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Walker C, Chandrasekaran A, Mansour D, Graham K, Torres A, Wang L, Lafer EM, Rangamani P, Stachowiak JC. Liquid-like condensates that bind actin drive filament polymerization and bundling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.04.592527. [PMID: 38826190 PMCID: PMC11142076 DOI: 10.1101/2024.05.04.592527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Liquid-like protein condensates perform diverse physiological functions. Previous work showed that VASP, a processive actin polymerase, forms condensates that polymerize and bundle actin. To minimize their curvature, filaments accumulated at the inner condensate surface, ultimately deforming the condensate into a rod-like shape, filled with a bundle of parallel filaments. Here we show that this behavior does not require proteins with specific polymerase activity. Specifically, we found that condensates composed of Lamellipodin, a protein that binds actin but is not an actin polymerase, were also capable of polymerizing and bundling actin filaments. To probe the minimum requirements for condensate-mediated actin bundling, we developed an agent-based computational model. Guided by its predictions, we hypothesized that any condensate-forming protein that binds actin could bundle filaments through multivalent crosslinking. To test this idea, we added an actin-binding motif to Eps15, a condensate-forming protein that does not normally bind actin. The resulting chimera formed condensates that drove efficient actin polymerization and bundling. Collectively, these findings broaden the family of proteins that could organize cytoskeletal filaments to include any actin-binding protein that participates in protein condensation.
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Affiliation(s)
- Caleb Walker
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
| | - Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Daniel Mansour
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Kristin Graham
- Cell and Molecular Biology, The University of Texas at Austin, Austin, TX, United States
| | - Andrea Torres
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
| | - Liping Wang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Eileen M. Lafer
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, United States
| | - Jeanne C. Stachowiak
- Biomedical Engineering, The University of Texas at Austin, Austin, TX, United States
- Chemical Engineering, The University of Texas at Austin, Austin, TX, United States
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2
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Phua DY, Sun X, Alushin GM. Force-activated zyxin assemblies coordinate actin nucleation and crosslinking to orchestrate stress fiber repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.17.594765. [PMID: 38798419 PMCID: PMC11118565 DOI: 10.1101/2024.05.17.594765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
As the cytoskeleton sustains cell and tissue forces, it incurs physical damage that must be repaired to maintain mechanical homeostasis. The LIM-domain protein zyxin detects force-induced ruptures in actin-myosin stress fibers, coordinating downstream repair factors to restore stress fiber integrity through unclear mechanisms. Here, we reconstitute stress fiber repair with purified proteins, uncovering detailed links between zyxin's force-regulated binding interactions and cytoskeletal dynamics. In addition to binding individual tensed actin filaments (F-actin), zyxin's LIM domains form force-dependent assemblies that bridge broken filament fragments. Zyxin assemblies engage repair factors through multi-valent interactions, coordinating nucleation of new F-actin by VASP and its crosslinking into aligned bundles by ɑ-actinin. Through these combined activities, stress fiber repair initiates within the cores of micron-scale damage sites in cells, explaining how these F-actin depleted regions are rapidly restored. Thus, zyxin's force-dependent organization of actin repair machinery inherently operates at the network scale to maintain cytoskeletal integrity.
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Affiliation(s)
- Donovan Y.Z. Phua
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Xiaoyu Sun
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
| | - Gregory M. Alushin
- Laboratory of Structural Biophysics and Mechanobiology, The Rockefeller University, New York, NY, USA
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3
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Aydin F, Katkar HH, Morganthaler A, Harker AJ, Kovar DR, Voth GA. Prediction of the essential intermolecular contacts for side-binding of VASP on F-actin. Cytoskeleton (Hoboken) 2024. [PMID: 38647032 DOI: 10.1002/cm.21864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 04/08/2024] [Accepted: 04/09/2024] [Indexed: 04/25/2024]
Abstract
Vasodilator-stimulated phosphoprotein (VASP) family proteins play a crucial role in mediating the actin network architecture in the cytoskeleton. The Ena/VASP homology 2 (EVH2) domain in each of the four identical arms of the tetrameric VASP consists of a loading poly-Pro region, a G-actin-binding domain (GAB), and an F-actin-binding domain (FAB). Together, the poly-Pro, GAB, and FAB domains allow VASP to bind to sides of actin filaments in a bundle, and recruit profilin-G-actin to processively elongate the filaments. The atomic resolution structure of the ternary complex, consisting of the loading poly-Pro region and GAB domain of VASP with profilin-actin, has been solved over a decade ago; however, a detailed structure of the FAB-F-actin complex has not been resolved to date. Experimental insights, based on homology of the FAB domain with the C region of WASP, have been used to hypothesize that the FAB domain binds to the cleft between subdomains 1 and 3 of F-actin. Here, in order to develop our understanding of the VASP-actin complex, we first augment known structural information about the GAB domain binding to actin with the missing FAB domain-actin structure, which we predict using homology modeling and docking simulations. In earlier work, we used mutagenesis and kinetic modeling to study the role of domain-level binding-unbinding kinetics of Ena/VASP on actin filaments in a bundle, specifically on the side of actin filaments. We further look at the nature of the side-binding of the FAB domain of VASP at the atomistic level using our predicted structure, and tabulate effective mutation sites on the FAB domain that would disrupt the VASP-actin complex. We test the binding affinity of Ena with mutated FAB domain using total internal reflection fluorescence microscopy experiments. The binding affinity of VASP is affected significantly for the mutant, providing additional support for our predicted structure.
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Affiliation(s)
- Fikret Aydin
- Department of Chemistry, The James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
| | - Harshwardhan H Katkar
- Department of Chemistry, The James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
| | - Alisha Morganthaler
- Department of Biochemistry and Molecular Biology and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, USA
| | - Alyssa J Harker
- Department of Biochemistry and Molecular Biology and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, USA
| | - David R Kovar
- Department of Biochemistry and Molecular Biology and Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois, USA
| | - Gregory A Voth
- Department of Chemistry, The James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
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4
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Chandrasekaran A, Graham K, Stachowiak JC, Rangamani P. Kinetic trapping organizes actin filaments within liquid-like protein droplets. Nat Commun 2024; 15:3139. [PMID: 38605007 PMCID: PMC11009352 DOI: 10.1038/s41467-024-46726-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 03/07/2024] [Indexed: 04/13/2024] Open
Abstract
Several actin-binding proteins (ABPs) phase separate to form condensates capable of curating the actin network shapes. Here, we use computational modeling to understand the principles of actin network organization within VASP condensate droplets. Our simulations reveal that the different actin shapes, namely shells, rings, and mixture states are highly dependent on the kinetics of VASP-actin interactions, suggesting that they arise from kinetic trapping. Specifically, we show that reducing the residence time of VASP on actin filaments reduces degree of bundling, thereby promoting assembly of shells rather than rings. We validate the model predictions experimentally using a VASP-mutant with decreased bundling capability. Finally, we investigate the ring opening within deformed droplets and found that the sphere-to-ellipsoid transition is favored under a wide range of filament lengths while the ellipsoid-to-rod transition is only permitted when filaments have a specific range of lengths. Our findings highlight key mechanisms of actin organization within phase-separated ABPs.
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Affiliation(s)
- Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, 92093-0411, USA
| | - Kristin Graham
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, 92093-0411, USA.
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5
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Charles-Orszag A, Petek-Seoane NA, Mullins RD. Archaeal actins and the origin of a multi-functional cytoskeleton. J Bacteriol 2024; 206:e0034823. [PMID: 38391233 PMCID: PMC10955848 DOI: 10.1128/jb.00348-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2024] Open
Abstract
Actin and actin-like proteins form filamentous polymers that carry out important cellular functions in all domains of life. In this review, we sketch a map of the function and regulation of actin-like proteins across bacteria, archaea, and eukarya, marking some of the terra incognita that remain in this landscape. We focus particular attention on archaea because mapping the structure and function of cytoskeletal systems across this domain promises to help us understand the evolutionary relationship between the (mostly) mono-functional actin-like filaments found in bacteria and the multi-functional actin cytoskeletons that characterize eukaryotic cells.
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Affiliation(s)
- Arthur Charles-Orszag
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, USA
| | - Natalie A. Petek-Seoane
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, USA
| | - R. Dyche Mullins
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, USA
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6
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Graham K, Chandrasekaran A, Wang L, Yang N, Lafer EM, Rangamani P, Stachowiak JC. Liquid-like condensates mediate competition between actin branching and bundling. Proc Natl Acad Sci U S A 2024; 121:e2309152121. [PMID: 38207079 PMCID: PMC10801869 DOI: 10.1073/pnas.2309152121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 11/21/2023] [Indexed: 01/13/2024] Open
Abstract
Cellular remodeling of actin networks underlies cell motility during key morphological events, from embryogenesis to metastasis. In these transformations, there is an inherent competition between actin branching and bundling, because steric clashes among branches create a mechanical barrier to bundling. Recently, liquid-like condensates consisting purely of proteins involved in either branching or bundling of the cytoskeleton have been found to catalyze their respective functions. Yet in the cell, proteins that drive branching and bundling are present simultaneously. In this complex environment, which factors determine whether a condensate drives filaments to branch or become bundled? To answer this question, we added the branched actin nucleator, Arp2/3, to condensates composed of VASP, an actin bundling protein. At low actin to VASP ratios, branching activity, mediated by Arp2/3, robustly inhibited VASP-mediated bundling of filaments, in agreement with agent-based simulations. In contrast, as the actin to VASP ratio increased, addition of Arp2/3 led to formation of aster-shaped structures, in which bundled filaments emerged from a branched actin core, analogous to filopodia emerging from a branched lamellipodial network. These results demonstrate that multi-component, liquid-like condensates can modulate the inherent competition between bundled and branched actin morphologies, leading to organized, higher-order structures, similar to those found in motile cells.
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Affiliation(s)
- Kristin Graham
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX78712
| | - Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA92093
| | - Liping Wang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX78229
| | - Noel Yang
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX78712
| | - Eileen M. Lafer
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX78229
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA92093
| | - Jeanne C. Stachowiak
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX78712
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX78712
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7
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McCormick LE, Suarez C, Herring LE, Cannon KS, Kovar DR, Brown NG, Gupton SL. Multi-monoubiquitylation controls VASP-mediated actin dynamics. J Cell Sci 2024; 137:jcs261527. [PMID: 38277158 PMCID: PMC10917064 DOI: 10.1242/jcs.261527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 12/13/2023] [Indexed: 01/13/2024] Open
Abstract
The actin cytoskeleton performs multiple cellular functions, and as such, actin polymerization must be tightly regulated. We previously demonstrated that reversible, non-degradative ubiquitylation regulates the function of the actin polymerase VASP in developing neurons. However, the underlying mechanism of how ubiquitylation impacts VASP activity was unknown. Here, we show that mimicking multi-monoubiquitylation of VASP at K240 and K286 negatively regulates VASP interactions with actin. Using in vitro biochemical assays, we demonstrate the reduced ability of multi-monoubiquitylated VASP to bind, bundle, and elongate actin filaments. However, multi-monoubiquitylated VASP maintained the ability to bind and protect barbed ends from capping protein. Finally, we demonstrate the electroporation of recombinant multi-monoubiquitylated VASP protein altered cell spreading morphology. Collectively, these results suggest a mechanism in which ubiquitylation controls VASP-mediated actin dynamics.
