The Experts below are selected from a list of 10845 Experts worldwide ranked by ideXlab platform
Emil Reisler - One of the best experts on this subject based on the ideXlab platform.
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F-actin dismantling through a redox-driven synergy between Mical and Cofilin
Nature Cell Biology, 2016Co-Authors: Elena E. Grintsevich, Jonathan R. Terman, Ruei Jiun Hung, Hunkar Gizem Yesilyurt, Shannon K. Rich, Emil ReislerAbstract:Grintsevich et al. discover that the redox enzyme Mical oxidizes F-actin to promote binding of the F-actin-severing protein Cofilin, and that the synergy of Mical and Cofilin is necessary and sufficient for F-actin disassembly in Drosophila . Numerous cellular functions depend on actin filament (F-actin) disassembly. The best-characterized disassembly proteins, the ADF (actin-depolymerizing factor)/Cofilins (encoded by the twinstar gene in Drosophila ), sever filaments and recycle monomers to promote actin assembly. Cofilin is also a relatively weak actin disassembler, posing questions about mechanisms of cellular F-actin destabilization. Here we uncover a key link to targeted F-actin disassembly by finding that F-actin is efficiently dismantled through a post-translational-mediated synergism between Cofilin and the actin-oxidizing enzyme Mical. We find that Mical-mediated oxidation of actin improves Cofilin binding to filaments, where their combined effect dramatically accelerates F-actin disassembly compared with either effector alone. This synergism is also necessary and sufficient for F-actin disassembly in vivo , magnifying the effects of both Mical and Cofilin on cellular remodelling, axon guidance and Semaphorin–Plexin repulsion. Mical and Cofilin, therefore, form a redox-dependent synergistic pair that promotes F-actin instability by rapidly dismantling F-actin and generating post-translationally modified actin that has altered assembly properties.
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f actin dismantling through a redox driven synergy between mical and Cofilin
Nature Cell Biology, 2016Co-Authors: Elena E. Grintsevich, Jonathan R. Terman, Ruei Jiun Hung, Hunkar Gizem Yesilyurt, Shannon K. Rich, Emil ReislerAbstract:Numerous cellular functions depend on actin filament (F-actin) disassembly. The best-characterized disassembly proteins, the ADF (actin-depolymerizing factor)/Cofilins (encoded by the twinstar gene in Drosophila), sever filaments and recycle monomers to promote actin assembly. Cofilin is also a relatively weak actin disassembler, posing questions about mechanisms of cellular F-actin destabilization. Here we uncover a key link to targeted F-actin disassembly by finding that F-actin is efficiently dismantled through a post-translational-mediated synergism between Cofilin and the actin-oxidizing enzyme Mical. We find that Mical-mediated oxidation of actin improves Cofilin binding to filaments, where their combined effect dramatically accelerates F-actin disassembly compared with either effector alone. This synergism is also necessary and sufficient for F-actin disassembly in vivo, magnifying the effects of both Mical and Cofilin on cellular remodelling, axon guidance and Semaphorin-Plexin repulsion. Mical and Cofilin, therefore, form a redox-dependent synergistic pair that promotes F-actin instability by rapidly dismantling F-actin and generating post-translationally modified actin that has altered assembly properties.
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Remodeling of Actin Filaments by Cofilin
Biophysical Journal, 2012Co-Authors: Vitold E. Galkin, Emil Reisler, Albina Orlova, Dmitri Kudryashov, Alexandr Soloduhin, Gunnar F. Schröder, Edward H. EgelmanAbstract:Cofilin/ADF proteins play key roles in the dynamics of actin. We used cryo-electron microscopy of uniformly decorated actin-Cofilin filaments to show that the Cofilin induced change in the filament twist is due to a unique conformation of the actin molecule unrelated to any previously observed state. The changes between the actin protomer in naked F-actin and in the actin-Cofilin filament are greater than the conformational changes between G- and F-actin. Cofilin/ADF proteins efficiently depolymerize F-actin only when bound at low stoichiometry to actin filaments. We also used cryo electron microscopy to reveal the structure of F-actin decorated with sub-stoichiometric amounts of Cofilin. Our results suggest that the structural state of actin protomers found within the uniformly decorated actin-Cofilin filaments can propagate towards the naked regions, and this cooperative propagation is uncoupled from the change in the helical twist of F-actin upon interaction with Cofilin. This illustrates the structural plasticity of actin and provides a structural mechanism for actin depolymerization by the ADF/Cofilin proteins.
