The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Jean-louis Martiel - One of the best experts on this subject based on the ideXlab platform.
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Actin Filament Strain Promotes Severing and Cofilin Dissociation.
Biophysical Journal, 2017Co-Authors: Anthony C Schramm, Laurent Blanchoin, Jean-louis Martiel, Glen M Hocky, Gregory A Voth, Enrique M De La CruzAbstract:Computational and structural studies have been indispensable in investigating the molecular origins of actin Filament mechanical properties and modulation by the regulatory severing protein cofilin. All-atom molecular dynamics simulations of cofilactin Filament structures determined by electron cryomicroscopy reveal how cofilin enhances the bending and twisting compliance of actin Filaments. Continuum mechanics models suggest that buckled cofilactin Filaments localize elastic energy at boundaries between bare and cofilin-decorated segments because of their nonuniform elasticity, thereby accelerating Filament severing. Here, we develop mesoscopic length-scale (cofil)actin Filament models and evaluate the effects of compressive and twisting loads on strain energy distribution at specific interprotein interfaces. The models reliably capture the Filament bending and torsional rigidities and intersubunit torsional flexibility measured experimentally with purified protein components. Buckling is predicted to enhance cofilactin Filament severing with minimal effects on cofilin occupancy, whereas Filament twisting enhances cofilin dissociation without compromising Filament integrity. Preferential severing at actin-cofilactin boundaries of buckled Filaments is more prominent than predicted by continuum models because of the enhanced spatial resolution. The models developed here will be valuable for evaluating the effects of Filament shape deformations on Filament stability and interactions with regulatory proteins, and analysis of single Filament manipulation assays.
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Mechanical heterogeneity favors fragmentation of strained actin Filaments
Biophysical Journal, 2015Co-Authors: Enrique M De La Cruz, Jean-louis Martiel, Laurent BlanchoinAbstract:We present a general model of actin Filament deformation and fragmentation in response to compressive forces. The elastic free energy density along Filaments is determined by their shape and mechanical properties, which were modeled in terms of bending, twisting, and twist-bend coupling elasticities. The elastic energy stored in Filament deformation (i.e., strain) tilts the fragmentation-annealing reaction free-energy profile to favor fragmentation. The energy gradient introduces a local shear force that accelerates Filament intersubunit bond rupture. The severing protein, cofilin, renders Filaments more compliant in bending and twisting. As a result, Filaments that are partially decorated with cofilin are mechanically heterogeneous (i.e., nonuniform) and display asymmetric shape deformations and energy profiles distinct from mechanically homogenous (i.e., uniform), bare actin, or saturated cofilactin Filaments. The local buckling strain depends on the relative size of the compliant segment as well as the bending and twisting rigidities of flanking regions. Filaments with a single bare/cofilin-decorated boundary localize energy and force adjacent to the boundary, within the compliant cofilactin segment. Filaments with small cofilin clusters were predicted to fragment within the compliant cofilactin rather than at boundaries. Neglecting contributions from twist-bend coupling elasticity underestimates the energy density and gradients along Filaments, and thus the net effects of Filament strain to fragmentation. Spatial confinement causes compliant cofilactin segments and Filaments to adopt higher deformation modes and store more elastic energy, thereby promoting fragmentation. The theory and simulations presented here establish a quantitative relationship between actin Filament fragmentation thermodynamics and elasticity, and reveal how local discontinuities in Filament mechanical properties introduced by regulatory proteins can modulate both the severing efficiency and location along Filaments. The emergent behavior of mechanically heterogeneous Filaments, particularly under confinement, emphasizes that severing in cells is likely to be influenced by multiple physical and chemical factors.
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Origin of twist-bend coupling in actin Filaments.
