WorldWideScience

Sample records for coordinate microtubule interactions

  1. The coordination of centromere replication, spindle formation, and kinetochore-microtubule interaction in budding yeast.

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    Hong Liu

    2008-11-01

    Full Text Available The kinetochore is a protein complex that assembles on centromeric DNA to mediate chromosome-microtubule interaction. Most eukaryotic cells form the spindle and establish kinetochore-microtubule interaction during mitosis, but budding yeast cells finish these processes in S-phase. It has long been noticed that the S-phase spindle in budding yeast is shorter than that in metaphase, but the biological significance of this short S-phase spindle structure remains unclear. We addressed this issue by using ask1-3, a temperature-sensitive kinetochore mutant that exhibits partially elongated spindles at permissive temperature in the presence of hydroxyurea (HU, a DNA synthesis inhibitor. After exposure to and removal of HU, ask1-3 cells show a delayed anaphase entry. This delay depends on the spindle checkpoint, which monitors kinetochore-microtubule interaction defects. Overproduction of microtubule-associated protein Ase1 or Cin8 also induces spindle elongation in HU-arrested cells. The spindle checkpoint-dependent anaphase entry delay is also observed after ASE1 or CIN8 overexpression in HU-arrested cells. Therefore, the shorter spindle in S-phase cells is likely to facilitate proper chromosome-microtubule interaction.

  2. Structural insights into microtubule doublet interactions inaxonemes

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    Downing, Kenneth H.; Sui, Haixin

    2007-06-06

    Coordinated sliding of microtubule doublets, driven by dynein motors, produces periodic beating of the axoneme. Recent structural studies of the axoneme have used cryo-electron tomography to reveal new details of the interactions among some of the multitude of proteins that form the axoneme and regulate its movement. Connections among the several sets of dyneins, in particular, suggest ways in which their actions may be coordinated. Study of the molecular architecture of isolated doublets has provided a structural basis for understanding the doublet's mechanical properties that are related to the bending of the axoneme, and has also offered insight into its potential role in the mechanism of dynein activity regulation.

  3. Interaction between microtubules and the Drosophila formin Cappuccino and its effect on actin assembly.

    Science.gov (United States)

    Roth-Johnson, Elizabeth A; Vizcarra, Christina L; Bois, Justin S; Quinlan, Margot E

    2014-02-14

    Formin family actin nucleators are potential coordinators of the actin and microtubule cytoskeletons, as they can both nucleate actin filaments and bind microtubules in vitro. To gain a more detailed mechanistic understanding of formin-microtubule interactions and formin-mediated actin-microtubule cross-talk, we studied microtubule binding by Cappuccino (Capu), a formin involved in regulating actin and microtubule organization during Drosophila oogenesis. We found that two distinct domains within Capu, FH2 and tail, work together to promote high-affinity microtubule binding. The tail domain appears to bind microtubules through nonspecific charge-based interactions. In contrast, distinct residues within the FH2 domain are important for microtubule binding. We also report the first visualization of a formin polymerizing actin filaments in the presence of microtubules. Interestingly, microtubules are potent inhibitors of the actin nucleation activity of Capu but appear to have little effect on Capu once it is bound to the barbed end of an elongating filament. Because Capu does not simultaneously bind microtubules and assemble actin filaments in vitro, its actin assembly and microtubule binding activities likely require spatial and/or temporal regulation within the Drosophila oocyte.

  4. Interaction between Microtubules and the Drosophila Formin Cappuccino and Its Effect on Actin Assembly*

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    Roth-Johnson, Elizabeth A.; Vizcarra, Christina L.; Bois, Justin S.; Quinlan, Margot E.

    2014-01-01

    Formin family actin nucleators are potential coordinators of the actin and microtubule cytoskeletons, as they can both nucleate actin filaments and bind microtubules in vitro. To gain a more detailed mechanistic understanding of formin-microtubule interactions and formin-mediated actin-microtubule cross-talk, we studied microtubule binding by Cappuccino (Capu), a formin involved in regulating actin and microtubule organization during Drosophila oogenesis. We found that two distinct domains within Capu, FH2 and tail, work together to promote high-affinity microtubule binding. The tail domain appears to bind microtubules through nonspecific charge-based interactions. In contrast, distinct residues within the FH2 domain are important for microtubule binding. We also report the first visualization of a formin polymerizing actin filaments in the presence of microtubules. Interestingly, microtubules are potent inhibitors of the actin nucleation activity of Capu but appear to have little effect on Capu once it is bound to the barbed end of an elongating filament. Because Capu does not simultaneously bind microtubules and assemble actin filaments in vitro, its actin assembly and microtubule binding activities likely require spatial and/or temporal regulation within the Drosophila oocyte. PMID:24362037

  5. The smallest active fragment of microtubule-associated protein 4 and its interaction with microtubules in phosphate buffer.

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    Hashi, Yurika; Nagase, Lisa; Matsushima, Kazuyuki; Kotani, Susumu

    2012-01-01

    To analyze the interaction between microtubule-associated protein (MAP) 4 and microtubules physicochemically, a MAP4 active site fragment was designed for nuclear magnetic resonance (NMR) use. The fragment was bacterially expressed and purified to homogeneity. The buffer conditions for NMR were optimized to support microtubule assembly. The fragment was found to bind to microtubules under the optimized buffer conditions.

  6. Proteomic Analysis of Microtubule Interacting Proteins over the Course of Xylem Tracheary Element Formation in Arabidopsis.

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    Derbyshire, Paul; Ménard, Delphine; Green, Porntip; Saalbach, Gerhard; Buschmann, Henrik; Lloyd, Clive W; Pesquet, Edouard

    2015-10-01

    Plant vascular cells, or tracheary elements (TEs), rely on circumferential secondary cell wall thickenings to maintain sap flow. The patterns in which TE thickenings are organized vary according to the underlying microtubule bundles that guide wall deposition. To identify microtubule interacting proteins present at defined stages of TE differentiation, we exploited the synchronous differentiation of TEs in Arabidopsis thaliana suspension cultures. Quantitative proteomic analysis of microtubule pull-downs, using ratiometric (14)N/(15)N labeling, revealed 605 proteins exhibiting differential accumulation during TE differentiation. Microtubule interacting proteins associated with membrane trafficking, protein synthesis, DNA/RNA binding, and signal transduction peaked during secondary cell wall formation, while proteins associated with stress peaked when approaching TE cell death. In particular, CELLULOSE SYNTHASE-INTERACTING PROTEIN1, already associated with primary wall synthesis, was enriched during secondary cell wall formation. RNAi knockdown of genes encoding several of the identified proteins showed that secondary wall formation depends on the coordinated presence of microtubule interacting proteins with nonoverlapping functions: cell wall thickness, cell wall homogeneity, and the pattern and cortical location of the wall are dependent on different proteins. Altogether, proteins linking microtubules to a range of metabolic compartments vary specifically during TE differentiation and regulate different aspects of wall patterning.

  7. ErbB2-dependent chemotaxis requires microtubule capture and stabilization coordinated by distinct signaling pathways.

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    Khedidja Benseddik

    Full Text Available Activation of the ErbB2 receptor tyrosine kinase stimulates breast cancer cell migration. Cell migration is a complex process that requires the synchronized reorganization of numerous subcellular structures including cell-to-matrix adhesions, the actin cytoskeleton and microtubules. How the multiple signaling pathways triggered by ErbB2 coordinate, in time and space, the various processes involved in cell motility, is poorly defined. We investigated the mechanism whereby ErbB2 controls microtubules and chemotaxis. We report that activation of ErbB2 increased both cell velocity and directed migration. Impairment of the Cdc42 and RhoA GTPases, but not of Rac1, prevented the chemotactic response. RhoA is a key component of the Memo/ACF7 pathway whereby ErbB2 controls microtubule capture at the leading edge. Upon Memo or ACF7 depletion, microtubules failed to reach the leading edge and cells lost their ability to follow the chemotactic gradient. Constitutive ACF7 targeting to the membrane in Memo-depleted cells reestablished directed migration. ErbB2-mediated activation of phospholipase C gamma (PLCγ also contributed to cell guidance. We further showed that PLCγ signaling, via classical protein kinases C, and Memo signaling converged towards a single pathway controlling the microtubule capture complex. Finally, inhibiting the PI3K/Akt pathway did not affect microtubule capture, but disturbed microtubule stability, which also resulted in defective chemotaxis. PI3K/Akt-dependent stabilization of microtubules involved repression of GSK3 activity on the one hand and inhibition of the microtubule destabilizing protein, Stathmin, on the other hand. Thus, ErbB2 triggers distinct and complementary pathways that tightly coordinate microtubule capture and microtubule stability to control chemotaxis.

  8. Daple Coordinates Planar Polarized Microtubule Dynamics in Ependymal Cells and Contributes to Hydrocephalus

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    Maki Takagishi

    2017-07-01

    Full Text Available Motile cilia in ependymal cells, which line the cerebral ventricles, exhibit a coordinated beating motion that drives directional cerebrospinal fluid (CSF flow and guides neuroblast migration. At the apical cortex of these multi-ciliated cells, asymmetric localization of planar cell polarity (PCP proteins is required for the planar polarization of microtubule dynamics, which coordinates cilia orientation. Daple is a disheveled-associating protein that controls the non-canonical Wnt signaling pathway and cell motility. Here, we show that Daple-deficient mice present hydrocephalus and their ependymal cilia lack coordinated orientation. Daple regulates microtubule dynamics at the anterior side of ependymal cells, which in turn orients the cilial basal bodies required for the directional cerebrospinal fluid flow. These results demonstrate an important role for Daple in planar polarity in motile cilia and provide a framework for understanding the mechanisms and functions of planar polarization in the ependymal cells.

  9. Kinetochore-Dependent Microtubule Rescue Ensures Their Efficient and Sustained Interactions in Early Mitosis

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    Gandhi, Sapan R.; Gierliński, Marek; Mino, Akihisa; Tanaka, Kozo; Kitamura, Etsushi; Clayton, Lesley; Tanaka, Tomoyuki U.

    2011-01-01

    Summary How kinetochores regulate microtubule dynamics to ensure proper kinetochore-microtubule interactions is unknown. Here, we studied this during early mitosis in Saccharomyces cerevisiae. When a microtubule shrinks and its plus end reaches a kinetochore bound to its lateral surface, the microtubule end attempts to tether the kinetochore. This process often fails and, responding to this failure, microtubule rescue (conversion from shrinkage to growth) occurs, preventing kinetochore detachment from the microtubule end. This rescue is promoted by Stu2 transfer (ortholog of vertebrate XMAP215/ch-TOG) from the kinetochore to the microtubule end. Meanwhile, microtubule rescue distal to the kinetochore is also promoted by Stu2, which is transported by a kinesin-8 motor Kip3 along the microtubule from the kinetochore. Microtubule extension following rescue facilitates interaction with other widely scattered kinetochores, diminishing long delays in collecting the complete set of kinetochores by microtubules. Thus, kinetochore-dependent microtubule rescue ensures efficient and sustained kinetochore-microtubule interactions in early mitosis. PMID:22075150

  10. Microtubule binding by the formin Cappuccino and its implications for Drosophila oogenesis

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    Roth-Johnson, Elizabeth Anne

    2014-01-01

    Coordination of actin and microtubule cytoskeletal networks is required for a number of fundamental cellular processes. Formin family actin nucleators are emerging coordinators of the actin and microtubule cytoskeletons, as they can both nucleate actin filaments and bind microtubules in vitro. To gain a more detailed mechanistic understanding of formin-microtubule interactions and formin-mediated actin-microtubule crosstalk, we studied microtubule binding by Cappuccino (Capu), a formin involv...

  11. Coordination of microtubule and microfilament dynamics by Drosophila Rho1, Spire and Cappuccino.

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    Rosales-Nieves, Alicia E; Johndrow, James E; Keller, Lani C; Magie, Craig R; Pinto-Santini, Delia M; Parkhurst, Susan M

    2006-04-01

    The actin-nucleation factors Spire and Cappuccino (Capu) regulate the onset of ooplasmic streaming in Drosophila melanogaster. Although this streaming event is microtubule-based, actin assembly is required for its timing. It is not understood how the interaction of microtubules and microfilaments is mediated in this context. Here, we demonstrate that Capu and Spire have microtubule and microfilament crosslinking activity. The spire locus encodes several distinct protein isoforms (SpireA, SpireC and SpireD). SpireD was recently shown to nucleate actin, but the activity of the other isoforms has not been addressed. We find that SpireD does not have crosslinking activity, whereas SpireC is a potent crosslinker. We show that SpireD binds to Capu and inhibits F-actin/microtubule crosslinking, and activated Rho1 abolishes this inhibition, establishing a mechanistic basis for the regulation of Capu and Spire activity. We propose that Rho1, cappuccino and spire are elements of a conserved developmental cassette that is capable of directly mediating crosstalk between microtubules and microfilaments.

  12. PACSIN1, a Tau-interacting protein, regulates axonal elongation and branching by facilitating microtubule instability.

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    Liu, Yingying; Lv, Kaosheng; Li, Zenglong; Yu, Albert C H; Chen, Jianguo; Teng, Junlin

    2012-11-16

    Tau is a major member of the neuronal microtubule-associated proteins. It promotes tubulin assembly and stabilizes axonal microtubules. Previous studies have demonstrated that Tau forms cross-bridges between microtubules, with some particles located on cross-bridges, suggesting that some proteins interact with Tau and might be involved in regulating Tau-related microtubule dynamics. This study reports that PACSIN1 interacts with Tau in axon. PACSIN1 blockade results in impaired axonal elongation and a higher number of primary axonal branches in mouse dorsal root ganglia neurons, which is induced by increasing the binding ability of Tau to microtubules. In PACSIN1-blocked dorsal root ganglia neurons, a greater amount of Tau is inclined to accumulate in the central domain of growth cones, and it promotes the stability of the microtubule network. Taken together, these results suggest that PACSIN1 is an important Tau binding partner in regulating microtubule dynamics and forming axonal plasticity.

  13. Xenopus oocyte wound healing as a model system for analysis of microtubule-actin interactions.

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    Zhang, Tong; Mandato, Craig A

    2007-01-01

    Microtubule-actin interactions are fundamental to many cellular processes such as cytokinesis and cellular locomotion. Investigating the mechanism of microtubule-actin interactions is the key to understand the cellular morphogenesis and related pathological processes. The abundance and highly dynamic nature of microtubules and F-actin raise a serious challenge when trying to distinguish between the real and fortuitous interactions within a cell. Xenopus oocyte wound model represents an ideal system to study microtubule-actin interactions as well as microtubule-dependent control of the actin polymerization. Here, we describe a series of cytoskeleton specific treatments in Xenopus oocyte wound healing experiments and use confocal fluorescence microscopy to analyze fixed oocytes to examine microtubule-actin interactions.

  14. The XMAP215-family protein DdCP224 is required for cortical interactions of microtubules

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    Hestermann Andrea

    2004-06-01

    Full Text Available Abstract Background Interactions of peripheral microtubule tips with the cell cortex are of crucial importance for nuclear migration, spindle orientation, centrosome positioning and directional cell movement. Microtubule plus end binding proteins are thought to mediate interactions of microtubule tips with cortical actin and membrane proteins in a dynein-dependent manner. XMAP215-family proteins are main regulators of microtubule plus end dynamics but so far they have not been implicated in the interactions of microtubule tips with the cell cortex. Results Here we show that overexpression of an N-terminal fragment of DdCP224, the Dictyostelium XMAP215 homologue, caused a collapse of the radial microtubule cytoskeleton, whereby microtubules lost contact with the cell cortex and were dragged behind like a comet tail of an unusually motile centrosome. This phenotype was indistinguishable from mutants overexpressing fragments of the dynein heavy chain or intermediate chain. Moreover, it was accompanied by dispersal of the Golgi apparatus and reduced cortical localization of the dynein heavy chain indicating a disrupted dynein/dynactin interaction. The interference of DdCP224 with cortical dynein function is strongly supported by the observations that DdCP224 and its N-terminal fragment colocalize with dynein and coimmunoprecipitate with dynein and dynactin. Conclusions Our data show that XMAP215-like proteins are required for the interaction of microtubule plus ends with the cell cortex in interphase cells and strongly suggest that this function is mediated by dynein.

  15. XTACC3-XMAP215 association reveals an asymmetric interaction promoting microtubule elongation

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    Mortuza, Gulnahar B.; Cavazza, Tommaso; Garcia-Mayoral, Maria Flor;

    2014-01-01

    chTOG is a conserved microtubule polymerase that catalyses the addition of tubulin dimers to promote microtubule growth. chTOG interacts with TACC3, a member of the transforming acidic coiled-coil (TACC) family. Here we analyse their association using the Xenopus homologues, XTACC3 (TACC3) and XM...

  16. Interactive domains in the molecular chaperone human alphaB crystallin modulate microtubule assembly and disassembly.

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    Joy G Ghosh

    Full Text Available Small heat shock proteins regulate microtubule assembly during cell proliferation and in response to stress through interactions that are poorly understood.Novel functions for five interactive sequences in the small heat shock protein and molecular chaperone, human alphaB crystallin, were investigated in the assembly/disassembly of microtubules and aggregation of tubulin using synthetic peptides and mutants of human alphaB crystallin.The interactive sequence (113FISREFHR(120 exposed on the surface of alphaB crystallin decreased microtubule assembly by approximately 45%. In contrast, the interactive sequences, (131LTITSSLSSDGV(142 and (156ERTIPITRE(164, corresponding to the beta8 strand and the C-terminal extension respectively, which are involved in complex formation, increased microtubule assembly by approximately 34-45%. The alphaB crystallin peptides, (113FISREFHR(120 and (156ERTIPITRE(164, inhibited microtubule disassembly by approximately 26-36%, and the peptides (113FISREFHR(120 and (131LTITSSLSSDGV(142 decreased the thermal aggregation of tubulin by approximately 42-44%. The (131LTITSSLSSDGV(142 and (156ERTIPITRE(164 peptides were more effective than the widely used anti-cancer drug, Paclitaxel, in modulating tubulinmicrotubule dynamics. Mutagenesis of these interactive sequences in wt human alphaB crystallin confirmed the effects of the alphaB crystallin peptides on microtubule assembly/disassembly and tubulin aggregation. The regulation of microtubule assembly by alphaB crystallin varied over a narrow range of concentrations. The assembly of microtubules was maximal at alphaB crystallin to tubulin molar ratios between 1:4 and 2:1, while molar ratios >2:1 inhibited microtubule assembly.Interactive sequences on the surface of human alphaB crystallin collectively modulate microtubule assembly through a dynamic subunit exchange mechanism that depends on the concentration and ratio of alphaB crystallin to tubulin. These are the first

  17. Toxicity and interaction of titanium dioxide nanoparticles with microtubule protein

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    Zahra Naghdi Gheshlaghi; Gholam Hossein Riazi; Shahin Ahmadian; Mahmoud Ghafari; Roya Mahinpour

    2008-01-01

    Titanium dioxide (TiO2) nanoparticles (NPs) are widely used in several manufactured products. The small size of NPs facilitates their uptake into cells as well as transcytosis across epithelial cells into blood and lymph circulation to reach different sites, such as the central nervous system. Different studies have shown the risks that TiO2 NPs in the neuronal system and other organs present. As membranebound layer aggregates or single particles, TiO2 NPs can enter not only cells, but also mitochondria and nuclei.Therefore these particles can interact with cytoplasmic proteins such as microtubules (MTs). MTs are cytoskeletal proteins that are essential in eukaryotic cells for a variety of functions, such as cellular transport, cell motility and mitosis. MTs in neurons are used to transport substances such as neurotransmitters. Single TiO2 NPs in cytoplasm can interact with these proteins and affect their crucial functions in different tissues. In this study, we showed the effects of TiO2 NPs on MT polymerization and structure using ultraviolet spectrophotometer and fluorometry. The fluorescent spectroscopy showed a significant tubulin conformational change in the presence of TiO2 NPs and the ultraviolet spectroscopy results showed that TiO2 NPs affect tubulin polymerization and decrease it. The aim of this study was to find the potential risks that TiO2 NPs pose to human organs and cells.

  18. Coordinating Interactions: The Event Coordination Notation

    DEFF Research Database (Denmark)

    Kindler, Ekkart

    on a much more technical level. The Event Coordination Notation (ECNO) allows modelling the behaviour of an application on a high level of abstraction that is closer to the application’s domain than to the software realizing it. Still, these models contain all necessary details for actually executing...... implementation of ECNO, which consists of a modelling environment based on Eclipse and the Eclipse Modeling Framework (EMF) and an execution engine, which fully supports all the concepts and features of ECNO discussed in this technical report. All the examples are based on EMF, but the ECNO Engine can be used......The purpose of a domain model is to concisely capture the concepts of an application’s domain, and their relation among each other. Even though the main purpose of domain models is not on implementing the application, major parts of an application can be generated from the application’s domain...

  19. Interaction of an Overexpressed gamma-Tubulin with Microtubules In Vivo and In Vitro.

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    Kofron, M; Nadezdina, E; Vassilev, A; Matuliene, J; Essner, R; Kato, J; Kuriyama, R

    1998-08-01

    gamma-Tubulin is an ubiquitous MTOC (microtubule-organizing center) component essential for the regulation of microtubule functions. A 1.8 kb cDNA coding for gamma-tubulin was isolated from CHO cells. Analysis of nucleotide sequence predicts a protein of 451 amino acids, which is over 97% identical to human and Xenopus gamma-tubulin. When CHO cells were transiently transfected with the gamma-tubulin clone, epitope-tagged full-length, as well as truncated polypeptides (amino acids 1-398 and 1-340), resulted in the formation of cytoplasmic foci of various sizes. Although one of the foci was identified as the centrosome, the rest of the dots were not associated with any other centrosomal components tested so far. The pattern of microtubule organization was not affected by induction of such gamma-tubulin-containing dots in transfected cells. In addition, the cytoplasmic foci were unable to serve as the site for microtubule regrowth in nocodazole-treated cells upon removal of the drug, suggesting that gamma-tubulin-containing foci were not involved in the activity for microtubule formation and organization. Using the monomeric form of Chlamydomonas gamma-tubulin purified from insect Sf9 cells (), interaction between gamma-tubulin and microtubules was further investigated by immunoelectron microscopy. Microtubules incubated with gamma-tubulin monomers in vitro were associated with more gold particles conjugated with gamma-tubulin than in controls where no exogenous gamma-tubulin was added. However, binding of gamma-tubulin to microtubules was not extensive and was easily lost during sample preparation. Although gamma-tubulin was detected at the minus end of microtubules several times more frequently than the plus end, the majority of gold particles were seen along the microtubule length. These results contradict the previous reports (; ), which might be ascribed to the difference in the level of protein expression in transfected cells.

  20. Encoding the microtubule structure: Allosteric interactions between the microtubule +TIP complex master regulators and TOG-domain proteins

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    Grimaldi, Ashley D; Zanic, Marija; Kaverina, Irina

    2015-01-01

    Since their initial discovery, the intriguing proteins of the +TIP network have been the focus of intense investigation. Although many of the individual +TIP functions have been revealed, the capacity for +TIP proteins to regulate each other has not been widely addressed. Importantly, recent studies involving EBs, the master regulators of the +TIP complex, and several TOG-domain proteins have uncovered a novel mechanism of mutual +TIP regulation: allosteric interactions through changes in microtubule structure. These findings have added another level of complexity to the existing evidence on +TIP regulation and highlight the cooperative nature of the +TIP protein network. PMID:25895033

  1. Kinetochore–microtubule error correction is driven by differentially regulated interaction modes

    OpenAIRE

    Kalantzaki, Maria; Kitamura, Etsushi; Zhang, Tongli; Mino, Akihisa; Novák, Béla; Tanaka, Tomoyuki U

    2015-01-01

    For proper chromosome segregation, sister kinetochores must interact with microtubules from opposite spindle poles (bi-orientation). To establish bi-orientation, aberrant kinetochore–microtubule attachments are disrupted (error correction) by Aurora B kinase (Ipl1 in budding yeast). Paradoxically, during this disruption, new attachments are still formed efficiently to allow fresh attempts at bi-orientation. How this is possible remains an enigma. Here we show that kinetochore attachment to th...

  2. Interactions of the HSV-1 UL25 Capsid Protein with Cellular Microtubule-associated Protein

    Institute of Scientific and Technical Information of China (English)

    Lei GUO; Ying ZHANG; Yan-chun CHE; Wen-juan WU; Wei-zhong LI; Li-chun WANG; Yun LIAO; Long-ding LIU; Qi-han LI

    2008-01-01

    An interaction between the HSV-1 UL25 capsid protein and cellular microtubule-associated protein was found using a yeast two-hybrid screen and β-D-galactosidase activity assays. Immunofluorescence microscopy of the UL25 protein demonstrated its co-localization with cellular microtubule-associated protein in the plasma membrane. Further investigations with deletion mutants suggest that UL25 is likely to have a function in the nucleus.

  3. Microtubules as key coordinators of nuclear envelope and endoplasmic reticulum dynamics during mitosis.

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    Schlaitz, Anne-Lore

    2014-07-01

    During mitosis, cells comprehensively restructure their interior to promote the faithful inheritance of DNA and cytoplasmic contents. In metazoans, this restructuring entails disassembly of the nuclear envelope, redistribution of its components into the endoplasmic reticulum (ER) and eventually nuclear envelope reassembly around the segregated chromosomes. The microtubule cytoskeleton has recently emerged as a critical regulator of mitotic nuclear envelope and ER dynamics. Microtubules and associated molecular motors tear open the nuclear envelope in prophase and remove nuclear envelope remnants from chromatin. Additionally, two distinct mechanisms of microtubule-based regulation of ER dynamics operate later in mitosis. First, association of the ER with microtubules is reduced, preventing invasion of ER into the spindle area, and second, organelle membrane is actively cleared from metaphase chromosomes. However, we are only beginning to understand the role of microtubules in shaping and distributing ER and other organelles during mitosis. © 2014 WILEY Periodicals, Inc.

  4. In vitro reconstitution of dynamic microtubules interacting with actin filament networks

    NARCIS (Netherlands)

    Preciado Lopez, M.; Huber, F.; Grigoriev, Ilya; Steinmetz, M.O.; Akhmanova, Anna; Dogterom, M.; Koenderink, G.H.

    2014-01-01

    Interactions between microtubules and actin filaments (F-actin) are essential for eukaryotic cell migration, polarization, growth, and division. Although the importance of these interactions has been long recognized, the inherent complexity of the cell interior hampers a detailed mechanistic study o

  5. Arabidopsis phospholipase D alpha 1-derived phosphatidic acid regulates microtubule organization and cell development under microtubule-interacting drugs treatment.

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    Zhang, Qun; Qu, Yana; Wang, Qing; Song, Ping; Wang, Peipei; Jia, Qianru; Guo, Jinhe

    2017-01-01

    Phospholipase D (PLD) and its product phosphatidic acid (PA) are emerging as essential regulators of cytoskeleton organization in plants. However, the underlying molecular mechanisms of PA-mediated microtubule reorganization in plants remain largely unknown. In this study, we used pharmacological and genetic approaches to analyze the function of Arabidopsis thaliana PLDα1 in the regulation of microtubule organization and cell development in response to microtubule-affecting drugs. Treatment with the microtubule-stabilizing drug paclitaxel resulted in less growth inhibition and decreased rightward slant of roots, longitudinal alignment of microtubules, and enhanced length of hypocotyl epidermal cells in the pldα1 mutant, the phenotype of which was rescued by exogenous application of PA. Moreover, the pldα1 mutant was sensitive to the microtubule-disrupting drugs oryzalin and propyzamide in terms of seedling survival ratio, left-skewing angle of roots and microtubule organization. In addition, both disruption and stabilization of microtubules induced by drugs activated PLDα1 activity. Our findings demonstrate that in A. thaliana, PLDα1/PA might regulate cell development by modulating microtubule organization in an activity-dependent manner.

  6. Meiosis I chromosome segregation is established through regulation of microtubule-kinetochore interactions.

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    Miller, Matthew P; Unal, Elçin; Brar, Gloria A; Amon, Angelika

    2012-12-18

    During meiosis, a single round of DNA replication is followed by two consecutive rounds of nuclear divisions called meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate, while sister chromatids remain together. Determining how this unusual chromosome segregation behavior is established is central to understanding germ cell development. Here we show that preventing microtubule-kinetochore interactions during premeiotic S phase and prophase I is essential for establishing the meiosis I chromosome segregation pattern. Premature interactions of kinetochores with microtubules transform meiosis I into a mitosis-like division by disrupting two key meiosis I events: coorientation of sister kinetochores and protection of centromeric cohesin removal from chromosomes. Furthermore we find that restricting outer kinetochore assembly contributes to preventing premature engagement of microtubules with kinetochores. We propose that inhibition of microtubule-kinetochore interactions during premeiotic S phase and prophase I is central to establishing the unique meiosis I chromosome segregation pattern.DOI:http://dx.doi.org/10.7554/eLife.00117.001.

  7. Kinetochore-microtubule error correction is driven by differentially regulated interaction modes.

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    Kalantzaki, Maria; Kitamura, Etsushi; Zhang, Tongli; Mino, Akihisa; Novák, Béla; Tanaka, Tomoyuki U

    2015-04-01

    For proper chromosome segregation, sister kinetochores must interact with microtubules from opposite spindle poles (bi-orientation). To establish bi-orientation, aberrant kinetochore-microtubule attachments are disrupted (error correction) by aurora B kinase (Ipl1 in budding yeast). Paradoxically, during this disruption, new attachments are still formed efficiently to enable fresh attempts at bi-orientation. How this is possible remains an enigma. Here we show that kinetochore attachment to the microtubule lattice (lateral attachment) is impervious to aurora B regulation, but attachment to the microtubule plus end (end-on attachment) is disrupted by this kinase. Thus, a new lateral attachment is formed without interference, then converted to end-on attachment and released if incorrect. This process continues until bi-orientation is established and stabilized by tension across sister kinetochores. We reveal how aurora B specifically promotes disruption of the end-on attachment through phospho-regulation of kinetochore components Dam1 and Ndc80. Our results reveal fundamental mechanisms for promoting error correction for bi-orientation.

  8. Microtubule-associated proteins and tubulin interaction by isothermal titration calorimetry.

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    Tsvetkov, P O; Barbier, P; Breuzard, G; Peyrot, V; Devred, F

    2013-01-01

    Microtubules play an important role in a number of vital cell processes such as cell division, intracellular transport, and cell architecture. The highly dynamic structure of microtubules is tightly regulated by a number of stabilizing and destabilizing microtubule-associated proteins (MAPs), such as tau and stathmin. Because of their importance, tubulin-MAPs interactions have been extensively studied using various methods that provide researchers with complementary but sometimes contradictory thermodynamic data. Isothermal titration calorimetry (ITC) is the only direct thermodynamic method that enables a full thermodynamic characterization (stoichiometry, enthalpy, entropy of binding, and association constant) of the interaction after a single titration experiment. This method has been recently applied to study tubulin-MAPs interactions in order to bring new insights into molecular mechanisms of tubulin regulation. In this chapter, we review the technical specificity of this method and then focus on the use of ITC in the investigation of tubulin-MAPs binding. We describe technical issues which could arise during planning and carrying out the ITC experiments, in particular with fragile proteins such as tubulin. Using examples of stathmin and tau, we demonstrate how ITC can be used to gain major insights into tubulin-MAP interaction. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Highly Transient Molecular Interactions Underlie the Stability of Kinetochore–Microtubule Attachment During Cell Division

    OpenAIRE

    Zaytsev, Anatoly V.; Ataullakhanov, Fazly I; Grishchuk, Ekaterina L.

    2013-01-01

    Chromosome segregation during mitosis is mediated by spindle microtubules that attach to chromosomal kinetochores with strong yet labile links. The exact molecular composition of the kinetochore–microtubule interface is not known but microtubules are thought to bind to kinetochores via the specialized microtubule-binding sites, which contain multiple microtubule-binding proteins. During prometaphase the lifetime of microtubule attachments is short but in metaphase it increases 3-fold, presuma...

  10. Coordinate transformation approach to social interactions

    Directory of Open Access Journals (Sweden)

    Steve W C Chang

    2013-08-01

    Full Text Available A coordinate transformation framework for understanding how neurons compute sensorimotor behaviors has generated significant advances towards our understanding of basic brain function. This influential scaffold focuses on neuronal encoding of spatial information represented in different coordinate systems (e.g., eye-centered, hand-centered and how multiple brain regions partake in transforming these signals in order to ultimately generate a motor output. A powerful analogy can be drawn from the coordinate transformation framework to better elucidate how the nervous system computes cognitive variables for social behavior. Of particular relevance is how the brain represents information with respect to oneself and other individuals, such as in reward outcome assignment during social exchanges, in order to influence social decisions. In this article, I outline how the coordinate transformation framework can help guide our understanding of neural computations resulting in social interactions. Implications for numerous psychiatric disorders with impaired representations of self and others are also discussed.

  11. TINA interacts with the NIMA kinase in Aspergillus nidulans and negatively regulates astral microtubules during metaphase arrest.

    Science.gov (United States)

    Osmani, Aysha H; Davies, Jonathan; Oakley, C Elizabeth; Oakley, Berl R; Osmani, Stephen A

    2003-08-01

    The tinA gene of Aspergillus nidulans encodes a protein that interacts with the NIMA mitotic protein kinase in a cell cycle-specific manner. Highly similar proteins are encoded in Neurospora crassa and Aspergillus fumigatus. TINA and NIMA preferentially interact in interphase and larger forms of TINA are generated during mitosis. Localization studies indicate that TINA is specifically localized to the spindle pole bodies only during mitosis in a microtubule-dependent manner. Deletion of tinA alone is not lethal but displays synthetic lethality in combination with the anaphase-promoting complex/cyclosome mutation bimE7. At the bimE7 metaphase arrest point, lack of TINA enhanced the nucleation of bundles of cytoplasmic microtubules from the spindle pole bodies. These microtubules interacted to form spindles joined in series via astral microtubules as revealed by live cell imaging. Because TINA is modified and localizes to the spindle pole bodies at mitosis, and lack of TINA causes enhanced production of cytoplasmic microtubules at metaphase arrest, we suggest TINA is involved in negative regulation of the astral microtubule organizing capacity of the spindle pole bodies during metaphase.

  12. FRET and FRAP imaging: approaches to characterise tau and stathmin interactions with microtubules in cells.

    Science.gov (United States)

    Nouar, Roqiya; Devred, François; Breuzard, Gilles; Peyrot, Vincent

    2013-04-01

    Microtubules (MTs) are involved in many crucial processes such as cell morphogenesis, mitosis and motility. These dynamic structures resulting from the complex assembly of tubulin are tightly regulated by stabilising MT-associated proteins (MAPs) such as tau and destabilising proteins, notably stathmin. Because of their key role, these MAPs and their interactions have been extensively studied using biochemical and biophysical approaches, particularly in vitro. Nevertheless, numerous questions remain unanswered and the mechanisms of interaction between MT and these proteins are still unclear in cells. Techniques coupling cell imaging and fluorescence methods, such as Förster resonance energy transfer and fluorescence recovery after photobleaching, are excellent tools to study these interactions in situ. After describing these methods, we will present emblematic data from the literature and unpublished experimental results from our laboratory concerning the interactions between MTs, tau and stathmin in cells.

  13. TCS1, a Microtubule-Binding Protein, Interacts with KCBP/ZWICHEL to Regulate Trichome Cell Shape in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Liangliang Chen

    2016-10-01

    Full Text Available How cell shape is controlled is a fundamental question in developmental biology, but the genetic and molecular mechanisms that determine cell shape are largely unknown. Arabidopsis trichomes have been used as a good model system to investigate cell shape at the single-cell level. Here we describe the trichome cell shape 1 (tcs1 mutants with the reduced trichome branch number in Arabidopsis. TCS1 encodes a coiled-coil domain-containing protein. Pharmacological analyses and observations of microtubule dynamics show that TCS1 influences the stability of microtubules. Biochemical analyses and live-cell imaging indicate that TCS1 binds to microtubules and promotes the assembly of microtubules. Further results reveal that TCS1 physically associates with KCBP/ZWICHEL, a microtubule motor involved in the regulation of trichome branch number. Genetic analyses indicate that kcbp/zwi is epistatic to tcs1 with respect to trichome branch number. Thus, our findings define a novel genetic and molecular mechanism by which TCS1 interacts with KCBP to regulate trichome cell shape by influencing the stability of microtubules.

  14. The von Hippel-Lindau tumour suppressor interacts with microtubules through kinesin-2

    NARCIS (Netherlands)

    Lolkema, M.P.J.K.; Mans, D.A.; Snijckers, C.M.J.T.; Noort, Mascha van; Beest, M. van; Voest, E.E.; Giles, R.H.

    2007-01-01

    Synthesis and maintenance of primary cilia are regulated by the von Hippel-Lindau (VHL) tumour suppressor protein. Recent studies indicate that this regulation is linked to microtubule-dependent functions of pVHL such as orienting microtubule growth and increasing plus-end microtubule stability, how

  15. G protein betagamma subunits interact with alphabeta- and gamma-tubulin and play a role in microtubule assembly in PC12 cells.

    Science.gov (United States)

    Montoya, Valentina; Gutierrez, Christina; Najera, Omar; Leony, Denisse; Varela-Ramirez, Armando; Popova, Juliana; Rasenick, Mark M; Das, Siddhartha; Roychowdhury, Sukla

    2007-12-01

    The betagamma subunit of G proteins (Gbetagamma) is known to transfer signals from cell surface receptors to intracellular effector molecules. Recent results suggest that Gbetagamma also interacts with microtubules and is involved in the regulation of the mitotic spindle. In the current study, the anti-microtubular drug nocodazole was employed to investigate the mechanism by which Gbetagamma interacts with tubulin and its possible implications in microtubule assembly in cultured PC12 cells. Nocodazole-induced depolymerization of microtubules drastically inhibited the interaction between Gbetagamma and tubulin. Gbetagamma was preferentially bound to microtubules and treatment with nocodazole suggested that the dissociation of Gbetagamma from microtubules is an early step in the depolymerization process. When microtubules were allowed to recover after removal of nocodazole, the tubulin-Gbetagamma interaction was restored. Unlike Gbetagamma, however, the interaction between tubulin and the alpha subunit of the Gs protein (Gsalpha) was not inhibited by nocodazole, indicating that the inhibition of tubulin-Gbetagamma interactions during microtubule depolymerization is selective. We found that Gbetagamma also interacts with gamma-tubulin, colocalizes with gamma-tubulin in centrosomes, and co-sediments in centrosomal fractions. The interaction between Gbetagamma and gamma-tubulin was unaffected by nocodazole, suggesting that the Gbetagamma-gamma-tubulin interaction is not dependent on assembled microtubules. Taken together, our results suggest that Gbetagamma may play an important and definitive role in microtubule assembly and/or stability. We propose that betagamma-microtubule interaction is an important step for G protein-mediated cell activation. These results may also provide new insights into the mechanism of action of anti-microtubule drugs.

  16. Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance

    Science.gov (United States)

    Tischfield, Max A.; Baris, Hagit N.; Wu, Chen; Rudolph, Guenther; Van Maldergem, Lionel; He, Wei; Chan, Wai-Man; Andrews, Caroline; Demer, Joseph L.; Robertson, Richard L.; Mackey, David A.; Ruddle, Jonathan B.; Bird, Thomas D.; Gottlob, Irene; Pieh, Christina; Traboulsi, Elias I.; Pomeroy, Scott L.; Hunter, David G.; Soul, Janet S.; Newlin, Anna; Sabol, Louise J.; Doherty, Edward J.; de Uzcátegui, Clara E.; de Uzcátegui, Nicolas; Collins, Mary Louise Z.; Sener, Emin C.; Wabbels, Bettina; Hellebrand, Heide; Meitinger, Thomas; de Berardinis, Teresa; Magli, Adriano; Schiavi, Costantino; Pastore-Trossello, Marco; Koc, Feray; Wong, Agnes M.; Levin, Alex V.; Geraghty, Michael T.; Descartes, Maria; Flaherty, Maree; Jamieson, Robyn V.; Møller, H. U.; Meuthen, Ingo; Callen, David F.; Kerwin, Janet; Lindsay, Susan; Meindl, Alfons; Gupta, Mohan L.; Pellman, David; Engle, Elizabeth C.

    2011-01-01

    We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific β-tubulin isotype III, result in a spectrum of human nervous system disorders we now call the TUBB3 syndromes. Each mutation causes the ocular motility disorder CFEOM3, whereas some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy. Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves, and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities. We show the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules. Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors. These findings demonstrate normal TUBB3 is required for axon guidance and maintenance in mammals. PMID:20074521

  17. Effects of mutual interaction of Laccaria laccata with Trichoderma harzianum and T. virens on the morphology of microtubules and mitochondria.

    Science.gov (United States)

    Zadworny, M; Tuszyńska, S; Samardakiewicz, S; Werner, A

    2007-01-01

    Organelles are known to respond to challenges caused by many stress factors. The morphology of the microtubular cytoskeleton and mitochondria during mutual interaction in coculture of Laccaria laccata with Trichoderma harzianum and T. virens were examined. Hyphae from the interaction region were sampled between 4 and 12 days of growth. Microtubules were labelled with a specific antibody and mitochondria with 3,3'-dihexyloxacarbocyanine iodide, and the organelles were examined microscopically. The morphology of microtubules and mitochondria were similar in all three fungi. Microtubules were arranged in long arrays parallel to the hyphal axis and mitochondria formed an interconnected network. In hyphae growing within the interaction zone, microtubules became wavy and eventually fragmented or depolymerised, and mitochondria also became fragmented. The effects were time-dependent. In general, the organelles of all three fungi were affected during the interaction, but L. laccata was affected the least and to the same extent by each of the saprotrophic fungi. The saprotrophic fungi were affected by L. laccata to a similar extent at 4 and 8 days of interaction. Our results suggest that the studied fungi antagonistically affect each other at the cellular level, although the mechanisms involved remain to be elucidated.

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

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    Qun Zhang

    2015-12-01

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

  19. Microtubule-Actin Cross-Linking Factor 1: Domains, Interaction Partners, and Tissue-Specific Functions.

    Science.gov (United States)

    Goryunov, Dmitry; Liem, Ronald K H

    2016-01-01

    The cytoskeleton of most eukaryotic cells is composed of three principal filamentous components: actin filaments, microtubules (MTs), and intermediate filaments. It is a highly dynamic system that plays crucial roles in a wide range of cellular processes, including migration, adhesion, cytokinesis, morphogenesis, intracellular traffic and signaling, and structural flexibility. Among the large number of cytoskeleton-associated proteins characterized to date, microtubule-actin cross-linking factor 1 (MACF1) is arguably the most versatile integrator and modulator of cytoskeleton-related processes. MACF1 belongs to the plakin family of proteins, and within it, to the spectraplakin subfamily. These proteins are characterized by the ability to bridge MT and actin cytoskeletal networks in a dynamic fashion, which underlies their involvement in the regulation of cell migration, axonal extension, and vesicular traffic. Studying MACF1 functions has provided insights not only into the regulation of the cytoskeleton but also into molecular mechanisms of both normal cellular physiology and cellular pathology. Multiple MACF1 isoforms exist, composed of a large variety of alternatively spliced domains. Each of these domains mediates a specific set of interactions and functions. These functions are manifested in tissue and cell-specific phenotypes observed in conditional MACF1 knockout mice. The conditional models described to date reveal critical roles of MACF1 in mammalian skin, nervous system, heart muscle, and intestinal epithelia. Complete elimination of MACF1 is early embryonic lethal, indicating an essential role for MACF1 in early development. Further studies of MACF1 domains and their interactions will likely reveal multiple new roles of this protein in various tissues.

  20. Mechanics of kinetochore microtubules and their interactions with chromosomes during cell division

    Science.gov (United States)

    Nazockdast, Ehssan; Fürthauer, Sebastian; Redemann, Stephanie; Baumgart, Johannes; Lindow, Norbert; Kratz, Andrea; Prohaska, Steffen; Müller-Reichert, Thomas; Shelley, Michael

    2016-11-01

    The accurate segregation of chromosomes, and subsequent cell division, in Eukaryotic cells is achieved by the interactions of an assembly of microtubules (MTs) and motor-proteins, known as the mitotic spindle. We use a combination of our computational platform for simulating cytoskeletal assemblies and our structural data from high-resolution electron tomography of the mitotic spindle, to study the kinetics and mechanics of MTs in the spindle, and their interactions with chromosomes during chromosome segregation in the first cell division in C.elegans embryo. We focus on kinetochore MTs, or KMTs, which have one end attached to a chromosome. KMTs are thought to be a key mechanical component in chromosome segregation. Using exploratory simulations of MT growth, bending, hydrodynamic interactions, and attachment to chromosomes, we propose a mechanical model for KMT-chromosome interactions that reproduces observed KMT length and shape distributions from electron tomography. We find that including detailed hydrodynamic interactions between KMTs is essential for agreement with the experimental observations.

  1. Response to microtubule-interacting agents in primary epithelial ovarian cancer cells

    Science.gov (United States)

    2013-01-01

    Background Ovarian cancer constitutes nearly 4% of all cancers among women and is the leading cause of death from gynecologic malignancies in the Western world. Standard first line adjuvant chemotherapy treatments include Paclitaxel (Taxol) and platinum-based agents. Taxol, epothilone B (EpoB) and discodermolide belong to a family of anti-neoplastic agents that specifically interferes with microtubules and arrests cells in the G2/M phase of the cell cycle. Despite initial success with chemotherapy treatment, many patients relapse due to chemotherapy resistance. In vitro establishment of primary ovarian cancer cells provides a powerful tool for better understanding the mechanisms of ovarian cancer resistance. We describe the generation and characterization of primary ovarian cancer cells derived from ascites fluids of patients with epithelial ovarian cancer. Methods Chemosensitivity of these cell lines to Taxol, EpoB and discodermolide was tested, and cell cycle analysis was compared to that of immortalized ovarian cancer cell lines SKOV3 and Hey. The relationship between drug resistance and αβ-tubulin and p53 status was also investigated. Results All newly generated primary cancer cells were highly sensitive to the drugs. αβ-tubulin mutation was not found in any primary cell lines tested. However, one cell line that harbors p53 mutation at residue 72 (Arg to Pro) exhibits altered cell cycle profile in response to all drug treatments. Immortalized ovarian cancer cells respond differently to EpoB treatment when compared to primary ovarian cancer cells, and p53 polymorphism suggests clinical significance in the anti-tumor response in patients. Conclusions The isolation and characterization of primary ovarian cancer cells from ovarian cancer patients’ specimens contribute to further understanding the nature of drug resistance to microtubule interacting agents (MIAs) currently used in clinical settings. PMID:23574945

  2. Study on interaction between microtubule associated protein tau and prion protein

    Institute of Scientific and Technical Information of China (English)

    HAN Jun; ZHOU Wei; DONG Xiaoping; ZHANG Jin; YAO Hailan; WANG Xiaofan; LI Feng; CHEN Lan; GAO Chen; GAO Jianmei; NIE Kai

    2006-01-01

    Microtubule-associated protein tau is considered to play roles in many neurodegenerative diseases including some transmissible spongiform encephalopathies. To address the possible molecular linkage of prion protein (PrP) and tau, a GST-fusion segment of human tau covering the three-repeat region and various PrP segments was used in the tests of GST pull-down and immunoprecipitation. We found tau protein interacted with various style prion proteins such as native prion protein (PrPC) or protease-resistant isoform (prpSc). Co-localization signals of tau and PrP were found in the CHO cell tranfected with both PrP and tau gene. The domain of interaction with tau was located at N-terminal of PrP (residues 23 to 91). The evidence of molecular interactions between PrP and tau protein highlights a potential role of tau in the biological function of PrP and the pathogenesis of TSEs.

  3. Regulation of a dynamic interaction between two microtubule-binding proteins, EB1 and TIP150, by the mitotic p300/CBP-associated factor (PCAF) orchestrates kinetochore microtubule plasticity and chromosome stability during mitosis.

    Science.gov (United States)

    Ward, Tarsha; Wang, Ming; Liu, Xing; Wang, Zhikai; Xia, Peng; Chu, Youjun; Wang, Xiwei; Liu, Lifang; Jiang, Kai; Yu, Huijuan; Yan, Maomao; Wang, Jianyu; Hill, Donald L; Huang, Yuejia; Zhu, Tongge; Yao, Xuebiao

    2013-05-31

    The microtubule cytoskeleton network orchestrates cellular dynamics and chromosome stability in mitosis. Although tubulin acetylation is essential for cellular plasticity, it has remained elusive how kinetochore microtubule plus-end dynamics are regulated by p300/CBP-associated factor (PCAF) acetylation in mitosis. Here, we demonstrate that the plus-end tracking protein, TIP150, regulates dynamic kinetochore-microtubule attachments by promoting the stability of spindle microtubule plus-ends. Suppression of TIP150 by siRNA results in metaphase alignment delays and perturbations in chromosome biorientation. TIP150 is a tetramer that binds an end-binding protein (EB1) dimer through the C-terminal domains, and overexpression of the C-terminal TIP150 or disruption of the TIP150-EB1 interface by a membrane-permeable peptide perturbs chromosome segregation. Acetylation of EB1-PCAF regulates the TIP150 interaction, and persistent acetylation perturbs EB1-TIP150 interaction and accurate metaphase alignment, resulting in spindle checkpoint activation. Suppression of the mitotic checkpoint serine/threonine protein kinase, BubR1, overrides mitotic arrest induced by impaired EB1-TIP150 interaction, but cells exhibit whole chromosome aneuploidy. Thus, the results identify a mechanism by which the TIP150-EB1 interaction governs kinetochore microtubule plus-end plasticity and establish that the temporal control of the TIP150-EB1 interaction by PCAF acetylation ensures chromosome stability in mitosis.

  4. Regulation of a Dynamic Interaction between Two Microtubule-binding Proteins, EB1 and TIP150, by the Mitotic p300/CBP-associated Factor (PCAF) Orchestrates Kinetochore Microtubule Plasticity and Chromosome Stability during Mitosis*

    Science.gov (United States)

    Ward, Tarsha; Wang, Ming; Liu, Xing; Wang, Zhikai; Xia, Peng; Chu, Youjun; Wang, Xiwei; Liu, Lifang; Jiang, Kai; Yu, Huijuan; Yan, Maomao; Wang, Jianyu; Hill, Donald L.; Huang, Yuejia; Zhu, Tongge; Yao, Xuebiao

    2013-01-01

    The microtubule cytoskeleton network orchestrates cellular dynamics and chromosome stability in mitosis. Although tubulin acetylation is essential for cellular plasticity, it has remained elusive how kinetochore microtubule plus-end dynamics are regulated by p300/CBP-associated factor (PCAF) acetylation in mitosis. Here, we demonstrate that the plus-end tracking protein, TIP150, regulates dynamic kinetochore-microtubule attachments by promoting the stability of spindle microtubule plus-ends. Suppression of TIP150 by siRNA results in metaphase alignment delays and perturbations in chromosome biorientation. TIP150 is a tetramer that binds an end-binding protein (EB1) dimer through the C-terminal domains, and overexpression of the C-terminal TIP150 or disruption of the TIP150-EB1 interface by a membrane-permeable peptide perturbs chromosome segregation. Acetylation of EB1-PCAF regulates the TIP150 interaction, and persistent acetylation perturbs EB1-TIP150 interaction and accurate metaphase alignment, resulting in spindle checkpoint activation. Suppression of the mitotic checkpoint serine/threonine protein kinase, BubR1, overrides mitotic arrest induced by impaired EB1-TIP150 interaction, but cells exhibit whole chromosome aneuploidy. Thus, the results identify a mechanism by which the TIP150-EB1 interaction governs kinetochore microtubule plus-end plasticity and establish that the temporal control of the TIP150-EB1 interaction by PCAF acetylation ensures chromosome stability in mitosis. PMID:23595990

  5. Accurate phosphoregulation of kinetochore–microtubule affinity requires unconstrained molecular interactions

    Science.gov (United States)

    Zaytsev, Anatoly V.; Sundin, Lynsie J.R.; DeLuca, Keith F.

    2014-01-01

    Accurate chromosome segregation relies on dynamic interactions between microtubules (MTs) and the NDC80 complex, a major kinetochore MT-binding component. Phosphorylation at multiple residues of its Hec1 subunit may tune kinetochore–MT binding affinity for diverse mitotic functions, but molecular details of such phosphoregulation remain elusive. Using quantitative analyses of mitotic progression in mammalian cells, we show that Hec1 phosphorylation provides graded control of kinetochore–MT affinity. In contrast, modeling the kinetochore interface with repetitive MT binding sites predicts a switchlike response. To reconcile these findings, we hypothesize that interactions between NDC80 complexes and MTs are not constrained, i.e., the NDC80 complexes can alternate their binding between adjacent kinetochore MTs. Experiments using cells with phosphomimetic Hec1 mutants corroborate predictions of such a model but not of the repetitive sites model. We propose that accurate regulation of kinetochore–MT affinity is driven by incremental phosphorylation of an NDC80 molecular “lawn,” in which the NDC80–MT bonds reorganize dynamically in response to the number and stability of MT attachments. PMID:24982430

  6. Molecular mechanisms of antitumor activity of taxanes. I. Interaction of docetaxel with microtubules

    Directory of Open Access Journals (Sweden)

    Sabina Tabaczar

    2010-11-01

    Full Text Available Docetaxel (Taxotere, a new semisynthetic taxoid, is a mitotic inhibitor, widely used in monotherapy or in combination with other anticancer drugs against many types of cancer. The structure and dynamics of microtubules as the main target for docetaxel activity inside the cell and the taxane-binding site on β-tubulin are discussed. Microtubules are highly dynamic assemblies of α- and β-tubulin. They readily polymerize and depolymerize in cells and these dynamic behaviours are crucial to cell mitosis. Microtubule instability is attributed to their capability to hydrolyze GTP to GDP, which causes their depolymerization. Addition of new α-, β-tubulin heterodimer bound to GTP leads to tubulin polymerization, which increases the length of the microtubule. Docetaxel alters the polymerization dynamics of microtubules, which causes blockage of cell mitosis, and consequently induces apoptotic and non-apoptotic cell death. Docetaxel specifically acts on the S, M and G2 phases of the cell cycle. This paper reviews the current state of knowledge related to the molecular mechanisms of docetaxel action on the cell cycle and microtubule dynamics. In addition, a brief survey of the present state of research on the new generation (2nd and 3rd of taxanes is presented.

  7. Linking cortical microtubule attachment and exocytosis [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Ivar Noordstra

    2017-04-01

    Full Text Available Exocytosis is a fundamental cellular process whereby secreted molecules are packaged into vesicles that move along cytoskeletal filaments and fuse with the plasma membrane. To function optimally, cells are strongly dependent on precisely controlled delivery of exocytotic cargo. In mammalian cells, microtubules serve as major tracks for vesicle transport by motor proteins, and thus microtubule organization is important for targeted delivery of secretory carriers. Over the years, multiple microtubule-associated and cortical proteins have been discovered that facilitate the interaction between the microtubule plus ends and the cell cortex. In this review, we focus on mammalian protein complexes that have been shown to participate in both cortical microtubule capture and exocytosis, thereby regulating the spatial organization of secretion. These complexes include microtubule plus-end tracking proteins, scaffolding factors, actin-binding proteins, and components of vesicle docking machinery, which together allow efficient coordination of cargo transport and release.

  8. TPX2 phosphorylation maintains metaphase spindle length by regulating microtubule flux

    Science.gov (United States)

    Fu, Jingyan; Bian, Minglei; Xin, Guangwei; Deng, Zhaoxuan; Luo, Jia; Guo, Xiao; Chen, Hao; Wang, Yao; Jiang, Qing

    2015-01-01

    A steady-state metaphase spindle maintains constant length, although the microtubules undergo intensive dynamics. Tubulin dimers are incorporated at plus ends of spindle microtubules while they are removed from the minus ends, resulting in poleward movement. Such microtubule flux is regulated by the microtubule rescue factors CLASPs at kinetochores and depolymerizing protein Kif2a at the poles, along with other regulators of microtubule dynamics. How microtubule polymerization and depolymerization are coordinated remains unclear. Here we show that TPX2, a microtubule-bundling protein and activator of Aurora A, plays an important role. TPX2 was phosphorylated by Aurora A during mitosis. Its phospho-null mutant caused short metaphase spindles coupled with low microtubule flux rate. Interestingly, phosphorylation of TPX2 regulated its interaction with CLASP1 but not Kif2a. The effect of its mutant in shortening the spindle could be rescued by codepletion of CLASP1 and Kif2a that abolished microtubule flux. Together we propose that Aurora A–dependent TPX2 phosphorylation controls mitotic spindle length through regulating microtubule flux. PMID:26240182

  9. Virtual Partner Interaction (VPI: exploring novel behaviors via coordination dynamics.

    Directory of Open Access Journals (Sweden)

    J A Scott Kelso

    Full Text Available Inspired by the dynamic clamp of cellular neuroscience, this paper introduces VPI -- Virtual Partner Interaction -- a coupled dynamical system for studying real time interaction between a human and a machine. In this proof of concept study, human subjects coordinate hand movements with a virtual partner, an avatar of a hand whose movements are driven by a computerized version of the Haken-Kelso-Bunz (HKB equations that have been shown to govern basic forms of human coordination. As a surrogate system for human social coordination, VPI allows one to examine regions of the parameter space not typically explored during live interactions. A number of novel behaviors never previously observed are uncovered and accounted for. Having its basis in an empirically derived theory of human coordination, VPI offers a principled approach to human-machine interaction and opens up new ways to understand how humans interact with human-like machines including identification of underlying neural mechanisms.

  10. Quantification of Aromaticity Based on Interaction Coordinates: A New Proposal.

    Science.gov (United States)

    Pandey, Sarvesh Kumar; Manogaran, Dhivya; Manogaran, Sadasivam; Schaefer, Henry F

    2016-05-12

    Attempts to establish degrees of aromaticity in molecules are legion. In the present study, we begin with a fictitious fragment arising from only those atoms contributing to the aromatic ring and having a force field projected from the original system. For example, in benzene, we adopt a fictitious C6 fragment with a force field projected from the full benzene force field. When one bond or angle is stretched and kept fixed, followed by a partial optimization for all other internal coordinates, structures change from their respective equilibria. These changes are the responses of all other internal coordinates for constraining the bond or angle by unit displacements and relaxing the forces on all other internal coordinates. The "interaction coordinate" derived from the redundant internal coordinate compliance constants measures how a bond (its electron density) responds for constrained optimization when another bond or angle is stretched by a specified unit (its electron density is perturbed by a finite amount). The sum of interaction coordinates (responses) of all bonded neighbors for all internal coordinates of the fictitious fragment is a measure of the strength of the σ and π electron interactions leading to aromatic stability. This sum, based on interaction coordinates, appears to be successful as an aromaticity index for a range of chemical systems. Since the concept involves analyzing a fragment rather than the whole molecule, this idea is more general and is likely to lead to new insights.

  11. Heat-shock protein 70 binds microtubules and interacts with kinesin in tobacco pollen tubes.

    Science.gov (United States)

    Parrotta, Luigi; Cresti, Mauro; Cai, Giampiero

    2013-09-01

    The heat-shock proteins of 70 kDa are a family of ubiquitously expressed proteins important for protein folding. Heat-shock protein 70 assists other nascent proteins to achieve the spatial structure and ultimately helps the cell to protect against stress factors, such as heat. These proteins are localized in different cellular compartments and are associated with the cytoskeleton. We identified a heat-shock protein 70 isoform in the pollen tube of tobacco that binds to microtubules in an ATP-dependent manner. The heat-shock protein 70 was identified as part of the so-called ATP-MAP (ATP-dependent microtubule-associated protein) fraction, which also includes the 90-kDa kinesin, a mitochondria-associated motor protein. The identity of heat-shock protein 70 was validated by immunological assays and mass spectrometry. Sequence analysis showed that this heat-shock protein 70 is more similar to specific heat-shock proteins of Arabidopsis than to corresponding proteins of tobacco. Two-dimensional electrophoresis indicated that this heat-shock protein 70 isoform only is part of the ATP-MAP fraction and that is associated with the mitochondria of pollen tubes. Sedimentation assays showed that the binding of heat-shock protein 70 to microtubules is not affected by AMPPNP but it increases in the presence of the 90-kDa kinesin. Binding of heat-shock protein 70 to microtubules occurs only partially in the presence of ATP but it does not occur if, in addition to ATP, the 90-kDa kinesin is also present. Data suggest that the binding (but not the release) of heat-shock protein 70 to microtubules is facilitated by the 90-kDa kinesin.

  12. Evolutionary games with coordination and self-dependent interactions

    Science.gov (United States)

    Király, Balázs; Szabó, György

    2017-01-01

    Multistrategy evolutionary games are studied on a square lattice when the pair interactions are composed of coordinations between strategy pairs and an additional term with self-dependent payoff. We describe a method for determining the strength of each elementary coordination component in n -strategy potential games. Using analytical and numerical methods, the presence and absence of Ising-type order-disorder phase transitions are studied when a single pair coordination is extended by some types of self-dependent elementary games. We also introduce noise-dependent three-strategy equivalents of the n -strategy elementary coordination games.

  13. Cep70 promotes microtubule assembly in vitro by increasing microtubule elongation

    Institute of Scientific and Technical Information of China (English)

    Xingjuan Shi; Jun Wang; Yunfan Yang; Yuan Ren; Jun Zhou; Dengwen Li

    2012-01-01

    Microtubules are dynamic cytoskeletal polymers present in all eukaryotic cells,In animal cells,they are organized by the centrosome,the major microtubule-organizing center.Many centrosomal proteins act coordinately to modulate microtubule assembly and organization.Our previous work has shown that Cep70,a novel centrosomal protein regulates microtubule assembly and organization in mammalian cells.However,the molecular details remain to be investigated,in this study,we investigated the molecular mechanism of how Cep70 regulates microtubule assembly using purified proteins.Our data showed that Cep70 increased the microtubule length without affecting the microtubule number in the purified system.These results demonstrate that Cep70 could directly regulate microtubule assembly by promoting microtubule elongation instead of microtubule nucleation.

  14. Uranyl-oxo coordination directed by non-covalent interactions.

    Science.gov (United States)

    Lewis, Andrew J; Yin, Haolin; Carroll, Patrick J; Schelter, Eric J

    2014-07-28

    Directed coordination of weakly Lewis acidic K(+) ions to weakly Lewis basic uranyl oxo ligands is accomplished through non-covalent cation-π and cation-F interactions for the first time. Comparison of a family of structurally related diarylamide ligands highlights the role that the cation-π and cation-F interactions play in guiding coordination. Cation binding to uranyl is demonstrated in the solid state and in solution, providing the shortest reported crystallographic uranyl-oxo to potassium distance. UV-Vis, TD-DFT calculations, and electrochemical measurements show that cation coordination directly impacts the electronics at the uranium(vi) cation.

  15. The microtubule plus-end tracking proteins SPR1 and EB1b interact to maintain polar cell elongation and directional organ growth in Arabidopsis.

    Science.gov (United States)

    Galva, Charitha; Kirik, Viktor; Lindeboom, Jelmer J; Kaloriti, Despoina; Rancour, David M; Hussey, Patrick J; Bednarek, Sebastian Y; Ehrhardt, David W; Sedbrook, John C

    2014-11-01

    The microtubule plus-end tracking proteins (+TIPs) END BINDING1b (EB1b) and SPIRAL1 (SPR1) are required for normal cell expansion and organ growth. EB proteins are viewed as central regulators of +TIPs and cell polarity in animals; SPR1 homologs are specific to plants. To explore if EB1b and SPR1 fundamentally function together, we combined genetic, biochemical, and cell imaging approaches in Arabidopsis thaliana. We found that eb1b-2 spr1-6 double mutant roots exhibit substantially more severe polar expansion defects than either single mutant, undergoing right-looping growth and severe axial twisting instead of waving on tilted hard-agar surfaces. Protein interaction assays revealed that EB1b and SPR1 bind each other and tubulin heterodimers, which is suggestive of a microtubule loading mechanism. EB1b and SPR1 show antagonistic association with microtubules in vitro. Surprisingly, our combined analyses revealed that SPR1 can load onto microtubules and function independently of EB1 proteins, setting SPR1 apart from most studied +TIPs in animals and fungi. Moreover, we found that the severity of defects in microtubule dynamics in spr1 eb1b mutant hypocotyl cells correlated well with the severity of growth defects. These data indicate that SPR1 and EB1b have complex interactions as they load onto microtubule plus ends and direct polar cell expansion and organ growth in response to directional cues.

  16. The Microtubule Plus-End Tracking Proteins SPR1 and EB1b Interact to Maintain Polar Cell Elongation and Directional Organ Growth in Arabidopsis[W

    Science.gov (United States)

    Galva, Charitha; Kirik, Viktor; Lindeboom, Jelmer J.; Kaloriti, Despoina; Rancour, David M.; Hussey, Patrick J.; Bednarek, Sebastian Y.; Ehrhardt, David W.; Sedbrook, John C.

    2014-01-01

    The microtubule plus-end tracking proteins (+TIPs) END BINDING1b (EB1b) and SPIRAL1 (SPR1) are required for normal cell expansion and organ growth. EB proteins are viewed as central regulators of +TIPs and cell polarity in animals; SPR1 homologs are specific to plants. To explore if EB1b and SPR1 fundamentally function together, we combined genetic, biochemical, and cell imaging approaches in Arabidopsis thaliana. We found that eb1b-2 spr1-6 double mutant roots exhibit substantially more severe polar expansion defects than either single mutant, undergoing right-looping growth and severe axial twisting instead of waving on tilted hard-agar surfaces. Protein interaction assays revealed that EB1b and SPR1 bind each other and tubulin heterodimers, which is suggestive of a microtubule loading mechanism. EB1b and SPR1 show antagonistic association with microtubules in vitro. Surprisingly, our combined analyses revealed that SPR1 can load onto microtubules and function independently of EB1 proteins, setting SPR1 apart from most studied +TIPs in animals and fungi. Moreover, we found that the severity of defects in microtubule dynamics in spr1 eb1b mutant hypocotyl cells correlated well with the severity of growth defects. These data indicate that SPR1 and EB1b have complex interactions as they load onto microtubule plus ends and direct polar cell expansion and organ growth in response to directional cues. PMID:25415978

  17. Microtubule-membrane interactions in cilia. I. Isolation and characterization of ciliary membranes from Tetrahymena pyriformis

    OpenAIRE

    1980-01-01

    Tetrahymena ciliary membranes were prepared by four different techniques, and their protein composition was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), electron microscopy, and two-dimensional thin-layer peptide mapping. Extraction of the isolated cilia by nonionic detergent solubilized the ciliary membranes but left the axonemal microtubules and dyneine arms intact, as determined by quantitative electron microscopy. The proteins solubilized by detergent ...

  18. Bimanual motor coordination controlled by cooperative interactions in intrinsic and extrinsic coordinates.

    Science.gov (United States)

    Sakurada, Takeshi; Ito, Koji; Gomi, Hiroaki

    2016-01-01

    Although strong motor coordination in intrinsic muscle coordinates has frequently been reported for bimanual movements, coordination in extrinsic visual coordinates is also crucial in various bimanual tasks. To explore the bimanual coordination mechanisms in terms of the frame of reference, here we characterized implicit bilateral interactions in visuomotor tasks. Visual perturbations (finger-cursor gain change) were applied while participants performed a rhythmic tracking task with both index fingers under an in-phase or anti-phase relationship in extrinsic coordinates. When they corrected the right finger's amplitude, the left finger's amplitude unintentionally also changed [motor interference (MI)], despite the instruction to keep its amplitude constant. Notably, we observed two specificities: one was large MI and low relative-phase variability (PV) under the intrinsic in-phase condition, and the other was large MI and high PV under the extrinsic in-phase condition. Additionally, using a multiple-interaction model, we successfully decomposed MI into intrinsic components caused by motor correction and extrinsic components caused by visual-cursor mismatch of the right finger's movements. This analysis revealed that the central nervous system facilitates MI by combining intrinsic and extrinsic components in the condition with in-phases in both intrinsic and extrinsic coordinates, and that under-additivity of the effects is explained by the brain's preference for the intrinsic interaction over extrinsic interaction. In contrast, the PV was significantly correlated with the intrinsic component, suggesting that the intrinsic interaction dominantly contributed to bimanual movement stabilization. The inconsistent features of MI and PV suggest that the central nervous system regulates multiple levels of bilateral interactions for various bimanual tasks.

  19. Molecular imprinting of protein by coordinate interaction

    Institute of Scientific and Technical Information of China (English)

    Jun Wang; Zhen Dong Hua; Zhi Yong Chen; Yuan Zong Li; Mei Ping Zhao

    2009-01-01

    In this article, a novel strong interaction by forming complex between bovine serum albumin (BSA) and copper ion was utilized for the preparation of molecular imprinted hydrogel in aqueous solution. Results show that the inclusion of copper ion in preparation can bridge the template BSA and functional monomers together and improve the imprinting effect compared to the polymer made without copper ion added. High selectivity factor and large adsorption capacity are also observed for the obtained BSA-imprinted hydrogel.

  20. The actin-binding protein capulet genetically interacts with the microtubule motor kinesin to maintain neuronal dendrite homeostasis.

    Directory of Open Access Journals (Sweden)

    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.

  1. An Integrative Perspective on Interpersonal Coordination in Interactive Team Sports

    Directory of Open Access Journals (Sweden)

    Silvan Steiner

    2017-08-01

    Full Text Available Interpersonal coordination is a key factor in team performance. In interactive team sports, the limited predictability of a constantly changing context makes coordination challenging. Approaches that highlight the support provided by environmental information and theories of shared mental models provide potential explanations of how interpersonal coordination can nonetheless be established. In this article, we first outline the main assumptions of these approaches and consider criticisms that have been raised with regard to each. The aim of this article is to define a theoretical perspective that integrates the coordination mechanisms of the two approaches. In doing so, we borrow from a theoretical outline of group action. According to this outline, group action based on a priori shared mental models is an example of how interpersonal coordination is established from the top down. Interpersonal coordination in reaction to the perception of affordances represents the bottom-up component of group action. Both components are inextricably involved in the coordination of interactive sports teams. We further elaborate on the theoretical outline to integrate a third, constructivist approach. Integrating this third approach helps to explain interpersonal coordination in game situations for which no shared mental models are established and game situations that remain ambiguous in terms of perceived affordances. The article describes how hierarchical, sequential, and complex dimensions of action organization are important aspects of this constructivist perspective and how mental models may be involved. A basketball example is used to illustrate how top-down, bottom-up and constructivist processes may be simultaneously involved in enabling interpersonal coordination. Finally, we present the implications for research and practice.

  2. Insights into the interaction of discodermolide and docetaxel with tubulin. Mapping the binding sites of microtubule-stabilizing agents by using an integrated NMR and computational approach.

    Science.gov (United States)

    Canales, Angeles; Rodríguez-Salarichs, Javier; Trigili, Chiara; Nieto, Lidia; Coderch, Claire; Andreu, José Manuel; Paterson, Ian; Jiménez-Barbero, Jesús; Díaz, J Fernando

    2011-08-19

    The binding interactions of two antitumor agents that target the paclitaxel site, docetaxel and discodermolide, to unassembled α/β-tubulin heterodimers and microtubules have been studied using biochemical and NMR techniques. The use of discodermolide as a water-soluble paclitaxel biomimetic and extensive NMR experiments allowed the detection of binding of microtubule-stabilizing agents to unassembled tubulin α/β-heterodimers. The bioactive 3D structures of docetaxel and discodermolide bound to α/β-heterodimers were elucidated and compared to those bound to microtubules, where subtle changes in the conformations of docetaxel in its different bound states were evident. Moreover, the combination of experimental TR-NOE and STD NMR data with CORCEMA-ST calculations indicate that docetaxel and discodermolide target an additional binding site at the pore of the microtubules, which is different from the internal binding site at the lumen previously determined by electron crystallography. Binding to this pore site can then be considered as the first ligand-protein recognition event that takes place in advance of the drug internalization process and interaction with the lumen of the microtubules.

  3. Multi-scale interactions in inter personal coordination

    Institute of Scientific and Technical Information of China (English)

    Tehran J. Davis; Thomas R. Brooks; James A. Dixon

    2016-01-01

    Background: Interpersonal coordination is an essential aspect of daily life, and crucial to performance in cooperative and competitive team sports. While empirical research has investigated interpersonal coordination using a wide variety of analytical tools and frameworks, to date very few studies have employed multifractal techniques to study the nature of interpersonal coordination across multiple spatiotemporal scales. In the present study we address this gap. Methods: We investigated the dynamics of a simple dyadic interpersonal coordination task where each participant manually controlled a virtual object in relation to that of his or her partner. We tested whether the resulting hand-movement time series exhibits multi-scale properties and whether those properties are associated with successful performance. Results: Using the formalism of multifractals, we show that the performance on the coordination task is strongly multi-scale, and that the multi-scale properties appear to arise from interaction-dominant dynamics. Further, we find that the measure of across-scale interactions, multifractal spectrum width, predicts successful performance at the level of the dyad. Conclusion: The results are discussed with respect to the implications of multifractals and interaction-dominance for understanding control in an interpersonal context.