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antagonistic effects of Cofilin beryllium fluoride complex and phalloidin on subdomain 2 and nucleotide binding cleft in f actin
Biophysical Journal, 2006Co-Authors: Andras Muhlrad, Dmitry Pavlov, Israel Ringel, Michael Y Peyser, Emil ReislerAbstract:Cofilin/ADF, beryllium fluoride complex (BeFx), and phalloidin have opposing effects on actin filament structure and dynamics. Cofilin/ADF decreases the stability of F-actin by enhancing disorder in subdomain 2, and by severing and accelerating the depolymerization of the filament. BeFx and phalloidin stabilize the subdomain 2 structure and decrease the critical concentration of actin, slowing the dissociation of monomers. Yeast Cofilin, unlike some other members of the Cofilin/ADF family, binds to F-actin in the presence of BeFx; however, the rate of its binding is strongly inhibited by BeFx and decreases with increasing pH. The inhibition of the Cofilin binding rate increases with the time of BeFx incubation with F-actin, indicating the existence of two BeFx-F-actin complexes. Cofilin dissociates BeFx from the filament, while BeFx does not bind to F-actin saturated with Cofilin, presumably because of the Cofilin-induced changes in the nucleotide-binding cleft of F-actin. These changes are apparent from the increase in the fluorescence intensity of F-actin bound ɛ-ADP upon Cofilin binding and a decrease in its accessibility to collisional quenchers. BeFx also affects the nucleotide-binding cleft of F-actin, as indicated by an increase in the fluorescence intensity of ɛ-ADP-F-actin. Phalloidin and Cofilin inhibit, but do not exclude each other binding to their complexes with F-actin. Phalloidin promotes the dissociation of Cofilin from F-actin and slowly reverses the Cofilin-induced disorder in the DNase I binding loop of subdomain 2.
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Actin filament severing by Cofilin.
Journal of Molecular Biology, 2006Co-Authors: Dmitry Pavlov, Andras Muhlrad, John A. Cooper, Martin A. Wear, Emil ReislerAbstract:Cofilin is essential for cell viability and for actin-based motility. Cofilin severs actin filaments, which enhances the dynamics of filament assembly. We investigated the mechanism of filament severing by Cofilin with direct fluorescence microscopy observation of single actin filaments in real time. In cells, actin filaments are likely to be attached at multiple points along their length, and we found that attaching filaments in such a manner greatly increased the efficiency of filament severing by Cofilin. Cofilin severing increased and then decreased with increasing concentration of Cofilin. Together, these results indicate that Cofilin severs the actin filament by a mechanism of allosteric and cooperative destabilization. Severing is more efficient when relaxation of this Cofilin-induced instability of the actin filament is inhibited by restricting the flexibility of the filament. These conclusions have particular relevance to Cofilin function during actin-based motility in cells and in synthetic systems.
Pekka Lappalainen - One of the best experts on this subject based on the ideXlab platform.
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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.
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Cofilin-2 controls actin filament length in muscle sarcomeres.
Developmental cell, 2014Co-Authors: Elena Kremneva, Roberto Dominguez, Maarit Hannele Makkonen, Aneta Skwarek-maruszewska, Gergana Gateva, Alphée Michelot, Pekka LappalainenAbstract:ADF/Cofilins drive cytoskeletal dynamics by promoting the disassembly of "aged" ADP-actin filaments. Mammals express several ADF/Cofilin isoforms, but their specific biochemical activities and cellular functions have not been studied in detail. Here, we demonstrate that the muscle-specific isoform Cofilin-2 promotes actin filament disassembly in sarcomeres to control the precise length of thin filaments in the contractile apparatus. In contrast to other isoforms, Cofilin-2 efficiently binds and disassembles both ADP- and ATP/ADP-Pi-actin filaments. We mapped surface-exposed Cofilin-2-specific residues required for ATP-actin binding and propose that these residues function as an "actin nucleotide-state sensor" among ADF/Cofilins. The results suggest that Cofilin-2 evolved specific biochemical and cellular properties that allow it to control actin dynamics in sarcomeres, where filament pointed ends may contain a mixture of ADP- and ATP/ADP-Pi-actin subunits. Our findings also offer a rationale for why Cofilin-2 mutations in humans lead to myopathies.
