1
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Pimm ML, Haarer BK, Nobles AD, Haney LM, Marcin AG, Alcaide Eligio M, Henty-Ridilla JL. Coordination of actin plus-end dynamics by IQGAP1, formin, and capping protein. J Cell Biol 2024; 223:e202305065. [PMID: 38787349 PMCID: PMC11117073 DOI: 10.1083/jcb.202305065] [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: 05/16/2023] [Revised: 04/01/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024] Open
Abstract
Cell processes require precise regulation of actin polymerization that is mediated by plus-end regulatory proteins. Detailed mechanisms that explain plus-end dynamics involve regulators with opposing roles, including factors that enhance assembly, e.g., the formin mDia1, and others that stop growth (capping protein, CP). We explore IQGAP1's roles in regulating actin filament plus-ends and the consequences of perturbing its activity in cells. We confirm that IQGAP1 pauses elongation and interacts with plus ends through two residues (C756 and C781). We directly visualize the dynamic interplay between IQGAP1 and mDia1, revealing that IQGAP1 displaces the formin to influence actin assembly. Using four-color TIRF, we show that IQGAP1's displacement activity extends to formin-CP "decision complexes," promoting end-binding protein turnover at plus-ends. Loss of IQGAP1 or its plus-end activities disrupts morphology and migration, emphasizing its essential role. These results reveal a new role for IQGAP1 in promoting protein turnover on filament ends and provide new insights into how plus-end actin assembly is regulated in cells.
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Affiliation(s)
- Morgan L. Pimm
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Brian K. Haarer
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Alexander D. Nobles
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Laura M. Haney
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Alexandra G. Marcin
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Marcela Alcaide Eligio
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Jessica L. Henty-Ridilla
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA
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2
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Sakamoto R, Murrell MP. Composite branched and linear F-actin maximize myosin-induced membrane shape changes in a biomimetic cell model. Commun Biol 2024; 7:840. [PMID: 38987288 DOI: 10.1038/s42003-024-06528-4] [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: 03/04/2024] [Accepted: 07/01/2024] [Indexed: 07/12/2024] Open
Abstract
The architecture of the actin cortex determines the generation and transmission of stresses, during key events from cell division to migration. However, its impact on myosin-induced cell shape changes remains unclear. Here, we reconstitute a minimal model of the actomyosin cortex with branched or linear F-actin architecture within giant unilamellar vesicles (GUVs, liposomes). Upon light activation of myosin, neither the branched nor linear F-actin architecture alone induces significant liposome shape changes. The branched F-actin network forms an integrated, membrane-bound "no-slip boundary" -like cortex that attenuates actomyosin contractility. By contrast, the linear F-actin network forms an unintegrated "slip boundary" -like cortex, where actin asters form without inducing membrane deformations. Notably, liposomes undergo significant deformations at an optimized balance of branched and linear F-actin networks. Our findings highlight the pivotal roles of branched F-actin in force transmission and linear F-actin in force generation to yield membrane shape changes.
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Affiliation(s)
- Ryota Sakamoto
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA
| | - Michael P Murrell
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA.
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA.
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, USA.
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3
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Zsolnay V, Gardel ML, Kovar DR, Voth GA. Cracked actin filaments as mechanosensitive receptors. Biophys J 2024:S0006-3495(24)00411-9. [PMID: 38894540 DOI: 10.1016/j.bpj.2024.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 05/10/2024] [Accepted: 06/14/2024] [Indexed: 06/21/2024] Open
Abstract
Actin filament networks are exposed to mechanical stimuli, but the effect of strain on actin filament structure has not been well established in molecular detail. This is a critical gap in understanding because the activity of a variety of actin-binding proteins has recently been determined to be altered by actin filament strain. We therefore used all-atom molecular dynamics simulations to apply tensile strains to actin filaments and find that changes in actin subunit organization are minimal in mechanically strained, but intact, actin filaments. However, a conformational change disrupts the critical D-loop to W-loop connection between longitudinal neighboring subunits, which leads to a metastable cracked conformation of the actin filament whereby one protofilament is broken prior to filament severing. We propose that the metastable crack presents a force-activated binding site for actin regulatory factors that specifically associate with strained actin filaments. Through protein-protein docking simulations, we find that 43 evolutionarily diverse members of the dual zinc-finger-containing LIM-domain family, which localize to mechanically strained actin filaments, recognize two binding sites exposed at the cracked interface. Furthermore, through its interactions with the crack, LIM domains increase the length of time damaged filaments remain stable. Our findings propose a new molecular model for mechanosensitive binding to actin filaments.
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Affiliation(s)
- Vilmos Zsolnay
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, Illinois
| | - Margaret L Gardel
- Department of Physics & Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois; Institute for Biophysical Dynamics and James Franck Institute, University of Chicago, Chicago, Illinois
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois; Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois.
| | - Gregory A Voth
- Institute for Biophysical Dynamics and James Franck Institute, University of Chicago, Chicago, Illinois; Department of Chemistry and Chicago Center for Theoretical Chemistry, University of Chicago, Chicago, Illinois.
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4
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Niedzialkowska E, Runyan LA, Kudryashova E, Egelman EH, Kudryashov DS. Stabilization of F-actin by Salmonella effector SipA resembles the structural effects of inorganic phosphate and phalloidin. Structure 2024; 32:725-738.e8. [PMID: 38518780 PMCID: PMC11162321 DOI: 10.1016/j.str.2024.02.022] [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: 01/02/2024] [Revised: 02/08/2024] [Accepted: 02/26/2024] [Indexed: 03/24/2024]
Abstract
Entry of Salmonella into host enterocytes relies on its pathogenicity island 1 effector SipA. We found that SipA binds to F-actin in a 1:2 stoichiometry with sub-nanomolar affinity. A cryo-EM reconstruction revealed that SipA's globular core binds at the groove between actin strands, whereas the extended C-terminal arm penetrates deeply into the inter-strand space, stabilizing F-actin from within. The unusually strong binding of SipA is achieved by a combination of fast association via the core and very slow dissociation dictated by the arm. Similar to Pi, BeF3, and phalloidin, SipA potently inhibited actin depolymerization by actin depolymerizing factor (ADF)/cofilin, which correlated with increased filament stiffness, supporting the hypothesis that F-actin's mechanical properties contribute to the recognition of its nucleotide state by protein partners. The remarkably strong binding to F-actin maximizes the toxin's effects at the injection site while minimizing global influence on the cytoskeleton and preventing pathogen detection by the host cell.
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Affiliation(s)
- Ewa Niedzialkowska
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Lucas A Runyan
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22903, USA.
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA.
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5
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Mooren OL, McConnell P, DeBrecht JD, Jaysingh A, Cooper JA. Reconstitution of Arp2/3-Nucleated Actin Assembly with CP, V-1 and CARMIL. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.593916. [PMID: 38798690 PMCID: PMC11118340 DOI: 10.1101/2024.05.13.593916] [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
Actin polymerization is often associated with membrane proteins containing capping-protein-interacting (CPI) motifs, such as CARMIL, CD2AP, and WASHCAP/Fam21. CPI motifs bind directly to actin capping protein (CP), and this interaction weakens the binding of CP to barbed ends of actin filaments, lessening the ability of CP to functionally cap those ends. The protein V-1 / myotrophin binds to the F-actin binding site on CP and sterically blocks CP from binding barbed ends. CPI-motif proteins also weaken the binding between V-1 and CP, which decreases the inhibitory effects of V-1, thereby freeing CP to cap barbed ends. Here, we address the question of whether CPI-motif proteins on a surface analogous to a membrane lead to net activation or inhibition of actin assembly nucleated by Arp2/3 complex. Using reconstitution with purified components, we discovered that CARMIL at the surface promotes and enhances actin assembly, countering the inhibitory effects of V-1 and thus activating CP. The reconstitution involves the presence of an Arp2/3 activator on the surface, along with Arp2/3 complex, V-1, CP, profilin and actin monomers in solution, recreating key features of cell physiology.
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Affiliation(s)
- Olivia L Mooren
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Patrick McConnell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - James D DeBrecht
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - Anshuman Jaysingh
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO
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6
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Liu T, Cao L, Mladenov M, Jegou A, Way M, Moores CA. Cortactin stabilizes actin branches by bridging activated Arp2/3 to its nucleated actin filament. Nat Struct Mol Biol 2024; 31:801-809. [PMID: 38267598 PMCID: PMC11102864 DOI: 10.1038/s41594-023-01205-2] [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: 07/25/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024]
Abstract
Regulation of the assembly and turnover of branched actin filament networks nucleated by the Arp2/3 complex is essential during many cellular processes, including cell migration and membrane trafficking. Cortactin is important for actin branch stabilization, but the mechanism by which this occurs is unclear. Given this, we determined the structure of vertebrate cortactin-stabilized Arp2/3 actin branches using cryogenic electron microscopy. We find that cortactin interacts with the new daughter filament nucleated by the Arp2/3 complex at the branch site, rather than the initial mother actin filament. Cortactin preferentially binds activated Arp3. It also stabilizes the F-actin-like interface of activated Arp3 with the first actin subunit of the new filament, and its central repeats extend along successive daughter-filament subunits. The preference of cortactin for activated Arp3 explains its retention at the actin branch and accounts for its synergy with other nucleation-promoting factors in regulating branched actin network dynamics.
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Affiliation(s)
- Tianyang Liu
- Institute of Structural and Molecular Biology, Birkbeck College, London, UK
| | - Luyan Cao
- The Francis Crick Institute, London, UK
| | | | - Antoine Jegou
- Université Paris Cité, CNRS, Institut Jacques Monod, Paris, France
| | - Michael Way
- The Francis Crick Institute, London, UK.
- Department of Infectious Disease, Imperial College, London, UK.
| | - Carolyn A Moores
- Institute of Structural and Molecular Biology, Birkbeck College, London, UK.
