1
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Homa KE, Hocky GM, Suarez C, Kovar DR. Arp2/3 complex- and formin-mediated actin cytoskeleton networks facilitate actin binding protein sorting in fission yeast. Eur J Cell Biol 2024; 103:151404. [PMID: 38493594 PMCID: PMC11211059 DOI: 10.1016/j.ejcb.2024.151404] [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: 11/07/2023] [Revised: 03/01/2024] [Accepted: 03/13/2024] [Indexed: 03/19/2024] Open
Abstract
While it is well-established that F-actin networks with specific organizations and dynamics are tightly regulated by distinct sets of associated actin-binding proteins (ABPs), how ABPs self-sort to particular F-actin networks remains largely unclear. We report that actin assembly factors Arp2/3 complex and formin Cdc12 tune the association of ABPs fimbrin Fim1 and tropomyosin Cdc8 to different F-actin networks in fission yeast. Genetic and pharmacological disruption of F-actin networks revealed that Fim1 is preferentially directed to Arp2/3-complex mediated actin patches, whereas Cdc8 is preferentially targeted to formin Cdc12-mediated filaments in the contractile ring. To investigate the role of Arp2/3 complex- and formin Cdc12-mediated actin assembly, we used four-color TIRF microscopy to observe the in vitro reconstitution of ABP sorting with purified proteins. Fim1 or Cdc8 alone bind similarly well to filaments assembled by either assembly factor. However, in 'competition' reactions containing both actin assembly factors and both ABPs, ∼2.0-fold more Fim1 and ∼3.5-fold more Cdc8 accumulates on Arp2/3 complex branch points and formin Cdc12-assembled actin filaments, respectively. These findings indicate that F-actin assembly factors Arp2/3 complex and formin Cdc12 help facilitate the recruitment of specific ABPs, thereby tuning ABP sorting and subsequently establishing the identity of F-actin networks in fission yeast.
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Affiliation(s)
- Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
| | - Glen M Hocky
- Department of Chemistry, New York University, New York, NY, United States
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, United States; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL, United States.
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2
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Yuan Z, Li P, Yang X, Cai X, Wu L, Zhao F, Wen W, Zhou M, Hou Y. FgPfn participates in vegetative growth, sexual reproduction, pathogenicity, and fungicides sensitivity via affecting both microtubules and actin in the filamentous fungus Fusarium graminearum. PLoS Pathog 2024; 20:e1012215. [PMID: 38701108 PMCID: PMC11095717 DOI: 10.1371/journal.ppat.1012215] [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: 11/02/2023] [Revised: 05/15/2024] [Accepted: 04/23/2024] [Indexed: 05/05/2024] Open
Abstract
Fusarium head blight (FHB), caused by Fusarium graminearum species complexes (FGSG), is an epidemic disease in wheat and poses a serious threat to wheat production and security worldwide. Profilins are a class of actin-binding proteins that participate in actin depolymerization. However, the roles of profilins in plant fungal pathogens remain largely unexplored. Here, we identified FgPfn, a homolog to profilins in F. graminearum, and the deletion of FgPfn resulted in severe defects in mycelial growth, conidia production, and pathogenicity, accompanied by marked disruptions in toxisomes formation and deoxynivalenol (DON) transport, while sexual development was aborted. Additionally, FgPfn interacted with Fgα1 and Fgβ2, the significant components of microtubules. The organization of microtubules in the ΔFgPfn was strongly inhibited under the treatment of 0.4 μg/mL carbendazim, a well-known group of tubulin interferers, resulting in increased sensitivity to carbendazim. Moreover, FgPfn interacted with both myosin-5 (FgMyo5) and actin (FgAct), the targets of the fungicide phenamacril, and these interactions were reduced after phenamacril treatment. The deletion of FgPfn disrupted the normal organization of FgMyo5 and FgAct cytoskeleton, weakened the interaction between FgMyo5 and FgAct, and resulting in increased sensitivity to phenamacril. The core region of the interaction between FgPfn and FgAct was investigated, revealing that the integrity of both proteins was necessary for their interaction. Furthermore, mutations in R72, R77, R86, G91, I101, A112, G113, and D124 caused the non-interaction between FgPfn and FgAct. The R86K, I101E, and D124E mutants in FgPfn resulted in severe defects in actin organization, development, and pathogenicity. Taken together, this study revealed the role of FgPfn-dependent cytoskeleton in development, DON production and transport, fungicides sensitivity in F. graminearum.
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Affiliation(s)
- Zhili Yuan
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Pengfei Li
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Xin Yang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Xiaowei Cai
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Luoyu Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Feifei Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Weidong Wen
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Mingguo Zhou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yiping Hou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
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3
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Oosterheert W, Boiero Sanders M, Funk J, Prumbaum D, Raunser S, Bieling P. Molecular mechanism of actin filament elongation by formins. Science 2024; 384:eadn9560. [PMID: 38603491 DOI: 10.1126/science.adn9560] [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: 01/09/2024] [Accepted: 03/05/2024] [Indexed: 04/13/2024]
Abstract
Formins control the assembly of actin filaments (F-actin) that drive cell morphogenesis and motility in eukaryotes. However, their molecular interaction with F-actin and their mechanism of action remain unclear. In this work, we present high-resolution cryo-electron microscopy structures of F-actin barbed ends bound by three distinct formins, revealing a common asymmetric formin conformation imposed by the filament. Formation of new intersubunit contacts during actin polymerization sterically displaces formin and triggers its translocation. This "undock-and-lock" mechanism explains how actin-filament growth is coordinated with formin movement. Filament elongation speeds are controlled by the positioning and stability of actin-formin interfaces, which distinguish fast and slow formins. Furthermore, we provide a structure of the actin-formin-profilin ring complex, which resolves how profilin is rapidly released from the barbed end during filament elongation.
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Affiliation(s)
- Wout Oosterheert
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Micaela Boiero Sanders
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Johanna Funk
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Daniel Prumbaum
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
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4
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Vizcaíno-Castillo A, Kotila T, Kogan K, Yanase R, Como J, Antenucci L, Michelot A, Sunter JD, Lappalainen P. Leishmania profilin interacts with actin through an unusual structural mechanism to control cytoskeletal dynamics in parasites. J Biol Chem 2024; 300:105740. [PMID: 38340794 PMCID: PMC10907219 DOI: 10.1016/j.jbc.2024.105740] [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: 10/20/2023] [Revised: 02/02/2024] [Accepted: 02/05/2024] [Indexed: 02/12/2024] Open
Abstract
Diseases caused by Leishmania and Trypanosoma parasites are a major health problem in tropical countries. Because of their complex life cycle involving both vertebrate and insect hosts, and >1 billion years of evolutionarily distance, the cell biology of trypanosomatid parasites exhibits pronounced differences to animal cells. For example, the actin cytoskeleton of trypanosomatids is divergent when compared with other eukaryotes. To understand how actin dynamics are regulated in trypanosomatid parasites, we focused on a central actin-binding protein profilin. Co-crystal structure of Leishmania major actin in complex with L. major profilin revealed that, although the overall folds of actin and profilin are conserved in eukaryotes, Leishmania profilin contains a unique α-helical insertion, which interacts with the target binding cleft of actin monomer. This insertion is conserved across the Trypanosomatidae family and is similar to the structure of WASP homology-2 (WH2) domain, a small actin-binding motif found in many other cytoskeletal regulators. The WH2-like motif contributes to actin monomer binding and enhances the actin nucleotide exchange activity of Leishmania profilin. Moreover, Leishmania profilin inhibited formin-catalyzed actin filament assembly in a mechanism that is dependent on the presence of the WH2-like motif. By generating profilin knockout and knockin Leishmania mexicana strains, we show that profilin is important for efficient endocytic sorting in parasites, and that the ability to bind actin monomers and proline-rich proteins, and the presence of a functional WH2-like motif, are important for the in vivo function of Leishmania profilin. Collectively, this study uncovers molecular principles by which profilin regulates actin dynamics in trypanosomatids.