Biophysical Journal, 2010Co-Authors: Enrique M De La Cruz, Jeremy Roland, Brannon R Mccullough, Laurent Blanchoin, Jean-louis MartielAbstract:Actin Filaments are semiflexible polymers that display large-scale conformational twisting and bending motions. Modulation of Filament bending and twisting dynamics has been linked to regulatory actin-binding protein function, Filament assembly and fragmentation, and overall cell motility. The relationship between actin Filament bending and twisting dynamics has not been evaluated. The numerical and analytical experiments presented here reveal that actin Filaments have a strong intrinsic twist-bend coupling that obligates the reciprocal interconversion of bending energy and twisting stress. We developed a mesoscopic model of actin Filaments that captures key documented features, including the subunit dimensions, interaction energies, helicity, and geometrical constraints coming from the double-stranded structure. The Filament bending and torsional rigidities predicted by the model are comparable to experimental values, demonstrating the capacity of the model to assess the mechanical properties of actin Filaments, including the coupling between twisting and bending motions. The predicted actin Filament twist-bend coupling is strong, with a persistence length of 0.15-0.4 μm depending on the actin-bound nucleotide. Twist-bend coupling is an emergent property that introduces local asymmetry to actin Filaments and contributes to their overall elasticity. Up to 60% of the Filament subunit elastic free energy originates from twist-bend coupling, with the largest contributions resulting under relatively small deformations. A comparison of Filaments with different architectures indicates that twist-bend coupling in actin Filaments originates from their double protoFilament and helical structure.
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stochastic severing of actin Filaments by actin depolymerizing factor cofilin controls the emergence of a steady dynamical regime
Biophysical Journal, 2008Co-Authors: Jeremy Roland, Laurent Blanchoin, Julien Berro, Alphee Michelot, Jean-louis MartielAbstract:Actin dynamics (i.e., polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned to explain the rapid actin Filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin Filament dynamics in the presence of actin depolymerizing factor (ADF)/cofilin. We limited the molecular mechanism to 1), the spontaneous growth of Filaments by polymerization of actin monomers, 2), the ageing of actin subunits in Filaments, 3), the cooperative binding of ADF/cofilin to actin Filament subunits, and 4), Filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we found that the average Filament length, AELae, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: � 2/3). We also showed that the average subunit residence time inside the Filament, AETae, depends on the actin monomer (power law: � 1/6) and ADF/ cofilin (power law: � 2/3) concentrations. In addition, Filament length fluctuations are ;20% of the average Filament length. Moreover, ADF/cofilin fragmentation while modulating Filament length keeps Filaments in a high molar ratio of ATP- or ADP-Pi versus ADP-bound subunits. This latter property has a protective effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin Filaments. Our analysis shows that ADF/cofilin regulation maintains actin Filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo.
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Stochastic severing of actin Filaments by ADF/cofilin controls the emergence of a steady dynamical regime.
Biophysical Journal, 2008Co-Authors: Jeremy Roland, Laurent Blanchoin, Julien Berro, Alphee Michelot, Jean-louis MartielAbstract:Actin dynamics (ie: polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned in order to explain the rapid actin Filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin Filament dynamics in the presence of ADF/cofilin. We limited the molecular mechanism to (1) the spontaneous growth of Filaments by polymerization of actin monomers, (2) the ageing of actin subunits in Filaments, (3) the cooperative binding of ADF/cofilin to actin Filament subunits, and (4) Filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we find that the average Filament length, < L >, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: -2/3). We also showed that the average subunit residence time inside the Filament, < T >, depends on the actin monomer (power law: -1/6) and ADF/cofilin (power law: -2/3) concentrations. In addition, Filament length fluctuations are ~ 20% of the average Filament length. Moreover, ADF/cofilin fragmentation while modulating Filament length keeps Filaments in a high molar ratio of ATP- or ADP-Pi- versus ADP-bound subunits. This latter property has a protecting effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin Filaments. Our analysis shows that ADF/cofilin regulation maintains actin Filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo.
Laurent Blanchoin - One of the best experts on this subject based on the ideXlab platform.
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Actin Filament Strain Promotes Severing and Cofilin Dissociation.
