, we observed a unilateral case of high origin and superficial ulnar artery in a human male cadaver. It originated from the brachial artery in the lower third of arm 4 cm above its bifurcation. From its origin, it passed downwards along the medial aspect of forearm, superficial to the flexors, entered hand superficial to the flexor retinaculum and formed superficial palmar arch. The knowledge of existence of a superficial ulnar artery is important during vascular and reconstructive surgery and also in evaluation of angiographic images. Superficial position makes it more vulnerable to trauma and more accessible to cannulation.

Formin' actin in the nucleus.

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Baarlink, Christian; Grosse, Robert

2014-01-01

Many if not most proteins can, under certain conditions, change cellular compartments, such as, for example, shuttling from the cytoplasm to the nucleus. Thus, many proteins may exert functions in various and very different subcellular locations, depending on the signaling context. A large amount of actin regulatory proteins has been detected in the mammalian cell nucleus, although their potential roles are much debated and are just beginning to emerge. Recently, members of the formin family of actin nucleators were also reported to dynamically localize to the nuclear environment. Here we discuss our findings that specific diaphanous-related formins can promote nuclear actin assembly in a signal-dependent manner.

Common Superficial Bursitis.

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Khodaee, Morteza

2017-02-15

Superficial bursitis most often occurs in the olecranon and prepatellar bursae. Less common locations are the superficial infrapatellar and subcutaneous (superficial) calcaneal bursae. Chronic microtrauma (e.g., kneeling on the prepatellar bursa) is the most common cause of superficial bursitis. Other causes include acute trauma/hemorrhage, inflammatory disorders such as gout or rheumatoid arthritis, and infection (septic bursitis). Diagnosis is usually based on clinical presentation, with a particular focus on signs of septic bursitis. Ultrasonography can help distinguish bursitis from cellulitis. Blood testing (white blood cell count, inflammatory markers) and magnetic resonance imaging can help distinguish infectious from noninfectious causes. If infection is suspected, bursal aspiration should be performed and fluid examined using Gram stain, crystal analysis, glucose measurement, blood cell count, and culture. Management depends on the type of bursitis. Acute traumatic/hemorrhagic bursitis is treated conservatively with ice, elevation, rest, and analgesics; aspiration may shorten the duration of symptoms. Chronic microtraumatic bursitis should be treated conservatively, and the underlying cause addressed. Bursal aspiration of microtraumatic bursitis is generally not recommended because of the risk of iatrogenic septic bursitis. Although intrabursal corticosteroid injections are sometimes used to treat microtraumatic bursitis, high-quality evidence demonstrating any benefit is unavailable. Chronic inflammatory bursitis (e.g., gout, rheumatoid arthritis) is treated by addressing the underlying condition, and intrabursal corticosteroid injections are often used. For septic bursitis, antibiotics effective against Staphylococcus aureus are generally the initial treatment, with surgery reserved for bursitis not responsive to antibiotics or for recurrent cases. Outpatient antibiotics may be considered in those who are not acutely ill; patients who are acutely ill

Measurement and Analysis of in vitro Actin Polymerization

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Doolittle, Lynda K.; Rosen, Michael K.; Padrick, Shae B.

2014-01-01

Summary The polymerization of actin underlies force generation in numerous cellular processes. While actin polymerization can occur spontaneously, cells maintain control over this important process by preventing actin filament nucleation and then allowing stimulated polymerization and elongation by several regulated factors. Actin polymerization, regulated nucleation and controlled elongation activities can be reconstituted in vitro, and used to probe the signaling cascades cells use to control when and where actin polymerization occurs. Introducing a pyrene fluorophore allows detection of filament formation by an increase in pyrene fluorescence. This method has been used for many years and continues to be broadly used, owing to its simplicity and flexibility. Here we describe how to perform and analyze these in vitro actin polymerization assays, with an emphasis on extracting useful descriptive parameters from kinetic data. PMID:23868594

Actin polymerisation at the cytoplasmic face of eukaryotic nuclei

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David-Watine Brigitte

2006-05-01

Full Text Available Abstract Background There exists abundant molecular and ultra-structural evidence to suggest that cytoplasmic actin can physically interact with the nuclear envelope (NE membrane system. However, this interaction has yet to be characterised in living interphase cells. Results Using a fluorescent conjugate of the actin binding drug cytochalasin D (CD-BODIPY we provide evidence that polymerising actin accumulates in vicinity to the NE. In addition, both transiently expressed fluorescent actin and cytoplasmic micro-injection of fluorescent actin resulted in accumulation of actin at the NE-membrane. Consistent with the idea that the cytoplasmic phase of NE-membranes can support this novel pool of perinuclear actin polymerisation we show that isolated, intact, differentiated primary hepatocyte nuclei support actin polymerisation in vitro. Further this phenomenon was inhibited by treatments hindering steric access to outer-nuclear-membrane proteins (e.g. wheat germ agglutinin, anti-nesprin and anti-nucleoporin antibodies. Conclusion We conclude that actin polymerisation occurs around interphase nuclei of living cells at the cytoplasmic phase of NE-membranes.

Hypertrophic stimulation increases beta-actin dynamics in adult feline cardiomyocytes.

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Sundaravadivel Balasubramanian

2010-07-01

Full Text Available The myocardium responds to hemodynamic stress through cellular growth and organ hypertrophy. The impact of cytoskeletal elements on this process, however, is not fully understood. While alpha-actin in cardiomyocytes governs muscle contraction in combination with the myosin motor, the exact role of beta-actin has not been established. We hypothesized that in adult cardiomyocytes, as in non-myocytes, beta-actin can facilitate cytoskeletal rearrangement within cytoskeletal structures such as Z-discs. Using a feline right ventricular pressure overload (RVPO model, we measured the level and distribution of beta-actin in normal and pressure overloaded myocardium. Resulting data demonstrated enriched levels of beta-actin and enhanced translocation to the Triton-insoluble cytoskeletal and membrane skeletal complexes. In addition, RVPO in vivo and in vitro hypertrophic stimulation with endothelin (ET or insulin in isolated adult cardiomyocytes enhanced the content of polymerized fraction (F-actin of beta-actin. To determine the localization and dynamics of beta-actin, we adenovirally expressed GFP-tagged beta-actin in isolated adult cardiomyocytes. The ectopically expressed beta-actin-GFP localized to the Z-discs, costameres, and cell termini. Fluorescence recovery after photobleaching (FRAP measurements of beta-actin dynamics revealed that beta-actin at the Z-discs is constantly being exchanged with beta-actin from cytoplasmic pools and that this exchange is faster upon hypertrophic stimulation with ET or insulin. In addition, in electrically stimulated isolated adult cardiomyocytes, while beta-actin overexpression improved cardiomyocyte contractility, immunoneutralization of beta-actin resulted in a reduced contractility suggesting that beta-actin could be important for the contractile function of adult cardiomyocytes. These studies demonstrate the presence and dynamics of beta-actin in the adult cardiomyocyte and reinforce its usefulness in measuring

Integrins in cell migration – the actin connection

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Vicente-Manzanares, Miguel; Choi, Colin Kiwon; Horwitz, Alan Rick

2008-01-01

The connection between integrins and actin is driving the field of cell migration in new directions. Integrins and actin are coupled through a physical linkage, which provides traction for migration. Recent studies show the importance of this linkage in regulating adhesion organization and development. Actin polymerization orchestrates adhesion assembly near the leading edge of a migrating cell, and the dynamic cross-linking of actin filaments promotes adhesion maturat...

Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae

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Benjamin B. A. Raymond

2018-02-01

Full Text Available Mycoplasma hyopneumoniae, an agriculturally important porcine pathogen, disrupts the mucociliary escalator causing ciliostasis, loss of cilial function, and epithelial cell death within the porcine lung. Losses to swine production due to growth rate retardation and reduced feed conversion efficiency are severe, and antibiotics are used heavily to control mycoplasmal pneumonia. Notably, little is known about the repertoire of host receptors that M. hyopneumoniae targets to facilitate colonization. Here we show, for the first time, that actin exists extracellularly on porcine epithelial monolayers (PK-15 using surface biotinylation and 3D-Structured Illumination Microscopy (3D-SIM, and that M. hyopneumoniae binds to the extracellular β-actin exposed on the surface of these cells. Consistent with this hypothesis we show: (i monoclonal antibodies that target β-actin significantly block the ability of M. hyopneumoniae to adhere and colonize PK-15 cells; (ii microtiter plate binding assays show that M. hyopneumoniae cells bind to monomeric G-actin in a dose dependent manner; (iii more than 100 M. hyopneumoniae proteins were recovered from affinity-chromatography experiments using immobilized actin as bait; and (iv biotinylated monomeric actin binds directly to M. hyopneumoniae proteins in ligand blotting studies. Specifically, we show that the P97 cilium adhesin possesses at least two distinct actin-binding regions, and binds monomeric actin with nanomolar affinity. Taken together, these observations suggest that actin may be an important receptor for M. hyopneumoniae within the swine lung and will aid in the future development of intervention strategies against this devastating pathogen. Furthermore, our observations have wider implications for extracellular actin as an important bacterial receptor.

Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae.

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Raymond, Benjamin B A; Madhkoor, Ranya; Schleicher, Ina; Uphoff, Cord C; Turnbull, Lynne; Whitchurch, Cynthia B; Rohde, Manfred; Padula, Matthew P; Djordjevic, Steven P

2018-01-01

Mycoplasma hyopneumoniae , an agriculturally important porcine pathogen, disrupts the mucociliary escalator causing ciliostasis, loss of cilial function, and epithelial cell death within the porcine lung. Losses to swine production due to growth rate retardation and reduced feed conversion efficiency are severe, and antibiotics are used heavily to control mycoplasmal pneumonia. Notably, little is known about the repertoire of host receptors that M. hyopneumoniae targets to facilitate colonization. Here we show, for the first time, that actin exists extracellularly on porcine epithelial monolayers (PK-15) using surface biotinylation and 3D-Structured Illumination Microscopy (3D-SIM), and that M. hyopneumoniae binds to the extracellular β-actin exposed on the surface of these cells. Consistent with this hypothesis we show: (i) monoclonal antibodies that target β-actin significantly block the ability of M. hyopneumoniae to adhere and colonize PK-15 cells; (ii) microtiter plate binding assays show that M. hyopneumoniae cells bind to monomeric G-actin in a dose dependent manner; (iii) more than 100 M. hyopneumoniae proteins were recovered from affinity-chromatography experiments using immobilized actin as bait; and (iv) biotinylated monomeric actin binds directly to M. hyopneumoniae proteins in ligand blotting studies. Specifically, we show that the P97 cilium adhesin possesses at least two distinct actin-binding regions, and binds monomeric actin with nanomolar affinity. Taken together, these observations suggest that actin may be an important receptor for M. hyopneumoniae within the swine lung and will aid in the future development of intervention strategies against this devastating pathogen. Furthermore, our observations have wider implications for extracellular actin as an important bacterial receptor.

IFT88 influences chondrocyte actin organization and biomechanics.

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Wang, Z; Wann, A K T; Thompson, C L; Hassen, A; Wang, W; Knight, M M

2016-03-01

Primary cilia are microtubule based organelles which control a variety of signalling pathways important in cartilage development, health and disease. This study examines the role of the intraflagellar transport (IFT) protein, IFT88, in regulating fundamental actin organisation and mechanics in articular chondrocytes. The study used an established chondrocyte cell line with and without hypomorphic mutation of IFT88 (IFT88(orpk)). Confocal microscopy was used to quantify F-actin and myosin IIB organisation. Viscoelastic cell and actin cortex mechanics were determined using micropipette aspiration with actin dynamics visualised in live cells transfected with LifeACT-GFP. IFT88(orpk) cells exhibited a significant increase in acto-myosin stress fibre organisation relative to wild-type (WT) cells in monolayer and an altered response to cytochalasin D. Rounded IFT88(orpk) cells cultured in suspension exhibited reduced cortical actin expression with reduced cellular equilibrium modulus. Micropipette aspiration resulted in reduced membrane bleb formation in IFT88(orpk) cells. Following membrane blebbing, IFT88(orpk) cells exhibited slower reformation of the actin cortex. IFT88(orpk) cells showed increased actin deformability and reduced cortical tension confirming that IFT regulates actin cortex mechanics. The reduced cortical tension is also consistent with the reduced bleb formation. This study demonstrates for the first time that the ciliary protein IFT88 regulates fundamental actin organisation and the stiffness of the actin cortex leading to alterations in cell deformation, mechanical properties and blebbing in an IFT88 chondrocyte cell line. This adds to the growing understanding of the role of primary cilia and IFT in regulating cartilage biology. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Biphasic interactions between a cationic dendrimer and actin.

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Ruenraroengsak, Pakatip; Florence, Alexander T

2010-12-01

Gene delivery systems face the problem not only of the route toward the cell and tissues in question, but also of the molecularly crowded environment of both the cytoplasm and the nucleus itself. One of the physical barriers in the cytoplasm for diffusing nanoparticles is an actin network. Here, we describe the finding that a self-fluorescent sixth generation cationic dendrimer (6 nm in diameter) interacts reversibly and possibly electrostatically with actin filaments in vitro. Not only does this interaction slow the diffusion of the dendrimer but it also affects actin polymerization in a biphasic manner. At low concentrations the dendrimer behaves like a G-binding actin protein, retarding actin polymerization, whereas at high concentrations the dendrimer acts as a nucleating protein accelerating the polymerization. Thus in vivo the diffusion of a dendrimer carrier such as this has both physical and chemical elements: by decreasing polymerization it might accelerate its own transport, and by enhancing actin polymerization retard it. This finding suggests that such a dendrimer may have a role as an anticancer agent through its inhibitory effect on actin polymerization.

Bacterial Actins? An Evolutionary Perspective

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Doolittle, Russell F.; York, Amanda L.

2003-01-01

According to the conventional wisdom, the existence of a cytoskeleton in eukaryotes and its absence in prokaryotes constitute a fundamental divide between the two domains of life. An integral part of the dogma is that a cytoskeleton enabled an early eukaryote to feed upon prokaryotes, a consequence of which was the occasional endosymbiosis and the eventual evolution of organelles. Two recent papers present compelling evidence that actin, one of the principal components of a cytoskeleton, has a homolog in Bacteria that behaves in many ways like eukaryotic actin. Sequence comparisons reveml that eukaryotic actin and the bacterial homolog (mreB protein), unlike many other proteins common to eukaryotes and Bacteria, have very different and more highly extended evolutionary histories.

Drenaje suplementario del sistema venoso superficial en colgajos pediculados Supplementary drainage of superficial venous system in pedicled flaps

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A. Fernández García

2012-06-01

Full Text Available Los colgajos pediculados pueden sufrir edema y congestión debido a que su drenaje a trevés del sistema venoso superfical es imposible y el flujo hacia el sistema profundo a nivel del pedículo es precario. Esta situación suele evolucionar hacia la necrosis parcial o la pérdida total del colgajo en pocas horas. La apertura del sistema venoso superficial permite el drenaje adecuado de los tejidos transferidos y evita estas complicaciones. Este artículo analiza el papel de las anastomosis microquirúrgicas en el sistema venoso superficial de los colgajos pediculados. Esta técnica permite comunicar el sistema venoso superfical de los tejidos transferidos con el sistema venoso superficial del territorio que rodea al defecto. Presentamos los resultados obtenidos con esta técnica en colgajos de perforante en hélice, colgajos miocutáneos, colgajos neurocutáneos y colgajos fasciograsos volteados.The pedicled flaps can suffer edema and congestion due to the impossibility of drainage toward the superficial venous system and the precarious flow via the deep system at the level of the pedicle. The evolution of this situation is usually partial necrosis or total loss of the flap in a few hours. The opening of the venous superficial system achieves an appropriate drainage of the transfered tissues and avoids these complications. In this article we analyze the role of the microsurgical anastomosis at the level of the superficial venous system of pedicled flaps. This technique allows to communicate the superficial venous system of the transfered tissues with the superficial venous system of the territory around the defect. We report the results with this method in propeller perforator flaps, miocutaneous flaps, neurocutaneous flaps and adipofascial turn over flaps.

Modified Functional Superficial Parotidectomy With Ligation of the Major Branch of the Parotid Duct Extending to the Superficial Lobe.

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Chang, Jung Woo; Leem, Soo Seong; Choi, Hwan Jun; Lee, Jang Hyun

2017-05-01

A functional superficial parotidectomy can maintain salivary function by preserving the Stensen duct. However, this technique still brings the possibility of salivary leakage, because major branches of the parotid duct from the resected site do not get ligated. To reduce this complication, this study introduces a modified technique with major branch ligation. From December 2008 to February 2015, 14 patients who underwent superficial parotidectomy were divided into 2 groups. Group A was treated with the modified functional superficial parotidectomy involving the major branch between the superficial lobe and parotid duct. Group B was treated with the conventional superficial parotidectomy without involving the major branch of the parotid duct. The clinical complications, period of Hemovac usage, and surgical duration were noted in each group. Two of 8 patients in group A had a major branch from Stensen duct that was ligated, and there was no evidence of salivary leakage or sialocele in any of the patients of group A, whereas group B contained 2 cases of salivary leakage, one of which became sialocele. Group A had a significantly longer Hemovac maintenance period than group B (P < 0.05), and the duration of surgery was also significantly different between the 2 groups (P < 0.05). Because a solitary major branch of the main parotid duct occasionally extends toward the superficial lobe, our modified technique-functional superficial parotidectomy with ligation of the major branch toward the superficial lobe-is a useful option for treatment of a benign parotid mass in such cases.

Stress generation by myosin minifilaments in actin bundles

International Nuclear Information System (INIS)

Dasanayake, Nilushi L; Carlsson, Anders E

2013-01-01

Forces and stresses generated by the action of myosin minifilaments are analyzed in idealized computer-generated actin bundles, and compared to results for isotropic actin networks. The bundles are generated as random collections of actin filaments in two dimensions with constrained orientations, crosslinked and attached to two fixed walls. Myosin minifilaments are placed on actin filament pairs and allowed to move and deform the network so that it exerts forces on the walls. The vast majority of simulation runs end with contractile minifilament stress, because minifilaments rotate into energetically stable contractile configurations. This process is aided by the bending and stretching of actin filaments, which accomodate minifilament rotation. Stresses for bundles are greater than those for isotropic networks, and antiparallel filaments generate more tension than parallel filaments. The forces transmitted by the actin network to the walls of the simulation cell often exceed the tension in the minifilament itself. (paper)

Developmental expression of the alpha-skeletal actin gene

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Vonk Freek J

2008-06-01

Full Text Available Abstract Background Actin is a cytoskeletal protein which exerts a broad range of functions in almost all eukaryotic cells. In higher vertebrates, six primary actin isoforms can be distinguished: alpha-skeletal, alpha-cardiac, alpha-smooth muscle, gamma-smooth muscle, beta-cytoplasmic and gamma-cytoplasmic isoactin. Expression of these actin isoforms during vertebrate development is highly regulated in a temporal and tissue-specific manner, but the mechanisms and the specific differences are currently not well understood. All members of the actin multigene family are highly conserved, suggesting that there is a high selective pressure on these proteins. Results We present here a model for the evolution of the genomic organization of alpha-skeletal actin and by molecular modeling, illustrate the structural differences of actin proteins of different phyla. We further describe and compare alpha-skeletal actin expression in two developmental stages of five vertebrate species (mouse, chicken, snake, salamander and fish. Our findings confirm that alpha-skeletal actin is expressed in skeletal muscle and in the heart of all five species. In addition, we identify many novel non-muscular expression domains including several in the central nervous system. Conclusion Our results show that the high sequence homology of alpha-skeletal actins is reflected by similarities of their 3 dimensional protein structures, as well as by conserved gene expression patterns during vertebrate development. Nonetheless, we find here important differences in 3D structures, in gene architectures and identify novel expression domains for this structural and functional important gene.

Changes in Actin Organization During the Cytotoxic Process

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Radosevic, K.; Radosevic, Katarina; van Leeuwen, Anne Marie T.; Segers-Nolten, Gezina M.J.; Figdor, Carl; de Grooth, B.G.; Greve, Jan

1994-01-01

Changes in organization of F-actin during the cytotoxic process between NK and K562 cells have been observed and studied using confpcal laser scanning microscopy and quantitative fluorescence microscopy. An increase in F-actin content and orientation of F-actin towards the target cell have been

Antibodies to actin in autoimmune haemolytic anaemia

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Ritzmann Mathias

2010-03-01

Full Text Available Abstract Background In autoimmune haemolytic anaemia (AIHA, autoreactive antibodies directed against red blood cells are up-regulated, leading to erythrocyte death. Mycoplasma suis infections in pigs induce AIHA of both the warm and cold types. The aim of this study was to identify the target autoantigens of warm autoreactive IgG antibodies. Sera from experimentally M. suis-infected pigs were screened for autoreactivity. Results Actin-reactive antibodies were found in the sera of 95% of all animals tested. The reactivity was species-specific, i.e. reactivity with porcine actin was significantly higher than with rabbit actin. Sera of animals previously immunised with the M. suis adhesion protein MSG1 showed reactivity with actin prior to infection with M. suis indicating that molecular mimicry is involved in the specific autoreactive mechanism. A potentially cross-reactive epitope was detected. Conclusions This is the first report of autoreactive anti-actin antibodies involved in the pathogenesis of autoimmune haemolytic anaemia.

Structural Basis of Actin Filament Nucleation by Tandem W Domains

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Chen, Xiaorui; Ni, Fengyun; Tian, Xia; Kondrashkina, Elena; Wang, Qinghua; Ma, Jianpeng

2013-01-01

SUMMARY Spontaneous nucleation of actin is very inefficient in cells. To overcome this barrier, cells have evolved a set of actin filament nucleators to promote rapid nucleation and polymerization in response to specific stimuli. However, the molecular mechanism of actin nucleation remains poorly understood. This is hindered largely by the fact that actin nucleus, once formed, rapidly polymerizes into filament, thus making it impossible to capture stable multisubunit actin nucleus. Here, we report an effective double-mutant strategy to stabilize actin nucleus by preventing further polymerization. Employing this strategy, we solved the crystal structure of AMPPNP-actin in complex with the first two tandem W domains of Cordon-bleu (Cobl), a potent actin filament nucleator. Further sequence comparison and functional studies suggest that the nucleation mechanism of Cobl is probably shared by the p53 cofactor JMY, but not Spire. Moreover, the double-mutant strategy opens the way for atomic mechanistic study of actin nucleation and polymerization. PMID:23727244

Probing GFP-actin diffusion in living cells using fluorescence correlation spectroscopy

International Nuclear Information System (INIS)

Engelke, Hanna; Heinrich, Doris; Rädler, Joachim O.

2010-01-01

The cytoskeleton of eukaryotic cells is continuously remodeled by polymerization and depolymerization of actin. Consequently, the relative content of polymerized filamentous actin (F-actin) and monomeric globular actin (G-actin) is subject to temporal and spatial fluctuations. Since fluorescence correlation spectroscopy (FCS) can measure the diffusion of fluorescently labeled actin it seems likely that FCS allows us to determine the dynamics and hence indirectly the structural properties of the cytoskeleton components with high spatial resolution. To this end we investigate the FCS signal of GFP-actin in living Dictyostelium discoideum cells and explore the inherent spatial and temporal signatures of the actin cytoskeleton. Using the free green fluorescent protein (GFP) as a reference, we find that actin diffusion inside cells is dominated by G-actin and slower than diffusion in diluted cell extract. The FCS signal in the dense cortical F-actin network near the cell membrane is probed using the cytoskeleton protein LIM and is found to be slower than cytosolic G-actin diffusion. Furthermore, we show that polymerization of the cytoskeleton induced by Jasplakinolide leads to a substantial decrease of G-actin diffusion. Pronounced fluctuations in the distribution of the FCS correlation curves can be induced by latrunculin, which is known to induce actin waves. Our work suggests that the FCS signal of GFP-actin in combination with scanning or spatial correlation techniques yield valuable information about the local dynamics and concomitant cytoskeletal properties

Chronic Actinic Dermatitis

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Bengü Çevirgen Cemil

2017-06-01

Full Text Available Chronic actinic dermatitis (CAD is characterized by persistent eczema-like lesions, mainly on sun-exposed sites, induced by ultraviolet B, sometimes ultraviolet A, and occasionally visible light. CAD is a rare photodermatitis. It is often associated with contact allergens including airborne allergens such as fragrances, plant antigens and topical medications. A 62 year old farmer is applied with eczematous lesions restricted to sun-exposed areas. Clinical findings and histopathologic features were consistent with the diagnosis of chronic actinic dermatitis. The patient also had contact allergy to multiple allergens. We present this case to emphasize the significance of patch test on CAD treatment and the success of topical tacrolimus and azathioprine.

Actinic Granuloma with Focal Segmental Glomerulosclerosis

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Ruedee Phasukthaworn

2016-02-01

Full Text Available Actinic granuloma is an uncommon granulomatous disease, characterized by annular erythematous plaque with central clearing predominately located on sun-damaged skin. The pathogenesis is not well understood, ultraviolet radiation is recognized as precipitating factor. We report a case of a 52-year-old woman who presented with asymptomatic annular erythematous plaques on the forehead and both cheeks persisting for 2 years. The clinical presentation and histopathologic findings support the diagnosis of actinic granuloma. During that period of time, she also developed focal segmental glomerulosclerosis. The association between actinic granuloma and focal segmental glomerulosclerosis needs to be clarified by further studies.

Ring closure in actin polymers

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Sinha, Supurna, E-mail: supurna@rri.res.in [Raman Research Institute, Bangalore 560080 (India); Chattopadhyay, Sebanti [Doon University, Dehradun 248001 (India)

2017-03-18

We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers. - Highlights: • Ring closure of biopolymers. • Worm like chain model. • Predictions for experiments.

The evolution of compositionally and functionally distinct actin filaments.

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Gunning, Peter W; Ghoshdastider, Umesh; Whitaker, Shane; Popp, David; Robinson, Robert C

2015-06-01

The actin filament is astonishingly well conserved across a diverse set of eukaryotic species. It has essentially remained unchanged in the billion years that separate yeast, Arabidopsis and man. In contrast, bacterial actin-like proteins have diverged to the extreme, and many of them are not readily identified from sequence-based homology searches. Here, we present phylogenetic analyses that point to an evolutionary drive to diversify actin filament composition across kingdoms. Bacteria use a one-filament-one-function system to create distinct filament systems within a single cell. In contrast, eukaryotic actin is a universal force provider in a wide range of processes. In plants, there has been an expansion of the number of closely related actin genes, whereas in fungi and metazoa diversification in tropomyosins has increased the compositional variety in actin filament systems. Both mechanisms dictate the subset of actin-binding proteins that interact with each filament type, leading to specialization in function. In this Hypothesis, we thus propose that different mechanisms were selected in bacteria, plants and metazoa, which achieved actin filament compositional variation leading to the expansion of their functional diversity. © 2015. Published by The Company of Biologists Ltd.

Morphodynamics of the Actin-Rich Cytoskeleton in Entamoeba histolytica

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Maria Manich

2018-05-01

Full Text Available Entamoeba histolytica is the anaerobic protozoan parasite responsible for human amoebiasis, the third most deadly parasitic disease worldwide. This highly motile eukaryotic cell invades human tissues and constitutes an excellent experimental model of cell motility and cell shape deformation. The absence of extranuclear microtubules in Entamoeba histolytica means that the actin-rich cytoskeleton takes on a crucial role in not only amoebic motility but also other processes sustaining pathogenesis, such as the phagocytosis of human cells and the parasite's resistance of host immune responses. Actin is highly conserved among eukaryotes, although diverse isoforms exist in almost all organisms studied to date. However, E. histolytica has a single actin protein, the structure of which differs significantly from those of its human homologs. Here, we studied the expression, structure and dynamics of actin in E. histolytica. We used molecular and cellular approaches to evaluate actin gene expression during intestinal invasion by E. histolytica trophozoites. Based on a three-dimensional structural bioinformatics analysis, we characterized protein domains differences between amoebic actin and human actin. Fine-tuned molecular dynamics simulations enabled us to examine protein motion and refine the three-dimensional structures of both actins, including elements potentially accounting for differences changes in the affinity properties of amoebic actin and deoxyribonuclease I. The dynamic, multifunctional nature of the amoebic cytoskeleton prompted us to examine the pleiotropic forms of actin structures within live E. histolytica cells; we observed the cortical cytoskeleton, stress fibers, “dot-like” structures, adhesion plates, and macropinosomes. In line with these data, a proteomics study of actin-binding proteins highlighted the Arp2/3 protein complex as a crucial element for the development of macropinosomes and adhesion plaques.

Coordination of membrane and actin cytoskeleton dynamics during filopodia protrusion.

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Changsong Yang

2009-05-01

Full Text Available Leading edge protrusion of migrating cells involves tightly coordinated changes in the plasma membrane and actin cytoskeleton. It remains unclear whether polymerizing actin filaments push and deform the membrane, or membrane deformation occurs independently and is subsequently stabilized by actin filaments. To address this question, we employed an ability of the membrane-binding I-BAR domain of IRSp53 to uncouple the membrane and actin dynamics and to induce filopodia in expressing cells. Using time-lapse imaging and electron microscopy of IRSp53-I-BAR-expressing B16F1 melanoma cells, we demonstrate that cells are not able to protrude or maintain durable long extensions without actin filaments in their interior, but I-BAR-dependent membrane deformation can create a small and transient space at filopodial tips that is subsequently filled with actin filaments. Moreover, the expressed I-BAR domain forms a submembranous coat that may structurally support these transient actin-free protrusions until they are further stabilized by the actin cytoskeleton. Actin filaments in the I-BAR-induced filopodia, in contrast to normal filopodia, do not have a uniform length, are less abundant, poorly bundled, and display erratic dynamics. Such unconventional structural organization and dynamics of actin in I-BAR-induced filopodia suggests that a typical bundle of parallel actin filaments is not necessary for generation and mechanical support of the highly asymmetric filopodial geometry. Together, our data suggest that actin filaments may not directly drive the protrusion, but only stabilize the space generated by the membrane deformation; yet, such stabilization is necessary for efficient protrusion.

The conserved Tarp actin binding domain is important for chlamydial invasion.

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Travis J Jewett

2010-07-01

Full Text Available The translocated actin recruiting phosphoprotein (Tarp is conserved among all pathogenic chlamydial species. Previous reports identified single C. trachomatis Tarp actin binding and proline rich domains required for Tarp mediated actin nucleation. A peptide antiserum specific for the Tarp actin binding domain was generated and inhibited actin polymerization in vitro and C. trachomatis entry in vivo, indicating an essential role for Tarp in chlamydial pathogenesis. Sequence analysis of Tarp orthologs from additional chlamydial species and C. trachomatis serovars indicated multiple putative actin binding sites. In order to determine whether the identified actin binding domains are functionally conserved, GST-Tarp fusions from multiple chlamydial species were examined for their ability to bind and nucleate actin. Chlamydial Tarps harbored variable numbers of actin binding sites and promoted actin nucleation as determined by in vitro polymerization assays. Our findings indicate that Tarp mediated actin binding and nucleation is a conserved feature among diverse chlamydial species and this function plays a critical role in bacterial invasion of host cells.

The superficial ulnar artery: development and clinical significance Artéria ulnar superficial: desenvolvimento e relevância clínica

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Srinivasulu Reddy

2007-09-01

Full Text Available The principal arteries of the upper limb show a wide range of variation that is of considerable interest to orthopedic surgeons, plastic surgeons, radiologists and anatomists. We present here a case of superficial ulnar artery found during the routine dissection of right upper limb of a 50-year-old male cadaver. The superficial ulnar artery originated from the brachial artery, crossed the median nerve anteriorly and ran lateral to this nerve and the brachial artery. The superficial ulnar artery in the arm gave rise to a narrow muscular branch to the biceps brachii. At the elbow level the artery ran superficial to the bicipital aponeurosis where it was crossed by the median cubital vein. It then ran downward and medially superficial to the forearm flexor muscles, and then downward to enter the hand. At the palm, it formed the superficial and deep palmar arches together with the branches of the radial artery. The presence of a superficial ulnar artery is clinically important when raising forearm flaps in reconstructive surgery. The embryology and clinical significance of the variation are discussed.As principais artérias do membro superior apresentam uma ampla variação, que é relativamente importante a cirurgiões ortopédicos e plásticos, radiologistas e anatomistas.Apresentamosumcaso de artéria ulnar superficial encontrada durante dissecção de rotina de membro superior direito de um cadáver masculino de 50 anos de idade.Aartéria ulnar superficial originava-se da artéria braquial, cruzava o nervo mediano anteriormente e percorria lateralmente esse nervo e a artéria braquial. A artéria ulnar superficial no braço deu origem a um ramo muscular estreito do músculo bíceps braquial. Ao nível do cotovelo, a artéria percorria superficialmente a aponeurose bicipital, onde era cruzada pela veia cubital mediana. Percorria, então, em sentido descendente e medialmente superficial aos músculos flexores do antebraço, e então descendia para

Superficies de segundo orden

OpenAIRE

Salazar Salazar, Luis Álvaro

1987-01-01

Este trabajo se propone poner al alcance de estudiantes de primeros semestres de carreras de aplicación de la matemática, un algoritmo proporcionado por el álgebra lineal, para tratar con mas generalidad, agilidad y libertad unos objetos de la geometría analítica de no fácil manipulación por otros métodos y que se conocen como superficies de segundo orden o superficies cuádricas. En este orden de ideas, el autor considera importante que con este tratamiento se incluya este tema en una asignat...

Dermal changes in superficial basal cell carcinoma, melanoma in situ and actinic keratosis and their implications

Science.gov (United States)

Kazlouskaya, Viktoryia; Malhotra, Saurabh; Navarro, Raquel; Wu, Karen Nguyen; Shvartsbeyn, Marianna; Shengli, Chen; Gui, Jiang; Elston, Dirk M.

2018-01-01

Background Basal cell carcinoma (BCC) has a characteristic stroma, but less is known about the dermal characteristics associated with melanoma in situ (MIS) and actinic keratosis (AK). Materials and methods Dermal changes were studied in 301 specimens of AK, BCC and MIS. Subsequently, blinded images of dermal changes from 90 randomly selected cases of those entities were used to assess the predictive value of the dermal changes. Agreement with the final diagnosis was calculated using kappa coefficient (κ). Results Fibromyxoid stroma was present in 82% of BCC cases; fibrous stroma was seen in 25% of BCC, 58% of MIS and 35.6% of AK specimens (p <0.05). A lichenoid inflammatory infiltrate was frequently associated with AK and a perifollicular infiltrate with periadnexal fibrosis with MIS. Blinded evaluation of images of the dermal changes associated with the tumors yielded the correct diagnosis in (54.4, 41.1 and 27.8%; average 41.2%) by the three appraisers. Coefficient of agreement in blinded imaged evaluation with the actual diagnosis was higher in the BCC and MIS compared with AK (κ = 0.37, p = 0.0001; κ = 0.2, p = 0.0005 and κ = −0.06, p = 0.84, respectively). Conclusion Dermal features may be helpful in predicting the correct diagnosis when tumor is not visible. PMID:24117926

Actin dynamics, architecture, and mechanics in cell motility.

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Blanchoin, Laurent; Boujemaa-Paterski, Rajaa; Sykes, Cécile; Plastino, Julie

2014-01-01

Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or "dashpots" (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.

Actin-cytoskeleton rearrangement modulates proton-induced uptake

Energy Technology Data Exchange (ETDEWEB)

Ben-Dov, Nadav [Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv (Israel); Korenstein, Rafi, E-mail: korens@post.tau.ac.il [Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv (Israel)

2013-04-15

Recently it has been shown that elevating proton concentration at the cell surface stimulates the formation of membrane invaginations and vesicles accompanied by an enhanced uptake of macromolecules. While the initial induction of inward membrane curvature was rationalized in terms of proton-based increase of charge asymmetry across the membrane, the mechanisms underlying vesicle formation and its scission are still unknown. In light of the critical role of actin in vesicle formation during endocytosis, the present study addresses the involvement of cytoskeletal actin in proton-induced uptake (PIU). The uptake of dextran-FITC is used as a measure for the factual fraction of inward invaginations that undergo scission from the cell's plasma membrane. Our findings show that the rate of PIU in suspended cells is constant, whereas the rate of PIU in adherent cells is gradually increased in time, saturating at the level possessed by suspended cells. This is consistent with pH induced gradual degradation of stress-fibers in adherent cells. Wortmannin and calyculin-A are able to elevate PIU by 25% in adherent cells but not in suspended cells, while cytochalasin-D, rapamycin and latrunculin-A elevate PIU both in adherent and suspended cells. However, extensive actin depolymerization by high concentrations of latrunculin-A is able to inhibit PIU. We conclude that proton-induced membrane vesiculation is restricted by the actin structural resistance to the plasma membrane bending. Nevertheless, a certain degree of cortical actin restructuring is required for the completion of the scission process. - Highlights: ► Acidification of cells' exterior enhances uptake of macromolecules by the cells. ► Disruption of actin stress fibers leads to enhancement of proton induced uptake. ► Extensive depolymerization of cellular actin attenuates proton-induced uptake.

Actin and Arp2/3 localize at the centrosome of interphase cells

Energy Technology Data Exchange (ETDEWEB)

Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan, E-mail: jan.gettemans@vib-ugent.be

2011-01-07

Research highlights: {yields} Actin was detected at the centrosome with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. {yields} Centrosomal actin was found in interphase but not mitotic MDA-MB-231 cells. {yields} Neither the anti-actin antibody C4 that binds to globular, monomer actin, nor the anti-actin antibody 2G2 that recognizes the nuclear conformation of actin detect actin at the centrosome. {yields} The Arp2/3 complex transiently localizes at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. -- Abstract: Although many actin binding proteins such as cortactin and the Arp2/3 activator WASH localize at the centrosome, the presence and conformation of actin at the centrosome has remained elusive. Here, we report the localization of actin at the centrosome in interphase but not in mitotic MDA-MB-231 cells. Centrosomal actin was detected with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. In addition, we report the transient presence of the Arp2/3 complex at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. Overexpression of an Arp2/3 component resulted in expansion of the pericentriolar matrix and selective accumulation of the Arp2/3 component in the pericentriolar matrix. Altogether, we hypothesize that the centrosome transiently recruits Arp2/3 to perform processes such as centrosome separation prior to mitotic entry, whereas the observed constitutive centrosomal actin staining in interphase cells reinforces the current model of actin-based centrosome reorientation toward the leading edge in migrating cells.

Actin and Arp2/3 localize at the centrosome of interphase cells

International Nuclear Information System (INIS)

Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan

2011-01-01

Research highlights: → Actin was detected at the centrosome with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. → Centrosomal actin was found in interphase but not mitotic MDA-MB-231 cells. → Neither the anti-actin antibody C4 that binds to globular, monomer actin, nor the anti-actin antibody 2G2 that recognizes the nuclear conformation of actin detect actin at the centrosome. → The Arp2/3 complex transiently localizes at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. -- Abstract: Although many actin binding proteins such as cortactin and the Arp2/3 activator WASH localize at the centrosome, the presence and conformation of actin at the centrosome has remained elusive. Here, we report the localization of actin at the centrosome in interphase but not in mitotic MDA-MB-231 cells. Centrosomal actin was detected with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. In addition, we report the transient presence of the Arp2/3 complex at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. Overexpression of an Arp2/3 component resulted in expansion of the pericentriolar matrix and selective accumulation of the Arp2/3 component in the pericentriolar matrix. Altogether, we hypothesize that the centrosome transiently recruits Arp2/3 to perform processes such as centrosome separation prior to mitotic entry, whereas the observed constitutive centrosomal actin staining in interphase cells reinforces the current model of actin-based centrosome reorientation toward the leading edge in migrating cells.

The 5’cap of Tobacco Mosaic Virus (TMV) is required for virion attachment to the actin/ER network during early infection

DEFF Research Database (Denmark)

Christensen, Nynne Meyn; Tilsner, Jens; Bell, Karen

to the motile cortical actin/ER network within minutes of injection. Granule movement on actin/ER was arrested by actin inhibitors indicating actindependent RNA movement. The 5’ methylguanosine TMV cap was shown to be required for vRNA anchoring to the ER. TMV vRNA lacking the 5’cap failed to form granules...... the fluorescent vRNA pool nor co-injected GFP left the injected trichome, indicating that the synthesis of unlabelled progeny viral (v)RNA is required to initiate cell-cell movement, and that virus movement is not accompanied by passive plasmodesmatal gating. Cy3-vRNA formed granules that became anchored...... on the same ER-bound granules, indicating that TMV virions may become attached to the ER prior to uncoating of the viral genome....

Incorporation of β-actin loading control into zymography.

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Govindasamy, Natasha; Yan, MengJie; Jurasz, Paul

2016-11-01

Gelatin zymography and immunoblot are widely used gel electrophoresis techniques to study matrix metalloproteinases-2 and -9. Each method has its advantages and disadvantages. Zymography is exquisitely sensitive but offers no loading control to ensure equal sample loading. Immunoblot is a 100-1000-fold less sensitive, but allows for the probing of a sample loading control such as β-actin to ensure accurate protein loading. In this report, we describe two simple protocols that combine gelatin zymography to study MMP-2 and -9 levels with an in-gel β-actin immunoblot loading control, thus combining sensitivity and accuracy in a single assay. The protocols incorporate the loading of molecular weight markers to demarcate MMP-2/-9 from the β-actin. The first protocol utilizes the overlay of a 10% zymography gel over a 5% Tris-Glycine separating gel from which the β-actin is transferred. The second protocol involves the direct transfer of the β-actin from a single 10% zymography gel.

Bacterial subversion of host actin dynamics at the plasma membrane.

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Carabeo, Rey

2011-10-01

Invasion of non-phagocytic cells by a number of bacterial pathogens involves the subversion of the actin cytoskeletal remodelling machinery to produce actin-rich cell surface projections designed to engulf the bacteria. The signalling that occurs to induce these actin-rich structures has considerable overlap among a diverse group of bacteria. The molecular organization within these structures act in concert to internalize the invading pathogen. This dynamic process could be subdivided into three acts - actin recruitment, engulfment, and finally, actin disassembly/internalization. This review will present the current state of knowledge of the molecular processes involved in each stage of bacterial invasion, and provide a perspective that highlights the temporal and spatial control of actin remodelling that occurs during bacterial invasion. © 2011 Blackwell Publishing Ltd.

A nucleator arms race: cellular control of actin assembly.

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Campellone, Kenneth G; Welch, Matthew D

2010-04-01

For over a decade, the actin-related protein 2/3 (ARP2/3) complex, a handful of nucleation-promoting factors and formins were the only molecules known to directly nucleate actin filament formation de novo. However, the past several years have seen a surge in the discovery of mammalian proteins with roles in actin nucleation and dynamics. Newly recognized nucleation-promoting factors, such as WASP and SCAR homologue (WASH), WASP homologue associated with actin, membranes and microtubules (WHAMM), and junction-mediating regulatory protein (JMY), stimulate ARP2/3 activity at distinct cellular locations. Formin nucleators with additional biochemical and cellular activities have also been uncovered. Finally, the Spire, cordon-bleu and leiomodin nucleators have revealed new ways of overcoming the kinetic barriers to actin polymerization.

Amphidinolide H, a novel type of actin-stabilizing agent isolated from dinoflagellate

International Nuclear Information System (INIS)

Saito, Shin-ya; Feng Jue; Kira, Atsushi; Kobayashi, Jun'ichi; Ohizumi, Yasushi

2004-01-01

The effect of novel cytotoxic marine macrolide, amphidinolide H (Amp-H), on actin dynamics was investigated in vitro. Amp-H attenuated actin depolymerization induced by diluting F-actin. This effect remained after washing out of unbound Amp-H by filtration. In the presence of either Amp-H or phalloidin, lag phase, which is the rate-limiting step of actin polymerization, was shortened. Phalloidin decreased the polymerization-rate whereas Amp-H did not. Meanwhile, the effects of both compounds were the same when barbed end of actin was capped by cytochalasin D. Quartz crystal microbalance system revealed interaction of Amp-H with G-actin and F-actin. Amp-H also enhanced the binding of phalloidin to F-actin. We concluded that Amp-H stabilizes actin in a different manner from that of phalloidin and serves as a novel pharmacological tool for analyzing actin-mediated cell function

Regulation of the actin cytoskeleton-plasma membrane interplay by phosphoinositides.

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Saarikangas, Juha; Zhao, Hongxia; Lappalainen, Pekka

2010-01-01

The plasma membrane and the underlying cortical actin cytoskeleton undergo continuous dynamic interplay that is responsible for many essential aspects of cell physiology. Polymerization of actin filaments against cellular membranes provides the force for a number of cellular processes such as migration, morphogenesis, and endocytosis. Plasma membrane phosphoinositides (especially phosphatidylinositol bis- and trisphosphates) play a central role in regulating the organization and dynamics of the actin cytoskeleton by acting as platforms for protein recruitment, by triggering signaling cascades, and by directly regulating the activities of actin-binding proteins. Furthermore, a number of actin-associated proteins, such as BAR domain proteins, are capable of directly deforming phosphoinositide-rich membranes to induce plasma membrane protrusions or invaginations. Recent studies have also provided evidence that the actin cytoskeleton-plasma membrane interactions are misregulated in a number of pathological conditions such as cancer and during pathogen invasion. Here, we summarize the wealth of knowledge on how the cortical actin cytoskeleton is regulated by phosphoinositides during various cell biological processes. We also discuss the mechanisms by which interplay between actin dynamics and certain membrane deforming proteins regulate the morphology of the plasma membrane.

The cell wall of Arabidopsis thaliana influences actin network dynamics.

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Tolmie, Frances; Poulet, Axel; McKenna, Joseph; Sassmann, Stefan; Graumann, Katja; Deeks, Michael; Runions, John

2017-07-20

In plant cells, molecular connections link the cell wall-plasma membrane-actin cytoskeleton to form a continuum. It is hypothesized that the cell wall provides stable anchor points around which the actin cytoskeleton remodels. Here we use live cell imaging of fluorescently labelled marker proteins to quantify the organization and dynamics of the actin cytoskeleton and to determine the impact of disrupting connections within the continuum. Labelling of the actin cytoskeleton with green fluorescent protein (GFP)-fimbrin actin-binding domain 2 (FABD2) resulted in a network composed of fine filaments and thicker bundles that appeared as a highly dynamic remodelling meshwork. This differed substantially from the GFP-Lifeact-labelled network that appeared much more sparse with thick bundles that underwent 'simple movement', in which the bundles slightly change position, but in such a manner that the structure of the network was not substantially altered during the time of observation. Label-dependent differences in actin network morphology and remodelling necessitated development of two new image analysis techniques. The first of these, 'pairwise image subtraction', was applied to measurement of the more rapidly remodelling actin network labelled with GFP-FABD2, while the second, 'cumulative fluorescence intensity', was used to measure bulk remodelling of the actin cytoskeleton when labelled with GFP-Lifeact. In each case, these analysis techniques show that the actin cytoskeleton has a decreased rate of bulk remodelling when the cell wall-plasma membrane-actin continuum is disrupted either by plasmolysis or with isoxaben, a drug that specifically inhibits cellulose deposition. Changes in the rate of actin remodelling also affect its functionality, as observed by alteration in Golgi body motility. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Surfing pathogens and the lessons learned for actin polymerization.

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Frischknecht, F; Way, M

2001-01-01

A number of unrelated bacterial species as well as vaccinia virus (ab)use the process of actin polymerization to facilitate and enhance their infection cycle. Studies into the mechanism by which these pathogens hijack and control the actin cytoskeleton have provided many interesting insights into the regulation of actin polymerization in migrating cells. This review focuses on what we have learnt from the actin-based motilities of Listeria, Shigella and vaccinia and discusses what we would still like to learn from our nasty friends, including enteropathogenic Escherichia coli and Rickettsia

WICH, a member of WASP-interacting protein family, cross-links actin filaments

International Nuclear Information System (INIS)

Kato, Masayoshi; Takenawa, Tadaomi

2005-01-01

In yeast, Verprolin plays an important role in rearrangement of the actin cytoskeleton. There are three mammalian homologues of Verprolin, WIP, CR16, and WICH, and all of them bind actin and Wiskott-Aldrich syndrome protein (WASP) and/or neural-WASP. Here, we describe a novel function of WICH. In vitro co-sedimentation analysis revealed that WICH not only binds to actin filaments but also cross-links them. Fluorescence and electron microscopy detected that this cross-linking results in straight bundled actin filaments. Overexpression of WICH alone in cultured fibroblast caused the formation of thick actin fibers. This ability of WICH depended on its own actin cross-linking activity. Importantly, the actin cross-linking activity of WICH was modified through a direct association with N-WASP. Taken together, these data suggest that WICH induces a bundled form of actin filament with actin cross-linking activity and the association with N-WASP suppresses that activity. WICH thus appears to be a novel actin bundling protein

Binding and assembly of actin filaments by plasma membranes from dictyostelium discoideum

International Nuclear Information System (INIS)

Schwartz, M.A.; Luna, E.J.

1986-01-01

The binding of native, 125 I-Bolton-Hunter-labeled actin to purified Dictyostelium discoideum plasma membranes was measured using a sedimentation assay. Binding was saturable only in the presence of the actin capping protein, gelsolin. The binding curves were sigmoidal, indicating positive cooperativity at low actin concentrations. This cooperativity appeared to be due to actin-actin associations during polymerization, since phalloidin converted the curve to a hyperbolic shape. This membrane-bound actin stained with rhodamine-phalloidin and was cross-linked by m-maleimidobenzoyl succinimide ester, a bifunctional cross-linker, into multimers with the same pattern observed for cross-linked F-actin. The authors conclude that D. discoideum plasma membranes bind actin specifically and saturably and that these membranes organize actin into filaments below the normal critical concentration for polymerization. This interaction probably occurs between multiple binding sites on the membrane and the side of the actin filament, and may be related to the clustering of membrane proteins

A peek into tropomyosin binding and unfolding on the actin filament.

Directory of Open Access Journals (Sweden)

Abhishek Singh

Full Text Available BACKGROUND: Tropomyosin is a prototypical coiled coil along its length with subtle variations in structure that allow interactions with actin and other proteins. Actin binding globally stabilizes tropomyosin. Tropomyosin-actin interaction occurs periodically along the length of tropomyosin. However, it is not well understood how tropomyosin binds actin. PRINCIPAL FINDINGS: Tropomyosin's periodic binding sites make differential contributions to two components of actin binding, cooperativity and affinity, and can be classified as primary or secondary sites. We show through mutagenesis and analysis of recombinant striated muscle alpha-tropomyosins that primary actin binding sites have a destabilizing coiled-coil interface, typically alanine-rich, embedded within a non-interface recognition sequence. Introduction of an Ala cluster in place of the native, more stable interface in period 2 and/or period 3 sites (of seven increased the affinity or cooperativity of actin binding, analysed by cosedimentation and differential scanning calorimetry. Replacement of period 3 with period 5 sequence, an unstable region of known importance for cooperative actin binding, increased the cooperativity of binding. Introduction of the fluorescent probe, pyrene, near the mutation sites in periods 2 and 3 reported local instability, stabilization by actin binding, and local unfolding before or coincident with dissociation from actin (measured using light scattering, and chain dissociation (analyzed using circular dichroism. CONCLUSIONS: This, and previous work, suggests that regions of tropomyosin involved in binding actin have non-interface residues specific for interaction with actin and an unstable interface that is locally stabilized upon binding. The destabilized interface allows residues on the coiled-coil surface to obtain an optimal conformation for interaction with actin by increasing the number of local substates that the side chains can sample. We suggest

Two Functionally Distinct Sources of Actin Monomers Supply the Leading Edge of Lamellipodia

Science.gov (United States)

Vitriol, Eric A.; McMillen, Laura M.; Kapustina, Maryna; Gomez, Shawn M.; Vavylonis, Dimitrios; Zheng, James Q.