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Affiliation(s)
| | - Tommi Kotila
- HiLIFE Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Konstantin Kogan
- HiLIFE Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Ryuji Yanase
- Oxford Brookes University, Department of Biological and Medical Sciences, Oxford, UK
| | - Juna Como
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Lina Antenucci
- HiLIFE Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Alphee Michelot
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Jack D Sunter
- Oxford Brookes University, Department of Biological and Medical Sciences, Oxford, UK.
| | - Pekka Lappalainen
- HiLIFE Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
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5
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Jiang X, Isogai T, Chi J, Danuser G. Fine-grained, nonlinear registration of live cell movies reveals spatiotemporal organization of diffuse molecular processes. PLoS Comput Biol 2022; 18:e1009667. [PMID: 36584219 PMCID: PMC9870159 DOI: 10.1371/journal.pcbi.1009667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 01/23/2023] [Accepted: 11/28/2022] [Indexed: 01/01/2023] Open
Abstract
We present an application of nonlinear image registration to align in microscopy time lapse sequences for every frame the cell outline and interior with the outline and interior of the same cell in a reference frame. The registration relies on a subcellular fiducial marker, a cell motion mask, and a topological regularization that enforces diffeomorphism on the registration without significant loss of granularity. This allows spatiotemporal analysis of extremely noisy and diffuse molecular processes across the entire cell. We validate the registration method for different fiducial markers by measuring the intensity differences between predicted and original time lapse sequences of Actin cytoskeleton images and by uncovering zones of spatially organized GEF- and GTPase signaling dynamics visualized by FRET-based activity biosensors in MDA-MB-231 cells. We then demonstrate applications of the registration method in conjunction with stochastic time-series analysis. We describe distinct zones of locally coherent dynamics of the cytoplasmic protein Profilin in U2OS cells. Further analysis of the Profilin dynamics revealed strong relationships with Actin cytoskeleton reorganization during cell symmetry-breaking and polarization. This study thus provides a framework for extracting information to explore functional interactions between cell morphodynamics, protein distributions, and signaling in cells undergoing continuous shape changes. Matlab code implementing the proposed registration method is available at https://github.com/DanuserLab/Mask-Regularized-Diffeomorphic-Cell-Registration.
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Affiliation(s)
- Xuexia Jiang
- Lyda Hill Department of Bioinformatics, UT Southwestern Medical Center, Dallas, Texas, United States of America
| | - Tadamoto Isogai
- Lyda Hill Department of Bioinformatics, UT Southwestern Medical Center, Dallas, Texas, United States of America
| | - Joseph Chi
- Lyda Hill Department of Bioinformatics, UT Southwestern Medical Center, Dallas, Texas, United States of America
| | - Gaudenz Danuser
- Lyda Hill Department of Bioinformatics, UT Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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6
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Schutt CE, Karlén M, Karlsson R. A structural model of the profilin-formin pacemaker system for actin filament elongation. Sci Rep 2022; 12:20515. [PMID: 36443454 PMCID: PMC9705415 DOI: 10.1038/s41598-022-25011-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 11/23/2022] [Indexed: 11/29/2022] Open
Abstract
The formins constitute a large class of multi-domain polymerases that catalyze the localization and growth of unbranched actin filaments in cells from yeast to mammals. The conserved FH2 domains form dimers that bind actin at the barbed end of growing filaments and remain attached as new subunits are added. Profilin-actin is recruited and delivered to the barbed end by formin FH1 domains via the binding of profilin to interspersed tracts of poly-L-proline. We present a structural model showing that profilin-actin can bind the FH2 dimer at the barbed end stabilizing a state where profilin prevents its associated actin subunit from directly joining the barbed end. It is only with the dissociation of profilin from the polymerase that an actin subunit rotates and docks into its helical position, consistent with observations that under physiological conditions optimal elongation rates depend on the dissociation rate of profilin, independently of cellular concentrations of actin subunits.
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Affiliation(s)
- Clarence E. Schutt
- grid.16750.350000 0001 2097 5006Department of Chemistry, Princeton University, Princeton, NJ USA
| | | | - Roger Karlsson
- Department of Molecular Biosciences, WGI, Stockholm University, Stockholm, Sweden.
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7
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Pimm ML, Liu X, Tuli F, Heritz J, Lojko A, Henty-Ridilla JL. Visualizing molecules of functional human profilin. eLife 2022; 11:e76485. [PMID: 35666129 PMCID: PMC9249392 DOI: 10.7554/elife.76485] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 06/06/2022] [Indexed: 11/20/2022] Open
Abstract
Profilin-1 (PFN1) is a cytoskeletal protein that regulates the dynamics of actin and microtubule assembly. Thus, PFN1 is essential for the normal division, motility, and morphology of cells. Unfortunately, conventional fusion and direct labeling strategies compromise different facets of PFN1 function. As a consequence, the only methods used to determine known PFN1 functions have been indirect and often deduced in cell-free biochemical assays. We engineered and characterized two genetically encoded versions of tagged PFN1 that behave identical to each other and the tag-free protein. In biochemical assays purified proteins bind to phosphoinositide lipids, catalyze nucleotide exchange on actin monomers, stimulate formin-mediated actin filament assembly, and bound tubulin dimers (kD = 1.89 µM) to impact microtubule dynamics. In PFN1-deficient mammalian cells, Halo-PFN1 or mApple-PFN1 (mAp-PEN1) restored morphological and cytoskeletal functions. Titrations of self-labeling Halo-ligands were used to visualize molecules of PFN1. This approach combined with specific function-disrupting point-mutants (Y6D and R88E) revealed PFN1 bound to microtubules in live cells. Cells expressing the ALS-associated G118V disease variant did not associate with actin filaments or microtubules. Thus, these tagged PFN1s are reliable tools for studying the dynamic interactions of PFN1 with actin or microtubules in vitro as well as in important cell processes or disease-states.