Biophysical Journal, 2017Co-Authors: Anthony C Schramm, Laurent Blanchoin, Jean-louis Martiel, Glen M Hocky, Gregory A Voth, Enrique M De La CruzAbstract:Computational and structural studies have been indispensable in investigating the molecular origins of actin Filament mechanical properties and modulation by the regulatory severing protein cofilin. All-atom molecular dynamics simulations of cofilactin Filament structures determined by electron cryomicroscopy reveal how cofilin enhances the bending and twisting compliance of actin Filaments. Continuum mechanics models suggest that buckled cofilactin Filaments localize elastic energy at boundaries between bare and cofilin-decorated segments because of their nonuniform elasticity, thereby accelerating Filament severing. Here, we develop mesoscopic length-scale (cofil)actin Filament models and evaluate the effects of compressive and twisting loads on strain energy distribution at specific interprotein interfaces. The models reliably capture the Filament bending and torsional rigidities and intersubunit torsional flexibility measured experimentally with purified protein components. Buckling is predicted to enhance cofilactin Filament severing with minimal effects on cofilin occupancy, whereas Filament twisting enhances cofilin dissociation without compromising Filament integrity. Preferential severing at actin-cofilactin boundaries of buckled Filaments is more prominent than predicted by continuum models because of the enhanced spatial resolution. The models developed here will be valuable for evaluating the effects of Filament shape deformations on Filament stability and interactions with regulatory proteins, and analysis of single Filament manipulation assays.
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Mechanical heterogeneity favors fragmentation of strained actin Filaments
Biophysical Journal, 2015Co-Authors: Enrique M De La Cruz, Jean-louis Martiel, Laurent BlanchoinAbstract:We present a general model of actin Filament deformation and fragmentation in response to compressive forces. The elastic free energy density along Filaments is determined by their shape and mechanical properties, which were modeled in terms of bending, twisting, and twist-bend coupling elasticities. The elastic energy stored in Filament deformation (i.e., strain) tilts the fragmentation-annealing reaction free-energy profile to favor fragmentation. The energy gradient introduces a local shear force that accelerates Filament intersubunit bond rupture. The severing protein, cofilin, renders Filaments more compliant in bending and twisting. As a result, Filaments that are partially decorated with cofilin are mechanically heterogeneous (i.e., nonuniform) and display asymmetric shape deformations and energy profiles distinct from mechanically homogenous (i.e., uniform), bare actin, or saturated cofilactin Filaments. The local buckling strain depends on the relative size of the compliant segment as well as the bending and twisting rigidities of flanking regions. Filaments with a single bare/cofilin-decorated boundary localize energy and force adjacent to the boundary, within the compliant cofilactin segment. Filaments with small cofilin clusters were predicted to fragment within the compliant cofilactin rather than at boundaries. Neglecting contributions from twist-bend coupling elasticity underestimates the energy density and gradients along Filaments, and thus the net effects of Filament strain to fragmentation. Spatial confinement causes compliant cofilactin segments and Filaments to adopt higher deformation modes and store more elastic energy, thereby promoting fragmentation. The theory and simulations presented here establish a quantitative relationship between actin Filament fragmentation thermodynamics and elasticity, and reveal how local discontinuities in Filament mechanical properties introduced by regulatory proteins can modulate both the severing efficiency and location along Filaments. The emergent behavior of mechanically heterogeneous Filaments, particularly under confinement, emphasizes that severing in cells is likely to be influenced by multiple physical and chemical factors.
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Origin of twist-bend coupling in actin Filaments.
Biophysical Journal, 2010Co-Authors: Enrique M De La Cruz, Jeremy Roland, Brannon R Mccullough, Laurent Blanchoin, Jean-louis MartielAbstract:Actin Filaments are semiflexible polymers that display large-scale conformational twisting and bending motions. Modulation of Filament bending and twisting dynamics has been linked to regulatory actin-binding protein function, Filament assembly and fragmentation, and overall cell motility. The relationship between actin Filament bending and twisting dynamics has not been evaluated. The numerical and analytical experiments presented here reveal that actin Filaments have a strong intrinsic twist-bend coupling that obligates the reciprocal interconversion of bending energy and twisting stress. We developed a mesoscopic model of actin Filaments that captures key documented features, including the subunit dimensions, interaction energies, helicity, and geometrical constraints coming from the double-stranded structure. The Filament bending and torsional rigidities predicted by the model are comparable to experimental values, demonstrating the capacity of the model to assess the mechanical properties of actin Filaments, including the coupling between twisting and bending motions. The predicted actin Filament twist-bend coupling is strong, with a persistence length of 0.15-0.4 μm depending on the actin-bound nucleotide. Twist-bend coupling is an emergent property that introduces local asymmetry to actin Filaments and contributes to their overall elasticity. Up to 60% of the Filament subunit elastic free energy originates from twist-bend coupling, with the largest contributions resulting under relatively small deformations. A comparison of Filaments with different architectures indicates that twist-bend coupling in actin Filaments originates from their double protoFilament and helical structure.
