The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Valerian V Dolja - One of the best experts on this subject based on the ideXlab platform.
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Myosin Motors
Cell Biology, 2020Co-Authors: Valerian V DoljaAbstract:Intracellular transport system. Because plant cells are relatively large and contain viscous cytosol packed with protein complexes, organelles, membrane-bound vesicles and other components, they need a dedicated system for active transport of these components to their proper destinations. For example, when a cell grows, the building materials for expanding the plasma membrane and cell wall should be delivered from the places of their synthesis to the cell periphery.Microtubules and microfilaments. Similar to other eukaryotic organisms, plants possess two major transport systems using the microtubules (MTs) and microfilaments (MFs) as tracks. Together, the MTs and MFs form highly dynamic cytoskeleton that organizes the intracellular space.Molecular motors. Molecular motors are large proteins or protein complexes that are capable of binding MTs or MFs and moving directionally along these cytoskeletal tracks together with the attached cargoes. Molecular motors are built from a motor or head domain that binds MTs or MFs and converts energy released from ATP hydrolysis into mechanical force and a tail that binds cargoes. The molecular motors that move along MTs are the kinesins and dyneins, whereas MF-associated motors are called the Myosins.Myosins. Various Myosins are present in all eukaryotes. The conventional class II Myosins found in animal muscle cells represent only one among over 20 classes in the Myosin superfamily. All organisms in the “green brunch” of life, from green algae to land plants, possess class XI Myosins that are closely related to class V Myosins conserved in animals, fungi, and some protists. In addition, plants possess class VIII Myosins that likely emerged from Myosins XI via tail truncation.Cytoplasmic streaming. Cytoplasmic streaming, one of the most striking features of plant cells, is a combination of various types of perpetual intracellular motion visible under contrast light microscope. Such motion reaches its extreme in the long cells of filamentous algae (up to 100 μm/s) and is typical of plant cells in general. A reliance of cytoplasmic streaming on the actoMyosin motility system was established long ago. Although it is assumed that this process contributes to the distribution of nutrients, organelles, and other components of cytosol, the exact mechanism or its biological significance is yet to be experimentally established.Transport and remodeling of the endomembranes. The interior of plant cells is compartmentalized by a complex and dynamic endomembrane system. The active transport of membrane-bound cargoes among ER, Golgi, plasma membrane, vacuole, and other organelles is mediated by a variety of carrier vesicles.Myosins XI are required for cell growth and plant development. Gene knockout analyses of the 13 Myosin XI genes in the model plant Arabidopsis showed that at least five of them are needed for the proper growth of plant cells and plant development. Elimination of these genes resulted in dwarfed plants that flowered later and produced fewer seeds.Cytoplasmic streaming and organelle trafficking are Myosin dependent. Myosin elimination results in reduced trafficking velocity of Golgi stacks, peroxisomes, and mitochondria, as well as reduced flow of ER along the MF bundles. When four highly expressed Myosin XI genes were knocked out in the same plant, the entire cytosol dynamics was put to a standstill.Specialized system of long-distance membrane transport in plants. To pull endomembranes around the cell, Myosins attach to the protein receptors called MyoB (for Myosin binding). Both the Myosin and MyoB receptors localize to small, vesicle-like bodies that incessantly move along the MF bundles. Because MyoB receptors are found only in land plants, the Myosin XI-MyoB transport system is considered plant specific.
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overlapping functions of the four class xi Myosins in arabidopsis growth root hair elongation and organelle motility
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Alexey I Prokhnevsky, Valera V Peremyslov, Valerian V DoljaAbstract:Flowering plants have evolved multigene families of the class XI Myosin motors, the functions of which remain poorly understood. Here, we investigated functional profiles of the Arabidopsis Myosins that belong to two paralogous pairs, XI-K/XI-1 and XI-2/XI-B, using single and double gene-knockout mutants. It was found that the Myosins XI-K, XI-2, and XI-B, but not XI-1 have overlapping and additive roles in the root hair elongation. A nonidentical set of the three Myosins, XI-K, XI-1, and XI-2, exhibited partially redundant and additive roles in the transport of Golgi stacks, peroxisomes, and mitochondria. Conspicuously, the double xi-k/1 knockout plants that showed the largest cumulative reduction of the organelle velocities also exhibited a stunted plant growth and reduced fecundity phenotype. Collectively, these results suggest that the rapid, Myosin-powered organelle trafficking is required for the optimal plant growth, whereas a distinct Myosin function, presumably the vesicular transport, is involved in elongation of the root hairs. In addition, our data imply that the Myosin gene duplication in plants has been followed by a gradual functional specialization of the resulting pairs of Myosin paralogs.