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7
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Pimm ML, Haarer BK, Nobles AD, Haney LM, Marcin AG, Marcela Alcaide Eligio, Henty-Ridilla JL. Coordination of actin plus-end dynamics by IQGAP1, formin, and capping protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.05.04.539490. [PMID: 37205555 PMCID: PMC10187324 DOI: 10.1101/2023.05.04.539490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Cell processes require precise regulation of actin polymerization that is mediated by plus-end regulatory proteins. Detailed mechanisms that explain plus-end dynamics involve regulators with opposing roles, including factors that enhance assembly, e.g., the formin mDia1, and others that stop growth (Capping Protein, CPz). We explore IQGAP1's roles regulating actin filament plus-ends and the consequences of perturbing its activity in cells. We confirm that IQGAP1 pauses elongation and interacts with plus ends through two residues (C756 and C781). We directly visualize the dynamic interplay between IQGAP1 and mDia1, revealing that IQGAP1 displaces the formin to influence actin assembly. Using four-color TIRF we show that IQGAP1's displacement activity extends to formin-CPz 'decision complexes', promoting end-binding protein turnover at plus-ends. Loss of IQGAP1 or its plus-end activities disrupts morphology and migration, emphasizing its essential role. These results reveal a new role for IQGAP1 in promoting protein turnover on filament ends and provide new insights into how plus-end actin assembly is regulated in cells.
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Affiliation(s)
- Morgan L Pimm
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Brian K Haarer
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Alexander D Nobles
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Laura M Haney
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Alexandra G Marcin
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Marcela Alcaide Eligio
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Jessica L Henty-Ridilla
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
- Department of Neuroscience & Physiology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
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8
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Narvaez-Ortiz HY, Lynch MJ, Liu SL, Fries A, Nolen BJ. Both Las17-binding sites on Arp2/3 complex are important for branching nucleation and assembly of functional endocytic actin networks in S. cerevisiae. J Biol Chem 2024; 300:105766. [PMID: 38367669 PMCID: PMC10944109 DOI: 10.1016/j.jbc.2024.105766] [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: 09/27/2023] [Revised: 02/07/2024] [Accepted: 02/12/2024] [Indexed: 02/19/2024] Open
Abstract
Arp2/3 complex nucleates branched actin filaments that drive membrane invagination during endocytosis and leading-edge protrusion in lamellipodia. Arp2/3 complex is maximally activated in vitro by binding of a WASP family protein to two sites-one on the Arp3 subunit and one spanning Arp2 and ARPC1-but the importance of each site in the regulation of force-producing actin networks is unclear. Here, we identify mutations in budding yeast Arp2/3 complex that decrease or block engagement of Las17, the budding yeast WASP, at each site. As in the mammalian system, both sites are required for maximal activation in vitro. Dimerization of Las17 partially restores activity of mutations at both CA-binding sites. Arp2/3 complexes defective at either site assemble force-producing actin networks in a bead motility assay, but their reduced activity hinders motility by decreasing actin assembly near the bead surface and by failing to suppress actin filament bundling within the networks. While even the most defective Las17-binding site mutants assembled actin filaments at endocytic sites, they showed significant internalization defects, potentially because they lack the proper architecture to drive plasma membrane remodeling. Together, our data indicate that both Las17-binding sites are important to assemble functional endocytic actin networks in budding yeast, but Arp2/3 complex retains some activity in vitro and in vivo even with a severe defect at either Las17-binding site.
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Affiliation(s)
- Heidy Y Narvaez-Ortiz
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA
| | - Michael J Lynch
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA
| | - Su-Ling Liu
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA
| | - Adam Fries
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA
| | - Brad J Nolen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA.
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9
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Xu M, Rutkowski DM, Rebowski G, Boczkowska M, Pollard LW, Dominguez R, Vavylonis D, Ostap EM. Myosin-I Synergizes with Arp2/3 Complex to Enhance Pushing Forces of Branched Actin Networks. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.09.579714. [PMID: 38405741 PMCID: PMC10888859 DOI: 10.1101/2024.02.09.579714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Myosin-Is colocalize with Arp2/3 complex-nucleated actin networks at sites of membrane protrusion and invagination, but the mechanisms by which myosin-I motor activity coordinates with branched actin assembly to generate force are unknown. We mimicked the interplay of these proteins using the "comet tail" bead motility assay, where branched actin networks are nucleated by Arp2/3 complex on the surface of beads coated with myosin-I and the WCA domain of N-WASP. We observed that myosin-I increased bead movement efficiency by thinning actin networks without affecting growth rates. Remarkably, myosin-I triggered symmetry breaking and comet-tail formation in dense networks resistant to spontaneous fracturing. Even with arrested actin assembly, myosin-I alone could break the network. Computational modeling recapitulated these observations suggesting myosin-I acts as a repulsive force shaping the network's architecture and boosting its force-generating capacity. We propose that myosin-I leverages its power stroke to amplify the forces generated by Arp2/3 complex-nucleated actin networks.
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Affiliation(s)
- Mengqi Xu
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | | | - Grzegorz Rebowski
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Malgorzata Boczkowska
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Luther W Pollard
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Roberto Dominguez
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | | | - E Michael Ostap
- Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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10
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Mooren OL, Stuchell-Brereton MD, McConnell P, Yan C, Wilkerson EM, Goldfarb D, Cooper JA, Sept D, Soranno A. Biophysical Mechanism of Allosteric Regulation of Actin Capping Protein. J Mol Biol 2023; 435:168342. [PMID: 37924863 PMCID: PMC10872493 DOI: 10.1016/j.jmb.2023.168342] [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: 08/13/2023] [Revised: 10/28/2023] [Accepted: 10/30/2023] [Indexed: 11/06/2023]
Abstract
Actin capping protein (CP) can be regulated by steric and allosteric mechanisms. The molecular mechanism of the allosteric regulation at a biophysical level includes linkage between the binding sites for three ligands: F-actin, Capping-Protein-Interacting (CPI) motifs, and V-1/myotrophin, based on biochemical functional studies and solvent accessibility experiments. Here, we investigated the mechanism of allosteric regulation at the atomic level using single-molecule Förster resonance energy transfer (FRET) and molecular dynamics (MD) to assess the conformational and structural dynamics of CP in response to linked-binding site ligands. In the absence of ligand, both single-molecule FRET and MD revealed two distinct conformations of CP in solution; previous crystallographic studies revealed only one. Interaction with CPI-motif peptides induced conformations within CP that bring the cap and stalk closer, while interaction with V-1 moves them away from one another. Comparing CPI-motif peptides from different proteins, we identified variations in CP conformations and dynamics that are specific to each CPI motif. MD simulations for CP alone and in complex with a CPI motif and V-1 reveal atomistic details of the conformational changes. Analysis of the interaction of CP with wild-type (wt) and chimeric CPI-motif peptides using single-molecule FRET, isothermal calorimetry (ITC) and MD simulation indicated that conformational and affinity differences are intrinsic to the C-terminal portion of the CPI motif. We conclude that allosteric regulation of CP involves changes in conformation that disseminate across the protein to link distinct binding-site functions. Our results provide novel insights into the biophysical mechanism of the allosteric regulation of CP.
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Affiliation(s)
- Olivia L Mooren
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States
| | - Melissa D Stuchell-Brereton
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States; Center for Biomolecular Condensates, Washington University in St Louis, St. Louis, MO, United States
| | - Patrick McConnell
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States
| | - Chenbo Yan
- Department of Biophysics, University of Michigan, Ann Arbor, MI, United States
| | - Emily M Wilkerson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States; Institute for Informatics, Washington University School of Medicine, St. Louis, MO, United States
| | - Dennis Goldfarb
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, United States; Institute for Informatics, Washington University School of Medicine, St. Louis, MO, United States
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States.
| | - David Sept
- Department of Biophysics, University of Michigan, Ann Arbor, MI, United States; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States.
| | - Andrea Soranno
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO, United States; Center for Biomolecular Condensates, Washington University in St Louis, St. Louis, MO, United States.
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11
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de Boer LL, Vanes L, Melgrati S, Biggs O'May J, Hayward D, Driscoll PC, Day J, Griffiths A, Magueta R, Morrell A, MacRae JI, Köchl R, Tybulewicz VLJ. T cell migration requires ion and water influx to regulate actin polymerization. Nat Commun 2023; 14:7844. [PMID: 38057317 PMCID: PMC10700356 DOI: 10.1038/s41467-023-43423-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 11/08/2023] [Indexed: 12/08/2023] Open
Abstract
Migration of T cells is essential for their ability to mount immune responses. Chemokine-induced T cell migration requires WNK1, a kinase that regulates ion influx into the cell. However, it is not known why ion entry is necessary for T cell movement. Here we show that signaling from the chemokine receptor CCR7 leads to activation of WNK1 and its downstream pathway at the leading edge of migrating CD4+ T cells, resulting in ion influx and water entry by osmosis. We propose that WNK1-induced water entry is required to swell the membrane at the leading edge, generating space into which actin filaments can polymerize, thereby facilitating forward movement of the cell. Given the broad expression of WNK1 pathway proteins, our study suggests that ion and water influx are likely to be essential for migration in many cell types, including leukocytes and metastatic tumor cells.