2015-01-01

Summary Lamellipodia, the sheet-like protrusions of motile cells, consist of networks of actin filaments (F-actin) regulated by the ordered assembly from and disassembly into actin monomers (G-actin). Traditionally, G-actin is thought to exist as a homogeneous pool. Here, we show that there are two functionally and molecularly distinct sources of G-actin that supply lamellipodial actin networks. G-actin originating from the cytosolic pool requires the monomer binding protein thymosin β4 (Tβ4) for optimal leading edge localization, is targeted to formins, and is responsible for creating an elevated G/F-actin ratio that promotes membrane protrusion. The second source of G-actin comes from recycled lamellipodia F-actin. Recycling occurs independently of Tβ4 and appears to regulate lamellipodia homeostasis. Tβ4-bound G-actin specifically localizes to the leading edge because it doesn’t interact with Arp2/3-mediated polymerization sites found throughout the lamellipodia. These findings demonstrate that actin networks can be constructed from multiple sources of monomers with discrete spatiotemporal functions. PMID:25865895

Automated detection of actinic keratoses in clinical photographs.

Science.gov (United States)

Hames, Samuel C; Sinnya, Sudipta; Tan, Jean-Marie; Morze, Conrad; Sahebian, Azadeh; Soyer, H Peter; Prow, Tarl W

2015-01-01

Clinical diagnosis of actinic keratosis is known to have intra- and inter-observer variability, and there is currently no non-invasive and objective measure to diagnose these lesions. The aim of this pilot study was to determine if automatically detecting and circumscribing actinic keratoses in clinical photographs is feasible. Photographs of the face and dorsal forearms were acquired in 20 volunteers from two groups: the first with at least on actinic keratosis present on the face and each arm, the second with no actinic keratoses. The photographs were automatically analysed using colour space transforms and morphological features to detect erythema. The automated output was compared with a senior consultant dermatologist's assessment of the photographs, including the intra-observer variability. Performance was assessed by the correlation between total lesions detected by automated method and dermatologist, and whether the individual lesions detected were in the same location as the dermatologist identified lesions. Additionally, the ability to limit false positives was assessed by automatic assessment of the photographs from the no actinic keratosis group in comparison to the high actinic keratosis group. The correlation between the automatic and dermatologist counts was 0.62 on the face and 0.51 on the arms, compared to the dermatologist's intra-observer variation of 0.83 and 0.93 for the same. Sensitivity of automatic detection was 39.5% on the face, 53.1% on the arms. Positive predictive values were 13.9% on the face and 39.8% on the arms. Significantly more lesions (p<0.0001) were detected in the high actinic keratosis group compared to the no actinic keratosis group. The proposed method was inferior to assessment by the dermatologist in terms of sensitivity and positive predictive value. However, this pilot study used only a single simple feature and was still able to achieve sensitivity of detection of 53.1% on the arms.This suggests that image analysis is

How capping protein enhances actin filament growth and nucleation on biomimetic beads.

Science.gov (United States)

Wang, Ruizhe; Carlsson, Anders E

2015-11-25

Capping protein (CP), which caps the growing ends of actin filaments, accelerates actin-based motility. Recent experiments on biomimetic beads have shown that CP also enhances the rate of actin filament nucleation. Proposed explanations for these phenomena include (i) the actin funneling hypothesis (AFH), in which the presence of CP increases the free-actin concentration, and (ii) the monomer gating model, in which CP binding to actin filament barbed ends makes more monomers available for filament nucleation. To establish how CP increases the rates of filament elongation and nucleation on biomimetic beads, we perform a quantitative modeling analysis of actin polymerization, using rate equations that include actin filament nucleation, polymerization and capping, as modified by monomer depletion near the surface of the bead. With one adjustable parameter, our simulation results match previously measured time courses of polymerized actin and filament number. The results support a version of the AFH where CP increases the local actin monomer concentration at the bead surface, but leaves the global free-actin concentration nearly constant. Because the rate of filament nucleation increases with the monomer concentration, the increased local monomer concentration enhances actin filament nucleation. We derive a closed-form formula for the characteristic CP concentration where the local free-actin concentration reaches half the bulk value, and find it to be comparable to the global Arp2/3 complex concentration. We also propose an experimental protocol for distinguishing branching nucleation of filaments from spontaneous nucleation.

Toward the Structure of Dynamic Membrane-Anchored Actin Networks

Science.gov (United States)

Weber, Igor

2007-01-01

In the cortex of a motile cell, membrane-anchored actin filaments assemble into structures of varying shape and function. Filopodia are distinguished by a core of bundled actin filaments within finger-like extensions of the membrane. In a recent paper by Medalia et al1 cryo-electron tomography has been used to reconstruct, from filopodia of Dictyostelium cells, the 3-dimensional organization of actin filaments in connection with the plasma membrane. A special arrangement of short filaments converging toward the filopod's tip has been called a “terminal cone”. In this region force is applied for protrusion of the membrane. Here we discuss actin organization in the filopodia of Dictyostelium in the light of current views on forces that are generated by polymerizing actin filaments, and on the resistance of membranes against deformation that counteracts these forces. PMID:19262130

Monoubiquitination Inhibits the Actin Bundling Activity of Fascin.

Science.gov (United States)

Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

2016-12-30

Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys 247 and Lys 250 , two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC 50 , delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Monoubiquitination Inhibits the Actin Bundling Activity of Fascin*

Science.gov (United States)

Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

2016-01-01

Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys247 and Lys250, two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC50, delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. PMID:27879315

A single charge in the actin binding domain of fascin can independently tune the linear and non-linear response of an actin bundle network.

Science.gov (United States)

Maier, M; Müller, K W; Heussinger, C; Köhler, S; Wall, W A; Bausch, A R; Lieleg, O

2015-05-01

Actin binding proteins (ABPs) not only set the structure of actin filament assemblies but also mediate the frequency-dependent viscoelastic moduli of cross-linked and bundled actin networks. Point mutations in the actin binding domain of those ABPs can tune the association and dissociation dynamics of the actin/ABP bond and thus modulate the network mechanics both in the linear and non-linear response regime. We here demonstrate how the exchange of a single charged amino acid in the actin binding domain of the ABP fascin triggers such a modulation of the network rheology. Whereas the overall structure of the bundle networks is conserved, the transition point from strain-hardening to strain-weakening sensitively depends on the cross-linker off-rate and the applied shear rate. Our experimental results are consistent both with numerical simulations of a cross-linked bundle network and a theoretical description of the bundle network mechanics which is based on non-affine bending deformations and force-dependent cross-link dynamics.

Imaging of the most frequent superficial soft-tissue sarcomas

International Nuclear Information System (INIS)

Morel, Melanie; Taieb, Sophie; Ceugnart, Luc; Penel, Nicolas; Mortier, Laurent; Vanseymortier, Luc; Robin, Y.M.; Gosset, Pierre; Cotten, Anne

2011-01-01

Superficial soft-tissue sarcomas are malignant mesenchymal tumors located within the cutaneous and/or subcutaneous layers. Most superficial soft-tissue sarcomas are low-grade tumors; yet, the risk of local recurrence is high, and initial wide surgery is the main prognostic factor. Some of these superficial sarcomas may grow, following an infiltrative pattern, and their real extent may be underestimated clinically. Imaging techniques are useful to determine precisely the real margins of the tumor, especially in cases of clinically doubtful or recurrent or large superficial lesions. Imaging tools enable one to determine the relationship with the superficial fascia separating the subcutaneous layer from the underlying muscle. In our institution ultrasonographic examination is followed by magnetic resonance (MR) imaging when the size of the lesion exceeds 3-5 cm. Imaging assessment is performed prior to biopsy, enabling optimal surgical management. Imaging features of the main superficial sarcomas are detailed in the following article, according to their major locations: those arising in the epidermis and/or dermis, which are most often diagnosed by dermatologists, and the subcutaneous sarcomas. (orig.)

Imaging of the most frequent superficial soft-tissue sarcomas

Energy Technology Data Exchange (ETDEWEB)

Morel, Melanie; Taieb, Sophie; Ceugnart, Luc [Centre Oscar Lambret, Department of Radiology, Lille (France); Penel, Nicolas [Centre Oscar Lambret, Department of Oncology, Lille (France); Mortier, Laurent [Centre Hospitalier Universitaire de Lille, Department of Dermatology, Hopital Claude Huriez, Lille (France); Vanseymortier, Luc [Centre Oscar Lambret, Department of Surgery, Lille (France); Robin, Y.M. [Centre Oscar Lambret, Departement of Pathology, Lille (France); Gosset, Pierre [Groupement Hospitalier de l' Institut Catholique-Faculte Libre de Medecine de Lille, Department of Pathology, Hopital Saint-Philibert, Lomme (France); Cotten, Anne [Centre Hospitalier Universitaire de Lille, Department of Musculoskeletal Radiology, Centre Hopital Roger Salengro, Lille (France)

2011-03-15

Superficial soft-tissue sarcomas are malignant mesenchymal tumors located within the cutaneous and/or subcutaneous layers. Most superficial soft-tissue sarcomas are low-grade tumors; yet, the risk of local recurrence is high, and initial wide surgery is the main prognostic factor. Some of these superficial sarcomas may grow, following an infiltrative pattern, and their real extent may be underestimated clinically. Imaging techniques are useful to determine precisely the real margins of the tumor, especially in cases of clinically doubtful or recurrent or large superficial lesions. Imaging tools enable one to determine the relationship with the superficial fascia separating the subcutaneous layer from the underlying muscle. In our institution ultrasonographic examination is followed by magnetic resonance (MR) imaging when the size of the lesion exceeds 3-5 cm. Imaging assessment is performed prior to biopsy, enabling optimal surgical management. Imaging features of the main superficial sarcomas are detailed in the following article, according to their major locations: those arising in the epidermis and/or dermis, which are most often diagnosed by dermatologists, and the subcutaneous sarcomas. (orig.)

Actin-myosin network is required for proper assembly of influenza virus particles

Energy Technology Data Exchange (ETDEWEB)

Kumakura, Michiko; Kawaguchi, Atsushi, E-mail: ats-kawaguchi@md.tsukuba.ac.jp; Nagata, Kyosuke, E-mail: knagata@md.tsukuba.ac.jp

2015-02-15

Actin filaments are known to play a central role in cellular dynamics. After polymerization of actin, various actin-crosslinking proteins including non-muscle myosin II facilitate the formation of spatially organized actin filament networks. The actin-myosin network is highly expanded beneath plasma membrane. The genome of influenza virus (vRNA) replicates in the cell nucleus. Then, newly synthesized vRNAs are nuclear-exported to the cytoplasm as ribonucleoprotein complexes (vRNPs), followed by transport to the beneath plasma membrane where virus particles assemble. Here, we found that, by inhibiting actin-myosin network formation, the virus titer tends to be reduced and HA viral spike protein is aggregated on the plasma membrane. These results indicate that the actin-myosin network plays an important role in the virus formation. - Highlights: • Actin-myosin network is important for the influenza virus production. • HA forms aggregations at the plasma membrane in the presence of blebbistatin. • M1 is recruited to the budding site through the actin-myosin network.

Actin-myosin network is required for proper assembly of influenza virus particles

International Nuclear Information System (INIS)

Kumakura, Michiko; Kawaguchi, Atsushi; Nagata, Kyosuke

2015-01-01

Actin filaments are known to play a central role in cellular dynamics. After polymerization of actin, various actin-crosslinking proteins including non-muscle myosin II facilitate the formation of spatially organized actin filament networks. The actin-myosin network is highly expanded beneath plasma membrane. The genome of influenza virus (vRNA) replicates in the cell nucleus. Then, newly synthesized vRNAs are nuclear-exported to the cytoplasm as ribonucleoprotein complexes (vRNPs), followed by transport to the beneath plasma membrane where virus particles assemble. Here, we found that, by inhibiting actin-myosin network formation, the virus titer tends to be reduced and HA viral spike protein is aggregated on the plasma membrane. These results indicate that the actin-myosin network plays an important role in the virus formation. - Highlights: • Actin-myosin network is important for the influenza virus production. • HA forms aggregations at the plasma membrane in the presence of blebbistatin. • M1 is recruited to the budding site through the actin-myosin network

Activation of the skeletal alpha-actin promoter during muscle regeneration.

Science.gov (United States)

Marsh, D R; Carson, J A; Stewart, L N; Booth, F W

1998-11-01

Little is known concerning promoter regulation of genes in regenerating skeletal muscles. In young rats, recovery of muscle mass and protein content is complete within 21 days. During the initial 5-10 days of regeneration, mRNA abundance for IGF-I, myogenin and MyoD have been shown to be dramatically increased. The skeletal alpha-actin promoter contains E box and serum response element (SRE) regulatory regions which are directly or indirectly activated by myogenin (or MyoD) and IGF-I proteins, respectively. We hypothesized that the skeletal alpha-actin promoter activity would increase during muscle regeneration, and that this induction would occur before muscle protein content returned to normal. Total protein content and the percentage content of skeletal alpha-actin protein was diminished at 4 and 8 days and re-accumulation had largely occurred by 16 days post-bupivacaine injection. Skeletal alpha-actin mRNA per whole muscle was decreased at day 8, and thereafter returned to control values. During regeneration at day 8, luciferase activity (a reporter of promoter activity) directed by -424 skeletal alpha-actin and -99 skeletal alpha-actin promoter constructs was increased by 700% and 250% respectively; however, at day 16, skeletal alpha-actin promoter activities were similar to control values. Thus, initial activation of the skeletal alpha-actin promoter is associated with regeneration of skeletal muscle, despite not being sustained during the later stages of regrowth. The proximal SRE of the skeletal alpha-actin promoter was not sufficient to confer a regeneration-induced promoter activation, despite increased serum response factor protein binding to this regulatory element in electrophoretic mobility shift assays. Skeletal alpha-actin promoter induction during regeneration is due to a combination of regulatory elements, at least including the SRE and E box.

The effect of pyrene labelling on the thermal stability of actin filaments

International Nuclear Information System (INIS)

Halasi, Szulamit; Papp, Gabor; Bugyi, Beata; Barko, Szilvia; Orban, Jozsef; Ujfalusi, Zoltan; Visegrady, Balazs

2006-01-01

The ability of actin to form filaments is fundamental to its biological function and often characterised by various methods in vitro. One of the most frequently used methods capitalises on the observation that the fluorescence emission of a pyrene label on the Cys-374 residue of actin is enhanced by a factor of ∼20 during polymerisation. This method inherently involves the chemical modification of actin monomers with pyrene. It was reported earlier that the pyrene labelling of actin monomers has only small effect on the polymerisation and depolymerisation rates of actin, indicating that the method is suitable to characterise the effect of actin-binding proteins or peptides on the polymerisation kinetics. In our present work we tested the effect of the pyrene labelling on the thermal denaturation of actin filaments by using the method of differential scanning calorimetry (DSC). By recording the heat denaturation profiles of unlabelled and pyrene labelled actin filaments we observed that pyrene labelling shifted the melting point (T m ) of actin filaments from 66 to 68 deg. C. A similar effect was detected in the presence of equimolar concentration of phalloidin where the T m shifted from 79 to 82 deg. C. We concluded that the observed pyrene labelling induced differences of the thermal denaturation of actin filaments were small. The DSC results, therefore, confirmed that the methods based on the measurements of pyrene intensity during actin polymerisation are suitable to characterise the polymerisation kinetics of actin under in vitro conditions

Changes in actin dynamics are involved in salicylic acid signaling pathway.

Science.gov (United States)

Matoušková, Jindřiška; Janda, Martin; Fišer, Radovan; Sašek, Vladimír; Kocourková, Daniela; Burketová, Lenka; Dušková, Jiřina; Martinec, Jan; Valentová, Olga

2014-06-01

Changes in actin cytoskeleton dynamics are one of the crucial players in many physiological as well as non-physiological processes in plant cells. Positioning of actin filament arrays is necessary for successful establishment of primary lines of defense toward pathogen attack, depolymerization leads very often to the enhanced susceptibility to the invading pathogen. On the other hand it was also shown that the disruption of actin cytoskeleton leads to the induction of defense response leading to the expression of PATHOGENESIS RELATED proteins (PR). In this study we show that pharmacological actin depolymerization leads to the specific induction of genes in salicylic acid pathway but not that involved in jasmonic acid signaling. Life imaging of leafs of Arabidopsis thaliana with GFP-tagged fimbrin (GFP-fABD2) treated with 1 mM salicylic acid revealed rapid disruption of actin filaments resembling the pattern viewed after treatment with 200 nM latrunculin B. The effect of salicylic acid on actin filament fragmentation was prevented by exogenous addition of phosphatidic acid, which binds to the capping protein and thus promotes actin polymerization. The quantitative evaluation of actin filament dynamics is also presented. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Superficial dose evaluation of four dose calculation algorithms

Science.gov (United States)

Cao, Ying; Yang, Xiaoyu; Yang, Zhen; Qiu, Xiaoping; Lv, Zhiping; Lei, Mingjun; Liu, Gui; Zhang, Zijian; Hu, Yongmei

2017-08-01

Accurate superficial dose calculation is of major importance because of the skin toxicity in radiotherapy, especially within the initial 2 mm depth being considered more clinically relevant. The aim of this study is to evaluate superficial dose calculation accuracy of four commonly used algorithms in commercially available treatment planning systems (TPS) by Monte Carlo (MC) simulation and film measurements. The superficial dose in a simple geometrical phantom with size of 30 cm×30 cm×30 cm was calculated by PBC (Pencil Beam Convolution), AAA (Analytical Anisotropic Algorithm), AXB (Acuros XB) in Eclipse system and CCC (Collapsed Cone Convolution) in Raystation system under the conditions of source to surface distance (SSD) of 100 cm and field size (FS) of 10×10 cm2. EGSnrc (BEAMnrc/DOSXYZnrc) program was performed to simulate the central axis dose distribution of Varian Trilogy accelerator, combined with measurements of superficial dose distribution by an extrapolation method of multilayer radiochromic films, to estimate the dose calculation accuracy of four algorithms in the superficial region which was recommended in detail by the ICRU (International Commission on Radiation Units and Measurement) and the ICRP (International Commission on Radiological Protection). In superficial region, good agreement was achieved between MC simulation and film extrapolation method, with the mean differences less than 1%, 2% and 5% for 0°, 30° and 60°, respectively. The relative skin dose errors were 0.84%, 1.88% and 3.90%; the mean dose discrepancies (0°, 30° and 60°) between each of four algorithms and MC simulation were (2.41±1.55%, 3.11±2.40%, and 1.53±1.05%), (3.09±3.00%, 3.10±3.01%, and 3.77±3.59%), (3.16±1.50%, 8.70±2.84%, and 18.20±4.10%) and (14.45±4.66%, 10.74±4.54%, and 3.34±3.26%) for AXB, CCC, AAA and PBC respectively. Monte Carlo simulation verified the feasibility of the superficial dose measurements by multilayer Gafchromic films. And the rank

Src kinases regulate de novo actin polymerization during exocytosis in neuroendocrine chromaffin cells.

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María José Olivares

Full Text Available The cortical actin network is dynamically rearranged during secretory processes. Nevertheless, it is unclear how de novo actin polymerization and the disruption of the preexisting actin network control transmitter release. Here we show that in bovine adrenal chromaffin cells, both formation of new actin filaments and disruption of the preexisting cortical actin network are induced by Ca2+ concentrations that trigger exocytosis. These two processes appear to regulate different stages of exocytosis; whereas the inhibition of actin polymerization with the N-WASP inhibitor wiskostatin restricts fusion pore expansion, thus limiting the release of transmitters, the disruption of the cortical actin network with cytochalasin D increases the amount of transmitter released per event. Further, the Src kinase inhibitor PP2, and cSrc SH2 and SH3 domains also suppress Ca2+-dependent actin polymerization, and slow down fusion pore expansion without disturbing the cortical F-actin organization. Finally, the isolated SH3 domain of c-Src prevents both the disruption of the actin network and the increase in the quantal release induced by cytochalasin D. These findings support a model where a rise in the cytosolic Ca2+ triggers actin polymerization through a mechanism that involves Src kinases. The newly formed actin filaments would speed up the expansion of the initial fusion pore, whereas the preexisting actin network might control a different step of the exocytosis process.

A Legionella Effector Disrupts Host Cytoskeletal Structure by Cleaving Actin.

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Yao Liu

2017-01-01

Full Text Available Legionella pneumophila, the etiological agent of Legionnaires' disease, replicates intracellularly in protozoan and human hosts. Successful colonization and replication of this pathogen in host cells requires the Dot/Icm type IVB secretion system, which translocates approximately 300 effector proteins into the host cell to modulate various cellular processes. In this study, we identified RavK as a Dot/Icm substrate that targets the host cytoskeleton and reduces actin filament abundance in mammalian cells upon ectopic expression. RavK harbors an H95EXXH99 motif associated with diverse metalloproteases, which is essential for the inhibition of yeast growth and for the induction of cell rounding in HEK293T cells. We demonstrate that the actin protein itself is the cellular target of RavK and that this effector cleaves actin at a site between residues Thr351 and Phe352. Importantly, RavK-mediated actin cleavage also occurs during L. pneumophila infection. Cleavage by RavK abolishes the ability of actin to form polymers. Furthermore, an F352A mutation renders actin resistant to RavK-mediated cleavage; expression of the mutant in mammalian cells suppresses the cell rounding phenotype caused by RavK, further establishing that actin is the physiological substrate of RavK. Thus, L. pneumophila exploits components of the host cytoskeleton by multiple effectors with distinct mechanisms, highlighting the importance of modulating cellular processes governed by the actin cytoskeleton in the intracellular life cycle of this pathogen.

Allyl Isothiocyanate Inhibits Actin-Dependent Intracellular Transport in Arabidopsis thaliana

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Bjørnar Sporsheim

2015-12-01

Full Text Available Volatile allyl isothiocyanate (AITC derives from the biodegradation of the glucosinolate sinigrin and has been associated with growth inhibition in several plants, including the model plant Arabidopsis thaliana. However, the underlying cellular mechanisms of this feature remain scarcely investigated in plants. In this study, we present evidence of an AITC-induced inhibition of actin-dependent intracellular transport in A. thaliana. A transgenic line of A. thaliana expressing yellow fluorescent protein (YFP-tagged actin filaments was used to show attenuation of actin filament movement by AITC. This appeared gradually in a time- and dose-dependent manner and resulted in actin filaments appearing close to static. Further, we employed four transgenic lines with YFP-fusion proteins labeling the Golgi apparatus, endoplasmic reticulum (ER, vacuoles and peroxisomes to demonstrate an AITC-induced inhibition of actin-dependent intracellular transport of or, in these structures, consistent with the decline in actin filament movement. Furthermore, the morphologies of actin filaments, ER and vacuoles appeared aberrant following AITC-exposure. However, AITC-treated seedlings of all transgenic lines tested displayed morphologies and intracellular movements similar to that of the corresponding untreated and control-treated plants, following overnight incubation in an AITC-absent environment, indicating that AITC-induced decline in actin-related movements is a reversible process. These findings provide novel insights into the cellular events in plant cells following exposure to AITC, which may further expose clues to the physiological significance of the glucosinolate-myrosinase system.

Actin is an essential component of plant gravitropic signaling pathways

Science.gov (United States)

Braun, Markus; Hauslage, Jens; Limbach, Christoph

2003-08-01

A role of the actin cytoskeleton in the different phases of gravitropism in higher plant organs seems obvious, but experimental evidence is still inconclusive and contradictory. In gravitropically tip-growing rhizoids and protonemata, however, it is well documented that actin is an essential component of the tip-growth machinery and is involved either in the cellular mechanisms that lead to gravity sensing and in the processes of the graviresponses that result in the reorientation of the growth direction. All these processes depend on a complexly organized and highly dynamic organization of actin filaments whose diverse functions are coordinated by numerous associated proteins. Actin filaments and myosins mediate the transport of secretory vehicles to the growing tip and precisely control the delivery of cell wall material. In addition, both cell types use a very efficient actomyosin-based system to control and correct the position of their statoliths and to direct sedimenting statoliths to confined graviperception sites at the plasma membrane. The studies presented in this paper provide evidence for the essential role of actin in plant gravity sensing and the gravitropic responses. A unique actin-organizing center exists in the tip of characean rhizoids and protonemata which is associated with and dynamically regulated by a specific set of actin-dynamizing proteins. It is concluded that this highly dynamic apical actin array is an essential prerequisite for gravity sensing and gravity-oriented tip growth.

F-actin distribution and function during sexual differentiation in Schizosaccharomyces pombe

DEFF Research Database (Denmark)

Petersen, J; Nielsen, O; Egel, R

1998-01-01

Sexual differentiation in Schizosaccharomyces pombe is induced from the G1 phase of the cell cycle by nitrogen starvation and the presence of mating pheromones. We describe the distribution of F-actin during sexual differentiation. Cortical F-actin dots have previously been shown to be restricted...... to one end of the rod shaped cell during the G1 phase of the cell cycle. Within half an hour of nitrogen starvation the distribution of cortical F-actin dots switched from being monopolar to bipolar. This was then reversed as the F-actin cytoskeleton repolarized so that cortical F-actin dots accumulated...

The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter

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Sérgio Carvalho Leite

2016-04-01

Full Text Available The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings.

The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter.

Science.gov (United States)

Leite, Sérgio Carvalho; Sampaio, Paula; Sousa, Vera Filipe; Nogueira-Rodrigues, Joana; Pinto-Costa, Rita; Peters, Luanne Laurel; Brites, Pedro; Sousa, Mónica Mendes

2016-04-19

The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Modelling phagosomal lipid networks that regulate actin assembly

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Schwarz Roland

2008-12-01

Full Text Available Abstract Background When purified phagosomes are incubated in the presence of actin under appropriate conditions, microfilaments start growing from the membrane in a process that is affected by ATP and the lipid composition of the membrane. Isolated phagosomes are metabolically active organelles that contain enzymes and metabolites necessary for lipid interconversion. Hence, addition of ATP, lipids, and actin to the system alter the steady-state composition of the phagosomal membrane at the same time that the actin nucleation is initiated. Our aim was to model all these processes in parallel. Results We compiled detailed experimental data on the effects of different lipids and ATP on actin nucleation and we investigated experimentally lipid interconversion and ATP metabolism in phagosomes by using suitable radioactive compounds. In a first step, a complex lipid network interconnected by chemical reactions catalyzed by known enzymes was modelled in COPASI (Complex Pathway Simulator. However, several lines of experimental evidence indicated that only the phosphatidylinositol branch of the network was active, an observation that dramatically reduced the number of parameters in the model. The results also indicated that a lipid network-independent ATP-consuming activity should be included in the model. When this activity was introduced, the set of differential equations satisfactorily reproduced the experimental data. On the other hand, a molecular mechanism connecting membrane lipids, ATP, and the actin nucleation process is still missing. We therefore adopted a phenomenological (black-box approach to represent the empirical observations. We proposed that lipids and ATP influence the dynamic interconversion between active and inactive actin nucleation sites. With this simple model, all the experimental data were satisfactorily fitted with a single positive parameter per lipid and ATP. Conclusion By establishing an active 'dialogue' between an

Dynamics of actin cables in polarized growth of the filamentous fungus Aspergillus nidulans

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Anna eBergs

2016-05-01

Full Text Available Highly polarized growth of filamentous fungi requires a continuous supply of proteins and lipids to the hyphal tip. This transport is managed by vesicle trafficking via the actin and microtubule cytoskeletons and their associated motor proteins. Particularly, actin cables originating from the hyphal tip are essential for hyphal growth. Although specific marker proteins to visualize actin cables have been developed in filamentous fungi, the exact organization and dynamics of actin cables has remained elusive. Here we visualized actin cables using tropomyosin (TpmA and Lifeact fused to fluorescent proteins in Aspergillus nidulans and studied the dynamics and regulation. GFP tagged TpmA visualized dynamic actin cables formed from the hyphal tip with cycles of elongation and shrinkage. The elongation and shrinkage rates of actin cables were similar and approximately 0.6 μm/s. Comparison of actin markers revealed that high concentrations of Lifeact reduced actin dynamics. Simultaneous visualization of actin cables and microtubules suggests temporally and spatially coordinated polymerization and depolymerization between the two cytoskeletons. Our results provide new insights into the molecular mechanism of ordered polarized growth regulated by actin cables and microtubules.

Engineering an artificial amoeba propelled by nanoparticle-triggered actin polymerization

Energy Technology Data Exchange (ETDEWEB)

Yi Jinsoo; Schmidt, Jacob; Chien Aichi; Montemagno, Carlo D [Department of Bioengineering, University of California Los Angeles, 420 Westwood Plaza, 7523 Boelter Hall, Los Angeles, CA 90095-1600 (United States)], E-mail: montemcd@ucmail.uc.edu

2009-02-25

We have engineered an amoeba system combining nanofabricated inorganic materials with biological components, capable of propelling itself via actin polymerization. The nanofabricated materials have a mechanism similar to the locomotion of the Listeria monocytogenes, food poisoning bacteria. The propulsive force generation utilizes nanoparticles made from nickel and gold functionalized with the Listeria monocytogenes transmembrane protein, ActA. These Listeria-mimic nanoparticles were in concert with actin, actin binding proteins, ATP (adenosine triphosphate) and encapsulated within a lipid vesicle. This system is an artificial cell, such as a vesicle, where artificial nanobacteria and actin polymerization machinery are used in driving force generators inside the cell. The assembled structure was observed to crawl on a glass surface analogously to an amoeba, with the speed of the movement dependent on the amount of actin monomers and ATP present.

Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.

Science.gov (United States)

Yokota, Etsuo; Tominaga, Motoki; Mabuchi, Issei; Tsuji, Yasunori; Staiger, Christopher J; Oiwa, Kazuhiro; Shimmen, Teruo

2005-10-01

From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).

Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

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Westendorf, Christian; Negrete, Jose; Bae, Albert J.; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-01-01

The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments. PMID:23431176

Actin grips: circular actin-rich cytoskeletal structures that mediate the wrapping of polymeric microfibers by endothelial cells.

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Jones, Desiree; Park, DoYoung; Anghelina, Mirela; Pécot, Thierry; Machiraju, Raghu; Xue, Ruipeng; Lannutti, John J; Thomas, Jessica; Cole, Sara L; Moldovan, Leni; Moldovan, Nicanor I

2015-06-01

Interaction of endothelial-lineage cells with three-dimensional substrates was much less studied than that with flat culture surfaces. We investigated the in vitro attachment of both mature endothelial cells (ECs) and of less differentiated EC colony-forming cells to poly-ε-capro-lactone (PCL) fibers with diameters in 5-20 μm range ('scaffold microfibers', SMFs). We found that notwithstanding the poor intrinsic adhesiveness to PCL, both cell types completely wrapped the SMFs after long-term cultivation, thus attaining a cylindrical morphology. In this system, both EC types grew vigorously for more than a week and became increasingly more differentiated, as shown by multiplexed gene expression. Three-dimensional reconstructions from multiphoton confocal microscopy images using custom software showed that the filamentous (F) actin bundles took a conspicuous ring-like organization around the SMFs. Unlike the classical F-actin-containing stress fibers, these rings were not associated with either focal adhesions or intermediate filaments. We also demonstrated that plasma membrane boundaries adjacent to these circular cytoskeletal structures were tightly yet dynamically apposed to the SMFs, for which reason we suggest to call them 'actin grips'. In conclusion, we describe a particular form of F-actin assembly with relevance for cytoskeletal organization in response to biomaterials, for endothelial-specific cell behavior in vitro and in vivo, and for tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

Nuclear actin filaments recruit cofilin and actin-related protein 3, and their formation is connected with a mitotic block

Czech Academy of Sciences Publication Activity Database

Kalendová, Alžběta; Kalasová, Ilona; Yamazaki, S.; Uličná, Lívia; Harata, M.; Hozák, Pavel

2014-01-01

Roč. 142, č. 2 (2014), s. 139-152 ISSN 0948-6143 R&D Projects: GA ČR GAP305/11/2232; GA MŠk LD12063; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378050 Keywords : nuclear actin * transcription * mitosis * actin-related protein 3 * cofilin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.927, year: 2013

Clinical Response to Ingenol Mebutate in Patients With Actinic Keratoses.

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Batalla, A; Flórez, Á; Feal, C; Peón, G; Abalde, M T; Salgado-Boquete, L; de la Torre, C

2015-12-01

Cryotherapy is the most common treatment for actinic keratosis, but its effect is limited to individual lesions. Several topical drugs, however, are available that, in addition to treating individual actinic keratoses, target field cancerization and thereby act on subclinical lesions. Examples are 5-fluorouracil, imiquimod, diclofenac, and ingenol mebutate. We report on 17 patients with actinic keratoses treated with ingenol mebutate and describe our findings on treatment effectiveness, adherence, and tolerance. Complete and partial response rates were 35% and 53%, respectively. Ninety-four percent of patients fully adhered to treatment and 18% developed severe local reactions. Ingenol mebutate is an effective treatment for actinic keratosis. Although it has a similar rate of local reactions to other treatments available for actinic keratosis, its short treatment regimen favors better adherence. Copyright © 2014 Elsevier España, S.L.U. y AEDV. All rights reserved.

Addition of electrophilic lipids to actin alters filament structure

International Nuclear Information System (INIS)

Gayarre, Javier; Sanchez, David; Sanchez-Gomez, Francisco J.; Terron, Maria C.; Llorca, Oscar; Perez-Sala, Dolores

2006-01-01

Pathophysiological processes associated with oxidative stress lead to the generation of reactive lipid species. Among them, lipids bearing unsaturated aldehyde or ketone moieties can form covalent adducts with cysteine residues and modulate protein function. Through proteomic techniques we have identified actin as a target for the addition of biotinylated analogs of the cyclopentenone prostaglandins 15-deoxy-Δ 12,14 -PGJ 2 (15d-PGJ 2 ) and PGA 1 in NIH-3T3 fibroblasts. This modification could take place in vitro and mapped to the protein C-terminal end. Other electrophilic lipids, like the isoprostane 8-iso-PGA 1 and 4-hydroxy-2-nonenal, also bound to actin. The C-terminal region of actin is important for monomer-monomer interactions and polymerization. Electron microscopy showed that actin treated with 15d-PGJ 2 or 4-hydroxy-2-nonenal formed filaments which were less abundant and displayed shorter length and altered structure. Streptavidin-gold staining allowed mapping of biotinylated 15d-PGJ 2 at sites of filament disruption. These results shed light on the structural implications of actin modification by lipid electrophiles

Spontaneous actin dynamics in contractile rings

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Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

Crosstalk between Rac1-mediated actin regulation and ROS production.

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Acevedo, Alejandro; González-Billault, Christian

2018-02-20

The small RhoGTPase Rac1 is implicated in a variety of events related to actin cytoskeleton rearrangement. Remarkably, another event that is completely different from those related to actin regulation has the same relevance; the Rac1-mediated production of reactive oxygen species (ROS) through NADPH oxidases (NOX). Each outcome involves different Rac1 downstream effectors; on one hand, events related to the actin cytoskeleton require Rac1 to bind to WAVEs proteins and PAKs that ultimately promote actin branching and turnover, on the other, NOX-derived ROS production demands active Rac1 to be bound to a cytosolic activator of NOX. How Rac1-mediated signaling ends up promoting actin-related events, NOX-derived ROS, or both is poorly understood. Rac1 regulators, including scaffold proteins, are known to exert tight control over its functions. Hence, evidence of Rac1 regulatory events leading to both actin remodeling and NOX-mediated ROS generation are discussed. Moreover, cellular functions linked to physiological and pathological conditions that exhibit crosstalk between Rac1 outcomes are analyzed, while plausible roles in neuronal functions (and dysfunctions) are highlighted. Together, discussed evidence shed light on cellular mechanisms which requires Rac1 to direct either actin- and/or ROS-related events, helping to understand crucial roles of Rac1 dual functionality. Copyright © 2018 Elsevier Inc. All rights reserved.

Actin-based gravity-sensing mechanisms in unicellular plant model systems

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Braun, Markus; Limbach, Christoph

2005-08-01

Considerable progress has been made in the understanding of the molecular and cellular mechanisms underlying gravity sensing and gravity-oriented polarized growth in single-celled rhizoids and protonemata of the characean algae. It is well known that the actin cytoskeleton plays a key role in these processes. Numerous actin-binding proteins control apical actin polymerization and the dynamic remodeling of the actin arrangement. An actomyosin-based system mediates the delivery and incorporation of secretory vesicles at the growing tip and coordinates the tip-high gradient of cytoplasmic free calcium which is required for local exocytosis. Additionally, the actomyosin system precisely controls the position of statoliths and, upon a change in orientation relative to the gravity vector, directs sedimenting statoliths to the confined graviperception sites of the plasma membrane where gravitropic signalling is initiated. The upward growth response of protonemata is preceded by an actin-dependent relocalization of the Ca2+-gradient to the upper flank. The downward growth response of rhizoids, however, is caused by differential growth of the opposite flankes due to a local reduction of cytoplasmic free calcium limited to the plasma membrane area where statoliths are sedimented. Thus, constant actin polymerization in the growing tip and the spatiotemporal control of actin remodeling are essential for gravity sensing and gravity-oriented polarized growth of characean rhizoids and protonemata.

Dual effect of pseudorabies virus growth factor (PRGF) displayed on actin cytoskeleton.

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Urbancíková, M; Vozárová, G; Lesko, J; Golais, F

1999-10-01

Pseudorabies virus growth factor (PRGF) was shown to possess transforming activity as well as transformation repressing activity in in vitro systems. In order to better understand these phenomena we studied actin cytoskeleton and its alterations induced by PRGF using normal human fibroblasts VH-10 and transformed cell line HeLa. For specific detection of filamentous actin cells were stained with phalloidin conjugated with fluorescein isothiocyanate (FITC)-phalloidin. PRGF was applied to VH-10 cells for various length of time from 10 min up to 48 h. The effect was very fast and changes in actin filament composition could be detected already after 10 min. In comparison to untreated cells the staining of treated cells was more diffuse and a number of actin microfilaments in individual stress fibers became reduced. After 30 min thick short actin bundles appeared in the perinuclear region. A 24-h exposure resulted in a large reduction of actin bundles. After additional 24 h a partial restoration of actin cytoskeleton in cells was observed. In transformed HeLa cells PRGF induced opposite process than in normal cells: the number of filamentous actin structures increased. We hypothesise that PRGF may act as a transcription-like factor and may initiate changes in gene expression which consequently result in actin cytoskeleton alterations.

Feedback Interactions of Polymerized Actin with the Cell Membrane: Waves, Pulses, and Oscillations

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Carlsson, Anders

Polymerized filaments of the protein actin have crucial functions in cell migration, and in bending the cell membrane to drive endocytosis or the formation of protrusions. The nucleation and polymerization of actin filaments are controlled by upstream agents in the cell membrane, including nucleation-promoting factors (NPFs) that activate the Arp2/3 complex to form new branches on pre-existing filaments. But polymerized actin (F-actin) also feeds back on the assembly of NPFs. We explore the effects of the resulting feedback loop of F-actin and NPFs on two phenomena: actin pulses that drive endocytosis in yeast, and actin waves traveling along the membrane of several cell types. In our model of endocytosis in yeast, the actin network is grown explicitly in three dimensions, exerts a negative feedback interaction on localized patch of NPFs in the membrane, and bends the membrane by exerting a distribution of forces. This model explains observed actin and NPF pulse dynamics, and the effects of several interventions including i) NPF mutations, ii) inhibition of actin polymerization, and iii) deletion of a protein that allows F-actin to bend the cell membrane. The model predicts that mutation of the active region of an NPF will enhance the accumulation of that NPF, and we confirm this prediction by quantitative fluorescence microscopy. For actin waves, we treat a similar model, with NPFs distributed over a larger region of the cell membrane. This model naturally generates actin waves, and predicts a transition from wave behavior to spatially localized oscillations when NPFs are confined to a small region. We also predict a transition from waves to static polarization as the negative-feedback coupling between F-actin and the NPFs is reduced. Supported by NIGMS Grant R01 GM107667.

Engineering Circular Gliding of Actin Filaments Along Myosin-Patterned DNA Nanotube Rings To Study Long-Term Actin-Myosin Behaviors.

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Hariadi, Rizal F; Appukutty, Abhinav J; Sivaramakrishnan, Sivaraj

2016-09-27

Nature has evolved molecular motors that are critical in cellular processes occurring over broad time scales, ranging from seconds to years. Despite the importance of the long-term behavior of molecular machines, topics such as enzymatic lifetime are underexplored due to the lack of a suitable approach for monitoring motor activity over long time periods. Here, we developed an "O"-shaped Myosin Empowered Gliding Assay (OMEGA) that utilizes engineered micron-scale DNA nanotube rings with precise arrangements of myosin VI to trap gliding actin filaments. This circular gliding assay platform allows the same individual actin filament to glide over the same myosin ensemble (50-1000 motors per ring) multiple times. First, we systematically characterized the formation of DNA nanotubes rings with 4, 6, 8, and 10 helix circumferences. Individual actin filaments glide along the nanotube rings with high processivity for up to 12.8 revolutions or 11 min in run time. We then show actin gliding speed is robust to variation in motor number and independent of ring curvature within our sample space (ring diameter of 0.5-4 μm). As a model application of OMEGA, we then analyze motor-based mechanical influence on "stop-and-go" gliding behavior of actin filaments, revealing that the stop-to-go transition probability is dependent on motor flexibility. Our circular gliding assay may provide a closed-loop platform for monitoring long-term behavior of broad classes of molecular motors and enable characterization of motor robustness and long time scale nanomechanical processes.

Prolactin promotes breast cancer cell migration through actin cytoskeleton remodeling

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Priscilla Ludovico da Silva

2015-12-01

Full Text Available The role of prolactin on breast cancer development and progression is debated. Breast cancer progression largely depends on cell movement and on the ability to remodel the actin cytoskeleton. In this process, actin-binding proteins are requested to achieve fibrillar actin de-polymerization and relocation at the cell membrane. Kinases such as focal adhesion kinase (FAK are later required to form actin/vinculin-enriched structures called focal adhesion complexes, which mediate firm adhesion to the extracellular matrix. These controllers are regulated by c-Src, which forms multiprotein signaling complexes with membrane receptors and is regulated by a number of hormones, including prolactin. We here show that breast cancer cells exposed to prolactin display an elevated c-Src expression and phosphorylation. In parallel, increased moesin and FAK expression and phosphorylation are found. These molecular changes are associated to relocation to the plasma membrane of cytoskeletal actin fibers and to increased horizontal cell movement. In conclusion, prolactin regulates actin remodeling and enhances breast cancer cell movement. This finding broadens the understanding of prolactin actions on breast cancer cells, highlighting new pathways that may be relevant to on breast cancer progression.

Scanning electron microscopy of superficial white onychomycosis*

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de Almeida Jr., Hiram Larangeira; Boabaid, Roberta Oliveira; Timm, Vitor; Silva, Ricardo Marques e; de Castro, Luis Antonio Suita

2015-01-01

Superficial white onychomycosis is characterized by opaque, friable, whitish superficial spots on the nail plate. We examined an affected halux nail of a 20-year-old male patient with scanning electron microscopy. The mycological examination isolated Trichophyton mentagrophytes. Abundant hyphae with the formation of arthrospores were found on the nail's surface, forming small fungal colonies. These findings showed the great capacity for dissemination of this form of onychomycosis. PMID:26560225

Cell stress promotes the association of phosphorylated HspB1 with F-actin.

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Joseph P Clarke

Full Text Available Previous studies have suggested that the small heat shock protein, HspB1, has a direct influence on the dynamics of cytoskeletal elements, in particular, filamentous actin (F-actin polymerization. In this study we have assessed the influence of HspB1 phosphorylation on its interaction(s with F-actin. We first determined the distribution of endogenous non-phosphorylated HspB1, phosphorylated HspB1 and F-actin in neuroendocrine PC12 cells by immunocytochemistry and confocal microscopy. We then investigated a potential direct interaction between HspB1 with F-actin by precipitating F-actin directly with biotinylated phalloidin followed by Western analyses; the reverse immunoprecipitation of HspB1 was also carried out. The phosphorylation influence of HspB1 in this interaction was investigated by using pharmacologic inhibition of p38 MAPK. In control cells, HspB1 interacts with F-actin as a predominantly non-phosphorylated protein, but subsequent to stress there is a redistribution of HspB1 to the cytoskeletal fraction and a significantly increased association of pHspB1 with F-actin. Our data demonstrate HspB1 is found in a complex with F-actin both in phosphorylated and non-phosphorylated forms, with an increased association of pHspB1 with F-actin after heat stress. Overall, our study combines both cellular and biochemical approaches to show cellular localization and direct demonstration of an interaction between endogenous HspB1 and F-actin using methodolgy that specifically isolates F-actin.

Cooperative and non-cooperative conformational changes of F-actin induced by cofilin

Energy Technology Data Exchange (ETDEWEB)

Aihara, Tomoki; Oda, Toshiro, E-mail: toda@spring8.or.jp

2013-05-31

Highlights: •Mobility of MTSL attached to C374 in F-actin became high upon addition of cofilin. •Change of motility of MTSL attached to C374 with cofilin-binding was cooperative. •Mobility of MTSL attached to V43C in F-actin became high upon addition of cofilin. •Change of motility of MTSL attached to V43C with cofilin-binding was linear. -- Abstract: Cofilin is an actin-binding protein that promotes F-actin depolymerization. It is well-known that cofilin-coated F-actin is more twisted than naked F-actin, and that the protomer is more tilted. However, the means by which the local changes induced by the binding of individual cofilin proteins proceed to the global conformational changes of the whole F-actin molecule remain unknown. Here we investigated the cofilin-induced changes in several parts of F-actin, through site-directed spin-label electron paramagnetic resonance spectroscopy analyses of recombinant actins containing single reactive cysteines. We found that the global, cooperative conformational changes induced by cofilin-binding, which were detected by the spin-label attached to the Cys374 residue, occurred without the detachment of the D-loop in subdomain 2 from the neighboring protomer. The two processes of local and global changes do not necessarily proceed in sequence.

Mechanical coupling between transsynaptic N-cadherin adhesions and actin flow stabilizes dendritic spines

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Chazeau, Anaël; Garcia, Mikael; Czöndör, Katalin; Perrais, David; Tessier, Béatrice; Giannone, Grégory; Thoumine, Olivier

2015-01-01

The morphology of neuronal dendritic spines is a critical indicator of synaptic function. It is regulated by several factors, including the intracellular actin/myosin cytoskeleton and transcellular N-cadherin adhesions. To examine the mechanical relationship between these molecular components, we performed quantitative live-imaging experiments in primary hippocampal neurons. We found that actin turnover and structural motility were lower in dendritic spines than in immature filopodia and increased upon expression of a nonadhesive N-cadherin mutant, resulting in an inverse relationship between spine motility and actin enrichment. Furthermore, the pharmacological stimulation of myosin II induced the rearward motion of actin structures in spines, showing that myosin II exerts tension on the actin network. Strikingly, the formation of stable, spine-like structures enriched in actin was induced at contacts between dendritic filopodia and N-cadherin–coated beads or micropatterns. Finally, computer simulations of actin dynamics mimicked various experimental conditions, pointing to the actin flow rate as an important parameter controlling actin enrichment in dendritic spines. Together these data demonstrate that a clutch-like mechanism between N-cadherin adhesions and the actin flow underlies the stabilization of dendritic filopodia into mature spines, a mechanism that may have important implications in synapse initiation, maturation, and plasticity in the developing brain. PMID:25568337

Initiation of DNA replication requires actin dynamics and formin activity.

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Parisis, Nikolaos; Krasinska, Liliana; Harker, Bethany; Urbach, Serge; Rossignol, Michel; Camasses, Alain; Dewar, James; Morin, Nathalie; Fisher, Daniel

2017-11-02

Nuclear actin regulates transcriptional programmes in a manner dependent on its levels and polymerisation state. This dynamics is determined by the balance of nucleocytoplasmic shuttling, formin- and redox-dependent filament polymerisation. Here, using Xenopus egg extracts and human somatic cells, we show that actin dynamics and formins are essential for DNA replication. In proliferating cells, formin inhibition abolishes nuclear transport and initiation of DNA replication, as well as general transcription. In replicating nuclei from transcriptionally silent Xenopus egg extracts, we identified numerous actin regulators, and disruption of actin dynamics abrogates nuclear transport, preventing NLS (nuclear localisation signal)-cargo release from RanGTP-importin complexes. Nuclear formin activity is further required to promote loading of cyclin-dependent kinase (CDK) and proliferating cell nuclear antigen (PCNA) onto chromatin, as well as initiation and elongation of DNA replication. Therefore, actin dynamics and formins control DNA replication by multiple direct and indirect mechanisms. © 2017 The Authors.

Chronophin activation is necessary in Doxorubicin-induced actin cytoskeleton alteration.

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Lee, Su Jin; Park, Jeen Woo; Kang, Beom Sik; Lee, Dong-Seok; Lee, Hyun-Shik; Choi, Sooyoung; Kwon, Oh-Shin

2017-06-01

Although doxorubicin (Dox)-induced oxidative stress is known to be associated with cytotoxicity, the precise mechanism remains unclear. Genotoxic stress not only generates free radicals, but also affects actin cytoskeleton stability. We showed that Dox-induced RhoA signaling stimulated actin cytoskeleton alterations, resulting in central stress fiber disruption at early time points and cell periphery cortical actin formation at a later stage, in HeLa cells. Interestingly, activation of a cofilin phosphatase, chronophin (CIN), was initially evoked by Dox-induced RhoA signaling, resulting in a rapid phosphorylated cofilin turnover leading to actin cytoskeleton remodeling. In addition, a novel interaction between CIN and 14-3-3ζ was detected in the absence of Dox treatment. We demonstrated that CIN activity is quite contrary to 14-3-3ζ binding, and the interaction leads to enhanced phosphorylated cofilin levels. Therefore, initial CIN activation regulation could be critical in Dox-induced actin cytoskeleton remodeling through RhoA/cofilin signaling. [BMB Reports 2017; 50(6): 335-340].