  4. The NMDAR subunit NR3A interacts with microtubule-associated protein 1S in the brain

    DEFF Research Database (Denmark)

    Eriksson, Maria; Samuelsson, Helena; Samuelsson, Eva-Britt;

    2007-01-01

    -proximal part of the NR3A C-terminus. MAP1S belongs to the same family as MAP1A and MAP1B, and was found to be abundant in both postnatal and adult rat brain. In hippocampal neurons the distribution-pattern of MAP1S resembled that of beta-tubulin III, but a fraction of the protein colocalized with synaptic......When screening a brain cDNA library, we found that the N-methyl-D-aspartate receptor subunit NR3A binds to microtubule-associated protein (MAP) 1S/chromosome 19 open reading frame 5 (C19ORF5). The interaction was confirmed in vitro and in vivo, and binding of MAP1S was localized to the membrane...

  5. Arabidopsis cortical microtubules position cellulose synthase delivery to the plasma membrane and interact with cellulose synthase trafficking compartments.

    NARCIS (Netherlands)

    Gutierrez, R.; Lindeboom, J.J.; Paredez, A.R.; Emons, A.M.C.; Ehrhardt, D.W.

    2009-01-01

    Plant cell morphogenesis relies on the organization and function of two polymer arrays separated by the plasma membrane: the cortical microtubule cytoskeleton and cellulose microfibrils in the cell wall. Studies using in vivo markers confirmed that one function of the cortical microtubule array is

  6. Arabidopsis cortical microtubules position cellulose synthase delivery to the plasma membrane and interact with cellulose synthase trafficking compartments.

    NARCIS (Netherlands)

    Gutierrez, R.; Lindeboom, J.J.; Paredez, A.R.; Emons, A.M.C.; Ehrhardt, D.W.

    2009-01-01

    Plant cell morphogenesis relies on the organization and function of two polymer arrays separated by the plasma membrane: the cortical microtubule cytoskeleton and cellulose microfibrils in the cell wall. Studies using in vivo markers confirmed that one function of the cortical microtubule array is t

  7. Quantitative Analysis of the Microtubule Interaction of Rabies Virus P3 Protein: Roles in Immune Evasion and Pathogenesis.

    Science.gov (United States)

    Brice, Aaron; Whelan, Donna R; Ito, Naoto; Shimizu, Kenta; Wiltzer-Bach, Linda; Lo, Camden Y; Blondel, Danielle; Jans, David A; Bell, Toby D M; Moseley, Gregory W

    2016-09-21

    Although microtubules (MTs) are known to have important roles in intracellular transport of many viruses, a number of reports suggest that specific viral MT-associated proteins (MAPs) target MTs to subvert distinct MT-dependent cellular processes. The precise functional importance of these interactions and their roles in pathogenesis, however, remain largely unresolved. To assess the association with disease of the rabies virus (RABV) MAP, P3, we quantitatively compared the phenotypes of P3 from a pathogenic RABV strain, Nishigahara (Ni) and a non-pathogenic Ni-derivative strain, Ni-CE. Using confocal/live-cell imaging and dSTORM super-resolution microscopy to quantify protein interactions with the MT network and with individual MT filaments, we found that the interaction by Ni-CE-P3 is significantly impaired compared with Ni-P3. This correlated with an impaired capacity to effect association of the transcription factor STAT1 with MTs and to antagonize interferon (IFN)/STAT1-dependent antiviral signaling. Importantly, we identified a single mutation in Ni-CE-P3 that is sufficient to inhibit MT-association and IFN-antagonist function of Ni-P3, and showed that this mutation alone attenuates the pathogenicity of RABV. These data provide evidence that the viral protein-MT interface has important roles in pathogenesis, suggesting that this interface could provide targets for vaccine/antiviral drug development.

  8. Association of hepatitis C virus replication complexes with microtubules and actin filaments is dependent on the interaction of NS3 and NS5A.

    Science.gov (United States)

    Lai, Chao-Kuen; Jeng, King-Song; Machida, Keigo; Lai, Michael M C

    2008-09-01

    The hepatitis C virus (HCV) RNA replication complex (RC), which is composed of viral nonstructural (NS) proteins and host cellular proteins, replicates the viral RNA genome in association with intracellular membranes. Two viral NS proteins, NS3 and NS5A, are essential elements of the RC. Here, by using immunoprecipitation and fluorescence resonance energy transfer assays, we demonstrated that NS3 and NS5A interact with tubulin and actin. Furthermore, immunofluorescence microscopy and electron microscopy revealed that HCV RCs were aligned along microtubules and actin filaments in both HCV replicon cells and HCV-infected cells. In addition, the movement of RCs was inhibited when microtubules or actin filaments were depolymerized by colchicine and cytochalasin B, respectively. Based on our observations, we propose that microtubules and actin filaments provide the tracks for the movement of HCV RCs to other regions in the cell, and the molecular interactions between RCs and microtubules, or RCs and actin filaments, are mediated by NS3 and NS5A.

  9. Arabidopsis GCP3-interacting protein 1/MOZART 1 is an integral component of the γ-tubulin-containing microtubule nucleating complex.

    Science.gov (United States)

    Nakamura, Masayoshi; Yagi, Noriyoshi; Kato, Takehide; Fujita, Satoshi; Kawashima, Noriyuki; Ehrhardt, David W; Hashimoto, Takashi

    2012-07-01

    Microtubules in eukaryotic cells are nucleated from ring-shaped complexes that contain γ-tubulin and a family of homologous γ-tubulin complex proteins (GCPs), but the subunit composition of the complexes can vary among fungi, animals and plants. Arabidopsis GCP3-interacting protein 1 (GIP1), a small protein with no homology to the GCP family, interacts with GCP3 in vitro, and is a plant homolog of vertebrate mitotic-spindle organizing protein associated with a ring of γ-tubulin 1 (MOZART1), a recently identified component of the γ-tubulin complex in human cell lines. In this study, we characterized two closely related Arabidopsis GIP1s: GIP1a and GIP1b. Single mutants of gip1a and gip1b were indistinguishable from wild-type plants, but their double mutant was embryonic lethal, and showed impaired development of male gametophytes. Functional fusions of GIP1a with green fluorescent protein (GFP) were used to purify GIP1a-containing complexes from Arabidopsis plants, which contained all the subunits (except NEDD1) previously identified in the Arabidopsis γ-tubulin complexes. GIP1a and GIP1b interacted specifically with Arabidopsis GCP3 in yeast. GFP-GIP1a labeled mitotic microtubule arrays in a pattern largely consistent with, but partly distinct from, the localization of the γ-tubulin complex containing GCP2 or GCP3 in planta. In interphase cortical arrays, the labeled complexes were preferentially recruited to existing microtubules, from which new microtubules were efficiently nucleated. However, in contrast to complexes labeled with tagged GCP2 or GCP3, their recruitment to cortical areas with no microtubules was rarely observed. These results indicate that GIP1/MOZART1 is an integral component of a subset of the Arabidopsis γ-tubulin complexes. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.

  10. Aging of dynamically stabilized microtubules

    CERN Document Server

    Ebbinghaus, M

    2009-01-01

    The microtubule network, an important part of the cytoskeleton, is constantly remodeled by alternating phases of growth and shrinkage of individual filaments. Plus-end tracking proteins (+TIPs) interact with the microtubule and in many cases alter its dynamics. While it is established that the prototypal CLIP-170 enhances microtubule stability by increasing rescues, the plus-end tracking mechanism is still under debate. We present a model for microtubule dynamics in which a rescue factor is dynamically added to the filament while growing. As a consequence, the filament shows aging behavior which should be experimentally accessible and thus allow one to exclude some hypothesized models of the inclusion of rescue factors at the microtubule plus end. Additionally, we show the strong influence of the cell geometry on the quantitative results.

  11. ADNP/NAP dramatically increase microtubule end-binding protein-Tau interaction: a novel avenue for protection against tauopathy.

    Science.gov (United States)

    Ivashko-Pachima, Y; Sayas, C Laura; Malishkevich, A; Gozes, I

    2017-01-24

    Activity-dependent neuroprotective protein (ADNP), vital for brain formation and cognitive function, is mutated in autism and linked to neurodegenerative/psychiatric diseases. An eight-amino-acid peptide snippet of ADNP, NAP (NAPVSIPQ), identified as a smallest active fragment, includes the SxIP microtubule (MT) end-binding protein (EB) association motif, and enhances ADNP-EB3 interaction. Depletion of EB1 or EB3 abolishes NAP protection against zinc intoxication. Furthermore, NAP enhances Tau-MT interaction, and Tau regulates the localization and function of EB1 and EB3 in developing neuronal cells. Here, we asked how NAP (ADNP) enhances Tau-MT interactions and whether this is mediated by EBs. We showed, for we believe the first time, that NAP augmented endogenous EB1 comet density in the N1E-115 neuroblastoma neuronal model. This finding was substantiated by cell transfection with fluorescent EB1 and live cell imaging. NAP increased comet amounts, length and speed. At the molecular level, NAP enhanced EB3 homodimer formation, while decreasing EB1-EB3 heterodimer content and driving EB1- and EB3-Tau interactions (dramatic 20-fold increases), leading to recruitment of EB1/EB3 and Tau to MTs under zinc intoxication. Our previous results showed that while NAP protected neuronal-like cells against oxidative stress, it did not protect NIH3T3 fibroblasts. Here, NAP did not protect NIH3T3 cells against zinc intoxication, unless these cells were transfected with Tau. Interestingly, other MT associated proteins (MAPs) may replace Tau, thus, EB-Tau (MAPs) interaction is identified as a novel target for endogenous ADNP neuroprotection, and a future target for drug development, with NAP as a prototype.Molecular Psychiatry advance online publication, 24 January 2017; doi:10.1038/mp.2016.255.

  12. Manipulation and quantification of microtubule lattice integrity

    Directory of Open Access Journals (Sweden)

    Taylor A. Reid

    2017-08-01

    Full Text Available Microtubules are structural polymers that participate in a wide range of cellular functions. The addition and loss of tubulin subunits allows the microtubule to grow and shorten, as well as to develop and repair defects and gaps in its cylindrical lattice. These lattice defects act to modulate the interactions of microtubules with molecular motors and other microtubule-associated proteins. Therefore, tools to control and measure microtubule lattice structure will be invaluable for developing a quantitative understanding of how the structural state of the microtubule lattice may regulate its interactions with other proteins. In this work, we manipulated the lattice integrity of in vitro microtubules to create pools of microtubules with common nucleotide states, but with variations in structural states. We then developed a series of novel semi-automated analysis tools for both fluorescence and electron microscopy experiments to quantify the type and severity of alterations in microtubule lattice integrity. These techniques will enable new investigations that explore the role of microtubule lattice structure in interactions with microtubule-associated proteins.

  13. Biological Fingerprinting Analysis of Interaction Between Taxoids in Taxus and Microtubule Protein by Microdialysis Coupled with High-performance Liquid Chromatography/Mass Spectrometry for Screening Antimicrotubule Agents

    Institute of Scientific and Technical Information of China (English)

    LEI Xiao-yuan; KONG Liang; SU Xing-ye; GUO Ming; ZOU Han-fa

    2008-01-01

    Some natural products,such as traditional Chinese medicines(TCMs),contain compounds with anticancer activity and have attracted a great interest in recent years as alternative anticancer therapies,A quick and convenient assay for screening antimicrotubule compounds in which in vitro microdialysis/high-performance liquid chromatography(HPLC) is used to monitor the binding of the compounds extracted from TCM Taxus cuspidata Siebold & Zucc(Taxus)to microtubules is reported,It was observed that the extract of Taxus contains at least five compounds which have affinity interaction with microtubules by biological fingerprinting analysis,and they were identified as the taxoids of taxol,baccatin Ⅲ,10-deacetylbaccatin Ⅲ(10-DAB),cephalomannine and 7-epi-10-deacetyltaxol (7-epi-10-DAT) based on the comparison of their high-performance liquid chromatographic/mass spectrometric and UV spectra with those of the standard samples,both assembly-promoting and disassembly-inhibiting characteristics of those compounds were evaluated,It was observed that baccatin Ⅲ and 10-DAB bound to microtubules and the binding degrees were influenced by GTP,Competitive binding behavior of taxol with other four taxoids to microtubules was also investigated.

  14. Centriolar CPAP/SAS-4 Imparts Slow Processive Microtubule Growth.

    Science.gov (United States)

    Sharma, Ashwani; Aher, Amol; Dynes, Nicola J; Frey, Daniel; Katrukha, Eugene A; Jaussi, Rolf; Grigoriev, Ilya; Croisier, Marie; Kammerer, Richard A; Akhmanova, Anna; Gönczy, Pierre; Steinmetz, Michel O

    2016-05-23

    Centrioles are fundamental and evolutionarily conserved microtubule-based organelles whose assembly is characterized by microtubule growth rates that are orders of magnitude slower than those of cytoplasmic microtubules. Several centriolar proteins can interact with tubulin or microtubules, but how they ensure the exceptionally slow growth of centriolar microtubules has remained mysterious. Here, we bring together crystallographic, biophysical, and reconstitution assays to demonstrate that the human centriolar protein CPAP (SAS-4 in worms and flies) binds and "caps" microtubule plus ends by associating with a site of β-tubulin engaged in longitudinal tubulin-tubulin interactions. Strikingly, we uncover that CPAP activity dampens microtubule growth and stabilizes microtubules by inhibiting catastrophes and promoting rescues. We further establish that the capping function of CPAP is important to limit growth of centriolar microtubules in cells. Our results suggest that CPAP acts as a molecular lid that ensures slow assembly of centriolar microtubules and, thereby, contributes to organelle length control.

  15. Rationality, morality and Economic Coordination: The Contours of Interaction

    Directory of Open Access Journals (Sweden)

    Sushentsova Maria, S.

    2017-06-01

    Full Text Available The article represents an overview of general tendencies in interaction between the notions of rationality and morality, and their influence on the foundations of economic coordination. Firstly, two main directions of evolution of rationality model are considered: the theory of perspectives of D. Kahneman and A. Tverski (the empirical restriction and economic imperialism of G. Becker (the conceptual widening, the role of the modern institutionalism being emphasized. The theoretical evolution of economic rationality had mainly instrumental character and didn’t change its ethical core – the central idea of welfare in economic motivation. In this regard, the two main ways of integration of rationality and morality in modern discussion are considered: conceptions of “multiple preferences” (1 and “moral obligations” (2. The first conception assumes the existence of stable beliefs or “meta-preferences”, which range ordinal desires or preferences. According to the second approach, a distinction of a qualitative nature is drawn between rational behavior, motivated by personal benefit or “sympathy”, and exclusively moral behavior, underlain by “obligation”. An approach according to which a distinction between rational and moral arguments is drawn, directly determines the principles of economic coordination, including the foundations of social justice. Among the latter, there are two ethical grounds – mutual benefit, based on the “sympathy” principle, and impartiality, grounded on the “obligation of power”. These conceptions imply the corresponding types of economic coordination: market-evolutional (focused on effectiveness and constructivist (focused on redistribution.

  16. Interactive and Lightweight Mechanisms to Coordinate Interpersonal Privacy in Mediated Communication

    Science.gov (United States)

    Romero, Natalia; Boer, Laurens; Markopoulos, Panos

    In this paper we describe three mechanisms that enable people to coordinate their interaction needs with others in their social network. The proposed designs are based on the Privacy Grounding Model [4] that argues the need for lightweight and interactive coordination mechanisms to support the dynamic and dialectic nature of interpersonal privacy coordination.

  17. Down-regulation of DNA topoisomerase IIalpha leads to prolonged cell cycle transit in G2 and early M phases and increased survival to microtubule-interacting agents.

    Science.gov (United States)

    Skladanowski, Andrzej; Côme, Marie-George; Sabisz, Michal; Escargueil, Alexandre E; Larsen, Annette K

    2005-09-01

    Microtubule binders are cell cycle-specific agents with preferential cytotoxicity toward mitotic cells. We have characterized vincristine-selected human leukemia cells to establish whether development of vincristine resistance was accompanied by changes in cell cycle kinetics and distribution. Our results indicate that vincristine resistance is accompanied by delayed G2 transit and prolonged early mitosis in both the absence and the presence of the microtubule binder nocodazole. The altered G2/M regulation is accompanied by resistance to short-term (12 h) but not continuous nocodazole exposure in agreement with the transient nature of the observed cell cycle alterations. Western blot analysis indicates that vincristine-selection is accompanied by down-regulation of topoisomerase IIalpha without detectable alterations of the other mitotic regulators studied, including Cdk1, p21, 14-3-3sigma, and 14-3-3epsilon. This was associated with at least 7-fold less chromosome-associated topoisomerase IIalpha, decreased catalytic activity, and cross-resistance to topoisomerase II inhibitors. Characterization of isogenic cell lines expressing different levels of topoisomerase II proteins shows that cellular levels of topoisomerase IIalpha, but not the closely related topoisomerase IIbeta, directly influence the cell cycle kinetics in G2 and early mitosis as well as the resistance to nocodazole. These results underline the importance of topoisomerase IIalpha in late G2 and early M phases and provide evidence for an as-yet-unsuspected interaction between topoisomerase II and microtubule-directed agents.

  18. Attentional Loads Associated with Interlimb Interactions Underlying Rhythmic Bimanual Coordination

    Science.gov (United States)

    Ridderikhoff, Arne; Peper, C. E.; Beek, Peter J.

    2008-01-01

    Studies of rhythmic bimanual coordination under dual-task conditions revealed (1) a dependence of secondary task performance on the stability of coordinative tasks, in that secondary task performance was better during in-phase than antiphase coordination, and (2) a shift in the mean relative phasing between the limbs compared to single-task…

  19. Physical Basis of Large Microtubule Aster Growth

    CERN Document Server

    Ishihara, Keisuke; Mitchison, Timothy J

    2016-01-01

    Microtubule asters - radial arrays of microtubules organized by centrosomes - play a fundamental role in the spatial coordination of animal cells. The standard model of aster growth assumes a fixed number of microtubules originating from the centrosomes. However, aster morphology in this model does not scale with cell size, and we recently found evidence for non-centrosomal microtubule nucleation. Here, we combine autocatalytic nucleation and polymerization dynamics to develop a biophysical model of aster growth. Our model predicts that asters expand as traveling waves and recapitulates all major aspects of aster growth. As the nucleation rate increases, the model predicts an explosive transition from stationary to growing asters with a discontinuous jump of the growth velocity to a nonzero value. Experiments in frog egg extract confirm the main theoretical predictions. Our results suggest that asters observed in large frog and amphibian eggs are a meshwork of short, unstable microtubules maintained by autoca...

  20. Highly cytotoxic DNA-interacting copper(II) coordination compounds.

    Science.gov (United States)

    Brissos, Rosa F; Torrents, Ester; dos Santos Mello, Francyelli Mariana; Carvalho Pires, Wanessa; Silveira-Lacerda, Elisângela de Paula; Caballero, Ana B; Caubet, Amparo; Massera, Chiara; Roubeau, Olivier; Teat, Simon J; Gamez, Patrick

    2014-10-01

    Four new Schiff-base ligands have been designed and prepared by condensation reaction between hydrazine derivatives (i.e. 2-hydrazinopyridine or 2-hydrazinoquinoline) and mono- or dialdehyde (3-tert-butyl-2-hydroxybenzaldehyde and 5-tert-butyl-2-hydroxyisophthalaldehyde, respectively). Six copper(II) coordination compounds of various nuclearities have been obtained from these ligands, which are formulated as [Cu(L1)Cl](CH3OH) (1), [Cu(L2)NO3] (2), [Cu2(L3)(ClO4)2(CH3O)(CH3OH)](CH3OH) (3), [Cu2(L4)(ClO4)(OH)(CH3OH)](ClO4) (4), [Cu8(L3)4(NO3)4(OH)5](NO3)3(CH3OH)5(H2O)8 (5) and [Cu3(HL2')4Cl6](CH3OH)6 (6), as revealed by single-crystal X-ray studies. Their DNA-interacting abilities have been investigated using different characterization techniques, which suggest that the metal complexes act as efficient DNA binders. Moreover, cytotoxicity assays with several cancer cell lines show that some of them are very active, as evidenced by the sub-micromolar IC50 values achieved in some cases.

  1. Mechanical stress induced mechanism of microtubule catastrophes.

    Science.gov (United States)

    Hunyadi, Viktória; Chrétien, Denis; Jánosi, Imre M

    2005-05-13

    Microtubules assembled in vitro from pure tubulin can switch occasionally from growing to shrinking states or resume assembly, an unusual behavior termed "dynamic instability of microtubule growth". Its origin remains unclear and several models have been proposed, including occasional switching of the microtubules into energetically unfavorable configurations during assembly. In this study, we have asked whether the excess energy accumulated in these configurations would be of sufficient magnitude to destabilize the capping region that must exist at the end of growing microtubules. For this purpose, we have analyzed the frequency distribution of microtubules assembled in vitro from pure tubulin, and modeled the different mechanical constraints accumulated in their wall. We find that the maximal excess energy that the microtubule lattice can store is in the order of 11 kBT per dimer. Configurations that require distortions up to approximately 20 kBT are allowed at the expense of a slight conformational change, and larger distortions are not observed. Modeling of the different elastic deformations suggests that the excess energy is essentially induced by protofilament skewing, microtubule radial curvature change and inter-subunit shearing, distortions that must destabilize further the tubulin subunits interactions. These results are consistent with the hypothesis that unfavorable closure events may trigger the catastrophes observed at low tubulin concentration in vitro. In addition, we propose a novel type of representation that describes the stability of microtubule assembly systems, and which might be of considerable interest to study the effects of stabilizing and destabilizing factors on microtubule structure and dynamics.

  2. Molecular interaction of TPPP with PrP antagonized the CytoPrP-induced disruption of microtubule structures and cytotoxicity.

    Directory of Open Access Journals (Sweden)

    Rui-Min Zhou

    Full Text Available BACKGROUND: Tubulin polymerization promoting protein/p25 (TPPP/p25, known as a microtubule-associated protein (MAP, is a brain-specific unstructured protein with a physiological function of stabilizing cellular microtubular ultrastructures. Whether TPPP involves in the normal functions of PrP or the pathogenesis of prion disease remains unknown. Here, we proposed the data that TPPP formed molecular complex with PrP. We also investigated its influence on the aggregation of PrP and fibrillization of PrP106-126 in vitro, its antagonization against the disruption of microtubule structures and cytotoxicity of cytosolic PrP in cells, and its alternation in the brains of scrapie-infected experimental hamsters. METHODOLOGY/PRINCIPAL FINDINGS: Using pull-down and immunoprecipitation assays, distinct molecular interaction between TPPP and PrP were identified and the segment of TPPP spanning residues 100-219 and the segment of PrP spanning residues 106-126 were mapped as the regions responsible for protein interaction. Sedimentation experiments found that TPPP increased the aggregation of full-length recombinant PrP (PrP23-231 in vitro. Transmission electron microscopy and Thioflavin T (ThT assays showed that TPPP enhanced fibril formation of synthetic peptide PrP106-126 in vitro. Expression of TPPP in the cultured cells did not obviously change the microtubule networks observed by a tubulin-specific immunofluorescent assay and cell growth features measured by CCK8 tests, but significantly antagonized the disruption of microtubule structures and rescued the cytotoxicity caused by the accumulation of cytosolic PrP (CytoPrP. Furthermore, Western blots identified that the levels of the endogenous TPPP in the brains of scrapie-infected experimental hamsters were significantly reduced. CONCLUSION/SIGNIFICANCE: Those data highlight TPPP may work as a protective factor for cells against the damage effects of the accumulation of abnormal forms of PrPs, besides its

  3. A novel model of interaction between high frequency electromagnetic non-ionizing fields and microtubules viewed as coupled two-degrees of freedom harmonic oscillators.

    Science.gov (United States)

    Caligiuri, Luigi Maxmilian

    2015-01-01

    The question regarding the potential biological and adverse health effects of non-ionizing electromagnetic fields on living organisms is of primary importance in biophysics and medicine. Despite the several experimental evidences showing such occurrence in a wide frequency range from extremely low frequency to microwaves, a definitive theoretical model able to explain a possible mechanism of interaction between electromagnetic fields and living matter, especially in the case of weak and very weak intensities, is still missing. In this paper it has been suggested a possible mechanism of interaction involving the resonant absorption of electromagnetic radiation by microtubules. To this aim these have been modeled as non-dissipative forced harmonic oscillators characterized by two coupled "macroscopic" degrees of freedom, respectively describing longitudinal and transversal vibrations induced by the electromagnetic field. We have shown that the proposed model, although at a preliminary stage, is able to explain the ability of even weak electromagnetic radiating electromagnetic fields to transfer high quantities of energy to living systems by means of a resonant mechanism, so capable to easily damage microtubules structure.

  4. Coordinate Descent Based Hierarchical Interactive Lasso Penalized Logistic Regression and Its Application to Classification Problems

    Directory of Open Access Journals (Sweden)

    Jin-Jia Wang

    2014-01-01

    Full Text Available We present the hierarchical interactive lasso penalized logistic regression using the coordinate descent algorithm based on the hierarchy theory and variables interactions. We define the interaction model based on the geometric algebra and hierarchical constraint conditions and then use the coordinate descent algorithm to solve for the coefficients of the hierarchical interactive lasso model. We provide the results of some experiments based on UCI datasets, Madelon datasets from NIPS2003, and daily activities of the elder. The experimental results show that the variable interactions and hierarchy contribute significantly to the classification. The hierarchical interactive lasso has the advantages of the lasso and interactive lasso.

  5. Mmb1p binds mitochondria to dynamic microtubules

    Science.gov (United States)

    Fu, Chuanhai; Jain, Deeptee; Costa, Judite; Velve-Casquillas, Guilhem; Tran, Phong T.

    2015-01-01

    Summary Background Mitochondria form a dynamics tubular network within the cell. Proper mitochondria movement and distribution are critical for their localized function in cell metabolism, growth, and survival. In mammalian cells, mechanisms of mitochondria positioning appear dependent on the microtubule cytoskeleton, with kinesin or dynein motors carrying mitochondria as cargos and distributing them throughout the microtubule network. Interestingly, the timescale of microtubule dynamics occurs in seconds, and the timescale of mitochondria distribution occurs in minutes. How does the cell couple these two time constants? Results Fission yeast also relies on microtubules for mitochondria distribution. We report here a new microtubule-dependent but motor-independent mechanism for proper mitochondria positioning in fission yeast. We identify the protein mmb1p, which binds to mitochondria and microtubules. Mmb1p attaches the tubular mitochondria to the microtubule lattice at multiple discrete interaction sites. Mmb1 deletion causes mitochondria to aggregate, with the long-term consequence of defective mitochondria distribution and cell death. Mmb1p decreases microtubule dynamicity. Conclusion Mmb1p is a new microtubule-mitochondria binding protein. We propose that mmb1p act to couple long-term mitochondria distribution to short-term microtubule dynamics by attenuating microtubule dynamics, thus enhancing the mitochondria-microtubule interaction time. PMID:21856157

  6. Coordination under global random interaction and local imitation

    NARCIS (Netherlands)

    Khan, A.

    2013-01-01

    We study stochastically stable behaviour in 2 x 2 coordination games where the risk-dominant equilibrium differs from the Pareto-efficient equilibrium. Individuals are randomly matched to another individual in the population (with full support) and they choose strategies by imitating the most succes

  7. Coordination under global random interaction and local imitation

    NARCIS (Netherlands)

    Khan, A.

    2013-01-01

    We study stochastically stable behaviour in 2 x 2 coordination games where the risk-dominant equilibrium differs from the Pareto-efficient equilibrium. Individuals are randomly matched to another individual in the population (with full support) and they choose strategies by imitating the most succes

  8. Movement of chromosomes with severed kinetochore microtubules.

    Science.gov (United States)

    Forer, Arthur; Johansen, Kristen M; Johansen, Jørgen

    2015-05-01

    Experiments dating from 1966 and thereafter showed that anaphase chromosomes continued to move poleward after their kinetochore microtubules were severed by ultraviolet microbeam irradiation. These observations were initially met with scepticism as they contradicted the prevailing view that kinetochore fibre microtubules pulled chromosomes to the pole. However, recent experiments using visible light laser microbeam irradiations have corroborated these earlier experiments as anaphase chromosomes again were shown to move poleward after their kinetochore microtubules were severed. Thus, multiple independent studies using different techniques have shown that chromosomes can indeed move poleward without direct microtubule connections to the pole, with only a kinetochore 'stub' of microtubules. An issue not yet settled is: what propels the disconnected chromosome? There are two not necessarily mutually exclusive proposals in the literature: (1) chromosome movement is propelled by the kinetochore stub interacting with non-kinetochore microtubules and (2) chromosome movement is propelled by a spindle matrix acting on the stub. In this review, we summarise the data indicating that chromosomes can move with severed kinetochore microtubules and we discuss proposed mechanisms for chromosome movement with severed kinetochore microtubules.

  9. Discodermolide interferes with the binding of tau protein to microtubules.

    Science.gov (United States)

    Kar, Santwana; Florence, Gordon J; Paterson, Ian; Amos, Linda A

    2003-03-27

    We investigated whether discodermolide, a novel antimitotic agent, affects the binding to microtubules of tau protein repeat motifs. Like taxol, the new drug reduces the proportion of tau that pellets with microtubules. Despite their differing structures, discodermolide, taxol and tau repeats all bind to a site on beta-tubulin that lies within the microtubule lumen and is crucial in controlling microtubule assembly. Low concentrations of tau still bind strongly to the outer surfaces of preformed microtubules when the acidic C-terminal regions of at least six tubulin dimers are available for interaction with each tau molecule; otherwise binding is very weak.

  10. Coordination polymers assembled through pi-pi interactions

    CERN Document Server

    Plummer, E A

    2001-01-01

    Chapter one is a review of the relevant literature. In chapter two the coordination chemistry of biphenyl-tailed terpyridines with octahedral metal dications is investigated. The effect of different metal ions on their aggregation modes in the solid state is also investigated. In chapter three the coordination chemistry of polyaryl-tailed terpyridines with octahedral metal dications is investigated. The effect of different aryl tails on their aggregation modes in the solid state is investigated. In chapter four the pi-pi aggregation of molecular boxes through biphenyl tails is studied. In chapter five the immobilisation of aryl tailed complexes into polyelectrolyte films has been investigated, and the arrangement of these complexes in the films has been compared with same complexes in the crystal, thus moving from three dimensional aggregation to two dimensions.

  11. Mechanism of the taking the coordinated decisions: interaction and adaptability

    Directory of Open Access Journals (Sweden)

    T.O. Zagornaya

    2011-10-01

    Full Text Available In article are motivated actual problems of the shaping the mechanism of the taking the coordinated decisions with provision for specifics of management process operation and developments enterprise in condition of the contradiction of the problems its functional subdivisions. Is it Also designed methods of the shaping the intercepting the functional subdivisions within the framework of procedures budgetation in accordance with principle complex decision making.

  12. Vfa1 binds to the N-terminal microtubule-interacting and trafficking (MIT) domain of Vps4 and stimulates its ATPase activity.

    Science.gov (United States)

    Vild, Cody J; Xu, Zhaohui

    2014-04-11

    The endosomal sorting complexes required for transport (ESCRT) are responsible for multivesicular body biogenesis, membrane abscission during cytokinesis, and retroviral budding. They function as transiently assembled molecular complexes on the membrane, and their disassembly requires the action of the AAA-ATPase Vps4. Vps4 is regulated by a multitude of ESCRT and ESCRT-related proteins. Binding of these proteins to Vps4 is often mediated via the microtubule-interacting and trafficking (MIT) domain of Vps4. Recently, a new Vps4-binding protein Vfa1 was identified in a yeast genetic screen, where overexpression of Vfa1 caused defects in vacuolar morphology. However, the function of Vfa1 and its role in vacuolar biology were largely unknown. Here, we provide the first detailed biochemical and biophysical study of Vps4-Vfa1 interaction. The MIT domain of Vps4 binds to the C-terminal 17 residues of Vfa1. This interaction is of high affinity and greatly stimulates the ATPase activity of Vps4. The crystal structure of the Vps4-Vfa1 complex shows that Vfa1 adopts a canonical MIT-interacting motif 2 structure that has been observed previously in other Vps4-ESCRT interactions. These findings suggest that Vfa1 is a novel positive regulator of Vps4 function.

  13. Vfa1 Binds to the N-terminal Microtubule-interacting and Trafficking (MIT) Domain of Vps4 and Stimulates Its ATPase Activity*

    Science.gov (United States)

    Vild, Cody J.; Xu, Zhaohui

    2014-01-01

    The endosomal sorting complexes required for transport (ESCRT) are responsible for multivesicular body biogenesis, membrane abscission during cytokinesis, and retroviral budding. They function as transiently assembled molecular complexes on the membrane, and their disassembly requires the action of the AAA-ATPase Vps4. Vps4 is regulated by a multitude of ESCRT and ESCRT-related proteins. Binding of these proteins to Vps4 is often mediated via the microtubule-interacting and trafficking (MIT) domain of Vps4. Recently, a new Vps4-binding protein Vfa1 was identified in a yeast genetic screen, where overexpression of Vfa1 caused defects in vacuolar morphology. However, the function of Vfa1 and its role in vacuolar biology were largely unknown. Here, we provide the first detailed biochemical and biophysical study of Vps4-Vfa1 interaction. The MIT domain of Vps4 binds to the C-terminal 17 residues of Vfa1. This interaction is of high affinity and greatly stimulates the ATPase activity of Vps4. The crystal structure of the Vps4-Vfa1 complex shows that Vfa1 adopts a canonical MIT-interacting motif 2 structure that has been observed previously in other Vps4-ESCRT interactions. These findings suggest that Vfa1 is a novel positive regulator of Vps4 function. PMID:24567329

  14. beta-Dystroglycan modulates the interplay between actin and microtubules in human-adhered platelets.

    Science.gov (United States)

    Cerecedo, Doris; Cisneros, Bulmaro; Suárez-Sánchez, Rocío; Hernández-González, Enrique; Galván, Iván

    2008-05-01

    To maintain the continuity of an injured blood vessel, platelets change shape, secrete granule contents, adhere, aggregate, and retract in a haemostatic plug. Ordered arrays of microtubules, microfilaments, and associated proteins are responsible for these platelet responses. In full-spread platelets, microfilament bundles in association with other cytoskeleton proteins are anchored in focal contacts. Recent studies in migrating cells suggest that co-ordination and direct physical interaction of microtubules and actin network modulate adhesion development. In platelets, we have proposed a feasible association between these two cytoskeletal systems, as well as the participation of the dystrophin-associated protein complex, as part of the focal adhesion complex. The present study analysed the participation of microtubules and actin during the platelet adhesion process. Confocal microscopy, fluorescence resonance transfer energy and immunoprecipitation assays were used to provide evidence of a cross-talk between these two cytoskeletal systems. Interestingly, beta-dystroglycan was found to act as an interplay protein between actin and microtubules and an additional communication between these two cytoskeleton networks was maintained through proteins of focal adhesion complex. Altogether our data are indicative of a dynamic co-participation of actin filaments and microtubules in modulating focal contacts to achieve platelet function.

  15. Microtubule-driven nuclear movements and linear elements as meiosis-specific characteristics of the fission yeasts Schizosaccharomyces versatilis and Schizosaccharomyces pombe.

    Science.gov (United States)

    Svoboda, A; Bähler, J; Kohli, J

    1995-11-01

    Meiotic prophase in Schizosaccharomyces pombe is characterized by striking nuclear movements and the formation of linear elements along chromosomes instead of tripartite synaptonemal complexes. We analysed the organization of nuclei and microtubules in cells of fission yeasts undergoing sexual differentiation. S. japonicus var. versatilis and S. pombe cells were studied in parallel, taking advantage of the better cytology in S. versatilis. During conjugation, microtubules were directed towards the mating projection. These microtubules seem to lead the haploid nuclei together in the zygote by interaction with the spindle pole bodies at the nuclear periphery. After karyogamy, arrays of microtubules emanating from the spindle pole body of the diploid nucleus extended to both cell poles. The same differentiated microtubule configuration was elaborated upon induction of azygotic meiosis in S. pombe. The cyclic movements of the elongated nuclei between the cell poles is reflected by a dynamic and coordinated shortening and lengthening of the two microtubule arrays. When the nucleus was at a cell end, one array was short while the other bridged the whole cell length. Experiments with inhibitors showed that microtubules are required for karyogamy and for the elongated shape and movement of nuclei during meiotic prophase. In both fission yeasts the SPBs and nucleoli are at the leading ends of the moving nuclei. Astral and cytoplasmic microtubules were also prominent during meiotic divisions and sporulation. We further show that in S. versatilis the linear elements formed during meiotic prophase are similar to those in S. pombe. Tripartite synaptonemal complexes were never detected. Taken together, these findings suggest that S. pombe and S. versatilis share basic characteristics in the organization of microtubules and the structure and behaviour of nuclei during their meiotic cell cycle. The prominent differentiations of microtubules and nuclei may be involved in the

  16. The C terminus of fragile X mental retardation protein interacts with the multi-domain Ran-binding protein in the microtubule-organising centre.

    Science.gov (United States)

    Menon, Rajesh P; Gibson, Toby J; Pastore, Annalisa

    2004-10-01

    Absence of the fragile X mental retardation protein (FMRP) causes fragile X syndrome, the most common form of hereditary mental retardation. FMRP is a mainly cytoplasmic protein thought to be involved in repression of translation, through a complex network of protein-protein and protein-RNA interactions. Most of the currently known protein partners of FMRP recognise the conserved N terminus of the protein. No interaction has yet been mapped to the highly charged, poorly conserved C terminus, so far thought to be involved in RNA recognition through an RGG motif. In the present study, we show that a two-hybrid bait containing residues 419-632 of human FMRP fishes out a protein that spans the sequence of the Ran-binding protein in the microtubule-organising centre (RanBPM/RanBP9). Specific interaction of RanBPM with FMRP was confirmed by in vivo and in vitro assays. In brain tissue sections, RanBPM is highly expressed in the neurons of cerebral cortex and the cerebellar purkinje cells, in a pattern similar to that described for FMRP. Sequence analysis shows that RanBPM is a multi-domain protein. The interaction with FMRP was mapped in a newly identified CRA motif present in the RanBPM C terminus. Our results suggest that the functional role of RanBPM binding is modulation of the RNA-binding properties of FMRP.

  17. Distinct mechanisms of recognizing endosomal sorting complex required for transport III (ESCRT-III) protein IST1 by different microtubule interacting and trafficking (MIT) domains.

    Science.gov (United States)

    Guo, Emily Z; Xu, Zhaohui

    2015-03-27

    The endosomal sorting complex required for transport (ESCRT) machinery is responsible for membrane remodeling in a number of biological processes including multivesicular body biogenesis, cytokinesis, and enveloped virus budding. In mammalian cells, efficient abscission during cytokinesis requires proper function of the ESCRT-III protein IST1, which binds to the microtubule interacting and trafficking (MIT) domains of VPS4, LIP5, and Spartin via its C-terminal MIT-interacting motif (MIM). Here, we studied the molecular interactions between IST1 and the three MIT domain-containing proteins to understand the structural basis that governs pairwise MIT-MIM interaction. Crystal structures of the three molecular complexes revealed that IST1 binds to the MIT domains of VPS4, LIP5, and Spartin using two different mechanisms (MIM1 mode versus MIM3 mode). Structural comparison revealed that structural features in both MIT and MIM contribute to determine the specific binding mechanism. Within the IST1 MIM sequence, two phenylalanine residues were shown to be important in discriminating MIM1 versus MIM3 binding. These observations enabled us to deduce a preliminary binding code, which we applied to provide CHMP2A, a protein that normally only binds the MIT domain in the MIM1 mode, the additional ability to bind the MIT domain of Spartin in the MIM3 mode. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Distinct Mechanisms of Recognizing Endosomal Sorting Complex Required for Transport III (ESCRT-III) Protein IST1 by Different Microtubule Interacting and Trafficking (MIT) Domains*

    Science.gov (United States)

    Guo, Emily Z.; Xu, Zhaohui

    2015-01-01

    The endosomal sorting complex required for transport (ESCRT) machinery is responsible for membrane remodeling in a number of biological processes including multivesicular body biogenesis, cytokinesis, and enveloped virus budding. In mammalian cells, efficient abscission during cytokinesis requires proper function of the ESCRT-III protein IST1, which binds to the microtubule interacting and trafficking (MIT) domains of VPS4, LIP5, and Spartin via its C-terminal MIT-interacting motif (MIM). Here, we studied the molecular interactions between IST1 and the three MIT domain-containing proteins to understand the structural basis that governs pairwise MIT-MIM interaction. Crystal structures of the three molecular complexes revealed that IST1 binds to the MIT domains of VPS4, LIP5, and Spartin using two different mechanisms (MIM1 mode versus MIM3 mode). Structural comparison revealed that structural features in both MIT and MIM contribute to determine the specific binding mechanism. Within the IST1 MIM sequence, two phenylalanine residues were shown to be important in discriminating MIM1 versus MIM3 binding. These observations enabled us to deduce a preliminary binding code, which we applied to provide CHMP2A, a protein that normally only binds the MIT domain in the MIM1 mode, the additional ability to bind the MIT domain of Spartin in the MIM3 mode. PMID:25657007

  19. The actin-microtubule cross-linking activity of Drosophila Short stop is regulated by intramolecular inhibition.

    Science.gov (United States)

    Applewhite, Derek A; Grode, Kyle D; Duncan, Mara C; Rogers, Stephen L

    2013-09-01

    Actin and microtubule dynamics must be precisely coordinated during cell migration, mitosis, and morphogenesis--much of this coordination is mediated by proteins that physically bridge the two cytoskeletal networks. We have investigated the regulation of the Drosophila actin-microtubule cross-linker Short stop (Shot), a member of the spectraplakin family. Our data suggest that Shot's cytoskeletal cross-linking activity is regulated by an intramolecular inhibitory mechanism. In its inactive conformation, Shot adopts a "closed" conformation through interactions between its NH(2)-terminal actin-binding domain and COOH-terminal EF-hand-GAS2 domain. This inactive conformation is targeted to the growing microtubule plus end by EB1. On activation, Shot binds along the microtubule through its COOH-terminal GAS2 domain and binds to actin with its NH(2)-terminal tandem CH domains. We propose that this mechanism allows Shot to rapidly cross-link dynamic microtubules in response to localized activating signals at the cell cortex.

  20. Mitotic Protein CSPP1 Interacts with CENP-H Protein to Coordinate Accurate Chromosome Oscillation in Mitosis.

    Science.gov (United States)

    Zhu, Lijuan; Wang, Zhikai; Wang, Wenwen; Wang, Chunli; Hua, Shasha; Su, Zeqi; Brako, Larry; Garcia-Barrio, Minerva; Ye, Mingliang; Wei, Xuan; Zou, Hanfa; Ding, Xia; Liu, Lifang; Liu, Xing; Yao, Xuebiao

    2015-11-06

    Mitotic chromosome segregation is orchestrated by the dynamic interaction of spindle microtubules with the kinetochores. During chromosome alignment, kinetochore-bound microtubules undergo dynamic cycles between growth and shrinkage, leading to an oscillatory movement of chromosomes along the spindle axis. Although kinetochore protein CENP-H serves as a molecular control of kinetochore-microtubule dynamics, the mechanistic link between CENP-H and kinetochore microtubules (kMT) has remained less characterized. Here, we show that CSPP1 is a kinetochore protein essential for accurate chromosome movements in mitosis. CSPP1 binds to CENP-H in vitro and in vivo. Suppression of CSPP1 perturbs proper mitotic progression and compromises the satisfaction of spindle assembly checkpoint. In addition, chromosome oscillation is greatly attenuated in CSPP1-depleted cells, similar to what was observed in the CENP-H-depleted cells. Importantly, CSPP1 depletion enhances velocity of kinetochore movement, and overexpression of CSPP1 decreases the speed, suggesting that CSPP1 promotes kMT stability during cell division. Specific perturbation of CENP-H/CSPP1 interaction using a membrane-permeable competing peptide resulted in a transient mitotic arrest and chromosome segregation defect. Based on these findings, we propose that CSPP1 cooperates with CENP-H on kinetochores to serve as a novel regulator of kMT dynamics for accurate chromosome segregation.

  1. How do strength and coordination recovery interact after stroke? A computational model for informing robotic training.

    Science.gov (United States)

    Norman, Sumner L; Lobo-Prat, Joan; Reinkensmeyer, David J

    2017-07-01

    Robotic devices can train strength, coordination, or a combination of both. If a robotic device focuses on coordination, what happens to strength recovery, and vice versa? Understanding this interaction could help optimize robotic training. We developed a computational neurorehabilitation model to gain insight into the interaction between strength and coordination recovery after stroke. In the model, the motor system recovers by optimizing the activity of residual corticospinal cells (focally connected, excitatory and inhibitory) and reticulospinal cells (diffusely connected and excitatory) to achieve a motor task. To do this, the model employs a reinforcement learning algorithm that uses stochastic search based on a reward signal produced by task execution. We simulated two tasks that require strength and coordination: a finger movement task and a bilateral wheelchair propulsion task. We varied the reward signal to value strength versus coordination, determined by a weighting factor. The model predicted a nonlinear relationship between strength and coordination recovery consistent with clinical data obtained for each task. The model also predicted that stroke can cause a competition between strength and coordination recovery, due to a scarcity of focal and inhibitory cells. These results provide a rationale for implementing robotic movement therapy that can adaptively alter the combination of force and coordination training to target desired components of motor recovery.

  2. Microtubules, Tubulins and Associated Proteins.

    Science.gov (United States)

    Raxworthy, Michael J.

    1988-01-01

    Reviews much of what is known about microtubules, which are biopolymers consisting predominantly of subunits of the globular protein, tubulin. Describes the functions of microtubules, their structure and assembly, microtube associated proteins, and microtubule-disrupting agents. (TW)

  3. Believing versus interacting: Behavioural and neural mechanisms underlying interpersonal coordination

    DEFF Research Database (Denmark)

    Konvalinka, Ivana; Bauer, Markus; Kilner, James

    When two people engage in a bidirectional interaction with each other, they use both bottom-up sensorimotor mechanisms such as monitoring and adapting to the behaviour of the other, as well as top-down cognitive processes, modulating their beliefs and allowing them to make decisions. Most researc...

  4. Motion Coordination and Adaptation Using Deception and Human Interactions

    Science.gov (United States)

    2016-11-18

    differential equation solvers, while only arithmetic calculations are needed in discrete time GT-DDP. Therefore, the time cost per iteration is faster...Using Control Lyapunov Functions and Optimal Control. Networks and Heterogeneous Media , Vol. 10, No. 3, pp. 609-630, Sept. 2015. 2. T. Setter, A...Swarm Interactions Using Control Lyapunov Functions and Optimal Control. Networks and Heterogeneous Media , Vol. 10, No. 3, pp. 609-630, Sept. 2015. T

  5. A Longitudinal Study of Coordination in Mother-Infant Vocal Interaction from Age 4 to 10 Months

    Science.gov (United States)

    Harder, Susanne; Lange, Theis; Hansen, Gert Foget; Vaever, Mette; Køppe, Simo

    2015-01-01

    This is a longitudinal study of development in coordinated mother-infant vocal interaction from 4 to 10 months (N = 41) focusing on the development of turn-taking patterns and time spent in coordinated vocal interaction. Data analyses were carried out using multistate analysis. Both mothers and infants were found to coordinate their own…

  6. Coordination and Crystallization Molecules: Their Interactions Affecting the Dimensionality of Metalloporphyrinic SCFs

    Directory of Open Access Journals (Sweden)

    Arkaitz Fidalgo-Marijuan

    2015-04-01

    Full Text Available Synthetic metalloporphyrin complexes are often used as analogues of natural systems, and they can be used for the preparation of new Solid Coordination Frameworks (SCFs. In this work, a series of six metalloporphyrinic compounds constructed from different meso substituted metalloporphyrins (phenyl, carboxyphenyl and sulfonatophenyl have been structurally characterized by means of single crystal X-ray diffraction, IR spectroscopy and elemental analysis. The compounds were classified considering the dimensionality of the crystal array, referred just to coordination bonds, into 0D, 1D and 2D compounds. This way, the structural features and relationships of those crystal structures were analyzed, in order to extract conclusions not only about the dimensionality of the networks but also about possible applications of the as-obtained compounds, focusing the interest on the interactions of coordination and crystallization molecules. These interactions provide the coordination bonds and the cohesion forces which produce SCFs with different dimensionalities.

  7. Microtubule doublets are double-track railways for intraflagellar transport trains.

    Science.gov (United States)

    Stepanek, Ludek; Pigino, Gaia

    2016-05-06

    The cilium is a large macromolecular machine that is vital for motility, signaling, and sensing in most eukaryotic cells. Its conserved core structure, the axoneme, contains nine microtubule doublets, each comprising a full A-microtubule and an incomplete B-microtubule. However, thus far, the function of this doublet geometry has not been understood. We developed a time-resolved correlative fluorescence and three-dimensional electron microscopy approach to investigate the dynamics of intraflagellar transport (IFT) trains, which carry ciliary building blocks along microtubules during the assembly and disassembly of the cilium. Using this method, we showed that each microtubule doublet is used as a bidirectional double-track railway: Anterograde IFT trains move along B-microtubules, and retrograde trains move along A-microtubules. Thus, the microtubule doublet geometry provides direction-specific rails to coordinate bidirectional transport of ciliary components.

  8. Coordinating cardiomyocyte interactions to direct ventricular chamber morphogenesis.

    Science.gov (United States)

    Han, Peidong; Bloomekatz, Joshua; Ren, Jie; Zhang, Ruilin; Grinstein, Jonathan D; Zhao, Long; Burns, C Geoffrey; Burns, Caroline E; Anderson, Ryan M; Chi, Neil C

    2016-06-29

    Many organs are composed of complex tissue walls that are structurally organized to optimize organ function. In particular, the ventricular myocardial wall of the heart comprises an outer compact layer that concentrically encircles the ridge-like inner trabecular layer. Although disruption in the morphogenesis of this myocardial wall can lead to various forms of congenital heart disease and non-compaction cardiomyopathies, it remains unclear how embryonic cardiomyocytes assemble to form ventricular wall layers of appropriate spatial dimensions and myocardial mass. Here we use advanced genetic and imaging tools in zebrafish to reveal an interplay between myocardial Notch and Erbb2 signalling that directs the spatial allocation of myocardial cells to their proper morphological positions in the ventricular wall. Although previous studies have shown that endocardial Notch signalling non-cell-autonomously promotes myocardial trabeculation through Erbb2 and bone morphogenetic protein (BMP) signalling, we discover that distinct ventricular cardiomyocyte clusters exhibit myocardial Notch activity that cell-autonomously inhibits Erbb2 signalling and prevents cardiomyocyte sprouting and trabeculation. Myocardial-specific Notch inactivation leads to ventricles of reduced size and increased wall thickness because of excessive trabeculae, whereas widespread myocardial Notch activity results in ventricles of increased size with a single-cell-thick wall but no trabeculae. Notably, this myocardial Notch signalling is activated non-cell-autonomously by neighbouring Erbb2-activated cardiomyocytes that sprout and form nascent trabeculae. Thus, these findings support an interactive cellular feedback process that guides the assembly of cardiomyocytes to morphologically create the ventricular myocardial wall and more broadly provide insight into the cellular dynamics of how diverse cell lineages organize to create form.

  9. A heart for interaction: Shared physiological dynamics and behavioral coordination in a collective, creative construction task.

    Science.gov (United States)

    Fusaroli, Riccardo; Bjørndahl, Johanne S; Roepstorff, Andreas; Tylén, Kristian

    2016-09-01

    Interpersonally shared physiological dynamics are increasingly argued to underlie rapport, empathy, and even team performance. Inspired by the model of interpersonal synergy, we critically investigate the presence, temporal development, possible mechanisms and impact of shared interpersonal heart rate (HR) dynamics during individual and collective creative LEGO® construction tasks. In Study 1 we show how shared HR dynamics are driven by a plurality of sources, including task constraints and behavioral coordination. Generally, shared HR dynamics are more prevalent in individual trials (involving participants doing the same things) than in collective ones (involving participants taking turns and performing complementary actions). However, when contrasted against virtual pairs, collective trials display more stable shared HR dynamics suggesting that online social interaction plays an important role. Furthermore, in contrast to individual trials, shared HR dynamics are found to increase across collective trials. Study 2 investigates which aspects of social interaction might drive these effects. We show that shared HR dynamics are statistically predicted by interpersonal speech and building coordination. In Study 3, we explore the relation between HR dynamics, behavioral coordination, and self-reported measures of rapport and group competence. Although behavioral coordination predicts rapport and group competence, shared HR dynamics do not. Although shared physiological dynamics were reliably observed in our study, our results warrant not to consider HR dynamics a general driving mechanism of social coordination. Behavioral coordination-on the other hand-seems to be more informative of both shared physiological dynamics and collective experience. (PsycINFO Database Record

  10. General theory for the mechanics of confined microtubule asters

    Science.gov (United States)

    Ma, Rui; Laan, Liedewij; Dogterom, Marileen; Pavin, Nenad; Jülicher, Frank

    2014-01-01

    In cells, dynamic microtubules organize into asters or spindles to assist positioning of organelles. Two types of forces are suggested to contribute to the positioning process: (i) microtubule-growth based pushing forces; and (ii) motor protein mediated pulling forces. In this paper, we present a general theory to account for aster positioning in a confinement of arbitrary shape. The theory takes account of microtubule nucleation, growth, catastrophe, slipping, as well as interaction with cortical force generators. We calculate microtubule distributions and forces acting on microtubule organizing centers in a sphere and in an ellipsoid. Positioning mechanisms based on both pushing forces and pulling forces can be distinguished in our theory for different parameter regimes or in different geometries. In addition, we investigate positioning of microtubule asters in the case of asymmetric distribution of motors. This analysis enables us to characterize situations relevant for Caenorrhabditis elegans embryos.

  11. The Ndc80 internal loop is required for recruitment of the Ska complex to establish end-on microtubule attachment to kinetochores

    DEFF Research Database (Denmark)

    Zhang, Gang; Kelstrup, Christian D; Hu, Xiao-Wen;

    2012-01-01

    the chromosomes and stable kinetochore fibers are absent. Through quantitative mass spectrometry and immunofluorescence we find that the binding of the Ska complex depends on the loop region explaining why end-on attachment is defective. This underscores the importance of the Ndc80 loop region in coordinating......The Ndc80 complex establishes end-on attachment of kinetochores to microtubules essential for chromosome segregation. The Ndc80 subunit is characterized by an N-terminal region, that binds directly to microtubules, and a long coiled-coil region that interacts with Nuf2. A loop region in Ndc80...

  12. Dynamics of Microtubule Instabilities

    CERN Document Server

    Antal, T; Redner, S

    2007-01-01

    We investigate the dynamics of an idealized model of microtubule growth that evolves by: (i) attachment of guanosine triphosphate (GTP) at rate lambda, (ii) conversion of GTP to guanosine diphosphate (GDP) at rate 1, and (iii) detachment of GDP at rate mu. As a function of these rates, a microtubule can grow steadily or its length can fluctuate wildly. For mu=0, we find the exact tubule and GTP cap length distributions, and power-law length distributions of GTP and GDP islands. For mu=infinity, we argue that the time between catastrophes, where the microtubule shrinks to zero length, scales as exp(lambda). We also find the phase boundary between a growing and shrinking microtubule.

  13. Interactions Between Metal Ions and Carbohydrates: Coordination Behavior of D-Ribose to Lanthanide Ions

    Institute of Scientific and Technical Information of China (English)

    苏允兰; 杨丽敏; 翁诗甫; 吴瑾光

    2002-01-01

    Lanthanum chloride α-D-ribopyranose pentahydrate complex was prepared and speculated its structure from the similar IR spectra of corresponding praseodymium and neodymium-D-ribose complexes, which reveal the coordination behavior of D-ribose to lanthanide ions and give us a model of the interactions between metal ions and carbohydrates.

  14. Nucleobase assemblies supported by uranyl cation coordination and other non-covalent interactions

    Indian Academy of Sciences (India)

    Jitendra Kumar; Sandeep Verma

    2011-11-01

    We describe synthesis and solid state structural description of uranyl complexes of carboxylate functionalized adenine and uracil derivatives. The metal coordination through carboxylate pendant leads to the formation of dimeric assemblies, whereas the directional nature of hydrogen bonding interaction supported by nucleobases and aqua ligands, result in the generation of complex 3-D architectures containing embedded nucleobase ribbons.

  15. The ability to induce microtubule acetylation is a general feature of formin proteins.

    Directory of Open Access Journals (Sweden)

    Susan F Thurston

    Full Text Available Cytoplasmic microtubules exist as distinct dynamic and stable populations within the cell. Stable microtubules direct and maintain cell polarity and it is thought that their stabilization is dependent on coordinative organization between the microtubule network and the actin cytoskeleton. A growing body of work suggests that some members of the formin family of actin remodeling proteins also regulate microtubule organization and stability. For example, we showed previously that expression of the novel formin INF1 is sufficient to induce microtubule stabilization and tubulin acetylation, but not tubulin detyrosination. An important issue with respect to the relationship between formins and microtubules is the determination of which formin domains mediate microtubule stabilization. INF1 has a distinct microtubule-binding domain at its C-terminus and the endogenous INF1 protein is associated with the microtubule network. Surprisingly, the INF1 microtubule-binding domain is not essential for INF1-induced microtubule acetylation. We show here that expression of the isolated FH1 + FH2 functional unit of INF1 is sufficient to induce microtubule acetylation independent of the INF1 microtubule-binding domain. It is not yet clear whether or not microtubule stabilization is a general property of all mammalian formins; therefore we expressed constitutively active derivatives of thirteen of the fifteen mammalian formin proteins in HeLa and NIH3T3 cells and measured their effects on stress fiber formation, MT organization and MT acetylation. We found that expression of the FH1 + FH2 unit of the majority of mammalian formins is sufficient to induce microtubule acetylation. Our results suggest that the regulation of microtubule acetylation is likely a general formin activity and that the FH2 should be thought of as a dual-function domain capable of regulating both actin and microtubule networks.

  16. Alignment of Microtubule Imagery

    OpenAIRE

    Yu, Feiyang; Oerlemans, Ard; Bakker, Erwin M.

    2011-01-01

    This work discusses preliminary work aimed at simulating and visualizing the growth process of a tiny structure inside the cell---the microtubule. Difficulty of recording the process lies in the fact that the tissue preparation method for electronic microscopes is highly destructive to live cells. Here in this paper, our approach is to take pictures of microtubules at different time slots and then appropriately combine these images into a coherent video. Experimental results are given on real...

  17. Alignment of Microtubule Imagery

    CERN Document Server

    Yu, Feiyang; Bakker, Erwin M

    2011-01-01

    This work discusses preliminary work aimed at simulating and visualizing the growth process of a tiny structure inside the cell---the microtubule. Difficulty of recording the process lies in the fact that the tissue preparation method for electronic microscopes is highly destructive to live cells. Here in this paper, our approach is to take pictures of microtubules at different time slots and then appropriately combine these images into a coherent video. Experimental results are given on real data.

  18. Multimodal microtubule binding by the Ndc80 kinetochore complex.

    Science.gov (United States)

    Alushin, Gregory M; Musinipally, Vivek; Matson, Daniel; Tooley, John; Stukenberg, P Todd; Nogales, Eva

    2012-11-01

    The Ndc80 complex is a key site of kinetochore-microtubule attachment during cell division. The human complex engages microtubules with a globular 'head' formed by tandem calponin-homology domains and an 80-amino-acid unstructured 'tail' that contains sites of phosphoregulation by the Aurora B kinase. Using biochemical, cell biological and electron microscopy analyses, we dissected the roles of the tail in binding of microtubules and mediation of cooperative interactions between Ndc80 complexes. Two segments of the tail that contain Aurora B phosphorylation sites become ordered at interfaces; one with tubulin and the second with an adjacent Ndc80 head on the microtubule surface, forming interactions that are disrupted by phosphorylation. We propose a model in which Ndc80's interaction with either growing or shrinking microtubule ends can be tuned by the phosphorylation state of its tail.

  19. Association between microtubules and Golgi vesicles isolated from rat parotid glands.

    Science.gov (United States)

    Coffe, G; Raymond, M N

    1990-01-01

    We report an isolation procedure of trans-Golgi vesicles (GVs) from rat parotid glands. Various organelle markers were used, particularly galactosyl transferase as a trans-Golgi marker, to test the purity of the GV fraction. A quantitative in vitro binding assay between microtubules and GVs is described. The vesicles were incubated with taxol-induced microtubules, layered between 50% and 43% sucrose cushions and subjected to centrifugation. Unlike free microtubules which were sedimented, the GV-bound microtubules co-migrated upward with GVs. Quantification of these bound microtubules was carried out by densitometric scanning of Coomassie blue-stained gels. The association between microtubules and GVs followed a saturation curve, with a plateau value of 20 micrograms of microtubule protein bound to 500 micrograms of GV fraction. The half-saturation of the GV sites was obtained with a microtubule concentration of 20 micrograms/ml. Electron microscopy of negatively stained re-floated material showed numerous microtubule-vesicle complexes. Coating of microtubules with an excess of brain microtubule-associated proteins (MAPs) abolished binding. In the absence of exogenous microtubules, we showed that the GV fraction was already interacting with a class of endogenous rat parotid microtubules. This class of colcemid and cold-stable microtubules represents 10-20% of the total tubulin content of the parotid cell.

  20. The microtubule-associated Rho activating factor GEF-H1 interacts with exocyst complex to regulate vesicle traffic.

    Science.gov (United States)

    Pathak, Ritu; Delorme-Walker, Violaine D; Howell, Michael C; Anselmo, Anthony N; White, Michael A; Bokoch, Gary M; Dermardirossian, Céline

    2012-08-14

    The exocyst complex plays a critical role in targeting and tethering vesicles to specific sites of the plasma membrane. These events are crucial for polarized delivery of membrane components to the cell surface, which is critical for cell motility and division. Though Rho GTPases are involved in regulating actin dynamics and membrane trafficking, their role in exocyst-mediated vesicle targeting is not very clear. Herein, we present evidence that depletion of GEF-H1, a guanine nucleotide exchange factor for Rho proteins, affects vesicle trafficking. Interestingly, we found that GEF-H1 directly binds to exocyst component Sec5 in a Ral GTPase-dependent manner. This interaction promotes RhoA activation, which then regulates exocyst assembly/localization and exocytosis. Taken together, our work defines a mechanism for RhoA activation in response to RalA-Sec5 signaling and involvement of GEF-H1/RhoA pathway in the regulation of vesicle trafficking.

  1. Leveraging Interaction History for Intelligent Configuration of Multiple Coordinated Views in Visualization Tools

    Energy Technology Data Exchange (ETDEWEB)

    Pachuilo, Andrew R [ORNL; Ragan, Eric [Texas A& M University; Goodall, John R [ORNL

    2016-01-01

    Visualization tools can take advantage of multiple coordinated views to support analysis of large, multidimensional data sets. Effective design of such views and layouts can be challenging, but understanding users analysis strategies can inform design improvements. We outline an approach for intelligent design configuration of visualization tools with multiple coordinated views, and we discuss a proposed software framework to support the approach. The proposed software framework could capture and learn from user interaction data to automate new compositions of views and widgets. Such a framework could reduce the time needed for meta analysis of the visualization use and lead to more effective visualization design.

  2. Microtubules Modulate F-actin Dynamics during Neuronal Polarization.

    Science.gov (United States)

    Zhao, Bing; Meka, Durga Praveen; Scharrenberg, Robin; König, Theresa; Schwanke, Birgit; Kobler, Oliver; Windhorst, Sabine; Kreutz, Michael R; Mikhaylova, Marina; Calderon de Anda, Froylan

    2017-08-29

    Neuronal polarization is reflected by different dynamics of microtubule and filamentous actin (F-actin). Axonal microtubules are more stable than those in the remaining neurites, while dynamics of F-actin in axonal growth cones clearly exceed those in their dendritic counterparts. However, whether a functional interplay exists between the microtubule network and F-actin dynamics in growing axons and whether this interplay is instrumental for breaking cellular symmetry is currently unknown. Here, we show that an increment on microtubule stability or number of microtubules is associated with increased F-actin dynamics. Moreover, we show that Drebrin E, an F-actin and microtubule plus-end binding protein, mediates this cross talk. Drebrin E segregates preferentially to growth cones with a higher F-actin treadmilling rate, where more microtubule plus-ends are found. Interruption of the interaction of Drebrin E with microtubules decreases F-actin dynamics and arrests neuronal polarization. Collectively the data show that microtubules modulate F-actin dynamics for initial axon extension during neuronal development.

  3. Intracellular clusterin interacts with brain isoforms of the bridging integrator 1 and with the microtubule-associated protein Tau in Alzheimer's disease.

    Directory of Open Access Journals (Sweden)

    Yuan Zhou

    Full Text Available Sporadic or late-onset Alzheimer's disease (AD is expected to affect 50% of individuals reaching 85 years of age. The most significant genetic risk factor for late-onset AD is the e4 allele of APOE gene encoding apolipoprotein E, a lipid carrier shown to modulate brain amyloid burden. Recent genome-wide association studies have uncovered additional single nucleotide polymorphisms (SNPs linked to AD susceptibility, including those in the CLU and BIN1 genes encoding for clusterin (CLU and the bridging integrator 1 (BIN1 proteins, respectively. Because CLU has been implicated in brain amyloid-β (Aβ clearance in mouse models of amyloid deposition, we sought to investigate whether an AD-linked SNP in the CLU gene altered Aβ42 biomarker levels in the cerebrospinal fluid (CSF. Instead, we found that the CLU rs11136000 SNP modified CSF levels of the microtubule-associated protein Tau in AD patients. We also found that an intracellular form of CLU (iCLU was upregulated in the brain of Tau overexpressing Tg4510 mice, but not in Tg2576 amyloid mouse model. By overexpressing iCLU and Tau in cell culture systems we discovered that iCLU was a Tau-interacting protein and that iCLU associated with brain-specific isoforms of BIN1, also recently identified as a Tau-binding protein. Through expression analysis of CLU and BIN1 variants, we found that CLU and BIN1 interacted via their coiled-coil motifs. In co-immunoprecipitation studies using human brain tissue, we showed that iCLU and the major BIN1 isoform expressed in neurons were associated with modified Tau species found in AD. Finally, we showed that expression of certain coding CLU variants linked to AD risk led to increased levels of iCLU. Together, our findings suggest that iCLU and BIN1 interaction might impact Tau function in neurons and uncover potential new mechanisms underlying the etiology of Tau pathology in AD.

  4. Quantum optical coherence in cytoskeletal microtubules: implications for brain function.

    Science.gov (United States)

    Jibu, M; Hagan, S; Hameroff, S R; Pribram, K H; Yasue, K

    1994-01-01

    'Laser-like,' long-range coherent quantum phenomena may occur biologically within cytoskeletal microtubules. This paper presents a theoretical prediction of the occurrence in biological media of the phenomena which we term 'superradiance' and 'self-induced transparency'. Interactions between the electric dipole field of water molecules confined within the hollow core of microtubules and the quantized electromagnetic radiation field are considered, and microtubules are theorized to play the roles of non-linear coherent optical devices. Superradiance is a specific quantum mechanical ordering phenomenon with characteristic times much shorter than those of thermal interaction. Consequently, optical signalling (and computation) in microtubules would be free from both thermal noise and loss. Superradiant optical computing in networks of microtubules and other cytoskeletal structures may provide a basis for biomolecular cognition and a substrate for consciousness.

  5. Human SAS-6 C-Terminus Nucleates and Promotes Microtubule Assembly in Vitro by Binding to Microtubules.

    Science.gov (United States)

    Gupta, Hindol; Badarudeen, Binshad; George, Athira; Thomas, Geethu Emily; Gireesh, K K; Manna, Tapas K

    2015-10-20

    Centrioles are essential components of the animal centrosome and play crucial roles in the formation of cilia and flagella. They are cylindrical structures composed of nine triplet microtubules organized around a central cartwheel. Recent studies have identified spindle assembly abnormal protein SAS-6 as a critical component necessary for formation of the cartwheel. However, the molecular details of how the cartwheel participates in centriolar microtubule assembly have not been clearly understood. In this report, we show that the C-terminal tail (residues 470-657) of human SAS-6, HsSAS-6 C, the region that has been shown to extend toward the centriolar wall where the microtubule triplets are organized, nucleated and induced microtubule polymerization in vitro. The N-terminus (residues 1-166) of HsSAS-6, the domain known to be involved in formation of the central hub of the cartwheel, did not, however, exert any effect on microtubule polymerization. HsSAS-6 C bound to the microtubules and localized along the lengths of the microtubules in vitro. Microtubule pull-down and coimmunoprecipitation (Co-IP) experiments with S-phase synchronized HeLa cell lysates showed that the endogenous HsSAS-6 coprecipitated with the microtubules, and it mediated interaction with tubulin. Isothermal calorimetry titration and size exclusion chromatography showed that HsSAS-6 C bound to the αβ-tubulin dimer in vitro. The results demonstrate that HsSAS-6 possesses an intrinsic microtubule assembly promoting activity and further implicate that its outer exposed C-terminal tail may play critical roles in microtubule assembly and stabilizing microtubule attachment with the centriolar cartwheel.

  6. A Q-based integrating interaction framework system for multi-agent coordination

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen-jie; SHENG Huan-ye; XIAO Zheng-guang

    2005-01-01

    Interaction is one of the crucial features of multi-agent systems, in which there are two kinds of interaction: agent-to-agent and human-to-agent. In order to unify the two kinds of interaction while designing multiagent systems, this paper introduces Q language-a scenario description language for designing interaction among agents and humans. Based on Q, we propose an integrating interaction framework system for multi-agent coordination, in which Q scenarios are used to uniformly describe both kinds of interactions. Being in accordance to the characteristics of Q language, the Q-based framework makes the interaction process open and easily understood by the users. Additionally, it makes specific applications of multi-agent systems easy to be established by application designers. By applying agent negotiation in agent-mediated e-commerce and agent cooperation in interoperable information query on the Semantic Web, we illustrate how the presented framework for multi-agent coordination is implemented in concrete applications. At the same time, these two different applications also demonstrate usability of the presented framework and verify validity of Q language.

  7. Interaction and Coordination among Nuclear Power Plants, Power Grids and Their Protection Systems

    Directory of Open Access Journals (Sweden)

    Guoyang Wu

    2016-04-01

    Full Text Available Nuclear power plants (NPPs have recently undergone rapid development in China. To improve the performance of both NPPs and grids during adverse conditions, a precise understanding of the coordination between NPPs and grids is required. Therefore, a new mathematical model with reasonable accuracy and reduced computational complexity is developed. This model is applicable to the short, mid, and long-term dynamic simulation of large-scale power systems. The effectiveness of the model is verified by using an actual NPP full-scope simulator as a reference. Based on this model, the interaction and coordination between NPPs and grids under the conditions of over-frequency, under-frequency and under-voltage are analyzed, with special stress applied to the effect of protection systems on the safe operation of both NPPs and power grids. Finally, the coordinated control principles and schemes, together with the recommended protection system values, are proposed for both NPPs and grids. These results show that coordination between the protection systems of NPPs and power networks is a crucial factor in ensuring the safe and stable operation of both NPPs and grids. The results can be used as a reference for coordination between NPPs and grids, as well as for parameter optimization of grid-related generator protection of NPPs.

  8. Do prokaryotes contain microtubules?

    Science.gov (United States)

    Bermudes, D.; Hinkle, G.; Margulis, L.

    1994-01-01

    In eukaryotic cells, microtubules are 24-nm-diameter tubular structures composed of a class of conserved proteins called tubulin. They are involved in numerous cell functions including ciliary motility, nerve cell elongation, pigment migration, centrosome formation, and chromosome movement. Although cytoplasmic tubules and fibers have been observed in bacteria, some with diameters similar to those of eukaryotes, no homologies to eukaryotic microtubules have been established. Certain groups of bacteria including azotobacters, cyanobacteria, enteric bacteria, and spirochetes have been frequently observed to possess microtubule-like structures, and others, including archaebacteria, have been shown to be sensitive to drugs that inhibit the polymerization of microtubules. Although little biochemical or molecular biological information is available, the differences observed among these prokaryotic structures suggest that their composition generally differs among themselves as well as from that of eukaryotes. We review the distribution of cytoplasmic tubules in prokaryotes, even though, in all cases, their functions remain unknown. At least some tend to occur in cells that are large, elongate, and motile, suggesting that they may be involved in cytoskeletal functions, intracellular motility, or transport activities comparable to those performed by eukaryotic microtubules. In Escherichia coli, the FtsZ protein is associated with the formation of a ring in the division zone between the newly forming offspring cells. Like tubulin, FtsZ is a GTPase and shares with tubulin a 7-amino-acid motif, making it a promising candidate in which to seek the origin of tubulins.