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Affiliation(s)
- Leonard L de Boer
- The Francis Crick Institute, London, NW1 1AT, UK
- Department of Immunology and Inflammation, Imperial College London, London, W12 0NN, UK
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, 171 65, Stockholm, Sweden
| | - Lesley Vanes
- The Francis Crick Institute, London, NW1 1AT, UK
| | - Serena Melgrati
- The Francis Crick Institute, London, NW1 1AT, UK
- Department of Immunology and Inflammation, Imperial College London, London, W12 0NN, UK
- Institute for Research in Biomedicine, Università della Svizzera Italiana, Bellinzona, Switzerland
| | | | - Darryl Hayward
- The Francis Crick Institute, London, NW1 1AT, UK
- GSK, Stevenage, SG1 2NY, UK
| | | | - Jason Day
- Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
| | - Alexander Griffiths
- London Metallomics Facility, Research Management & Innovation Directorate, King's College London, London, SE1 1UL, UK
| | - Renata Magueta
- London Metallomics Facility, Research Management & Innovation Directorate, King's College London, London, SE1 1UL, UK
| | - Alexander Morrell
- London Metallomics Facility, Research Management & Innovation Directorate, King's College London, London, SE1 1UL, UK
| | | | - Robert Köchl
- The Francis Crick Institute, London, NW1 1AT, UK
- Kings College London, London, SE1 9RT, UK
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12
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Goode BL, Eskin J, Shekhar S. Mechanisms of actin disassembly and turnover. J Cell Biol 2023; 222:e202309021. [PMID: 37948068 PMCID: PMC10638096 DOI: 10.1083/jcb.202309021] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/21/2023] [Accepted: 10/23/2023] [Indexed: 11/12/2023] Open
Abstract
Cellular actin networks exhibit a wide range of sizes, shapes, and architectures tailored to their biological roles. Once assembled, these filamentous networks are either maintained in a state of polarized turnover or induced to undergo net disassembly. Further, the rates at which the networks are turned over and/or dismantled can vary greatly, from seconds to minutes to hours or even days. Here, we review the molecular machinery and mechanisms employed in cells to drive the disassembly and turnover of actin networks. In particular, we highlight recent discoveries showing that specific combinations of conserved actin disassembly-promoting proteins (cofilin, GMF, twinfilin, Srv2/CAP, coronin, AIP1, capping protein, and profilin) work in concert to debranch, sever, cap, and depolymerize actin filaments, and to recharge actin monomers for new rounds of assembly.
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Affiliation(s)
- Bruce L. Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA, USA
| | - Julian Eskin
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA, USA
| | - Shashank Shekhar
- Departments of Physics, Cell Biology and Biochemistry, Emory University, Atlanta, GA, USA
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13
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Towsif EM, Shekhar S. Cyclase-associated protein is a pro-formin anti-capping processive depolymerase of actin barbed and pointed ends. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569482. [PMID: 38076850 PMCID: PMC10705416 DOI: 10.1101/2023.11.30.569482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Cellular actin networks display distinct assembly and disassembly dynamics resulting from multicomponent reactions occurring primarily at the two ends and the sides of actin filaments [1-3]. While barbed ends are considered the hotspot of actin assembly [4], disassembly is thought to primarily occur via reactions on filament sides and pointed ends [3, 5-11]. Cyclase-associated protein (CAP) has emerged as the main protagonist of actin disassembly and remodeling - it collaborates with cofilin to increase pointed-end depolymerization by 300-fold [6, 7], promotes filament "coalescence" in presence of Abp1 [12], and accelerates nucleotide exchange to regenerate monomers for new rounds of assembly [13-15]. CAP has also been reported to enhance cofilin-mediated severing [16, 17], but these claims have since been challenged [7]. Using microfluidics-assisted three-color single-molecule imaging, we now reveal that CAP also has important functions at filament barbed ends. We reveal that CAP is a processive barbed-end depolymerase capable of tracking both ends of the filament. Each CAP binding event leads to removal of about 5,175 and 620 subunits from the barbed and pointed ends respectively. We find that the WH2 domain is essential, and the CARP domain is dispensable for barbed-end depolymerization. We show that CAP co-localizes with barbed-end bound formin and capping protein, in the process increasing residence time of formin by 10-fold and promoting dissociation of CP by 4-fold. Our barbed-end observations combined with previously reported activities of CAP at pointed ends and sides, firmly establish CAP as a key player in actin dynamics.
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Affiliation(s)
- Ekram M. Towsif
- Departments of Physics, Cell biology and Biochemistry, Emory University, Atlanta, GA 30322, USA
| | - Shashank Shekhar
- Departments of Physics, Cell biology and Biochemistry, Emory University, Atlanta, GA 30322, USA
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14
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Alimov N, Hoeprich GJ, Padrick SB, Goode BL. Cyclase-associated protein interacts with actin filament barbed ends to promote depolymerization and formin displacement. J Biol Chem 2023; 299:105367. [PMID: 37863260 PMCID: PMC10692737 DOI: 10.1016/j.jbc.2023.105367] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 10/04/2023] [Accepted: 10/12/2023] [Indexed: 10/22/2023] Open
Abstract
Cyclase-associated protein (CAP) has emerged as a central player in cellular actin turnover, but its molecular mechanisms of action are not yet fully understood. Recent studies revealed that the N terminus of CAP interacts with the pointed ends of actin filaments to accelerate depolymerization in conjunction with cofilin. Here, we use in vitro microfluidics-assisted TIRF microscopy to show that the C terminus of CAP promotes depolymerization at the opposite (barbed) ends of actin filaments. In the absence of actin monomers, full-length mouse CAP1 and C-terminal halves of CAP1 (C-CAP1) and CAP2 (C-CAP2) accelerate barbed end depolymerization. Using mutagenesis and structural modeling, we show that these activities are mediated by the WH2 and CARP domains of CAP. In addition, we observe that CAP collaborates with profilin to accelerate barbed end depolymerization and that these effects depend on their direct interaction, providing the first known example of CAP-profilin collaborative effects in regulating actin. In the presence of actin monomers, CAP1 attenuates barbed end growth and promotes formin dissociation. Overall, these findings demonstrate that CAP uses distinct domains and mechanisms to interact with opposite ends of actin filaments and drive turnover. Further, they contribute to the emerging view of actin barbed ends as sites of dynamic molecular regulation, where numerous proteins compete and cooperate with each other to tune polymer dynamics, similar to the rich complexity seen at microtubule ends.
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Affiliation(s)
- Nikita Alimov
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, USA
| | - Gregory J Hoeprich
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, USA
| | - Shae B Padrick
- Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts, USA.
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15
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Gélin M, Schaeffer A, Gaillard J, Guérin C, Vianay B, Orhant-Prioux M, Braun M, Leterrier C, Blanchoin L, Théry M. Microtubules under mechanical pressure can breach dense actin networks. J Cell Sci 2023; 136:jcs261667. [PMID: 37870087 DOI: 10.1242/jcs.261667] [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: 09/21/2023] [Accepted: 09/25/2023] [Indexed: 10/24/2023] Open
Abstract
The crosstalk between the actin network and microtubules is essential for cell polarity. It orchestrates microtubule organization within the cell, driven by the asymmetry of actin architecture along the cell periphery. The physical intertwining of these networks regulates spatial organization and force distribution in the microtubule network. Although their biochemical interactions are becoming clearer, the mechanical aspects remain less understood. To explore this mechanical interplay, we developed an in vitro reconstitution assay to investigate how dynamic microtubules interact with various actin filament structures. Our findings revealed that microtubules can align and move along linear actin filament bundles through polymerization force. However, they are unable to pass through when encountering dense branched actin meshworks, similar to those present in the lamellipodium along the periphery of the cell. Interestingly, immobilizing microtubules through crosslinking with actin or other means allow the buildup of pressure, enabling them to breach these dense actin barriers. This mechanism offers insights into microtubule progression towards the cell periphery, with them overcoming obstacles within the denser parts of the actin network and ultimately contributing to cell polarity establishment.
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Affiliation(s)
- Matthieu Gélin
- Université Paris cité, CEA, INSERM, Institut de Recherche Saint Louis, UMR976 HIPI, CytoMorpho Lab, Avenue Claude Vellefaux, 75010 Paris, France
| | - Alexandre Schaeffer
- Université Paris cité, CEA, INSERM, Institut de Recherche Saint Louis, UMR976 HIPI, CytoMorpho Lab, Avenue Claude Vellefaux, 75010 Paris, France
| | - Jérémie Gaillard
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, Avenue des Martyrs, 38054 Grenoble, France
| | - Christophe Guérin
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, Avenue des Martyrs, 38054 Grenoble, France
| | - Benoit Vianay
- Université Paris cité, CEA, INSERM, Institut de Recherche Saint Louis, UMR976 HIPI, CytoMorpho Lab, Avenue Claude Vellefaux, 75010 Paris, France
| | - Magali Orhant-Prioux
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, Avenue des Martyrs, 38054 Grenoble, France
| | - Marcus Braun
- Institute of Biotechnology, Czech Academy of Sciences, BIOCEV, 25250 Vestec, Prague West, Czech Republic
| | - Christophe Leterrier
- Aix Marseille Université, CNRS, INP UMR7051, NeuroCyto, 13385, Marseille, France
| | - Laurent Blanchoin
- Université Paris cité, CEA, INSERM, Institut de Recherche Saint Louis, UMR976 HIPI, CytoMorpho Lab, Avenue Claude Vellefaux, 75010 Paris, France
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, Avenue des Martyrs, 38054 Grenoble, France
| | - Manuel Théry
- Université Paris cité, CEA, INSERM, Institut de Recherche Saint Louis, UMR976 HIPI, CytoMorpho Lab, Avenue Claude Vellefaux, 75010 Paris, France
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, UMR5168-LPCV, CytoMorpho Lab, Avenue des Martyrs, 38054 Grenoble, France
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16
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Oosterheert W, Blanc FEC, Roy A, Belyy A, Sanders MB, Hofnagel O, Hummer G, Bieling P, Raunser S. Molecular mechanisms of inorganic-phosphate release from the core and barbed end of actin filaments. Nat Struct Mol Biol 2023; 30:1774-1785. [PMID: 37749275 PMCID: PMC10643162 DOI: 10.1038/s41594-023-01101-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 08/18/2023] [Indexed: 09/27/2023]
Abstract
The release of inorganic phosphate (Pi) from actin filaments constitutes a key step in their regulated turnover, which is fundamental to many cellular functions. The mechanisms underlying Pi release from the core and barbed end of actin filaments remain unclear. Here, using human and bovine actin isoforms, we combine cryo-EM with molecular-dynamics simulations and in vitro reconstitution to demonstrate how actin releases Pi through a 'molecular backdoor'. While constantly open at the barbed end, the backdoor is predominantly closed in filament-core subunits and opens only transiently through concerted amino acid rearrangements. This explains why Pi escapes rapidly from the filament end but slowly from internal subunits. In a nemaline-myopathy-associated actin variant, the backdoor is predominantly open in filament-core subunits, resulting in accelerated Pi release and filaments with drastically shortened ADP-Pi caps. Our results provide the molecular basis for Pi release from actin and exemplify how a disease-linked mutation distorts the nucleotide-state distribution and atomic structure of the filament.
