1
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Theophall GG, Ramirez LMS, Premo A, Reverdatto S, Manigrasso MB, Yepuri G, Burz DS, Ramasamy R, Schmidt AM, Shekhtman A. Disruption of the productive encounter complex results in dysregulation of DIAPH1 activity. J Biol Chem 2023; 299:105342. [PMID: 37832872 PMCID: PMC10656230 DOI: 10.1016/j.jbc.2023.105342] [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: 08/05/2023] [Revised: 09/27/2023] [Accepted: 10/06/2023] [Indexed: 10/15/2023] Open
Abstract
The diaphanous-related formin, Diaphanous 1 (DIAPH1), is required for the assembly of Filamentous (F)-actin structures. DIAPH1 is an intracellular effector of the receptor for advanced glycation end products (RAGE) and contributes to RAGE signaling and effects such as increased cell migration upon RAGE stimulation. Mutations in DIAPH1, including those in the basic "RRKR" motif of its autoregulatory domain, diaphanous autoinhibitory domain (DAD), are implicated in hearing loss, macrothrombocytopenia, and cardiovascular diseases. The solution structure of the complex between the N-terminal inhibitory domain, DID, and the C-terminal DAD, resolved by NMR spectroscopy shows only transient interactions between DID and the basic motif of DAD, resembling those found in encounter complexes. Cross-linking studies placed the RRKR motif into the negatively charged cavity of DID. Neutralizing the cavity resulted in a 5-fold decrease in the binding affinity and 4-fold decrease in the association rate constant of DAD for DID, indicating that the RRKR interactions with DID form a productive encounter complex. A DIAPH1 mutant containing a neutralized RRKR binding cavity shows excessive colocalization with actin and is unresponsive to RAGE stimulation. This is the first demonstration of a specific alteration of the surfaces responsible for productive encounter complexation with implications for human pathology.
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Affiliation(s)
- Gregory G Theophall
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA
| | - Lisa M S Ramirez
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA
| | - Aaron Premo
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA
| | - Sergey Reverdatto
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA
| | - Michaele B Manigrasso
- Department of Medicine, Diabetes Research Program, New York University Grossman School of Medicine, New York, New York, USA
| | - Gautham Yepuri
- Department of Medicine, Diabetes Research Program, New York University Grossman School of Medicine, New York, New York, USA
| | - David S Burz
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA
| | - Ravichandran Ramasamy
- Department of Medicine, Diabetes Research Program, New York University Grossman School of Medicine, New York, New York, USA
| | - Ann Marie Schmidt
- Department of Medicine, Diabetes Research Program, New York University Grossman School of Medicine, New York, New York, USA
| | - Alexander Shekhtman
- Department of Chemistry, State University of New York at Albany, Albany, New York, USA.
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2
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Chiereghin C, Robusto M, Massa V, Castorina P, Ambrosetti U, Asselta R, Soldà G. Role of Cytoskeletal Diaphanous-Related Formins in Hearing Loss. Cells 2022; 11:cells11111726. [PMID: 35681420 PMCID: PMC9179844 DOI: 10.3390/cells11111726] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 05/16/2022] [Accepted: 05/18/2022] [Indexed: 02/04/2023] Open
Abstract
Hearing relies on the proper functioning of auditory hair cells and on actin-based cytoskeletal structures. Diaphanous-related formins (DRFs) are evolutionarily conserved cytoskeletal proteins that regulate the nucleation of linear unbranched actin filaments. They play key roles during metazoan development, and they seem particularly pivotal for the correct physiology of the reproductive and auditory systems. Indeed, in Drosophila melanogaster, a single diaphanous (dia) gene is present, and mutants show sterility and impaired response to sound. Vertebrates, instead, have three orthologs of the diaphanous gene: DIAPH1, DIAPH2, and DIAPH3. In humans, defects in DIAPH1 and DIAPH3 have been associated with different types of hearing loss. In particular, heterozygous mutations in DIAPH1 are responsible for autosomal dominant deafness with or without thrombocytopenia (DFNA1, MIM #124900), whereas regulatory mutations inducing the overexpression of DIAPH3 cause autosomal dominant auditory neuropathy 1 (AUNA1, MIM #609129). Here, we provide an overview of the expression and function of DRFs in normal hearing and deafness.
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Affiliation(s)
- Chiara Chiereghin
- IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089 Milan, Italy; (C.C.); (R.A.)
| | - Michela Robusto
- Experimental Therapeutics Program, IFOM ETS—The AIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy;
| | - Valentina Massa
- Dipartimento di Scienze della Salute, Università degli Studi di Milano, Via Di Rudinì 8, 20146 Milan, Italy;
| | | | - Umberto Ambrosetti
- Dipartimento di Scienze Cliniche e di Comunità, Università degli Studi di Milano and Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, UO Audiologia, Via F. Sforza 35, 20122 Milan, Italy;
| | - Rosanna Asselta
- IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089 Milan, Italy; (C.C.); (R.A.)
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072 Milan, Italy
| | - Giulia Soldà
- IRCCS Humanitas Research Hospital, Via Manzoni 56, 20089 Milan, Italy; (C.C.); (R.A.)
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072 Milan, Italy
- Correspondence:
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3
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Bharadwaj R, Bhattacharya A, Somlata. Coordinated activity of amoebic formin and profilin are essential for phagocytosis. Mol Microbiol 2021; 116:974-995. [PMID: 34278607 DOI: 10.1111/mmi.14787] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 07/15/2021] [Accepted: 07/16/2021] [Indexed: 10/24/2022]
Abstract
For the protist parasite Entamoeba histolytica, endocytic processes, such as phagocytosis, are essential for its survival in the human gut. The actin cytoskeleton is involved in the formation of pseudopods and phagosomal vesicles by incorporating a number of actin-binding and modulating proteins along with actin in a temporal manner. The actin dynamics, which comprises polymerization, branching, and depolymerization is very tightly regulated and takes place directionally at the sites of initiation of phagocytosis. Formin and profilin are two actin-binding proteins that are known to regulate actin cytoskeleton dynamics and thereby, endocytic processes. In this article, we report the participation of formin and profilin in E. histolytica phagocytosis and propose that these two proteins interact with each other and their sequential recruitment at the site is required for the successful completion of phagocytosis. The evidence is based on detailed microscopic, live imaging, interaction studies, and expression downregulation. The cells downregulated for expression of formin show absence of profilin at the site of phagocytosis, whereas downregulation of profilin does not affect formin localization.
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Affiliation(s)
- Ravi Bharadwaj
- Department of Medicine, UMass Medical School, Worcester, MA, USA
| | | | - Somlata
- Multidisciplinary Centre for Advanced Research and Studies, Jamia Millia Islamia, New Delhi, India
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4
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Rabbolini D, Liang HPH, Morel-Kopp MC, Connor D, Whittaker S, Dunkley S, Donikian D, Kondo M, Chen W, Stevenson WS, Campbell H, Joseph J, Ward C, Brighton T, Chen VM. Building platelet phenotypes: diaphanous-related formin 1 (DIAPH1)-related disorder. Platelets 2021; 33:432-442. [PMID: 34223798 DOI: 10.1080/09537104.2021.1937593] [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: 10/20/2022]
Abstract
Variants of the Diaphanous-Related Formin 1 (DIAPH-1) gene have recently been reported causing inherited macrothrombocytopenia. The essential/"diagnostic" characteristics associated with the disorder are emerging; however, robust and complete criteria are not established. Here, we report the first cases of DIAPH1-related disorder in Australia caused by the autosomal dominant gain-of-function DIAPH1 R1213X variant formed by truncation of the protein within the diaphanous auto-regulatory domain (DAD) with loss of regulatory motifs responsible for autoinhibitory interactions within the DIAPH1 protein. We affirm phenotypic changes induced by the DIAPH1 R1213X variant to include macrothrombocytopenia, early-onset progressive sensorineural hearing loss, and mild asymptomatic neutropenia. High-resolution microscopy confirms perturbations of cytoskeletal dynamics caused by the DIAPH1 variant and we extend the repertoire of changes generated by this variant to include alteration of procoagulant platelet formation and possible dental anomalies.