  9. A study of microtubule dipole lattices

    Science.gov (United States)

    Nandi, Shubhendu

    Microtubules are cytoskeletal protein polymers orchestrating a host of important cellular functions including, but not limited to, cell support, cell division, cell motility and cell transport. In this thesis, we construct a toy-model of the microtubule lattice composed of vector Ising spins representing tubulin molecules, the building block of microtubules. Nearest-neighbor and next-to-nearest neighbor interactions are considered within an anisotropic dielectric medium. As a consequence of the helical topology, we observe that certain spin orientations render the lattice frustrated with nearest neighbor ferroelectric and next-to-nearest neighbor antiferroelectric bonds. Under these conditions, the lattice displays the remarkable property of stabilizing certain spin patterns that are robust to thermal fluctuations. We model this behavior in the framework of a generalized Ising model known as the J1 - J2 model and theoretically determine the set of stable patterns. Employing Monte-Carlo methods, we demonstrate the stability of such patterns in the microtubule lattice at human physiological temperatures. This suggests a novel biological mechanism for storing information in living organisms, whereby the tubulin spin (dipole moment) states become information bits and information gets stored in microtubules in a way that is robust to thermal fluctuations.

  10. Dual Logic and Cerebral Coordinates for Reciprocal Interaction in Eye Contact

    Science.gov (United States)

    Lee, Ray F.

    2015-01-01

    In order to scientifically study the human brain’s response to face-to-face social interaction, the scientific method itself needs to be reconsidered so that both quantitative observation and symbolic reasoning can be adapted to the situation where the observer is also observed. In light of the recent development of dyadic fMRI which can directly observe dyadic brain interacting in one MRI scanner, this paper aims to establish a new form of logic, dual logic, which provides a theoretical platform for deductive reasoning in a complementary dual system with emergence mechanism. Applying the dual logic in the dfMRI experimental design and data analysis, the exogenous and endogenous dual systems in the BOLD responses can be identified; the non-reciprocal responses in the dual system can be suppressed; a cerebral coordinate for reciprocal interaction can be generated. Elucidated by dual logic deductions, the cerebral coordinate for reciprocal interaction suggests: the exogenous and endogenous systems consist of the empathy network and the mentalization network respectively; the default-mode network emerges from the resting state to activation in the endogenous system during reciprocal interaction; the cingulate plays an essential role in the emergence from the exogenous system to the endogenous system. Overall, the dual logic deductions are supported by the dfMRI experimental results and are consistent with current literature. Both the theoretical framework and experimental method set the stage to formally apply the scientific method in studying complex social interaction. PMID:25885446

  11. Electrostatically enhanced FF interactions through hydrogen bonding, halogen bonding and metal coordination: an ab initio study.

    Science.gov (United States)

    Bauzá, Antonio; Frontera, Antonio

    2016-07-27

    In this manuscript the ability of hydrogen and halogen bonding interactions, as well as metal coordination to enhance FF interactions involving fluorine substituted aromatic rings has been studied at the RI-MP2/def2-TZVPD level of theory. We have used 4-fluoropyridine, 4-fluorobenzonitrile, 3-(4-fluorophenyl)propiolonitrile and their respective meta derivatives as aromatic compounds. In addition, we have used HF and IF as hydrogen and halogen bond donors, respectively, and Ag(i) as the coordination metal. Furthermore, we have also used HF as an electron rich fluorine donor entity, thus establishing FF interactions with the above mentioned aromatic systems. Moreover, a CSD (Cambridge Structural Database) search has been carried out and some interesting examples have been found, highlighting the impact of FF interactions involving aromatic fluorine atoms in solid state chemistry. Finally, cooperativity effects between FF interactions and both hydrogen and halogen bonding interactions have been analyzed and compared. We have also used Bader's theory of "atoms in molecules" to further describe the cooperative effects.

  12. Binding of Substrates to the Central Pore of the Vps4 ATPase Is Autoinhibited by the Microtubule Interacting and Trafficking (MIT) Domain and Activated by MIT Interacting Motifs (MIMs)*

    Science.gov (United States)

    Han, Han; Monroe, Nicole; Votteler, Jörg; Shakya, Binita; Sundquist, Wesley I.; Hill, Christopher P.

    2015-01-01

    The endosomal sorting complexes required for transport (ESCRT) pathway drives reverse topology membrane fission events within multiple cellular pathways, including cytokinesis, multivesicular body biogenesis, repair of the plasma membrane, nuclear membrane vesicle formation, and HIV budding. The AAA ATPase Vps4 is recruited to membrane necks shortly before fission, where it catalyzes disassembly of the ESCRT-III lattice. The N-terminal Vps4 microtubule-interacting and trafficking (MIT) domains initially bind the C-terminal MIT-interacting motifs (MIMs) of ESCRT-III subunits, but it is unclear how the enzyme then remodels these substrates in response to ATP hydrolysis. Here, we report quantitative binding studies that demonstrate that residues from helix 5 of the Vps2p subunit of ESCRT-III bind to the central pore of an asymmetric Vps4p hexamer in a manner that is dependent upon the presence of flexible nucleotide analogs that can mimic multiple states in the ATP hydrolysis cycle. We also find that substrate engagement is autoinhibited by the Vps4p MIT domain and that this inhibition is relieved by binding of either Type 1 or Type 2 MIM elements, which bind the Vps4p MIT domain through different interfaces. These observations support the model that Vps4 substrates are initially recruited by an MIM-MIT interaction that activates the Vps4 central pore to engage substrates and generate force, thereby triggering ESCRT-III disassembly. PMID:25833946

  13. Binding of Substrates to the Central Pore of the Vps4 ATPase Is Autoinhibited by the Microtubule Interacting and Trafficking (MIT) Domain and Activated by MIT Interacting Motifs (MIMs).

    Science.gov (United States)

    Han, Han; Monroe, Nicole; Votteler, Jörg; Shakya, Binita; Sundquist, Wesley I; Hill, Christopher P

    2015-05-22

    The endosomal sorting complexes required for transport (ESCRT) pathway drives reverse topology membrane fission events within multiple cellular pathways, including cytokinesis, multivesicular body biogenesis, repair of the plasma membrane, nuclear membrane vesicle formation, and HIV budding. The AAA ATPase Vps4 is recruited to membrane necks shortly before fission, where it catalyzes disassembly of the ESCRT-III lattice. The N-terminal Vps4 microtubule-interacting and trafficking (MIT) domains initially bind the C-terminal MIT-interacting motifs (MIMs) of ESCRT-III subunits, but it is unclear how the enzyme then remodels these substrates in response to ATP hydrolysis. Here, we report quantitative binding studies that demonstrate that residues from helix 5 of the Vps2p subunit of ESCRT-III bind to the central pore of an asymmetric Vps4p hexamer in a manner that is dependent upon the presence of flexible nucleotide analogs that can mimic multiple states in the ATP hydrolysis cycle. We also find that substrate engagement is autoinhibited by the Vps4p MIT domain and that this inhibition is relieved by binding of either Type 1 or Type 2 MIM elements, which bind the Vps4p MIT domain through different interfaces. These observations support the model that Vps4 substrates are initially recruited by an MIM-MIT interaction that activates the Vps4 central pore to engage substrates and generate force, thereby triggering ESCRT-III disassembly. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. A Perylene-Based Microporous Coordination Polymer Interacts Selectively with Electron-Poor Aromatics.

    Science.gov (United States)

    Tran, Ly D; Ma, Jialiu; Wong-Foy, Antek G; Matzger, Adam J

    2016-04-11

    The design, synthesis, and properties of the new microporous coordination polymer UMCM-310 are described. The unique electronic character of the perylene-based linker enables selective interaction with electron-poor aromatics leading to efficient separation of nitroaromatics. UMCM-310 possesses high surface area and large pore size and thus permits the separation of large organic molecules based on adsorption rather than size exclusion.

  15. CYLD Regulates Noscapine Activity in Acute Lymphoblastic Leukemia via a Microtubule-Dependent Mechanism.

    Science.gov (United States)

    Yang, Yunfan; Ran, Jie; Sun, Lei; Sun, Xiaodong; Luo, Youguang; Yan, Bing; Tala; Liu, Min; Li, Dengwen; Zhang, Lei; Bao, Gang; Zhou, Jun

    2015-01-01

    Noscapine is an orally administrable drug used worldwide for cough suppression and has recently been demonstrated to disrupt microtubule dynamics and possess anticancer activity. However, the molecular mechanisms regulating noscapine activity remain poorly defined. Here we demonstrate that cylindromatosis (CYLD), a microtubule-associated tumor suppressor protein, modulates the activity of noscapine both in cell lines and in primary cells of acute lymphoblastic leukemia (ALL). Flow cytometry and immunofluorescence microscopy reveal that CYLD increases the ability of noscapine to induce mitotic arrest and apoptosis. Examination of cellular microtubules as well as in vitro assembled microtubules shows that CYLD enhances the effect of noscapine on microtubule polymerization. Microtubule cosedimentation and fluorescence titration assays further reveal that CYLD interacts with microtubule outer surface and promotes noscapine binding to microtubules. These findings thus demonstrate CYLD as a critical regulator of noscapine activity and have important implications for ALL treatment.

  16. The Gas2 family protein Pigs is a microtubule +TIP that affects cytoskeleton organisation.

    Science.gov (United States)

    Girdler, Gemma C; Applewhite, Derek A; Perry, Wick M G; Rogers, Stephen L; Röper, Katja

    2016-01-01

    Coordination between different cytoskeletal systems is crucial for many cell biological functions, including cell migration and mitosis, and also plays an important role during tissue morphogenesis. Proteins of the class of cytoskeletal crosslinkers, or cytolinkers, have the ability to interact with more than one cytoskeletal system at a time and are prime candidates to mediate any coordination. One such class comprises the Gas2-like proteins, combining a conserved calponin-homology-type actin-binding domain and a Gas2 domain predicted to bind microtubules (MTs). This domain combination is also found in spectraplakins, huge cytolinkers that play important roles in many tissues in both invertebrates and vertebrates. Here, we dissect the ability of the single Drosophila Gas2-like protein Pigs to interact with both actin and MT cytoskeletons, both in vitro and in vivo, and illustrate complex regulatory interactions that determine the localisation of Pigs to and its effects on the cytoskeleton.

  17. A NOVEL ADAPTIVE σ COORDINATE MODEL AND ITS APPLICATIONS TO WAVE AND STRUCTURE INTERACTION

    Institute of Scientific and Technical Information of China (English)

    SU Xiao-hui; ZOU De-gao; ZHANG Jian-tao; LESCHKA Stefan; LIN Peng-zhi; ZHANG Kai-lin

    2012-01-01

    In this paper,a novel adaptive mesh σ coordinate model is proposed for the studies of Wave and Structure Interaction (WSI).The model is validated by using the case of a solitary wave movement in an open channel with constant water depth and the case of nonbreaking solitary wave propagating over a step.Numerical results agree well with the analytical solutions obtained based on the Boussinesq theory,the laboratory data and other numerical model results.The proposed model is then used to study a solitary wave interacting with a suspended fixed structure.

  18. Applying the Density Matrix Expansion with Coordinate-Space Chiral Interactions

    CERN Document Server

    Dyhdalo, A; Furnstahl, R J

    2016-01-01

    We apply the density matrix expansion (DME) at Hartree-Fock level with long-range chiral effective field theory interactions defined in coordinate space up to next-to-next-to-leading order. We consider chiral potentials both with and without explicit Delta isobars. The challenging algebra associated with applying the DME to three-nucleon forces is tamed using a new organization scheme, which will also facilitate generalizations. We include local regulators on the interactions to mitigate the effects of singular potentials on the DME couplings and simplify the optimization of generalized Skyrme-like functionals.

  19. Roles for microtubule and microfilament cytoskeletons in animal cell cytokinesis

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhongcai; CAI Shang; JIANG Qing; ZHANG Chuanmao; TANG Xiaowei

    2005-01-01

    Microtubule and microfilament cytoskeletons play key roles in the whole process of cytokinesis. Although a number of hypotheses have been proposed to elucidate the mechanism of cytokinesis by microtubule and actin filament cytoskeletons, many reports are conflicting. In our study, combining the cytoskeletons drug treatments with the time-lapse video technology, we retested the key roles of microtubule and actin filament in cytokinesis. The results showed that depolymerization of microtubules by Nocodazole after the initiation of furrowing would not inhibit the furrow ingression, but obviously decrease the stiffness of daughter cells. Depolymerizing actin filaments by Cytochalasin B before metaphase would inhibit the initiation of furrowing but not chromosome segregation, resulting in the formation of binucleate cells; however, depolymerizing actin filaments during anaphase would prevent furrowing and lead to the regress of established furrow, also resulting in the formation of binucleate cells. Further, depolymerizing microtubules and actin filaments simultaneously after metaphase would cause the quick regress of the furrow and the formation of binucleate cells. From these results we propose that a successful cytokinesis requires functions and coordination of both the microtubule and actin filament cytoskeletons. Microtubule cytoskeleton may function in the positioning and initiation of cleavage furrow, and the actin filament cytoskeleton may play key roles in the initiation and ingression of the furrow.

  20. Tensile stress stimulates microtubule outgrowth in living cells

    Science.gov (United States)

    Kaverina, Irina; Krylyshkina, Olga; Beningo, Karen; Anderson, Kurt; Wang, Yu-Li; Small, J. Victor

    2002-01-01

    Cell motility is driven by the sum of asymmetric traction forces exerted on the substrate through adhesion foci that interface with the actin cytoskeleton. Establishment of this asymmetry involves microtubules, which exert a destabilising effect on adhesion foci via targeting events. Here, we demonstrate the existence of a mechano-sensing mechanism that signals microtubule polymerisation and guidance of the microtubules towards adhesion sites under increased stress. Stress was applied either by manipulating the body of cells moving on glass with a microneedle or by stretching a flexible substrate that cells were migrating on. We propose a model for this mechano-sensing phenomenon whereby microtubule polymerisation is stimulated and guided through the interaction of a microtubule tip complex with actin filaments under tension.

  1. Insights from an erroneous kinetochore-microtubule attachment state.

    Science.gov (United States)

    Cane, Stuart; McGilvray, Philip T; Maresca, Thomas J

    2013-01-01

    Faithful distribution of the genome requires that sister kinetochores, which assemble on each chromatid during cell division, interact with dynamic microtubules from opposite spindle poles in a configuration called chromosome biorientation. Biorientation produces tension that increases the affinity of kinetochores for microtubules via ill-defined mechanisms. Non-bioriented kinetochore-microtubule (kt-MT) interactions are prevalent but short-lived due to an error correction pathway that reduces the affinity of kinetochores for microtubules. Interestingly, incorrect kt-MT interactions can be stabilized by experimentally applying force to misoriented chromosomes. Here, a live-cell force assay is utilized to characterize the molecular composition of a common type of improper kt-MT attachment. Our force-related studies are also discussed in the context of current models for tension-dependent stabilization of kt-MT interactions.

  2. KIF7 Controls the Proliferation of Cells of the Respiratory Airway through Distinct Microtubule Dependent Mechanisms.

    Directory of Open Access Journals (Sweden)

    Garry L Coles

    2015-10-01

    Full Text Available The cell cycle must be tightly coordinated for proper control of embryonic development and for the long-term maintenance of organs such as the lung. There is emerging evidence that Kinesin family member 7 (Kif7 promotes Hedgehog (Hh signaling during embryonic development, and its misregulation contributes to diseases such as ciliopathies and cancer. Kif7 encodes a microtubule interacting protein that controls Hh signaling through regulation of microtubule dynamics within the primary cilium. However, whether Kif7 has a function in nonciliated cells remains largely unknown. The role Kif7 plays in basic cell biological processes like cell proliferation or cell cycle progression also remains to be elucidated. Here, we show that Kif7 is required for coordination of the cell cycle, and inactivation of this gene leads to increased cell proliferation in vivo and in vitro. Immunostaining and transmission electron microscopy experiments show that Kif7dda/dda mutant lungs are hyperproliferative and exhibit reduced alveolar epithelial cell differentiation. KIF7 depleted C3H10T1/2 fibroblasts and Kif7dda/dda mutant mouse embryonic fibroblasts have increased growth rates at high cellular densities, suggesting that Kif7 may function as a general regulator of cellular proliferation. We ascertained that in G1, Kif7 and microtubule dynamics regulate the expression and activity of several components of the cell cycle machinery known to control entry into S phase. Our data suggest that Kif7 may function to regulate the maintenance of the respiratory airway architecture by controlling cellular density, cell proliferation, and cycle exit through its role as a microtubule associated protein.

  3. Microtubule's conformational cap

    DEFF Research Database (Denmark)

    Chretien, D.; Janosi, I.; Taveau, J.C.

    1999-01-01

    The molecular mechanisms that allow elongation of the unstable microtubule lattice remain unclear. It is usually thought that the GDP-liganded tubulin lattice is capped by a small layer of GTP- or GDP-P(i)-liganded molecules, the so called "GTP-cap". Here, we point-out that the elastic properties...

  4. Coordinated development of muscles and tendon-like structures: early interactions in the Drosophila leg

    Directory of Open Access Journals (Sweden)

    cedric esoler

    2016-02-01

    Full Text Available The formation of the musculoskeletal system is a remarkable example of tissue assembly. In both vertebrates and invertebrates, precise connectivity between muscles and skeleton (or exoskeleton via tendons or equivalent structures is fundamental for movement and stability of the body. The molecular and cellular processes underpinning muscle formation are well established and significant advances have been made in understanding tendon development. However, the mechanisms contributing to proper connection between these two tissues have received less attention. Observations of coordinated development of tendons and muscles suggest these tissues may interact during the different steps in their development. There is growing evidence that, depending on animal model and muscle type, these interactions can take place from progenitor induction to the final step of the formation of the musculoskeletal system. Here we briefly review and compare the mechanisms behind muscle and tendon interaction throughout the development of vertebrates and Drosophila before going on to discuss our recent findings on the coordinated development of muscles and tendon-like structures in Drosophila leg. By altering apodeme formation (the functional Drosophila equivalent of tendons in vertebrates during the early steps of leg development, we affect the spatial localisation of subsequent myoblasts. These findings provide the first evidence of the developmental impact of early interactions between muscle and tendon-like precursors, and confirm the appendicular Drosophila muscle system as a valuable model for studying these processes.

  5. [Functional role of dragonfly legs before and after hatching: reorganization of coordinating interactions].

    Science.gov (United States)

    Sviderskiĭ, V L; Plotnikova, S I; Gorelkin, V S; Severina, I Iu; Isavnina, I L

    2012-11-01

    The characteristics of a structure-functional organization of leg apparatus were examined in the dragonfly Aeshna grandis: larvae of the final stadium, which legs perform a locomotion function and adults (imago) rising on a wing, which legs lose a locomotion function and are used mainly for catching a prey in the air. It has been demonstrated that legs of the imago practically do not differ from those of the larva either in shape or in proportion of segments of the leg and all changes in the functional role of legs of the imago are implemented due to modifications of mechanisms of limb muscle control and an appropriate reorganization or coordinating interactions. As it is proved by the obtained data, this reorganization concerns mechanisms of the generation of motor commands as well as close coordination of the activity of wing and leg apparatus and some others. The abovementioned mechanisms are discussed.

  6. Collaboration, credibility, compassion, and coordination: professional nurse communication skill sets in health care team interactions.

    Science.gov (United States)

    Apker, Julie; Propp, Kathleen M; Zabava Ford, Wendy S; Hofmeister, Nancee

    2006-01-01

    This study explored how nurses communicate professionalism in interactions with members of their health care teams. Extant research show that effective team communication is a vital aspect of a positive nursing practice environment, a setting that has been linked to enhanced patient outcomes. Although communication principles are emphasized in nursing education as an important component of professional nursing practice, actual nurse interaction skills in team-based health care delivery remain understudied. Qualitative analysis of interview transcripts with 50 participants at a large tertiary hospital revealed four communicative skill sets exemplified by nursing professionals: collaboration, credibility, compassion, and coordination. Study findings highlight specific communicative behaviors associated with each skill set that exemplify nurse professionalism to members of health care teams. Theoretical and pragmatic conclusions are drawn regarding the communicative responsibilities of professional nurses in health care teams. Specific interaction techniques that nurses could use in nurse-team communication are then offered for use in baccalaureate curriculum and organizational in-service education.

  7. Social coordination in toddler's word learning: interacting systems of perception and action

    Science.gov (United States)

    Pereira, Alfredo; Smith, Linda; Yu, Chen

    2008-06-01

    We measured turn-taking in terms of hand and head movements and asked if the global rhythm of the participants' body activity relates to word learning. Six dyads composed of parents and toddlers (M=18 months) interacted in a tabletop task wearing motion-tracking sensors on their hands and head. Parents were instructed to teach the labels of 10 novel objects and the child was later tested on a name-comprehension task. Using dynamic time warping, we compared the motion data of all body-part pairs, within and between partners. For every dyad, we also computed an overall measure of the quality of the interaction, that takes into consideration the state of interaction when the parent uttered an object label and the overall smoothness of the turn-taking. The overall interaction quality measure was correlated with the total number of words learned. In particular, head movements were inversely related to other partner's hand movements, and the degree of bodily coupling of parent and toddler predicted the words that children learned during the interaction. The implications of joint body dynamics to understanding joint coordination of activity in a social interaction, its scaffolding effect on the child's learning and its use in the development of artificial systems are discussed.

  8. Visual information gain and task asymmetry interact in bimanual force coordination and control.

    Science.gov (United States)

    Hu, Xiaogang; Newell, Karl M

    2011-08-01

    This study examined the question of whether and how the influence of visual information on force coordination patterns is dependent on the settings of a task asymmetry constraint. In a bimanual isometric force experiment, the task asymmetry was manipulated via imposing different coefficients on the index finger forces such that the weighted sum of the finger forces matched the target force. The environmental constraint was quantified by the visual performance error and was manipulated through the change of visual gain (number of pixels on the screen representing the unit of force). The constraint arising from the individual was quantified by the bilateral coupling effect (i.e., symmetric force production) between hands. The results revealed improved performance in terms of lower variability and performance error and more complex total force structure with higher visual gain. The influence of visual gain on the force coordination pattern, however, was found to be dependent on the task coefficients imposed on the finger forces. Namely, the force sharing between hands became more symmetric with high visual gain only when the right finger force had the higher coefficient, and an error-compensatory strategy was evident with high gain only when symmetric coefficients were imposed on the two fingers. The findings support the proposition that the motor coordination and control patterns are organized by the interactive influence of different categories of constraints where the functional influence of the information provided is dependent on the motor output.

  9. Motion Intention Analysis-Based Coordinated Control for Amputee-Prosthesis Interaction

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2010-01-01

    Full Text Available To study amputee-prosthesis (AP interaction, a novel reconfigurable biped robot was designed and fabricated. In homogeneous configuration, two identical artificial legs (ALs were used to simulate the symmetrical lower limbs of a healthy person. Linear inverted pendulum model combining with ZMP stability criterion was used to generate the gait trajectories of ALs. To acquire interjoint coordination for healthy gait, rate gyroscopes were mounted on CoGs of thigh and shank of both legs. By employing principal component analysis, the measured angular velocities were processed and the motion synergy was obtained in the final. Then, one of two ALs was replaced by a bionic leg (BL, and the biped robot was changed into heterogeneous configuration to simulate the AP coupling system. To realize symmetrical stable walking, master/slave coordinated control strategy is proposed. According to information acquired by gyroscopes, BL recognized the motion intention of AL and reconstructed its kinematic variables based on interjoint coordination. By employing iterative learning control, gait tracking of BL to AL was archived. Real environment robot walking experiments validated the correctness and effectiveness of the proposed scheme.

  10. Regulation of localization and activity of the microtubule depolymerase MCAK.

    Science.gov (United States)

    Tanenbaum, Marvin E; Medema, René H; Akhmanova, Anna

    2011-03-01

    Mitotic Centromere Associated Kinesin (MCAK) is a potent microtubule depolymerizing and catastrophe-inducing factor, which uses the energy of ATP hydrolysis to destabilize microtubule ends. MCAK is localized to inner centromeres, kinetochores and spindle poles of mitotic cells, and is also present in the cytoplasm. Both in interphase and in mitosis, MCAK can specifically accumulate at the growing microtubule ends. Here we discuss the mechanisms, which modulate subcellular localization and activity of MCAK through the interaction with the End Binding (EB) proteins and phosphorylation.

  11. Microtubule Dynamics and Oscillating State for Mitotic Spindle

    CERN Document Server

    Rashid-Shomali, Safura

    2010-01-01

    We present a physical mechanism that can cause the mitotic spindle to oscillate. The driving force for this mechanism emerges from the polymerization of astral microtubules interacting with the cell cortex. We show that Brownian ratchet model for growing microtubules reaching the cell cortex, mediate an effective mass to the spindle body and therefore force it to oscillate. We compare the predictions of this mechanism with the previous mechanisms which were based on the effects of motor proteins. Finally we combine the effects of microtubules polymerization and motor proteins, and present the detailed phase diagram for possible oscillating states.

  12. Queueing induced by bidirectional motor motion near the end of a microtubule

    Science.gov (United States)

    Ashwin, Peter; Lin, Congping; Steinberg, Gero

    2010-11-01

    Recent live observations of motors in long-range microtubule (MT) dependent transport in the fungus Ustilago maydis have reported bidirectional motion of dynein and an accumulation of the motors at the polymerization-active (the plus-end) of the microtubule. Quantitative data derived from in vivo observation of dynein has enabled us to develop an accurate, quantitatively-valid asymmetric simple exclusion process (ASEP) model that describes the coordinated motion of anterograde and retrograde motors sharing a single oriented microtubule. We give approximate expressions for the size and distribution of the accumulation, and discuss queueing properties for motors entering this accumulation. We show for this ASEP model, that the mean accumulation can be modeled as an M/M/∞ queue that is Poisson distributed with mean Farr/pd , where Farr is the flux of motors that arrives at the tip and pd is the rate at which individual motors change direction from anterograde to retrograde motion. Deviations from this can in principle be used to gain information about other processes at work in the accumulation. Furthermore, our work is a significant step toward a mathematical description of the complex interactions of motors in cellular long-range transport of organelles.

  13. Inter-domain Cooperation in INCENP Promotes Aurora B Relocation from Centromeres to Microtubules

    Directory of Open Access Journals (Sweden)

    Armando van der Horst

    2015-07-01

    Full Text Available The chromosomal passenger complex is essential for error-free chromosome segregation and proper execution of cytokinesis. To coordinate nuclear division with cytoplasmic division, its enzymatic subunit, Aurora B, relocalizes from centromeres in metaphase to the spindle midzone in anaphase. In budding yeast, this requires dephosphorylation of the microtubule-binding (MTB domain of the INCENP analog Sli15. The mechanistic basis for this relocalization in metazoans is incompletely understood. We demonstrate that the putative coiled-coil domain within INCENP drives midzone localization of Aurora B via a direct, electrostatic interaction with microtubules. Furthermore, we provide evidence that the CPC multimerizes via INCENP’s centromere-targeting domain (CEN box, which increases the MTB affinity of INCENP. In (prometaphase, the MTB affinity of INCENP is outcompeted by the affinity of its CEN box for centromeres, while at anaphase onset—when the histone mark H2AT120 is dephosphorylated—INCENP and Aurora B switch from centromere to microtubule localization.

  14. Cell Biology: Microtubule Collisions to the Rescue.

    Science.gov (United States)

    Gardner, Melissa K

    2016-12-19

    The proper regulation of microtubule lengths is fundamental to their cellular function. New work now reports that the collision of a growing microtubule end with another object, such as a microtubule, can contribute to the regulation of microtubule lengths by leaving behind damage that ultimately acts to stabilize the microtubule network. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Event heap: a coordination infrastructure for dynamic heterogeneous application interactions in ubiquitous computing environments

    Science.gov (United States)

    Johanson, Bradley E.; Fox, Armando; Winograd, Terry A.; Hanrahan, Patrick M.

    2010-04-20

    An efficient and adaptive middleware infrastructure called the Event Heap system dynamically coordinates application interactions and communications in a ubiquitous computing environment, e.g., an interactive workspace, having heterogeneous software applications running on various machines and devices across different platforms. Applications exchange events via the Event Heap. Each event is characterized by a set of unordered, named fields. Events are routed by matching certain attributes in the fields. The source and target versions of each field are automatically set when an event is posted or used as a template. The Event Heap system implements a unique combination of features, both intrinsic to tuplespaces and specific to the Event Heap, including content based addressing, support for routing patterns, standard routing fields, limited data persistence, query persistence/registration, transparent communication, self-description, flexible typing, logical/physical centralization, portable client API, at most once per source first-in-first-out ordering, and modular restartability.

  16. Electrostatically biased binding of kinesin to microtubules.

    Directory of Open Access Journals (Sweden)

    Barry J Grant

    2011-11-01

    Full Text Available The minimum motor domain of kinesin-1 is a single head. Recent evidence suggests that such minimal motor domains generate force by a biased binding mechanism, in which they preferentially select binding sites on the microtubule that lie ahead in the progress direction of the motor. A specific molecular mechanism for biased binding has, however, so far been lacking. Here we use atomistic Brownian dynamics simulations combined with experimental mutagenesis to show that incoming kinesin heads undergo electrostatically guided diffusion-to-capture by microtubules, and that this produces directionally biased binding. Kinesin-1 heads are initially rotated by the electrostatic field so that their tubulin-binding sites face inwards, and then steered towards a plus-endwards binding site. In tethered kinesin dimers, this bias is amplified. A 3-residue sequence (RAK in kinesin helix alpha-6 is predicted to be important for electrostatic guidance. Real-world mutagenesis of this sequence powerfully influences kinesin-driven microtubule sliding, with one mutant producing a 5-fold acceleration over wild type. We conclude that electrostatic interactions play an important role in the kinesin stepping mechanism, by biasing the diffusional association of kinesin with microtubules.

  17. CSPP and CSPP-L associate with centrosomes and microtubules and differently affect microtubule organization.

    Science.gov (United States)

    Patzke, Sebastian; Stokke, Trond; Aasheim, Hans-Christian

    2006-10-01

    We recently described the identification of a centrosome/spindle pole associated protein, CSPP, involved in cell cycle progression. Here we report a CSPP isoform denoted CSPP-L, with a 294 amino acids longer N-terminus and a 51 amino acids insertion located in the coiled-coil mid-domain. Expression analysis indicates an inverse cell cycle dependent regulation. CSPP mRNA expression is highest in G1 whereas CSPP-L expression is highest in G2/M. Ectopic expression of CSPP-L impairs cell cycle progression weaker in G1 than CSPP. Furthermore, normal mitotic phenotypes were observed in CSPP-L but not in CSPP transfectants. CSPP-L relocates from spindle microtubules and poles in metaphase to the mid-spindle in anaphase and concentrates at the mid-body in telophase/cytokinesis. CSPP-L high-expressing mitotic cells were predominantly characterized by lagging chromosomes or monopolar spindles, in contrast to the predominant multipolar spindles observed with CSPP expression. The different effects of CSPP and CSPP-L on microtubule organization in mitosis depend on the coiled-coil mid-domain insertion. The common C-terminal domain is required to repress that activity until mitosis. Notably, this C-terminal domain alone can associate with centrosomes in a microtubule independent manner. Taken together, CSPP and CSPP-L interact with centrosomes and microtubules and can differently affect microtubule organization. Copyright 2006 Wiley-Liss, Inc.

  18. Learning a new bimanual coordination pattern: interlimb interactions, attentional focus, and transfer.

    Science.gov (United States)

    de Boer, Betteco J; Peper, C Lieke E; Beek, Peter J

    2013-01-01

    Because bimanual coordinative stability is governed by interlimb coupling, we examined how learning a new pattern (90°) was reflected in changes in the underlying interlimb interactions. Three interlimb interaction sources were distinguished: integrated timing of feedforward control signals, error corrections based on perceived relative phase, and phase entrainment by contralateral afference. By comparing 4 tasks that involve these interactions to a different extent, changes in the stabilizing contributions of these coupling sources could be studied. Furthermore, we studied how the learning process and changes in the underlying interactions were influenced by attentional focus (internal vs. external), and we examined retention of the learned pattern and transfer to the mirror-symmetrical pattern (270°). Results showed that stability and accuracy of the new pattern increased significantly with learning, due to improved integrated timing and error correction. Integrated timing improved first, possibly providing a reference frame for the error corrections that subsequently became more effective. Despite some qualitative differences in the learning process, neither performance of the learned pattern nor the underlying interlimb interactions was influenced by attentional focus. Whereas the learned pattern improved directly after practice, transfer followed later, suggesting that a more general representation was formed at a slower rate after practice.

  19. Interaction of Waves, Surface Currents, and Turbulence: the Application of Surface-Following Coordinate Systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface waves comprise an important aspect of the interaction between the atmosphere and the ocean, so a dynamically consistent framework for modelling atmosphere-ocean interaction must take account of surface waves, either implicitly or explicitly. In order to calculate the effect of wind forcing on waves and currents, and vice versa, it is necessary to employ a consistent formulation of the energy and momentum balance within the airflow, wave field, and water column. It is very advantageous to apply surface-following coordinate systems, whereby the steep gradients in mean flow properties near the air-water interface in the cross-interface direction may be resolved over distances which are much smaller than the height of the waves themselves. We may account for the waves explicitly by employing a numerical spectral wave model, and applying a suitable theory of wave-mean flow interaction. If the mean flow is small compared with the wave phase speed, perturbation expansions of the hydrodynamic equations in a Lagrangian or generalized Lagrangian mean framework are useful: for stronger flows, such as for wind blowing over waves, the presence of critical levels where the mean flow velocity is equal to the wave phase speed necessitates the application of more general types of surface-following coordinate system. The interaction of the flow of air and water and associated differences in temperature and the concentration of various substances (such as gas species) gives rise to a complex boundary-layer structure at a wide range of vertical scales, from the sub-millimetre scales of gaseous diffusion, to several tens of metres for the turbulent Ekman layer. The balance of momentum, heat, and mass is also affected significantly by breaking waves, which act to increase the effective area of the surface for mass transfer, and increase turbulent diffusive fluxes via the conversion of wave energy to turbulent kinetic energy.

  20. Microtubules accelerate the kinase activity of Aurora-B by a reduction in dimensionality.

    Science.gov (United States)

    Noujaim, Michael; Bechstedt, Susanne; Wieczorek, Michal; Brouhard, Gary J

    2014-01-01

    Aurora-B is the kinase subunit of the Chromosome Passenger Complex (CPC), a key regulator of mitotic progression that corrects improper kinetochore attachments and establishes the spindle midzone. Recent work has demonstrated that the CPC is a microtubule-associated protein complex and that microtubules are able to activate the CPC by contributing to Aurora-B auto-phosphorylation in trans. Aurora-B activation is thought to occur when the local concentration of Aurora-B is high, as occurs when Aurora-B is enriched at centromeres. It is not clear, however, whether distributed binding to large structures such as microtubules would increase the local concentration of Aurora-B. Here we show that microtubules accelerate the kinase activity of Aurora-B by a "reduction in dimensionality." We find that microtubules increase the kinase activity of Aurora-B toward microtubule-associated substrates while reducing the phosphorylation levels of substrates not associated to microtubules. Using the single molecule assay for microtubule-associated proteins, we show that a minimal CPC construct binds to microtubules and diffuses in a one-dimensional (1D) random walk. The binding of Aurora-B to microtubules is salt-dependent and requires the C-terminal tails of tubulin, indicating that the interaction is electrostatic. We show that the rate of Aurora-B auto-activation is faster with increasing concentrations of microtubules. Finally, we demonstrate that microtubules lose their ability to stimulate Aurora-B when their C-terminal tails are removed by proteolysis. We propose a model in which microtubules act as scaffolds for the enzymatic activity of Aurora-B. The scaffolding activity of microtubules enables rapid Aurora-B activation and efficient phosphorylation of microtubule-associated substrates.

  1. Influenza virus A/Beijing/501/2009(H1N1 NS1 interacts with β-tubulin and induces disruption of the microtubule network and apoptosis on A549 cells.

    Directory of Open Access Journals (Sweden)

    Xueqing Han

    Full Text Available NS1 of influenza A virus is a key multifunctional protein that plays various roles in regulating viral replication mechanisms, host innate/adaptive immune responses, and cellular signalling pathways. These functions rely on its ability to participate in a multitude of protein-protein and protein-RNA interactions. To gain further insight into the role of NS1, a tandem affinity purification (TAP method was utilized to find unknown interaction partner of NS1. The protein complexes of NS1 and its interacting partner were purified from A549 cell using TAP-tagged NS1 as bait, and co-purified cellular factors were identified by mass spectrometry (MS. We identified cellular β-tubulin as a novel interaction partner of NS1. The RNA-binding domain of NS1 interacts with β-tubulin through its RNA-binding domain, as judged by a glutathione S-transferase (GST pull-down assay with the GST-fused functional domains of NS1. Immunofluorescence analysis further revealed that NS1 with β-tubulin co-localized in the nucleus. In addition, the disruption of the microtubule network and apoptosis were also observed on NS1-transfected A549 cells. Our findings suggest that influenza A virus may utilize its NS1 protein to interact with cellular β-tubulin to further disrupt normal cell division and induce apoptosis. Future work will illustrate whether this interaction is uniquely specific to the 2009 pandemic H1N1 virus.

  2. Monitoring and talking to the room: autochthonous coordination patterns in team interaction and performance.

    Science.gov (United States)

    Kolbe, Michaela; Grote, Gudela; Waller, Mary J; Wacker, Johannes; Grande, Bastian; Burtscher, Michael J; Spahn, Donat R

    2014-11-01

    This paper builds on and extends theory on team functioning in high-risk environments. We examined 2 implicit coordination behaviors that tend to emerge autochthonously within high-risk teams: team member monitoring and talking to the room. Focusing on nonrandom patterns of behavior, we examined sequential patterns of team member monitoring and talking to the room in higher- and lower-performing action teams working in a high-risk health care environment. Using behavior observation methods, we coded verbal and nonverbal behaviors of 27 anesthesia teams performing an induction of general anesthesia in a natural setting and assessed team performance with a Delphi-validated checklist-based performance measure. Lag sequential analyses revealed that higher-performing teams were characterized by patterns in which team member monitoring was followed by speaking up, providing assistance, and giving instructions and by patterns in which talking to the room was followed by further talking to the room and not followed by instructions. Higher- and lower-performing teams did not differ with respect to the frequency of team member monitoring and talking to the room occurrence. The results illustrate the importance of patterns of autochthonous coordination behaviors and demonstrate that the interaction patterns, as opposed to the behavior frequencies, discriminated higher- from lower-performing teams. Implications for future research and for team training are included. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  3. Modeling microtubule oscillations

    DEFF Research Database (Denmark)

    Jobs, E.; Wolf, D.E.; Flyvbjerg, H.

    1997-01-01

    Synchronization of molecular reactions in a macroscopic volume may cause the volume's physical properties to change dynamically and thus reveal much about the reactions. As an example, experimental time series for so-called microtubule oscillations are analyzed in terms of a minimal model...... for this complex polymerization-depolymerization cycle. The model reproduces well the qualitatively different time series that result from different experimental conditions, and illuminates the role and importance of individual processes in the cycle. Simple experiments are suggested that can further test...... and define the model and the polymer's reaction cycle....

  4. Folding of the Tau Protein on Microtubules.

    Science.gov (United States)

    Kadavath, Harindranath; Jaremko, Mariusz; Jaremko, Łukasz; Biernat, Jacek; Mandelkow, Eckhard; Zweckstetter, Markus

    2015-08-24

    Microtubules are regulated by microtubule-associated proteins. However, little is known about the structure of microtubule-associated proteins in complex with microtubules. Herein we show that the microtubule-associated protein Tau, which is intrinsically disordered in solution, locally folds into a stable structure upon binding to microtubules. While Tau is highly flexible in solution and adopts a β-sheet structure in amyloid fibrils, in complex with microtubules the conserved hexapeptides at the beginning of the Tau repeats two and three convert into a hairpin conformation. Thus, binding to microtubules stabilizes a unique conformation in Tau. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Influence of predominant patterns of coordination on the exploitation of interaction torques in a two-joint rhythmic arm movement.

    Science.gov (United States)

    de Rugy, Aymar; Riek, Stephan; Carson, Richard G

    2006-11-01

    In this study we investigate the coordination between rhythmic flexion-extension (FE) and supination-pronation (SP) movements at the elbow joint-complex, while manipulating the intersegmental dynamics by means of a 2-degrees of freedom (df) robot arm. We hypothesized that constraints imposed by the structure of the neuromuscular-skeletal system would (1) result in predominant pattern(s) of coordination in the absence of interaction torques and (2) influence the capabilities of participants to exploit artificially induced interaction torques. Two experiments were conducted in which different conditions of interaction torques were applied on the SP-axis as a function of FE movements. These conditions promoted different patterns of coordination between the 2-df. Control trials conducted in the absence of interaction torques revealed that both the in-phase (supination synchronized with flexion) and the anti-phase (pronation synchronized with flexion) patterns were spontaneously established by participants. The predominance of these patterns of coordination is explained in terms of the mechanical action of bi-articular muscles acting at the elbow joint-complex, and in terms of the reflexes that link the activity of the muscles involved. Results obtained in the different conditions of interaction torques revealed that those neuromuscular-skeletal constraints either impede or favor the exploitation of intersegmental dynamics depending on the context. Interaction torques were indeed found to be exploited to a greater extent in conditions in which the profiles of interaction torques favored one of the two predominant patterns of coordination (i.e., in-phase or anti-phase) as opposed to other patterns of coordination (e.g., 90 degrees or 270 degrees). Those results are discussed in relation to recent studies reporting exploitation of interaction torques in the context of rhythmic movements.

  6. A Heart for Interaction: Physiological Entrainment and Behavioral Coordination in a Collective, Creative Construction Task

    CERN Document Server

    Fusaroli, Riccardo; Roepstoff, Andreas; Tylén, Kristian

    2015-01-01

    Interpersonal physiological entrainment is increasingly argued to underlie rapport, empathy and even team performance. Inspired by the model of interpersonal synergy, we investigate the presence, temporal development, possible mechanisms and impact of interpersonal heart rate entrainment during individual and collective creative LEGO construction tasks. In Study 1 we show how HR entrainment is driven by a plurality of sources including task constraints and behavioral coordination. Generally, HR entrainment is more prevalent in individual trials (involving participants doing the same things) than in collective ones (involving participants taking turns and performing complementary actions). However, when contrasted against virtual pairs, collective trials display more stable HR entrainment supporting the idea that online social interaction plays a role. Furthermore, HR entrainment is found to grow across collective but not individual trials. In Study 2 we further show that in collective trials the dynamics of H...

  7. Developmental cartography: coordination via hormonal and genetic interactions during gynoecium formation.

    Science.gov (United States)

    Deb, Joyita; Bland, Heather M; Østergaard, Lars

    2017-09-26

    Development in multicellular organisms requires the establishment of tissue identity through polarity cues. The Arabidopsis gynoecium presents an excellent model to study this coordination, as it comprises a complex tissue structure which is established through multiple polarity systems. The gynoecium is derived from the fusion of two carpels and forms in the centre of the flower. Many regulators of carpel development also have roles in leaf development, emphasizing the evolutionary origin of carpels as modified leaves. The gynoecium can therefore be considered as having evolved from a simple setup followed by adjustment in tissue polarity to facilitate efficient reproduction. Here, we discuss concepts to understand how hormonal and genetic systems interact to pattern the gynoecium. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  8. The Ndc80 complex uses a tripartite attachment point to couple microtubule depolymerization to chromosome movement.

    Science.gov (United States)

    Tooley, John G; Miller, Stephanie A; Stukenberg, P Todd

    2011-04-15

    In kinetochores, the Ndc80 complex couples the energy in a depolymerizing microtubule to perform the work of moving chromosomes. The complex directly binds microtubules using an unstructured, positively charged N-terminal tail located on Hec1/Ndc80. Hec1/Ndc80 also contains a calponin homology domain (CHD) that increases its affinity for microtubules in vitro, yet whether it is required in cells and how the tail and CHD work together are critical unanswered questions. Human kinetochores containing Hec1/Ndc80 with point mutations in the CHD fail to align chromosomes or form productive microtubule attachments. Kinetochore architecture and spindle checkpoint protein recruitment are unaffected in these mutants, and the loss of CHD function cannot be rescued by removing Aurora B sites from the tail. The interaction between the Hec1/Ndc80 CHD and a microtubule is facilitated by positively charged amino acids on two separate regions of the CHD, and both are required for kinetochores to make stable attachments to microtubules. Chromosome congression in cells also requires positive charge on the Hec1 tail to facilitate microtubule contact. In vitro binding data suggest that charge on the tail regulates attachment by directly increasing microtubule affinity as well as driving cooperative binding of the CHD. These data argue that in vertebrates there is a tripartite attachment point facilitating the interaction between Hec1/Ndc80 and microtubules. We discuss how such a complex microtubule-binding interface may facilitate the coupling of depolymerization to chromosome movement.

  9. Mechanical modulation of cardiac microtubules.

    Science.gov (United States)

    White, Ed

    2011-07-01

    Microtubules are a major component of the cardiac myocyte cytoskeleton. Interventions that alter it may influence cardiac mechanical and electrical activity by disrupting the trafficking of proteins to and from the surface membrane by molecular motors such as dynein, which use microtubules as tracks to step along. Free tubulin dimers may transfer GTP to the α-subunits of G-proteins, thus an increase in free tubulin could increase the activity of G-proteins; evidence for and against such a role exists. There is more general agreement that microtubules act as compression-resisting structures within myocytes, influencing visco-elasticity of myocytes and increasing resistance to shortening when proliferated and resisting deformation from longitudinal shear stress. In response to pressure overload, there can be post-translational modifications resulting in more stable microtubules and an increase in microtubule density. This is accompanied by contractile dysfunction of myocytes which can be reversed by microtubule disruption. There are reports of mechanically induced changes in electrical activity that are dependent upon microtubules, but at present, a consensus is lacking on whether disruption or proliferation would be beneficial in the prevention of arrhythmias. Microtubules certainly play a role in the response of cardiac myocytes to mechanical stimulation, the exact nature and significance of this role is still to be fully determined.

  10. Analysis of Soybean Microtubule Persistence Length; New Evidence on the Correlation between Structural Composition and Mechanical Properties

    Science.gov (United States)

    Shojania Feizabadi, Mitra; Winton, Carly; Barrientos, Jimmy

    2012-02-01

    Recent studies on microtubules composed of different β tubulin isotypes indicate their different functionality in terms of their dynamical behavior or the mechanism of their interaction with chemotherapeutic drugs. Along these lines, the result of our recent study measuring the rigidity of neural and non-neural samples of microtubules with different β tubulin isotype compositions suggests that the distinguished mechanical properties of microtubules, such as rigidity, may also be associated with the different distribution of their β tubulin isotypes. In our current study, we have reported the persistence length of a single soybean microtubule. This plant microtubule has a structural composition different from that of mammalian microtubules. Under the same experimental methods of measurement, the soybean microtubules showed a different persistence length as compared to the value of the persistence length that we estimated in the study of both single Bovine Brain and MCF7 microtubules.

  11. Multiscale Polar Theory of Microtubule and Motor-Protein Assemblies

    Science.gov (United States)

    Gao, Tong; Blackwell, Robert; Glaser, Matthew A.; Betterton, M. D.; Shelley, Michael J.

    2015-01-01

    Microtubules and motor proteins are building blocks of self-organized subcellular biological structures such as the mitotic spindle and the centrosomal microtubule array. These same ingredients can form new “bioactive” liquid-crystalline fluids that are intrinsically out of equilibrium and which display complex flows and defect dynamics. It is not yet well understood how microscopic activity, which involves polarity-dependent interactions between motor proteins and microtubules, yields such larger-scale dynamical structures. In our multiscale theory, Brownian dynamics simulations of polar microtubule ensembles driven by cross-linking motors allow us to study microscopic organization and stresses. Polarity sorting and cross-link relaxation emerge as two polar-specific sources of active destabilizing stress. On larger length scales, our continuum Doi-Onsager theory captures the hydrodynamic flows generated by polarity-dependent active stresses. The results connect local polar structure to flow structures and defect dynamics. PMID:25679909

  12. Polo-like kinase 1 regulates Nlp, a centrosome protein involved in microtubule nucleation.

    Science.gov (United States)

    Casenghi, Martina; Meraldi, Patrick; Weinhart, Ulrike; Duncan, Peter I; Körner, Roman; Nigg, Erich A

    2003-07-01

    In animal cells, most microtubules are nucleated at centrosomes. At the onset of mitosis, centrosomes undergo a structural reorganization, termed maturation, which leads to increased microtubule nucleation activity. Centrosome maturation is regulated by several kinases, including Polo-like kinase 1 (Plk1). Here, we identify a centrosomal Plk1 substrate, termed Nlp (ninein-like protein), whose properties suggest an important role in microtubule organization. Nlp interacts with two components of the gamma-tubulin ring complex and stimulates microtubule nucleation. Plk1 phosphorylates Nlp and disrupts both its centrosome association and its gamma-tubulin interaction. Overexpression of an Nlp mutant lacking Plk1 phosphorylation sites severely disturbs mitotic spindle formation. We propose that Nlp plays an important role in microtubule organization during interphase, and that the activation of Plk1 at the onset of mitosis triggers the displacement of Nlp from the centrosome, allowing the establishment of a mitotic scaffold with enhanced microtubule nucleation activity.

  13. Fluorescent taxoids as probes of the microtubule cytoskeleton.

    Science.gov (United States)

    Evangelio, J A; Abal, M; Barasoain, I; Souto, A A; Lillo, M P; Acuña, A U; Amat-Guerri, F; Andreu, J M

    1998-01-01

    microtubules at the telophase spindle equator and the central part of the midbody in cytokinesis (instead of the dark zone frequently observed with immunofluorescence), suggesting a predominant interaction of FLUTAX with sites at which tubulin is newly polymerized. Nanomolar concentrations of FLUTAX also permit specific imaging of centrosomes, half-spindles and midbodies in growing U937 cells.

  14. Supporting human interaction and human resources coordination in distributed clinical guidelines.

    Science.gov (United States)

    Bottrighi, Alessio; Torchio, Mauro; Montani, Stefania; Molino, Gianpaolo; Terenziani, Paolo

    2010-01-01

    Clinical guidelines (GL) play an important role in medical practice: the one of optimizing the quality of patient care on the basis of the best and most recent evidence based medicine. In order to achieve this goal, the interaction between different actors, who cooperate in the execution of the same GL, is a crucial issue. As a matter of fact, in many cases (e.g. in chronic disease treatment) the GL execution requires that patient treatment is not performed/completed in the hospital, but is continued in different contexts (e.g. at home, or in the general practitioner's ambulatory), under the responsibility of different actors. In this situation, the correct interaction and communication between the actors themselves is critical for the quality of care, and human resources coordination is a key issue to be addressed by the managers of the involved healthcare service. In this paper we describe how computerized GL management can be extended in order to support such needs, and we illustrate our approach by means of a practical case study.

  15. Unmanned Aerial Systems during the Coordinated Investigation of Climate-Cryosphere Interaction at Svalbard, Norway

    Science.gov (United States)

    Burkhart, J. F.; Bates, T. S.; Quinn, P.; Storvold, R.; Herber, A.; Vitale, V.; Lesenkov, S.; Cicci/Vauuav Science Team

    2011-12-01

    During Spring 2011 an intensive investigation of climate-cryosphere interaction was conducted in Svalbard, Norway. A primary objective of the campaign was to investigate processes related to the deposition of aerosols to the Arctic cryosphere. Moreover, the campaign provided a first-time opportunity to test several novel data acquisition platforms. Of interest to this session are the three Unmanned Aerial System (UAS) platforms that flew cooperatively with oversight from the Norwegian Civil Aviation Authority (CAA). The campaign presented the unique opportunity for a CAA to regulate UAS platforms; both private and foreign government-owned aircraft (Norway, USA, and Russia). Further, it highlighted challenges, both political and logistical, related to conducting such an operation. We present an overview of the 'Coordinated Investigation of Climate-Cryosphere Interaction' campaign, and highlight the novel and valuable contributions from each of the UAS platforms. Our presentation includes an overview of the different platform capabilities, a discussion of the scientific merits of the platforms, insight into the political process for UAS operations in the Arctic, and a summary of the acquired contributions toward the goals of the CICCI project.

  16. TOG Proteins Are Spatially Regulated by Rac-GSK3β to Control Interphase Microtubule Dynamics.

    Directory of Open Access Journals (Sweden)

    Kathryn P Trogden

    Full Text Available Microtubules are regulated by a diverse set of proteins that localize to microtubule plus ends (+TIPs where they regulate dynamic instability and mediate interactions with the cell cortex, actin filaments, and organelles. Although individual +TIPs have been studied in depth and we understand their basic contributions to microtubule dynamics, there is a growing body of evidence that these proteins exhibit cross-talk and likely function to collectively integrate microtubule behavior and upstream signaling pathways. In this study, we have identified a novel protein-protein interaction between the XMAP215 homologue in Drosophila, Mini spindles (Msps, and the CLASP homologue, Orbit. These proteins have been shown to promote and suppress microtubule dynamics, respectively. We show that microtubule dynamics are regionally controlled in cells by Rac acting to suppress GSK3β in the peripheral lamellae/lamellipodium. Phosphorylation of Orbit by GSK3β triggers a relocalization of Msps from the microtubule plus end to the lattice. Mutation of the Msps-Orbit binding site revealed that this interaction is required for regulating microtubule dynamic instability in the cell periphery. Based on our findings, we propose that Msps is a novel Rac effector that acts, in partnership with Orbit, to regionally regulate microtubule dynamics.

  17. Coordination between digit forces and positions: interactions between anticipatory and feedback control.

    Science.gov (United States)

    Fu, Qiushi; Santello, Marco

    2014-04-01

    Humans adjust digit forces to compensate for trial-to-trial variability in digit placement during object manipulation, but the underlying control mechanisms remain to be determined. We hypothesized that such digit position/force coordination was achieved by both visually guided feed-forward planning and haptic-based feedback control. The question arises about the time course of the interaction between these two mechanisms. This was tested with a task in which subjects generated torque (± 70 N·mm) on a virtual object to control a cursor moving to target positions to catch a falling ball, using a virtual reality environment and haptic devices. The width of the virtual object was varied between large (L) and small (S). These object widths result in significantly different horizontal digit relative positions and require different digit forces to exert the same task torque. After training, subjects were tested with random sequences of L and S widths with or without visual information about object width. We found that visual cues allowed subjects to plan manipulation forces before contact. In contrast, when visual cues were not available to predict digit positions, subjects implemented a "default" digit force plan that was corrected after digit contact to eventually accomplish the task. The time course of digit forces revealed that force development was delayed in the absence of visual cues. Specifically, the appropriate digit force adjustments were made 250-300 ms after initial object contact. This result supports our hypothesis and further reveals that haptic feedback alone is sufficient to implement digit force-position coordination.

  18. The non-catalytic domains of Drosophila katanin regulate its abundance and microtubule-disassembly activity.

    Directory of Open Access Journals (Sweden)

    Kyle D Grode

    Full Text Available Microtubule severing is a biochemical reaction that generates an internal break in a microtubule and regulation of microtubule severing is critical for cellular processes such as ciliogenesis, morphogenesis, and meiosis and mitosis. Katanin is a conserved heterodimeric ATPase that severs and disassembles microtubules, but the molecular determinants for regulation of microtubule severing by katanin remain poorly defined. Here we show that the non-catalytic domains of Drosophila katanin regulate its abundance and activity in living cells. Our data indicate that the microtubule-interacting and trafficking (MIT domain and adjacent linker region of the Drosophila katanin catalytic subunit Kat60 cooperate to regulate microtubule severing in two distinct ways. First, the MIT domain and linker region of Kat60 decrease its abundance by enhancing its proteasome-dependent degradation. The Drosophila katanin regulatory subunit Kat80, which is required to stabilize Kat60 in cells, conversely reduces the proteasome-dependent degradation of Kat60. Second, the MIT domain and linker region of Kat60 augment its microtubule-disassembly activity by enhancing its association with microtubules. On the basis of our data, we propose that the non-catalytic domains of Drosophila katanin serve as the principal sites of integration of regulatory inputs, thereby controlling its ability to sever and disassemble microtubules.

  19. Changes in microtubule stability and density in myelin-deficient shiverer mouse CNS axons

    Science.gov (United States)

    Kirkpatrick, L. L.; Witt, A. S.; Payne, H. R.; Shine, H. D.; Brady, S. T.

    2001-01-01

    Altered axon-Schwann cell interactions in PNS myelin-deficient Trembler mice result in changed axonal transport rates, neurofilament and microtubule-associated protein phosphorylation, neurofilament density, and microtubule stability. To determine whether PNS and CNS myelination have equivalent effects on axons, neurofilaments, and microtubules in CNS, myelin-deficient shiverer axons were examined. The genetic defect in shiverer is a deletion in the myelin basic protein (MBP) gene, an essential component of CNS myelin. As a result, shiverer mice have little or no compact CNS myelin. Slow axonal transport rates in shiverer CNS axons were significantly increased, in contrast to the slowing in demyelinated PNS nerves. Even more striking were substantial changes in the composition and properties of microtubules in shiverer CNS axons. The density of axonal microtubules is increased, reflecting increased expression of tubulin in shiverer, and the stability of microtubules is drastically reduced in shiverer axons. Shiverer transgenic mice with two copies of a wild-type myelin basic protein transgene have an intermediate level of compact myelin, making it possible to determine whether the actual level of compact myelin is an important regulator of axonal microtubules. Both increased microtubule density and reduced microtubule stability were still observed in transgenic mouse nerves, indicating that signals beyond synaptogenesis and the mere presence of compact myelin are required for normal regulation of the axonal microtubule cytoskeleton.

  20. A plus-end raft to control microtubule dynamics and function.

    Science.gov (United States)

    Galjart, Niels; Perez, Franck

    2003-02-01

    Cells require a properly oriented and organised microtubule array to transmit positional information. Recent data have revealed a heterogeneous population of microtubule-binding proteins that accumulates mainly at distal ends of polymerising microtubules. Two mechanisms may account for this concentration: transient immobilisation, which involves association of proteins with growing ends, followed by release more proximally; and deposition at ends via a molecular motor. As with lipid rafts, protein concentration at distal ends may allow a cascade of interactions in the restricted area of a microtubule plus end. This may, in turn, control the dynamic behaviour of this cytoskeletal network and its anchoring to other structures.

  1. Microtubule self-organisation depends upon gravity

    Science.gov (United States)

    Tabony, J.; Pochon, N.; Papaseit, C.

    2001-01-01

    The molecular processes by which gravity is transduced into biological systems are poorly, if at all, understood. Under equilibrium conditions, chemical and biochemical structures do not depend upon gravity. It has been proposed that biological systems might show a gravity dependence by way of the bifurcation properties of certain types of non-linear chemical reactions that are far-from-equilibrium. We have found that in-vitro preparations of microtubules, an important element of the cellular cytoskeleton, show this type of behaviour. On earth, the solutions show macroscopic self-ordering, and the morphology of the structures that form depend upon the orientation of the sample with respect to gravity at a critical moment at an early stage in the development of the self-organised state. An experiment carried out in a sounding rocket, showed that as predicted by theories of this type, no self-organisation occurs when the microtubules are assembled under low gravity conditions. This is an experimental demonstration of how a very simple biochemical system, containing only two molecules, can be gravity sensitive. At a molecular level this behaviour results from an interaction of gravity with macroscopic concentration and density fluctuations that arise from the processes of microtubule contraction and elongation.

  2. Coordinated modular functionality and prognostic potential of a heart failure biomarker-driven interaction network

    Directory of Open Access Journals (Sweden)

    Wagner Daniel R

    2010-05-01

    Full Text Available Abstract Background The identification of potentially relevant biomarkers and a deeper understanding of molecular mechanisms related to heart failure (HF development can be enhanced by the implementation of biological network-based analyses. To support these efforts, here we report a global network of protein-protein interactions (PPIs relevant to HF, which was characterized through integrative bioinformatic analyses of multiple sources of "omic" information. Results We found that the structural and functional architecture of this PPI network is highly modular. These network modules can be assigned to specialized processes, specific cellular regions and their functional roles tend to partially overlap. Our results suggest that HF biomarkers may be defined as key coordinators of intra- and inter-module communication. Putative biomarkers can, in general, be distinguished as "information traffic" mediators within this network. The top high traffic proteins are encoded by genes that are not highly differentially expressed across HF and non-HF patients. Nevertheless, we present evidence that the integration of expression patterns from high traffic genes may support accurate prediction of HF. We quantitatively demonstrate that intra- and inter-module functional activity may be controlled by a family of transcription factors known to be associated with the prevention of hypertrophy. Conclusion The systems-driven analysis reported here provides the basis for the identification of potentially novel biomarkers and understanding HF-related mechanisms in a more comprehensive and integrated way.

  3. Modeling Ferro- and Antiferromagnetic Interactions in Metal-Organic Coordination Networks

    CERN Document Server

    Faraggi, Marisa N; Stepanow, Sebastian; Tseng, Tzu-Chun; Abdurakhmanova, Nasiba; Kley, Christopher Seiji; Langner, Alexander; Sessi, Violetta; Kern, Klaus; Arnau, Andres

    2014-01-01

    Magnetization curves of two rectangular metal-organic coordination networks formed by the organic ligand TCNQ (7,7,8,8-tetracyanoquinodimethane) and two different (Mn and Ni) 3d transition metal atoms [M(3d)] show marked differences that are explained using first principles density functional theory and model calculations. We find that the existence of a weakly dispersive hybrid band with M(3d) and TCNQ character crossing the Fermi level is determinant for the appearance of ferromagnetic coupling between metal centers, as it is the case of the metallic system Ni-TCNQ but not of the insulating system Mn-TCNQ. The spin magnetic moment localized at the Ni atoms induces a significant spin polarization in the organic molecule; the corresponding spin density being delocalized along the whole system. The exchange interaction between localized spins at Ni centers and the itinerant spin density is ferromagnetic. Based on two different model Hamiltonians, we estimate the strength of exchange couplings between magnetic ...

  4. Coordinated X-ray and Optical observations of Star-Planet Interaction in HD 17156

    CERN Document Server

    Maggio, A; Scandariato, G; Lanza, A F; Sciortino, S; Borsa, F; Bonomo, A S; Claudi, R; Covino, E; Desidera, S; Gratton, R; Micela, G; Pagano, I; Piotto, G; Sozzetti, A; Cosentino, R; Maldonado, J

    2015-01-01

    The large number of close-in Jupiter-size exoplanets prompts the question whether star-planet interaction (SPI) effects can be detected. We focused our attention on the system HD 17156, having a Jupiter-mass planet in a very eccentric orbit. Here we present results of the XMM-Newton observations and of a five month coordinated optical campaign with the HARPS-N spectrograph. We observed HD 17156 with XMM-Newton when the planet was approaching the apoastron and then at the following periastron passage, quasi simultaneously with HARPS-N. We obtained a clear ($\\approx 5.5\\sigma$) X-ray detection only at the periastron visit, accompanied by a significant increase of the $R'_{\\rm HK}$ chromospheric index. We discuss two possible scenarios for the activity enhancement: magnetic reconnection and flaring or accretion onto the star of material tidally stripped from the planet. In any case, this is possibly the first evidence of a magnetic SPI effect caught in action.

  5. Multi-modal microtubule binding by the Ndc80 kinetochore complex

    Science.gov (United States)

    Alushin, Gregory M.; Musinipally, Vivek; Matson, Daniel; Tooley, John; Stukenberg, P. Todd; Nogales, Eva

    2012-01-01

    Summary The Ndc80 complex is a key site of kinetochore-microtubule attachment during cell division. The human complex engages microtubules with a globular “head” formed by tandem calponin-homology domains and an 80 amino-acid unstructured “tail” that contains sites of phospho-regulation by the Aurora B kinase. Using biochemical, cell biological, and electron microscopy analyses, we have dissected the tail’s roles in microtubule binding and mediating cooperative interactions between Ndc80 complexes. Two segments of the tail that contain Aurora B sites become ordered at interfaces; one with tubulin and the second with an adjacent Ndc80 head on the microtubule surface, forming interactions which are disrupted by phosphorylation. We propose a model in which Ndc80’s interaction with either growing or shrinking microtubule ends can be tuned by the phosphorylation state of its tail. PMID:23085714

  6. Persistence Length of Stable Microtubules

    Science.gov (United States)

    Hawkins, Taviare; Mirigian, Matthew; Yasar, M. Selcuk; Ross, Jennifer

    2011-03-01

    Microtubules are a vital component of the cytoskeleton. As the most rigid of the cytoskeleton filaments, they give shape and support to the cell. They are also essential for intracellular traffic by providing the roadways onto which organelles are transported, and they are required to reorganize during cellular division. To perform its function in the cell, the microtubule must be rigid yet dynamic. We are interested in how the mechanical properties of stable microtubules change over time. Some ``stable'' microtubules of the cell are recycled after days, such as in the axons of neurons or the cilia and flagella. We measured the persistence length of freely fluctuating taxol-stabilized microtubules over the span of a week and analyzed them via Fourier decomposition. As measured on a daily basis, the persistence length is independent of the contour length. Although measured over the span of the week, the accuracy of the measurement and the persistence length varies. We also studied how fluorescently-labeling the microtubule affects the persistence length and observed that a higher labeling ratio corresponded to greater flexibility. National Science Foundation Grant No: 0928540 to JLR.

  7. Motility and microtubule depolymerization mechanisms of the Kinesin-8 motor, KIF19A

    Science.gov (United States)

    Wang, Doudou; Nitta, Ryo; Morikawa, Manatsu; Yajima, Hiroaki; Inoue, Shigeyuki; Shigematsu, Hideki; Kikkawa, Masahide; Hirokawa, Nobutaka

    2016-01-01

    The kinesin-8 motor, KIF19A, accumulates at cilia tips and controls cilium length. Defective KIF19A leads to hydrocephalus and female infertility because of abnormally elongated cilia. Uniquely among kinesins, KIF19A possesses the dual functions of motility along ciliary microtubules and depolymerization of microtubules. To elucidate the molecular mechanisms of these functions we solved the crystal structure of its motor domain and determined its cryo-electron microscopy structure complexed with a microtubule. The features of KIF19A that enable its dual function are clustered on its microtubule-binding side. Unexpectedly, a destabilized switch II coordinates with a destabilized L8 to enable KIF19A to adjust to both straight and curved microtubule protofilaments. The basic clusters of L2 and L12 tether the microtubule. The long L2 with a characteristic acidic-hydrophobic-basic sequence effectively stabilizes the curved conformation of microtubule ends. Hence, KIF19A utilizes multiple strategies to accomplish the dual functions of motility and microtubule depolymerization by ATP hydrolysis. DOI: http://dx.doi.org/10.7554/eLife.18101.001 PMID:27690357

  8. Implications of Shared Interactive Displays for Work at a Surgery Ward: Coordination, Articulation Work and Context-awareness

    DEFF Research Database (Denmark)

    Bossen, Claus; Jensen, Lis Witte Kjær

    2008-01-01

    We report on experiences gained from the use at a surgery ward of shared interactive displays to support coordination and communication.  The displays merge large displays, video feed, RFID tag, chat and mobile phones to facilitate better coordination and articulation of work tasks and enhance co...... appropriate meaning to new clues by clinicians and learning new ways of cooperating. Trade-offs had to be made, since work and benefits were differentially redistributed. We propose that computer support for medical work should support flexible appropriation and learning....

  9. The octarepeat region of hamster PrP (PrP51-91) enhances the formation of microtubule and antagonize Cu~(2+)-induced microtubule-disrupting activity

    Institute of Scientific and Technical Information of China (English)

    Xiaoli Li; Chenfang Dong; Song Shi; Guirong Wang; Yuan Li; Xin Wang; Qi Shi; Chan Tian; Ruimin Zhou; Chen Gao; Xiaoping Dong

    2009-01-01

    Prion protein (PrP) is considered to associate with microtubule and its major component, tubulin. In the present study, octarepeat region of PrP (PrP51-91) was expressed in prokaryotic-expressing system. Using GST pull-down assay and co-immunoprecipitation, the mol-ecular interaction between PrP51-91 and tubulin was observed. Our data also demonstrated that PrP51-91 could efficiently stimulate microtubule assembly in vitro, indicating a potential effect of PrP on microtu-bule dynamics. Moreover, PrP51-91 was confirmed to be able to antagonize Cu~(2+)-induced microtubule-disrupt-ing activity in vivo, partially protecting against Cu~(2+) intoxication to culture cells and stabilize cellular micro-tubule structure. The association of the octarepeat region of PrP with tubulin may further provide insight into the biological function of PrP in the neurons.

  10. Implications of Shared Interactive Displays for Work at a Surgery Ward: Coordination, Articulation Work and Context-awareness

    DEFF Research Database (Denmark)

    Bossen, Claus; Jensen, Lis Witte Kjær

    2008-01-01

    context-awareness of collaborating physicians, nurses and surgery technicians. We focus on the implication of the systems for work and describe the changes in coordination, articulation work and context-awareness that occurred. This implied creating a fit between technology and work, attributing......We report on experiences gained from the use at a surgery ward of shared interactive displays to support coordination and communication.  The displays merge large displays, video feed, RFID tag, chat and mobile phones to facilitate better coordination and articulation of work tasks and enhance...... appropriate meaning to new clues by clinicians and learning new ways of cooperating. Trade-offs had to be made, since work and benefits were differentially redistributed. We propose that computer support for medical work should support flexible appropriation and learning....

  11. ISA-MIP: A co-ordinated intercomparison of Interactive Stratospheric Aerosol models

    Science.gov (United States)

    Timmreck, Claudia; Mann, Graham; Aquila, Valentina; Bruehl, Christoph; Chin, Mian; Dohmse, Sandip; English, Jason; Lee, Lindsay; Mills, Michael; Hommel, Rene; Neely, Ryan; Schmidt, Anja; Sheng, Jianxiong; Toohey, Matthew; Weisenstein, Debra

    2016-04-01

    The SPARC activity, "Stratospheric Sulfur and its Role in Climate" (SSiRC) was initiated to coordinate international research activities on modelling and observation of stratospheric sulphate aerosols (and precursor gases) in order to assess its climate forcing and feedback. With several international activities to extend and improve observational stratospheric aerosol capabilities and data sets, and a growing number of global models treating stratospheric aerosol interactively, a new model intercomparison activity "ISA-MIP" has been established in the frame of SSIRC. ISA-MIP will compare interactive stratospheric aerosol (ISA) models using a range of observations to constrain and improve the models and to provide a sound scientific basis for future work. Four ISA-MIP experiments have been designed to assess different periods of the obervational stratospheric aerosol record, and to explore key processes which influence the formation and temporal development of stratospheric aerosol. The "Background" experiment will focus on the role of microphysical and transport processes under volcanically quiescent conditions, where the stratospheric aerosol size distribution is only modulated by seasonal circulations. The "Model intercomparison of Transient Aerosol Record" (MiTAR) experiment will focus on addressing the role of small- to moderate-magnitude volcanic eruptions and transport processes in the upper troposphere - lower stratosphere (UTLS) aerosols loading over the period 1998-2011. Background and MiTAR simulations will be compared to recent in-situ and satellite observations to evaluate the performances of the model and understand their strengths and weaknesses. Two further experiments investigate the radiative forcing from historical major eruptions. The Historical Eruptions SO2 Emission Assessment (HErSEA) will involve models carrying out mini-ensembles of the stratospheric aerosol perturbations from each of the 1963 Agung, 1982 El Chichon and 1991 Pinatubo

  12. Push or Pull? -- Cryo-Electron Microscopy of Microtubule's Dynamic Instability and Its Roles in the Kinetochore

    Science.gov (United States)

    Wang, Hong-Wei

    2009-03-01

    Microtubule is a biopolymer made up of alpha-beta-tubulin heterodimers. The tubulin dimers assemble head-to-tail as protofilaments and about 13 protofilaments interact laterally to form a hollow cylindrical structure which is the microtubule. As the major cytoskeleton in all eukaryotic cells, microtubules have the intrinsic property to switch stochastically between growth and shrinkage phases, a phenomenon termed as their dynamic instability. Microtubule's dynamic instability is closely related to the types of nucleotide (GTP or GDP) that binds to the beta-tubulin. We have biochemically trapped two types of assembly states of tubulin with GTP or GDP bound representing the polymerizing and depolymerizing ends of microtubules respectively. Using cryo-electron microscopy, we have elucidated the structures of these intermediate assemblies, showing that tubulin protofilaments demonstrate various curvatures and form different types of lateral interactions depending on the nucleotide states of tubulin and the temperature. Our work indicates that during the microtubule's dynamic cycle, tubulin undergoes various assembly states. These states, different from the straight microtubule, lend the highly dynamic and complicated behavior of microtubules. Our study of microtubule's interaction with certain kinetochore complexes suggests that the intermediate assemblies are responsible for specific mechanical forces that are required during the mitosis or meiosis. Our discoveries strongly suggest that a microtubule is a molecular machine rather than a simple cellular scaffold.