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Affiliation(s)
- Wout Oosterheert
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Florian E C Blanc
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Ankit Roy
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Alexander Belyy
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Micaela Boiero Sanders
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Oliver Hofnagel
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
- Institute for Biophysics, Goethe University, Frankfurt am Main, Germany.
| | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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17
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Sitarska E, Almeida SD, Beckwith MS, Stopp J, Czuchnowski J, Siggel M, Roessner R, Tschanz A, Ejsing C, Schwab Y, Kosinski J, Sixt M, Kreshuk A, Erzberger A, Diz-Muñoz A. Sensing their plasma membrane curvature allows migrating cells to circumvent obstacles. Nat Commun 2023; 14:5644. [PMID: 37704612 PMCID: PMC10499897 DOI: 10.1038/s41467-023-41173-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 08/22/2023] [Indexed: 09/15/2023] Open
Abstract
To navigate through diverse tissues, migrating cells must balance persistent self-propelled motion with adaptive behaviors to circumvent obstacles. We identify a curvature-sensing mechanism underlying obstacle evasion in immune-like cells. Specifically, we propose that actin polymerization at the advancing edge of migrating cells is inhibited by the curvature-sensitive BAR domain protein Snx33 in regions with inward plasma membrane curvature. The genetic perturbation of this machinery reduces the cells' capacity to evade obstructions combined with faster and more persistent cell migration in obstacle-free environments. Our results show how cells can read out their surface topography and utilize actin and plasma membrane biophysics to interpret their environment, allowing them to adaptively decide if they should move ahead or turn away. On the basis of our findings, we propose that the natural diversity of BAR domain proteins may allow cells to tune their curvature sensing machinery to match the shape characteristics in their environment.
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Affiliation(s)
- Ewa Sitarska
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, EMBL and Heidelberg University, Heidelberg, Germany
| | - Silvia Dias Almeida
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Division of Medical Image Computing, German Cancer Research Center (DKFZ), 69120, Heidelberg, Germany
| | | | - Julian Stopp
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - Jakub Czuchnowski
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Marc Siggel
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
| | - Rita Roessner
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
| | - Aline Tschanz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Collaboration for joint PhD degree between EMBL and Heidelberg University, Faculty of Biosciences, EMBL and Heidelberg University, Heidelberg, Germany
| | - Christer Ejsing
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
- Department of Biochemistry and Molecular Biology, Villum Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, 5230, Odense, Denmark
| | - Yannick Schwab
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Jan Kosinski
- EMBL Hamburg, European Molecular Biology Laboratory, 22607, Hamburg, Germany
- Centre for Structural Systems Biology, 22607, Hamburg, Germany
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Michael Sixt
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - Anna Kreshuk
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Anna Erzberger
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany
| | - Alba Diz-Muñoz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117, Heidelberg, Germany.
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18
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Chen X, Li Y, Guo M, Xu B, Ma Y, Zhu H, Feng XQ. Polymerization force-regulated actin filament-Arp2/3 complex interaction dominates self-adaptive cell migrations. Proc Natl Acad Sci U S A 2023; 120:e2306512120. [PMID: 37639611 PMCID: PMC10483647 DOI: 10.1073/pnas.2306512120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/23/2023] [Indexed: 08/31/2023] Open
Abstract
Cells migrate by adapting their leading-edge behaviors to heterogeneous extracellular microenvironments (ECMs) during cancer invasions and immune responses. Yet it remains poorly understood how such complicated dynamic behaviors emerge from millisecond-scale assembling activities of protein molecules, which are hard to probe experimentally. To address this gap, we establish a spatiotemporal "resistance-adaptive propulsion" theory based on the interactions between Arp2/3 complexes and polymerizing actin filaments and a multiscale dynamic modeling system spanning from molecular proteins to the cell. We quantitatively find that cells can accurately self-adapt propulsive forces to overcome heterogeneous ECMs via a resistance-triggered positive feedback mechanism, dominated by polymerization-induced actin filament bending and the bending-regulated actin-Arp2/3 binding. However, for high resistance regions, resistance triggers a negative feedback, hindering branched filament assembly, which adapts cellular morphologies to circumnavigate the obstacles. Strikingly, the synergy of the two opposite feedbacks not only empowers the cell with both powerful and flexible migratory capabilities to deal with complex ECMs but also enables efficient utilization of intracellular proteins by the cell. In addition, we identify that the nature of cell migration velocity depending on ECM history stems from the inherent temporal hysteresis of cytoskeleton remodeling. We also show that directional cell migration is dictated by the competition between the local stiffness of ECMs and the local polymerizing rate of actin network caused by chemotactic cues. Our results reveal that it is the polymerization force-regulated actin filament-Arp2/3 complex binding interaction that dominates self-adaptive cell migrations in complex ECMs, and we provide a predictive theory and a spatiotemporal multiscale modeling system at the protein level.
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Affiliation(s)
- Xindong Chen
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing100084, China
- School of Engineering, Cardiff University, CardiffCF24 3AA, United Kingdom
| | - Yuhui Li
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire et Végétale, Interdisciplinary Research Institute of Grenoble, Commissariat à l’Énergie Atomique et aux Énergies Alternatives/CNRS/Université Grenoble Alpes, Grenoble38054, France
| | - Ming Guo
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Bowen Xu
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing100084, China
| | - Yanhui Ma
- School of Engineering, Cardiff University, CardiffCF24 3AA, United Kingdom
| | - Hanxing Zhu
- School of Engineering, Cardiff University, CardiffCF24 3AA, United Kingdom
| | - Xi-Qiao Feng
- Institute of Biomechanics and Medical Engineering, Department of Engineering Mechanics, Tsinghua University, Beijing100084, China
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19
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Singh Y, Hocky GM, Nolen BJ. Molecular dynamics simulations support a multistep pathway for activation of branched actin filament nucleation by Arp2/3 complex. J Biol Chem 2023; 299:105169. [PMID: 37595874 PMCID: PMC10514467 DOI: 10.1016/j.jbc.2023.105169] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 08/10/2023] [Accepted: 08/12/2023] [Indexed: 08/20/2023] Open
Abstract
Actin-related protein 2/3 complex (Arp2/3 complex) catalyzes the nucleation of branched actin filaments that push against membranes in processes like cellular motility and endocytosis. During activation by WASP proteins, the complex must bind WASP and engage the side of a pre-existing (mother) filament before a branched filament is nucleated. Recent high-resolution structures of activated Arp2/3 complex revealed two major sets of activating conformational changes. How these activating conformational changes are triggered by interactions of Arp2/3 complex with actin filaments and WASP remains unclear. Here we use a recent high-resolution structure of Arp2/3 complex at a branch junction to design all-atom molecular dynamics simulations that elucidate the pathway between the active and inactive states. We ran a total of ∼4.6 microseconds of both unbiased and steered all-atom molecular dynamics simulations starting from three different binding states, including Arp2/3 complex within a branch junction, bound only to a mother filament, and alone in solution. These simulations indicate that the contacts with the mother filament are mostly insensitive to the massive rigid body motion that moves Arp2 and Arp3 into a short pitch helical (filament-like) arrangement, suggesting actin filaments alone do not stimulate the short pitch conformational change. In contrast, contacts with the mother filament stabilize subunit flattening in Arp3, an intrasubunit change that converts Arp3 from a conformation that mimics an actin monomer to one that mimics a filamentous actin subunit. Our results support a multistep activation pathway that has important implications for understanding how WASP-mediated activation allows Arp2/3 complex to assemble force-producing actin networks.
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Affiliation(s)
| | - Glen M Hocky
- Department of Chemistry, New York University; Simons Center for Computational Physical Chemistry, New York University.
| | - Brad J Nolen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon.
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20
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Mooren OL, Stuchell-Brereton MD, McConnell P, Yan C, Wilkerson EM, Goldfarb D, Cooper JA, Sept D, Soranno A. Biophysical Mechanism of Allosteric Regulation of Actin Capping Protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.16.553570. [PMID: 37645735 PMCID: PMC10462145 DOI: 10.1101/2023.08.16.553570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Actin capping protein (CP) can be regulated by steric and allosteric mechanisms. The molecular mechanism of the allosteric regulation at a biophysical level includes linkage between the binding sites for three ligands: F-actin, Capping-Protein-Interacting (CPI) motifs, and V-1/myotrophin, based on biochemical functional studies and solvent accessibility experiments. Here, we investigated the mechanism of allosteric regulation at the atomic level using single-molecule Förster resonance energy transfer (FRET) and molecular dynamics (MD) to assess the conformational and structural dynamics of CP in response to linked-binding site ligands. In the absence of ligand, both single-molecule FRET and MD revealed two distinct conformations of CP in solution; previous crystallographic studies revealed only one. CPI-motif peptide association induced conformational changes within CP that propagate in one direction, while V-1 association induced conformational changes in the opposite direction. Comparing CPI-motif peptides from different proteins, we identified variations in CP conformations and dynamics that are specific to each CPI motif. MD simulations for CP alone and in complex with a CPI motif and V-1 reveal atomistic details of the conformational changes. Analysis of the interaction of CP with wildtype (wt) and chimeric CPI-motif peptides using single-molecule FRET, isothermal calorimetry (ITC) and MD simulation indicated that conformational and affinity differences are intrinsic to the C-terminal portion of the CPI-motif. We conclude that allosteric regulation of CP involves changes in conformation that disseminate across the protein to link distinct binding-site functions. Our results provide novel insights into the biophysical mechanism of the allosteric regulation of CP.