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Actin Filament dynamics are dominated by rapid growth and severing activity in the Arabidopsis cortical array.
Journal of Cell Biology, 2009Co-Authors: Christopher J Staiger, Michael B Sheahan, Parul Khurana, Xia Wang, David W Mccurdy, Laurent BlanchoinAbstract:Metazoan cells harness the power of actin dynamics to create cytoskeletal arrays that stimulate protrusions and drive intracellular organelle movements. In plant cells, the actin cytoskeleton is understood to participate in cell elongation; however, a detailed description and molecular mechanism(s) underpinning Filament nucleation, growth, and turnover are lacking. Here, we use variable-angle epifluorescence microscopy (VAEM) to examine the organization and dynamics of the cortical cytoskeleton in growing and nongrowing epidermal cells. One population of Filaments in the cortical array, which most likely represent single actin Filaments, is randomly oriented and highly dynamic. These Filaments grow at rates of 1.7 microm/s, but are generally short-lived. Instead of depolymerization at their ends, actin Filaments are disassembled by severing activity. Remodeling of the cortical actin array also features Filament buckling and straightening events. These observations indicate a mechanism inconsistent with treadmilling. Instead, cortical actin Filament dynamics resemble the stochastic dynamics of an in vitro biomimetic system for actin assembly.
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stochastic severing of actin Filaments by actin depolymerizing factor cofilin controls the emergence of a steady dynamical regime
Biophysical Journal, 2008Co-Authors: Jeremy Roland, Laurent Blanchoin, Julien Berro, Alphee Michelot, Jean-louis MartielAbstract:Actin dynamics (i.e., polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned to explain the rapid actin Filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin Filament dynamics in the presence of actin depolymerizing factor (ADF)/cofilin. We limited the molecular mechanism to 1), the spontaneous growth of Filaments by polymerization of actin monomers, 2), the ageing of actin subunits in Filaments, 3), the cooperative binding of ADF/cofilin to actin Filament subunits, and 4), Filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we found that the average Filament length, AELae, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: � 2/3). We also showed that the average subunit residence time inside the Filament, AETae, depends on the actin monomer (power law: � 1/6) and ADF/ cofilin (power law: � 2/3) concentrations. In addition, Filament length fluctuations are ;20% of the average Filament length. Moreover, ADF/cofilin fragmentation while modulating Filament length keeps Filaments in a high molar ratio of ATP- or ADP-Pi versus ADP-bound subunits. This latter property has a protective effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin Filaments. Our analysis shows that ADF/cofilin regulation maintains actin Filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo.
Enrique M De La Cruz - One of the best experts on this subject based on the ideXlab platform.
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Actin Filament Strain Promotes Severing and Cofilin Dissociation.
Biophysical Journal, 2017Co-Authors: Anthony C Schramm, Laurent Blanchoin, Jean-louis Martiel, Glen M Hocky, Gregory A Voth, Enrique M De La CruzAbstract:Computational and structural studies have been indispensable in investigating the molecular origins of actin Filament mechanical properties and modulation by the regulatory severing protein cofilin. All-atom molecular dynamics simulations of cofilactin Filament structures determined by electron cryomicroscopy reveal how cofilin enhances the bending and twisting compliance of actin Filaments. Continuum mechanics models suggest that buckled cofilactin Filaments localize elastic energy at boundaries between bare and cofilin-decorated segments because of their nonuniform elasticity, thereby accelerating Filament severing. Here, we develop mesoscopic length-scale (cofil)actin Filament models and evaluate the effects of compressive and twisting loads on strain energy distribution at specific interprotein interfaces. The models reliably capture the Filament bending and torsional rigidities and intersubunit torsional flexibility measured experimentally with purified protein components. Buckling is predicted to enhance cofilactin Filament severing with minimal effects on cofilin occupancy, whereas Filament twisting enhances cofilin dissociation without compromising Filament integrity. Preferential severing at actin-cofilactin boundaries of buckled Filaments is more prominent than predicted by continuum models because of the enhanced spatial resolution. The models developed here will be valuable for evaluating the effects of Filament shape deformations on Filament stability and interactions with regulatory proteins, and analysis of single Filament manipulation assays.