  13. A Database of Transition-Metal-Coordinated Peptide Cross-Sections: Selective Interaction with Specific Amino Acid Residues

    Science.gov (United States)

    Dilger, Jonathan M.; Glover, Matthew S.; Clemmer, David E.

    2017-07-01

    Ion mobility mass spectrometry (IMS-MS) techniques were used to generate a database of 2288 collision cross sections of transition-metal-coordinated tryptic peptide ions. This database consists of cross sections for 1253 [Pep + X]2+ and 1035 [Pep + X + H]3+, where X2+ corresponds to Mn2+, Co2+, Ni2+, Cu2+, or Zn2+. This number of measurements enables the extraction of structural trends for transition-metal-coordinated peptide ions. The range of structures and changes in collision cross sections for X2+-coordinated species (compared with protonated species of the same charge state) is similar to Mg2+-coordinated species. This suggests that the structures are largely determined by similarities in cation size with differences among the cross section distributions presumably caused by X2+ interactions with specific functional groups offered by the residue R-groups or the peptide backbone. Cross section contributions for individual residues upon X2+ solvation are assessed with the derivation of intrinsic size parameters (ISPs). The comparison of the [Pep + X]2+ ISPs with those previously reported for [Pep + Mg]2+ ions displays a lower contribution to the cross section for His, carboxyamidomethylated Cys, and Met, and is consistent with specific metal-residue interactions identified within protein X-ray crystallography databases.

  14. The impact of lone pair-π interactions on photochromic properties in 1-D naphthalene diimide coordination networks.

    Science.gov (United States)

    Liu, Jian-Jun; Guan, Ying-Fang; Chen, Yong; Lin, Mei-Jin; Huang, Chang-Cang; Dai, Wen-Xin

    2015-10-21

    Lone pair-π interaction is an important but less studied binding force. Generally, it is too weak to influence the physical properties of supramolecular systems. Herein we reported the first example exhibiting the impact of lone pair-π interactions on photochromic properties of naphthalene diimide based coordination networks. In three isostructural 1-D networks, [(DPNDI)ZnX2] (DPNDI = N,N-di(4-pyridyl)-1,4,5,8-naphthalene diimide, X = Cl for 1, X = Br for 2 and X = I for 3), they exhibit different electron-transfer photochromic behaviors due to different lone pair-π interactions between the capped halogen atoms and electron-deficient DPNDI moieties. Specifically, 1 and 2 but not 3 are photochromic, which is attributed to a stronger lone pair-π interaction in 3 than those in 1 and 2. This study anticipates breaking a new path for designing novel photochromic materials through such unnoticeable supramolecular interactions.

  15. Redundant internal coordinates, compliance constants and non-bonded interactions - some new insights

    Indian Academy of Sciences (India)

    Moumita Majumder; Sadasivam Manogaran

    2013-01-01

    A long standing problem in normal mode analysis is identifying the right internal coordinates given only the cartesian coordinates, the masses of the atoms and the cartesian force constants without using any other additional chemical information. A possible solution is suggested here as drawing the normal modes obtained from the mass weighted cartesian force constant matrix and identifying the correct bonds and angles from the normal mode pictures. If chosen properly, the internal coordinates will have minimum mixing in the normal mode representation. This can in principle lead to an automation algorithm. A complete basis of internal coordinates is defined as the minimum number of valence internal coordinates that describe all the normal modes as completely as possible. It was shown in the literature that the relaxed force constants could be used as a measure of bond order in all atom-atom distance coordinates. Some of the bonded and non-bonded atom pairs can have similar values of the relaxed force constants and hence to use the relaxed force constant as a measure of bond order we need to separate the bonded pairs from the non-bonded ones. This needs extra chemical information of which pairs are bonded. The new definition of complete basis of non-redundant valence internal coordinates helps to identify the bonded pairs effectively without extra information. The hydrogen bonded water clusters (H2O), n = 2-6, methane dimer and methane-water complex are used as examples to verify that the relaxed force constants of bonded pairs are indeed a measure of bond order.

  16. Kinetochore-microtubule attachment is sufficient to satisfy the human spindle assembly checkpoint.

    Science.gov (United States)

    Etemad, Banafsheh; Kuijt, Timo E F; Kops, Geert J P L

    2015-12-01

    The spindle assembly checkpoint (SAC) is a genome surveillance mechanism that protects against aneuploidization. Despite profound progress on understanding mechanisms of its activation, it remains unknown what aspect of chromosome-spindle interactions is monitored by the SAC: kinetochore-microtubule attachment or the force generated by dynamic microtubules that signals stable biorientation of chromosomes? To answer this, we uncoupled these two processes by expressing a non-phosphorylatable version of the main microtubule-binding protein at kinetochores (HEC1-9A), causing stabilization of incorrect kinetochore-microtubule attachments despite persistent activity of the error-correction machinery. The SAC is fully functional in HEC1-9A-expressing cells, yet cells in which chromosomes cannot biorient but are stably attached to microtubules satisfy the SAC and exit mitosis. SAC satisfaction requires neither intra-kinetochore stretching nor dynamic microtubules. Our findings support the hypothesis that in human cells the end-on interactions of microtubules with kinetochores are sufficient to satisfy the SAC without the need for microtubule-based pulling forces.

  17. Coordination studies of the metal center of hemocyanin by {sup 199m}Hg nuclear quadrupole interaction

    Energy Technology Data Exchange (ETDEWEB)

    Troeger, W.; Ctortecka, B. [Nukleare Festkoerperphysik, Univ. Leipzig (Germany); Faller, P. [Nukleare Festkoerperphysik, Univ. Leipzig (Germany); Biochemisches Inst., Univ. Zuerich (Switzerland); Decker, H. [Nukleare Festkoerperphysik, Univ. Leipzig (Germany); Inst. fuer Molekulare Biophysik, Univ. Mainz (Germany)

    2002-07-01

    The nuclear quadrupole interaction of {sup 199m}Hg monitored by time differential perturbed angular correlations of {gamma}-rays was employed to investigate the binding of Hg(II) to the binuclear metal site in the copper protein hemocyanin Eurypelma californicum. The data indicate that Hg(II) occupies the two metal sites and alters the metal site geometry from a trigonal to a diagonal coordination. (orig.)

  18. Principal coordinate analysis of genotype × environment interaction for grain yield of bread wheat in the semi-arid regions

    Directory of Open Access Journals (Sweden)

    Sabaghnia Naser

    2013-01-01

    Full Text Available Multi-environmental trials have significant main effects and significant multiplicative genotype × environment (GE interaction effect. Principal coordinate analysis (PCOA offers a more appropriate statistical analysis to deal with such situations, compared to traditional statistical methods. Eighteen bread wheat genotypes were grown in four semi-arid regions over three year seasons to study the GE interaction and yield stability and obtained data on grain yield were analyzed using PCOA. Combined analysis of variance indicated that all of the studied effects including the main effects of genotype and environments as well as the GE interaction were highly significant. According to grand means and total mean yield, test environments were grouped to two main groups as high mean yield (H and low mean yield (L. There were five H test environments and six L test environments which analyzed in the sequential cycles. For each cycle, both scatter point diagram and minimum spanning tree plot were drawn. The identified most stable genotypes with dynamic stability concept and based on the minimum spanning tree plots and centroid distances were G1 (3310.2 kg ha-1 and G5 (3065.6 kg ha-1, and therefore could be recommended for unfavorable or poor conditions. Also, genotypes G7 (3047.2 kg ha-1 and G16 (3132.3 kg ha-1 were located several times in the vertex positions of high cycles according to the principal coordinates analysis. The principal coordinates analysis provided useful and interesting ways of investigating GE interaction of barley genotypes. Finally, the results of principal coordinates analysis in general confirmed the breeding value of the genotypes, obtained on the basis of the yield stability evaluation.

  19. Quantum effects in cation interactions with first and second coordination shell ligands in metalloproteins.

    Science.gov (United States)

    Ngo, Van; da Silva, Mauricio C; Kubillus, Maximilian; Li, Hui; Roux, Benoît; Elstner, Marcus; Cui, Qiang; Salahub, Dennis R; Noskov, Sergei Yu

    2015-10-13

    electrostatic properties of the protein sites and the importance of specific ion-protein interactions. One of the most interesting findings is that secondary coordination shells of proteins are noticeably perturbed in a cation-dependent manner, showing significant delocalization and long-range effects of charge transfer and polarization upon binding Ca(2+).

  20. The kinesin-13 KLP10A motor regulates oocyte spindle length and affects EB1 binding without altering microtubule growth rates

    Directory of Open Access Journals (Sweden)

    Kevin K. Do

    2014-06-01

    Full Text Available Kinesin-13 motors are unusual in that they do not walk along microtubules, but instead diffuse to the ends, where they remove tubulin dimers, regulating microtubule dynamics. Here we show that Drosophila kinesin-13 klp10A regulates oocyte meiosis I spindle length and is haplo-insufficient – KLP10A, reduced by RNAi or a loss-of-function P element insertion mutant, results in elongated and mispositioned oocyte spindles, and abnormal cortical microtubule asters and aggregates. KLP10A knockdown by RNAi does not significantly affect microtubule growth rates in oocyte spindles, but, unexpectedly, EB1 binding and unbinding are slowed, suggesting a previously unobserved role for kinesin-13 in mediating EB1 binding interactions with microtubules. Kinesin-13 may regulate spindle length both by disassembling subunits from microtubule ends and facilitating EB1 binding to plus ends. We also observe an increased number of paused microtubules in klp10A RNAi knockdown spindles, consistent with a reduced frequency of microtubule catastrophes. Overall, our findings indicate that reduced kinesin-13 decreases microtubule disassembly rates and affects EB1 interactions with microtubules, rather than altering microtubule growth rates, causing spindles to elongate and abnormal cortical microtubule asters and aggregates to form.

  1. The coordination of boundary tones and its interaction with prominence1

    Science.gov (United States)

    Katsika, Argyro; Krivokapić, Jelena; Mooshammer, Christine; Tiede, Mark; Goldstein, Louis

    2014-01-01

    This study investigates the coordination of boundary tones as a function of stress and pitch accent. Boundary tone coordination has not been experimentally investigated previously, and the effect of prominence on this coordination, and whether it is lexical (stress-driven) or phrasal (pitch accent-driven) in nature is unclear. We assess these issues using a variety of syntactic constructions to elicit different boundary tones in an Electromagnetic Articulography (EMA) study of Greek. The results indicate that the onset of boundary tones co-occurs with the articulatory target of the final vowel. This timing is further modified by stress, but not by pitch accent: boundary tones are initiated earlier in words with non-final stress than in words with final stress regardless of accentual status. Visual data inspection reveals that phrase-final words are followed by acoustic pauses during which specific articulatory postures occur. Additional analyses show that these postures reach their achievement point at a stable temporal distance from boundary tone onsets regardless of stress position. Based on these results and parallel findings on boundary lengthening reported elsewhere, a novel approach to prosody is proposed within the context of Articulatory Phonology: rather than seeing prosodic (lexical and phrasal) events as independent entities, a set of coordination relations between them is suggested. The implications of this account for prosodic architecture are discussed. PMID:25300341

  2. Grades Degrade Group Coordination: Deteriorated Interactions and Performance in a Cooperative Motor Task

    Science.gov (United States)

    Hayek, Anne-Sophie; Toma, Claudia; Guidotti, Sofia; Oberlé, Dominique; Butera, Fabrizio

    2017-01-01

    At school, pupils often cooperate on common projects and must coordinate their different individual actions. However, grades are pervasively used even in cooperative situations, which make the pupils' differences in achievement and their relative rank salient and may reduce their inclination to work constructively with others. Thus, we…

  3. Taking and Coordinating Perspectives: From Prereflective Interactivity, through Reflective Intersubjectivity, to Metareflective Sociality

    Science.gov (United States)

    Martin, Jack; Sokol, Bryan W.; Elfers, Theo

    2008-01-01

    Despite being eclipsed in recent years by simulation theory, theory of mind and accounts of executive functioning, social-relational approaches to perspective taking and coordination based on the ideas of Jean Piaget and George Herbert Mead have never completely disappeared from the literature of developmental psychology. According to the…

  4. Taking and Coordinating Perspectives: From Prereflective Interactivity, through Reflective Intersubjectivity, to Metareflective Sociality

    Science.gov (United States)

    Martin, Jack; Sokol, Bryan W.; Elfers, Theo

    2008-01-01

    Despite being eclipsed in recent years by simulation theory, theory of mind and accounts of executive functioning, social-relational approaches to perspective taking and coordination based on the ideas of Jean Piaget and George Herbert Mead have never completely disappeared from the literature of developmental psychology. According to the…

  5. Grades Degrade Group Coordination: Deteriorated Interactions and Performance in a Cooperative Motor Task

    Science.gov (United States)

    Hayek, Anne-Sophie; Toma, Claudia; Guidotti, Sofia; Oberlé, Dominique; Butera, Fabrizio

    2017-01-01

    At school, pupils often cooperate on common projects and must coordinate their different individual actions. However, grades are pervasively used even in cooperative situations, which make the pupils' differences in achievement and their relative rank salient and may reduce their inclination to work constructively with others. Thus, we…

  6. Association of Hepatitis C Virus Replication Complexes with Microtubules and Actin Filaments Is Dependent on the Interaction of NS3 and NS5A▿

    OpenAIRE

    Lai, Chao-Kuen; Jeng, King-Song; Machida, Keigo; Lai, Michael M. C.

    2008-01-01

    The hepatitis C virus (HCV) RNA replication complex (RC), which is composed of viral nonstructural (NS) proteins and host cellular proteins, replicates the viral RNA genome in association with intracellular membranes. Two viral NS proteins, NS3 and NS5A, are essential elements of the RC. Here, by using immunoprecipitation and fluorescence resonance energy transfer assays, we demonstrated that NS3 and NS5A interact with tubulin and actin. Furthermore, immunofluorescence microscopy and electron...

  7. Termination of Protofilament Elongation by Eribulin Induces Lattice Defects that Promote Microtubule Catastrophes.

    Science.gov (United States)

    Doodhi, Harinath; Prota, Andrea E; Rodríguez-García, Ruddi; Xiao, Hui; Custar, Daniel W; Bargsten, Katja; Katrukha, Eugene A; Hilbert, Manuel; Hua, Shasha; Jiang, Kai; Grigoriev, Ilya; Yang, Chia-Ping H; Cox, David; Horwitz, Susan Band; Kapitein, Lukas C; Akhmanova, Anna; Steinmetz, Michel O

    2016-07-11

    Microtubules are dynamic polymers built of tubulin dimers that attach in a head-to-tail fashion to form protofilaments, which further associate laterally to form a tube. Asynchronous elongation of individual protofilaments can potentially lead to an altered microtubule-end structure that promotes sudden depolymerization, termed catastrophe [1-4]. However, how the dynamics of individual protofilaments relates to overall growth persistence has remained unclear. Here, we used the microtubule targeting anti-cancer drug Eribulin [5-7] to explore the consequences of stalled protofilament elongation on microtubule growth. Using X-ray crystallography, we first revealed that Eribulin binds to a site on β-tubulin that is required for protofilament plus-end elongation. Based on the structural information, we engineered a fluorescent Eribulin molecule. We demonstrate that single Eribulin molecules specifically interact with microtubule plus ends and are sufficient to either trigger a catastrophe or induce slow and erratic microtubule growth in the presence of EB3. Interestingly, we found that Eribulin increases the frequency of EB3 comet "splitting," transient events where a slow and erratically progressing comet is followed by a faster comet. This observation possibly reflects the "healing" of a microtubule lattice. Because EB3 comet splitting was also observed in control microtubules in the absence of any drugs, we propose that Eribulin amplifies a natural pathway toward catastrophe by promoting the arrest of protofilament elongation.

  8. Microtubule drugs: action, selectivity, and resistance across the kingdoms of life.

    Science.gov (United States)

    Dostál, V; Libusová, L

    2014-09-01

    Microtubule drugs such as paclitaxel, colchicine, vinblastine, trifluralin, or oryzalin form a chemically diverse group that has been reinforced by a large number of novel compounds over time. They all share the ability to change microtubule properties. The profound effects of disrupted microtubule systems on cell physiology can be used in research as well as anticancer treatment and agricultural weed control. The activity of microtubule drugs generally depends on their binding to α- and β-tubulin subunits. The microtubule drugs are often effective only in certain taxonomic groups, while other organisms remain resistant. Available information on the molecular basis of this selectivity is summarized. In addition to reviewing published data, we performed sequence data mining, searching for kingdom-specific signatures in plant, animal, fungal, and protozoan tubulin sequences. Our findings clearly correlate with known microtubule drug resistance determinants and add more amino acid positions with a putative effect on drug-tubulin interaction. The issue of microtubule network properties in plant cells producing microtubule drugs is also addressed.

  9. A stochastic model for microtubule motors describes the in vivo cytoplasmic transport of human adenovirus.

    Directory of Open Access Journals (Sweden)

    Mattia Gazzola

    2009-12-01

    Full Text Available Cytoplasmic transport of organelles, nucleic acids and proteins on microtubules is usually bidirectional with dynein and kinesin motors mediating the delivery of cargoes in the cytoplasm. Here we combine live cell microscopy, single virus tracking and trajectory segmentation to systematically identify the parameters of a stochastic computational model of cargo transport by molecular motors on microtubules. The model parameters are identified using an evolutionary optimization algorithm to minimize the Kullback-Leibler divergence between the in silico and the in vivo run length and velocity distributions of the viruses on microtubules. The present stochastic model suggests that bidirectional transport of human adenoviruses can be explained without explicit motor coordination. The model enables the prediction of the number of motors active on the viral cargo during microtubule-dependent motions as well as the number of motor binding sites, with the protein hexon as the binding site for the motors.

  10. A stochastic model for microtubule motors describes the in vivo cytoplasmic transport of human adenovirus.

    Science.gov (United States)

    Gazzola, Mattia; Burckhardt, Christoph J; Bayati, Basil; Engelke, Martin; Greber, Urs F; Koumoutsakos, Petros

    2009-12-01

    Cytoplasmic transport of organelles, nucleic acids and proteins on microtubules is usually bidirectional with dynein and kinesin motors mediating the delivery of cargoes in the cytoplasm. Here we combine live cell microscopy, single virus tracking and trajectory segmentation to systematically identify the parameters of a stochastic computational model of cargo transport by molecular motors on microtubules. The model parameters are identified using an evolutionary optimization algorithm to minimize the Kullback-Leibler divergence between the in silico and the in vivo run length and velocity distributions of the viruses on microtubules. The present stochastic model suggests that bidirectional transport of human adenoviruses can be explained without explicit motor coordination. The model enables the prediction of the number of motors active on the viral cargo during microtubule-dependent motions as well as the number of motor binding sites, with the protein hexon as the binding site for the motors.

  11. A Stochastic Multiscale Model That Explains the Segregation of Axonal Microtubules and Neurofilaments in Neurological Diseases.

    Directory of Open Access Journals (Sweden)

    Chuan Xue

    2015-08-01

    Full Text Available The organization of the axonal cytoskeleton is a key determinant of the normal function of an axon, which is a long thin projection of a neuron. Under normal conditions two axonal cytoskeletal polymers, microtubules and neurofilaments, align longitudinally in axons and are interspersed in axonal cross-sections. However, in many neurotoxic and neurodegenerative disorders, microtubules and neurofilaments segregate apart from each other, with microtubules and membranous organelles clustered centrally and neurofilaments displaced to the periphery. This striking segregation precedes the abnormal and excessive neurofilament accumulation in these diseases, which in turn leads to focal axonal swellings. While neurofilament accumulation suggests an impairment of neurofilament transport along axons, the underlying mechanism of their segregation from microtubules remains poorly understood for over 30 years. To address this question, we developed a stochastic multiscale model for the cross-sectional distribution of microtubules and neurofilaments in axons. The model describes microtubules, neurofilaments and organelles as interacting particles in a 2D cross-section, and is built upon molecular processes that occur on a time scale of seconds or shorter. It incorporates the longitudinal transport of neurofilaments and organelles through this domain by allowing stochastic arrival and departure of these cargoes, and integrates the dynamic interactions of these cargoes with microtubules mediated by molecular motors. Simulations of the model demonstrate that organelles can pull nearby microtubules together, and in the absence of neurofilament transport, this mechanism gradually segregates microtubules from neurofilaments on a time scale of hours, similar to that observed in toxic neuropathies. This suggests that the microtubule-neurofilament segregation can be a consequence of the selective impairment of neurofilament transport. The model generates the

  12. DESIGN MECHANISM OF PLAYERS’ COORDINATION IN DYNAMIC GAME FOR MAXIMIZING THE EFFECTIVENESS OF THEIR INTERACTIONS

    Directory of Open Access Journals (Sweden)

    Artem O. Pichugin

    2014-01-01

    Full Text Available Quite often within the activity subjects are compelled to interact with other subjects of one system. And this interaction can have antagonistic character in spite of the fact that they are within one system, and game by which interaction in systems is described, isn’t game with the zero sum. In the article the mechanism which allows to change interaction of players from antagonism to cooperation is offered.

  13. Interaction between interpersonal and postural coordination during frequency scaled rhythmic sway: the role of dance expertise.

    Science.gov (United States)

    Sofianidis, George; Elliott, Mark T; Wing, Alan M; Hatzitaki, Vassilia

    2015-01-01

    Light fingertip touch between partners swaying rhythmically side by side evokes interpersonal synchrony. In non-dancers and dancers swaying to a metronome, we examined the effects of frequency scaling and touch between the partners on both postural (ankle-hip) and inter-personal coordination. In both groups, touch did not interfere with the ankle-hip coordination. In non-dancers but not dancers, increasing frequency resulted in a loss of the ankle-hip coupling that was accompanied by a reduction of the touch mediated interpersonal synchrony. It is suggested that the effect of touch on interpersonal synchrony depends on the reliability of the haptic information sensed at the fingertip and assumes an in phase ankle-hip coupling. These findings have implications in clinical practice when using touch to help balance impaired individuals.

  14. Seawater-Assisted Self-Healing of Catechol Polymers via Hydrogen Bonding and Coordination Interactions.

    Science.gov (United States)

    Li, Jincai; Ejima, Hirotaka; Yoshie, Naoko

    2016-07-27

    It is highly desirable to prevent crack formation in polymeric materials at an early stage and to extend their lifespan, particularly when repairs to these materials would be difficult for humans. Here, we designed and synthesized catechol-functionalized polymers that can self-heal in seawater through hydrogen bonding and coordination. These bioinspired acrylate polymers are originally viscous materials, but after coordination with environmentally safe, common metal cations in seawater, namely, Ca(2+) and Mg(2+), the mechanical properties of the polymers were greatly enhanced from viscous to tough, hard materials. Reduced swelling in seawater compared with deionized water owing to the higher osmotic pressure resulted in greater toughness (∼5 MPa) and self-healing efficiencies (∼80%).

  15. High-Dimensional Data Visualization by Interactive Construction of Low-Dimensional Parallel Coordinate Plots

    OpenAIRE

    Itoh, Takayuki; Kumar, Ashnil; Klein, Karsten; Kim, Jinman

    2016-01-01

    Parallel coordinate plots (PCPs) are among the most useful techniques for the visualization and exploration of high-dimensional data spaces. They are especially useful for the representation of correlations among the dimensions, which identify relationships and interdependencies between variables. However, within these high-dimensional spaces, PCPs face difficulties in displaying the correlation between combinations of dimensions and generally require additional display space as the number of...

  16. Optomechanical proposal for monitoring microtubule mechanical vibrations

    Science.gov (United States)

    Barzanjeh, Sh.; Salari, V.; Tuszynski, J. A.; Cifra, M.; Simon, C.

    2017-07-01

    Microtubules provide the mechanical force required for chromosome separation during mitosis. However, little is known about the dynamic (high-frequency) mechanical properties of microtubules. Here, we theoretically propose to control the vibrations of a doubly clamped microtubule by tip electrodes and to detect its motion via the optomechanical coupling between the vibrational modes of the microtubule and an optical cavity. In the presence of a red-detuned strong pump laser, this coupling leads to optomechanical-induced transparency of an optical probe field, which can be detected with state-of-the art technology. The center frequency and line width of the transparency peak give the resonance frequency and damping rate of the microtubule, respectively, while the height of the peak reveals information about the microtubule-cavity field coupling. Our method opens the new possibilities to gain information about the physical properties of microtubules, which will enhance our capability to design physical cancer treatment protocols as alternatives to chemotherapeutic drugs.

  17. Detailed Per-residue Energetic Analysis Explains the Driving Force for Microtubule Disassembly.

    Directory of Open Access Journals (Sweden)

    Ahmed T Ayoub

    2015-06-01

    Full Text Available Microtubules are long filamentous hollow cylinders whose surfaces form lattice structures of αβ-tubulin heterodimers. They perform multiple physiological roles in eukaryotic cells and are targets for therapeutic interventions. In our study, we carried out all-atom molecular dynamics simulations for arbitrarily long microtubules that have either GDP or GTP molecules in the E-site of β-tubulin. A detailed energy balance of the MM/GBSA inter-dimer interaction energy per residue contributing to the overall lateral and longitudinal structural stability was performed. The obtained results identified the key residues and tubulin domains according to their energetic contributions. They also identified the molecular forces that drive microtubule disassembly. At the tip of the plus end of the microtubule, the uneven distribution of longitudinal interaction energies within a protofilament generates a torque that bends tubulin outwardly with respect to the cylinder's axis causing disassembly. In the presence of GTP, this torque is opposed by lateral interactions that prevent outward curling, thus stabilizing the whole microtubule. Once GTP hydrolysis reaches the tip of the microtubule (lateral cap, lateral interactions become much weaker, allowing tubulin dimers to bend outwards, causing disassembly. The role of magnesium in the process of outward curling has also been demonstrated. This study also showed that the microtubule seam is the most energetically labile inter-dimer interface and could serve as a trigger point for disassembly. Based on a detailed balance of the energetic contributions per amino acid residue in the microtubule, numerous other analyses could be performed to give additional insights into the properties of microtubule dynamic instability.

  18. Microtubule-microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes.

    Science.gov (United States)

    Lu, Wen; Winding, Michael; Lakonishok, Margot; Wildonger, Jill; Gelfand, Vladimir I

    2016-08-23

    Cytoplasmic streaming in Drosophila oocytes is a microtubule-based bulk cytoplasmic movement. Streaming efficiently circulates and localizes mRNAs and proteins deposited by the nurse cells across the oocyte. This movement is driven by kinesin-1, a major microtubule motor. Recently, we have shown that kinesin-1 heavy chain (KHC) can transport one microtubule on another microtubule, thus driving microtubule-microtubule sliding in multiple cell types. To study the role of microtubule sliding in oocyte cytoplasmic streaming, we used a Khc mutant that is deficient in microtubule sliding but able to transport a majority of cargoes. We demonstrated that streaming is reduced by genomic replacement of wild-type Khc with this sliding-deficient mutant. Streaming can be fully rescued by wild-type KHC and partially rescued by a chimeric motor that cannot move organelles but is active in microtubule sliding. Consistent with these data, we identified two populations of microtubules in fast-streaming oocytes: a network of stable microtubules anchored to the actin cortex and free cytoplasmic microtubules that moved in the ooplasm. We further demonstrated that the reduced streaming in sliding-deficient oocytes resulted in posterior determination defects. Together, we propose that kinesin-1 slides free cytoplasmic microtubules against cortically immobilized microtubules, generating forces that contribute to cytoplasmic streaming and are essential for the refinement of posterior determinants.

  19. Long-term simulation of large deformation, mechano-chemical fluid-structure interactions in ALE and fully Eulerian coordinates

    Science.gov (United States)

    Frei, S.; Richter, T.; Wick, T.

    2016-09-01

    In this work, we develop numerical schemes for mechano-chemical fluid-structure interactions with long-term effects. We investigate a model of a growing solid interacting with an incompressible fluid. A typical example for such a situation is the formation and growth of plaque in blood vessels. This application includes two particular difficulties: First, growth may lead to very large deformations, up to full clogging of the fluid domain. We derive a simplified set of equations including a fluid-structure interaction system coupled to an ODE model for plaque growth in Arbitrary Lagrangian Eulerian (ALE) coordinates and in Eulerian coordinates. The latter novel technique is capable of handling very large deformations up to contact. The second difficulty stems from the different time scales: while the dynamics of the fluid demand to resolve a scale of seconds, growth typically takes place in a range of months. We propose a temporal two-scale approach using local small-scale problems to compute an effective wall stress that will enter a long-scale problem. Our proposed techniques are substantiated with several numerical tests that include comparisons of the Eulerian and ALE approaches as well as convergence studies.

  20. Interaction between the premotor processes of eye and hand movements: possible mechanism underlying eye-hand coordination.

    Science.gov (United States)

    Hiraoka, Koichi; Kurata, Naoatsu; Sakaguchi, Masato; Nonaka, Kengo; Matsumoto, Naoto

    2014-03-01

    Interaction between the execution process of eye movement and that of hand movement must be indispensable for eye-hand coordination. The present study investigated corticospinal excitability in the hand muscles during the premotor processes of eye and/or hand movement to elucidate interaction between these processes. Healthy humans performed a precued reaction task of eye and/or finger movement and motor-evoked potentials in the hand muscles were evoked in the reaction time. Leftward eye movement suppressed corticospinal excitability in the right abductor digiti minimi muscle only when little finger abduction was simultaneously executed. Corticospinal excitability in the first dorsal interosseous muscle was not suppressed by eye movement regardless of whether or not it was accompanied by finger movement. Suppression of corticospinal excitability in the hand muscles induced by eye movement in the premotor period depends on the direction of eye movement, the muscle tested, and the premotor process of the tested muscle. The suppression may reflect interaction between the motor process of eye movement and that of hand movement particularly active during eye-hand coordination tasks during which both processes proceed.

  1. Siderophore biosynthesis coordinately modulated the virulence-associated interactive metabolome of uropathogenic Escherichia coli and human urine.

    Science.gov (United States)

    Su, Qiao; Guan, Tianbing; Lv, Haitao

    2016-04-14

    Uropathogenic Escherichia coli (UPEC) growth in women's bladders during urinary tract infection (UTI) incurs substantial chemical exchange, termed the "interactive metabolome", which primarily accounts for the metabolic costs (utilized metabolome) and metabolic donations (excreted metabolome) between UPEC and human urine. Here, we attempted to identify the individualized interactive metabolome between UPEC and human urine. We were able to distinguish UPEC from non-UPEC by employing a combination of metabolomics and genetics. Our results revealed that the interactive metabolome between UPEC and human urine was markedly different from that between non-UPEC and human urine, and that UPEC triggered much stronger perturbations in the interactive metabolome in human urine. Furthermore, siderophore biosynthesis coordinately modulated the individualized interactive metabolome, which we found to be a critical component of UPEC virulence. The individualized virulence-associated interactive metabolome contained 31 different metabolites and 17 central metabolic pathways that were annotated to host these different metabolites, including energetic metabolism, amino acid metabolism, and gut microbe metabolism. Changes in the activities of these pathways mechanistically pinpointed the virulent capability of siderophore biosynthesis. Together, our findings provide novel insights into UPEC virulence, and we propose that siderophores are potential targets for further discovery of drugs to treat UPEC-induced UTI.

  2. [Impairment of social interaction, coordination disorder, and hypersensitivity in Asperger's syndrome].

    Science.gov (United States)

    Asai, Tomoko; Sugiyam, Toshiro

    2007-03-01

    Asperger's syndrome is not accompanied with intellectual disability, however it has social impairments as well as autism and demonstrates failure to develop peer relationships according to each life stage. Social reciprocal behavior deficits are revealed typically during childhood. On the other hand, after school age these deficits are modified by environmental factors that may induce secondary disorders consequently. Hypersensitivity and coordination disorder, which are not included in diagnostic criteria for Asperger's syndrome, are often in presence. These symptoms are diminished and rarely interfere daily living as growth. However they may keep Asperger's syndrome individuals from adapting to others, so we need to take it into consideration.

  3. Mechanism for the catastrophe-promoting activity of the microtubule destabilizer Op18/stathmin.

    Science.gov (United States)

    Gupta, Kamlesh K; Li, Chunlei; Duan, Aranda; Alberico, Emily O; Kim, Oleg V; Alber, Mark S; Goodson, Holly V

    2013-12-17

    Regulation of microtubule dynamic instability is crucial for cellular processes, ranging from mitosis to membrane transport. Stathmin (also known as oncoprotein 18/Op18) is a prominent microtubule destabilizer that acts preferentially on microtubule minus ends. Stathmin has been studied intensively because of its association with multiple types of cancer, but its mechanism of action remains controversial. Two models have been proposed. One model is that stathmin promotes microtubule catastrophe indirectly, and does so by sequestering tubulin; the other holds that stathmin alters microtubule dynamics by directly destabilizing growing microtubules. Stathmin's sequestration activity is well established, but the mechanism of any direct action is mysterious because stathmin binds to microtubules very weakly. To address these issues, we have studied interactions between stathmin and varied tubulin polymers. We show that stathmin binds tightly to Dolastatin-10 tubulin rings, which mimic curved tubulin protofilaments, and that stathmin depolymerizes stabilized protofilament-rich polymers. These observations lead us to propose that stathmin promotes catastrophe by binding to and acting upon protofilaments exposed at the tips of growing microtubules. Moreover, we suggest that stathmin's minus-end preference results from interactions between stathmin's N terminus and the surface of α-tubulin that is exposed only at the minus end. Using computational modeling of microtubule dynamics, we show that these mechanisms could account for stathmin's observed activities in vitro, but that both the direct and sequestering activities are likely to be relevant in a cellular context. Taken together, our results suggest that stathmin can promote catastrophe by direct action on protofilament structure and interactions.

  4. Probing a self-assembled fd virus membrane with a microtubule

    Science.gov (United States)

    Xie, Sheng; Pelcovits, Robert A.; Hagan, Michael F.

    2016-06-01

    The self-assembly of highly anisotropic colloidal particles leads to a rich variety of morphologies whose properties are just beginning to be understood. This article uses computer simulations to probe a particle-scale perturbation of a commonly studied colloidal assembly, a monolayer membrane composed of rodlike fd viruses in the presence of a polymer depletant. Motivated by experiments currently in progress, we simulate the interaction between a microtubule and a monolayer membrane as the microtubule "pokes" and penetrates the membrane face-on. Both the viruses and the microtubule are modeled as hard spherocylinders of the same diameter, while the depletant is modeled using ghost spheres. We find that the force exerted on the microtubule by the membrane is zero either when the microtubule is completely outside the membrane or when it has fully penetrated the membrane. The microtubule is initially repelled by the membrane as it begins to penetrate but experiences an attractive force as it penetrates further. We assess the roles played by translational and rotational fluctuations of the viruses and the osmotic pressure of the polymer depletant. We find that rotational fluctuations play a more important role than the translational ones. The dependence on the osmotic pressure of the depletant of the width and height of the repulsive barrier and the depth of the attractive potential well is consistent with the assumed depletion-induced attractive interaction between the microtubule and viruses. We discuss the relevance of these studies to the experimental investigations.

  5. Single micelle force microscopy reveals the coordination interaction between catechol and Fe33+

    Science.gov (United States)

    Li, Yiran; Cao, Yi; Wang, Wei

    Metal coordination bonds are widely found in natural adhesive, load-bearing, and protective materials, which are thought to be responsible for their high strength and toughness. However, it remains unknown how the metal-ligand complexes could give rise to such superb mechanical properties. Here, combining single molecule force spectroscopy and quantum calculation, we study the mechanical properties of individual catechol-Fe3 + complexes, the key elements accounting for the high toughness and extensibility of byssal threads of marine mussels. We find that catechol-Fe3 + complexes possess a unique combination of mechanical features, including high mechanical stability, fast reformation kinetics, and stoichiometry-dependent mechanics. Therefore, they can serve as sacrificial bonds to efficiently dissipate energy in the material, quickly recover the mechanical properties when load is released, and be responsive to environmental conditions. Our study provides the mechanistic understanding of the coordination bond-mediated mechanical properties of biogenetic materials, and could guide future rational design and regulation of the mechanical properties of synthetic materials.

  6. Atomic-resolution structure of the CAP-Gly domain of dynactin on polymeric microtubules determined by magic angle spinning NMR spectroscopy

    Science.gov (United States)

    Yan, Si; Guo, Changmiao; Hou, Guangjin; Zhang, Huilan; Lu, Xingyu; Williams, John Charles; Polenova, Tatyana

    2015-01-01

    Microtubules and their associated proteins perform a broad array of essential physiological functions, including mitosis, polarization and differentiation, cell migration, and vesicle and organelle transport. As such, they have been extensively studied at multiple levels of resolution (e.g., from structural biology to cell biology). Despite these efforts, there remain significant gaps in our knowledge concerning how microtubule-binding proteins bind to microtubules, how dynamics connect different conformational states, and how these interactions and dynamics affect cellular processes. Structures of microtubule-associated proteins assembled on polymeric microtubules are not known at atomic resolution. Here, we report a structure of the cytoskeleton-associated protein glycine-rich (CAP-Gly) domain of dynactin motor on polymeric microtubules, solved by magic angle spinning NMR spectroscopy. We present the intermolecular interface of CAP-Gly with microtubules, derived by recording direct dipolar contacts between CAP-Gly and tubulin using double rotational echo double resonance (dREDOR)-filtered experiments. Our results indicate that the structure adopted by CAP-Gly varies, particularly around its loop regions, permitting its interaction with multiple binding partners and with the microtubules. To our knowledge, this study reports the first atomic-resolution structure of a microtubule-associated protein on polymeric microtubules. Our approach lays the foundation for atomic-resolution structural analysis of other microtubule-associated motors. PMID:26604305

  7. Atomic-resolution structure of the CAP-Gly domain of dynactin on polymeric microtubules determined by magic angle spinning NMR spectroscopy.

    Science.gov (United States)

    Yan, Si; Guo, Changmiao; Hou, Guangjin; Zhang, Huilan; Lu, Xingyu; Williams, John Charles; Polenova, Tatyana

    2015-11-24

    Microtubules and their associated proteins perform a broad array of essential physiological functions, including mitosis, polarization and differentiation, cell migration, and vesicle and organelle transport. As such, they have been extensively studied at multiple levels of resolution (e.g., from structural biology to cell biology). Despite these efforts, there remain significant gaps in our knowledge concerning how microtubule-binding proteins bind to microtubules, how dynamics connect different conformational states, and how these interactions and dynamics affect cellular processes. Structures of microtubule-associated proteins assembled on polymeric microtubules are not known at atomic resolution. Here, we report a structure of the cytoskeleton-associated protein glycine-rich (CAP-Gly) domain of dynactin motor on polymeric microtubules, solved by magic angle spinning NMR spectroscopy. We present the intermolecular interface of CAP-Gly with microtubules, derived by recording direct dipolar contacts between CAP-Gly and tubulin using double rotational echo double resonance (dREDOR)-filtered experiments. Our results indicate that the structure adopted by CAP-Gly varies, particularly around its loop regions, permitting its interaction with multiple binding partners and with the microtubules. To our knowledge, this study reports the first atomic-resolution structure of a microtubule-associated protein on polymeric microtubules. Our approach lays the foundation for atomic-resolution structural analysis of other microtubule-associated motors.

  8. Microtubule as nanobioelectronic nonlinear circuit

    Directory of Open Access Journals (Sweden)

    Sekulić Dalibor L.

    2012-01-01

    Full Text Available In recent years, the use of biological molecules has offered exciting alternatives to conventional synthetic methods. Specific methods use various biological templates to direct the deposition and patterning of inorganic materials. Here we have established a new electrical model of microtubules as a biological nanoscale circuit based on polyelectrolyte features of cylindrical biopolymers. Our working hypothesis is that microtubules play an active role in sub-cellular computation and signaling via electronic and protonic conductivity and can thus be made useful in hybrid materials that offer novel electronic characteristics. We verify these hypotheses both computationally and analytically through a quantitative model based on the atomic resolution structures of the key functional proteins.

  9. Microtubules in Dendritic Spine Development

    OpenAIRE

    2008-01-01

    It is generally believed that only the actin cytoskeleton resides in dendritic spines and controls spine morphology and plasticity. Here we report that microtubules (MTs) are present in spines and that shRNA knockdown of the MT-plus end binding protein EB3 significantly reduces spine formation. Furthermore, stabilization and inhibition of MTs by low doses of taxol and nocodazole enhance and impair spine formation elicited by BDNF, respectively. Therefore, MTs play an important role in the con...

  10. Control of high affinity interactions in the talin C terminus: how talin domains coordinate protein dynamics in cell adhesions.

    Science.gov (United States)

    Himmel, Mirko; Ritter, Anett; Rothemund, Sven; Pauling, Björg V; Rottner, Klemens; Gingras, Alexandre R; Ziegler, Wolfgang H

    2009-05-15

    In cell-extracellular matrix junctions (focal adhesions), the cytoskeletal protein talin is central to the connection of integrins to the actin cytoskeleton. Talin is thought to mediate this connection via its two integrin, (at least) three actin, and several vinculin binding sites. The binding sites are cryptic in the head-to-rod autoinhibited cytoplasmic form of the protein and require (stepwise) conformational activation. This activation process, however, remains poorly understood, and there are contradictory models with respect to the determinants of adhesion site localization. Here, we report turnover rates and protein-protein interactions in a range of talin rod domain constructs varying in helix bundle structure. We conclude that several bundles of the C terminus cooperate to regulate targeting and concomitantly tailor high affinity interactions of the talin rod in cell adhesions. Intrinsic control of ligand binding activities is essential for the coordination of adhesion site function of talin.

  11. A NudE/14-3-3 pathway coordinates Dynein and the Kinesin Khc73 to position the mitotic spindle

    OpenAIRE

    2013-01-01

    Mitotic spindle position is controlled by interactions of cortical molecular motors with astral microtubules. In animal cells, Partner of Inscuteable (Pins) acts at the cortex to coordinate the activity of Dynein and Kinesin-73 (Khc73; Kif13B in mammals) to orient the spindle. Though the two motors move in opposite directions, their synergistic activity is required for robust Pins-mediated spindle orientation. Here we identify a physical connection between Dynein and Khc73 that mediates coope...

  12. A Heart for Interaction: Shared Physiological Dynamics and Behavioral Coordination in a Collective, Creative Construction Task

    DEFF Research Database (Denmark)

    Fusaroli, Riccardo; Stege Bjørndahl, Johanne; Roepstorff, Andreas;

    2016-01-01

    participants doing the same things) than in collective ones (involving participants taking turns and performing complementary actions). However, when contrasted against virtual pairs, collective trials display more stable shared HR dynamics suggesting that online social interaction plays an important role...

  13. Responsive supramolecular polymer metallogel constructed by orthogonal coordination-driven self-assembly and host/guest interactions.

    Science.gov (United States)

    Yan, Xuzhou; Cook, Timothy R; Pollock, J Bryant; Wei, Peifa; Zhang, Yanyan; Yu, Yihua; Huang, Feihe; Stang, Peter J

    2014-03-26

    An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained.

  14. Plk phosphorylation regulates the microtubule-stabilizing protein TCTP.

    Science.gov (United States)

    Yarm, Frederic R

    2002-09-01

    The mitotic polo-like kinases have been implicated in the formation and function of bipolar spindles on the basis of their respective localizations and mutant phenotypes. To date, this putative regulation has been limited to a kinesin-like motor protein, a centrosomal structural protein, and two microtubule-associated proteins (MAPs). In this study, another spindle-regulating protein, the mammalian non-MAP microtubule-binding and -stabilizing protein, the translationally controlled tumor protein (TCTP), was identified as a putative Plk-interacting clone by a two-hybrid screen. Plk phosphorylates TCTP on two serine residues in vitro and cofractionates with the majority of kinase activity toward TCTP in mitotic cell lysates. In addition, these sites were demonstrated to be phosphorylated in vivo. Overexpression of a Plk phosphorylation site-deficient mutant of TCTP induced a dramatic increase in the number of multinucleate cells, rounded cells with condensed ball-like nuclei, and cells undergoing cell death, similar to both the reported anti-Plk antibody microinjection and the low-concentration taxol treatment phenotypes. These results suggest that phosphorylation decreases the microtubule-stabilizing activity of TCTP and promotes the increase in microtubule dynamics that occurs after metaphase.

  15. EWSR1 regulates mitosis by dynamically influencing microtubule acetylation.

    Science.gov (United States)

    Wang, Yi-Long; Chen, Hui; Zhan, Yi-Qun; Yin, Rong-Hua; Li, Chang-Yan; Ge, Chang-Hui; Yu, Miao; Yang, Xiao-Ming

    2016-08-17

    EWSR1, participating in transcription and splicing, has been identified as a translocation partner for various transcription factors, resulting in translocation, which in turn plays crucial roles in tumorigenesis. Recent studies have investigated the role of EWSR1 in mitosis. However, the effect of EWSR1 on mitosis is poorly understood. Here, we observed that depletion of EWSR1 resulted in cell cycle arrest in the mitotic phase, mainly due to an increase in the time from nuclear envelope breakdown to metaphase, resulting in a high percentage of unaligned chromosomes and multipolar spindles. We also demonstrated that EWSR1 is a spindle-associated protein that interacts with α-tubulin during mitosis. EWSR1 depletion increased the cold-sensitivity of spindle microtubules, and decreased the rate of spindle assembly. EWSR1 regulated the level of microtubule acetylation in the mitotic spindle; microtubule acetylation was rescued in EWSR1-depleted mitotic cells following suppression of HDAC6 activity by its specific inhibitor or siRNA treatment. In summary, these results suggest that EWSR1 regulates the acetylation of microtubules in a cell cycle-dependent manner through its dynamic location on spindle MTs, and may be a novel regulator for mitosis progress independent of its translocation.

  16. Tau Induces Cooperative Taxol Binding to Microtubules

    Science.gov (United States)

    Ross, Jennifer; Santangelo, Christian; Victoria, Makrides; Fygenson, Deborah

    2004-03-01

    Taxol and tau are two ligands which stabilize the microtubule (MT) lattice. Taxol is an anti-mitotic drug that binds β tubulin in the MT interior. Tau is a MT-associated protein that binds both α and β tubulin on the MT exterior. Both taxol and tau reduce MT dynamics and promote tubulin polymerization. Tau alone also acts as a buttress to bundle, stiffen, and space MTs. A structural study recently suggested that taxol and tau may interact by binding to the same site. Using fluorescence recovery after photobleaching, we find that tau induces taxol to bind MTs cooperatively depending on the tau concentration. We develop a model that correctly fits the data in the absence of tau and yields a measure of taxol cooperativity when tau is present.

  17. Microtubule dynamics: Caps, catastrophes, and coupled hydrolysis

    DEFF Research Database (Denmark)

    Flyvbjerg, H.; Holy, T.E.; Leibler, S.

    1996-01-01

    individual tubulin dimers, an ignored. In this cap model, GTP hydrolysis is assumed to be stochastic and uncoupled to microtubule growth. Different rates of hydrolysis are assumed for GTP in the cap's interior and for GTP at its boundary with hydrolyzed parts of the microtubule. Expectation values...... and probability distributions relating to available experimental data are derived. Caps are found to be short and the total rate of hydrolysis at a microtubule end is found to be dynamically coupled to growth. The so-called catastrophe rate is a simple function of the microtubule growth rare and fits experimental...... of microtubule growth before dilution. The GTP content of microtubules is found and its rare of hydrolysis is determined under the circumstances created in an experiment designed to measure this GTP content. It is concluded that this experiment's failure to register any GTP content is consistent with the model...

  18. INTERACTIONS BETWEEN CORONAL MASS EJECTIONS VIEWED IN COORDINATED IMAGING AND IN SITU OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying D.; Luhmann, Janet G.; Moestl, Christian; Martinez-Oliveros, Juan C.; Bale, Stuart D.; Lin, Robert P. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Harrison, Richard A. [Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot (United Kingdom); Temmer, Manuela [Institute of Physics, University of Graz (Austria); Webb, David F. [Institute for Scientific Research, Boston College, Newton, MA 02459 (United States); Odstrcil, Dusan, E-mail: liuxying@ssl.berkeley.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2012-02-20

    The successive coronal mass ejections (CMEs) from 2010 July 30 to August 1 present us the first opportunity to study CME-CME interactions with unprecedented heliospheric imaging and in situ observations from multiple vantage points. We describe two cases of CME interactions: merging of two CMEs launched close in time and overtaking of a preceding CME by a shock wave. The first two CMEs on August 1 interact close to the Sun and form a merged front, which then overtakes the July 30 CME near 1 AU, as revealed by wide-angle imaging observations. Connections between imaging observations and in situ signatures at 1 AU suggest that the merged front is a shock wave, followed by two ejecta observed at Wind which seem to have already merged. In situ measurements show that the CME from July 30 is being overtaken by the shock at 1 AU and is significantly compressed, accelerated, and heated. The interaction between the preceding ejecta and shock also results in variations in the shock strength and structure on a global scale, as shown by widely separated in situ measurements from Wind and STEREO B. These results indicate important implications of CME-CME interactions for shock propagation, particle acceleration, and space weather forecasting.

  19. Interactions between Coronal Mass Ejections Viewed in Coordinated Imaging and In Situ Observations

    Science.gov (United States)

    Liu, Ying D.; Luhmann, Janet G.; Moestl, Christian; Martinez-Oliveros, Juan C.; Bale, Stewart D.; Lin, Robert P.; Harrison, Richard A.; Temmer, Manuela; Webb, David F.; Odstrcil, Dusan

    2013-01-01

    The successive coronal mass ejections (CMEs) from 2010 July 30 - August 1 present us the first opportunity to study CME-CME interactions with unprecedented heliospheric imaging and in situ observations from multiple vantage points. We describe two cases of CME interactions: merging of two CMEs launched close in time and overtaking of a preceding CME by a shock wave. The first two CMEs on August 1 interact close to the Sun and form a merged front, which then overtakes the July 30 CME near 1 AU, as revealed by wide-angle imaging observations. Connections between imaging observations and in situ signatures at 1 AU suggest that the merged front is a shock wave, followed by two ejecta observed at Wind which seem to have already merged. In situ measurements show that the CME from July 30 is being overtaken by the shock at 1 AU and is significantly compressed, accelerated and heated. The interaction between the preceding ejecta and shock also results in variations in the shock strength and structure on a global scale, as shown by widely separated in situ measurements from Wind and STEREO B. These results indicate important implications of CME-CME interactions for shock propagation, particle acceleration and space weather forecasting.

  20. Symmetry Breaking in an Edgeless Epithelium by Fat2-Regulated Microtubule Polarity

    Directory of Open Access Journals (Sweden)

    Dong-Yuan Chen

    2016-05-01

    Full Text Available Planar cell polarity (PCP information is a critical determinant of organ morphogenesis. While PCP in bounded epithelial sheets is increasingly well understood, how PCP is organized in tubular and acinar tissues is not. Drosophila egg chambers (follicles are an acinus-like “edgeless epithelium” and exhibit a continuous, circumferential PCP that does not depend on pathways active in bounded epithelia; this follicle PCP directs formation of an ellipsoid rather than a spherical egg. Here, we apply an imaging algorithm to “unroll” the entire 3D tissue surface and comprehensively analyze PCP onset. This approach traces chiral symmetry breaking to plus-end polarity of microtubules in the germarium, well before follicles form and rotate. PCP germarial microtubules provide chiral information that predicts the direction of whole-tissue rotation as soon as independent follicles form. Concordant microtubule polarity, but not microtubule alignment, requires the atypical cadherin Fat2, which acts at an early stage to translate plus-end bias into coordinated actin-mediated collective cell migration. Because microtubules are not required for PCP or migration after follicle rotation initiates, while dynamic actin and extracellular matrix are, polarized microtubules lie at the beginning of a handoff mechanism that passes early chiral PCP of the cytoskeleton to a supracellular planar polarized extracellular matrix and elongates the organ.

  1. Detailed Per-residue Energetic Analysis Explains the Driving Force for Microtubule Disassembly

    OpenAIRE

    Ayoub, Ahmed T.; Mariusz Klobukowski; Tuszynski, Jack A

    2015-01-01

    Microtubules are long filamentous hollow cylinders whose surfaces form lattice structures of αβ-tubulin heterodimers. They perform multiple physiological roles in eukaryotic cells and are targets for therapeutic interventions. In our study, we carried out all-atom molecular dynamics simulations for arbitrarily long microtubules that have either GDP or GTP molecules in the E-site of β-tubulin. A detailed energy balance of the MM/GBSA inter-dimer interaction energy per residue contributing to t...

  2. Expression of Nucleolin Affects Microtubule Dynamics.

    Directory of Open Access Journals (Sweden)

    Xavier Gaume

    Full Text Available Nucleolin is present in diverse cellular compartments and is involved in a variety of cellular processes from nucleolar structure and function to intracellular trafficking, cell adhesion and migration. Recently, nucleolin has been localized at the mature centriole where it is involved in microtubule nucleation and anchoring. Although this new function of nucleolin linked to microtubule regulation has been identified, the global effects of nucleolin on microtubule dynamics have not been addressed yet. In the present study, we analyzed the roles of nucleolin protein levels on global microtubule dynamics by tracking the EB3 microtubule plus end binding protein in live cells. We have found that during microtubule growth phases, nucleolin affects both the speed and life time of polymerization and by analyzing catastrophe events, we showed that nucleolin reduces catastrophe frequency. This new property of nucleolin was then confirmed in a cold induced microtubule depolymerization experiment in which we have found that cold resistant microtubules were totally destabilized in nucleolin depleted cells. Altogether, our data demonstrate a new function of nucleolin on microtubule stabilization, thus bringing novel insights into understanding the multifunctional properties of nucleolin in healthy and cancer cells.

  3. Aurora B suppresses microtubule dynamics and limits central spindle size by locally activating KIF4A

    Science.gov (United States)

    Nunes Bastos, Ricardo; Gandhi, Sapan R.; Baron, Ryan D.; Gruneberg, Ulrike; Nigg, Erich A.

    2013-01-01

    Anaphase central spindle formation is controlled by the microtubule-stabilizing factor PRC1 and the kinesin KIF4A. We show that an MKlp2-dependent pool of Aurora B at the central spindle, rather than global Aurora B activity, regulates KIF4A accumulation at the central spindle. KIF4A phosphorylation by Aurora B stimulates the maximal microtubule-dependent ATPase activity of KIF4A and promotes its interaction with PRC1. In the presence of phosphorylated KIF4A, microtubules grew more slowly and showed long pauses in growth, resulting in the generation of shorter PRC1-stabilized microtubule overlaps in vitro. Cells expressing only mutant forms of KIF4A lacking the Aurora B phosphorylation site overextended the anaphase central spindle, demonstrating that this regulation is crucial for microtubule length control in vivo. Aurora B therefore ensures that suppression of microtubule dynamic instability by KIF4A is restricted to a specific subset of microtubules and thereby contributes to central spindle size control in anaphase. PMID:23940115

  4. α-Synuclein Fibrils Exhibit Gain of Toxic Function, Promoting Tau Aggregation and Inhibiting Microtubule Assembly*

    Science.gov (United States)

    Oikawa, Takayuki; Nonaka, Takashi; Terada, Makoto; Tamaoka, Akira; Hisanaga, Shin-ichi; Hasegawa, Masato

    2016-01-01

    α-Synuclein is the major component of Lewy bodies and Lewy neurites in Parkinson disease and dementia with Lewy bodies and of glial cytoplasmic inclusions in multiple system atrophy. It has been suggested that α-synuclein fibrils or intermediate protofibrils in the process of fibril formation may have a toxic effect on neuronal cells. In this study, we investigated the ability of soluble monomeric α-synuclein to promote microtubule assembly and the effects of conformational changes of α-synuclein on Tau-promoted microtubule assembly. In marked contrast to previous findings, monomeric α-synuclein had no effect on microtubule polymerization. However, both α-synuclein fibrils and protofibrils inhibited Tau-promoted microtubule assembly. The inhibitory effect of α-synuclein fibrils was greater than that of the protofibrils. Dot blot overlay assay and spin-down techniques revealed that α-synuclein fibrils bind to Tau and inhibit microtubule assembly by depleting the Tau available for microtubule polymerization. Using various deletion mutants of α-synuclein and Tau, the acidic C-terminal region of α-synuclein and the basic central region of Tau were identified as regions involved in the binding. Furthermore, introduction of α-synuclein fibrils into cultured cells overexpressing Tau protein induced Tau aggregation. These results raise the possibility that α-synuclein fibrils interact with Tau, inhibit its function to stabilize microtubules, and also promote Tau aggregation, leading to dysfunction of neuronal cells. PMID:27226637

  5. Laulimalide induces dose-dependent modulation of microtubule behaviour in the C. elegans embryo.

    Directory of Open Access Journals (Sweden)

    Megha Bajaj

    Full Text Available Laulimalide is a microtubule-binding drug that was originally isolated from marine sponges. High concentrations of laulimalide stabilize microtubules and inhibit cell division similarly to paclitaxel; however, there are important differences with respect to the nature of the specific cellular defects between these two drugs and their binding sites on the microtubule. In this study, we used Caenorhabditis elegans embryos to investigate the acute effects of laulimalide on microtubules in vivo, with a direct comparison to paclitaxel. We observed surprising dose-dependent effects for laulimalide, whereby microtubules were stabilized at concentrations above 100 nM, but destabilized at concentrations between 50 and 100 nM. Despite this behaviour at low concentrations, laulimalide acted synergistically with paclitaxel to stabilize microtubules when both drugs were used at sub-effective concentrations, consistent with observations of synergistic interactions between these two drugs in other systems. Our results indicate that laulimalide induces a concentration-dependent, biphasic change in microtubule polymer dynamics in the C. elegans embryo.

  6. Clostridium difficile toxin CDT induces formation of microtubule-based protrusions and increases adherence of bacteria.

    Directory of Open Access Journals (Sweden)

    Carsten Schwan

    2009-10-01

    Full Text Available Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis by production of the Rho GTPase-glucosylating toxins A and B. Recently emerging hypervirulent Clostridium difficile strains additionally produce the binary ADP-ribosyltransferase toxin CDT (Clostridium difficile transferase, which ADP-ribosylates actin and inhibits actin polymerization. Thus far, the role of CDT as a virulence factor is not understood. Here we report by using time-lapse- and immunofluorescence microscopy that CDT and other binary actin-ADP-ribosylating toxins, including Clostridium botulinum C2 toxin and Clostridium perfringens iota toxin, induce redistribution of microtubules and formation of long (up to >150 microm microtubule-based protrusions at the surface of intestinal epithelial cells. The toxins increase the length of decoration of microtubule plus-ends by EB1/3, CLIP-170 and CLIP-115 proteins and cause redistribution of the capture proteins CLASP2 and ACF7 from microtubules at the cell cortex into the cell interior. The CDT-induced microtubule protrusions form a dense meshwork at the cell surface, which wrap and embed bacterial cells, thereby largely increasing the adherence of Clostridia. The study describes a novel type of microtubule structure caused by less efficient microtubule capture and offers a new perspective for the pathogenetic role of CDT and other binary actin-ADP-ribosylating toxins in host-pathogen interactions.

  7. Visualization of microtubule growth in living platelets reveals a dynamic marginal band with multiple microtubules

    NARCIS (Netherlands)

    S. Patel-Hett (Sunita); J.L. Richardson (Jennifer); H. Schulze (Harald); K. Drabek (Ksenija); N.A. Isaac (Natasha); K. Hoffmeister (Karin); R.A. Shivdasani (Ramesh); J.C. Bulinski (J. Chloë); N.J. Galjart (Niels); J.H. Hartwig (John); J. Italiano (Joseph)

    2008-01-01

    textabstractThe marginal band of microtubules maintains the discoid shape of resting blood platelets. Although studies of platelet microtubule coil structure conclude that it is composed of a single microtubule, no investigations of its dynamics exist. In contrast to previous studies, permeabilized

  8. Coordination of tooth morphogenesis and neuronal development through tissue interactions: lessons from mouse models.

    Science.gov (United States)

    Luukko, Keijo; Kettunen, Päivi

    2014-07-15

    In addition to being an advantageous model to investigate general molecular mechanisms of organ formation, the tooth is a distinct target organ for peripheral nerve innervation. These nerves are required for the function and protection of the teeth and, as shown in fish, also for their regeneration. This review focuses on recent findings of the local tissue interactions and molecular signaling mechanisms that regulate the early nerve arrival and patterning of mouse mandibular molar tooth sensory innervation. Dental sensory nerve growth and patterning is a stepwise process that is intimately linked to advancing tooth morphogenesis. In particular, nerve growth factor and semaphorin 3A serve as essential functions during and are iteratively used at different stages of tooth innervation. The tooth germ controls development of its own nerve supply, and similar to the development of the tooth organ proper, tissue interactions between dental epithelial and mesenchymal tissues control the establishment of tooth innervation. Tgf-β, Wnt, and Fgf signaling, which regulate tooth formation, are implicated to mediate these interactions. Therefore, tissue interactions mediated by conserved signal families may constitute key mechanism for the integration of tooth organogenesis and development of its peripheral nerve supply. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Interactions between Coronal Mass Ejections Viewed in Coordinated Imaging and In Situ Observations

    CERN Document Server

    Liu, Ying D; Mostl, Christian; Martinez-Oliveros, Juan C; Bale, Stuart D; Lin, Robert P; Harrison, Richard A; Temmer, Manuela; Webb, David F; Odstrcil, Dusan

    2012-01-01

    The successive coronal mass ejections (CMEs) from 2010 July 30 - August 1 present us the first opportunity to study CME-CME interactions with unprecedented heliospheric imaging and in situ observations from multiple vantage points. We describe two cases of CME interactions: merging of two CMEs launched close in time and overtaking of a preceding CME by a shock wave. The first two CMEs on August 1 interact close to the Sun and form a merged front, which then overtakes the July 30 CME near 1 AU, as revealed by wide-angle imaging observations. Connections between imaging observations and in situ signatures at 1 AU suggest that the merged front is a shock wave, followed by two ejecta observed at Wind which seem to have already merged. In situ measurements show that the CME from July 30 is being overtaken by the shock at 1 AU and is significantly compressed, accelerated and heated. The interaction between the preceding ejecta and shock also results in variations in the shock strength and structure on a global scal...

  10. Nonlinear Dynamics of Dipoles in Microtubules: Pseudo-Spin Model

    CERN Document Server

    Nesterov, Alexander I; Berman, Gennady P; Mavromatos, Nick E

    2016-01-01

    We perform a theoretical study of the dynamics of the electric field excitations in a microtubule by taking into consideration the realistic cylindrical geometry, dipole-dipole interactions of the tubulin-based protein heterodimers, the radial electric field produced by the solvent, and a possible degeneracy of energy states of individual heterodimers. The consideration is done in the frames of the classical pseudo-spin model. We derive the system of nonlinear dynamical ordinary differential equations of motion for interacting dipoles, and the continuum version of these equations. We obtain the solutions of these equations in the form of snoidal waves, solitons, kinks, and localized spikes. Our results will help to a better understanding of the functional properties of microtubules including the motor protein dynamics and the information transfer processes. Our considerations are based on classical dynamics. Some speculations on the role of possible quantum effects are also made.

  11. Nonlinear dynamics of dipoles in microtubules: Pseudospin model.

    Science.gov (United States)

    Nesterov, Alexander I; Ramírez, Mónica F; Berman, Gennady P; Mavromatos, Nick E

    2016-06-01

    We perform a theoretical study of the dynamics of the electric field excitations in a microtubule by taking into consideration the realistic cylindrical geometry, dipole-dipole interactions of the tubulin-based protein heterodimers, the radial electric field produced by the solvent, and a possible degeneracy of energy states of individual heterodimers. The consideration is done in the frame of the classical pseudospin model. We derive the system of nonlinear dynamical partial differential equations of motion for interacting dipoles and the continuum version of these equations. We obtain the solutions of these equations in the form of snoidal waves, solitons, kinks, and localized spikes. Our results will help to achieve a better understanding of the functional properties of microtubules including the motor protein dynamics and the information transfer processes. Our considerations are based on classical dynamics. Some speculations on the role of possible quantum effects are also made.

  12. Coordination of Pancreatic HCO3- Secretion by Protein-Protein Interaction between Membrane Transporters

    Directory of Open Access Journals (Sweden)

    Lee MG

    2001-07-01

    Full Text Available Increasing evidence suggests that protein-protein interaction is essential in many biological processes including epithelial transport. In this report, we discuss the significance of protein interactions to HCO(3(- secretion in pancreatic duct cells. In pancreatic ducts HCO(3(- secretion is mediated by cystic fibrosis transmembrane conductance regulator (CFTR activated luminal Cl(-/HCO(3(- exchange activity and HCO(3(- absorption is achieved by Na(+-dependent mechanisms including Na(+/H(+ exchanger 3 (NHE3. We found biochemical and functional association between CFTR and NHE3. In addition, protein binding through PDZ modules is needed for this regulatory interaction. CFTR affected NHE3 activities in two ways. Acutely, CFTR augmented the cAMP-dependent inhibition of NHE3. In a chronic mechanism, CFTR increases the luminal expression of Na(+/H(+ exchange in pancreatic duct cells. These findings reveal that protein complexes in the plasma membrane of pancreatic duct cells are highly organized for efficient HCO(3(- secretion.

  13. Microtubule heterogeneity of Ornithogalum umbellatum ovary epidermal cells: non-stable cortical microtubules and stable lipotubuloid microtubules

    Directory of Open Access Journals (Sweden)

    Maria Kwiatkowska

    2011-07-01

    Full Text Available Lipotubuloids, structures containing lipid bodies and microtubules, are described in ovary epidermalcells of Ornithogalum umbellatum. Microtubules of lipotubuloids can be fixed in electron microscope fixativecontaining only buffered OsO4 or in glutaraldehyde with OsO4 post-fixation, or in a mixture of OsO4 and glutaraldehyde[1]. None of these substances fixes cortical microtubules of ovary epidermis of this plant which ischaracterized by dynamic longitudinal growth. However, cortical microtubules can be fixed with cold methanolaccording immunocytological methods with the use of b-tubulin antibodies and fluorescein. The existence ofcortical microtubules has also been evidenced by EM observations solely after the use of taxol, microtubulestabilizer, and fixation in a glutaraldehyde/OsO4 mixture. These microtubules mostly lie transversely, sometimesobliquely, and rarely parallel to the cell axis. Staining, using Ruthenium Red and silver hexamine, has revealedthat lipotubuloid microtubules surface is covered with polysaccharides. The presumption has been made thatthe presence of a polysaccharide layer enhances the stability of lipotubuloid microtubules.

  14. Metal Ion Coordination Essential for Specific Molecular Interactions of Butea monosperma Lectin: ITC and MD Simulation Studies.

    Science.gov (United States)

    Abhilash, J; Haridas, M

    2015-05-01

    Crystal structure of Butea monosperma seed lectin (BML) was analyzed and the metal ion geometry identified. In order to understand the role of metal ions for the structural stability and ligand binding, studies of demetallized protein were carried out. Binding of different ligands like GalNAc, lactose, and galactose onto native and demetallized protein was studied by isothermal titration calorimetry as well as molecular simulation methods. Molecular dynamics was applied to the structure after removing the coordinates of metal ions, to identify the effect of demetallization in silico. Docking studies of different sugar molecules as well as the fungal α-amylase was carried out and compared the interactions in the native and apo states. It was found that metal ions are important for the ligand binding with increased affinity. However, their absence did not make any alteration to the secondary structure. Though the metal ions were not coordinated to the loops contacting the α-amylase, the absence of metal ions reduced the protein-protein binding strength due to long-range changes in irregular structures of the lectin.

  15. Stochastic Model of Microtubule Dynamics

    Science.gov (United States)

    Hryniv, Ostap; Martínez Esteban, Antonio

    2017-10-01

    We introduce a continuous time stochastic process on strings made of two types of particle, whose dynamics mimics that of microtubules in a living cell. The long term behaviour of the system is described in terms of the velocity v of the string end. We show that v is an analytic function of its parameters and study its monotonicity properties. We give a complete characterisation of the phase diagram of the model and derive several criteria of the growth (v>0) and the shrinking (v<0) regimes of the dynamics.

  16. Five-coordinated oxovanadium(IV) complexes derived from amino acids and ciprofloxacin: synthesis, spectral, antimicrobial, and DNA interaction approach.

    Science.gov (United States)

    Patel, M N; Patel, S H; Chhasatia, M R; Parmar, P A

    2008-12-15

    Five-coordinated oxovanadium(IV) complexes with ciprofloxacin and various uninegative bidentate amino acids have been prepared. The structure of complexes has been investigated using spectral, physicochemical, mass spectroscopy, and elemental analyses. The antimicrobial activities (MIC) of the complexes, ligands, metal salt, and some standard drugs have been evaluated using the doubling dilution technique against Staphylococcus aureus, Bacillus subtilis, Serratia marcescens (gram-positive), and Pseudomonas aeruginosa, and Escherichia coli (gram-negative) bacteria. The result shows the significant increase in the antibacterial activity of the ligand, metal, and ciprofloxacin on complexation. The interaction of the complexes with pBR322 DNA has been investigated using spectroscopic, gel electrophoresis, and viscometric techniques. This shows that the complexes can bind to pBR322 DNA by the intercalative mode. The superoxide dismutase-like activity of the complexes has been determined.

  17. Social coordination in animal vocal interactions. Is there any evidence of turn-taking? The starling as an animal model.

    Science.gov (United States)

    Henry, Laurence; Craig, Adrian J F K; Lemasson, Alban; Hausberger, Martine

    2015-01-01

    Turn-taking in conversation appears to be a common feature in various human cultures and this universality raises questions about its biological basis and evolutionary trajectory. Functional convergence is a widespread phenomenon in evolution, revealing sometimes striking functional similarities between very distant species even though the mechanisms involved may be different. Studies on mammals (including non-human primates) and bird species with different levels of social coordination reveal that temporal and structural regularities in vocal interactions may depend on the species' social structure. Here we test the hypothesis that turn-taking and associated rules of conversations may be an adaptive response to the requirements of social life, by testing the applicability of turn-taking rules to an animal model, the European starling. Birdsong has for many decades been considered as one of the best models of human language and starling songs have been well described in terms of vocal production and perception. Starlings do have vocal interactions where alternating patterns predominate. Observational and experimental data on vocal interactions reveal that (1) there are indeed clear temporal and structural regularities, (2) the temporal and structural patterning is influenced by the immediate social context, the general social situation, the individual history, and the internal state of the emitter. Comparison of phylogenetically close species of Sturnids reveals that the alternating pattern of vocal interactions varies greatly according to the species' social structure, suggesting that interactional regularities may have evolved together with social systems. These findings lead to solid bases of discussion on the evolution of communication rules in relation to social evolution. They will be discussed also in terms of processes, at the light of recent neurobiological findings.

  18. Gaia-GOSA: An interactive service for coordination of asteroid observation campaigns

    Science.gov (United States)

    Santana-Ros, Toni; Bartczak, Przemyslaw; Michalowski, Tadeusz; Marciniak, Anna; Butkiewicz-Bak, Magda; Dudziński, Grzegorz

    2016-10-01

    We describe the Gaia-Ground-based Observational Service for Asteroids (www.gaiagosa.eu), which is a website aiming to facilitate asteroid observers in contributing to the Gaia mission by gathering lightcurves of selected targets.There are many asteroids which lightcurves cannot be covered during one observing run, like slow rotators,with periods longer than 12 hours. There are also targets with periods commensurate with the Earth's day, sotheir lightcurves cannot be covered by observing from one site only. There are also targets of special interest,like binary objects, where a large amount of data is needed. For all targets like those mentioned above, acoordination of observers is needed, also to avoid unnecessary duplication of data gathering.To that end we have created Gaia-GOSA, a web service which allows coordination between observers, focuseson interesting targets and may avoid observers to unnecessary gather data of the same object at the sametime. Furthermore, it is not necessary to be an advanced observer to contribute to the project. The websiteprepares the observing plan, providing all the necessary information to point your telescope. Thesubscription is free and observers with any level of experience are welcome.All the data gathered by Gaia-GOSA users will be reduced and analyzed by astronomers from the Astronomical Observatory of Adam Mickiewicz University in Poznan (AO AMU). The resulting catalogue, containing all the lightcurves obtained, will be used to enhance the results of the Gaia (cornerstone European Space Agency's mission) inversion algorithm.The project has been developed under funding from the European Space Agency (ESA) and initially was only devoted to help users in planning photometric observations of asteroids. However, in this poster we also present an extended version of the website, which also aims to publish predictions of stellar occultations for selected targets. This work has been done in the framework of the Small Bodies: Near

  19. Quantitative micro-CT based coronary artery profiling using interactive local thresholding and cylindrical coordinates.