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21
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Wang KH, Chang JY, Li FA, Wu KY, Hsu SH, Chen YJ, Chu TL, Lin J, Hsu HM. An Atypical F-Actin Capping Protein Modulates Cytoskeleton Behaviors Crucial for Trichomonas vaginalis Colonization. Microbiol Spectr 2023; 11:e0059623. [PMID: 37310229 PMCID: PMC10434240 DOI: 10.1128/spectrum.00596-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 05/22/2023] [Indexed: 06/14/2023] Open
Abstract
Cytoadherence and migration are crucial for pathogens to establish colonization in the host. In contrast to a nonadherent isolate of Trichomonas vaginalis, an adherent one expresses more actin-related machinery proteins with more active flagellate-amoeboid morphogenesis, amoeba migration, and cytoadherence, activities that were abrogated by an actin assembly blocker. By immunoprecipitation coupled with label-free quantitative proteomics, an F-actin capping protein (T. vaginalis F-actin capping protein subunit α [TvFACPα]) was identified from the actin-centric interactome. His-TvFACPα was detected at the barbed end of a growing F-actin filament, which inhibited elongation and possessed atypical activity in binding G-actin in in vitro assays. TvFACPα partially colocalized with F-actin at the parasite pseudopod protrusion and formed a protein complex with α-actin through its C-terminal domain. Meanwhile, TvFACPα overexpression suppressed F-actin polymerization, amoeboid morphogenesis, and cytoadherence in this parasite. Ser2 phosphorylation of TvFACPα enriched in the amoeboid stage of adhered trophozoites was reduced by a casein kinase II (CKII) inhibitor. Site-directed mutagenesis and CKII inhibitor treatment revealed that Ser2 phosphorylation acts as a switching signal to alter TvFACPα actin-binding activity and the consequent actin cytoskeleton behaviors. Through CKII signaling, TvFACPα also controls the conversion of adherent trophozoites from amoeboid migration to the flagellate form with axonemal motility. Together, CKII-dependent Ser2 phosphorylation regulates TvFACPα binding to actin to fine-tune cytoskeleton dynamics and drive crucial behaviors underlying host colonization by T. vaginalis. IMPORTANCE Trichomoniasis is one of the most prevalent nonviral sexually transmitted diseases. T. vaginalis cytoadherence to urogenital epithelium cells is the first step in the colonization of the host. However, studies on the mechanisms of cytoadherence have focused mainly on the role of adhesion molecules, and their effects are limited when analyzed by loss- or gain-of-function assays. This study proposes an extra pathway in which the actin cytoskeleton mediated by a capping protein α-subunit may play roles in parasite morphogenesis, cytoadherence, and motility, which are crucial for colonization. Once the origin of the cytoskeleton dynamics could be manipulated, the consequent activities would be controlled as well. This mechanism may provide new potential therapeutic targets to impair this parasite infection and relieve the increasing impact of drug resistance on clinical and public health.
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Affiliation(s)
- Kai-Hsuan Wang
- Department of Tropical Medicine and Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Jing-Yang Chang
- Department of Tropical Medicine and Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Fu-An Li
- The Proteomic Core, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Kuan-Yi Wu
- Department of Tropical Medicine and Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Shu-Hao Hsu
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yen-Ju Chen
- Department of Tropical Medicine and Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | | | - Jessica Lin
- Taipei First Girls High School, Taipei, Taiwan
| | - Hong-Ming Hsu
- Department of Tropical Medicine and Parasitology, College of Medicine, National Taiwan University, Taipei, Taiwan
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22
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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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23
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van Eeuwen T, Boczkowska M, Rebowski G, Carman PJ, Fregoso FE, Dominguez R. Transition State of Arp2/3 Complex Activation by Actin-Bound Dimeric Nucleation-Promoting Factor. Proc Natl Acad Sci U S A 2023; 120:e2306165120. [PMID: 37549294 PMCID: PMC10434305 DOI: 10.1073/pnas.2306165120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Accepted: 07/03/2023] [Indexed: 08/09/2023] Open
Abstract
Arp2/3 complex generates branched actin networks that drive fundamental processes such as cell motility and cytokinesis. The complex comprises seven proteins, including actin-related proteins (Arps) 2 and 3 and five scaffolding proteins (ArpC1-ArpC5) that mediate interactions with a pre-existing (mother) actin filament at the branch junction. Arp2/3 complex exists in two main conformations, inactive with the Arps interacting end-to-end and active with the Arps interacting side-by-side like subunits of the short-pitch helix of the actin filament. Several cofactors drive the transition toward the active state, including ATP binding to the Arps, WASP-family nucleation-promoting factors (NPFs), actin monomers, and binding of Arp2/3 complex to the mother filament. The precise contribution of each cofactor to activation is poorly understood. We report the 3.32-Å resolution cryo-electron microscopy structure of a transition state of Arp2/3 complex activation with bound constitutively dimeric NPF. Arp2/3 complex-binding region of the NPF N-WASP was fused C-terminally to the α and β subunits of the CapZ heterodimer. One arm of the NPF dimer binds Arp2 and the other binds actin and Arp3. The conformation of the complex is intermediate between those of inactive and active Arp2/3 complex. Arp2, Arp3, and actin also adopt intermediate conformations between monomeric (G-actin) and filamentous (F-actin) states, but only actin hydrolyzes ATP. In solution, the transition complex is kinetically shifted toward the short-pitch conformation and has higher affinity for F-actin than inactive Arp2/3 complex. The results reveal how all the activating cofactors contribute in a coordinated manner toward Arp2/3 complex activation.
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Affiliation(s)
- Trevor van Eeuwen
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Malgorzata Boczkowska
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Grzegorz Rebowski
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Peter J. Carman
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Fred E. Fregoso
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Roberto Dominguez
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA19104
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24
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Kramer DA, Narvaez-Ortiz HY, Patel U, Shi R, Shen K, Nolen BJ, Roche J, Chen B. The intrinsically disordered cytoplasmic tail of a dendrite branching receptor uses two distinct mechanisms to regulate the actin cytoskeleton. eLife 2023; 12:e88492. [PMID: 37555826 PMCID: PMC10411975 DOI: 10.7554/elife.88492] [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: 04/10/2023] [Accepted: 05/01/2023] [Indexed: 08/10/2023] Open
Abstract
Dendrite morphogenesis is essential for neural circuit formation, yet the molecular mechanisms underlying complex dendrite branching remain elusive. Previous studies on the highly branched Caenorhabditis elegans PVD sensory neuron identified a membrane co-receptor complex that links extracellular signals to intracellular actin remodeling machinery, promoting high-order dendrite branching. In this complex, the claudin-like transmembrane protein HPO-30 recruits the WAVE regulatory complex (WRC) to dendrite branching sites, stimulating the Arp2/3 complex to polymerize actin. We report here our biochemical and structural analysis of this interaction, revealing that the intracellular domain (ICD) of HPO-30 is intrinsically disordered and employs two distinct mechanisms to regulate the actin cytoskeleton. First, HPO-30 ICD binding to the WRC requires dimerization and involves the entire ICD sequence, rather than a short linear peptide motif. This interaction enhances WRC activation by the GTPase Rac1. Second, HPO-30 ICD directly binds to the sides and barbed end of actin filaments. Binding to the barbed end requires ICD dimerization and inhibits both actin polymerization and depolymerization, resembling the actin capping protein CapZ. These dual functions provide an intriguing model of how membrane proteins can integrate distinct mechanisms to fine-tune local actin dynamics.
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Affiliation(s)
- Daniel A Kramer
- Roy J Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State UniversityAmesUnited States
| | - Heidy Y Narvaez-Ortiz
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Urval Patel
- Roy J Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State UniversityAmesUnited States
| | - Rebecca Shi
- Department of Biology, Stanford UniversityStanfordUnited States
- Neurosciences IDP, Stanford UniversityStanfordUnited States
| | - Kang Shen
- Department of Biology, Stanford UniversityStanfordUnited States
- Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Brad J Nolen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of OregonEugeneUnited States
| | - Julien Roche
- Roy J Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State UniversityAmesUnited States
| | - Baoyu Chen
- Roy J Carver Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State UniversityAmesUnited States
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25
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Zhang Q, Wan M, Kudryashova E, Kudryashov DS, Mao Y. Membrane-dependent actin polymerization mediated by the Legionella pneumophila effector protein MavH. PLoS Pathog 2023; 19:e1011512. [PMID: 37463171 PMCID: PMC10381072 DOI: 10.1371/journal.ppat.1011512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/26/2023] [Indexed: 07/20/2023] Open
Abstract
L. pneumophila propagates in eukaryotic cells within a specialized niche, the Legionella-containing vacuole (LCV). The infection process is controlled by over 330 effector proteins delivered through the type IV secretion system. In this study, we report that the Legionella MavH effector localizes to endosomes and remodels host actin cytoskeleton in a phosphatidylinositol 3-phosphate (PI(3)P) dependent manner when ectopically expressed. We show that MavH recruits host actin capping protein (CP) and actin to the endosome via its CP-interacting (CPI) motif and WH2-like actin-binding domain, respectively. In vitro assays revealed that MavH stimulates actin assembly on PI(3)P-containing liposomes causing their tubulation. In addition, the recruitment of CP by MavH negatively regulates F-actin density at the membrane. We further show that, in L. pneumophila-infected cells, MavH appears around the LCV at the very early stage of infection and facilitates bacterium entry into the host. Together, our results reveal a novel mechanism of membrane tubulation induced by membrane-dependent actin polymerization catalyzed by MavH that contributes to the early stage of L. pneumophila infection by regulating host actin dynamics.
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Affiliation(s)
- Qing Zhang
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Min Wan
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, United States of America
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio, United States of America
| | - Yuxin Mao
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
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26
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Ulrichs H, Gaska I, Shekhar S. Multicomponent regulation of actin barbed end assembly by twinfilin, formin and capping protein. Nat Commun 2023; 14:3981. [PMID: 37414761 PMCID: PMC10326068 DOI: 10.1038/s41467-023-39655-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 06/22/2023] [Indexed: 07/08/2023] Open
Abstract
Cells control actin assembly by regulating reactions at actin filament barbed ends. Formins accelerate elongation, capping protein (CP) arrests growth and twinfilin promotes depolymerization at barbed ends. How these distinct activities get integrated within a shared cytoplasm is unclear. Using microfluidics-assisted TIRF microscopy, we find that formin, CP and twinfilin can simultaneously bind filament barbed ends. Three‑color, single-molecule experiments reveal that twinfilin cannot bind barbed ends occupied by formin unless CP is present. This trimeric complex is short-lived (~1 s), and results in dissociation of CP by twinfilin, promoting formin-based elongation. Thus, the depolymerase twinfilin acts as a pro-formin pro-polymerization factor when both CP and formin are present. While one twinfilin binding event is sufficient to displace CP from the barbed-end trimeric complex, ~31 twinfilin binding events are required to remove CP from a CP-capped barbed end. Our findings establish a paradigm where polymerases, depolymerases and cappers together tune actin assembly.