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Affiliation(s)
- David Rabbolini
- Department of Haematology, Lismore Base Hospital, Lismore, NSW, Australia.,Northern Blood Research Centre, Kolling Institute of Medical Research, University of Sydney, Sydney, NSW, Australia
| | - Hai Po Helena Liang
- Platelets, Thrombosis and Cancer Research Laboratory, ANZAC Research Institute and Concord Repatriation Hospital, Concord, NSW, Australia
| | - Marie-Christine Morel-Kopp
- Northern Blood Research Centre, Kolling Institute of Medical Research, University of Sydney, Sydney, NSW, Australia
| | - David Connor
- St Vincent's Centre for Applied Medical Research, Sydney, NSW, Australia
| | - Shane Whittaker
- Platelets, Thrombosis and Cancer Research Laboratory, ANZAC Research Institute and Concord Repatriation Hospital, Concord, NSW, Australia
| | - Scott Dunkley
- Department of Haematology, The Royal Prince Alfred Hospital, Sydney, NSW, Australia
| | - Dea Donikian
- Department of Haematology, Prince of Wales Hospital, Sydney, NSW, Australia.,Haematology NSW Health Pathology Randwick, Sydney, NSW, Australia
| | - Mayuko Kondo
- Department of Haematology, Prince of Wales Hospital, Sydney, NSW, Australia.,Haematology NSW Health Pathology Randwick, Sydney, NSW, Australia
| | - Walter Chen
- Northern Blood Research Centre, Kolling Institute of Medical Research, University of Sydney, Sydney, NSW, Australia
| | - William S Stevenson
- Northern Blood Research Centre, Kolling Institute of Medical Research, University of Sydney, Sydney, NSW, Australia.,Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, NSW, Australia
| | - Heather Campbell
- Platelets, Thrombosis and Cancer Research Laboratory, ANZAC Research Institute and Concord Repatriation Hospital, Concord, NSW, Australia
| | - Joanne Joseph
- St Vincent's Centre for Applied Medical Research, Sydney, NSW, Australia.,Department of Haematology, St Vincent's Hospital, Sydney, NSW, Australia
| | - Christopher Ward
- Northern Blood Research Centre, Kolling Institute of Medical Research, University of Sydney, Sydney, NSW, Australia.,Department of Haematology and Transfusion Medicine, Royal North Shore Hospital, Sydney, NSW, Australia
| | - Timothy Brighton
- Department of Haematology, Prince of Wales Hospital, Sydney, NSW, Australia.,Haematology NSW Health Pathology Randwick, Sydney, NSW, Australia
| | - Vivien M Chen
- Platelets, Thrombosis and Cancer Research Laboratory, ANZAC Research Institute and Concord Repatriation Hospital, Concord, NSW, Australia.,Department of Haematology, Concord Repatriation General Hospital, Sydney, NSW, Australia
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5
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Chen A, Arora PD, Lai CC, Copeland JW, Moraes TF, McCulloch CA, Lavoie BD, Wilde A. The scaffold-protein IQGAP1 enhances and spatially restricts the actin-nucleating activity of Diaphanous-related formin 1 (DIAPH1). J Biol Chem 2020; 295:3134-3147. [PMID: 32005666 DOI: 10.1074/jbc.ra119.010476] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 01/24/2020] [Indexed: 11/06/2022] Open
Abstract
The actin cytoskeleton is a dynamic array of filaments that undergoes rapid remodeling to drive many cellular processes. An essential feature of filament remodeling is the spatio-temporal regulation of actin filament nucleation. One family of actin filament nucleators, the Diaphanous-related formins, is activated by the binding of small G-proteins such as RhoA. However, RhoA only partially activates formins, suggesting that additional factors are required to fully activate the formin. Here we identify one such factor, IQ motif containing GTPase activating protein-1 (IQGAP1), which enhances RhoA-mediated activation of the Diaphanous-related formin (DIAPH1) and targets DIAPH1 to the plasma membrane. We find that the inhibitory intramolecular interaction within DIAPH1 is disrupted by the sequential binding of RhoA and IQGAP1. Binding of RhoA and IQGAP1 robustly stimulates DIAPH1-mediated actin filament nucleation in vitro In contrast, the actin capping protein Flightless-I, in conjunction with RhoA, only weakly stimulates DIAPH1 activity. IQGAP1, but not Flightless-I, is required to recruit DIAPH1 to the plasma membrane where actin filaments are generated. These results indicate that IQGAP1 enhances RhoA-mediated activation of DIAPH1 in vivo Collectively these data support a model where the combined action of RhoA and an enhancer ensures the spatio-temporal regulation of actin nucleation to stimulate robust and localized actin filament production in vivo.
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Affiliation(s)
- Anan Chen
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Pam D Arora
- Faculty of Dentistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Christine C Lai
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - John W Copeland
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | | | - Brigitte D Lavoie
- Department Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada
| | - Andrew Wilde
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1M1, Canada; Department Molecular Genetics, University of Toronto, Toronto, Ontario M5G 1M1, Canada.
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6
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Kollárová E, Baquero Forero A, Stillerová L, Přerostová S, Cvrčková F. Arabidopsis Class II Formins AtFH13 and AtFH14 Can Form Heterodimers but Exhibit Distinct Patterns of Cellular Localization. Int J Mol Sci 2020; 21:E348. [PMID: 31948069 PMCID: PMC6982070 DOI: 10.3390/ijms21010348] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 12/30/2019] [Accepted: 01/03/2020] [Indexed: 12/25/2022] Open
Abstract
Formins are evolutionarily conserved multi-domain proteins participating in the control of both actin and microtubule dynamics. Angiosperm formins form two evolutionarily distinct families, Class I and Class II, with class-specific domain layouts. The model plant Arabidopsis thaliana has 21 formin-encoding loci, including 10 Class II members. In this study, we analyze the subcellular localization of two A. thaliana Class II formins exhibiting typical domain organization, the so far uncharacterized formin AtFH13 (At5g58160) and its distant homolog AtFH14 (At1g31810), previously reported to bind microtubules. Fluorescent protein-tagged full length formins and their individual domains were transiently expressed in Nicotiana benthamiana leaves under the control of a constitutive promoter and their subcellular localization (including co-localization with cytoskeletal structures and the endoplasmic reticulum) was examined using confocal microscopy. While the two formins exhibit distinct and only partially overlapping localization patterns, they both associate with microtubules via the conserved formin homology 2 (FH2) domain and with the periphery of the endoplasmic reticulum, at least in part via the N-terminal PTEN (Phosphatase and Tensin)-like domain. Surprisingly, FH2 domains of AtFH13 and AtFH14 can form heterodimers in the yeast two-hybrid assay-a first case of potentially biologically relevant formin heterodimerization mediated solely by the FH2 domain.
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Affiliation(s)
| | | | | | | | - Fatima Cvrčková
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, Viničná 5, CZ 128 44 Prague, Czech Republic; (E.K.); (A.B.F.); (L.S.); (S.P.)