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Structural basis and evolutionary origin of actin filament capping by twinfilin
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Ville O Paavilainen, Marie-france Carlier, Maarit Hellman, Emmanuèle Helfer, Miia Bovellan, Arto Annila, Perttu Permi, Pekka LappalainenAbstract:Dynamic reorganization of the actin cytoskeleton is essential for motile and morphological processes in all eukaryotic cells. One highly conserved protein that regulates actin dynamics is twinfilin, which both sequesters actin monomers and caps actin filament barbed ends. Twinfilin is composed of two ADF/Cofilin-like domains , Twf-N and Twf-C. Here, we reveal by systematic domain-swapping/inactivation analysis that the two functional ADF-H domains of twinfilin are required for barbed-end capping and that Twf-C plays a critical role in this process. However, these domains are not functionally equivalent. NMR-structure and mutagenesis analyses, together with biochemical and motility assays showed that Twf-C, in addition to its binding to G-actin, interacts with the sides of actin filaments like ADF/Cofilins, whereas Twf-N binds only G-actin. Our results indicate that during filament barbed-end capping, Twf-N interacts with the terminal actin subunit, whereas Twf-C binds between two adjacent subunits at the side of the filament. Thus, the domain requirement for actin filament capping by twinfilin is remarkably similar to that of gelsolin family proteins, suggesting the existence of a general barbed-end capping mechanism. Furthermore, we demonstrate that a synthetic protein consisting of duplicated ADF/Cofilin domains caps actin filament barbed ends, providing evidence that the barbed-end capping activity of twinfilin arose through a duplication of an ancient ADF/Cofilin-like domain.
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actin depolymerizing factor and Cofilin 1 play overlapping roles in promoting rapid f actin depolymerization in mammalian nonmuscle cells
Molecular Biology of the Cell, 2004Co-Authors: Pirta Hotulainen, Eija Paunola, Maria K. Vartiainen, Pekka LappalainenAbstract:Actin-depolymerizing factor (ADF)/Cofilins are small actin-binding proteins found in all eukaryotes. In vitro, ADF/Cofilins promote actin dynamics by depolymerizing and severing actin filaments. However, whether ADF/Cofilins contribute to actin dynamics in cells by disassembling “old” actin filaments or by promoting actin filament assembly through their severing activity is a matter of controversy. Analysis of mammalian ADF/Cofilins is further complicated by the presence of multiple isoforms, which may contribute to actin dynamics by different mechanisms. We show that two isoforms, ADF and Cofilin-1, are expressed in mouse NIH 3T3, B16F1, and Neuro 2A cells. Depleting Cofilin-1 and/or ADF by siRNA leads to an accumulation of F-actin and to an increase in cell size. Cofilin-1 and ADF seem to play overlapping roles in cells, because the knockdown phenotype of either protein could be rescued by overexpression of the other one. Cofilin-1 and ADF knockdown cells also had defects in cell motility and cytokinesis, and these defects were most pronounced when both ADF and Cofilin-1 were depleted. Fluorescence recovery after photobleaching analysis and studies with an actin monomer-sequestering drug, latrunculin-A, demonstrated that these phenotypes arose from diminished actin filament depolymerization rates. These data suggest that mammalian ADF and Cofilin-1 promote cytoskeletal dynamics by depolymerizing actin filaments and that this activity is critical for several processes such as cytokinesis and cell motility.