    Science.gov (United States)

    Panetta, Daniele; Pelosi, Gualtiero; Viglione, Federica; Kusmic, Claudia; Terreni, Marianna; Belcari, Nicola; Guerra, Alberto Del; Athanasiou, Lambros; Exarchos, Themistoklis; Fotiadis, Dimitrios I; Filipovic, Nenad; Trivella, Maria Giovanna; Salvadori, Piero A; Parodi, Oberdan

    2015-01-01

    Micro-CT is an established imaging technique for high-resolution non-destructive assessment of vascular samples, which is gaining growing interest for investigations of atherosclerotic arteries both in humans and in animal models. However, there is still a lack in the definition of micro-CT image metrics suitable for comprehensive evaluation and quantification of features of interest in the field of experimental atherosclerosis (ATS). A novel approach to micro-CT image processing for profiling of coronary ATS is described, providing comprehensive visualization and quantification of contrast agent-free 3D high-resolution reconstruction of full-length artery walls. Accelerated coronary ATS has been induced by high fat cholesterol-enriched diet in swine and left coronary artery (LCA) harvested en bloc for micro-CT scanning and histologic processing. A cylindrical coordinate system has been defined on the image space after curved multiplanar reformation of the coronary vessel for the comprehensive visualization of the main vessel features such as wall thickening and calcium content. A novel semi-automatic segmentation procedure based on 2D histograms has been implemented and the quantitative results validated by histology. The potentiality of attenuation-based micro-CT at low kV to reliably separate arterial wall layers from adjacent tissue as well as identify wall and plaque contours and major tissue components has been validated by histology. Morphometric indexes from histological data corresponding to several micro-CT slices have been derived (double observer evaluation at different coronary ATS stages) and highly significant correlations (R2 > 0.90) evidenced. Semi-automatic morphometry has been validated by double observer manual morphometry of micro-CT slices and highly significant correlations were found (R2 > 0.92). The micro-CT methodology described represents a handy and reliable tool for quantitative high resolution and contrast agent free full length

  20. Secondary interactions or ligand scrambling? Subtle steric effects govern the iridium(I) coordination chemistry of phosphoramidite ligands.

    Science.gov (United States)

    Osswald, Tina; Rüegger, Heinz; Mezzetti, Antonio

    2010-01-25

    The like and unlike isomers of phosphoramidite (P*) ligands are found to react differently with iridium(I), which is a key to explaining the apparently inconsistent results obtained by us and other research groups in a variety of catalytic reactions. Thus, the unlike diastereoisomer (aR,S,S)-[IrCl(cod)(1 a)] (2 a; cod=1,5-cyclooctadiene, 1 a=(aR,S,S)-(1,1'-binaphthalene)-2,2'-diyl bis(1-phenylethyl)phosphoramidite) forms, upon chloride abstraction, the monosubstituted complex (aR,S,S)-[Ir(cod)(1,2-eta-1 a,kappaP)](+) (3 a), which contains a chelating P* ligand that features an eta(2) interaction between a dangling phenyl group and iridium. Under analogous conditions, the like analogue (aR,R,R)-1 a' gives the disubstituted species (aR,R,R)-[Ir(cod)(1 a',kappaP)(2)](+) (4 a') with monodentate P* ligands. The structure of 3 a was assessed by a combination of X-ray and NMR spectroscopic studies, which indicate that it is the configuration of the binaphthol moiety (and not that of the dangling benzyl N groups) that determines the configuration of the complex. The effect of the relative configuration of the P* ligand on its iridium(I) coordination chemistry is discussed in the context of our preliminary catalytic results and of apparently random results obtained by other groups in the iridium(I)-catalyzed asymmetric allylic alkylation of allylic acetates and in rhodium(I)-catalyzed asymmetric cycloaddition reactions. Further studies with the unlike ligand (aS,R,R)-(1,1'-binaphthalene)-2,2'-diyl bis{[1-(1-naphthalene-1-yl)ethyl]phosphoramidite} (1 b) showed a yet different coordination mode, that is, the eta(4)-arene-metal interaction in (aS,R,R)-[Ir(cod)(1,2,3,4-eta-1 b,kappaP)](+) (3 b).

  1. Coordination and redox properties of copper interaction with α-synuclein.

    Science.gov (United States)

    Valensin, Daniela; Dell'Acqua, Simone; Kozlowski, Henryk; Casella, Luigi

    2016-10-01

    Parkinson's disease (PD) is a severe neurodegenerative disorder affecting movements. After Alzheimer's disease, it is the most common form of neurodegeneration. PD is characterized by the loss of neurons producing dopamine and by the presence of protein aggregates in the brain, known as Lewy bodies. The main constituent of Lewy bodies is the misfolded form of α-synuclein (αSyn), able to form oligomers and fibrils. In addition to protein aggregation, brain damage induced by oxidative stress, is also a frequent phenomenon in PD. αSyn is able to bind Copper ions in both Cu(II) and Cu(I) oxidation states. The metal binding is also maintained when αSyn interacts with membranes. Interestingly, copper binding to αSyn has strong impact either in protein misfolding or in free radical formation, such to provide a link between protein aggregation and oxidative damage. In this review the role of copper and αSyn in PD is discussed with a particular emphasis to elucidate (i) the interaction between copper and αSyn; (ii) the reactivity and (iii) potential toxicity associated with copper-αSyn complexes.

  2. Kinesin-12 motors cooperate to suppress microtubule catastrophes and drive the formation of parallel microtubule bundles.

    Science.gov (United States)

    Drechsler, Hauke; McAinsh, Andrew D

    2016-03-22

    Human Kinesin-12 (hKif15) plays a crucial role in assembly and maintenance of the mitotic spindle. These functions of hKif15 are partially redundant with Kinesin-5 (Eg5), which can cross-link and drive the extensile sliding of antiparallel microtubules. Although both motors are known to be tetramers, the functional properties of hKif15 are less well understood. Here we reveal how single or multiple Kif15 motors can cross-link, transport, and focus the plus-ends of intersecting microtubules. During transport, Kif15 motors step simultaneously along both microtubules with relative microtubule transport driven by a velocity differential between motor domain pairs. Remarkably, this differential is affected by the underlying intersection geometry: the differential is low on parallel and extreme on antiparallel microtubules where one motor domain pair becomes immobile. As a result, when intersecting microtubules are antiparallel, canonical transport of one microtubule along the other is allowed because one motor is firmly attached to one microtubule while it is stepping on the other. When intersecting microtubules are parallel, however, Kif15 motors can drive (biased) parallel sliding because the motor simultaneously steps on both microtubules that it cross-links. These microtubule rearrangements will focus microtubule plus-ends and finally lead to the formation of parallel bundles. At the same time, Kif15 motors cooperate to suppress catastrophe events at polymerizing microtubule plus-ends, raising the possibility that Kif15 motors may synchronize the dynamics of bundles that they have assembled. Thus, Kif15 is adapted to operate on parallel microtubule substrates, a property that clearly distinguishes it from the other tetrameric spindle motor, Eg5.

  3. Mobility of Taxol in Microtubule Bundles

    Science.gov (United States)

    Ross, J.

    2003-06-01

    Mobility of taxol inside microtubules was investigated using fluorescence recovery after photobleaching (FRAP) on flow-aligned bundles. Bundles were made of microtubules with either GMPCPP or GTP at the exchangeable site on the tubulin dimer. Recovery times were sensitive to bundle thickness and packing, indicating that taxol molecules are able to move laterally through the bundle. The density of open binding sites along a microtubule was varied by controlling the concentration of taxol in solution for GMPCPP samples. With > 63% sites occupied, recovery times were independent of taxol concentration and, therefore, inversely proportional to the microscopic dissociation rate, k_{off}. It was found that 10*k_{off} (GMPCPP) ~ k_{off} (GTP), consistent with, but not fully accounting for, the difference in equilibrium constants for taxol on GMPCPP and GTP microtubules. With taxol along the microtubule interior is hindered by rebinding events when open sites are within ~7 nm of each other.

  4. Coordinate regulation of G protein signaling via dynamic interactions of receptor and GAP.

    Directory of Open Access Journals (Sweden)

    Marc Turcotte

    Full Text Available Signal output from receptor-G-protein-effector modules is a dynamic function of the nucleotide exchange activity of the receptor, the GTPase-accelerating activity of GTPase-activating proteins (GAPs, and their interactions. GAPs may inhibit steady-state signaling but may also accelerate deactivation upon removal of stimulus without significantly inhibiting output when the receptor is active. Further, some effectors (e.g., phospholipase C-beta are themselves GAPs, and it is unclear how such effectors can be stimulated by G proteins at the same time as they accelerate G protein deactivation. The multiple combinations of protein-protein associations and interacting regulatory effects that allow such complex behaviors in this system do not permit the usual simplifying assumptions of traditional enzyme kinetics and are uniquely subject to systems-level analysis. We developed a kinetic model for G protein signaling that permits analysis of both interactive and independent G protein binding and regulation by receptor and GAP. We evaluated parameters of the model (all forward and reverse rate constants by global least-squares fitting to a diverse set of steady-state GTPase measurements in an m1 muscarinic receptor-G(q-phospholipase C-beta1 module in which GTPase activities were varied by approximately 10(4-fold. We provide multiple tests to validate the fitted parameter set, which is consistent with results from the few previous pre-steady-state kinetic measurements. Results indicate that (1 GAP potentiates the GDP/GTP exchange activity of the receptor, an activity never before reported; (2 exchange activity of the receptor is biased toward replacement of GDP by GTP; (3 receptor and GAP bind G protein with negative cooperativity when G protein is bound to either GTP or GDP, promoting rapid GAP binding and dissociation; (4 GAP indirectly stabilizes the continuous binding of receptor to G protein during steady-state GTPase hydrolysis, thus further

  5. Histone Chaperone FACT Coordinates Nucleosome Interaction through Multiple Synergistic Binding Events*

    Science.gov (United States)

    Winkler, Duane D.; Muthurajan, Uma M.; Hieb, Aaron R.; Luger, Karolin

    2011-01-01

    In eukaryotic cells, DNA maintenance requires ordered disassembly and re-assembly of chromatin templates. These processes are highly regulated and require extrinsic factors such as chromatin remodelers and histone chaperones. The histone chaperone FACT (facilitates chromatin transcription) is a large heterodimeric complex with roles in transcription, replication, and repair. FACT promotes and subsequently restricts access to DNA as a result of dynamic nucleosome reorganization. However, until now, there lacked a truly quantitative assessment of the critical contacts mediating FACT function. Here, we demonstrate that FACT binds histones, DNA, and intact nucleosomes at nanomolar concentrations. We also determine roles for the histone tails in free histone and nucleosome binding by FACT. Furthermore, we propose that the conserved acidic C-terminal domain of the FACT subunit Spt16 actively displaces nucleosomal DNA to provide access to the histone octamer. Experiments with tri-nucleosome arrays indicate a possible mode for FACT binding within chromatin. Together, the data reveal that specific FACT subunits synchronize interactions with various target sites on individual nucleosomes to generate a high affinity binding event and promote reorganization. PMID:21969370

  6. Histone chaperone FACT coordinates nucleosome interaction through multiple synergistic binding events.

    Science.gov (United States)

    Winkler, Duane D; Muthurajan, Uma M; Hieb, Aaron R; Luger, Karolin

    2011-12-02

    In eukaryotic cells, DNA maintenance requires ordered disassembly and re-assembly of chromatin templates. These processes are highly regulated and require extrinsic factors such as chromatin remodelers and histone chaperones. The histone chaperone FACT (facilitates chromatin transcription) is a large heterodimeric complex with roles in transcription, replication, and repair. FACT promotes and subsequently restricts access to DNA as a result of dynamic nucleosome reorganization. However, until now, there lacked a truly quantitative assessment of the critical contacts mediating FACT function. Here, we demonstrate that FACT binds histones, DNA, and intact nucleosomes at nanomolar concentrations. We also determine roles for the histone tails in free histone and nucleosome binding by FACT. Furthermore, we propose that the conserved acidic C-terminal domain of the FACT subunit Spt16 actively displaces nucleosomal DNA to provide access to the histone octamer. Experiments with tri-nucleosome arrays indicate a possible mode for FACT binding within chromatin. Together, the data reveal that specific FACT subunits synchronize interactions with various target sites on individual nucleosomes to generate a high affinity binding event and promote reorganization.

  7. Autoinhibition of TBCB regulates EB1-mediated microtubule dynamics.

    Science.gov (United States)

    Carranza, Gerardo; Castaño, Raquel; Fanarraga, Mónica L; Villegas, Juan Carlos; Gonçalves, João; Soares, Helena; Avila, Jesus; Marenchino, Marco; Campos-Olivas, Ramón; Montoya, Guillermo; Zabala, Juan Carlos

    2013-01-01

    Tubulin cofactors (TBCs) participate in the folding, dimerization, and dissociation pathways of the tubulin dimer. Among them, TBCB and TBCE are two CAP-Gly domain-containing proteins that together efficiently interact with and dissociate the tubulin dimer. In the study reported here we showed that TBCB localizes at spindle and midzone microtubules during mitosis. Furthermore, the motif DEI/M-COO(-) present in TBCB, which is similar to the EEY/F-COO(-) element characteristic of EB proteins, CLIP-170, and α-tubulin, is required for TBCE-TBCB heterodimer formation and thus for tubulin dimer dissociation. This motif is responsible for TBCB autoinhibition, and our analysis suggests that TBCB is a monomer in solution. Mutants of TBCB lacking this motif are derepressed and induce microtubule depolymerization through an interaction with EB1 associated with microtubule tips. TBCB is also able to bind to the chaperonin complex CCT containing α-tubulin, suggesting that it could escort tubulin to facilitate its folding and dimerization, recycling or degradation.

  8. Allosteric interactions coordinate catalytic activity between successive metabolic enzymes in the tryptophan synthase bienzyme complex.

    Science.gov (United States)

    Brzović, P S; Ngo, K; Dunn, M F

    1992-04-21

    Tryptophan synthase from enteric bacteria is an alpha 2 beta 2 bienzyme complex that catalyzes the final two reactions in the biosynthesis of L-tryptophan (L-Trp) from 3-indole-D-glycerol 3'-phosphate (IGP) and L-serine (L-Ser). The bienzyme complex exhibits reciprocal ligand-mediated allosteric interactions between the heterologous subunits [Houben, K., & Dunn, M. F. (1990) Biochemistry 29, 2421-2429], but the relationship between allostery and catalysis had not been completely defined. We have utilized rapid-scanning stopped-flow (RSSF) UV-visible spectroscopy to study the relationship between allostery and catalysis in the alpha beta-reaction catalyzed by the bienzyme complex from Salmonella typhimurium. The pre-steady-state spectral changes that occur when L-Ser and IGP are mixed simultaneously with the alpha 2 beta 2 complex show that IGP binding to the alpha-site accelerates the formation of alpha-aminoacrylate [E(A-A)] from L-Ser at the beta-site. Through the use of L-Ser analogues, we show herein that the formation of the E(A-A) intermediate is the chemical signal which triggers the conformational transition that activates the alpha-subunit. beta-subunit ligands, such as L-Trp, that react to form covalent intermediates at the beta-site, but are incapable of E(A-A) formation, do not stimulate the activity of the alpha-subunit. Titration experiments show that the affinity of G3P and GP at the alpha-site is dependent upon the nature of the chemical intermediate present at the beta-active site.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. A Preliminary Study on the Use of Haptic Feedback to Assist Users with Impaired Arm Coordination During Mouse Interactions

    Directory of Open Access Journals (Sweden)

    N. G. Tsagarakis

    2011-01-01

    Full Text Available Physical movement impairments caused by central nervous system dysfunction or by muscle spasms generated from other neurological damage or dysfunction can often make it difficult or impossible for affected individuals to interact with computer generated environments using the conventional mouse interfaces. This work investigates the use of a 2 dimensional haptic device as an assistive robotic aid to minimize the effects of the pathological absence of motor control on the upper limb in impaired users while using a mouse interface. The haptic system used in this research is a two degree of freedom (DOF Pantograph planar device. To detect the intended user motion, the device is equipped with force sensing allowing the monitoring of the user applied loads. Impedance based techniques are used to develop a “clumsy” motion suppression control system. The erratic motion suppression techniques and the experimental system setup are evaluated in two dimensional tracking tasks using a human subject with failure of the gross coordination of the upper limb muscle movements resulting from a disorder called ‘Muscle Ataxia’. The results presented demonstrate the ability of the system to improve the tracking performance of the impaired user while interacting with a simple computer generated 2D space.

  10. Interaction of Imidazole Containing Hydroxamic Acids with Fe(III: Hydroxamate Versus Imidazole Coordination of the Ligands

    Directory of Open Access Journals (Sweden)

    Etelka Farkas

    2007-01-01

    Full Text Available Solution equilibrium studies on Fe(III complexes formed with imidazole-4-carbohydroxamic acid (Im-4-Cha, N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha, imidazole-4-acetohydroxamic acid (Im-4-Aha, and histidinehydroxamic acid (Hisha have been performed by using pH-potentiometry, UV-visible spectrophotometry, EPR, ESI-MS, and H-NMR methods. All of the obtained results demonstrate that the imidazole moiety is able to play an important role very often in the interaction with Fe(III, even if this metal ion prefers the hydroxamate chelates very much. If the imidazole moiety is in α-position to the hydroxamic one (Im-4-Cha and N-Me-Im-4-Cha its coordination to the metal ion is indicated unambiguously by our results. Interestingly, parallel formation of (Nimidazole, Ohydroxamate, and (Ohydroxamate, Ohydroxamate type chelates seems probable with N-Me-Im-4-Cha. The imidazole is in β-position to the hydroxamic moiety in Im-4-Aha and an intermolecular noncovalent (mainly H-bonding interaction seems to organize the intermediate-protonated molecules in this system. Following the formation of mono- and bishydroxamato mononuclear complexes, only EPR silent species exists in the Fe(III-Hisha system above pH 4, what suggests the rather significant “assembler activity” of the imidazole (perhaps together with the ammonium moiety.

  11. Interaction of imidazole containing hydroxamic acids with Fe(III): hydroxamate versus imidazole coordination of the ligands.

    Science.gov (United States)

    Farkas, Etelka; Bátka, Dávid; Csóka, Hajnalka; Nagy, Nóra V

    2007-01-01

    Solution equilibrium studies on Fe(III) complexes formed with imidazole-4-carbohydroxamic acid (Im-4-Cha), N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha), imidazole-4-acetohydroxamic acid (Im-4-Aha), and histidinehydroxamic acid (Hisha) have been performed by using pH-potentiometry, UV-visible spectrophotometry, EPR, ESI-MS, and H1-NMR methods. All of the obtained results demonstrate that the imidazole moiety is able to play an important role very often in the interaction with Fe(III), even if this metal ion prefers the hydroxamate chelates very much. If the imidazole moiety is in alpha-position to the hydroxamic one (Im-4-Cha and N-Me-Im-4-Cha) its coordination to the metal ion is indicated unambiguously by our results. Interestingly, parallel formation of (Nimidazole, Ohydroxamate), and (Ohydroxamate, Ohydroxamate) type chelates seems probable with N-Me-Im-4-Cha. The imidazole is in beta-position to the hydroxamic moiety in Im-4-Aha and an intermolecular noncovalent (mainly H-bonding) interaction seems to organize the intermediate-protonated molecules in this system. Following the formation of mono- and bishydroxamato mononuclear complexes, only EPR silent species exists in the Fe(III)-Hisha system above pH 4, what suggests the rather significant "assembler activity" of the imidazole (perhaps together with the ammonium moiety).

  12. LARG and mDia1 link Galpha12/13 to cell polarity and microtubule dynamics.

    Science.gov (United States)

    Goulimari, Polyxeni; Knieling, Helga; Engel, Ulrike; Grosse, Robert

    2008-01-01

    Regulation of cell polarity is a process observed in all cells. During directed migration, cells orientate their microtubule cytoskeleton and the microtubule-organizing-center (MTOC), which involves integrins and downstream Cdc42 and glycogen synthase kinase-3beta activity. However, the contribution of G protein-coupled receptor signal transduction for MTOC polarity is less well understood. Here, we report that the heterotrimeric Galpha(12) and Galpha(13) proteins are necessary for MTOC polarity and microtubule dynamics based on studies using Galpha(12/13)-deficient mouse embryonic fibroblasts. Cell polarization involves the Galpha(12/13)-interacting leukemia-associated RhoGEF (LARG) and the actin-nucleating diaphanous formin mDia1. Interestingly, LARG associates with pericentrin and localizes to the MTOC and along microtubule tracks. We propose that Galpha(12/13) proteins exert essential functions linking extracellular signals to microtubule dynamics and cell polarity via RhoGEF and formin activity.

  13. Cytosolic Proteins From Tobacco Pollen Tubes That Crosslink Microtubules and Actin Filaments In Vitro Are Metabolic Enzymes

    NARCIS (Netherlands)

    Romagnoli, Silvia; Faleri, Claudia; Bini, Luca; Baskin, Tobias I.; Cresti, Mauro

    2010-01-01

    In plant cells, many processes require cooperative action of both microtubules and actin filaments, but proteins mediating interactions between these cytoskeletal members are mostly undiscovered. Here, we attempt to identify such proteins by affinity purification. Cytosol from Nicotiana tabacum (tob

  14. An epigenetic regulator emerges as microtubule minus-end binding and stabilizing factor in mitosis.

    Science.gov (United States)

    Meunier, Sylvain; Shvedunova, Maria; Van Nguyen, Nhuong; Avila, Leonor; Vernos, Isabelle; Akhtar, Asifa

    2015-08-05

    The evolutionary conserved NSL complex is a prominent epigenetic regulator controlling expression of thousands of genes. Here we uncover a novel function of the NSL complex members in mitosis. As the cell enters mitosis, KANSL1 and KANSL3 undergo a marked relocalisation from the chromatin to the mitotic spindle. By stabilizing microtubule minus ends in a RanGTP-dependent manner, they are essential for spindle assembly and chromosome segregation. Moreover, we identify KANSL3 as a microtubule minus-end-binding protein, revealing a new class of mitosis-specific microtubule minus-end regulators. By adopting distinct functions in interphase and mitosis, KANSL proteins provide a link to coordinate the tasks of faithful expression and inheritance of the genome during different phases of the cell cycle.

  15. Alkoxide coordination of iron(III) protoporphyrin IX by antimalarial quinoline methanols: a key interaction observed in the solid-state and solution.

    Science.gov (United States)

    Gildenhuys, Johandie; Sammy, Chandre J; Müller, Ronel; Streltsov, Victor A; le Roex, Tanya; Kuter, David; de Villiers, Katherine A

    2015-10-14

    The quinoline methanol antimalarial drug mefloquine is a structural analogue of the Cinchona alkaloids, quinine and quinidine. We have elucidated the single crystal X-ray diffraction structure of the complexes formed between racemic erythro mefloquine and ferriprotoporphyrin IX (Fe(iii)PPIX) and show that alkoxide coordination is a key interaction in the solid-state. Mass spectrometry confirms the existence of coordination complexes of quinine, quinidine and mefloquine to Fe(iii)PPIX in acetonitrile. The length of the iron(iii)-O bond in the quinine and quinidine complexes as determined by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy unequivocally confirms that coordination of the quinoline methanol compounds to Fe(iii)PPIX occurs in non-aqueous aprotic solution via their benzylic alkoxide functional group. UV-visible spectrophotometric titrations of the low-spin bis-pyridyl-Fe(iii)PPIX complex with each of the quinoline methanol compounds results in the displacement of a single pyridine molecule and subsequent formation of a six-coordinate pyridine-Fe(iii)PPIX-drug complex. We propose that formation of the drug-Fe(iii)PPIX coordination complexes is favoured in a non-aqueous environment, such as that found in lipid bodies or membranes in the malaria parasite, and that their existence may contribute to the mechanism of haemozoin inhibition or other toxicity effects that lead ultimately to parasite death. In either case, coordination is a key interaction to be considered in the design of novel antimalarial drug candidates.

  16. A Systems Biology Approach to the Coordination of Defensive and Offensive Molecular Mechanisms in the Innate and Adaptive Host-Pathogen Interaction Networks.

    Science.gov (United States)

    Wu, Chia-Chou; Chen, Bor-Sen

    2016-01-01

    Infected zebrafish coordinates defensive and offensive molecular mechanisms in response to Candida albicans infections, and invasive C. albicans coordinates corresponding molecular mechanisms to interact with the host. However, knowledge of the ensuing infection-activated signaling networks in both host and pathogen and their interspecific crosstalk during the innate and adaptive phases of the infection processes remains incomplete. In the present study, dynamic network modeling, protein interaction databases, and dual transcriptome data from zebrafish and C. albicans during infection were used to infer infection-activated host-pathogen dynamic interaction networks. The consideration of host-pathogen dynamic interaction systems as innate and adaptive loops and subsequent comparisons of inferred innate and adaptive networks indicated previously unrecognized crosstalk between known pathways and suggested roles of immunological memory in the coordination of host defensive and offensive molecular mechanisms to achieve specific and powerful defense against pathogens. Moreover, pathogens enhance intraspecific crosstalk and abrogate host apoptosis to accommodate enhanced host defense mechanisms during the adaptive phase. Accordingly, links between physiological phenomena and changes in the coordination of defensive and offensive molecular mechanisms highlight the importance of host-pathogen molecular interaction networks, and consequent inferences of the host-pathogen relationship could be translated into biomedical applications.

  17. Decoherence Time of a Microtubule

    CERN Document Server

    Hiramatsu, T; Sakakibara, K; Hiramatsu, Takashi; Matsui, Tetsuo; Sakakibara, Kazuhiko

    2006-01-01

    We formulate and study a quantum field theory of a microtubule, a basic element of living cells. Following the quantum theory of consciousness by Hameroff and Penrose, we let the system to make self-reductions, and measure the decoherence time $\\tau_N$ (the mean interval between two successive reductions) of a cluster consisting of more than $N$ neighboring cells (tubulins). $\\tau_N$ is interpreted as an instance of the stream of consciousness. For a sufficiently small electron hopping amplitude, $\\tau_N$ obeys an exponential law, $\\tau_N \\sim \\exp(c' N)$, and may take realistic values $\\tau_N $ \\raisebox{-0.5ex} {$\\stackrel{>}{\\sim}$} $ 10^{-2}$ sec for $N \\raisebox{-0.5ex} {$\\stackrel{>}{\\sim}$} 1100$.

  18. ATPase Cycle of the Nonmotile Kinesin NOD Allows Microtubule End Tracking and Drives Chromosome Movement

    Energy Technology Data Exchange (ETDEWEB)

    Cochran, J.; Sindelar, C; Mulko, N; Collins, K; Kong, S; Hawley, R; Kull, F

    2009-01-01

    Segregation of nonexchange chromosomes during Drosophila melanogaster meiosis requires the proper function of NOD, a nonmotile kinesin-10. We have determined the X-ray crystal structure of the NOD catalytic domain in the ADP- and AMPPNP-bound states. These structures reveal an alternate conformation of the microtubule binding region as well as a nucleotide-sensitive relay of hydrogen bonds at the active site. Additionally, a cryo-electron microscopy reconstruction of the nucleotide-free microtubule-NOD complex shows an atypical binding orientation. Thermodynamic studies show that NOD binds tightly to microtubules in the nucleotide-free state, yet other nucleotide states, including AMPPNP, are weakened. Our pre-steady-state kinetic analysis demonstrates that NOD interaction with microtubules occurs slowly with weak activation of ADP product release. Upon rapid substrate binding, NOD detaches from the microtubule prior to the rate-limiting step of ATP hydrolysis, which is also atypical for a kinesin. We propose a model for NOD's microtubule plus-end tracking that drives chromosome movement.

  19. Kar3Vik1 uses a minus-end directed powerstroke for movement along microtubules.

    Directory of Open Access Journals (Sweden)

    Julia Cope

    Full Text Available We have used cryo-electron microscopy (cryo-EM and helical averaging to examine the 3-D structure of the heterodimeric kinesin-14 Kar3Vik1 complexed to microtubules at a resolution of 2.5 nm. 3-D maps were obtained at key points in Kar3Vik1's nucleotide hydrolysis cycle to gain insight into the mechanism that this motor uses for retrograde motility. In all states where Kar3Vik1 maintained a strong interaction with the microtubule, we found, as observed by cryo-EM, that the motor bound with one head domain while the second head extended outwards. 3-D reconstructions of Kar3Vik1-microtubule complexes revealed that in the nucleotide-free state, the motor's coiled-coil stalk points toward the plus-end of the microtubule. In the ATP-state, the outer head is shown to undergo a large rotation that reorients the stalk ∼75° to point toward the microtubule minus-end. To determine which of the two heads binds to tubulin in each nucleotide state, we employed specific Nanogold®-labeling of Vik1. The resulting maps confirmed that in the nucleotide-free, ATP and ADP+Pi states, Kar3 maintains contact with the microtubule surface, while Vik1 extends away from the microtubule and tracks with the coiled-coil as it rotates towards the microtubule minus-end. While many previous investigations have focused on the mechanisms of homodimeric kinesins, this work presents the first comprehensive study of the powerstroke of a heterodimeric kinesin. The stalk rotation shown here for Kar3Vik1 is highly reminiscent of that reported for the homodimeric kinesin-14 Ncd, emphasizing the conservation of a mechanism for minus-end directed motility.

  20. A mechanism for reorientation of cortical microtubule arrays driven by microtubule severing.

    Science.gov (United States)

    Lindeboom, Jelmer J; Nakamura, Masayoshi; Hibbel, Anneke; Shundyak, Kostya; Gutierrez, Ryan; Ketelaar, Tijs; Emons, Anne Mie C; Mulder, Bela M; Kirik, Viktor; Ehrhardt, David W

    2013-12-06

    Environmental and hormonal signals cause reorganization of microtubule arrays in higher plants, but the mechanisms driving these transitions have remained elusive. The organization of these arrays is required to direct morphogenesis. We discovered that microtubule severing by the protein katanin plays a crucial and unexpected role in the reorientation of cortical arrays, as triggered by blue light. Imaging and genetic experiments revealed that phototropin photoreceptors stimulate katanin-mediated severing specifically at microtubule intersections, leading to the generation of new microtubules at these locations. We show how this activity serves as the basis for a mechanism that amplifies microtubules orthogonal to the initial array, thereby driving array reorientation. Our observations show how severing is used constructively to build a new microtubule array.

  1. A microtubule interactome: complexes with roles in cell cycle and mitosis.

    Directory of Open Access Journals (Sweden)

    Julian R Hughes

    2008-04-01

    Full Text Available The microtubule (MT cytoskeleton is required for many aspects of cell function, including the transport of intracellular materials, the maintenance of cell polarity, and the regulation of mitosis. These functions are coordinated by MT-associated proteins (MAPs, which work in concert with each other, binding MTs and altering their properties. We have used a MT cosedimentation assay, combined with 1D and 2D PAGE and mass spectrometry, to identify over 250 MAPs from early Drosophila embryos. We have taken two complementary approaches to analyse the cellular function of novel MAPs isolated using this approach. First, we have carried out an RNA interference (RNAi screen, identifying 21 previously uncharacterised genes involved in MT organisation. Second, we have undertaken a bioinformatics analysis based on binary protein interaction data to produce putative interaction networks of MAPs. By combining both approaches, we have identified and validated MAP complexes with potentially important roles in cell cycle regulation and mitosis. This study therefore demonstrates that biologically relevant data can be harvested using such a multidisciplinary approach, and identifies new MAPs, many of which appear to be important in cell division.

  2. GIT1 enhances neurite outgrowth by stimulating microtubule assembly

    Institute of Scientific and Technical Information of China (English)

    Yi-sheng Li; Li-xia Qin; Jie Liu; Wei-liang Xia; Jian-ping Li; Hai-lian Shen; Wei-Qiang Gao

    2016-01-01

    GIT1, a G-protein-coupled receptor kinase interacting protein, has been reported to be involved in neurite outgrowth. However, the neu-robiological functions of the protein remain unclear. In this study, we found that GIT1 was highly expressed in the nervous system, and its expression was maintained throughout all stages of neuritogenesis in the brain. In primary cultured mouse hippocampal neurons from GIT1 knockout mice, there was a signiifcant reduction in total neurite length per neuron, as well as in the average length of axon-like struc-tures, which could not be prevented by nerve growth factor treatment. Overexpression of GIT1 signiifcantly promoted axon growth and fully rescued the axon outgrowth defect in the primary hippocampal neuron cultures from GIT1 knockout mice. The GIT1 N terminal region, including the ADP ribosylation factor-GTPase activating protein domain, the ankyrin domains and the Spa2 homology domain, were sufifcient to enhance axonal extension. Importantly, GIT1 bound to many tubulin proteins and microtubule-associated proteins, and it accelerated microtubule assemblyin vitro. Collectively, our ifndings suggest that GIT1 promotes neurite outgrowth, at least partially by stimulating microtubule assembly. This study provides new insight into the cellular and molecular pathogenesis of GIT1-associated neuro-logical diseases.

  3. GIT1 enhances neurite outgrowth by stimulating microtubule assembly

    Directory of Open Access Journals (Sweden)

    Yi-sheng Li

    2016-01-01

    Full Text Available GIT1, a G-protein-coupled receptor kinase interacting protein, has been reported to be involved in neurite outgrowth. However, the neurobiological functions of the protein remain unclear. In this study, we found that GIT1 was highly expressed in the nervous system, and its expression was maintained throughout all stages of neuritogenesis in the brain. In primary cultured mouse hippocampal neurons from GIT1 knockout mice, there was a significant reduction in total neurite length per neuron, as well as in the average length of axon-like structures, which could not be prevented by nerve growth factor treatment. Overexpression of GIT1 significantly promoted axon growth and fully rescued the axon outgrowth defect in the primary hippocampal neuron cultures from GIT1 knockout mice. The GIT1 N terminal region, including the ADP ribosylation factor-GTPase activating protein domain, the ankyrin domains and the Spa2 homology domain, were sufficient to enhance axonal extension. Importantly, GIT1 bound to many tubulin proteins and microtubule-associated proteins, and it accelerated microtubule assembly in vitro. Collectively, our findings suggest that GIT1 promotes neurite outgrowth, at least partially by stimulating microtubule assembly. This study provides new insight into the cellular and molecular pathogenesis of GIT1-associated neurological diseases.

  4. Of "Ens" "n" "Ands": Observations on the Phonetic Make-Up of a Coordinator and Its Uses in Talk-in-Interaction

    Science.gov (United States)

    Barth-Weingarten, Dagmar

    2012-01-01

    In grammar books, the various functions of "and" as phrasal coordinator and clausal conjunction are treated as standard knowledge. In addition, studies on the uses of "and" in everyday talk-in-interaction have described its discourse-organizational functions on a more global level. In the phonetic literature, in turn, a range of phonetic forms of…

  5. Acid-base characterization, coordination properties towards copper(II) ions and DNA interaction studies of ribavirin, an antiviral drug.

    Science.gov (United States)

    Nagaj, Justyna; Starosta, Radosław; Jeżowska-Bojczuk, Małgorzata

    2015-01-01

    We have studied processes of copper(II) ion binding by ribavirin, an antiviral agent used in treating hepatitis C, which is accompanied usually by an increased copper level in the serum and liver tissue. Protonation equilibria and Cu(II) binding were investigated using the UV-visible, EPR and NMR spectroscopic techniques as well as the DFT (density functional theory) calculations. The spectroscopic data suggest that the first complex is formed in the water solution at pH as low as 0.5. In this compound Cu(II) ion is bound to one of the nitrogen atoms from the triazole ring. Above pH6.0, the metal ion is surrounded by two nitrogen and two oxygen atoms from two ligand molecules. The DFT calculations allowed to determine the exact structure of this complex. We found that in the lowest energy isomer two molecules of the ligand coordinate via O and N4 atoms in trans positions. The hypothetical oxidative properties of the investigated system were also examined. It proved not to generate plasmid DNA scission products. However, the calf thymus (CT)-DNA binding studies showed that it reacts with ribavirin and its cupric complex. Moreover, the interaction with the complex is much more efficient.

  6. Flexible Yttrium Coordination Geometry Inhibits “Bare-Metal” Guest Interactions in the Metal-Organic Framework Y(btc

    Directory of Open Access Journals (Sweden)

    Josie E. Auckett

    2016-10-01

    Full Text Available Y(btc (btc = 1,3,5-benzenetricarboxylate is a metal-organic framework that exhibits significant adsorption of industrially-relevant gases such as H2, CH4, and O2. Previous studies have noted a surprising lack of close interactions between the adsorbed guest molecules and Y, despite the apparent availability of a “bare-metal” binding site. We have extended our previous work in a detailed investigation of the adsorption behaviours of CO2, CD4, and O2 in Y(btc over a range of concentrations using in situ neutron powder diffraction methods. The O–Y–O bond angles enclosing the bare-metal site are found to change considerably depending on the type and quantity of guest molecules present. Multiple binding sites are found for each guest species, and the largest changes in O–Y–O angles are accompanied by changes in the filling sequences of the binding sites, pointing to an important interplay between guest-induced framework distortions and binding site accessibility. These results suggest the potential for coordinatively flexible rare-earth metal centres to promote guest-selective binding in metal-organic frameworks.

  7. Structural comparison of the Caenorhabditis elegans and human Ndc80 complexes bound to microtubules reveals distinct binding behavior

    Science.gov (United States)

    Wilson-Kubalek, Elizabeth M.; Cheeseman, Iain M.; Milligan, Ronald A.

    2016-01-01

    During cell division, kinetochores must remain tethered to the plus ends of dynamic microtubule polymers. However, the molecular basis for robust kinetochore–microtubule interactions remains poorly understood. The conserved four-subunit Ndc80 complex plays an essential and direct role in generating dynamic kinetochore–microtubule attachments. Here we compare the binding of the Caenorhabditis elegans and human Ndc80 complexes to microtubules at high resolution using cryo–electron microscopy reconstructions. Despite the conserved roles of the Ndc80 complex in diverse organisms, we find that the attachment mode of these complexes for microtubules is distinct. The human Ndc80 complex binds every tubulin monomer along the microtubule protofilament, whereas the C. elegans Ndc80 complex binds more tightly to β-tubulin. In addition, the C. elegans Ndc80 complex tilts more toward the adjacent protofilament. These structural differences in the Ndc80 complex between different species may play significant roles in the nature of kinetochore–microtubule interactions. PMID:26941333

  8. One-parameter nonrelativistic supersymmetry for microtubules

    CERN Document Server

    Rosu, H C

    2003-01-01

    The simple supersymmetric model of Caticha [PRA 51, 4264 (1995)], as used by Rosu [PRE 55, 2038 (1997)] for microtubules, is generalized to the case of Mielnik's one-parameter nonrelativistic susy [JMP 25, 3387 (1984)

  9. Synergistic suppression of microtubule dynamics by discodermolide and paclitaxel in non-small cell lung carcinoma cells.

    Science.gov (United States)

    Honore, Stéphane; Kamath, Kathy; Braguer, Diane; Horwitz, Susan Band; Wilson, Leslie; Briand, Claudette; Jordan, Mary Ann

    2004-07-15

    Discodermolide is a new microtubule-targeted antimitotic drug in Phase I clinical trials that, like paclitaxel, stabilizes microtubule dynamics and enhances microtubule polymer mass in vitro and in cells. Despite their apparently similar binding sites on microtubules, discodermolide acts synergistically with paclitaxel to inhibit proliferation of A549 human lung cancer cells (L. Martello et al., Clin. Cancer Res., 6: 1978-1987, 2000). To understand their synergy, we examined the effects of the two drugs singly and in combination in A549 cells and found that, surprisingly, their antiproliferative synergy is related to their ability to synergistically inhibit microtubule dynamic instability and mitosis. The combination of discodermolide and paclitaxel at their antiproliferative IC(50)s (7 nm for discodermolide and 2 nm for paclitaxel) altered all of the parameters of dynamic instability synergistically except the time-based rescue frequency. For example, together the drugs inhibited overall microtubule dynamicity by 71%, but each drug individually inhibited dynamicity by only 24%, giving a combination index (CI) of 0.23. Discodermolide and paclitaxel also synergistically blocked cell cycle progression at G(2)-M (41, 9.6, and 16% for both drugs together, for discodermolide alone, and for paclitaxel alone, respectively; CI = 0.59), and they synergistically enhanced apoptosis (CI = 0.85). Microtubules are unique receptors for drugs. The results suggest that ligands that bind to large numbers of binding sites on an individual microtubule can interact in a poorly understood manner to synergistically suppress microtubule dynamic instability and inhibit both mitosis and cell proliferation, with important consequences for combination clinical therapy with microtubule-targeted drugs.

  10. Exposure of beta-tubulin regions defined by antibodies on an Arabidopsis thaliana microtubule protofilament model and in the cells

    Directory of Open Access Journals (Sweden)

    Sulimenko Tetyana

    2010-02-01

    Full Text Available Abstract Background The function of the cortical microtubules, composed of αβ-tubulin heterodimers, is linked to their organizational state which is subject to spatial and temporal modulation by environmental cues. The role of tubulin posttranslational modifications in these processes is largely unknown. Although antibodies against small tubulin regions represent useful tool for studying molecular configuration of microtubules, data on the exposure of tubulin epitopes on plant microtubules are still limited. Results Using homology modeling we have generated an Arabidopsis thaliana microtubule protofilament model that served for the prediction of surface exposure of five β-tubulin epitopes as well as tyrosine residues. Peptide scans newly disclosed the position of epitopes detected by antibodies 18D6 (β1-10, TUB2.1 (β426-435 and TU-14 (β436-445. Experimental verification of the results by immunofluorescence microscopy revealed that the exposure of epitopes depended on the mode of fixation. Moreover, homology modeling showed that only tyrosines in the C-terminal region of β-tubulins (behind β425 were exposed on the microtubule external side. Immunofluorescence microscopy revealed tyrosine phosphorylation of microtubules in plant cells, implying that β-tubulins could be one of the targets for tyrosine kinases. Conclusions We predicted surface exposure of five β-tubulin epitopes, as well as tyrosine residues, on the surface of A. thaliana microtubule protofilament model, and validated the obtained results by immunofluorescence microscopy on cortical microtubules in cells. The results suggest that prediction of epitope exposure on microtubules by means of homology modeling combined with site-directed antibodies can contribute to a better understanding of the interactions of plant microtubules with associated proteins.

  11. Motor function in interpolar microtubules during metaphase

    OpenAIRE

    Deutsch, J. M.; Lewis, Ian P.

    2013-01-01

    We analyze experimental observations of microtubules undergoing small fluctuations about a "balance point" when mixed in solution of two different kinesin motor proteins, KLP61F and Ncd. It has been proposed that the microtubule movement is due to stochastic variations in the densities of the two species of motor proteins. We test this hypothesis here by showing how it maps onto a one-dimensional random walk in a random environment. Our estimate of the amplitude of the fluctuations agrees wit...

  12. Wave->Diffusion Transition in Microtubules

    OpenAIRE

    2005-01-01

    In this paper the heat transport in microtubules (MT) is investigated. When the dimension of the structure is of the order of the de Broglie wave length the transport phenomena must be analyzed within quantum mechanics. In this paper we developed the Dirac type thermal equation for MT .The solution of the equation-the temperature fields for electrons can be wave type or diffusion type depending on the dynamics of the scattering. Key words: Microtubules ultrashort laser pulses, Dirac thermal e...

  13. Tau neurofibrillary pathology and microtubule stability.

    Science.gov (United States)

    Michaelis, Mary L; Dobrowsky, Rick T; Li, Guibin

    2002-12-01

    We previously reported that nonomolar concentrations of Taxol and several structurally diverse microtubule (MT)-stabilizing agents significantly enhanced the survival of neurons in the presence of fibrils of amyloid beta peptide (Abeta). Pretreatment of neurons with MT-stabilizing drugs also blocked Abeta-induced activation of tau hyperphosphorylation. Although tau is a substrate for several kinases, we initially focused on cdk5, as this tau kinase has been shown to be activated in Abeta-treated neurons and Alzheimer's disease (AD) brain. In an in vitro kinase assay, Taxol inhibited activation of cdk5 by Abeta. In addition, the proposed cellular cascade in which calpain activation leads to cleavage of the cdk5 regulator, p35, to the strong kinase activator p25 was also prevented. Taxol did not directly inhibit the activity of either cdk5 or calpain, indicating that other cellular components are required for the effect of the drug on Abeta activation of tau phosphorylation. Our results suggest that drugs that interact with MTs can alter signaling events in neurons, possibly because some MTs play a role in organizing protein complexes involved in responses to Abeta. Thus the cytoskeletal network may serve as a biosensor of cellular well-being.

  14. The Salmonella effector SseJ disrupts microtubule dynamics when ectopically expressed in normal rat kidney cells

    Science.gov (United States)

    Raines, Sally A.; Hodgkinson, Michael R.; Dowle, Adam A.

    2017-01-01

    Salmonella effector protein SseJ is secreted by Salmonella into the host cell cytoplasm where it can then modify host cell processes. Whilst host cell small GTPase RhoA has previously been shown to activate the acyl-transferase activity of SseJ we show here an un-described effect of SseJ protein production upon microtubule dynamism. SseJ prevents microtubule collapse and this is independent of SseJ’s acyl-transferase activity. We speculate that the effects of SseJ on microtubules would be mediated via its known interactions with the small GTPases of the Rho family. PMID:28235057

  15. A novel p21-activated kinase binds the actin and microtubule networks and induces microtubule stabilization

    Science.gov (United States)

    Cau, Julien; Faure, Sandrine; Comps, Michel; Delsert, Claude; Morin, Nathalie

    2001-01-01

    Coordination of the different cytoskeleton networks in the cell is of central importance for morphogenesis, organelle transport, and motility. The Rho family proteins are well characterized for their effects on the actin cytoskeleton, but increasing evidence indicates that they may also control microtubule (MT) dynamics. Here, we demonstrate that a novel Cdc42/Rac effector, X-p21-activated kinase (PAK)5, colocalizes and binds to both the actin and MT networks and that its subcellular localization is regulated during cell cycle progression. In transfected cells, X-PAK5 promotes the formation of stabilized MTs that are associated in bundles and interferes with MTs dynamics, slowing both the elongation and shrinkage rates and inducing long paused periods. X-PAK5 subcellular localization is regulated tightly, since coexpression with active Rac or Cdc42 induces its shuttling to actin-rich structures. Thus, X-PAK5 is a novel MT-associated protein that may communicate between the actin and MT networks during cellular responses to environmental conditions. PMID:11733543

  16. Facile preparation of robust microcapsules by manipulating metal-coordination interaction between biomineral layer and bioadhesive layer.

    Science.gov (United States)

    Zhang, Lei; Shi, Jiafu; Jiang, Zhongyi; Jiang, Yanjun; Meng, Ruijie; Zhu, Yuanyuan; Liang, Yanpeng; Zheng, Yang

    2011-02-01

    A novel approach combining biomimetic mineralization and bioadhesion is proposed to prepare robust and versatile organic-inorganic hybrid microcapsules. More specifically, these microcapsules are fabricated by sequential deposition of inorganic layer and organic layer on the surface of CaCO(3) microparticles, followed by the dissolution of CaCO(3) microparticles using EDTA. During the preparation process, protamine induces the hydrolysis and condensation of titania or silica precursor to form the inorganic layer or the biomineral layer. The organic layer or bioadhesive layer was formed through the rapid, spontaneous oxidative polymerization of dopamine into polydopamine (PDA) on the surface of the biomineral layer. There exist multiple interactions between the inorganic layer and the organic layer. Thus, the as-prepared organic-inorganic hybrid microcapsules acquire much higher mechanical stability and surface reactivity than pure titania or pure silica microcapsules. Furthermore, protamine/titania/polydopamine hybrid microcapsules display superior mechanical stability to protamine/silica/polydopamine hybrid microcapsules because of the formation of Ti(IV)-catechol coordination complex between the biomineral layer and the bioadhesive layer. As an example of application, three enzymes are respectively immobilized through physical encapsulation in the lumen, in situ entrapment within the wall and chemical attachment on the out surface of the hybrid microcapsules. The as-constructed multienzyme system displays higher catalytic activity and operational stability. Hopefully, the approach developed in this study will evolve as a generic platform for facile and controllable preparation of organic-inorganic hybrid materials with different compositions and shapes for a variety of applications in catalysis, sensor, drug/gene delivery.

  17. Spatiotemporal Regulation of Nuclear Transport Machinery and Microtubule Organization

    Directory of Open Access Journals (Sweden)

    Naoyuki Okada

    2015-08-01

    Full Text Available Spindle microtubules capture and segregate chromosomes and, therefore, their assembly is an essential event in mitosis. To carry out their mission, many key players for microtubule formation need to be strictly orchestrated. Particularly, proteins that assemble the spindle need to be translocated at appropriate sites during mitosis. A small GTPase (hydrolase enzyme of guanosine triphosphate, Ran, controls this translocation. Ran plays many roles in many cellular events: nucleocytoplasmic shuttling through the nuclear envelope, assembly of the mitotic spindle, and reorganization of the nuclear envelope at the mitotic exit. Although these events are seemingly distinct, recent studies demonstrate that the mechanisms underlying these phenomena are substantially the same as explained by molecular interplay of the master regulator Ran, the transport factor importin, and its cargo proteins. Our review focuses on how the transport machinery regulates mitotic progression of cells. We summarize translocation mechanisms governed by Ran and its regulatory proteins, and particularly focus on Ran-GTP targets in fission yeast that promote spindle formation. We also discuss the coordination of the spatial and temporal regulation of proteins from the viewpoint of transport machinery. We propose that the transport machinery is an essential key that couples the spatial and temporal events in cells.

  18. Two lanthanum(III) complexes containing η2-pyrazolate and η2-1,2,4-triazolate ligands: intramolecular C-H...N/O interactions and coordination geometries.

    Science.gov (United States)

    Wang, Yu-Long; Feng, Meng; Tao, Xian; Tang, Qing-Yun; Shen, Ying-Zhong

    2013-01-01

    The lanthanum(III) complexes tris(3,5-diphenylpyrazolato-κ(2)N,N')tris(tetrahydrofuran-κO)lanthanum(III) tetrahydrofuran monosolvate, [La(C(15)H(11)N(2))(3)(C(4)H(8)O)(3)]·C(4)H(8)O, (I), and tris(3,5-diphenyl-1,2,4-triazolato-κ(2)N(1),N(2))tris(tetrahydrofuran-κO)lanthanum(III), [La(C(14)H(10)N(3))(3)(C(4)H(8)O)(3)], (II), both contain La(III) atoms coordinated by three heterocyclic ligands and three tetrahydrofuran ligands, but their coordination geometries differ. Complex (I) has a mer-distorted octahedral geometry, while complex (II) has a fac-distorted configuration. The difference in the coordination geometries and the existence of asymmetric La-N bonding in the two complexes is associated with intramolecular C-H...N/O interactions between the ligands.

  19. The role of microtubule-associated protein 1B in axonal growth and neuronal migration in the central nervous system

    Institute of Scientific and Technical Information of China (English)

    Maoguang Yang; Xiaoyu Yang; Minfei Wu; Peng Xia; Chunxin Wang; Peng Yan; Qi Gao; Jian Liu; Haitao Wang; Xingwei Duan

    2012-01-01

    In this review, we discuss the role of microtubule-associated protein 1B (MAP1B) and its phosphorylation in axonal development and regeneration in the central nervous system. MAP1B exhibits similar functions during axonal development and regeneration. MAP1B and phosphorylated MAP1B in neurons and axons maintain a dynamic balance between cytoskeletal components, and regulate the stability and interaction of microtubules and actin to promote axonal growth, neural connectivity and regeneration in the central nervous system.

  20. Luminal localization of α-tubulin K40 acetylation by cryo-EM analysis of fab-labeled microtubules.

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    Virupakshi Soppina

    Full Text Available The αβ-tubulin subunits of microtubules can undergo a variety of evolutionarily-conserved post-translational modifications (PTMs that provide functional specialization to subsets of cellular microtubules. Acetylation of α-tubulin residue Lysine-40 (K40 has been correlated with increased microtubule stability, intracellular transport, and ciliary assembly, yet a mechanistic understanding of how acetylation influences these events is lacking. Using the anti-acetylated tubulin antibody 6-11B-1 and electron cryo-microscopy, we demonstrate that the K40 acetylation site is located inside the microtubule lumen and thus cannot directly influence events on the microtubule surface, including kinesin-1 binding. Surprisingly, the monoclonal 6-11B-1 antibody recognizes both acetylated and deacetylated microtubules. These results suggest that acetylation induces structural changes in the K40-containing loop that could have important functional consequences on microtubule stability, bending, and subunit interactions. This work has important implications for acetylation and deacetylation reaction mechanisms as well as for interpreting experiments based on 6-11B-1 labeling.

  1. [Disruption of organization of mitotic microtubules in root meristem cells of Allium cepa induced by chloral hydrate].

    Science.gov (United States)

    Smirnova, E A; Svetlitskaia, O M; Chentsov, Iu S

    2002-01-01

    Data are presented on the effect of chlorahydrate on microtubule organization in the root meristem of Allium cepa. Our studies show that an incomplete preprophase band commonly appears during G2-prophase transition, yet the major effect is the lack of perinuclear microtubules, leading to inhibition of the prophase spindle formation and transition to C-mitosis. Upon chloralhydrate treatment of metaphase cells, we found cells with chromosomes regularly aligned within the metaphase plate and differently disorganized mitotic spindles. Concurrently, C-metaphase cells with remnants of kinetochore fibers were present. In addition, normal bipolar and abnormal irregular types of chromosome segregation were detected, this representing multipolar and diffuse anaphases. The major difference between them is the presence of polar microtubules during multipolar anaphase, and their lacking during diffuse anaphase. Alternatively, microtubule clusters between segregated groups of chromosomes are typical for cells with diffuse anaphase. During bipolar anaphase, excessive aster-like microtubules emanate from the spindle poles, and in telophase accessory phragmoplasts are observed at the cell periphery. The formation of incomplete phragmoplasts was observed after normal bipolar and abnormal chromosome segregation. We conclude that chloralhydrate may affect the nuclear surface capability to initiate the growth of perinuclear microtubules, thus blocking the prophase spindle formation. It also disturbs the spatial interaction between microtubules, which is crucial for the formation and functioning of various microtubular systems (preprophase band, spindle and phragmoplast).

  2. Dynamics and regulation of plant interphase microtubules: a comparative view.

    Science.gov (United States)

    Hashimoto, Takashi

    2003-12-01

    Microtubule and actin cytoskeletons are fundamental to a variety of cellular activities within eukaryotic organisms. Extensive information on the dynamics and functions of microtubules, as well as on their regulatory proteins, have been revealed in fungi and animals, and corresponding pictures are now slowly emerging in plants. During interphase, plant cells contain highly dynamic cortical microtubules that organize into ordered arrays, which are apparently regulated by distinct groups of microtubule regulators. Comparison with fungal and animal microtubules highlights both conserved and unique mechanisms for the regulation of the microtubule cytoskeleton in plants.

  3. Sugar-metal ion interactions: the complicated coordination structures of cesium ion with D-ribose and myo-inositol.

    Science.gov (United States)

    Hu, Haijian; Xue, Junhui; Wen, Xiaodong; Li, Weihong; Zhang, Chao; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Bu, Xiaoxia; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

    2013-11-18

    The novel cesium chloride-D-ribose complex (CsCl·C5H10O5; Cs-R) and cesium chloride-myo-inositol complex (CsCl·C6H12O6; Cs-I) have been synthesized and characterized using X-ray diffraction and FTIR, FIR, THz, and Raman spectroscopy. Cs(+) is eight-coordinated to three chloride ions, O1 and O2 from one D-ribose molecule, O1 from another D-ribose molecule, and O4 and O5 from the third D-ribose molecule in Cs-R. For one D-ribose molecule, the oxygen atom O1 in the ring is coordinated to two cesium ions as an oxygen bridge, O2 is cocoordinated with O1 to one of the two cesium ions, and O4 and O5 are coordinated to the third cesium ion, respectively. O3 does not coordinate to metal ions and only takes part in forming hydrogen bonds. One chloride ion is connected to three cesium ions. Thus, a complicated structure of Cs-D-ribose forms. For Cs-I, Cs(+) is 10-coordinated to three chloride ions, O1 and O2 from one myo-inositol molecule, O3 and O4 from another myo-inositol molecule, O5 and O6 from the third myo-inositol molecule, and O6 from the fourth myo-inositol molecule. One metal ion is connected to four ligands, and one myo-inositol is coordinated to four Cs(+) ions, which is also a complicated coordination structure. Crystal structure results, FTIR, FIR, THz, and Raman spectra provide detailed information on the structure and coordination of hydroxyl groups to metal ions in the cesium chloride-D-ribose and cesium chloride-myo-inositol complexes.

  4. Intermediate filament-associated cytolinker plectin 1c destabilizes microtubules in keratinocytes

    Science.gov (United States)

    Valencia, Rocio G.; Walko, Gernot; Janda, Lubomir; Novacek, Jirka; Mihailovska, Eva; Reipert, Siegfried; Andrä-Marobela, Kerstin; Wiche, Gerhard

    2013-01-01

    The transition of microtubules (MTs) from an assembled to a disassembled state plays an essential role in several cellular functions. While MT dynamics are often linked to those of actin filaments, little is known about whether intermediate filaments (IFs) have an influence on MT dynamics. We show here that plectin 1c (P1c), one of the multiple isoforms of the IF-associated cytolinker protein plectin, acts as an MT destabilizer. We found that MTs in P1c-deficient (P1c−/−) keratinocytes are more resistant toward nocodazole-induced disassembly and display increased acetylation. In addition, live imaging of MTs in P1c−/−, as well as in plectin-null, cells revealed decreased MT dynamics. Increased MT stability due to P1c deficiency led to changes in cell shape, increased velocity but loss of directionality of migration, smaller-sized focal adhesions, higher glucose uptake, and mitotic spindle aberrations combined with reduced growth rates of cells. On the basis of ex vivo and in vitro experimental approaches, we suggest a mechanism for MT destabilization in which isoform-specific binding of P1c to MTs antagonizes the MT-stabilizing and assembly-promoting function of MT-associated proteins through an inhibitory function exerted by plectin's SH3 domain. Our results open new perspectives on cytolinker-coordinated IF-MT interaction and its physiological significance. PMID:23363598

  5. A polarised population of dynamic microtubules mediates homeostatic length control in animal cells.

    Directory of Open Access Journals (Sweden)

    Remigio Picone

    Full Text Available Because physical form and function are intimately linked, mechanisms that maintain cell shape and size within strict limits are likely to be important for a wide variety of biological processes. However, while intrinsic controls have been found to contribute to the relatively well-defined shape of bacteria and yeast cells, the extent to which individual cells from a multicellular animal control their plastic form remains unclear. Here, using micropatterned lines to limit cell extension to one dimension, we show that cells spread to a characteristic steady-state length that is independent of cell size, pattern width, and cortical actin. Instead, homeostatic length control on lines depends on a population of dynamic microtubules that lead during cell extension, and that are aligned along the long cell axis as the result of interactions of microtubule plus ends with the lateral cell cortex. Similarly, during the development of the zebrafish neural tube, elongated neuroepithelial cells maintain a relatively well-defined length that is independent of cell size but dependent upon oriented microtubules. A simple, quantitative model of cellular extension driven by microtubules recapitulates cell elongation on lines, the steady-state distribution of microtubules, and cell length homeostasis, and predicts the effects of microtubule inhibitors on cell length. Together this experimental and theoretical analysis suggests that microtubule dynamics impose unexpected limits on cell geometry that enable cells to regulate their length. Since cells are the building blocks and architects of tissue morphogenesis, such intrinsically defined limits may be important for development and homeostasis in multicellular organisms.

  6. Distinct pose of discodermolide in taxol binding pocket drives a complementary mode of microtubule stabilization.

    Science.gov (United States)

    Khrapunovich-Baine, Marina; Menon, Vilas; Verdier-Pinard, Pascal; Smith, Amos B; Angeletti, Ruth Hogue; Fiser, Andras; Horwitz, Susan Band; Xiao, Hui

    2009-12-15

    The microtubule cytoskeleton has proven to be an effective target for cancer therapeutics. One class of drugs, known as microtubule stabilizing agents (MSAs), binds to microtubule polymers and stabilizes them against depolymerization. The prototype of this group of drugs, Taxol, is an effective chemotherapeutic agent used extensively in the treatment of human ovarian, breast, and lung carcinomas. Although electron crystallography and photoaffinity labeling experiments determined that the binding site for Taxol is in a hydrophobic pocket in beta-tubulin, little was known about the effects of this drug on the conformation of the entire microtubule. A recent study from our laboratory utilizing hydrogen-deuterium exchange (HDX) in concert with various mass spectrometry (MS) techniques has provided new information on the structure of microtubules upon Taxol binding. In the current study we apply this technique to determine the binding mode and the conformational effects on chicken erythrocyte tubulin (CET) of another MSA, discodermolide, whose synthetic analogues may have potential use in the clinic. We confirmed that, like Taxol, discodermolide binds to the taxane binding pocket in beta-tubulin. However, as opposed to Taxol, which has major interactions with the M-loop, discodermolide orients itself away from this loop and toward the N-terminal H1-S2 loop. Additionally, discodermolide stabilizes microtubules mainly via its effects on interdimer contacts, specifically on the alpha-tubulin side, and to a lesser extent on interprotofilament contacts between adjacent beta-tubulin subunits. Also, our results indicate complementary stabilizing effects of Taxol and discodermolide on the microtubules, which may explain the synergy observed between the two drugs in vivo.

  7. α-Synuclein Fibrils Exhibit Gain of Toxic Function, Promoting Tau Aggregation and Inhibiting Microtubule Assembly.

    Science.gov (United States)

    Oikawa, Takayuki; Nonaka, Takashi; Terada, Makoto; Tamaoka, Akira; Hisanaga, Shin-Ichi; Hasegawa, Masato

    2016-07-15

    α-Synuclein is the major component of Lewy bodies and Lewy neurites in Parkinson disease and dementia with Lewy bodies and of glial cytoplasmic inclusions in multiple system atrophy. It has been suggested that α-synuclein fibrils or intermediate protofibrils in the process of fibril formation may have a toxic effect on neuronal cells. In this study, we investigated the ability of soluble monomeric α-synuclein to promote microtubule assembly and the effects of conformational changes of α-synuclein on Tau-promoted microtubule assembly. In marked contrast to previous findings, monomeric α-synuclein had no effect on microtubule polymerization. However, both α-synuclein fibrils and protofibrils inhibited Tau-promoted microtubule assembly. The inhibitory effect of α-synuclein fibrils was greater than that of the protofibrils. Dot blot overlay assay and spin-down techniques revealed that α-synuclein fibrils bind to Tau and inhibit microtubule assembly by depleting the Tau available for microtubule polymerization. Using various deletion mutants of α-synuclein and Tau, the acidic C-terminal region of α-synuclein and the basic central region of Tau were identified as regions involved in the binding. Furthermore, introduction of α-synuclein fibrils into cultured cells overexpressing Tau protein induced Tau aggregation. These results raise the possibility that α-synuclein fibrils interact with Tau, inhibit its function to stabilize microtubules, and also promote Tau aggregation, leading to dysfunction of neuronal cells. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Taxol crystals can masquerade as stabilized microtubules.

    Directory of Open Access Journals (Sweden)

    Margit Foss

    Full Text Available Taxol is a potent anti-mitotic drug used in chemotherapy, angioplastic stents, and cell biology research. By binding and stabilizing microtubules, Taxol inhibits their dynamics, crucial for cell division, motility, and survival. The drug has also been reported to induce formation of asters and bundles composed of stabilized microtubules. Surprisingly, at commonly used concentrations, Taxol forms crystals that rapidly bind fluorescent tubulin subunits, generating structures with an uncanny resemblance to microtubule asters and bundles. Kinetic and topological considerations suggest that tubulin subunits, rather than microtubules, bind the crystals. This sequestration of tubulin from the subunit pool would be expected to shift the equilibrium of free to polymerized tubulin to disfavor assembly. Our results imply that some previously reported Taxol-induced asters or bundles could include or be composed of tubulin-decorated Taxol crystals. Thus, reevaluation of certain morphological, chemical, and physical properties of Taxol-treated microtubules may be necessary. Moreover, our findings suggest a novel mechanism for chemotherapy-induced cytotoxicity in non-dividing cells, with far-reaching medical implications.

  9. The Effect of the Crocus Sativus L. Carotenoid, Crocin, on the Polymerization of Microtubules, in Vitro

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    Hossein Zarei Jaliani

    2013-01-01

    Full Text Available Objective(s: Crocin, as the main carotenoid of saffron, has shown anti-tumor activity both in vitro and in vivo. Crocin might interact with cellular proteins and modulate their functions, but the exact target of this carotenoid and the other compounds of the saffron have not been discovered yet. Microtubular proteins, as one of the most important proteins inside the cells, have several functions in nearly all kinds of cellular processes. The aim of this study was to investigate whether crocin affects microtubule polymerization and tubulin structure. Materials and Methods: Microtubules were extracted from sheep brains after two cycles of temperature-dependant assembly-disassembly in the polymerization buffer (PMG. Then phosphocellulose P11 column was used to prepare MAP-free tubulin. Turbidimetric assay of microtubules was performed by incubation of tubulins at 37 ºC in PIPES buffer. To investigate the intrinsic fluorescence spectra of tubulins, the emission spectra of tryptophans was monitored. To test the interaction of crocin with tubulin in more details, ANS has been used. Results: Crocin extremely affected the tubulin polymerization and structure. Ultraviolet spectroscopy indicated that crocin increased polymerization of microtubules by nearly a factor of two. Fluorescence spectroscopic data also pointed to significant conformational changes of tubulin. Conclusion: We showed that crocin increased tubulin polymerization and microtubule nucleation rate and this effect was concentration dependant. After entering cell, crocin can modulate cellular proteins and their functions. Concerning the results of this study, crocin would be able to affect several cell processes through interaction with tubulin proteins or microtubules.

  10. Microtubules and Lis-1/NudE/dynein regulate invasive cell-on-cell migration in Drosophila.

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    Nachen Yang

    Full Text Available The environment through which cells migrate in vivo differs considerably from the in vitro environment where cell migration is often studied. In vivo many cells migrate in crowded and complex 3-dimensional tissues and may use other cells as the substratum on which they move. This includes neurons, glia and their progenitors in the brain. Here we use a Drosophila model of invasive, collective migration in a cellular environment to investigate the roles of microtubules and microtubule regulators in this type of cell movement. Border cells are of epithelial origin and have no visible microtubule organizing center (MTOC. Interestingly, microtubule plus-end growth was biased away from the leading edge. General perturbation of the microtubule cytoskeleton and analysis by live imaging showed that microtubules in both the migrating cells and the substrate cells affect movement. Also, whole-tissue and cell autonomous deletion of the microtubule regulator Stathmin had distinct effects. A screen of 67 genes encoding microtubule interacting proteins uncovered cell autonomous requirements for Lis-1, NudE and Dynein in border cell migration. Net cluster migration was decreased, with initiation of migration and formation of dominant front cell protrusion being most dramatically affected. Organization of cells within the cluster and localization of cell-cell adhesion molecules were also abnormal. Given the established role of Lis-1 in migrating neurons, this could indicate a general role of Lis-1/NudE, Dynein and microtubules, in cell-on-cell migration. Spatial regulation of cell-cell adhesion may be a common theme, consistent with observing both cell autonomous and non-autonomous requirements in both systems.

  11. Anion-induced Ag(I) self-assemblies with electron deficient aromatic ligands: anion-π-system interactions as a driving force for templated coordination networks.

    Science.gov (United States)

    Safin, Damir A; Pialat, Amélie; Leitch, Alicea A; Tumanov, Nikolay A; Korobkov, Ilia; Filinchuk, Yaroslav; Brusso, Jaclyn L; Murugesu, Muralee

    2015-06-11

    Three novel 1D, 2D and 3D coordination polymers were successfully isolated using nitrogen based 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine (BPymTz) and 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) ligands with Ag(I) ions. The formation of these supramolecular assemblies was templated through anion-π-system interactions.

  12. Sugar-metal ion interactions: The coordination behavior of cesium ion with lactose, D-arabinose and L-arabinose

    Science.gov (United States)

    Jiang, Ye; Xue, Junhui; Wen, Xiaodong; Zhai, Yanjun; Yang, Limin; Xu, Yizhuang; Zhao, Guozhong; Kou, Kuan; Liu, Kexin; Chen, Jia'er; Wu, Jinguang

    2016-04-01

    The novel cesium chloride-lactose complex (CsCl·C12H22O10 (Cs-Lac), cesium chloride-D-arabinose and L-arabinose complexes (CsCl·C5H10O5, Cs-D-Ara and Cs-L-Ara) have been synthesized and characterized using X-ray diffraction, FTIR, FIR, THz and Raman spectroscopies. Cs+ is 9-coordinated to two chloride ions and seven hydroxyl groups from five lactose molecules in Cs-Lac. In the structures of CsCl-D-arabinose and CsCl-L-arabinose complexes, two kinds of Cs+ ions coexist in the structures. Cs1 is 10-coordinated with two chloride ions and eight hydroxyl groups from five arabinose molecule; Cs2 is 9-coordinated to three chloride ions and six hydroxyl groups from five arabinose molecules. Two coordination modes of arabinose coexist in the structures. α-D-arabinopyranose and α-L-arabinopyranose appear in the structures of Cs-D-Ara and Cs-L-Ara complexes. FTIR and Raman results indicate variations of hydrogen bonds and the conformation of the ligands after complexation. FIR and THz spectra also confirm the formation of Cs-complexes. Crystal structure, FTIR, FIR, THz and Raman spectra provide detailed information on the structure and coordination of hydroxyl groups to metal ions in the cesium chloride-lactose, cesium chloride-D- and L-arabinose complexes.

  13. Mto2 multisite phosphorylation inactivates non-spindle microtubule nucleation complexes during mitosis.

    Science.gov (United States)

    Borek, Weronika E; Groocock, Lynda M; Samejima, Itaru; Zou, Juan; de Lima Alves, Flavia; Rappsilber, Juri; Sawin, Kenneth E

    2015-01-01

    Microtubule nucleation is highly regulated during the eukaryotic cell cycle, but the underlying molecular mechanisms are largely unknown. During mitosis in fission yeast Schizosaccharomyces pombe, cytoplasmic microtubule nucleation ceases simultaneously with intranuclear mitotic spindle assembly. Cytoplasmic nucleation depends on the Mto1/2 complex, which binds and activates the γ-tubulin complex and also recruits the γ-tubulin complex to both centrosomal (spindle pole body) and non-centrosomal sites. Here we show that the Mto1/2 complex disassembles during mitosis, coincident with hyperphosphorylation of Mto2 protein. By mapping and mutating multiple Mto2 phosphorylation sites, we generate mto2-phosphomutant strains with enhanced Mto1/2 complex stability, interaction with the γ-tubulin complex and microtubule nucleation activity. A mutant with 24 phosphorylation sites mutated to alanine, mto2[24A], retains interphase-like behaviour even in mitotic cells. This provides a molecular-level understanding of how phosphorylation 'switches off' microtubule nucleation complexes during the cell cycle and, more broadly, illuminates mechanisms regulating non-centrosomal microtubule nucleation.

  14. Direct observation of the binding state of the kinesin head to the microtubule.

    Science.gov (United States)

    Guydosh, Nicholas R; Block, Steven M

    2009-09-03

    The dimeric motor protein kinesin-1 converts chemical energy from ATP hydrolysis into mechanical work used to transport cargo along microtubules. Cargo attached to the kinesin stalk moves processively in 8-nm increments as its twin motor domains (heads) carry out an asymmetric, 'hand-over-hand' walk. The extent of individual head interactions with the microtubule during stepping, however, remains controversial. A major experimental limitation has been the lack of a means to monitor the attachment of an individual head to the microtubule during movement, necessitating indirect approaches. Here we report the development of a single-molecule assay that can directly report head binding in a walking kinesin molecule, and show that only a single head is bound to the microtubule between steps at low ATP concentrations. A bead was linked to one of the two kinesin heads by means of a short DNA tether and used to apply rapidly alternating hindering and assisting loads with an optical trap. The time-dependent difference between forwards and backwards displacements of the bead alternated between two discrete values during stepping, corresponding to those intervals when the linked head adopted a bound or an unbound state. The linked head could only rebind the microtubule once ATP had become bound to its partner head.

  15. 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.

  16. Mto2 multisite phosphorylation inactivates non-spindle microtubule nucleation complexes during mitosis

    Science.gov (United States)

    Borek, Weronika E.; Groocock, Lynda M.; Samejima, Itaru; Zou, Juan; de Lima Alves, Flavia; Rappsilber, Juri; Sawin, Kenneth E.