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7
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Merino F, Pospich S, Raunser S. Towards a structural understanding of the remodeling of the actin cytoskeleton. Semin Cell Dev Biol 2019; 102:51-64. [PMID: 31836290 PMCID: PMC7221352 DOI: 10.1016/j.semcdb.2019.11.018] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 11/27/2019] [Accepted: 11/28/2019] [Indexed: 12/03/2022]
Abstract
Actin filaments (F-actin) are a key component of eukaryotic cells. Whether serving as a scaffold for myosin or using their polymerization to push onto cellular components, their function is always related to force generation. To control and fine-tune force production, cells have a large array of actin-binding proteins (ABPs) dedicated to control every aspect of actin polymerization, filament localization, and their overall mechanical properties. Although great advances have been made in our biochemical understanding of the remodeling of the actin cytoskeleton, the structural basis of this process is still being deciphered. In this review, we summarize our current understanding of this process. We outline how ABPs control the nucleation and disassembly, and how these processes are affected by the nucleotide state of the filaments. In addition, we highlight recent advances in the understanding of actomyosin force generation, and describe recent advances brought forward by the developments of electron cryomicroscopy.
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Affiliation(s)
- Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Sabrina Pospich
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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8
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Funk J, Merino F, Venkova L, Heydenreich L, Kierfeld J, Vargas P, Raunser S, Piel M, Bieling P. Profilin and formin constitute a pacemaker system for robust actin filament growth. eLife 2019; 8:50963. [PMID: 31647411 PMCID: PMC6867828 DOI: 10.7554/elife.50963] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022] Open
Abstract
The actin cytoskeleton drives many essential biological processes, from cell morphogenesis to motility. Assembly of functional actin networks requires control over the speed at which actin filaments grow. How this can be achieved at the high and variable levels of soluble actin subunits found in cells is unclear. Here we reconstitute assembly of mammalian, non-muscle actin filaments from physiological concentrations of profilin-actin. We discover that under these conditions, filament growth is limited by profilin dissociating from the filament end and the speed of elongation becomes insensitive to the concentration of soluble subunits. Profilin release can be directly promoted by formin actin polymerases even at saturating profilin-actin concentrations. We demonstrate that mammalian cells indeed operate at the limit to actin filament growth imposed by profilin and formins. Our results reveal how synergy between profilin and formins generates robust filament growth rates that are resilient to changes in the soluble subunit concentration.
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Affiliation(s)
- Johanna Funk
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Felipe Merino
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | | | | | - Jan Kierfeld
- Physics Department, TU Dortmund University, Dortmund, Germany
| | | | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | | | - Peter Bieling
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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9
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Kim BJ, Ueyama T, Miyoshi T, Lee S, Han JH, Park HR, Kim AR, Oh J, Kim MY, Kang YS, Oh DY, Yun J, Hwang SM, Kim NKD, Park WY, Kitajiri SI, Choi BY. Differential disruption of autoinhibition and defect in assembly of cytoskeleton during cell division decide the fate of human DIAPH1-related cytoskeletopathy. J Med Genet 2019; 56:818-827. [DOI: 10.1136/jmedgenet-2019-106282] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 06/24/2019] [Accepted: 07/09/2019] [Indexed: 12/25/2022]
Abstract
BackgroundDiaphanous-related formin 1 (DIA1), which assembles the unbranched actin microfilament and microtubule cytoskeleton, is encoded by DIAPH1. Constitutive activation by the disruption of autoinhibitory interactions between the N-terminal diaphanous inhibitory domain (DID) and C-terminal diaphanous autoregulatory domain (DAD) dysregulates DIA1, resulting in both hearing loss and blood cell abnormalities.Methods and resultsHere, we report the first constitutively active mutant in the DID (p.A265S) of humans with only hearing loss and not blood cell abnormality through whole exome sequencing. The previously reported DAD mutants and our DID mutant (p.A265S) shared the finding of diminished autoinhibitory interaction, abnormally upregulated actin polymerisation activity and increased localisations at the plasma membrane. However, the obvious defect in the DIA1-driven assembly of cytoskeleton ‘during cell division’ was only from the DAD mutants, not from p.A265S, which did not show any blood cell abnormality. We also evaluated the five DID mutants in the hydrophobic pocket since four of these five additional mutants were predicted to critically disrupt interaction between the DID and DAD. These additional pathogenic DID mutants revealed varying degrees of defect in the DIA1-driven cytoskeleton assembly, including nearly normal phenotype during cell division as well as obvious impaired autoinhibition, again coinciding with our key observation in DIA1 mutant (p.A265S) in the DID.ConclusionHere, we report the first mutant in the DID of humans with only hearing loss. The differential cell biological phenotypes of DIA1 during cell division appear to be potential determinants of the clinical severity of DIAPH1-related cytoskeletopathy in humans.
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10
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Phenotype description and response to thrombopoietin receptor agonist in DIAPH1-related disorder. Blood Adv 2019; 2:2341-2346. [PMID: 30232087 DOI: 10.1182/bloodadvances.2018020370] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 08/01/2018] [Indexed: 12/13/2022] Open
Abstract
Key Points
DIAPH1-related disorder has a bilineage hematological phenotype of macrothrombocytopenia and neutropenia associated with hearing loss. Eltrombopag increased proplatelet formation from cultured DIAPH1-related disorder megakaryocytes and improved platelet counts in vivo.
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11
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Abstract
Formin homology proteins (formins) are a highly conserved family of cytoskeletal remodeling proteins that are involved in a diverse array of cellular functions. Formins are best known for their ability to regulate actin dynamics, but the same functional domains also govern stability and organization of microtubules. It is thought that this dual activity allows them to coordinate the activity of these two major cytoskeletal networks and thereby influence cellular architecture. Golgi ribbon assembly is dependent upon cooperative interactions between actin filaments and cytoplasmic microtubules originating both at the Golgi itself and from the centrosome. Similarly, centrosome assembly, centriole duplication, and centrosome positioning are also reliant on a dialogue between both cytoskeletal networks. As presented in this chapter, a growing body of evidence suggests that multiple formin proteins play essential roles in these central cellular processes.
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Affiliation(s)
- John Copeland
- Faculty of Medicine, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada.
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12
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Courtemanche N. Mechanisms of formin-mediated actin assembly and dynamics. Biophys Rev 2018; 10:1553-1569. [PMID: 30392063 DOI: 10.1007/s12551-018-0468-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 10/18/2018] [Indexed: 12/14/2022] Open
Abstract
Cellular viability requires tight regulation of actin cytoskeletal dynamics. Distinct families of nucleation-promoting factors enable the rapid assembly of filament nuclei that elongate and are incorporated into diverse and specialized actin-based structures. In addition to promoting filament nucleation, the formin family of proteins directs the elongation of unbranched actin filaments. Processive association of formins with growing filament ends is achieved through continuous barbed end binding of the highly conserved, dimeric formin homology (FH) 2 domain. In cooperation with the FH1 domain and C-terminal tail region, FH2 dimers mediate actin subunit addition at speeds that can dramatically exceed the rate of spontaneous assembly. Here, I review recent biophysical, structural, and computational studies that have provided insight into the mechanisms of formin-mediated actin assembly and dynamics.
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Affiliation(s)
- Naomi Courtemanche
- Department of Genetics, Cell and Developmental Biology, University of Minnesota, 420 Washington Ave SE, 6-130 MCB, Minneapolis, MN, 55455, USA.