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two class xi Myosins function in organelle trafficking and root hair development in arabidopsis
Plant Physiology, 2008Co-Authors: Valera V Peremyslov, Alexey I Prokhnevsky, Dror Avisar, Valerian V DoljaAbstract:Multigene families encoding class XI Myosins are conserved in higher plants, however, little information is available on specific functions of these ubiquitous molecular motors. We isolated gene knockout mutants for all 13 class XI Myosins present in Arabidopsis (Arabidopsis thaliana) genome. Inactivation of 11 Myosin genes resulted in no discernible phenotypes under the normal growth conditions. In contrast, the knockouts of the remaining two Myosin genes, XI-2 (formerly MYA2) and XI-K, exhibited similar defects in root hair elongation suggesting that the Myosin-driven motility plays a significant role in a polar tip growth. Strikingly, inactivation of each of these Myosins also reduced trafficking of Golgi stacks, peroxisomes, and mitochondria in root hairs and in leaf epidermal cells. These results indicate that Myosins XI-K and XI-2 play major and overlapping roles in the cell dynamics in Arabidopsis and highlight the redundant nature of Myosin function in plants.
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Myosin xi k is required for rapid trafficking of golgi stacks peroxisomes and mitochondria in leaf cells of nicotiana benthamiana
Plant Physiology, 2008Co-Authors: Dror Avisar, Alexey I Prokhnevsky, Kira S Makarova, Eugene V Koonin, Valerian V DoljaAbstract:A prominent feature of plant cells is the rapid, incessant movement of the organelles traditionally defined as cytoplasmic streaming and attributed to actoMyosin motility. We sequenced six complete Nicotiana benthamiana cDNAs that encode class XI and class VIII Myosins. Phylogenetic analysis indicates that these two classes of Myosins diverged prior to the radiation of green algae and land plants from a common ancestor and that the common ancestor of land plants likely possessed at least seven Myosins. We further report here that movement of Golgi stacks, mitochondria, and peroxisomes in the leaf cells of N. benthamiana is mediated mainly by Myosin XI-K. Suppression of Myosin XI-K function using dominant negative inhibition or RNA interference dramatically reduced movement of each of these organelles. When similar approaches were used to inhibit functions of Myosin XI-2 or XI-F, only moderate to marginal effects were observed. Organelle trafficking was virtually unaffected in response to inhibition of each of the three class VIII Myosins. Interestingly, none of the tested six Myosins appears to be involved in light-induced movements of chloroplasts. Taken together, these data strongly suggest that Myosin XI-K has a major role in trafficking of Golgi stacks, mitochondria, and peroxisomes, whereas Myosins XI-2 and XI-F might perform accessory functions in this process. In addition, our analysis of thousands of individual organelles revealed independent movement patterns for Golgi stacks, mitochondria, and peroxisomes, indicating that the notion of coordinated cytoplasmic streaming is not generally applicable to higher plants.
Mark S. Mooseker - One of the best experts on this subject based on the ideXlab platform.
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membrane cytoskeletal crosstalk mediated by Myosin i regulates adhesion turnover during phagocytosis
Nature Communications, 2019Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Paolo Maiuri, John M Heddleston, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W OakesAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We find that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we find that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a mechanism involving membrane-cytoskeletal crosstalk for phagocytic cup closure.
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Membrane-cytoskeletal crosstalk mediated by Myosin-I regulates adhesion turnover during phagocytosis
Nature Communications, 2019Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Qingsen Li, Paolo Maiuri, John M Heddleston, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W OakesAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We find that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we find that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a mechanism involving membrane-cytoskeletal crosstalk for phagocytic cup closure.Phagocytosis of pathogens is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface. Here authors show that Myosin 1e and Myosin 1f link the actin cytoskeleton to the membrane and are required for efficient phagocytosis of antibody-opsonized targets.
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membrane cytoskeleton mechanical feedback mediated by Myosin i controls phagocytic efficiency
bioRxiv, 2018Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Paolo Maiuri, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W Oakes, Mira KrendelAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We have found that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we found that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a novel role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a model for a membrane-tension based feedback mechanism for phagocytic cup closure.