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structural conservation between the actin monomer binding sites of twinfilin and actin depolymerizing factor adf Cofilin
Journal of Biological Chemistry, 2002Co-Authors: Ville O Paavilainen, Pauli J Ojala, M C Merckel, Sandra Falck, Ehmke Pohl, Matthias Wilmanns, Pekka LappalainenAbstract:Abstract Twinfilin is an evolutionarily conserved actin monomer-binding protein that regulates cytoskeletal dynamics in organisms from yeast to mammals. It is composed of two actin-depolymerization factor homology (ADF-H) domains that show ∼20% sequence identity to ADF/Cofilin proteins. In contrast to ADF/Cofilins, which bind both G-actin and F-actin and promote filament depolymerization, twinfilin interacts only with G-actin. To elucidate the molecular mechanisms of twinfilin-actin monomer interaction, we determined the crystal structure of the N-terminal ADF-H domain of twinfilin and mapped its actin-binding site by site-directed mutagenesis. This domain has similar overall structure to ADF/Cofilins, and the regions important for actin monomer binding in ADF/Cofilins are especially well conserved in twinfilin. Mutagenesis studies show that the N-terminal ADF-H domain of twinfilin and ADF/Cofilins also interact with actin monomers through similar interfaces, although the binding surface is slightly extended in twinfilin. In contrast, the regions important for actin-filament interactions in ADF/Cofilins are structurally different in twinfilin. This explains the differences in actin-interactions (monomer versus filament binding) between twinfilin and ADF/Cofilins. Taken together, our data show that the ADF-H domain is a structurally conserved actin-binding motif and that relatively small structural differences at the actin interfaces of this domain are responsible for the functional variation between the different classes of ADF-H domain proteins.
James R Bamburg - One of the best experts on this subject based on the ideXlab platform.
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adf Cofilin regulates actomyosin assembly through competitive inhibition of myosin ii binding to f actin
Developmental Cell, 2012Co-Authors: Oneil Wiggan, Alisa E Shaw, Jennifer G Deluca, James R BamburgAbstract:The contractile actin cortex is important for diverse fundamental cell processes, but little is known about how the assembly of F-actin and myosin II motors is regulated. We report that depletion of actin depolymerizing factor (ADF)/Cofilin proteins in human cells causes increased contractile cortical actomyosin assembly. Remarkably, our data reveal that the major cellular defects resulting from ADF/Cofilin depletion, including cortical F-actin accumulation, were largely due to excessive myosin II activity. We identify that ADF/Cofilins from unicellular organisms to humans share a conserved activity to inhibit myosin II binding to F-actin, indicating a mechanistic rationale for our cellular results. Our study establishes an essential requirement for ADF/Cofilin proteins in the control of normal cortical contractility and in processes such as mitotic karyokinesis. We propose that ADF/Cofilin proteins are necessary for controlling actomyosin assembly and intracellular contractile force generation, a function of equal physiological importance to their established roles in mediating F-actin turnover.
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redundant and non redundant functions of actin depolymerizing factor adf and Cofilin in metastasis review
2011Co-Authors: Lubna H Tahtamouni, James R BamburgAbstract:Tumor cell motility is the hallmark of invasion and an essential step in metastasis. Cellular changes that occur during the progression of cancer affect proteins that drive actin dynamics; these changes modulate cell cycle progression and lead to more invasive cancers. Actin depolymerizing factor (ADF)/Cofilins (actin dynamizing proteins) and their regulatory proteins are involved in the initiation of early steps in cell motility. ADF/Cofilins play important roles in various stages of cancer progression including cell polarization and polarized migration, escape from apoptosis, and secretion of metalloproteases, all of which are important in metastasis. Vertebrates express ADF, Cofilin-1 and Cofilin-2, and even though ADF and Cofilin have many qualitatively similar biochemical properties, they differ quantitatively in actin interaction and in some types of regulation and, thus, are not functionally identical. This review compares the activities of these two proteins with respect to how they may function during tumor cell invasion. Understanding the molecular pathways of tumor invasion will provide new diagnostic approaches and targets for the treatment of metastatic cancer. ﺮﺒﺘﻌﺗ