Nanosecond electric pulses trigger actin responses in plant cells

International Nuclear Information System (INIS)

Berghoefer, Thomas; Eing, Christian; Flickinger, Bianca; Hohenberger, Petra; Wegner, Lars H.; Frey, Wolfgang; Nick, Peter

2009-01-01

We have analyzed the cellular effects of nanosecond pulsed electrical fields on plant cells using fluorescently tagged marker lines in the tobacco cell line BY-2 and confocal laser scanning microscopy. We observe a disintegration of the cytoskeleton in the cell cortex, followed by contraction of actin filaments towards the nucleus, and disintegration of the nuclear envelope. These responses are accompanied by irreversible permeabilization of the plasma membrane manifest as uptake of Trypan Blue. By pretreatment with the actin-stabilizing drug phalloidin, the detachment of transvacuolar actin from the cell periphery can be suppressed, and this treatment can also suppress the irreversible perforation of the plasma membrane. We discuss these findings in terms of a model, where nanosecond pulsed electric fields trigger actin responses that are key events in the plant-specific form of programmed cell death.

A glycolytic metabolon in Saccharomyces cerevisiae is stabilized by F-actin.

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Araiza-Olivera, Daniela; Chiquete-Felix, Natalia; Rosas-Lemus, Mónica; Sampedro, José G; Peña, Antonio; Mujica, Adela; Uribe-Carvajal, Salvador

2013-08-01

In the Saccharomyces cerevisiae glycolytic pathway, 11 enzymes catalyze the stepwise conversion of glucose to two molecules of ethanol plus two CO₂ molecules. In the highly crowded cytoplasm, this pathway would be very inefficient if it were dependent on substrate/enzyme diffusion. Therefore, the existence of a multi-enzymatic glycolytic complex has been suggested. This complex probably uses the cytoskeleton to stabilize the interaction of the various enzymes. Here, the role of filamentous actin (F-actin) in stabilization of a putative glycolytic metabolon is reported. Experiments were performed in isolated enzyme/actin mixtures, cytoplasmic extracts and permeabilized yeast cells. Polymerization of actin was promoted using phalloidin or inhibited using cytochalasin D or latrunculin. The polymeric filamentous F-actin, but not the monomeric globular G-actin, stabilized both the interaction of isolated glycolytic pathway enzyme mixtures and the whole fermentation pathway, leading to higher fermentation activity. The associated complexes were resistant against inhibition as a result of viscosity (promoted by the disaccharide trehalose) or inactivation (using specific enzyme antibodies). In S. cerevisiae, a glycolytic metabolon appear to assemble in association with F-actin. In this complex, fermentation activity is enhanced and enzymes are partially protected against inhibition by trehalose or by antibodies. © 2013 FEBS.

Interactions between globular proteins and F-actin in isotonic saline solution.

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Lakatos, S; Minton, A P

1991-10-05

Solutions of each of three different globular proteins (cytochrome c, chromophorically labeled serum albumin, and chromophorically labeled aldolase), mixed with another unlabeled globular protein or with fibrous actin, were prepared in pH 8.0 Tris-HCl buffer containing 0.15 M NaCl. Each solution was centrifuged at low speed, at 5 degrees C, until unassociated globular protein in solution achieved sedimentation equilibrium. Individual absorbance gradients of both macrosolutes in the mixtures subsequent to centrifugation were obtained via optical scans of the centrifuge tubes at two wavelengths. The gradients of each macrosolute in mixtures of two globular proteins revealed no association of globular proteins under the conditions of these experiments, but perturbation of the gradients of serum albumin, aldolase, and cytochrome c in the presence of F-actin indicated association of all three globular proteins with F-actin. Perturbation of actin gradients in the presence of serum albumin and aldolase suggested partial depolymerization of the F-actin by the globular protein. Analysis of the data with a simple phenomenological model relating free globular protein, bound globular protein, and total actin concentration provided estimates of the respective equilibrium constants for association of serum albumin and aldolase with F-actin, under the conditions of these experiments, of the order of 0.1 microM-1.

Actin is closely associated with RNA polymerase II and involved in activation of gene transcription

International Nuclear Information System (INIS)

Zhu Xiaojuan; Zeng Xianlu; Huang Baiqu; Hao, Shui

2004-01-01

Biochemical and morphological studies have demonstrated the presence of actin in the nucleus of different eukaryotic cells, whereas its role remains unclear. In this work, we studied the interaction and the functional relationship between nuclear actin and RNA polymerase II (RNAP II). The immunofluorescence study demonstrated a clear co-localization of nuclear actin with RNAP II in HeLa cells. Meanwhile, actin can be immunoprecipitated by anti-RNAP II antibody, indicating that they could interact with each other. Treatment of cells with α-amanitin induced the formation of actin bundle network in the nucleoplasm. Blocking of the formation of filamentous actin (F-actin) by cytochalasin B modified the distribution of actin. Although the actin content remained unchanged in resting and concanavalinA stimulated mouse lymphocytes, the actin content in the nuclei showed a progressive increase after stimulation. Furthermore, the antibody against actin blocked RNA synthesis in a eukaryotic in vitro transcription system. These observations implicate that nuclear actin interacts with RNAP II and may have function on the RNAP II-mediated transcription

Clinico Mycological Study of Superficial Mycoses

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Rachana J. Magdum

2016-10-01

Full Text Available Background: Generally it is well established fact that geographical distribution of the fungi may change from time to time; hence this study was planned. Aim and Objectives: To analyze the prevalence of superficial mycoses, its clinical presentation and species identification of the fungal isolates responsible for the disease. Material and Methods: A total 125 clinically diagnosed cases of superficial mycoses visiting Dermatology and Venereology outpatient department of Bharati Hospital, Sangli, for a period of one year were included in the study. Specimens like skin scrapping, nail clipping, hair were collected and subjected to KOH mount and culture. Identification of species was done by macroscopic examination of culture, tease mount and other physiological tests including Urease test, Hair perforation tests and Germ tube test. Results: Superficial mycosis was more common in the age group of 21-30 years (28% and in males (60.8%. The infection was more common in students (29.6%. Tinea corporis (42.4% was the commonest clinical type followed by tinea cruris (22.4%. 61.6% cases were positive by direct microscopy and 60.8% cases showed culture positive. Out of 125 samples, dermatophytes were grown in 63 cases (82.89% followed by non dermatophytic moulds in 10 cases (13.16% and Candida albicans in 3 cases (3.95%. The most common isolate among dermtophytosis was T. rubrum (46.05% followed by T. mentagrophyte (25%. Conclusion: It was concluded that along with dermatophytes, non dermatophytic moulds are also important to cause of superficial mycoses

The assembly of MreB, a prokaryotic homolog of actin.

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Esue, Osigwe; Cordero, Maria; Wirtz, Denis; Tseng, Yiider

2005-01-28

MreB, a major component of the bacterial cytoskeleton, exhibits high structural homology to its eukaryotic counterpart actin. Live cell microscopy studies suggest that MreB molecules organize into large filamentous spirals that support the cell membrane and play a key shape-determining function. However, the basic properties of MreB filament assembly remain unknown. Here, we studied the assembly of Thermotoga maritima MreB triggered by ATP in vitro and compared it to the well-studied assembly of actin. These studies show that MreB filament ultrastructure and polymerization depend crucially on temperature as well as the ions present on solution. At the optimal growth temperature of T. maritima, MreB assembly proceeded much faster than that of actin, without nucleation (or nucleation is highly favorable and fast) and with little or no contribution from filament end-to-end annealing. MreB exhibited rates of ATP hydrolysis and phosphate release similar to that of F-actin, however, with a critical concentration of approximately 3 nm, which is approximately 100-fold lower than that of actin. Furthermore, MreB assembled into filamentous bundles that have the ability to spontaneously form ring-like structures without auxiliary proteins. These findings suggest that despite high structural homology, MreB and actin display significantly different assembly properties.

Characterization of a porcine model of chronic superficial varicose veins.

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Jones, Gregory T; Grant, Mark W; Thomson, Ian A; Hill, B Geraldine; van Rij, André M

2009-06-01

Previous animal models of venous disease, while inducing venous hypertension and valvular insufficiency, do not produce superficial varicose veins. In this study, we aimed to develop and characterize a pig-based model of superficial varicose veins. Right femoral arteriovenous fistulae (AVF) were surgically fashioned in young adult pigs. Animals were examined at postoperative times up to 15 weeks to determine the development of varicose veins and measurement of both blood pressure and flow velocities within the superficial thigh veins. Histology and vascular corrosion casts were used to characterize the resulting structural venous alterations. Porcine pathophysiological features were compared with those of human primary superficial varicose veins. Gross superficial varicosities developed over the ipsilateral medial thigh region after an initial lag period of 1-2 weeks. Veins demonstrated retrograde filling with valvular incompetence, and a moderate, non-pulsatile, venous hypertension, which was altered by changes in posture and Valsalva. Venous blood flow velocities were elevated to 15-30 cm/s in varicose veins. Structurally, pig varicose veins were enlarged, tortuous, had valvular degeneration, and regions of focal medial atrophy with or without overlying intimal thickening. The superficial varicose veins, which developed within this model, have a pathophysiology that is consistent with that observed in humans. The porcine femoral AVF model is proposed as a suitable experimental model to evaluate the pathobiology of superficial venous disease. It may also be suitable for the evaluation of treatment interventions including drug therapy.

Superficial herpes simplex virus wound infection following lung transplantation.

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Karolak, Wojtek; Wojarski, Jacek; Zegleń, Sławomir; Ochman, Marek; Urlik, Maciej; Hudzik, Bartosz; Wozniak-Grygiel, Elzbieta; Maruszewski, Marcin

2017-08-01

Surgical site infections (SSIs) are infections of tissues, organs, or spaces exposed by surgeons during performance of an invasive procedure. SSIs are classified into superficial, which are limited to skin and subcutaneous tissues, and deep. The incidence of deep SSIs in lung transplant (LTx) patients is estimated at 5%. No reports have been published as to the incidence of superficial SSIs specifically in LTx patients. Common sense would dictate that the majority of superficial SSIs would be bacterial. Uncommonly, fungal SSIs may occur, and we believe that no reports exist as to the incidence of viral wound infections in LTx patients, or in any solid organ transplant patients. We report a de novo superficial wound infection with herpes simplex virus following lung transplantation, its possible source, treatment, and resolution. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Ultrastructural localization of actin and actin-binding proteins in the nucleus

Czech Academy of Sciences Publication Activity Database

Dingová, Hana; Fukalová, Jana; Maninová, Miloslava; Philimonenko, Vlada; Hozák, Pavel

2009-01-01

Roč. 131, č. 3 (2009), s. 425-434 ISSN 0948-6143 R&D Projects: GA MŠk LC545 Grant - others:MŠk(CZ) LC06063 Program:LC Institutional research plan: CEZ:AV0Z50520514 Keywords : nuclear actin * ultrastructure * actin–binding proteins Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.021, year: 2009

G-actin sequestering protein thymosin-β4 regulates the activity of myocardin-related transcription factor.

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Morita, Tsuyoshi; Hayashi, Ken'ichiro

2013-08-02

Myocardin-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). MRTFs contain three copies of the RPEL motif at their N-terminus, and they bind to monomeric globular actin (G-actin). Previous studies illustrate that G-actin binding inhibits MRTF activity by preventing the MRTFs nuclear accumulation. In the living cells, the majority of G-actin is sequestered by G-actin binding proteins that prevent spontaneous actin polymerization. Here, we demonstrate that the most abundant G-actin sequestering protein thymosin-β4 (Tβ4) was involved in the regulation of subcellular localization and activity of MRTF-A. Tβ4 competed with MRTF-A for G-actin binding; thus, interfering with G-actin-MRTF-A complex formation. Tβ4 overexpression induced the MRTF-A nuclear accumulation and activation of MRTF-SRF signaling. The activation rate of MRTF-A by the Tβ4 mutant L17A, whose affinity for G-actin is very low, was lower than that by wild-type Tβ4. In contrast, the β-actin mutant 3DA, which has a lower affinity for Tβ4, more effectively suppressed MRTF-A activity than wild-type β-actin. Furthermore, ectopic Tβ4 increased the endogenous expression of SRF-dependent actin cytoskeletal genes. Thus, Tβ4 is an important MRTF regulator that controls the G-actin-MRTFs interaction. Copyright © 2013 Elsevier Inc. All rights reserved.

Actin depolymerization enhances adipogenic differentiation in human stromal stem cells

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Li Chen

2018-05-01

Full Text Available Human stromal stem cells (hMSCs differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs: Cofilin 1 (CFL1 and Destrin (DSTN or treating the cells by Phalloidin reduced adipocyte differentiation as evidenced by decreased number of mature adipocytes and decreased adipocyte specific gene expression (ADIPOQ, LPL, PPARG, FABP4. In contrast, disruption of actin cytoskeleton by Cytochalasin D enhanced adipocyte differentiation. Follow up studies revealed that the effects of CFL1 on adipocyte differentiation depended on the activity of LIM domain kinase 1 (LIMK1 which is the major upstream kinase of CFL1. Inhibiting LIMK by its specific chemical inhibitor LIMKi inhibited the phosphorylation of CFL1 and actin polymerization, and enhanced the adipocyte differentiation. Moreover, treating hMSCs by Cytochalasin D inhibited ERK and Smad2 signaling and this was associated with enhanced adipocyte differentiation. On the other hand, Phalloidin enhanced ERK and Smad2 signaling, but inhibited adipocyte differentiation which was rescued by ERK specific chemical inhibitor U0126. Our data provide a link between restructuring of hMSCs cytoskeleton and hMSCs lineage commitment and differentiation. Keywords: Actin cytoskeleton, Actin depolymerizing factors, Adipocyte differentiation, Human stromal stem cells

Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton

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Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

2003-01-01

The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90 degrees reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90 degrees. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.

Understanding the three-dimensional anatomy of the superficial lymphatics of the limbs.

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Tourani, Saam S; Taylor, G Ian; Ashton, Mark W

2014-11-01

There are minimal data in the current literature regarding the depth of the superficial lymphatic collectors of the limbs in relation to the various subcutaneous tissue layers. Injection, microdissection, radiographic, and histologic studies of the superficial lymphatics and the subcutaneous tissues of 32 limbs from 15 human cadavers were performed. Five layers were consistently identified in the integument of all the upper and lower limb specimens: (1) skin, (2) subcutaneous fat, (3) superficial fascia, (4) loose areolar tissue, and (5) deep fascia. Layer 2 was further divided into superficial (2a) and deep (2c) compartments by a thin, transparent, horizontal septum (layer 2b). The main superficial veins and the superficial nerves coursed in layer 4. The lymphatic collectors were found at layer 2c and layer 4. The use of consistent nomenclature to describe the subcutaneous tissue layers facilitates a greater understanding and discussion of the anatomy. In lymphovenous anastomosis for the treatment of lymphedema, indocyanine green lymphography is an unreliable method for identification of the superficial collectors of the thigh. The medial proximal leg, the dorsum of the wrist over the anatomical snuffbox, and the volar proximal forearm provide suitable areas for locating superficial collectors with nearby matching size veins. In vertical medial thigh lift, choosing a dissection plane superficial to the great saphenous vein is unlikely to preserve the collectors of the ventromedial bundle.

Axon initial segment cytoskeleton comprises a multiprotein submembranous coat containing sparse actin filaments

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Jones, Steven L.; Korobova, Farida

2014-01-01

The axon initial segment (AIS) of differentiated neurons regulates action potential initiation and axon–dendritic polarity. The latter function depends on actin dynamics, but actin structure and functions at the AIS remain unclear. Using platinum replica electron microscopy (PREM), we have characterized the architecture of the AIS cytoskeleton in mature and developing hippocampal neurons. The AIS cytoskeleton assembly begins with bundling of microtubules and culminates in formation of a dense, fibrillar–globular coat over microtubule bundles. Immunogold PREM revealed that the coat contains a network of known AIS proteins, including ankyrin G, spectrin βIV, neurofascin, neuronal cell adhesion molecule, voltage-gated sodium channels, and actin filaments. Contrary to existing models, we find neither polarized actin arrays, nor dense actin meshworks in the AIS. Instead, the AIS contains two populations of sparse actin filaments: short, stable filaments and slightly longer dynamic filaments. We propose that stable actin filaments play a structural role for formation of the AIS diffusion barrier, whereas dynamic actin may promote AIS coat remodeling. PMID:24711503

Disruption of microtubule network rescues aberrant actin comets in dynamin2-depleted cells.

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Yuji Henmi

Full Text Available A large GTPase dynamin, which is required for endocytic vesicle formation, regulates the actin cytoskeleton through its interaction with cortactin. Dynamin2 mutants impair the formation of actin comets, which are induced by Listeria monocytogenes or phosphatidylinositol-4-phosphate 5-kinase. However, the role of dynamin2 in the regulation of the actin comet is still unclear. Here we show that aberrant actin comets in dynamin2-depleted cells were rescued by disrupting of microtubule networks. Depletion of dynamin2, but not cortactin, significantly reduced the length and the speed of actin comets induced by Listeria. This implies that dynamin2 may regulate the actin comet in a cortactin-independent manner. As dynamin regulates microtubules, we investigated whether perturbation of microtubules would rescue actin comet formation in dynamin2-depleted cells. Treatment with taxol or colchicine created a microtubule-free space in the cytoplasm, and made no difference between control and dynamin2 siRNA cells. This suggests that the alteration of microtubules by dynamin2 depletion reduced the length and the speed of the actin comet.

Social network extraction based on Web: 1. Related superficial methods

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Khairuddin Matyuso Nasution, Mahyuddin

2018-01-01

Often the nature of something affects methods to resolve the related issues about it. Likewise, methods to extract social networks from the Web, but involve the structured data types differently. This paper reveals several methods of social network extraction from the same sources that is Web: the basic superficial method, the underlying superficial method, the description superficial method, and the related superficial methods. In complexity we derive the inequalities between methods and so are their computations. In this case, we find that different results from the same tools make the difference from the more complex to the simpler: Extraction of social network by involving co-occurrence is more complex than using occurrences.

[Superficial venous thrombosis. A state of art].

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Sándor, Tamás

2017-01-01

For a long time superficial thrombophlebitis has been thought to be a rather benign condition. Recently, when duplex ultrasound technique is used for the diagnosis more and more often, the disease is proved to be more dangerous than anticipated. Thrombosis propagates to the deep veins in 6-44% and pulmonary embolism was observed on the patients in 1,5-33%. We can calculate venous thromboembolic complications on every fourth patient. Diagnosis is clinical, but duplex ultrasound examination is mandatory, for estimation of the thrombus extent, for exclusion of the deep venous thrombosis and for follow up. Both legs should be checked with ultrasound, because simultaneous deep venous thrombosis can develop on the contralateral limb. Two different forms can be distinguished: superficial venous thrombosis with, or without varicose veins. In cases of spontaneous, non varicous form, especially when the process is migrating or recurrent, a careful clinical examination is necessery for exclusion of malignant diseases and thrombophilia. The treatment options are summarised on the basis of recent international consensus statements. The American and German guidelines are similar. Compression and mobilisation are cornerstones of the therapy. For a short segment thrombosis non steroidal antiinflammatory drugs are effective. For longer segments low molecular-weight heparins are preferred. Information on the effect of the novel oral anticoagulants for the therapy is lacking but they may appear to be effective in the future for this indication. When thrombus is close to the sapheno-femoral or sapheno-popliteal junction crossectomy (high ligation), or low molecular-weight heparin in therapeutic doses are indicated. The term superficial thrombophlebitis should be discouraged, because inflammation and infection is not the primary pathology. It should be called correctly superficial venous thrombosis in order to avoid the unnecessary administration of antibiotics and the misconception

All-Round Manipulation of the Actin Cytoskeleton by HIV.

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Ospina Stella, Alberto; Turville, Stuart

2018-02-05

While significant progress has been made in terms of human immunodeficiency virus (HIV) therapy, treatment does not represent a cure and remains inaccessible to many people living with HIV. Continued mechanistic research into the viral life cycle and its intersection with many aspects of cellular biology are not only fundamental in the continued fight against HIV, but also provide many key observations of the workings of our immune system. Decades of HIV research have testified to the integral role of the actin cytoskeleton in both establishing and spreading the infection. Here, we review how the virus uses different strategies to manipulate cellular actin networks and increase the efficiency of various stages of its life cycle. While some HIV proteins seem able to bind to actin filaments directly, subversion of the cytoskeleton occurs indirectly by exploiting the power of actin regulatory proteins, which are corrupted at multiple levels. Furthermore, this manipulation is not restricted to a discrete class of proteins, but rather extends throughout all layers of the cytoskeleton. We discuss prominent examples of actin regulators that are exploited, neutralized or hijacked by the virus, and address how their coordinated deregulation can lead to changes in cellular behavior that promote viral spreading.

Live cell imaging of mitochondrial movement along actin cables in budding yeast.

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Fehrenbacher, Kammy L; Yang, Hyeong-Cheol; Gay, Anna Card; Huckaba, Thomas M; Pon, Liza A

2004-11-23

Mitochondrial inheritance is essential for cell division. In budding yeast, mitochondrial movement from mother to daughter requires (1) actin cables, F-actin bundles that undergo retrograde movement during elongation from buds into mother cells; (2) the mitochore, a mitochondrial protein complex implicated in linking mitochondria to actin cables; and (3) Arp2/3 complex-mediated force generation on mitochondria. We observed three new classes of mitochondrial motility: anterograde movement at velocities of 0.2-0.33 microm/s, retrograde movement at velocities of 0.26-0.51 microm/s, and no net anterograde or retrograde movement. In all cases, motile mitochondria were associated with actin cables undergoing retrograde flow at velocities of 0.18-0.62 microm/s. Destabilization of actin cables or mutations of the mitochore blocked all mitochondrial movements. In contrast, mutations in the Arp2/3 complex affected anterograde but not retrograde mitochondrial movements. Actin cables are required for movement of mitochondria, secretory vesicles, mRNA, and spindle alignment elements in yeast. We provide the first direct evidence that one of the proposed cargos use actin cables as tracks. In the case of mitochondrial inheritance, anterograde movement drives transfer of the organelle from mothers to buds, while retrograde movement contributes to retention of the organelle in mother cells. Interaction of mitochondria with actin cables is required for anterograde and retrograde movement. In contrast, force generation on mitochondria is required only for anterograde movement. Finally, we propose a novel mechanism in which actin cables serve as "conveyor belts" that drive retrograde organelle movement.

Curvature and torsion in growing actin networks

International Nuclear Information System (INIS)

Shaevitz, Joshua W; Fletcher, Daniel A

2008-01-01

Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque

Release of muscle α-actin into serum after intensive exercise

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A Martínez-Amat

2010-12-01

Full Text Available Purpose: To study the effects of high-level matches on serum alpha actin and other muscle damage markers in teams of rugby and handball players. Methods: Blood samples were drawn from 23 sportsmen: 13 rugby players and 10 handball players. One sample was drawn with the player at rest before the match and one immediately after the match. Immunoassays were used to determine troponin I, troponin T, LDH, and myoglobin concentrations. Western blot and densitometry were used to measure α-actin concentrations. Muscle injury was defined by a total CK value of > 500 IU/L (Rosalki method. Results: Mean pre- and post-match serum alpha-actin values were, respectively, 7.16 and 26.47 μg/ml in the handball group and 1.24 and 20.04 μg/ml in the rugby team. CPK, LDH and myoglobin but not troponin 1 levels also significantly differed between these time points. According to these results, large amounts of α-actin are released into peripheral blood immediately after intense physical effort. Possible cross-interference between skeletal and cardiac muscle damage can be discriminated by the combined use of α-actin and troponin I. Conclusion: The significant increase in alpha-actin after a high-level match may be a reliable marker for the early diagnosis and hence more effective treatment of muscle injury.

Actinic cell effects after radiotherapy for cervical cancer

International Nuclear Information System (INIS)

Padilha, C.M.L.; Bergmann, A.; Chaves, C.B.P.; Thuler, L.C.S.; Araújo Junior, M.L.C.; Souza, S.A.L. de

2017-01-01

Introduction: It is very common for patients with cervical cancer to be referred to the radiotherapy when the disease is in advanced stages, this fact determines high rates of locoregional recurrence. Radiation treatment causes actinic morphological changes, not only in neoplastic epithelial cells, but also in normal cells. These changes induced by radiation, often make difficult the differential diagnosis of the residual lesion, resulting in a dilemma in cytopathological follow-up. Objective: To describe the actinic cytopathologic changes in patients submitted to radiotherapy for cervical cancer. Methodology: The re-evaluation of cytopathologic smears and description of actinic cytopathic effects were performed. This information was complemented by the cytopathological report of the smears, available in the archives of the Division of Pathology (DIPAT) / INCA. Results: The most frequent cytopathological changes observed were: nuclear activation, cytoplasmic enhancement, cytoplasmic vacuolisation, eosinophilia, polychromasia, multinucleated giant cells, binucleation, nuclear vacuolisation, prominent nucleoli, as well as presence of leukocyte exudate. Conclusion: The cytopathological diagnosis of tumor persistence or recurrence after radiotherapy is always a great challenge for the professional, even the experienced one. Studies and reports in the literature on actinic cytopathologic changes and radiotherapy are scarce

Espins and the actin cytoskeleton of hair cell stereocilia and sensory cell microvilli

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Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Mugnaini, Enrico; Bartles, James R.

2008-01-01

The espins are novel actin-bundling proteins that are produced in multiple isoforms from a single gene. They are present at high concentration in the parallel actin bundle of hair cell stereocilia and are the target of deafness mutations in mice and humans. Espins are also enriched in the microvilli of taste receptor cells, solitary chemoreceptor cells, vomeronasal sensory neurons and Merkel cells, suggesting that espins play important roles in the microvillar projections of vertebrate sensory cells. Espins are potent actin-bundling proteins that are not inhibited by Ca2+. In cells, they efficiently elongate parallel actin bundles and, thereby, help determine the steady-state length of microvilli and stereocilia. Espins bind actin monomer via their WH2 domain and can assemble actin bundles in cells. Certain espin isoforms can also bind phosphatidylinositol 4,5-bisphosphate, profilins or SH3 proteins. These biological activities distinguish espins from other actin-bundling proteins and may make them well-suited to sensory cells. PMID:16909209

A Gly65Val substitution in an actin, GhACT_LI1, disrupts cell polarity and membrane anchoring of F-actin resulting in dwarf, lintless Li1 cotton plants

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• Actin polymerizes to form the cytoskeleton and organize polar growth in all eukaryotic cells. Species with numerous actin genes are especially useful for the dissection of actin molecular function due to redundancy and neofunctionalization. Here, we investigated the role of a cotton (Gossypium hi...

Actinic reticuloid. Diagnostics

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E. V. Sokolovskiy

2016-01-01

Full Text Available This article is about the case of actinic reticuloid - the rare dermatosis which clinical presentation is similar to atopic dermatitis, T-cell lymphoma. Good treatment effect was obtained by long cycles (2 cycles for 3 months of hydroxychloroquine and sun protective therapy included sunscreens SPF 50, nicotinic acid, sun-safe clothes which blocked ultraviolet radiation without any glucocorticosteroid drugs and cytostatic treatment.

The actin cytoskeleton may control the polar distribution of an auxin transport protein

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Muday, G. K.; Hu, S.; Brady, S. R.; Davies, E. (Principal Investigator)

2000-01-01

The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

Major Superficial White Matter Abnormalities in Huntington's Disease

Science.gov (United States)

Phillips, Owen R.; Joshi, Shantanu H.; Squitieri, Ferdinando; Sanchez-Castaneda, Cristina; Narr, Katherine; Shattuck, David W.; Caltagirone, Carlo; Sabatini, Umberto; Di Paola, Margherita

2016-01-01

Background: The late myelinating superficial white matter at the juncture of the cortical gray and white matter comprising the intracortical myelin and short-range association fibers has not received attention in Huntington's disease. It is an area of the brain that is late myelinating and is sensitive to both normal aging and neurodegenerative disease effects. Therefore, it may be sensitive to Huntington's disease processes. Methods: Structural MRI data from 25 Pre-symptomatic subjects, 24 Huntington's disease patients and 49 healthy controls was run through a cortical pattern-matching program. The surface corresponding to the white matter directly below the cortical gray matter was then extracted. Individual subject's Diffusion Tensor Imaging (DTI) data was aligned to their structural MRI data. Diffusivity values along the white matter surface were then sampled at each vertex point. DTI measures with high spatial resolution across the superficial white matter surface were then analyzed with the General Linear Model to test for the effects of disease. Results: There was an overall increase in the axial and radial diffusivity across much of the superficial white matter (p < 0.001) in Pre-symptomatic subjects compared to controls. In Huntington's disease patients increased diffusivity covered essentially the whole brain (p < 0.001). Changes are correlated with genotype (CAG repeat number) and disease burden (p < 0.001). Conclusions: This study showed broad abnormalities in superficial white matter even before symptoms are present in Huntington's disease. Since, the superficial white matter has a unique microstructure and function these abnormalities suggest it plays an important role in the disease. PMID:27242403

Dynamics of actin-based movement by Rickettsia rickettsii in vero cells.

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Heinzen, R A; Grieshaber, S S; Van Kirk, L S; Devin, C J

1999-08-01

Actin-based motility (ABM) is a virulence mechanism exploited by invasive bacterial pathogens in the genera Listeria, Shigella, and Rickettsia. Due to experimental constraints imposed by the lack of genetic tools and their obligate intracellular nature, little is known about rickettsial ABM relative to Listeria and Shigella ABM systems. In this study, we directly compared the dynamics and behavior of ABM of Rickettsia rickettsii and Listeria monocytogenes. A time-lapse video of moving intracellular bacteria was obtained by laser-scanning confocal microscopy of infected Vero cells synthesizing beta-actin coupled to green fluorescent protein (GFP). Analysis of time-lapse images demonstrated that R. rickettsii organisms move through the cell cytoplasm at an average rate of 4.8 +/- 0.6 micrometer/min (mean +/- standard deviation). This speed was 2.5 times slower than that of L. monocytogenes, which moved at an average rate of 12.0 +/- 3.1 micrometers/min. Although rickettsiae moved more slowly, the actin filaments comprising the actin comet tail were significantly more stable, with an average half-life approximately three times that of L. monocytogenes (100.6 +/- 19.2 s versus 33.0 +/- 7.6 s, respectively). The actin tail associated with intracytoplasmic rickettsiae remained stationary in the cytoplasm as the organism moved forward. In contrast, actin tails of rickettsiae trapped within the nucleus displayed dramatic movements. The observed phenotypic differences between the ABM of Listeria and Rickettsia may indicate fundamental differences in the mechanisms of actin recruitment and polymerization.

A Novel Actinic Keratosis Field Assessment Scale for Grading Actinic Keratosis Disease Severity.

Science.gov (United States)

Dréno, Brigitte; Cerio, Rino; Dirschka, Thomas; Nart, Ignasi Figueras; Lear, John T; Peris, Ketty; de Casas, Andrés Ruiz; Kaleci, Shaniko; Pellacani, Giovanni

2017-10-02

Actinic keratosis (AK) lesions are surrounded by field cancerization (areas of subclinical, non-visible sun damage). Existing AK grading tools rely on AK counts, which are not reproducible. An Actinic Keratosis Field Assessment Scale (AK-FAS) for grading the severity of AK/field was developed. Standardized photographs of patients representing the full range of AK severity were collected. Six investigators independently rated each photograph according to 3 criteria: AK area (total skin area affected by AK lesions), hyperkeratosis and sun damage. Inter-rater reproducibility was good for all 3 criteria. Validation of the AK-FAS showed good reproducibility for AK area and hyperkeratosis, even for dermatologists untrained on use of the scale. In conclusion, the AK-FAS is objective, easy to use and implement, and reproducible. It incorporates assessment of the entire field affected by AK instead of relying on lesion counts. Use of the AK-FAS may standardize AK diagnosis, making it relevant to routine clinical practice.

Formation of actin networks in microfluidic concentration gradients

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Natalja eStrelnikova

2016-05-01

Full Text Available The physical properties of cytoskeletal networks are contributors in a number of mechanical responses of cells including cellular deformation and locomotion, and are crucial for the proper action of living cells. Local chemical gradients modulate cytoskeletal functionality including the interactions of the cytoskeleton with other cellular components. Actin is a major constituent of the cytoskeleton. Introducing a microfluidic-based platform, we explored the impact of concentration gradients on the formation and structural properties of actin networks. Microfluidics-controlled flow-free steady state experimental conditions allow for the generation of chemical gradients of different profiles, such as linear or step-like. We discovered specific features of actin networks emerging in defined gradients. In particular, we analyzed the effects of spatial conditions on network properties, bending rigidities of network links, and the network elasticity.

Investigating sub-spine actin dynamics in rat hippocampal neurons with super-resolution optical imaging.

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Vedakumar Tatavarty

Full Text Available Morphological changes in dendritic spines represent an important mechanism for synaptic plasticity which is postulated to underlie the vital cognitive phenomena of learning and memory. These morphological changes are driven by the dynamic actin cytoskeleton that is present in dendritic spines. The study of actin dynamics in these spines traditionally has been hindered by the small size of the spine. In this study, we utilize a photo-activation localization microscopy (PALM-based single-molecule tracking technique to analyze F-actin movements with approximately 30-nm resolution in cultured hippocampal neurons. We were able to observe the kinematic (physical motion of actin filaments, i.e., retrograde flow and kinetic (F-actin turn-over dynamics of F-actin at the single-filament level in dendritic spines. We found that F-actin in dendritic spines exhibits highly heterogeneous kinematic dynamics at the individual filament level, with simultaneous actin flows in both retrograde and anterograde directions. At the ensemble level, movements of filaments integrate into a net retrograde flow of approximately 138 nm/min. These results suggest a weakly polarized F-actin network that consists of mostly short filaments in dendritic spines.

Investigating sub-spine actin dynamics in rat hippocampal neurons with super-resolution optical imaging.

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Tatavarty, Vedakumar; Kim, Eun-Ji; Rodionov, Vladimir; Yu, Ji

2009-11-09

Morphological changes in dendritic spines represent an important mechanism for synaptic plasticity which is postulated to underlie the vital cognitive phenomena of learning and memory. These morphological changes are driven by the dynamic actin cytoskeleton that is present in dendritic spines. The study of actin dynamics in these spines traditionally has been hindered by the small size of the spine. In this study, we utilize a photo-activation localization microscopy (PALM)-based single-molecule tracking technique to analyze F-actin movements with approximately 30-nm resolution in cultured hippocampal neurons. We were able to observe the kinematic (physical motion of actin filaments, i.e., retrograde flow) and kinetic (F-actin turn-over) dynamics of F-actin at the single-filament level in dendritic spines. We found that F-actin in dendritic spines exhibits highly heterogeneous kinematic dynamics at the individual filament level, with simultaneous actin flows in both retrograde and anterograde directions. At the ensemble level, movements of filaments integrate into a net retrograde flow of approximately 138 nm/min. These results suggest a weakly polarized F-actin network that consists of mostly short filaments in dendritic spines.

Real-world approach to actinic keratosis management

DEFF Research Database (Denmark)

Dirschka, Thomas; Gupta, Girish; Micali, Giuseppe

2017-01-01

Actinic keratosis (AK) is a chronic skin disease in which multiple clinical and subclinical lesions co-exist across large areas of sun-exposed skin, resulting in field cancerisation. Lesions require treatment because of their potential to transform into invasive squamous cell carcinoma. This arti......Actinic keratosis (AK) is a chronic skin disease in which multiple clinical and subclinical lesions co-exist across large areas of sun-exposed skin, resulting in field cancerisation. Lesions require treatment because of their potential to transform into invasive squamous cell carcinoma...

Gamma interferon-induced guanylate binding protein 1 is a novel actin cytoskeleton remodeling factor.

Science.gov (United States)

Ostler, Nicole; Britzen-Laurent, Nathalie; Liebl, Andrea; Naschberger, Elisabeth; Lochnit, Günter; Ostler, Markus; Forster, Florian; Kunzelmann, Peter; Ince, Semra; Supper, Verena; Praefcke, Gerrit J K; Schubert, Dirk W; Stockinger, Hannes; Herrmann, Christian; Stürzl, Michael

2014-01-01

Gamma interferon (IFN-γ) regulates immune defenses against viruses, intracellular pathogens, and tumors by modulating cell proliferation, migration, invasion, and vesicle trafficking processes. The large GTPase guanylate binding protein 1 (GBP-1) is among the cellular proteins that is the most abundantly induced by IFN-γ and mediates its cell biologic effects. As yet, the molecular mechanisms of action of GBP-1 remain unknown. Applying an interaction proteomics approach, we identified actin as a strong and specific binding partner of GBP-1. Furthermore, GBP-1 colocalized with actin at the subcellular level and was both necessary and sufficient for the extensive remodeling of the fibrous actin structure observed in IFN-γ-exposed cells. These effects were dependent on the oligomerization and the GTPase activity of GBP-1. Purified GBP-1 and actin bound to each other, and this interaction was sufficient to impair the formation of actin filaments in vitro, as demonstrated by atomic force microscopy, dynamic light scattering, and fluorescence-monitored polymerization. Cosedimentation and band shift analyses demonstrated that GBP-1 binds robustly to globular actin and slightly to filamentous actin. This indicated that GBP-1 may induce actin remodeling via globular actin sequestering and/or filament capping. These results establish GBP-1 as a novel member within the family of actin-remodeling proteins specifically mediating IFN-γ-dependent defense strategies.

Actin cytoskeleton modulates calcium signaling during maturation of starfish oocytes.

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Kyozuka, Keiichiro; Chun, Jong T; Puppo, Agostina; Gragnaniello, Gianni; Garante, Ezio; Santella, Luigia

2008-08-15

Before successful fertilization can occur, oocytes must undergo meiotic maturation. In starfish, this can be achieved in vitro by applying 1-methyladenine (1-MA). The immediate response to 1-MA is the fast Ca2+ release in the cell cortex. Here, we show that this Ca2+ wave always initiates in the vegetal hemisphere and propagates through the cortex, which is the space immediately under the plasma membrane. We have observed that alteration of the cortical actin cytoskeleton by latrunculin-A and jasplakinolide can potently affect the Ca2+ waves triggered by 1-MA. This indicates that the cortical actin cytoskeleton modulates Ca2+ release during meiotic maturation. The Ca2+ wave was inhibited by the classical antagonists of the InsP(3)-linked Ca2+ signaling pathway, U73122 and heparin. To our surprise, however, these two inhibitors induced remarkable actin hyper-polymerization in the cell cortex, suggesting that their inhibitory effect on Ca2+ release may be attributed to the perturbation of the cortical actin cytoskeleton. In post-meiotic eggs, U73122 and jasplakinolide blocked the elevation of the vitelline layer by uncaged InsP(3), despite the massive release of Ca2+, implying that exocytosis of the cortical granules requires not only a Ca2+ rise, but also regulation of the cortical actin cytoskeleton. Our results suggest that the cortical actin cytoskeleton of starfish oocytes plays critical roles both in generating Ca2+ signals and in regulating cortical granule exocytosis.

Functional characterisation of filamentous actin probe expression in neuronal cells.

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Shrujna Patel

Full Text Available Genetically encoded filamentous actin probes, Lifeact, Utrophin and F-tractin, are used as tools to label the actin cytoskeleton. Recent evidence in several different cell types indicates that these probes can cause changes in filamentous actin dynamics, altering cell morphology and function. Although these probes are commonly used to visualise actin dynamics in neurons, their effects on axonal and dendritic morphology has not been systematically characterised. In this study, we quantitatively analysed the effect of Lifeact, Utrophin and F-tractin on neuronal morphogenesis in primary hippocampal neurons. Our data show that the expression of actin-tracking probes significantly impacts on axonal and dendrite growth these neurons. Lifeact-GFP expression, under the control of a pBABE promoter, caused a significant decrease in total axon length, while another Lifeact-GFP expression, under the control of a CAG promoter, decreased the length and complexity of dendritic trees. Utr261-EGFP resulted in increased dendritic branching but Utr230-EGFP only accumulated in cell soma, without labelling any neurites. Lifeact-7-mEGFP and F-tractin-EGFP in a pEGFP-C1 vector, under the control of a CMV promoter, caused only minor changes in neuronal morphology as detected by Sholl analysis. The results of this study demonstrate the effects that filamentous actin tracking probes can have on the axonal and dendritic compartments of neuronal cells and emphasise the care that must be taken when interpreting data from experiments using these probes.

Hippocampal Dendritic Spines Are Segregated Depending on Their Actin Polymerization.

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Domínguez-Iturza, Nuria; Calvo, María; Benoist, Marion; Esteban, José Antonio; Morales, Miguel

2016-01-01

Dendritic spines are mushroom-shaped protrusions of the postsynaptic membrane. Spines receive the majority of glutamatergic synaptic inputs. Their morphology, dynamics, and density have been related to synaptic plasticity and learning. The main determinant of spine shape is filamentous actin. Using FRAP, we have reexamined the actin dynamics of individual spines from pyramidal hippocampal neurons, both in cultures and in hippocampal organotypic slices. Our results indicate that, in cultures, the actin mobile fraction is independently regulated at the individual spine level, and mobile fraction values do not correlate with either age or distance from the soma. The most significant factor regulating actin mobile fraction was the presence of astrocytes in the culture substrate. Spines from neurons growing in the virtual absence of astrocytes have a more stable actin cytoskeleton, while spines from neurons growing in close contact with astrocytes show a more dynamic cytoskeleton. According to their recovery time, spines were distributed into two populations with slower and faster recovery times, while spines from slice cultures were grouped into one population. Finally, employing fast lineal acquisition protocols, we confirmed the existence of loci with high polymerization rates within the spine.

Actin Cytoskeleton Manipulation by Effector Proteins Secreted by Diarrheagenic Escherichia coli Pathotypes

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Fernando Navarro-Garcia

2013-01-01

Full Text Available The actin cytoskeleton is a dynamic structure necessary for cell and tissue organization, including the maintenance of epithelial barriers. Disruption of the epithelial barrier coincides with alterations of the actin cytoskeleton in several disease states. These disruptions primarily affect the paracellular space, which is normally regulated by tight junctions. Thereby, the actin cytoskeleton is a common and recurring target of bacterial virulence factors. In order to manipulate the actin cytoskeleton, bacteria secrete and inject toxins and effectors to hijack the host cell machinery, which interferes with host-cell pathways and with a number of actin binding proteins. An interesting model to study actin manipulation by bacterial effectors is Escherichia coli since due to its genome plasticity it has acquired diverse genetic mobile elements, which allow having different E. coli varieties in one bacterial species. These E. coli pathotypes, including intracellular and extracellular bacteria, interact with epithelial cells, and their interactions depend on a specific combination of virulence factors. In this paper we focus on E. coli effectors that mimic host cell proteins to manipulate the actin cytoskeleton. The study of bacterial effector-cytoskeleton interaction will contribute not only to the comprehension of the molecular causes of infectious diseases but also to increase our knowledge of cell biology.

G-actin sequestering protein thymosin-β4 regulates the activity of myocardin-related transcription factor

International Nuclear Information System (INIS)

Morita, Tsuyoshi; Hayashi, Ken’ichiro

2013-01-01

Highlights: •Tβ4 competed with MRTF-A for G-actin binding. •Tβ4 activated the MRTF–SRF signaling pathway. •Tβ4 increased the endogenous expression of SRF-dependent genes. -- Abstract: Myocardin-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). MRTFs contain three copies of the RPEL motif at their N-terminus, and they bind to monomeric globular actin (G-actin). Previous studies illustrate that G-actin binding inhibits MRTF activity by preventing the MRTFs nuclear accumulation. In the living cells, the majority of G-actin is sequestered by G-actin binding proteins that prevent spontaneous actin polymerization. Here, we demonstrate that the most abundant G-actin sequestering protein thymosin-β4 (Tβ4) was involved in the regulation of subcellular localization and activity of MRTF-A. Tβ4 competed with MRTF-A for G-actin binding; thus, interfering with G-actin–MRTF-A complex formation. Tβ4 overexpression induced the MRTF-A nuclear accumulation and activation of MRTF–SRF signaling. The activation rate of MRTF-A by the Tβ4 mutant L17A, whose affinity for G-actin is very low, was lower than that by wild-type Tβ4. In contrast, the β-actin mutant 3DA, which has a lower affinity for Tβ4, more effectively suppressed MRTF-A activity than wild-type β-actin. Furthermore, ectopic Tβ4 increased the endogenous expression of SRF-dependent actin cytoskeletal genes. Thus, Tβ4 is an important MRTF regulator that controls the G-actin–MRTFs interaction

G-actin sequestering protein thymosin-β4 regulates the activity of myocardin-related transcription factor

Energy Technology Data Exchange (ETDEWEB)

Morita, Tsuyoshi, E-mail: tsuyo@nbiochem.med.osaka-u.ac.jp; Hayashi, Ken’ichiro

2013-08-02

Highlights: •Tβ4 competed with MRTF-A for G-actin binding. •Tβ4 activated the MRTF–SRF signaling pathway. •Tβ4 increased the endogenous expression of SRF-dependent genes. -- Abstract: Myocardin-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). MRTFs contain three copies of the RPEL motif at their N-terminus, and they bind to monomeric globular actin (G-actin). Previous studies illustrate that G-actin binding inhibits MRTF activity by preventing the MRTFs nuclear accumulation. In the living cells, the majority of G-actin is sequestered by G-actin binding proteins that prevent spontaneous actin polymerization. Here, we demonstrate that the most abundant G-actin sequestering protein thymosin-β4 (Tβ4) was involved in the regulation of subcellular localization and activity of MRTF-A. Tβ4 competed with MRTF-A for G-actin binding; thus, interfering with G-actin–MRTF-A complex formation. Tβ4 overexpression induced the MRTF-A nuclear accumulation and activation of MRTF–SRF signaling. The activation rate of MRTF-A by the Tβ4 mutant L17A, whose affinity for G-actin is very low, was lower than that by wild-type Tβ4. In contrast, the β-actin mutant 3DA, which has a lower affinity for Tβ4, more effectively suppressed MRTF-A activity than wild-type β-actin. Furthermore, ectopic Tβ4 increased the endogenous expression of SRF-dependent actin cytoskeletal genes. Thus, Tβ4 is an important MRTF regulator that controls the G-actin–MRTFs interaction.

NHERF1 regulates actin cytoskeleton organization through modulation of α-actinin-4 stability.

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Sun, Licui; Zheng, Junfang; Wang, Qiqi; Song, Ran; Liu, Hua; Meng, Ran; Tao, Tao; Si, Yang; Jiang, Wenguo; He, Junqi

2016-02-01

The actin cytoskeleton is composed of a highly dynamic network of filamentous proteins, yet the molecular mechanism that regulates its organization and remodeling remains elusive. In this study, Na(+)/H(+) exchanger regulatory factor (NHERF)-1 loss-of-function and gain-of-function experiments reveal that polymerized actin cytoskeleton (F-actin) in HeLa cells is disorganized by NHERF1, whereas actin protein expression levels exhibit no detectable change. To elucidate the molecular mechanism underlying actin cytoskeleton disorganization by NHERF1, a combined 2-dimensional electrophoresis-matrix-assisted laser desorption/ionization-time of flight mass spectrometry approach was used to screen for proteins regulated by NHERF1 in HeLa cells. α-Actinin-4, an actin cross-linking protein, was identified. Glutathione S-transferase pull-down and coimmunoprecipitation studies showed the α-actinin-4 carboxyl-terminal region specifically interacted with the NHERF1 postsynaptic density 95/disc-large/zona occludens-1 domain. The NHERF1/α-actinin-4 interaction increased α-actinin-4 ubiquitination and decreased its expression levels, resulting in actin cytoskeleton disassembly. Our study identified α-actinin-4 as a novel NHERF1 interaction partner and provided new insights into the regulatory mechanism of the actin cytoskeleton by NHERF1. © FASEB.

Actin depolymerization enhances adipogenic differentiation in human stromal stem cells

DEFF Research Database (Denmark)

Chen, Li; Hu, Huimin; Qiu, Weimin

2018-01-01

Human stromal stem cells (hMSCs) differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined...... the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) or treating the cells by Phalloidin reduced adipocyte...

Superficial or deep implantation of motor nerve after denervation: an experimental study--superficial or deep implantation of motor nerve.

Science.gov (United States)

Askar, Ibrahím; Sabuncuoglu, Bízden Tavíl

2002-01-01

Neurorraphy, conventional nerve grafting technique, and artificial nerve conduits are not enough for repair in severe injuries of peripheral nerves, especially when there is separation of motor nerve from muscle tissue. In these nerve injuries, reinnervation is indicated for neurotization. The distal end of a peripheral nerve is divided into fascicles and implanted into the aneural zone of target muscle tissue. It is not known how deeply fascicles should be implanted into muscle tissue. A comparative study of superficial and deep implantation of separated motor nerve into muscle tissue is presented in the gastrocnemius muscle of rabbits. In this experimental study, 30 white New Zealand rabbits were used and divided into 3 groups of 10 rabbits each. In the first group (controls, group I), only surgical exposure of the gastrocnemius muscle and motor nerve (tibial nerve) was done without any injury to nerves. In the superficial implantation group (group II), tibial nerves were separated and divided into their own fascicles. These fascicles were implanted superficially into the lateral head of gastrocnemius muscle-aneural zone. In the deep implantation group (group III), the tibial nerves were separated and divided into their own fascicles. These fascicles were implanted around the center of the muscle mass, into the lateral head of the gastrocnemius muscle-aneural zone. Six months later, histopathological changes and functional recovery of the gastrocnemius muscle were investigated. Both experimental groups had less muscular weight than in the control group. It was found that functional recovery was achieved in both experimental groups, and was better in the superficial implantation group than the deep implantation group. EMG recordings revealed that polyphasic and late potentials were frequently seen in both experimental groups. Degeneration and regeneration of myofibrils were observed in both experimental groups. New motor end-plates were formed in a scattered

Probing cytoplasmic organization and the actin cytoskeleton of plant cells with optical tweezers

NARCIS (Netherlands)

Ketelaar, T.; Honing, van der H.S.; Emons, A.M.C.

2010-01-01

In interphase plant cells, the actin cytoskeleton is essential for intracellular transport and organization. To fully understand how the actin cytoskeleton functions as the structural basis for cytoplasmic organization, both molecular and physical aspects of the actin organization have to be

Decidable and undecidable arithmetic functions in actin filament networks

Science.gov (United States)

Schumann, Andrew

2018-01-01

The plasmodium of Physarum polycephalum is very sensitive to its environment, and reacts to stimuli with appropriate motions. Both the sensory and motor stages of these reactions are explained by hydrodynamic processes, based on fluid dynamics, with the participation of actin filament networks. This paper is devoted to actin filament networks as a computational medium. The point is that actin filaments, with contributions from many other proteins like myosin, are sensitive to extracellular stimuli (attractants as well as repellents), and appear and disappear at different places in the cell to change aspects of the cell structure—e.g. its shape. By assembling and disassembling actin filaments, some unicellular organisms, like Amoeba proteus, can move in response to various stimuli. As a result, these organisms can be considered a simple reversible logic gate—extracellular signals being its inputs and motions its outputs. In this way, we can implement various logic gates on amoeboid behaviours. These networks can embody arithmetic functions within p-adic valued logic. Furthermore, within these networks we can define the so-called diagonalization for deducing undecidable arithmetic functions.