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13
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Hallin EI, Eriksen MS, Baryshnikov S, Nikolaienko O, Grødem S, Hosokawa T, Hayashi Y, Bramham CR, Kursula P. Structure of monomeric full-length ARC sheds light on molecular flexibility, protein interactions, and functional modalities. J Neurochem 2018; 147:323-343. [DOI: 10.1111/jnc.14556] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 06/29/2018] [Accepted: 07/12/2018] [Indexed: 12/18/2022]
Affiliation(s)
- Erik I. Hallin
- Department of Biomedicine; University of Bergen; Bergen Norway
| | - Maria S. Eriksen
- Department of Biomedicine; University of Bergen; Bergen Norway
- K.G. Jebsen Centre for Neuropsychiatric Disorders; University of Bergen; Bergen Norway
| | - Sergei Baryshnikov
- Department of Biomedicine; University of Bergen; Bergen Norway
- K.G. Jebsen Centre for Neuropsychiatric Disorders; University of Bergen; Bergen Norway
| | - Oleksii Nikolaienko
- Department of Biomedicine; University of Bergen; Bergen Norway
- K.G. Jebsen Centre for Neuropsychiatric Disorders; University of Bergen; Bergen Norway
| | - Sverre Grødem
- Department of Biomedicine; University of Bergen; Bergen Norway
- K.G. Jebsen Centre for Neuropsychiatric Disorders; University of Bergen; Bergen Norway
| | - Tomohisa Hosokawa
- Department of Pharmacology; Kyoto University Graduate School of Medicine; Kyoto Japan
| | - Yasunori Hayashi
- Department of Pharmacology; Kyoto University Graduate School of Medicine; Kyoto Japan
| | - Clive R. Bramham
- Department of Biomedicine; University of Bergen; Bergen Norway
- K.G. Jebsen Centre for Neuropsychiatric Disorders; University of Bergen; Bergen Norway
| | - Petri Kursula
- Department of Biomedicine; University of Bergen; Bergen Norway
- Faculty of Biochemistry and Molecular Medicine; University of Oulu; Oulu Finland
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14
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Nurden P, Nurden A, Favier R, Gleyze M. Management of pregnancy for a patient with the new syndromic macrothrombocytopenia, DIAPH1-related disease. Platelets 2018; 29:737-738. [PMID: 29985732 DOI: 10.1080/09537104.2018.1492710] [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] [Indexed: 01/02/2023]
Abstract
The number of genes involved in the identification of macrothrombocytopenia (MTP) is growing but the clinical consequences for the affected patients are not well determined. Here, we report the management of the bleeding risk for a patient with the newly reported and rare DIAPH1-related disease during surgery for infertility and then during her subsequent pregnancy. The R1213* DIAPH1 variant responsible for a mild bleeding syndrome in six families was considered a potential risk factor for our patient. Preliminary laparoscopic surgery was followed by neosalpingostomy to open the obstructed fallopian tube that was followed by an ectopic pregnancy requiring further surgery, tranexamic acid was used on each occasion and no bleeding complications were observed. A second pregnancy proceeded to term; the mother's platelet count was controlled throughout the gestation period and remained close to her basal values. No bleeding occurred at delivery or during the postpartum period. In conclusion, with strict repeated assessments of blood parameters and maintenance of the platelet count, the bleeding risk in pregnancy in DIAPH1-related disease can be successfully controlled.
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Affiliation(s)
- Paquita Nurden
- a Institut Hospitalo-Universitaire LIRYC , Hôpital Xavier Arnozan , Pessac , France
| | - Alan Nurden
- a Institut Hospitalo-Universitaire LIRYC , Hôpital Xavier Arnozan , Pessac , France
| | - Rémi Favier
- b Assistance Publique-Hôpitaux de Paris , Hôpital A Trousseau , Paris , France
| | - Matthieu Gleyze
- c Service de Gynécologie-Obstétrique , Hôpital Pellegrin , Bordeaux , France
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15
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Hegsted A, Yingling CV, Pruyne D. Inverted formins: A subfamily of atypical formins. Cytoskeleton (Hoboken) 2017; 74:405-419. [PMID: 28921928 DOI: 10.1002/cm.21409] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/22/2017] [Accepted: 08/31/2017] [Indexed: 12/25/2022]
Abstract
Formins are a family of regulators of actin and microtubule dynamics that are present in almost all eukaryotes. These proteins are involved in many cellular processes, including cytokinesis, stress fiber formation, and cell polarization. Here we review one subfamily of formins, the inverted formins. Inverted formins as a group break several formin stereotypes, having atypical biochemical properties and domain organization, and they have been linked to kidney disease and neuropathy in humans. In this review, we will explore recent research on members of the inverted formin sub-family in mammals, zebrafish, fruit flies, and worms.
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Affiliation(s)
- Anna Hegsted
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Curtis V Yingling
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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16
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Isogai T, van der Kammen R, Bleijerveld OB, Goerdayal SS, Argenzio E, Altelaar AFM, Innocenti M. Quantitative Proteomics Illuminates a Functional Interaction between mDia2 and the Proteasome. J Proteome Res 2016; 15:4624-4637. [PMID: 27769112 DOI: 10.1021/acs.jproteome.6b00718] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Formin mDia2 is a cytoskeleton-regulatory protein that switches reversibly between a closed, autoinhibited and an open, active conformation. Although the open conformation of mDia2 induces actin assembly thereby controlling many cellular processes, mDia2 possesses also actin-independent and conformation-insensitive scaffolding roles related to microtubules and p53, respectively. Thus, we hypothesize that mDia2 may have other unappreciated functions and regulatory modes. Here we identify and validate proteasome and Ubiquitin as mDia2-interacting partners using stable isotope labeling with amino acids in cell culture-based quantitative proteomics and biochemistry, respectively. Although mDia2 is ubiquitinated, binds ubiquitinated proteins and free Ubiquitin, it is not a proteasome substrate. Surprisingly, knockdown of mDia2 increases the activity of the proteasome in vitro, whereas mDia2 overexpression has opposite effects only when it adopts the open conformation and cannot induce actin assembly. Consistently, a combination of candidate and unbiased proteome-wide analyses indicates that mDia2 regulates the cellular levels of proteasome substrate β-catenin and a number of ubiquitinated actin-regulatory proteins. Hence, these findings add more complexity to the mDia2 activity cycle by showing that the open conformation may control actin dynamics also through actin-independent regulation of the proteasome.
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Affiliation(s)
| | | | | | - Soenita S Goerdayal
- Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University , 3584 CH Utrecht, The Netherlands
| | | | - A F Maarten Altelaar
- Biomolecular Mass Spectrometry and Proteomics Group, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University , 3584 CH Utrecht, The Netherlands.,Netherlands Proteomics Centre and Cancer Genomics Centre, 3584 CH Utrecht, The Netherlands
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17
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Ueyama T, Ninoyu Y, Nishio SY, Miyoshi T, Torii H, Nishimura K, Sugahara K, Sakata H, Thumkeo D, Sakaguchi H, Watanabe N, Usami SI, Saito N, Kitajiri SI. Constitutive activation of DIA1 (DIAPH1) via C-terminal truncation causes human sensorineural hearing loss. EMBO Mol Med 2016; 8:1310-1324. [PMID: 27707755 PMCID: PMC5090661 DOI: 10.15252/emmm.201606609] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
DIAPH1 encodes human DIA1, a formin protein that elongates unbranched actin. The c.3634+1G>T DIAPH1 mutation causes autosomal dominant nonsyndromic sensorineural hearing loss, DFNA1, characterized by progressive deafness starting in childhood. The mutation occurs near the C‐terminus of the diaphanous autoregulatory domain (DAD) of DIA1, which interacts with its N‐terminal diaphanous inhibitory domain (DID), and may engender constitutive activation of DIA1. However, the underlying pathogenesis that causes DFNA1 is unclear. We describe a novel patient‐derived DIAPH1 mutation (c.3610C>T) in two unrelated families, which results in early termination prior to a basic amino acid motif (RRKR1204–1207) at the DAD C‐terminus. The mutant DIA1(R1204X) disrupted the autoinhibitory DID‐DAD interaction and was constitutively active. This unscheduled activity caused increased rates of directional actin polymerization movement and induced formation of elongated microvilli. Mice expressing FLAG‐tagged DIA1(R1204X) experienced progressive deafness and hair cell loss at the basal turn and had various morphological abnormalities in stereocilia (short, fused, elongated, sparse). Thus, the basic region of the DAD mediates DIA1 autoinhibition; disruption of the DID‐DAD interaction and consequent activation of DIA1(R1204X) causes DFNA1.
