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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Heissler SM, Chinthalapudi K. Structural and functional mechanisms of actin isoforms. FEBS J 2024. [PMID: 38779987 DOI: 10.1111/febs.17153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 04/01/2024] [Accepted: 04/23/2024] [Indexed: 05/25/2024]
Abstract
Actin is a highly conserved and fundamental protein in eukaryotes and participates in a broad spectrum of cellular functions. Cells maintain a conserved ratio of actin isoforms, with muscle and non-muscle actins representing the main actin isoforms in muscle and non-muscle cells, respectively. Actin isoforms have specific and redundant functional roles and display different biochemistries, cellular localization, and interactions with myosins and actin-binding proteins. Understanding the specific roles of actin isoforms from the structural and functional perspective is crucial for elucidating the intricacies of cytoskeletal dynamics and regulation and their implications in health and disease. Here, we review how the structure contributes to the functional mechanisms of actin isoforms with a special emphasis on the questions of how post-translational modifications and disease-linked mutations affect actin isoforms biochemistry, function, and interaction with actin-binding proteins and myosin motors.
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Affiliation(s)
- Sarah M Heissler
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, USA
| | - Krishna Chinthalapudi
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, USA
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3
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Baro L, Almhassneh RA, Islam A, Juanes MA. Tumor invasiveness is regulated by the concerted function of APC, formins, and Arp2/3 complex. iScience 2024; 27:109687. [PMID: 38680662 PMCID: PMC11053316 DOI: 10.1016/j.isci.2024.109687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 02/23/2024] [Accepted: 04/05/2024] [Indexed: 05/01/2024] Open
Abstract
Tumor cell invasion is the initial step in metastasis, the leading cause of death from cancer. Invasion requires protrusive cellular structures that steer the migration of leader cells emanating from the tumor mass toward neighboring tissues. Actin is central to these processes and is therefore the prime target of drugs known as migrastatics. However, the broad effects of general actin inhibitors limit their therapeutic use. Here, we delineate the roles of specific actin nucleators in tuning actin-rich invasive protrusions and pinpoint potential pharmacological targets. We subject colorectal cancer spheroids embedded in collagen matrix-a preclinical model mirroring solid tumor invasiveness-to pharmacologic and/or genetic treatment of specific actin arrays to assess their roles in invasiveness. Our data reveal coordinated yet distinct involvement of actin networks nucleated by adenomatous polyposis coli, formins, and actin-related protein 2/3 complex in the biogenesis and maintenance of invasive protrusions. These findings may open avenues for better targeted therapies.
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Affiliation(s)
- Lautaro Baro
- Cytoskeletal Dynamics in Cell Migration and Cancer Invasion Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
- School of Health and Life Sciences, Teesside University, Middlesbrough TS1 3BX, UK
- National Horizons Centre, Teesside University, Darlington DL1 1HG, UK
| | - Rabeah A. Almhassneh
- Cytoskeletal Dynamics in Cell Migration and Cancer Invasion Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Asifa Islam
- School of Health and Life Sciences, Teesside University, Middlesbrough TS1 3BX, UK
- National Horizons Centre, Teesside University, Darlington DL1 1HG, UK
| | - M. Angeles Juanes
- Cytoskeletal Dynamics in Cell Migration and Cancer Invasion Laboratory, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
- School of Health and Life Sciences, Teesside University, Middlesbrough TS1 3BX, UK
- National Horizons Centre, Teesside University, Darlington DL1 1HG, UK
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4
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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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5
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Petitjean II, Tran QD, Goutou A, Kabir Z, Wiche G, Leduc C, Koenderink GH. Reconstitution of cytolinker-mediated crosstalk between actin and vimentin. Eur J Cell Biol 2024; 103:151403. [PMID: 38503131 DOI: 10.1016/j.ejcb.2024.151403] [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: 10/27/2023] [Revised: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 03/21/2024] Open
Abstract
Cell shape and motility are determined by the cytoskeleton, an interpenetrating network of actin filaments, microtubules, and intermediate filaments. The biophysical properties of each filament type individually have been studied extensively by cell-free reconstitution. By contrast, the interactions between the three cytoskeletal networks are relatively unexplored. They are coupled via crosslinkers of the plakin family such as plectin. These are challenging proteins for reconstitution because of their giant size and multidomain structure. Here we engineer a recombinant actin-vimentin crosslinker protein called 'ACTIF' that provides a minimal model system for plectin, recapitulating its modular design with actin-binding and intermediate filament-binding domains separated by a coiled-coil linker for dimerisation. We show by fluorescence and electron microscopy that ACTIF has a high binding affinity for vimentin and actin and creates mixed actin-vimentin bundles. Rheology measurements show that ACTIF-mediated crosslinking strongly stiffens actin-vimentin composites. Finally, we demonstrate the modularity of this approach by creating an ACTIF variant with the intermediate filament binding domain of Adenomatous Polyposis Coli. Our protein engineering approach provides a new cell-free system for the biophysical characterization of intermediate filament-binding crosslinkers and for understanding the mechanical synergy between actin and vimentin in mesenchymal cells.
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Affiliation(s)
- Irene Istúriz Petitjean
- Department of Bionanoscience & Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, the Netherlands
| | - Quang D Tran
- CNRS, Institut Jacques Monod, Université Paris Cité, Paris F-75013, France
| | - Angeliki Goutou
- Department of Bionanoscience & Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, the Netherlands
| | - Zima Kabir
- Department of Bionanoscience & Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, the Netherlands
| | - Gerhard Wiche
- Max Perutz Laboratories, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Cécile Leduc
- CNRS, Institut Jacques Monod, Université Paris Cité, Paris F-75013, France.
| | - Gijsje H Koenderink
- Department of Bionanoscience & Kavli Institute of Nanoscience, Delft University of Technology, 2629 HZ, Delft, the Netherlands.
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6
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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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7
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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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8
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Le Chua X, Tong CS, Xǔ XJ, Su M, Xiao S, Wu X, Wu M. Competition and Synergy of Arp2/3 and Formins in Nucleating Actin Waves. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.13.557508. [PMID: 37745345 PMCID: PMC10515902 DOI: 10.1101/2023.09.13.557508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
The assembly and disassembly of actin filaments and their regulatory proteins are crucial for maintaining cell structure or changing physiological state. However, because of the tremendous global impact of actin on diverse cellular processes, dissecting the specific role of actin regulatory proteins remains challenging. In this study, we employ actin waves that propagate on the cortex of mast cell to investigate the interplay between formins and the Arp2/3 complex in the nucleating and turnover of cortical actin. Our findings reveal that the recruitment of FMNL1 and mDia3 precedes the Arp2/3 complex in cortical actin waves. Membrane and GTPase-interaction can drive oscillations of FMNL1 in an actin-dependent manner, but active Cdc42 waves or constitutively-active FMNL1 mutant can form without actin waves. In addition to the apparent coordinated assembly of formins and Arp2/3, we further reveal their antagonism, where inhibition of Arp2/3 complex by CK-666 led to a transient increase in the recruitment of formins and actin polymerization. Our analysis suggest that the antagonism could not be explained for the competition between FMNL1 and Arp2/3 for monomeric actin. Rather, it is regulated by a limited pool of their common upstream regulator, Cdc42, whose level is negatively regulated by Arp2/3. Collectively, our study highlights the multifaceted interactions, cooperative or competitive, between formins and Arp2/3 complex, in the intricate and dynamic control of actin cytoskeletal network.