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Affiliation(s)
- Laura E. McCormick
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Laura E. Herring
- Michael Hooker Proteomics Core, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kevin S. Cannon
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - David R. Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
| | - Nicholas G. Brown
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stephanie L. Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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8
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Mann N, Hill J, Wang K, Hughes RM. OptoProfilin: A Single Component Biosensor of Applied Cellular Stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.04.560945. [PMID: 37873064 PMCID: PMC10592976 DOI: 10.1101/2023.10.04.560945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
The actin cytoskeleton is a biosensor of cellular stress and a potential prognosticator of human disease. In particular, aberrant cytoskeletal structures such as cofilin-actin rods and stress granules formed in response to energetic and oxidative stress are closely linked to neurodegenerative diseases such as Alzheimer's, Parkinson's, and ALS. Whether these cytoskeletal phenomena can be harnessed for the development of biosensors for cytoskeletal dysfunction and, by extension, neurodegenerative disease progression, remains an open question. In this work, we describe the design and development of an optogenetic iteration of profilin, an actin monomer binding protein with critical functions in cytoskeletal dynamics. We demonstrate that this optically activated profilin ('OptoProfilin') can act as an optically triggered biosensor of applied cellular stress in select immortalized cell lines. Notably, OptoProfilin is a single component biosensor, likely increasing its utility for experimentalists. While a large body of preexisting work closely links profilin activity with cellular stress and neurodegenerative disease, this, to our knowledge, is the first example of profilin as an optogenetic biosensor of stress-induced changes in the cytoskeleton.
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Affiliation(s)
- Noah Mann
- Department of Chemistry, East Carolina University, Greenville, North Carolina, United States
| | - Jahiem Hill
- Department of Chemistry, East Carolina University, Greenville, North Carolina, United States
| | - Kenneth Wang
- Department of Chemistry, Davidson College, Davidson, North Carolina, United States
| | - Robert M. Hughes
- Department of Chemistry, East Carolina University, Greenville, North Carolina, United States
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9
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Suarez C, Winkelman JD, Harker AJ, Ye HJ, McCall PM, Morganthaler AN, Gardel ML, Kovar DR. Reconstitution of the transition from a lamellipodia- to filopodia-like actin network with purified proteins. Eur J Cell Biol 2023; 102:151367. [PMID: 37890285 DOI: 10.1016/j.ejcb.2023.151367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 09/29/2023] [Accepted: 10/19/2023] [Indexed: 10/29/2023] Open
Abstract
How cells utilize complex mixtures of actin binding proteins to assemble and maintain functionally diverse actin filament networks with distinct architectures and dynamics within a common cytoplasm is a longstanding question in cell biology. A compelling example of complex and specialized actin structures in cells are filopodia which sense extracellular chemical and mechanical signals to help steer motile cells. Filopodia have distinct actin architecture, composed of long, parallel actin filaments bundled by fascin, which form finger-like membrane protrusions. Elongation of the parallel actin filaments in filopodia can be mediated by two processive actin filament elongation factors, formin and Ena/VASP, which localize to the tips of filopodia. There remains debate as to how the architecture of filopodia are generated, with one hypothesis proposing that filopodia are generated from the lamellipodia, which consists of densely packed, branched actin filaments nucleated by Arp2/3 complex and kept short by capping protein. It remains unclear if different actin filament elongation factors are necessary and sufficient to facilitate the emergence of filopodia with diverse characteristics from a highly dense network of short-branched capped filaments. To address this question, we combined bead motility and micropatterning biomimetic assays with multi-color Total Internal Reflection Fluorescence microscopy imaging, to successfully reconstitute the formation of filopodia-like networks (FLN) from densely-branched lamellipodia-like networks (LLN) with eight purified proteins (actin, profilin, Arp2/3 complex, Wasp pWA, fascin, capping protein, VASP and formin mDia2). Saturating capping protein concentrations inhibit FLN assembly, but the addition of either formin or Ena/VASP differentially rescues the formation of FLN from LLN. Specifically, we found that formin/mDia2-generated FLNs are relatively long and lack capping protein, whereas VASP-generated FLNs are comparatively short and contain capping protein, indicating that the actin elongation factor can affect the architecture and composition of FLN emerging from LLN. Our biomimetic reconstitution systems reveal that formin or VASP are necessary and sufficient to induce the transition from a LLN to a FLN, and establish robust in vitro platforms to investigate FLN assembly mechanisms.
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Affiliation(s)
- Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA.
| | - Jonathan D Winkelman
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Alyssa J Harker
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Hannah J Ye
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Patrick M McCall
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA
| | - Alisha N Morganthaler
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Margaret L Gardel
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA; Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA; Pritzker School for Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
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10
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Valdivia A, Avalos AM, Leyton L. Thy-1 (CD90)-regulated cell adhesion and migration of mesenchymal cells: insights into adhesomes, mechanical forces, and signaling pathways. Front Cell Dev Biol 2023; 11:1221306. [PMID: 38099295 PMCID: PMC10720913 DOI: 10.3389/fcell.2023.1221306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/25/2023] [Indexed: 12/17/2023] Open
Abstract
Cell adhesion and migration depend on the assembly and disassembly of adhesive structures known as focal adhesions. Cells adhere to the extracellular matrix (ECM) and form these structures via receptors, such as integrins and syndecans, which initiate signal transduction pathways that bridge the ECM to the cytoskeleton, thus governing adhesion and migration processes. Integrins bind to the ECM and soluble or cell surface ligands to form integrin adhesion complexes (IAC), whose composition depends on the cellular context and cell type. Proteomic analyses of these IACs led to the curation of the term adhesome, which is a complex molecular network containing hundreds of proteins involved in signaling, adhesion, and cell movement. One of the hallmarks of these IACs is to sense mechanical cues that arise due to ECM rigidity, as well as the tension exerted by cell-cell interactions, and transduce this force by modifying the actin cytoskeleton to regulate cell migration. Among the integrin/syndecan cell surface ligands, we have described Thy-1 (CD90), a GPI-anchored protein that possesses binding domains for each of these receptors and, upon engaging them, stimulates cell adhesion and migration. In this review, we examine what is currently known about adhesomes, revise how mechanical forces have changed our view on the regulation of cell migration, and, in this context, discuss how we have contributed to the understanding of signaling mechanisms that control cell adhesion and migration.
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Affiliation(s)
- Alejandra Valdivia
- Division of Cardiology, Department of Medicine, Emory University, Atlanta, GA, United States
| | - Ana María Avalos
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile
| | - Lisette Leyton
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Center for Studies on Exercise, Metabolism and Cancer (CEMC), Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile
- Advanced Center for Chronic Diseases (ACCDiS), Faculty of Chemical and Pharmaceutical Sciences & Faculty of Medicine, Universidad de Chile, Santiago, Chile
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11
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Rahikainen R, Vester SK, Turkki P, Janosko CP, Deiters A, Hytönen VP, Howarth M. Visible Light-Induced Specific Protein Reaction Delineates Early Stages of Cell Adhesion. J Am Chem Soc 2023; 145:24459-24465. [PMID: 38104267 PMCID: PMC10655181 DOI: 10.1021/jacs.3c07827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 12/19/2023]
Abstract
Light is well-established for control of bond breakage but not for control of specific bond formation in complex environments. We previously engineered the diffusion-limited reactivity of the SpyTag003 peptide with its protein partner SpyCatcher003 through spontaneous isopeptide bond formation. This system enables precise and irreversible assembly of biological building blocks with applications from biomaterials to vaccines. Here we establish a system for the rapid control of this amide bond formation with visible light. We have generated a caged SpyCatcher003, which allows light triggering of covalent bond formation to SpyTag003 in mammalian cells. Photocaging is achieved through site-specific incorporation of an unnatural coumarin-lysine at the reactive site of SpyCatcher003. We showed a uniform specific reaction in cell lysate upon light activation. We then used the spatiotemporal precision of a 405 nm confocal laser for uncaging in seconds, probing the earliest events in mechanotransduction by talin, the key force sensor between the cytoskeleton and the extracellular matrix. Reconstituting talin induced rapid biphasic extension of lamellipodia, revealing the kinetics of talin-regulated cell spreading and polarization. Thereafter we determined the hierarchy of the recruitment of key components for cell adhesion. Precise control over site-specific protein reaction with visible light creates diverse opportunities for cell biology and nanoassembly.
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Affiliation(s)
- Rolle Rahikainen
- Faculty
of Medicine and Health Technology, Tampere
University, Arvo Ylpön katu 34, 33520 Tampere, Finland
- Fimlab
Laboratories, Biokatu 4, 33520 Tampere, Finland
| | - Susan K. Vester
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| | - Paula Turkki
- Faculty
of Medicine and Health Technology, Tampere
University, Arvo Ylpön katu 34, 33520 Tampere, Finland
- Fimlab
Laboratories, Biokatu 4, 33520 Tampere, Finland
| | - Chasity P. Janosko
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Alexander Deiters
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Vesa P. Hytönen
- Faculty
of Medicine and Health Technology, Tampere
University, Arvo Ylpön katu 34, 33520 Tampere, Finland
- Fimlab
Laboratories, Biokatu 4, 33520 Tampere, Finland
| | - Mark Howarth
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
- Department
of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, U.K.
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12
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Molina M, Way LE, Ren Z, Liao Q, Guerra B, Shields B, Wang X, Kim H. A framework to validate fluorescently labeled DNA-binding proteins for single-molecule experiments. CELL REPORTS METHODS 2023; 3:100614. [PMID: 37832544 PMCID: PMC10626211 DOI: 10.1016/j.crmeth.2023.100614] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 07/28/2023] [Accepted: 09/20/2023] [Indexed: 10/15/2023]
Abstract
Due to the enhanced labeling capability of maleimide-based fluorescent probes, lysine-cysteine-lysine (KCK) tags are frequently added to proteins for visualization. In this study, we employed an in vitro single-molecule DNA flow-stretching assay as a sensitive way to assess the impact of the KCK tag on the property of DNA-binding proteins. Using Bacillus subtilis ParB as an example, we show that, although no noticeable changes were detected by in vivo fluorescence imaging and chromatin immunoprecipitation (ChIP) assays, the KCK tag substantially altered ParB's DNA compaction rates and its response to nucleotide binding and to the presence of the specific sequence (parS) on the DNA. While it is typically assumed that short peptide tags minimally perturb protein function, our results urge researchers to carefully validate the use of tags for protein labeling. Our comprehensive analysis can be expanded and used as a guide to assess the impacts of other tags on DNA-binding proteins in single-molecule assays.