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Affiliation(s)
- Takehiko Ueyama
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe, Japan
| | - Yuzuru Ninoyu
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe, Japan
| | - Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Takushi Miyoshi
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hiroko Torii
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Koji Nishimura
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuma Sugahara
- Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, Ube, Japan
| | | | - Dean Thumkeo
- Medical Innovation Center, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Hirofumi Sakaguchi
- Department of Otolaryngology-Head and Neck Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Naoki Watanabe
- Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan.,Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto, Japan
| | - Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Naoaki Saito
- Laboratory of Molecular Pharmacology, Biosignal Research Center, Kobe University, Kobe, Japan
| | - Shin-Ichiro Kitajiri
- Department of Otolaryngology, Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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18
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A gain-of-function variant in DIAPH1 causes dominant macrothrombocytopenia and hearing loss. Blood 2016; 127:2903-14. [PMID: 26912466 DOI: 10.1182/blood-2015-10-675629] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/16/2016] [Indexed: 12/25/2022] Open
Abstract
Macrothrombocytopenia (MTP) is a heterogeneous group of disorders characterized by enlarged and reduced numbers of circulating platelets, sometimes resulting in abnormal bleeding. In most MTP, this phenotype arises because of altered regulation of platelet formation from megakaryocytes (MKs). We report the identification of DIAPH1, which encodes the Rho-effector diaphanous-related formin 1 (DIAPH1), as a candidate gene for MTP using exome sequencing, ontological phenotyping, and similarity regression. We describe 2 unrelated pedigrees with MTP and sensorineural hearing loss that segregate with a DIAPH1 R1213* variant predicting partial truncation of the DIAPH1 diaphanous autoregulatory domain. The R1213* variant was linked to reduced proplatelet formation from cultured MKs, cell clustering, and abnormal cortical filamentous actin. Similarly, in platelets, there was increased filamentous actin and stable microtubules, indicating constitutive activation of DIAPH1. Overexpression of DIAPH1 R1213* in cells reproduced the cytoskeletal alterations found in platelets. Our description of a novel disorder of platelet formation and hearing loss extends the repertoire of DIAPH1-related disease and provides new insight into the autoregulation of DIAPH1 activity.
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19
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Shekhar S, Kerleau M, Kühn S, Pernier J, Romet-Lemonne G, Jégou A, Carlier MF. Formin and capping protein together embrace the actin filament in a ménage à trois. Nat Commun 2015; 6:8730. [PMID: 26564775 PMCID: PMC4660058 DOI: 10.1038/ncomms9730] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 09/24/2015] [Indexed: 11/09/2022] Open
Abstract
Proteins targeting actin filament barbed ends play a pivotal role in motile processes. While formins enhance filament assembly, capping protein (CP) blocks polymerization. On their own, they both bind barbed ends with high affinity and very slow dissociation. Their barbed-end binding is thought to be mutually exclusive. CP has recently been shown to be present in filopodia and controls their morphology and dynamics. Here we explore how CP and formins may functionally coregulate filament barbed-end assembly. We show, using kinetic analysis of individual filaments by microfluidics-assisted fluorescence microscopy, that CP and mDia1 formin are able to simultaneously bind barbed ends. This is further confirmed using single-molecule imaging. Their mutually weakened binding enables rapid displacement of one by the other. We show that formin FMNL2 behaves similarly, thus suggesting that this is a general property of formins. Implications in filopodia regulation and barbed-end structural regulation are discussed.
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Affiliation(s)
- Shashank Shekhar
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Mikael Kerleau
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Sonja Kühn
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Julien Pernier
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Guillaume Romet-Lemonne
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Antoine Jégou
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
| | - Marie-France Carlier
- Cytoskeleton Dynamics and Cell Motility, Department of Biochemistry, Biophysics and Structural Biology, I2BC, CNRS, 91198 Gif-sur-Yvette, France
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20
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Park E, Graziano BR, Zheng W, Garabedian M, Goode BL, Eck MJ. Structure of a Bud6/Actin Complex Reveals a Novel WH2-like Actin Monomer Recruitment Motif. Structure 2015; 23:1492-1499. [PMID: 26118535 DOI: 10.1016/j.str.2015.05.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 04/22/2015] [Accepted: 05/11/2015] [Indexed: 10/23/2022]
Abstract
In budding yeast, the actin-binding protein Bud6 cooperates with formins Bni1 and Bnr1 to catalyze the assembly of actin filaments. The nucleation-enhancing activity of Bud6 requires both a "core" domain that binds to the formin and a "flank" domain that binds monomeric actin. Here, we describe the structure of the Bud6 flank domain in complex with actin. Two helices in Bud6(flank) interact with actin; one binds in a groove at the barbed end of the actin monomer in a manner closely resembling the helix of WH2 domains, a motif found in many actin nucleation factors. The second helix rises along the face of actin. Mutational analysis verifies the importance of these Bud6-actin contacts for nucleation-enhancing activity. The Bud6 binding site on actin overlaps with that of the formin FH2 domain and is also incompatible with inter-subunit contacts in F-actin, suggesting that Bud6 interacts only transiently with actin monomers during filament nucleation.
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Affiliation(s)
- Eunyoung Park
- Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA
| | - Brian R Graziano
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Wei Zheng
- Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA
| | - Mikael Garabedian
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Bruce L Goode
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454, USA
| | - Michael J Eck
- Department of Cancer Biology, Dana-Farber Cancer Institute, SM1036, 450 Brookline Avenue, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02215, USA.
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21
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Brenig J, de Boor S, Knyphausen P, Kuhlmann N, Wroblowski S, Baldus L, Scislowski L, Artz O, Trauschies P, Baumann U, Neundorf I, Lammers M. Structural and Biochemical Basis for the Inhibitory Effect of Liprin-α3 on Mouse Diaphanous 1 (mDia1) Function. J Biol Chem 2015; 290:14314-27. [PMID: 25911102 DOI: 10.1074/jbc.m114.621946] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Indexed: 11/06/2022] Open
Abstract
Diaphanous-related formins are eukaryotic actin nucleation factors regulated by an autoinhibitory interaction between the N-terminal RhoGTPase-binding domain (mDiaN) and the C-terminal Diaphanous-autoregulatory domain (DAD). Although the activation of formins by Rho proteins is well characterized, its inactivation is only marginally understood. Recently, liprin-α3 was shown to interact with mDia1. Overexpression of liprin-α3 resulted in a reduction of the cellular actin filament content. The molecular mechanisms of how liprin-α3 exerts this effect and counteracts mDia1 activation by RhoA are unknown. Here, we functionally and structurally define a minimal liprin-α3 core region, sufficient to recapitulate the liprin-α3 determined mDia1-respective cellular functions. We show that liprin-α3 alters the interaction kinetics and thermodynamics of mDiaN with RhoA·GTP and DAD. RhoA displaces liprin-α3 allosterically, whereas DAD competes with liprin-α3 for a highly overlapping binding site on mDiaN. Liprin-α3 regulates actin polymerization by lowering the regulatory potency of RhoA and DAD on mDiaN. We present a model of a mechanistically unexplored and new aspect of mDiaN regulation by liprin-α3.