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Affiliation(s)
- Xiang Le Chua
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biological Sciences, Centre for Bioimaging Sciences, Singapore 117557
| | - Chee San Tong
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biological Sciences, Centre for Bioimaging Sciences, Singapore 117557
| | - X J Xǔ
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Physics, Yale University, New Haven, CT 06511, USA
| | - Maohan Su
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biological Sciences, Centre for Bioimaging Sciences, Singapore 117557
- Mechanobiology Institute, National University of Singapore, Singapore 117411
| | - Shengping Xiao
- Department of Biological Sciences, Centre for Bioimaging Sciences, Singapore 117557
| | - Xudong Wu
- School of Life Sciences, Westlake University, Hangzhou, China 310024
| | - Min Wu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
- Department of Biological Sciences, Centre for Bioimaging Sciences, Singapore 117557
- Department of Physics, Yale University, New Haven, CT 06511, USA
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9
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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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10
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Ulrichs H, Gaska I, Shekhar S. Multicomponent regulation of actin barbed end assembly by twinfilin, formin and capping protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.24.538010. [PMID: 37163095 PMCID: PMC10168238 DOI: 10.1101/2023.04.24.538010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Living cells assemble their actin networks by regulating reactions at the barbed end of actin filaments. Formins accelerate elongation, capping protein (CP) arrests growth and twinfilin promotes depolymerization at barbed ends. How cells integrate these disparate activities within a shared cytoplasm to produce diverse actin networks, each with distinct morphologies and finely tuned assembly kinetics, is unclear. We used microfluidics-assisted TIRF microscopy to investigate how formin mDia1, CP and twinfilin influence the elongation of actin filament barbed ends. We discovered that the three proteins can simultaneously bind a barbed end in a multiprotein complex. Three-color single molecule experiments showed that twinfilin cannot bind actin filament ends occupied by formin mDia1 unless CP is present. The trimeric complex is short-lived (∼1s) and results in rapid dissociation of CP by twinfilin causing resumption of rapid formin- based elongation. Thus, the depolymerase twinfilin acts as a pro-formin factor that promotes polymerization when both CP and formin are present. While a single twinfilin binding event is sufficient to displace CP from the trimeric complex, it takes about 30 independent twinfilin binding events to remove capping protein from CP-bound barbed end. Our findings establish a new paradigm in which polymerases, depolymerases and cappers work in concert to tune cellular actin assembly.
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Affiliation(s)
- Heidi Ulrichs
- Department of Physics, Emory University, Atlanta, GA 30322
- Department of Cell Biology, Emory University, Atlanta, GA 30322
| | - Ignas Gaska
- Department of Physics, Emory University, Atlanta, GA 30322
- Department of Cell Biology, Emory University, Atlanta, GA 30322
| | - Shashank Shekhar
- Department of Physics, Emory University, Atlanta, GA 30322
- Department of Cell Biology, Emory University, Atlanta, GA 30322
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11
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Gaeta IM, Tyska MJ. BioID2 screening identifies KIAA1671 as an EPS8 proximal factor that marks sites of microvillus growth. Mol Biol Cell 2023; 34:ar31. [PMID: 36790915 PMCID: PMC10092648 DOI: 10.1091/mbc.e22-11-0498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
Microvilli are defining morphological features of the apical surfaces in diverse epithelial tissues. To develop our understanding of microvillus biogenesis, we used a biotin proximity-labeling approach to uncover new molecules enriched near EPS8, a well-studied marker of the microvillus distal tip compartment. Mass spectrometry of biotinylated hits identified KIAA1671, a large (∼200 kDa), disordered, and previously uncharacterized protein. Based on immunofluorescent staining and expression of fluorescent protein-tagged constructs, we found that KIAA1671 localizes to the base of the brush border in native intestinal tissue and polarized epithelial-cell culture models, as well as dynamic actin-rich structures in unpolarized, nonepithelial cell types. Live imaging also revealed that during the early stages of microvillar growth, KIAA1671 colocalizes with EPS8 in diffraction-limited puncta. However, once elongation of the core bundle begins, these two factors separate, with EPS8 tracking the distal end and KIAA1671 remaining behind at the base of the structure. These results suggest that KIAA1671 cooperates with EPS8 and potentially other assembly factors to initiate growth of microvilli on the apical surface. These findings offer new details on how transporting epithelial cells builds the brush border and may inform our understanding of how apical specializations are assembled in other epithelial contexts.
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Affiliation(s)
- Isabella M Gaeta
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
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12
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Tsukita K, Kitamata M, Kashihara H, Yano T, Fujiwara I, Day TF, Katsuno T, Kim J, Takenaga F, Tanaka H, Park S, Miyata M, Watanabe H, Kondoh G, Takahashi R, Tamura A, Tsukita S. Phase separation of an actin nucleator by junctional microtubules regulates epithelial function. SCIENCE ADVANCES 2023; 9:eadf6358. [PMID: 36791197 PMCID: PMC9931218 DOI: 10.1126/sciadv.adf6358] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 01/18/2023] [Indexed: 06/18/2023]
Abstract
Liquid-liquid phase separation (LLPS) is involved in various dynamic biological phenomena. In epithelial cells, dynamic regulation of junctional actin filaments tethered to the apical junctional complex (AJC) is critical for maintaining internal homeostasis against external perturbations; however, the role of LLPS in this process remains unknown. Here, after identifying a multifunctional actin nucleator, cordon bleu (Cobl), as an AJC-enriched microtubule-associated protein, we conducted comprehensive in vitro and in vivo analyses. We found that apical microtubules promoted LLPS of Cobl at the AJC, and Cobl actin assembly activity increased upon LLPS. Thus, microtubules spatiotemporally regulated junctional actin assembly for epithelial morphogenesis and paracellular barriers. Collectively, these findings established that LLPS of the actin nucleator Cobl mediated dynamic microtubule-actin cross-talk in junctions, which fine-tuned the epithelial barrier.
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Affiliation(s)
- Kazuto Tsukita
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
- Department of Neurology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Manabu Kitamata
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hiroka Kashihara
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Tomoki Yano
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
- Department of Organoid Medicine, Sakaguchi Laboratory, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Ikuko Fujiwara
- Departments of Materials Science and Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
- Graduate School of Science, Osaka Metropolitan University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Timothy F. Day
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Tatsuya Katsuno
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
- Center for Anatomical, Pathological and Forensic Medical Researches, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Jaewon Kim
- Graduate School of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Fumiko Takenaga
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hiroo Tanaka
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
- Department of Pharmacology, Teikyo University School of Medicine, Itabashi-ku, Tokyo 173-8605, Japan
| | - Sungsu Park
- Graduate School of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Korea
| | - Makoto Miyata
- Graduate School of Science, Osaka Metropolitan University, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Hitomi Watanabe
- Laboratory of Integrative Biological Science, Institute for Frontier Life and Medical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Gen Kondoh
- Laboratory of Integrative Biological Science, Institute for Frontier Life and Medical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Ryosuke Takahashi
- Department of Neurology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
| | - Atsushi Tamura
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
- Department of Pharmacology, Teikyo University School of Medicine, Itabashi-ku, Tokyo 173-8605, Japan
| | - Sachiko Tsukita
- Advanced Comprehensive Research Organization, Teikyo University, Itabashi-ku, Tokyo 173-0003, Japan
- Laboratory of Barriology and Cell Biology, Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
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13
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Actin: Static and Dynamic Studies. Methods Mol Biol 2023; 2604:13-24. [PMID: 36773222 DOI: 10.1007/978-1-0716-2867-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The actin cytoskeleton is a highly dynamic network in plant cells, which is precisely regulated by numerous actin-binding proteins. Hence, characterizing the biochemical activities of actin-binding proteins is of great importance. Here we describe methods for determining the binding and bundling of microfilaments as well as methods for visualizing microfilaments using fluorescent phalloidin and single-molecule TIRF imaging.
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14
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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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15
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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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16
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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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17
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Banerjee DS, Banerjee S. Emergence and maintenance of variable-length actin filaments in a limiting pool of building blocks. Biophys J 2022; 121:2436-2448. [PMID: 35598045 DOI: 10.1016/j.bpj.2022.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 04/10/2022] [Accepted: 05/13/2022] [Indexed: 11/16/2022] Open
Abstract
Actin is one of the key structural components of the eukaryotic cytoskeleton that regulates cellular architecture and mechanical properties. Dynamic regulation of actin filament length and organization is essential for the control of many physiological processes including cell adhesion, motility and division. While previous studies have mostly focused on the mechanisms controlling the mean length of individual actin filaments, it remains poorly understood how distinct actin filament populations in cells maintain different lengths using the same set of molecular building blocks. Here we develop a theoretical model for the length regulation of multiple actin filaments by nucleation and growth rate modulation by actin binding proteins in a limiting pool of monomers. We first show that spontaneous nucleation of actin filaments naturally leads to heterogeneities in filament length distribution. We then investigate the effects of filament growth inhibition by capping proteins and growth promotion by formin proteins on filament length distribution. We find that filament length heterogeneity can be increased by growth inhibition, whereas growth promoters do not significantly affect length heterogeneity. Interestingly, a competition between filament growth inhibitors and growth promoters can give rise to bimodal filament length distribution as well as a highly heterogeneous length distribution with large statistical dispersion. We quantitatively predict how heterogeneity in actin filament length can be modulated by tuning F-actin nucleation and growth rates in order to create distinct filament subpopulations with different lengths. SIGNIFICANCE: Actin filaments organize into different functional network architectures within eukaryotic cells. To maintain distinct actin network architectures, it is essential to regulate the lengths of actin filaments. While the mechanisms controlling the lengths of individual actin filaments have been extensively studied, the regulation of length heterogeneity in actin filament populations is not well understood. Here we show that the modulation of actin filament growth and nucleation rates by actin binding proteins can regulate actin length distribution and create distinct sub-populations with different lengths. In particular, by tuning concentrations of formin, profilin and capping proteins, various aspects of actin filament length distribution can be controlled. Insights gained from our results may have significant implications for the regulation of actin filament length heterogeneity and architecture within a cell.