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Affiliation(s)
- Morgan L Pimm
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
| | - Xinbei Liu
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
| | - Farzana Tuli
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
| | - Jennifer Heritz
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
| | - Ashley Lojko
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
| | - Jessica L Henty-Ridilla
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical UniversitySyracuseUnited States
- Department of Neuroscience and Physiology, SUNY Upstate Medical UniversitySyracuseUnited States
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8
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Narvaez-Ortiz HY, Nolen BJ. Unconcerted conformational changes in Arp2/3 complex integrate multiple activating signals to assemble functional actin networks. Curr Biol 2022; 32:975-987.e6. [PMID: 35090589 PMCID: PMC8930562 DOI: 10.1016/j.cub.2022.01.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 11/25/2021] [Accepted: 01/04/2022] [Indexed: 11/16/2022]
Abstract
Arp2/3 complex nucleates branched actin filaments important for processes such as DNA repair, endocytosis, and cellular motility. Multiple factors are required to activate branching nucleation by Arp2/3 complex, including a WASP family protein and a pre-existing actin filament. Activation is achieved through two major conformational changes-subunit flattening and movement into the short pitch conformation-that allow the actin-related proteins (Arps) within the complex (Arp2 and Arp3) to mimic filamentous actin subunits, thereby templating new filament assembly. Some models suggest that these changes are concerted and stimulated cooperatively by WASP and actin filaments, but how Arp2/3 complex integrates signals from multiple factors to drive switch-like activation of branching nucleation has been unknown. Here, we use biochemical assays to show that instead of a concerted mechanism, signal integration by Arp2/3 complex occurs via distinct and unconcerted conformational changes; WASP stimulates the short pitch arrangement of Arp2 and Arp3, while actin filaments trigger a different activation step. An engineered Arp2/3 complex that bypasses the need for WASP but not actin filaments in activation potently assembles isotropic actin networks but fails to assemble sustained force-producing actin networks in bead motility assays. The engineered complex, which is crosslinked into the short pitch conformation, fails to target nucleation to the surface of the bead, creating unproductive branching events that deplete unpolymerized actin and halt assembly. Together, our data demonstrate the requirement for multifactor signal integration by Arp2/3 complex and highlight the importance of both the WASP- and actin filament-mediated activation steps in the assembly of functional actin networks.
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Affiliation(s)
- Heidy Y Narvaez-Ortiz
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Brad J Nolen
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
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9
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Boiero Sanders M, Toret CP, Guillotin A, Antkowiak A, Vannier T, Robinson RC, Michelot A. Specialization of actin isoforms derived from the loss of key interactions with regulatory factors. EMBO J 2022; 41:e107982. [PMID: 35178724 PMCID: PMC8886540 DOI: 10.15252/embj.2021107982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 01/19/2022] [Accepted: 01/21/2022] [Indexed: 11/09/2022] Open
Abstract
A paradox of eukaryotic cells is that while some species assemble a complex actin cytoskeleton from a single ortholog, other species utilize a greater diversity of actin isoforms. The physiological consequences of using different actin isoforms, and the molecular mechanisms by which highly conserved actin isoforms are segregated into distinct networks, are poorly known. Here, we sought to understand how a simple biological system, composed of a unique actin and a limited set of actin‐binding proteins, reacts to a switch to heterologous actin expression. Using yeast as a model system and biomimetic assays, we show that such perturbation causes drastic reorganization of the actin cytoskeleton. Our results indicate that defective interaction of a heterologous actin for important regulators of actin assembly limits certain actin assembly pathways while reinforcing others. Expression of two heterologous actin variants, each specialized in assembling a different network, rescues cytoskeletal organization and confers resistance to external perturbation. Hence, while species using a unique actin have homeostatic actin networks, actin assembly pathways in species using several actin isoforms may act more independently.
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Affiliation(s)
| | - Christopher P Toret
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Audrey Guillotin
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Adrien Antkowiak
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Thomas Vannier
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Robert C Robinson
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama, Japan.,School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Alphée Michelot
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
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10
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Liu X, Pimm ML, Haarer B, Brawner AT, Henty-Ridilla JL. Biochemical characterization of actin assembly mechanisms with ALS-associated profilin variants. Eur J Cell Biol 2022; 101:151212. [PMID: 35248815 PMCID: PMC10163920 DOI: 10.1016/j.ejcb.2022.151212] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 02/23/2022] [Accepted: 02/25/2022] [Indexed: 12/26/2022] Open
Abstract
Eight separate mutations in the actin-binding protein profilin-1 have been identified as a rare cause of amyotrophic lateral sclerosis (ALS). Profilin is essential for many neuronal cell processes through its regulation of lipids, nuclear signals, and cytoskeletal dynamics, including actin filament assembly. Direct interactions between profilin and actin monomers inhibit actin filament polymerization. In contrast, profilin can also stimulate polymerization by simultaneously binding actin monomers and proline-rich tracts found in other proteins. Whether the ALS-associated mutations in profilin compromise these actin assembly functions is unclear. We performed a quantitative biochemical comparison of the direct and formin mediated impact for the eight ALS-associated profilin variants on actin assembly using classic protein-binding and single-filament microscopy assays. We determined that the binding constant of each profilin for actin monomers generally correlates with the actin nucleation strength associated with each ALS-related profilin. In the presence of formin, the A20T, R136W, Q139L, and C71G variants failed to activate the elongation phase of actin assembly. This diverse range of formin-activities is not fully explained through profilin-poly-L-proline (PLP) interactions, as all ALS-associated variants bind a formin-derived PLP peptide with similar affinities. However, chemical denaturation experiments suggest that the folding stability of these profilins impact some of these effects on actin assembly. Thus, changes in profilin protein stability and alterations in actin filament polymerization may both contribute to the profilin-mediated actin disruptions in ALS.
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Affiliation(s)
- Xinbei Liu
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Morgan L Pimm
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Brian Haarer
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Andrew T Brawner
- Department of Neuroscience & Physiology, 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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11
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Boiero Sanders M, Antkowiak A, Michelot A. Diversity from similarity: cellular strategies for assigning particular identities to actin filaments and networks. Open Biol 2020; 10:200157. [PMID: 32873155 PMCID: PMC7536088 DOI: 10.1098/rsob.200157] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The actin cytoskeleton has the particularity of being assembled into many functionally distinct filamentous networks from a common reservoir of monomeric actin. Each of these networks has its own geometrical, dynamical and mechanical properties, because they are capable of recruiting specific families of actin-binding proteins (ABPs), while excluding the others. This review discusses our current understanding of the underlying molecular mechanisms that cells have developed over the course of evolution to segregate ABPs to appropriate actin networks. Segregation of ABPs requires the ability to distinguish actin networks as different substrates for ABPs, which is regulated in three different ways: (1) by the geometrical organization of actin filaments within networks, which promotes or inhibits the accumulation of ABPs; (2) by the identity of the networks' filaments, which results from the decoration of actin filaments with additional proteins such as tropomyosin, from the use of different actin isoforms or from covalent modifications of actin; (3) by the existence of collaborative or competitive binding to actin filaments between two or multiple ABPs. This review highlights that all these effects need to be taken into account to understand the proper localization of ABPs in cells, and discusses what remains to be understood in this field of research.
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Affiliation(s)
- Micaela Boiero Sanders
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Adrien Antkowiak
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Alphée Michelot
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
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12
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Skruber K, Warp PV, Shklyarov R, Thomas JD, Swanson MS, Henty-Ridilla JL, Read TA, Vitriol EA. Arp2/3 and Mena/VASP Require Profilin 1 for Actin Network Assembly at the Leading Edge. Curr Biol 2020; 30:2651-2664.e5. [PMID: 32470361 DOI: 10.1016/j.cub.2020.04.085] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 03/09/2020] [Accepted: 04/29/2020] [Indexed: 12/27/2022]
Abstract
Cells have many types of actin structures, which must assemble from a common monomer pool. Yet, it remains poorly understood how monomers are distributed to and shared between different filament networks. Simplified model systems suggest that monomers are limited and heterogeneous, which alters actin network assembly through biased polymerization and internetwork competition. However, less is known about how monomers influence complex actin structures, where different networks competing for monomers overlap and are functionally interdependent. One example is the leading edge of migrating cells, which contains filament networks generated by multiple assembly factors. The leading edge dynamically switches between the formation of different actin structures, such as lamellipodia or filopodia, by altering the balance of these assembly factors' activities. Here, we sought to determine how the monomer-binding protein profilin 1 (PFN1) controls the assembly and organization of actin in mammalian cells. Actin polymerization in PFN1 knockout cells was severely disrupted, particularly at the leading edge, where both Arp2/3 and Mena/VASP-based filament assembly was inhibited. Further studies showed that in the absence of PFN1, Arp2/3 no longer localizes to the leading edge and Mena/VASP is non-functional. Additionally, we discovered that discrete stages of internetwork competition and collaboration between Arp2/3 and Mena/VASP networks exist at different PFN1 concentrations. Low levels of PFN1 caused filopodia to form exclusively at the leading edge, while higher concentrations inhibited filopodia and favored lamellipodia and pre-filopodia bundles. These results demonstrate that dramatic changes to actin architecture can be made simply by modifying PFN1 availability.