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Localization of unconventional Myosins V and VI in neuronal growth cones
Journal of Neurobiology, 2000Co-Authors: Daniel M. Suter, Paul Forscher, Foued Salmen Espindola, Mark S. MoosekerAbstract:Class V and VI Myosins, two of the six known classes of actin-based motor genes expressed in vertebrate brain (Class I, II, V, VI, IX, and XV), have been suggested to be organelle motors. In this report, the neuronal expression and subcellular localization of chicken brain Myosin V and Myosin VI is examined. Both Myosins are expressed in brain during embryogenesis. In cultured dorsal root ganglion (DRG) neurons, immunolocalization of Myosin V and Myosin VI revealed a similar distribution for these two Myosins. Both are present within cell bodies, neurites and growth cones. Both of these Myosins exhibit punctate labeling patterns that are found in the same subcellular region as microtubules in growth cone central domains. In peripheral growth cone domains, where individual puncta are more readily resolved, we observe a similar number of Myosin V and Myosin VI puncta. However, less than 20% of Myosin V and Myosin VI puncta colocalize with each other in the peripheral domains. After live cell extraction, punctate staining of Myosin V and Myosin VI is reduced in peripheral domains. However, we do not detect such changes in the central domains, suggesting that these Myosins are associated with cytoskeletal/organelle structures. In peripheral growth cone domains Myosin VI exhibits a higher extractability than Myosin V. This difference between Myosin V and VI was also found in a biochemical growth cone particle preparation from brain, suggesting that a significant portion of these two motors has a distinct subcellular distribution. © 2000 John Wiley & Sons, Inc. J Neurobiol 42: 370–382, 2000
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unconventional Myosins in cell movement membrane traffic and signal transduction
Science, 1998Co-Authors: Valerie Mermall, Penny L Post, Mark S. MoosekerAbstract:In the past few years genetic, biochemical, and cytolocalization data have implicated members of the Myosin superfamily of actin-based molecular motors in a variety of cellular functions including membrane trafficking, cell movements, and signal transduction. The importance of Myosins is illustrated by the identification of Myosin genes as targets for disease-causing mutations. The task at hand is to decipher how the multitude of Myosins function at both the molecular and cellular level—a task facilitated by our understanding of Myosin structure and function in muscle.
Patrick W Oakes - One of the best experts on this subject based on the ideXlab platform.
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Membrane-cytoskeletal crosstalk mediated by Myosin-I regulates adhesion turnover during phagocytosis
Nature Communications, 2019Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Qingsen Li, Paolo Maiuri, John M Heddleston, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W OakesAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We find that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we find that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a mechanism involving membrane-cytoskeletal crosstalk for phagocytic cup closure.Phagocytosis of pathogens is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface. Here authors show that Myosin 1e and Myosin 1f link the actin cytoskeleton to the membrane and are required for efficient phagocytosis of antibody-opsonized targets.
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membrane cytoskeletal crosstalk mediated by Myosin i regulates adhesion turnover during phagocytosis
Nature Communications, 2019Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Paolo Maiuri, John M Heddleston, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W OakesAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We find that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we find that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a mechanism involving membrane-cytoskeletal crosstalk for phagocytic cup closure.
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membrane cytoskeleton mechanical feedback mediated by Myosin i controls phagocytic efficiency
bioRxiv, 2018Co-Authors: Sarah R. Barger, Nicholas S. Reilly, Maria S. Shutova, Paolo Maiuri, Tatyana Svitkina, Mark S. Mooseker, Richard A Flavell, Patrick W Oakes, Mira KrendelAbstract:Phagocytosis of invading pathogens or cellular debris requires a dramatic change in cell shape driven by actin polymerization. For antibody-covered targets, phagocytosis is thought to proceed through the sequential engagement of Fc-receptors on the phagocyte with antibodies on the target surface, leading to the extension and closure of the phagocytic cup around the target. We have found that two actin-dependent molecular motors, class 1 Myosins Myosin 1e and Myosin 1f, are specifically localized to Fc-receptor adhesions and required for efficient phagocytosis of antibody-opsonized targets. Using primary macrophages lacking both Myosin 1e and Myosin 1f, we found that without the actin-membrane linkage mediated by these Myosins, the organization of individual adhesions is compromised, leading to excessive actin polymerization, slower adhesion turnover, and deficient phagocytic internalization. This work identifies a novel role for class 1 Myosins in coordinated adhesion turnover during phagocytosis and supports a model for a membrane-tension based feedback mechanism for phagocytic cup closure.
Alexey I Prokhnevsky - One of the best experts on this subject based on the ideXlab platform.