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activated actin depolymerizing factor Cofilin sequesters phosphorylated microtubule associated protein during the assembly of alzheimer like neuritic cytoskeletal striations
The Journal of Neuroscience, 2009Co-Authors: Ineka T Whiteman, Othon L Gervasio, Karen M Cullen, Erica V Jeong, Paul K Witting, Shane T Antao, Laurie S Minamide, James R Bamburg, Gilles J Guillemin, Claire GoldsburyAbstract:In Alzheimer9s disease (AD), rod-like Cofilin aggregates (Cofilin–actin rods) and thread-like inclusions containing phosphorylated microtubule-associated protein (pMAP) tau form in the brain (neuropil threads), and the extent of their presence correlates with cognitive decline and disease progression. The assembly mechanism of these respective pathological lesions and the relationship between them is poorly understood, yet vital to understanding the causes of sporadic AD. We demonstrate that, during mitochondrial inhibition, activated actin-depolymerizing factor (ADF)/Cofilin assemble into rods along processes of cultured primary neurons that recruit pMAP/tau and mimic neuropil threads. Fluorescence resonance energy transfer analysis revealed colocalization of Cofilin-GFP (green fluorescent protein) and pMAP in rods, suggesting their close proximity within a cytoskeletal inclusion complex. The relationship between pMAP and Cofilin–actin rods was further investigated using actin-modifying drugs and small interfering RNA knockdown of ADF/Cofilin in primary neurons. The results suggest that activation of ADF/Cofilin and generation of Cofilin–actin rods is required for the subsequent recruitment of pMAP into the inclusions. Additionally, we were able to induce the formation of pMAP-positive ADF/Cofilin rods by exposing cells to exogenous amyloid-β (Aβ) peptides. These results reveal a common pathway for pMAP and Cofilin accumulation in neuronal processes. The requirement of activated ADF/Cofilin for the sequestration of pMAP suggests that neuropil thread structures in the AD brain may be initiated by elevated Cofilin activation and F-actin bundling that can be caused by oxidative stress, mitochondrial dysfunction, or Aβ peptides, all suspected initiators of synaptic loss and neurodegeneration in AD.
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Activated Actin-Depolymerizing Factor/Cofilin Sequesters Phosphorylated Microtubule-Associated Protein during the Assembly of Alzheimer-Like Neuritic Cytoskeletal Striations
The Journal of Neuroscience, 2009Co-Authors: Ineka T Whiteman, Othon L Gervasio, Karen M Cullen, Erica V Jeong, Paul K Witting, Shane T Antao, Laurie S Minamide, James R Bamburg, Gilles J Guillemin, Claire GoldsburyAbstract:In Alzheimer's disease (AD), rod-like Cofilin aggregates (Cofilin–actin rods) and thread-like inclusions containing phosphorylated microtubule-associated protein (pMAP) tau form in the brain (neuropil threads), and the extent of their presence correlates with cognitive decline and disease progression. The assembly mechanism of these respective pathological lesions and the relationship between them is poorly understood, yet vital to understanding the causes of sporadic AD. We demonstrate that, during mitochondrial inhibition, activated actin-depolymerizing factor (ADF)/Cofilin assemble into rods along processes of cultured primary neurons that recruit pMAP/tau and mimic neuropil threads. Fluorescence resonance energy transfer analysis revealed colocalization of Cofilin-GFP (green fluorescent protein) and pMAP in rods, suggesting their close proximity within a cytoskeletal inclusion complex. The relationship between pMAP and Cofilin–actin rods was further investigated using actin-modifying drugs and small interfering RNA knockdown of ADF/Cofilin in primary neurons. The results suggest that activation of ADF/Cofilin and generation of Cofilin–actin rods is required for the subsequent recruitment of pMAP into the inclusions. Additionally, we were able to induce the formation of pMAP-positive ADF/Cofilin rods by exposing cells to exogenous amyloid-β (Aβ) peptides. These results reveal a common pathway for pMAP and Cofilin accumulation in neuronal processes. The requirement of activated ADF/Cofilin for the sequestration of pMAP suggests that neuropil thread structures in the AD brain may be initiated by elevated Cofilin activation and F-actin bundling that can be caused by oxidative stress, mitochondrial dysfunction, or Aβ peptides, all suspected initiators of synaptic loss and neurodegeneration in AD.