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Affiliation(s)
- Miranda Molina
- Biochemistry and Molecular Biology Program, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA; Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA
| | - Lindsey E Way
- Department of Biology, Indiana University, 1001 E 3(rd) St., Bloomington, IN 47405, USA
| | - Zhongqing Ren
- Department of Biology, Indiana University, 1001 E 3(rd) St., Bloomington, IN 47405, USA
| | - Qin Liao
- Department of Biology, Indiana University, 1001 E 3(rd) St., Bloomington, IN 47405, USA
| | - Bianca Guerra
- Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA
| | - Brandon Shields
- Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA
| | - Xindan Wang
- Department of Biology, Indiana University, 1001 E 3(rd) St., Bloomington, IN 47405, USA.
| | - HyeongJun Kim
- Biochemistry and Molecular Biology Program, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA; Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, TX 78539, USA.
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13
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Lambert C, Schmidt K, Karger M, Stadler M, Stradal TEB, Rottner K. Cytochalasans and Their Impact on Actin Filament Remodeling. Biomolecules 2023; 13:1247. [PMID: 37627312 PMCID: PMC10452583 DOI: 10.3390/biom13081247] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 07/28/2023] [Accepted: 08/06/2023] [Indexed: 08/27/2023] Open
Abstract
The eukaryotic actin cytoskeleton comprises the protein itself in its monomeric and filamentous forms, G- and F-actin, as well as multiple interaction partners (actin-binding proteins, ABPs). This gives rise to a temporally and spatially controlled, dynamic network, eliciting a plethora of motility-associated processes. To interfere with the complex inter- and intracellular interactions the actin cytoskeleton confers, small molecular inhibitors have been used, foremost of all to study the relevance of actin filaments and their turnover for various cellular processes. The most prominent inhibitors act by, e.g., sequestering monomers or by interfering with the polymerization of new filaments and the elongation of existing filaments. Among these inhibitors used as tool compounds are the cytochalasans, fungal secondary metabolites known for decades and exploited for their F-actin polymerization inhibitory capabilities. In spite of their application as tool compounds for decades, comprehensive data are lacking that explain (i) how the structural deviances of the more than 400 cytochalasans described to date influence their bioactivity mechanistically and (ii) how the intricate network of ABPs reacts (or adapts) to cytochalasan binding. This review thus aims to summarize the information available concerning the structural features of cytochalasans and their influence on the described activities on cell morphology and actin cytoskeleton organization in eukaryotic cells.
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Affiliation(s)
- Christopher Lambert
- Molecular Cell Biology Group, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Department of Microbial Drugs, Helmholtz Centre for Infection Research and German Centre for Infection Research (DZIF), Partner Site Hannover/Braunschweig, Inhoffenstrasse 7, 38124 Braunschweig, Germany;
| | - Katharina Schmidt
- Department of Cell Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Marius Karger
- Molecular Cell Biology Group, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
| | - Marc Stadler
- Department of Microbial Drugs, Helmholtz Centre for Infection Research and German Centre for Infection Research (DZIF), Partner Site Hannover/Braunschweig, Inhoffenstrasse 7, 38124 Braunschweig, Germany;
| | - Theresia E. B. Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Klemens Rottner
- Molecular Cell Biology Group, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Department of Cell Biology, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Braunschweig Integrated Centre of Systems Biology (BRICS), 38106 Braunschweig, Germany
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14
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McCormick LE, Suarez C, Herring LE, Cannon KS, Kovar DR, Brown NG, Gupton SL. Multi-monoubiquitination controls VASP-mediated actin dynamics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.16.549237. [PMID: 37503134 PMCID: PMC10370145 DOI: 10.1101/2023.07.16.549237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/29/2023]
Abstract
The actin cytoskeleton performs multiple cellular functions, and as such, actin polymerization must be tightly regulated. We previously demonstrated that reversible, non-degradative ubiquitination regulates the function of the actin polymerase VASP in developing neurons. However, the underlying mechanism of how ubiquitination impacts VASP activity was unknown. Here we show that mimicking multi-monoubiquitination of VASP at K240 and K286 negatively regulates VASP interactions with actin. Using in vitro biochemical assays, we demonstrate the reduced ability of multi-monoubiquitinated VASP to bind, bundle, and elongate actin filaments. However, multi-monoubiquitinated VASP maintained the ability to bind and protect barbed ends from capping protein. Lastly, we demonstrate the introduction of recombinant multi-monoubiquitinated VASP protein altered cell spreading morphology. Collectively, these results suggest a mechanism in which ubiquitination controls VASP-mediated actin dynamics.
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Affiliation(s)
- Laura E McCormick
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
| | - Laura E Herring
- Michael Hooker Proteomics Core, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Kevin S Cannon
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
| | - Nicholas G Brown
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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15
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Benz PM, Frömel T, Laban H, Zink J, Ulrich L, Groneberg D, Boon RA, Poley P, Renne T, de Wit C, Fleming I. Cardiovascular Functions of Ena/VASP Proteins: Past, Present and Beyond. Cells 2023; 12:1740. [PMID: 37443774 PMCID: PMC10340426 DOI: 10.3390/cells12131740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 06/18/2023] [Accepted: 06/21/2023] [Indexed: 07/15/2023] Open
Abstract
Actin binding proteins are of crucial importance for the spatiotemporal regulation of actin cytoskeletal dynamics, thereby mediating a tremendous range of cellular processes. Since their initial discovery more than 30 years ago, the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family has evolved as one of the most fascinating and versatile family of actin regulating proteins. The proteins directly enhance actin filament assembly, but they also organize higher order actin networks and link kinase signaling pathways to actin filament assembly. Thereby, Ena/VASP proteins regulate dynamic cellular processes ranging from membrane protrusions and trafficking, and cell-cell and cell-matrix adhesions, to the generation of mechanical tension and contractile force. Important insights have been gained into the physiological functions of Ena/VASP proteins in platelets, leukocytes, endothelial cells, smooth muscle cells and cardiomyocytes. In this review, we summarize the unique and redundant functions of Ena/VASP proteins in cardiovascular cells and discuss the underlying molecular mechanisms.
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Affiliation(s)
- Peter M. Benz
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
| | - Timo Frömel
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Hebatullah Laban
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Joana Zink
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Lea Ulrich
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Dieter Groneberg
- Institute of Physiology I, University of Würzburg, 97070 Würzburg, Germany
| | - Reinier A. Boon
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
- Cardiopulmonary Institute, 60596 Frankfurt am Main, Germany
- Centre of Molecular Medicine, Institute of Cardiovascular Regeneration, Goethe-University, 60596 Frankfurt am Main, Germany
- Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Centre, 1081 HZ Amsterdam, The Netherlands
| | - Philip Poley
- Institut für Physiologie, Universität zu Lübeck, 23562 Lübeck, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Hamburg/Kiel/Lübeck, 23562 Lübeck, Germany
| | - Thomas Renne
- Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
- Center for Thrombosis and Hemostasis (CTH), Johannes Gutenberg University Medical Center, 55131 Mainz, Germany
- Irish Centre for Vascular Biology, School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland, D02 VN51 Dublin, Ireland
| | - Cor de Wit
- Institut für Physiologie, Universität zu Lübeck, 23562 Lübeck, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Hamburg/Kiel/Lübeck, 23562 Lübeck, Germany
| | - Ingrid Fleming
- Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
- German Centre of Cardiovascular Research (DZHK), Partner Site Rhein-Main, 60596 Frankfurt am Main, Germany
- Cardiopulmonary Institute, 60596 Frankfurt am Main, Germany
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16
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Graham K, Chandrasekaran A, Wang L, Yang N, Lafer EM, Rangamani P, Stachowiak JC. Liquid-like condensates mediate competition between actin branching and bundling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.23.546267. [PMID: 37425724 PMCID: PMC10327076 DOI: 10.1101/2023.06.23.546267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Cellular remodeling of actin networks underlies cell motility during key morphological events, from embryogenesis to metastasis. In these transformations there is an inherent competition between actin branching and bundling, because steric clashes among branches create a mechanical barrier to bundling. Recently, liquid-like condensates consisting purely of proteins involved in either branching or bundling of the cytoskeleton have been found to catalyze their respective functions. Yet in the cell, proteins that drive branching and bundling are present simultaneously. In this complex environment, which factors determine whether a condensate drives filaments to branch versus becoming bundled? To answer this question, we added the branched actin nucleator, Arp2/3, to condensates composed of VASP, an actin bundling protein. At low actin to VASP ratios, branching activity, mediated by Arp2/3, robustly inhibited VASP-mediated bundling of filaments, in agreement with agent-based simulations. In contrast, as the actin to VASP ratio increased, addition of Arp2/3 led to formation of aster-shaped structures, in which bundled filaments emerged from a branched actin core, analogous to filopodia emerging from a branched lamellipodial network. These results demonstrate that multi-component, liquid-like condensates can modulate the inherent competition between bundled and branched actin morphologies, leading to organized, higher-order structures, similar to those found in motile cells.
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Affiliation(s)
- Kristin Graham
- University of Texas at Austin, Department of Biomedical Engineering
| | | | - Liping Wang
- University of Texas Health Science Center at San Antonio, Department of Biochemistry and Structural Biology
| | - Noel Yang
- University of Texas at Austin, Department of Biomedical Engineering
| | - Eileen M. Lafer
- University of Texas Health Science Center at San Antonio, Department of Biochemistry and Structural Biology
| | - Padmini Rangamani
- University of California San Diego, Department of Mechanical and Aerospace Engineering
| | - Jeanne C. Stachowiak
- University of Texas at Austin, Department of Biomedical Engineering
- University of Texas at Austin, Department of Chemical Engineering
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17
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Carman PJ, Barrie KR, Rebowski G, Dominguez R. Structures of the free and capped ends of the actin filament. Science 2023; 380:1287-1292. [PMID: 37228182 PMCID: PMC10880383 DOI: 10.1126/science.adg6812] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/17/2023] [Indexed: 05/27/2023]
Abstract
The barbed and pointed ends of the actin filament (F-actin) are the sites of growth and shrinkage and the targets of capping proteins that block subunit exchange, including CapZ at the barbed end and tropomodulin at the pointed end. We describe cryo-electron microscopy structures of the free and capped ends of F-actin. Terminal subunits at the free barbed end adopt a "flat" F-actin conformation. CapZ binds with minor changes to the barbed end but with major changes to itself. By contrast, subunits at the free pointed end adopt a "twisted" monomeric actin (G-actin) conformation. Tropomodulin binding forces the second subunit into an F-actin conformation. The structures reveal how the ends differ from the middle in F-actin and how these differences control subunit addition, dissociation, capping, and interactions with end-binding proteins.
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Affiliation(s)
- Peter J. Carman
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
| | - Kyle R. Barrie
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
| | - Grzegorz Rebowski
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
| | - Roberto Dominguez
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania; Philadelphia, Pennsylvania, USA
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18
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Molina M, Way LE, Ren Z, Liao Q, Wang X, Kim H. Using DNA flow-stretching assay as a tool to validate the tagging of DNA-binding proteins for single-molecule experiments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.19.533373. [PMID: 36993356 PMCID: PMC10055205 DOI: 10.1101/2023.03.19.533373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Due to the enhanced labeling capability of maleimide-based fluorescent probes, lysine-cysteine-lysine (KCK) tags are frequently added to proteins for visualization. In this study, we employed in vitro single-molecule DNA flow-stretching assay as a sensitive way to assess the impact of the KCK-tag on the property of DNA-binding proteins. Using Bacillus subtilis ParB as an example, we show that, although no noticeable changes were detected by in vivo fluorescence imaging and chromatin immunoprecipitation (ChIP) assays, the KCK-tag substantially altered ParB's DNA compaction rates, its response to nucleotide binding and to the presence of the specific sequence (parS) on the DNA. While it is typically assumed that short peptide tags minimally perturb protein function, our results urge researchers to carefully validate the use of tags for protein labeling. Our comprehensive analysis can be expanded and used as a guide to assess the impacts of other tags on DNA-binding proteins in single-molecule assays.