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Affiliation(s)
- Kristen Skruber
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA; Center for Translational Research in Neurodegenerative Disease, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Peyton V Warp
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Rachael Shklyarov
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - James D Thomas
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics, and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics, and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Jessica L Henty-Ridilla
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, NY 13210, USA
| | - Tracy-Ann Read
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA; Center for Translational Research in Neurodegenerative Disease, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Eric A Vitriol
- Department of Anatomy and Cell Biology, University of Florida, College of Medicine, Gainesville, FL 32610, USA; Center for Translational Research in Neurodegenerative Disease, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
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13
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Barger SR, James ML, Pellenz CD, Krendel M, Sirotkin V. Human myosin 1e tail but not motor domain replaces fission yeast Myo1 domains to support myosin-I function during endocytosis. Exp Cell Res 2019; 384:111625. [PMID: 31542284 DOI: 10.1016/j.yexcr.2019.111625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/13/2019] [Accepted: 09/15/2019] [Indexed: 10/26/2022]
Abstract
In both unicellular and multicellular organisms, long-tailed class I myosins function in clathrin-mediated endocytosis. Myosin 1e (Myo1e) in vertebrates and Myo1 in fission yeast have similar domain organization, yet whether these proteins or their individual protein domains are functionally interchangeable remains unknown. In an effort to assess functional conservation of class I myosins, we tested whether human Myo1e could replace Myo1 in fission yeast Schizosaccharomyces pombe and found that it was unable to substitute for yeast Myo1. To determine if any individual protein domain is responsible for the inability of Myo1e to function in yeast, we created human-yeast myosin-I chimeras. By functionally testing these chimeric myosins in vivo, we concluded that the Myo1e motor domain is unable to function in yeast, even when combined with the yeast Myo1 tail and a full complement of yeast regulatory light chains. Conversely, the Myo1e tail, when attached to the yeast Myo1 motor domain, supports localization to endocytic actin patches and partially rescues the endocytosis defect in myo1Δ cells. Further dissection showed that both the TH1 and TH2-SH3 domains in the human Myo1e tail are required for localization and function of chimeric myosin-I at endocytic sites. Overall, this study provides insights into the role of individual myosin-I domains, expands the utility of fission yeast as a simple model system to study the effects of disease-associated MYO1E mutations, and supports a model of co-evolution between a myosin motor and its actin track.
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Affiliation(s)
- Sarah R Barger
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Michael L James
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Christopher D Pellenz
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Mira Krendel
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA.
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA.
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14
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Courtemanche N. Mechanisms of formin-mediated actin assembly and dynamics. Biophys Rev 2018; 10:1553-1569. [PMID: 30392063 DOI: 10.1007/s12551-018-0468-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 10/18/2018] [Indexed: 12/14/2022] Open
Abstract
Cellular viability requires tight regulation of actin cytoskeletal dynamics. Distinct families of nucleation-promoting factors enable the rapid assembly of filament nuclei that elongate and are incorporated into diverse and specialized actin-based structures. In addition to promoting filament nucleation, the formin family of proteins directs the elongation of unbranched actin filaments. Processive association of formins with growing filament ends is achieved through continuous barbed end binding of the highly conserved, dimeric formin homology (FH) 2 domain. In cooperation with the FH1 domain and C-terminal tail region, FH2 dimers mediate actin subunit addition at speeds that can dramatically exceed the rate of spontaneous assembly. Here, I review recent biophysical, structural, and computational studies that have provided insight into the mechanisms of formin-mediated actin assembly and dynamics.
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Affiliation(s)
- Naomi Courtemanche
- Department of Genetics, Cell and Developmental Biology, University of Minnesota, 420 Washington Ave SE, 6-130 MCB, Minneapolis, MN, 55455, USA.
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15
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Genomes of Asgard archaea encode profilins that regulate actin. Nature 2018; 562:439-443. [DOI: 10.1038/s41586-018-0548-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 08/23/2018] [Indexed: 11/08/2022]
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16
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Gau D, Lewis T, McDermott L, Wipf P, Koes D, Roy P. Structure-based virtual screening identifies a small-molecule inhibitor of the profilin 1-actin interaction. J Biol Chem 2017; 293:2606-2616. [PMID: 29282288 DOI: 10.1074/jbc.m117.809137] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 12/08/2017] [Indexed: 01/01/2023] Open
Abstract
Profilin 1 (Pfn1) is an important regulator of the actin cytoskeleton and plays a vital role in many actin-based cellular processes. Therefore, identification of a small-molecule intervention strategy targeted against the Pfn1-actin interaction could have broad utility in cytoskeletal research and further our understanding of the role of Pfn1 in actin-mediated biological processes. Based on an already resolved Pfn1-actin complex crystal structure, we performed structure-based virtual screening of small-molecule libraries to seek inhibitors of the Pfn1-actin interaction. We identified compounds that match the pharmacophore of the key actin residues of Pfn1-actin interaction and therefore have the potential to act as competitive inhibitors of this interaction. Subsequent biochemical assays identified two candidate compounds with nearly identical structures that can mitigate the effect of Pfn1 on actin polymerization in vitro As a further proof-of-concept test for cellular effects of these compounds, we performed proximity ligation assays in endothelial cells (ECs) to demonstrate compound-induced inhibition of Pfn1-actin interaction. Consistent with the important role of Pfn1 in regulating actin polymerization and various fundamental actin-based cellular activities (migration and proliferation), treatment of these compounds reduced the overall level of cellular filamentous (F) actin, slowed EC migration and proliferation, and inhibited the angiogenic ability of ECs both in vitro and ex vivo In summary, this study provides the first proof of principle of small-molecule-mediated interference with the Pfn1-actin interaction. Our findings may have potential general utility for perturbing actin-mediated cellular activities and biological processes.