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Mechanical heterogeneity favors fragmentation of strained actin Filaments
Biophysical Journal, 2015Co-Authors: Enrique M De La Cruz, Jean-louis Martiel, Laurent BlanchoinAbstract:We present a general model of actin Filament deformation and fragmentation in response to compressive forces. The elastic free energy density along Filaments is determined by their shape and mechanical properties, which were modeled in terms of bending, twisting, and twist-bend coupling elasticities. The elastic energy stored in Filament deformation (i.e., strain) tilts the fragmentation-annealing reaction free-energy profile to favor fragmentation. The energy gradient introduces a local shear force that accelerates Filament intersubunit bond rupture. The severing protein, cofilin, renders Filaments more compliant in bending and twisting. As a result, Filaments that are partially decorated with cofilin are mechanically heterogeneous (i.e., nonuniform) and display asymmetric shape deformations and energy profiles distinct from mechanically homogenous (i.e., uniform), bare actin, or saturated cofilactin Filaments. The local buckling strain depends on the relative size of the compliant segment as well as the bending and twisting rigidities of flanking regions. Filaments with a single bare/cofilin-decorated boundary localize energy and force adjacent to the boundary, within the compliant cofilactin segment. Filaments with small cofilin clusters were predicted to fragment within the compliant cofilactin rather than at boundaries. Neglecting contributions from twist-bend coupling elasticity underestimates the energy density and gradients along Filaments, and thus the net effects of Filament strain to fragmentation. Spatial confinement causes compliant cofilactin segments and Filaments to adopt higher deformation modes and store more elastic energy, thereby promoting fragmentation. The theory and simulations presented here establish a quantitative relationship between actin Filament fragmentation thermodynamics and elasticity, and reveal how local discontinuities in Filament mechanical properties introduced by regulatory proteins can modulate both the severing efficiency and location along Filaments. The emergent behavior of mechanically heterogeneous Filaments, particularly under confinement, emphasizes that severing in cells is likely to be influenced by multiple physical and chemical factors.
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Actin Filament severing by vertebrate cofilin is driven by linked cation release
2014Co-Authors: Hyeran Kang, Emil Reisler, Brannon R Mccullough, Alphee Michelot, Michael J. Bradley, Elena E. Grintsevich, Mark Hochstrasser, Enrique M De La CruzAbstract:The dynamic remodeling of actin cytoskeleton drives cell movement. The essential actin regulatory protein cofilin accelerates actin remodeling by severing Filaments and increasing the concentration of free Filament ends from which subunits add and dissociate. Cofilin binding dissociates actin-associated cations and enhances Filament bending and twisting compliance. The linkage between cofilin-mediated cation release, Filament mechanics and severing activity has not been firmly established. Here, we demonstrate that cofilin-dependent cation release from a discrete, Filament-specific cation binding site enhances the bending and twisting flexibility of actin Filaments and that this local change in Filament mechanics is required for severing.
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Origin of twist-bend coupling in actin Filaments.
Biophysical Journal, 2010Co-Authors: Enrique M De La Cruz, Jeremy Roland, Brannon R Mccullough, Laurent Blanchoin, Jean-louis MartielAbstract:Actin Filaments are semiflexible polymers that display large-scale conformational twisting and bending motions. Modulation of Filament bending and twisting dynamics has been linked to regulatory actin-binding protein function, Filament assembly and fragmentation, and overall cell motility. The relationship between actin Filament bending and twisting dynamics has not been evaluated. The numerical and analytical experiments presented here reveal that actin Filaments have a strong intrinsic twist-bend coupling that obligates the reciprocal interconversion of bending energy and twisting stress. We developed a mesoscopic model of actin Filaments that captures key documented features, including the subunit dimensions, interaction energies, helicity, and geometrical constraints coming from the double-stranded structure. The Filament bending and torsional rigidities predicted by the model are comparable to experimental values, demonstrating the capacity of the model to assess the mechanical properties of actin Filaments, including the coupling between twisting and bending motions. The predicted actin Filament twist-bend coupling is strong, with a persistence length of 0.15-0.4 μm depending on the actin-bound nucleotide. Twist-bend coupling is an emergent property that introduces local asymmetry to actin Filaments and contributes to their overall elasticity. Up to 60% of the Filament subunit elastic free energy originates from twist-bend coupling, with the largest contributions resulting under relatively small deformations. A comparison of Filaments with different architectures indicates that twist-bend coupling in actin Filaments originates from their double protoFilament and helical structure.