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Affiliation(s)
- Heidi Ulrichs
- Department of Physics, Emory University, Atlanta, GA, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA
| | - Ignas Gaska
- Department of Physics, Emory University, Atlanta, GA, 30322, USA
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA
| | - Shashank Shekhar
- Department of Physics, Emory University, Atlanta, GA, 30322, USA.
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA.
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27
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Zsolnay V, Gardel ML, Kovar DR, Voth GA. Cracked actin filaments as mechanosensitive receptors. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546553. [PMID: 37425801 PMCID: PMC10327158 DOI: 10.1101/2023.06.26.546553] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Actin filament networks are exposed to mechanical stimuli, but the effect of strain on actin filament structure has not been well-established in molecular detail. This is a critical gap in understanding because the activity of a variety of actin-binding proteins have recently been determined to be altered by actin filament strain. We therefore used all-atom molecular dynamics simulations to apply tensile strains to actin filaments and find that changes in actin subunit organization are minimal in mechanically strained, but intact, actin filaments. However, a conformational change disrupts the critical D-loop to W-loop connection between longitudinal neighboring subunits, which leads to a metastable cracked conformation of the actin filament, whereby one protofilament is broken prior to filament severing. We propose that the metastable crack presents a force-activated binding site for actin regulatory factors that specifically associate with strained actin filaments. Through protein-protein docking simulations, we find that 43 evolutionarily-diverse members of the dual zinc finger containing LIM domain family, which localize to mechanically strained actin filaments, recognize two binding sites exposed at the cracked interface. Furthermore, through its interactions with the crack, LIM domains increase the length of time damaged filaments remain stable. Our findings propose a new molecular model for mechanosensitive binding to actin filaments.
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Affiliation(s)
- Vilmos Zsolnay
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL
| | - Margaret L. Gardel
- Department of Physics & Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL
- Institute for Biophysical Dynamics and James Franck Institute, University of Chicago, Chicago, IL
| | - David R. Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL
| | - Gregory A. Voth
- Institute for Biophysical Dynamics and James Franck Institute, University of Chicago, Chicago, IL
- Department of Chemistry and Chicago Center for Theoretical Chemistry, University of Chicago, Chicago, IL
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28
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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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29
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Li N, Chen S, Xu K, He MT, Dong MQ, Zhang QC, Gao N. Structural basis of membrane skeleton organization in red blood cells. Cell 2023; 186:1912-1929.e18. [PMID: 37044097 DOI: 10.1016/j.cell.2023.03.017] [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: 09/12/2022] [Revised: 02/12/2023] [Accepted: 03/15/2023] [Indexed: 04/14/2023]
Abstract
The spectrin-based membrane skeleton is a ubiquitous membrane-associated two-dimensional cytoskeleton underneath the lipid membrane of metazoan cells. Mutations of skeleton proteins impair the mechanical strength and functions of the membrane, leading to several different types of human diseases. Here, we report the cryo-EM structures of the native spectrin-actin junctional complex (from porcine erythrocytes), which is a specialized short F-actin acting as the central organizational unit of the membrane skeleton. While an α-/β-adducin hetero-tetramer binds to the barbed end of F-actin as a flexible cap, tropomodulin and SH3BGRL2 together create an absolute cap at the pointed end. The junctional complex is strengthened by ring-like structures of dematin in the middle actin layers and by patterned periodic interactions with tropomyosin over its entire length. This work serves as a structural framework for understanding the assembly and dynamics of membrane skeleton and offers insights into mechanisms of various ubiquitous F-actin-binding factors in other F-actin systems.
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Affiliation(s)
- Ningning Li
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China; Changping Laboratory, Beijing 102206, China.
| | - Siyi Chen
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China; Changping Laboratory, Beijing 102206, China; Changping Laboratory Graduate Program, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China
| | - Kui Xu
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Meng-Ting He
- National Institute of Biological Sciences, Beijing 102206, China; Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 100084, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences, Beijing 102206, China; Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 100084, China
| | - Qiangfeng Cliff Zhang
- MOE Key Laboratory of Bioinformatics, Center for Synthetic and Systems Biology, Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China; Changping Laboratory, Beijing 102206, China; National Biomedical Imaging Center, Peking University, Beijing 100871, China.
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30
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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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31
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Colin A, Kotila T, Guérin C, Orhant-Prioux M, Vianay B, Mogilner A, Lappalainen P, Théry M, Blanchoin L. Recycling of the actin monomer pool limits the lifetime of network turnover. EMBO J 2023; 42:e112717. [PMID: 36912152 PMCID: PMC10152149 DOI: 10.15252/embj.2022112717] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 02/10/2023] [Accepted: 02/21/2023] [Indexed: 03/14/2023] Open
Abstract
Intracellular organization is largely mediated by actin turnover. Cellular actin networks continuously assemble and disassemble, while maintaining their overall appearance. This behavior, called "dynamic steady state," allows cells to sense and adapt to their environment. However, how structural stability can be maintained during the constant turnover of a limited actin monomer pool is poorly understood. To answer this question, we developed an experimental system where polystyrene beads are propelled by an actin comet in a microwell containing a limited amount of components. We used the speed and the size of the actin comet tails to evaluate the system's monomer consumption and its lifetime. We established the relative contribution of actin assembly, disassembly, and recycling for a bead movement over tens of hours. Recycling mediated by cyclase-associated protein (CAP) is the key step in allowing the reuse of monomers for multiple assembly cycles. ATP supply and protein aging are also factors that limit the lifetime of actin turnover. This work reveals the balancing mechanism for long-term network assembly with a limited amount of building blocks.
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Affiliation(s)
- Alexandra Colin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Tommi Kotila
- Institute of Biotechnology and Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Christophe Guérin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Magali Orhant-Prioux
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Benoit Vianay
- CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
| | - Alex Mogilner
- Courant Institute of Mathematical Sciences, New York University, New York, NY, USA.,Department of Biology, New York University, New York, NY, USA
| | - Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Manuel Théry
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
| | - Laurent Blanchoin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
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32
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Deciphering the molecular mechanisms of actin cytoskeleton regulation in cell migration using cryo-EM. Biochem Soc Trans 2023; 51:87-99. [PMID: 36695514 PMCID: PMC9987995 DOI: 10.1042/bst20220221] [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: 12/01/2022] [Revised: 01/12/2023] [Accepted: 01/12/2023] [Indexed: 01/26/2023]
Abstract
The actin cytoskeleton plays a key role in cell migration and cellular morphodynamics in most eukaryotes. The ability of the actin cytoskeleton to assemble and disassemble in a spatiotemporally controlled manner allows it to form higher-order structures, which can generate forces required for a cell to explore and navigate through its environment. It is regulated not only via a complex synergistic and competitive interplay between actin-binding proteins (ABP), but also by filament biochemistry and filament geometry. The lack of structural insights into how geometry and ABPs regulate the actin cytoskeleton limits our understanding of the molecular mechanisms that define actin cytoskeleton remodeling and, in turn, impact emerging cell migration characteristics. With the advent of cryo-electron microscopy (cryo-EM) and advanced computational methods, it is now possible to define these molecular mechanisms involving actin and its interactors at both atomic and ultra-structural levels in vitro and in cellulo. In this review, we will provide an overview of the available cryo-EM methods, applicable to further our understanding of the actin cytoskeleton, specifically in the context of cell migration. We will discuss how these methods have been employed to elucidate ABP- and geometry-defined regulatory mechanisms in initiating, maintaining, and disassembling cellular actin networks in migratory protrusions.
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33
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Wirshing AC, Rodriguez SG, Goode BL. Evolutionary tuning of barbed end competition allows simultaneous construction of architecturally distinct actin structures. J Cell Biol 2023; 222:213854. [PMID: 36729023 PMCID: PMC9929936 DOI: 10.1083/jcb.202209105] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/01/2022] [Accepted: 01/13/2023] [Indexed: 02/03/2023] Open
Abstract
How cells simultaneously assemble actin structures of distinct sizes, shapes, and filamentous architectures is still not well understood. Here, we used budding yeast as a model to investigate how competition for the barbed ends of actin filaments might influence this process. We found that while vertebrate capping protein (CapZ) and formins can simultaneously associate with barbed ends and catalyze each other's displacement, yeast capping protein (Cap1/2) poorly displaces both yeast and vertebrate formins. Consistent with these biochemical differences, in vivo formin-mediated actin cable assembly was strongly attenuated by the overexpression of CapZ but not Cap1/2. Multiwavelength live cell imaging further revealed that actin patches in cap2∆ cells acquire cable-like features over time, including recruitment of formins and tropomyosin. Together, our results suggest that the activities of S. cerevisiae Cap1/2 have been tuned across evolution to allow robust cable assembly by formins in the presence of high cytosolic levels of Cap1/2, which conversely limit patch growth and shield patches from formins.