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Affiliation(s)
- David Gau
- From the Departments of Bioengineering
| | | | | | - Peter Wipf
- From the Departments of Bioengineering.,Chemistry
| | | | - Partha Roy
- From the Departments of Bioengineering, .,Cell Biology, and.,Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15219
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17
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Henty-Ridilla JL, Juanes MA, Goode BL. Profilin Directly Promotes Microtubule Growth through Residues Mutated in Amyotrophic Lateral Sclerosis. Curr Biol 2017; 27:3535-3543.e4. [PMID: 29129529 PMCID: PMC5772683 DOI: 10.1016/j.cub.2017.10.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/31/2017] [Accepted: 10/02/2017] [Indexed: 12/11/2022]
Abstract
Profilin is an abundant actin monomer-binding protein with critical actin regulatory roles in vivo [1, 2]. However, profilin also influences microtubule dynamics in cells, which may be mediated in part through its interactions with formins that in turn bind microtubules [3, 4]. Specific residues on human profilin-1 (PFN1) are mutated in patients with amyotrophic lateral sclerosis (ALS) [5, 6]. However, the observation that some ALS-linked PFN1 mutants fail to alter cellular actin organization or dynamics [5-8] or in vitro actin-monomer affinity [9] has been perplexing, given that profilin is best understood as an actin regulator. Here, we investigated direct effects of profilin on microtubule dynamics and whether ALS-linked mutations in PFN1 disrupt such functions. We found that human, fly, and yeast profilin homologs all directly enhance microtubule growth rate by several-fold in vitro. Microtubule stimulatory effects were unaffected by mutations in the canonical actin- or poly-proline-binding sites of profilin. Instead, microtubule activities depended on specific surface residues on profilin mutated in ALS patients. Furthermore, microtubule effects were attenuated by increasing concentrations of actin monomers, suggesting competition between actin and microtubules for binding profilin. Consistent with these biochemical observations, a 2-fold increase in the expression level of wild-type PFN1, but not the ALS-linked PFN1 mutants, increased microtubule growth rates in cells. Together, these results demonstrate that profilin directly enhances the growth rate of microtubules. They further suggest that ALS-linked mutations in PFN1 may perturb cellular microtubule dynamics and/or the coordination between the actin and microtubule cytoskeletons, leading to motor neuron degeneration.
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Affiliation(s)
| | - M Angeles Juanes
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA
| | - Bruce L Goode
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA.
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18
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Zimmermann D, Homa KE, Hocky GM, Pollard LW, De La Cruz EM, Voth GA, Trybus KM, Kovar DR. Mechanoregulated inhibition of formin facilitates contractile actomyosin ring assembly. Nat Commun 2017; 8:703. [PMID: 28951543 PMCID: PMC5614989 DOI: 10.1038/s41467-017-00445-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 06/27/2017] [Indexed: 11/20/2022] Open
Abstract
Cytokinesis physically separates dividing cells by forming a contractile actomyosin ring. The fission yeast contractile ring has been proposed to assemble by Search-Capture-Pull-Release from cytokinesis precursor nodes that include the molecular motor type-II myosin Myo2 and the actin assembly factor formin Cdc12. By successfully reconstituting Search-Capture-Pull in vitro, we discovered that formin Cdc12 is a mechanosensor, whereby myosin pulling on formin-bound actin filaments inhibits Cdc12-mediated actin assembly. We mapped Cdc12 mechanoregulation to its formin homology 1 domain, which facilitates delivery of new actin subunits to the elongating actin filament. Quantitative modeling suggests that the pulling force of the myosin propagates through the actin filament, which behaves as an entropic spring, and thereby may stretch the disordered formin homology 1 domain and impede formin-mediated actin filament elongation. Finally, live cell imaging of mechano-insensitive formin mutant cells established that mechanoregulation of formin Cdc12 is required for efficient contractile ring assembly in vivo. The fission yeast cytokinetic ring assembles by Search-Capture-Pull-Release from precursor nodes that include formin Cdc12 and myosin Myo2. The authors reconstitute Search-Capture-Pull in vitro and find that Myo2 pulling on Cdc12-associated actin filaments mechano-inhibits Cdc12-mediated assembly, which enables proper ring assembly in vivo.
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Affiliation(s)
- Dennis Zimmermann
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA
| | - Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA
| | - Glen M Hocky
- Department of Chemistry, The James Franck Institute and Institute for Biophysical Dynamics and Computation Institute, The University of Chicago, 5735 S. Ellis Ave., Searle Chemistry Laboratory 231, Chicago, IL, 60637, USA
| | - Luther W Pollard
- Department of Molecular Physiology and Biophysics, University of Vermont, 149 Beaumont Ave., HSRF 130, Burlington, VT, 05405, USA
| | - Enrique M De La Cruz
- Department of Molecular Biophysics and Biochemistry, Yale University, PO Box 208114, 266 Whitney Ave., New Haven, CT, 06520-8114, USA
| | - Gregory A Voth
- Department of Chemistry, The James Franck Institute and Institute for Biophysical Dynamics and Computation Institute, The University of Chicago, 5735 S. Ellis Ave., Searle Chemistry Laboratory 231, Chicago, IL, 60637, USA.
| | - Kathleen M Trybus
- Department of Molecular Physiology and Biophysics, University of Vermont, 149 Beaumont Ave., HSRF 130, Burlington, VT, 05405, USA.
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA. .,Department of Biochemistry and Molecular Biology, The University of Chicago, 920 E. 58th St., CSLC 212, Chicago, IL, 60637, USA.
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19
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Sviridova E, Rezacova P, Bondar A, Veverka V, Novak P, Schenk G, Svergun DI, Kuta Smatanova I, Bumba L. Structural basis of the interaction between the putative adhesion-involved and iron-regulated FrpD and FrpC proteins of Neisseria meningitidis. Sci Rep 2017; 7:40408. [PMID: 28084396 PMCID: PMC5233953 DOI: 10.1038/srep40408] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 12/06/2016] [Indexed: 01/14/2023] Open
Abstract
The iron-regulated protein FrpD from Neisseria meningitidis is an outer membrane lipoprotein that interacts with very high affinity (Kd ~ 0.2 nM) with the N-terminal domain of FrpC, a Type I-secreted protein from the Repeat in ToXin (RTX) protein family. In the presence of Ca2+, FrpC undergoes Ca2+ -dependent protein trans-splicing that includes an autocatalytic cleavage of the Asp414-Pro415 peptide bond and formation of an Asp414-Lys isopeptide bond. Here, we report the high-resolution structure of FrpD and describe the structure-function relationships underlying the interaction between FrpD and FrpC1-414. We identified FrpD residues involved in FrpC1-414 binding, which enabled localization of FrpD within the low-resolution SAXS model of the FrpD-FrpC1-414 complex. Moreover, the trans-splicing activity of FrpC resulted in covalent linkage of the FrpC1-414 fragment to plasma membrane proteins of epithelial cells in vitro, suggesting that formation of the FrpD-FrpC1-414 complex may be involved in the interaction of meningococci with the host cell surface.