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actin Filament remodeling by actin depolymerization factor cofilin
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Jim Pfaendtner, Enrique M De La Cruz, Gregory A VothAbstract:We investigate, using molecular dynamics, how the severing protein, actin depolymerization factor (ADF)/cofilin, modulates the structure, conformational dynamics, and mechanical properties of actin Filaments. The actin and cofilactin Filament bending stiffness and corresponding persistence lengths obtained from all-atom simulations are comparable to values obtained from analysis of thermal fluctuations in Filament shape. Filament flexibility is strongly affected by the nucleotide-linked conformation of the actin subdomain 2 DNase-I binding loop and the Filament radial mass density distribution. ADF/cofilin binding between subdomains 1 and 3 of a Filament subunit triggers reorganization of subdomain 2 of the neighboring subunit such that the DNase-I binding loop (DB-loop) moves radially away from the Filament. Repositioning of the neighboring subunit DB-loop significantly weakens subunit interactions along the long-pitch helix and lowers the Filament bending rigidity. Lateral Filament contacts between the hydrophobic loop and neighboring short-pitch helix monomers in native Filaments are also compromised with cofilin binding. These works provide a molecular interpretation of biochemical solution studies documenting the disruption of Filament subunit interactions and also reveal the molecular basis of actin Filament allostery and its linkage to ADF/cofilin binding.
Guillaume Rometlemonne - One of the best experts on this subject based on the ideXlab platform.
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torsional stress generated by adf cofilin on cross linked actin Filaments boosts their severing
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Hugo Wioland, Antoine Jegou, Guillaume RometlemonneAbstract:: Proteins of the actin depolymerizing factor (ADF)/cofilin family are the central regulators of actin Filament disassembly. A key function of ADF/cofilin is to sever actin Filaments. However, how it does so in a physiological context, where Filaments are interconnected and under mechanical stress, remains unclear. Here, we monitor and quantify the action of ADF/cofilin in different mechanical situations by using single-molecule, single-Filament, and Filament network techniques, coupled to microfluidics. We find that local curvature favors severing, while tension surprisingly has no effect on cofilin binding and weakly enhances severing. Remarkably, we observe that Filament segments that are held between two anchoring points, thereby constraining their twist, experience a mechanical torque upon cofilin binding. We find that this ADF/cofilin-induced torque does not hinder ADF/cofilin binding, but dramatically enhances severing. A simple model, which faithfully recapitulates our experimental observations, indicates that the ADF/cofilin-induced torque increases the severing rate constant 100-fold. A consequence of this mechanism, which we verify experimentally, is that cross-linked Filament networks are severed by cofilin far more efficiently than nonconnected Filaments. We propose that this mechanochemical mechanism is critical to boost ADF/cofilin's ability to sever highly connected Filament networks in cells.
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torsional stress generated by adf cofilin on cross linked actin Filaments boosts their severing
bioRxiv, 2018Co-Authors: Hugo Wioland, Antoine Jegou, Guillaume RometlemonneAbstract:Proteins of the Actin Depolymerizing Factor (ADF)/cofilin family are the central regulators of actin Filament disassembly. A key function of ADF/cofilin is to sever actin Filaments. However, how it does so in a physiological context, where Filaments are interconnected and under mechanical stress, remains unclear. Here, we monitor and quantify the action of ADF/cofilin in different mechanical situations by using single molecule, single Filament, and Filament network techniques, coupled to microfluidics. We find that local curvature favors severing, while tension surprisingly has no effect on either cofilin binding or severing. Remarkably, we observe that Filament segments that are held between two anchoring points, thereby constraining their twist, experience a mechanical torque upon cofilin binding. We find that this ADF/cofilin-induced torque does not hinder ADF/cofilin binding, but dramatically enhances severing. A simple model, which faithfully recapitulates our experimental observations, indicates that the ADF/cofilin-induced torque increases the severing rate constant 100-fold. A consequence of this mechanism, which we verify experimentally, is that cross-linked Filament networks are severed by cofilin far more efficiently than non-connected Filaments. We propose that this mechano-chemical mechanism is critical to boost ADF/cofilin's ability to sever highly connected Filament networks in cells.