    2015-01-01

    Microtubule nucleation is highly regulated during the eukaryotic cell cycle, but the underlying molecular mechanisms are largely unknown. During mitosis in fission yeast Schizosaccharomyces pombe, cytoplasmic microtubule nucleation ceases simultaneously with intranuclear mitotic spindle assembly. Cytoplasmic nucleation depends on the Mto1/2 complex, which binds and activates the γ-tubulin complex and also recruits the γ-tubulin complex to both centrosomal (spindle pole body) and non-centrosomal sites. Here we show that the Mto1/2 complex disassembles during mitosis, coincident with hyperphosphorylation of Mto2 protein. By mapping and mutating multiple Mto2 phosphorylation sites, we generate mto2-phosphomutant strains with enhanced Mto1/2 complex stability, interaction with the γ-tubulin complex and microtubule nucleation activity. A mutant with 24 phosphorylation sites mutated to alanine, mto2[24A], retains interphase-like behaviour even in mitotic cells. This provides a molecular-level understanding of how phosphorylation ‘switches off' microtubule nucleation complexes during the cell cycle and, more broadly, illuminates mechanisms regulating non-centrosomal microtubule nucleation. PMID:26243668

  17. Cytoplasmic retention of a nucleocytoplasmic protein TBC1D3 by microtubule network is required for enhanced EGFR signaling.

    Directory of Open Access Journals (Sweden)

    Ze He

    Full Text Available The hominoid oncogene TBC1D3 enhances epidermal growth factor receptor (EGFR signaling and induces cell transformation. However, little is known regarding its spatio-temporal regulation and mechanism of tumorigenesis. In the current study, we identified the microtubule subunit β-tubulin as a potential interaction partner for TBC1D3 using affinity purification combined with mass spectrometry analysis. The interaction between TBC1D3 and β-tubulin was confirmed by co-immunoprecipitation. Using the same method, we also revealed that TBC1D3 co-precipitated with endogenous α-tubulin, another subunit of the microtubule. In agreement with these results, microtubule cosedimentation assays showed that TBC1D3 associated with the microtubule network. The β-tubulin-interacting site of TBC1D3 was mapped to amino acids 286∼353 near the C-terminus of the TBC domain. Deletion mutation within these amino acids was shown to abolish the interaction of TBC1D3 with β-tubulin. Interestingly, the deletion mutation caused a complete loss of TBC1D3 from the cytoplasmic filamentous and punctate structures, and TBC1D3 instead appeared in the nucleus. Consistent with this, wild-type TBC1D3 exhibited the same nucleocytoplasmic distribution in cells treated with the microtubule depolymerizing agent nocodazole, suggesting that the microtubule network associates with and retains TBC1D3 in the cytoplasm. We further found that deficiency in β-tubulin-interacting resulted in TBC1D3's inability to inhibit c-Cbl recruitment and EGFR ubiquitination, ultimately leading to dysregulation of EGFR degradation and signaling. Taken together, these studies indicate a novel model by which the microtubule network regulates EGFR stability and signaling through tubulin dimer/oligomer interaction with the nucleocytoplasmic protein TBC1D3.

  18. Kinetochore-microtubule attachment is sufficient to satisfy the human spindle assembly checkpoint

    NARCIS (Netherlands)

    Etemad, Banafsheh; Kuijt, Timo E F; Kops, Geert J P L

    2015-01-01

    The spindle assembly checkpoint (SAC) is a genome surveillance mechanism that protects against aneuploidization. Despite profound progress on understanding mechanisms of its activation, it remains unknown what aspect of chromosome-spindle interactions is monitored by the SAC: kinetochore-microtubule

  19. Polycations XX: New Monodentate Cationic Ligands and Their Coordination with Ruthenium for the Construction of Complexes Expressing Enhanced Interaction with DNA

    Directory of Open Access Journals (Sweden)

    Leslie Babukutty

    2012-01-01

    Full Text Available Prior investigations from this laboratory concerned with the preparation of new types of organic cations for a variety of biological and nonbiological applications have been extended to the preparation of cation-bearing ligands with nitrogen coordinating sites for use in complexation reactions with ruthenium cores. The syntheses of new cationic ligands as well as ruthenium complexes bearing them are reported here. The introduction of these new types of ligands is intended to provide to the complexes an enhanced ability to interact with DNA, and thereby to have the potential to be enhanced antitumor agents. Preliminary observations of their interactions with DNA are presented.

  20. Titanium dioxide nanoparticles alter cellular morphology via disturbing the microtubule dynamics

    Science.gov (United States)

    Mao, Zhilei; Xu, Bo; Ji, Xiaoli; Zhou, Kun; Zhang, Xuemei; Chen, Minjian; Han, Xiumei; Tang, Qiusha; Wang, Xinru; Xia, Yankai

    2015-04-01

    Titanium dioxide (TiO2) nanoparticles (NPs) have been widely used in our daily lives, for example, in the areas of sunscreens, cosmetics, toothpastes, food products, and nanomedical reagents. Recently, increasing concern has been raised about their neurotoxicity, but the mechanisms underlying such toxic effects are still unknown. In this work, we employed a human neuroblastoma cell line (SH-SY5Y) to study the effects of TiO2 NPs on neurological systems. Our results showed that TiO2 NPs did not affect cell viability but induced noticeable morphological changes until 100 μg ml-1. Immunofluorescence detection showed disorder, disruption, retraction, and decreased intensity of the microtubules after TiO2 NPs treatment. Both α and β tubule expressions did not change in the TiO2 NP-treated group, but the percentage of soluble tubules was increased. A microtubule dynamic study in living cells indicated that TiO2 NPs caused a lower growth rate and a higher shortening rate of microtubules as well as shortened lifetimes of de novo microtubules. TiO2 NPs did not cause changes in the expression and phosphorylation state of tau proteins, but a tau-TiO2 NP interaction was observed. TiO2 NPs could interact with tubule heterodimers, microtubules and tau proteins, which led to the instability of microtubules, thus contributing to the neurotoxicity of TiO2 NPs.Titanium dioxide (TiO2) nanoparticles (NPs) have been widely used in our daily lives, for example, in the areas of sunscreens, cosmetics, toothpastes, food products, and nanomedical reagents. Recently, increasing concern has been raised about their neurotoxicity, but the mechanisms underlying such toxic effects are still unknown. In this work, we employed a human neuroblastoma cell line (SH-SY5Y) to study the effects of TiO2 NPs on neurological systems. Our results showed that TiO2 NPs did not affect cell viability but induced noticeable morphological changes until 100 μg ml-1. Immunofluorescence detection showed disorder

  1. AMYLOID-β PEPTIDE BINDS TO MICROTUBULE-ASSOCIATED PROTEIN 1B (MAP1B)

    Science.gov (United States)

    Gevorkian, Goar; Gonzalez-Noriega, Alfonso; Acero, Gonzalo; Ordoñez, Jorge; Michalak, Colette; Munguia, Maria Elena; Govezensky, Tzipe; Cribbs, David H.; Manoutcharian, Karen

    2008-01-01

    Extracellular and intraneuronal formation of amyloid-beta aggregates have been demonstrated to be involved in the pathogenesis of Alzheimer’s disease. However, the precise mechanism of amyloid-beta neurotoxicity is not completely understood. Previous studies suggest that binding of amyloid-beta to a number of targets have deleterious effects on cellular functions. In the present study we have shown for the first time that amyloid-beta 1-42 bound to a peptide comprising the microtubule binding domain of the heavy chain of microtubule-associated protein 1B by the screening of a human brain cDNA library expressed on M13 phage. This interaction may explain, in part, the loss of neuronal cytoskeletal integrity, impairment of microtubule-dependent transport and synaptic dysfunction observed previously in Alzheimer’s disease. PMID:18079022

  2. Chromator is required for proper microtubule spindle formation and mitosis in Drosophila.

    Science.gov (United States)

    Ding, Yun; Yao, Changfu; Lince-Faria, Mariana; Rath, Uttama; Cai, Weili; Maiato, Helder; Girton, Jack; Johansen, Kristen M; Johansen, Jørgen

    2009-10-01

    The chromodomain protein, Chromator, has been shown to have multiple functions that include regulation of chromatin structure as well as coordination of muscle remodeling during metamorphosis depending on the developmental context. In this study we show that mitotic neuroblasts from brain squash preparations from larvae heteroallelic for the two Chromator loss-of-function alleles Chro(71) and Chro(612) have severe microtubule spindle and chromosome segregation defects that were associated with a reduction in brain size. The microtubule spindles formed were incomplete, unfocused, and/or without clear spindle poles and at anaphase chromosomes were lagging and scattered. Time-lapse analysis of mitosis in S2 cells depleted of Chromator by RNAi treatment suggested that the lagging and scattered chromosome phenotypes were caused by incomplete alignment of chromosomes at the metaphase plate, possibly due to a defective spindle-assembly checkpoint, as well as of frayed and unstable microtubule spindles during anaphase. Expression of full-length Chromator transgenes under endogenous promoter control restored both microtubule spindle morphology as well as brain size strongly indicating that the observed mutant defects were directly attributable to lack of Chromator function.

  3. Microtubule-binding protein doublecortin-like kinase 1 (DCLK1) guides kinesin-3-mediated cargo transport to dendrites.

    Science.gov (United States)

    Lipka, Joanna; Kapitein, Lukas C; Jaworski, Jacek; Hoogenraad, Casper C

    2016-02-01

    In neurons, the polarized distribution of vesicles and other cellular materials is established through molecular motors that steer selective transport between axons and dendrites. It is currently unclear whether interactions between kinesin motors and microtubule-binding proteins can steer polarized transport. By screening all 45 kinesin family members, we systematically addressed which kinesin motors can translocate cargo in living cells and drive polarized transport in hippocampal neurons. While the majority of kinesin motors transport cargo selectively into axons, we identified five members of the kinesin-3 (KIF1) and kinesin-4 (KIF21) subfamily that can also target dendrites. We found that microtubule-binding protein doublecortin-like kinase 1 (DCLK1) labels a subset of dendritic microtubules and is required for KIF1-dependent dense-core vesicles (DCVs) trafficking into dendrites and dendrite development. Our study demonstrates that microtubule-binding proteins can provide local signals for specific kinesin motors to drive polarized cargo transport.

  4. Measurement of Binding Force between Microtubule-Associated Protein and Microtubule

    Institute of Scientific and Technical Information of China (English)

    XU Chun-Hua; GUO Hong-Lian; QU E; LI Zhao-Lin; YUAN Ming; CHENG Bing-Ying; ZHANG Dao-Zhong

    2007-01-01

    Microtubule-associated proteins (MAPs) are important proteins in cells. They can regulate the organization,dynamics and function of microtubules. We measure the binding force between microtubule and a new plant MAP, i.e. AtMAP65-1, by dual-optical tweezers. The force is obtained to be 14.6±3.5 pN from the data statistics and analysis. This force measurement is helpful to understand the function and mechanism of MAPs from the mechanical point of view and lays the groundwork for future measurements of the mechanical properties of other biological macro-molecules.

  5. Microtubules: A network for solitary waves

    Directory of Open Access Journals (Sweden)

    Zdravković Slobodan

    2017-01-01

    Full Text Available In the present paper we deal with nonlinear dynamics of microtubules. The structure and role of microtubules in cells are explained as well as one of models explaining their dynamics. Solutions of the crucial nonlinear differential equation depend on used mathematical methods. Two commonly used procedures, continuum and semi-discrete approximations, are explained. These solutions are solitary waves usually called as kink solitons, breathers and bell-type solitons. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45010

  6. Electrophilic Ln(III) cations protected by C-F → Ln interactions and their coordination chemistry with weak σ- and π-donors.

    Science.gov (United States)

    Yin, Haolin; Lewis, Andrew J; Carroll, Patrick; Schelter, Eric J

    2013-07-15

    A homoleptic cerium(III) amide complex, Ce(NPh(F)2)3 (1-Ce) (Ph(F) = pentafluorophenyl), in an unusual pseudo-trigonal planar geometry featuring six C-F → Ce interactions was prepared. The C-F → Ln interactions in solution were evident by comparison of the (19)F NMR shifts for the paramagnetic 1-Ce with those of the 4f(0) lanthanum(III) analogue. Coordination of weak σ- and π-donors, including ethers and neutral arene molecules, was achieved by the reversible displacement of the weak C-F → Ce interactions. Computational studies on Ce(NPh(F)2)3 and Ce(NPh(F)2)3(η(6)-C6H3Me3) provide information on the F → Ce interactions and Ce-η(6)-arene bonding.

  7. GDP-tubulin incorporation into growing microtubules modulates polymer stability.

    Science.gov (United States)

    Valiron, Odile; Arnal, Isabelle; Caudron, Nicolas; Job, Didier

    2010-06-04

    Microtubule growth proceeds through the endwise addition of nucleotide-bound tubulin dimers. The microtubule wall is composed of GDP-tubulin subunits, which are thought to come exclusively from the incorporation of GTP-tubulin complexes at microtubule ends followed by GTP hydrolysis within the polymer. The possibility of a direct GDP-tubulin incorporation into growing polymers is regarded as hardly compatible with recent structural data. Here, we have examined GTP-tubulin and GDP-tubulin incorporation into polymerizing microtubules using a minimal assembly system comprised of nucleotide-bound tubulin dimers, in the absence of free nucleotide. We find that GDP-tubulin complexes can efficiently co-polymerize with GTP-tubulin complexes during microtubule assembly. GDP-tubulin incorporation into microtubules occurs with similar efficiency during bulk microtubule assembly as during microtubule growth from seeds or centrosomes. Microtubules formed from GTP-tubulin/GDP-tubulin mixtures display altered microtubule dynamics, in particular a decreased shrinkage rate, apparently due to intrinsic modifications of the polymer disassembly properties. Thus, although microtubules polymerized from GTP-tubulin/GDP-tubulin mixtures or from homogeneous GTP-tubulin solutions are both composed of GDP-tubulin subunits, they have different dynamic properties, and this may reveal a novel form of microtubule "structural plasticity."

  8. GDP-Tubulin Incorporation into Growing Microtubules Modulates Polymer Stability*

    Science.gov (United States)

    Valiron, Odile; Arnal, Isabelle; Caudron, Nicolas; Job, Didier

    2010-01-01

    Microtubule growth proceeds through the endwise addition of nucleotide-bound tubulin dimers. The microtubule wall is composed of GDP-tubulin subunits, which are thought to come exclusively from the incorporation of GTP-tubulin complexes at microtubule ends followed by GTP hydrolysis within the polymer. The possibility of a direct GDP-tubulin incorporation into growing polymers is regarded as hardly compatible with recent structural data. Here, we have examined GTP-tubulin and GDP-tubulin incorporation into polymerizing microtubules using a minimal assembly system comprised of nucleotide-bound tubulin dimers, in the absence of free nucleotide. We find that GDP-tubulin complexes can efficiently co-polymerize with GTP-tubulin complexes during microtubule assembly. GDP-tubulin incorporation into microtubules occurs with similar efficiency during bulk microtubule assembly as during microtubule growth from seeds or centrosomes. Microtubules formed from GTP-tubulin/GDP-tubulin mixtures display altered microtubule dynamics, in particular a decreased shrinkage rate, apparently due to intrinsic modifications of the polymer disassembly properties. Thus, although microtubules polymerized from GTP-tubulin/GDP-tubulin mixtures or from homogeneous GTP-tubulin solutions are both composed of GDP-tubulin subunits, they have different dynamic properties, and this may reveal a novel form of microtubule “structural plasticity.” PMID:20371874

  9. A spectroscopic study on the coordination and solution structures of the interaction systems between biperoxidovanadate complexes and the pyrazolylpyridine-like ligands.

    Science.gov (United States)

    Yu, Xian-Yong; Deng, Lin; Zheng, Baishu; Zeng, Bi-Rong; Yi, Pinggui; Xu, Xin

    2014-01-28

    In order to understand the substitution effects of pyrazolylpyridine (pzpy) on the coordination reaction equilibria, the interactions between a series of pzpy-like ligands and biperoxidovanadate ([OV(O2)2(D2O)](-)/[OV(O2)2(HOD)](-), abbrv. bpV) have been explored using a combination of multinuclear ((1)H, (13)C, and (51)V) magnetic resonance, heteronuclear single quantum coherence (HSQC), and variable temperature NMR in a 0.15 mol L(-1) NaCl D2O solution that mimics the physiological conditions. Both the direct NMR data and the equilibrium constants are reported for the first time. A series of new hepta-coordinated peroxidovanadate species [OV(O2)2L](-) (L = pzpy-like chelating ligands) are formed due to several competitive coordination interactions. According to the equilibrium constants for products between bpV and the pzpy-like ligands, the relative affinity of the ligands is found to be pzpy > 2-Ester-pzpy ≈ 2-Me-pzpy ≈ 2-Amide-pzpy > 2-Et-pzpy. In the interaction system between bpV and pzpy, a pair of isomers (Isomers A and B) are observed in aqueous solution, which are attributed to different types of coordination modes between the metal center and the ligands, while the crystal structure of NH4[OV(O2)2(pzpy)]·6H2O (CCDC 898554) has the same coordination structure as Isomer A (the main product for pzpy). For the N-substituted ligands, however, Isomer A or B type complexes can also be observed in solution but the molar ratios of the isomer are reversed (i.e., Isomer B type is the main product). These results demonstrate that when the N atom in the pyrazole ring has a substitution group, hydrogen bonding (from the H atom in the pyrazole ring), the steric effect (from alkyl) and the solvation effect (from the ester or amide group) can jointly affect the coordination reaction equilibrium.

  10. Stathmin regulates microtubule dynamics and microtubule organizing center polarization in activated T cells.

    Science.gov (United States)

    Filbert, Erin L; Le Borgne, Marie; Lin, Joseph; Heuser, John E; Shaw, Andrey S

    2012-06-01

    Polarization of T cells involves reorientation of the microtubule organizing center (MTOC). Because activated ERK is localized at the immunological synapse, we investigated its role by showing that ERK activation is important for MTOC polarization. Suspecting that ERK phosphorylates a regulator of microtubules, we next focused on stathmin, a known ERK substrate. Our work indicates that during T cell activation, ERK is recruited to the synapse, allowing it to phosphorylate stathmin molecules near the immunological synapse. Supporting an important role of stathmin phosphorylation in T cell activation, we showed that T cell activation results in increased microtubule growth rate dependent on the presence of stathmin. The significance of this finding was demonstrated by results showing that CTLs from stathmin(-/-) mice displayed defective MTOC polarization and defective target cell cytolysis. These data implicate stathmin as a regulator of the microtubule network during T cell activation.

  11. The formin DIAPH1 (mDia1) regulates megakaryocyte proplatelet formation by remodeling the actin and microtubule cytoskeletons.

    Science.gov (United States)

    Pan, Jiajia; Lordier, Larissa; Meyran, Deborah; Rameau, Philippe; Lecluse, Yann; Kitchen-Goosen, Susan; Badirou, Idinath; Mokrani, Hayat; Narumiya, Shuh; Alberts, Arthur S; Vainchenker, William; Chang, Yunhua

    2014-12-18

    Megakaryocytes are highly specialized precursor cells that produce platelets via cytoplasmic extensions called proplatelets. Proplatelet formation (PPF) requires profound changes in microtubule and actin organization. In this work, we demonstrated that DIAPH1 (mDia1), a mammalian homolog of Drosophila diaphanous that works as an effector of the small GTPase Rho, negatively regulates PPF by controlling the dynamics of the actin and microtubule cytoskeletons. Moreover, we showed that inhibition of both DIAPH1 and the Rho-associated protein kinase (Rock)/myosin pathway increased PPF via coordination of both cytoskeletons. We provide evidence that 2 major effectors of the Rho GTPase pathway (DIAPH1 and Rock/myosin II) are involved not only in Rho-mediated stress fibers assembly, but also in the regulation of microtubule stability and dynamics during PPF.

  12. Microtubules guide root hair tip growth

    NARCIS (Netherlands)

    Sieberer, B.; Ketelaar, M.J.; Esseling, J.J.; Emons, A.M.C.

    2005-01-01

    The ability to establish cell polarity is crucial to form and function of an individual cell. Polarity underlies critical processes during cell development, such as cell growth, cell division, cell differentiation and cell signalling. Interphase cytoplasmic microtubules in tip-growing fission yeast

  13. Microtubules guide root hair tip growth

    NARCIS (Netherlands)

    Sieberer, B.; Ketelaar, M.J.; Esseling, J.J.; Emons, A.M.C.

    2005-01-01

    The ability to establish cell polarity is crucial to form and function of an individual cell. Polarity underlies critical processes during cell development, such as cell growth, cell division, cell differentiation and cell signalling. Interphase cytoplasmic microtubules in tip-growing fission yeast

  14. Invariant Manifolds and Collective Coordinates

    CERN Document Server

    Papenbrock, T

    2001-01-01

    We introduce suitable coordinate systems for interacting many-body systems with invariant manifolds. These are Cartesian in coordinate and momentum space and chosen such that several components are identically zero for motion on the invariant manifold. In this sense these coordinates are collective. We make a connection to Zickendraht's collective coordinates and present certain configurations of few-body systems where rotations and vibrations decouple from single-particle motion. These configurations do not depend on details of the interaction.

  15. Verbal Interactional Dominance and Coordinative Structure of Speech Rhythms of Staff and Clients with an Intellectual Disability

    NARCIS (Netherlands)

    Reuzel, Ellen; Embregts, Petri J. C. M.; Bosman, Anna M. T.; Cox, Ralf F. A.; van Nieuwenhuijzen, Maroesjka; Jahoda, Andrew

    2014-01-01

    Social interactions between staff and clients with an intellectual disability contain synchronized turn-taking patterns. Synchrony can increase rapport and cooperation between individuals. This study investigated whether verbal interactional dominance and balance, an indication of attunement between

  16. Engineering Functionalization in a Supramolecular Polymer: Hierarchical Self-Organization of Triply Orthogonal Non-covalent Interactions on a Supramolecular Coordination Complex Platform.

    Science.gov (United States)

    Zhou, Zhixuan; Yan, Xuzhou; Cook, Timothy R; Saha, Manik Lal; Stang, Peter J

    2016-01-27

    Here we present a method for the construction of functionalizable supramolecular polymers by controlling three orthogonal interactions within a single system: (i) coordination-driven self-assembly; (ii) H-bonding; and (iii) host-guest interactions between crown ether and dialkylammonium substrates. Three unique molecules constitute the supramolecular construct, including a 2-ureido-4-pyrimidinone (UPy)-functionalized rigid dipyridyl donor and a complementary organoplatinum(II) acceptor decorated with a crown ether moiety that provide the basis for self-assembly and polymerization. The final host-guest interaction is demonstrated by using one of two dialkylammonium molecules containing fluorophores that bind to the benzo-21-crown-7 (B21C7) groups of the acceptors, providing a spectroscopic handle to evaluate the functionalization. An initial coordination-driven self-assembly yields hexagonal metallacycles with alternating UPy and B21C7 groups at their vertices. The assembly does not interfere with H-bonding between the UPy groups, which link the discrete metallacycles into a supramolecular network, leaving the B21C7 groups free for functionalization via host-guest chemistry. The resultant network results in a cavity-cored metallogel at high concentrations or upon solvent swelling. The light-emitting properties of the dialkylammonium substrates were transferred to the network upon host-guest binding. This method is compatible with any dialkylammonium substrate that does not disrupt coordination nor H-bonding, and thus, the unification of these three orthogonal interactions represents a simple yet highly efficient strategy to obtain supramolecular polymeric materials with desirable functionality.

  17. Doublecortin Is Excluded from Growing Microtubule Ends and Recognizes the GDP-Microtubule Lattice.

    Science.gov (United States)

    Ettinger, Andreas; van Haren, Jeffrey; Ribeiro, Susana A; Wittmann, Torsten

    2016-06-20

    Many microtubule (MT) functions are mediated by a diverse class of proteins (+TIPs) at growing MT plus ends that control intracellular MT interactions and dynamics and depend on end-binding proteins (EBs) [1]. Cryoelectron microscopy has recently identified the EB binding site as the interface of four tubulin dimers that undergoes a conformational change in response to β-tubulin GTP hydrolysis [2, 3]. Doublecortin (DCX), a MT-associated protein (MAP) required for neuronal migration during cortical development [4, 5], binds to the same site as EBs [6], and recent in vitro studies proposed DCX localization to growing MT ends independent of EBs [7]. Because this conflicts with observations in neurons [8, 9] and the molecular function of DCX is not well understood, we revisited intracellular DCX dynamics at low expression levels. Here, we report that DCX is not a +TIP in cells but, on the contrary, is excluded from the EB1 domain. In addition, we find that DCX-MT interactions are highly sensitive to MT geometry. In cells, DCX binding was greatly reduced at MT segments with high local curvature. Remarkably, this geometry-dependent binding to MTs was completely reversed in the presence of taxanes, which reconciles incompatible observations in cells [9] and in vitro [10]. We propose a model explaining DCX specificity for different MT geometries based on structural changes induced by GTP hydrolysis that decreases the spacing between adjacent tubulin dimers [11]. Our data are consistent with a unique mode of MT interaction in which DCX specifically recognizes this compacted GDP-like MT lattice.

  18. Cell cycle regulation of tubulin RNA level, tubulin protein synthesis, and assembly of microtubules in Physarum.

    Science.gov (United States)

    Schedl, T; Burland, T G; Gull, K; Dove, W F

    1984-07-01

    The temporal relationship between tubulin expression and the assembly of the mitotic spindle microtubules has been investigated during the naturally synchronous cell cycle of the Physarum plasmodium. The cell cycle behavior of the tubulin isoforms was examined by two-dimensional gel electrophoresis of proteins labeled in vivo and by translation of RNA in vitro. alpha 1-, alpha 2-, beta 1-, and beta 2-tubulin synthesis increases coordinately until metaphase, and then falls, with beta 2 falling more rapidly than beta 1. Nucleic acid hybridization demonstrated that alpha- and beta-tubulin RNAs accumulate coordinately during G2, peaking at metaphase. Quantitative analysis demonstrated that alpha-tubulin RNA increases with apparent exponential kinetics, peaking with an increase over the basal level of greater than 40-fold. After metaphase, tubulin RNA levels fall exponentially, with a short half-life (19 min). Electron microscopic analysis of the plasmodium showed that the accumulation of tubulin RNA begins long before the polymerization of mitotic spindle microtubules. By contrast, the decay of tubulin RNA after metaphase coincides with the depolymerization of the spindle microtubules.

  19. Distinction between coordination and phosphine ligand oxidation: interactions of di- and triphosphines with Pn(3+) (Pn = P, As, Sb, Bi).

    Science.gov (United States)

    Chitnis, Saurabh S; Vos, Kevin A; Burford, Neil; McDonald, Robert; Ferguson, Michael J

    2016-01-14

    Reactions of polydentate phosphines with sources of Pn(3+) (Pn = P, As, Sb, Bi) yield complexes of Pn(1+) (Pn = P, As) or Pn(3+) (Pn = Sb, Bi) acceptors. The distinction between coordination of a phosphine center to Pn and oxidation of a phosphine ligand is dependent on Pn. The first structurally verified triphosphine complexes of Sb(III) and Bi(III) acceptors are reported.

  20. Integrin-linked kinase regulates interphase and mitotic microtubule dynamics.

    Directory of Open Access Journals (Sweden)

    Simin Lim

    Full Text Available Integrin-linked kinase (ILK localizes to both focal adhesions and centrosomes in distinct multiprotein complexes. Its dual function as a kinase and scaffolding protein has been well characterized at focal adhesions, where it regulates integrin-mediated cell adhesion, spreading, migration and signaling. At the centrosomes, ILK regulates mitotic spindle organization and centrosome clustering. Our previous study showed various spindle defects after ILK knockdown or inhibition that suggested alteration in microtubule dynamics. Since ILK expression is frequently elevated in many cancer types, we investigated the effects of ILK overexpression on microtubule dynamics. We show here that overexpressing ILK in HeLa cells was associated with a shorter duration of mitosis and decreased sensitivity to paclitaxel, a chemotherapeutic agent that suppresses microtubule dynamics. Measurement of interphase microtubule dynamics revealed that ILK overexpression favored microtubule depolymerization, suggesting that microtubule destabilization could be the mechanism behind the decreased sensitivity to paclitaxel, which is known to stabilize microtubules. Conversely, the use of a small molecule inhibitor selective against ILK, QLT-0267, resulted in suppressed microtubule dynamics, demonstrating a new mechanism of action for this compound. We further show that treatment of HeLa cells with QLT-0267 resulted in higher inter-centromere tension in aligned chromosomes during mitosis, slower microtubule regrowth after cold depolymerization and the presence of a more stable population of spindle microtubules. These results demonstrate that ILK regulates microtubule dynamics in both interphase and mitotic cells.

  1. KATNAL1 regulation of sertoli cell microtubule dynamics is essential for spermiogenesis and male fertility.

    Directory of Open Access Journals (Sweden)

    Lee B Smith

    Full Text Available Spermatogenesis is a complex process reliant upon interactions between germ cells (GC and supporting somatic cells. Testicular Sertoli cells (SC support GCs during maturation through physical attachment, the provision of nutrients, and protection from immunological attack. This role is facilitated by an active cytoskeleton of parallel microtubule arrays that permit transport of nutrients to GCs, as well as translocation of spermatids through the seminiferous epithelium during maturation. It is well established that chemical perturbation of SC microtubule remodelling leads to premature GC exfoliation demonstrating that microtubule remodelling is an essential component of male fertility, yet the genes responsible for this process remain unknown. Using a random ENU mutagenesis approach, we have identified a novel mouse line displaying male-specific infertility, due to a point mutation in the highly conserved ATPase domain of the novel KATANIN p60-related microtubule severing protein Katanin p60 subunit A-like1 (KATNAL1. We demonstrate that Katnal1 is expressed in testicular Sertoli cells (SC from 15.5 days post-coitum (dpc and that, consistent with chemical disruption models, loss of function of KATNAL1 leads to male-specific infertility through disruption of SC microtubule dynamics and premature exfoliation of spermatids from the seminiferous epithelium. The identification of KATNAL1 as an essential regulator of male fertility provides a significant novel entry point into advancing our understanding of how SC microtubule dynamics promotes male fertility. Such information will have resonance both for future treatment of male fertility and the development of non-hormonal male contraceptives.

  2. GTSE1 is a microtubule plus-end tracking protein that regulates EB1-dependent cell migration.

    Directory of Open Access Journals (Sweden)

    Massimilano Scolz

    Full Text Available The regulation of cell migration is a highly complex process that is often compromised when cancer cells become metastatic. The microtubule cytoskeleton is necessary for cell migration, but how microtubules and microtubule-associated proteins regulate multiple pathways promoting cell migration remains unclear. Microtubule plus-end binding proteins (+TIPs are emerging as important players in many cellular functions, including cell migration. Here we identify a +TIP, GTSE1, that promotes cell migration. GTSE1 accumulates at growing microtubule plus ends through interaction with the EB1+TIP. The EB1-dependent +TIP activity of GTSE1 is required for cell migration, as well as for microtubule-dependent disassembly of focal adhesions. GTSE1 protein levels determine the migratory capacity of both nontransformed and breast cancer cell lines. In breast cancers, increased GTSE1 expression correlates with invasive potential, tumor stage, and time to distant metastasis, suggesting that misregulation of GTSE1 expression could be associated with increased invasive potential.

  3. Thymoquinone disrupts the microtubule dynamics in fission yeast Schizosaccharomyces pombe

    Directory of Open Access Journals (Sweden)

    Nusrat Masood

    2016-11-01

    Full Text Available Mad2 deletion strain of Schizosaccharomyces pombe was found to be sensitive to thymoquinone, a signature molecule present in Nigella sativa in a dose-dependent manner. Mad2 protein is an indispensable part of mitotic spindle checkpoint complex and is required for the cell cycle arrest in response to the spindle defects. Although the expression of α tubulin was not affected in thymoquinone treated cells, but the expression of β-tubulin was reduced. Further, the absence of microtubule in thymoquinone treated cells suggests its involvement in tubulin polymerization. Molecular docking studies revealed that thymoquinone specifically binds to β-tubulin near the Taxotere binding site of Tub1 (Tubulin α-β dimer. These studies additionally showed that thymoquinone interacts with the residues present in chain B, which is an inherent part of Mad2 protein of mitotic checkpoint complex (MCC. We concluded that the thymoquinone disrupts the microtubule polymerization that leads to the requirement of spindle checkpoint protein for the cell survival.

  4. Verbal interactional dominance and coordinative structure of speech rhythms of staff and clients with an intellectual disability.

    Science.gov (United States)

    Reuzel, Ellen; Embregts, Petri J C M; Bosman, Anna M T; Cox, Ralf F A; van Nieuwenhuijzen, Maroesjka; Jahoda, Andrew

    2014-10-01

    Social interactions between staff and clients with an intellectual disability contain synchronized turn-taking patterns. Synchrony can increase rapport and cooperation between individuals. This study investigated whether verbal interactional dominance and balance, an indication of attunement between staff and clients with ID, are associated with synchrony of turn-taking patterns during staff-client interactions and whether the level of dominance and balance is related to the observed quality of the social interactions. Nineteen staff members video-recorded a social interaction with one of their clients in which the client asked for support. The recordings were analyzed using Cross Recurrence Quantification Analysis and Initiative Response Analysis. Fifteen staff observers as well as client observers completed a questionnaire on the quality of the video-recorded interactions. Staff and clients' patterns of verbal interactional dominance and balance were associated with the synchrony of their turn-taking behaviors. Staff's dominance was associated with a higher level of synchrony of turn taking, whereas client's dominance was associated with a lower level of synchrony. The patterns of verbal interactional dominance and balance were associated with staff observer reports about the quality of the interactions. The study suggested that staff and clients have a tendency to be sensitive to different aspects of interactions, which in turn may have different functions.

  5. Mechanical properties of organelles driven by microtubule-dependent molecular motors in living cells.

    Directory of Open Access Journals (Sweden)

    Luciana Bruno

    Full Text Available The organization of the cytoplasm is regulated by molecular motors which transport organelles and other cargoes along cytoskeleton tracks. Melanophores have pigment organelles or melanosomes that move along microtubules toward their minus and plus end by the action of cytoplasmic dynein and kinesin-2, respectively. In this work, we used single particle tracking to characterize the mechanical properties of motor-driven organelles during transport along microtubules. We tracked organelles with high temporal and spatial resolutions and characterized their dynamics perpendicular to the cytoskeleton track. The quantitative analysis of these data showed that the dynamics is due to a spring-like interaction between melanosomes and microtubules in a viscoelastic microenvironment. A model based on a generalized Langevin equation explained these observations and predicted that the stiffness measured for the motor complex acting as a linker between organelles and microtubules is ∼ one order smaller than that determined for motor proteins in vitro. This result suggests that other biomolecules involved in the interaction between motors and organelles contribute to the mechanical properties of the motor complex. We hypothesise that the high flexibility observed for the motor linker may be required to improve the efficiency of the transport driven by multiple copies of motor molecules.

  6. The polarity protein Par6 is coupled to the microtubule network during molluscan early embryogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Homma, Taihei [Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shimizu, Miho [Kuroda Chiromorphology Team, ERATO-SORST, JST, Komaba, Meguro-ku, Tokyo 153-8902 (Japan); Kuroda, Reiko, E-mail: ckuroda@mail.ecc.u-tokyo.ac.jp [Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kuroda Chiromorphology Team, ERATO-SORST, JST, Komaba, Meguro-ku, Tokyo 153-8902 (Japan); Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902 (Japan)

    2011-01-07

    Research highlights: {yields} The cDNAs encoding Par6 and aPKC homologues were cloned from the snail Lymnaea stagnalis. {yields} L. stagnalis Par6 directly interacts with tubulin and microtubules and localizes to the microtubule cytoskeleton during the early embryogenesis. {yields} Identical sequence and localization of LsPar6 for the dextral and the sinistral snails exclude the possibility of the gene being the primary determinant of body handedness. -- Abstract: Cell polarity, which directs the orientation of asymmetric cell division and segregation of fate determinants, is a fundamental feature of development and differentiation. Regulators of polarity have been extensively studied, and the critical importance of the Par (partitioning-defective) complex as the polarity machinery is now recognized in a wide range of eukaryotic systems. The Par polarity module is evolutionarily conserved, but its mechanism and cooperating factors vary among different systems. Here we describe the cloning and characterization of a pond snail Lymnaea stagnalis homologue of partitioning-defective 6 (Lspar6). The protein product LsPar6 shows high affinity for microtubules and localizes to the mitotic apparatus during embryonic cell division. In vitro assays revealed direct binding of LsPar6 to tubulin and microtubules, which is the first evidence of the direct interaction between the two proteins. The interaction is mediated by two distinct regions of LsPar6 both located in the N-terminal half. Atypical PKC, a functional partner of Par6, was also found to localize to the mitotic spindle. These results suggest that the L. stagnalis Par complex employs the microtubule network in cell polarity processes during the early embryogenesis. Identical sequence and localization of LsPar6 for the dextral and the sinistral snails exclude the possibility of the gene being the primary determinant of handedness.

  7. The Microtubule Regulatory Protein Stathmin Is Required to Maintain the Integrity of Axonal Microtubules in Drosophila.

    Directory of Open Access Journals (Sweden)

    Jason E Duncan

    Full Text Available Axonal transport, a form of long-distance, bi-directional intracellular transport that occurs between the cell body and synaptic terminal, is critical in maintaining the function and viability of neurons. We have identified a requirement for the stathmin (stai gene in the maintenance of axonal microtubules and regulation of axonal transport in Drosophila. The stai gene encodes a cytosolic phosphoprotein that regulates microtubule dynamics by partitioning tubulin dimers between pools of soluble tubulin and polymerized microtubules, and by directly binding to microtubules and promoting depolymerization. Analysis of stai function in Drosophila, which has a single stai gene, circumvents potential complications with studies performed in vertebrate systems in which mutant phenotypes may be compensated by genetic redundancy of other members of the stai gene family. This has allowed us to identify an essential function for stai in the maintenance of the integrity of axonal microtubules. In addition to the severe disruption in the abundance and architecture of microtubules in the axons of stai mutant Drosophila, we also observe additional neurological phenotypes associated with loss of stai function including a posterior paralysis and tail-flip phenotype in third instar larvae, aberrant accumulation of transported membranous organelles in stai deficient axons, a progressive bang-sensitive response to mechanical stimulation reminiscent of the class of Drosophila mutants used to model human epileptic seizures, and a reduced adult lifespan. Reductions in the levels of Kinesin-1, the primary anterograde motor in axonal transport, enhance these phenotypes. Collectively, our results indicate that stai has an important role in neuronal function, likely through the maintenance of microtubule integrity in the axons of nerves of the peripheral nervous system necessary to support and sustain long-distance axonal transport.

  8. The N-terminal domain of DDA3 regulates the spindle-association of the microtubule depolymerase Kif2a and controls the mitotic function of DDA3.

    Science.gov (United States)

    Jang, Chang-Young; Fang, Guowei

    2009-10-01

    DDA3 is a microtubule-associated protein that controls chromosome congression and segregation by regulating the dynamics of the mitotic spindle. Depletion of DDA3 alters spindle structure, generates unaligned chromosomes at metaphase, and delays the mitotic progression. DDA3 interacts with the microtubule depolymerase Kif2a and controls the association of Kif2a to the mitotic spindle and the dynamic turnover of microtubules in the spindle. To understand the function and regulation of DDA3, we analyzed its domain structure and found that the C-terminal domain of DDA3 directly binds to microtubules in vitro and associates with the mitotic spindle in vivo. The N-terminal domain of DDA3 does not interact with microtubules, but acts dominant negatively over the wild-type protein. Ectopic expression of this domain prevents the endogenous DDA3 from association with the spindle and results in a high frequency of unaligned chromosomes in metaphase cells, a phenotype similar to that in metaphase cells depleted of DDA3. Mechanistically, expression of N-terminal DDA3 reduces the amount of spindle-associated Kif2a and increases the spindle microtubule density, pheno-copying those in DDA3-depleted cells. We conclude that DDA3 has a distinct domain structure. The C-terminal domain confers its ability to associate with the mitotic spindle, while the regulatory N-terminal domain controls the microtubule-binding by the C-terminal domain and determines the cellular activity of the DDA3 protein.

  9. Spindle pole body-anchored Kar3 drives the nucleus along microtubules from another nucleus in preparation for nuclear fusion during yeast karyogamy.

    Science.gov (United States)

    Gibeaux, Romain; Politi, Antonio Z; Nédélec, François; Antony, Claude; Knop, Michael

    2013-02-01

    Nuclear migration during yeast karyogamy, termed nuclear congression, is required to initiate nuclear fusion. Congression involves a specific regulation of the microtubule minus end-directed kinesin-14 motor Kar3 and a rearrangement of the cytoplasmic microtubule attachment sites at the spindle pole bodies (SPBs). However, how these elements interact to produce the forces necessary for nuclear migration is less clear. We used electron tomography, molecular genetics, quantitative imaging, and first principles modeling to investigate how cytoplasmic microtubules are organized during nuclear congression. We found that Kar3, with the help of its light chain, Cik1, is anchored during mating to the SPB component Spc72 that also serves as a nucleator and anchor for microtubules via their minus ends. Moreover, we show that no direct microtubule-microtubule interactions are required for nuclear migration. Instead, SPB-anchored Kar3 exerts the necessary pulling forces laterally on microtubules emanating from the SPB of the mating partner nucleus. Therefore, a twofold symmetrical application of the core principle that drives nuclear migration in higher cells is used in yeast to drive nuclei toward each other before nuclear fusion.

  10. Resolving bundled microtubules using anti-tubulin nanobodies.

    Science.gov (United States)

    Mikhaylova, Marina; Cloin, Bas M C; Finan, Kieran; van den Berg, Robert; Teeuw, Jalmar; Kijanka, Marta M; Sokolowski, Mikolaj; Katrukha, Eugene A; Maidorn, Manuel; Opazo, Felipe; Moutel, Sandrine; Vantard, Marylin; Perez, Frank; van Bergen en Henegouwen, Paul M P; Hoogenraad, Casper C; Ewers, Helge; Kapitein, Lukas C

    2015-08-11

    Microtubules are hollow biopolymers of 25-nm diameter and are key constituents of the cytoskeleton. In neurons, microtubules are organized differently between axons and dendrites, but their precise organization in different compartments is not completely understood. Super-resolution microscopy techniques can detect specific structures at an increased resolution, but the narrow spacing between neuronal microtubules poses challenges because most existing labelling strategies increase the effective microtubule diameter by 20-40 nm and will thereby blend neighbouring microtubules into one structure. Here we develop single-chain antibody fragments (nanobodies) against tubulin to achieve super-resolution imaging of microtubules with a decreased apparent diameter. To test the resolving power of these novel probes, we generate microtubule bundles with a known spacing of 50-70 nm and successfully resolve individual microtubules. Individual bundled microtubules can also be resolved in different mammalian cells, including hippocampal neurons, allowing novel insights into fundamental mechanisms of microtubule organization in cell- and neurobiology.

  11. How do Plants Organize Microtubules Without a Centrosome?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A microtubule nucleates from a γ-tubulin complex, which consists of γ-tubulin, proteins from the SPC97/SPC98 family, and the WD40 motif protein GCP-WD. We analyzed the phylogenetic relationships of the genes encoding these proteins and found that the components of this complex are widely conserved among land plants and other eukaryotes. By contrast,the interphase and mitotic arrays of microtubules in land plants differ from those in other eukaryotes. In the interphase cortical array, the majority of microtubules nucleate on existing microtubules in the absence of conspicuous microtubule organizing centers (MTOCs), such as a centrosome. During mitosis, the spindle also forms in the absence of conspicuous MTOCs. Both poles of the spindle are broad, and branched structures of microtubules called microtubule converging centers form at the poles. In this review, we hypothesize that the microtubule converging centers form via microtubuledependent microtubule nucleation, as in the case of the interphase arrays. The evolutionary insights arising from the molecular basis of the diversity in microtubule organization are discussed.

  12. Interconnections between cell wall polymers, wall mechanics, and cortical microtubules: Teasing out causes and consequences.

    Science.gov (United States)

    Xiao, Chaowen; Anderson, Charles T

    2016-09-01

    In plants, cell wall components including cellulose, hemicelluloses, and pectins interact with each other to form complex extracellular network structures that control cell growth and maintain cell shape. However, it is still not clear exactly how different wall polymers interact, how the conformations and interactions of cell wall polymers relate to wall mechanics, and how these factors impinge on intracellular structures such as the cortical microtubule cytoskeleton. Here, based on studies of Arabidopsis thaliana xxt1 xxt2 mutants, which lack detectable xyloglucan in their walls and display aberrant wall mechanics, altered cellulose patterning and biosynthesis, and reduced cortical microtubule stability, we discuss the potential relationships between cell wall biosynthesis, wall mechanics, and cytoskeletal dynamics in an effort to better understand their roles in controlling plant growth and morphogenesis.

  13. Motor protein accumulation on antiparallel microtubule overlaps

    CERN Document Server

    Kuan, Hui-Shun

    2015-01-01

    Biopolymers serve as one-dimensional tracks on which motor proteins move to perform their biological roles. Motor protein phenomena have inspired theoretical models of one-dimensional transport, crowding, and jamming. Experiments studying the motion of Xklp1 motors on reconstituted antiparallel microtubule overlaps demonstrated that motors recruited to the overlap walk toward the plus end of individual microtubules and frequently switch between filaments. We study a model of this system that couples the totally asymmetric simple exclusion process (TASEP) for motor motion with switches between antiparallel filaments and binding kinetics. We determine steady-state motor density profiles for fixed-length overlaps using exact and approximate solutions of the continuum differential equations and compare to kinetic Monte Carlo simulations. The center region, far from the overlap ends, has a constant motor density as one would na\\"ively expect. However, rather than following a simple binding equilibrium, the center ...

  14. Microtubule-Targeting Therapy for Prostate Cancer

    Science.gov (United States)

    2007-02-01

    Cancer1828 Mol Cancer Ther 2005;4(12). December 2005 22. Sambrook J, Fritsch EF, Maniatis T. Molecular cloning : a laboratory manual. 2nd ed. Cold Spring...Harbor (NY): Cold Spring Harbor Laboratory; 1989. 23. Zhu XX, Kozarsky K, Strahler JR, et al. Molecular cloning of a novel human leukemia-associated...of Cancer Research, Abstract #4940, 2005. 3. Mistry, SJ, Atweh, GF. Microtubule targeting therapy: Anti-stathmin based molecular cancer

  15. Relativistic effects in the tidal interaction between a white dwarf and a massive black hole in Fermi normal coordinates

    CERN Document Server

    Cheng, Roseanne M

    2013-01-01

    We consider tidal encounters between a white dwarf and an intermediate mass black hole. Both weak encounters and those at the threshold of disruption are modeled. The numerical code combines mesh-based (PPM) hydrodynamics, a spectral method (FFT) solution of the self-gravity, and a general relativistic Fermi normal coordinate (FNC) system that follows the star and debris. FNCs provide an expansion of the black hole tidal field that includes quadrupole and higher multipole moments and relativistic corrections. We compute the mass loss from the white dwarf that occurs in weak tidal encounters. Secondly, we compute carefully the energy deposition onto the star, examining the effects of non-radial and radial mode excitation, surface layer heating, mass loss, and relativistic orbital motion. We find evidence of a slight relativistic suppression in tidal energy transfer. Tidal energy deposition is compared to orbital energy loss due to gravitational bremsstrahlung and the combined losses are used to estimate tidal ...

  16. NGF causes TrkA to specifically attract microtubules to lipid rafts.

    Directory of Open Access Journals (Sweden)

    Shona Pryor

    Full Text Available Membrane protein sorting is mediated by interactions between proteins and lipids. One mechanism that contributes to sorting involves patches of lipids, termed lipid rafts, which are different from their surroundings in lipid and protein composition. Although the nerve growth factor (NGF receptors, TrkA and p75(NTR collaborate with each other at the plasma membrane to bind NGF, these two receptors are endocytosed separately and activate different cellular responses. We hypothesized that receptor localization in membrane rafts may play a role in endocytic sorting. TrkA and p75(NTR both reside in detergent-resistant membranes (DRMs, yet they responded differently to a variety of conditions. The ganglioside, GM1, caused increased association of NGF, TrkA, and microtubules with DRMs, but a decrease in p75(NTR. When microtubules were induced to polymerize and attach to DRMs by in vitro reactions, TrkA, but not p75(NTR, was bound to microtubules in DRMs and in a detergent-resistant endosomal fraction. NGF enhanced the interaction between TrkA and microtubules in DRMs, yet tyrosine phosphorylated TrkA was entirely absent in DRMs under conditions where activated TrkA was detected in detergent-sensitive membranes and endosomes. These data indicate that TrkA and p75(NTR partition into membrane rafts by different mechanisms, and that the fraction of TrkA that associates with DRMs is internalized but does not directly form signaling endosomes. Rather, by attracting microtubules to lipid rafts, TrkA may mediate other processes such as axon guidance.

  17. MICROTUBULE ORGANIZATION 1 regulates structure and function of microtubule arrays during mitosis and cytokinesis in the Arabidopsis root.

    Science.gov (United States)

    Kawamura, Eiko; Himmelspach, Regina; Rashbrooke, Madeleine C; Whittington, Angela T; Gale, Kevin R; Collings, David A; Wasteneys, Geoffrey O

    2006-01-01

    MICROTUBULE ORGANIZATION 1 (MOR1) is a plant member of the highly conserved MAP215/Dis1 family of microtubule-associated proteins. Prior studies with the temperature-sensitive mor1 mutants of Arabidopsis (Arabidopsis thaliana), which harbor single amino acid substitutions in an N-terminal HEAT repeat, proved that MOR1 regulates cortical microtubule organization and function. Here we demonstrate by use of live cell imaging and immunolabeling that the mor1-1 mutation generates specific defects in the microtubule arrays of dividing vegetative cells. Unlike the universal cortical microtubule disorganization in elongating mor1-1 cells, disruption of mitotic and cytokinetic microtubule arrays was not detected in all dividing cells. Nevertheless, quantitative analysis identified distinct defects in preprophase bands (PPBs), spindles, and phragmoplasts. In nearly one-half of dividing cells at the restrictive temperature of 30 degrees C, PPBs were not detected prior to spindle formation, and those that did form were often disrupted. mor1-1 spindles and phragmoplasts were short and abnormally organized and persisted for longer times than in wild-type cells. The reduced length of these arrays predicts that the component microtubule lengths are also reduced, suggesting that microtubule length is a critical determinant of spindle and phragmoplast structure, orientation, and function. Microtubule organizational defects led to aberrant chromosomal arrangements, misaligned or incomplete cell plates, and multinucleate cells. Antiserum raised against an N-terminal MOR1 sequence labeled the full length of microtubules in interphase arrays, PPBs, spindles, and phragmoplasts. Continued immunolabeling of the disorganized and short microtubules of mor1-1 at the restrictive temperature demonstrated that the mutant mor1-1(L174F) protein loses function without dissociating from microtubules, providing important insight into the mechanism by which MOR1 may regulate microtubule length.

  18. Tuning microtubule-based transport via filamentous MAPs: the problem of dynein

    Science.gov (United States)

    Vershinin, Michael; Xu, Jing; Razafsky, David S.; King, Stephen J.; Gross, Steven P.

    2010-01-01

    We recently proposed that regulating the single-to-multiple motor transition was a likely strategy for regulating kinesin-based transport in vivo. Here, we use an in vitro bead assay coupled with an optical trap to investigate how this proposed regulatory mechanism affects dynein-based transport. We show that tau’s regulation of kinesin function can proceed without interfering with dynein-based transport. Surprisingly, at extremely high tau levels—where kinesin cannot bind microtubules—dynein can still contact microtubules. The difference between tau’s effects on kinesin- and dynein-based motility suggests that tau can be used to tune relative amounts of plus-end and minus-end directed transport. As in the case of kinesin, we find that the 3RS isoform of tau is a more potent inhibitor of dynein binding to microtubules. We show that this isoform-specific effect is not due to steric interference of tau’s projection domains, but rather due to tau’s interactions with the motor at the microtubule surface. Nonetheless, we do observe a modest steric interference effect of tau away from the microtubule and discuss the potential implications of this for molecular motor structure. PMID:18373727

  19. Conformational mechanism for the stability of microtubule-kinetochore attachments

    CERN Document Server

    Bertalan, Zsolt; Maiato, Helder; Zapperi, Stefano

    2014-01-01

    Regulating the stability of microtubule(MT)-kinetochore attachments is fundamental to avoiding mitotic errors and ensure proper chromosome segregation during cell division. While biochemical factors involved in this process have been identified, its mechanics still needs to be better understood. Here we introduce and simulate a mechanical model of MT-kinetochore interactions in which the stability of the attachment is ruled by the geometrical conformations of curling MT-protofilaments entangled in kinetochore fibrils. The model allows us to reproduce with good accuracy in vitro experimental measurements of the detachment times of yeast kinetochores from MTs under external pulling forces. Numerical simulations suggest that geometrical features of MT-protofilaments may play an important role in the switch between stable and unstable attachments.

  20. The Role of Molecular Microtubule Motors and the Microtubule Cytoskeleton in Stress Granule Dynamics

    Directory of Open Access Journals (Sweden)

    Kristen M. Bartoli

    2011-01-01

    Full Text Available Stress granules (SGs are cytoplasmic foci that appear in cells exposed to stress-induced translational inhibition. SGs function as a triage center, where mRNAs are sorted for storage, degradation, and translation reinitiation. The underlying mechanisms of SGs dynamics are still being characterized, although many key players have been identified. The main components of SGs are stalled 48S preinitiation complexes. To date, many other proteins have also been found to localize in SGs and are hypothesized to function in SG dynamics. Most recently, the microtubule cytoskeleton and associated motor proteins have been demonstrated to function in SG dynamics. In this paper, we will discuss current literature examining the function of microtubules and the molecular microtubule motors in SG assembly, coalescence, movement, composition, organization, and disassembly.

  1. Cellular Samurai: katanin and the severing of microtubules.

    Science.gov (United States)

    Quarmby, L

    2000-08-01

    Recent biochemical studies of the AAA ATPase, katanin, provide a foundation for understanding how microtubules might be severed along their length. These in vitro studies are complemented by a series of recent reports of direct in vivo observation of microtubule breakage, which indicate that the in vitro phenomenon of catalysed microtubule severing is likely to be physiological. There is also new evidence that microtubule severing by katanin is important for the production of non-centrosomal microtubules in cells such as neurons and epithelial cells. Although it has been difficult to establish the role of katanin in mitosis, new genetic evidence indicates that a katanin-like protein, MEI-1, plays an essential role in meiosis in C. elegans. Finally, new proteins involved in the severing of axonemal microtubules have been discovered in the deflagellation system of Chlamydomonas.

  2. Microtubule Associated Proteins in Plants and the Processes They Manage

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Microtubule associated proteins (MAPs) are proteins that physically bind to microtubules in eukaryotes. MAPs play important roles in regulating the polymerization and organization of microtubules and in using the ensuing microtubule arrays to carry out a variety of cellular functions. In plants, MAPs manage the construction, repositioning, and dismantling of four distinct microtubule arrays throughout the cell cycle. Three of these arrays, the cortical array, the preprophase band,and the phragmoplast, are prominent to plants and are responsible for facilitating cell wall deposition and modification,transducing signals, demarcating the plane of cell division, and forming the new cell plate during cytokinesis, This review highlights important aspects of how MAPs in plants establish and maintain microtubule arrays as well as regulate cell growth, cell division, and cellular responses to the environment.

  3. Cortical microtubule arrays are initiated from a nonrandom prepattern driven by atypical microtubule initiation.

    Science.gov (United States)

    Lindeboom, Jelmer J; Lioutas, Antonios; Deinum, Eva E; Tindemans, Simon H; Ehrhardt, David W; Emons, Anne Mie C; Vos, Jan W; Mulder, Bela M

    2013-03-01

    The ordered arrangement of cortical microtubules in growing plant cells is essential for anisotropic cell expansion and, hence, for plant morphogenesis. These arrays are dismantled when the microtubule cytoskeleton is rearranged during mitosis and reassembled following completion of cytokinesis. The reassembly of the cortical array has often been considered as initiating from a state of randomness, from which order arises at least partly through self-organizing mechanisms. However, some studies have shown evidence for ordering at early stages of array assembly. To investigate how cortical arrays are initiated in higher plant cells, we performed live-cell imaging studies of cortical array assembly in tobacco (Nicotiana tabacum) Bright Yellow-2 cells after cytokinesis and drug-induced disassembly. We found that cortical arrays in both cases did not initiate randomly but with a significant overrepresentation of microtubules at diagonal angles with respect to the cell axis, which coincides with the predominant orientation of the microtubules before their disappearance from the cell cortex in preprophase. In Arabidopsis (Arabidopsis thaliana) root cells, recovery from drug-induced disassembly was also nonrandom and correlated with the organization of the previous array, although no diagonal bias was observed in these cells. Surprisingly, during initiation, only about one-half of the new microtubules were nucleated from locations marked by green fluorescent protein-γ-tubulin complex protein2-tagged γ-nucleation complexes (γ-tubulin ring complex), therefore indicating that a large proportion of early polymers was initiated by a noncanonical mechanism not involving γ-tubulin ring complex. Simulation studies indicate that the high rate of noncanonical initiation of new microtubules has the potential to accelerate the rate of array repopulation.

  4. RUN COORDINATION

    CERN Multimedia

    Christophe Delaere

    2013-01-01

    The focus of Run Coordination during LS1 is to monitor closely the advance of maintenance and upgrade activities, to smooth interactions between subsystems and to ensure that all are ready in time to resume operations in 2015 with a fully calibrated and understood detector. After electricity and cooling were restored to all equipment, at about the time of the last CMS week, recommissioning activities were resumed for all subsystems. On 7 October, DCS shifts began 24/7 to allow subsystems to remain on to facilitate operations. That culminated with the Global Run in November (GriN), which   took place as scheduled during the week of 4 November. The GriN has been the first centrally managed operation since the beginning of LS1, and involved all subdetectors but the Pixel Tracker presently in a lab upstairs. All nights were therefore dedicated to long stable runs with as many subdetectors as possible. Among the many achievements in that week, three items may be highlighted. First, the Strip...

  5. EphrinB1/EphB3b Coordinate Bidirectional Epithelial-Mesenchymal Interactions Controlling Liver Morphogenesis and Laterality

    DEFF Research Database (Denmark)

    Cayuso, Jordi; Dzementsei, Aliaksandr; Fischer, Johanna C

    2016-01-01

    and adjacent lateral plate mesoderm (LPM), resulting in asymmetric positioning of the zebrafish liver. EphrinB1 in hepatoblasts regulates directional migration and mediates interactions with the LPM, where EphB3b controls polarity and movement of the LPM. EphB3b in the LPM concomitantly repels hepatoblasts...

  6. Janus Compounds, 5-Chloro-N4-methyl-N4-aryl-9H-pyrimido[4,5-b]indole-2,4-diamines, Cause Both Microtubule Depolymerizing and Stabilizing Effects

    Directory of Open Access Journals (Sweden)

    Cristina C. Rohena

    2016-12-01

    Full Text Available While evaluating a large library of compounds designed to inhibit microtubule polymerization, we identified four compounds that have unique effects on microtubules. These compounds cause mixed effects reminiscent of both microtubule depolymerizers and stabilizers. Immunofluorescence evaluations showed that each compound initially caused microtubule depolymerization and, surprisingly, with higher concentrations, microtubule bundles were also observed. There were subtle differences in the propensity to cause these competing effects among the compounds with a continuum of stabilizing and destabilizing effects. Tubulin polymerization experiments confirmed the differential effects and, while each of the compounds increased the initial rate of tubulin polymerization at high concentrations, total tubulin polymer was not enhanced at equilibrium, likely because of the dueling depolymerization effects. Modeling studies predict that the compounds bind to tubulin within the colchicine site and confirm that there are differences in their potential interactions that might underlie their distinct effects on microtubules. Due to their dual properties of microtubule stabilization and destabilization, we propose the name Janus for these compounds after the two-faced Roman god. The identification of synthetically tractable, small molecules that elicit microtubule stabilizing effects is a significant finding with the potential to identify new mechanisms of microtubule stabilization.

  7. The National Parliamentary Arena and Methods of Open Coordination: Explaining the Frequency of OMC-related Executive-legislature Interactions

    Directory of Open Access Journals (Sweden)

    Rik de Ruiter

    2011-02-01

    Full Text Available This article tests the importance of different factors for the frequency with which information from open methods of coordination (OMCs is used in parliamentary debates. Previous research has shown that OMCs provide the executive and the legislature with information on best and worst national policy practices, enabling them to adopt different strategies. First, a national government can fame its own policies with the use of information from OMCs. Second, information from OMCs can be used by parliamentarians of opposition parties to shame the policies of the incumbent government. A study of Dutch parliamentary debates indicates that the Dutch government uses more information from OMCs to fame its own policies when OMCs have a developed infrastructure and/or a treaty base. Parliamentarians from opposition parties use more information from OMCs adopted for policy areas in which there was already EU-level activity prior to the OMC, and the government provided information on the substance of OMCs to members of national parliaments.

  8. CLIP-170 facilitates the formation of kinetochore-microtubule attachments.

    Science.gov (United States)

    Tanenbaum, Marvin E; Galjart, Niels; van Vugt, Marcel A T M; Medema, René H

    2006-01-11

    CLIP-170 is a microtubule 'plus end tracking' protein involved in several microtubule-dependent processes in interphase. At the onset of mitosis, CLIP-170 localizes to kinetochores, but at metaphase, it is no longer detectable at kinetochores. Although RNA interference (RNAi) experiments have suggested an essential role for CLIP-170 during mitosis, the molecular function of CLIP-170 in mitosis has not yet been revealed. Here, we used a combination of high-resolution microscopy and RNAi-mediated depletion to study the function of CLIP-170 in mitosis. We found that CLIP-170 dynamically localizes to the outer most part of unattached kinetochores and to the ends of growing microtubules. In addition, we provide evidence that a pool of CLIP-170 is transported along kinetochore-microtubules by the dynein/dynactin complex. Interference with CLIP-170 expression results in defective chromosome congression and diminished kinetochore-microtubule attachments, but does not detectibly affect microtubule dynamics or kinetochore-microtubule stability. Taken together, our results indicate that CLIP-170 facilitates the formation of kinetochore-microtubule attachments, possibly through direct capture of microtubules at the kinetochore.

  9. Deceivingly dynamic: Learning-dependent changes in stathmin and microtubules.

    Science.gov (United States)

    Uchida, Shusaku; Shumyatsky, Gleb P

    2015-10-01

    Microtubules, one of the major cytoskeletal structures, were previously considered stable and only indirectly involved in synaptic structure and function in mature neurons. However, recent evidence demonstrates that microtubules are dynamic and have an important role in synaptic structure, synaptic plasticity, and memory. In particular, learning induces changes in microtubule turnover and stability, and pharmacological manipulation of microtubule dynamics alters synaptic plasticity and long-term memory. These learning-induced changes in microtubules are controlled by the phosphoprotein stathmin, whose only known cellular activity is to negatively regulate microtubule formation. During the first eight hours following learning, changes in the phosphorylation of stathmin go through two phases causing biphasic shifts in microtubules stability/instability. These shifts, in turn, regulate memory formation by controlling in the second phase synaptic transport of the GluA2 subunit of AMPA receptors. Improper regulation of stathmin and microtubule dynamics has been observed in aged animals and in patients with Alzheimer's disease and depression. Thus, recent work on stathmin and microtubules has identified new molecular players in the early stages of memory encoding.

  10. Calculation of the Electromagnetic Field Around a Microtubule

    Directory of Open Access Journals (Sweden)

    D. Havelka

    2009-01-01

    Full Text Available Microtubules are important structures in the cytoskeleton which organizes the cell. A single microtubule is composed of electrically polar structures, tubulin heterodimers, which have a strong electric dipole moment. Vibrations are expected to be generated in microtubules, thus tubulin heterodimers oscillate as electric dipoles. This gives rise to an electromagnetic field which is detected around the cells. We calculate here the electromagnetic field of microtubules if they are excited at 1 GHz. This paper includes work done for the bachelor thesis of the first author. 

  11. Molecular architecture of axonemal microtubule doublets revealedby cryo-electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sui, Haixin; Downing, Kenneth H.

    2006-05-22

    The axoneme, which forms the core of eukaryotic flagella and cilia, is one of the largest macromolecular machines with a structure that is largely conserved from protists to mammals. Microtubule doublets are structural components of axonemes containing a number of proteins besides tubulin, and are usually found in arrays of nine doublets arranged around two singlet microtubules. Coordinated sliding of adjacent doublets, which involves a host of other proteins in the axoneme, produces periodic beating movements of the axoneme. We have obtained a 3D density map of intact microtubule doublets using cryo-electron tomography and image averaging. Our map, with a resolution of about 3 nm, provides insights into locations of particular proteins within the doublets and the structural features of the doublets that define their mechanical properties. We identify likely candidates for several of these non-tubulin components of the doublets. This work offers novel insight on how tubulin protofilaments and accessory proteins attach together to form the doublets and provides a structural basis for understanding doublet function in axonemes.

  12. HILI destabilizes microtubules by suppressing phosphorylation and Gigaxonin-mediated degradation of TBCB

    Science.gov (United States)

    Tan, Hao; Liao, Hua; Zhao, Lianfang; Lu, Yilu; Jiang, Siyuan; Tao, Dachang; Liu, Yunqiang; Ma, Yongxin

    2017-01-01

    Human PIWIL2, aka HILI, is a member of PIWI protein family and overexpresses in various tumors. However, the underlying mechanisms of HILI in tumorigenesis remain largely unknown. TBCB has a critical role in regulating microtubule dynamics and is overexpressed in many cancers. Here we report that HILI inhibits Gigaxonin-mediated TBCB ubiquitination and degradation by interacting with TBCB, promoting the binding between HSP90 and TBCB, and suppressing the interaction between Gigaxonin and TBCB. Meanwhile, HILI can also reduce phosphorylation level of TBCB induced by PAK1. Our results showed that HILI suppresses microtubule polymerization and promotes cell proliferation, migration and invasion via TBCB for the first time, revealing a novel mechanism for HILI in tumorigenesis. PMID:28393858

  13. Cap-Gly proteins at microtubule plus ends: is EB1 detyrosination involved?

    Science.gov (United States)

    Bosson, Anouk; Soleilhac, Jean-Marc; Valiron, Odile; Job, Didier; Andrieux, Annie; Moutin, Marie-Jo

    2012-01-01

    Localization of CAP-Gly proteins such as CLIP170 at microtubule+ends results from their dual interaction with α-tubulin and EB1 through their C-terminal amino acids -EEY. Detyrosination (cleavage of the terminal tyrosine) of α-tubulin by tubulin-carboxypeptidase abolishes CLIP170 binding. Can detyrosination affect EB1 and thus regulate the presence of CLIP170 at microtubule+ends as well? We developed specific antibodies to discriminate tyrosinated vs detyrosinated forms of EB1 and detected only tyrosinated EB1 in fibroblasts, astrocytes, and total brain tissue. Over-expressed EB1 was not detyrosinated in cells and chimeric EB1 with the eight C-terminal amino acids of α-tubulin was only barely detyrosinated. Our results indicate that detyrosination regulates CLIPs interaction with α-tubulin, but not with EB1. They highlight the specificity of carboxypeptidase toward tubulin.

  14. Cap-Gly proteins at microtubule plus ends: is EB1 detyrosination involved?

    Directory of Open Access Journals (Sweden)

    Anouk Bosson

    Full Text Available Localization of CAP-Gly proteins such as CLIP170 at microtubule+ends results from their dual interaction with α-tubulin and EB1 through their C-terminal amino acids -EEY. Detyrosination (cleavage of the terminal tyrosine of α-tubulin by tubulin-carboxypeptidase abolishes CLIP170 binding. Can detyrosination affect EB1 and thus regulate the presence of CLIP170 at microtubule+ends as well? We developed specific antibodies to discriminate tyrosinated vs detyrosinated forms of EB1 and detected only tyrosinated EB1 in fibroblasts, astrocytes, and total brain tissue. Over-expressed EB1 was not detyrosinated in cells and chimeric EB1 with the eight C-terminal amino acids of α-tubulin was only barely detyrosinated. Our results indicate that detyrosination regulates CLIPs interaction with α-tubulin, but not with EB1. They highlight the specificity of carboxypeptidase toward tubulin.

  15. Interaction of Dialkyltin(Ⅳ) Bishydroxamates with 5'-AMP or DNA: the Impact of Carbon Chain Length to Coordination Properties

    Institute of Scientific and Technical Information of China (English)

    SHANG Xian-Mei; WU Ji-Zhou; LI Qing-Shan

    2008-01-01

    Two diorganotin(Ⅳ) complexes, [Me2Sn(4-FC6H4C(O)NHO)2] (1) and [Bu2Sn(4-FC6H4C(O)NHO)2] (2), were synthesized. The action mode of the diorganotin(Ⅳ) complexes with adenosine-5'-monophosphate (5'-AMP) or DNA under different conditions and different time was investigated by high-solution 1H NMR and 31P NMR technology and UV spectroscopy. The complexes 1 and 2 which have different carbon chain lengths exhibited different action modes with mononucleotide or DNA. The interaction of 2 with 5'-AMP resulted in significant chemical shift of H(8), H(2) and 31P. A hyperchromic effect of DNA could be observed due to the interaction of 2 with DNA, while interaction of 1 with 5'-AMP or DNA could only cause obvious change of chemical shift of 31P. The results indicate that the complex 2 is the first case which could selectively bind to both the N(1) atom of the base and the phosphate oxygen atom of 5'-AMP near a physiological condition, and may further destroy the helical structure of DNA, while 1 may merely bind to the phosphate oxygen atom of 5'-AMP and cause the contraction of the DNA helical structure.The results first reveal that the organic group R may not only help the membrane transference of the diorganotin compounds but also play an important role in the action mode with DNA.

  16. APP interacts with LRP4 and agrin to coordinate the development of the neuromuscular junction in mice

    Science.gov (United States)

    Choi, Hong Y; Liu, Yun; Tennert, Christian; Sugiura, Yoshie; Karakatsani, Andromachi; Kröger, Stephan; Johnson, Eric B; Hammer, Robert E; Lin, Weichun; Herz, Joachim

    2013-01-01

    ApoE, ApoE receptors and APP cooperate in the pathogenesis of Alzheimer’s disease. Intriguingly, the ApoE receptor LRP4 and APP are also required for normal formation and function of the neuromuscular junction (NMJ). In this study, we show that APP interacts with LRP4, an obligate co-receptor for muscle-specific tyrosine kinase (MuSK). Agrin, a ligand for LRP4, also binds to APP and co-operatively enhances the interaction of APP with LRP4. In cultured myotubes, APP synergistically increases agrin-induced acetylcholine receptor (AChR) clustering. Deletion of the transmembrane domain of LRP4 (LRP4 ECD) results in growth retardation of the NMJ, and these defects are markedly enhanced in APP−/−;LRP4ECD/ECD mice. Double mutant NMJs are significantly reduced in size and number, resulting in perinatal lethality. Our findings reveal novel roles for APP in regulating neuromuscular synapse formation through hetero-oligomeric interaction with LRP4 and agrin and thereby provide new insights into the molecular mechanisms that govern NMJ formation and maintenance. DOI: http://dx.doi.org/10.7554/eLife.00220.001 PMID:23986861

  17. Individual-Environment Interactions in Swimming: The Smallest Unit for Analysing the Emergence of Coordination Dynamics in Performance?

    Science.gov (United States)

    Guignard, Brice; Rouard, Annie; Chollet, Didier; Hart, John; Davids, Keith; Seifert, Ludovic

    2017-02-08

    Displacement in competitive swimming is highly dependent on fluid characteristics, since athletes use these properties to propel themselves. It is essential for sport scientists and practitioners to clearly identify the interactions that emerge between each individual swimmer and properties of an aquatic environment. Traditionally, the two protagonists in these interactions have been studied separately. Determining the impact of each swimmer's movements on fluid flow, and vice versa, is a major challenge. Classic biomechanical research approaches have focused on swimmers' actions, decomposing stroke characteristics for analysis, without exploring perturbations to fluid flows. Conversely, fluid mechanics research has sought to record fluid behaviours, isolated from the constraints of competitive swimming environments (e.g. analyses in two-dimensions, fluid flows passively studied on mannequins or robot effectors). With improvements in technology, however, recent investigations have focused on the emergent circular couplings between swimmers' movements and fluid dynamics. Here, we provide insights into concepts and tools that can explain these on-going dynamic interactions in competitive swimming within the theoretical framework of ecological dynamics.

  18. Interplay between kinesin-1 and cortical dynein during axonal outgrowth and microtubule organization in Drosophila neurons.

    Science.gov (United States)

    del Castillo, Urko; Winding, Michael; Lu, Wen; Gelfand, Vladimir I

    2015-12-28

    In this study, we investigated how microtubule motors organize microtubules in Drosophila neurons. We showed that, during the initial stages of axon outgrowth, microtubules display mixed polarity and minus-end-out microtubules push the tip of the axon, consistent with kinesin-1 driving outgrowth by sliding antiparallel microtubules. At later stages, the microtubule orientation in the axon switches from mixed to uniform polarity with plus-end-out. Dynein knockdown prevents this rearrangement and results in microtubules of mixed orientation in axons and accumulation of microtubule minus-ends at axon tips. Microtubule reorganization requires recruitment of dynein to the actin cortex, as actin depolymerization phenocopies dynein depletion, and direct recruitment of dynein to the membrane bypasses the actin requirement. Our results show that cortical dynein slides 'minus-end-out' microtubules from the axon, generating uniform microtubule arrays. We speculate that differences in microtubule orientation between axons and dendrites could be dictated by differential activity of cortical dynein.