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Affiliation(s)
- Julian Brenig
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Susanne de Boor
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Philipp Knyphausen
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Nora Kuhlmann
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Sarah Wroblowski
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Linda Baldus
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Lukas Scislowski
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Oliver Artz
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Philip Trauschies
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
| | - Ulrich Baumann
- the Institute for Biochemistry, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany
| | - Ines Neundorf
- the Institute for Biochemistry, University of Cologne, Zülpicher Strasse 47, 50674 Cologne, Germany
| | - Michael Lammers
- From the Institute for Genetics and Cologne Excellence Cluster on Cellular Stress Responses in Aging-associated Diseases (CECAD), Joseph-Stelzmann-Strasse 26, University of Cologne, 50931 Cologne, Germany and
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22
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Abstract
Formin proteins were recognized as effectors of Rho GTPases some 15 years ago. They contribute to different cellular actin cytoskeleton structures by their ability to polymerize straight actin filaments at the barbed end. While not all formins necessarily interact with Rho GTPases, a subgroup of mammalian formins, termed Diaphanous-related formins or DRFs, were shown to be activated by small GTPases of the Rho superfamily. DRFs are autoinhibited in the resting state by an N- to C-terminal interaction that renders the central actin polymerization domain inactive. Upon the interaction with a GTP-bound Rho, Rac, or Cdc42 GTPase, the C-terminal autoregulation domain is displaced from its N-terminal recognition site and the formin becomes active to polymerize actin filaments. In this review we discuss the current knowledge on the structure, activation, and function of formin-GTPase interactions for the mammalian formin families Dia, Daam, FMNL, and FHOD. We describe both direct and indirect interactions of formins with GTPases, which lead to formin activation and cytoskeletal rearrangements. The multifaceted function of formins as effector proteins of Rho GTPases thus reflects the diversity of the actin cytoskeleton in cells.
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Affiliation(s)
- Sonja Kühn
- Center of Advanced European Studies and Research (caesar); Group Physical Biochemistry; Bonn, Germany
| | - Matthias Geyer
- Center of Advanced European Studies and Research (caesar); Group Physical Biochemistry; Bonn, Germany
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23
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Truong D, Copeland JW, Brumell JH. Bacterial subversion of host cytoskeletal machinery: hijacking formins and the Arp2/3 complex. Bioessays 2014; 36:687-96. [PMID: 24849003 DOI: 10.1002/bies.201400038] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The host actin nucleation machinery is subverted by many bacterial pathogens to facilitate their entry, motility, replication, and survival. The majority of research conducted in the past primarily focused on exploitation of a host actin nucleator, the Arp2/3 complex, by bacterial pathogens. Recently, new studies have begun to explore the role of formins, another family of host actin nucleators, in bacterial pathogenesis. This review provides an overview of recent advances in the study of the exploitation of the Arp2/3 complex and formins by bacterial pathogens. Secreted bacterial effector proteins seem to manipulate the regulation of these actin nucleators or functionally mimic them to drive bacterial entry, motility and survival within host cells. An enhanced understanding of how formins are exploited will provide us with greater insight into how a fundamental eurkaryotic cellular process is utilized by bacteria and will also advance our knowledge of host-pathogen interactions.
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Affiliation(s)
- Dorothy Truong
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
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24
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Randall TS, Ehler E. A formin-g role during development and disease. Eur J Cell Biol 2014; 93:205-11. [PMID: 24342720 DOI: 10.1016/j.ejcb.2013.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/15/2013] [Accepted: 11/18/2013] [Indexed: 11/22/2022] Open
Abstract
Several different protein families were shown to be involved in the regulation of actin filament formation and have been studied extensively in processes such as cell migration. Among them are members of the formin family, which tend to promote the formation of linear actin filaments. Studies in recent years, often using loss of function animal models, have indicated that formin family members play roles beyond cell motility in vitro and are involved in processes ranging from tissue morphogenesis and cell differentiation to diseases such as cancer and cardiomyopathy. Therefore the aim of this review is to discuss these findings and to start putting them into a subcellular context.
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Affiliation(s)
- Thomas S Randall
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom
| | - Elisabeth Ehler
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom.
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25
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Lash LL, Wallar BJ, Turner JD, Vroegop SM, Kilkuskie RE, Kitchen-Goosen SM, Xu HE, Alberts AS. Small-molecule intramimics of formin autoinhibition: a new strategy to target the cytoskeletal remodeling machinery in cancer cells. Cancer Res 2014; 73:6793-803. [PMID: 24242070 DOI: 10.1158/0008-5472.can-13-1593] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although the cancer cell cytoskeleton is a clinically validated target, few new strategies have emerged for selectively targeting cell division by modulating the cytoskeletal structure, particularly ways that could avoid the cardiotoxic and neurotoxic effects of current agents such as taxanes. We address this gap by describing a novel class of small-molecule agonists of the mammalian Diaphanous (mDia)-related formins, which act downstream of Rho GTPases to assemble actin filaments, and their organization with microfilaments to establish and maintain cell polarity during migration and asymmetric division. GTP-bound Rho activates mDia family members by disrupting the interaction between the DID and DAD autoregulatory domains, which releases the FH2 domain to modulate actin and microtubule dynamics. In screening for DID-DAD disruptors that activate mDia, we identified two molecules called intramimics (IMM-01 and -02) that were sufficient to trigger actin assembly and microtubule stabilization, serum response factor-mediated gene expression, cell-cycle arrest, and apoptosis. In vivo analysis of IMM-01 and -02 established their ability to slow tumor growth in a mouse xenograft model of colon cancer. Taken together, our work establishes the use of intramimics and mDia-related formins as a new general strategy for therapeutic targeting of the cytoskeletal remodeling machinery of cancer cells.
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Affiliation(s)
- L Leanne Lash
- Authors' Affiliations: Laboratories of Cell Structure and Signal Integration and Structural Sciences, Van Andel Research Institute; Grand Valley State University, Grand Rapids; and Michigan High Throughput Screening Center, Kalamazoo, Michigan
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26
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Ucar H, Tachibana K, Kishimoto T. The Mos-MAPK pathway regulates Diaphanous-related formin activity to drive cleavage furrow closure during polar body extrusion in starfish oocytes. J Cell Sci 2013; 126:5153-65. [PMID: 24046444 DOI: 10.1242/jcs.130476] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Maintenance of spindle attachment to the cortex and formation of the cleavage furrow around the protruded spindle are essential for polar body extrusion (PBE) during meiotic maturation of oocytes. Although spindle movement to the cortex has been well-studied, how the spindle is maintained at the cortex during PBE is unknown. Here, we show that activation of Diaphanous-related formin mediated by mitogen-activated protein kinase (MAPK) is required for tight spindle attachment to the cortex and cleavage furrow closure during PBE in starfish (Asterina pectinifera) oocytes. A. pectinifera Diaphanous-related formin (ApDia) had a distinct localization in immature oocytes and was localized to the cleavage furrow during PBE. Inhibition of the Mos-MAPK pathway or the actin nucleating activity of formin homology 2 domain prevented cleavage furrow closure and resulted in PBE failure. In MEK/MAPK-inhibited oocytes, activation of ApDia by relief of its intramolecular inhibition restored PBE. In summary, this study elucidates a link between the Mos-MAPK pathway and Diaphanous-related formins, that is responsible for maintaining tight spindle attachment to the cortex and cleavage furrow closure during PBE.