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Affiliation(s)
- Alison C.E. Wirshing
- https://ror.org/05abbep66Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA, USA
| | - Sofia Gonzalez Rodriguez
- https://ror.org/05abbep66Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA, USA
| | - Bruce L. Goode
- https://ror.org/05abbep66Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA, USA,Correspondence to Bruce L. Goode:
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34
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Bieling P, Rottner K. From WRC to Arp2/3: Collective molecular mechanisms of branched actin network assembly. Curr Opin Cell Biol 2023; 80:102156. [PMID: 36868090 DOI: 10.1016/j.ceb.2023.102156] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 01/30/2023] [Accepted: 01/31/2023] [Indexed: 03/05/2023]
Abstract
Branched actin networks have emerged as major force-generating structures driving the protrusions in various distinct cell types and processes, ranging from lamellipodia operating in mesenchymal and epithelial cell migration or tails pushing intracellular pathogens and vesicles to developing spine heads on neurons. Many key molecular features are conserved among all those Arp2/3 complex-containing, branched actin networks. Here, we will review recent progress in our molecular understanding of the core biochemical machinery driving branched actin nucleation, from the generation of filament primers to Arp2/3 activator recruitment, regulation and turnover. Due to the wealth of information on distinct, Arp2/3 network-containing structures, we are largely focusing-in an exemplary fashion-on canonical lamellipodia of mesenchymal cells, which are regulated by Rac GTPases, their downstream effector WAVE Regulatory Complex and its target Arp2/3 complex. Novel insight additionally confirms that WAVE and Arp2/3 complexes regulate or are themselves tuned by additional prominent actin regulatory factors, including Ena/VASP family members and heterodimeric capping protein. Finally, we are considering recent insights into effects exerted by mechanical force, both at the branched network and individual actin regulator level.
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Affiliation(s)
- Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany; Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany.
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35
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Zhang Q, Wan M, Mao Y. Membrane-dependent actin polymerization mediated by the Legionella pneumophila effector protein MavH. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.24.525393. [PMID: 36747622 PMCID: PMC9900769 DOI: 10.1101/2023.01.24.525393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
L. pneumophila propagates in eukaryotic cells within a specialized niche, the Legionella -containing vacuole (LCV). The infection process is controlled by over 330 effector proteins delivered through the type IV secretion system. In this study, we report that the Legionella MavH effector harbors a lipid-binding domain that specifically recognizes PI(3)P (phosphatidylinositol 3-phosphate) and localizes to endosomes when ectopically expressed. We show that MavH recruits host actin capping proteins (CP) and actin to the endosome via its CP interacting (CPI) motif and WH2-like actin-binding domain, respectively. In vitro assays revealed that MavH stimulates robust actin polymerization only in the presence of PI(3)P-containing liposomes and the recruitment of CP by MavH negatively regulates F-actin density at the membrane. Furthermore, in L. pneumophila -infected cells, MavH can be detected around the LCV at the very early stage of infection. Together, our results reveal a novel mechanism of membrane-dependent actin polymerization catalyzed by MavH that may play a role at the early stage of L. pneumophila infection by regulating host actin dynamics.
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Affiliation(s)
- Qing Zhang
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Min Wan
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Yuxin Mao
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.,Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.,Corresponding Author: , Telephone: 607-255-0783
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36
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Sun B, Kekenes-Huskey PM. Myofilament-associated proteins with intrinsic disorder (MAPIDs) and their resolution by computational modeling. Q Rev Biophys 2023; 56:e2. [PMID: 36628457 PMCID: PMC11070111 DOI: 10.1017/s003358352300001x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The cardiac sarcomere is a cellular structure in the heart that enables muscle cells to contract. Dozens of proteins belong to the cardiac sarcomere, which work in tandem to generate force and adapt to demands on cardiac output. Intriguingly, the majority of these proteins have significant intrinsic disorder that contributes to their functions, yet the biophysics of these intrinsically disordered regions (IDRs) have been characterized in limited detail. In this review, we first enumerate these myofilament-associated proteins with intrinsic disorder (MAPIDs) and recent biophysical studies to characterize their IDRs. We secondly summarize the biophysics governing IDR properties and the state-of-the-art in computational tools toward MAPID identification and characterization of their conformation ensembles. We conclude with an overview of future computational approaches toward broadening the understanding of intrinsic disorder in the cardiac sarcomere.
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Affiliation(s)
- Bin Sun
- Research Center for Pharmacoinformatics (The State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), Department of Medicinal Chemistry and Natural Medicine Chemistry, College of Pharmacy, Harbin Medical University, Harbin 150081, China
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37
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Maufront J, Guichard B, Cao LY, Cicco AD, Jégou A, Romet-Lemonne G, Bertin A. Direct observation of the conformational states of formin mDia1 at actin filament barbed ends and along the filament. Mol Biol Cell 2022; 34:ar2. [PMID: 36383775 PMCID: PMC9816646 DOI: 10.1091/mbc.e22-10-0472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The fine regulation of actin polymerization is essential to control cell motility and architecture and to perform essential cellular functions. Formins are key regulators of actin filament assembly, known to processively elongate filament barbed ends and increase their polymerization rate. Different models have been extrapolated to describe the molecular mechanism governing the processive motion of formin FH2 domains at polymerizing barbed ends. Using negative stain electron microscopy, we directly identified for the first time two conformations of the mDia1 formin FH2 domains in interaction with the barbed ends of actin filaments. These conformations agree with the speculated open and closed conformations of the "stair-stepping" model. We observed the FH2 dimers to be in the open conformation for 79% of the data, interacting with the two terminal actin subunits of the barbed end while they interact with three actin subunits in the closed conformation. In addition, we identified and characterized the structure of single FH2 dimers encircling the core of actin filaments, and reveal their ability to spontaneously depart from barbed ends.
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Affiliation(s)
- Julien Maufront
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie,75005 Paris, France
| | - Bérengère Guichard
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Lu-Yan Cao
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France
| | - Aurélie Di Cicco
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie,75005 Paris, France
| | - Antoine Jégou
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France,*Address correspondence to: Aurélie Bertin (); Guillaume Romet-Lemonne (); Antoine Jégou ()
| | - Guillaume Romet-Lemonne
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France,*Address correspondence to: Aurélie Bertin (); Guillaume Romet-Lemonne (); Antoine Jégou ()
| | - Aurélie Bertin
- Institut Curie, Université PSL, Sorbonne Université, CNRS UMR 168, Laboratoire Physico Chimie Curie,75005 Paris, France,*Address correspondence to: Aurélie Bertin (); Guillaume Romet-Lemonne (); Antoine Jégou ()
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38
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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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39
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Kudryashova E, Ankita, Ulrichs H, Shekhar S, Kudryashov DS. Pointed-end processive elongation of actin filaments by Vibrio effectors VopF and VopL. SCIENCE ADVANCES 2022; 8:eadc9239. [PMID: 36399577 PMCID: PMC9674292 DOI: 10.1126/sciadv.adc9239] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 10/03/2022] [Indexed: 07/20/2023]
Abstract
According to the cellular actin dynamics paradigm, filaments grow at their barbed ends and depolymerize predominantly from their pointed ends to form polar structures and do productive work. We show that actin can elongate at the pointed end when assisted by Vibrio VopF/L toxins, which act as processive polymerases. In cells, processively moving VopF/L speckles are inhibited by factors blocking the pointed but not barbed ends. Multispectral single-molecule imaging confirmed that VopF molecules associate with the pointed end, actively promoting its elongation even in the presence of profilin. Consequently, VopF/L can break the actin cytoskeleton's polarity by compromising actin-based cellular processes. Therefore, actin filament design allows processive growth at both ends, which suggests unforeseen possibilities for cellular actin organization, particularly in specialized cells and compartments.
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Affiliation(s)
- Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Ankita
- Department of Physics, Emory University, Atlanta, GA 30322, USA
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Heidi Ulrichs
- Department of Physics, Emory University, Atlanta, GA 30322, USA
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Shashank Shekhar
- Department of Physics, Emory University, Atlanta, GA 30322, USA
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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40
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Mogilner A, Miles CE. Mechanosensation: Capping actin filaments for robustness. Curr Biol 2022; 32:R1033-R1035. [DOI: 10.1016/j.cub.2022.09.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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41
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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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42
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Romet-Lemonne G. Under the hood of a moving cell. eLife 2022; 11:81108. [PMID: 35894589 PMCID: PMC9328760 DOI: 10.7554/elife.81108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Experiments using purified proteins reveal how the network of filaments that underlie cell movement becomes denser when pushing against a stronger mechanical force.
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43
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Belyy A, Lindemann F, Roderer D, Funk J, Bardiaux B, Protze J, Bieling P, Oschkinat H, Raunser S. Mechanism of threonine ADP-ribosylation of F-actin by a Tc toxin. Nat Commun 2022; 13:4202. [PMID: 35858890 PMCID: PMC9300711 DOI: 10.1038/s41467-022-31836-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 07/01/2022] [Indexed: 11/25/2022] Open
Abstract
Tc toxins deliver toxic enzymes into host cells by a unique injection mechanism. One of these enzymes is the actin ADP-ribosyltransferase TccC3, whose activity leads to the clustering of the cellular cytoskeleton and ultimately cell death. Here, we show in atomic detail how TccC3 modifies actin. We find that the ADP-ribosyltransferase does not bind to G-actin but interacts with two consecutive actin subunits of F-actin. The binding of TccC3 to F-actin occurs via an induced-fit mechanism that facilitates access of NAD+ to the nucleotide binding pocket. The following nucleophilic substitution reaction results in the transfer of ADP-ribose to threonine-148 of F-actin. We demonstrate that this site-specific modification of F-actin prevents its interaction with depolymerization factors, such as cofilin, which impairs actin network turnover and leads to steady actin polymerization. Our findings reveal in atomic detail a mechanism of action of a bacterial toxin through specific targeting and modification of F-actin. Entomopathogenic bacteria used for pest control secrete potent Tc toxins. Here, the authors combine biochemistry, solution and solid-state NMR spectroscopy and cryo-EM to show in atomic detail how the toxin disrupts the host cell cytoskeleton and kills the target cell.
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Affiliation(s)
- Alexander Belyy
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Florian Lindemann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Daniel Roderer
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Johanna Funk
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Benjamin Bardiaux
- Institut Pasteur, Université Paris Cité, CNRS UMR3528, Structural Bioinformatics Unit, 25-28 Rue du Docteur Roux, F-75015, Paris, France
| | - Jonas Protze
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125, Berlin, Germany
| | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany
| | - Hartmut Oschkinat
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Rössle-Str. 10, 13125, Berlin, Germany.
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str. 11, 44227, Dortmund, Germany.