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Affiliation(s)
- Deb Sankar Banerjee
- Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213, USA
| | - Shiladitya Banerjee
- Carnegie Mellon University, Department of Physics, Pittsburgh, PA 15213, USA
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18
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Fang X, Svitkina TM. Adenomatous polyposis coli (APC) in cell migration. Eur J Cell Biol 2022; 101:151228. [DOI: 10.1016/j.ejcb.2022.151228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/15/2022] [Accepted: 04/20/2022] [Indexed: 12/22/2022] Open
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19
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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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20
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Abstract
The precise assembly and disassembly of actin filaments is required for several cellular processes, and their regulation has been scrutinized for decades. Twenty years ago, a handful of studies marked the advent of a new type of experiment to study actin dynamics: using optical microscopy to look at individual events, taking place on individual filaments in real time. Here, we summarize the main characteristics of this approach and how it has changed our ability to understand actin assembly dynamics. We also highlight some of its caveats and reflect on what we have learned over the past 20 years, leading us to propose a set of guidelines, which we hope will contribute to a better exploitation of this powerful tool.
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21
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Ordabayev YA, Friedman LJ, Gelles J, Theobald DL. Bayesian machine learning analysis of single-molecule fluorescence colocalization images. eLife 2022; 11:73860. [PMID: 35319463 PMCID: PMC9183235 DOI: 10.7554/elife.73860] [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: 09/14/2021] [Accepted: 03/19/2022] [Indexed: 01/07/2023] Open
Abstract
Multi-wavelength single-molecule fluorescence colocalization (CoSMoS) methods allow elucidation of complex biochemical reaction mechanisms. However, analysis of CoSMoS data is intrinsically challenging because of low image signal-to-noise ratios, non-specific surface binding of the fluorescent molecules, and analysis methods that require subjective inputs to achieve accurate results. Here, we use Bayesian probabilistic programming to implement Tapqir, an unsupervised machine learning method that incorporates a holistic, physics-based causal model of CoSMoS data. This method accounts for uncertainties in image analysis due to photon and camera noise, optical non-uniformities, non-specific binding, and spot detection. Rather than merely producing a binary 'spot/no spot' classification of unspecified reliability, Tapqir objectively assigns spot classification probabilities that allow accurate downstream analysis of molecular dynamics, thermodynamics, and kinetics. We both quantitatively validate Tapqir performance against simulated CoSMoS image data with known properties and also demonstrate that it implements fully objective, automated analysis of experiment-derived data sets with a wide range of signal, noise, and non-specific binding characteristics.
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Affiliation(s)
| | - Larry J Friedman
- Department of Biochemistry, Brandeis UniversityWalthamUnited States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis UniversityWalthamUnited States
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22
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Xie Y, Zhou F, Ma Q, Lu L, Miao Y. A teamwork promotion of formin-mediated actin nucleation by Bud6 and Aip5 in Saccharomyces cerevisiae. Mol Biol Cell 2021; 33:ar19. [PMID: 34818061 PMCID: PMC9236144 DOI: 10.1091/mbc.e21-06-0285] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Actin nucleation is achieved by collaborative teamwork of actin nucleator factors (NFs) and nucleation-promoting factors (NPFs) into functional protein complexes. Selective inter- and intramolecular interactions between the nucleation complex constituents enable diverse modes of complex assembly in initiating actin polymerization on demand. Budding yeast has two formins, Bni1 and Bnr1, which are teamed up with different NPFs. However, the selective pairing between formin NFs and NPFs into the nucleation core for actin polymerization is not completely understood. By examining the functions and interactions of NPFs and NFs via biochemistry, genetics, and mathematical modeling approaches, we found that two NPFs, Aip5 and Bud6, showed joint teamwork effort with Bni1 and Bnr1, respectively, by interacting with the C-terminal intrinsically disordered region (IDR) of formin, in which two NPFs work together to promote formin-mediated actin nucleation. Although the C-terminal IDRs of Bni1 and Bnr1 are distinct in length, each formin IDR orchestrates the recruitment of Bud6 and Aip5 cooperatively by different positioning strategies to form a functional complex. Our study demonstrated the dynamic assembly of the actin nucleation complex by recruiting multiple partners in budding yeast, which may be a general feature for effective actin nucleation by formins.
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Affiliation(s)
- Ying Xie
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Feng Zhou
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Qianqian Ma
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Lanyuan Lu
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Yansong Miao
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
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23
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Hoeprich GJ, Sinclair AN, Shekhar S, Goode BL. Single-molecule imaging of IQGAP1 regulating actin filament dynamics. Mol Biol Cell 2021; 33:ar2. [PMID: 34731043 PMCID: PMC8886817 DOI: 10.1091/mbc.e21-04-0211] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
IQGAP is a conserved family of actin-binding proteins with essential roles in cell motility, cytokinesis, and cell adhesion, yet there remains a limited understanding of how IQGAP proteins directly influence actin filament dynamics. To close this gap, we used single-molecule and single-filament total internal reflection fluorescence microscopy to observe IQGAP regulating actin dynamics in real time. To our knowledge, this is the first study to do so. Our results demonstrate that full-length human IQGAP1 forms dimers that stably bind to actin filament sides and transiently cap barbed ends. These interactions organize filaments into thin bundles, suppress barbed end growth, and inhibit filament disassembly. Surprisingly, each activity depends on distinct combinations of IQGAP1 domains and/or dimerization, suggesting that different mechanisms underlie each functional effect on actin. These observations have important implications for how IQGAP functions as an actin regulator in vivo and how it may be regulated in different biological settings.
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Affiliation(s)
- Gregory J Hoeprich
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02453, USA
| | - Amy N Sinclair
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02453, USA
| | - Shashank Shekhar
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02453, USA.,Present address: Departments of Physics and Cell Biology, Emory University, Atlanta, GA 30322
| | - Bruce L Goode
- Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02453, USA
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24
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Izadi M, Seemann E, Schlobinski D, Schwintzer L, Qualmann B, Kessels MM. Functional interdependence of the actin nucleator Cobl and Cobl-like in dendritic arbor development. eLife 2021; 10:67718. [PMID: 34264190 PMCID: PMC8282341 DOI: 10.7554/elife.67718] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 06/30/2021] [Indexed: 12/14/2022] Open
Abstract
Local actin filament formation is indispensable for development of the dendritic arbor of neurons. We show that, surprisingly, the action of single actin filament-promoting factors was insufficient for powering dendritogenesis. Instead, this required the actin nucleator Cobl and its only evolutionary distant ancestor Cobl-like acting interdependently. This coordination between Cobl-like and Cobl was achieved by physical linkage by syndapins. Syndapin I formed nanodomains at convex plasma membrane areas at the base of protrusive structures and interacted with three motifs in Cobl-like, one of which was Ca2+/calmodulin-regulated. Consistently, syndapin I, Cobl-like’s newly identified N terminal calmodulin-binding site and the single Ca2+/calmodulin-responsive syndapin-binding motif all were critical for Cobl-like’s functions. In dendritic arbor development, local Ca2+/CaM-controlled actin dynamics thus relies on regulated and physically coordinated interactions of different F-actin formation-promoting factors and only together they have the power to bring about the sophisticated neuronal morphologies required for neuronal network formation in mammals.