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Affiliation(s)
- Miranda Molina
- Biochemistry and Molecular Biology Program, University of Texas Rio Grande Valley, Edinburg, Texas, United States of America
- Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, Texas, United States of America
- These authors contributed equally
| | - Lindsey E. Way
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, Indiana, United States of America
- These authors contributed equally
| | - Zhongqing Ren
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, Indiana, United States of America
| | - Qin Liao
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, Indiana, United States of America
| | - Xindan Wang
- Department of Biology, Indiana University, 1001 E 3rd St, Bloomington, Indiana, United States of America
| | - HyeongJun Kim
- Biochemistry and Molecular Biology Program, University of Texas Rio Grande Valley, Edinburg, Texas, United States of America
- Department of Physics and Astronomy, University of Texas Rio Grande Valley, Edinburg, Texas, United States of America
- Lead contact
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19
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Parker SS, Ly KT, Grant AD, Sweetland J, Wang AM, Parker JD, Roman MR, Saboda K, Roe DJ, Padi M, Wolgemuth CW, Langlais P, Mouneimne G. EVL and MIM/MTSS1 regulate actin cytoskeletal remodeling to promote dendritic filopodia in neurons. J Cell Biol 2023; 222:e202106081. [PMID: 36828364 PMCID: PMC9998662 DOI: 10.1083/jcb.202106081] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 11/22/2022] [Accepted: 01/20/2023] [Indexed: 02/25/2023] Open
Abstract
Dendritic spines are the postsynaptic compartment of a neuronal synapse and are critical for synaptic connectivity and plasticity. A developmental precursor to dendritic spines, dendritic filopodia (DF), facilitate synapse formation by sampling the environment for suitable axon partners during neurodevelopment and learning. Despite the significance of the actin cytoskeleton in driving these dynamic protrusions, the actin elongation factors involved are not well characterized. We identified the Ena/VASP protein EVL as uniquely required for the morphogenesis and dynamics of DF. Using a combination of genetic and optogenetic manipulations, we demonstrated that EVL promotes protrusive motility through membrane-direct actin polymerization at DF tips. EVL forms a complex at nascent protrusions and DF tips with MIM/MTSS1, an I-BAR protein important for the initiation of DF. We proposed a model in which EVL cooperates with MIM to coalesce and elongate branched actin filaments, establishing the dynamic lamellipodia-like architecture of DF.
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Affiliation(s)
- Sara S. Parker
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Kenneth Tran Ly
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Adam D. Grant
- Cancer Biology Program, University of Arizona Cancer Center, Tucson, AZ, USA
| | - Jillian Sweetland
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Ashley M. Wang
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - James D. Parker
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Mackenzie R. Roman
- Division of Endocrinology, Department of Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Kathylynn Saboda
- University of Arizona Cancer Center and Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, USA
| | - Denise J. Roe
- University of Arizona Cancer Center and Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, USA
| | - Megha Padi
- Cancer Biology Program, University of Arizona Cancer Center, Tucson, AZ, USA
- Department of Molecular and Cellular Biology, College of Science, University of Arizona, Tucson, AZ, USA
| | - Charles W. Wolgemuth
- University of Arizona Cancer Center and Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ, USA
- Department of Molecular and Cellular Biology, College of Science, University of Arizona, Tucson, AZ, USA
- Department of Physics, College of Science, University of Arizona, Tucson, AZ, USA
- Johns Hopkins Physical Sciences-Oncology Center, Johns Hopkins University, Baltimore, MD, USA
| | - Paul Langlais
- Division of Endocrinology, Department of Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
| | - Ghassan Mouneimne
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
- Cancer Biology Program, University of Arizona Cancer Center, Tucson, AZ, USA
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20
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Graham K, Chandrasekaran A, Wang L, Ladak A, Lafer EM, Rangamani P, Stachowiak JC. Liquid-like VASP condensates drive actin polymerization and dynamic bundling. NATURE PHYSICS 2023; 19:574-585. [PMID: 38405682 PMCID: PMC10887402 DOI: 10.1038/s41567-022-01924-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 12/15/2022] [Indexed: 02/27/2024]
Abstract
The organization of actin filaments into bundles is required for cellular processes such as motility, morphogenesis, and cell division. Filament bundling is controlled by a network of actin-binding proteins. Recently, several proteins that comprise this network have been found to undergo liquid-liquid phase separation. How might liquid-like condensates contribute to filament bundling? Here, we show that the processive actin polymerase and bundling protein, VASP, forms liquid-like droplets under physiological conditions. As actin polymerizes within VASP droplets, elongating filaments partition to the edges of the droplet to minimize filament curvature, forming an actin-rich ring within the droplet. The rigidity of this ring is balanced by the droplet's surface tension, as predicted by a continuum-scale computational model. However, as actin polymerizes and the ring grows thicker, its rigidity increases and eventually overcomes the surface tension of the droplet, deforming into a linear bundle. The resulting bundles contain long, parallel actin filaments that grow from their tips. Significantly, the fluid nature of the droplets is critical for bundling, as more solid droplets resist deformation, preventing filaments from rearranging to form bundles. Once the parallel arrangement of filaments is created within a VASP droplet, it propagates through the addition of new actin monomers to achieve a length that is many times greater than the initial droplet. This droplet-based mechanism of bundling may be relevant to the assembly of cellular architectures rich in parallel actin filaments, such as filopodia, stress fibers, and focal adhesions.
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Affiliation(s)
- Kristin Graham
- University of Texas at Austin, Department of Biomedical Engineering
| | | | - Liping Wang
- University of Texas Health Science Center at San Antonio, Department of Biochemistry and Structural Biology
| | - Aly Ladak
- University of Texas at Austin, Department of Biomedical Engineering
| | - Eileen M Lafer
- University of Texas Health Science Center at San Antonio, Department of Biochemistry and Structural Biology
| | - Padmini Rangamani
- University of California San Diego, Department of Mechanical and Aerospace Engineering
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21
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Hein JI, Scholz J, Körber S, Kaufmann T, Faix J. Unleashed Actin Assembly in Capping Protein-Deficient B16-F1 Cells Enables Identification of Multiple Factors Contributing to Filopodium Formation. Cells 2023; 12:cells12060890. [PMID: 36980231 PMCID: PMC10047565 DOI: 10.3390/cells12060890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 03/08/2023] [Accepted: 03/10/2023] [Indexed: 03/16/2023] Open
Abstract
Background: Filopodia are dynamic, finger-like actin-filament bundles that overcome membrane tension by forces generated through actin polymerization at their tips to allow extension of these structures a few microns beyond the cell periphery. Actin assembly of these protrusions is regulated by accessory proteins including heterodimeric capping protein (CP) or Ena/VASP actin polymerases to either terminate or promote filament growth. Accordingly, the depletion of CP in B16-F1 melanoma cells was previously shown to cause an explosive formation of filopodia. In Ena/VASP-deficient cells, CP depletion appeared to result in ruffling instead of inducing filopodia, implying that Ena/VASP proteins are absolutely essential for filopodia formation. However, this hypothesis was not yet experimentally confirmed. Methods: Here, we used B16-F1 cells and CRISPR/Cas9 technology to eliminate CP either alone or in combination with Ena/VASP or other factors residing at filopodia tips, followed by quantifications of filopodia length and number. Results: Unexpectedly, we find massive formations of filopodia even in the absence of CP and Ena/VASP proteins. Notably, combined inactivation of Ena/VASP, unconventional myosin-X and the formin FMNL3 was required to markedly impair filopodia formation in CP-deficient cells. Conclusions: Taken together, our results reveal that, besides Ena/VASP proteins, numerous other factors contribute to filopodia formation.
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Affiliation(s)
| | | | | | | | - Jan Faix
- Correspondence: ; Tel.: +49-511-532-2928
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22
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Mechanisms of Foreign Body Giant Cell Formation in Response to Implantable Biomaterials. Polymers (Basel) 2023; 15:polym15051313. [PMID: 36904554 PMCID: PMC10007405 DOI: 10.3390/polym15051313] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 02/19/2023] [Accepted: 02/22/2023] [Indexed: 03/08/2023] Open
Abstract
Long term function of implantable biomaterials are determined by their integration with the host's body. Immune reactions against these implants could impair the function and integration of the implants. Some biomaterial-based implants lead to macrophage fusion and the formation of multinucleated giant cells, also known as foreign body giant cells (FBGCs). FBGCs may compromise the biomaterial performance and may lead to implant rejection and adverse events in some cases. Despite their critical role in response to implants, there is a limited understanding of cellular and molecular mechanisms involved in forming FBGCs. Here, we focused on better understanding the steps and mechanisms triggering macrophage fusion and FBGCs formation, specifically in response to biomaterials. These steps included macrophage adhesion to the biomaterial surface, fusion competency, mechanosensing and mechanotransduction-mediated migration, and the final fusion. We also described some of the key biomarkers and biomolecules involved in these steps. Understanding these steps on a molecular level would lead to enhance biomaterials design and improve their function in the context of cell transplantation, tissue engineering, and drug delivery.
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Ena/VASP clustering at microspike tips involves lamellipodin but not I-BAR proteins, and absolutely requires unconventional myosin-X. Proc Natl Acad Sci U S A 2023; 120:e2217437120. [PMID: 36598940 PMCID: PMC9926217 DOI: 10.1073/pnas.2217437120] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Sheet-like membrane protrusions at the leading edge, termed lamellipodia, drive 2D-cell migration using active actin polymerization. Microspikes comprise actin-filament bundles embedded within lamellipodia, but the molecular mechanisms driving their formation and their potential functional relevance have remained elusive. Microspike formation requires the specific activity of clustered Ena/VASP proteins at their tips to enable processive actin assembly in the presence of capping protein, but the factors and mechanisms mediating Ena/VASP clustering are poorly understood. Systematic analyses of B16-F1 melanoma mutants lacking potential candidate proteins revealed that neither inverse BAR-domain proteins, nor lamellipodin or Abi is essential for clustering, although they differentially contribute to lamellipodial VASP accumulation. In contrast, unconventional myosin-X (MyoX) identified here as proximal to VASP was obligatory for Ena/VASP clustering and microspike formation. Interestingly, and despite the invariable distribution of other relevant marker proteins, the width of lamellipodia in MyoX-KO mutants was significantly reduced as compared with B16-F1 control, suggesting that microspikes contribute to lamellipodium stability. Consistently, MyoX removal caused marked defects in protrusion and random 2D-cell migration. Strikingly, Ena/VASP-deficiency also uncoupled MyoX cluster dynamics from actin assembly in lamellipodia, establishing their tight functional association in microspike formation.