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overlapping functions of the four class xi Myosins in arabidopsis growth root hair elongation and organelle motility
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Alexey I Prokhnevsky, Valera V Peremyslov, Valerian V DoljaAbstract:Flowering plants have evolved multigene families of the class XI Myosin motors, the functions of which remain poorly understood. Here, we investigated functional profiles of the Arabidopsis Myosins that belong to two paralogous pairs, XI-K/XI-1 and XI-2/XI-B, using single and double gene-knockout mutants. It was found that the Myosins XI-K, XI-2, and XI-B, but not XI-1 have overlapping and additive roles in the root hair elongation. A nonidentical set of the three Myosins, XI-K, XI-1, and XI-2, exhibited partially redundant and additive roles in the transport of Golgi stacks, peroxisomes, and mitochondria. Conspicuously, the double xi-k/1 knockout plants that showed the largest cumulative reduction of the organelle velocities also exhibited a stunted plant growth and reduced fecundity phenotype. Collectively, these results suggest that the rapid, Myosin-powered organelle trafficking is required for the optimal plant growth, whereas a distinct Myosin function, presumably the vesicular transport, is involved in elongation of the root hairs. In addition, our data imply that the Myosin gene duplication in plants has been followed by a gradual functional specialization of the resulting pairs of Myosin paralogs.
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two class xi Myosins function in organelle trafficking and root hair development in arabidopsis
Plant Physiology, 2008Co-Authors: Valera V Peremyslov, Alexey I Prokhnevsky, Dror Avisar, Valerian V DoljaAbstract:Multigene families encoding class XI Myosins are conserved in higher plants, however, little information is available on specific functions of these ubiquitous molecular motors. We isolated gene knockout mutants for all 13 class XI Myosins present in Arabidopsis (Arabidopsis thaliana) genome. Inactivation of 11 Myosin genes resulted in no discernible phenotypes under the normal growth conditions. In contrast, the knockouts of the remaining two Myosin genes, XI-2 (formerly MYA2) and XI-K, exhibited similar defects in root hair elongation suggesting that the Myosin-driven motility plays a significant role in a polar tip growth. Strikingly, inactivation of each of these Myosins also reduced trafficking of Golgi stacks, peroxisomes, and mitochondria in root hairs and in leaf epidermal cells. These results indicate that Myosins XI-K and XI-2 play major and overlapping roles in the cell dynamics in Arabidopsis and highlight the redundant nature of Myosin function in plants.
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Myosin xi k is required for rapid trafficking of golgi stacks peroxisomes and mitochondria in leaf cells of nicotiana benthamiana
Plant Physiology, 2008Co-Authors: Dror Avisar, Alexey I Prokhnevsky, Kira S Makarova, Eugene V Koonin, Valerian V DoljaAbstract:A prominent feature of plant cells is the rapid, incessant movement of the organelles traditionally defined as cytoplasmic streaming and attributed to actoMyosin motility. We sequenced six complete Nicotiana benthamiana cDNAs that encode class XI and class VIII Myosins. Phylogenetic analysis indicates that these two classes of Myosins diverged prior to the radiation of green algae and land plants from a common ancestor and that the common ancestor of land plants likely possessed at least seven Myosins. We further report here that movement of Golgi stacks, mitochondria, and peroxisomes in the leaf cells of N. benthamiana is mediated mainly by Myosin XI-K. Suppression of Myosin XI-K function using dominant negative inhibition or RNA interference dramatically reduced movement of each of these organelles. When similar approaches were used to inhibit functions of Myosin XI-2 or XI-F, only moderate to marginal effects were observed. Organelle trafficking was virtually unaffected in response to inhibition of each of the three class VIII Myosins. Interestingly, none of the tested six Myosins appears to be involved in light-induced movements of chloroplasts. Taken together, these data strongly suggest that Myosin XI-K has a major role in trafficking of Golgi stacks, mitochondria, and peroxisomes, whereas Myosins XI-2 and XI-F might perform accessory functions in this process. In addition, our analysis of thousands of individual organelles revealed independent movement patterns for Golgi stacks, mitochondria, and peroxisomes, indicating that the notion of coordinated cytoplasmic streaming is not generally applicable to higher plants.
James R Sellers - One of the best experts on this subject based on the ideXlab platform.
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Regulation of nonmuscle Myosin II by tropoMyosin.
Biochemistry, 2014Co-Authors: Bipasha Barua, Attila Nagy, James R Sellers, Sarah E. Hitchcock-degregoriAbstract:The actin cytoskeleton carries out cellular functions, including division, migration, adhesion, and intracellular transport, that require a variety of actin binding proteins, including Myosins. Our focus here is on class II nonmuscle Myosin isoforms, NMIIA, NMIIB, and NMIIC, and their regulation by the actin binding protein, tropoMyosin. NMII Myosins are localized to different populations of stress fibers and the contractile ring, structures involved in force generation required for cell migration, adhesion, and cytokinesis. The stress fibers and contractile ring that contain NMII Myosins also contain tropoMyosin. Four mammalian genes encode more than 40 tropoMyosins. TropoMyosins inhibit or activate actoMyosin MgATPase and motility depending on the Myosin and tropoMyosin isoform. In vivo, tropoMyosins play a role in cell migration, adhesion, cytokinesis, and NMII isoform localization in an isoform-specific manner. We postulate that the isoform-specific tropoMyosin localization and effect on NMII isoform ...