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Affiliation(s)
- Maryam Izadi
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
| | - Eric Seemann
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
| | - Dirk Schlobinski
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
| | - Lukas Schwintzer
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
| | - Britta Qualmann
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
| | - Michael M Kessels
- Institute of Biochemistry I, Jena University Hospital/Friedrich-Schiller-University Jena, Jena, Germany
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25
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Mylvaganam S, Freeman SA, Grinstein S. The cytoskeleton in phagocytosis and macropinocytosis. Curr Biol 2021; 31:R619-R632. [PMID: 34033794 DOI: 10.1016/j.cub.2021.01.036] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cells of the innate immune system, notably macrophages, neutrophils and dendritic cells, perform essential antimicrobial and homeostatic functions. These functions rely on the dynamic surveillance of the environment supported by the formation of elaborate membrane protrusions. Such protrusions - pseudopodia, lamellipodia and filopodia - facilitate the sampling of the surrounding fluid by macropinocytosis, as well as the engulfment of particulates by phagocytosis. Both processes entail extreme plasma membrane deformations that require the coordinated rearrangement of cytoskeletal polymers, which exert protrusive force and drive membrane coalescence and scission. The resulting vacuolar compartments undergo pronounced remodeling and ultimate resolution by mechanisms that also involve the cytoskeleton. Here, we describe the regulation and functions of cytoskeletal assembly and remodeling during macropinocytosis and phagocytosis.
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Affiliation(s)
- Sivakami Mylvaganam
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Sergio Grinstein
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, 686 Bay Street, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
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26
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Karlsson R, Dráber P. Profilin-A master coordinator of actin and microtubule organization in mammalian cells. J Cell Physiol 2021; 236:7256-7265. [PMID: 33821475 DOI: 10.1002/jcp.30379] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/08/2021] [Accepted: 03/12/2021] [Indexed: 12/17/2022]
Abstract
The last two decades have witnessed a tremendous increase in cell biology data. Not least is this true for studies of the dynamic organization of the microfilament and microtubule systems in animal cells where analyses of the molecular components and their interaction patterns have deepened our understanding of these complex force-generating machineries. Previous observations of a molecular cross-talk between the two systems have now led to the realization of the existence of several intricate mechanisms operating to maintain their coordinated cellular organization. In this short review, we relate to this development by discussing new results concerning the function of the actin regulator profilin 1 as a control component of microfilament-microtubule cross-talk.
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Affiliation(s)
- Roger Karlsson
- Department of Molecular Biosciences, WGI, Stockholm University, Stockholm, Sweden
| | - Pavel Dráber
- Department of Biology of Cytoskeleton, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
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27
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28
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Efimova N, Yang C, Chia JX, Li N, Lengner CJ, Neufeld KL, Svitkina TM. Branched actin networks are assembled on microtubules by adenomatous polyposis coli for targeted membrane protrusion. J Cell Biol 2021; 219:151902. [PMID: 32597939 PMCID: PMC7480092 DOI: 10.1083/jcb.202003091] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 05/26/2020] [Accepted: 05/28/2020] [Indexed: 12/26/2022] Open
Abstract
Cell migration is driven by pushing and pulling activities of the actin cytoskeleton, but migration directionality is largely controlled by microtubules. This function of microtubules is especially critical for neuron navigation. However, the underlying mechanisms are poorly understood. Here we show that branched actin filament networks, the main pushing machinery in cells, grow directly from microtubule tips toward the leading edge in growth cones of hippocampal neurons. Adenomatous polyposis coli (APC), a protein with both tumor suppressor and cytoskeletal functions, concentrates at the microtubule-branched network interface, whereas APC knockdown nearly eliminates branched actin in growth cones and prevents growth cone recovery after repellent-induced collapse. Conversely, encounters of dynamic APC-positive microtubule tips with the cell edge induce local actin-rich protrusions. Together, we reveal a novel mechanism of cell navigation involving APC-dependent assembly of branched actin networks on microtubule tips.
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Affiliation(s)
- Nadia Efimova
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA
| | - Changsong Yang
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA
| | - Jonathan X Chia
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA
| | - Ning Li
- Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | - Christopher J Lengner
- Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA.,Department of Cell and Developmental Biology, Perelman School of Medicine and Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA
| | - Kristi L Neufeld
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS
| | - Tatyana M Svitkina
- Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA
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29
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Rands TJ, Goode BL. Bil2 Is a Novel Inhibitor of the Yeast Formin Bnr1 Required for Proper Actin Cable Organization and Polarized Secretion. Front Cell Dev Biol 2021; 9:634587. [PMID: 33634134 PMCID: PMC7900418 DOI: 10.3389/fcell.2021.634587] [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: 11/28/2020] [Accepted: 01/20/2021] [Indexed: 11/21/2022] Open
Abstract
Cell growth in budding yeast depends on rapid and on-going assembly and turnover of polarized actin cables, which direct intracellular transport of post-Golgi vesicles to the bud tip. Saccharomyces cerevisiae actin cables are polymerized by two formins, Bni1 and Bnr1. Bni1 assembles cables in the bud, while Bnr1 is anchored to the bud neck and assembles cables that specifically extend filling the mother cell. Here, we report a formin regulatory role for YGL015c, a previously uncharacterized open reading frame, which we have named Bud6 Interacting Ligand 2 (BIL2). bil2Δ cells display defects in actin cable architecture and partially-impaired secretory vesicle transport. Bil2 inhibits Bnr1-mediated actin filament nucleation in vitro, yet has no effect on the rate of Bnr1-mediated filament elongation. This activity profile for Bil2 resembles that of another yeast formin regulator, the F-BAR protein Hof1, and we find that bil2Δ with hof1Δ are synthetic lethal. Unlike Hof1, which localizes exclusively to the bud neck, GFP-Bil2 localizes to the cytosol, secretory vesicles, and sites of polarized cell growth. Further, we provide evidence that Hof1 and Bil2 inhibitory effects on Bnr1 are overcome by distinct mechanisms. Together, our results suggest that Bil2 and Hof1 perform distinct yet genetically complementary roles in inhibiting the actin nucleation activity of Bnr1 to control actin cable assembly and polarized secretion.
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Affiliation(s)
- Thomas J Rands
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA, United States
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA, United States
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30
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Dimchev V, Lahmann I, Koestler SA, Kage F, Dimchev G, Steffen A, Stradal TEB, Vauti F, Arnold HH, Rottner K. Induced Arp2/3 Complex Depletion Increases FMNL2/3 Formin Expression and Filopodia Formation. Front Cell Dev Biol 2021; 9:634708. [PMID: 33598464 PMCID: PMC7882613 DOI: 10.3389/fcell.2021.634708] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Accepted: 01/07/2021] [Indexed: 01/12/2023] Open
Abstract
The Arp2/3 complex generates branched actin filament networks operating in cell edge protrusion and vesicle trafficking. Here we employ a conditional knockout mouse model permitting tissue- or cell-type specific deletion of the murine Actr3 gene (encoding Arp3). A functional Actr3 gene appeared essential for fibroblast viability and growth. Thus, we developed cell lines for exploring the consequences of acute, tamoxifen-induced Actr3 deletion causing near-complete loss of functional Arp2/3 complex expression as well as abolished lamellipodia formation and membrane ruffling, as expected. Interestingly, Arp3-depleted cells displayed enhanced rather than reduced cell spreading, employing numerous filopodia, and showed little defects in the rates of random cell migration. However, both exploration of new space by individual cells and collective migration were clearly compromised by the incapability to efficiently maintain directionality of migration, while the principal ability to chemotax was only moderately affected. Examination of actin remodeling at the cell periphery revealed reduced actin turnover rates in Arp2/3-deficient cells, clearly deviating from previous sequestration approaches. Most surprisingly, induced removal of Arp2/3 complexes reproducibly increased FMNL formin expression, which correlated with the explosive induction of filopodia formation. Our results thus highlight both direct and indirect effects of acute Arp2/3 complex removal on actin cytoskeleton regulation.
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Affiliation(s)
- Vanessa Dimchev
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Ines Lahmann
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany
| | - Stefan A Koestler
- Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Frieda Kage
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Georgi Dimchev
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Anika Steffen
- Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Theresia E B Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Franz Vauti
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany
| | - Hans-Henning Arnold
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany
| | - Klemens Rottner
- Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany.,Braunschweig Integrated Centre of Systems Biology (BRICS), Braunschweig, Germany
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31
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Pinto-Costa R, Sousa MM. Microtubules, actin and cytolinkers: how to connect cytoskeletons in the neuronal growth cone. Neurosci Lett 2021; 747:135693. [PMID: 33529653 DOI: 10.1016/j.neulet.2021.135693] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 01/12/2021] [Accepted: 01/16/2021] [Indexed: 01/20/2023]
Abstract
Cytolinkers ensure the integration of the different cytoskeleton components in the neuronal growth cone during development and in the course of axon regeneration. In neurons, an integrated skeleton guarantees appropriate function, and connectivity of high order circuits. Over the past years, several cytoskeleton regulatory proteins with actin-microtubule crosslinking activity have been identified. In neurons, the importance of spectrins, formins and other cytolinkers capable of coupling actin and microtubules has been extensively highlighted during axon outgrowth and guidance. In this Review, we discuss the current knowledge on cytolinkers specifically expressed in the neuronal growth cone of developing and regenerating axons.