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Pokrant T, Hein JI, Körber S, Disanza A, Pich A, Scita G, Rottner K, Faix J. Ena/VASP clustering at microspike tips involves lamellipodin but not I-BAR proteins, and absolutely requires unconventional myosin-X. Proc Natl Acad Sci U S A 2023. [PMID: 36598940 DOI: 10.1101/2022.05.12.491613] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
Sheet-like membrane protrusions at the leading edge, termed lamellipodia, drive 2D-cell migration using active actin polymerization. Microspikes comprise actin-filament bundles embedded within lamellipodia, but the molecular mechanisms driving their formation and their potential functional relevance have remained elusive. Microspike formation requires the specific activity of clustered Ena/VASP proteins at their tips to enable processive actin assembly in the presence of capping protein, but the factors and mechanisms mediating Ena/VASP clustering are poorly understood. Systematic analyses of B16-F1 melanoma mutants lacking potential candidate proteins revealed that neither inverse BAR-domain proteins, nor lamellipodin or Abi is essential for clustering, although they differentially contribute to lamellipodial VASP accumulation. In contrast, unconventional myosin-X (MyoX) identified here as proximal to VASP was obligatory for Ena/VASP clustering and microspike formation. Interestingly, and despite the invariable distribution of other relevant marker proteins, the width of lamellipodia in MyoX-KO mutants was significantly reduced as compared with B16-F1 control, suggesting that microspikes contribute to lamellipodium stability. Consistently, MyoX removal caused marked defects in protrusion and random 2D-cell migration. Strikingly, Ena/VASP-deficiency also uncoupled MyoX cluster dynamics from actin assembly in lamellipodia, establishing their tight functional association in microspike formation.
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Affiliation(s)
- Thomas Pokrant
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Jens Ingo Hein
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Sarah Körber
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Andrea Disanza
- IFOM ETS (Istituto Fondazione di Oncologia Molecolare ETS), - The AIRC (Italian Association for Cancer Research) Institute of Molecular Oncology, 20139 Milan, Italy
| | - Andreas Pich
- Research Core Unit Proteomics, Hannover Medical School, 30625 Hannover, Germany
| | - Giorgio Scita
- IFOM ETS (Istituto Fondazione di Oncologia Molecolare ETS), - The AIRC (Italian Association for Cancer Research) Institute of Molecular Oncology, 20139 Milan, Italy
- Department of Oncology and Haemato-Oncology, University of Milan, 20139 Milan, Italy
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany
- Molecular Cell Biology Group, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
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Lappalainen P, Kotila T, Jégou A, Romet-Lemonne G. Biochemical and mechanical regulation of actin dynamics. Nat Rev Mol Cell Biol 2022; 23:836-852. [PMID: 35918536 DOI: 10.1038/s41580-022-00508-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2022] [Indexed: 12/30/2022]
Abstract
Polymerization of actin filaments against membranes produces force for numerous cellular processes, such as migration, morphogenesis, endocytosis, phagocytosis and organelle dynamics. Consequently, aberrant actin cytoskeleton dynamics are linked to various diseases, including cancer, as well as immunological and neurological disorders. Understanding how actin filaments generate forces in cells, how force production is regulated by the interplay between actin-binding proteins and how the actin-regulatory machinery responds to mechanical load are at the heart of many cellular, developmental and pathological processes. During the past few years, our understanding of the mechanisms controlling actin filament assembly and disassembly has evolved substantially. It has also become evident that the activities of key actin-binding proteins are not regulated solely by biochemical signalling pathways, as mechanical regulation is critical for these proteins. Indeed, the architecture and dynamics of the actin cytoskeleton are directly tuned by mechanical load. Here we discuss the general mechanisms by which key actin regulators, often in synergy with each other, control actin filament assembly, disassembly, and monomer recycling. By using an updated view of actin dynamics as a framework, we discuss how the mechanics and geometry of actin networks control actin-binding proteins, and how this translates into force production in endocytosis and mesenchymal cell migration.
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Affiliation(s)
- Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, Helsinki, Finland.
| | - Tommi Kotila
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, Helsinki, Finland
| | - Antoine Jégou
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
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26
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Montaño-Rendón F, Walpole GF, Krause M, Hammond GR, Grinstein S, Fairn GD. PtdIns(3,4)P2, Lamellipodin, and VASP coordinate actin dynamics during phagocytosis in macrophages. J Cell Biol 2022; 221:e202207042. [PMID: 36165850 PMCID: PMC9521245 DOI: 10.1083/jcb.202207042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/29/2022] [Accepted: 08/31/2022] [Indexed: 11/22/2022] Open
Abstract
Phosphoinositides are pivotal regulators of vesicular traffic and signaling during phagocytosis. Phagosome formation, the initial step of the process, is characterized by local membrane remodeling and reorganization of the actin cytoskeleton that leads to formation of the pseudopods that drive particle engulfment. Using genetically encoded fluorescent probes, we found that upon particle engagement a localized pool of PtdIns(3,4)P2 is generated by the sequential activities of class I phosphoinositide 3-kinases and phosphoinositide 5-phosphatases. Depletion of this locally generated pool of PtdIns(3,4)P2 blocks pseudopod progression and ultimately phagocytosis. We show that the PtdIns(3,4)P2 effector Lamellipodin (Lpd) is recruited to nascent phagosomes by PtdIns(3,4)P2. Furthermore, we show that silencing of Lpd inhibits phagocytosis and produces aberrant pseudopodia with disorganized actin filaments. Finally, vasodilator-stimulated phosphoprotein (VASP) was identified as a key actin-regulatory protein mediating phagosome formation downstream of Lpd. Mechanistically, our findings imply that a pathway involving PtdIns(3,4)P2, Lpd, and VASP mediates phagocytosis at the stage of particle engulfment.
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Affiliation(s)
- Fernando Montaño-Rendón
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Glenn F.W. Walpole
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Matthias Krause
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, UK
| | - Gerald R.V. Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Sergio Grinstein
- Division of Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, Ontario, Canada
| | - Gregory D. Fairn
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, Ontario, Canada
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
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27
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Tsai FC, Henderson JM, Jarin Z, Kremneva E, Senju Y, Pernier J, Mikhajlov O, Manzi J, Kogan K, Le Clainche C, Voth GA, Lappalainen P, Bassereau P. Activated I-BAR IRSp53 clustering controls the formation of VASP-actin-based membrane protrusions. SCIENCE ADVANCES 2022; 8:eabp8677. [PMID: 36240267 PMCID: PMC9565809 DOI: 10.1126/sciadv.abp8677] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Filopodia are actin-rich membrane protrusions essential for cell morphogenesis, motility, and cancer invasion. How cells control filopodium initiation on the plasma membrane remains elusive. We performed experiments in cellulo, in vitro, and in silico to unravel the mechanism of filopodium initiation driven by the membrane curvature sensor IRSp53 (insulin receptor substrate protein of 53 kDa). We showed that full-length IRSp53 self-assembles into clusters on membranes depending on PIP2. Using well-controlled in vitro reconstitution systems, we demonstrated that IRSp53 clusters recruit the actin polymerase VASP (vasodilator-stimulated phosphoprotein) to assemble actin filaments locally on membranes, leading to the generation of actin-filled membrane protrusions reminiscent of filopodia. By pulling membrane nanotubes from live cells, we observed that IRSp53 can only be enriched and trigger actin assembly in nanotubes at highly dynamic membrane regions. Our work supports a regulation mechanism of IRSp53 in its attributes of curvature sensation and partner recruitment to ensure a precise spatial-temporal control of filopodium initiation.
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Affiliation(s)
- Feng-Ching Tsai
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
- Corresponding author. (F.-C.T.); (G.A.V.); (P.L.); (P.B.)
| | - J. Michael Henderson
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et Infection, Institut Pasteur, Université de Paris, CNRS UMR 3691, 75015 Paris, France
| | - Zack Jarin
- Pritzker School for Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Elena Kremneva
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Yosuke Senju
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama, Japan
| | - Julien Pernier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Oleg Mikhajlov
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - John Manzi
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - Konstantin Kogan
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Christophe Le Clainche
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Gregory A. Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
- Corresponding author. (F.-C.T.); (G.A.V.); (P.L.); (P.B.)
| | - Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
- Corresponding author. (F.-C.T.); (G.A.V.); (P.L.); (P.B.)
| | - Patricia Bassereau
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
- Corresponding author. (F.-C.T.); (G.A.V.); (P.L.); (P.B.)
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Tsai FC, Henderson JM, Jarin Z, Kremneva E, Senju Y, Pernier J, Mikhajlov O, Manzi J, Kogan K, Le Clainche C, Voth GA, Lappalainen P, Bassereau P. Activated I-BAR IRSp53 clustering controls the formation of VASP-actin-based membrane protrusions. SCIENCE ADVANCES 2022; 8:eabp8677. [PMID: 36240267 DOI: 10.1101/2022.03.04.483020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Filopodia are actin-rich membrane protrusions essential for cell morphogenesis, motility, and cancer invasion. How cells control filopodium initiation on the plasma membrane remains elusive. We performed experiments in cellulo, in vitro, and in silico to unravel the mechanism of filopodium initiation driven by the membrane curvature sensor IRSp53 (insulin receptor substrate protein of 53 kDa). We showed that full-length IRSp53 self-assembles into clusters on membranes depending on PIP2. Using well-controlled in vitro reconstitution systems, we demonstrated that IRSp53 clusters recruit the actin polymerase VASP (vasodilator-stimulated phosphoprotein) to assemble actin filaments locally on membranes, leading to the generation of actin-filled membrane protrusions reminiscent of filopodia. By pulling membrane nanotubes from live cells, we observed that IRSp53 can only be enriched and trigger actin assembly in nanotubes at highly dynamic membrane regions. Our work supports a regulation mechanism of IRSp53 in its attributes of curvature sensation and partner recruitment to ensure a precise spatial-temporal control of filopodium initiation.
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Affiliation(s)
- Feng-Ching Tsai
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - J Michael Henderson
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
- Unité de Trafic Membranaire et Pathogénèse, Département de Biologie Cellulaire et Infection, Institut Pasteur, Université de Paris, CNRS UMR 3691, 75015 Paris, France
| | - Zack Jarin
- Pritzker School for Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Elena Kremneva
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Yosuke Senju
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama, Japan
| | - Julien Pernier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Oleg Mikhajlov
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - John Manzi
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
| | - Konstantin Kogan
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Christophe Le Clainche
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Gregory A Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
| | - Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Sciences, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
| | - Patricia Bassereau
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France
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Visweshwaran SP, Nayab H, Hoffmann L, Gil M, Liu F, Kühne R, Maritzen T. Ena/VASP proteins at the crossroads of actin nucleation pathways in dendritic cell migration. Front Cell Dev Biol 2022; 10:1008898. [PMID: 36274843 PMCID: PMC9581539 DOI: 10.3389/fcell.2022.1008898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 09/12/2022] [Indexed: 12/05/2022] Open
Abstract
As sentinels of our immune system dendritic cells (DCs) rely on efficient cell migration for patrolling peripheral tissues and delivering sampled antigens to secondary lymphoid organs for the activation of T-cells. Dynamic actin polymerization is key to their macropinocytic and migratory properties. Both major actin nucleation machineries, formins and the Arp2/3 complex, are critical for different aspects of DC functionality, by driving the generation of linear and branched actin filaments, respectively. However, the importance of a third group of actin nucleators, the Ena/VASP family, has not been addressed yet. Here, we show that the two family members Evl and VASP are expressed in murine DCs and that their loss negatively affects DC macropinocytosis, spreading, and migration. Our interactome analysis reveals Ena/VASP proteins to be ideally positioned for orchestrating the different actin nucleation pathways by binding to the formin mDia1 as well as to the WAVE regulatory complex, a stimulator of Arp2/3. In fact, Evl/VASP deficient murine DCs are more vulnerable to inhibition of Arp2/3 demonstrating that Ena/VASP proteins contribute to the robustness and efficiency of DC migration.