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αvβ3 integrin and Cofilin modulate K1735 melanoma cell invasion
Experimental cell research, 2005Co-Authors: Dongmin Dang, James R Bamburg, Daniel M. RamosAbstract:Cytoskeletal reorganization is partially mediated through Cofilin, an actin assembly regulatory protein. Cofilin activity is modulated by reversible phosphorylation at Ser3. In this study, using K1735 murine melanoma cells, we examined the relationship between beta3-integrin expression, phosphorylation of Cofilin, and metalloproteinase production. The levels of phosphorylated Cofilin were 10-fold higher in cells expressing alphavbeta3 than in alphavbeta3-negative cells when plated on vitronectin for 30 min. However, by 60 min, phosphorylation of Cofilin was greater in the beta3-negative cells. Expression of the wild type (WT) or non-phosphorylatable Cofilin (A3 mutant) increased melanoma cell migration on vitronectin and invasion through a reconstituted basement membrane. Expression of a pseudophosphorylated, poorly active Cofilin (E3 mutant) reduced cell motility. Expression of active Cofilin accelerated the phosphorylation of FAK at Y397 and at Y576, strongly implicating Cofilin as a mediator of cell signaling. The expression of MT1-MMP and MMP2 was also increased by expression of wild type or A3 Cofilin. A 50% reduction of both enzymes was observed by the expression of the E3 Cofilin. Overexpression of non-phosphorylatable Cofilin was sufficient to induce the expression of MT1-MMP and MMP2 in the beta3-negative M2Tbeta3 cells. Interestingly, the invasion of M2Tbeta3 cells could be sustained by overexpression of Cofilin A3. These results suggest that the integrin alphavbeta3 and Cofilin together regulate K1735 melanoma cell invasion.
Elena E. Grintsevich - One of the best experts on this subject based on the ideXlab platform.
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F-actin dismantling through a redox-driven synergy between Mical and Cofilin
Nature Cell Biology, 2016Co-Authors: Elena E. Grintsevich, Jonathan R. Terman, Ruei Jiun Hung, Hunkar Gizem Yesilyurt, Shannon K. Rich, Emil ReislerAbstract:Grintsevich et al. discover that the redox enzyme Mical oxidizes F-actin to promote binding of the F-actin-severing protein Cofilin, and that the synergy of Mical and Cofilin is necessary and sufficient for F-actin disassembly in Drosophila . Numerous cellular functions depend on actin filament (F-actin) disassembly. The best-characterized disassembly proteins, the ADF (actin-depolymerizing factor)/Cofilins (encoded by the twinstar gene in Drosophila ), sever filaments and recycle monomers to promote actin assembly. Cofilin is also a relatively weak actin disassembler, posing questions about mechanisms of cellular F-actin destabilization. Here we uncover a key link to targeted F-actin disassembly by finding that F-actin is efficiently dismantled through a post-translational-mediated synergism between Cofilin and the actin-oxidizing enzyme Mical. We find that Mical-mediated oxidation of actin improves Cofilin binding to filaments, where their combined effect dramatically accelerates F-actin disassembly compared with either effector alone. This synergism is also necessary and sufficient for F-actin disassembly in vivo , magnifying the effects of both Mical and Cofilin on cellular remodelling, axon guidance and Semaphorin–Plexin repulsion. Mical and Cofilin, therefore, form a redox-dependent synergistic pair that promotes F-actin instability by rapidly dismantling F-actin and generating post-translationally modified actin that has altered assembly properties.
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f actin dismantling through a redox driven synergy between mical and Cofilin
Nature Cell Biology, 2016Co-Authors: Elena E. Grintsevich, Jonathan R. Terman, Ruei Jiun Hung, Hunkar Gizem Yesilyurt, Shannon K. Rich, Emil ReislerAbstract:Numerous cellular functions depend on actin filament (F-actin) disassembly. The best-characterized disassembly proteins, the ADF (actin-depolymerizing factor)/Cofilins (encoded by the twinstar gene in Drosophila), sever filaments and recycle monomers to promote actin assembly. Cofilin is also a relatively weak actin disassembler, posing questions about mechanisms of cellular F-actin destabilization. Here we uncover a key link to targeted F-actin disassembly by finding that F-actin is efficiently dismantled through a post-translational-mediated synergism between Cofilin and the actin-oxidizing enzyme Mical. We find that Mical-mediated oxidation of actin improves Cofilin binding to filaments, where their combined effect dramatically accelerates F-actin disassembly compared with either effector alone. This synergism is also necessary and sufficient for F-actin disassembly in vivo, magnifying the effects of both Mical and Cofilin on cellular remodelling, axon guidance and Semaphorin-Plexin repulsion. Mical and Cofilin, therefore, form a redox-dependent synergistic pair that promotes F-actin instability by rapidly dismantling F-actin and generating post-translationally modified actin that has altered assembly properties.
David G Drubin - One of the best experts on this subject based on the ideXlab platform.