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Affiliation(s)
- Rita Pinto-Costa
- Nerve Regeneration Group, i3S-Instituto de Investigação e Inovação em Saúde and IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135, Porto, Portugal
| | - Monica Mendes Sousa
- Nerve Regeneration Group, i3S-Instituto de Investigação e Inovação em Saúde and IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135, Porto, Portugal.
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32
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Juanes MA. Cytoskeletal Control and Wnt Signaling-APC's Dual Contributions in Stem Cell Division and Colorectal Cancer. Cancers (Basel) 2020; 12:E3811. [PMID: 33348689 PMCID: PMC7766042 DOI: 10.3390/cancers12123811] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 12/12/2020] [Accepted: 12/15/2020] [Indexed: 12/12/2022] Open
Abstract
Intestinal epithelium architecture is sustained by stem cell division. In principle, stem cells can divide symmetrically to generate two identical copies of themselves or asymmetrically to sustain tissue renewal in a balanced manner. The choice between the two helps preserve stem cell and progeny pools and is crucial for tissue homeostasis. Control of spindle orientation is a prime contributor to the specification of symmetric versus asymmetric cell division. Competition for space within the niche may be another factor limiting the stem cell pool. An integrative view of the multiple links between intracellular and extracellular signals and molecular determinants at play remains a challenge. One outstanding question is the precise molecular roles of the tumour suppressor Adenomatous polyposis coli (APC) for sustaining gut homeostasis through its respective functions as a cytoskeletal hub and a down regulator in Wnt signalling. Here, we review our current understanding of APC inherent activities and partners in order to explore novel avenues by which APC may act as a gatekeeper in colorectal cancer and as a therapeutic target.
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Affiliation(s)
- M. Angeles Juanes
- School of Health and Life Science, Teesside University, Middlesbrough TS1 3BX, UK;
- National Horizons Centre, Teesside University, 38 John Dixon Lane, Darlington DL1 1HG, UK
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33
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Juanes MA, Fees C, Hoeprich GJ, Jaiswal R, Goode BL. EB1 Directly Regulates APC-Mediated Actin Nucleation. Curr Biol 2020; 30:4763-4772.e8. [PMID: 33007249 PMCID: PMC7726095 DOI: 10.1016/j.cub.2020.08.094] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 07/07/2020] [Accepted: 08/26/2020] [Indexed: 02/01/2023]
Abstract
EB1 was discovered 25 years ago as a binding partner of the tumor suppressor adenomatous polyposis coli (APC) [1]; however, the significance of EB1-APC interactions has remained poorly understood. EB1 functions at the center of a network of microtubule end-tracking proteins (+TIPs) [2-5], and APC binding to EB1 promotes EB1 association with microtubule ends and microtubule stabilization [6, 7]. Whether EB1 interactions govern functions of APC beyond microtubule regulation has not been explored. The C-terminal basic domain of APC (APC-B) directly nucleates actin assembly, and this activity is required in vivo for directed cell migration and for maintaining normal levels of F-actin [8-10]. Here, we show that EB1 binds APC-B and inhibits its actin nucleation function by blocking actin monomer recruitment. Consistent with these biochemical observations, knocking down EB1 increases F-actin levels in cells, and this can be rescued by disrupting APC-mediated actin nucleation. Conversely, overexpressing EB1 decreases F-actin levels and impairs directed cell migration without altering microtubule organization and independent of its direct binding interactions with microtubules. Overall, our results define a new function for EB1 in negatively regulating APC-mediated actin assembly. Combining these findings with other recent studies showing that APC interactions regulate EB1-dependent effects on microtubule dynamics [7], we propose that EB1-APC interactions govern bidirectional cytoskeletal crosstalk by coordinating microtubule and actin dynamics.
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Affiliation(s)
- Maria Angeles Juanes
- Biology Department, Brandeis University, 415 South street, Waltham MA 02454, USA,School of Health and Life Science, Teesside University, Middlesbrough, TS1 3BX, United Kingdom,For correspondence: (Lead Contact),
| | - Colby Fees
- Biology Department, Brandeis University, 415 South street, Waltham MA 02454, USA
| | - Gregory J. Hoeprich
- Biology Department, Brandeis University, 415 South street, Waltham MA 02454, USA
| | - Richa Jaiswal
- Biology Department, Brandeis University, 415 South street, Waltham MA 02454, USA
| | - Bruce L. Goode
- Biology Department, Brandeis University, 415 South street, Waltham MA 02454, USA,For correspondence: (Lead Contact),
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34
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Cao L, Yonis A, Vaghela M, Barriga EH, Chugh P, Smith MB, Maufront J, Lavoie G, Méant A, Ferber E, Bovellan M, Alberts A, Bertin A, Mayor R, Paluch EK, Roux PP, Jégou A, Romet-Lemonne G, Charras G. SPIN90 associates with mDia1 and the Arp2/3 complex to regulate cortical actin organization. Nat Cell Biol 2020; 22:803-814. [PMID: 32572169 DOI: 10.1038/s41556-020-0531-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/04/2020] [Indexed: 01/02/2023]
Abstract
Cell shape is controlled by the submembranous cortex, an actomyosin network mainly generated by two actin nucleators: the Arp2/3 complex and the formin mDia1. Changes in relative nucleator activity may alter cortical organization, mechanics and cell shape. Here we investigate how nucleation-promoting factors mediate interactions between nucleators. In vitro, the nucleation-promoting factor SPIN90 promotes formation of unbranched filaments by Arp2/3, a process thought to provide the initial filament for generation of dendritic networks. Paradoxically, in cells, SPIN90 appears to favour a formin-dominated cortex. Our in vitro experiments reveal that this feature stems mainly from two mechanisms: efficient recruitment of mDia1 to SPIN90-Arp2/3 nucleated filaments and formation of a ternary SPIN90-Arp2/3-mDia1 complex that greatly enhances filament nucleation. Both mechanisms yield rapidly elongating filaments with mDia1 at their barbed ends and SPIN90-Arp2/3 at their pointed ends. Thus, in networks, SPIN90 lowers branching densities and increases the proportion of long filaments elongated by mDia1.
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Affiliation(s)
- Luyan Cao
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - Amina Yonis
- London Centre for Nanotechnology, University College London, London, UK.,Department of Cell and Developmental Biology, University College London, London, UK
| | - Malti Vaghela
- London Centre for Nanotechnology, University College London, London, UK.,Department of Physics and Astronomy, University College London, London, UK
| | - Elias H Barriga
- Department of Cell and Developmental Biology, University College London, London, UK.,Instituto Gulbenkian de Ciência, Oeiras, Portugal
| | - Priyamvada Chugh
- MRC-Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Matthew B Smith
- MRC-Laboratory for Molecular Cell Biology, University College London, London, UK.,The Francis Crick institute, London, UK
| | - Julien Maufront
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France.,Sorbonne Universités, Paris, France
| | - Geneviève Lavoie
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec, Canada
| | - Antoine Méant
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec, Canada
| | - Emma Ferber
- London Centre for Nanotechnology, University College London, London, UK
| | - Miia Bovellan
- London Centre for Nanotechnology, University College London, London, UK.,Department of Cell and Developmental Biology, University College London, London, UK
| | - Art Alberts
- Van Andel research institute, Grand Rapids, MI, USA
| | - Aurélie Bertin
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, Paris, France.,Sorbonne Universités, Paris, France
| | - Roberto Mayor
- Department of Cell and Developmental Biology, University College London, London, UK
| | - Ewa K Paluch
- MRC-Laboratory for Molecular Cell Biology, University College London, London, UK.,Institute for the Physics of Living Systems, University College London, London, UK.,Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Philippe P Roux
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec, Canada.,Department of Pathology and Cell Biology, Université de Montréal, Montréal, Canada
| | - Antoine Jégou
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France.
| | | | - Guillaume Charras
- London Centre for Nanotechnology, University College London, London, UK. .,Department of Cell and Developmental Biology, University College London, London, UK. .,Institute for the Physics of Living Systems, University College London, London, UK.