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Affiliation(s)
- Ekaterina Sviridova
- Faculty of Science, University of South Bohemia Ceske Budejovice, Branisovska 1760, 37005 Ceske Budejovice, Czech Republic.,Center for Nanobiology and Structural Biology, Institute of Microbiology, Czech Academy of Sciences, Zamek 136, 37333 Nove Hrady, Czech Republic
| | - Pavlina Rezacova
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague, Czech Republic
| | - Alexey Bondar
- Center for Nanobiology and Structural Biology, Institute of Microbiology, Czech Academy of Sciences, Zamek 136, 37333 Nove Hrady, Czech Republic.,Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague, Czech Republic
| | - Vaclav Veverka
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nam. 2, 16610 Prague, Czech Republic
| | - Petr Novak
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic
| | - Gundolf Schenk
- EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Dmitri I Svergun
- EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany
| | - Ivana Kuta Smatanova
- Faculty of Science, University of South Bohemia Ceske Budejovice, Branisovska 1760, 37005 Ceske Budejovice, Czech Republic.,Center for Nanobiology and Structural Biology, Institute of Microbiology, Czech Academy of Sciences, Zamek 136, 37333 Nove Hrady, Czech Republic
| | - Ladislav Bumba
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic
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20
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Zhang S, Liu C, Wang J, Ren Z, Staiger CJ, Ren H. A Processive Arabidopsis Formin Modulates Actin Filament Dynamics in Association with Profilin. MOLECULAR PLANT 2016; 9:900-10. [PMID: 26996265 DOI: 10.1016/j.molp.2016.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 02/28/2016] [Accepted: 03/04/2016] [Indexed: 05/08/2023]
Abstract
Formins are conserved regulators of actin cytoskeletal organization and dynamics that have been implicated to be important for cell division and cell polarity. The mechanism by which diverse formins regulate actin dynamics in plants is still not well understood. Using in vitro single-molecule imaging technology, we directly observed that the FH1-FH2 domain of an Arabidopsis thaliana formin, AtFH14, processively attaches to the barbed end of actin filaments as a dimer and slows their elongation rate by 90%. The attachment persistence of FH1-FH2 is concentration dependent. Furthermore, by use of the triple-color total internal reflection fluorescence microscopy, we found that ABP29, a barbed-end capping protein, competes with FH1-FH2 at the filament barbed end, where its binding is mutually exclusive with AtFH14. In the presence of different plant profilin isoforms, FH1-FH2 enhances filament elongation rates from about 10 to 42 times. Filaments buckle when FH1-FH2 is anchored specifically to cover slides, further indicating that AtFH14 moves processively on the elongating barbed end. At high concentration, AtFH14 bundles actin filaments randomly into antiparallel or parallel spindle-like structures; however, the FH1-FH2-mediated bundles become thinner and longer in the presence of plant profilins. This is the direct demonstration of a processive formin from plants. Our results also illuminate the molecular mechanism of AtFH14 in regulating actin dynamics via association with profilin.
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Affiliation(s)
- Sha Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Chang Liu
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Jiaojiao Wang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Zhanhong Ren
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China
| | - Christopher J Staiger
- Department of Biological Sciences, Purdue University, Hansen Life Sciences Research Building, West Lafayette, IN 47907-2064, USA
| | - Haiyun Ren
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China.
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21
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Tariq N, Basharat Z, Butt S, Baig DN. Distribution analysis of profilin isoforms at transcript resolution with mRNA-seq and secondary structure in various organs of Rattus norvegicus. Gene 2016; 589:49-55. [PMID: 27185630 DOI: 10.1016/j.gene.2016.05.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 11/15/2022]
Abstract
Profilin (Pfn) is an actin binding protein, ubiquitously found in mammals and is essential for the actin polymerization in cells. In brain, it plays a pivotal role in neurogenesis and synapse formation by interacting with various proteins. Four Pfn isoforms have been identified in mammals. This study presents the identification and transcriptional expression of various Pfn isoforms (Pfn1, Pfn2, Pfn3 and Pfn4) in brain, heart, kidney, liver, and muscle and testis of Rattus norvegicus. Organs have been classified into groups based on some similarities. Group I includes brain and testis, Group II includes skeletal muscle and heart, while Group III includes kidney and liver. Pfn1 has been identified in all groups, Pfn2 and Pfn3 have been identified in group I, group III and in one organ (skeletal muscle) of group II. To the best of the authors knowledge, no report of Pfn1 and Pfn2 presence in testis, Pfn3 in brain, liver and skeletal muscle, Pfn4 in kidney and skeletal muscle exists to date. Transcriptional expression showed variations among expression level of different Pfn isoforms in various organs with respect to the control gene GADPH. We hypothesize that this could be attributed to profilin isoform specific mRNA structure and corresponding motifs, which generally contribute to similar or varied decay rates, cellular localization, post transcriptional regulation pattern and ligand binding.
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Affiliation(s)
- Naila Tariq
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
| | - Zarrin Basharat
- Department of Environmental Sciences, Fatima Jinnah Women University, 46000 Rawalpindi, Pakistan
| | - Saba Butt
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
| | - Deeba Noreen Baig
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
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22
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Bhargav SP, Vahokoski J, Kallio JP, Torda AE, Kursula P, Kursula I. Two independently folding units of Plasmodium profilin suggest evolution via gene fusion. Cell Mol Life Sci 2015; 72:4193-203. [PMID: 26012696 PMCID: PMC11113795 DOI: 10.1007/s00018-015-1932-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/13/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
Abstract
Gene fusion is a common mechanism of protein evolution that has mainly been discussed in the context of multidomain or symmetric proteins. Less is known about fusion of ancestral genes to produce small single-domain proteins. Here, we show with a domain-swapped mutant Plasmodium profilin that this small, globular, apparently single-domain protein consists of two foldons. The separation of binding sites for different protein ligands in the two halves suggests evolution via an ancient gene fusion event, analogous to the formation of multidomain proteins. Finally, the two fragments can be assembled together after expression as two separate gene products. The possibility to engineer both domain-swapped dimers and half-profilins that can be assembled back to a full profilin provides perspectives for engineering of novel protein folds, e.g., with different scaffolding functions.
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Affiliation(s)
| | - Juha Vahokoski
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland
| | - Juha Pekka Kallio
- Helmholtz Centre for Infection Research, Notkestrasse 85, 22607, Hamburg, Germany
- German Electron Synchrotron (DESY), Notkestrasse 85, 22607, Hamburg, Germany
| | - Andrew E Torda
- Centre for Bioinformatics, University of Hamburg, Bundesstrasse 43, 20146, Hamburg, Germany
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland
- Biocenter Oulu, University of Oulu, P.O. Box 5000, 90014, Oulu, Finland
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
| | - Inari Kursula
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland.
- Helmholtz Centre for Infection Research, Notkestrasse 85, 22607, Hamburg, Germany.
- German Electron Synchrotron (DESY), Notkestrasse 85, 22607, Hamburg, Germany.
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
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23
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Baker JL, Courtemanche N, Parton DL, McCullagh M, Pollard TD, Voth GA. Electrostatic interactions between the Bni1p Formin FH2 domain and actin influence actin filament nucleation. Structure 2014; 23:68-79. [PMID: 25482541 DOI: 10.1016/j.str.2014.10.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 10/03/2014] [Accepted: 10/21/2014] [Indexed: 10/24/2022]
Abstract
Formins catalyze nucleation and growth of actin filaments. Here, we study the structure and interactions of actin with the FH2 domain of budding yeast formin Bni1p. We built an all-atom model of the formin dimer on an Oda actin filament 7-mer and studied structural relaxation and interprotein interactions by molecular dynamics simulations. These simulations produced a refined model for the FH2 dimer associated with the barbed end of the filament and showed electrostatic interactions between the formin knob and actin target-binding cleft. Mutations of two formin residues contributing to these interactions (R1423N, K1467L, or both) reduced the interaction energies between the proteins, and in coarse-grained simulations, the formin lost more interprotein contacts with an actin dimer than with an actin 7-mer. Biochemical experiments confirmed a strong influence of these mutations on Bni1p-mediated actin filament nucleation, but not elongation, suggesting that different interactions contribute to these two functions of formins.