  19. Team coordination dynamics.

    Science.gov (United States)

    Gorman, Jamie C; Amazeen, Polemnia G; Cooke, Nancy J

    2010-07-01

    Team coordination consists of both the dynamics of team member interaction and the environmental dynamics to which a team is subjected. Focusing on dynamics, an approach is developed that contrasts with traditional aggregate-static concepts of team coordination as characterized by the shared mental model approach. A team coordination order parameter was developed to capture momentary fluctuations in coordination. Team coordination was observed in three-person uninhabited air vehicle teams across two experimental sessions. The dynamics of the order parameter were observed under changes of a team familiarity control parameter. Team members returned for the second session to either the same (Intact) or different (Mixed) team. 'Roadblock' perturbations, or novel changes in the task environment, were introduced in order to probe the stability of team coordination. Nonlinear dynamic methods revealed differences that a traditional approach did not: Intact and Mixed team coordination dynamics looked very different; Mixed teams were more stable than Intact teams and explored the space of solutions without the need for correction. Stability was positively correlated with the number of roadblock perturbations that were overcome successfully. The novel and non-intuitive contribution of a dynamical analysis was that Mixed teams, who did not have a long history working together, were more adaptive. Team coordination dynamics carries new implications for traditional problems such as training adaptive teams.

  20. Coordinated turn-and-reach movements. I. Anticipatory compensation for self-generated coriolis and interaction torques.

    Science.gov (United States)

    Pigeon, Pascale; Bortolami, Simone B; DiZio, Paul; Lackner, James R

    2003-01-01

    When reaching movements involve simultaneous trunk rotation, additional interaction torques are generated on the arm that are absent when the trunk is stable. To explore whether the CNS compensates for such self-generated interaction torques, we recorded hand trajectories in reaching tasks involving various amplitudes and velocities of arm extension and trunk rotation. Subjects pointed to three targets on a surface slightly above waist level. Two of the target locations were chosen so that a similar arm configuration relative to the trunk would be required for reaching to them, one of these targets requiring substantial trunk rotation, the other very little. Significant trunk rotation was necessary to reach the third target, but the arm's radial distance to the body remained virtually unchanged. Subjects reached at two speeds-a natural pace (slow) and rapidly (fast)-under normal lighting and in total darkness. Trunk angular velocity and finger velocity relative to the trunk were higher in the fast conditions but were not affected by the presence or absence of vision. Peak trunk velocity increased with increasing trunk rotation up to a maximum of 200 degrees /s. In slow movements, peak finger velocity relative to the trunk was smaller when trunk rotation was necessary to reach the targets. In fast movements, peak finger velocity was approximately 1.7 m/s for all targets. Finger trajectories were more curved when reaching movements involved substantial trunk rotation; however, the terminal errors and the maximal deviation of the trajectory from a straight line were comparable in slow and fast movements. This pattern indicates that the larger Coriolis, centripetal, and inertial interaction torques generated during rapid reaches were compensated by additional joint torques. Trajectory characteristics did not vary with the presence or absence of vision, indicating that visual feedback was unnecessary for anticipatory compensations. In all reaches involving trunk

  1. Rare π5^6Pb Interactions in a Two-dimensional Rare Metal-organic Coordination Polymer with Two Distinct Kinds of Axially Chiral Units

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    A new metal-organic coordination polymer [Pb(mfpdc)(CH3OH)]n (1, mfpdc = 2,6-dimethyl-4-(2-furanyl) pyridine-3,5-dicarboxylate) was synthesized and characterized by single-crystal X-ray analyses. The crystal is orthorhombic, space group Pbca, a = 15.6297(18), b = 9.4803(11), c = 18.598(2) A, V= 2755.8(6) A3, Z = 8, Mr= 498.44, Dc= 2.403 Mg/m3, F(000) = 1872, the final R = 0.0275 and wR = 0.0726 (1 〉 2σ(I)). There are interesting polynuclear zigzag (PbOs)n chains in the structure of 1, and there have interesting axially chiral S- and R-unit Pb4L units constructed from prochiral organic ligands through C-H...O bonding. The (R/S)-Pb4L units by sharing Pb centers generate a 2-D coordination network, in which there exist rare n65Pb (3.2610 A) interactions. The solid-state photoluminescent emission of compound 1 appears at 487 nm.

  2. Studying neuronal microtubule organization and microtubule-associated proteins using single molecule localization microscopy

    NARCIS (Netherlands)

    Chazeau, Anaël; Katrukha, Eugene A; Hoogenraad, Casper C; Kapitein, Lukas C

    2016-01-01

    The formation and maintenance of highly polarized neurons critically depends on the proper organization of the microtubule (MT) cytoskeleton. In axons, MTs are uniformly oriented with their plus-end pointing outward whereas in mature dendrites MTs have mixed orientations. MT organization and dynamic

  3. Co+-H interaction inspired alternate coordination geometries of biologically important cob(I)alamin: possible structural and mechanistic consequences for methyltransferases.

    Science.gov (United States)

    Kumar, Manoj; Hirao, Hajime; Kozlowski, Pawel M

    2012-10-01

    A detailed computational analysis employing density functional theory (DFT), atoms in molecules, and quantum mechanics/molecular mechanics (QM/MM) tools has been performed to investigate the primary coordination environment of cob(I)alamin (Co(+)Cbx), which is a ubiquitous B(12) intermediate in methyltransferases and ATP:corrinoid adenosyltransferases. The DFT calculations suggest that the simplified (Co(+)Cbl) as well as the complete (Co(+)Cbi) complexes can adapt to the square pyramidal or octahedral coordination geometry owing to the unconventional H-bonding between the Co(+) ion and its axial ligands. These Co(+)-H bonds contain appreciable amounts of electrostatic, charge transfer, long-range correlation, and dispersion components. The computed reduction potentials of the Co(2+)/Co(+) couple imply that the Co(+)-H(H(2)O) interaction causes a greater anodic shift [5-98 mV vs. the normal hydrogen electrode (NHE) in chloroform solvent] than the analogous Co(+)-H(imidazole) interaction (1 mV vs. NHE) in the reduction potential of the Co(2+)/Co(+) couple. This may explain why a β-axial H(2)O ligand has specifically been found in the active sites of certain methyltransferases. The QM/MM analysis of methionine synthase bound Co(+)Cbx (Protein Data Bank ID 1BMT, resolution 3.0 Å) indicates that the enzyme-bound Co(+)Cbx can also form a Co(+)-H bond, but can only exist in square pyramidal form because of the steric constraints imposed by the cellular environment. The present calculations thus support a recently proposed alternate mechanism for the enzyme-bound Co(2+)/Co(+) reduction that involves the conversion of square pyramidal Co(2+)Cbx into square pyramidal Co(+)Cbx (Kumar and Kozlowski in Angew. Chem. Int. Ed. 50:8702-8705, 2011).

  4. Assembly of bipolar microtubule structures by passive cross-linkers and molecular motors

    Science.gov (United States)

    Johann, D.; Goswami, D.; Kruse, K.

    2016-06-01

    During cell division, sister chromatids are segregated by the mitotic spindle, a bipolar assembly of interdigitating antiparallel polar filaments called microtubules. The spindle contains the midzone, a stable region of overlapping antiparallel microtubules, that is essential for maintaining bipolarity. Although a lot is known about the molecular players involved, the mechanism underlying midzone formation and maintenance is still poorly understood. We study the interaction of polar filaments that are cross-linked by molecular motors moving directionally and by passive cross-linkers diffusing along microtubules. Using a particle-based stochastic model, we find that the interplay of motors and passive cross-linkers can generate a stable finite overlap between a pair of antiparallel polar filaments. We develop a mean-field theory to study this mechanism in detail and investigate the influence of steric interactions between motors and passive cross-linkers on the overlap dynamics. In the presence of interspecies steric interactions, passive cross-linkers mimic the behavior of molecular motors and stable finite overlaps are generated even for non-cross-linking motors. Finally, we develop a mean-field theory for a bundle of aligned polar filaments and show that they can self-organize into a spindlelike pattern. Our work suggests possible ways as to how cells can generate spindle midzones and control their extensions.

  5. The effects of the phospholipase D-antagonist 1-butanol on seedling development and microtubule organisation in Arabidopsis.

    Science.gov (United States)

    Gardiner, John; Collings, David A; Harper, John D I; Marc, Jan

    2003-07-01

    The organisation of plant microtubules into distinct arrays during the cell cycle requires interactions with partner proteins. Having recently identified a 90-kDa phospholipase D (PLD) that associates with microtubules and the plasma membrane [Gardiner et al. (2001) Plant Cell 13: 2143], we exposed seeds and young seedlings of Arabidopsis to 1-butanol, a specific inhibitor of PLD-dependent production of the signalling molecule phosphatidic acid (PA). When added to agar growth media, 0.2% 1-butanol strongly inhibited the emergence of the radicle and cotyledons, while 0.4% 1-butanol effectively blocked germination. When normal seedlings were transferred onto media containing 0.2% and 0.4% 1-butanol, the inhibitor retarded root growth by about 40% and 90%, respectively, by reducing cell elongation. Inhibited plants showed significant swelling in the root elongation zone, bulbous or branched root hairs, and modified cotyledon morphology. Confocal immunofluorescence microscopy of root tips revealed that 1-butanol disrupted the organisation of interphase cortical microtubules. Butanol isomers that do not inhibit PLD-dependent PA production, 2- and 3-butanol, had no effect on seed germination, seedling growth, or microtubule organisation. We propose that production of PA by PLD may be required for normal microtubule organisation and hence normal growth in Arabidopsis.

  6. Dynamic and coordinated single-molecular interactions at TM4SF5-enriched microdomains guide invasive behaviors in 2- and 3-dimensional environments.

    Science.gov (United States)

    Kim, Hye-Jin; Kwon, Sojung; Nam, Seo Hee; Jung, Jae Woo; Kang, Minkyung; Ryu, Jihye; Kim, Ji Eon; Cheong, Jin-Gyu; Cho, Chang Yun; Kim, Somi; Song, Dae-Geun; Kim, Yong-Nyun; Kim, Tai Young; Jung, Min-Kyo; Lee, Kyung-Min; Pack, Chan-Gi; Lee, Jung Weon

    2017-04-01

    Membrane proteins sense extracellular cues and transduce intracellular signaling to coordinate directionality and speed during cellular migration. They are often localized to specific regions, as with lipid rafts or tetraspanin-enriched microdomains; however, the dynamic interactions of tetraspanins with diverse receptors within tetraspanin-enriched microdomains on cellular surfaces remain largely unexplored. Here, we investigated effects of tetraspan(in) TM4SF5 (transmembrane 4 L6 family member 5)-enriched microdomains (T5ERMs) on the directionality of cell migration. Physical association of TM4SF5 with epidermal growth factor receptor (EGFR) and integrin α5 was visualized by live fluorescence cross-correlation spectroscopy and higher-resolution microscopy at the leading edge of migratory cells, presumably forming TM4SF5-enriched microdomains. Whereas TM4SF5 and EGFR colocalized at the migrating leading region more than at the rear, TM4SF5 and integrin α5 colocalized evenly throughout cells. Cholesterol depletion and disruption in TM4SF5 post-translational modifications, including N-glycosylation and palmitoylation, altered TM4SF5 interactions and cellular localization, which led to less cellular migration speed and directionality in 2- or 3-dimensional conditions. TM4SF5 controlled directional cell migration and invasion, and importantly, these TM4SF5 functions were dependent on cholesterol, TM4SF5 post-translational modifications, and EGFR and integrin α5 activity. Altogether, we showed that TM4SF5 dynamically interacted with EGFR and integrin α5 in migratory cells to control directionality and invasion.-Kim, H.-J., Kwon, S., Nam, S. H., Jung, J. W., Kang, M., Ryu, J., Kim, J. E., Cheong, J.-G., Cho, C. Y., Kim, S., Song, D.-G., Kim, Y.-N., Kim, T. Y., Jung, M.-K., Lee, K.-M., Pack, C.-G., Lee, J. W. Dynamic and coordinated single-molecular interactions at TM4SF5-enriched microdomains guide invasive behaviors in 2- and 3-dimensional environments. © FASEB.

  7. Poisson Coordinates.

    Science.gov (United States)

    Li, Xian-Ying; Hu, Shi-Min

    2013-02-01

    Harmonic functions are the critical points of a Dirichlet energy functional, the linear projections of conformal maps. They play an important role in computer graphics, particularly for gradient-domain image processing and shape-preserving geometric computation. We propose Poisson coordinates, a novel transfinite interpolation scheme based on the Poisson integral formula, as a rapid way to estimate a harmonic function on a certain domain with desired boundary values. Poisson coordinates are an extension of the Mean Value coordinates (MVCs) which inherit their linear precision, smoothness, and kernel positivity. We give explicit formulas for Poisson coordinates in both continuous and 2D discrete forms. Superior to MVCs, Poisson coordinates are proved to be pseudoharmonic (i.e., they reproduce harmonic functions on n-dimensional balls). Our experimental results show that Poisson coordinates have lower Dirichlet energies than MVCs on a number of typical 2D domains (particularly convex domains). As well as presenting a formula, our approach provides useful insights for further studies on coordinates-based interpolation and fast estimation of harmonic functions.

  8. Microtubules: dynamically unstable stochastic phase-switching polymers

    Science.gov (United States)

    Zakharov, P. N.; Arzhanik, V. K.; Ulyanov, E. V.; Gudimchuk, N. B.; Ataullakhanov, F. I.

    2016-08-01

    One of the simplest molecular motors, a biological microtubule, is reviewed as an example of a highly nonequilibrium molecular machine capable of stochastic transitions between slow growth and rapid disassembly phases. Basic properties of microtubules are described, and various approaches to simulating their dynamics, from statistical chemical kinetics models to molecular dynamics models using the Metropolis Monte Carlo and Brownian dynamics methods, are outlined.

  9. Resolving bundled microtubules using anti-tubulin nanobodies

    NARCIS (Netherlands)

    Mikhaylova, Marina; Cloin, Bas M C; Finan, Kieran; van den Berg, Robert; Teeuw, Jalmar; Kijanka, Marta M; Sokolowski, Mikolaj; Katrukha, Eugene A; Maidorn, Manuel; Opazo, Felipe; Moutel, Sandrine; Vantard, Marylin; Perez, Frank; van Bergen en Henegouwen, Paul M P; Hoogenraad, Casper C; Ewers, Helge; Kapitein, Lukas C

    2015-01-01

    Microtubules are hollow biopolymers of 25-nm diameter and are key constituents of the cytoskeleton. In neurons, microtubules are organized differently between axons and dendrites, but their precise organization in different compartments is not completely understood. Super-resolution microscopy techn

  10. EB1 targets to kinetochores with attached, polymerizing microtubules.

    Science.gov (United States)

    Tirnauer, Jennifer S; Canman, Julie C; Salmon, E D; Mitchison, Timothy J

    2002-12-01

    Microtubule polymerization dynamics at kinetochores is coupled to chromosome movements, but its regulation there is poorly understood. The plus end tracking protein EB1 is required both for regulating microtubule dynamics and for maintaining a euploid genome. To address the role of EB1 in aneuploidy, we visualized its targeting in mitotic PtK1 cells. Fluorescent EB1, which localized to polymerizing ends of astral and spindle microtubules, was used to track their polymerization. EB1 also associated with a subset of attached kinetochores in late prometaphase and metaphase, and rarely in anaphase. Localization occurred in a narrow crescent, concave toward the centromere, consistent with targeting to the microtubule plus end-kinetochore interface. EB1 did not localize to kinetochores lacking attached kinetochore microtubules in prophase or early prometaphase, or upon nocodazole treatment. By time lapse, EB1 specifically targeted to kinetochores moving antipoleward, coupled to microtubule plus end polymerization, and not during plus end depolymerization. It localized independently of spindle bipolarity, the spindle checkpoint, and dynein/dynactin function. EB1 is the first protein whose targeting reflects kinetochore directionality, unlike other plus end tracking proteins that show enhanced kinetochore binding in the absence of microtubules. Our results suggest EB1 may modulate kinetochore microtubule polymerization and/or attachment.

  11. Dynamic microtubules regulate dendritic spine morphology and synaptic plasticity

    NARCIS (Netherlands)

    Jaworski, J.; Kapitein, L.C.; Montenegro Gouveia, S.; Dortland, B.R.; Wulf, P.S.; Grigoriev, I.; Camera, P.; Spangler, S.A.; Di Stefano, P.; Demmers, J.; Krugers, H.; Defilippi, P.; Akhmanova, A.; Hoogenraad, C.C.

    2009-01-01

    Dendritic spines are the major sites of excitatory synaptic input, and their morphological changes have been linked to learning and memory processes. Here, we report that growing microtubule plus ends decorated by the microtubule tip-tracking protein EB3 enter spines and can modulate spine morpholog

  12. Molecular Pathway of Microtubule Organization at the Golgi Apparatus

    NARCIS (Netherlands)

    Wu, Jingchao; de Heus, Cecilia; Liu, Qingyang; Bouchet, Benjamin P; Noordstra, Ivar; Jiang, Kai; Hua, Shasha; Martin, Maud; Yang, Chao; Grigoriev, Ilya; Katrukha, Eugene A; Altelaar, A F Maarten; Hoogenraad, Casper C; Qi, Robert Z; Klumperman, Judith; Akhmanova, Anna

    2016-01-01

    The Golgi apparatus controls the formation of non-centrosomal microtubule arrays important for Golgi organization, polarized transport, cell motility, and cell differentiation. Here, we show that CAMSAP2 stabilizes and attaches microtubule minus ends to the Golgi through a complex of AKAP450 and myo

  13. CLIP-170 facilitates the formation of kinetochore-microtubule attachments

    NARCIS (Netherlands)

    Tanenbaum, ME; Galjart, N; van Vugt, MATM; Medema, RH

    2006-01-01

    CLIP-170 is a microtubule 'plus end tracking' protein involved in several microtubule-dependent processes in interphase. At the onset of mitosis, CLIP-170 localizes to kinetochores, but at metaphase, it is no longer detectable at kinetochores. Although RNA interference (RNAi) experiments have

  14. Calmodulin immunolocalization to cortical microtubules is calcium independent

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, D.D.; Cyr, R.J.

    1992-01-01

    Calcium affects the stability of cortical microtubules (MTs) in lysed protoplasts. This calmodulin (CaM)-mediated interaction may provide a mechanism that serves to integrate cellular behavior with MT function. To test the hypothesis that CaM associates with these MTs, monoclonal antibodies were produced against CaM, and one (designated mAb1D10), was selected for its suitability as an immunocytochemical reagent. It is shown that CaM associates with the cortical Mats of cultured carrot (Daucus carota L.) and tobacco (Nicotiana tobacum L.) cells. Inasmuch as CaM interacts with calcium and affects the behavior of these Mats, we hypothesized that calcium would alter this association. To test this, protoplasts containing taxol-stabilized Mats were lysed in the presence of various concentrations of calcium and examined for the association of Cam with cortical Mats. At 1 [mu]M calcium, many protoplasts did not have CaM in association with the cortical Mats, while at 3.6 [mu]M calcium, this association was completely abolished. The results are discussed in terms of a model in which CaM associates with Mats via two types of interactions; one calcium dependent and one independent.

  15. Calmodulin immunolocalization to cortical microtubules is calcium independent

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, D.D.; Cyr, R.J.

    1992-12-31

    Calcium affects the stability of cortical microtubules (MTs) in lysed protoplasts. This calmodulin (CaM)-mediated interaction may provide a mechanism that serves to integrate cellular behavior with MT function. To test the hypothesis that CaM associates with these MTs, monoclonal antibodies were produced against CaM, and one (designated mAb1D10), was selected for its suitability as an immunocytochemical reagent. It is shown that CaM associates with the cortical Mats of cultured carrot (Daucus carota L.) and tobacco (Nicotiana tobacum L.) cells. Inasmuch as CaM interacts with calcium and affects the behavior of these Mats, we hypothesized that calcium would alter this association. To test this, protoplasts containing taxol-stabilized Mats were lysed in the presence of various concentrations of calcium and examined for the association of Cam with cortical Mats. At 1 {mu}M calcium, many protoplasts did not have CaM in association with the cortical Mats, while at 3.6 {mu}M calcium, this association was completely abolished. The results are discussed in terms of a model in which CaM associates with Mats via two types of interactions; one calcium dependent and one independent.

  16. Toward coordinated space-based air quality, carbon cycle, and ecosystem measurements to quantify air quality-ecosystem interactions

    Science.gov (United States)

    Neu, J. L.; Schimel, D.; Lerdau, M.; Drewry, D.; Fu, D.; Payne, V.; Bowman, K. W.; Worden, J. R.

    2016-12-01

    Tropospheric ozone concentrations are increasing in many regions of the world, and this ozone can severely damage vegetation. Ozone enters plants through their stomata and oxidizes tissues, inhibiting physiology and decreasing ecosystem productivity. Ozone has been experimentally shown to reduce crop production, with important implications for global food security as concentrations rise. Ozone damage to forests also alters productivity and carbon storage and may drive changes in species distributions and biodiversity. Process-based quantitative estimates of these ozone impacts on terrestrial ecosystems at continental to global scales as well as of feedbacks to air quality via production of volatile organic compounds (VOCs) are thus crucial to sustainable development planning. We demonstrate that leveraging planned and proposed missions to measure ozone, formaldehyde, and isoprene along with solar-induced fluorescence (SiF), evapotranspiration, and plant nitrogen content can meet the requirements of an integrated observing system for air quality-ecosystem interactions while also meeting the needs of the individual Air Quality, Carbon Cycle, and Ecosystems communities.

  17. Dipole—Dipole Interaction and the Directional Motion of Brownian

    Institute of Scientific and Technical Information of China (English)

    YUHui; ZHAOTong-Jun; 等

    2002-01-01

    The electric field of the microtubule is calculated according to its dipole distribution.The conformational change of a molecular motor is described by the rotation of a dipole which interacts with the microtubule.The numerical simulation for the particle currend shows that this interaction helps to produce a directional motion along the microtubule.And the average displacement executes step changes that resemble the experimental result for kinesin motors.

  18. Understanding social motor coordination.

    Science.gov (United States)

    Schmidt, R C; Fitzpatrick, Paula; Caron, Robert; Mergeche, Joanna

    2011-10-01

    Recently there has been much interest in social coordination of motor movements, or as it is referred to by some researchers, joint action. This paper reviews the cognitive perspective's common coding/mirror neuron theory of joint action, describes some of its limitations and then presents the behavioral dynamics perspective as an alternative way of understanding social motor coordination. In particular, behavioral dynamics' ability to explain the temporal coordination of interacting individuals is detailed. Two experiments are then described that demonstrate how dynamical processes of synchronization are apparent in the coordination underlying everyday joint actions such as martial art exercises, hand-clapping games, and conversations. The import of this evidence is that emergent dynamic patterns such as synchronization are the behavioral order that any neural substrate supporting joint action (e.g., mirror systems) would have to sustain.

  19. Invariant manifolds and collective coordinates

    Energy Technology Data Exchange (ETDEWEB)

    Papenbrock, T. [Centro Internacional de Ciencias, Cuernavaca, Morelos (Mexico); Institute for Nuclear Theory, University of Washington, Seattle, WA (United States); Seligman, T.H. [Centro Internacional de Ciencias, Cuernavaca, Morelos (Mexico); Centro de Ciencias Fisicas, University of Mexico (UNAM), Cuernavaca (Mexico)

    2001-09-14

    We introduce suitable coordinate systems for interacting many-body systems with invariant manifolds. These are Cartesian in coordinate and momentum space and chosen such that several components are identically zero for motion on the invariant manifold. In this sense these coordinates are collective. We make a connection to Zickendraht's collective coordinates and present certain configurations of few-body systems where rotations and vibrations decouple from single-particle motion. These configurations do not depend on details of the interaction. (author)

  20. Of ens 'n' ands: observations on the phonetic make-up of a coordinator and its uses in talk-in-interaction.

    Science.gov (United States)

    Barth-Weingarten, Dagmar

    2012-03-01

    In grammar books, the various functions of and as phrasal coordinator and clausal conjunction are treated as standard knowledge. In addition, studies on the uses of and in everyday talk-in-interaction have described its discourse-organizational functions on a more global level. In the phonetic literature, in turn, a range of phonetic forms of and have been listed. Yet, so far few studies have related the phonetic features of and to its function. This contribution surveys a range of phonetic forms of and in a corpus of private American English telephone conversations. It shows that the use of forms such as [ænd], [εn], or [en], among others, is not random but, in essence, correlates with the syntactic-pragmatic scope of and and the cognitive closeness of the items the and connects. This, in turn, allows the phonetic design of and to contribute to the organization of turn-taking. The findings presented are based on conversation-analytic and interactional-linguistic methodology, which includes quantitative analyses.

  1. PSD-95 alters microtubule dynamics via an association with EB3

    Science.gov (United States)

    Sweet, Eric S.; Previtera, Michelle L.; Fernández, Jose R.; Charych, Erik I.; Tseng, Chia-Yi; Kwon, Munjin; Starovoytov, Valentin; Zheng, James Q.; Firestein, Bonnie L.

    2011-01-01

    Little is known about how the neuronal cytoskeleton is regulated when a dendrite decides whether to branch or not. Previously, we reported that postsynaptic density protein 95 (PSD-95) acts as a stop signal for dendrite branching. It is yet to be elucidated how PSD-95 affects the cytoskeleton and how this regulation relates to the dendritic arbor. Here, we show that the SH3 (src homology 3) domain of PSD-95 interacts with a proline-rich region within the microtubule end-binding protein EB3. Overexpression of PSD-95 or mutant EB3 results in a decreased lifetime of EB3 comets in dendrites. In line with these data, transfected rat neurons show that overexpression of PSD-95 results in less organized microtubules at dendritic branch points and decreased dendritogensis. The interaction between PSD-95 and EB3 elucidates a function for a novel region of EB3 and provides a new and important mechanism for the regulation of microtubules in determining dendritic morphology. PMID:21248129

  2. Polygamain, a new microtubule depolymerizing agent that occupies a unique pharmacophore in the colchicine site.

    Science.gov (United States)

    Hartley, R M; Peng, J; Fest, G A; Dakshanamurthy, S; Frantz, D E; Brown, M L; Mooberry, S L

    2012-03-01

    Bioassay-guided fractionation was used to isolate the lignan polygamain as the microtubule-active constituent in the crude extract of the Mountain torchwood, Amyris madrensis. Similar to the effects of the crude plant extract, polygamain caused dose-dependent loss of cellular microtubules and the formation of aberrant mitotic spindles that led to G(2)/M arrest. Polygamain has potent antiproliferative activities against a wide range of cancer cell lines, with an average IC(50) of 52.7 nM. Clonogenic studies indicate that polygamain effectively inhibits PC-3 colony formation and has excellent cellular persistence after washout. In addition, polygamain is able to circumvent two clinically relevant mechanisms of drug resistance, the expression of P-glycoprotein and the βIII isotype of tubulin. Studies with purified tubulin show that polygamain inhibits the rate and extent of purified tubulin assembly and displaces colchicine, indicating a direct interaction of polygamain within the colchicine binding site on tubulin. Polygamain has structural similarities to podophyllotoxin, and molecular modeling simulations were conducted to identify the potential orientations of these compounds within the colchicine binding site. These studies suggest that the benzodioxole group of polygamain occupies space similar to the trimethoxyphenyl group of podophyllotoxin but with distinct interactions within the hydrophobic pocket. Our results identify polygamain as a new microtubule destabilizer that seems to occupy a unique pharmacophore within the colchicine site of tubulin. This new pharmacophore will be used to design new colchicine site compounds that might provide advantages over the current agents.

  3. Mathematical modeling of the intracellular protein dynamics: the importance of active transport along microtubules.

    Science.gov (United States)

    Szymańska, Zuzanna; Parisot, Martin; Lachowicz, Mirosław

    2014-12-21

    In this paper we propose a mathematical model of protein and mRNA transport inside a cell. The spatio-temporal model takes into account the active transport along microtubules in the cytoplasm as well as diffusion and is able to reproduce the oscillatory changes in protein concentration observed in many experimental data. In the model the protein and the mRNA interact with each other that allows us to classify the model as a simple gene regulatory network. The proposed model is generic and may be adapted to specific signaling pathways. On the basis of numerical simulations, we formulate a new hypothesis that the oscillatory dynamics is allowed by the mRNA active transport along microtubules from the nucleus to distant locations.

  4. Stimulation of Vesicular Stomatitis Virus in vitro RNA Synthesis by Microtubule-Associated Proteins

    Science.gov (United States)

    Hill, Virginia M.; Harmon, Shirley A.; Summers, Donald F.

    1986-08-01

    Microtubule-associated proteins purified from bovine brains stimulated the in vitro transcription and replication reactions of vesicular stomatitis virus. The products of these reactions were intact messenger or genome-sized RNA species. A preparation from HeLa cells containing tubulin and microtubule-associated proteins also stimulated vesicular stomatitis virus transcription in vitro. This observation is in accord with previous studies, which suggested that a host cell factor was involved with the function of the vesicular stomatitis virus RNA polymerase, and others that indicated that several animal viruses displayed an association with host cell cytoskeletal elements during their replication cycles. We show evidence in this report of a host cell protein that seems to have a functional role in interacting with the virion polymerase.

  5. Asymptotic Analysis of Microtubule-Based Transport by Multiple Identical Molecular Motors

    CERN Document Server

    McKinley, Scott A; Fricks, John; Kramer, Peter R

    2011-01-01

    We describe a system of stochastic differential equations (SDEs) which model the interaction between processive molecular motors, such as kinesin and dynein, and the biomolecular cargo they tow as part of microtubule-based intracellular transport. We show that the classical experimental environment fits within a parameter regime which is qualitatively distinct from conditions one expects to find in living cells. Through an asymptotic analysis of our system of SDEs, we develop a means for applying in vitro observations of the nonlinear response by motors to forces induced on the attached cargo to make analytical predictions for two parameter regimes that have thus far eluded direct experimental observation: 1) highly viscous in vivo transport and 2) dynamics when multiple identical motors are attached to the cargo and microtubule.

  6. A hybrid consisting of coordination polymer and noncovalent organic networks: a highly ordered 2-D phenol network assembled by edge-to-face pi-pi interactions.

    Science.gov (United States)

    Ko, Jung Woo; Min, Kil Sik; Suh, Myunghyun Paik

    2002-04-22

    A 2-D metal-organic open framework having 1-D channels, [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).18H(2)O (1), was constructed by the self-assembly of the Cu(II) complex of hexaazamacrocycle A (A = C(10)H(26)N(6)) with sodium 1,3,5-benzenetricarboxylate (BTC(3)(-)) in DMSO-H(2)O solution. 1 crystallizes in the trigonal space group P with a = b = 17.705(1) A, c = 6.940(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 1884.0(3) A(3), Z = 1, and rho(calcd) = 1.428 g cm(-3). The X-ray crystal structure of 1 indicates that each Cu(II) macrocyclic unit binds two BTC(3-) ions in a trans position and each BTC(3-) ion coordinates three Cu(II) macrocyclic complexes to form 2-D coordination polymer layers with honeycomb cavities (effective size 8.1 A), and the layers are packed to generate 1-D channels perpendicularly to the 2-D layers. Solid 1 binds guest molecules such as MeOH, EtOH, and PhOH with different binding constant and capacity. By the treatment of 1 with aqueous solution of phenol, a hybrid solid [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).9PhOH.6H(2)O (2) was assembled. 2 crystallizes in the trigonal R3 space group with a = b = 20.461(1) A, c = 24.159(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 8759.2(7) A(3), Z = 3, and rho(calcd) = 1.280 g cm(-3). In 2, highly ordered 2-D noncovalent phenol layers are formed by the edge-to-face pi-pi interactions between the phenol molecules and are alternately packed with the coordination polymer layers in the crystal lattice.

  7. Stochastic models for plant microtubule self-organization and structure.

    Science.gov (United States)

    Eren, Ezgi C; Dixit, Ram; Gautam, Natarajan

    2015-12-01

    One of the key enablers of shape and growth in plant cells is the cortical microtubule (CMT) system, which is a polymer array that forms an appropriately-structured scaffolding in each cell. Plant biologists have shown that stochastic dynamics and simple rules of interactions between CMTs can lead to a coaligned CMT array structure. However, the mechanisms and conditions that cause CMT arrays to become organized are not well understood. It is prohibitively time-consuming to use actual plants to study the effect of various genetic mutations and environmental conditions on CMT self-organization. In fact, even computer simulations with multiple replications are not fast enough due to the spatio-temporal complexity of the system. To redress this shortcoming, we develop analytical models and methods for expeditiously computing CMT system metrics that are related to self-organization and array structure. In particular, we formulate a mean-field model to derive sufficient conditions for the organization to occur. We show that growth-prone dynamics itself is sufficient to lead to organization in presence of interactions in the system. In addition, for such systems, we develop predictive methods for estimation of system metrics such as expected average length and number of CMTs over time, using a stochastic fluid-flow model, transient analysis, and approximation algorithms tailored to our problem. We illustrate the effectiveness of our approach through numerical test instances and discuss biological insights.

  8. A thermodynamic model of microtubule assembly and disassembly.

    Directory of Open Access Journals (Sweden)

    Bernard M A G Piette

    Full Text Available Microtubules are self-assembling polymers whose dynamics are essential for the normal function of cellular processes including chromosome separation and cytokinesis. Therefore understanding what factors effect microtubule growth is fundamental to our understanding of the control of microtubule based processes. An important factor that determines the status of a microtubule, whether it is growing or shrinking, is the length of the GTP tubulin microtubule cap. Here, we derive a Monte Carlo model of the assembly and disassembly of microtubules. We use thermodynamic laws to reduce the number of parameters of our model and, in particular, we take into account the contribution of water to the entropy of the system. We fit all parameters of the model from published experimental data using the GTP tubulin dimer attachment rate and the lateral and longitudinal binding energies of GTP and GDP tubulin dimers at both ends. Also we calculate and incorporate the GTP hydrolysis rate. We have applied our model and can mimic published experimental data, which formerly suggested a single layer GTP tubulin dimer microtubule cap, to show that these data demonstrate that the GTP cap can fluctuate and can be several microns long.

  9. A thermodynamic model of microtubule assembly and disassembly.

    Science.gov (United States)

    Piette, Bernard M A G; Liu, Junli; Peeters, Kasper; Smertenko, Andrei; Hawkins, Timothy; Deeks, Michael; Quinlan, Roy; Zakrzewski, Wojciech J; Hussey, Patrick J

    2009-08-11

    Microtubules are self-assembling polymers whose dynamics are essential for the normal function of cellular processes including chromosome separation and cytokinesis. Therefore understanding what factors effect microtubule growth is fundamental to our understanding of the control of microtubule based processes. An important factor that determines the status of a microtubule, whether it is growing or shrinking, is the length of the GTP tubulin microtubule cap. Here, we derive a Monte Carlo model of the assembly and disassembly of microtubules. We use thermodynamic laws to reduce the number of parameters of our model and, in particular, we take into account the contribution of water to the entropy of the system. We fit all parameters of the model from published experimental data using the GTP tubulin dimer attachment rate and the lateral and longitudinal binding energies of GTP and GDP tubulin dimers at both ends. Also we calculate and incorporate the GTP hydrolysis rate. We have applied our model and can mimic published experimental data, which formerly suggested a single layer GTP tubulin dimer microtubule cap, to show that these data demonstrate that the GTP cap can fluctuate and can be several microns long.

  10. An improved quantitative analysis method for plant cortical microtubules.

    Science.gov (United States)

    Lu, Yi; Huang, Chenyang; Wang, Jia; Shang, Peng

    2014-01-01

    The arrangement of plant cortical microtubules can reflect the physiological state of cells. However, little attention has been paid to the image quantitative analysis of plant cortical microtubules so far. In this paper, Bidimensional Empirical Mode Decomposition (BEMD) algorithm was applied in the image preprocessing of the original microtubule image. And then Intrinsic Mode Function 1 (IMF1) image obtained by decomposition was selected to do the texture analysis based on Grey-Level Cooccurrence Matrix (GLCM) algorithm. Meanwhile, in order to further verify its reliability, the proposed texture analysis method was utilized to distinguish different images of Arabidopsis microtubules. The results showed that the effect of BEMD algorithm on edge preserving accompanied with noise reduction was positive, and the geometrical characteristic of the texture was obvious. Four texture parameters extracted by GLCM perfectly reflected the different arrangements between the two images of cortical microtubules. In summary, the results indicate that this method is feasible and effective for the image quantitative analysis of plant cortical microtubules. It not only provides a new quantitative approach for the comprehensive study of the role played by microtubules in cell life activities but also supplies references for other similar studies.

  11. An Improved Quantitative Analysis Method for Plant Cortical Microtubules

    Directory of Open Access Journals (Sweden)

    Yi Lu

    2014-01-01

    Full Text Available The arrangement of plant cortical microtubules can reflect the physiological state of cells. However, little attention has been paid to the image quantitative analysis of plant cortical microtubules so far. In this paper, Bidimensional Empirical Mode Decomposition (BEMD algorithm was applied in the image preprocessing of the original microtubule image. And then Intrinsic Mode Function 1 (IMF1 image obtained by decomposition was selected to do the texture analysis based on Grey-Level Cooccurrence Matrix (GLCM algorithm. Meanwhile, in order to further verify its reliability, the proposed texture analysis method was utilized to distinguish different images of Arabidopsis microtubules. The results showed that the effect of BEMD algorithm on edge preserving accompanied with noise reduction was positive, and the geometrical characteristic of the texture was obvious. Four texture parameters extracted by GLCM perfectly reflected the different arrangements between the two images of cortical microtubules. In summary, the results indicate that this method is feasible and effective for the image quantitative analysis of plant cortical microtubules. It not only provides a new quantitative approach for the comprehensive study of the role played by microtubules in cell life activities but also supplies references for other similar studies.

  12. Microtubules in the Cerebral Cortex: Role in Memory and Consciousness

    Science.gov (United States)

    Woolf, Nancy J.

    This chapter raises the question whether synaptic connections in the cerebral cortex are adequate in accounting for higher cognition, especially cognition involving multimodal processing. A recent and novel approach to brain mechanics is outlined, one that involves microtubules and microtubule-associated protein-2 (MAP2). In addition to effects on the neuronal membrane, neurotransmitters exert actions on microtubules. These neurotransmitter effects alter the MAP2 phosphorylation state and rates of microtubule polymerization and transport. It is argued that these processes are important to the physical basis of memory and consciousness. In support of this argument, MAP2 is degraded with learning in discrete cortical modules. How this relates to synaptic change related to learning is unknown. The specific proposal is advanced that learning alters microtubules in the subsynaptic zone lying beneath the synapse, and that this forms the physical basis of long-term memory storage because microtubule networks determine the synapse strength by directing contacts with actin filaments and transport of synaptic proteins. It is argued that this is more probable than memory-related physical storage in the synapse itself. Comparisons to consciousness are made and it is concluded that there is a link between microtubules, memory and consciousness.

  13. Nonlinear dynamics of C-terminal tails in cellular microtubules

    Science.gov (United States)

    Sekulic, Dalibor L.; Sataric, Bogdan M.; Zdravkovic, Slobodan; Bugay, Aleksandr N.; Sataric, Miljko V.

    2016-07-01

    The mechanical and electrical properties, and information processing capabilities of microtubules are the permanent subject of interest for carrying out experiments in vitro and in silico, as well as for theoretical attempts to elucidate the underlying processes. In this paper, we developed a new model of the mechano-electrical waves elicited in the rows of very flexible C-terminal tails which decorate the outer surface of each microtubule. The fact that C-terminal tails play very diverse roles in many cellular functions, such as recruitment of motor proteins and microtubule-associated proteins, motivated us to consider their collective dynamics as the source of localized waves aimed for communication between microtubule and associated proteins. Our approach is based on the ferroelectric liquid crystal model and it leads to the effective asymmetric double-well potential which brings about the conditions for the appearance of kink-waves conducted by intrinsic electric fields embedded in microtubules. These kinks can serve as the signals for control and regulation of intracellular traffic along microtubules performed by processive motions of motor proteins, primarly from kinesin and dynein families. On the other hand, they can be precursors for initiation of dynamical instability of microtubules by recruiting the proper proteins responsible for the depolymerization process.

  14. Oscillatory fluid flow influences primary cilia and microtubule mechanics.

    Science.gov (United States)

    Espinha, Lina C; Hoey, David A; Fernandes, Paulo R; Rodrigues, Hélder C; Jacobs, Christopher R

    2014-07-01

    Many tissues are sensitive to mechanical stimuli; however, the mechanotransduction mechanism used by cells remains unknown in many cases. The primary cilium is a solitary, immotile microtubule-based extension present on nearly every mammalian cell which extends from the basal body. The cilium is a mechanosensitive organelle and has been shown to transduce fluid flow-induced shear stress in tissues, such as the kidney and bone. The majority of microtubules assemble from the mother centriole (basal body), contributing significantly to the anchoring of the primary cilium. Several studies have attempted to quantify the number of microtubules emanating from the basal body and the results vary depending on the cell type. It has also been shown that cellular response to shear stress depends on microtubular integrity. This study hypothesizes that changing the microtubule attachment of primary cilia in response to a mechanical stimulus could change primary cilia mechanics and, possibly, mechanosensitivity. Oscillatory fluid flow was applied to two different cell types and the microtubule attachment to the ciliary base was quantified. For the first time, an increase in microtubules around primary cilia both with time and shear rate in response to oscillatory fluid flow stimulation was demonstrated. Moreover, it is presented that the primary cilium is required for this loading-induced cellular response. This study has demonstrated a new role for the cilium in regulating alterations in the cytoplasmic microtubule network in response to mechanical stimulation, and therefore provides a new insight into how cilia may regulate its mechanics and thus the cells mechanosensitivity.

  15. Crowding of molecular motors determines microtubule depolymerization

    CERN Document Server

    Reese, Louis; Frey, Erwin

    2011-01-01

    Assembly and disassembly dynamics of microtubules (MTs) is tightly controlled by MT associated proteins. Here, we investigate how plus-end-directed depolymerases of the kinesin-8 family regulate MT depolymerization dynamics. Employing an individual-based model, we reproduce experimental findings. Moreover, crowding is identified as the key regulatory mechanism of depolymerization dynamics. Our analysis gives two qualitatively distinct regimes. For motor densities above a particular threshold, a macroscopic traffic jam emerges at the plus-end and the MT dynamics become independent of the motor concentration. Below this threshold, microscopic traffic jams at the tip arise which cancel out the effect of the depolymerization kinetics such that the depolymerization speed is solely determined by the motor density. Because this density changes over the MT length, length-dependent regulation is possible. Remarkably, motor cooperativity does not affect the depolymerization speed but only the end-residence time of depo...

  16. Centrosome and microtubule instability in aging Drosophila cells

    Science.gov (United States)

    Schatten, H.; Chakrabarti, A.; Hedrick, J.

    1999-01-01

    Several cytoskeletal changes are associated with aging which includes alterations in muscle structure leading to muscular atrophy, and weakening of the microtubule network which affects cellular secretion and maintenance of cell shape. Weakening of the microtubule network during meiosis in aging oocytes can result in aneuploidy or trisomic zygotes with increasing maternal age. Imbalances of cytoskeletal organization can lead to disease such as Alzheimer's, muscular disorders, and cancer. Because many cytoskeletal diseases are related to age we investigated the effects of aging on microtubule organization in cell cultures of the Drosophila cell model system (Schneider S-1 and Kc23 cell lines). This cell model is increasingly being used as an alternative system to mammalian cell cultures. Drosophila cells are amenable to genetic manipulations and can be used to identify and manipulate genes which are involved in the aging processes. Immunofluorescence, scanning, and transmission electron microscopy were employed for the analysis of microtubule organizing centers (centrosomes) and microtubules at various times after subculturing cells in fresh medium. Our results reveal that centrosomes and the microtubule network becomes significantly affected in aging cells after 5 days of subculture. At 5-14 days of subculture, 1% abnormal out of 3% mitoses were noted which were clearly distinguishable from freshly subcultured control cells in which 3% of cells undergo normal mitosis with bipolar configurations. Microtubules are also affected in the midbody during cell division. The midbody in aging cells becomes up to 10 times longer when compared with midbodies in freshly subcultured cells. During interphase, microtubules are often disrupted and disorganized, which may indicate improper function related to transport of cell organelles along microtubules. These results are likely to help explain some cytoskeletal disorders and diseases related to aging.

  17. Acentrosomal Microtubule Assembly in Mitosis: The Where, When, and How.

    Science.gov (United States)

    Meunier, Sylvain; Vernos, Isabelle

    2016-02-01

    In mitosis the cell assembles the bipolar spindle, a microtubule (MT)-based apparatus that segregates the duplicated chromosomes into two daughter cells. Most animal cells enter mitosis with duplicated centrosomes that provide an active source of dynamic MTs. However, it is now established that spindle assembly relies on the nucleation of acentrosomal MTs occurring around the chromosomes after nuclear envelope breakdown, and on pre-existing microtubules. Where chromosome-dependent MT nucleation occurs, when MT amplification takes place and how the two pathways function are still key questions that generate some controversies. We reconcile the data and present an integrated model accounting for acentrosomal microtubule assembly in the dividing cell.

  18. Structural microtubule cap: Stability, catastrophe, rescue, and third state

    DEFF Research Database (Denmark)

    Flyvbjerg, H.; Chretien, D.; Janosi, I.M.

    2002-01-01

    Microtubules polymerize from GTP-liganded tubulin dinners, but are essentially made of GDP-liganded tubulin. We investigate the tug-of-war resulting from the fact that GDP-liganded tubulin favors a curved configuration, but is forced to remain in a straight one when part of a microtubule. We point...... of two well-established facts: protofilaments made of GDP-liganded tubulin have intrinsic curvature, and microtubules are elastic, made from material that can yield to forces, in casu its own intrinsic forces. We explore possible properties of this structural cap, and demonstrate 1) how it allows both...

  19. Mitochondrial inheritance is mediated by microtubules in mammalian cell division.

    Science.gov (United States)

    Lawrence, Elizabeth; Mandato, Craig

    2013-11-01

    The mitochondrial network fragments and becomes uniformly dispersed within the cytoplasm when mammalian cells enter mitosis. Such morphology and distribution of mitochondria was previously thought to facilitate the stochastic inheritance of mitochondria by daughter cells. In contrast, we recently reported that mitochondria in dividing mammalian cells are inherited by an ordered mechanism of inheritance mediated by microtubules. We showed that mitochondria are progressively enriched at the cell equator and depleted at the poles throughout division. Furthermore, the mitochondrial distribution during division is dependent on microtubules, indicating an ordered inheritance strategy. The microtubule-mediated positioning of mitochondria in dividing mammalian cells may have functional consequences for cell division and/or mitochondrial inheritance.

  20. Visualizing and Analyzing Branching Microtubule Nucleation Using Meiotic Xenopus Egg Extracts and TIRF Microscopy

    Science.gov (United States)

    King, Matthew; Petry, Sabine

    2016-01-01

    Mitotic and meiotic spindles consist primarily of microtubules, which originate from centrosomes and within the vicinity of chromatin. Indirect evidence suggested that microtubules also originate throughout the spindle, but the high microtubule density within the spindle precludes the direct observation of this phenomenon. By using meiotic Xenopus laevis egg extract and employing total internal reflection (TIRF) microscopy, microtubule nucleation from preexisting microtubules could be demonstrated and analyzed. Branching microtubule nucleation is an ideal mechanism to assemble and maintain a mitotic spindle, because microtubule numbers are amplified while preserving their polarity. Here, we describe the assays that made these findings possible and the experiments that helped identify the key molecular players involved. PMID:27193844

  1. Seven-coordinate iron complex as a ditopic receptor for lithium salts: study of host-guest interactions and substitution behavior.

    Science.gov (United States)

    Sarauli, David; Popova, Vesselina; Zahl, Achim; Puchta, Ralph; Ivanović-Burmazović, Ivana

    2007-09-17

    Interactions between the seven-coordinate tweezerlike [Fe(dapsox)(H2O)2]ClO4 complex (H2dapsox = 2,6-diacetylpyridine-bis(semioxamazide)) with different lithium salts (LiOTf, LiClO4, LiBF4, and LiPF6) in CH3CN have been investigated by electrochemical, spectrophotometric, 7Li and 19F NMR, kinetic, and DFT methods. It has been demonstrated that this complex acts as ditopic receptor, showing spectral and electrochemical ion-pair-sensing capability for different lithium salts. In general, the apparent binding constants for lithium salts increase in the order LiOTf LiBF4. From the electrochemical measurements, the apparent lithium salt binding constants for the Fe(III) and Fe(II) forms of the complex have been obtained, suggesting a stronger host-guest interaction with the reduced form of the complex. In the presence of LiPF6, the solution chemistry is more complex because of the hydrolysis of PF6-. The kinetics of the complexation of [Fe(dapsox)(CH3CN)2]+ by thiocyanate at -15 degrees C in acetonitrile in the presence of 0.2 M NBu4OTf shows two steps with the following rate constants and activation parameters: k(1) = 411 +/- 14 M(-1) s(-1); DeltaH(1) not equal = 9 +/- 2 kJ mol(-1); DeltaS1 not equal = -159 +/- 6 J K(-1) mol(-1); k(2) = 52 +/- 1 M(-1) s(-1); DeltaH(2) not equal = 4 +/- 1 kJ mol(-1); DeltaS(2) not equal = -195 +/- 3 J K(-1) mol(-1). The very negative DeltaS not equal values are consistent with an associative (A) mechanism. Under the same conditions but with 0.2 M LiOTf, k1Li and k2Li are 1605 +/- 51 and 106 +/- 2 M(-1) s(-1), respectively. The increased rate constants for the {[Fe(dapsox)(CH3CN)2] x LiOTf}+ adduct are in agreement with an associative mechanism. Kinetic and spectrophotometric titration measurements show stronger interaction between the lithium salt and the anion-substituted forms, [Fe(dapsox)(CH3CN)(NCS)] and [Fe(dapsox)(NCS)2]-, of the complex. These experiments demonstrate that in nonaqueous media lithium salts cannot be simply used as

  2. Effects of the KIF2C neck peptide on microtubules: lateral disintegration of microtubules and β-structure formation.

    Science.gov (United States)

    Shimizu, Youské; Shimizu, Takashi; Nara, Masayuki; Kikumoto, Mahito; Kojima, Hiroaki; Morii, Hisayuki

    2013-04-01

    Members of the kinesin-13 sub-family, including KIF2C, depolymerize microtubules. The positive charge-rich 'neck' region extending from the N-terminus of the catalytic head is considered to be important in the depolymerization activity. Chemically synthesized peptides, covering the basic region (A182-E200), induced a sigmoidal increase in the turbidity of a microtubule suspension. The increase was suppressed by salt addition or by reduction of basicity by amino acid substitutions. Electron microscopic observations revealed ring structures surrounding the microtubules at high peptide concentrations. Using the peptide A182-D218, we also detected free thin straight filaments, probably protofilaments disintegrated from microtubules. Therefore, the neck region, even without the catalytic head domain, may induce lateral disintegration of microtubules. With microtubules lacking anion-rich C-termini as a result of subtilisin treatment, addition of the peptide induced only a moderate increase in turbidity, and rings and protofilaments were rarely detected, while aggregations, also thought to be caused by lateral disintegration, were often observed in electron micrographs. Thus, the C-termini are not crucial for the action of the peptides in lateral disintegration but contribute to structural stabilization of the protofilaments. Previous structural studies indicated that the neck region of KIF2C is flexible, but our IR analysis suggests that the cation-rich region (K190-A204) forms β-structure in the presence of microtubules, which may be of significance with regard to the action of the neck region. Therefore, the neck region of KIF2C is sufficient to cause disintegration of microtubules into protofilaments, and this may contribute to the ability of KIF2C to cause depolymerization of microtubules.

  3. A new function of microtubule-associated protein tau: involvement in chromosome stability.

    Science.gov (United States)

    Rossi, Giacomina; Dalprà, Leda; Crosti, Francesca; Lissoni, Sara; Sciacca, Francesca L; Catania, Marcella; Di Fede, Giuseppe; Mangieri, Michela; Giaccone, Giorgio; Croci, Danilo; Tagliavini, Fabrizio

    2008-06-15

    Tau is a microtubule-associated protein that promotes assembly and stabilization of cytoskeleton microtubules. It is mostly expressed in neuronal and glial cells but it is also present in non-neural cells such as fibroblasts and lymphocytes. An altered tau produces cytoskeleton pathology resulting in neurodegenerative diseases such as Alzheimer's disease and tauopathies. Tau has been suggested to be a multifunctional protein, due to its localization in different cellular compartments. However its further functions are still unclear. We analyzed the distribution of tau in human skin fibroblasts showing its localization in the nucleus and along mitotic chromosomes. Then, we investigated if an altered tau, such as the P301L mutated protein associated with frontotemporal dementia, could produce nuclear pathology. We found that patients carrying the mutation consistently had several chromosome aberrations in their fibroblasts and lymphocytes: chromosome and chromatid breakages or gaps, aneuploidies, translocations, in addition to chromatin bridges and decondensed chromosomes. Our findings argue for a role of tau in chromosome stability by means of its interaction with both microtubules and chromatin.

  4. SAS-6 engineering reveals interdependence between cartwheel and microtubules in determining centriole architecture.

    Science.gov (United States)

    Hilbert, Manuel; Noga, Akira; Frey, Daniel; Hamel, Virginie; Guichard, Paul; Kraatz, Sebastian H W; Pfreundschuh, Moritz; Hosner, Sarah; Flückiger, Isabelle; Jaussi, Rolf; Wieser, Mara M; Thieltges, Katherine M; Deupi, Xavier; Müller, Daniel J; Kammerer, Richard A; Gönczy, Pierre; Hirono, Masafumi; Steinmetz, Michel O

    2016-04-01

    Centrioles are critical for the formation of centrosomes, cilia and flagella in eukaryotes. They are thought to assemble around a nine-fold symmetric cartwheel structure established by SAS-6 proteins. Here, we have engineered Chlamydomonas reinhardtii SAS-6-based oligomers with symmetries ranging from five- to ten-fold. Expression of a SAS-6 mutant that forms six-fold symmetric cartwheel structures in vitro resulted in cartwheels and centrioles with eight- or nine-fold symmetries in vivo. In combination with Bld10 mutants that weaken cartwheel-microtubule interactions, this SAS-6 mutant produced six- to eight-fold symmetric cartwheels. Concurrently, the microtubule wall maintained eight- and nine-fold symmetries. Expressing SAS-6 with analogous mutations in human cells resulted in nine-fold symmetric centrioles that exhibited impaired length and organization. Together, our data suggest that the self-assembly properties of SAS-6 instruct cartwheel symmetry, and lead us to propose a model in which the cartwheel and the microtubule wall assemble in an interdependent manner to establish the native architecture of centrioles.

  5. Introduction to Coordination Chemistry

    CERN Document Server

    Lawrance, Geoffrey Alan

    2010-01-01

    Introduction to Coordination Chemistry examines and explains how metals and molecules that bind as ligands interact, and the consequences of this assembly process. This book describes the chemical and physical properties and behavior of the complex assemblies that form, and applications that may arise as a result of these properties. Coordination complexes are an important but often hidden part of our world?even part of us?and what they do is probed in this book. This book distills the essence of this topic for undergraduate students and for research scientists.

  6. Modeling the Effects of Drug Binding on the Dynamic Instability of Microtubules

    CERN Document Server

    Hinow, Peter; Lopus, Manu; Jordan, Mary Ann; Tuszynski, Jack A

    2010-01-01

    We propose a stochastic model that accounts for the growth, catastrophe and rescue processes of steady state microtubules assembled from MAP-free tubulin. Both experimentally and theoretically we study the perturbation of microtubule dynamic instability by S-methyl-D-DM1, a synthetic derivative of the microtubule-targeted agent maytansine and a potential anticancer agent. We find that to be an effective suppressor of microtubule dynamics a drug must primarily suppress the loss of GDP tubulin from the microtubule tip.

  7. Efficient event-driven simulations shed new light on microtubule organization in the plant cortical array

    Science.gov (United States)

    Tindemans, Simon H.; Deinum, Eva E.; Lindeboom, Jelmer J.; Mulder, Bela M.

    2014-04-01

    The dynamics of the plant microtubule cytoskeleton is a paradigmatic example of the complex spatiotemporal processes characterising life at the cellular scale. This system is composed of large numbers of spatially extended particles, each endowed with its own intrinsic stochastic dynamics, and is capable of non-equilibrium self-organisation through collisional interactions of these particles. To elucidate the behaviour of such a complex system requires not only conceptual advances, but also the development of appropriate computational tools to simulate it. As the number of parameters involved is large and the behaviour is stochastic, it is essential that these simulations be fast enough to allow for an exploration of the phase space and the gathering of sufficient statistics to accurately pin down the average behaviour as well as the magnitude of fluctuations around it. Here we describe a simulation approach that meets this requirement by adopting an event-driven methodology that encompasses both the spontaneous stochastic changes in microtubule state as well as the deterministic collisions. In contrast with finite time step simulations this technique is intrinsically exact, as well as several orders of magnitude faster, which enables ordinary PC hardware to simulate systems of ˜ 10^3 microtubules on a time scale ˜ 10^{3} faster than real time. In addition we present new tools for the analysis of microtubule trajectories on curved surfaces. We illustrate the use of these methods by addressing a number of outstanding issues regarding the importance of various parameters on the transition from an isotropic to an aligned and oriented state.

  8. Efficient event-driven simulations shed new light on microtubule organisation in the plant cortical array

    Directory of Open Access Journals (Sweden)

    Simon H. Tindemans

    2014-04-01

    Full Text Available The dynamics of the plant microtubule cytoskeleton is a paradigmatic example of the complex spatiotemporal processes characterising life at the cellular scale. This system is composed of large numbers of spatially extended particles, each endowed with its own intrinsic stochastic dynamics, and is capable of non-equilibrium self-organisation through collisional interactions of these particles. To elucidate the behaviour of such a complex system requires not only conceptual advances, but also the development of appropriate computational tools to simulate it. As the number of parameters involved is large and the behaviour is stochastic, it is essential that these simulations be fast enough to allow for an exploration of the phase space and the gathering of sufficient statistics to accurately pin down the average behaviour as well as the magnitude of fluctuations around it. Here we describe a simulation approach that meets this requirement by adopting an event-driven methodology that encompasses both the spontaneous stochastic changes in microtubule state as well as the deterministic collisions. In contrast with finite time step simulations this technique is intrinsically exact, as well as several orders of magnitude faster, which enables ordinary PC hardware to simulate systems of $sim 10^3$ microtubules on a time scale $sim 10^{3}$ faster than real time. In addition we present new tools for the analysis of microtubule trajectories on curved surfaces. We illustrate the use of these methods by addressing a number of outstanding issues regarding the importance of various parameters on the transition from an isotropic to an aligned and oriented state.

  9. Identification of interphase functions for the NIMA kinase involving microtubules and the ESCRT pathway.

    Directory of Open Access Journals (Sweden)

    Meera Govindaraghavan

    2014-03-01

    Full Text Available The Never in Mitosis A (NIMA kinase (the founding member of the Nek family of kinases has been considered a mitotic specific kinase with nuclear restricted roles in the model fungus Aspergillus nidulans. By extending to A. nidulans the results of a synthetic lethal screen performed in Saccharomyces cerevisiae using the NIMA ortholog KIN3, we identified a conserved genetic interaction between nimA and genes encoding proteins of the Endosomal Sorting Complex Required for Transport (ESCRT pathway. Absence of ESCRT pathway functions in combination with partial NIMA function causes enhanced cell growth defects, including an inability to maintain a single polarized dominant cell tip. These genetic insights suggest NIMA potentially has interphase functions in addition to its established mitotic functions at nuclei. We therefore generated endogenously GFP-tagged NIMA (NIMA-GFP which was fully functional to follow its interphase locations using live cell spinning disc 4D confocal microscopy. During interphase some NIMA-GFP locates to the tips of rapidly growing cells and, when expressed ectopically, also locates to the tips of cytoplasmic microtubules, suggestive of non-nuclear interphase functions. In support of this, perturbation of NIMA function either by ectopic overexpression or through partial inactivation results in marked cell tip growth defects with excess NIMA-GFP promoting multiple growing cell tips. Ectopic NIMA-GFP was found to locate to the plus ends of microtubules in an EB1 dependent manner, while impairing NIMA function altered the dynamic localization of EB1 and the cytoplasmic microtubule network. Together, our genetic and cell biological analyses reveal novel non-nuclear interphase functions for NIMA involving microtubules and the ESCRT pathway for normal polarized fungal cell tip growth. These insights extend the roles of NIMA both spatially and temporally and indicate that this conserved protein kinase could help integrate cell

  10. Identification of interphase functions for the NIMA kinase involving microtubules and the ESCRT pathway.

    Directory of Open Access Journals (Sweden)

    Meera Govindaraghavan

    2014-03-01

    Full Text Available The Never in Mitosis A (NIMA kinase (the founding member of the Nek family of kinases has been considered a mitotic specific kinase with nuclear restricted roles in the model fungus Aspergillus nidulans. By extending to A. nidulans the results of a synthetic lethal screen performed in Saccharomyces cerevisiae using the NIMA ortholog KIN3, we identified a conserved genetic interaction between nimA and genes encoding proteins of the Endosomal Sorting Complex Required for Transport (ESCRT pathway. Absence of ESCRT pathway functions in combination with partial NIMA function causes enhanced cell growth defects, including an inability to maintain a single polarized dominant cell tip. These genetic insights suggest NIMA potentially has interphase functions in addition to its established mitotic functions at nuclei. We therefore generated endogenously GFP-tagged NIMA (NIMA-GFP which was fully functional to follow its interphase locations using live cell spinning disc 4D confocal microscopy. During interphase some NIMA-GFP locates to the tips of rapidly growing cells and, when expressed ectopically, also locates to the tips of cytoplasmic microtubules, suggestive of non-nuclear interphase functions. In support of this, perturbation of NIMA function either by ectopic overexpression or through partial inactivation results in marked cell tip growth defects with excess NIMA-GFP promoting multiple growing cell tips. Ectopic NIMA-GFP was found to locate to the plus ends of microtubules in an EB1 dependent manner, while impairing NIMA function altered the dynamic localization of EB1 and the cytoplasmic microtubule network. Together, our genetic and cell biological analyses reveal novel non-nuclear interphase functions for NIMA involving microtubules and the ESCRT pathway for normal polarized fungal cell tip growth. These insights extend the roles of NIMA both spatially and temporally and indicate that this conserved protein kinase could help integrate cell

  11. The Role of Microtubule Movement in Bidirectional Organelle Transport

    National Research Council Canada - National Science Library

    Igor M. Kulić; André E. X. Brown; Hwajin Kim; Comert Kural; Benjamin Blehm; Paul R. Selvin; Philip C. Nelson; Vladimir I. Gelfand

    2008-01-01

    We study the role of microtubule movement in bidirectional organelle transport in Drosophila S2 cells and show that EGFP-tagged peroxisomes in cells serve as sensitive probes of motor induced, noisy cytoskeletal motions...

  12. Mechanical Models of Microtubule Bundle Collapse in Alzheimer's Disease

    Science.gov (United States)

    Sendek, Austin; Singh, Rajiv; Cox, Daniel

    2013-03-01

    Amyloid-beta aggregates initiate Alzheimer's disease, and downstream trigger degradation of tau proteins that act as microtubule bundle stabilizers and mechanical spacers. Currently it is unclear which of tau cutting by proteases, tau phosphorylation, or tau aggregation are responsible for cytoskeleton degradation., We construct a percolation simulation of the microtubule bundle using a molecular spring model for the taus and including depletion force attraction between microtubules and membrane/actin cytoskeletal surface tension. The simulation uses a fictive molecular dynamics to model the motion of the individual microtubules within the bundle as a result of random tau removal, and calculates the elastic modulus of the bundle as the tau concentration falls. We link the tau removal steps to kinetic tau steps in various models of tau degradation. Supported by US NSF Grant DMR 1207624

  13. Microtubule as a Transmission Line for Ionic Currents

    Institute of Scientific and Technical Information of China (English)

    ILI(C) D.I.; SATARI(C) M.V.; RALEVI(C) N.

    2009-01-01

    We establish a new model for ionic waves along microtubules based on polyelectrolyte features of cylindrical biopolymers. The nonlinear transmission line described by a nonlinear differential equation is obtained with stable kink solution pertinent to the shape of the front of accompanying potential. The localized ionic wave could be used to explain the behavior of microtubules as biomolecular transistors capable of amplifying electrical information in neurons.

  14. Gap junction protein connexin-43 interacts directly with microtubules

    NARCIS (Netherlands)

    Giepmans, B N; Verlaan, I; Hengeveld, T; Janssen, H; Calafat, J; Falk, M M; Moolenaar, W H

    2001-01-01

    Gap junctions are specialized cell-cell junctions that mediate intercellular communication. They are composed of connexin proteins, which form transmembrane channels for small molecules [1, 2]. The C-terminal tail of connexin-43 (Cx43), the most widely expressed connexin member, has been implicated

  15. 协调博弈的摆动均衡:企业核心层关系的一个分析%The Pendulous Equilibrium of Coordination Game: An Analysis of the Interaction in the Senior Managers in a Firm

    Institute of Scientific and Technical Information of China (English)

    李璐

    2005-01-01

    This paper is focusing on the interaction between the senior managers of a firm for a long-term, which is of high uncertainty. By doubting and improving the theory of residual control and public domain, the paper reveals the micro-mechanism of a long-term-game between the senior managers of the firm in condition of an incomplete contract by using the analysis of coordination game.In general,we can summarize the long-term-game into the pendulous equilibrium of coordination game.

  16. Nonlinear dynamics of C–terminal tails in cellular microtubules

    Energy Technology Data Exchange (ETDEWEB)

    Sekulic, Dalibor L., E-mail: dalsek@uns.ac.rs; Sataric, Bogdan M.; Sataric, Miljko V. [University of Novi Sad, Faculty of Technical Sciences, Novi Sad (Serbia); Zdravkovic, Slobodan [University of Belgrade, Institute of Nuclear Sciences Vinca, Belgrade (Serbia); Bugay, Aleksandr N. [Laboratory of Radiation Biology, Joint Institute for Nuclear Research, Dubna (Russian Federation)

    2016-07-15

    The mechanical and electrical properties, and information processing capabilities of microtubules are the permanent subject of interest for carrying out experiments in vitro and in silico, as well as for theoretical attempts to elucidate the underlying processes. In this paper, we developed a new model of the mechano–electrical waves elicited in the rows of very flexible C–terminal tails which decorate the outer surface of each microtubule. The fact that C–terminal tails play very diverse roles in many cellular functions, such as recruitment of motor proteins and microtubule–associated proteins, motivated us to consider their collective dynamics as the source of localized waves aimed for communication between microtubule and associated proteins. Our approach is based on the ferroelectric liquid crystal model and it leads to the effective asymmetric double-well potential which brings about the conditions for the appearance of kink–waves conducted by intrinsic electric fields embedded in microtubules. These kinks can serve as the signals for control and regulation of intracellular traffic along microtubules performed by processive motions of motor proteins, primarly from kinesin and dynein families. On the other hand, they can be precursors for initiation of dynamical instability of microtubules by recruiting the proper proteins responsible for the depolymerization process.

  17. Dynein prevents erroneous kinetochore-microtubule attachments in mitosis.

    Science.gov (United States)

    Barisic, Marin; Maiato, Helder

    2015-01-01

    Equal distribution of the genetic material during cell division relies on efficient congression of chromosomes to the metaphase plate. Prior to their alignment, the Dynein motor recruited to kinetochores transports a fraction of laterally-attached chromosomes along microtubules toward the spindle poles. By doing that, Dynein not only contributes to chromosome movements, but also prevents premature stabilization of end-on kinetochore-microtubule attachments. This is achieved by 2 parallel mechanisms: 1) Dynein-mediated poleward movement of chromosomes counteracts opposite polar-ejection forces (PEFs) on chromosome arms by the microtubule plus-end-directed motors chromokinesins. Otherwise, they could stabilize erroneous syntelic kinetochore-microtubule attachments and lead to the random ejection of chromosomes away from the spindle poles; and 2) By transporting chromosomes to the spindle poles, Dynein brings the former to the zone of highest Aurora A kinase activity, further destabilizing kinetochore-microtubule attachments. Thus, Dynein plays an important role in keeping chromosome segregation error-free by preventing premature stabilization of kinetochore-microtubule attachments near the spindle poles.

  18. Cortical microtubules are responsible for gravity resistance in plants.

    Science.gov (United States)

    Hoson, Takayuki; Matsumoto, Shouhei; Soga, Kouichi; Wakabayashi, Kazuyuki

    2010-06-01

    Mechanical resistance to the gravitational force is a principal gravity response in plants distinct from gravitropism. In the final step of gravity resistance, plants increase the rigidity of their cell walls. Here we discuss the role of cortical microtubules, which sustain the function of the cell wall, in gravity resistance. Hypocotyls of Arabidopsis tubulin mutants were shorter and thicker than the wild-type, and showed either left-handed or right-handed helical growth at 1 g. The degree of twisting phenotype was intensified under hypergravity conditions. Hypergravity also induces reorientation of cortical microtubules from transverse to longitudinal directions in epidermal cells. In tubulin mutants, the percentage of cells with longitudinal microtubules was high even at 1 g, and it was further increased by hypergravity. The left-handed helical growth mutants had right-handed microtubule arrays, whereas the right-handed mutant had left-handed arrays. Moreover, blockers of mechanoreceptors suppressed both the twisting phenotype and reorientation of microtubules in tubulin mutants. These results support the hypothesis that cortical microtubules play an essential role in maintenance of normal growth phenotype against the gravitational force, and suggest that mechanoreceptors are involved in signal perception in gravity resistance. Space experiments will confirm whether this view is applicable to plant resistance to 1 g gravity, as to the resistance to hypergravity.

  19. TECHNICAL COORDINATION

    CERN Multimedia

    A. Ball

    Overview From a technical perspective, CMS has been in “beam operation” state since 6th November. The detector is fully closed with all components operational and the magnetic field is normally at the nominal 3.8T. The UXC cavern is normally closed with the radiation veto set. Access to UXC is now only possible during downtimes of LHC. Such accesses must be carefully planned, documented and carried out in agreement with CMS Technical Coordination, Experimental Area Management, LHC programme coordination and the CCC. Material flow in and out of UXC is now strictly controlled. Access to USC remains possible at any time, although, for safety reasons, it is necessary to register with the shift crew in the control room before going down.It is obligatory for all material leaving UXC to pass through the underground buffer zone for RP scanning, database entry and appropriate labeling for traceability. Technical coordination (notably Stephane Bally and Christoph Schaefer), the shift crew and run ...

  20. Axial thiophenolate coordination on diiron(III)bisporphyrin: influence of heme-heme interactions on structure, function and electrochemical properties of the individual heme center.

    Science.gov (United States)

    Sil, Debangsu; Tuglak Khan, Firoz Shah; Rath, Sankar Prasad

    2014-11-17

    The binding of a series of substituted thiophenols as axial ligands on a highly flexible ethane-bridged diiron(III)bisporphyrin framework has been investigated as a model of diheme proteins. Spectroscopic characterization reveals a high-spin (S = 5/2) state of iron for all of the pentacoordinate thiophenolato complexes. In the UV-visible spectra of the complexes, the positions of the Soret and band I have been found to be dependent on the pKa of thiophenols. The alternating shift pattern, which has opposite sign of the chemical shifts for meta- vs. ortho- and para-protons in the (1)H NMR spectra, is attributed to negative and positive spin densities, respectively, on thiophenolate carbon atoms and is indicative of π-spin delocalization to the bound thiophenolate ligand. The Fe(III)/Fe(II) redox couple of the complexes bears a linear relationship with the pKa of thiophenol and is found to be positively shifted with decreasing pKa. The effect of the electronic nature of the substituent on the thiophenolate ring has also been demonstrated in which a large potential range of 540 mV was observed (in contrast to the value of only 270 mV in case of monoheme analogues) for the Fe(III)/Fe(II) redox couple on going from monoheme to diheme and is attributed to the interheme interaction. Also, the Fe(III)/Fe(II) redox potential of the thiophenolato complexes has been found to be more positively shifted compared to their phenolato analogues, which was further supported by DFT calculation. The addition of another thiophenol at the sixth axial position of the five-coordinate thiophenolato complex causes a change in iron spin from high (S = 5/2) to low (S = 1/2) along with a large positive shift of 490 mV for the Fe(III)/Fe(II) redox couple.