Actin and myosin contribute to mammalian mitochondrial DNA maintenance

Science.gov (United States)

Reyes, A.; He, J.; Mao, C. C.; Bailey, L. J.; Di Re, M.; Sembongi, H.; Kazak, L.; Dzionek, K.; Holmes, J. B.; Cluett, T. J.; Harbour, M. E.; Fearnley, I. M.; Crouch, R. J.; Conti, M. A.; Adelstein, R. S.; Walker, J. E.; Holt, I. J.

2011-01-01

Mitochondrial DNA maintenance and segregation are dependent on the actin cytoskeleton in budding yeast. We found two cytoskeletal proteins among six proteins tightly associated with rat liver mitochondrial DNA: non-muscle myosin heavy chain IIA and β-actin. In human cells, transient gene silencing of MYH9 (encoding non-muscle myosin heavy chain IIA), or the closely related MYH10 gene (encoding non-muscle myosin heavy chain IIB), altered the topology and increased the copy number of mitochondrial DNA; and the latter effect was enhanced when both genes were targeted simultaneously. In contrast, genetic ablation of non-muscle myosin IIB was associated with a 60% decrease in mitochondrial DNA copy number in mouse embryonic fibroblasts, compared to control cells. Gene silencing of β-actin also affected mitochondrial DNA copy number and organization. Protease-protection experiments and iodixanol gradient analysis suggest some β-actin and non-muscle myosin heavy chain IIA reside within human mitochondria and confirm that they are associated with mitochondrial DNA. Collectively, these results strongly implicate the actomyosin cytoskeleton in mammalian mitochondrial DNA maintenance. PMID:21398640

Roles of Asp179 and Glu270 in ADP-Ribosylation of Actin by Clostridium perfringens Iota Toxin.

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Alexander Belyy

Full Text Available Clostridium perfringens iota toxin is a binary toxin composed of the enzymatically active component Ia and receptor binding component Ib. Ia is an ADP-ribosyltransferase, which modifies Arg177 of actin. The previously determined crystal structure of the actin-Ia complex suggested involvement of Asp179 of actin in the ADP-ribosylation reaction. To gain more insights into the structural requirements of actin to serve as a substrate for toxin-catalyzed ADP-ribosylation, we engineered Saccharomyces cerevisiae strains, in which wild type actin was replaced by actin variants with substitutions in residues located on the Ia-actin interface. Expression of the actin mutant Arg177Lys resulted in complete resistance towards Ia. Actin mutation of Asp179 did not change Ia-induced ADP-ribosylation and growth inhibition of S. cerevisiae. By contrast, substitution of Glu270 of actin inhibited the toxic action of Ia and the ADP-ribosylation of actin. In vitro transcribed/translated human β-actin confirmed the crucial role of Glu270 in ADP-ribosylation of actin by Ia.

Plant vegetative and animal cytoplasmic actins share functional competence for spatial development with protists.

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Kandasamy, Muthugapatti K; McKinney, Elizabeth C; Roy, Eileen; Meagher, Richard B

2012-05-01

Actin is an essential multifunctional protein encoded by two distinct ancient classes of genes in animals (cytoplasmic and muscle) and plants (vegetative and reproductive). The prevailing view is that each class of actin variants is functionally distinct. However, we propose that the vegetative plant and cytoplasmic animal variants have conserved functional competence for spatial development inherited from an ancestral protist actin sequence. To test this idea, we ectopically expressed animal and protist actins in Arabidopsis thaliana double vegetative actin mutants that are dramatically altered in cell and organ morphologies. We found that expression of cytoplasmic actins from humans and even a highly divergent invertebrate Ciona intestinalis qualitatively and quantitatively suppressed the root cell polarity and organ defects of act8 act7 mutants and moderately suppressed the root-hairless phenotype of act2 act8 mutants. By contrast, human muscle actins were unable to support prominently any aspect of plant development. Furthermore, actins from three protists representing Choanozoa, Archamoeba, and green algae efficiently suppressed all the phenotypes of both the plant mutants. Remarkably, these data imply that actin's competence to carry out a complex suite of processes essential for multicellular development was already fully developed in single-celled protists and evolved nonprogressively from protists to plants and animals.

The RhoGAP Stard13 controls insulin secretion through F-actin remodeling

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Heike Naumann

2018-02-01

Full Text Available Objective: Actin cytoskeleton remodeling is necessary for glucose-stimulated insulin secretion in pancreatic β-cells. A mechanistic understanding of actin dynamics in the islet is paramount to a better comprehension of β-cell dysfunction in diabetes. Here, we investigate the Rho GTPase regulator Stard13 and its role in F-actin cytoskeleton organization and islet function in adult mice. Methods: We used Lifeact-EGFP transgenic animals to visualize actin cytoskeleton organization and dynamics in vivo in the mouse islets. Furthermore, we applied this model to study actin cytoskeleton and insulin secretion in mutant mice deleted for Stard13 selectively in pancreatic cells. We isolated transgenic islets for 3D-imaging and perifusion studies to measure insulin secretion dynamics. In parallel, we performed histological and morphometric analyses of the pancreas and used in vivo approaches to study glucose metabolism in the mouse. Results: In this study, we provide the first genetic evidence that Stard13 regulates insulin secretion in response to glucose. Postnatally, Stard13 expression became restricted to the mouse pancreatic islets. We showed that Stard13 deletion results in a marked increase in actin polymerization in islet cells, which is accompanied by severe reduction of insulin secretion in perifusion experiments. Consistently, Stard13-deleted mice displayed impaired glucose tolerance and reduced glucose-stimulated insulin secretion. Conclusions: Taken together, our results suggest a previously unappreciated role for the RhoGAP protein Stard13 in the interplay between actin cytoskeletal remodeling and insulin secretion. Keywords: F-actin, Insulin secretion, Islet, Pancreas, Lifeact, Stard13

FIMBRIN1 is involved in lily pollen tube growth by stabilizing the actin fringe.

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Su, Hui; Zhu, Jinsheng; Cai, Chao; Pei, Weike; Wang, Jiaojiao; Dong, Huaijian; Ren, Haiyun

2012-11-01

An actin fringe structure in the subapex plays an important role in pollen tube tip growth. However, the precise mechanism by which the actin fringe is generated and maintained remains largely unknown. Here, we cloned a 2606-bp full-length cDNA encoding a deduced 77-kD fimbrin-like protein from lily (Lilium longiflorum), named FIMBRIN1 (FIM1). Ll-FIM1 was preferentially expressed in pollen and concentrated at actin fringe in the subapical region, as well as in longitudinal actin-filament bundles in the shank of pollen tubes. Microinjection of Ll-FIM1 antibody into lily pollen tubes inhibited tip growth and disrupted the actin fringe. Furthermore, we verified the function of Ll-FIM1 in the fim5 mutant of its closest relative, Arabidopsis thaliana. Pollen tubes of fim5 mutants grew with a larger diameter in early stages but could recover into normal forms in later stages, despite significantly slower growth rates. The actin fringe of the fim5 mutants, however, was impaired during both early and late stages. Impressively, stable expression of fim5pro:GFP:Ll-FIM1 rescued the actin fringe and the growth rate of Arabidopsis fim5 pollen tubes. In vitro biochemical analysis showed that Ll-FIM1 could bundle actin filaments. Thus, our study has identified a fimbrin that may stabilize the actin fringe by cross-linking actin filaments into bundles, which is important for proper tip growth of lily pollen tubes.

The actin homologue MreB organizes the bacterial cell membrane

NARCIS (Netherlands)

Strahl, H.; Burmann, F.; Hamoen, L.W.

2014-01-01

The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate

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

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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.

HISTOPATHOLOGY OF MARGINAL SUPERFICIAL PERIODONTIUM AT MENOPAUSE

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A. Georgescu

2012-03-01

Full Text Available Premises: Sexual hormones may affect the general health condition of women, as early as puberty, continuing during pregnancy and also after menopause. Variations of the hormonal levels may cause different – either local or general – pathological modifications. Sexual hormones may also affect periodontal status, favourizing gingival inflammations and reducing periodontal resistance to the action of the bacterial plaque. Scope: Establishment of the correlations between the debut or the manifestation of menopause and the modifications produced in the superficial periodontium. Materials and method: Clinical and paraclinical investigations were performed on female patients with ages between 45 and 66 years, involving macroscopic, microscopic and radiological recording of the aspect of the superificial periodontium (gingiva. Results: Analysis of the histological sections evidenced atrophic and involutive modifications in the marginal superficial periodontium of female patients at menopause. Conclusions: Sexual hormones intervene in the histological equilibrium of the marginal superficial periodontium, influencing the periodontal health status, which explains the correlation between the subjective symptomatology specific to menopause and the histopatological aspect at epithelial level.

Diagnosis and treatment of superficial esophageal cancer.

Science.gov (United States)

Barret, Maximilien; Prat, Frédéric

2018-01-01

Endoscopy allows for the screening, early diagnosis, treatment and follow up of superficial esophageal cancer. Endoscopic submucosal dissection has become the gold standard for the resection of superficial squamous cell neoplasia. Combinations of endoscopic mucosal resection and radiofrequency ablation are the mainstay of the management of Barrett's associated neoplasia. However, protruded, non-lifting or large lesions may be better managed by endoscopic submucosal dissection. Novel ablation tools, such as argon plasma coagulation with submucosal lifting and cryoablation balloons, are being developed for the treatment of residual Barrett's esophagus, since iatrogenic strictures still hamper the development of extensive circumferential resections in the esophagus. Optimal surveillance modalities after endoscopic resection are still to be determined. The assessment of the risk of lymph-node metastases, as well as of the need for additional treatments based on qualitative and quantitative histological criteria, balanced to the patient's condition, requires a dedicated multidisciplinary team decision process. The need for trained endoscopists, expert pathologists and surgeons, and specialized multidisciplinary meetings underlines the role of expert centers in the management of superficial esophageal cancer.

Coexistence of adult-onset actinic prurigo and shampoo dermatitis: A case report

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Tsung-Ju Lee

2018-06-01

Full Text Available Actinic prurigo is a rare and acquired idiopathic photodermatosis. It usually shows childhood onset and female predominance. Here, we present an unusual case of a male patient with coexistence of adult-onset actinic prurigo and shampoo-induced allergic contact dermatitis. He was initially diagnosed with actinic prurigo. However, after detailed examination of the distribution of the rash, careful collection of his history, and interpretation of the results of histopathologic analysis, photo test, patch test, and photopatch test, coexistence of adult-onset actinic prurigo and shampoo-induced allergic contact dermatitis associated with cocamidopropyl betaine was diagnosed. The rash improved after appropriate use of sunscreen and avoidance of shampoo containing this allergen. Dermatologists should be aware of the possibility of concurrent photodermatitis and contact dermatitis. Keywords: Actinic prurigo, Cocamidopropyl betaine, Contact dermatitis, Photosensitivity, Shampoo dermatitis

Multiple roles for the actin cytoskeleton during regulated exocytosis

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Porat-Shliom, Natalie; Milberg, Oleg; Masedunskas, Andrius; Weigert, Roberto

2014-01-01

Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e. secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules. PMID:22986507

Local superficial hyperthermia in combination with low-dose radiation therapy for palliation of superficially localized metastases

International Nuclear Information System (INIS)

Owczarek, G.; Miszczyk, L.

2005-01-01

Full text: The aim of this study is to evaluate the response of superficially located metastases and local toxicity to microwave hyperthermia combined with radiation therapy. From May 2003 through December 2004 58 patients (33 male, 25 female; mean age 60 years) with lymph nodes or skin metastases were treated with microwave superficial hyperthermia combined with low-dose radiation therapy. Hyperthermia was administered twice weekly with high frequency applicator (∼900 Mhz) with water bolus. The temperature was set to 43 o C for 45 minutes. Radiotherapy was performed daily with dose 2 Gy or 4 Gy per fraction, to a total dose 20 Gy. There were 47 patients with carcinoma, 4 with sarcoma, 7 with melanoma. Treated regions were: head and neck (37 patients), chest wall 8, abdomen wall and groins 4, upper and lower limb 2 and 8 patients respectively. Primary tumor sites were: head and neck region (9 patients), lung 15, alimentary tract 8, breast 5, soft tissue 8, urogenital 4 and 9 patients with primary tumor site unknown. The toxicity was evaluated using 6 step scale: 0-no skin reaction, 1-faint red mark, 2-distinct red mark, 3-blisters, 4-brown mark, 5-necrosis. Presence of pain and its intensity were also analyzed. Diameter of tumor after the treatment was observed. Complete response was achieved in 5 patients (8.5 %), and partial response in 29 patients (50 %), no response was observed in 12 patients (20 %) and progression of tumor in 7 patients (12 %). No skin reaction was observed in 3 patients, faint red mark in 14 patients, distinct red mark in 28 patients, blisters in 8 patients, brown mark in 4 patients and necrosis in 1 patient. The pain occurred in 9 patients but it was no the cause of stopping treatment. Local superficial hyperthermia combined with low-dose radiation therapy is an effective method of treatment in a proportion of patients with superficial metastases. This combination of treatment modalities is well tolerated and is useful for palliation

Liquid nitrogen for the treatment of actinic keratosis: a longitudinal assessment.

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Ianhez, Mayra; Miot, Hélio Amante; Bagatin, Edileia

2014-08-01

Cryosurgery with liquid nitrogen is one of the most used treatments for actinic keratosis. We aimed to study the effectiveness of two consecutive sessions of cryosurgery for actinic keratosis and investigate factors associated with its therapeutic success. Hence, we conducted a longitudinal study including 92 patients of both sexes, aged 50-75 years with 5-50 actinic keratosis on the face and forearms, who underwent cryosurgery and treatment with sunscreen SPF 30, at baseline and after 120 days. The lesions were counted in duplicate by the same examiner before the start of treatment and after 120 (N=92) and 300 days (N=33), represented by their medians and quartiles and compared using the generalized linear mixed effects model (negative binomial). Treatment behavior was investigated in relation to sex, age, education, skin type, smoking, sun exposure at work and the use of aspirin, anti-inflammatory and angiotensin-converting enzyme inhibitors. There was a significant reduction in the actinic keratosis count on the face and forearms (pliquid nitrogen reduced the actinic keratosis count. Copyright © 2014 Elsevier Inc. All rights reserved.

The structure of the actin-smooth muscle myosin motor domain complex in the rigor state.

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Banerjee, Chaity; Hu, Zhongjun; Huang, Zhong; Warrington, J Anthony; Taylor, Dianne W; Trybus, Kathleen M; Lowey, Susan; Taylor, Kenneth A

2017-12-01

Myosin-based motility utilizes catalysis of ATP to drive the relative sliding of F-actin and myosin. The earliest detailed model based on cryo-electron microscopy (cryoEM) and X-ray crystallography postulated that higher actin affinity and lever arm movement were coupled to closure of a feature of the myosin head dubbed the actin-binding cleft. Several studies since then using crystallography of myosin-V and cryoEM structures of F-actin bound myosin-I, -II and -V have provided details of this model. The smooth muscle myosin II interaction with F-actin may differ from those for striated and non-muscle myosin II due in part to different lengths of important surface loops. Here we report a ∼6 Å resolution reconstruction of F-actin decorated with the nucleotide-free recombinant smooth muscle myosin-II motor domain (MD) from images recorded using a direct electron detector. Resolution is highest for F-actin and the actin-myosin interface (3.5-4 Å) and lowest (∼6-7 Å) for those parts of the MD at the highest radius. Atomic models built into the F-actin density are quite comparable to those previously reported for rabbit muscle actin and show density from the bound ADP. The atomic model of the MD, is quite similar to a recently published structure of vertebrate non-muscle myosin II bound to F-actin and a crystal structure of nucleotide free myosin-V. Larger differences are observed when compared to the cryoEM structure of F-actin decorated with rabbit skeletal muscle myosin subfragment 1. The differences suggest less closure of the 50 kDa domain in the actin bound skeletal muscle myosin structure. Copyright © 2017 Elsevier Inc. All rights reserved.

Superficial parotidectomy via facelift incision

NARCIS (Netherlands)

Lohuis, Peter J. F. M.; Tan, M. Liane; Bonte, Katrien; van den Brekel, Michiel W. M.; Balm, Alfons J. M.; Vermeersch, Hubert B.

2009-01-01

The stigma of a visually prominent facial scar following parotid surgery can be distressing to a young patient. The surgical technique of parotidectomy via a facelift incision is described and evaluated. Thirty patients with a benign lesion of the parotid gland underwent a partial superficial

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

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Bailly, Aurelien; Zwiewka, Marta; Sovero, Valpuri; Ge, Pei; Aryal, Bibek; Hao, Pengchao; Linnert, Miriam; Burgardt, Noelia Inés; Lücke, Christian; Weiwad, Matthias; Michel, Max; Weiergräber, Oliver H.; Pollmann, Stephan; Azzarello, Elisa; Fukao, Yoichiro; Hoffmann, Céline; Wedlich-Söldner, Roland

2016-01-01

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity. PMID:27053424

Physiological Laterality of Superficial Cerebral Veins on Susceptibility-Weighted Imaging.

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Matsushima, Satoshi; Shimizu, Tetsuya; Gomi, Taku; Fukuda, Kunihiko

The purpose of this study is to evaluate whether laterality of the superficial cerebral veins can be seen on susceptibility-weighted imaging (SWI) in patients with no intracranial lesions that affect venous visualization. We retrospectively evaluated 386 patients who underwent brain magnetic resonance imaging including SWI in our institute. Patients with a lesion with the potential to affect venous visualization on SWI were excluded. Two neuroradiologists visually evaluated the findings and scored the visualization of the superficial cerebral veins. Of the 386 patients, 315 (81.6%) showed no obvious laterality on venous visualization, 64 (16.6%) showed left-side dominant laterality, and 7 (1.8%) showed right-side dominant laterality. Left-side dominant physiological laterality exists in the visualization of the superficial cerebral veins on SWI. Therefore, when recognizing left-side dominant laterality of the superficial cerebral veins on SWI, the radiologist must also consider the possibility of physiological laterality.

System-wide organization of actin cytoskeleton determines organelle transport in hypocotyl plant cells

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Nowak, Jacqueline; Ivakov, Alexander; Somssich, Marc; Persson, Staffan; Nikoloski, Zoran

2017-01-01

The actin cytoskeleton is an essential intracellular filamentous structure that underpins cellular transport and cytoplasmic streaming in plant cells. However, the system-level properties of actin-based cellular trafficking remain tenuous, largely due to the inability to quantify key features of the actin cytoskeleton. Here, we developed an automated image-based, network-driven framework to accurately segment and quantify actin cytoskeletal structures and Golgi transport. We show that the actin cytoskeleton in both growing and elongated hypocotyl cells has structural properties facilitating efficient transport. Our findings suggest that the erratic movement of Golgi is a stable cellular phenomenon that might optimize distribution efficiency of cell material. Moreover, we demonstrate that Golgi transport in hypocotyl cells can be accurately predicted from the actin network topology alone. Thus, our framework provides quantitative evidence for system-wide coordination of cellular transport in plant cells and can be readily applied to investigate cytoskeletal organization and transport in other organisms. PMID:28655850

F-actin distribution at nodes of Ranvier and Schmidt-Lanterman incisures in mammalian sciatic nerves.

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Kun, Alejandra; Canclini, Lucía; Rosso, Gonzalo; Bresque, Mariana; Romeo, Carlos; Hanusz, Alicia; Cal, Karina; Calliari, Aldo; Sotelo Silveira, José; Sotelo, José R

2012-07-01

Very little is known about the function of the F-actin cytoskeleton in the regeneration and pathology of peripheral nerve fibers. The actin cytoskeleton has been associated with maintenance of tissue structure, transmission of traction and contraction forces, and an involvement in cell motility. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and intracellular transport therein. In this work, we analyze the distribution of F-actin at Schmidt-Lanterman Incisures (SLI) and nodes of Ranvier (NR) domains in normal, regenerating and pathologic Trembler J (TrJ/+) sciatic nerve fibers, of rats and mice. F-actin was quantified and it was found increased in TrJ/+, both in SLI and NR. However, SLI and NR of regenerating rat sciatic nerve did not show significant differences in F-actin, as compared with normal nerves. Cytochalasin-D and Latrunculin-A were used to disrupt the F-actin network in normal and regenerating rat sciatic nerve fibers. Both drugs disrupt F-actin, but in different ways. Cytochalasin-D did not disrupt Schwann cell (SC) F-actin at the NR. Latrunculin-A did not disrupt F-actin at the boundary region between SC and axon at the NR domain. We surmise that the rearrangement of F-actin in neurological disorders, as presented here, is an important feature of TrJ/+ pathology as a Charcot-Marie-Tooth (CMT) model. Copyright © 2012 Wiley Periodicals, Inc.

Characterization of the activities of actin-affecting drugs on tumor cell migration

International Nuclear Information System (INIS)

Hayot, Caroline; Debeir, Olivier; Ham, Philippe van; Damme, Marc van; Kiss, Robert; Decaestecker, Christine

2006-01-01

Metastases kill 90% of cancer patients. It is thus a major challenge in cancer therapy to inhibit the spreading of tumor cells from primary tumor sites to those particular organs where metastases are likely to occur. Whereas the actin cytoskeleton is a key component involved in cell migration, agents targeting actin dynamics have been relatively poorly investigated. Consequently, valuable in vitro pharmacological tools are needed to selectively identify this type of agent. In response to the absence of any standardized process, the present work aims to develop a multi-assay strategy for screening actin-affecting drugs with anti-migratory potentials. To validate our approach, we used two cancer cell lines (MCF7 and A549) and three actin-affecting drugs (cytochalasin D, latrunculin A, and jasplakinolide). We quantified the effects of these drugs on the kinetics of actin polymerization in tubes (by means of spectrofluorimetry) and on the dynamics of actin cytoskeletons within whole cells (by means of fluorescence microscopy). Using quantitative videomicroscopy, we investigated the actual effects of the drugs on cell motility. Finally, the combined drug effects on cell motility and cell growth were evaluated by means of a scratch-wound assay. While our results showed concordant drug-induced effects on actin polymerization occurring in vitro in test tubes and within whole cells, the whole cell assay appeared more sensitive than the tube assay. The inhibition of actin polymerization induced by cytochalasin D was paralleled by a decrease in cell motility for both cell types. In the case of jasplakinolide, which induces actin polymerization, while it significantly enhanced the locomotion of the A549 cells, it significantly inhibited that of the MCF-7 ones. All these effects were confirmed by means of the scratch-wound assay except of the jasplakinolide-induced effects on MCF-7 cell motility. These later seemed compensated by an additional effect occurring during wound

Sensory role of actin in auxin-dependent responses of tobacco BY-2.

Science.gov (United States)

Huang, Xiang; Maisch, Jan; Nick, Peter

2017-11-01

Polar auxin transport depends on the polar localization of auxin-efflux carriers. The cycling of these carriers between cell interior and plasma membrane depends on actin. The dynamic of actin not only affects auxin transport, but also changes the auxin-responsiveness. To study the potential link between auxin responsiveness and actin dynamics, we investigated developmental responses of the non-transformed BY-2 (Nicotiana tabacum L. cv Bright Yellow 2) cell line and the transgenic BY-2 strain GF11 (stably transformed BY-2 cells with a GFP-fimbrin actin-binding domain 2 construct). The developmental process was divided into three distinct stages: cell cycling, cell elongation and file disintegration. Several phenotypes were measured to monitor the cellular responses to different concentrations of exogenous natural auxin (Indole-3-acetic acid, IAA). We found that auxin stimulated and prolonged the mitotic activity, and delayed the exit from the proliferation phase. However, both responses were suppressed in the GF11 line. At the stationary phase of the cultivation cycle, auxin strongly accelerated the cell file disintegration. Interestingly, it was not suppressed but progressed to a more complete disintegration in the GF11 line. During the cultivation cycle, we also followed the organization of actin in the GF11 line and did not detect any significant difference in actin organization from untreated control or exogenous IAA treatment. Therefore, our findings indicate that the specific differences observed in the GF11 line must be linked with a function of actin that is not structural. It means that there is a sensory role of actin for auxin signaling. Copyright © 2017 Elsevier GmbH. All rights reserved.

T lymphocyte migration: an action movie starring the actin and associated actors

Directory of Open Access Journals (Sweden)

Loïc eDupré

2015-11-01

Full Text Available The actin cytoskeleton is composed of a dynamic filament meshwork that builds the architecture of the cell to sustain its fundamental properties. This physical structure is characterized by a continuous remodeling, which allows cells to accomplish complex motility steps such as directed migration, crossing of biological barriers and interaction with other cells. T lymphocytes excel in these motility steps to ensure their immune surveillance duties. In particular, actin cytoskeleton remodeling is key to facilitate the journey of T lymphocytes through distinct tissue environments and to tune their stop and go behavior during the scanning of antigen-presenting cells. The molecular mechanisms controlling actin cytoskeleton remodeling during T lymphocyte motility have been only partially unraveled, since the function of many actin regulators has not yet been assessed in these cells. Our review aims to integrate the current knowledge into a comprehensive picture of how the actin cytoskeleton drives T lymphocyte migration. We will present the molecular actors that control actin cytoskeleton remodeling, as well as their role in the different T lymphocyte motile steps. We will also highlight which challenges remain to be addressed experimentally and which approaches appear promising to tackle them.

T Lymphocyte Migration: An Action Movie Starring the Actin and Associated Actors.

Science.gov (United States)

Dupré, Loïc; Houmadi, Raïssa; Tang, Catherine; Rey-Barroso, Javier

2015-01-01

The actin cytoskeleton is composed of a dynamic filament meshwork that builds the architecture of the cell to sustain its fundamental properties. This physical structure is characterized by a continuous remodeling, which allows cells to accomplish complex motility steps such as directed migration, crossing of biological barriers, and interaction with other cells. T lymphocytes excel in these motility steps to ensure their immune surveillance duties. In particular, actin cytoskeleton remodeling is a key to facilitate the journey of T lymphocytes through distinct tissue environments and to tune their stop and go behavior during the scanning of antigen-presenting cells. The molecular mechanisms controlling actin cytoskeleton remodeling during T lymphocyte motility have been only partially unraveled, since the function of many actin regulators has not yet been assessed in these cells. Our review aims to integrate the current knowledge into a comprehensive picture of how the actin cytoskeleton drives T lymphocyte migration. We will present the molecular actors that control actin cytoskeleton remodeling, as well as their role in the different T lymphocyte motile steps. We will also highlight which challenges remain to be addressed experimentally and which approaches appear promising to tackle them.

Phosphorylation of actin-binding protein (ABP-280; filamin) by tyrosine kinase p56lck modulates actin filament cross-linking.

Science.gov (United States)

Pal Sharma, C; Goldmann, Wolfgang H

2004-01-01

Actin-binding protein (ABP-280; filamin) is a phosphoprotein present in the periphery of the cytoplasm where it can cross-link actin filaments, associate with lipid membranes, and bind to membrane surface receptors. Given its function and localization in the cell, we decided to investigate the possibility of whether it serves as substrate for p56lck, a lymphocyte-specific member of the src family of protein tyrosine kinases associated with cell surface glycoproteins. The interaction of p56lck with membrane glycoproteins is important for cell development and functional activation. Here, we show that purified p56lck interacts and catalyzes in vitro kinase reactions. Tyrosine phosphorylation by p56lck is restricted to a single peptide of labeled ABP-280 shown by protease digest. The addition of phorbol ester to cells results in the inhibition of phosphorylation of ABP-280 by p56lck. These results show a decrease in phosphorylation suggesting conformationally induced regulation. Dynamic light scattering confirmed increased actin filament cross-linking due to phosphorylation of ABP-280 by p56lck.

Organization and dynamics of the actin cytoskeleton during dendritic spine morphological remodeling.

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Chazeau, Anaël; Giannone, Grégory

2016-08-01

In the central nervous system, most excitatory post-synapses are small subcellular structures called dendritic spines. Their structure and morphological remodeling are tightly coupled to changes in synaptic transmission. The F-actin cytoskeleton is the main driving force of dendritic spine remodeling and sustains synaptic plasticity. It is therefore essential to understand how changes in synaptic transmission can regulate the organization and dynamics of actin binding proteins (ABPs). In this review, we will provide a detailed description of the organization and dynamics of F-actin and ABPs in dendritic spines and will discuss the current models explaining how the actin cytoskeleton sustains both structural and functional synaptic plasticity.

Inhibiting actin depolymerization enhances osteoblast differentiation and bone formation in human stromal stem cells

DEFF Research Database (Denmark)

Chen, Li; Shi, Kaikai; Frary, Charles

2015-01-01

Remodeling of the actin cytoskeleton through actin dynamics is involved in a number of biological processes, but its role in human stromal (skeletal) stem cells (hMSCs) differentiation is poorly understood. In the present study, we demonstrated that stabilizing actin filaments by inhibiting gene...... expression of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) in hMSCs, enhanced cell viability and differentiation into osteoblastic cells (OB) in vitro, as well as heterotopic bone formation in vivo. Similarly, treating hMSC with Phalloidin, which is known to stabilize...... polymerized actin filaments, increased hMSCs viability and OB differentiation. Conversely, Cytocholasin D, an inhibitor of actin polymerization, reduced cell viability and inhibited OB differentiation of hMSC. At a molecular level, preventing Cofilin phosphorylation through inhibition of LIM domain kinase 1...

Pharmacoeconomic Considerations in Treating Actinic Keratosis: An Update.

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Vale, Spencer M; Hill, Dane; Feldman, Steven R

2017-02-01

Actinic keratosis is one of the most common dermatological diagnoses worldwide, especially among the elderly, fair-skinned, and immunocompromised, and is associated with a risk of transformation to skin cancer. With actinic keratosis and skin cancer prevalence increasing as the aged population expands in the US, optimizing treatment strategies may produce cost savings for the healthcare system. Since the time of our last review in 2008, investigation of the economic considerations in treating actinic keratosis has advanced. To provide an update of treatment cost effectiveness and to review factors relating to the costs of care, we conducted a systematic review of pharmacoeconomic publications since December 2008. We identified 11 pharmacoeconomic studies, with one cost-of-treatment, five cost-effectiveness, and five cost-utility analyses. Photodynamic therapy (PDT) was well tolerated and produced a favorable cosmetic outcome in most studies. Ingenol mebutate, the newest but most expensive topical field therapy, 5-fluorouracil, and PDT were the most cost-effective treatments in our review. Patient adherence to therapy and the management of adverse effects were significant contributors to treatment costs. In the US, treatment guidelines and formalized cost-effectiveness analyses for actinic keratosis are absent from the recent literature. Future pharmacoeconomic investigation will depend on up-to-date comparative efficacy data, as well as clarification of rates of, and management strategies for, adverse effects, therapeutic non-adherence, and lesion recurrence.

Suspected Pulmonary Metastasis of Actinic Cutaneous Squamous Cell Carcinoma

Directory of Open Access Journals (Sweden)

Monet E. Meter

2017-01-01

Full Text Available Introduction. It is rare for actinic or squamous cell carcinoma (SCC in situ to metastasize. Case Presentation. A 67-year-old male had a significant medical history including severe psoriatic arthritis treated with UVB, methotrexate, and rapamycin. He had twenty-five different skin excisions of actinic keratosis four of which were invasive SCC. Our patient developed shortness of breath necessitating a visit to the emergency department. A CT scan of his chest revealed a mass in the right lower lung. A subsequent biopsy of the mass revealed well-differentiated SCC. He underwent thoracoscopic surgery with wedge resection of the lung lesion. Discussion. Actinic keratosis (AK is considered precancerous and associated with UV exposure. It exists as a continuum of progression with low potential for malignancy. The majority of invasive SCCs are associated with malignant progression of AK, but only 5–10% of AKs will progress to malignant potential. Conclusion. In this case, a new finding of lung SCC in the setting of multiple invasive actinic cutaneous SCC associated with a history of extensive UV light exposure and immunosuppression supports a metastatic explanation for lung cancer.

Live cell imaging of actin dynamics in dexamethasone-treated porcine trabecular meshwork cells.

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Fujimoto, Tomokazu; Inoue, Toshihiro; Inoue-Mochita, Miyuki; Tanihara, Hidenobu

2016-04-01

The regulation of the actin cytoskeleton in trabecular meshwork (TM) cells is important for controlling outflow of the aqueous humor. In some reports, dexamethasone (DEX) increased the aqueous humor outflow resistance and induced unusual actin structures, such as cross-linked actin networks (CLAN), in TM cells. However, the functions and dynamics of CLAN in TM cells are not completely known, partly because actin stress fibers have been observed only in fixed cells. We conducted live-cell imaging of the actin dynamics in TM cells with or without DEX treatment. An actin-green fluorescent protein (GFP) fusion construct with a modified insect virus was transfected into porcine TM cells. Time-lapse imaging of live TM cells treated with 25 μM Y-27632 and 100 nM DEX was performed using an inverted fluorescence microscope. Fluorescent images were recorded every 15 s for 30 min after Y-27632 treatment or every 30 min for 72 h after DEX treatment. The GFP-actin was expressed in 22.7 ± 10.9% of the transfected TM cells. In live TM cells, many actin stress fibers were observed before the Y-27632 treatment. Y-27632 changed the cell shape and decreased stress fibers in a time-dependent manner. In fixed cells, CLAN-like structures were seen in 26.5 ± 1.7% of the actin-GFP expressed PTM cells treated with DEX for 72 h. In live imaging, there was 28% CLAN-like structure formation at 72 h after DEX treatment, and the lifetime of CLAN-like structures increased after DEX treatment. The DEX-treated cells with CLAN-like structures showed less migration than DEX-treated cells without CLAN-like structures. Furthermore, the control cells (without DEX treatment) with CLAN-like structures also showed less migration than the control cells without CLAN-like structures. These results suggested that CLAN-like structure formation was correlated with cell migration in TM cells. Live cell imaging of the actin cytoskeleton provides valuable information on the actin dynamics in TM

Distortion of the Actin A-Triad Results in Contractile Disinhibition and Cardiomyopathy

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Meera C. Viswanathan

2017-09-01

Full Text Available Striated muscle contraction is regulated by the movement of tropomyosin over the thin filament surface, which blocks or exposes myosin binding sites on actin. Findings suggest that electrostatic contacts, particularly those between K326, K328, and R147 on actin and tropomyosin, establish an energetically favorable F-actin-tropomyosin configuration, with tropomyosin positioned in a location that impedes actomyosin associations and promotes relaxation. Here, we provide data that directly support a vital role for these actin residues, termed the A-triad, in tropomyosin positioning in intact functioning muscle. By examining the effects of an A295S α-cardiac actin hypertrophic cardiomyopathy-causing mutation, over a range of increasingly complex in silico, in vitro, and in vivo Drosophila muscle models, we propose that subtle A-triad-tropomyosin perturbation can destabilize thin filament regulation, which leads to hypercontractility and triggers disease. Our efforts increase understanding of basic thin filament biology and help unravel the mechanistic basis of a complex cardiac disorder.

Computations in the deep vs superficial layers of the cerebral cortex.

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Rolls, Edmund T; Mills, W Patrick C

2017-11-01

A fundamental question is how the cerebral neocortex operates functionally, computationally. The cerebral neocortex with its superficial and deep layers and highly developed recurrent collateral systems that provide a basis for memory-related processing might perform somewhat different computations in the superficial and deep layers. Here we take into account the quantitative connectivity within and between laminae. Using integrate-and-fire neuronal network simulations that incorporate this connectivity, we first show that attractor networks implemented in the deep layers that are activated by the superficial layers could be partly independent in that the deep layers might have a different time course, which might because of adaptation be more transient and useful for outputs from the neocortex. In contrast the superficial layers could implement more prolonged firing, useful for slow learning and for short-term memory. Second, we show that a different type of computation could in principle be performed in the superficial and deep layers, by showing that the superficial layers could operate as a discrete attractor network useful for categorisation and feeding information forward up a cortical hierarchy, whereas the deep layers could operate as a continuous attractor network useful for providing a spatially and temporally smooth output to output systems in the brain. A key advance is that we draw attention to the functions of the recurrent collateral connections between cortical pyramidal cells, often omitted in canonical models of the neocortex, and address principles of operation of the neocortex by which the superficial and deep layers might be specialized for different types of attractor-related memory functions implemented by the recurrent collaterals. Copyright © 2017 Elsevier Inc. All rights reserved.

Long-term evolution of superficial optic disc drusen

DEFF Research Database (Denmark)

Larsen, Lasse Malmqvist; Lund-Andersen, Henrik; Hamann, Steffen

2017-01-01

with hereditary ODD were included. Results: Mean age at initial and follow-up examination was, respectively, 16.8 and 73.3 years. The median follow-up time was 56 years. A minimal or non-existing change in superficial ODD anatomy (size and number) was seen in 10 of 12 eyes. There was a tendency towards more......Purpose: Optic disc drusen (ODD) is hyaline deposits in the optic nerve head seen in 1-2% of the population. Long-term evolution of ODD anatomy and visual field defects in ODD patients is a key factor for learning more about pathophysiology and prognosis of the condition. With a median follow......-up period of 56 years, this is the first study that evaluates superficial optic disc anatomy and visual fields in patients with ODD over a life span. Methods: Observational case series investigating progression of superficial optic disc anatomy and visual fields in ODD patients. Eight patients...

What factors control superficial lava dome explosivity?

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Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J

2015-09-30

Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management.

Daam1 regulates fascin for actin assembly in mouse oocyte meiosis.

Science.gov (United States)

Lu, Yujie; Zhang, Yu; Pan, Meng-Hao; Kim, Nam-Hyung; Sun, Shao-Chen; Cui, Xiang-Shun

2017-07-18

As a formin protein, Daam1 (Dishevelled-associated activator of morphogenesis 1) is reported to regulate series of cell processes like endocytosis, cell morphology and migration via its effects on actin assembly in mitosis. However, whether Daam1 plays roles in female meiosis remains uncertain. In this study, we investigated the expression and functions of Daam1 during mouse oocyte meiosis. Our results indicated that Daam1 localized at the cortex of oocytes, which was similar with actin filaments. After Daam1 morpholino (MO) microinjection, the expression of Daam1 significantly decreased, which resulted in the failure of oocyte polar body extrusion. These results might be due to the defects of actin assembly, since the decreased fluorescence intensity of actin filaments in oocyte cortex and cytoplasm were observed. However, Daam1 knockdown seemed not to affect the meiotic spindle movement. In addition, we found that fascin might be the down effector of Daam1, since the protein expression of fascin decreased after Daam1 knockdown. Thus, our data suggested that Daam1 affected actin assembly during oocyte meiotic division via the regulation of fascin expression.

Spatially restricted actin-regulatory signaling contributes to synapse morphology

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Nicholson, Daniel A.; Cahill, Michael E.; Tulisiak, Christopher T.; Geinisman, Yuri; Penzes, Peter

2012-01-01

The actin cytoskeleton in dendritic spines is organized into microdomains, but how signaling molecules that regulate actin are spatially governed is incompletely understood. Here we examine how the localization of the RacGEF kalirin-7, a well-characterized regulator of actin in spines, varies as a function of postsynaptic density (PSD) area and spine volume. Using serial section electron microscopy (EM), we find that extrasynaptic, but not synaptic, expression of kalirin-7 varies directly with synapse size and spine volume. Moreover, we find that overall expression levels of kalirin-7 differ in spines bearing perforated and non-perforated synapses, due primarily to extrasynaptic pools of kalirin-7 expression in the former. Overall, our findings indicate that kalirin-7 is differentially compartmentalized in spines as a function of both synapse morphology and spine size. PMID:22458534

Cofilin phosphorylation is elevated after F-actin disassembly induced by Rac1 depletion.

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Liu, Linna; Li, Jing; Zhang, Liwang; Zhang, Feng; Zhang, Rong; Chen, Xiang; Brakebusch, Cord; Wang, Zhipeng; Liu, Xinyou

2015-01-01

Cytoskeletal reorganization is essential to keratinocyte function. Rac1 regulates cytoskeletal reorganization through signaling pathways such as the cofilin cascade. Cofilin severs actin filaments after activation by dephosphorylation. Rac1 was knocked out in mouse keratinocytes and it was found that actin filaments disassembled. In the epidermis of mice in which Rac1 was knocked out only in keratinocytes, cofilin phosphorylation was aberrantly elevated, corresponding to repression of the phosphatase slingshot1 (SSH1). These effects were independent of the signaling pathways for p21-activated kinase/LIM kinase (Pak/LIMK), protein kinase C, or protein kinase D or generation of reactive oxygen species. Similarly, when actin polymerization was specifically inhibited or Rac1 was knocked down, cofilin phosphorylation was enhanced and SSH1 was repressed. Repression of SSH1 partially blocked actin depolymerization induced by Rac1 depletion. Therefore, aberrant cofilin phosphorylation that induces actin polymerization might be a consequence of actin disassembly induced by the absence of Rac1. © 2015 International Union of Biochemistry and Molecular Biology.

WHAMM links actin assembly via the Arp2/3 complex to autophagy.

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Kast, David J; Dominguez, Roberto

2015-01-01

Macroautophagy (hereafter autophagy) is the process by which cytosolic material destined for degradation is enclosed inside a double-membrane cisterna known as the autophagosome and processed for secretion and/or recycling. This process requires a large collection of proteins that converge on certain sites of the ER membrane to generate the autophagosome membrane. Recently, it was shown that actin accumulates around autophagosome precursors and could play a role in this process, but the mechanism and role of actin polymerization in autophagy were unknown. Here, we discuss our recent finding that the nucleation-promoting factor (NPF) WHAMM recruits and activates the Arp2/3 complex for actin assembly at sites of autophagosome formation on the ER. Using high-resolution, live-cell imaging, we showed that WHAMM forms dynamic puncta on the ER that comigrate with several autophagy markers, and propels the spiral movement of these puncta by an Arp2/3 complex-dependent actin comet tail mechanism. In starved cells, WHAMM accumulates at the interface between neighboring autophagosomes, whose number and size increases with WHAMM expression. Conversely, knocking down WHAMM, inhibiting the Arp2/3 complex or interfering with actin polymerization reduces the size and number of autophagosomes. These findings establish a link between Arp2/3 complex-mediated actin assembly and autophagy.

Superficie Específica y Estado Vital de la Materia

OpenAIRE

J. Hernando Ordoñez

1992-01-01

Se propone reemplazar el término de materia viva por el de estado vital de la materia por considerarlo adecuado, pues la materia es la misma, lo que cambia es su estado. Se estudia la relación entre la superficie específica y el estado vital de la materia. Constante del estado vital y el valor crítico de la superficie específica. Qué es la fuerza de inducción vital? Diferenciación funcional de las células. Cómo regula la unidad biológica su superficie específica? La materia que piens...

Altered Cell Mechanics from the Inside: Dispersed Single Wall Carbon Nanotubes Integrate with and Restructure Actin

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Mohammad F. Islam

2012-05-01

Full Text Available With a range of desirable mechanical and optical properties, single wall carbon nanotubes (SWCNTs are a promising material for nanobiotechnologies. SWCNTs also have potential as biomaterials for modulation of cellular structures. Previously, we showed that highly purified, dispersed SWCNTs grossly alter F-actin inside cells. F-actin plays critical roles in the maintenance of cell structure, force transduction, transport and cytokinesis. Thus, quantification of SWCNT-actin interactions ranging from molecular, sub-cellular and cellular levels with both structure and function is critical for developing SWCNT-based biotechnologies. Further, this interaction can be exploited, using SWCNTs as a unique actin-altering material. Here, we utilized molecular dynamics simulations to explore the interactions of SWCNTs with actin filaments. Fluorescence lifetime imaging microscopy confirmed that SWCNTs were located within ~5 nm of F-actin in cells but did not interact with G-actin. SWCNTs did not alter myosin II sub-cellular localization, and SWCNT treatment in cells led to significantly shorter actin filaments. Functionally, cells with internalized SWCNTs had greatly reduced cell traction force. Combined, these results demonstrate direct, specific SWCNT alteration of F-actin structures which can be exploited for SWCNT-based biotechnologies and utilized as a new method to probe fundamental actin-related cellular processes and biophysics.

SUPERFICIAL CERVICAL PLEXUS BLOCK

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Komang Mega Puspadisari

2014-01-01

Full Text Available Superficial cervical plexus block is one of the regional anesthesia in  neck were limited to thesuperficial fascia. Anesthesia is used to relieve pain caused either during or after the surgery iscompleted. This technique can be done by landmark or with ultrasound guiding. The midpointof posterior border of the Sternocleidomastoid was identified and the prosedure done on thatplace or on the level of cartilage cricoid.

Comparative genome analysis reveals a conserved family of actin-like proteins in apicomplexan parasites

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Sibley L David

2005-12-01

Full Text Available Abstract Background The phylum Apicomplexa is an early-branching eukaryotic lineage that contains a number of important human and animal pathogens. Their complex life cycles and unique cytoskeletal features distinguish them from other model eukaryotes. Apicomplexans rely on actin-based motility for cell invasion, yet the regulation of this system remains largely unknown. Consequently, we focused our efforts on identifying actin-related proteins in the recently completed genomes of Toxoplasma gondii, Plasmodium spp., Cryptosporidium spp., and Theileria spp. Results Comparative genomic and phylogenetic studies of apicomplexan genomes reveals that most contain only a single conventional actin and yet they each have 8–10 additional actin-related proteins. Among these are a highly conserved Arp1 protein (likely part of a conserved dynactin complex, and Arp4 and Arp6 homologues (subunits of the chromatin-remodeling machinery. In contrast, apicomplexans lack canonical Arp2 or Arp3 proteins, suggesting they lost the Arp2/3 actin polymerization complex on their evolutionary path towards intracellular parasitism. Seven of these actin-like proteins (ALPs are novel to apicomplexans. They show no phylogenetic associations to the known Arp groups and likely serve functions specific to this important group of intracellular parasites. Conclusion The large diversity of actin-like proteins in apicomplexans suggests that the actin protein family has diverged to fulfill various roles in the unique biology of intracellular parasites. Conserved Arps likely participate in vesicular transport and gene expression, while apicomplexan-specific ALPs may control unique biological traits such as actin-based gliding motility.

The unique organization of filamentous actin in the medullary canal of the medulla oblongata.

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Tan, Bai-Hong; Guo, Chun-Yan; Xiong, Tian-Qing; Chen, Ling-Meng; Li, Yan-Chao

2017-04-01

In the central canal, F-actin is predominantly localized in the apical region, forming a ring-like structure around the circumference of the lumen. However, an exception is found in the medulla oblongata, where the apical F-actin becomes interrupted in the ventral aspect of the canal. To clarify the precise localization of F-actin, the fluorescence signals for F-actin were converted to the peroxidase/DAB reaction products in this study by a phalloidin-based ultrastructural technique, which demonstrated that F-actin is located mainly in the microvilli and terminal webs in the ependymocytes. It is because the ventrally oriented ependymocytes do not possess well-developed microvilli or terminal web that led to a discontinuous labeling of F-actin in the medullary canal. Since spinal motions can change the shape and size of the central canal, we next examined the cytoskeletons in the medullary canal in both rats and monkeys, because these two kinds of animals show different kinematics at the atlanto-occipital articulation. Our results first demonstrated that the apical F-actin in the medullary canal is differently organized in the animals with different head-neck kinemics, which suggests that the mechanic stretching of spinal motions is capable of inducing F-actin reorganization and the subsequent cell-shape changes in the central canal. Copyright © 2017 Elsevier Ltd. All rights reserved.

The ADF/Cofilin-Pathway and Actin Dynamics in Podocyte Injury

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Beina Teng

2012-01-01

Full Text Available ADF/cofilins are the major regulators of actin dynamics in mammalian cells. The activation of ADF/cofilins is controlled by a variety of regulatory mechanisms. Dysregulation of ADF/cofilin may result in loss of a precisely organized actin cytoskeletal architecture and can reduce podocyte migration and motility. Recent studies suggest that cofilin-1 can be regulated through several extracellular signals and slit diaphragm proteins. Cofilin knockdown and knockout animal models show dysfunction of glomerular barrier and filtration with foot process effacement and loss of secondary foot processes. This indicates that cofilin-1 is necessary for modulating actin dynamics in podocytes. Podocyte alterations in actin architecture may initiate or aid the progression of a large variety of glomerular diseases, and cofilin activity is required for reorganization of an intact filtration barrier. Since almost all proteinuric diseases result from a similar phenotype with effacement of the foot processes, we propose that cofilin-1 is at the centre stage of the development of proteinuria and thus may be an attractive drug target for antiproteinuric treatment strategies.

Axonal regeneration and neuronal function are preserved in motor neurons lacking ß-actin in vivo.

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Thomas R Cheever

2011-03-01

Full Text Available The proper localization of ß-actin mRNA and protein is essential for growth cone guidance and axon elongation in cultured neurons. In addition, decreased levels of ß-actin mRNA and protein have been identified in the growth cones of motor neurons cultured from a mouse model of Spinal Muscular Atrophy (SMA, suggesting that ß-actin loss-of-function at growth cones or pre-synaptic nerve terminals could contribute to the pathogenesis of this disease. However, the role of ß-actin in motor neurons in vivo and its potential relevance to disease has yet to be examined. We therefore generated motor neuron specific ß-actin knock-out mice (Actb-MNsKO to investigate the function of ß-actin in motor neurons in vivo. Surprisingly, ß-actin was not required for motor neuron viability or neuromuscular junction maintenance. Skeletal muscle from Actb-MNsKO mice showed no histological indication of denervation and did not significantly differ from controls in several measurements of physiologic function. Finally, motor axon regeneration was unimpaired in Actb-MNsKO mice, suggesting that ß-actin is not required for motor neuron function or regeneration in vivo.

The interplay between viscoelastic and thermodynamic properties determines the birefringence of F-actin gels.

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Helfer, Emmanuèle; Panine, Pierre; Carlier, Marie-France; Davidson, Patrick

2005-07-01

F-actin gels of increasing concentrations (25-300 microM) display in vitro a progressive onset of birefringence due to orientational ordering of actin filaments. At F-actin concentrations mechanical stresses stored in the gels. In contrast, at F-actin concentrations > or =100 microM, gels display spontaneous birefringence recovery, at rest, which is the sign of true nematic ordering, in good agreement with statistical physics models of the isotropic/nematic transition. Well-aligned samples of F-actin gels could be produced and their small-angle x-ray scattering patterns are quite anisotropic. These patterns show no sign of filament positional short-range order and could be modeled by averaging the form factor with the Maier-Saupe nematic distribution function. The derived nematic order parameter S of the gels ranged from S = 0.7 at 300 microM to S = 0.4 at 25 microM. Both birefringence and small-angle x-ray scattering data indicate that, even in absence of cross-linking proteins, spontaneous cooperative alignment of actin filaments may arise in motile regions of living cells where F-actin concentrations can reach values of a few 100 microM.