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Li TD, Bieling P, Weichsel J, Mullins RD, Fletcher DA. The molecular mechanism of load adaptation by branched actin networks. eLife 2022; 11:e73145. [PMID: 35748355 PMCID: PMC9328761 DOI: 10.7554/elife.73145] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 06/07/2022] [Indexed: 11/13/2022] Open
Abstract
Branched actin networks are self-assembling molecular motors that move biological membranes and drive many important cellular processes, including phagocytosis, endocytosis, and pseudopod protrusion. When confronted with opposing forces, the growth rate of these networks slows and their density increases, but the stoichiometry of key components does not change. The molecular mechanisms governing this force response are not well understood, so we used single-molecule imaging and AFM cantilever deflection to measure how applied forces affect each step in branched actin network assembly. Although load forces are observed to increase the density of growing filaments, we find that they actually decrease the rate of filament nucleation due to inhibitory interactions between actin filament ends and nucleation promoting factors. The force-induced increase in network density turns out to result from an exponential drop in the rate constant that governs filament capping. The force dependence of filament capping matches that of filament elongation and can be explained by expanding Brownian Ratchet theory to cover both processes. We tested a key prediction of this expanded theory by measuring the force-dependent activity of engineered capping protein variants and found that increasing the size of the capping protein increases its sensitivity to applied forces. In summary, we find that Brownian Ratchets underlie not only the ability of growing actin filaments to generate force but also the ability of branched actin networks to adapt their architecture to changing loads.
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Affiliation(s)
- Tai-De Li
- Department of Bioengineering & Biophysics Program, University of California, BerkeleyBerkeleyUnited States
- Division of Biological Systems & Engineering, Lawrence Berkeley National LaboratoryBerkeleyUnited States
- Advanced Science Research Center, City University of New YorkNew YorkUnited States
| | - Peter Bieling
- Division of Biological Systems & Engineering, Lawrence Berkeley National LaboratoryBerkeleyUnited States
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
- Department of Systemic Cell Biology, Max Planck Institute of Molecular PhysiologyDortmundGermany
| | - Julian Weichsel
- Department of Chemistry, University of California, BerkeleyBerkeleyUnited States
| | - R Dyche Mullins
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute, University of California, San FranciscoSan FranciscoUnited States
| | - Daniel A Fletcher
- Department of Bioengineering & Biophysics Program, University of California, BerkeleyBerkeleyUnited States
- Division of Biological Systems & Engineering, Lawrence Berkeley National LaboratoryBerkeleyUnited States
- Chan Zuckerberg BiohubSan FranciscoUnited States
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45
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Structural basis of rapid actin dynamics in the evolutionarily divergent Leishmania parasite. Nat Commun 2022; 13:3442. [PMID: 35705539 PMCID: PMC9200798 DOI: 10.1038/s41467-022-31068-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 06/01/2022] [Indexed: 11/08/2022] Open
Abstract
Actin polymerization generates forces for cellular processes throughout the eukaryotic kingdom, but our understanding of the ‘ancient’ actin turnover machineries is limited. We show that, despite > 1 billion years of evolution, pathogenic Leishmania major parasite and mammalian actins share the same overall fold and co-polymerize with each other. Interestingly, Leishmania harbors a simple actin-regulatory machinery that lacks cofilin ‘cofactors’, which accelerate filament disassembly in higher eukaryotes. By applying single-filament biochemistry we discovered that, compared to mammalian proteins, Leishmania actin filaments depolymerize more rapidly from both ends, and are severed > 100-fold more efficiently by cofilin. Our high-resolution cryo-EM structures of Leishmania ADP-, ADP-Pi- and cofilin-actin filaments identify specific features at actin subunit interfaces and cofilin-actin interactions that explain the unusually rapid dynamics of parasite actin filaments. Our findings reveal how divergent parasites achieve rapid actin dynamics using a remarkably simple set of actin-binding proteins, and elucidate evolution of the actin cytoskeleton. The authors report here the structure-function analysis of highly divergent actin from Leishmania parasite. The study reveals remarkably rapid dynamics of parasite actin as well as the underlying molecular basis, thus providing insight into evolution of the actin cytoskeleton.
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46
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The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:ijms23105306. [PMID: 35628117 PMCID: PMC9140763 DOI: 10.3390/ijms23105306] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
The actin containing tropomyosin and troponin decorated thin filaments form one of the crucial components of the contractile apparatus in muscles. The thin filaments are organized into densely packed lattices interdigitated with myosin-based thick filaments. The crossbridge interactions between these myofilaments drive muscle contraction, and the degree of myofilament overlap is a key factor of contractile force determination. As such, the optimal length of the thin filaments is critical for efficient activity, therefore, this parameter is precisely controlled according to the workload of a given muscle. Thin filament length is thought to be regulated by two major, but only partially understood mechanisms: it is set by (i) factors that mediate the assembly of filaments from monomers and catalyze their elongation, and (ii) by factors that specify their length and uniformity. Mutations affecting these factors can alter the length of thin filaments, and in human cases, many of them are linked to debilitating diseases such as nemaline myopathy and dilated cardiomyopathy.
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47
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Kaplan C, Kenny SJ, Chen X, Schöneberg J, Sitarska E, Diz-Muñoz A, Akamatsu M, Xu K, Drubin DG. Load adaptation by endocytic actin networks. Mol Biol Cell 2022; 33:ar50. [PMID: 35389747 PMCID: PMC9265150 DOI: 10.1091/mbc.e21-11-0589] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Clathrin-mediated endocytosis (CME) robustness under elevated membrane tension is maintained by actin assembly-mediated force generation. However, whether more actin assembles at endocytic sites in response to increased load has not previously been investigated. Here actin network ultrastructure at CME sites was examined under low and high membrane tension. Actin and N-WASP spatial organization indicate that actin polymerization initiates at the base of clathrin-coated pits and that the network then grows away from the plasma membrane. Actin network height at individual CME sites was not coupled to coat shape, raising the possibility that local differences in mechanical load feed back on assembly. By manipulating membrane tension and Arp2/3 complex activity we tested the hypothesis that actin assembly at CME sites increases in response to elevated load. Indeed, in response to elevated membrane tension, actin grew higher, resulting in greater coverage of the clathrin coat, and CME slowed. When membrane tension was elevated and the Arp2/3 complex was inhibited, shallow clathrin-coated pits accumulated, indicating that this adaptive mechanism is especially crucial for coat curvature generation. We propose that actin assembly increases in response to increased load to ensure CME robustness over a range of plasma membrane tensions. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].
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Affiliation(s)
- Charlotte Kaplan
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220
| | - Sam J Kenny
- Department of Chemistry, University of California, Berkeley, CA 94720-3220
| | - Xuyan Chen
- Department of Chemistry, University of California, Berkeley, CA 94720-3220
| | - Johannes Schöneberg
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220.,Center for Neural Circuits and Behavior, University of California, San Diego, CA 92093
| | - Ewa Sitarska
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg
| | - Alba Diz-Muñoz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory Heidelberg, Meyerhofstrasse 1, 69117 Heidelberg
| | - Matthew Akamatsu
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, CA 94720-3220.,Chan Zuckerberg Biohub, San Francisco, CA 94158
| | - David G Drubin
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220
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48
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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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Gao J, Nakamura F. Actin-Associated Proteins and Small Molecules Targeting the Actin Cytoskeleton. Int J Mol Sci 2022; 23:ijms23042118. [PMID: 35216237 PMCID: PMC8880164 DOI: 10.3390/ijms23042118] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 02/06/2023] Open
Abstract
Actin-associated proteins (AAPs) act on monomeric globular actin (G-actin) and polymerized filamentous actin (F-actin) to regulate their dynamics and architectures which ultimately control cell movement, shape change, division; organelle localization and trafficking. Actin-binding proteins (ABPs) are a subset of AAPs. Since actin was discovered as a myosin-activating protein (hence named actin) in 1942, the protein has also been found to be expressed in non-muscle cells, and numerous AAPs continue to be discovered. This review article lists all of the AAPs discovered so far while also allowing readers to sort the list based on the names, sizes, functions, related human diseases, and the dates of discovery. The list also contains links to the UniProt and Protein Atlas databases for accessing further, related details such as protein structures, associated proteins, subcellular localization, the expression levels in cells and tissues, mutations, and pathology. Because the actin cytoskeleton is involved in many pathological processes such as tumorigenesis, invasion, and developmental diseases, small molecules that target actin and AAPs which hold potential to treat these diseases are also listed.
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Structure and function of an atypical homodimeric actin capping protein from the malaria parasite. Cell Mol Life Sci 2022; 79:125. [PMID: 35132495 PMCID: PMC8821504 DOI: 10.1007/s00018-021-04032-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 10/28/2021] [Accepted: 11/09/2021] [Indexed: 11/27/2022]
Abstract
Apicomplexan parasites, such as Plasmodium spp., rely on an unusual actomyosin motor, termed glideosome, for motility and host cell invasion. The actin filaments are maintained by a small set of essential regulators, which provide control over actin dynamics in the different stages of the parasite life cycle. Actin filament capping proteins (CPs) are indispensable heterodimeric regulators of actin dynamics. CPs have been extensively characterized in higher eukaryotes, but their role and functional mechanism in Apicomplexa remain enigmatic. Here, we present the first crystal structure of a homodimeric CP from the malaria parasite and compare the homo- and heterodimeric CP structures in detail. Despite retaining several characteristics of a canonical CP, the homodimeric Plasmodium berghei (Pb)CP exhibits crucial differences to the canonical heterodimers. Both homo- and heterodimeric PbCPs regulate actin dynamics in an atypical manner, facilitating rapid turnover of parasite actin, without affecting its critical concentration. Homo- and heterodimeric PbCPs show partially redundant activities, possibly to rescue actin filament capping in life cycle stages where the β-subunit is downregulated. Our data suggest that the homodimeric PbCP also influences actin kinetics by recruiting lateral actin dimers. This unusual function could arise from the absence of a β-subunit, as the asymmetric PbCP homodimer lacks structural elements essential for canonical barbed end interactions suggesting a novel CP binding mode. These findings will facilitate further studies aimed at elucidating the precise actin filament capping mechanism in Plasmodium.
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