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Temperature dependent measurements reveal similarities between muscle and non-muscle Myosin motility
Journal of Muscle Research and Cell Motility, 2012Co-Authors: Christopher M. Yengo, Yasuharu Takagi, James R SellersAbstract:We examined the temperature dependence of muscle and non-muscle Myosin (heavy meroMyosin, HMM) with in vitro motility and actin-activated ATPase assays. Our results indicate that Myosin V (MV) has a temperature dependence that is similar in both ATPase and motility assays. We demonstrate that skeletal muscle Myosin (SK), smooth muscle Myosin (SM), and non-muscle Myosin IIA (NM) have different temperature dependence in ATPase compared to in vitro motility assays. In the class II Myosins we examined (SK, SM, and NM) the rate-limiting step in ATPase assays is thought to be attachment to actin or phosphate release, while for in vitro motility assays it is controversial. In MV the rate-limiting step for both in vitro motility and ATPase assays is known to be ADP release. Consequently, in MV the temperature dependence of the ADP release rate constant is similar to the temperature dependence of in vitro motility. Interestingly, the temperature dependence of the ADP release rate constant of SM and NM was shifted toward the in vitro motility temperature dependence. Our results suggest that the rate-limiting step in SK, SM, and NM may shift from attachment-limited in solution to detachment limited in the in vitro motility assay. Internal strain within the Myosin molecule or by neighboring Myosin motors may slow ADP release which becomes rate-limiting in the in vitro motility assay. Within this small subset of Myosins examined, the in vitro sliding velocity correlates reasonably well with actin-activated ATPase activity, which was suggested by the original study by Barany (J Gen Physiol 50:197–218, 1967 ).
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Regulation of Myosin 5a and Myosin 7a
Biochemical Society Transactions, 2011Co-Authors: Verl B. Siththanandan, James R SellersAbstract:The Myosin superfamily is diverse in its structure, kinetic mechanisms and cellular function. The enzymatic activities of most Myosins are regulated by some means such as Ca2+ ion binding, phosphorylation or binding of other proteins. In the present review, we discuss the structural basis for the regulation of mammalian Myosin 5a and Drosophila Myosin 7a. We show that, although both Myosins have a folded inactive state in which domains in the Myosin tail interact with the motor domain, the details of the regulation of these two Myosins differ greatly. Abbreviations: FERM, 4.1/ezrin/radixin/moesin; GST, glutathione transferase; GTD, globular tail domain; HMM, heavy meroMyosin; MyTH, Myosin tail homology; SH3, Src homology 3; TIRF, total internal reflection fluorescence
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Folding and regulation in Myosins II and V
Journal of Muscle Research and Cell Motility, 2007Co-Authors: James R Sellers, Peter J. KnightAbstract:The enzymatic activity of many Myosins is regulated by various means including calcium binding, phosphorylation or binding of receptor molecules. In this review we compare and contrast the regulation of smooth muscle Myosin II and Myosin Va with particular emphasis on the structural basis for the regulation. Both Myosins adopt folded compact conformations in their off states, but the details of the conformations are markedly different. In the regulated smooth muscle Myosin II, the key feature is an asymmetric interaction between the two heads of the molecule with contributions of specific tail–head interactions. In Myosin V the key feature is an interaction between the heads and the globular tail domain.
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Specificity of blebbistatin, an inhibitor of Myosin II
Journal of Muscle Research & Cell Motility, 2004Co-Authors: John Limouze, Aaron F. Straight, Timothy Mitchison, James R SellersAbstract:Blebbistatin is a small molecule inhibitor discovered in a screen for inhibitors of nonmuscle Myosin IIA. We have examined the specificity and potency of the drug by assaying its effects on the actin-activated MgATPase assay of diverse members of the Myosin superfamily. Blebbistatin potently inhibits several striated muscle Myosins as well as vertebrate nonmuscle Myosin IIA and IIB with IC_50 values ranging from 0.5 to 5 μM. Interestingly, smooth muscle which is highly homologous to vertebrate nonmuscle Myosin is only poorly inhibited (IC_50=80 μM). The drug potently inhibits Dictyostelium Myosin II, but poorly inhibits Acanthamoeba Myosin II. Blebbistatin did not inhibit representative Myosin superfamily members from classes I, V, and X.