The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration

Energy Technology Data Exchange (ETDEWEB)

Blom, Magdalena; Reis, Katarina [Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm (Sweden); Heldin, Johan [Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala SE-751 22 Uppsala (Sweden); Kreuger, Johan [Department of Medical Cell Biology, Science for Life Laboratory, Uppsala University, SE-751 23 Uppsala (Sweden); Aspenström, Pontus, E-mail: pontus.aspenstrom@ki.se [Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm (Sweden)

2017-03-15

RhoD belongs to the Rho GTPases, a protein family responsible for the regulation and organization of the actin cytoskeleton, and, consequently, many cellular processes like cell migration, cell division and vesicle trafficking. Here, we demonstrate that the actin cytoskeleton is dynamically regulated by increased or decreased protein levels of RhoD. Ectopic expression of RhoD has previously been shown to give an intertwined weave of actin filaments. We show that this RhoD-dependent effect is detected in several cell types and results in a less dynamic actin filament system. In contrast, RhoD depletion leads to increased actin filament-containing structures, such as cortical actin, stress fibers and edge ruffles. Moreover, vital cellular functions such as cell migration and proliferation are defective when RhoD is silenced. Taken together, we present data suggesting that RhoD is an important component in the control of actin dynamics and directed cell migration. - Highlights: • Increased RhoD expression leads to loss of actin structures, e.g. stress fibers and gives rise to decreased actin dynamics. • RhoD knockdown induces various actin-containing structures such as edge ruffles, stress fibers and cortical actin, in a cell-type specific manner. • RhoD induces specific actin rearrangements depending on its subcellular localization. • RhoD knockdown has effects on cellular processes, such as directed cell migration and proliferation.

The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration

International Nuclear Information System (INIS)

Blom, Magdalena; Reis, Katarina; Heldin, Johan; Kreuger, Johan; Aspenström, Pontus

2017-01-01

RhoD belongs to the Rho GTPases, a protein family responsible for the regulation and organization of the actin cytoskeleton, and, consequently, many cellular processes like cell migration, cell division and vesicle trafficking. Here, we demonstrate that the actin cytoskeleton is dynamically regulated by increased or decreased protein levels of RhoD. Ectopic expression of RhoD has previously been shown to give an intertwined weave of actin filaments. We show that this RhoD-dependent effect is detected in several cell types and results in a less dynamic actin filament system. In contrast, RhoD depletion leads to increased actin filament-containing structures, such as cortical actin, stress fibers and edge ruffles. Moreover, vital cellular functions such as cell migration and proliferation are defective when RhoD is silenced. Taken together, we present data suggesting that RhoD is an important component in the control of actin dynamics and directed cell migration. - Highlights: • Increased RhoD expression leads to loss of actin structures, e.g. stress fibers and gives rise to decreased actin dynamics. • RhoD knockdown induces various actin-containing structures such as edge ruffles, stress fibers and cortical actin, in a cell-type specific manner. • RhoD induces specific actin rearrangements depending on its subcellular localization. • RhoD knockdown has effects on cellular processes, such as directed cell migration and proliferation.

Anti-actin IgA antibodies in severe coeliac disease.

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Granito, A; Muratori, P; Cassani, F; Pappas, G; Muratori, L; Agostinelli, D; Veronesi, L; Bortolotti, R; Petrolini, N; Bianchi, F B; Volta, U

2004-08-01

Anti-actin IgA antibodies have been found in sera of coeliacs. Our aim was to define the prevalence and clinical significance of anti-actin IgA in coeliacs before and after gluten withdrawal. One hundred and two biopsy-proven coeliacs, 95 disease controls and 50 blood donors were studied. Anti-actin IgA were evaluated by different methods: (a) antimicrofilament positivity on HEp-2 cells and on cultured fibroblasts by immunofluorescence; (b) anti-actin positivity by enzyme-linked immuosorbent assay (ELISA); and (c) presence of the tubular/glomerular pattern of anti-smooth muscle antibodies on rat kidney sections by immunofluorescence. Antimicrofilament IgA were present in 27% of coeliacs and in none of the controls. Antimicrofilament antibodies were found in 25 of 54 (46%) coeliacs with severe villous atrophy and in three of 48 (6%) with mild damage (P < 0.0001). In the 20 patients tested, antimicrofilaments IgA disappeared after gluten withdrawal in accordance with histological recovery. Our study shows a significant correlation between antimicrofilament IgA and the severity of intestinal damage in untreated coeliacs. The disappearance of antimicrofilament IgA after gluten withdrawal predicts the normalization of intestinal mucosa and could be considered a useful tool in the follow-up of severe coeliac disease.

Genomic instability in human actinic keratosis and squamous cell carcinoma

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Cabral, Luciana Sanches; Neto, Cyro Festa; Sanches, José A; Ruiz, Itamar R G

2011-01-01

OBJECTIVE: To compare the repetitive DNA patterns of human actinic keratoses and squamous cell carcinomas to determine the genetic alterations that are associated with malignant transformation. INTRODUCTION: Cancer cells are prone to genomic instability, which is often due to DNA polymerase slippage during the replication of repetitive DNA and to mutations in the DNA repair genes. The progression of benign actinic keratoses to malignant squamous cell carcinomas has been proposed by several authors. MATERIAL AND METHODS: Eight actinic keratoses and 24 squamous cell carcinomas (SCC), which were pair-matched to adjacent skin tissues and/or leucocytes, were studied. The presence of microsatellite instability (MSI) and the loss of heterozygosity (LOH) in chromosomes 6 and 9 were investigated using nine PCR primer pairs. Random Amplified Polymorphic DNA patterns were also evaluated using eight primers. RESULTS: MSI was detected in two (D6S251, D9S50) of the eight actinic keratosis patients. Among the 8 patients who had squamous cell carcinoma-I and provided informative results, a single patient exhibited two LOH (D6S251, D9S287) and two instances of MSI (D9S180, D9S280). Two LOH and one example of MSI (D6S251) were detected in three out of the 10 patients with squamous cell carcinoma-II. Among the four patients with squamous cell carcinoma-III, one patient displayed three MSIs (D6S251, D6S252, and D9S180) and another patient exhibited an MSI (D9S280). The altered random amplified polymorphic DNA ranged from 70% actinic keratoses, 76% squamous cell carcinoma-I, and 90% squamous cell carcinoma-II, to 100% squamous cell carcinoma-III. DISCUSSION: The increased levels of alterations in the microsatellites, particularly in D6S251, and the random amplified polymorphic DNA fingerprints were statistically significant in squamous cell carcinomas, compared with actinic keratoses. CONCLUSION: The overall alterations that were observed in the repetitive DNA of actinic keratoses and

Human myosin VIIa is a very slow processive motor protein on various cellular actin structures.

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Sato, Osamu; Komatsu, Satoshi; Sakai, Tsuyoshi; Tsukasaki, Yoshikazu; Tanaka, Ryosuke; Mizutani, Takeomi; Watanabe, Tomonobu M; Ikebe, Reiko; Ikebe, Mitsuo

2017-06-30

Human myosin VIIa (MYO7A) is an actin-linked motor protein associated with human Usher syndrome (USH) type 1B, which causes human congenital hearing and visual loss. Although it has been thought that the role of human myosin VIIa is critical for USH1 protein tethering with actin and transportation along actin bundles in inner-ear hair cells, myosin VIIa's motor function remains unclear. Here, we studied the motor function of the tail-truncated human myosin VIIa dimer (HM7AΔTail/LZ) at the single-molecule level. We found that the HM7AΔTail/LZ moves processively on single actin filaments with a step size of 35 nm. Dwell-time distribution analysis indicated an average waiting time of 3.4 s, yielding ∼0.3 s -1 for the mechanical turnover rate; hence, the velocity of HM7AΔTail/LZ was extremely slow, at 11 nm·s -1 We also examined HM7AΔTail/LZ movement on various actin structures in demembranated cells. HM7AΔTail/LZ showed unidirectional movement on actin structures at cell edges, such as lamellipodia and filopodia. However, HM7AΔTail/LZ frequently missed steps on actin tracks and exhibited bidirectional movement at stress fibers, which was not observed with tail-truncated myosin Va. These results suggest that the movement of the human myosin VIIa motor protein is more efficient on lamellipodial and filopodial actin tracks than on stress fibers, which are composed of actin filaments with different polarity, and that the actin structures influence the characteristics of cargo transportation by human myosin VIIa. In conclusion, myosin VIIa movement appears to be suitable for translocating USH1 proteins on stereocilia actin bundles in inner-ear hair cells. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Selective, retrieval-independent disruption of methamphetamine-associated memory by actin depolymerization.

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Young, Erica J; Aceti, Massimiliano; Griggs, Erica M; Fuchs, Rita A; Zigmond, Zachary; Rumbaugh, Gavin; Miller, Courtney A

2014-01-15

Memories associated with drugs of abuse, such as methamphetamine (METH), increase relapse vulnerability to substance use disorder. There is a growing consensus that memory is supported by structural and functional plasticity driven by F-actin polymerization in postsynaptic dendritic spines at excitatory synapses. However, the mechanisms responsible for the long-term maintenance of memories, after consolidation has occurred, are largely unknown. Conditioned place preference (n = 112) and context-induced reinstatement of self-administration (n = 19) were used to assess the role of F-actin polymerization and myosin II, a molecular motor that drives memory-promoting dendritic spine actin polymerization, in the maintenance of METH-associated memories and related structural plasticity. Memories formed through association with METH but not associations with foot shock or food reward were disrupted by a highly-specific actin cycling inhibitor when infused into the amygdala during the postconsolidation maintenance phase. This selective effect of depolymerization on METH-associated memory was immediate, persistent, and did not depend upon retrieval or strength of the association. Inhibition of non-muscle myosin II also resulted in a disruption of METH-associated memory. Thus, drug-associated memories seem to be actively maintained by a unique form of cycling F-actin driven by myosin II. This finding provides a potential therapeutic approach for the selective treatment of unwanted memories associated with psychiatric disorders that is both selective and does not rely on retrieval of the memory. The results further suggest that memory maintenance depends upon the preservation of polymerized actin. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Self-assembly of actin monomers into long filaments: Brownian Dynamics simulations

DEFF Research Database (Denmark)

Shillcock, Julian C.

2009-01-01

Brownian dynamics simulations are used to study the dynamical process of self-assembly of actin monomers into long filaments containing up to 1000 actin protomers. In order to overcome the large separation of time scales between the diffusive motion of the freemonomers and the relatively slow....../detachment events. When a single filament is allowed to grow in a bath of constant concentration of free ADP-actin monomers, its growth rate increases linearly with the free monomer concentration in quantitative agreement with in vitro experiments. Theresults also show that the waiting time is governed by...

Sirtuin1 Maintains Actin Cytoskeleton by Deacetylation of Cortactin in Injured Podocytes

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Motonishi, Shuta; Wada, Takehiko; Ishimoto, Yu; Ohse, Takamoto; Matsusaka, Taiji; Kubota, Naoto; Shimizu, Akira; Kadowaki, Takashi; Tobe, Kazuyuki

2015-01-01

Recent studies have highlighted the renoprotective effect of sirtuin1 (SIRT1), a deacetylase that contributes to cellular regulation. However, the pathophysiologic role of SIRT1 in podocytes remains unclear. Here, we investigated the function of SIRT1 in podocytes. We first established podocyte-specific Sirt1 knockout (SIRT1pod−/−) mice. We then induced glomerular disease by nephrotoxic serum injection. The increase in urinary albumin excretion and BUN and the severity of glomerular injury were all significantly greater in SIRT1pod−/− mice than in wild-type mice. Western blot analysis and immunofluorescence showed a significant decrease in podocyte-specific proteins in SIRT1pod−/− mice, and electron microscopy showed marked exacerbation of podocyte injury, including actin cytoskeleton derangement in SIRT1pod−/− mice compared with wild-type mice. Protamine sulfate-induced podocyte injury was also exacerbated by podocyte-specific SIRT1 deficiency. In vitro, actin cytoskeleton derangement in H2O2-treated podocytes became prominent when the cells were pretreated with SIRT1 inhibitors. Conversely, this H2O2-induced derangement was ameliorated by SIRT1 activation. Furthermore, SIRT1 activation deacetylated the actin-binding and -polymerizing protein cortactin in the nucleus and facilitated deacetylated cortactin localization in the cytoplasm. Cortactin knockdown or inhibition of the nuclear export of cortactin induced actin cytoskeleton derangement and dissociation of cortactin from F-actin, suggesting the necessity of cytoplasmic cortactin for maintenance of the actin cytoskeleton. Taken together, these findings indicate that SIRT1 protects podocytes and prevents glomerular injury by deacetylating cortactin and thereby, maintaining actin cytoskeleton integrity. PMID:25424328

Efficacy of ingenol mebutate gel for actinic keratosis in patients treated by thiazide diuretics

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Campione E

2016-11-01

Full Text Available Elena Campione,1 Monia Di Prete,1 Laura Diluvio,1 Luca Bianchi,1 Augusto Orlandi2 1Department of Dermatology, 2Department of Pathology, University of Rome Tor Vergata, Rome, Italy Abstract: Actinic keratosis (AK is considered as superficial squamous cell carcinoma. Chronic sun exposure plays a central role in its pathogenesis. In particular, ultraviolet B radiation causes direct damage to the DNA, producing pyrimidine dimers that suppress the protective role of p53. Other risk factors include advanced age, male sex, and fair skin type. Even some drugs used for treating blood hypertension, such as thiazide diuretics, can increase the risk of developing AK. Their photosensitizing action seems to be connected with reactive oxygen species production. We report our experience on ten patients affected by multiple AK, in therapy with thiazide diuretics, treated by ingenol mebutate gel. AK was clinically and dermoscopically evaluated at baseline and after 30 days from the beginning of the treatment. Moreover, patients were screened for vitamin D3 values and reported a general hypovitaminosis status. To our knowledge, we report for the first time the efficacy of ingenol mebutate gel in this group of patients, particularly at risk of developing AK. Keywords: anticancer agents, antitumor activity, cancer cells, skin precancerous lesion

The Stationary-Phase Cells of Saccharomyces cerevisiae Display Dynamic Actin Filaments Required for Processes Extending Chronological Life Span.

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Vasicova, Pavla; Lejskova, Renata; Malcova, Ivana; Hasek, Jiri

2015-11-01

Stationary-growth-phase Saccharomyces cerevisiae yeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. In S. cerevisiae stationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Our in vivo analyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficient cox4Δ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Review of photodynamic therapy with 5-methyl aminolevulinate in actinic keratosis, epidermoid carcinoma and basal cell carcinoma

International Nuclear Information System (INIS)

Fallas Moya, Said

2013-01-01

A bibliographic review was conduced on the use of 5-methyl aminolevulinate in dermatology, specifically in the treatment of actinic keratosis, epidermoid carcinoma and basal cell carcinoma. The basic fundamentals of photodynamic therapy are described. The preparation and method of use of photodynamic therapy with 5-methyl aminolevulinate (MAL-PDT) are detailed. The clinical studies that were realized with photodynamic therapy for the treatment of actinic keratosis, epidermoid carcinoma and basal cell carcinoma are mentioned. Different photo-inducible agents and other current therapeutic options of first-line are compared. The MAL-PDT has have the advantage of to present less side effects and the same have been more tolerable than liquid nitrogen and 5 fluorouracil. The MAL-PDT has been considered as an effective option for the treatment of Bowen's disease. Invasive epidermoid carcinoma has existed without evidence to support the routine use of this therapeutic. For superficial basal cell carcinoma, the MAL-PDT has presented a high cure rate and transient and manageable side effects in extensive and multiple lesions. The MAL-PDT has been an effective and safe treatment in patients with basal cell carcinoma, for those with less depth of 2mm. The MAL-PDT could play an important role in the field of prevention with immunosuppressed patients, particularly, those that have required transplant and its immunosuppression has been pharmacological. The use or not of the MAL-PDT, should be evaluated individually for each patient and to have suitable characteristics for each disease that was cited in this review. The photodynamic therapy with 5-methyl aminolevulinate has been a therapeutic modality of considerable economy, however, it should be evaluated in the context of number of inquiries and side effects that have offered other therapeutic modalities [es

Mena–GRASP65 interaction couples actin polymerization to Golgi ribbon linking

Science.gov (United States)

Tang, Danming; Zhang, Xiaoyan; Huang, Shijiao; Yuan, Hebao; Li, Jie; Wang, Yanzhuang

2016-01-01

In mammalian cells, the Golgi reassembly stacking protein 65 (GRASP65) has been implicated in both Golgi stacking and ribbon linking by forming trans-oligomers through the N-terminal GRASP domain. Because the GRASP domain is globular and relatively small, but the gaps between stacks are large and heterogeneous, it remains puzzling how GRASP65 physically links Golgi stacks into a ribbon. To explore the possibility that other proteins may help GRASP65 in ribbon linking, we used biochemical methods and identified the actin elongation factor Mena as a novel GRASP65-binding protein. Mena is recruited onto the Golgi membranes through interaction with GRASP65. Depleting Mena or disrupting actin polymerization resulted in Golgi fragmentation. In cells, Mena and actin were required for Golgi ribbon formation after nocodazole washout; in vitro, Mena and microfilaments enhanced GRASP65 oligomerization and Golgi membrane fusion. Thus Mena interacts with GRASP65 to promote local actin polymerization, which facilitates Golgi ribbon linking. PMID:26538023

Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis1[OPEN

Science.gov (United States)

Cao, Lingyan; Blanchoin, Laurent; Staiger, Christopher J.

2016-01-01

Actin filaments in plant cells are incredibly dynamic; they undergo incessant remodeling and assembly or disassembly within seconds. These dynamic events are choreographed by a plethora of actin-binding proteins, but the exact mechanisms are poorly understood. Here, we dissect the contribution of Arabidopsis (Arabidopsis thaliana) PROFILIN1 (PRF1), a conserved actin monomer-binding protein, to actin organization and single filament dynamics during axial cell expansion of living epidermal cells. We found that reduced PRF1 levels enhanced cell and organ growth. Surprisingly, we observed that the overall frequency of nucleation events in prf1 mutants was dramatically decreased and that a subpopulation of actin filaments that assemble at high rates was reduced. To test whether profilin cooperates with plant formin proteins to execute actin nucleation and rapid filament elongation in cells, we used a pharmacological approach. Here, we used Small Molecule Inhibitor of Formin FH2 (SMIFH2), after validating its mode of action on a plant formin in vitro, and observed a reduced nucleation frequency of actin filaments in live cells. Treatment of wild-type epidermal cells with SMIFH2 mimicked the phenotype of prf1 mutants, and the nucleation frequency in prf1-2 mutant was completely insensitive to these treatments. Our data provide compelling evidence that PRF1 coordinates the stochastic dynamic properties of actin filaments by modulating formin-mediated actin nucleation and assembly during plant cell expansion. PMID:26574597

DETERMINATION OF SUPERFICIAL ABSORBED DOSE FROM EXTERNAL EXPOSURE OF WEAKLY PENETRATING RADIATIONS

Institute of Scientific and Technical Information of China (English)

陈丽姝

1994-01-01

The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported.The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin,cornea,sclera,anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D(0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6mm are also obtained with Cross's methods.They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.

Rapid and dynamic arginylation of the leading edge β-actin is required for cell migration.

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Pavlyk, Iuliia; Leu, Nicolae A; Vedula, Pavan; Kurosaka, Satoshi; Kashina, Anna

2018-04-01

β-actin plays key roles in cell migration. Our previous work demonstrated that β-actin in migratory non-muscle cells is N-terminally arginylated and that this arginylation is required for normal lamellipodia extension. Here, we examined the function of β-actin arginylation in cell migration. We found that arginylated β-actin is concentrated at the leading edge of lamellipodia and that this enrichment is abolished after serum starvation as well as in contact-inhibited cells in confluent cultures, suggesting that arginylated β-actin at the cell leading edge is coupled to active migration. Arginylated actin levels exhibit dynamic changes in response to cell stimuli, lowered after serum starvation and dramatically elevating within minutes after cell stimulation by readdition of serum or lysophosphatidic acid. These dynamic changes require active translation and are not seen in confluent contact-inhibited cell cultures. Microinjection of arginylated actin antibodies into cells severely and specifically inhibits their migration rates. Together, these data strongly suggest that arginylation of β-actin is a tightly regulated dynamic process that occurs at the leading edge of locomoting cells in response to stimuli and is integral to the signaling network that regulates cell migration. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Oral acetylsalicylic acid and prevalence of actinic keratosis.

Science.gov (United States)

Schmitt, Juliano; Miot, Hélio

2014-01-01

To investigate the influence of a regular oral use of acetylsalicylic acid in the prevalence of actinic keratosis. A case-control study with dermatologic outpatients above 50 years of age assessed between 2009 and 2011. Cases were defined as those who had been under regular use of oral acetylsalicylic acid for more than six consecutive months. The assessment focused on: age, sex, skin-type, tobacco smoking, use of medication, occurrence of individual or family skin cancer, and sunscreen and sun exposure habits. Actinic keratoses were counted in the medial region of the face and upper limbs. Counts were adjusted by co-variables based on a generalized linear model. A total of 74 cases and 216 controls were assessed. The median time of acetylsalicylic acid use was 36 months. Cases differed from controls as to the highest age, highest prevalence of use of angiotensin-converting enzyme inhibitors and fewer keratosis on the face and on the upper limbs (pkeratosis and upper-limb erythematous actinic keratosis (pkeratosis, especially facial and erythematous ones.

Structural Polymorphism of the Actin-Espin System: A Prototypical System of Filaments and Linkers in Stereocilia

International Nuclear Information System (INIS)

Purdy, Kirstin R.; Wong, Gerard C. L.; Bartles, James R.

2007-01-01

We examine the interaction between cytoskeletal F-actin and espin 3A, a prototypical actin bundling protein found in sensory cell microvilli, including ear cell stereocilia. Espin induces twist distortions in F-actin as well as facilitates bundle formation. Mutations in one of the two F-actin binding sites of espin, which have been implicated in deafness, can tune espin-actin interactions and radically transform the system's phase behavior. These results are compared to recent theoretical work on the general phase behavior linker-rod systems

Superficial Priming in Episodic Recognition

Science.gov (United States)

Dopkins, Stephen; Sargent, Jesse; Ngo, Catherine T.

2010-01-01

We explored the effect of superficial priming in episodic recognition and found it to be different from the effect of semantic priming in episodic recognition. Participants made recognition judgments to pairs of items, with each pair consisting of a prime item and a test item. Correct positive responses to the test item were impeded if the prime…

Actin Nemaline Myopathy Mouse Reproduces Disease, Suggests Other Actin Disease Phenotypes and Provides Cautionary Note on Muscle Transgene Expression

Science.gov (United States)

Ravenscroft, Gianina; Jackaman, Connie; Sewry, Caroline A.; McNamara, Elyshia; Squire, Sarah E.; Potter, Allyson C.; Papadimitriou, John; Griffiths, Lisa M.; Bakker, Anthony J.; Davies, Kay E.; Laing, Nigel G.; Nowak, Kristen J.

2011-01-01

Mutations in the skeletal muscle α-actin gene (ACTA1) cause congenital myopathies including nemaline myopathy, actin aggregate myopathy and rod-core disease. The majority of patients with ACTA1 mutations have severe hypotonia and do not survive beyond the age of one. A transgenic mouse model was generated expressing an autosomal dominant mutant (D286G) of ACTA1 (identified in a severe nemaline myopathy patient) fused with EGFP. Nemaline bodies were observed in multiple skeletal muscles, with serial sections showing these correlated to aggregates of the mutant skeletal muscle α-actin-EGFP. Isolated extensor digitorum longus and soleus muscles were significantly weaker than wild-type (WT) muscle at 4 weeks of age, coinciding with the peak in structural lesions. These 4 week-old mice were ∼30% less active on voluntary running wheels than WT mice. The α-actin-EGFP protein clearly demonstrated that the transgene was expressed equally in all myosin heavy chain (MHC) fibre types during the early postnatal period, but subsequently became largely confined to MHCIIB fibres. Ringbinden fibres, internal nuclei and myofibrillar myopathy pathologies, not typical features in nemaline myopathy or patients with ACTA1 mutations, were frequently observed. Ringbinden were found in fast fibre predominant muscles of adult mice and were exclusively MHCIIB-positive fibres. Thus, this mouse model presents a reliable model for the investigation of the pathobiology of nemaline body formation and muscle weakness and for evaluation of potential therapeutic interventions. The occurrence of core-like regions, internal nuclei and ringbinden will allow analysis of the mechanisms underlying these lesions. The occurrence of ringbinden and features of myofibrillar myopathy in this mouse model of ACTA1 disease suggests that patients with these pathologies and no genetic explanation should be screened for ACTA1 mutations. PMID:22174871

Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

Science.gov (United States)

Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

2016-07-21

Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

Reversibility and Viscoelastic Properties of Micropillar Supported and Oriented Magnesium Bundled F-Actin.

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Timo Maier

Full Text Available Filamentous actin is one of the most important cytoskeletal elements. Not only is it responsible for the elastic properties of many cell types, but it also plays a vital role in cellular adhesion and motility. Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers. Utilizing a unique pillar-structured microfluidic device, we investigated the time dependence of bundling kinetics of pillar supported free-standing actin filaments. Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner. The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.

Cortical actin nodes: Their dynamics and recruitment of podosomal proteins as revealed by super-resolution and single-molecule microscopy

Science.gov (United States)

Shirai, Yuki M.; Tsunoyama, Taka A.; Hiramoto-Yamaki, Nao; Hirosawa, Koichiro M.; Shibata, Akihiro C. E.; Kondo, Kenichi; Tsurumune, Atsushi; Ishidate, Fumiyoshi; Kusumi, Akihiro

2017-01-01

Electron tomography of the plasma membrane (PM) identified several layers of cortical actin meshwork running parallel to the PM cytoplasmic surface throughout the PM. Here, cortical actin structures and dynamics were examined in living cells, using super-resolution microscopy, with (x,y)- and z-resolutions of ~140 and ~400 nm, respectively, and single-molecule imaging. The super-resolution microscopy identified sub-micron-sized actin clusters that appeared identical by both phalloidin post-fixation staining and Lifeact-mGFP expression followed by fixation, and therefore, these actin clusters were named “actin-pl-clusters”. In live cells, the actin-pl-clusters visualized by Lifeact-mGFP linked two or more actin filaments in the fine actin meshwork, acting as a node of the meshwork, and dynamically moved on/along the meshwork in a myosin II-dependent manner. Their formation depended on the Arp2/3 activities, suggesting that the movements could involve both the myosin motor activity and actin polymerization-depolymerization. The actin-pl-clusters differ from the actin nodes/asters found previously after latrunculin treatments, since myosin II and filamin A were not colocalized with the actin-pl-clusters, and the actin-pl-clusters were much smaller than the previously reported nodes/asters. The Lifeact linked to a fluorescently-labeled transmembrane peptide from syntaxin4 (Lifeact-TM) expressed in the PM exhibited temporary immobilization in the PM regions on which actin-pl-clusters and stress fibers were projected, showing that ≥66% of actin-pl-clusters and 89% of stress fibers were located in close proximity (within 3.5 nm) to the PM cytoplasmic surface. Podosome-associated cytoplasmic proteins, Tks4, Tks5, cortactin, and N-WASP, were transiently recruited to actin-pl-clusters, and thus, we propose that actin-pl-clusters also represent “actin podosome-like clusters”. PMID:29190677

Comparisons of actin filament disruptors and Rho kinase inhibitors as potential antiglaucoma medications

OpenAIRE

Tian, Baohe; Kaufman, Paul L

2012-01-01

Dynamics of the actin cytoskeleton in the trabecular meshwork play a crucial role in the regulation of trabecular outflow resistance. The actin filament disruptors and Rho kinase inhibitors affect the dynamics of the actomyosin system by either disrupting the actin filaments or inhibiting the Rho kinase-activated cellular contractility. Both approaches induce similar morphological changes and resistance decreases in the trabecular outflow pathway, and thus both have potential as antiglaucoma ...

Pigmented basal cell carcinoma mimicking a superficial spreading melanoma

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Paula Hasbún Acuña

2016-12-01

Full Text Available Resumen El carcinoma basocelular es el cáncer de piel más frecuente, especialmente en personas de edad avanzada. El carcinoma basocelular pigmentado es una variante poco común que se ha descrito en la literatura como una lesión nodular hiperpigmentada. En raras ocasiones puede presentarse en forma de una extensa placa pigmentada, la cual puede ser clínicamente indistinguible del melanoma maligno de extensión superficial y de la enfermedad de Bowen. La dermatoscopía tiene una alta sensibilidad en el diagnóstico del carcinoma basocelular, cuando se utilizan los criterios de Menzies, aunque el diagnóstico final es histopatológico. El objetivo del presente trabajo es reportar y analizar el caso de una paciente con un extenso carcinoma basocelular superficial pigmentado, que simula un melanoma maligno de extensión superficial.

The roles of the actin cytoskeleton in fear memory formation

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Raphael eLamprecht

2011-07-01

Full Text Available The formation and storage of fear memory is needed to adapt behavior and avoid danger during subsequent fearful events. However, fear memory may also play a significant role in stress and anxiety disorders. When fear becomes disproportionate to that necessary to cope with a given stimulus, or begins to occur in inappropriate situations, a fear or anxiety disorder exists. Thus, the study of cellular and molecular mechanisms underpinning fear memory may shed light on the formation of memory and on anxiety and stress related disorders. Evidence indicates that fear learning leads to changes in neuronal synaptic transmission and morphology in brain areas underlying fear memory formation including the amygdala and hippocampus. The actin cytoskeleton has been shown to participate in these key neuronal processes. Recent findings show that the actin cytoskeleton is needed for fear memory formation and extinction. Moreover, the actin cytoskeleton is involved in synaptic plasticity and in neuronal morphogenesis in brain areas that mediate fear memory. The actin cytoskeleton may therefore mediate between synaptic transmission during fear learning and long-term cellular alterations mandatory for fear memory formation.

Title: Cytoskeletal proteins in cortical development and diseasesubtitle: Actin associated proteins in periventricular heterotopia

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Gewei eLian

2015-04-01

Full Text Available The actin cytoskeleton regulates many important cellular processes in the brain, including cell division and proliferation, migration, and cytokinesis and differentiation. These developmental processes can be regulated through actin dependent vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape. Many of these processes are mediated by extensive and intimate interactions of actin with cellular membranes and proteins. Disruption in the actin cytoskeleton in the brain gives rise to periventricular heterotopia (PH, a malformation of cortical development, characterized by abnormal neurons clustered deep in the brain along the lateral ventricles. This disorder can give rise to seizures, dyslexia and psychiatric disturbances. Anatomically, PH is characterized by a smaller brain (impaired proliferation, heterotopia (impaired initial migration and disruption along the neuroependymal lining (impaired cell-cell adhesion. Genes causal for PH have also been implicated in actin-dependent processes. The current review provides mechanistic insight into actin cytoskeletal regulation of cortical development in the context of this malformation of cortical development.

Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness

Science.gov (United States)

Kang, Hyeran; Bradley, Michael J.; McCullough, Brannon R.; Pierre, Anaëlle; Grintsevich, Elena E.; Reisler, Emil; De La Cruz, Enrique M.

2012-01-01

The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as “polymerization” and “stiffness” sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments. PMID:23027950

The effect of ionizing radiation on the filamentous actin of vascular endothelial cell

International Nuclear Information System (INIS)

Yao Xiaowu; Chen Shisheng; Yang Lihe; Lin Juelong; Yang Haiwei

2006-01-01

Objective: To observe the ionizing radiation effect on filamentous actin of vascular endothelial cell and explore its mechanism. Methods: The vascular endothelial cells were irradiated with 0, 2, 4, 6, 8, 10 and 12 Gy 60 Co γ-rays. The cytoskeleton was observed with CLSM at 6 hs after the irradiation and the cytoskeleton protein F-actin detected with flow cytometry after 12 and 24 hs. Results: The damage to cytoskeletons increased with the radiation dose. The cytoskeleton protein F-actin was significantly decreased at 12 hs after the irradiation, and then recovered after 24 hs. Conclusion: Ionizing radiation caused vascular endothelial cell injury by damaging the cytoskeleton and depolymerizating the F-actin. (authors)

Actin-Dependent Alterations of Dendritic Spine Morphology in Shankopathies

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Tasnuva Sarowar

2016-01-01

Full Text Available Shank proteins (Shank1, Shank2, and Shank3 act as scaffolding molecules in the postsynaptic density of many excitatory neurons. Mutations in SHANK genes, in particular SHANK2 and SHANK3, lead to autism spectrum disorders (ASD in both human and mouse models. Shank3 proteins are made of several domains—the Shank/ProSAP N-terminal (SPN domain, ankyrin repeats, SH3 domain, PDZ domain, a proline-rich region, and the sterile alpha motif (SAM domain. Via various binding partners of these domains, Shank3 is able to bind and interact with a wide range of proteins including modulators of small GTPases such as RICH2, a RhoGAP protein, and βPIX, a RhoGEF protein for Rac1 and Cdc42, actin binding proteins and actin modulators. Dysregulation of all isoforms of Shank proteins, but especially Shank3, leads to alterations in spine morphogenesis, shape, and activity of the synapse via altering actin dynamics. Therefore, here, we highlight the role of Shank proteins as modulators of small GTPases and, ultimately, actin dynamics, as found in multiple in vitro and in vivo models. The failure to mediate this regulatory role might present a shared mechanism in the pathophysiology of autism-associated mutations, which leads to dysregulation of spine morphogenesis and synaptic signaling.

The integrin-actin connection, an eternal love affair

DEFF Research Database (Denmark)

Brakebusch, Cord; Fässler, Reinhard

2003-01-01

Integrin receptors connect the extracellular matrix to the actin cytoskeleton. This interaction can be viewed as a cyclical liaison, which develops again and again at new adhesion sites only to cease at sites of de-adhesion. Recent work has demonstrated that multidomain proteins play crucial roles...... in the integrin-actin connection by providing a high degree of regulation adjusted to the needs of the cell. In this review we present several examples of this paradigm and with special emphasis on the ILK-PINCH-parvin complex, which amply demonstrates how structural and signalling functions are linked together....

Actin Filaments and Myosin I Alpha Cooperate with Microtubules for the Movement of LysosomesV⃞

OpenAIRE

Cordonnier, Marie-Neige; Dauzonne, Daniel; Louvard, Daniel; Coudrier, Evelyne

2001-01-01

An earlier report suggested that actin and myosin I alpha (MMIα), a myosin associated with endosomes and lysosomes, were involved in the delivery of internalized molecules to lysosomes. To determine whether actin and MMIα were involved in the movement of lysosomes, we analyzed by time-lapse video microscopy the dynamic of lysosomes in living mouse hepatoma cells (BWTG3 cells), producing green fluorescent protein actin or a nonfunctional domain of MMIα. In GFP-actin cells, lysosomes displayed ...

Actin depolymerization enhances adipogenic differentiation in human stromal stem cells.

Science.gov (United States)

Chen, Li; Hu, Huimin; Qiu, Weimin; Shi, Kaikai; Kassem, Moustapha

2018-05-01

Human stromal stem cells (hMSCs) differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) or treating the cells by Phalloidin reduced adipocyte differentiation as evidenced by decreased number of mature adipocytes and decreased adipocyte specific gene expression (ADIPOQ, LPL, PPARG, FABP4). In contrast, disruption of actin cytoskeleton by Cytochalasin D enhanced adipocyte differentiation. Follow up studies revealed that the effects of CFL1 on adipocyte differentiation depended on the activity of LIM domain kinase 1 (LIMK1) which is the major upstream kinase of CFL1. Inhibiting LIMK by its specific chemical inhibitor LIMKi inhibited the phosphorylation of CFL1 and actin polymerization, and enhanced the adipocyte differentiation. Moreover, treating hMSCs by Cytochalasin D inhibited ERK and Smad2 signaling and this was associated with enhanced adipocyte differentiation. On the other hand, Phalloidin enhanced ERK and Smad2 signaling, but inhibited adipocyte differentiation which was rescued by ERK specific chemical inhibitor U0126. Our data provide a link between restructuring of hMSCs cytoskeleton and hMSCs lineage commitment and differentiation. Copyright © 2018 Elsevier B.V. All rights reserved.

Cadmium-induced glutathionylation of actin occurs through a ROS-independent mechanism: Implications for cytoskeletal integrity

Energy Technology Data Exchange (ETDEWEB)

Choong, Grace; Liu, Ying; Xiao, Weiqun; Templeton, Douglas M., E-mail: doug.templeton@utoronto.ca

2013-10-15

Cadmium disrupts the actin cytoskeleton in rat mesangial cells, and we have previously shown that this involves a complex interplay involving activation of kinase signaling, protein translocation, and disruption of focal adhesions. Here we investigate the role that glutathionylation of actin plays in Cd{sup 2+}-associated cytoskeletal reorganization. Low concentrations of Cd{sup 2+} (0.5–2 μM) caused an increase in actin glutathionylation by 6 h, whereas at higher concentrations glutathionylation remained at basal levels. Although oxidation with diamide increased glutathionylation, reactive oxygen species (ROS) were not involved in the Cd{sup 2+}-dependent effect, as only Cd{sup 2+} concentrations above 2 μM were sufficient to increase ROS. However, low [Cd{sup 2+}] increased total glutathione levels without affecting the ratio of reduced/oxidized glutathione, and inhibition of glutathione synthesis suppressed actin glutathionylation. Cadmium increased the activity of the enzyme glutaredoxin, which influences the equilibrium between glutathionylated and deglutathionylated proteins and thus may influence levels of glutathionylated actin. Together these observations show that cadmium-dependent effects on actin glutathionylation are affected by glutathione metabolism and not by direct effects of ROS on thiol chemistry. In vitro polymerization assays with glutathionylated actin show a decreased rate of polymerization. In contrast, immunofluorescence of cytoskeletal structure in intact cells suggests that increases in actin glutathionylation accompanying increased glutathione levels occurring under low Cd{sup 2+} exposure are protective in vivo, with cytoskeletal disruption ensuing only when higher Cd{sup 2+} concentrations increase ROS levels and prevent an increase in actin–glutathione conjugates. - Highlights: • Cadmium disrupts the actin cytoskeleton in mesangial cells. • Cadmium induces glutathionylation of actin at low concentrations. �

Cadmium-induced glutathionylation of actin occurs through a ROS-independent mechanism: Implications for cytoskeletal integrity

International Nuclear Information System (INIS)

Choong, Grace; Liu, Ying; Xiao, Weiqun; Templeton, Douglas M.

2013-01-01

Cadmium disrupts the actin cytoskeleton in rat mesangial cells, and we have previously shown that this involves a complex interplay involving activation of kinase signaling, protein translocation, and disruption of focal adhesions. Here we investigate the role that glutathionylation of actin plays in Cd 2+ -associated cytoskeletal reorganization. Low concentrations of Cd 2+ (0.5–2 μM) caused an increase in actin glutathionylation by 6 h, whereas at higher concentrations glutathionylation remained at basal levels. Although oxidation with diamide increased glutathionylation, reactive oxygen species (ROS) were not involved in the Cd 2+ -dependent effect, as only Cd 2+ concentrations above 2 μM were sufficient to increase ROS. However, low [Cd 2+ ] increased total glutathione levels without affecting the ratio of reduced/oxidized glutathione, and inhibition of glutathione synthesis suppressed actin glutathionylation. Cadmium increased the activity of the enzyme glutaredoxin, which influences the equilibrium between glutathionylated and deglutathionylated proteins and thus may influence levels of glutathionylated actin. Together these observations show that cadmium-dependent effects on actin glutathionylation are affected by glutathione metabolism and not by direct effects of ROS on thiol chemistry. In vitro polymerization assays with glutathionylated actin show a decreased rate of polymerization. In contrast, immunofluorescence of cytoskeletal structure in intact cells suggests that increases in actin glutathionylation accompanying increased glutathione levels occurring under low Cd 2+ exposure are protective in vivo, with cytoskeletal disruption ensuing only when higher Cd 2+ concentrations increase ROS levels and prevent an increase in actin–glutathione conjugates. - Highlights: • Cadmium disrupts the actin cytoskeleton in mesangial cells. • Cadmium induces glutathionylation of actin at low concentrations. • Glutathionylation requires glutathione

Multidrug Resistance-Related Protein 1 (MRP1) Function and Localization Depend on Cortical Actin

NARCIS (Netherlands)

Hummel, Ina; Klappe, Karin; Ercan, Cigdem; Kok, Jan Willem

MRP1 (ABCC1) is known to be localized in lipid rafts. Here we show in two different cell lines that localization of Mrp1/MRP1 (Abcc1/ABCC1) in lipid rafts and its function as an efflux pump are dependent on cortical actin. Latrunculin B disrupts both cortical actin and actin stress fibers. This

Actinic prurigo in Scandinavian adolescent successfully treated with cyclosporine A

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Jan C. Sitek

2017-06-01

Full Text Available Actinic prurigo is a pruritic sun-induced dermatosis classified among the immunologically mediated photodermatoses. The disease is a well-known entity among Native Americans and in Central and South America, however rare in Caucasians with only a few reports from Australia, Britain and France. We report the first case of actinic prurigo in a Scandinavian patient, responding favorably to systemic treatment with cyclosporine A.

Actinic Prurigo in Scandinavian Adolescent Successfully Treated with Cyclosporine A.

Science.gov (United States)

Sitek, Jan C

2017-03-13

Actinic prurigo is a pruritic sun-induced dermatosis classified among the immunologically mediated photodermatoses. The disease is a well-known entity among Native Americans and in Central and South America, however rare in Caucasians with only a few reports from Australia, Britain and France. We report the first case of actinic prurigo in a Scandinavian patient, responding favorably to systemic treatment with cyclosporine A.

Coronin 3 involvement in F-actin-dependent processes at the cell cortex

International Nuclear Information System (INIS)

Rosentreter, Andre; Hofmann, Andreas; Xavier, Charles-Peter; Stumpf, Maria; Noegel, Angelika A.; Clemen, Christoph S.

2007-01-01

The actin interaction of coronin 3 has been mainly documented by in vitro experiments. Here, we discuss coronin 3 properties in the light of new structural information and focus on assays that reflect in vivo roles of coronin 3 and its impact on F-actin-associated functions. Using GFP-tagged coronin 3 fusion proteins and RNAi silencing we show that coronin 3 has roles in wound healing, protrusion formation, cell proliferation, cytokinesis, endocytosis, axonal growth, and secretion. During formation of cell protrusions actin accumulation precedes the focal enrichment of coronin 3 suggesting a role for coronin 3 in events that follow the initial F-actin assembly. Moreover, we show that coronin 3 similar to other coronins interacts with the Arp2/3-complex and cofilin indicating that this family in general is involved in regulating Arp2/3-mediated events

Inverse relationship between TCTP/RhoA and p53/ /cyclin A/actin expression in ovarian cancer cells Inverse relationship between TCTP/RhoA and p53/ /cyclin A/actin expression in ovarian cancer cells

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Malgorzata Kloc

2012-10-01

Full Text Available The translationally controlled tumor protein (TCTP plays a role in cell growth, cell cycle and cancer
progression. TCTP controls negatively the stability of the p53 tumor suppressor protein and interacts with the
cellular cytoskeleton. The deregulation of the actin and cytokeratin cytoskeleton is responsible for the increased
migratory activity of tumor cells and is linked with poor patient outcome. Recent studies indicate that cyclin A,
a key regulator of cell cycle, controls actin organization and negatively regulates cell motility via regulation of RhoA
expression. We studied the organization of actin and cytokeratin cytoskeleton and the expression of TCTP, p53,
cyclin A, RhoA and actin in HIO180 non-transformed ovarian epithelial cells, and OVCAR3 and SKOV3 (expressing
low level of inducible p53 ovarian epithelial cancer cells with different metastatic potential. Immunostaining
and ultrastructural analyses illustrated a dramatic difference in the organization of the cytokeratin and actin
filaments in non-transformed versus cancer cell lines. We also determined that there is an inverse relationship between
the level of TCTP/RhoA and actin/p53/cyclin A expression in ovarian cancer cell lines. This previously unidentified
negative relationship between TCTP/RhoA and actin/p53/cyclin A may suggest that this interaction is linked
with the high aggressiveness of ovarian cancers.The translationally controlled tumor protein (TCTP plays a role in cell growth, cell cycle and cancer
progression. TCTP controls negatively the stability of the p53 tumor suppressor protein and interacts with the
cellular cytoskeleton. The deregulation of the actin and cytokeratin cytoskeleton is responsible for the increased
migratory activity of tumor cells and is linked with poor patient outcome. Recent studies indicate that cyclin A,
a key regulator of cell cycle, controls actin organization

The role of antihistamines in chronic actinic dermatitis treatment

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E. V. Orlov

2016-01-01

Full Text Available Inveterate actinic dermatitis is an immunologically mediated photodermatosis characterized by itchy eczematous dermhelminthiasis exposed to sunlight. The disease proceeds in the same way as the atopic eczema or atopic dermatitis. The treatment of patients with inveterate actinic dermatitis is similar to the treatment of patients with atopic dermatitis and eczema. Administration of the modern antihistaminic preparation desloratadine (Aerius in the treatment has a positive effect on the skin process relief and on some cellular and humoral immunity factors.

Mutations in actin used for structural studies partially disrupt β-thymosin/WH2 domains interaction.

Science.gov (United States)

Deville, Célia; Girard-Blanc, Christine; Assrir, Nadine; Nhiri, Naïma; Jacquet, Eric; Bontems, François; Renault, Louis; Petres, Stéphane; van Heijenoort, Carine

2016-10-01

Understanding the structural basis of actin cytoskeleton remodeling requires stabilization of actin monomers, oligomers, and filaments in complex with partner proteins, using various biochemical strategies. Here, we report a dramatic destabilization of the dynamic interaction with a model β-thymosin/WH2 domain induced by mutations in actin. This result underlines that mutant actins should be used with prudence to characterize interactions with intrinsically disordered partners as destabilization of dynamic interactions, although identifiable by NMR, may be invisible to other structural techniques. It also highlights how both β-thymosin/WH2 domains and actin tune local structure and dynamics in regulatory processes involving intrinsically disordered domains. © 2016 Federation of European Biochemical Societies.

Regulation of myosin IIA and filamentous actin during insulin-stimulated glucose uptake in 3T3-L1 adipocytes

International Nuclear Information System (INIS)

Stall, Richard; Ramos, Joseph; Kent Fulcher, F.; Patel, Yashomati M.

2014-01-01

Insulin stimulated glucose uptake requires the colocalization of myosin IIA (MyoIIA) and the insulin-responsive glucose transporter 4 (GLUT4) at the plasma membrane for proper GLUT4 fusion. MyoIIA facilitates filamentous actin (F-actin) reorganization in various cell types. In adipocytes F-actin reorganization is required for insulin-stimulated glucose uptake. What is not known is whether MyoIIA interacts with F-actin to regulate insulin-induced GLUT4 fusion at the plasma membrane. To elucidate the relationship between MyoIIA and F-actin, we examined the colocalization of MyoIIA and F-actin at the plasma membrane upon insulin stimulation as well as the regulation of this interaction. Our findings demonstrated that MyoIIA and F-actin colocalized at the site of GLUT4 fusion with the plasma membrane upon insulin stimulation. Furthermore, inhibition of MyoII with blebbistatin impaired F-actin localization at the plasma membrane. Next we examined the regulatory role of calcium in MyoIIA-F-actin colocalization. Reduced calcium or calmodulin levels decreased colocalization of MyoIIA and F-actin at the plasma membrane. While calcium alone can translocate MyoIIA it did not stimulate F-actin accumulation at the plasma membrane. Taken together, we established that while MyoIIA activity is required for F-actin localization at the plasma membrane, it alone is insufficient to localize F-actin to the plasma membrane. - Highlights: • Insulin induces colocalization of MyoIIA and F-actin at the cortex in adipocytes. • MyoIIA is necessary but not sufficient to localize F-actin at the cell cortex. • MyoIIA-F-actin colocalization is regulated by calcium and calmodulin

Model for adhesion clutch explains biphasic relationship between actin flow and traction at the cell leading edge

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Craig, Erin M.; Stricker, Jonathan; Gardel, Margaret L.; Mogilner, Alex

2015-01-01

Cell motility relies on the continuous reorganization of a dynamic actin-myosin-adhesion network at the leading edge of the cell, in order to generate protrusion at the leading edge and traction between the cell and its external environment. We analyze experimentally measured spatial distributions of actin flow, traction force, myosin density, and adhesion density in control and pharmacologically perturbed epithelial cells in order to develop a mechanical model of the actin-adhesion-myosin self-organization at the leading edge. A model in which the F-actin network is treated as a viscous gel, and adhesion clutch engagement is strengthened by myosin but weakened by actin flow, can explain the measured molecular distributions and correctly predict the spatial distributions of the actin flow and traction stress. We test the model by comparing its predictions with measurements of the actin flow and traction stress in cells with fast and slow actin polymerization rates. The model predicts how the location of the lamellipodium-lamellum boundary depends on the actin viscosity and adhesion strength. The model further predicts that the location of the lamellipodium-lamellum boundary is not very sensitive to the level of myosin contraction. PMID:25969948

Superficial x-ray in-vivo dosimetry with MOSFET detectors

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Cancer Services, Wollongong, NSW

2004-01-01

Full text: This note investigates in-vivo dosimetry using a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) for radiotherapy treatment at superficial and orthovoltage x-ray energies. This was performed within one fraction of the patient's treatment. Standard measurements along with energy response of the detector are given. Results showed that the MOSFET measurements in-vivo agreed with calculated results on average within ± 5.6% over all superficial and orthovoltage energies. These variations were slightly larger than TLD results with variations between measured and calculated results being ± 5.0% for the same patient measurements. The MOSFET device provides adequate in-vivo dosimetry for superficial and orthovoltage energy treatments with the accuracy of the measurements seeming to be relatively on par with TLD in our case. The MOSFET does have the advantage of returning a relatively immediate dosimetric result after irradiation. Copyright (2004) Australasian College of Physical Scientists and Engineers in Medicine

Actin cytoskeleton rearrangements in Arabidopsis roots under stress and during gravitropic response

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Pozhvanov, Gregory; Medvedev, Sergei; Suslov, Dmitry; Demidchik, Vadim

Among environmental factors, gravity vector is the only one which is constant in direction and accompanies the whole plant ontogenesis. That said, gravity vector can be considered as an essential factor for correct development of plants. Gravitropism is a plant growth response against changing its position relative to the gravity vector. It is well estableshed that gravitropism is directed by auxin redistribution across the gravistimulated organ. In addition to auxin, actin cytoskeleton was shown to be involved in gravitropism at different stages: gravity perception, signal transduction and gravitropic bending formation. However, the relationship between IAA and actin is still under discussion. In this work we studied rearrangements of actin cytoskeleton during root gravitropic response. Actin microfilaments were visualized in vivo in GFP-fABD2 transgenic Arabidopsis plants, and their angle distribution was acquired from MicroFilament Analyzer software. The curvature of actin microfilaments in root elongation zone was shown to be increased within 30-60 min of gravistimulation, the fraction of axially oriented microfilaments decreased with a concomitant increase in the fraction of oblique and transversally oriented microfilaments. In particular, the fraction of transversally oriented microfilaments (i.e. parallel to the gravity vector) increased 3-5 times. Under 10 min of sub-lethal salt stress impact, actin microfilament orientations widened from an initial axial orientation to a set of peaks at 15(°) , 45(°) and 90(°) . We conclude that the actin cytoskeleton rearrangements observed are associated with the regulation of basic mechanisms of cell extension growth by which the gravitropic bending is formed. Having common stress-related features, gravity-induced actin cytoskeleton rearrangement is slower but results in higher number of g-vector-parallel microfilaments when compared to salt stress-induced rearrangement. Also, differences in gravistimulated root

The actin homologue MreB organizes the bacterial cell membrane

OpenAIRE

Strahl, Henrik; Bürmann, Frank; Hamoen, Leendert W.