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Aip1p Interacts with Cofilin to Disassemble Actin Filaments
The Journal of cell biology, 1999Co-Authors: Avital A. Rodal, Pekka Lappalainen, David G Drubin, Jonathan Wendell Tetreault, David C. AmbergAbstract:Actin interacting protein 1 (Aip1) is a conserved component of the actin cytoskeleton first identified in a two-hybrid screen against yeast actin. Here, we report that Aip1p also interacts with the ubiquitous actin depolymerizing factor Cofilin. A two-hybrid–based approach using Cofilin and actin mutants identified residues necessary for the interaction of actin, Cofilin, and Aip1p in an apparent ternary complex. Deletion of the AIP1 gene is lethal in combination with Cofilin mutants or act1-159 , an actin mutation that slows the rate of actin filament disassembly in vivo. Aip1p localizes to cortical actin patches in yeast cells, and this localization is disrupted by specific actin and Cofilin mutations. Further, Aip1p is required to restrict Cofilin localization to cortical patches. Finally, biochemical analyses show that Aip1p causes net depolymerization of actin filaments only in the presence of Cofilin and that Cofilin enhances binding of Aip1p to actin filaments. We conclude that Aip1p is a Cofilin-associated protein that enhances the filament disassembly activity of Cofilin and restricts Cofilin localization to cortical actin patches.
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essential functions and actin binding surfaces of yeast Cofilin revealed by systematic mutagenesis
The EMBO Journal, 1997Co-Authors: Pekka Lappalainen, Elena V Fedorov, Alexander A Fedorov, Steven C Almo, David G DrubinAbstract:Cofilin stimulates actin filament turnover in vivo. The phenotypes of twenty yeast Cofilin mutants generated by systematic mutagenesis were determined. Ten grew as well as the wild type and showed no cytoskeleton defects, seven were recessive-lethal and three were conditional-lethal and caused severe actin organization defects. Biochemical characterization of interactions between nine mutant yeast Cofilins and yeast actin provided evidence that F-actin binding and depolymerization are essential Cofilin functions. Locating the mutated residues on the yeast Cofilin molecular structure allowed several important conclusions to be drawn. First, residues required for actin monomer binding are proximal to each other. Secondly, additional residues are required for interactions with actin filaments; these residues might bind an adjacent subunit in the actin filament. Thirdly, despite striking structural similarity, Cofilin interacts with actin in a different manner from gelsolin segment-1. Fourthly, a previously unrecognized Cofilin function or interaction is suggested by identification of spatially proximal residues important for Cofilin function in vivo, but not for actin interactions in vitro. Finally, mutation of the Cofilin N-terminus suggests that its sequence is conserved because of its critical role in actin interactions, not because it is sometimes a target for protein kinases.
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Cofilin is an essential component of the yeast cortical cytoskeleton.
The Journal of cell biology, 1993Co-Authors: A L Moon, Paul A. Janmey, K A Louie, David G DrubinAbstract:We have biochemically identified the Saccharomyces cerevisiae homologue of the mammalian actin binding protein Cofilin. Cofilin and related proteins isolated from diverse organisms are low molecular weight proteins (15-20 kD) that possess several activities in vitro. All bind to monomeric actin and sever filaments, and some can stably associate with filaments. In this study, we demonstrate using viscosity, sedimentation, and actin assembly rate assays that yeast Cofilin (16 kD) possesses all of these properties. Cloning and sequencing of the S. cerevisiae Cofilin gene (COF1) revealed that yeast Cofilin is 41% identical in amino acid sequence to mammalian Cofilin and, surprisingly, has homology to a protein outside the family of Cofilin-like proteins. The NH2-terminal 16kD of Abp1p, a 65-kD yeast protein identified by its ability to bind to actin filaments, is 23% identical to yeast Cofilin. Immunofluorescence experiments showed that, like Abp1p, Cofilin is associated with the membrane actin cytoskeleton. A complete disruption of the COF1 gene was created in diploid cells. Sporulation and tetrad analysis revealed that yeast Cofilin has an essential function in vivo. Although Abp1p shares sequence similarity with Cofilin and has the same distribution as Cofilin in the cell, multiple copies of the ABP1 gene cannot compensate for the loss of Cofilin. Thus, Cofilin and Abp1p are structurally related but functionally distinct components of the yeast membrane cytoskeleton.