  1. Microtubules, polarity and vertebrate neural tube morphogenesis.

    Science.gov (United States)

    Cearns, Michael D; Escuin, Sarah; Alexandre, Paula; Greene, Nicholas D E; Copp, Andrew J

    2016-07-01

    Microtubules (MTs) are key cellular components, long known to participate in morphogenetic events that shape the developing embryo. However, the links between the cellular functions of MTs, their effects on cell shape and polarity, and their role in large-scale morphogenesis remain poorly understood. Here, these relationships were examined with respect to two strategies for generating the vertebrate neural tube: bending and closure of the mammalian neural plate; and cavitation of the teleost neural rod. The latter process has been compared with 'secondary' neurulation that generates the caudal spinal cord in mammals. MTs align along the apico-basal axis of the mammalian neuroepithelium early in neural tube closure, participating functionally in interkinetic nuclear migration, which indirectly impacts on cell shape. Whether MTs play other functional roles in mammalian neurulation remains unclear. In the zebrafish, MTs are important for defining the neural rod midline prior to its cavitation, both by localizing apical proteins at the tissue midline and by orienting cell division through a mirror-symmetric MT apparatus that helps to further define the medial localization of apical polarity proteins. Par proteins have been implicated in centrosome positioning in neuroepithelia as well as in the control of polarized morphogenetic movements in the neural rod. Understanding of MT functions during early nervous system development has so far been limited, partly by techniques that fail to distinguish 'cause' from 'effect'. Future developments will likely rely on novel ways to selectively impair MT function in order to investigate the roles they play.

  2. The Katanin Microtubule Severing Protein in Plants

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Katanin is a heterodimeric microtubule (MT) severing protein that uses energy from ATP hydrolysis to generate internal breaks along MTs. Katanin p60, one of the two subunits, possesses ATPase and MT-bindinglsevering activities, and the p80 subunit is responsible for targeting of katanin to certain subcellular locations. In animals, katanin plays an important role in the release of MTs from their nucleation sites in the centrosome. It is also involved in severing MTs into smaller fragments which can serve as templates for further polymerization to increase MT number during meiotic and mitotic spindle assembly. Katanin homologs are present in a wide variety of plant species. The Arabidopsis katanin homolog has been shown to possess ATP-dependent MT severing activity in vitro and exhibit a punctate localization pattern at the cell cortex and the perinuclear region. Disruption of katanin functions by genetic mutations causes a delay in the disappearance of the perinuclear MT array and results in an aberrant organization of cortical MTs in elongating cells. Consequently, katanin mutations lead to defects in cell elongation, cellulose microfibril deposition, and hormonal responses. Studies of katanin in plants provide new insights into our understanding of its roles in cellular functions.

  3. Statistical mechanics provides novel insights into microtubule stability and mechanism of shrinkage.

    Science.gov (United States)

    Jain, Ishutesh; Inamdar, Mandar M; Padinhateeri, Ranjith

    2015-02-01

    Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs). We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (E(s)(m)) has to be comparable to the strength of the curvature energy (E(b)(m)) such that E(s)(m) - E(b)(m) ≈ 1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length.

  4. Statistical mechanics provides novel insights into microtubule stability and mechanism of shrinkage.

    Directory of Open Access Journals (Sweden)

    Ishutesh Jain

    2015-02-01

    Full Text Available Microtubules are nano-machines that grow and shrink stochastically, making use of the coupling between chemical kinetics and mechanics of its constituent protofilaments (PFs. We investigate the stability and shrinkage of microtubules taking into account inter-protofilament interactions and bending interactions of intrinsically curved PFs. Computing the free energy as a function of PF tip position, we show that the competition between curvature energy, inter-PF interaction energy and entropy leads to a rich landscape with a series of minima that repeat over a length-scale determined by the intrinsic curvature. Computing Langevin dynamics of the tip through the landscape and accounting for depolymerization, we calculate the average unzippering and shrinkage velocities of GDP protofilaments and compare them with the experimentally known results. Our analysis predicts that the strength of the inter-PF interaction (E(s(m has to be comparable to the strength of the curvature energy (E(b(m such that E(s(m - E(b(m ≈ 1kBT, and questions the prevalent notion that unzippering results from the domination of bending energy of curved GDP PFs. Our work demonstrates how the shape of the free energy landscape is crucial in explaining the mechanism of MT shrinkage where the unzippered PFs will fluctuate in a set of partially peeled off states and subunit dissociation will reduce the length.

  5. In vitro assembly of plant tubulin in the absence of microtubule-stabilizing reagents

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The assembly of microtubules is essential for physiological functions of microtubules. Addition of microtubule-stabilizing reagents or microtubule "seeds" is usually necessary for plant tubulin assembly in vitro, which hinders the investigation of plant microtubule dynamics. In the present note, highly purified plant tubulins have been obtained from lily pollen, a non-microtubule-stabilizing reagent or microtubule "seed" system for plant tubulin assembly has been established and the analysis of plant tubulin assembly performed. Experiment results showed that purified tubulin polymerized in vitro, and a typical microtubule structure was observed with electron microscopy. The kinetics curve of tubulin assembly exhibited typical "parabola". The presence of taxol significantly altered the character of plant tubulin assembly, including that abnormal microtubules were assembled and the critical concentration for plant tubulin assembly was decreased exceedingly from 3 mg/mL in the absence of taxol to 0.043 mg/mL in the presence of taxol.

  6. The dual specificity phosphatase Cdc14B bundles and stabilizes microtubules

    Energy Technology Data Exchange (ETDEWEB)

    Plumley, Hyekyung [ORNL; Liu, Yie [ORNL; Gomez, Marla V [ORNL; Wang, Yisong [ORNL

    2005-01-01

    The Cdc14 dual-specificity phosphatases regulate key events in the eukaryotic cell cycle. However, little is known about the function of mammalian CDC14B family members. Here, we demonstrate that subcellular localization of CDC14B protein is cell cycle regulated. CDC14B can bind, bundle, and stabilize microtubules in vitro independently of its catalytic activity. Basic amino acid residues within the nucleolar targeting domain are important for both retaining CDC14B in the nucleolus and preventing microtubule bundling. Overexpression of CDC14B resulted in the formation of cytoplasmic CDC14B and microtubule bundles in interphase cells. These microtubule bundles were resistant to microtubule depolymerization reagents and enriched in acetylated -tubulin. Expression of cytoplasmic forms of CDC14B impaired microtubule nucleation from the microtubule organization center. CDC14B is thus a novel microtubule-bundling and -stabilizing protein, whose regulated subcellular localization may help modulate spindle and microtubule dynamics in mitosis.

  7. On the significance of microtubule flexural behavior in cytoskeletal mechanics.

    Directory of Open Access Journals (Sweden)

    Mehrdad Mehrbod

    Full Text Available Quantitative description of cell mechanics has challenged biological scientists for the past two decades. Various structural models have been attempted to analyze the structure of the cytoskeleton. One important aspect that has been largely ignored in all these modeling approaches is related to the flexural and buckling behavior of microtubular filaments. The objective of this paper is to explore the influence of this flexural and buckling behavior in cytoskeletal mechanics.In vitro the microtubules are observed to buckle in the first mode, reminiscent of a free, simply-supported beam. In vivo images of microtubules, however, indicate that the buckling mostly occurs in higher modes. This buckling mode switch takes place mostly because of the lateral support of microtubules via their connections to actin and intermediate filaments. These lateral loads are exerted throughout the microtubule length and yield a considerable bending behavior that, unless properly accounted for, would produce erroneous results in the modeling and analysis of the cytoskeletal mechanics.One of the promising attempts towards mechanical modeling of the cytoskeleton is the tensegrity model, which simplifies the complex network of cytoskeletal filaments into a combination merely of tension-bearing actin filaments and compression-bearing microtubules. Interestingly, this discrete model can qualitatively explain many experimental observations in cell mechanics. However, evidence suggests that the simplicity of this model may undermine the accuracy of its predictions, given the model's underlying assumption that "every single member bears solely either tensile or compressive behavior," i.e. neglecting the flexural behavior of the microtubule filaments. We invoke an anisotropic continuum model for microtubules and compare the bending energy stored in a single microtubule with its axial strain energy at the verge of buckling. Our results suggest that the bending energy can

  8. Microtubules Are Essential for Guard-Cell Function in Vicia and Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    William Eisinger; David Ehrhardt; Winslow Briggs

    2012-01-01

    Radially arranged cortical microtubules are a prominent feature of guard cells.Guard cells expressing GFPtubulin showed consistent changes in the appearance of microtubules when stomata opened or closed.Guard cells showed fewer microtubule structures as stomata closed,whether induced by transfer to darkness,ABA,hydrogen peroxide,or sodium hydrogen carbonate.Guard cells kept in the dark (closed stomata) showed increases in microtubule structures and stomatal aperture on light treatment.GFP-EB1,marking microtubule growing plus ends,showed no change in number of plus ends or velocity of assembly on stomatal closure.Since the number of growing plus ends and the rate of plus-end growth did not change when microtubule structure numbers declined,microtubule instability and/or rearrangement must be responsible for the apparent loss of microtubules.Guard cells with closed stomata showed more cytosolic GFP-fluorescence than those with open stomata as cortical microtubules became disassembled,although with a large net loss in total fluorescence.Microtubule-targeted drugs blocked guard-cell function in Vicia and Arabidopsis.Oryzalin disrupted guard-cell microtubules and prevented stomatal opening and taxol stabilized guard-cell microtubules and delayed stomatal closure.Gas exchange measurements indicated that the transgenes for fluorescent-labeled proteins did not disrupt normal stomatal function.These dynamic changes in guard-cell microtubules combined with our inhibitor studies provide evidence for an active role of microtubules in guard-cell function.

  9. LKB1 destabilizes microtubules in myoblasts and contributes to myoblast differentiation.

    Directory of Open Access Journals (Sweden)

    Isma Mian

    Full Text Available BACKGROUND: Skeletal muscle myoblast differentiation and fusion into multinucleate myotubes is associated with dramatic cytoskeletal changes. We find that microtubules in differentiated myotubes are highly stabilized, but premature microtubule stabilization blocks differentiation. Factors responsible for microtubule destabilization in myoblasts have not been identified. FINDINGS: We find that a transient decrease in microtubule stabilization early during myoblast differentiation precedes the ultimate microtubule stabilization seen in differentiated myotubes. We report a role for the serine-threonine kinase LKB1 in both microtubule destabilization and myoblast differentiation. LKB1 overexpression reduced microtubule elongation in a Nocodazole washout assay, and LKB1 RNAi increased it, showing LKB1 destabilizes microtubule assembly in myoblasts. LKB1 levels and activity increased during myoblast differentiation, along with activation of the known LKB1 substrates AMP-activated protein kinase (AMPK and microtubule affinity regulating kinases (MARKs. LKB1 overexpression accelerated differentiation, whereas RNAi impaired it. CONCLUSIONS: Reduced microtubule stability precedes myoblast differentiation and the associated ultimate microtubule stabilization seen in myotubes. LKB1 plays a positive role in microtubule destabilization in myoblasts and in myoblast differentiation. This work suggests a model by which LKB1-induced microtubule destabilization facilitates the cytoskeletal changes required for differentiation. Transient destabilization of microtubules might be a useful strategy for enhancing and/or synchronizing myoblast differentiation.

  10. Integrins Regulate Apical Constriction via Microtubule Stabilization in the Drosophila Eye Disc Epithelium

    Directory of Open Access Journals (Sweden)

    Vilaiwan M. Fernandes

    2014-12-01

    Full Text Available During morphogenesis, extracellular signals trigger actomyosin contractility in subpopulations of cells to coordinate changes in cell shape. To illuminate the link between signaling-mediated tissue patterning and cytoskeletal remodeling, we study the progression of the morphogenetic furrow (MF, the wave of apical constriction that traverses the Drosophila eye imaginal disc preceding photoreceptor neurogenesis. Apical constriction depends on actomyosin contractility downstream of the Hedgehog (Hh and bone morphogenetic protein (BMP pathways. We identify a role for integrin adhesion receptors in MF progression. We show that Hh and BMP regulate integrin expression, the loss of which disrupts apical constriction and slows furrow progression; conversely, elevated integrins accelerate furrow progression. We present evidence that integrins regulate MF progression by promoting microtubule stabilization, since reducing microtubule stability rescues integrin-mediated furrow acceleration. Thus, integrins act as a genetic link between tissue-level signaling events and morphological change at the cellular level, leading to morphogenesis and neurogenesis in the eye.

  11. A hopping mechanism for cargo transport by molecular motors in crowded microtubules

    CERN Document Server

    Goldman, Carla

    2010-01-01

    Most models designed to study the bidirectional movement of cargos as they are driven by molecular motors rely on the idea that motors of different polarities can be coordinated by external agents if arranged into a motor-cargo complex to perform the necessary work [gross04]. Although these models have provided us with important insights into these phenomena, there are still many unanswered questions regarding the mechanisms through which the movement of the complex takes place on crowded microtubules. For example (i) how does cargo-binding affect motor motility? and in connection with that - (ii) how does the presence of other motors (and also other cargos) on the microtubule affect the motility of the motor-cargo complex? We discuss these questions from a different perspective. The movement of a cargo is conceived here as a hopping process resulting from the transference of cargo between neighboring motors. In the light of this, we examine the conditions under which cargo might display bidirectional movemen...

  12. PDK1-Akt pathway regulates radial neuronal migration and microtubules in the developing mouse neocortex.

    Science.gov (United States)

    Itoh, Yasuhiro; Higuchi, Maiko; Oishi, Koji; Kishi, Yusuke; Okazaki, Tomohiko; Sakai, Hiroshi; Miyata, Takaki; Nakajima, Kazunori; Gotoh, Yukiko

    2016-05-24

    Neurons migrate a long radial distance by a process known as locomotion in the developing mammalian neocortex. During locomotion, immature neurons undergo saltatory movement along radial glia fibers. The molecular mechanisms that regulate the speed of locomotion are largely unknown. We now show that the serine/threonine kinase Akt and its activator phosphoinositide-dependent protein kinase 1 (PDK1) regulate the speed of locomotion of mouse neocortical neurons through the cortical plate. Inactivation of the PDK1-Akt pathway impaired the coordinated movement of the nucleus and centrosome, a microtubule-dependent process, during neuronal migration. Moreover, the PDK1-Akt pathway was found to control microtubules, likely by regulating the binding of accessory proteins including the dynactin subunit p150(glued) Consistent with this notion, we found that PDK1 regulates the expression of cytoplasmic dynein intermediate chain and light intermediate chain at a posttranscriptional level in the developing neocortex. Our results thus reveal an essential role for the PDK1-Akt pathway in the regulation of a key step of neuronal migration.

  13. An E3-14.7K peptide that promotes microtubules-mediated transport of plasmid DNA increases polyplexes transfection efficiency.

    Science.gov (United States)

    Pigeon, Lucie; Gonçalves, Cristine; Gosset, David; Pichon, Chantal; Midoux, Patrick

    2013-11-25

    Chemical vectors as cationic polymers and cationic lipids are promising alternatives to viral vectors for gene therapy. Beside endosome escape and nuclear import, plasmid DNA (pDNA) migration in the cytosol toward the nuclear envelope is also regarded as a limiting step for efficient DNA transfection with non-viral vectors. Here, the interaction between E3-14.7K and FIP-1 to favor migration of pDNA along microtubules is exploited. E3-14.7K is an early protein of human adenoviruses that interacts via FIP-1 (Fourteen.7K Interacting Protein 1) protein with the light-chain components of the human microtubule motor protein dynein (TCTEL1). This peptide is conjugated with pDNA and mediates interaction of pDNA in vitro with isolated microtubules as well as with microtubules in cellulo. Videomicroscopy and tracking treatment of images clearly demonstrate that P79-98/pDNA conjugate exhibits a linear transport with large amplitude along microtubules upon 2 h transfection with polyplexes whereas control pDNA conjugate exhibits small non-directional movements in the cytoplasm. Remarkably, P79-98/peGFP polyplexes enhance by a factor 2.5 (up to 76%) the number of transfected cells. The results demonstrate, for the first time, that the transfection efficiency of polyplexes can be drastically increased when the microtubules migration of pDNA is facilitated by a peptide allowing pDNA docking to TCTEL1. This is a real breakthrough in the non viral gene delivery field that opens hope to build artificial viruses.

  14. Gene organization, evolution and expression of the microtubule-associated protein ASAP (MAP9

    Directory of Open Access Journals (Sweden)

    Giorgi Dominique

    2008-09-01

    Full Text Available Abstract Background ASAP is a newly characterized microtubule-associated protein (MAP essential for proper cell-cycling. We have previously shown that expression deregulation of human ASAP results in profound defects in mitotic spindle formation and mitotic progression leading to aneuploidy, cytokinesis defects and/or cell death. In the present work we analyze the structure and evolution of the ASAP gene, as well as the domain composition of the encoded protein. Mouse and Xenopus cDNAs were cloned, the tissue expression characterized and the overexpression profile analyzed. Results Bona fide ASAP orthologs are found in vertebrates with more distantly related potential orthologs in invertebrates. This single-copy gene is conserved in mammals where it maps to syntenic chromosomal regions, but is also clearly identified in bird, fish and frog. The human gene is strongly expressed in brain and testis as a 2.6 Kb transcript encoding a ~110 KDa protein. The protein contains MAP, MIT-like and THY domains in the C-terminal part indicative of microtubule interaction, while the N-terminal part is more divergent. ASAP is composed of ~42% alpha helical structures, and two main coiled-coil regions have been identified. Different sequence features may suggest a role in DNA damage response. As with human ASAP, the mouse and Xenopus proteins localize to the microtubule network in interphase and to the mitotic spindle during mitosis. Overexpression of the mouse protein induces mitotic defects similar to those observed in human. In situ hybridization in testis localized ASAP to the germ cells, whereas in culture neurons ASAP localized to the cell body and growing neurites. Conclusion The conservation of ASAP indicated in our results reflects an essential function in vertebrates. We have cloned the ASAP orthologs in mouse and Xenopus, two valuable models to study the function of ASAP. Tissue expression of ASAP revealed a high expression in brain and testis, two

  15. TECHNICAL COORDINATION

    CERN Multimedia

    A. Ball

    2010-01-01

    Operational Experience At the end of the first full-year running period of LHC, CMS is established as a reliable, robust and mature experiment. In particular common systems and infrastructure faults accounted for <0.6 % CMS downtime during LHC pp physics. Technical operation throughout the entire year was rather smooth, the main faults requiring UXC access being sub-detector power systems and rack-cooling turbines. All such problems were corrected during scheduled technical stops, in the shadow of tunnel access needed by the LHC, or in negotiated accesses or access extensions. Nevertheless, the number of necessary accesses to the UXC averaged more than one per week and the technical stops were inevitably packed with work packages, typically 30 being executed within a few days, placing a high load on the coordination and area management teams. It is an appropriate moment for CMS Technical Coordination to thank all those in many CERN departments and in the Collaboration, who were involved in CMS techni...

  16. Measuring cohesion between macromolecular filaments, one pair at a time: Depletion-induced microtubule binding

    CERN Document Server

    Hilitski, Feodor; Cajamarca, Luis; Hagan, Michael F; Grason, Gregory M; Dogic, Zvonimir

    2014-01-01

    In presence of non-adsorbing polymers, colloidal particles experience a ubiquitous attractive interactions induced by the depletion mechanism. We measure the depletion interaction between a pair of microtubule filaments by a method that combines optical trapping, single molecule imaging and umbrella sampling. By quantifying the dependence of filament cohesion on both polymer concentration and solution ionic strength, we demonstrate that the minimal model of depletion based, on the Asakura-Oosawa theory, fails to describe the experimental data. By measuring the cohesion strength in two- and three- filament bundles we verify pairwise additivity of the depletion interaction for the specific experimental conditions. The described experimental technique can be used to measure pairwise interactions between various biological or synthetic filaments, thus complementing information extracted from bulk osmotic stress experiments.

  17. A Quantitative Method for Microtubule Analysis in Fluorescence Images.

    Science.gov (United States)

    Lan, Xiaodong; Li, Lingfei; Hu, Jiongyu; Zhang, Qiong; Dang, Yongming; Huang, Yuesheng

    2015-12-01

    Microtubule analysis is of significant value for a better understanding of normal and pathological cellular processes. Although immunofluorescence microscopic techniques have proven useful in the study of microtubules, comparative results commonly rely on a descriptive and subjective visual analysis. We developed an objective and quantitative method based on image processing and analysis of fluorescently labeled microtubular patterns in cultured cells. We used a multi-parameter approach by analyzing four quantifiable characteristics to compose our quantitative feature set. Then we interpreted specific changes in the parameters and revealed the contribution of each feature set using principal component analysis. In addition, we verified that different treatment groups could be clearly discriminated using principal components of the multi-parameter model. High predictive accuracy of four commonly used multi-classification methods confirmed our method. These results demonstrated the effectiveness and efficiency of our method in the analysis of microtubules in fluorescence images. Application of the analytical methods presented here provides information concerning the organization and modification of microtubules, and could aid in the further understanding of structural and functional aspects of microtubules under normal and pathological conditions.

  18. Intracellular spatial localization regulated by the microtubule network.

    Directory of Open Access Journals (Sweden)

    Jing Chen

    Full Text Available The commonly recognized mechanisms for spatial regulation inside the cell are membrane-bounded compartmentalization and biochemical association with subcellular organelles. We use computational modeling to investigate another spatial regulation mechanism mediated by the microtubule network in the cell. Our results demonstrate that the mitotic spindle can impose strong sequestration and concentration effects on molecules with binding affinity for microtubules, especially dynein-directed cargoes. The model can recapitulate the essence of three experimental observations on distinct microtubule network morphologies: the sequestration of germ plasm components by the mitotic spindles in the Drosophila syncytial embryo, the asymmetric cell division initiated by the time delay in centrosome maturation in the Drosophila neuroblast, and the diffusional block between neighboring energids in the Drosophila syncytial embryo. Our model thus suggests that the cell cycle-dependent changes in the microtubule network are critical for achieving different spatial regulation effects. The microtubule network provides a spatially extensive docking platform for molecules and gives rise to a "structured cytoplasm", in contrast to a free and fluid environment.

  19. Microtubules contribute to maintain nucleus shape in epithelial cell monolayer

    Science.gov (United States)

    Tremblay, Dominique; Andrzejewski, Lukasz; Pelling, Andrew

    2013-03-01

    INTRODUCTION: Tissue strains can result in significant nuclear deformations and may regulate gene expression. However, the precise role of the cytoskeleton in regulating nuclear mechanics remains poorly understood. Here, we investigate the nuclear deformability of Madin-Darky canine kidney cells (MDCK) under various stretching conditions to clarify the role of the microtubules and actin network on the mechanical behavior of the nucleus. METHODS: A custom-built cell-stretching device allowing for real time imaging of MDCK nuclei was used. Cells were seeded on a silicone membrane coated with rat-tail collagen I. A nuclear stain, Hoechst-33342, was used to image nuclei during stretching. We exposed cells to a compressive and non-compressive stretching strain field of 25%. Nocodazole and cytochalasin-D were used to depolymerize the microtubules and actin network. RESULTS: Nuclei in control cells stretched more along their minor axis than major axis with a deformation of 5% and 2% respectively. This anisotropy vanished completely in microtubule-deprived cells and these cells showed a very high nuclear deformability along the minor axis when exposed to a compressive stretching strain field. CONCLUSIONS: The microtubules drive the anisotropic deformability of MDCK nuclei in a monolayer and maintain nuclear shape when exposed to compressive strain. Such intrinsic mechanical behavior indicates that microtubules are essential to maintain nuclear shape and may prevent down regulation of gene expression.

  20. The feasibility of coherent energy transfer in microtubules.

    Science.gov (United States)

    Craddock, Travis John Adrian; Friesen, Douglas; Mane, Jonathan; Hameroff, Stuart; Tuszynski, Jack A

    2014-11-06

    It was once purported that biological systems were far too 'warm and wet' to support quantum phenomena mainly owing to thermal effects disrupting quantum coherence. However, recent experimental results and theoretical analyses have shown that thermal energy may assist, rather than disrupt, quantum coherent transport, especially in the 'dry' hydrophobic interiors of biomolecules. Specifically, evidence has been accumulating for the necessary involvement of quantum coherent energy transfer between uniquely arranged chromophores in light harvesting photosynthetic complexes. The 'tubulin' subunit proteins, which comprise microtubules, also possess a distinct architecture of chromophores, namely aromatic amino acids, including tryptophan. The geometry and dipolar properties of these aromatics are similar to those found in photosynthetic units indicating that tubulin may support coherent energy transfer. Tubulin aggregated into microtubule geometric lattices may support such energy transfer, which could be important for biological signalling and communication essential to living processes. Here, we perform a computational investigation of energy transfer between chromophoric amino acids in tubulin via dipole excitations coupled to the surrounding thermal environment. We present the spatial structure and energetic properties of the tryptophan residues in the microtubule constituent protein tubulin. Plausibility arguments for the conditions favouring a quantum mechanism of signal propagation along a microtubule are provided. Overall, we find that coherent energy transfer in tubulin and microtubules is biologically feasible.

  1. Fission yeast mtr1p regulates interphase microtubule cortical dwell-time

    Directory of Open Access Journals (Sweden)

    Frédérique Carlier-Grynkorn

    2014-06-01

    Full Text Available The microtubule cytoskeleton plays important roles in cell polarity, motility and division. Microtubules inherently undergo dynamic instability, stochastically switching between phases of growth and shrinkage. In cells, some microtubule-associated proteins (MAPs and molecular motors can further modulate microtubule dynamics. We present here the fission yeast mtr1+, a new regulator of microtubule dynamics that appears to be not a MAP or a motor. mtr1-deletion (mtr1Δ primarily results in longer microtubule dwell-time at the cell tip cortex, suggesting that mtr1p acts directly or indirectly as a destabilizer of microtubules. mtr1p is antagonistic to mal3p, the ortholog of mammalian EB1, which stabilizes microtubules. mal3Δ results in short microtubules, but can be partially rescued by mtr1Δ, as the double mutant mal3Δ mtr1Δ exhibits longer microtubules than mal3Δ single mutant. By sequence homology, mtr1p is predicted to be a component of the ribosomal quality control complex. Intriguingly, deletion of a predicted ribosomal gene, rps1801, also resulted in longer microtubule dwell-time similar to mtr1Δ. The double-mutant mal3Δ rps1801Δ also exhibits longer microtubules than mal3Δ single mutant alone. Our study suggests a possible involvement of mtr1p and the ribosome complex in modulating microtubule dynamics.

  2. Microtubule–microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes

    Science.gov (United States)

    Lu, Wen; Winding, Michael; Lakonishok, Margot; Wildonger, Jill

    2016-01-01

    Cytoplasmic streaming in Drosophila oocytes is a microtubule-based bulk cytoplasmic movement. Streaming efficiently circulates and localizes mRNAs and proteins deposited by the nurse cells across the oocyte. This movement is driven by kinesin-1, a major microtubule motor. Recently, we have shown that kinesin-1 heavy chain (KHC) can transport one microtubule on another microtubule, thus driving microtubule–microtubule sliding in multiple cell types. To study the role of microtubule sliding in oocyte cytoplasmic streaming, we used a Khc mutant that is deficient in microtubule sliding but able to transport a majority of cargoes. We demonstrated that streaming is reduced by genomic replacement of wild-type Khc with this sliding-deficient mutant. Streaming can be fully rescued by wild-type KHC and partially rescued by a chimeric motor that cannot move organelles but is active in microtubule sliding. Consistent with these data, we identified two populations of microtubules in fast-streaming oocytes: a network of stable microtubules anchored to the actin cortex and free cytoplasmic microtubules that moved in the ooplasm. We further demonstrated that the reduced streaming in sliding-deficient oocytes resulted in posterior determination defects. Together, we propose that kinesin-1 slides free cytoplasmic microtubules against cortically immobilized microtubules, generating forces that contribute to cytoplasmic streaming and are essential for the refinement of posterior determinants. PMID:27512034

  3. Pseudomonas aeruginosa exotoxin Y-mediated tau hyperphosphorylation impairs microtubule assembly in pulmonary microvascular endothelial cells.

    Directory of Open Access Journals (Sweden)

    Ron Balczon

    Full Text Available Pseudomonas aeruginosa uses a type III secretion system to introduce the adenylyl and guanylyl cyclase exotoxin Y (ExoY into the cytoplasm of endothelial cells. ExoY induces Tau hyperphosphorylation and insolubility, microtubule breakdown, barrier disruption and edema, although the mechanism(s responsible for microtubule breakdown remain poorly understood. Here we investigated both microtubule behavior and centrosome activity to test the hypothesis that ExoY disrupts microtubule dynamics. Fluorescence microscopy determined that infected pulmonary microvascular endothelial cells contained fewer microtubules than control cells, and further studies demonstrated that the microtubule-associated protein Tau was hyperphosphorylated following infection and dissociated from microtubules. Disassembly/reassembly studies determined that microtubule assembly was disrupted in infected cells, with no detectable effects on either microtubule disassembly or microtubule nucleation by centrosomes. This effect of ExoY on microtubules was abolished when the cAMP-dependent kinase phosphorylation site (Ser-214 on Tau was mutated to a non-phosphorylatable form. These studies identify Tau in microvascular endothelial cells as the target of ExoY in control of microtubule architecture following pulmonary infection by Pseudomonas aeruginosa and demonstrate that phosphorylation of tau following infection decreases microtubule assembly.

  4. Coordination Capacity

    CERN Document Server

    Cuff, Paul; Cover, Thomas

    2009-01-01

    We develop elements of a theory of cooperation and coordination in networks. Rather than considering a communication network as a means of distributing information, or of reconstructing random processes at remote nodes, we ask what dependence can be established among the nodes given the communication constraints. Specifically, in a network with communication rates between the nodes, we ask what is the set of all achievable joint distributions p(x1, ..., xm) of actions at the nodes on the network. Several networks are solved, including arbitrarily large cascade networks. Distributed cooperation can be the solution to many problems such as distributed games, distributed control, and establishing mutual information bounds on the influence of one part of a physical system on another.

  5. A Barley ROP GTPase ACTIVATING PROTEIN Associates with Microtubules and Regulates Entry of the Barley Powdery Mildew Fungus into Leaf Epidermal Cells[C][W

    Science.gov (United States)

    Hoefle, Caroline; Huesmann, Christina; Schultheiss, Holger; Börnke, Frederik; Hensel, Götz; Kumlehn, Jochen; Hückelhoven, Ralph

    2011-01-01

    Little is known about the function of host factors involved in disease susceptibility. The barley (Hordeum vulgare) ROP (RHO of plants) G-protein RACB is required for full susceptibility of the leaf epidermis to invasion by the biotrophic fungus Blumeria graminis f. sp hordei. Stable transgenic knockdown of RACB reduced the ability of barley to accommodate haustoria of B. graminis in intact epidermal leaf cells and to form hairs on the root epidermis, suggesting that RACB is a common element of root hair outgrowth and ingrowth of haustoria in leaf epidermal cells. We further identified a barley MICROTUBULE-ASSOCIATED ROP-GTPASE ACTIVATING PROTEIN (MAGAP1) interacting with RACB in yeast and in planta. Fluorescent MAGAP1 decorated cortical microtubules and was recruited by activated RACB to the cell periphery. Under fungal attack, MAGAP1-labeled microtubules built a polarized network at sites of successful defense. By contrast, microtubules loosened where the fungus succeeded in penetration. Genetic evidence suggests a function of MAGAP1 in limiting susceptibility to penetration by B. graminis. Additionally, MAGAP1 influenced the polar organization of cortical microtubules. These results add to our understanding of how intact plant cells accommodate fungal infection structures and suggest that RACB and MAGAP1 might be antagonistic players in cytoskeleton organization for fungal entry. PMID:21685259

  6. Waves of actin and microtubule polymerization drive microtubule-based transport and neurite growth before single axon formation

    Science.gov (United States)

    Winans, Amy M; Collins, Sean R; Meyer, Tobias

    2016-01-01

    Many developing neurons transition through a multi-polar state with many competing neurites before assuming a unipolar state with one axon and multiple dendrites. Hallmarks of the multi-polar state are large fluctuations in microtubule-based transport into and outgrowth of different neurites, although what drives these fluctuations remains elusive. We show that actin waves, which stochastically migrate from the cell body towards neurite tips, direct microtubule-based transport during the multi-polar state. Our data argue for a mechanical control system whereby actin waves transiently widen the neurite shaft to allow increased microtubule polymerization to direct Kinesin-based transport and create bursts of neurite extension. Actin waves also require microtubule polymerization, arguing that positive feedback links these two components. We propose that actin waves create large stochastic fluctuations in microtubule-based transport and neurite outgrowth, promoting competition between neurites as they explore the environment until sufficient external cues can direct one to become the axon. DOI: http://dx.doi.org/10.7554/eLife.12387.001 PMID:26836307

  7. Taxol(®): The First Microtubule Stabilizing Agent.

    Science.gov (United States)

    Yang, Chia-Ping Huang; Horwitz, Susan Band

    2017-08-09

    Taxol(®), an antitumor drug with significant activity, is the first microtubule stabilizing agent described in the literature. This short review of the mechanism of action of Taxol(®) emphasizes the research done in the Horwitz' laboratory. It discusses the contribution of photoaffinity labeled analogues of Taxol(®) toward our understanding of the binding site of the drug on the microtubule. The importance of hydrogen/deuterium exchange experiments to further our insights into the stabilization of microtubules by Taxol(®) is addressed. The development of drug resistance, a major problem that arises in the clinic, is discussed. Studies describing differential drug binding to distinct β-tubulin isotypes are presented. Looking forward, it is suggested that the β-tubulin isotype content of a tumor may influence its responses to Taxol(®).

  8. Quantum Computation in Brain Microtubules? Decoherence and Biological Feasibility

    CERN Document Server

    Hagan, S; Tuszynski, J A

    2000-01-01

    The Penrose-Hameroff (`Orch OR') model of quantum computation in brain microtubules has been criticized as regards the issue of environmental decoherence. A recent report by Tegmark finds that microtubules can maintain quantum coherence for only $10^{-13}$ s, far too short to be neurophysiologically relevant. Here, we critically examine the assumptions behind Tegmark's calculation and find that: 1) Tegmark's commentary is not aimed at an existing model in the literature but rather at a hybrid that replaces the superposed protein conformations of the `Orch OR' theory with a soliton in superposition along the microtubule, 2) Tegmark predicts decreasing decoherence times at lower temperature, in direct contradiction of the observed behavior of quantum states, 3) recalculation after correcting Tegmark's equation for differences between his model and the `Orch OR' model (superposition separation, charge vs. dipole, dielectric constant) lengthens the decoherence time to $10^{-5} - 10^{-4}$ s and invalidates a criti...

  9. Disruption of microtubule integrity initiates mitosis during CNS repair.

    Science.gov (United States)

    Bossing, Torsten; Barros, Claudia S; Fischer, Bettina; Russell, Steven; Shepherd, David

    2012-08-14

    Mechanisms of CNS repair have vital medical implications. We show that traumatic injury to the ventral midline of the embryonic Drosophila CNS activates cell divisions to replace lost cells. A pilot screen analyzing transcriptomes of single cells during repair pointed to downregulation of the microtubule-stabilizing GTPase mitochondrial Rho (Miro) and upregulation of the Jun transcription factor Jun-related antigen (Jra). Ectopic Miro expression can prevent midline divisions after damage, whereas Miro depletion destabilizes cortical β-tubulin and increases divisions. Disruption of cortical microtubules, either by chemical depolymerization or by overexpression of monomeric tubulin, triggers ectopic mitosis in the midline and induces Jra expression. Conversely, loss of Jra renders midline cells unable to replace damaged siblings. Our data indicate that upon injury, the integrity of the microtubule cytoskeleton controls cell division in the CNS midline, triggering extra mitosis to replace lost cells. The conservation of the identified molecules suggests that similar mechanisms may operate in vertebrates.

  10. Testing the nature of reaction coordinate describing interaction of H2 with carbonyl carbon, activated by Lewis acid complexation, and the Lewis basic solvent: A Born-Oppenheimer molecular dynamics study with explicit solvent

    Science.gov (United States)

    Heshmat, Mojgan; Privalov, Timofei

    2017-09-01

    Using Born-Oppenheimer molecular dynamics (BOMD), we explore the nature of interactions between H2 and the activated carbonyl carbon, C(carbonyl), of the acetone-B(C6F5)3 adduct surrounded by an explicit solvent (1,4-dioxane). BOMD simulations at finite (non-zero) temperature with an explicit solvent produced long-lasting instances of significant vibrational perturbation of the H—H bond and H2-polarization at C(carbonyl). As far as the characteristics of H2 are concerned, the dynamical transient state approximates the transition-state of the heterolytic H2-cleavage. The culprit is the concerted interactions of H2 with C(carbonyl) and a number of Lewis basic solvent molecules—i.e., the concerted C(carbonyl)⋯H2⋯solvent interactions. On one hand, the results presented herein complement the mechanistic insight gained from our recent transition-state calculations, reported separately from this article. But on the other hand, we now indicate that an idea of the sufficiency of just one simple reaction coordinate in solution-phase reactions can be too simplistic and misleading. This article goes in the footsteps of the rapidly strengthening approach of investigating molecular interactions in large molecular systems via "computational experimentation" employing, primarily, ab initio molecular dynamics describing reactants-interaction without constraints of the preordained reaction coordinate and/or foreknowledge of the sampling order parameters.

  11. Microtubule stabilization reduces scarring and causes axon regeneration after spinal cord injury

    NARCIS (Netherlands)

    F. Hellal (Farida); A. Hurtado (Andres); J. Ruschel (Jörg); K.C. Flynn (Kevin); C.J. Laskowski (Claudia); M. Umlauf (Martina); L.C. Kapitein (Lukas); D. Strikis (Dinara); V. Lemmon (Vance); J. Bixby (John); C.C. Hoogenraad (Casper); F. Bradke (Frank)

    2011-01-01

    textabstractHypertrophic scarring and poor intrinsic axon growth capacity constitute major obstacles for spinal cord repair. These processes are tightly regulated by microtubule dynamics. Here, moderate microtubule stabilization decreased scar formation after spinal cord injury in rodents through va

  12. Active self-organization of microtubules in an inert chamber system

    National Research Council Canada - National Science Library

    Arif Md Rashedul Kabir; Daisuke Inoue; Akira Kakugo; Kazuki Sada; Jian Ping Gong

    2012-01-01

    Microtubule-kinesin system is considered as a building block for the construction of artificial biomachines, and active self-organization of microtubules has been used to integrate their structural...

  13. Microtubule stability and MAPI B upregulation control neuritogenesis in CAD cells

    Institute of Scientific and Technical Information of China (English)

    Wen LI; Jin-tang XIA; Yue FENG

    2006-01-01

    Aim: To study the role of microtubule dynamics and microtubule associated protein 1B (MAP1B) in regulation of the neurite extension in CAD catecholaminergic neuronal cell line. Methods: The neuritogenesis of the CAD cells was abolished by inhibiting microtubule polymerization with nocodazole and by blocking microtubule depolymerization with taxol. MAP1B and tubulin protein expression was detected by Western blot. Immunofluorescent staining of tubulins was observed by fluorescent and confocal microscopy. Results: Microtubule dynamics was essential for CAD neurite extension. Dosage analysis revealed that neurite extension was much more sensitive to nocodazole than to taxol, suggesting a functional requirement for highly active microtubule assembly. A remarkable upregulation of MAP1B protein was detected during neurite extension accompanied with increased microtubule stability. Conclusion: Upregulation of MAP1B leads to the stabilization of newly formed microtubules in the developing neurites, which in turn promotes neurite extension.

  14. Microtubules and associated molecular motors in Neurospora crassa.

    Science.gov (United States)

    Mouriño-Pérez, Rosa Reyna; Riquelme, Meritxell; Callejas-Negrete, Olga Alicia; Galván-Mendoza, José Iván

    2016-01-01

    The cytoskeleton provides structure, shape and movement to various cells. Microtubules (MTs) are tubular structures made of α and β-tubulin heterodimers organized in 13 protofilaments, forming a hollow cylinder. A vast group of MT-associated proteins determines the function, behavior and interaction of the MTs with other cellular components. Among these proteins, molecular motors such as the dynein-dynactin complex and kinesin superfamily play roles in MT organization and organelle transport. This article focuses on the MT cytoskeleton and associated molecular motors in the filamentous fungus Neurospora crassa In addition to reviewing current available information for this fungus and contrasting it with knowledge of other fungal species, we present new experimental results that support the role of dynein, dynactin and conventional kinesin in MT organization, dynamics and transport of subcellular structures (nuclei and secretory vesicles). In wild type hyphae of N. crassa, cytoplasmic MTs are arranged longitudinally along hyphae and display a helical curvature. They interlace with one another to form a network throughout the cytoplasm. N. crassa dynein and dynactin mutants have a scant and disorganized MT cytoskeleton, an erratic and reduced Spitzenkörper (Spk) and distorted hyphal morphology. In contrast, hyphae of mutants with defective conventional kinesin exhibit only minor disruptions in MT and Spk organization. Although nuclear positioning is affected in all mutants, the MT-associated motor proteins are not major contributors to nuclear movement during hyphal growth. Cytoplasmic bulk flow is the vehicle for nuclear displacement in growing hyphal regions of N. crassa Motors are involved in nuclei saltatory movements in both retrograde or anterograde direction. In the dynein and kinesin mutants, micro and macrovesicles can reach the Spk, although growth is slightly impaired and the Spk displays an erratic path. Hyphal growth requires MTs, and their associated

  15. Kinetochore microtubule establishment is defective in oocytes from aged mice.

    Science.gov (United States)

    Shomper, Maria; Lappa, Christina; FitzHarris, Greg

    2014-01-01

    Errors in chromosome segregation in mammalian oocytes increase in number with advancing maternal age, and are a major cause of pregnancy loss. Why chromosome segregation errors are more common in oocytes from older females remains poorly understood. In mitosis, accurate chromosome segregation is enabled by attachment of kinetochores to microtubules from appropriate spindle poles, and erroneous attachments increase the likelihood of mis-segregation. Whether attachment errors are responsible for age-related oocyte aneuploidy is unknown. Here we report that oocytes from naturally aged mice exhibit substantially increased chromosome misalignment, and fewer kinetochore pairs that make stable end-on attachments to the appropriate spindle poles compared with younger oocytes. The profile of mis-attachments exhibited is consistent with the types of chromosome segregation error observed in aged oocytes. Loss of chromosome cohesion, which is a feature of oocytes from older females, causes altered kinetochore geometry in meiosis-I. However, this has only a minor impact upon MT attachment, indicating that cohesion loss is not the primary cause of aneuploidy in meiosis-I. In meiosis-II, on the other hand, age-related cohesion loss plays a direct role in errors, since prematurely individualized sister chromatids misalign and misattach to spindle MTs. Thus, whereas cohesion loss leading to precocious sister chromatid separation is a direct cause of errors in meiosis-II, cohesion loss plays a more minor role in the etiology of aneuploidy in meiosis-I. Our data introduce altered MT-kinetochore interactions as a lesion that explains aneuploidy in meiosis-I in older females.

  16. The cell morphogenesis gene ANGUSTIFOLIA encodes a CtBP/BARS-like protein and is involved in the control of the microtubule cytoskeleton.

    Science.gov (United States)

    Folkers, U; Kirik, V; Schöbinger, U; Falk, S; Krishnakumar, S; Pollock, M A; Oppenheimer, D G; Day, I; Reddy, A S M; Jürgens, G; Hülskamp, M; Reddy, A R

    2002-03-15

    The ANGUSTIFOLIA (AN) gene is required for leaf hair (trichome) branching and is also involved in polarized expansion underlying organ shape. Here we show that the AN gene encodes a C-terminal binding proteins/brefeldin A ADP-ribosylated substrates (CtBP/BARS) related protein. AN is expressed at low levels in all organs and the AN protein is localized in the cytoplasm. In an mutant trichomes, the organization of the actin cytoskeleton is normal but the distribution of microtubules is aberrant. A role of AN in the control of the microtubule cytoskeleton is further supported by the finding that AN genetically and physically interacts with ZWICHEL, a kinesin motor molecule involved in trichome branching. Our data suggest that CtBP/BARS-like protein function in plants is directly associated with the microtubule cytoskeleton.

  17. Septins localize to microtubules during nutritional limitation in Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Vázquez de Aldana Carlos R

    2008-10-01

    Full Text Available Abstract Background In Saccharomyces cerevisiae, nutrient limitation stimulates diploid cells to undergo DNA replication and meiosis, followed by the formation of four haploid spores. Septins are a family of proteins that assemble a ring structure at the mother-daughter neck during vegetative growth, where they control cytokinesis. In sporulating cells, the septin ring disassembles and septins relocalize to the prospore membrane. Results Here, we demonstrate that nutrient limitation triggers a change in the localization of at least two vegetative septins (Cdc10 and Cdc11 from the bud neck to the microtubules. The association of Cdc10 and Cdc11 with microtubules persists into meiosis, and they are found associated with the meiotic spindle until the end of meiosis II. In addition, the meiosis-specific septin Spr28 displays similar behavior, suggesting that this is a common feature of septins. Septin association to microtubules is a consequence of the nutrient limitation signal, since it is also observed when haploid cells are incubated in sporulation medium and when haploid or diploid cells are grown in medium containing non-fermentable carbon sources. Moreover, during meiosis II, when the nascent prospore membrane is formed, septins moved from the microtubules to this membrane. Proper organization of the septins on the membrane requires the sporulation-specific septins Spr3 and Spr28. Conclusion Nutrient limitation in S. cerevisiae triggers the sporulation process, but it also induces the disassembly of the septin bud neck ring and relocalization of the septin subunits to the nucleus. Septins remain associated with microtubules during the meiotic divisions and later, during spore morphogenesis, they are detected associated to the nascent prospore membranes surrounding each nuclear lobe. Septin association to microtubules also occurs during growth in non-fermentable carbon sources.

  18. Microtubule affinity-regulating kinase 4: structure, function, and regulation.

    Science.gov (United States)

    Naz, Farha; Anjum, Farah; Islam, Asimul; Ahmad, Faizan; Hassan, Md Imtaiyaz

    2013-11-01

    MAP/Microtubule affinity-regulating kinase 4 (MARK4) belongs to the family of serine/threonine kinases that phosphorylate the microtubule-associated proteins (MAP) causing their detachment from the microtubules thereby increasing microtubule dynamics and facilitating cell division, cell cycle control, cell polarity determination, cell shape alterations, etc. The MARK4 gene encodes two alternatively spliced isoforms, L and S that differ in their C-terminal region. These isoforms are differentially regulated in human tissues including central nervous system. MARK4L is a 752-residue-long polypeptide that is divided into three distinct domains: (1) protein kinase domain (59-314), (2) ubiquitin-associated domain (322-369), and (3) kinase-associated domain (703-752) plus 54 residues (649-703) involved in the proper folding and function of the enzyme. In addition, residues 65-73 are considered to be the ATP-binding domain and Lys88 is considered as ATP-binding site. Asp181 has been proposed to be the active site of MARK4 that is activated by phosphorylation of Thr214 side chain. The isoform MARK4S is highly expressed in the normal brain and is presumably involved in neuronal differentiation. On the other hand, the isoform MARK4L is upregulated in hepatocarcinoma cells and gliomas suggesting its involvement in cell cycle. Several biological functions are also associated with MARK4 including microtubule bundle formation, nervous system development, and positive regulation of programmed cell death. Therefore, MARK4 is considered as the most suitable target for structure-based rational drug design. Our sequence, structure- and function-based analysis should be helpful for better understanding of mechanisms of regulation of microtubule dynamics and MARK4 associated diseases.

  19. Effect of microtubule-associated protein tau in dynamics of single-headed motor proteins KIF1A

    CERN Document Server

    Sparacino, J; Lamberti, P W

    2013-01-01

    Intracellular transport based on molecular motors and its regulation are crucial to the functioning of cells. Filamentary tracks of the cells are abundantly decorated with non-motile microtubule-associated proteins, such as tau. Motivated by experiments on kinesin-tau interactions [Dixit et al. Science 319, 1086 (2008)] we developed a stochastic model of interacting single-headed motor proteins KIF1A that also takes into account the interactions between motor proteins and tau molecules. Our model reproduce experimental observations and predicts significant effects of tau on bound time and run length which suggest an important role of tau in regulation of kinesin-based transport.

  20. TCTEX1D4, a novel protein phosphatase 1 interactor: connecting the phosphatase to the microtubule network

    Directory of Open Access Journals (Sweden)

    Luís Korrodi-Gregório

    2013-03-01

    Reversible phosphorylation plays an important role as a mechanism of intracellular control in eukaryotes. PPP1, a major eukaryotic Ser/Thr-protein phosphatase, acquires its specificity by interacting with different protein regulators, also known as PPP1 interacting proteins (PIPs. In the present work we characterized a physiologically relevant PIP in testis. Using a yeast two-hybrid screen with a human testis cDNA library, we identified a novel PIP of PPP1CC2 isoform, the T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4 that has recently been described as a Tctex1 dynein light chain family member. The overlay assays confirm that TCTEX1D4 interacts with the different spliced isoforms of PPP1CC. Also, the binding domain occurs in the N-terminus, where a consensus PPP1 binding motif (PPP1BM RVSF is present. The distribution of TCTEX1D4 in testis suggests its involvement in distinct functions, such as TGFβ signaling at the blood–testis barrier and acrosome cap formation. Immunofluorescence in human ejaculated sperm shows that TCTEX1D4 is present in the flagellum and in the acrosome region of the head. Moreover, TCTEX1D4 and PPP1 co-localize in the microtubule organizing center (MTOC and microtubules in cell cultures. Importantly, the TCTEX1D4 PPP1BM seems to be relevant for complex formation, for PPP1 retention in the MTOC and movement along microtubules. These novel results open new avenues to possible roles of this dynein, together with PPP1. In essence TCTEX1D4/PPP1C complex appears to be involved in microtubule dynamics, sperm motility, acrosome reaction and in the regulation of the blood–testis barrier.

  1. TCTEX1D4, a novel protein phosphatase 1 interactor: connecting the phosphatase to the microtubule network

    Science.gov (United States)

    Korrodi-Gregório, Luís; Vieira, Sandra I.; Esteves, Sara L. C.; Silva, Joana V.; Freitas, Maria João; Brauns, Ann-Kristin; Luers, Georg; Abrantes, Joana; Esteves, Pedro J.; da Cruz e Silva, Odete A. B.; Fardilha, Margarida; da Cruz e Silva, Edgar F.

    2013-01-01

    Summary Reversible phosphorylation plays an important role as a mechanism of intracellular control in eukaryotes. PPP1, a major eukaryotic Ser/Thr-protein phosphatase, acquires its specificity by interacting with different protein regulators, also known as PPP1 interacting proteins (PIPs). In the present work we characterized a physiologically relevant PIP in testis. Using a yeast two-hybrid screen with a human testis cDNA library, we identified a novel PIP of PPP1CC2 isoform, the T-complex testis expressed protein 1 domain containing 4 (TCTEX1D4) that has recently been described as a Tctex1 dynein light chain family member. The overlay assays confirm that TCTEX1D4 interacts with the different spliced isoforms of PPP1CC. Also, the binding domain occurs in the N-terminus, where a consensus PPP1 binding motif (PPP1BM) RVSF is present. The distribution of TCTEX1D4 in testis suggests its involvement in distinct functions, such as TGFβ signaling at the blood–testis barrier and acrosome cap formation. Immunofluorescence in human ejaculated sperm shows that TCTEX1D4 is present in the flagellum and in the acrosome region of the head. Moreover, TCTEX1D4 and PPP1 co-localize in the microtubule organizing center (MTOC) and microtubules in cell cultures. Importantly, the TCTEX1D4 PPP1BM seems to be relevant for complex formation, for PPP1 retention in the MTOC and movement along microtubules. These novel results open new avenues to possible roles of this dynein, together with PPP1. In essence TCTEX1D4/PPP1C complex appears to be involved in microtubule dynamics, sperm motility, acrosome reaction and in the regulation of the blood–testis barrier. PMID:23789093

  2. Live Cell Imaging Reveals Structural Associations between the Actin and Microtubule Cytoskeleton in Arabidopsis [W] [OA

    Science.gov (United States)

    Sampathkumar, Arun; Lindeboom, Jelmer J.; Debolt, Seth; Gutierrez, Ryan; Ehrhardt, David W.; Ketelaar, Tijs; Persson, Staffan

    2011-01-01

    In eukaryotic cells, the actin and microtubule (MT) cytoskeletal networks are dynamic structures that organize intracellular processes and facilitate their rapid reorganization. In plant cells, actin filaments (AFs) and MTs are essential for cell growth and morphogenesis. However, dynamic interactions between these two essential components in live cells have not been explored. Here, we use spinning-disc confocal microscopy to dissect interaction and cooperation between cortical AFs and MTs in Arabidopsis thaliana, utilizing fluorescent reporter constructs for both components. Quantitative analyses revealed altered AF dynamics associated with the positions and orientations of cortical MTs. Reorganization and reassembly of the AF array was dependent on the MTs following drug-induced depolymerization, whereby short AFs initially appeared colocalized with MTs, and displayed motility along MTs. We also observed that light-induced reorganization of MTs occurred in concert with changes in AF behavior. Our results indicate dynamic interaction between the cortical actin and MT cytoskeletons in interphase plant cells. PMID:21693695

  3. Three-dimensional reconstruction of tubulin sheets and re-investigation of microtubule surface lattice.

    Science.gov (United States)

    Schultheiss, R; Mandelkow, E

    1983-10-25

    Sheets are incomplete microtubule walls observed as polymorphic variants of microtubule assembly. Their substructure is similar to that of microtubules, as shown by two-dimensional optical and computer reconstruction. We have extended earlier studies by computing a three-dimensional reconstruction. From a re-investigation of the surface lattice it appears that the three-start helix of microtubules is right-handed rather than left-handed.

  4. S. pombe kinesins-8 promote both nucleation and catastrophe of microtubules.

    Directory of Open Access Journals (Sweden)

    Muriel Erent

    Full Text Available The kinesins-8 were originally thought to be microtubule depolymerases, but are now emerging as more versatile catalysts of microtubule dynamics. We show here that S. pombe Klp5-436 and Klp6-440 are non-processive plus-end-directed motors whose in vitro velocities on S. pombe microtubules at 7 and 23 nm s(-1 are too slow to keep pace with the growing tips of dynamic interphase microtubules in living S. pombe. In vitro, Klp5 and 6 dimers exhibit a hitherto-undescribed combination of strong enhancement of microtubule nucleation with no effect on growth rate or catastrophe frequency. By contrast in vivo, both Klp5 and Klp6 promote microtubule catastrophe at cell ends whilst Klp6 also increases the number of interphase microtubule arrays (IMAs. Our data support a model in which Klp5/6 bind tightly to free tubulin heterodimers, strongly promoting the nucleation of new microtubules, and then continue to land as a tubulin-motor complex on the tips of growing microtubules, with the motors then dissociating after a few seconds residence on the lattice. In vivo, we predict that only at cell ends, when growing microtubule tips become lodged and their growth slows down, will Klp5/6 motor activity succeed in tracking growing microtubule tips. This mechanism would allow Klp5/6 to detect the arrival of microtubule tips at cells ends and to amplify the intrinsic tendency for microtubules to catastrophise in compression at cell ends. Our evidence identifies Klp5 and 6 as spatial regulators of microtubule dynamics that enhance both microtubule nucleation at the cell centre and microtubule catastrophe at the cell ends.

  5. Kinesin-3 in the basidiomycete Ustilago maydis transports organelles along the entire microtubule array.

    Science.gov (United States)

    Steinberg, Gero

    2015-01-01

    The molecular motor kinesin-3 transports early endosomes along microtubules in filamentous fungi. It was reported that kinesin-3 from the ascomycete fungi Aspergillus nidulans and Neurospora crassa use a subset of post-translationally modified and more stable microtubules. Here, I show that kinesin-3 from the basidiomycete Ustilago maydis moves along all hyphal microtubules. This difference is likely due to variation in cell cycle control and associated organization of the microtubule array.

  6. In vivo and in vitro effects of the mitochondrial uncoupler FCCP on microtubules.

    OpenAIRE

    Maro, B.; Marty, M C; Bornens, M

    1982-01-01

    FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone), a potent uncoupler of oxidative phosphorylation, induces the complete disruption of cellular microtubules. A further analysis of this effect on BHK21 cells has shown that a decrease in the number of microtubules can be observed 15 min after adding FCCP and there is complete disruption after 60 min. Regrowth of microtubules was initiated 30 min after removal of FCCP, in marked contrast with the rapid reversion observed when microtubules...

  7. RUN COORDINATION

    CERN Multimedia

    C. Delaere

    2013-01-01

    Since the LHC ceased operations in February, a lot has been going on at Point 5, and Run Coordination continues to monitor closely the advance of maintenance and upgrade activities. In the last months, the Pixel detector was extracted and is now stored in the pixel lab in SX5; the beam pipe has been removed and ME1/1 removal has started. We regained access to the vactank and some work on the RBX of HB has started. Since mid-June, electricity and cooling are back in S1 and S2, allowing us to turn equipment back on, at least during the day. 24/7 shifts are not foreseen in the next weeks, and safety tours are mandatory to keep equipment on overnight, but re-commissioning activities are slowly being resumed. Given the (slight) delays accumulated in LS1, it was decided to merge the two global runs initially foreseen into a single exercise during the week of 4 November 2013. The aim of the global run is to check that we can run (parts of) CMS after several months switched off, with the new VME PCs installed, th...

  8. Sliding of microtubules by a team of dynein motors: Understanding the effect of spatial distribution of motor tails and mutual exclusion of motor heads on microtubules

    Science.gov (United States)

    Singh, Hanumant Pratap; Takshak, Anjneya; Mall, Utkarsh; Kunwar, Ambarish

    2016-06-01

    Molecular motors are natural nanomachines that use the free energy released from ATP hydrolysis to generate mechanical forces. Cytoplasmic dynein motors often work collectively as a team to drive important processes such as axonal growth, proplatelet formation and mitosis, as forces generated by single motors are insufficient. A large team of dynein motors is used to slide cytoskeletal microtubules with respect to one another during the process of proplatelet formation and axonal growth. These motors attach to a cargo microtubule via their tail domains, undergo the process of detachment and reattachment of their head domains on another track microtubule, while sliding the cargo microtubule along the track. Traditional continuum/mean-field approaches used in the past are not ideal for studying the sliding mechanism of microtubules, as they ignore spatial and temporal fluctuations due to different possible distributions of motor tails on cargo filament, as well as binding/unbinding of motors from their track. Therefore, these models cannot be used to address important questions such as how the distribution of motor tails on microtubules, or how the mutual exclusion of motor heads on microtubule tracks affects the sliding velocity of cargo microtubule. To answer these, here we use a computational stochastic model where we model each dynein motor explicitly. In our model, we use both random as well as uniform distributions of dynein motors on cargo microtubule, as well as mutual exclusion of motors on microtubule tracks. We find that sliding velocities are least affected by the distribution of motor tails on microtubules, whereas they are greatly affected by mutual exclusion of motor heads on microtubule tracks. We also find that sliding velocity depends on the length of cargo microtubule if mutual exclusion among motor heads is considered.

  9. catena-Poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] (-4-nitrobenzoato-O,O')]: A barium(II) coordination polymer showing O-H$\\cdots$O and C-H$\\cdots$O interactions

    Indian Academy of Sciences (India)

    Bikshandarkoil R Srinivasan; Jyoti V Sawant; Sarvesh C Sawant; Pallepogu Raghavaiah

    2007-11-01

    The reaction of barium carbonate with 4-nitrobenzoic acid (4-nbaH) results in the formation of a Ba(II) coordination polymer, catena-poly[[(pentaaqua)(4-nitrobenzoato-O,O')barium(II)](-4-nitrobenzoato-O,O')] 1. The polymeric compound [[Ba(H2O)5(4-nba-O,O')](-4-nba-O,O')] 1 was characterized by elemental analysis, IR and UV-Vis spectra, weight loss studies, X-ray powder diffraction and its structure determined. In 1 five water molecules are coordinated to the central metal and one of the 4-nba ligands is bonded to Ba(II) in a bidentate manner (4-nba-O,O') through the carboxylate O atoms. The [(pentaaqua)(4-nitrobenzoato-O,O')barium(II)] units are linked into an infinite one-dimensional chain along -axis with the aid of the second 4-nba anion, which functions as a bridging bidentate (-4-nba-O,O') ligand. This results in nine coordination around each Ba(II) ion in the coordination polymer. A long Ba$\\cdots$Ba distance of 6.750(1) Å is observed between adjacent Ba(II) ions in the chain and the oxygen atoms of the carboxylate group and the nitro functionalities of the 4-nba ligand are involved in several O-H$\\cdots$O and C-H$\\cdots$O interactions.

  10. Identification of a Novel Microtubule-Binding Protein in Giardia lamblia.

    Science.gov (United States)

    Kim, Juri; Park, Soon-Jung

    2016-08-01

    Giardia lamblia is a protozoan that causes diarrheal diseases in humans. Cytoskeletal structures of Giardia trophozoites must be finely reorganized during cell division. To identify Giardia proteins which interact with microtubules (MTs), Giardia lysates were incubated with in vitro-polymerized MTs and then precipitated by ultracentifugation. A hypothetical protein (GL50803_8405) was identified in the precipitated fraction with polymerized MTs and was named GlMBP1 (G. lamblia microtubule-binding protein 1). Interaction of GlMBP1 with MTs was confirmed by MT binding assays using recombinant GlMBP1 (rGlMBP1). In vivo expression of GlMBP1 was shown by a real-time PCR and western blot analysis using anti-rGlMBP1 antibodies. Transgenic G. lamblia trophozoites were constructed by integrating a chimeric gene encoding hemagglutinin (HA)-tagged GlMBP1 into a Giardia chromosome. Immunofluorescence assays of this transgenic G. lamblia, using anti-HA antibodies, revealed that GlMBP1 mainly localized at the basal bodies, axonemes, and median bodies of G. lamblia trophozoites. This result indicates that GlMBP1 is a component of the G. lamblia cytoskeleton.

  11. Phospholipase D activation correlates with microtubule reorganization in living plant cells

    NARCIS (Netherlands)

    P.B. Dhonukshe; A.M. Laxalt; J. Goedhart; Th.W.J. Gadella; T. Munnik

    2003-01-01

    A phospholipase D (PLD) was shown recently to decorate microtubules in plant cells. Therefore, we used tobacco BY-2 cells expressing the microtubule reporter GFP-MAP4 to test whether PLD activation affects the organization of plant microtubules. Within 30 min of adding n-butanol, a potent activator

  12. Dietary flavonoid fisetin binds to β-tubulin and disrupts microtubule dynamics in prostate cancer cells

    OpenAIRE

    Mukhtar, Eiman; Adhami, Vaqar Mustafa; Sechi, Mario; Mukhtar, Hasan

    2015-01-01

    Microtubule targeting based therapies have revolutionized cancer treatment; however, resistance and side effects remain a major limitation. Therefore, novel strategies that can overcome these limitations are urgently needed. We made a novel discovery that fisetin, a hydroxyflavone, is a microtubule stabilizing agent. Fisetin binds to tubulin and stabilizes microtubules with binding characteristics far superior than paclitaxel. Surface plasmon resonance and computational docking studies sugges...

  13. Dietary flavonoid fisetin binds to β-tubulin and disrupts microtubule dynamics in prostate cancer cells

    OpenAIRE

    Mukhtar, Eiman; Adhami, Vaqar Mustafa; Sechi, Mario; Mukhtar, Hasan

    2015-01-01

    Microtubule targeting based therapies have revolutionized cancer treatment; however, resistance and side effects remain a major limitation. Therefore, novel strategies that can overcome these limitations are urgently needed. We made a novel discovery that fisetin, a hydroxyflavone, is a microtubule stabilizing agent. Fisetin binds to tubulin and stabilizes microtubules with binding characteristics far superior than paclitaxel. Surface plasmon resonance and computational docking studies sugges...

  14. Cortical Microtubule Arrays Are Initiated from a Nonrandom Prepattern Driven by Atypical Microtubule Initiation1[W][OA

    Science.gov (United States)

    Lindeboom, Jelmer J.; Lioutas, Antonios; Deinum, Eva E.; Tindemans, Simon H.; Ehrhardt, David W.; Emons, Anne Mie C.; Vos, Jan W.; Mulder, Bela M.

    2013-01-01

    The ordered arrangement of cortical microtubules in growing plant cells is essential for anisotropic cell expansion and, hence, for plant morphogenesis. These arrays are dismantled when the microtubule cytoskeleton is rearranged during mitosis and reassembled following completion of cytokinesis. The reassembly of the cortical array has often been considered as initiating from a state of randomness, from which order arises at least partly through self-organizing mechanisms. However, some studies have shown evidence for ordering at early stages of array assembly. To investigate how cortical arrays are initiated in higher plant cells, we performed live-cell imaging studies of cortical array assembly in tobacco (Nicotiana tabacum) Bright Yellow-2 cells after cytokinesis and drug-induced disassembly. We found that cortical arrays in both cases did not initiate randomly but with a significant overrepresentation of microtubules at diagonal angles with respect to the cell axis, which coincides with the predominant orientation of the microtubules before their disappearance from the cell cortex in preprophase. In Arabidopsis (Arabidopsis thaliana) root cells, recovery from drug-induced disassembly was also nonrandom and correlated with the organization of the previous array, although no diagonal bias was observed in these cells. Surprisingly, during initiation, only about one-half of the new microtubules were nucleated from locations marked by green fluorescent protein-γ-tubulin complex protein2-tagged γ-nucleation complexes (γ-tubulin ring complex), therefore indicating that a large proportion of early polymers was initiated by a noncanonical mechanism not involving γ-tubulin ring complex. Simulation studies indicate that the high rate of noncanonical initiation of new microtubules has the potential to accelerate the rate of array repopulation. PMID:23300168

  15. Chemical genetic approach identifies microtubule affinity-regulating kinase 1 as a leucine-rich repeat kinase 2 substrate.

    Science.gov (United States)

    Krumova, Petranka; Reyniers, Lauran; Meyer, Marc; Lobbestael, Evy; Stauffer, Daniela; Gerrits, Bertran; Muller, Lionel; Hoving, Sjouke; Kaupmann, Klemens; Voshol, Johannes; Fabbro, Doriano; Bauer, Andreas; Rovelli, Giorgio; Taymans, Jean-Marc; Bouwmeester, Tewis; Baekelandt, Veerle

    2015-07-01

    Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of autosomal-dominant forms of Parkinson's disease. LRRK2 is a modular, multidomain protein containing 2 enzymatic domains, including a kinase domain, as well as several protein-protein interaction domains, pointing to a role in cellular signaling. Although enormous efforts have been made, the exact pathophysiologic mechanisms of LRRK2 are still not completely known. In this study, we used a chemical genetics approach to identify LRRK2 substrates from mouse brain. This approach allows the identification of substrates of 1 particular kinase in a complex cellular environment. Several of the identified peptides are involved in the regulation of microtubule (MT) dynamics, including microtubule-associating protein (MAP)/microtubule affinity-regulating kinase 1 (MARK1). MARK1 is a serine/threonine kinase known to phosphorylate MT-binding proteins such as Tau, MAP2, and MAP4 at KXGS motifs leading to MT destabilization. In vitro kinase assays and metabolic-labeling experiments in living cells confirmed MARK1 as an LRRK2 substrate. Moreover, we also showed that LRRK2 and MARK1 are interacting in eukaryotic cells. Our findings contribute to the identification of physiologic LRRK2 substrates and point to a potential mechanism explaining the reported effects of LRRK2 on neurite morphology.

  16. Electric fields generated by synchronized oscillations of microtubules, centrosomes and chromosomes regulate the dynamics of mitosis and meiosis

    Directory of Open Access Journals (Sweden)

    Zhao Yue

    2012-07-01

    Full Text Available Abstract Super-macromolecular complexes play many important roles in eukaryotic cells. Classical structural biological studies focus on their complicated molecular structures, physical interactions and biochemical modifications. Recent advances concerning intracellular electric fields generated by cell organelles and super-macromolecular complexes shed new light on the mechanisms that govern the dynamics of mitosis and meiosis. In this review we synthesize this knowledge to provide an integrated theoretical model of these cellular events. We suggest that the electric fields generated by synchronized oscillation of microtubules, centrosomes, and chromatin fibers facilitate several events during mitosis and meiosis, including centrosome trafficking, chromosome congression in mitosis and synapsis between homologous chromosomes in meiosis. These intracellular electric fields are generated under energy excitation through the synchronized electric oscillations of the dipolar structures of microtubules, centrosomes and chromosomes, three of the super-macromolecular complexes within an animal cell.

  17. Electric fields generated by synchronized oscillations of microtubules, centrosomes and chromosomes regulate the dynamics of mitosis and meiosis.

    Science.gov (United States)

    Zhao, Yue; Zhan, Qimin

    2012-07-02

    Super-macromolecular complexes play many important roles in eukaryotic cells. Classical structural biological studies focus on their complicated molecular structures, physical interactions and biochemical modifications. Recent advances concerning intracellular electric fields generated by cell organelles and super-macromolecular complexes shed new light on the mechanisms that govern the dynamics of mitosis and meiosis. In this review we synthesize this knowledge to provide an integrated theoretical model of these cellular events. We suggest that the electric fields generated by synchronized oscillation of microtubules, centrosomes, and chromatin fibers facilitate several events during mitosis and meiosis, including centrosome trafficking, chromosome congression in mitosis and synapsis between homologous chromosomes in meiosis. These intracellular electric fields are generated under energy excitation through the synchronized electric oscillations of the dipolar structures of microtubules, centrosomes and chromosomes, three of the super-macromolecular complexes within an animal cell.

  18. Structural analysis of microtubule-kinesin complex; Mota tanpakushitsu bunshi no kozo kaiseki ni yoru undo hassei kiko no kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Toyoshima, Yoko [University of Tokyo, Tokyo (Japan). Graduate School of Arts and Sciences

    1998-12-16

    To understand the molecular mechanism of motor proteins which work in cell motility, the information of three dimensional structure of the complex between motor proteins and cytoskeletal filaments is important. Although crystal sacarato of kinesin motor domain and tubulin are determined respectively, their relative position in interacting state is unidentified. In this study, we made a series of several mutant kinesin motor domains which have reactive cystein using protein engineering methods, and labelled with gold clusters. Next, we formed the complex of these proteins and microtubules, and then embedded in amorphous ice. Three dimensional reconstitution of the complexes from the electron microscopic images can decide the position of the specific residue and relative position of kinesin motor domain and microtubules, which brings the structural basis to elucidate the molecular mechanism of motor proteins. (author)

  19. Two-dimensional supramolecular networks via C-H$\\cdots$Cl and N-H$\\cdots$Cl interactions utilizing bidentate neutral pyridine amide coordinated MnIICl2 tectons

    Indian Academy of Sciences (India)

    Wilson Jacob; Rabindranath Mukherjee

    2008-09-01

    Reaction of -(phenyl)-2-pyridinecarboxamide (HL1) and -(-tolyl)-2-pyridinecarboxamide (HL2) ligands with MnCl2.4H2O affords complexes [(HL1)2MnCl2] 1 and [(HL2)2MnCl2] 2. The structures of 1 and 2 were determined by three-dimensional X-ray crystallography revealing that the MnII ions assume distorted octahedral geometry with coordination by two HL1/HL2 ligands providing two pyridine N and two amide O and two chloride ions. Notably, secondary interactions [C-H$\\cdots$Cl (pyridine 3-H hydrogen) and N-H$\\cdots$Cl (amide NH hydrogen)] triggered by MnII-coordinated chloride ions acting as hydrogen bonding acceptors generate self-complementary dimeric tectons, which lead to 2D supramolecular architectures.

  20. Modulation of microtubule assembly by the HIV-1 Tat protein is strongly dependent on zinc binding to Tat

    Directory of Open Access Journals (Sweden)

    Muller Sylviane

    2008-07-01

    Full Text Available Abstract Background During HIV-1 infection, the Tat protein plays a key role by transactivating the transcription of the HIV-1 proviral DNA. In addition, Tat induces apoptosis of non-infected T lymphocytes, leading to a massive loss of immune competence. This apoptosis is notably mediated by the interaction of Tat with microtubules, which are dynamic components essential for cell structure and division. Tat binds two Zn2+ ions through its conserved cysteine-rich region in vitro, but the role of zinc in the structure and properties of Tat is still controversial. Results To investigate the role of zinc, we first characterized Tat apo- and holo-forms by fluorescence correlation spectroscopy and time-resolved fluorescence spectroscopy. Both of the Tat forms are monomeric and poorly folded but differ by local conformational changes in the vicinity of the cysteine-rich region. The interaction of the two Tat forms with tubulin dimers and microtubules was monitored by analytical ultracentrifugation, turbidity measurements and electron microscopy. At 20°C, both of the Tat forms bind tubulin dimers, but only the holo-Tat was found to form discrete complexes. At 37°C, both forms promoted the nucleation and increased the elongation rates of tubulin assembly. However, only the holo-Tat increased the amount of microtubules, decreased the tubulin critical concentration, and stabilized the microtubules. In contrast, apo-Tat induced a large amount of tubulin aggregates. Conclusion Our data suggest that holo-Tat corresponds to the active form, responsible for the Tat-mediated apoptosis.