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Affiliation(s)
- Hasan Ucar
- Laboratory of Cell and Developmental Biology, Graduate School of Bioscience, Tokyo Institute of Technology, Yokohama 226-8501, Japan
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27
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Affiliation(s)
- Dennis Breitsprecher
- Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA
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28
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Ramabhadran V, Hatch AL, Higgs HN. Actin monomers activate inverted formin 2 by competing with its autoinhibitory interaction. J Biol Chem 2013; 288:26847-55. [PMID: 23921379 DOI: 10.1074/jbc.m113.472415] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
INF2 is an unusual formin protein in that it accelerates both actin polymerization and depolymerization, the latter through an actin filament-severing activity. Similar to other formins, INF2 possesses a dimeric formin homology 2 (FH2) domain that binds filament barbed ends and is critical for polymerization and depolymerization activities. In addition, INF2 binds actin monomers through its diaphanous autoregulatory domain (DAD) that resembles a Wiskott-Aldrich syndrome protein homology 2 (WH2) sequence C-terminal to the FH2 that participates in both polymerization and depolymerization. INF2-DAD is also predicted to participate in an autoinhibitory interaction with the N-terminal diaphanous inhibitory domain (DID). In this work, we show that actin monomer binding to the DAD of INF2 competes with the DID/DAD interaction, thereby activating actin polymerization. INF2 is autoinhibited in cells because mutation of a key DID residue results in constitutive INF2 activity. In contrast, purified full-length INF2 is constitutively active in biochemical actin polymerization assays containing only INF2 and actin monomers. Addition of proteins that compete with INF2-DAD for actin binding (profilin or the WH2 from Wiskott-Aldrich syndrome protein) decrease full-length INF2 activity while not significantly decreasing activity of an INF2 construct lacking the DID sequence. Profilin-mediated INF2 inhibition is relieved by an anti-N-terminal antibody for INF2 that blocks the DID/DAD interaction. These results suggest that free actin monomers can serve as INF2 activators by competing with the DID/DAD interaction. We also find that, in contrast to past results, the DID-containing N terminus of INF2 does not directly bind the Rho GTPase Cdc42.
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Affiliation(s)
- Vinay Ramabhadran
- From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755
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29
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Maiti S, Michelot A, Gould C, Blanchoin L, Sokolova O, Goode BL. Structure and activity of full-length formin mDia1. Cytoskeleton (Hoboken) 2013; 69:393-405. [PMID: 22605659 DOI: 10.1002/cm.21033] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Formins are a conserved family of actin assembly-promoting factors with essential and diverse biological roles. Most of our biochemical understanding of formin effects on actin dynamics is derived from studies using formin fragments. In addition, all structural information on formins has been limited to fragments. This has left open key questions about the structure, activity and regulation of intact formin proteins. Here, we isolated full-length mouse mDia1 (mDia1-FL) and found that it forms tightly autoinhibited dimers that can only be partially activated by RhoA. We solved the structure of autoinhibited mDia1-FL using electron microscopy and single particle analysis. Docking of crystal structures into the three dimensional reconstruction revealed that the fork-shaped N-terminal diaphanous inhibitory domain-coiled coil domain region hangs over the ring-shaped formin homology (FH)2 domain, suggesting that autoinhibition results from steric obstruction of actin binding. Deletion of the C-terminal diaphanous autoregulatory domain extended mDia1 structure and activated it for actin assembly. Using total internal reflection fluorescence microscopy, we observed that RhoA-activated mDia1-FL persistently accelerated filament elongation in the presence of profilin similar to mDia1 FH1-FH2 fragment. These observations validate the known activities of FH1-FH2 fragments as reflecting those of the intact molecule. Our results further suggest that mDia1-FL does not readily snap back into the autoinhibited conformation and dissociate from growing filament ends, and thus additional factors may be required to displace formins and restrict filament length.
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Affiliation(s)
- Sankar Maiti
- Biology Department, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
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Thompson ME, Heimsath EG, Gauvin TJ, Higgs HN, Kull FJ. FMNL3 FH2-actin structure gives insight into formin-mediated actin nucleation and elongation. Nat Struct Mol Biol 2012; 20:111-8. [PMID: 23222643 PMCID: PMC3876896 DOI: 10.1038/nsmb.2462] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 11/05/2012] [Indexed: 01/27/2023]
Abstract
Formins are actin assembly factors that act in a variety of actin-based processes. The conserved formin homology 2 (FH2) domain promotes filament nucleation and influences elongation via interaction with the barbed end. FMNL3 is a formin that induces assembly of filopodia but whose FH2 domain is a poor nucleator. The 3.4 Å structure of an FMNL3 FH2 dimer in complex with tetramethylrhodamine-actin uncovers details of formin-regulated actin elongation. We observe distinct FH2-actin binding regions; interactions in the knob and coiled-coil subdomains are necessary for actin binding while those in the lasso/post interface are important for the stepping mechanism. Biochemical and cellular experiments test the importance of individual residues for function. This structure provides details for FH2 mediated filament elongation via processive capping and supports a model in which C-terminal non-FH2 residues of FMNL3 are required to stabilize the filament nucleus.
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Affiliation(s)
- Morgan E Thompson
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
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31
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Bosch DE, Yang B, Siderovski DP. Entamoeba histolytica Rho1 regulates actin polymerization through a divergent, diaphanous-related formin. Biochemistry 2012; 51:8791-801. [PMID: 23050667 PMCID: PMC3491106 DOI: 10.1021/bi300954g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Entamoeba histolytica requires a dynamic actin cytoskeleton for intestinal and systemic pathogenicity. Diaphanous-related formins represent an important family of actin regulators that are activated by Rho GTPases. The E. histolytica genome encodes a large family of Rho GTPases and three diaphanous-related formins, of which EhFormin1 is known to regulate mitosis and cytokinesis in trophozoites. We demonstrate that EhFormin1 modulates actin polymerization through its formin homology 2 domain. Despite a highly divergent diaphanous autoinhibitory domain, EhFormin1 is autoinhibited by an N- and C-terminal intramolecular interaction but activated upon binding of EhRho1 to the N-terminal domain tandem. A crystal structure of the EhRho1·GTPγS-EhFormin1 complex illustrates an EhFormin1 conformation that diverges from mammalian mDia1 and lacks a secondary interaction with a Rho insert helix. The structural model also highlights residues required for specific recognition of the EhRho1 GTPase and suggests that the molecular mechanisms of EhFormin1 autoinhibition and activation differ from those of mammalian homologues.
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Affiliation(s)
- Dustin E. Bosch
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365 USA
| | - Bing Yang
- Department of Cell and Developmental Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365 USA
| | - David P. Siderovski
- Department of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, WV 26506-9229 USA,Address correspondence to Dr. David P. Siderovski, 3051 Robert C. Byrd Health Sciences Center, West Virginia University School of Medicine, Morgantown, WV 26506-9229 USA. Tel: 304-293-4991;
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Bor B, Vizcarra CL, Phillips ML, Quinlan ME. Autoinhibition of the formin Cappuccino in the absence of canonical autoinhibitory domains. Mol Biol Cell 2012; 23:3801-13. [PMID: 22875983 PMCID: PMC3459857 DOI: 10.1091/mbc.e12-04-0288] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The Fmn-family formin Cappuccino does not contain classical autoihibitory domains but is autoinhibited. The N-terminus inhibits actin nucleation and competes with elongation. Formins are a conserved family of proteins known to enhance actin polymerization. Most formins are regulated by an intramolecular interaction. The Drosophila formin, Cappuccino (Capu), was believed to be an exception. Capu does not contain conserved autoinhibitory domains and can be regulated by a second protein, Spire. We report here that Capu is, in fact, autoinhibited. The N-terminal half of Capu (Capu-NT) potently inhibits nucleation and binding to the barbed end of elongating filaments by the C-terminal half of Capu (Capu-CT). Hydrodynamic analysis indicates that Capu-NT is a dimer, similar to the N-termini of other formins. These data, combined with those from circular dichroism, suggest, however, that it is structurally distinct from previously described formin inhibitory domains. Finally, we find that Capu-NT binds to a site within Capu-CT that overlaps with the Spire-binding site, the Capu-tail. We propose models for the interaction between Spire and Capu in light of the fact that Capu can be regulated by autoinhibition.