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Affiliation(s)
| | - Hafiza Nayab
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Lennart Hoffmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Marine Gil
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Fan Liu
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Ronald Kühne
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
- Department of Nanophysiology, Technische Universität Kaiserslautern, Kaiserslautern, Germany
- *Correspondence: Tanja Maritzen,
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30
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Alqassim SS. Functional Mimicry of Eukaryotic Actin Assembly by Pathogen Effector Proteins. Int J Mol Sci 2022; 23:ijms231911606. [PMID: 36232907 PMCID: PMC9569871 DOI: 10.3390/ijms231911606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 09/21/2022] [Accepted: 09/22/2022] [Indexed: 11/16/2022] Open
Abstract
The actin cytoskeleton lies at the heart of many essential cellular processes. There are hundreds of proteins that cells use to control the size and shape of actin cytoskeletal networks. As such, various pathogens utilize different strategies to hijack the infected eukaryotic host actin dynamics for their benefit. These include the control of upstream signaling pathways that lead to actin assembly, control of eukaryotic actin assembly factors, encoding toxins that distort regular actin dynamics, or by encoding effectors that directly interact with and assemble actin filaments. The latter class of effectors is unique in that, quite often, they assemble actin in a straightforward manner using novel sequences, folds, and molecular mechanisms. The study of these mechanisms promises to provide major insights into the fundamental determinants of actin assembly, as well as a deeper understanding of host-pathogen interactions in general, and contribute to therapeutic development efforts targeting their respective pathogens. This review discusses mechanisms and highlights shared and unique features of actin assembly by pathogen effectors that directly bind and assemble actin, focusing on eukaryotic actin nucleator functional mimics Rickettsia Sca2 (formin mimic), Burkholderia BimA (Ena/VASP mimic), and Vibrio VopL (tandem WH2-motif mimic).
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Affiliation(s)
- Saif S Alqassim
- College of Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Building 14, Dubai Health Care City, Dubai P.O. Box 505055, United Arab Emirates
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31
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Thompson SB, Waldman MM, Jacobelli J. Polymerization power: effectors of actin polymerization as regulators of T lymphocyte migration through complex environments. FEBS J 2022; 289:6154-6171. [PMID: 34273243 PMCID: PMC8761786 DOI: 10.1111/febs.16130] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 05/24/2021] [Accepted: 07/16/2021] [Indexed: 11/26/2022]
Abstract
During their life span, T cells are tasked with patrolling the body for potential pathogens. To do so, T cells migrate through numerous distinct anatomical sites and tissue environments with different biophysical characteristics. To migrate through these different environments, T cells use various motility strategies that rely on actin network remodeling to generate shape changes and mechanical forces. In this review, we initially discuss the migratory journey of T cells and then cover the actin polymerization effectors at play in T cells, and finally, we focus on the function of these effectors of actin cytoskeleton remodeling in mediating T-cell migration through diverse tissue environments. Specifically, we will discuss the current state of the field pertaining to our understanding of the roles in T-cell migration played by members of the three main families of actin polymerization machinery: the Arp2/3 complex; formin proteins; and Ena/VASP proteins.
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Affiliation(s)
- Scott B. Thompson
- Department of Immunology and Microbiology, University of Colorado School of Medicine
| | - Monique M. Waldman
- Department of Immunology and Microbiology, University of Colorado School of Medicine
- Barbara Davis Research Center, University of Colorado School of Medicine
| | - Jordan Jacobelli
- Department of Immunology and Microbiology, University of Colorado School of Medicine
- Barbara Davis Research Center, University of Colorado School of Medicine
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32
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Nast-Kolb T, Bleicher P, Payr M, Bausch AR. VASP localization to lipid bilayers induces polymerization driven actin bundle formation. Mol Biol Cell 2022; 33:ar91. [PMID: 35830600 PMCID: PMC9582628 DOI: 10.1091/mbc.e21-11-0577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Actin bundles constitute important cytoskeleton structures and enable a scaffold for force transmission inside cells. Actin bundles are formed by proteins, with multiple F-actin binding domains cross-linking actin filaments to each other. Vasodilator-stimulated phosphoprotein (VASP) has mostly been reported as an actin elongator, but it has been shown to be a bundling protein as well and is found in bundled actin structures at filopodia and adhesion sites. Based on in vitro experiments, it remains unclear when and how VASP can act as an actin bundler or elongator. Here we demonstrate that VASP bound to membranes facilitates the formation of large actin bundles during polymerization. The alignment by polymerization requires the fluidity of the lipid bilayers. The mobility within the bilayer enables VASP to bind to filaments and capture and track growing barbed ends. VASP itself phase separates into a protein-enriched phase on the bilayer. This VASP-rich phase nucleates and accumulates at bundles during polymerization, which in turn leads to a reorganization of the underlying lipid bilayer. Our findings demonstrate that the nature of VASP localization is decisive for its function. The up-concentration based on VASP’s affinity to actin during polymerization enables it to simultaneously fulfill the function of an elongator and a bundler.
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Affiliation(s)
- T Nast-Kolb
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and
| | - P Bleicher
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and.,Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892
| | - M Payr
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and.,Structural and Computational Biology Unit, EMBL Heidelberg, Meyerhoferstr. 1, 69117 Heidelberg, Germany
| | - A R Bausch
- Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747 Garching, Germany
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33
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Kotschenreuther K, Yan S, Kofler DM. Migration and homeostasis of regulatory T cells in rheumatoid arthritis. Front Immunol 2022; 13:947636. [PMID: 36016949 PMCID: PMC9398455 DOI: 10.3389/fimmu.2022.947636] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/20/2022] [Indexed: 12/17/2022] Open
Abstract
Regulatory T (Treg) cells are garnering increased attention in research related to autoimmune diseases, including rheumatoid arthritis (RA). They play an essential role in the maintenance of immune homeostasis by restricting effector T cell activity. Reduced functions and frequencies of Treg cells contribute to the pathogenesis of RA, a common autoimmune disease which leads to systemic inflammation and erosive joint destruction. Treg cells from patients with RA are characterized by impaired functions and by an altered phenotype. They show increased plasticity towards Th17 cells and a reduced suppressive capacity. Besides the suppressive function of Treg cells, their effectiveness is determined by their ability to migrate into inflamed tissues. In the past years, new mechanisms involved in Treg cell migration have been identified. One example of such a mechanism is the phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Efficient migration of Treg cells requires the presence of VASP. IL-6, a cytokine which is abundantly present in the peripheral blood and in the synovial tissue of RA patients, induces posttranslational modifications of VASP. Recently, it has been shown in mice with collagen-induced arthritis (CIA) that this IL-6 mediated posttranslational modification leads to reduced Treg cell trafficking. Another protein which facilitates Treg cell migration is G-protein-signaling modulator 2 (GPSM2). It modulates G-protein coupled receptor functioning, thereby altering the cellular activity initiated by cell surface receptors in response to extracellular signals. The almost complete lack of GPSM2 in Treg cells from RA patients contributes to their reduced ability to migrate towards inflammatory sites. In this review article, we highlight the newly identified mechanisms of Treg cell migration and review the current knowledge about impaired Treg cell homeostasis in RA.
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Affiliation(s)
- Konstantin Kotschenreuther
- Laboratory of Molecular Immunology, Division of Rheumatology and Clinical Immunology, Department I of Internal Medicine, Faculty of Medicine, University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Shuaifeng Yan
- Laboratory of Molecular Immunology, Division of Rheumatology and Clinical Immunology, Department I of Internal Medicine, Faculty of Medicine, University Hospital Cologne, University of Cologne, Cologne, Germany
| | - David M. Kofler
- Laboratory of Molecular Immunology, Division of Rheumatology and Clinical Immunology, Department I of Internal Medicine, Faculty of Medicine, University Hospital Cologne, University of Cologne, Cologne, Germany
- Center for Integrated Oncology Aachen Bonn Cologne Duesseldorf, Cologne, Germany
- *Correspondence: David M. Kofler,
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Triantopoulou N, Vidaki M. Local mRNA translation and cytoskeletal reorganization: Mechanisms that tune neuronal responses. Front Mol Neurosci 2022; 15:949096. [PMID: 35979146 PMCID: PMC9376447 DOI: 10.3389/fnmol.2022.949096] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/07/2022] [Indexed: 12/31/2022] Open
Abstract
Neurons are highly polarized cells with significantly long axonal and dendritic extensions that can reach distances up to hundreds of centimeters away from the cell bodies in higher vertebrates. Their successful formation, maintenance, and proper function highly depend on the coordination of intricate molecular networks that allow axons and dendrites to quickly process information, and respond to a continuous and diverse cascade of environmental stimuli, often without enough time for communication with the soma. Two seemingly unrelated processes, essential for these rapid responses, and thus neuronal homeostasis and plasticity, are local mRNA translation and cytoskeletal reorganization. The axonal cytoskeleton is characterized by high stability and great plasticity; two contradictory attributes that emerge from the powerful cytoskeletal rearrangement dynamics. Cytoskeletal reorganization is crucial during nervous system development and in adulthood, ensuring the establishment of proper neuronal shape and polarity, as well as regulating intracellular transport and synaptic functions. Local mRNA translation is another mechanism with a well-established role in the developing and adult nervous system. It is pivotal for axonal guidance and arborization, synaptic formation, and function and seems to be a key player in processes activated after neuronal damage. Perturbations in the regulatory pathways of local translation and cytoskeletal reorganization contribute to various pathologies with diverse clinical manifestations, ranging from intellectual disabilities (ID) to autism spectrum disorders (ASD) and schizophrenia (SCZ). Despite the fact that both processes are essential for the orchestration of pathways critical for proper axonal and dendritic function, the interplay between them remains elusive. Here we review our current knowledge on the molecular mechanisms and specific interaction networks that regulate and potentially coordinate these interconnected processes.