2014-01-01

The eukaryotic cortical actin cytoskeleton creates specific lipid domains, including lipid rafts, which determine the distribution of many membrane proteins. Here we show that the bacterial actin homologue MreB displays a comparable activity. MreB forms membrane-associated filaments that coordinate bacterial cell wall synthesis. We noticed that the MreB cytoskeleton influences fluorescent staining of the cytoplasmic membrane. Detailed analyses combining an array of mutants, using specific lip...

Clinicomycological Characterization of Superficial Mycoses from a Tertiary Care Hospital in Nepal.

Science.gov (United States)

Khadka, Sundar; Sherchand, Jeevan Bahadur; Pokharel, Dinesh Binod; Pokhrel, Bharat Mani; Mishra, Shyam Kumar; Dhital, Subhash; Rijal, Basista

2016-01-01

Background . Superficial mycosis is a common fungal infection worldwide, mainly caused by dermatophytes. However, the prevalence of species varies geographically. In addition, fungal treatment is best guided according to species isolated. This study was carried out to determine the clinical as well as mycological profile of superficial mycoses in a tertiary care hospital, Nepal. Methods . This was a prospective case-control laboratory based study conducted over a period of six months from January to June 2014 at Tribhuvan University Teaching Hospital, Nepal. A total of 200 specimens were collected from the patients suspected of superficial mycoses. The specimens were macroscopically as well as microscopically examined. The growth was observed up to 4 weeks. Results. Out of total 200 specimens from the patients suspected of superficial mycoses, tinea corporis 50 (25%) was most common clinical types. KOH mount was positive in 89 (44.5%) and culture was positive in 111 (55.5%). Trichophyton mentagrophytes 44 (39.6%) was the most common isolate. Conclusions. The diagnostic yields of KOH mount and culture were found to be complementary to each other. Thus both the methods added with clinical findings are equally important to establish superficial mycosis.

Clinicomycological Characterization of Superficial Mycoses from a Tertiary Care Hospital in Nepal

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Sundar Khadka

2016-01-01

Full Text Available Background. Superficial mycosis is a common fungal infection worldwide, mainly caused by dermatophytes. However, the prevalence of species varies geographically. In addition, fungal treatment is best guided according to species isolated. This study was carried out to determine the clinical as well as mycological profile of superficial mycoses in a tertiary care hospital, Nepal. Methods. This was a prospective case-control laboratory based study conducted over a period of six months from January to June 2014 at Tribhuvan University Teaching Hospital, Nepal. A total of 200 specimens were collected from the patients suspected of superficial mycoses. The specimens were macroscopically as well as microscopically examined. The growth was observed up to 4 weeks. Results. Out of total 200 specimens from the patients suspected of superficial mycoses, tinea corporis 50 (25% was most common clinical types. KOH mount was positive in 89 (44.5% and culture was positive in 111 (55.5%. Trichophyton mentagrophytes 44 (39.6% was the most common isolate. Conclusions. The diagnostic yields of KOH mount and culture were found to be complementary to each other. Thus both the methods added with clinical findings are equally important to establish superficial mycosis.

Time-sequential observation of spindle and phragmoplast orientation in BY-2 cells with altered cortical actin microfilament patterning.

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Kojo, Kei H; Yasuhara, Hiroki; Hasezawa, Seiichiro

2014-01-01

Precise division plane determination is essential for plant development. At metaphase, a dense actin microfilament meshwork appears on both sides of the cell center, forming a characteristic cortical actin microfilament twin peak pattern in BY-2 cells. We previously reported a strong correlation between altered cortical actin microfilament patterning and an oblique mitotic spindle orientation, implying that these actin microfilament twin peaks play a role in the regulation of mitotic spindle orientation. In the present study, time-sequential observation was used to reveal the progression from oblique phragmoplast to oblique cell plate orientation in cells with altered cortical actin microfilament patterning. In contrast to cells with normal actin microfilament twin peaks, oblique phragmoplast reorientation was rarely observed in cells with altered cortical actin microfilament patterning. These results support the important roles of cortical actin microfilament patterning in division plane orientation.

Region-Specific Involvement of Actin Rearrangement-Related Synaptic Structure Alterations in Conditioned Taste Aversion Memory

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Bi, Ai-Ling; Wang, Yue; Li, Bo-Qin; Wang, Qian-Qian; Ma, Ling; Yu, Hui; Zhao, Ling; Chen, Zhe-Yu

2010-01-01

Actin rearrangement plays an essential role in learning and memory; however, the spatial and temporal regulation of actin dynamics in different phases of associative memory has not been fully understood. Here, using the conditioned taste aversion (CTA) paradigm, we investigated the region-specific involvement of actin rearrangement-related…

Trauma ocupacional por corpo estranho corneano superficial Occupational trauma due to superficial corneal foreign body

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Vanessa Miroski Gerente

2008-04-01

Full Text Available OBJETIVO: Avaliar a epidemiologia do trauma ocular por corpo estranho superficial de córnea. MÉTODOS: Os pacientes atendidos no Pronto-Socorro da Universidade Federal de São Paulo entre abril e junho de 2005 que apresentaram corpo estranho superficial de córnea foram entrevistados. Foram avaliados: sexo, idade, profissão, registro legal do emprego, uso, disponibilidade e tipo de equipamentos de proteção utilizados e a fiscalização do seu uso. O conhecimento das complicações deste tipo de acidente também foi avaliado. Os resultados foram analisados com teste do qui quadrado ou teste de Fisher. RESULTADOS: Foram entrevistados 123 pacientes. Apenas 3 eram do sexo feminino e a idade média foi de 36 anos. A maioria destes traumas ocorreu no ambiente de trabalho (86,2% e 58,4% não possuíam registro legal do emprego. As profissões mais freqüentemente envolvidas foram serralheiro, pedreiro e metalúrgico. Em 79,8% dos locais de trabalho havia equipamentos de proteção e 85,3% dos pacientes eram orientados a usá-los. Em 52,4% dos locais sua utilização era fiscalizada, mas apenas 34,2% usavam no momento do trauma. A utilização foi mais freqüente (p=0,008 e fiscalização mais presente (p=0,0415 entre pacientes com registro legal de emprego. Questionados sobre os riscos, 68,9% dos pacientes tinham consciência das complicações graves deste tipo de acidente. CONCLUSÃO: A maioria dos pacientes tem conhecimento sobre a gravidade do trauma ocular e este tipo de lesão ocorre mesmo em locais com equipamentos de proteção disponíveis, alguns deles até durante o seu uso. Os dados sugerem que enfoque maior da prevenção deve ser na fiscalização e utilização de equipamentos adequados.PURPOSE: To evaluate the epidemiology of superficial corneal foreign body. METHODS: Patients who were seen at the Emergency Service of the Federal University of São Paulo, from April/05 to June/05, were screened and those with superficial corneal

An F-actin-depleted zone is present at the hyphal tip of invasive hyphae of Neurospora crassa.

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Suei, S; Garrill, A

2008-01-01

The distribution of filamentous actin (F-actin) in invasive and noninvasive hyphae of the ascomycete Neurospora crassa was investigated. Eighty six percent of noninvasive hyphae had F-actin in the tip region compared to only 9% of invasive hyphae. The remaining 91% of the invasive hyphae had no obvious tip high concentration of F-actin staining; instead they had an F-actin-depleted zone in this region, although some F-actin, possibly associated with the Spitzenkörper, remained at the tip. The size of the F-actin-depleted zone in invasive hyphae increased with an increase in agar concentration. The membrane stain FM 4-64 reveals a slightly larger accumulation of vesicles at the tips of invasive hyphae relative to noninvasive hyphae, although this difference is unlikely to be sufficient to account for the exclusion of F-actin from the depleted zone. Antibodies raised against the actin filament-severing protein cofilin from both yeast and human cells localize to the tips of invasive hyphae. The human cofilin antibody shows a more random distribution in noninvasive hyphae locating primarily at the hyphal periphery but with some diffuse cytoplasmic staining. This antibody also identifies a single band at 21 kDa in immunoblots of whole hyphal fractions. These data suggest that a protein with epitopic similarity to cofilin may function in F-actin dynamics that underlie invasive growth. The F-actin-depleted zone may play a role in the regulation of tip yielding to turgor pressure, thus increasing the protrusive force necessary for invasive growth.

Role of ANC-1 in tethering nuclei to the actin cytoskeleton.

Science.gov (United States)

Starr, Daniel A; Han, Min

2002-10-11

Mutations in anc-1 (nuclear anchorage defective) disrupt the positioning of nuclei and mitochondria in Caenorhabditis elegans. ANC-1 is shown to consist of mostly coiled regions with a nuclear envelope localization domain (called the KASH domain) and an actin-binding domain; this structure was conserved with the Drosophila protein Msp-300 and the mammalian Syne proteins. Antibodies against ANC-1 localized cytoplasmically and were enriched at the nuclear periphery in an UNC-84-dependent manner. Overexpression of the KASH domain or the actin-binding domain caused a dominant negative anchorage defect. Thus, ANC-1 may connect nuclei to the cytoskeleton by interacting with UNC-84 at the nuclear envelope and with actin in the cytoplasm.

Creatine kinase and alpha-actin mRNA levels decrease in diabetic rat hearts

International Nuclear Information System (INIS)

Popovich, B.; Barrieux, A.; Dillmann, W.H.

1987-01-01

Diabetic cardiomyopathy is associated with cardiac atrophy and isoenzyme redistribution. To determine if tissue specific changes occur in mRNAs coding for α-actin and creatine kinase (CK), they performed RNA blot analysis. Total ventricular RNA from control (C) and 4 wk old diabetic (D) rats were hybridized with 32 P cDNA probes for α-actin and CK. A tissue independent cDNA probe, CHOA was also used. Signal intensity was quantified by photodensitometry. D CK mRNA was 47 +/- 16% lower in D vs C. Insulin increases CK mRNA by 20% at 1.5 hs, and completely reverses the deficit after 4 wks. D α-actin mRNA is 66 +/- 18% lower in D vs C. Insulin normalized α-actin mRNA by 5 hs. CHOA mRNA is unchanged in D vs C, but D + insulin CHOA mRNA is 30 +/- 2% lower than C. In rats with diabetic cardiomyopathy, muscle specific CK and α-actin mRNAs are decreased. Insulin treatment reverses these changes

Actin restructuring during Salmonella typhimurium infection investigated by confocal and super-resolution microscopy

Science.gov (United States)

Han, Jason J.; Kunde, Yuliya A.; Hong-Geller, Elizabeth; Werner, James H.

2014-01-01

We have used super-resolution optical microscopy and confocal microscopy to visualize the cytoskeletal restructuring of HeLa cells that accompanies and enables Salmonella typhimurium internalization. Herein, we report the use of confocal microscopy to verify and explore infection conditions that would be compatible with super-resolution optical microscopy, using Alexa-488 labeled phalloidin to stain the actin cytoskeletal network. While it is well known that actin restructuring and cytoskeletal rearrangements often accompany and assist in bacterial infection, most studies have employed conventional diffraction-limited fluorescence microscopy to explore these changes. Here we show that the superior spatial resolution provided by single-molecule localization methods (such as direct stochastic optical reconstruction microscopy) enables more precise visualization of the nanoscale changes in the actin cytoskeleton that accompany bacterial infection. In particular, we found that a thin (100-nm) ring of actin often surrounds an invading bacteria 10 to 20 min postinfection, with this ring being transitory in nature. We estimate that a few hundred monofilaments of actin surround the S. typhimurium in this heretofore unreported bacterial internalization intermediate.

A Nanodiamond-peptide Bioconjugate for Fluorescence and ODMR Microscopy of a Single Actin Filament.

Science.gov (United States)

Genjo, Takuya; Sotoma, Shingo; Tanabe, Ryotaro; Igarashi, Ryuji; Shirakawa, Masahiro

2016-01-01

Recently, the importance of conformational changes in actin filaments induced by mechanical stimulation of a cell has been increasingly recognized, especially in terms of mechanobiology. Despite its fundamental importance, however, long-term observation of a single actin filament by fluorescent microscopy has been difficult because of the low photostability of traditional fluorescent molecules. This paper reports a novel molecular labeling system for actin filaments using fluorescent nanodiamond (ND) particles harboring nitrogen-vacancy centers; ND has flexible chemical modifiability, extremely high photostability and biocompatibility, and provides a variety of physical information quantitatively via optically detected magnetic resonance (ODMR) measurements. We performed the chemical surface modification of an ND with the actin filament-specific binding peptide Lifeact and observed colocalization of pure Lifeact-modified ND and actin filaments by the ODMR selective imaging protocol, suggesting the capability of long-term observation and quantitative analysis of a single molecule by using an ND particle.

In silico reconstitution of actin-based symmetry breaking and motility.

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Mark J Dayel

2009-09-01

Full Text Available Eukaryotic cells assemble viscoelastic networks of crosslinked actin filaments to control their shape, mechanical properties, and motility. One important class of actin network is nucleated by the Arp2/3 complex and drives both membrane protrusion at the leading edge of motile cells and intracellular motility of pathogens such as Listeria monocytogenes. These networks can be reconstituted in vitro from purified components to drive the motility of spherical micron-sized beads. An Elastic Gel model has been successful in explaining how these networks break symmetry, but how they produce directed motile force has been less clear. We have combined numerical simulations with in vitro experiments to reconstitute the behavior of these motile actin networks in silico using an Accumulative Particle-Spring (APS model that builds on the Elastic Gel model, and demonstrates simple intuitive mechanisms for both symmetry breaking and sustained motility. The APS model explains observed transitions between smooth and pulsatile motion as well as subtle variations in network architecture caused by differences in geometry and conditions. Our findings also explain sideways symmetry breaking and motility of elongated beads, and show that elastic recoil, though important for symmetry breaking and pulsatile motion, is not necessary for smooth directional motility. The APS model demonstrates how a small number of viscoelastic network parameters and construction rules suffice to recapture the complex behavior of motile actin networks. The fact that the model not only mirrors our in vitro observations, but also makes novel predictions that we confirm by experiment, suggests that the model captures much of the essence of actin-based motility in this system.

Plant Vegetative and Animal Cytoplasmic Actins Share Functional Competence for Spatial Development with Protists[W][OA

Science.gov (United States)

Kandasamy, Muthugapatti K.; McKinney, Elizabeth C.; Roy, Eileen; Meagher, Richard B.

2012-01-01

Actin is an essential multifunctional protein encoded by two distinct ancient classes of genes in animals (cytoplasmic and muscle) and plants (vegetative and reproductive). The prevailing view is that each class of actin variants is functionally distinct. However, we propose that the vegetative plant and cytoplasmic animal variants have conserved functional competence for spatial development inherited from an ancestral protist actin sequence. To test this idea, we ectopically expressed animal and protist actins in Arabidopsis thaliana double vegetative actin mutants that are dramatically altered in cell and organ morphologies. We found that expression of cytoplasmic actins from humans and even a highly divergent invertebrate Ciona intestinalis qualitatively and quantitatively suppressed the root cell polarity and organ defects of act8 act7 mutants and moderately suppressed the root-hairless phenotype of act2 act8 mutants. By contrast, human muscle actins were unable to support prominently any aspect of plant development. Furthermore, actins from three protists representing Choanozoa, Archamoeba, and green algae efficiently suppressed all the phenotypes of both the plant mutants. Remarkably, these data imply that actin’s competence to carry out a complex suite of processes essential for multicellular development was already fully developed in single-celled protists and evolved nonprogressively from protists to plants and animals. PMID:22589468

Force Exertion and Transmission in Cross-Linked Actin Networks

Science.gov (United States)

Stam, Samantha

Cells are responsive to external cues in their environment telling them to proliferate or migrate within their surrounding tissue. Sensing of cues that are mechanical in nature, such stiffness of a tissue or forces transmitted from other cells, is believed to involve the cytoskeleton of a cell. The cytoskeleton is a complex network of proteins consisting of polymers that provide structural support, motor proteins that remodel these structures, and many others. We do not yet have a complete understanding of how cytoskeletal components respond to either internal or external mechanical force and stiffness. Such an understanding should involve mechanisms by which constituent molecules, such as motor proteins, are responsive to mechanics. Additionally, physical models of how forces are transmitted through biopolymer networks are necessary. My research has focused on networks formed by the cytoskeletal filament actin and the molecular motor protein myosin II. Actin filaments form networks and bundles that form a structural framework of the cell, and myosin II slides actin filaments. In this thesis, we show that stiffness of an elastic load that opposes myosin-generated actin sliding has a very sharp effect on the myosin force output in simulations. Secondly, we show that the stiffness and connectivity of cytoskeletal filaments regulates the contractility and anisotropy of network deformations that transmit force on material length scales. Together, these results have implications for predicting and interpreting the deformations and forces in biopolymeric active materials.

Quantitative fluorescence in situ hybridization measurement of telomere length in skin with/without sun exposure or actinic keratosis.

Science.gov (United States)

Ikeda, Hiroyuki; Aida, Junko; Hatamochi, Atsushi; Hamasaki, Yoichiro; Izumiyama-Shimomura, Naotaka; Nakamura, Ken-Ichi; Ishikawa, Naoshi; Poon, Steven S; Fujiwara, Mutsunori; Tomita, Ken-Ichiro; Hiraishi, Naoki; Kuroiwa, Mie; Matsuura, Masaaki; Sanada, Yukihiro; Kawano, Youichi; Arai, Tomio; Takubo, Kaiyo

2014-03-01

Chromosomal and genomic instability due to telomere dysfunction is known to play an important role in carcinogenesis. To study telomere shortening in the epidermis surrounding actinic keratosis, we measured telomere lengths of basal, parabasal, and suprabasal cells in epidermis with actinic keratosis (actinic keratosis group, n = 18) and without actinic keratosis (sun-protected, n = 15, and sun-exposed, n = 13 groups) and in actinic keratosis itself as well as in dermal fibroblasts in the 3 groups, using quantitative fluorescence in situ hybridization. Among the 3 cell types, telomeres of basal cells were not always the longest, suggesting that tissue stem cells are not necessarily located among basal cells. Telomeres of basal cells in the sun-exposed group were shorter than those in the sun-protected group. Telomeres in the background of actinic keratosis and in actinic keratosis itself and those of fibroblasts in actinic keratosis were significantly shorter than those in the controls. Our findings demonstrate that sun exposure induces telomere shortening and that actinic keratosis arises from epidermis with shorter telomeres despite the absence of any histologic atypia. © 2014.

Structure and Function of an Actin-Based Filter in the Proximal Axon

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Varuzhan Balasanyan

2017-12-01

Full Text Available Summary: The essential organization of microtubules within neurons has been described; however, less is known about how neuronal actin is arranged and the functional implications of its arrangement. Here, we describe, in live cells, an actin-based structure in the proximal axon that selectively prevents some proteins from entering the axon while allowing the passage of others. Concentrated patches of actin in proximal axons are present shortly after axonal specification in rat and zebrafish neurons imaged live, and they mark positions where anterogradely traveling vesicles carrying dendritic proteins halt and reverse. Patches colocalize with the ARP2/3 complex, and when ARP2/3-mediated nucleation is blocked, a dendritic protein mislocalizes to the axon. Patches are highly dynamic, with few persisting longer than 30 min. In neurons in culture and in vivo, actin appears to form a contiguous, semipermeable barrier, despite its apparently sparse distribution, preventing axonal localization of constitutively active myosin Va but not myosin VI. : Balasanyan et al. find dynamic patches of actin in proximal axons of live neurons, mature and newly differentiated, in culture and in vivo. Patches contribute to a filter that sequesters some proteins within the somatodendritic domain while allowing others to pass into the axon, leading to polarized localization of proteins.

Ultrasound of musculoskeletal soft-tissue tumors superficial to the investing fascia.

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Hung, Esther Hiu Yee; Griffith, James Francis; Ng, Alex Wing Hung; Lee, Ryan Ka Lok; Lau, Domily Ting Yi; Leung, Jason Chi Shun

2014-06-01

The objective of our study was to evaluate the diagnostic accuracy of ultrasound in assessing musculoskeletal soft-tissue tumors superficial to the investing fascia. Seven hundred fourteen superficial soft-tissue tumors evaluated with ultrasound by two musculoskeletal radiologists were retrospectively reviewed. In all ultrasound reports, the reporting radiologists provided one, two, or three diagnoses depending on their perceived level of diagnostic certainty. Two hundred forty-seven tumors had subsequent histologic correlation, thus allowing the accuracy of the ultrasound diagnosis to be determined. Images of the lesions with a discordant ultrasound diagnosis and histologic diagnosis were reviewed, and the ultrasound features were further classified as concordant with the known histologic diagnosis, concordant with the known histologic diagnosis with atypical features present, or discordant with the known histologic diagnosis. Four hundred sixty-seven tumors without pathologic confirmation were followed up clinically. Overall the accuracy of ultrasound examination for assessing superficial soft-tissue masses was 79.0% when all differential diagnoses were considered and 77.0% when only the first differential diagnosis was considered. The sensitivity and specificity of the first ultrasound diagnosis were 95.2% and 94.3%, respectively, for lipoma; 73.0% and 97.7% for vascular malformation; 80.0% and 95.4% for epidermoid cyst; and 68.8% and 95.2% for nerve sheath tumor. Reduced observer awareness of specific tumor entities tended to contribute to underdiagnosis more than poor specificity of ultrasound findings. Most tumors (236/247, 96%) were benign. The sensitivity and specificity of ultrasound for identifying malignant superficial soft-tissue tumors was 94.1% and 99.7%, respectively. The diagnostic accuracy of ultrasound in the assessment of superficial musculoskeletal soft-tissue tumors is high and can be improved through increased radiologist awareness of less

A function for filamentous alpha-smooth muscle actin: Retardation of motility in human breast fibroblasts

DEFF Research Database (Denmark)

Rønnov-Jessen, Lone; Petersen, Ole William

1996-01-01

.8 and 3.0 microns/h, respectively. To knock out the alpha-sm actin protein, several antisense phosphorothioate oligodeoxynucleotide (ODNs) were tested. One of these, 3'UTI, which is complementary to a highly evolutionary conserved 3' untranslated (3'UT) sequence of alpha-sm actin mRNA, was found to block...... alpha-sm actin synthesis completely without affecting the synthesis of any other proteins as analyzed by two-dimensional gel electrophoresis. Targeting by antisense 3'UTI significantly increased motility compared with the corresponding sense ODN. alpha-Sm actin inhibition also led to the formation...

Covalent and non-covalent chemical engineering of actin for biotechnological applications.

Science.gov (United States)

Kumar, Saroj; Mansson, Alf

2017-11-15

The cytoskeletal filaments are self-assembled protein polymers with 8-25nm diameters and up to several tens of micrometres length. They have a range of pivotal roles in eukaryotic cells, including transportation of intracellular cargoes (primarily microtubules with dynein and kinesin motors) and cell motility (primarily actin and myosin) where muscle contraction is one example. For two decades, the cytoskeletal filaments and their associated motor systems have been explored for nanotechnological applications including miniaturized sensor systems and lab-on-a-chip devices. Several developments have also revolved around possible exploitation of the filaments alone without their motor partners. Efforts to use the cytoskeletal filaments for applications often require chemical or genetic engineering of the filaments such as specific conjugation with fluorophores, antibodies, oligonucleotides or various macromolecular complexes e.g. nanoparticles. Similar conjugation methods are also instrumental for a range of fundamental biophysical studies. Here we review methods for non-covalent and covalent chemical modifications of actin filaments with focus on critical advantages and challenges of different methods as well as critical steps in the conjugation procedures. We also review potential uses of the engineered actin filaments in nanotechnological applications and in some key fundamental studies of actin and myosin function. Finally, we consider possible future lines of investigation that may be addressed by applying chemical conjugation of actin in new ways. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

FIMBRIN1 Is Involved in Lily Pollen Tube Growth by Stabilizing the Actin Fringe[C][W][OA

Science.gov (United States)

Su, Hui; Zhu, Jinsheng; Cai, Chao; Pei, Weike; Wang, Jiaojiao; Dong, Huaijian; Ren, Haiyun

2012-01-01

An actin fringe structure in the subapex plays an important role in pollen tube tip growth. However, the precise mechanism by which the actin fringe is generated and maintained remains largely unknown. Here, we cloned a 2606-bp full-length cDNA encoding a deduced 77-kD fimbrin-like protein from lily (Lilium longiflorum), named FIMBRIN1 (FIM1). Ll-FIM1 was preferentially expressed in pollen and concentrated at actin fringe in the subapical region, as well as in longitudinal actin-filament bundles in the shank of pollen tubes. Microinjection of Ll-FIM1 antibody into lily pollen tubes inhibited tip growth and disrupted the actin fringe. Furthermore, we verified the function of Ll-FIM1 in the fim5 mutant of its closest relative, Arabidopsis thaliana. Pollen tubes of fim5 mutants grew with a larger diameter in early stages but could recover into normal forms in later stages, despite significantly slower growth rates. The actin fringe of the fim5 mutants, however, was impaired during both early and late stages. Impressively, stable expression of fim5pro:GFP:Ll-FIM1 rescued the actin fringe and the growth rate of Arabidopsis fim5 pollen tubes. In vitro biochemical analysis showed that Ll-FIM1 could bundle actin filaments. Thus, our study has identified a fimbrin that may stabilize the actin fringe by cross-linking actin filaments into bundles, which is important for proper tip growth of lily pollen tubes. PMID:23150633

Cofilin phosphorylation is elevated after F-actin disassembly induced by Rac1 depletion

DEFF Research Database (Denmark)

Liu, Linna; Li, Jing; Zhang, Liwang

2015-01-01

Cytoskeletal reorganization is essential to keratinocyte function. Rac1 regulates cytoskeletal reorganization through signaling pathways such as the cofilin cascade. Cofilin severs actin filaments after activation by dephosphorylation. Rac1 was knocked out in mouse keratinocytes and it was found...... that actin filaments disassembled. In the epidermis of mice in which Rac1 was knocked out only in keratinocytes, cofilin phosphorylation was aberrantly elevated, corresponding to repression of the phosphatase slingshot1 (SSH1). These effects were independent of the signaling pathways for p21-activated kinase....../LIM kinase (Pak/LIMK), protein kinase C, or protein kinase D or generation of reactive oxygen species. Similarly, when actin polymerization was specifically inhibited or Rac1 was knocked down, cofilin phosphorylation was enhanced and SSH1 was repressed. Repression of SSH1 partially blocked actin...

Photodynamic therapy for actinic keratosis in organ transplant patients

DEFF Research Database (Denmark)

Basset-Seguin, N; Baumann Conzett, K; Gerritsen, M J P

2013-01-01

Background The incidence of actinic keratoses (AK) and non-melanoma skin cancer (NMSC) in organ transplant recipients (OTRs) is significantly higher than in immunocompetent patients. Rates of progression and recurrence following treatment are higher too, in part due to the effects of the immunosu......Background The incidence of actinic keratoses (AK) and non-melanoma skin cancer (NMSC) in organ transplant recipients (OTRs) is significantly higher than in immunocompetent patients. Rates of progression and recurrence following treatment are higher too, in part due to the effects...... investigate induced immunosuppression with PDT in healthy volunteers....

Volumetric Modulated Arc Therapy (VMAT) Treatment Planning for Superficial Tumors

International Nuclear Information System (INIS)

Zacarias, Albert S.; Brown, Mellonie F.; Mills, Michael D.

2010-01-01

The physician's planning objective is often a uniform dose distribution throughout the planning target volume (PTV), including superficial PTVs on or near the surface of a patient's body. Varian's Eclipse treatment planning system uses a progressive resolution optimizer (PRO), version 8.2.23, for RapidArc dynamic multileaf collimator volumetric modulated arc therapy planning. Because the PRO is a fast optimizer, optimization convergence errors (OCEs) produce dose nonuniformity in the superficial area of the PTV. We present a postsurgical cranial case demonstrating the recursive method our clinic uses to produce RapidArc treatment plans. The initial RapidArc treatment plan generated using one 360 o arc resulted in substantial dose nonuniformity in the superficial section of the PTV. We demonstrate the use of multiple arcs to produce improved dose uniformity in this region. We also compare the results of this superficial dose compensation method to the results of a recursive method of dose correction that we developed in-house to correct optimization convergence errors in static intensity-modulated radiation therapy treatment plans. The results show that up to 4 arcs may be necessary to provide uniform dose to the surface of the PTV with the current version of the PRO.

Case for diagnosis. Actinic prurigo.

Science.gov (United States)

Daldon, Patricia Erica Christofoletti; Pascini, Mirella; Correa, Mariane

2010-01-01

A 13-year-old black boy had pruritic papular and nodular lesions on his forearms associated to edema of the lower lip, photophobia, conjunctivitis and pterygium. Skin biopsy of the lower lip revealed acanthosis, spongiosis with dermal perivascular mononuclear cell infiltration composed by lymphocytes, plasma cells and eosinophils consistent with actinic prurigo. Lesions improved considerably with the use of thalidomide 100mg/ day.

Actin based processes that could determine the cytoplasmic architecture of plant cells

NARCIS (Netherlands)

Honing, van der H.S.; Emons, A.M.C.; Ketelaar, M.J.

2007-01-01

Actin polymerisation can generate forces that are necessary for cell movement, such as the propulsion of a class of bacteria, including Listeria, and the protrusion of migrating animal cells. Force generation by the actin cytoskeleton in plant cells has not been studied. One process in plant cells

Azadirachtin(A) distinctively modulates subdomain 2 of actin - novel mechanism to induce depolymerization revealed by molecular dynamics study.

Science.gov (United States)

Pravin Kumar, R; Roopa, L; Sudheer Mohammed, M M; Kulkarni, Naveen

2016-12-01

Azadirachtin(A) (AZA), a potential insecticide from neem, binds to actin and induces depolymerization in Drosophila. AZA binds to the pocket same as that of Latrunculin A (LAT), but LAT inhibits actin polymerization by stiffening the actin structure and affects the ADP-ATP exchange. The mechanism by which AZA induces actin depolymerization is not clearly understood. Therefore, different computational experiments were conducted to delineate the precise mechanism of AZA-induced actin depolymerization. Molecular dynamics studies showed that AZA strongly interacted with subdomain 2 and destabilized the interactions between subdomain 2 of one actin and subdomains 1 and 4 of the adjacent actin, causing the separation of actin subunits. The separation was observed between subdomain 3 of subunit n and subdomain 4 of subunit n + 2. However, the specific triggering point for the separation of the subunits was the destabilization of direct interactions between subdomain 2 of subunit n (Arg39, Val45, Gly46 and Arg62) and subdomain 4 of subunit n + 2 (Asp286, Ile287, Asp288, Ile289, Asp244 and Lys291). These results reveal a unique mechanism of an actin filament modulator that induces depolymerization. This mechanism of AZA can be used to design similar molecules against mammalian actins for cancer therapy.

Superficial siderosis of the central nervous system - A case report

International Nuclear Information System (INIS)

Mannalini, S.

1997-01-01

There is little information on superficial siderosis of the central nervous system (CNS) in the literature, mainly due to the rarity of the disease, the difficulties in diagnosis (autopsy pre magnetic resonance imaging (MRI)) and the long latency of the symptoms. With the advent of MRI, for the first time we are able to make a positive in vivo diagnosis. But this comes at a time of less disease incidence, and little clinical awareness. MRI is able to make the diagnosis because of the strong paramagnetic effect of haemosiderin, the blood by-product that is deposited on the brain surface in superficial siderosis of the CNS. The ability of the brain to biosynthesize ferritin in response to prolonged contact with haemosiderin is thought to be the most important factor in the pathogenesis of superficial siderosis. (author)

Volumetric and superficial characterization of carbon activated; Caracterizacion volumetrica y superficial de carbon activado

Energy Technology Data Exchange (ETDEWEB)

Carrera G, L.M.; Garcia S, I.; Jimenez B, J.; Solache R, M.; Lopez M, B.; Bulbulian G, S.; Olguin G, M.T. [Departamento de Quimica, Gerencia de Ciencias Basicas, Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

2000-07-01

The activated carbon is the resultant material of the calcination process of natural carbonated materials as coconut shells or olive little bones. It is an excellent adsorbent of diluted substances, so much in colloidal form, as in particles form. Those substances are attracted and retained by the carbon surface. In this work is make the volumetric and superficial characterization of activated carbon treated thermically (300 Centigrade) in function of the grain size average. (Author)

Cell Adhesions: Actin-Based Modules that Mediate Cell-Extracellular Matrix and Cell-Cell Interactions

Science.gov (United States)

Bachir, Alexia; Horwitz, Alan Rick; Nelson, W. James; Bianchini, Julie M.

2018-01-01

Cell adhesions link cells to the extracellular matrix (ECM) and to each other, and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping functional modules. These modules establish physical association with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as sense and translate the mechanical properties of the cellular environment to changes in cell organization and behavior. In this chapter we discuss the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions, and how adhesion molecules mediate crosstalk between cell-ECM and cell-cell adhesion sites. PMID:28679638

Molecular analysis of an actin gene, CarACT1, from chickpea (Cicer arietinum L.).

Science.gov (United States)

Peng, Hui; Cheng, Huiying; Yu, Xingwang; Shi, Qinghua; Zhang, Hua; Li, Jiangui; Ma, Hao

2010-02-01

Actins are ubiquitous and highly conserved proteins that play key roles in cell formation and cellular activities. In this study, an actin gene was isolated from chickpea for the first time and designated as CarACT1 (for Cicer arietinum L. actin gene 1; Genbank accession no. EU529707). It encoded a putative protein with 377 amino acids and contained five exons and four introns within genomic DNA sequence. CarACT1 was localized in cytoplasm and showed high similarity to other well known actins from various species. Reverse transcription-polymerase chain reaction (RT-PCR) assay proved that CarACT1 transcripts were ubiquitously accumulated in all major organs, such as seedling roots, stems, leaves, flowers, young pods, and seeds, as well as in diverse developmental stages, such as leaf senescence, seed development and germination. Our results suggested that CarACT1 is an actin gene with physiological functions and may be served as a potential reference gene for transcription level of interesting genes in chickpea.

Three-day Field Treatment with Ingenol Disoxate (LEO 43204) for Actinic Keratosis

Science.gov (United States)

Tyring, Stephen; Nahm, Walter K.; Østerdal, Marie Louise; Petersen, Astrid H.; Berman, Brian

2017-01-01

OBJECTIVE: The purpose of this study was to evaluate the safety and efficacy of ingenol disoxate gel using a once-daily, three-day field treatment regimen in patients with actinic keratosis. DESIGN: This was a Phase II, multicenter, open-label trial (clinicaltrials.gov: NCT02305888). SETTING: The study was conducted in 20 trial sites in the United States. PARTICIPANTS: Participants included patients with 5 to 20 clinically typical actinic keratosis lesions on the full face/chest (250cm2), scalp (25–250cm2), or the trunk/extremities (250cm2). MEASUREMENTS: We measured incidence of dose-limiting events based on local skin responses. Percentage reduction in actinic keratosis lesion count from baseline, complete clearance, and partial clearance (≥75%) of actinic keratosis lesions were assessed at Week 8. RESULTS: Nine of 63 (14.3%) patients in the face/chest group reported dose-limiting events; zero of 63 patients in the scalp group reported dose-limiting events; and 11 of 62 (17.7%) patients in the trunk/extremities group reported dose-limiting events. Mean composite local skin response scores peaked at Day 4, then rapidly declined, reaching or approaching baseline levels by Week 4. Less than five percent of patients reported severe adverse events; the most common treatment-related adverse events were application site pain and pruritus. The reduction in actinic keratosis lesion count was 78.9, 76.3, and 69.1 percent for the face/chest, scalp, and trunk/extremities groups, respectively. Complete clearance was achieved in 36.5, 39.7, and 22.6 percent of patients in the face/chest, scalp, and trunk/extremities groups, respectively. Partial clearance was achieved in 71.4, 65.1, and 50.0 percent of patients in the face/chest, scalp, and trunk/extremities groups, respectively. CONCLUSION: Ingenol disoxate demonstrated adverse events and local skin reaction profiles similar to results seen in trials evaluating shorter two-day regimens and was effective in patients with

Electron Tomography of Cryofixed, Isometrically Contracting Insect Flight Muscle Reveals Novel Actin-Myosin Interactions

International Nuclear Information System (INIS)

Wu, Shenping; Liu, Jun; Reedy, Mary C.; Tregear, Richard T.; Winkler, Hanspeter; Franzini-Armstrong, Clara; Sasaki, Hiroyuki; Lucaveche, Carmen; Goldman, Yale E.; Reedy, Michael K.; Taylor, Kenneth A.

2010-01-01

Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ. We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the 'target zone', situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77 o /12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127 o range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening. We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very different from

Electron tomography of cryofixed, isometrically contracting insect flight muscle reveals novel actin-myosin interactions.

Directory of Open Access Journals (Sweden)

Shenping Wu

2010-09-01

Full Text Available Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ.We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the "target zone", situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77°/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127° range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening.We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very

Capu and Spire Assemble a Cytoplasmic Actin~Mesh that Maintains Microtubule Organization in the Drosophila Oocyte

DEFF Research Database (Denmark)

Dahlgaard, K.; Raposo, A.A.S.F.; Niccoli, T.

2007-01-01

Mutants in the actin nucleators Cappuccino and Spire disrupt the polarized microtubule network in the Drosophila oocyte that defines the anterior-posterior axis, suggesting that microtubule organization depends on actin. Here, we show that Cappuccino and Spire organize an isotropic mesh of actin...

Clinicopahological features of superficial basaloid squamous cell carcinoma of the esophagus.

Science.gov (United States)

Oguma, J; Ozawa, S; Kazuno, A; Nitta, M; Ninomiya, Y; Tomita, S

2017-12-01

Basaloid squamous cell carcinoma (BSC) of the esophagus is classified as an epithelial malignant tumor and is a rare variant of squamous cell carcinoma (SCC). Most previous reports have suggested that advanced BSC has a poorer prognosis than typical SCC because of its high biological malignancy, but the biological activity of superficial BSC remains unclear. Twenty cases of superficial BSC, which underwent surgical resection in Tokai University Hospital between January 2004 and December 2013, were analyzed retrospectively. Among these cases, 19 cases with a T1 depth of invasion (BSC group) were compared with 180 cases of SCC that were resected during the same period and were pathologically diagnosed as T1 (SCC group). The frequency of lymph node metastasis in the T1 BSC group was significantly lower (2 patients, 11%) than that in the SCC group (84 patients, 47%) (P = 0.005). The frequency of lymphatic invasion in the BSC group was also lower (9 patients, 47%) than that in the SCC group (131 patients, 73%) (P = 0.021). The pathological type of the metastatic lymph node was BSC in all the superficial BSC cases with lymph node metastasis. This study demonstrated that lymph node metastasis was less likely to occur in cases with superficial BSC than in cases with superficial SCC. © The Authors 2017. Published by Oxford University Press on behalf of International Society for Diseases of the Esophagus. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The interaction between the adaptor protein APS and Enigma is involved in actin organisation

DEFF Research Database (Denmark)

Barres, Romain; Gonzalez, Teresa; Le Marchand-Brustel, Yannick

2005-01-01

that was previously shown to be associated with the actin cytoskeleton. In HEK 293 cells, Enigma interacted specifically with APS, but not with the APS-related protein SH2-B. This interaction required the NPTY motif of APS and the LIM domains of Enigma. In NIH-3T3 cells that express the insulin receptor, Enigma...... cytoskeleton organisation, expression of Enigma alone led to the formation of F-actin clusters. Similar alteration in actin cytoskeleton organisation was observed in cells expressing both Enigma and APS with a mutation in the NPTY motif. These results identify Enigma as a novel APS-binding protein and suggest...... that the APS/Enigma complex plays a critical role in actin cytoskeleton organisation....

Espins are multifunctional actin cytoskeletal regulatory proteins in the microvilli of chemosensory and mechanosensory cells

Science.gov (United States)

Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Changyaleket, Benjarat; Whitlon, Donna S.; Mugnaini, Enrico; Bartles, James R.

2010-01-01

Espins are associated with the parallel actin bundles of hair cell stereocilia and are the target of mutations that cause deafness and vestibular dysfunction in mice and humans. Here, we report that espins are also concentrated in the microvilli of a number of other sensory cells: vomeronasal organ sensory neurons, solitary chemoreceptor cells, taste cells and Merkel cells. Moreover, we show that hair cells and these other sensory cells contain novel espin isoforms that arise from a different transcriptional start site and differ significantly from other espin isoforms in their complement of ligand-binding activities and their effects on actin polymerization. The novel espin isoforms of sensory cells bundled actin filaments with high affinity in a Ca2+-resistant fashion, bound actin monomer via a WASP homology 2 domain, bound profilin via a single proline-rich peptide, and caused a dramatic elongation of microvillus-type parallel actin bundles in transfected epithelial cells. In addition, the novel espin isoforms of sensory cells differed from other espin isoforms in that they potently inhibited actin polymerization in vitro, did not bind the Src homology 3 domain of the adapter protein insulin receptor substrate p53 and did not bind the acidic, signaling phospholipid phosphatidylinositol 4,5- bisphosphate. Thus, the espins constitute a family of multifunctional actin cytoskeletal regulatory proteins with the potential to differentially influence the organization, dimensions, dynamics and signaling capabilities of the actin filament-rich, microvillus-type specializations that mediate sensory transduction in a variety of mechanosensory and chemosensory cells. PMID:15190118

The F-Actin Binding Protein Cortactin Regulates the Dynamics of the Exocytotic Fusion Pore through its SH3 Domain

Science.gov (United States)

González-Jamett, Arlek M.; Guerra, María J.; Olivares, María J.; Haro-Acuña, Valentina; Baéz-Matus, Ximena; Vásquez-Navarrete, Jacqueline; Momboisse, Fanny; Martinez-Quiles, Narcisa; Cárdenas, Ana M.

2017-01-01

Upon cell stimulation, the network of cortical actin filaments is rearranged to facilitate the neurosecretory process. This actin rearrangement includes both disruption of the preexisting actin network and de novo actin polymerization. However, the mechanism by which a Ca2+ signal elicits the formation of new actin filaments remains uncertain. Cortactin, an actin-binding protein that promotes actin polymerization in synergy with the nucleation promoting factor N-WASP, could play a key role in this mechanism. We addressed this hypothesis by analyzing de novo actin polymerization and exocytosis in bovine adrenal chromaffin cells expressing different cortactin or N-WASP domains, or cortactin mutants that fail to interact with proline-rich domain (PRD)-containing proteins, including N-WASP, or to be phosphorylated by Ca2+-dependent kinases, such as ERK1/2 and Src. Our results show that the activation of nicotinic receptors in chromaffin cells promotes cortactin translocation to the cell cortex, where it colocalizes with actin filaments. We further found that, in association with PRD-containing proteins, cortactin contributes to the Ca2+-dependent formation of F-actin, and regulates fusion pore dynamics and the number of exocytotic events induced by activation of nicotinic receptors. However, whereas the actions of cortactin on the fusion pore dynamics seems to depend on the availability of monomeric actin and its phosphorylation by ERK1/2 and Src kinases, cortactin regulates the extent of exocytosis by a mechanism independent of actin polymerization. Together our findings point out a role for cortactin as a critical modulator of actin filament formation and exocytosis in neuroendocrine cells. PMID:28522963

Filament formation of the Escherichia coli actin-related protein, MreB, in fission yeast.

Science.gov (United States)

Srinivasan, Ramanujam; Mishra, Mithilesh; Murata-Hori, Maki; Balasubramanian, Mohan K

2007-02-06

Proteins structurally related to eukaryotic actins have recently been identified in several prokaryotic organisms. These actin-like proteins (MreB and ParM) and the deviant Walker A ATPase (SopA) play a key role in DNA segregation and assemble into polymers in vitro and in vivo. MreB also plays a role in cellular morphogenesis. Whereas the dynamic properties of eukaryotic actins have been extensively characterized, those of bacterial actins are only beginning to emerge. We have established the fission yeast Schizosaccharomyces pombe as a cellular model for the functional analysis of the Escherichia coli actin-related protein MreB. We show that MreB organizes into linear bundles that grow in a symmetrically bidirectional manner at 0.46 +/- 0.03 microm/min, with new monomers and/or oligomers being added along the entire length of the bundle. Organization of linear arrays was dependent on the ATPase activity of MreB, and their alignment along the cellular long axis was achieved by sliding along the cortex of the cylindrical part of the cell. The cell ends appeared to provide a physical barrier for bundle elongation. These experiments provide new insights into the mechanism of assembly and organization of the bacterial actin cytoskeleton.

Disassembly of actin structures by nanosecond pulsed electric field is a downstream effect of cell swelling.

Science.gov (United States)

Pakhomov, Andrei G; Xiao, Shu; Pakhomova, Olga N; Semenov, Iurii; Kuipers, Marjorie A; Ibey, Bennett L

2014-12-01

Disruption of the actin cytoskeleton structures was reported as one of the characteristic effects of nanosecond-duration pulsed electric field (nsPEF) in both mammalian and plant cells. We utilized CHO cells that expressed the monomeric fluorescent protein (mApple) tagged to actin to test if nsPEF modifies the cell actin directly or as a consequence of cell membrane permeabilization. A train of four 600-ns pulses at 19.2 kV/cm (2 Hz) caused immediate cell membrane poration manifested by YO-PRO-1 dye uptake, gradual cell rounding and swelling. Concurrently, bright actin features were replaced by dimmer and uniform fluorescence of diffuse actin. To block the nsPEF-induced swelling, the bath buffer was isoosmotically supplemented with an electropore-impermeable solute (sucrose). A similar addition of a smaller, electropore-permeable solute (adonitol) served as a control. We demonstrated that sucrose efficiently blocked disassembly of actin features by nsPEF, whereas adonitol did not. Sucrose also attenuated bleaching of mApple-tagged actin in nsPEF-treated cells (as integrated over the cell volume), although did not fully prevent it. We conclude that disintegration of the actin cytoskeleton was a result of cell swelling, which, in turn, was caused by cell permeabilization by nsPEF and transmembrane diffusion of solutes which led to the osmotic imbalance. Copyright © 2014 Elsevier B.V. All rights reserved.

Actinic inspection of multilayer defects on EUV masks

International Nuclear Information System (INIS)

Barty, A; Liu, Y; Gullikson, E; Taylor, J S; Wood, O

2005-01-01

The production of defect-free mask blanks, and the development of techniques for inspecting and qualifying EUV mask blanks, remains a key challenge for EUV lithography. In order to ensure a reliable supply of defect-free mask blanks, it is necessary to develop techniques to reliably and accurately detect defects on un-patterned mask blanks. These inspection tools must be able to accurately detect all critical defects whilst simultaneously having the minimum possible false-positive detection rate. There continues to be improvement in high-speed non-actinic mask blank inspection tools, and it is anticipated that these tools can and will be used by industry to qualify EUV mask blanks. However, the outstanding question remains one of validating that non-actinic inspection techniques are capable of detecting all printable EUV defects. To qualify the performance of non-actinic inspection tools, a unique dual-mode EUV mask inspection system has been installed at the Advanced Light Source (ALS) synchrotron at Lawrence Berkeley National Laboratory. In high-speed inspection mode, whole mask blanks are scanned for defects using 13.5-nm wavelength light to identify and map all locations on the mask that scatter a significant amount of EUV light. In imaging, or defect review mode, a zone plate is placed in the reflected beam path to image a region of interest onto a CCD detector with an effective resolution on the mask of 100-nm or better. Combining the capabilities of the two inspection tools into one system provides the unique capability to determine the coordinates of native defects that can be used to compare actinic defect inspection with visible light defect inspection tools under commercial development, and to provide data for comparing scattering models for EUV mask defects

Nck adaptor proteins link Tks5 to invadopodia actin regulation and ECM degradation.

Science.gov (United States)

Stylli, Stanley S; Stacey, T T I; Verhagen, Anne M; Xu, San San; Pass, Ian; Courtneidge, Sara A; Lock, Peter

2009-08-01

Invadopodia are actin-based projections enriched with proteases, which invasive cancer cells use to degrade the extracellular matrix (ECM). The Phox homology (PX)-Src homology (SH)3 domain adaptor protein Tks5 (also known as SH3PXD2A) cooperates with Src tyrosine kinase to promote invadopodia formation but the underlying pathway is not clear. Here we show that Src phosphorylates Tks5 at Y557, inducing it to associate directly with the SH3-SH2 domain adaptor proteins Nck1 and Nck2 in invadopodia. Tks5 mutants unable to bind Nck show reduced matrix degradation-promoting activity and recruit actin to invadopodia inefficiently. Conversely, Src- and Tks5-driven matrix proteolysis and actin assembly in invadopodia are enhanced by Nck1 or Nck2 overexpression and inhibited by Nck1 depletion. We show that clustering at the plasma membrane of the Tks5 inter-SH3 region containing Y557 triggers phosphorylation at this site, facilitating Nck recruitment and F-actin assembly. These results identify a Src-Tks5-Nck pathway in ECM-degrading invadopodia that shows parallels with pathways linking several mammalian and pathogen-derived proteins to local actin regulation.

The actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

Science.gov (United States)

Westendorf, Christian; Negrete, Jose, Jr.; Bae, Albert; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-03-01

We report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. The averaged F-actin response of many cells to a short-time pulse of cAMP is reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. We systematically exposed a large number of cells to periodic pulse trains. The results indicate a resonance peak at periodic inputs of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the actin regulatory network. To quantitatively test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and Aip1. These served as markers of the F-actin disassembly process and thus allow us to estimate the delay time. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed experimentally. Financial support by the Max-Planck Society and the DFG (SFB 937).

Interaction of cytochalasin D with actin filaments in the presence of ADP and ATP.