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35
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Abstract
Directed cell migration is critical for embryogenesis and organ development, wound healing and the immune response. Microtubules are dynamic polymers that control directional migration through a number of coordinated processes: microtubules are the tracks for long-distance intracellular transport, crucial for delivery of new membrane components and signalling molecules to the leading edge of a migrating cell and the recycling of adhesion receptors. Microtubules act as force generators and compressive elements to support sustained cell protrusions. The assembly and disassembly of microtubules is coupled to Rho GTPase signalling, thereby controlling actin polymerisation, myosin-driven contractility and the turnover of cellular adhesions locally. Cross-talk of actin and microtubule dynamics is mediated through a number of common binding proteins and regulators. Furthermore, cortical microtubule capture sites are physically linked to focal adhesions, facilitating the delivery of secretory vesicles and efficient cross-talk. Here we summarise the diverse functions of microtubules during cell migration, aiming to show how they contribute to the spatially and temporally coordinated sequence of events that permit efficient, directional and persistent migration.
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36
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Baumann S, Komissarov A, Gili M, Ruprecht V, Wieser S, Maurer SP. A reconstituted mammalian APC-kinesin complex selectively transports defined packages of axonal mRNAs. SCIENCE ADVANCES 2020; 6:eaaz1588. [PMID: 32201729 PMCID: PMC7069705 DOI: 10.1126/sciadv.aaz1588] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/17/2019] [Indexed: 05/31/2023]
Abstract
Through the asymmetric distribution of messenger RNAs (mRNAs), cells spatially regulate gene expression to create cytoplasmic domains with specialized functions. In neurons, mRNA localization is required for essential processes such as cell polarization, migration, and synaptic plasticity underlying long-term memory formation. The essential components driving cytoplasmic mRNA transport in neurons and mammalian cells are not known. We report the first reconstitution of a mammalian mRNA transport system revealing that the tumor suppressor adenomatous polyposis coli (APC) forms stable complexes with the axonally localized β-actin and β2B-tubulin mRNAs, which are linked to a kinesin-2 via the cargo adaptor KAP3. APC activates kinesin-2, and both proteins are sufficient to drive specific transport of defined mRNA packages. Guanine-rich sequences located in 3'UTRs of axonal mRNAs increase transport efficiency and balance the access of different mRNAs to the transport system. Our findings reveal a minimal set of proteins sufficient to transport mammalian mRNAs.
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Affiliation(s)
- Sebastian Baumann
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Doctor Aiguader 88, Barcelona 08003, Spain
| | - Artem Komissarov
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Doctor Aiguader 88, Barcelona 08003, Spain
| | - Maria Gili
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Doctor Aiguader 88, Barcelona 08003, Spain
| | - Verena Ruprecht
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Doctor Aiguader 88, Barcelona 08003, Spain
| | | | - Sebastian P. Maurer
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology (BIST), Doctor Aiguader 88, Barcelona 08003, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
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37
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Li Z, Lee H, Eskin SG, Ono S, Zhu C, McIntire LV. Mechanochemical coupling of formin-induced actin interaction at the level of single molecular complex. Biomech Model Mechanobiol 2020; 19:1509-1521. [PMID: 31965350 DOI: 10.1007/s10237-019-01284-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 12/24/2019] [Indexed: 01/08/2023]
Abstract
Formins promote actin assembly and are involved in force-dependent cytoskeletal remodeling. However, how force alters the formin functions still needs to be investigated. Here, using atomic force microscopy and biomembrane force probe, we investigated how mechanical force affects formin-mediated actin interactions at the level of single molecular complexes. The biophysical parameters of G-actin/G-actin (GG) or G-actin/F-actin (GF) interactions were measured under force loading in the absence or presence of two C-terminal fragments of the mouse formin mDia1: mDia1Ct that contains formin homology 2 domain (FH2) and diaphanous autoregulatory domain (DAD) and mDia1Ct-ΔDAD that contains only FH2. Under force-free conditions, neither association nor dissociation kinetics of GG and GF interactions were significantly affected by mDia1Ct or mDia1Ct-ΔDAD. Under tensile forces (0-7 pN), the average lifetimes of these bonds were prolonged and molecular complexes were stiffened in the presence of mDia1Ct, indicating mDia1Ct association kinetically stabilizes and mechanically strengthens bonds of the dimer and at the end of the F-actin under force. Interestingly, mDia1Ct-ΔDAD prolonged the lifetime of GF but not GG bond under force, suggesting the DAD domain is critical for mDia1Ct to strengthen GG interaction. These data unravel the mechanochemical coupling in formin-induced actin assembly and provide evidence to understand the initiation of formin-mediated actin elongation and nucleation.
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Affiliation(s)
- Zhenhai Li
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive NW, Atlanta, GA, 30332, USA.,Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai Institute of Applied Mathematics and Mechanics, School of Mechanics and Engineering Science, Shanghai University, Shanghai, 200072, China
| | - Hyunjung Lee
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive NW, Atlanta, GA, 30332, USA
| | - Suzanne G Eskin
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive NW, Atlanta, GA, 30332, USA
| | - Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, GA, 30322, USA.
| | - Cheng Zhu
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive NW, Atlanta, GA, 30332, USA. .,George W Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
| | - Larry V McIntire
- Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive NW, Atlanta, GA, 30332, USA.
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38
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Davison A. Flipping Shells! Unwinding LR Asymmetry in Mirror-Image Molluscs. Trends Genet 2020; 36:189-202. [PMID: 31952839 DOI: 10.1016/j.tig.2019.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/08/2019] [Accepted: 12/06/2019] [Indexed: 12/11/2022]
Abstract
In seeking to understand the establishment of left-right (LR) asymmetry, a limiting factor is that most animals are ordinarily invariant in their asymmetry, except when manipulated or mutated. It is therefore surprising that the wider scientific field does not appear to fully appreciate the remarkable fact that normal development in molluscs, especially snails, can flip between two chiral types without pathology. Here, I describe recent progress in understanding the evolution, development, and genetics of chiral variation in snails, and place it in context with other animals. I argue that the natural variation of snails is a crucial resource towards understanding the invariance in other animal groups and, ultimately, will be key in revealing the common factors that define cellular and organismal LR asymmetry.
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Affiliation(s)
- Angus Davison
- School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, UK.
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39
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Pollard LW, Garabedian MV, Alioto SL, Shekhar S, Goode BL. Genetically inspired in vitro reconstitution of Saccharomyces cerevisiae actin cables from seven purified proteins. Mol Biol Cell 2020; 31:335-347. [PMID: 31913750 PMCID: PMC7183793 DOI: 10.1091/mbc.e19-10-0576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
A major goal of synthetic biology is to define the minimal cellular machinery required to assemble a biological structure in its simplest form. Here, we focused on Saccharomyces cerevisiae actin cables, which provide polarized tracks for intracellular transport and maintain defined lengths while continuously undergoing rapid assembly and turnover. Guided by the genetic requirements for proper cable assembly and dynamics, we show that seven evolutionarily conserved S. cerevisiae proteins (actin, formin, profilin, tropomyosin, capping protein, cofilin, and AIP1) are sufficient to reconstitute the formation of cables that undergo polarized turnover and maintain steady-state lengths similar to actin cables in vivo. Further, the removal of individual proteins from this simple in vitro reconstitution system leads to cable defects that closely approximate in vivo cable phenotypes caused by disrupting the corresponding genes. Thus, a limited set of molecular components is capable of self-organizing into dynamic, micron-scale actin structures with features similar to cables in living cells.