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adf cofilin accelerates actin dynamics by severing Filaments and promoting their depolymerization at both ends
Current Biology, 2017Co-Authors: Hugo Wioland, Berengere Guichard, Yosuke Senju, Sarah Myram, Antoine Jegou, Pekka Lappalainen, Guillaume RometlemonneAbstract:Summary Actin-depolymerizing factor (ADF)/cofilins contribute to cytoskeletal dynamics by promoting rapid actin Filament disassembly. In the classical view, ADF/cofilin sever Filaments, and capping proteins block Filament barbed ends whereas pointed ends depolymerize, at a rate that is still debated. Here, by monitoring the activity of the three mammalian ADF/cofilin isoforms on individual skeletal muscle and cytoplasmic actin Filaments, we directly quantify the reactions underpinning Filament severing and depolymerization from both ends. We find that, in the absence of monomeric actin, soluble ADF/cofilin can associate with bare Filament barbed ends to accelerate their depolymerization. Compared to bare Filaments, ADF/cofilin-saturated Filaments depolymerize faster from their pointed ends and slower from their barbed ends, resulting in similar depolymerization rates at both ends. This effect is isoform specific because depolymerization is faster for ADF- than for cofilin-saturated Filaments. We also show that, unexpectedly, ADF/cofilin-saturated Filaments qualitatively differ from bare Filaments: their barbed ends are very difficult to cap or elongate, and consequently undergo depolymerization even in the presence of capping protein and actin monomers. Such depolymerizing ADF/cofilin-decorated barbed ends are produced during 17% of severing events. They are also the dominant fate of Filament barbed ends in the presence of capping protein, because capping allows growing ADF/cofilin domains to reach the barbed ends, thereby promoting their uncapping and subsequent depolymerization. Our experiments thus reveal how ADF/cofilin, together with capping protein, control the dynamics of actin Filament barbed and pointed ends. Strikingly, our results propose that significant barbed-end depolymerization may take place in cells.
Hugo Wioland - One of the best experts on this subject based on the ideXlab platform.
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torsional stress generated by adf cofilin on cross linked actin Filaments boosts their severing
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Hugo Wioland, Antoine Jegou, Guillaume RometlemonneAbstract:: Proteins of the actin depolymerizing factor (ADF)/cofilin family are the central regulators of actin Filament disassembly. A key function of ADF/cofilin is to sever actin Filaments. However, how it does so in a physiological context, where Filaments are interconnected and under mechanical stress, remains unclear. Here, we monitor and quantify the action of ADF/cofilin in different mechanical situations by using single-molecule, single-Filament, and Filament network techniques, coupled to microfluidics. We find that local curvature favors severing, while tension surprisingly has no effect on cofilin binding and weakly enhances severing. Remarkably, we observe that Filament segments that are held between two anchoring points, thereby constraining their twist, experience a mechanical torque upon cofilin binding. We find that this ADF/cofilin-induced torque does not hinder ADF/cofilin binding, but dramatically enhances severing. A simple model, which faithfully recapitulates our experimental observations, indicates that the ADF/cofilin-induced torque increases the severing rate constant 100-fold. A consequence of this mechanism, which we verify experimentally, is that cross-linked Filament networks are severed by cofilin far more efficiently than nonconnected Filaments. We propose that this mechanochemical mechanism is critical to boost ADF/cofilin's ability to sever highly connected Filament networks in cells.