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Affiliation(s)
- Joseph L Baker
- Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA
| | - Naomi Courtemanche
- Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA
| | - Daniel L Parton
- Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
| | - Martin McCullagh
- Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Department of Molecular Biophysics and Biochemistry, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA; Department of Cell Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103, USA
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, IL 60637, USA; Computation Institute, The University of Chicago, 5735 S. Ellis Avenue, Chicago, IL 60637, USA.
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24
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Bestul AJ, Christensen JR, Grzegorzewska AP, Burke TA, Sees JA, Carroll RT, Sirotkin V, Keenan RJ, Kovar DR. Fission yeast profilin is tailored to facilitate actin assembly by the cytokinesis formin Cdc12. Mol Biol Cell 2014; 26:283-93. [PMID: 25392301 PMCID: PMC4294675 DOI: 10.1091/mbc.e13-05-0281] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The evolutionarily conserved small actin-monomer binding protein profilin is believed to be a housekeeping factor that maintains a general pool of unassembled actin. However, despite similar primary sequences, structural folds, and affinities for G-actin and poly-L-proline, budding yeast profilin ScPFY fails to complement fission yeast profilin SpPRF temperature-sensitive mutant cdc3-124 cells. To identify profilin's essential properties, we built a combinatorial library of ScPFY variants containing either WT or SpPRF residues at multiple positions and carried out a genetic selection to isolate variants that support life in fission yeast. We subsequently engineered ScPFY(9-Mut), a variant containing nine substitutions in the actin-binding region, which complements cdc3-124 cells. ScPFY(9-Mut), but not WT ScPFY, suppresses severe cytokinesis defects in cdc3-124 cells. Furthermore, the major activity rescued by ScPFY(9-Mut) is the ability to enhance cytokinesis formin Cdc12-mediated actin assembly in vitro, which allows cells to assemble functional contractile rings. Therefore an essential role of profilin is to specifically facilitate formin-mediated actin assembly for cytokinesis in fission yeast.
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Affiliation(s)
- Andrew J Bestul
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Jenna R Christensen
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | | | - Thomas A Burke
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Jennifer A Sees
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637
| | - Robert T Carroll
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637 Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637
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25
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Affiliation(s)
- Dennis Breitsprecher
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA
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26
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Ti SC, Pollard TD. Purification of actin from fission yeast Schizosaccharomyces pombe and characterization of functional differences from muscle actin. J Biol Chem 2010; 286:5784-92. [PMID: 21148484 DOI: 10.1074/jbc.m110.199794] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Fission yeast Schizosaccharomyces pombe is an important genetic model organism for studying the mechanisms of endocytosis and cytokinesis. However, most work on the biochemical properties of fission yeast actin-binding proteins has been done with skeletal muscle actin for matters of convenience. When simulations of mathematical models of the mechanism of endocytosis were compared with events in live cells, some of the reactions appeared to be much faster than observed in biochemical experiments with muscle actin. Here, we used gelsolin affinity chromatography to purify actin from fission yeast. S. pombe actin shares many properties with skeletal muscle actin but has higher intrinsic nucleotide exchange rate, faster trimer nucleus formation, faster phosphate dissociation rate from polymerized actin, and faster nucleation of actin filaments with Arp2/3 complex. These properties close the gap between the biochemistry and predictions made by mathematical models of endocytosis in S. pombe cells.
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Affiliation(s)
- Shih-Chieh Ti
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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27
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Profilin1 regulates PI(3,4)P2 and lamellipodin accumulation at the leading edge thus influencing motility of MDA-MB-231 cells. Proc Natl Acad Sci U S A 2010; 107:21547-52. [PMID: 21115820 DOI: 10.1073/pnas.1002309107] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Profilin1, a ubiquitously expressed actin-binding protein, plays a critical role in cell migration through actin cytoskeletal regulation. Given the traditional view of profilin1 as a promigratory molecule, it is difficult to reconcile observations that profilin1 is down-regulated in various invasive adenocarcinomas and that reduced profilin1 expression actually confers increased motility to certain adenocarcinoma cells. In this study, we show that profilin1 negatively regulates lamellipodin targeting to the leading edge in MDA-MB-231 breast cancer cells and normal cells; profilin1 depletion increases lamellipodin concentration at the lamellipodial tip (where it binds Ena/VASP), and this mediates the hypermotility. We report that the molecular mechanism underlying profilin1's modulation of lamellipodin localization relates to phosphoinositide control. Specifically, we show that phosphoinositide binding of profilin1 inhibits the motility of MDA-MB-231 cells by negatively regulating PI(3,4)P(2) at the membrane and thereby limiting recruitment of lamellipodin [a PI(3,4)P(2)-binding protein] and Ena/VASP to the leading edge. In summary, this study uncovers a unique biological consequence of profilin1-phosphoinositide interaction, thus providing direct evidence of profilin1's regulation of cell migration independent of its actin-related activity.
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28
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Kucera K, Koblansky AA, Saunders LP, Frederick KB, De La Cruz EM, Ghosh S, Modis Y. Structure-based analysis of Toxoplasma gondii profilin: a parasite-specific motif is required for recognition by Toll-like receptor 11. J Mol Biol 2010; 403:616-29. [PMID: 20851125 DOI: 10.1016/j.jmb.2010.09.022] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 09/02/2010] [Accepted: 09/08/2010] [Indexed: 11/19/2022]
Abstract
Profilins promote actin polymerization by exchanging ADP for ATP on monomeric actin and delivering ATP-actin to growing filament barbed ends. Apicomplexan protozoa such as Toxoplasma gondii invade host cells using an actin-dependent gliding motility. Toll-like receptor (TLR) 11 generates an innate immune response upon sensing T. gondii profilin (TgPRF). The crystal structure of TgPRF reveals a parasite-specific surface motif consisting of an acidic loop, followed by a long β-hairpin. A series of structure-based profilin mutants show that TLR11 recognition of the acidic loop is responsible for most of the interleukin (IL)-12 secretion response to TgPRF in peritoneal macrophages. Deletion of both the acidic loop and the β-hairpin completely abrogates IL-12 secretion. Insertion of the T. gondii acidic loop and β-hairpin into yeast profilin is sufficient to generate TLR11-dependent signaling. Substitution of the acidic loop in TgPRF with the homologous loop from the apicomplexan parasite Cryptosporidium parvum does not affect TLR11-dependent IL-12 secretion, while substitution with the acidic loop from Plasmodium falciparum results in reduced but significant IL-12 secretion. We conclude that the parasite-specific motif in TgPRF is the key molecular pattern recognized by TLR11. Unlike other profilins, TgPRF slows nucleotide exchange on monomeric rabbit actin and binds rabbit actin weakly. The putative TgPRF actin-binding surface includes the β-hairpin and diverges widely from the actin-binding surfaces of vertebrate profilins.
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Affiliation(s)
- Kaury Kucera
- Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
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29
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Fine-tuning of neuronal architecture requires two profilin isoforms. Proc Natl Acad Sci U S A 2010; 107:15780-5. [PMID: 20798032 DOI: 10.1073/pnas.1004406107] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two profilin isoforms (PFN1 and PFN2a) are expressed in the mammalian brain. Although profilins are essential for regulating actin dynamics in general, the specific role of these isoforms in neurons has remained elusive. We show that knockdown of the neuron-specific PFN2a results in a significant reduction in dendrite complexity and spine numbers of hippocampal neurons. Overexpression of PFN1 in PFN2a-deficient neurons prevents the loss of spines but does not restore dendritic complexity. Furthermore, we show that profilins are involved in differentially regulating actin dynamics downstream of the pan-neurotrophin receptor (p75(NTR)), a receptor engaged in modulating neuronal morphology. Overexpression of PFN2a restores the morphological changes in dendrites caused by p75(NTR) overexpression, whereas PFN1 restores the normal spine density. Our data assign specific functions to the two PFN isoforms, possibly attributable to different affinities for potent effectors also involved in actin dynamics, and suggest that they are important for the signal-dependent fine-tuning of neuronal architecture.