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Affiliation(s)
| | | | | | | | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA 02454
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40
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Bradley AO, Vizcarra CL, Bailey HM, Quinlan ME. Spire stimulates nucleation by Cappuccino and binds both ends of actin filaments. Mol Biol Cell 2019; 31:273-286. [PMID: 31877067 PMCID: PMC7183766 DOI: 10.1091/mbc.e19-09-0550] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The actin nucleators Spire and Cappuccino synergize to promote actin assembly, but the mechanism of their synergy is controversial. Together these proteins promote the formation of actin meshes, which are conserved structures that regulate the establishment of oocyte polarity. Direct interaction between Spire and Cappuccino is required for oogenesis and for in vitro synergistic actin assembly. This synergy is proposed to be driven by elongation and the formation of a ternary complex at filament barbed ends, or by nucleation and interaction at filament pointed ends. To mimic the geometry of Spire and Cappuccino in vivo, we immobilized Spire on beads and added Cappuccino and actin. Barbed ends, protected by Cappuccino, grow away from the beads while pointed ends are retained, as expected for nucleation-driven synergy. We found that Spire is sufficient to bind barbed ends and retain pointed ends of actin filaments near beads and we identified Spire’s barbed-end binding domain. Loss of barbed-end binding increases nucleation by Spire and synergy with Cappuccino in bulk pyrene assays and on beads. Importantly, genetic rescue by the loss-of-function mutant indicates that barbed-end binding is not necessary for oogenesis. Thus, increased nucleation is a critical element of synergy both in vitro and in vivo.
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Affiliation(s)
- Alexander O Bradley
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Christina L Vizcarra
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Hannah M Bailey
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Margot E Quinlan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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41
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Juanes MA, Isnardon D, Badache A, Brasselet S, Mavrakis M, Goode BL. The role of APC-mediated actin assembly in microtubule capture and focal adhesion turnover. J Cell Biol 2019; 218:3415-3435. [PMID: 31471457 PMCID: PMC6781439 DOI: 10.1083/jcb.201904165] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 07/11/2019] [Accepted: 07/26/2019] [Indexed: 12/16/2022] Open
Abstract
Actin assembly by APC maintains proper organization and dynamics of F-actin at focal adhesions. This, in turn, impacts the organization of other molecular components and the responsiveness of focal adhesions to microtubule capture and autophagosome-induced disassembly. Focal adhesion (FA) turnover depends on microtubules and actin. Microtubule ends are captured at FAs, where they induce rapid FA disassembly. However, actin’s roles are less clear. Here, we use polarization-resolved microscopy, FRAP, live cell imaging, and a mutant of Adenomatous polyposis coli (APC-m4) defective in actin nucleation to investigate the role of actin assembly in FA turnover. We show that APC-mediated actin assembly is critical for maintaining normal F-actin levels, organization, and dynamics at FAs, along with organization of FA components. In WT cells, microtubules are captured repeatedly at FAs as they mature, but once a FA reaches peak maturity, the next microtubule capture event leads to delivery of an autophagosome, triggering FA disassembly. In APC-m4 cells, microtubule capture frequency and duration are altered, and there are long delays between autophagosome delivery and FA disassembly. Thus, APC-mediated actin assembly is required for normal feedback between microtubules and FAs, and maintaining FAs in a state “primed” for microtubule-induced turnover.
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Affiliation(s)
| | - Daniel Isnardon
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Ali Badache
- Centre de Recherche en Cancérologie de Marseille, Institut National de la Santé et de la Recherche Médicale, Institut Paoli-Calmettes, Aix-Marseille Université, Centre National de la Recherche Scientifique, Marseille, France
| | - Sophie Brasselet
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Centrale Marseille, Institut Fresnel, Marseille, France
| | - Manos Mavrakis
- Aix-Marseille Université, Centre National de la Recherche Scientifique, Centrale Marseille, Institut Fresnel, Marseille, France
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA
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The Cytoskeleton-A Complex Interacting Meshwork. Cells 2019; 8:cells8040362. [PMID: 31003495 PMCID: PMC6523135 DOI: 10.3390/cells8040362] [Citation(s) in RCA: 173] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/22/2022] Open
Abstract
The cytoskeleton of animal cells is one of the most complicated and functionally versatile structures, involved in processes such as endocytosis, cell division, intra-cellular transport, motility, force transmission, reaction to external forces, adhesion and preservation, and adaptation of cell shape. These functions are mediated by three classical cytoskeletal filament types, as follows: Actin, microtubules, and intermediate filaments. The named filaments form a network that is highly structured and dynamic, responding to external and internal cues with a quick reorganization that is orchestrated on the time scale of minutes and has to be tightly regulated. Especially in brain tumors, the cytoskeleton plays an important role in spreading and migration of tumor cells. As the cytoskeletal organization and regulation is complex and many-faceted, this review aims to summarize the findings about cytoskeletal filament types, including substructures formed by them, such as lamellipodia, stress fibers, and interactions between intermediate filaments, microtubules and actin. Additionally, crucial regulatory aspects of the cytoskeletal filaments and the formed substructures are discussed and integrated into the concepts of cell motility. Even though little is known about the impact of cytoskeletal alterations on the progress of glioma, a final point discussed will be the impact of established cytoskeletal alterations in the cellular behavior and invasion of glioma.
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Schaefer KN, Peifer M. Wnt/Beta-Catenin Signaling Regulation and a Role for Biomolecular Condensates. Dev Cell 2019; 48:429-444. [PMID: 30782412 PMCID: PMC6386181 DOI: 10.1016/j.devcel.2019.01.025] [Citation(s) in RCA: 119] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 12/06/2018] [Accepted: 01/29/2019] [Indexed: 12/19/2022]
Abstract
Wnt/β-Catenin signaling plays key roles in tissue homeostasis and cell fate decisions in embryonic and post-embryonic development across the animal kingdom. As a result, pathway mutations are associated with developmental disorders and many human cancers. The multiprotein destruction complex keeps signaling off in the absence of Wnt ligands and needs to be downregulated for pathway activation. We discuss new insights into destruction complex activity and regulation, highlighting parallels to the control of other cell biological processes by biomolecular condensates that form by phase separation to suggest that the destruction complex acts as a biomolecular condensate in Wnt pathway regulation.
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Affiliation(s)
- Kristina N Schaefer
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Mark Peifer
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biology, University of North Carolina at Chapel Hill, CB#3280, Chapel Hill, NC 27599-3280, USA; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Ginosyan AA, Grintsevich EE, Reisler E. Neuronal drebrin A directly interacts with mDia2 formin to inhibit actin assembly. Mol Biol Cell 2019; 30:646-657. [PMID: 30625038 PMCID: PMC6589693 DOI: 10.1091/mbc.e18-10-0639] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Dendritic spines (DS) are actin-rich postsynaptic terminals of neurons that are critical for higher-order brain functions. Maturation of DS is accompanied by a change in actin architecture from linear to branched filamentous structures. Presumably, the underlying cause of this is a switch in a mode of actin assembly from formin-driven to Arp2/3-mediated via an undefined mechanism. Here we present data suggesting that neuron-specific actin-binding drebrin A may be a part of such a switch. It is well documented that DS are highly enriched in drebrin A, which is critical for their plasticity and function. At the same time, mDia2 is known to mediate the formation of filopodia-type (immature) spines. We found that neuronal drebrin A directly interacts with mDia2 formin. Drebrin inhibits formin-mediated nucleation of actin and abolishes mDia2-induced actin bundling. Using truncated protein constructs we identified the domain requirements for drebrin–mDia2 interaction. We hypothesize that accumulation of drebrin A in DS (that coincides with spine maturation) leads to inhibition of mDia2-driven actin polymerization and, therefore, may contribute to a change in actin architecture from linear to branched filaments.