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Torsional stress generated by ADF/cofilin on cross-linked actin Filaments boosts their severing
Proceedings of the National Academy of Sciences of the United States of America, 2019Co-Authors: Hugo Wioland, Antoine Jegou, Guillaume Romet-lemonneAbstract:Proteins of the actin depolymerizing factor (ADF)/cofilin family are the central regulators of actin Filament disassembly. A key function of ADF/cofilin is to sever actin Filaments. However, how it does so in a physiological context, where Filaments are interconnected and under mechanical stress, remains unclear. Here, we monitor and quantify the action of ADF/cofilin in different mechanical situations by using single-molecule, single-Filament, and Filament network techniques, coupled to microfluidics. We find that local curvature favors severing, while tension surprisingly has no effect on cofilin binding and weakly enhances severing. Remarkably, we observe that Filament segments that are held between two anchoring points, thereby constraining their twist, experience a mechanical torque upon cofilin binding. We find that this ADF/ cofilin-induced torque does not hinder ADF/cofilin binding, but dramatically enhances severing. A simple model, which faithfully recapitulates our experimental observations, indicates that the ADF/cofilin-induced torque increases the severing rate constant 100-fold. A consequence of this mechanism, which we verify experimentally , is that cross-linked Filament networks are severed by cofilin far more efficiently than nonconnected Filaments. We propose that this mechanochemical mechanism is critical to boost ADF/cofilin's ability to sever highly connected Filament networks in cells. cytoskeleton | mechanotransduction | actin dynamics | microfluidics
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torsional stress generated by adf cofilin on cross linked actin Filaments boosts their severing
bioRxiv, 2018Co-Authors: Hugo Wioland, Antoine Jegou, Guillaume RometlemonneAbstract:Proteins of the Actin Depolymerizing Factor (ADF)/cofilin family are the central regulators of actin Filament disassembly. A key function of ADF/cofilin is to sever actin Filaments. However, how it does so in a physiological context, where Filaments are interconnected and under mechanical stress, remains unclear. Here, we monitor and quantify the action of ADF/cofilin in different mechanical situations by using single molecule, single Filament, and Filament network techniques, coupled to microfluidics. We find that local curvature favors severing, while tension surprisingly has no effect on either cofilin binding or severing. Remarkably, we observe that Filament segments that are held between two anchoring points, thereby constraining their twist, experience a mechanical torque upon cofilin binding. We find that this ADF/cofilin-induced torque does not hinder ADF/cofilin binding, but dramatically enhances severing. A simple model, which faithfully recapitulates our experimental observations, indicates that the ADF/cofilin-induced torque increases the severing rate constant 100-fold. A consequence of this mechanism, which we verify experimentally, is that cross-linked Filament networks are severed by cofilin far more efficiently than non-connected Filaments. We propose that this mechano-chemical mechanism is critical to boost ADF/cofilin's ability to sever highly connected Filament networks in cells.
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adf cofilin accelerates actin dynamics by severing Filaments and promoting their depolymerization at both ends
Current Biology, 2017Co-Authors: Hugo Wioland, Berengere Guichard, Yosuke Senju, Sarah Myram, Antoine Jegou, Pekka Lappalainen, Guillaume RometlemonneAbstract:Summary Actin-depolymerizing factor (ADF)/cofilins contribute to cytoskeletal dynamics by promoting rapid actin Filament disassembly. In the classical view, ADF/cofilin sever Filaments, and capping proteins block Filament barbed ends whereas pointed ends depolymerize, at a rate that is still debated. Here, by monitoring the activity of the three mammalian ADF/cofilin isoforms on individual skeletal muscle and cytoplasmic actin Filaments, we directly quantify the reactions underpinning Filament severing and depolymerization from both ends. We find that, in the absence of monomeric actin, soluble ADF/cofilin can associate with bare Filament barbed ends to accelerate their depolymerization. Compared to bare Filaments, ADF/cofilin-saturated Filaments depolymerize faster from their pointed ends and slower from their barbed ends, resulting in similar depolymerization rates at both ends. This effect is isoform specific because depolymerization is faster for ADF- than for cofilin-saturated Filaments. We also show that, unexpectedly, ADF/cofilin-saturated Filaments qualitatively differ from bare Filaments: their barbed ends are very difficult to cap or elongate, and consequently undergo depolymerization even in the presence of capping protein and actin monomers. Such depolymerizing ADF/cofilin-decorated barbed ends are produced during 17% of severing events. They are also the dominant fate of Filament barbed ends in the presence of capping protein, because capping allows growing ADF/cofilin domains to reach the barbed ends, thereby promoting their uncapping and subsequent depolymerization. Our experiments thus reveal how ADF/cofilin, together with capping protein, control the dynamics of actin Filament barbed and pointed ends. Strikingly, our results propose that significant barbed-end depolymerization may take place in cells.