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30
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Paul AS, Pollard TD. Review of the mechanism of processive actin filament elongation by formins. ACTA ACUST UNITED AC 2009; 66:606-17. [PMID: 19459187 DOI: 10.1002/cm.20379] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We review recent structural and biophysical studies of the mechanism of action of formins, proteins that direct the assembly of unbranched actin filaments for cytokinetic contractile rings and other cellular structures. Formins use free actin monomers to nucleate filaments and then remain bound to the barbed ends of these filaments as they elongate. In addition to variable regulatory domains, formins typically have formin homology 1 (FH1) and formin homology 2 (FH2) domains. FH1 domains have multiple binding sites for profilin, an abundant actin monomer binding protein. FH2 homodimers encircle the barbed end of a filament. Most FH2 domains inhibit actin filament elongation, but FH1 domains concentrate multiple profilin-actin complexes near the end of the filament. FH1 domains transfer actin very rapidly onto the barbed end of the filament, allowing elongation at rates that exceed the rate of elongation by the addition of free actin monomers diffusing in solution. Binding of actin to the end of the filament provides the energy for the highly processive movement of the FH2 as a filament adds thousands of actin subunits. These biophysical insights provide the context to understand how formins contribute to actin assembly in cells. Cell Motil. Cytoskeleton 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Aditya S Paul
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
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31
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Krishnan K, Moens PDJ. Structure and functions of profilins. Biophys Rev 2009; 1:71-81. [PMID: 28509986 PMCID: PMC5425664 DOI: 10.1007/s12551-009-0010-y] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Revised: 05/07/2009] [Accepted: 05/13/2009] [Indexed: 10/20/2022] Open
Abstract
Profilins are small actin-binding proteins found in eukaryotes and certain viruses that are involved in cell development, cytokinesis, membrane trafficking, and cell motility. Originally identified as an actin sequestering/binding protein, profilin has been involved in actin polymerization dynamics. It catalyzes the exchange of ADP/ATP in actin and increases the rate of polymerization. Profilins also interact with polyphosphoinositides (PPI) and proline-rich domains containing proteins. Through its interaction with PPIs, profilin has been linked to signaling pathways between the cell membrane and the cytoskeleton, while its role in membrane trafficking has been associated with its interaction with proline-rich domain-containing proteins. Depending on the organism, profilin is present in a various number of isoforms. Four isoforms of profilin have been reported in higher organisms, while only one or two isoforms are expressed in single-cell organisms. The affinity of these isoforms for their ligands varies between isoforms and should therefore modulate their functions. However, the significance and the functions of the different isoforms are not yet fully understood. The structures of many profilin isoforms have been solved both in the presence and the absence of actin and poly-L-proline. These structural studies will greatly improve our understanding of the differences and similarities between the different profilins. Structural stability studies of different profilins are also shedding some light on our understanding of the profilin/ligand interactions. Profilin is a multifaceted protein for which a dramatic increase in potential functions has been found in recent years; as such, it has been implicated in a variety of physiological and pathological processes.
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Affiliation(s)
- Kannan Krishnan
- Centre for Bioactive Discovery in Health and Ageing, School of Science and Technology, University of New England, McClymont Bldg, Armidale, NSW, 2351, Australia
| | - Pierre D J Moens
- Centre for Bioactive Discovery in Health and Ageing, School of Science and Technology, University of New England, McClymont Bldg, Armidale, NSW, 2351, Australia.
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32
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Current awareness on yeast. Yeast 2009. [DOI: 10.1002/yea.1622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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33
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Wen KK, Rubenstein PA. Differential regulation of actin polymerization and structure by yeast formin isoforms. J Biol Chem 2009; 284:16776-16783. [PMID: 19386598 DOI: 10.1074/jbc.m109.006981] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The budding yeast formins, Bnr1 and Bni1, behave very differently with respect to their interactions with muscle actin. However, the mechanisms underlying these differences are unclear, and these formins do not interact with muscle actin in vivo. We use yeast wild type and mutant actins to further assess these differences between Bnr1 and Bni1. Low ionic strength G-buffer does not promote actin polymerization. However, Bnr1, but not Bni1, causes the polymerization of pyrene-labeled Mg-G-actin in G-buffer into single filaments based on fluorometric and EM observations. Polymerization by Bnr1 does not occur with Ca-G-actin. By cosedimentation, maximum filament formation occurs at a Bnr1:actin ratio of 1:2. The interaction of Bnr1 with pyrene-labeled S265C Mg-actin yields a pyrene excimer peak, from the cross-strand interaction of pyrene probes, which only occurs in the context of F-actin. In F-buffer, Bnr1 promotes much faster yeast actin polymerization than Bni1. It also bundles the F-actin in contrast to the low ionic strength situation where only single filaments form. Thus, the differences previously observed with muscle actin are not actin isoform-specific. The binding of both formins to F-actin saturate at an equimolar ratio, but only about 30% of each formin cosediments with F-actin. Finally, addition of Bnr1 but not Bni1 to pyrene-labeled wild type and S265C Mg-F actins enhanced the pyrene- and pyrene-excimer fluorescence, respectively, suggesting Bnr1 also alters F-actin structure. These differences may facilitate the ability of Bnr1 to form the actin cables needed for polarized delivery of nutrients and organelles to the growing yeast bud.
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Affiliation(s)
- Kuo-Kuang Wen
- From the Department of Biochemistry, Roy A. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242
| | - Peter A Rubenstein
- From the Department of Biochemistry, Roy A. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242.
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34
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Profilin 1 is required for abscission during late cytokinesis of chondrocytes. EMBO J 2009; 28:1157-69. [PMID: 19262563 DOI: 10.1038/emboj.2009.58] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 02/11/2009] [Indexed: 01/20/2023] Open
Abstract
Profilins are key factors for dynamic rearrangements of the actin cytoskeleton. However, the functions of profilins in differentiated mammalian cells are uncertain because profilin deficiency is early embryonic lethal for higher eukaryotes. To examine profilin function in chondrocytes, we disrupted the profilin 1 gene in cartilage (Col2pfn1). Homozygous Col2pfn1 mice develop progressive chondrodysplasia caused by disorganization of the growth plate and defective chondrocyte cytokinesis, indicated by the appearance of binucleated cells. Surprisingly, Col2pfn1 chondrocytes assemble and contract actomyosin rings normally during cell division; however, they display defects during late cytokinesis as they frequently fail to complete abscission due to their inability to develop strong traction forces. This reduced force generation results from an impaired formation of lamellipodia, focal adhesions and stress fibres, which in part could be linked to an impaired mDia1-mediated actin filament elongation. Neither an actin nor a poly-proline binding-deficient profilin 1 is able to rescue the defects. Taken together, our results demonstrate that profilin 1 is not required for actomyosin ring formation in dividing chondrocytes but necessary to generate sufficient force for abscission during late cytokinesis.
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