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Affiliation(s)
- Nikoletta Triantopoulou
- Division of Basic Sciences, Medical School, University of Crete, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Greece
| | - Marina Vidaki
- Division of Basic Sciences, Medical School, University of Crete, Heraklion, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), Heraklion, Greece
- *Correspondence: Marina Vidaki,
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Dhanda AS, Guttman JA. Localization of host endocytic and actin-associated proteins during Shigella flexneri intracellular motility and intercellular spreading. Anat Rec (Hoboken) 2022; 306:1088-1110. [PMID: 35582740 DOI: 10.1002/ar.24955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/24/2022] [Accepted: 04/27/2022] [Indexed: 11/10/2022]
Abstract
Shigella flexneri (S. flexneri), the causative agent of bacillary dysentery, uses an effector-mediated strategy to hijack host cells and cause disease. To propagate and spread within human tissues, S. flexneri bacteria commandeer the host actin cytoskeleton to generate slender actin-rich comet tails to move intracellularly, and later, plasma membrane actin-based protrusions to move directly between adjacent host cells. To facilitate intercellular bacterial spreading, large micron-sized endocytic-like membrane invaginations form at the periphery of neighboring host cells that come into contact with S. flexneri-containing membrane protrusions. While S. flexneri comet tails and membrane protrusions consist primarily of host actin cytoskeletal proteins, S. flexneri membrane invaginations remain poorly understood with only clathrin and the clathrin adapter epsin-1 localized to the structures. Tangentially, we recently reported that Listeria monocytogenes, another actin-hijacking pathogen, exploits an assortment of caveolar and actin-bundling proteins at their micron-sized membrane invaginations formed during their cell-to-cell movement. Thus, to further characterize the S. flexneri disease process, we set out to catalog the distribution of a variety of actin-associated and caveolar proteins during S. flexneri actin-based motility and cell-to-cell spreading. Here we show that actin-associated proteins found at L. monocytogenes comet tails and membrane protrusions mimic those present at S. flexneri comet tails with the exception of α-actinins 1 and 4, which were shed from S. flexneri membrane protrusions. We also demonstrate that all known host endocytic components found at L. monocytogenes membrane invaginations are also present at those formed during S. flexneri infections.
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Affiliation(s)
- Aaron Singh Dhanda
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Julian Andrew Guttman
- Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada
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The branching code: A model of actin-driven dendrite arborization. Cell Rep 2022; 39:110746. [PMID: 35476974 DOI: 10.1016/j.celrep.2022.110746] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 12/24/2021] [Accepted: 04/06/2022] [Indexed: 11/21/2022] Open
Abstract
The cytoskeleton is crucial for defining neuronal-type-specific dendrite morphologies. To explore how the complex interplay of actin-modulatory proteins (AMPs) can define neuronal types in vivo, we focused on the class III dendritic arborization (c3da) neuron of Drosophila larvae. Using computational modeling, we reveal that the main branches (MBs) of c3da neurons follow general models based on optimal wiring principles, while the actin-enriched short terminal branches (STBs) require an additional growth program. To clarify the cellular mechanisms that define this second step, we thus concentrated on STBs for an in-depth quantitative description of dendrite morphology and dynamics. Applying these methods systematically to mutants of six known and novel AMPs, we revealed the complementary roles of these individual AMPs in defining STB properties. Our data suggest that diverse dendrite arbors result from a combination of optimal-wiring-related growth and individualized growth programs that are neuron-type specific.
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Faix J, Rottner K. Ena/VASP proteins in cell edge protrusion, migration and adhesion. J Cell Sci 2022; 135:274697. [DOI: 10.1242/jcs.259226] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
ABSTRACT
The tightly coordinated, spatiotemporal control of actin filament remodeling provides the basis of fundamental cellular processes, such as cell migration and adhesion. Specific protein assemblies, composed of various actin-binding proteins, are thought to operate in these processes to nucleate and elongate new filaments, arrange them into complex three-dimensional (3D) arrays and recycle them to replenish the actin monomer pool. Actin filament assembly is not only necessary to generate pushing forces against the leading edge membrane or to propel pathogens through the cytoplasm, but also coincides with the generation of stress fibers (SFs) and focal adhesions (FAs) that generate, transmit and sense mechanical tension. The only protein families known to date that directly enhance the elongation of actin filaments are formins and the family of Ena/VASP proteins. Their mechanisms of action, however, in enhancing processive filament elongation are distinct. The aim of this Review is to summarize our current knowledge on the molecular mechanisms of Ena/VASP-mediated actin filament assembly, and to discuss recent insights into the cell biological functions of Ena/VASP proteins in cell edge protrusion, migration and adhesion.
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Affiliation(s)
- Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technical University Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
- Molecular Cell Biology Group, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
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Abstract
The precise assembly and disassembly of actin filaments is required for several cellular processes, and their regulation has been scrutinized for decades. Twenty years ago, a handful of studies marked the advent of a new type of experiment to study actin dynamics: using optical microscopy to look at individual events, taking place on individual filaments in real time. Here, we summarize the main characteristics of this approach and how it has changed our ability to understand actin assembly dynamics. We also highlight some of its caveats and reflect on what we have learned over the past 20 years, leading us to propose a set of guidelines, which we hope will contribute to a better exploitation of this powerful tool.
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aVASP boosts protrusive activity of macroendocytic cups and drives phagosome rocketing after internalization. Eur J Cell Biol 2022; 101:151200. [DOI: 10.1016/j.ejcb.2022.151200] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/29/2022] Open
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Funk J, Merino F, Schaks M, Rottner K, Raunser S, Bieling P. A barbed end interference mechanism reveals how capping protein promotes nucleation in branched actin networks. Nat Commun 2021; 12:5329. [PMID: 34504078 PMCID: PMC8429771 DOI: 10.1038/s41467-021-25682-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 08/18/2021] [Indexed: 12/26/2022] Open
Abstract
Heterodimeric capping protein (CP/CapZ) is an essential factor for the assembly of branched actin networks, which push against cellular membranes to drive a large variety of cellular processes. Aside from terminating filament growth, CP potentiates the nucleation of actin filaments by the Arp2/3 complex in branched actin networks through an unclear mechanism. Here, we combine structural biology with in vitro reconstitution to demonstrate that CP not only terminates filament elongation, but indirectly stimulates the activity of Arp2/3 activating nucleation promoting factors (NPFs) by preventing their association to filament barbed ends. Key to this function is one of CP's C-terminal "tentacle" extensions, which sterically masks the main interaction site of the terminal actin protomer. Deletion of the β tentacle only modestly impairs capping. However, in the context of a growing branched actin network, its removal potently inhibits nucleation promoting factors by tethering them to capped filament ends. End tethering of NPFs prevents their loading with actin monomers required for activation of the Arp2/3 complex and thus strongly inhibits branched network assembly both in cells and reconstituted motility assays. Our results mechanistically explain how CP couples two opposed processes-capping and nucleation-in branched actin network assembly.
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Affiliation(s)
- Johanna Funk
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.,Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Matthias Schaks
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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Murk K, Ornaghi M, Schiweck J. Profilin Isoforms in Health and Disease - All the Same but Different. Front Cell Dev Biol 2021; 9:681122. [PMID: 34458253 PMCID: PMC8387879 DOI: 10.3389/fcell.2021.681122] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/12/2021] [Indexed: 12/11/2022] Open
Abstract
Profilins are small actin binding proteins, which are structurally conserved throughout evolution. They are probably best known to promote and direct actin polymerization. However, they also participate in numerous cell biological processes beyond the roles typically ascribed to the actin cytoskeleton. Moreover, most complex organisms express several profilin isoforms. Their cellular functions are far from being understood, whereas a growing number of publications indicate that profilin isoforms are involved in the pathogenesis of various diseases. In this review, we will provide an overview of the profilin family and "typical" profilin properties including the control of actin dynamics. We will then discuss the profilin isoforms of higher animals in detail. In terms of cellular functions, we will focus on the role of Profilin 1 (PFN1) and Profilin 2a (PFN2a), which are co-expressed in the central nervous system. Finally, we will discuss recent findings that link PFN1 and PFN2a to neurological diseases, such as amyotrophic lateral sclerosis (ALS), Fragile X syndrome (FXS), Huntington's disease and spinal muscular atrophy (SMA).
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Affiliation(s)
- Kai Murk
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Marta Ornaghi
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Juliane Schiweck
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
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42
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Lu Q, Barlow DE, Haridas D. Differential detection of immune cell activation by label-free radiation pressure force. Analyst 2021; 146:5150-5159. [PMID: 34286712 DOI: 10.1039/d1an01066b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Label-free radiation pressure force analysis using a microfluidic platform is applied to the differential detection of innate immune cell activation. Murine-derived peritoneal macrophages (IC-21) are used as a model system and the activation of IC-21 cells by lipopolysaccharide (LPS) and interferon gamma (IFN-γ) to M1 pro-inflammatory phenotype is confirmed by RNA gene sequencing and nitric oxide production. The mean cell size determined by radiation pressure force analysis increases slightly after the activation (4 to 6%) and the calculated percentage of population overlaps between the control and the activated group after 14 and 24 h stimulations are at 79% and 77%. Meanwhile the mean cell velocity decreases more significantly after the activation (14% to 15%) and the calculated percentage of population overlaps between the control and the activated group after 14 and 24 h stimulations are only at 14% and 13%. The results demonstrate that the majority of the activated cells acquire a lower velocity than the cells from the control group without changes in cell size. For comparison label-free flow cytometry analysis of living IC-21 cells under the same stimulation conditions are performed and the results show population shifts towards larger values in both forward scatter and side scatter, but the calculated percentage of population overlaps in all case are significant (70% to 83%). Cell images obtained during radiation pressure force analysis by a CCD camera, and by optical microscopy and atomic force microscopy (AFM) reveal correlations between the cell activation by LPS/IFN-γ, the increase in cell complexity and surface roughness, and enhanced back scattered light by the activated cells. The unique relationship predicted by Mie's theory between the radiation pressure force exerted on the cell and the angular distribution of the scattered light by the cell which is influenced by its size, complexity, and surface conditions, endows the cell velocity based measurement by radiation pressure force analysis with high sensitivity in differentiating immune cell activation.
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Affiliation(s)
- Qin Lu
- Naval Research Laboratory, Chemistry Division, 4555 Overlook Ave., S.W. Washington, D.C. 20375, USA.
| | - Daniel E Barlow
- Naval Research Laboratory, Chemistry Division, 4555 Overlook Ave., S.W. Washington, D.C. 20375, USA.
| | - Dhanya Haridas
- Naval Research Laboratory, Chemistry Division, 4555 Overlook Ave., S.W. Washington, D.C. 20375, USA.
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Arthur AL, Crawford A, Houdusse A, Titus MA. VASP-mediated actin dynamics activate and recruit a filopodia myosin. eLife 2021; 10:68082. [PMID: 34042588 PMCID: PMC8352590 DOI: 10.7554/elife.68082] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 05/20/2021] [Indexed: 11/17/2022] Open
Abstract
Filopodia are thin, actin-based structures that cells use to interact with their environments. Filopodia initiation requires a suite of conserved proteins but the mechanism remains poorly understood. The actin polymerase VASP and a MyTH-FERM (MF) myosin, DdMyo7 in amoeba, are essential for filopodia initiation. DdMyo7 is localized to dynamic regions of the actin-rich cortex. Analysis of VASP mutants and treatment of cells with anti-actin drugs shows that myosin recruitment and activation in Dictyostelium requires localized VASP-dependent actin polymerization. Targeting of DdMyo7 to the cortex alone is not sufficient for filopodia initiation; VASP activity is also required. The actin regulator locally produces a cortical actin network that activates myosin and together they shape the actin network to promote extension of parallel bundles of actin during filopodia formation. This work reveals how filopodia initiation requires close collaboration between an actin-binding protein, the state of the actin cytoskeleton and MF myosin activity.