Science.gov (United States)

Carlier, M F; Criquet, P; Pantaloni, D; Korn, E D

1986-02-15

Cytochalasin D strongly inhibits the faster components in the reactions of actin filament depolymerization and elongation in the presence of 10 mM Tris-Cl-, pH 7.8, 0.2 mM dithiothreitol, 1 mM MgCl2, 0.1 mM CaCl2, and 0.2 mM ATP or ADP. Assuming an exclusive and total capping of the barbed end by the drug, the kinetic parameters derived at saturation by cytochalasin D refer to the pointed end and are 10-15-fold lower than at the barbed end. In ATP, the critical concentration increases with cytochalasin D up to 12-fold its value when both ends are free; as a result of the lowering of the free energy of nucleation by cytochalasin D, short oligomers of F-actin exist just above and below the critical concentration. Cytochalasin D interacts strongly with the barbed ends independently of the ADP-G-actin concentration (K = 0.5 nM-1). In contrast, the affinity of cytochalasin D decreases cooperatively with increasing ATP-G-actin concentration. These data are equally well accounted for by two different models: either cytochalasin D binds very poorly to ATP-capped filament ends whose proportion increases with actin concentration, or cytochalasin D binds equally well to ATP-ends and ADP-ends and also binds to actin dimers in ATP but not in ADP. A linear actin concentration dependence of the rate of growth was found at the pointed end, consistent with the virtual absence of an ATP cap at that end.

Localization of Myosin and Actin in the Pelage and Whisker Hair Follicles of Rat

International Nuclear Information System (INIS)

Morioka, Kiyokazu; Matsuzaki, Toshiyuki; Takata, Kuniaki

2006-01-01

The combined effects of myosin II and actin enable muscle and nonmuscle cells to generate forces required for muscle contraction, cell division, cell migration, cellular morphological changes, the maintenance of cellular tension and polarity, and so on. However, except for the case of muscle contraction, the details are poorly understood. We focus on nonmuscle myosin and actin in the formation and maintenance of hair and skin, which include highly active processes in mammalian life with respect to the cellular proliferation, differentiation, and movement. The localization of nonmuscle myosin II and actin in neonatal rat dorsal skin, mystacial pad, hair follicles, and vibrissal follicles was studied by immunohistochemical technique to provide the basis for the elucidation of the roles of these proteins. Specificities of the antibodies were verified by using samples from the relevant tissues and subjecting them to immunoblotting test prior to morphological analyses. The myosin and actin were abundant and colocalized in the spinous and granular layers but scarce in the basal layer of the dorsal and mystacial epidermis. In hair and vibrissal follicles, nonmuscle myosin and actin were colocalized in the outer root sheath and some hair matrix cells adjoining dermal papillae. In contrast, most areas of the inner root sheath and hair matrix appeared to comprise very small amounts of myosin and actin. Hair shaft may comprise significant myosin during the course of its keratinization. These results suggest that the actin-myosin system plays a part in cell movement, differentiation, protection and other key functions of skin and hair cells

Biomass torrefaction characteristics in inert and oxidative atmospheres at various superficial velocities.

Science.gov (United States)

Chen, Wei-Hsin; Lu, Ke-Miao; Liu, Shih-Hsien; Tsai, Chi-Ming; Lee, Wen-Jhy; Lin, Ta-Chang

2013-10-01

The reaction characteristics of four biomass materials (i.e. oil palm fiber, coconut fiber, eucalyptus, and Cryptomeria japonica) with non-oxidative and oxidative torrefaction at various superficial velocities are investigated where nitrogen and air are used as carrier gases. Three torrefaction temperatures of 250, 300, and 350 °C are considered. At a given temperature, the solid yield of biomass is not affected by N2 superficial velocity, revealing that the thermal degradation is controlled by heat and mass transfer in biomass. Increasing air superficial velocity decreases the solid yield, especially in oil palm fiber and coconut fiber, implying that the torrefaction reaction of biomass is dominated by surface oxidation. There exists an upper limit of air superficial velocity in the decrement of solid yield, suggesting that beyond this limit the thermal degradation of biomass is no longer governed by surface oxidation, but rather is controlled by internal mass transport. Copyright © 2013 Elsevier Ltd. All rights reserved.

Prokaryotic DNA segregation by an actin-like filament

DEFF Research Database (Denmark)

Møller-Jensen, Jakob; Bugge Jensen, Rasmus; Löwe, Jan

2002-01-01

The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par forms dynamic actin-like filaments with prop...... point for ParM polymerization. Hence, we provide evidence for a simple prokaryotic analogue of the eukaryotic mitotic spindle apparatus.......The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par forms dynamic actin-like filaments...

Plasticity of the actin cytoskeleton in response to extracellular matrix nanostructure and dimensionality

NARCIS (Netherlands)

Starke, J.; Wehrle-Haller, B.; Friedl, P.

2014-01-01

Mobile cells discriminate and adapt to mechanosensory input from extracellular matrix (ECM) topographies to undergo actin-based polarization, shape change and migration. We tested 'cell-intrinsic' and adaptive components of actin-based cell migration in response to widely used in vitro

Dissecting the actin cortex density and membrane-cortex distance in living cells by super-resolution microscopy

DEFF Research Database (Denmark)

Clausen, M. P.; Colin-York, H.; Schneider, Falk

2017-01-01

and accurately measure the density distribution of the cortical actin cytoskeleton and the distance between the actin cortex and the membrane in live Jurkat T-cells. We found an asymmetric cortical actin density distribution with a mean width of 230 (+105/-125) nm. The spatial distances measured between...

Aneurysm of the superficial femoral artery in an infant

Energy Technology Data Exchange (ETDEWEB)

Watanabe, M.; Komuro, H.; Matoba, K.; Kaneko, M. [Dept. of Paediatric Surgery, Inst. of Clinical Medicine, Univ. of Tsukuba, Ibaraki (Japan); Niitsu, M.; Itai, Y. [Dept. of Radiology, Inst. of Clinical Medicine, Univ. of Tsukuba, Ibaraki (Japan)

2003-04-01

An isolated arterial aneurysm in childhood is extremely rare. We report a 1-year-old girl with an aneurysm of the right superficial femoral artery, presenting as an asymptomatic mass of the thigh. The aneurysm involved the whole superficial femoral artery (9 cm in length), and surgical treatment would have required replacement of the affected artery. Conservative treatment was chosen, influenced by the patient's rapid growth at that time. Non-invasive, 3-D contrast-enhanced magnetic resonance angiography (MRA) was useful as an alternative to conventional angiography for detailed evaluation of the femoral arteries, including the aneurysm. (orig.)

DNA repair deficiency in lymphocytes from patients with actinic keratosis

International Nuclear Information System (INIS)

Abo-Darub, J.M.; Mackie, R.; Pitts, J.D.

1978-01-01

DNA repair activity was measured in peripheral blood lymphocytes from 18 patients with Actinic Keratosis and 18 age-matched control subjects, by comparing the incorporation of 3 H-thymidine into cells after irradiation with ultraviolet light with that into unirradiated cells. The incorporation was followed autoradiographically or by measuring acid insoluble radioactivity in cells labelled in the presence of hydroxyurea. The repair activity in lymphocytes from Actinic keratosis patients was only 47.1% (+-6.5%) of that in cells from the control subjects

Imaging actinic keratosis by high-definition optical coherence tomography. Histomorphologic correlation

DEFF Research Database (Denmark)

Boone, Marc A L M; Norrenberg, Sarah; Jemec, Gregor B E

2013-01-01

With the continued development of non-invasive therapies for actinic keratosis such as PDT and immune therapies, the non-invasive diagnosis and monitoring become increasingly relevant. High-definition optical coherence tomography is a high-resolution imaging tool, with micrometre resolution in both...... transversal and axial directions, enable to visualize individual cells up to a depth of around 570 μm filling the imaging gap between conventional optical coherence tomography and reflectance confocal microscopy. We sought to determine the feasibility of detecting and grading of actinic keratosis...... by this technique using criteria defined for reflectance confocal microscopy compared to histology. In this pilot study, skin lesions of 17 patients with a histologically proven actinic keratosis were imaged by high-definition optical coherence tomography just before excision and images analysed qualitatively...

Two Crosslinking Technologies for Superficial Reticular Dermis Injection: A Comparative Ultrasound and Histologic Study

OpenAIRE

Micheels, Patrick; Besse, Stéphanie; Sarazin, Didier

2017-01-01

Background: Few hyaluronic acid fillers have been developed for superficial injection. Objective: To compare the diffusion and integration properties of cohesive polydensified matrix and Vycross® technology hyaluronic acid fillers with lidocaine following injection into the superficial reticular dermis. Methods and materials: Two subjects received two injections each of cohesive polydensified matrix and Vycross® hyaluronic acid (0.2mL/site) in the superficial reticular dermis of the buttock u...

Is chloroplast import of photosynthesis proteins facilitated by an actin-TOC-TIC-VIPP1 complex?

Science.gov (United States)

Jouhet, Juliette; Gray, John C

2009-10-01

Actin filaments are major components of the cytoskeleton that interact with chloroplast envelope membranes to allow chloroplast positioning and movement, stromule mobility and gravitropism perception. We recently reported that Toc159, a component of the TOC complex of the chloroplast protein import apparatus, interacts directly with actin. The interaction of Toc159 and actin was identified by co-immunoprecipitation and co-sedimentation experiments with detergent-solubilised pea chloroplast envelope membranes. In addition, many of the components of the TOC-TIC protein import apparatus and VIPP1 (vesicle-inducing protein in plastids 1) were identified by mass spectroscopy in the material co-immunoprecipitated with antibodies to actin. Toc159 is the receptor for the import of photosynthesis proteins and VIPP1 is involved in thylakoid membrane formation by inducing vesicle formation from the chloroplast inner envelope membrane, suggesting we may have identified an actin-TOC-TIC-VIPP1 complex that may provide a means of channeling cytosolic preproteins to the thylakoid membrane. The interaction of Toc159 with actin may facilitate exchange between the putative soluble and membrane forms of Toc159 and promote the interaction of cytosolic preproteins with the TOC complex.

Rho-GTPase effector ROCK phosphorylates cofilin in actin-meditated cytokinesis during mouse oocyte meiosis.

Science.gov (United States)

Duan, Xing; Liu, Jun; Dai, Xiao-Xin; Liu, Hong-Lin; Cui, Xiang-Shun; Kim, Nam-Hyung; Wang, Zhen-Bo; Wang, Qiang; Sun, Shao-Chen

2014-02-01

During oocyte meiosis, a spindle forms in the central cytoplasm and migrates to the cortex. Subsequently, the oocyte extrudes a small body and forms a highly polarized egg; this process is regulated primarily by actin. ROCK is a Rho-GTPase effector that is involved in various cellular functions, such as stress fiber formation, cell migration, tumor cell invasion, and cell motility. In this study, we investigated possible roles for ROCK in mouse oocyte meiosis. ROCK was localized around spindles after germinal vesicle breakdown and was colocalized with cytoplasmic actin and mitochondria. Disrupting ROCK activity by RNAi or an inhibitor resulted in cell cycle progression and polar body extrusion failure. Time-lapse microscopy showed that this may have been due to spindle migration and cytokinesis defects, as chromosomes segregated but failed to extrude a polar body and then realigned. Actin expression at oocyte membranes and in cytoplasm was significantly decreased after these treatments. Actin caps were also disrupted, which was confirmed by a failure to form cortical granule-free domains. The mitochondrial distribution was also disrupted, which indicated that mitochondria were involved in the ROCK-mediated actin assembly. In addition, the phosphorylation levels of Cofilin, a downstream molecule of ROCK, decreased after disrupting ROCK activity. Thus, our results indicated that a ROCK-Cofilin-actin pathway regulated meiotic spindle migration and cytokinesis during mouse oocyte maturation.

Malignant transformation of superficial peritoneal endometriosis lesion.

Science.gov (United States)

Marchand, Eva; Hequet, Delphine; Thoury, Anne; Barranger, Emmanuel

2013-08-26

A 63-year-old woman with no medical history underwent an abdominal surgery with hysterectomy and bilateral salpingo-oophorectomy for a 10 cm peritoneal cyst with increased cancer antigene-125. A large suspicious tumour of the Douglas space, with contact to the uterus and the rectal wall was described. The rest of the exploration was normal, specially the rest of the peritoneum. Histopathology revealed a malignant transformation of a superficial peritoneal endometriosis. Secondary surgery was thus completed by laparoscopy with bilateral pelvic and para-aortic lymph node dissections, omentectomy and multiple peritoneal biopsies. All staging samples were free of cancer; therefore no complementary therapy was administered. After 18 months of follow-up, consisting of clinical examination and pelvis magnetic resonance imaging every 6 months, we did not observe any recurrence. Malignant transformation of superficial peritoneal endometriosis is a rare disease and surgical management seems to be the main treatment.

Control of Electrostatic Interactions Between F-Actin And Genetically Modified Lysozyme in Aqueous Media

International Nuclear Information System (INIS)

Sanders, L.K.; Xian, W.; Guaqueta, C.; Strohman, M.; Vrasich, C.R.; Luijten, E.; Wong, G.C.L.

2009-01-01

The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

Castelli di carta. La piega per la costruzione di superfici articolate

Directory of Open Access Journals (Sweden)

Andrea Casale

2012-06-01

Full Text Available L’antica arte del piegare la carta, l’Origami, sta vivendo un rinnovato interesse che coinvolge molti aspetti della ricerca.  Con il termine origami, si intende lo studio del modo di piegare il foglio di carta per imporgli una specifica forma.  La superficie tassellata per mezzo di specifiche pieghe, si propone come un nuovo soggetto di studio: la superficie piegata articolata. La forma congiunta al movimento, assume un particolare interesse nella contemporanea ricerca geometrica e architettonica. Il panorama contemporaneo, propone opere di architettura “responsiva”, capaci di modificare le proprie caratteristiche per adeguarsi a nuove condizioni. La superficie piegata articolata sembra particolarmente adatta a descrivere questo modo d’intendere l’architettura, reagendo a diverse volontà e di conseguenza modificando la propria conformazione attraverso un attento controllo progettuale della forma.

Valoración de la superficie del dializador en la hemodiafiltración on-line. Elección objetiva de la superficie del dializador

Directory of Open Access Journals (Sweden)

Francisco Maduell

2015-05-01

Conclusión: El incremento del 40% y el 80% de la superficie conlleva un aumento del volumen convectivo de un 6 y un 16% respectivamente, aunque se evidenció una reducción en su máximo rendimiento, mostrando mínimas diferencias tanto en el volumen convectivo como en la capacidad depurativa cuando el CUF era superior a 45 ml/h/mmHg. Es recomendable optimizar el rendimiento de los dializadores a la mínima superficie posible adecuando la prescripción de tratamiento.

Triptolide disrupts the actin-based Sertoli-germ cells adherens junctions by inhibiting Rho GTPases expression

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiang; Zhao, Fang [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China); Lv, Zhong-ming; Shi, Wei-qin [Jiangsu Provincial Center for Disease Control and Prevention, Nanjing (China); Zhang, Lu-yong, E-mail: lyzhang@cpu.edu.cn [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China); Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing (China); State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009 (China); Yan, Ming, E-mail: brookming@cpu.edu.cn [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China)

2016-11-01

Triptolide (TP), derived from the medicinal plant Triterygium wilfordii Hook. f. (TWHF), is a diterpene triepoxide with variety biological and pharmacological activities. However, TP has been restricted in clinical application due to its narrow therapeutic window especially in reproductive system. During spermatogenesis, Sertoli cell cytoskeleton plays an essential role in facilitating germ cell movement and cell-cell actin-based adherens junctions (AJ). At Sertoli cell-spermatid interface, the anchoring device is a kind of AJ, known as ectoplasmic specializations (ES). In this study, we demonstrate that β-actin, an important component of cytoskeleton, has been significantly down-regulated after TP treatment. TP can inhibit the expression of Rho GTPase such as, RhoA, RhoB, Cdc42 and Rac1. Downstream of Rho GTPase, Rho-associated protein kinase (ROCKs) gene expressions were also suppressed by TP. F-actin immunofluorescence proved that TP disrupts Sertoli cells cytoskeleton network. As a result of β-actin down-regulation, TP treatment increased expression of testin, which indicating ES has been disassembled. In summary, this report illustrates that TP induces cytoskeleton dysfunction and disrupts cell-cell adherens junctions via inhibition of Rho GTPases. - Highlights: • Triptolide induced the disruption of Sertoli-germ cell adherens junction. • Rho GTPases expression and actin dynamics have been suppressed by triptolide. • Actin-based adherens junction is a potential antifertility target of triptolide. • Rho-Rock is involved in the regulation of actin dynamics.

Triptolide disrupts the actin-based Sertoli-germ cells adherens junctions by inhibiting Rho GTPases expression

International Nuclear Information System (INIS)

Wang, Xiang; Zhao, Fang; Lv, Zhong-ming; Shi, Wei-qin; Zhang, Lu-yong; Yan, Ming

2016-01-01

Triptolide (TP), derived from the medicinal plant Triterygium wilfordii Hook. f. (TWHF), is a diterpene triepoxide with variety biological and pharmacological activities. However, TP has been restricted in clinical application due to its narrow therapeutic window especially in reproductive system. During spermatogenesis, Sertoli cell cytoskeleton plays an essential role in facilitating germ cell movement and cell-cell actin-based adherens junctions (AJ). At Sertoli cell-spermatid interface, the anchoring device is a kind of AJ, known as ectoplasmic specializations (ES). In this study, we demonstrate that β-actin, an important component of cytoskeleton, has been significantly down-regulated after TP treatment. TP can inhibit the expression of Rho GTPase such as, RhoA, RhoB, Cdc42 and Rac1. Downstream of Rho GTPase, Rho-associated protein kinase (ROCKs) gene expressions were also suppressed by TP. F-actin immunofluorescence proved that TP disrupts Sertoli cells cytoskeleton network. As a result of β-actin down-regulation, TP treatment increased expression of testin, which indicating ES has been disassembled. In summary, this report illustrates that TP induces cytoskeleton dysfunction and disrupts cell-cell adherens junctions via inhibition of Rho GTPases. - Highlights: • Triptolide induced the disruption of Sertoli-germ cell adherens junction. • Rho GTPases expression and actin dynamics have been suppressed by triptolide. • Actin-based adherens junction is a potential antifertility target of triptolide. • Rho-Rock is involved in the regulation of actin dynamics.

Impaired recycling of synaptic vesicles after acute perturbation of the presynaptic actin cytoskeleton

DEFF Research Database (Denmark)

Shupliakov, Oleg; Bloom, Ona; Gustafsson, Jenny S

2002-01-01

Actin is an abundant component of nerve terminals that has been implicated at multiple steps of the synaptic vesicle cycle, including reversible anchoring, exocytosis, and recycling of synaptic vesicles. In the present study we used the lamprey reticulospinal synapse to examine the role of actin ...

Cations Stiffen Actin Filaments by Adhering a Key Structural Element to Adjacent Subunits

Science.gov (United States)

2016-01-01

Ions regulate the assembly and mechanical properties of actin filaments. Recent work using structural bioinformatics and site-specific mutagenesis favors the existence of two discrete and specific divalent cation binding sites on actin filaments, positioned in the long axis between actin subunits. Cation binding at one site drives polymerization, while the other modulates filament stiffness and plays a role in filament severing by the regulatory protein, cofilin. Existing structural methods have not been able to resolve filament-associated cations, and so in this work we turn to molecular dynamics simulations to suggest a candidate binding pocket geometry for each site and to elucidate the mechanism by which occupancy of the “stiffness site” affects filament mechanical properties. Incorporating a magnesium ion in the “polymerization site” does not seem to require any large-scale change to an actin subunit’s conformation. Binding of a magnesium ion in the “stiffness site” adheres the actin DNase-binding loop (D-loop) to its long-axis neighbor, which increases the filament torsional stiffness and bending persistence length. Our analysis shows that bound D-loops occupy a smaller region of accessible conformational space. Cation occupancy buries key conserved residues of the D-loop, restricting accessibility to regulatory proteins and enzymes that target these amino acids. PMID:27146246

Superficial fungal infections.

Science.gov (United States)

Schwartz, Robert A

Superficial fungal infections arise from a pathogen that is restricted to the stratum corneum, with little or no tissue reaction. In this Seminar, three types of infection will be covered: tinea versicolor, piedra, and tinea nigra. Tinea versicolor is common worldwide and is caused by Malassezia spp, which are human saprophytes that sometimes switch from yeast to pathogenic mycelial form. Malassezia furfur, Malassezia globosa, and Malassezia sympodialis are most closely linked to tinea versicolor. White and black piedra are both common in tropical regions of the world; white piedra is also endemic in temperate climates. Black piedra is caused by Piedraia hortae; white piedra is due to pathogenic species of the Trichosporon genus. Tinea nigra is also common in tropical areas and has been confused with melanoma.

Correlated waves of actin filaments and PIP3 in Dictyostelium cells.

Science.gov (United States)

Asano, Yukako; Nagasaki, Akira; Uyeda, Taro Q P

2008-12-01

Chemotaxis-deficient amiB-null mutant Dictyostelium cells show two distinct movements: (1) they extend protrusions randomly without net displacements; (2) they migrate persistently and unidirectionally in a keratocyte-like manner. Here, we monitored the intracellular distribution of phosphatidylinositol (3,4,5)-trisphosphate (PIP(3)) to gain insight into roles PIP(3) plays in those spontaneous motilities. In keratocyte-like cells, PIP(3) showed convex distribution over the basal membrane, with no anterior enrichment. In stalled cells, as well as in wild type cells, PIP(3) repeated wave-like changes, including emergence, expansion and disappearance, on the basal membrane. The waves induced lamellipodia when they approached the cell edge, and the advancing speed of the waves was comparable to the migration speed of the keratocyte-like cells. LY294002, an inhibitor of PI3 kinase, abolished PIP(3) waves in stalled cells and stopped keratocyte-like cells. These results together suggested that keratocyte-like cells are "surfing" on the PIP(3) waves by coupling steady lamellipodial protrusions to the PIP(3) waves. Simultaneous live observation of actin filaments and PIP(3) in wild type or stalled amiB(-) cells indicated that the PIP(3) waves were correlated with wave-like distributions of actin filaments. Most notably, PIP(3) waves often followed actin waves, suggesting that PIP(3) induces local depolymerization of actin filaments. Consistent with this idea, cortical accumulation of PIP(3) was often correlated with local retraction of the periphery. We propose that the waves of PIP(3) and actin filaments are loosely coupled with each other and play important roles in generating spontaneous cell polarity. Copyright 2008 Wiley-Liss, Inc.

Molecular typing of Trichomonas vaginalis isolates by actin gene sequence analysis and carriage of T. vaginalis viruses.

Science.gov (United States)

Masha, Simon C; Cools, Piet; Crucitti, Tania; Sanders, Eduard J; Vaneechoutte, Mario

2017-10-30

The protozoan parasite Trichomonas vaginalis is the most common non-viral, sexually transmitted pathogen. Although T. vaginalis is highly prevalent among women in Kenya, there is lack of data regarding genetic diversity of isolates currently in circulation in Kenya. Typing was performed on 22 clinical isolates of T. vaginalis collected from women attending the antenatal care clinic at Kilifi County Hospital, Kenya, in 2015. Genotyping followed a previously proposed restriction fragment length polymorphism (RFLP) scheme, which involved in silico cleavage of the amplified actin gene by HindII, MseI and RsaI restriction enzymes. Phylogenetic analysis of all the sequences was performed to confirm the results obtained by RFLP-analysis and to assess the diversity within the RFLP genotypes. Additionally, we determined carriage of the four different types of Trichomonas vaginalis viruses (TVVs) by polymerase chain reaction. In silico RFLP-analysis revealed five actin genotypes; 50.0% of the isolates were of actin genotype E, 27.3% of actin genotype N, 13.6% of actin genotype G and 4.5% of actin genotypes I and P. Phylogenetic analysis was in agreement with the RFLP-analysis, with the different actin genotypes clustering together. Prevalence of TVVs was 43.5% (95% confidence interval, CI: 23.2-65.5). TVV1 was the most prevalent, present in 39.1% of the strains and 90% of the T. vaginalis isolates which harbored TVVs had more than one type of TVV. None of the isolates of actin genotype E harbored any TVV. The presence of five actin genotypes in our study suggests notable diversity among T. vaginalis isolates occurring among pregnant women in Kilifi, Kenya. Isolates of the most prevalent actin genotype E lacked TVVs. We found no association between T. vaginalis genotype, carriage of TVVs and symptoms. Further studies with higher number of strains should be conducted in order to corroborate these results.

Loss of γ-cytoplasmic actin triggers myofibroblast transition of human epithelial cells.

Science.gov (United States)

Lechuga, Susana; Baranwal, Somesh; Li, Chao; Naydenov, Nayden G; Kuemmerle, John F; Dugina, Vera; Chaponnier, Christine; Ivanov, Andrei I

2014-10-15

Transdifferentiation of epithelial cells into mesenchymal cells and myofibroblasts plays an important role in tumor progression and tissue fibrosis. Such epithelial plasticity is accompanied by dramatic reorganizations of the actin cytoskeleton, although mechanisms underlying cytoskeletal effects on epithelial transdifferentiation remain poorly understood. In the present study, we observed that selective siRNA-mediated knockdown of γ-cytoplasmic actin (γ-CYA), but not β-cytoplasmic actin, induced epithelial-to-myofibroblast transition (EMyT) of different epithelial cells. The EMyT manifested by increased expression of α-smooth muscle actin and other contractile proteins, along with inhibition of genes responsible for cell proliferation. Induction of EMyT in γ-CYA-depleted cells depended on activation of serum response factor and its cofactors, myocardial-related transcriptional factors A and B. Loss of γ-CYA stimulated formin-mediated actin polymerization and activation of Rho GTPase, which appear to be essential for EMyT induction. Our findings demonstrate a previously unanticipated, unique role of γ-CYA in regulating epithelial phenotype and suppression of EMyT that may be essential for cell differentiation and tissue fibrosis. © 2014 Lechuga, Baranwal, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Modulation of actin dynamics as potential macrophage subtype-targeting anti-tumour strategy.

Science.gov (United States)

Pergola, Carlo; Schubert, Katrin; Pace, Simona; Ziereisen, Jana; Nikels, Felix; Scherer, Olga; Hüttel, Stephan; Zahler, Stefan; Vollmar, Angelika M; Weinigel, Christina; Rummler, Silke; Müller, Rolf; Raasch, Martin; Mosig, Alexander; Koeberle, Andreas; Werz, Oliver

2017-01-30

Tumour-associated macrophages mainly comprise immunosuppressive M2 phenotypes that promote tumour progression besides anti-tumoural M1 subsets. Selective depletion or reprogramming of M2 may represent an innovative anti-cancer strategy. The actin cytoskeleton is central for cellular homeostasis and is targeted for anti-cancer chemotherapy. Here, we show that targeting G-actin nucleation using chondramide A (ChA) predominantly depletes human M2 while promoting the tumour-suppressive M1 phenotype. ChA reduced the viability of M2, with minor effects on M1, but increased tumour necrosis factor (TNF)α release from M1. Interestingly, ChA caused rapid disruption of dynamic F-actin filaments and polymerization of G-actin, followed by reduction of cell size, binucleation and cell division, without cellular collapse. In M1, but not in M2, ChA caused marked activation of SAPK/JNK and NFκB, with slight or no effects on Akt, STAT-1/-3, ERK-1/2, and p38 MAPK, seemingly accounting for the better survival of M1 and TNFα secretion. In a microfluidically-supported human tumour biochip model, circulating ChA-treated M1 markedly reduced tumour cell viability through enhanced release of TNFα. Together, ChA may cause an anti-tumoural microenvironment by depletion of M2 and activation of M1, suggesting induction of G-actin nucleation as potential strategy to target tumour-associated macrophages in addition to neoplastic cells.

Isoflurane reversibly destabilizes hippocampal dendritic spines by an actin-dependent mechanism.

Directory of Open Access Journals (Sweden)

Jimcy Platholi

Full Text Available General anesthetics produce a reversible coma-like state through modulation of excitatory and inhibitory synaptic transmission. Recent evidence suggests that anesthetic exposure can also lead to sustained cognitive dysfunction. However, the subcellular effects of anesthetics on the structure of established synapses are not known. We investigated effects of the widely used volatile anesthetic isoflurane on the structural stability of hippocampal dendritic spines, a postsynaptic structure critical to excitatory synaptic transmission in learning and memory. Exposure to clinical concentrations of isoflurane induced rapid and non-uniform shrinkage and loss of dendritic spines in mature cultured rat hippocampal neurons. Spine shrinkage was associated with a reduction in spine F-actin concentration. Spine loss was prevented by either jasplakinolide or cytochalasin D, drugs that prevent F-actin disassembly. Isoflurane-induced spine shrinkage and loss were reversible upon isoflurane elimination. Thus, isoflurane destabilizes spine F-actin, resulting in changes to dendritic spine morphology and number. These findings support an actin-based mechanism for isoflurane-induced alterations of synaptic structure in the hippocampus. These reversible alterations in dendritic spine structure have important implications for acute anesthetic effects on excitatory synaptic transmission and synaptic stability in the hippocampus, a locus for anesthetic-induced amnesia, and have important implications for anesthetic effects on synaptic plasticity.

Mena-GRASP65 interaction couples actin polymerization to Golgi ribbon linking.

Science.gov (United States)

Tang, Danming; Zhang, Xiaoyan; Huang, Shijiao; Yuan, Hebao; Li, Jie; Wang, Yanzhuang

2016-01-01

In mammalian cells, the Golgi reassembly stacking protein 65 (GRASP65) has been implicated in both Golgi stacking and ribbon linking by forming trans-oligomers through the N-terminal GRASP domain. Because the GRASP domain is globular and relatively small, but the gaps between stacks are large and heterogeneous, it remains puzzling how GRASP65 physically links Golgi stacks into a ribbon. To explore the possibility that other proteins may help GRASP65 in ribbon linking, we used biochemical methods and identified the actin elongation factor Mena as a novel GRASP65-binding protein. Mena is recruited onto the Golgi membranes through interaction with GRASP65. Depleting Mena or disrupting actin polymerization resulted in Golgi fragmentation. In cells, Mena and actin were required for Golgi ribbon formation after nocodazole washout; in vitro, Mena and microfilaments enhanced GRASP65 oligomerization and Golgi membrane fusion. Thus Mena interacts with GRASP65 to promote local actin polymerization, which facilitates Golgi ribbon linking. © 2016 Tang et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Actin and Endocytosis in Budding Yeast

Science.gov (United States)

Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

2015-01-01

Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed. PMID:25657349

Experiments on the superficial irradiation of spherical vegetables and fruits

International Nuclear Information System (INIS)

Kalman, B.; Kiraly, Z.

1974-01-01

A revolving facility was made for the homogeneous superficial irradiation of spherical vegetables and fruits (apricot, peach, tomato, apple, etc.) with fast electrons. After the building of the technological apparatus described in detail, dosimetrical measurements were carried out by a Van de Graff generator of 2 MV and it was proved, that the superficial irradiation had a smaller effect on the quality of the fresh fruits, than of the stored ones. The developed apparatus can be altered according to the ripe-rate of the products. (K.A.)

Elucidating Key Motifs Required for Arp2/3-Dependent and Independent Actin Nucleation by Las17/WASP

Science.gov (United States)

Urbanek, Agnieszka N.; Smaczynska-de Rooij, Iwona I.

2016-01-01

Actin nucleation is the key rate limiting step in the process of actin polymerization, and tight regulation of this process is critical to ensure actin filaments form only at specific times and at defined regions of the cell. Arp2/3 is a well-characterised protein complex that can promote nucleation of new filaments, though its activity requires additional nucleation promotion factors (NPFs). The best recognized of these factors are the WASP family of proteins that contain binding motifs for both monomeric actin and for Arp2/3. Previously we demonstrated that the yeast WASP homologue, Las17, in addition to activating Arp2/3 can also nucleate actin filaments de novo, independently of Arp2/3. This activity is dependent on its polyproline rich region. Through biochemical and in vivo analysis we have now identified key motifs within the polyproline region that are required for nucleation and elongation of actin filaments, and have addressed the role of the WH2 domain in the context of actin nucleation without Arp2/3. We have also demonstrated that full length Las17 is able to bind liposomes giving rise to the possibility of direct linkage of nascent actin filaments to specific membrane sites to which Las17 has been recruited. Overall, we propose that Las17 functions as the key initiator of de novo actin filament formation at endocytic sites by nucleating, elongating and tethering nascent filaments which then serve as a platform for Arp2/3 recruitment and function. PMID:27637067

Characterization of f-actin tryptophan phosphorescence in the presence and absence of tryptophan-free myosin motor domain.

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Bódis, Emöke; Strambini, Giovanni B; Gonnelli, Margherita; Málnási-Csizmadia, András; Somogyi, Béla

2004-08-01

The effect of binding the Trp-free motor domain mutant of Dictyostelium discoideum, rabbit skeletal muscle myosin S1, and tropomyosin on the dynamics and conformation of actin filaments was characterized by an analysis of steady-state tryptophan phosphorescence spectra and phosphorescence decay kinetics over a temperature range of 140-293 K. The binding of the Trp-free motor domain mutant of D. discoideum to actin caused red shifts in the phosphorescence spectrum of two internal Trp residues of actin and affected the intrinsic lifetime of each emitter, decreasing by roughly twofold the short phosphorescence lifetime components (tau(1) and tau(2)) and increasing by approximately 20% the longest component (tau(3)). The alteration of actin phosphorescence by the motor protein suggests that i), structural changes occur deep down in the core of actin and that ii), subtle changes in conformation appear also on the surface but in regions distant from the motor domain binding site. When actin formed complexes with skeletal S1, an extra phosphorescence lifetime component appeared (tau(4), twice as long as tau(3)) in the phosphorescence decay that is absent in the isolated proteins. The lack of this extra component in the analogous actin-Trp-free motor domain mutant of D. discoideum complex suggests that it should be assigned to Trps in S1 that in the complex attain a more compact local structure. Our data indicated that the binding of tropomyosin to actin filaments had no effect on the structure or flexibility of actin observable by this technique.

Spatiotemporal dynamics of actin remodeling and endomembrane trafficking in alveolar epithelial type I cell wound healing.

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Godin, Lindsay M; Vergen, Jorge; Prakash, Y S; Pagano, Richard E; Hubmayr, Rolf D

2011-04-01

Alveolar epithelial type I cell (ATI) wounding is prevalent in ventilator-injured lungs and likely contributes to pathogenesis of "barotrauma" and "biotrauma." In experimental models most wounded alveolar cells repair plasma membrane (PM) defects and survive insults. Considering the force balance between edge energy at the PM wound margins and adhesive interactions of the lipid bilayer with the underlying cytoskeleton (CSK), we tested the hypothesis that subcortical actin depolymerization is a key facilitator of PM repair. Using real-time fluorescence imaging of primary rat ATI transfected with a live cell actin-green fluorescent protein construct (Lifeact-GFP) and loaded with N-rhodamine phosphatidylethanolamine (PE), we examined the spatial and temporal coordination between cytoskeletal remodeling and PM repair following micropuncture. Membrane integrity was inferred from the fluorescence intensity profiles of the cytosolic label calcein AM. Wounding led to rapid depolymerization of the actin CSK near the wound site, concurrent with accumulation of endomembrane-derived N-rhodamine PE. Both responses were sustained until PM integrity was reestablished, which typically occurs between ∼10 and 40 s after micropuncture. Only thereafter did the actin CSK near the wound begin to repolymerize, while the rate of endomembrane lipid accumulation decreased. Between 60 and 90 s after successful PM repair, after translocation of the actin nucleation factor cortactin, a dense actin fiber network formed. In cells that did not survive micropuncture injury, actin remodeling did not occur. These novel results highlight the importance of actin remodeling in ATI cell repair and suggest molecular targets for modulating the repair process.

[The coiled bodies and satellite microbodies of the oocyte nuclei in hibernating Rana temporaria frogs contain actin].

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Tsvetkov, A G; Kvasov, I D; Khaĭtlina, S Iu; Parfenov, V N

1997-01-01

Immunocytochemical analysis of preparation of dispersed nuclei content in oocytes of III-IV stages of oogenesis, in terms of Dumont (1972), from hibernating grass frogs using monoclonal antibodies against actin, revealed two types of intranuclear structures containing this protein: coiled bodies (CB) and satellite microbodies (SM). Staining of these preparations with Rhodamin-phalloidin, known specifically to interact with fibrillar actin, did not reveal it in these structures. Results of our biochemical studies, using protease ESP32 specifically cutting only globular actin, are suggesting that both CB and SM contain globular actin. Gall et al. (1975) proposed that CB may be involved in assembling and sorting of small nuclear RNA for the three main RNA processing pathways: pre-mRNA splicing, pre-rRNA processing, and histone pre-mRNA 3'-end formation. Our finding of actin in CB allows a suggestion on actin involvement in the transport of RNA processing complexes from CB to some actual places where processing of RNA takes place. According to our previous data (Tsvetkov, Parfenov., 1994), SM participate in the karyosphere capsule formation. This process is preceded by SM fusion triggered presumably by actin.

Boron nitride nanotube-mediated stimulation modulates F/G-actin ratio and mechanical properties of human dermal fibroblasts

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Ricotti, Leonardo; das Neves, Ricardo Pires; Ciofani, Gianni; Canale, Claudio; Nitti, Simone; Mattoli, Virgilio; Mazzolai, Barbara; Ferreira, Lino; Menciassi, Arianna

2014-02-01

F/G-actin ratio modulation is known to have an important role in many cell functions and in the regulation of specific cell behaviors. Several attempts have been made in the latest decades to finely control actin production and polymerization, in order to promote certain cell responses. In this paper we demonstrate the possibility of modulating F/G-actin ratio and mechanical properties of normal human dermal fibroblasts by using boron nitride nanotubes dispersed in the culture medium and by stimulating them with ultrasound transducers. Increasing concentrations of nanotubes were tested with the cells, without any evidence of cytotoxicity up to 10 μg/ml concentration of nanoparticles. Cells treated with nanoparticles and ultrasound stimulation showed a significantly higher F/G-actin ratio in comparison with the controls, as well as a higher Young's modulus. Assessment of Cdc42 activity revealed that actin nucleation/polymerization pathways, involving Rho GTPases, are probably influenced by nanotube-mediated stimulation, but they do not play a primary role in the significant increase of F/G-actin ratio of treated cells, such effect being mainly due to actin overexpression.

EZH2-mediated α-actin methylation needs lncRNA TUG1, and promotes the cortex cytoskeleton formation in VSMCs.

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Chen, Rong; Kong, Peng; Zhang, Fan; Shu, Ya-Nan; Nie, Xi; Dong, Li-Hua; Lin, Yan-Ling; Xie, Xiao-Li; Zhao, Li-Li; Zhang, Xiang-Jian; Han, Mei

2017-06-15

Recent studies have revealed that long non-coding RNAs (lncRNAs) participate in vascular homeostasis and pathophysiological conditions development. But still very few literatures elucidate the regulatory mechanism of non-coding RNAs in this biological process. Here we identified lncRNA taurine up-regulated gene 1 (TUG1) in rat vascular smooth muscle cells (VSMCs), and got 4612bp nucleotide sequence. The expression level of TUG1 RNA was increased in synthetic VSMCs by real-time PCR analysis. Meanwhile, the expression of enhancer of zeste homolog 2 (EZH2) (TUG1 binding protein) increased in cytoplasm of VSMCs under the same conditions. Immunofluoresce analysis displayed the colocalization of EZH2 with α-actin in cytoplasm and F-actin in cell edge ruffles. This leads us to hypothesize the existence of cytoplasmic TUG1/EZH2/α-actin complex. Using RNA pull down assay, we found that TUG1 interacted with both EZH2 and α-actin. Disruption of TUG1 abolished the interaction of EZH2 with α-actin, and accelerated depolymerization of F-actin in VSMCs. Based on EZH2 methyltransferase activity and the potential methylation sites in α-actin structure, we revealed that α-actin was lysine-methylated. Furthermore, the methylation of α-actin was inhibited by knockdown of TUG1. In conclusion, these findings partly suggested that EZH2-mediated methylation of α-actin may be dependent on TUG1, and thereby promotes cortex F-actin polymerization in synthetic VSMCs. Copyright © 2017. Published by Elsevier B.V.

Contribution of the LIM domain and nebulin-repeats to the interaction of Lasp-2 with actin filaments and focal adhesions.

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Hiroyuki Nakagawa

Full Text Available Lasp-2 binds to actin filaments and concentrates in the actin bundles of filopodia and lamellipodia in neural cells and focal adhesions in fibroblastic cells. Lasp-2 has three structural regions: a LIM domain, a nebulin-repeat region, and an SH3 domain; however, the region(s responsible for its interactions with actin filaments and focal adhesions are still unclear. In this study, we revealed that the N-terminal fragment from the LIM domain to the first nebulin-repeat module (LIM-n1 retained actin-binding activity and showed a similar subcellular localization to full-length lasp-2 in neural cells. The LIM domain fragment did not interact with actin filaments or localize to actin filament bundles. In contrast, LIM-n1 showed a clear subcellular localization to filopodial actin bundles. Although truncation of the LIM domain caused the loss of F-actin binding activity and the accumulation of filopodial actin bundles, these truncated fragments localized to focal adhesions. These results suggest that lasp-2 interactions with actin filaments are mediated through the cooperation of the LIM domain and the first nebulin-repeat module in vitro and in vivo. Actin filament binding activity may be a major contributor to the subcellular localization of lasp-2 to filopodia but is not crucial for lasp-2 recruitment to focal adhesions.

Multiple essential functions of Plasmodium falciparum actin-1 during malaria blood-stage development.

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Das, Sujaan; Lemgruber, Leandro; Tay, Chwen L; Baum, Jake; Meissner, Markus

2017-08-15

The phylum Apicomplexa includes intracellular parasites causing immense global disease burden, the deadliest of them being the human malaria parasite Plasmodium falciparum, which invades and replicates within erythrocytes. The cytoskeletal protein actin is well conserved within apicomplexans but divergent from mammalian actins, and was primarily reported to function during host cell invasion. However, novel invasion mechanisms have been described for several apicomplexans, and specific functions of the acto-myosin system are being reinvestigated. Of the two actin genes in P. falciparum, actin-1 (pfact1) is ubiquitously expressed in all life-cycle stages and is thought to be required for erythrocyte invasion, although its functions during parasite development are unknown, and definitive in vivo characterisation during invasion is lacking. Here we have used a conditional Cre-lox system to investigate the functions of PfACT1 during P. falciparum blood-stage development and host cell invasion. We demonstrate that PfACT1 is crucially required for segregation of the plastid-like organelle, the apicoplast, and for efficient daughter cell separation during the final stages of cytokinesis. Surprisingly, we observe that egress from the host cell is not an actin-dependent process. Finally, we show that parasites lacking PfACT1 are capable of microneme secretion, attachment and formation of a junction with the erythrocyte, but are incapable of host cell invasion. This study provides important mechanistic insights into the definitive essential functions of PfACT1 in P. falciparum, which are not only of biological interest, but owing to functional divergence from mammalian actins, could also form the basis for the development of novel therapeutics against apicomplexans.

Rictor positively regulates B cell receptor signaling by modulating actin reorganization via ezrin.

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Lu Huang

2017-08-01

Full Text Available As the central hub of the metabolism machinery, the mammalian target of rapamycin complex 2 (mTORC2 has been well studied in lymphocytes. As an obligatory component of mTORC2, the role of Rictor in T cells is well established. However, the role of Rictor in B cells still remains elusive. Rictor is involved in B cell development, especially the peripheral development. However, the role of Rictor on B cell receptor (BCR signaling as well as the underlying cellular and molecular mechanism is still unknown. This study used B cell-specfic Rictor knockout (KO mice to investigate how Rictor regulates BCR signaling. We found that the key positive and negative BCR signaling molecules, phosphorylated Brutons tyrosine kinase (pBtk and phosphorylated SH2-containing inositol phosphatase (pSHIP, are reduced and enhanced, respectively, in Rictor KO B cells. This suggests that Rictor positively regulates the early events of BCR signaling. We found that the cellular filamentous actin (F-actin is drastically increased in Rictor KO B cells after BCR stimulation through dysregulating the dephosphorylation of ezrin. The high actin-ezrin intensity area restricts the lateral movement of BCRs upon stimulation, consequently reducing BCR clustering and BCR signaling. The reduction in the initiation of BCR signaling caused by actin alteration is associated with a decreased humoral immune response in Rictor KO mice. The inhibition of actin polymerization with latrunculin in Rictor KO B cells rescues the defects of BCR signaling and B cell differentiation. Overall, our study provides a new pathway linking cell metablism to BCR activation, in which Rictor regulates BCR signaling via actin reorganization.

The N-terminal tropomyosin- and actin-binding sites are important for leiomodin 2's function.

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Ly, Thu; Moroz, Natalia; Pappas, Christopher T; Novak, Stefanie M; Tolkatchev, Dmitri; Wooldridge, Dayton; Mayfield, Rachel M; Helms, Gregory; Gregorio, Carol C; Kostyukova, Alla S

2016-08-15

Leiomodin is a potent actin nucleator related to tropomodulin, a capping protein localized at the pointed end of the thin filaments. Mutations in leiomodin-3 are associated with lethal nemaline myopathy in humans, and leiomodin-2-knockout mice present with dilated cardiomyopathy. The arrangement of the N-terminal actin- and tropomyosin-binding sites in leiomodin is contradictory and functionally not well understood. Using one-dimensional nuclear magnetic resonance and the pointed-end actin polymerization assay, we find that leiomodin-2, a major cardiac isoform, has an N-terminal actin-binding site located within residues 43-90. Moreover, for the first time, we obtain evidence that there are additional interactions with actin within residues 124-201. Here we establish that leiomodin interacts with only one tropomyosin molecule, and this is the only site of interaction between leiomodin and tropomyosin. Introduction of mutations in both actin- and tropomyosin-binding sites of leiomodin affected its localization at the pointed ends of the thin filaments in cardiomyocytes. On the basis of our new findings, we propose a model in which leiomodin regulates actin poly-merization dynamics in myocytes by acting as a leaky cap at thin filament pointed ends. © 2016 Ly, Moroz, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Evaluating optimal superficial limb perfusion at different angles using non-invasive micro-lightguide spectrophotometry.

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Darmanin, Geraldine; Jaggard, Matthew; Hettiaratchy, Shehan; Nanchahal, Jagdeep; Jain, Abhilash

2013-06-01

It is common practice to elevate the limbs postoperatively to reduce oedema and hence optimise perfusion and facilitate rehabilitation. However, elevation may be counterproductive as it reduces the mean perfusion pressure. There are no clear data on the optimal position of the limbs even in normal subjects. The optimal position of limbs was investigated in 25 healthy subjects using a non-invasive micro-lightguide spectrophotometry system "O2C", which indirectly measures skin and superficial tissue perfusion through blood flow, oxygen saturation and relative haemoglobin concentration. We found a reduction in skin and superficial tissue blood flow of 17% (p=0.0001) on arm elevation (180° shoulder flexion) as compared to heart level and an increase in skin and superficial tissue blood flow of 25% (p=0.02) on forearm elevation of 45°. Lower limb skin and superficial tissue blood flow decreased by 15% (p=0.004) on elevation to 47 cm and by 70% on dependency (p=0.0001) compared to heart level. However, on elevation of the lower limb there was also a 28% reduction in superficial venous pooling (p=0.0001) compared to heart level. In the normal limb, the position for optimal superficial perfusion of the upper limb is with the arm placed at heart level and forearm at 45°. In the lower limb the optimal position for superficial perfusion would be at heart level. However, some degree of elevation may be useful if there is an element of venous congestion. Copyright © 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Pdlim7 Regulates Arf6-Dependent Actin Dynamics and Is Required for Platelet-Mediated Thrombosis in Mice.

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Alexander E Urban

Full Text Available Upon vessel injury, platelets become activated and rapidly reorganize their actin cytoskeleton to adhere to the site of endothelial damage, triggering the formation of a fibrin-rich plug to prevent further blood loss. Inactivation of Pdlim7 provides the new perspective that regulation of actin cytoskeletal changes in platelets is dependent on the encoded PDZ-LIM protein. Loss-of-function of Pdlim7 triggers hypercoagulopathy and causes significant perinatal lethality in mice. Our in vivo and in vitro studies reveal that Pdlim7 is dynamically distributed along actin fibers, and lack of Pdlim7 leads to a marked inability to rearrange the actin cytoskeleton. Specifically, the absence of Pdlim7 prevents platelets from bundling actin fibers into a concentric ring that defines the round spread shape of activated platelets. Similarly, in mouse embryonic fibroblasts, loss of Pdlim7 abolishes the formation of stress fibers needed to adopt the typical elongated fibroblast shape. In addition to revealing a fundamental cell biological role in actin cytoskeletal organization, we also demonstrate a function of Pdlim7 in regulating the cycling between the GTP/GDP-bound states of Arf6. The small GTPase Arf6 is an essential factor required for actin dynamics, cytoskeletal rearrangements, and platelet activation. Consistent with our findings of significantly elevated initial F-actin ratios and subsequent morphological aberrations, loss of Pdlim7 causes a shift in balance towards an increased Arf6-GTP level in resting platelets. These findings identify a new Pdlim7-Arf6 axis controlling actin dynamics and implicate Pdlim7 as a primary endogenous regulator of platelet-dependent hemostasis.

Disruption of the actin cytoskeleton results in the promotion of gravitropism in inflorescence stems and hypocotyls of Arabidopsis

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Yamamoto, Kazuyoshi; Kiss, John Z.

2002-01-01

The actin cytoskeleton is hypothesized to play a major role in gravity perception and transduction mechanisms in roots of plants. To determine whether actin microfilaments (MFs) are involved in these processes in stem-like organs, we studied gravitropism in Arabidopsis inflorescence stems and hypocotyls. Localization studies using Alexa Fluor-phalloidin in conjugation with confocal microscopy demonstrated a longitudinally and transversely oriented actin MF network in endodermal cells of stems and hypocotyls. Latrunculin B (Lat-B) treatment of hypocotyls caused depolymerization of actin MFs in endodermal cells and a significant reduction of hypocotyl growth rates. Actin MFs in Lat-B-treated inflorescence stems also were disrupted, but growth rates were not affected. Despite disruption of the actin cytoskeleton in these two organs, Lat-B-treated stems and hypocotyls exhibited a promotion of gravitropic curvature in response to reorientation. In contrast, Lat-B reduced gravitropic curvature in roots but also reduced the growth rate. Thus, in contrast to prevailing hypotheses, our results suggest that actin MFs are not a necessary component of gravitropism in inflorescence stems and hypocotyls. Furthermore, this is the first study to demonstrate a prominent actin MF network in endodermal cells in the putative gravity-perceiving cells in stems.

The actin-like MreB proteins in Bacillus subtilis: a new turn.