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Affiliation(s)
- Batbileg Bor
- Molecular Biology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA 90095-1570, USA
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Mi-Mi L, Votra S, Kemphues K, Bretscher A, Pruyne D. Z-line formins promote contractile lattice growth and maintenance in striated muscles of C. elegans. ACTA ACUST UNITED AC 2012; 198:87-102. [PMID: 22753896 PMCID: PMC3392944 DOI: 10.1083/jcb.201202053] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle contraction depends on interactions between actin and myosin filaments organized into sarcomeres, but the mechanism by which actin filaments incorporate into sarcomeres remains unclear. We have found that, during larval development in Caenorhabditis elegans, two members of the actin-assembling formin family, CYK-1 and FHOD-1, are present in striated body wall muscles near or on sarcomere Z lines, where barbed ends of actin filaments are anchored. Depletion of either formin during this period stunted growth of the striated contractile lattice, whereas their simultaneous reduction profoundly diminished lattice size and number of striations per muscle cell. CYK-1 persisted at Z lines in adulthood, and its near complete depletion from adults triggered phenotypes ranging from partial loss of Z line-associated filamentous actin to collapse of the contractile lattice. These results are, to our knowledge, the first genetic evidence implicating sarcomere-associated formins in the in vivo organization of the muscle cytoskeleton.
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Affiliation(s)
- Lei Mi-Mi
- Department of Cell and Developmental Biology, State University of NY Upstate Medical University, Syracuse, NY 13210, USA
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Ignatev A, Bhargav SP, Vahokoski J, Kursula P, Kursula I. The lasso segment is required for functional dimerization of the Plasmodium formin 1 FH2 domain. PLoS One 2012; 7:e33586. [PMID: 22428073 PMCID: PMC3302767 DOI: 10.1371/journal.pone.0033586] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 02/16/2012] [Indexed: 11/25/2022] Open
Abstract
Apicomplexan parasites, such as the malaria-causing Plasmodium species, utilize a unique way of locomotion and host cell invasion. This substrate-dependent gliding motility requires rapid cycling of actin between the monomeric state and very short, unbranched filaments. Despite the crucial role of actin polymerization for the survival of the malaria parasite, the majority of Plasmodium cellular actin is present in the monomeric form. Plasmodium lacks most of the canonical actin nucleators, and formins are essentially the only candidates for this function in all Apicomplexa. The malaria parasite has two formins, containing conserved formin homology (FH) 2 and rudimentary FH1 domains. Here, we show that Plasmodium falciparum formin 1 associates with and nucleates both mammalian and Plasmodium actin filaments. Although Plasmodium profilin alone sequesters actin monomers, thus inhibiting polymerization, its monomer-sequestering activity does not compete with the nucleating activity of formin 1 at an equimolar profilin-actin ratio. We have determined solution structures of P. falciparum formin 1 FH2 domain both in the presence and absence of the lasso segment and the FH1 domain, and show that the lasso is required for the assembly of functional dimers.
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Affiliation(s)
| | | | - Juha Vahokoski
- Department of Biochemistry, University of Oulu, Oulu, Finland
| | - Petri Kursula
- Department of Biochemistry, University of Oulu, Oulu, Finland
- Biocenter Oulu, University of Oulu, Oulu, Finland
- Department of Chemistry, Centre for Structural Systems Biology, Helmholtz Centre for Infection Research, University of Hamburg, and German Electron Synchrotron (DESY), Hamburg, Germany
| | - Inari Kursula
- Department of Biochemistry, University of Oulu, Oulu, Finland
- Department of Chemistry, Centre for Structural Systems Biology, Helmholtz Centre for Infection Research, University of Hamburg, and German Electron Synchrotron (DESY), Hamburg, Germany
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Graziano BR, DuPage AG, Michelot A, Breitsprecher D, Moseley JB, Sagot I, Blanchoin L, Goode BL. Mechanism and cellular function of Bud6 as an actin nucleation-promoting factor. Mol Biol Cell 2011; 22:4016-28. [PMID: 21880892 PMCID: PMC3204064 DOI: 10.1091/mbc.e11-05-0404] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Bud6 functions as an actin nucleation–promoting factor (NPF) for Bni1; thus formins can depend on NPFs like the Arp2/3 complex. Unexpected parallels exist between Bud6 and WASp. Bud6 is the first nonmetazoan example of formins pairing with actin monomer–binding proteins to stimulate nucleation, akin to Spire-Capu and APC-mDia1 Formins are a conserved family of actin assembly–promoting factors with diverse biological roles, but how their activities are regulated in vivo is not well understood. In Saccharomyces cerevisiae, the formins Bni1 and Bnr1 are required for the assembly of actin cables and polarized cell growth. Proper cable assembly further requires Bud6. Previously it was shown that Bud6 enhances Bni1-mediated actin assembly in vitro, but the biochemical mechanism and in vivo role of this activity were left unclear. Here we demonstrate that Bud6 specifically stimulates the nucleation rather than the elongation phase of Bni1-mediated actin assembly, defining Bud6 as a nucleation-promoting factor (NPF) and distinguishing its effects from those of profilin. We generated alleles of Bud6 that uncouple its interactions with Bni1 and G-actin and found that both interactions are critical for NPF activity. Our data indicate that Bud6 promotes filament nucleation by recruiting actin monomers to Bni1. Genetic analysis of the same alleles showed that Bud6 regulation of formin activity is critical for normal levels of actin cable assembly in vivo. Our results raise important mechanistic parallels between Bud6 and WASP, as well as between Bud6 and other NPFs that interact with formins such as Spire.
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Affiliation(s)
- Brian R Graziano
- Department of Biology and Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA
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Gorelik R, Yang C, Kameswaran V, Dominguez R, Svitkina T. Mechanisms of plasma membrane targeting of formin mDia2 through its amino terminal domains. Mol Biol Cell 2010; 22:189-201. [PMID: 21119010 PMCID: PMC3020915 DOI: 10.1091/mbc.e10-03-0256] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We investigated the poorly understood mechanism of plasma membrane targeting of formin mDia2 and found that its N terminus plays important roles in this process by binding acidic phospholipids through its N-terminal basic domain and by binding small GTPase Rif through direct interaction with the GTPase binding region and the diaphanous inhibitory domain. The formin mDia2 mediates the formation of lamellipodia and filopodia during cell locomotion. The subcellular localization of activated mDia2 depends on interactions with actin filaments and the plasma membrane. We investigated the poorly understood mechanism of plasma membrane targeting of mDia2 and found that the entire N-terminal region of mDia2 preceding the actin-polymerizing formin homology domains 1 and 2 (FH1–FH2) module was potently targeted to the membrane. This localization was enhanced by Rif, but not by other tested small GTPases, and depended on a positively charged N-terminal basic domain (BD). The BD bound acidic phospholipids in vitro, suggesting that in vivo it may associate with the plasma membrane through electrostatic interactions. Unexpectedly, a fragment consisting of the GTPase-binding region and the diaphanous inhibitory domain (G-DID), thought to mediate the interaction with GTPases, was not targeted to the plasma membrane even in the presence of constitutively active Rif. Addition of the BD or dimerization/coiled coil domains to G-DID rescued plasma membrane targeting in cells. Direct binding of Rif to mDia2 N terminus required the presence of both G and DID. These results suggest that the entire N terminus of mDia2 serves as a coincidence detection module, directing mDia2 to the plasma membrane through interactions with phospholipids and activated Rif.
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Affiliation(s)
- Roman Gorelik
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA
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