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Affiliation(s)
- Ashley L Arthur
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Amy Crawford
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
| | - Anne Houdusse
- Structural Motility, Institut Curie, Paris Université Sciences et Lettres, Sorbonne Université, Paris, France
| | - Margaret A Titus
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, United States
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Abstract
A new study reports that the actin-monomer-binding protein profilin 1 dictates protrusion character at the cell edge. These findings help explain how distinct, tunable actin polymerization pathways collaborate to form higher-order cellular structures.
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45
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The multiple roles of actin-binding proteins at invadopodia. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021. [PMID: 33962752 DOI: 10.1016/bs.ircmb.2021.03.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Invadopodia are actin-rich membrane protrusions that facilitate cancer cell dissemination by focusing on proteolytic activity and clearing paths for migration through physical barriers, such as basement membranes, dense extracellular matrices, and endothelial cell junctions. Invadopodium formation and activity require spatially and temporally regulated changes in actin filament organization and dynamics. About three decades of research have led to a remarkable understanding of how these changes are orchestrated by sequential recruitment and coordinated activity of different sets of actin-binding proteins. In this chapter, we provide an update on the roles of the actin cytoskeleton during the main stages of invadopodium development with a particular focus on actin polymerization machineries and production of pushing forces driving extracellular matrix remodeling.
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46
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Karlsson R, Dráber P. Profilin-A master coordinator of actin and microtubule organization in mammalian cells. J Cell Physiol 2021; 236:7256-7265. [PMID: 33821475 DOI: 10.1002/jcp.30379] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/08/2021] [Accepted: 03/12/2021] [Indexed: 12/17/2022]
Abstract
The last two decades have witnessed a tremendous increase in cell biology data. Not least is this true for studies of the dynamic organization of the microfilament and microtubule systems in animal cells where analyses of the molecular components and their interaction patterns have deepened our understanding of these complex force-generating machineries. Previous observations of a molecular cross-talk between the two systems have now led to the realization of the existence of several intricate mechanisms operating to maintain their coordinated cellular organization. In this short review, we relate to this development by discussing new results concerning the function of the actin regulator profilin 1 as a control component of microfilament-microtubule cross-talk.
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Affiliation(s)
- Roger Karlsson
- Department of Molecular Biosciences, WGI, Stockholm University, Stockholm, Sweden
| | - Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
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47
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Dobramysl U, Jarsch IK, Inoue Y, Shimo H, Richier B, Gadsby JR, Mason J, Szałapak A, Ioannou PS, Correia GP, Walrant A, Butler R, Hannezo E, Simons BD, Gallop JL. Stochastic combinations of actin regulatory proteins are sufficient to drive filopodia formation. J Cell Biol 2021; 220:e202003052. [PMID: 33740033 PMCID: PMC7980258 DOI: 10.1083/jcb.202003052] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 11/23/2020] [Accepted: 01/12/2021] [Indexed: 11/22/2022] Open
Abstract
Assemblies of actin and its regulators underlie the dynamic morphology of all eukaryotic cells. To understand how actin regulatory proteins work together to generate actin-rich structures such as filopodia, we analyzed the localization of diverse actin regulators within filopodia in Drosophila embryos and in a complementary in vitro system of filopodia-like structures (FLSs). We found that the composition of the regulatory protein complex where actin is incorporated (the filopodial tip complex) is remarkably heterogeneous both in vivo and in vitro. Our data reveal that different pairs of proteins correlate with each other and with actin bundle length, suggesting the presence of functional subcomplexes. This is consistent with a theoretical framework where three or more redundant subcomplexes join the tip complex stochastically, with any two being sufficient to drive filopodia formation. We provide an explanation for the observed heterogeneity and suggest that a mechanism based on multiple components allows stereotypical filopodial dynamics to arise from diverse upstream signaling pathways.
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Affiliation(s)
- Ulrich Dobramysl
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Iris Katharina Jarsch
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Yoshiko Inoue
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Hanae Shimo
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Benjamin Richier
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Jonathan R. Gadsby
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Julia Mason
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Alicja Szałapak
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Pantelis Savvas Ioannou
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | | | - Astrid Walrant
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Richard Butler
- Gurdon Institute, University of Cambridge, Cambridge, UK
| | - Edouard Hannezo
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Benjamin D. Simons
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK
| | - Jennifer L. Gallop
- Gurdon Institute, University of Cambridge, Cambridge, UK
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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48
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Mwangangi DM, Manser E, Robinson RC. The structure of the actin filament uncapping complex mediated by twinfilin. SCIENCE ADVANCES 2021; 7:eabd5271. [PMID: 33571120 PMCID: PMC7840138 DOI: 10.1126/sciadv.abd5271] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 12/08/2020] [Indexed: 05/25/2023]
Abstract
Uncapping of actin filaments is essential for driving polymerization and depolymerization dynamics from capping protein-associated filaments; however, the mechanisms of uncapping leading to rapid disassembly are unknown. Here, we elucidated the x-ray crystal structure of the actin/twinfilin/capping protein complex to address the mechanisms of twinfilin uncapping of actin filaments. The twinfilin/capping protein complex binds to two G-actin subunits in an orientation that resembles the actin filament barbed end. This suggests an unanticipated mechanism by which twinfilin disrupts the stable capping of actin filaments by inducing a G-actin conformation in the two terminal actin subunits. Furthermore, twinfilin disorders critical actin-capping protein interactions, which will assist in the dissociation of capping protein, and may promote filament uncapping through a second mechanism involving V-1 competition for an actin-binding surface on capping protein. The extensive interactions with capping protein indicate that the evolutionary conserved role of twinfilin is to uncap actin filaments.
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Affiliation(s)
- Dennis M Mwangangi
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis, Singapore 138673, Singapore
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
| | - Edward Manser
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis, Singapore 138673, Singapore
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore
| | - Robert C Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Biopolis, Singapore 138673, Singapore.
- School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong 21210, Thailand
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama 700-8530, Japan
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Ree R, Kind L, Kaziales A, Varland S, Dai M, Richter K, Drazic A, Arnesen T. PFN2 and NAA80 cooperate to efficiently acetylate the N-terminus of actin. J Biol Chem 2020; 295:16713-16731. [PMID: 32978259 PMCID: PMC7864067 DOI: 10.1074/jbc.ra120.015468] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 09/22/2020] [Indexed: 12/01/2022] Open
Abstract
The actin cytoskeleton is of profound importance to cell shape, division, and intracellular force generation. Profilins bind to globular (G-)actin and regulate actin filament formation. Although profilins are well-established actin regulators, the distinct roles of the dominant profilin, profilin 1 (PFN1), versus the less abundant profilin 2 (PFN2) remain enigmatic. In this study, we use interaction proteomics to discover that PFN2 is an interaction partner of the actin N-terminal acetyltransferase NAA80, and further confirm this by analytical ultracentrifugation. Enzyme assays with NAA80 and different profilins demonstrate that PFN2 binding specifically increases the intrinsic catalytic activity of NAA80. NAA80 binds PFN2 through a proline-rich loop, deletion of which abrogates PFN2 binding. Small-angle X-ray scattering shows that NAA80, actin, and PFN2 form a ternary complex and that NAA80 has partly disordered regions in the N-terminus and the proline-rich loop, the latter of which is partly ordered upon PFN2 binding. Furthermore, binding of PFN2 to NAA80 via the proline-rich loop promotes binding between the globular domains of actin and NAA80, and thus acetylation of actin. However, the majority of cellular NAA80 is stably bound to PFN2 and not to actin, and we propose that this complex acetylates G-actin before it is incorporated into filaments. In conclusion, we reveal a functionally specific role of PFN2 as a stable interactor and regulator of the actin N-terminal acetyltransferase NAA80, and establish the modus operandi for NAA80-mediated actin N-terminal acetylation, a modification with a major impact on cytoskeletal dynamics.
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Affiliation(s)
- Rasmus Ree
- Department of Biomedicine, University of Bergen, Bergen, Norway.
| | - Laura Kind
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Anna Kaziales
- Department of Chemistry, Technische Universität München, Garching, Germany
| | - Sylvia Varland
- Department of Biomedicine, University of Bergen, Bergen, Norway; Department of Biological Sciences, University of Bergen, Bergen, Norway
| | - Minglu Dai
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Klaus Richter
- Department of Chemistry, Technische Universität München, Garching, Germany
| | - Adrian Drazic
- Department of Biomedicine, University of Bergen, Bergen, Norway.
| | - Thomas Arnesen
- Department of Biomedicine, University of Bergen, Bergen, Norway; Department of Biological Sciences, University of Bergen, Bergen, Norway; Department of Surgery, Haukeland University Hospital, Bergen, Norway
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Abou-Ghali M, Kusters R, Körber S, Manzi J, Faix J, Sykes C, Plastino J. Capping protein is dispensable for polarized actin network growth and actin-based motility. J Biol Chem 2020; 295:15366-15375. [PMID: 32868296 DOI: 10.1074/jbc.ra120.015009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/26/2020] [Indexed: 11/06/2022] Open
Abstract
Heterodimeric capping protein (CP) binds the rapidly growing barbed ends of actin filaments and prevents the addition (or loss) of subunits. Capping activity is generally considered to be essential for actin-based motility induced by Arp2/3 complex nucleation. By stopping barbed end growth, CP favors nucleation of daughter filaments at the functionalized surface where the Arp2/3 complex is activated, thus creating polarized network growth, which is necessary for movement. However, here using an in vitro assay where Arp2/3 complex-based actin polymerization is induced on bead surfaces in the absence of CP, we produce robust polarized actin growth and motility. This is achieved either by adding the actin polymerase Ena/VASP or by boosting Arp2/3 complex activity at the surface. Another actin polymerase, the formin FMNL2, cannot substitute for CP, showing that polymerase activity alone is not enough to override the need for CP. Interfering with the polymerase activity of Ena/VASP, its surface recruitment or its bundling activity all reduce Ena/VASP's ability to maintain polarized network growth in the absence of CP. Taken together, our findings show that CP is dispensable for polarized actin growth and motility in situations where surface-directed polymerization is favored by whatever means over the growth of barbed ends in the network.
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Affiliation(s)
- Majdouline Abou-Ghali
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, Paris, France; Sorbonne Université, Paris, France
| | - Remy Kusters
- Centre de Recherche Interdisciplinaire, Université de Paris, INSERM U1284, Paris, France
| | - Sarah Körber
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany
| | - John Manzi
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, Paris, France; Sorbonne Université, Paris, France
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany
| | - Cécile Sykes
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, Paris, France; Sorbonne Université, Paris, France
| | - Julie Plastino
- Laboratoire Physico-Chimie Curie, Institut Curie, PSL Research University, CNRS, Paris, France; Sorbonne Université, Paris, France.
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