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Chastanet, Arnaud; Carballido-Lopez, Rut

2012-06-01

A decade ago, two breakthrough descriptions were reported: 1) the first helix-like protein localization pattern of MreB and its paralog Mbl in Bacillus subtilis and 2) the crystal structure of Thermotoga maritima MreB1, which was remarkably similar to that of actin. These discoveries strongly stimulated the field of bacterial development, leading to the identification of many new cytoskeletal proteins (1) and the publication of many studies describing the helical patterns of protein, DNA and even lipid domains. However, today, new breakthroughs are shaking up what had become a dogma. Instead of helical structures, MreBs appear to form discrete patches that move circumferentially around the cell, questioning the idea of MreB cables forming an actin-like cytoskeleton. Furthermore, increasing evidence of biochemical properties that are unlike the properties of actin suggest that the molecular behavior of MreB proteins may be different. The aim of this review is to summarize the current knowledge of the so-called "actin-like" MreB cytoskeleton through a discussion of the model Gram-positive bacterium B. subtilis and the most recent findings in this rapidly evolving research field.

Actin capping protein and its inhibitor CARMIL: how intrinsically disordered regions function

International Nuclear Information System (INIS)

Takeda, Shuichi; Maéda, Yuichiro; Koike, Ryotaro; Ota, Motonori; Nitanai, Yasushi; Minakata, Shiho

2011-01-01

The actin capping protein (CP) tightly binds to the barbed end of actin filaments to block further elongation. The β-tentacle in CP is an important region that ensures stable interaction with actin filaments. CARMIL inhibits the interaction of CP with actin filaments via the C-terminal portion containing the CP-binding motif, located in an intrinsically disordered region. We have proposed an allosteric inhibition model in which CARMIL suppresses CP by the population shift mechanism. Here, we solved a crystal structure of CP in complex with a CARMIL-derived peptide, CA32. The new structure clearly represents the α-helical form of the β-tentacle that was invisible in other CP/CARMIL peptide complex structures. In addition, we exhaustively performed a normal mode analysis with the elastic network model on all available crystal structures of the CP/CARMIL peptide complexes, including the new structure. We concluded that the CP-binding motif is necessary and sufficient for altering the fluctuation of CP, which is essential for attenuating the barbed-end-capping activity along the population shift mechanism. The roles and functions of the β-tentacle and the CP-binding motif are discussed in terms of their intrinsically disordered nature

Displacement of the mitotic apparatuses by centrifugation reveals cortical actin organization during cytokinesis in cultured tobacco BY-2 cells.

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Arima, Kengo; Tamaoki, Daisuke; Mineyuki, Yoshinobu; Yasuhara, Hiroki; Nakai, Tomonori; Shimmen, Teruo; Yoshihisa, Tohru; Sonobe, Seiji

2018-06-19

In plant cytokinesis, actin is thought to be crucial in cell plate guidance to the cortical division zone (CDZ), but its organization and function are not fully understood. To elucidate actin organization during cytokinesis, we employed an experimental system, in which the mitotic apparatus is displaced and separated from the CDZ by centrifugation and observed using a global-local live imaging microscope that enabled us to record behavior of actin filaments in the CDZ and the whole cell division process in parallel. In this system, returning movement of the cytokinetic apparatus in cultured-tobacco BY-2 cells occurs, and there is an advantage to observe actin organization clearly during the cytokinetic phase because more space was available between the CDZ and the distantly formed phragmoplast. Actin cables were clearly observed between the CDZ and the phragmoplast in BY-2 cells expressing GFP-fimbrin after centrifugation. Both the CDZ and the edge of the expanding phragmoplast had actin bulges. Using live-cell imaging including the global-local live imaging microscopy, we found actin filaments started to accumulate at the actin-depleted zone when cell plate expansion started even in the cell whose cell plate failed to reach the CDZ. These results suggest that specific accumulation of actin filaments at the CDZ and the appearance of actin cables between the CDZ and the phragmoplast during cell plate formation play important roles in the guidance of cell plate edges to the CDZ.

Actin dynamics at focal adhesions: a common endpoint and putative therapeutic target for proteinuric kidney diseases.

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Sever, Sanja; Schiffer, Mario

2018-06-01

Proteinuria encompasses diverse causes including both genetic diseases and acquired forms such as diabetic and hypertensive nephropathy. The basis of proteinuria is a disturbance in size selectivity of the glomerular filtration barrier, which largely depends on the podocyte: a terminally differentiated epithelial cell type covering the outer surface of the glomerulus. Compromised podocyte structure is one of the earliest signs of glomerular injury. The phenotype of diverse animal models and podocyte cell culture firmly established the essential role of the actin cytoskeleton in maintaining functional podocyte structure. Podocyte foot processes, actin-based membrane extensions, contain 2 molecularly distinct "hubs" that control actin dynamics: a slit diaphragm and focal adhesions. Although loss of foot processes encompasses disassembly of slit diaphragm multiprotein complexes, as long as cells are attached to the glomerular basement membrane, focal adhesions will be the sites in which stress due to filtration flow is counteracted by forces generated by the actin network in foot processes. Numerous studies within last 20 years have identified actin binding and regulatory proteins as well as integrins as essential components of signaling and actin dynamics at focal adhesions in podocytes, suggesting that some of them may become novel, druggable targets for proteinuric kidney diseases. Here we review evidence supporting the idea that current treatments for chronic kidney diseases beneficially and directly target the podocyte actin cytoskeleton associated with focal adhesions and suggest that therapeutic reagents that target the focal adhesion-regulated actin cytoskeleton in foot processes have potential to modernize treatments for chronic kidney diseases. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Increased actin polymerization and stabilization interferes with neuronal function and survival in the AMPKγ mutant Loechrig.

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Mandy Cook

Full Text Available loechrig (loe mutant flies are characterized by progressive neuronal degeneration, behavioral deficits, and early death. The mutation is due to a P-element insertion in the gene for the γ-subunit of the trimeric AMP-activated protein kinase (AMPK complex, whereby the insertion affects only one of several alternative transcripts encoding a unique neuronal isoform. AMPK is a cellular energy sensor that regulates a plethora of signaling pathways, including cholesterol and isoprenoid synthesis via its downstream target hydroxy-methylglutaryl (HMG-CoA reductase. We recently showed that loe interferes with isoprenoid synthesis and increases the prenylation and thereby activation of RhoA. During development, RhoA plays an important role in neuronal outgrowth by activating a signaling cascade that regulates actin dynamics. Here we show that the effect of loe/AMPKγ on RhoA prenylation leads to a hyperactivation of this signaling pathway, causing increased phosphorylation of the actin depolymerizating factor cofilin and accumulation of filamentous actin. Furthermore, our results show that the resulting cytoskeletal changes in loe interfere with neuronal growth and disrupt axonal integrity. Surprisingly, these phenotypes were enhanced by expressing the Slingshot (SSH phosphatase, which during development promotes actin depolymerization by dephosphorylating cofilin. However, our studies suggest that in the adult SSH promotes actin polymerization, supporting in vitro studies using human SSH1 that suggested that SSH can also stabilize and bundle filamentous actin. Together with the observed increase in SSH levels in the loe mutant, our experiments suggest that in mature neurons SSH may function as a stabilization factor for filamentous actin instead of promoting actin depolymerization.

New Topical Treatment Options for Actinic Keratosis: A Systematic Review.

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Stockfleth, Eggert; Sibbring, Gillian C; Alarcon, Ivette

2016-01-01

This systematic review compared the relative efficacy of 5-fluorouracil 0.5% in salicylic acid 10% (5-FU/SA), ingenol mebutate (IMB) and imiquimod 2.5%/3.75% (IMI) for actinic keratosis on the face, forehead or scalp. Only 11 publications, relating to 7 randomised controlled trials, met inclusion criteria and it was only possible to compare the effect of all 3 treatments on complete clinical clearance, and the effect of 5-FU/SA and IMB on actinic keratosis recurrence rate. Despite a higher vehicle response rate for 5-FU/SA, complete clinical clearance was higher than IMB and IMI (55.4, 42.2, and 25.0-30.6/34.0-35.6%, [corrected] respectively). 5-FU/SA was also associated with lower actinic keratosis recurrence rate than IMB at 12 months post-treatment (32.7 vs. 53.9%). Although qualitative assessment suggested a numerical advantage of 5-FU/SA over IMB and IMI in terms of complete clinical clearance and sustained clearance, clinical data from longer term trials, with comparable outcome measures, are required to corroborate these findings.

Molecular typing of Trichomonas vaginalis isolates by actin gene sequence analysis and carriage of T. vaginalis viruses

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Simon C. Masha

2017-10-01

Full Text Available Abstract Background The protozoan parasite Trichomonas vaginalis is the most common non-viral, sexually transmitted pathogen. Although T. vaginalis is highly prevalent among women in Kenya, there is lack of data regarding genetic diversity of isolates currently in circulation in Kenya. Methods Typing was performed on 22 clinical isolates of T. vaginalis collected from women attending the antenatal care clinic at Kilifi County Hospital, Kenya, in 2015. Genotyping followed a previously proposed restriction fragment length polymorphism (RFLP scheme, which involved in silico cleavage of the amplified actin gene by HindII, MseI and RsaI restriction enzymes. Phylogenetic analysis of all the sequences was performed to confirm the results obtained by RFLP-analysis and to assess the diversity within the RFLP genotypes. Additionally, we determined carriage of the four different types of Trichomonas vaginalis viruses (TVVs by polymerase chain reaction. Results In silico RFLP-analysis revealed five actin genotypes; 50.0% of the isolates were of actin genotype E, 27.3% of actin genotype N, 13.6% of actin genotype G and 4.5% of actin genotypes I and P. Phylogenetic analysis was in agreement with the RFLP-analysis, with the different actin genotypes clustering together. Prevalence of TVVs was 43.5% (95% confidence interval, CI: 23.2–65.5. TVV1 was the most prevalent, present in 39.1% of the strains and 90% of the T. vaginalis isolates which harbored TVVs had more than one type of TVV. None of the isolates of actin genotype E harbored any TVV. Conclusion The presence of five actin genotypes in our study suggests notable diversity among T. vaginalis isolates occurring among pregnant women in Kilifi, Kenya. Isolates of the most prevalent actin genotype E lacked TVVs. We found no association between T. vaginalis genotype, carriage of TVVs and symptoms. Further studies with higher number of strains should be conducted in order to corroborate these results.

When fat is not bad: the regulation of actin dynamics by phospholipid signaling molecules

Czech Academy of Sciences Publication Activity Database

Pleskot, Roman; Pejchar, Přemysl; Staiger, Ch. J.; Potocký, Martin

2014-01-01

Roč. 5, JAN 2014 (2014) ISSN 1664-462X R&D Projects: GA ČR GA13-19073S Institutional support: RVO:61389030 Keywords : actin * actin-binding proteins * capping protein Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.948, year: 2014

MOSFET dosimetry in-vivo at superficial and orthovoltage x-ray energies

International Nuclear Information System (INIS)

Cheung, T.; Yu, P.K.N.; Butson, M.J.; Illawarra Cancer Care Centre, Wollongong, NSW

2003-01-01

This note investigates in-vivo dosimetry using a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) for radiotherapy treatment at superficial and orthovoltage x-ray energies. This was performed within one fraction of the patients treatment. Standard measurements along with energy response of the detector are given. Results showed that the MOSFET measurements in-vivo agreed with calculated results on average within ± 5.6% over all superficial and orthovoltage energies. These variations were slightly larger than TLD results with variations between measured and calculated results being ± 5.0% for the same patient measurements. The MOSFET device provides adequate in-vivo dosimetry for superficial and orthovoltage energy treatments with the accuracy of the measurements seeming to be relatively on par with TLD in our case. The MOSFET does have the advantage of returning a relatively immediate dosimetric result after irradiation. Copyright (2003) Australasian College of Physical Scientists and Engineers in Medicine

Skin manifestations in a case of trisomy 16 mosaicism

DEFF Research Database (Denmark)

Ousager, Lilian Bomme; Brandrup, Flemming; Andersen, Charlotte Brasch

2006-01-01

We present a 48-year-old man with unilateral dermatological manifestations including hypertrichosis, telangiectasia, hyperkeratosis and hyperpigmentation. Additional findings included skeletal abnormalities and left-sided hearing loss. Skin biopsies showed changes characteristic of porokeratosis....

Use of superficial peroneal nerve graft for treating peripheral nerve injuries

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Samuel Ribak

2016-02-01

Full Text Available ABSTRACT OBJECTIVE: To evaluate the clinical results from treating chronic peripheral nerve injuries using the superficial peroneal nerve as a graft donor source. METHODS: This was a study on eleven patients with peripheral nerve injuries in the upper limbs that were treated with grafts from the sensitive branch of the superficial peroneal nerve. The mean time interval between the dates of the injury and surgery was 93 days. The ulnar nerve was injured in eight cases and the median nerve in six. There were three cases of injury to both nerves. In the surgery, a longitudinal incision was made on the anterolateral face of the ankle, thus viewing the superficial peroneal nerve, which was located anteriorly to the extensor digitorum longus muscle. Proximally, the deep fascia between the extensor digitorum longus and the peroneal longus muscles was dissected. Next, the motor branch of the short peroneal muscle (one of the branches of the superficial peroneal nerve was identified. The proximal limit of the sensitive branch was found at this point. RESULTS: The average space between the nerve stumps was 3.8 cm. The average length of the grafts was 16.44 cm. The number of segments used was two to four cables. In evaluating the recovery of sensitivity, 27.2% evolved to S2+, 54.5% to S3 and 18.1% to S3+. Regarding motor recovery, 72.7% presented grade 4 and 27.2% grade 3. There was no motor deficit in the donor area. A sensitive deficit in the lateral dorsal region of the ankle and the dorsal region of the foot was observed. None of the patients presented complaints in relation to walking. CONCLUSIONS: Use of the superficial peroneal nerve as a graft source for treating peripheral nerve injuries is safe and provides good clinical results similar to those from other nerve graft sources.

Bacterial actin MreB assembles in complex with cell shape protein RodZ.

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van den Ent, Fusinita; Johnson, Christopher M; Persons, Logan; de Boer, Piet; Löwe, Jan

2010-03-17

Bacterial actin homologue MreB is required for cell shape maintenance in most non-spherical bacteria, where it assembles into helical structures just underneath the cytoplasmic membrane. Proper assembly of the actin cytoskeleton requires RodZ, a conserved, bitopic membrane protein that colocalises to MreB and is essential for cell shape determination. Here, we present the first crystal structure of bacterial actin engaged with a natural partner and provide a clear functional significance of the interaction. We show that the cytoplasmic helix-turn-helix motif of Thermotoga maritima RodZ directly interacts with monomeric as well as filamentous MreB and present the crystal structure of the complex. In vitro and in vivo analyses of mutant T. maritima and Escherichia coli RodZ validate the structure and reveal the importance of the MreB-RodZ interaction in the ability of cells to propagate as rods. Furthermore, the results elucidate how the bacterial actin cytoskeleton might be anchored to the membrane to help constrain peptidoglycan synthesis in the periplasm.

Enhancement of radiosensitivity in H1299 cancer cells by actin-associated protein cofilin

International Nuclear Information System (INIS)

Lee, Y.-J.; Sheu, T.-J.; Keng, Peter C.

2005-01-01

Cofilin is an actin-associated protein that belongs to the actin depolymerization factor/cofilin family and is important for regulation of actin dynamics. Cofilin can import actin monomers into the nucleus under certain stress conditions, however the biological effects of nuclear transport are unclear. In this study, we found that over-expression of cofilin led to increased radiation sensitivity in human non-small lung cancer H1299 cells. Cell survival as determined by colony forming assay showed that cells over-expressing cofilin were more sensitive to ionizing radiation (IR) than normal cells. To determine whether the DNA repair capacity was altered in cofilin over-expressing cells, comet assays were performed on irradiated cells. Repair of DNA damage caused by ionizing radiation was detected in cofilin over-expressing cells after 24 h of recovery. Consistent with this observation, the key components for repair of DNA double-strand breaks, including Rad51, Rad52, and Ku70/Ku80, were down-regulated in cofilin over-expressing cells after IR exposure. These findings suggest that cofilin can influence radiosensitivity by altering DNA repair capacity

Superficies in the form of the right to superpose

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Simona CHIRICĂ

2015-06-01

Full Text Available The purpose of this paper is to present the current legal framework related to the superficies right in the form of the right to superpose, and especially to draw the attention and put certain question marks regarding the actuality or even the urgency of the need for regulation regarding the right to superpose. First, as a preliminary aspect, in order to emphasize the historical evolution of the superficies right, we will briefly present the development of this concept starting from the Roman law up to the present date. Second, by analysing the relevant legislation, the doctrine and the jurisprudence, the authors set themselves to present the main methods for constituting the superficies right. Third, the characteristics related to the right to superpose will be correlatively laid out. Fourth, the possibility to obtain a building permit on the basis of the right to superpose will also be analysed. Fifth, the recently entered-into-force legislative framework regarding the registration of the right to superpose and of the building thus erected is presented. Last but not least, the conclusions of this paper are presented, highlighting the necessity for more clearly defined rules regulating the legal status of the right to superpose, in order to avoid any confusions and inconsistencies in practice.

Actin filaments regulate the adhesion between the plasma membrane and the cell wall of tobacco guard cells.

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Yu, Qin; Ren, Jing-Jing; Kong, Lan-Jing; Wang, Xiu-Ling

2018-01-01

During the opening and closing of stomata, guard cells undergo rapid and reversible changes in their volume and shape, which affects the adhesion of the plasma membrane (PM) to the cell wall (CW). The dynamics of actin filaments in guard cells are involved in stomatal movement by regulating structural changes and intracellular signaling. However, it is unclear whether actin dynamics regulate the adhesion of the PM to the CW. In this study, we investigated the relationship between actin dynamics and PM-CW adhesion by the hyperosmotic-induced plasmolysis of tobacco guard cells. We found that actin filaments in guard cells were depolymerized during mannitol-induced plasmolysis. The inhibition of actin dynamics by treatment with latrunculin B or jasplakinolide and the disruption of the adhesion between the PM and the CW by treatment with RGDS peptide (Arg-Gly-Asp-Ser) enhanced guard cell plasmolysis. However, treatment with latrunculin B alleviated the RGDS peptide-induced plasmolysis and endocytosis. Our results reveal that the actin depolymerization is involved in the regulation of the PW-CW adhesion during hyperosmotic-induced plasmolysis in tobacco guard cells.

Estudio comparativo de la rugosidad superficial en cerámicas de ultra baja fusión

OpenAIRE

Ccahuana Vásquez, Vanessa Zulema; Leite de Oliveira Morais, Andréia Alves; Sussumu Nishioka, Renato; Tomomitsu Kimpara, Estevão

2015-01-01

El objetivo de este trabajo fue comparar la rugosidad superficial en cerámicas de baja y ultra baja fusión, después del pulido mecánico y exposición a un medio corrosivo in vitro. El análisis de la superficie (Ra) fue realizado con un rugosímetro. Se confeccionaron 72 discos, divididos en cuatro grupos según el sistema cerámico utilizado: VitadurAplha (G1), Titankeramik (G2), HeraCeram (G3) y Finesse (G4), y según el tratamiento de superficie: (A) especímenes sin tratamiento de superficie. (B...

Pneumodissection for skin protection in image-guided cryoablation of superficial musculoskeletal tumours.

Science.gov (United States)

Maybody, Majid; Tang, Peter Q; Moskowitz, Chaya S; Hsu, Meier; Yarmohammadi, Hooman; Boas, F Edward

2017-03-01

Pneumodissection is described as a simple method for preventing skin injury during cryoablation of superficial musculoskeletal tumours. Superficial tumour cryoablations performed from 2009 to 2015 were retrospectively reviewed. Pneumodissection was performed in 13 patients when the shortest tumour-skin distance was less than 25 mm. Indications were pain palliation (n = 9) and local tumour control (n = 4). Patients, target tumours, technical characteristics and complications up to 60 days post ablation were reviewed. The ice ball-skin distances with and without pneumodissection were compared by a paired t-test and further assessed for association with covariates using ANCOVA. Technical success for ablation was 12 of 13. The mean shortest tumour-skin distance was 15.0 mm (3.2-24.5 mm). The mean thickness of pneumodissection was 9.6 mm (5.2-16.6 mm) resulting in mean elevation of skin of 3.4 mm (1.2-5.3 mm). Mean shortest ice ball-skin distance after pneumodissection was 10.5 mm (4.2-19.7 mm). No infection or systemic air embolism was noted. No intraprocedural frostbite was observed. Pneumodissection is feasible, effective and safe in protecting the skin during image-guided cryoablation of superficial tumours. • Frostbite during image-guided cryoablation of superficial tumours is commonly under-reported. • Frostbites are painful and may introduce infection into the superficial ablation zone. • Warm compress, saline and CO 2 have shortcomings in protecting the skin. • Pneumodissection is free, readily available, easy to use and safe and effective.

Actin and myosin regulate cytoplasm stiffness in plant cells: a study using optical tweezers

NARCIS (Netherlands)

Honing, van der H.S.; Ruijter, de N.C.A.; Emons, A.M.C.; Ketelaar, T.

2010-01-01

Here, we produced cytoplasmic protrusions with optical tweezers in mature BY-2 suspension cultured cells to study the parameters involved in the movement of actin filaments during changes in cytoplasmic organization and to determine whether stiffness is an actin-related property of plant cytoplasm.

Use your eyes - metallographic versus superficial traces of the crafting of Bronze Age ornaments

DEFF Research Database (Denmark)

Nørgaard, Heide Wrobel

and superficial archaeological examinations can be used to understand prehistoric craft. Furthermore, it will show that with an intensive knowledge about previous scientific investigations the superficial traces preserved can reveal a great amount of information and could talk for themselves. Taking as an example...... the early and middle Bronze Age bronze ornaments from North Germany, superficial traces of the metal crafting process, visible with the naked eye, will be compared with metallographic images. The aim of this presentation is to give an overview over the crafting traces everybody could see (with a bit...

β-actin shows limited mobility and is only required for supraphysiological insulin-stimulated glucose transport in young adult soleus muscle

DEFF Research Database (Denmark)

Madsen, Agnete Louise Bjerregaard; Knudsen, Jonas Roland; Henriquez-Olguin, Carlos

2018-01-01

Studies in skeletal muscle cell cultures suggest that the cortical actin cytoskeleton is a major requirement for insulin-stimulated glucose transport, implicating the β-actin isoform which, in many cell types, is the main actin isoform. However, it is not clear that β-actin plays such a role...... in mature mouse muscle under the majority of the tested conditions. Thus, our work reveals fundamental differences in the role of the cortical β-actin cytoskeleton in mature muscle compared to cell culture....

Review of photodynamic therapy in actinic keratosis and basal cell carcinoma

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Marica B Ericson

2008-03-01

Full Text Available Marica B Ericson1,2, Ann-Marie Wennberg1, Olle Larkö11Department of Dermatology; 2Department of Physics, Göteborg University, Göteborg, SwedenAbstract: The number of non-melanoma skin cancers is increasing worldwide, and so also the demand for effective treatment modalities. Topical photodynamic therapy (PDT using aminolaevulinic acid or its methyl ester has recently become good treatment options for actinic keratosis and basal cell carcinoma; especielly when treating large areas and areas with field cancerization. The cure rates are usually good, and the cosmetic outcomes excellent. The only major side effect reported is the pain experienced by the patients during treatment. This review covers the fundamental aspects of topical PDT and its application for treatment of actinic keratosis and basal cell carcinoma. Both potentials and limitations will be reviewed, as well as some recent development within the field.Keywords: photodynamic therapy, actinic keratosis, basal cell carcinoma

The actin-binding protein capulet genetically interacts with the microtubule motor kinesin to maintain neuronal dendrite homeostasis.

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Paul M B Medina

Full Text Available BACKGROUND: Neurons require precise cytoskeletal regulation within neurites, containing microtubule tracks for cargo transport in axons and dendrites or within synapses containing organized actin. Due to the unique architecture and specialized function of neurons, neurons are particularly susceptible to perturbation of the cytoskeleton. Numerous actin-binding proteins help maintain proper cytoskeletal regulation. METHODOLOGY/PRINCIPAL FINDINGS: From a Drosophila forward genetic screen, we identified a mutation in capulet--encoding a conserved actin-binding protein--that causes abnormal aggregates of actin within dendrites. Through interaction studies, we demonstrate that simultaneous genetic inactivation of capulet and kinesin heavy chain, a microtubule motor protein, produces elongate cofilin-actin rods within dendrites but not axons. These rods resemble actin-rich structures induced in both mammalian neurodegenerative and Drosophila Alzheimer's models, but have not previously been identified by loss of function mutations in vivo. We further demonstrate that mitochondria, which are transported by Kinesin, have impaired distribution along dendrites in a capulet mutant. While Capulet and Cofilin may biochemically cooperate in certain circumstances, in neuronal dendrites they genetically antagonize each other. CONCLUSIONS/SIGNIFICANCE: The present study is the first molecularly defined loss of function demonstration of actin-cofilin rods in vivo. This study suggests that simultaneous, seemingly minor perturbations in neuronal dendrites can synergize producing severe abnormalities affecting actin, microtubules and mitochondria/energy availability in dendrites. Additionally, as >90% of Alzheimer's and Parkinson's cases are sporadic this study suggests mechanisms by which multiple mutations together may contribute to neurodegeneration instead of reliance on single mutations to produce disease.

Intravesical Gemcitabine for Treatment of Superficial Bladder ...

African Journals Online (AJOL)

Objectives: Intravesical Bacillus Calmette-Guérin (BCG) vaccine is the mainstay of treatment and prophylaxis in superficial bladder cancer (SBC) as it reduces tumor recurrence and disease progression. About one-third of patients do not respond to BCG. The aim of this study was to determine the efficacy of intravesical ...

Interventions for actinic keratoses.

Science.gov (United States)

Gupta, Aditya K; Paquet, Maryse; Villanueva, Elmer; Brintnell, William

2012-12-12

Actinic keratoses are a skin disease caused by long-term sun exposure, and their lesions have the potential to develop into squamous cell carcinoma. Treatments for actinic keratoses are sought for cosmetic reasons, for the relief of associated symptoms, or for the prevention of skin cancer development. Detectable lesions are often associated with alteration of the surrounding skin (field) where subclinical lesions might be present. The interventions available for the treatment of actinic keratoses include individual lesion-based (e.g. cryotherapy) or field-directed (e.g. topical) treatments. These might vary in terms of efficacy, safety, and cosmetic outcomes. To assess the effects of topical, oral, mechanical, and chemical interventions for actinic keratosis. We searched the following databases up to March 2011: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library, MEDLINE (from 2005), EMBASE (from 2010), and LILACS (from 1982). We also searched trials registers, conference proceedings, and grey literature sources. Randomised controlled trials (RCTs) comparing the treatment of actinic keratoses with either placebo, vehicle, or another active therapy. At least two authors independently abstracted data, which included adverse events, and assessed the quality of evidence. We performed meta-analysis to calculate a weighted treatment effect across trials, and we expressed the results as risk ratios (RR) and 95% confidence intervals (CI) for dichotomous outcomes (e.g. participant complete clearance rates), and mean difference (MD) and 95% CI for continuous outcomes (e.g. mean reduction in lesion counts). We included 83 RCTs in this review, with a total of 10,036 participants. The RCTs covered 18 topical treatments, 1 oral treatment, 2 mechanical interventions, and 3 chemical interventions, including photodynamic therapy (PDT). Most of the studies lacked descriptions of some methodological details, such as the generation of the randomisation

Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions.

Science.gov (United States)

Lechuga, Susana; Baranwal, Somesh; Ivanov, Andrei I

2015-05-01

Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis. Copyright © 2015 the American Physiological Society.

Persistent inhibition of pore-based cell migration by sub-toxic doses of miuraenamide, an actin filament stabilizer.

Science.gov (United States)

Moser, Christina; Rüdiger, Daniel; Förster, Florian; von Blume, Julia; Yu, Peng; Kuster, Bernhard; Kazmaier, Uli; Vollmar, Angelika M; Zahler, Stefan

2017-11-27

Opposed to tubulin-binding agents, actin-binding small molecules have not yet become part of clinical tumor treatment, most likely due to the fear of general cytotoxicity. Addressing this problem, we investigated the long-term efficacy of sub-toxic doses of miuraenamide, an actin filament stabilizing natural compound, on tumor cell (SKOV3) migration. No cytotoxic effects or persistent morphological changes occurred at a concentration of miuraenamide of 20 nM. After 72 h treatment with this concentration, nuclear stiffness was increased, causing reduced migration through pores in a Boyden chamber, while cell migration and chemotaxis per se were unaltered. A concomitant time-resolved proteomic approach showed down regulation of a protein cluster after 56 h treatment. This cluster correlated best with the Wnt signaling pathway. A further analysis of the actin associated MRTF/SRF signaling showed a surprising reduction of SRF-regulated proteins. In contrast to acute effects of actin-binding compounds on actin at high concentrations, long-term low-dose treatment elicits much more subtle but still functionally relevant changes beyond simple destruction of the cytoskeleton. These range from biophysical parameters to regulation of protein expression, and may help to better understand the complex biology of actin, as well as to initiate alternative regimes for the testing of actin-targeting drugs.

DNA Double-Strand Breaks Induce the Nuclear Actin Filaments Formation in Cumulus-Enclosed Oocytes but Not in Denuded Oocytes.

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Ming-Hong Sun

Full Text Available As a gamete, oocyte needs to maintain its genomic integrity and passes this haploid genome to the next generation. However, fully-grown mouse oocyte cannot respond to DNA double-strand breaks (DSBs effectively and it is also unable to repair them before the meiosis resumption. To compensate for this disadvantage and control the DNA repair events, oocyte needs the cooperation with its surrounding cumulus cells. Recently, evidences have shown that nuclear actin filament formation plays roles in cellular DNA DSB repair. To explore whether these nuclear actin filaments are formed in the DNA-damaged oocytes, here, we labeled the filament actins in denuded oocytes (DOs and cumulus-enclosed oocytes (CEOs. We observed that the nuclear actin filaments were formed only in the DNA-damaged CEOs, but not in DOs. Formation of actin filaments in the nucleus was an event downstream to the DNA damage response. Our data also showed that the removal of cumulus cells led to a reduction in the nuclear actin filaments in oocytes. Knocking down of the Adcy1 gene in cumulus cells did not affect the formation of nuclear actin filaments in oocytes. Notably, we also observed that the nuclear actin filaments in CEOs could be induced by inhibition of gap junctions. From our results, it was confirmed that DNA DSBs induce the nuclear actin filament formation in oocyte and which is controlled by the cumulus cells.

SYP73 Anchors the ER to the Actin Cytoskeleton for Maintenance of ER Integrity and Streaming in Arabidopsis.

Science.gov (United States)

Cao, Pengfei; Renna, Luciana; Stefano, Giovanni; Brandizzi, Federica

2016-12-05

The endoplasmic reticulum (ER) is an essential organelle that spreads throughout the cytoplasm as one interconnected network of narrow tubules and dilated cisternae that enclose a single lumen. The ER network undergoes extensive remodeling, which critically depends on membrane-cytoskeleton interactions [1]. In plants, the ER is also highly mobile, and its streaming contributes significantly to the movement of other organelles [2, 3]. The remodeling and motility of the plant ER rely mainly on actin [4] and to a minor extent on microtubules [5]. Although a three-way interaction between the ER, cytosolic myosin-XI, and F-actin mediates the plant ER streaming [6], the mechanisms underlying stable interaction of the ER membrane with actin are unknown. Early electron microscopy studies suggested a direct attachment of the plant ER with actin filaments [7, 8], but it is plausible that yet-unknown proteins facilitate anchoring of the ER membrane with the cytoskeleton. We demonstrate here that SYP73, a member of the plant Syp7 subgroup of SNARE proteins [9] containing actin-binding domains, is a novel ER membrane-associated actin-binding protein. We show that overexpression of SYP73 causes a striking rearrangement of the ER over actin and that, similar to mutations of myosin-XI [4, 10, 11], loss of SYP73 reduces ER streaming and affects overall ER network morphology and plant growth. We propose a model for plant ER remodeling whereby the dynamic rearrangement and streaming of the ER network depend on the propelling action of myosin-XI over actin coupled with a SYP73-mediated bridging, which dynamically anchors the ER membrane with actin filaments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Total Synthesis of (-)-Doliculide, Structure-Activity Relationship Studies and Its Binding to F-Actin

NARCIS (Netherlands)

Matcha, Kiran; Madduri, Ashoka V. R.; Roy, Sayantani; Ziegler, Slava; Waldmann, Herbert; Hirsch, Anna K. H.; Minnaard, Adriaan J.

2012-01-01

Actin, an abundant protein in most eukaryotic cells, is one of the targets in cancer research. Recently, a great deal of attention has been paid to the synthesis and function of actin-targeting compounds and their use as effective molecular probes in chemical biology. In this study, we have

A consensus approach to improving patient adherence and persistence with topical treatment for actinic keratosis.

Science.gov (United States)

Stockfleth, Eggert; Peris, Ketty; Guillen, Carlos; Cerio, Rino; Basset-Seguin, Nicole; Foley, Peter; Sanches, José; Culshaw, Alex; Erntoft, Sandra; Lebwohl, Mark

2015-01-01

Topical therapy is important in the treatment of actinic keratosis, but guidance for improving adherence/persistence during topical therapy is still lacking. To utilize expert consensus to generate a list of recommendations to improve real-world efficacy when prescribing topical therapy for actinic keratosis. An expert panel of eight dermatologists was convened to generate recommendations based on facilitated discussion and consensus generation using a modified Delphi session. The recommendations were ratified with the expert panel. Facilitated discussion generated 31 issues within five themes, which were prioritized using expert voting. Consensus was achieved on the importance of short and simple treatment regimens for maximizing patient compliance, physician awareness of the progression of actinic keratosis to squamous cell carcinoma, provision of appropriate patient information, and the use of effective communication strategies to educate physicians about actinic keratosis. Based on these key findings, eight recommendations were generated. The recommendations will assist physicians when prescribing topical actinic keratosis therapy. Further research should focus on the types of patient outcomes that are influenced by the characteristics of topical field therapy. © 2015 The Authors. International Journal of Dermatology published by John Wiley & Sons Ltd on behalf of International Society of Dermatology.

Vascular patterns of upper limb: an anatomical study with accent on superficial brachial artery

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David Kachlik

2011-02-01

Full Text Available The aim of the study was to evaluate the terminal segmentation of the axillary artery and to present four cases of anomalous branching of the axillary artery, the superficial brachial artery (arteria brachialis superficialis, which is defined as the brachial artery that runs superficially to the median nerve. Totally, 130 cadaveric upper arms embalmed by classical formaldehyde technique from collections of the Department of Anatomy, Third Faculty of Medicine, Charles University in Prague, were macroscopically dissected with special focus on the branching arrangement of the axillary artery. The most distal part of the axillary artery (infrapectoral part terminated in four cases as a bifurcation into two terminal branches: the superficial brachial artery and profunda brachii artery, denominated according to their relation to the median nerve. The profunda brachii artery primarily gave rise to the main branches of the infrapectoral part of the axillary artery. The superficial brachial artery descended to the cubital fossa where it assumed the usual course of the brachial artery in two cases and in the other two cases its branches (the radial and ulnar arteries passed superficially to the flexors. The incidence of the superficial brachial artery in our study was 5% of cases. The reported incidence is a bit contradictory, from 0.12% to 25% of cases. The anatomical knowledge of the axillary region is of crucial importance for neurosurgeons and specialists using the radiodiagnostic techniques, particularly in cases involving traumatic injuries. The improved knowledge would allow more accurate diagnostic interpretations and surgical treatment.

Superficial evolution and compacting aptitude of uranium dioxide powders

International Nuclear Information System (INIS)

Danroc, J.

1982-04-01

Long term storage of UO 2 powder improves slightly shaping and solidity of compacted powder. The aim of this work is the study of material evolution and the increase of this evolution rate for application to industrial fabrication. Aging in wet air at different temperatures is examined. Evolution of texture and superficial composition is followed. Below 80 0 C UO 3 , 2H 2 O is formed at crystal surface and thermal decomposition gives different hydrates. Kinetics of the transformation is studied. Oxidohydratation in liquid phase is rapid with hydrogen peroxide. The aged or treated material is compacted and mechanical behaviour is examined. Improvement is explained by inter-layer water molecule of the superficial hydrate giving lubricant and pseudo-plastic properties [fr

Caracterizacion dosimetrica del equipo de Terapia Superficial Therapax del Hospital Mexico

International Nuclear Information System (INIS)

Bernui De Vivanco, Maria Giselle; Rojas Rivas, Jorge; Cardenas Retuerto, Augusto

2007-01-01

The Servicio de Radioterapia of the Hospital Mexico in San Jose, Costa Rica has a Superficial Therapy equipment Therapax model DXT 300. It describes the measurements for the dosimetric characterization of the configurations 100 kVp, 25 mA and filter of 2.4 mm of Al, and 250 kVp, 10 mA and filter of 2.5 mm of Cu, taking into account that the uncertainties in the measurements of the superficial therapy equipment are higher than in the rank of the megavoltage [es

Comportamiento a fatiga del acero sae 4140 usando alta rugosidad superficial y ambiente corrosivo

OpenAIRE

CEBALLOS, WILSON FERNANDO; GÓMEZ, ADOLFO LEÓN; CORONADO, JOHN JAIRO

2010-01-01

En este artículo se presenta el estudio del comportamiento a fatiga del acero SAE 4140 en condiciones diferentes: superficie pulida (acabado espejo), ambiente corrosivo (jugo de caña de azúcar), alta rugosidad superficial (superficie equivalente a la encontrada típicamente en los ejes de molino de caña) y una condición que involucra la combinación de las dos últimas. Las anteriores condiciones están presentes en los ejes de maza de molino de caña de azúcar durante el proceso de molienda. Se r...

COMPORTAMIENTO A FATIGA DEL ACERO SAE 4140 USANDO ALTA RUGOSIDAD SUPERFICIAL Y AMBIENTE CORROSIVO

OpenAIRE

CEBALLOS, WILSON FERNANDO; GÓMEZ, ADOLFO LEÓN; CORONADO, JOHN JAIRO

2010-01-01

En este artículo se presenta el estudio del comportamiento a fatiga del acero SAE 4140 en condiciones diferentes: superficie pulida (acabado espejo), ambiente corrosivo (jugo de caña de azúcar), alta rugosidad superficial (superficie equivalente a la encontrada típicamente en los ejes de molino de caña) y una condición que involucra la combinación de las dos últimas. Las anteriores condiciones están presentes en los ejes de maza de molino de caña de azúcar durante el proceso de molienda. Se r...

Actin polymerization in the endosomal pathway, but not on the Coxiella-containing vacuole, is essential for pathogen growth.

Directory of Open Access Journals (Sweden)

Heather E Miller

2018-04-01

Full Text Available Coxiella burnetii is an intracellular bacterium that replicates within an expansive phagolysosome-like vacuole. Fusion between the Coxiella-containing vacuole (CCV and late endosomes/multivesicular bodies requires Rab7, the HOPS tethering complex, and SNARE proteins, with actin also speculated to play a role. Here, we investigated the importance of actin in CCV fusion. Filamentous actin patches formed around the CCV membrane that were preferred sites of vesicular fusion. Accordingly, the mediators of endolysosomal fusion Rab7, VAMP7, and syntaxin 8 were concentrated in CCV actin patches. Generation of actin patches required C. burnetii type 4B secretion and host retromer function. Patches decorated with VPS29 and VPS35, components of the retromer, FAM21 and WASH, members of the WASH complex that engage the retromer, and Arp3, a component of the Arp2/3 complex that generates branched actin filaments. Depletion by siRNA of VPS35 or VPS29 reduced CCV actin patches and caused Rab7 to uniformly distribute in the CCV membrane. C. burnetii grew normally in VPS35 or VPS29 depleted cells, as well as WASH-knockout mouse embryo fibroblasts, where CCVs are devoid of actin patches. Endosome recycling to the plasma membrane and trans-Golgi of glucose transporter 1 (GLUT1 and cationic-independent mannose-6-phosphate receptor (CI-M6PR, respectively, was normal in infected cells. However, siRNA knockdown of retromer resulted in aberrant trafficking of GLUT1, but not CI-M6PR, suggesting canonical retrograde trafficking is unaffected by retromer disruption. Treatment with the specific Arp2/3 inhibitor CK-666 strongly inhibited CCV formation, an effect associated with altered endosomal trafficking of transferrin receptor. Collectively, our results show that CCV actin patches generated by retromer, WASH, and Arp2/3 are dispensable for CCV biogenesis and stability. However, Arp2/3-mediated production of actin filaments required for cargo transport within the

Isolated core vs. superficial cooling effects on virtual maze navigation.

Science.gov (United States)

Payne, Jennifer; Cheung, Stephen S

2007-07-01

Cold impairs cognitive performance and is a common occurrence in many survival situations. Altered behavior patterns due to impaired navigation abilities in cold environments are potential problems in lost-person situations. We investigated the separate effects of low core temperature and superficial cooling on a spatially demanding virtual navigation task. There were 12 healthy men who were passively cooled via 15 degrees C water immersion to a core temperature of 36.0 degrees C, then transferred to a warm (40 degrees C) water bath to eliminate superficial shivering while completing a series of 20 virtual computer mazes. In a control condition, subjects rested in a thermoneutral (approximately 35 degrees C) bath for a time-matched period before being transferred to a warm bath for testing. Superficial cooling and distraction were achieved by whole-body immersion in 35 degree water for a time-matched period, followed by lower leg immersion in 10 degree C water for the duration of the navigational tests. Mean completion time and mean error scores for the mazes were not significantly different (p > 0.05) across the core cooling (16.59 +/- 11.54 s, 0.91 +/- 1.86 errors), control (15.40 +/- 8.85 s, 0.82 +/- 1.76 errors), and superficial cooling (15.19 +/- 7.80 s, 0.77 +/- 1.40 errors) conditions. Separately reducing core temperature or increasing cold sensation in the lower extremities did not influence performance on virtual computer mazes, suggesting that navigation is more resistive to cooling than other, simpler cognitive tasks. Further research is warranted to explore navigational ability at progressively lower core and skin temperatures, and in different populations.

The apical actin fringe contributes to localized cell wall deposition and polarized growth in the lily pollen tube.

Science.gov (United States)

Rounds, Caleb M; Hepler, Peter K; Winship, Lawrence J

2014-09-01

In lily (Lilium formosanum) pollen tubes, pectin, a major component of the cell wall, is delivered through regulated exocytosis. The targeted transport and secretion of the pectin-containing vesicles may be controlled by the cortical actin fringe at the pollen tube apex. Here, we address the role of the actin fringe using three different inhibitors of growth: brefeldin A, latrunculin B, and potassium cyanide. Brefeldin A blocks membrane trafficking and inhibits exocytosis in pollen tubes; it also leads to the degradation of the actin fringe and the formation of an aggregate of filamentous actin at the base of the clear zone. Latrunculin B, which depolymerizes filamentous actin, markedly slows growth but allows focused pectin deposition to continue. Of note, the locus of deposition shifts frequently and correlates with changes in the direction of growth. Finally, potassium cyanide, an electron transport chain inhibitor, briefly stops growth while causing the actin fringe to completely disappear. Pectin deposition continues but lacks focus, instead being delivered in a wide arc across the pollen tube tip. These data support a model in which the actin fringe contributes to the focused secretion of pectin to the apical cell wall and, thus, to the polarized growth of the pollen tube. © 2014 American Society of Plant Biologists. All Rights Reserved.

Functional compartmentalization of the human superficial masseter muscle.

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Rodrigo A Guzmán-Venegas

Full Text Available Some muscles have demonstrated a differential recruitment of their motor units in relation to their location and the nature of the motor task performed; this involves functional compartmentalization. There is little evidence that demonstrates the presence of a compartmentalization of the superficial masseter muscle during biting. The aim of this study was to describe the topographic distribution of the activity of the superficial masseter (SM muscle's motor units using high-density surface electromyography (EMGs at different bite force levels. Twenty healthy natural dentate participants (men: 4; women: 16; age 20±2 years; mass: 60±12 kg, height: 163±7 cm were selected from 316 volunteers and included in this study. Using a gnathodynamometer, bites from 20 to 100% maximum voluntary bite force (MVBF were randomly requested. Using a two-dimensional grid (four columns, six electrodes located on the dominant SM, EMGs in the anterior, middle-anterior, middle-posterior and posterior portions were simultaneously recorded. In bite ranges from 20 to 60% MVBF, the EMG activity was higher in the anterior than in the posterior portion (p-value = 0.001.The center of mass of the EMG activity was displaced towards the posterior part when bite force increased (p-value = 0.001. The topographic distribution of EMGs was more homogeneous at high levels of MVBF (p-value = 0.001. The results of this study show that the superficial masseter is organized into three functional compartments: an anterior, a middle and a posterior compartment. However, this compartmentalization is only seen at low levels of bite force (20-60% MVBF.

[Occupational trauma due to superficial corneal foreign body].

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Gerente, Vanessa Miroski; Melo, Gustavo Barreto de; Regatieri, Caio Vinícius Saito; Alvarenga, Lênio Souza; Martins, Elizabeth Nogueira

2008-01-01

To evaluate the epidemiology of superficial corneal foreign body. Patients who were seen at the Emergency Service of the Federal University of São Paulo, from April/05 to June/05, were screened and those with superficial corneal foreign body were interviewed. Data regarding gender, age, occupation, employment status, availability and use of protective devices and supervision of their use were collected. Awareness of the possible complications was also assessed. Results were analyzed using chi-square or Fisher exact test. One hundred twenty-three patients were interviewed. Only 3 patients were female. The mean age was 36 years. Most injuries occurred at the workplace (86.2%), and 58.4% of the patients did not have a legal employment registration. The occupational activities most frequently reported were construction related activities (44.3%) and welding/soldering (11.3%). In most workplaces (79.8%) protective devices were available and 85.3% of the patients were instructed to use them. A safety device was being used during the accident in 34.2% of the cases and this was more frequent among patients that had legal employment registry (p=0.008) and among those under supervision (p=0.0415). The majority of the patients (68.9%) were aware of the risk of severe complications. Most patients with superficial corneal foreign body are aware of its severe complications and injuries usually occur in places where safety devices are available and often during their use. Our findings suggest that prevention should focus on supervision and correct use of safety devices.

Actin and microtubule networks contribute differently to cell response for small and large strains

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Kubitschke, H.; Schnauss, J.; Nnetu, K. D.; Warmt, E.; Stange, R.; Kaes, J.

2017-09-01

Cytoskeletal filaments provide cells with mechanical stability and organization. The main key players are actin filaments and microtubules governing a cell’s response to mechanical stimuli. We investigated the specific influences of these crucial components by deforming MCF-7 epithelial cells at small (≤5% deformation) and large strains (>5% deformation). To understand specific contributions of actin filaments and microtubules, we systematically studied cellular responses after treatment with cytoskeleton influencing drugs. Quantification with the microfluidic optical stretcher allowed capturing the relative deformation and relaxation of cells under different conditions. We separated distinctive deformational and relaxational contributions to cell mechanics for actin and microtubule networks for two orders of magnitude of drug dosages. Disrupting actin filaments via latrunculin A, for instance, revealed a strain-independent softening. Stabilizing these filaments by treatment with jasplakinolide yielded cell softening for small strains but showed no significant change at large strains. In contrast, cells treated with nocodazole to disrupt microtubules displayed a softening at large strains but remained unchanged at small strains. Stabilizing microtubules within the cells via paclitaxel revealed no significant changes for deformations at small strains, but concentration-dependent impact at large strains. This suggests that for suspended cells, the actin cortex is probed at small strains, while at larger strains; the whole cell is probed with a significant contribution from the microtubules.

Clinicomycological Characterization of Superficial Mycoses from a Tertiary Care Hospital in Nepal

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Khadka, Sundar; Sherchand, Jeevan Bahadur; Pokharel, Dinesh Binod; Pokhrel, Bharat Mani; Mishra, Shyam Kumar; Dhital, Subhash; Rijal, Basista

2016-01-01

Background. Superficial mycosis is a common fungal infection worldwide, mainly caused by dermatophytes. However, the prevalence of species varies geographically. In addition, fungal treatment is best guided according to species isolated. This study was carried out to determine the clinical as well as mycological profile of superficial mycoses in a tertiary care hospital, Nepal. Methods. This was a prospective case-control laboratory based study conducted over a period of six months from Janua...

Topographical anatomy of superficial veins, cutaneous nerves, and arteries at venipuncture sites in the cubital fossa.

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Mikuni, Yuko; Chiba, Shoji; Tonosaki, Yoshikazu

2013-01-01

We investigated correlations among the superficial veins, cutaneous nerves, arteries, and venous valves in 128 cadaveric arms in order to choose safe venipuncture sites in the cubital fossa. The running patterns of the superficial veins were classified into four types (I-IV) and two subtypes (a and b). In types I and II, the median cubital vein (MCV) was connected obliquely between the cephalic and basilic veins in an N-shape, while the median antebrachial vein (MAV) opened into the MCV in type I and into the basilic vein in type II. In type III, the MCV did not exist. In type IV, additional superficial veins above the cephalic and basilic veins were developed around the cubital fossa. In types Ib-IVb, the accessory cephalic vein was developed under the same conditions as seen in types Ia-IVa, respectively. The lateral cutaneous nerve of the forearm descended deeply along the cephalic vein in 124 cases (97 %), while the medial cutaneous nerve of the forearm descended superficially along the basilic vein in 94 (73 %). A superficial brachial artery was found in 27 cases (21 %) and passed deeply under the ulnar side of the MCV. A median superficial antebrachial artery was found in 1 case (1 %), which passed deeply under the ulnar side of the MCV and ran along the MAV. Venous valves were found at 239 points in 28 cases with superficial veins, with a single valve seen at 79 points (33 %) and double valves at 160 points (67 %). At the time of intravenous injection, caution is needed regarding the locations of cutaneous nerves, brachial and superficial brachial arteries, and venous valves. The area ranging from the middle segment of the MCV to the confluence between the MCV and cephalic vein appears to be a relatively safe venipuncture site.

Managment of superficial infantile capillary hemangiomas with topical timolol maleate solution.

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Rizvi, Syed Ali Raza; Yusuf, Faraz; Sharma, Rajeev; Rizvi, Syed Wajahat Ali

2015-01-01

Capillary hemangioma is the most common benign tumor of eyelids and orbit in children. Recently, a topical beta blocker has been reported as an effective treatment for superficial capillary hemangiomas. We present a case report of two children having large capillary hemangiomas who responded well to topical treatment by 0.5% timolol maleate solution. After 12 months of treatment, the lesion has significantly reduced in size, thickness, and color in both cases. Thus, we conclude that long-term use of topical 0.5% timolol maleate solution is safe and effective in treating superficial capillary hemangiomas.

Effects of polymerization and nucleotide identity on the conformational dynamics of the bacterial actin homolog MreB.

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Colavin, Alexandre; Hsin, Jen; Huang, Kerwyn Casey

2014-03-04