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Affiliation(s)
- Anush A Ginosyan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
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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: 85] [Impact Index Per Article: 14.2] [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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Johnston AB, Hilton DM, McConnell P, Johnson B, Harris MT, Simone A, Amarasinghe GK, Cooper JA, Goode BL. A novel mode of capping protein-regulation by twinfilin. eLife 2018; 7:41313. [PMID: 30351272 PMCID: PMC6249002 DOI: 10.7554/elife.41313] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 10/22/2018] [Indexed: 12/29/2022] Open
Abstract
Cellular actin assembly is controlled at the barbed ends of actin filaments, where capping protein (CP) limits polymerization. Twinfilin is a conserved in vivo binding partner of CP, yet the significance of this interaction has remained a mystery. Here, we discover that the C-terminal tail of Twinfilin harbors a CP-interacting (CPI) motif, identifying it as a novel CPI-motif protein. Twinfilin and the CPI-motif protein CARMIL have overlapping binding sites on CP. Further, Twinfilin binds competitively with CARMIL to CP, protecting CP from barbed-end displacement by CARMIL. Twinfilin also accelerates dissociation of the CP inhibitor V-1, restoring CP to an active capping state. Knockdowns of Twinfilin and CP each cause similar defects in cell morphology, and elevated Twinfilin expression rescues defects caused by CARMIL hyperactivity. Together, these observations define Twinfilin as the first ‘pro-capping’ ligand of CP and lead us to propose important revisions to our understanding of the CP regulatory cycle. Plant and animal cells are supported by skeleton-like structures that can grow and shrink beneath the cell membrane, pushing and pulling on the edges of the cell. This scaffolding network – known as the cytoskeleton – contains long strands, or filaments, made from many identical copies of a protein called actin. The shape of the actin proteins allows them to slot together, end-to-end, and allows the strands to grow and shrink on-demand. When the strands are the correct length, the cell caps the growing ends with a protein known as Capping Protein. This helps to stabilize the cell’s skeleton, preventing the strands from getting any longer, or any shorter. Proteins that interfere with the activity of Capping Protein allow the actin strands to grow or shrink. Some, like a protein called V-1, attach to Capping Protein and get in the way so that it cannot sit on the ends of the actin strands. Others, like CARMIL, bind to Capping Protein and change its shape, making it more likely to fall off the strands. So far, no one had found a partner that helps Capping Protein limit the growth of the actin cytoskeleton. A protein called Twinfilin often appears alongside Capping Protein, but the two proteins seemed to have no influence on each other, and had what appeared to be different roles. Whilst Capping Protein blocks growth and stabilizes actin strands, Twinfilin speeds up their disassembly at their ends. But Johnston, Hilton et al. now reveal that the two proteins actually work together. Twinfilin helps Capping Protein resist the effects of CARMIL and V-1, and Capping Protein puts Twinfilin at the end of the strand. Thus, when Capping Protein is finally removed by CARMIL, Twinfilin carries on with disassembling the actin strands. The tail of the Twinfilin protein looks like part of the CARMIL protein, suggesting that they might interact with Capping Protein in the same way. Attaching a fluorescent tag to the Twinfilin tail revealed that the two proteins compete to attach to the same part of the Capping Protein. When mouse cells produced extra Twinfilin, it blocked the effects of CARMIL, helping to grow the actin strands. V-1 attaches to Capping Protein in a different place, but Twinfilin was also able to interfere with its activity. When Twinfilin attached to the CARMIL binding site, it did not directly block V-1 binding, but it made the protein more likely to fall off. Understanding how the actin cytoskeleton moves is a key question in cell biology, but it also has applications in medicine. Twinfilin plays a role in the spread of certain blood cancer cells, and in the formation of elaborate structures in the inner ear that help us hear. Understanding how Twinfilin and Capping Protein interact could open paths to new therapies for a range of medical conditions.
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Affiliation(s)
- Adam B Johnston
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, United States
| | - Denise M Hilton
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, United States
| | - Patrick McConnell
- Department of Biochemistry and Molecular Biophysics, Washington University, St Louis, United states
| | - Britney Johnson
- Department of Pathology and Immunology, Washington University, St Louis, United States
| | - Meghan T Harris
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, United States
| | - Avital Simone
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, United States
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University, St Louis, United States
| | - John A Cooper
- Department of Biochemistry and Molecular Biophysics, Washington University, St Louis, United states
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, United States
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Molinar-Inglis O, Oliver SL, Rudich P, Kunttas E, McCartney BM. APC2 associates with the actin cortex through a multipart mechanism to regulate cortical actin organization and dynamics in the Drosophila ovary. Cytoskeleton (Hoboken) 2018; 75:323-335. [PMID: 30019417 DOI: 10.1002/cm.21471] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 05/24/2018] [Accepted: 06/19/2018] [Indexed: 01/20/2023]
Abstract
The actin cortex that lines the plasma membrane of most eukaryotic cells resists external mechanical forces and plays critical roles in a variety of cellular processes including morphogenesis, cytokinesis, and cell migration. Despite its ubiquity and significance, we understand relatively little about the composition, dynamics, and structure of the actin cortex. Adenomatous polyposis coli (APC) proteins regulate the actin and microtubule cytoskeletons through a variety of mechanisms, and in some contexts, APC proteins are cortically enriched. Here we show that APC2 regulates cortical actin dynamics in the follicular epithelium and the nurse cells of the Drosophila ovary and in addition affects the distribution of cortical actin at the apical side of the follicular epithelium. To understand how APC2 influences these properties of the actin cortex, we investigated the mechanisms controlling the cortical localization of APC2 in S2 cultured cells. We previously showed that the N-terminal half of APC2 containing the Armadillo repeats and the C-terminal 30 amino acids (C30) are together necessary and sufficient for APC2's cortical localization. Our work presented here supports a model that cortical localization of APC2 is governed in part by self-association through the N-terminal APC Self-Association Domain (ASAD) and a highly conserved coiled-coil within the C30 domain.
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Affiliation(s)
- Olivia Molinar-Inglis
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Stacie L Oliver
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Paige Rudich
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Ezgi Kunttas
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Brooke M McCartney
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania
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49
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Garabedian MV, Stanishneva-Konovalova T, Lou C, Rands TJ, Pollard LW, Sokolova OS, Goode BL. Integrated control of formin-mediated actin assembly by a stationary inhibitor and a mobile activator. J Cell Biol 2018; 217:3512-3530. [PMID: 30076201 PMCID: PMC6168263 DOI: 10.1083/jcb.201803164] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/20/2018] [Accepted: 07/17/2018] [Indexed: 12/15/2022] Open
Abstract
This study shows that in vivo actin nucleation by the yeast formin Bnr1 is controlled through the coordinated effects of two distinct regulators, a stationary inhibitor (the F-BAR protein Hof1) and a mobile activator (Bud6), establishing a positive feedback loop for precise spatial and temporal control of actin assembly. Formins are essential actin assembly factors whose activities are controlled by a diverse array of binding partners. Until now, most formin ligands have been studied on an individual basis, leaving open the question of how multiple inputs are integrated to regulate formins in vivo. Here, we show that the F-BAR domain of Saccharomyces cerevisiae Hof1 interacts with the FH2 domain of the formin Bnr1 and blocks actin nucleation. Electron microscopy of the Hof1–Bnr1 complex reveals a novel dumbbell-shaped structure, with the tips of the F-BAR holding two FH2 dimers apart. Deletion of Hof1’s F-BAR domain in vivo results in disorganized actin cables and secretory defects. The formin-binding protein Bud6 strongly alleviates Hof1 inhibition in vitro, and bud6Δ suppresses hof1Δ defects in vivo. Whereas Hof1 stably resides at the bud neck, we show that Bud6 is delivered to the neck on secretory vesicles. We propose that Hof1 and Bud6 functions are intertwined as a stationary inhibitor and a mobile activator, respectively.
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Affiliation(s)
- Mikael V Garabedian
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA
| | | | - Chenyu Lou
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA
| | - Thomas J Rands
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA
| | - Luther W Pollard
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA
| | - Olga S Sokolova
- Bioengineering Department, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA
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50
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Wu SZ, Bezanilla M. Actin and microtubule cross talk mediates persistent polarized growth. J Cell Biol 2018; 217:3531-3544. [PMID: 30061106 PMCID: PMC6168251 DOI: 10.1083/jcb.201802039] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 05/08/2018] [Accepted: 07/10/2018] [Indexed: 11/25/2022] Open
Abstract
How the actin and microtubule cytoskeletons work together during diverse cellular functions is unclear. Wu et al. describe an apical actin pool in plant cells organized by a microtubule template at the site of polarized growth. Disconnecting the two cytoskeletons by removing class VIII myosins alters both cytoskeletal structures and impairs polarized growth. Coordination between actin and microtubules is important for numerous cellular processes in diverse eukaryotes. In plants, tip-growing cells require actin for cell expansion and microtubules for orientation of cell expansion, but how the two cytoskeletons are linked is an open question. In tip-growing cells of the moss Physcomitrella patens, we show that an actin cluster near the cell apex dictates the direction of rapid cell expansion. Formation of this structure depends on the convergence of microtubules near the cell tip. We discovered that microtubule convergence requires class VIII myosin function, and actin is necessary for myosin VIII–mediated focusing of microtubules. The loss of myosin VIII function affects both networks, indicating functional connections among the three cytoskeletal components. Our data suggest that microtubules direct localization of formins, actin nucleation factors, that generate actin filaments further focusing microtubules, thereby establishing a positive feedback loop ensuring that actin polymerization and cell expansion occur at a defined site resulting in persistent polarized growth.
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Affiliation(s)
- Shu-Zon Wu
- Department of Biological Sciences, Dartmouth College, Hanover, NH
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