1
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Palmer NJ, Barrie KR, Dominguez R. Mechanisms of actin filament severing and elongation by formins. Nature 2024; 632:437-442. [PMID: 38843827 PMCID: PMC11375965 DOI: 10.1038/s41586-024-07637-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 05/31/2024] [Indexed: 08/02/2024]
Abstract
Humans express 15 formins that play crucial roles in actin-based processes, including cytokinesis, cell motility and mechanotransduction1,2. However, the lack of structures bound to the actin filament (F-actin) has been a major impediment to understanding formin function. Whereas formins are known for their ability to nucleate and elongate F-actin3-7, some formins can additionally depolymerize, sever or bundle F-actin. Two mammalian formins, inverted formin 2 (INF2) and diaphanous 1 (DIA1, encoded by DIAPH1), exemplify this diversity. INF2 shows potent severing activity but elongates weakly8-11 whereas DIA1 has potent elongation activity but does not sever4,8. Using cryo-electron microscopy (cryo-EM) we show five structural states of INF2 and two of DIA1 bound to the middle and barbed end of F-actin. INF2 and DIA1 bind differently to these sites, consistent with their distinct activities. The formin-homology 2 and Wiskott-Aldrich syndrome protein-homology 2 (FH2 and WH2, respectively) domains of INF2 are positioned to sever F-actin, whereas DIA1 appears unsuited for severing. These structures also show how profilin-actin is delivered to the fast-growing barbed end, and how this is followed by a transition of the incoming monomer into the F-actin conformation and the release of profilin. Combined, the seven structures presented here provide step-by-step visualization of the mechanisms of F-actin severing and elongation by formins.
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Affiliation(s)
- Nicholas J Palmer
- Department of Physiology and Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Kyle R Barrie
- Department of Physiology and Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Roberto Dominguez
- Department of Physiology and Biochemistry and Molecular Biophysics Graduate Group, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
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2
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Wojnacki J, Quassollo G, Bordenave MD, Unsain N, Martínez GF, Szalai AM, Pertz O, Gundersen GG, Bartolini F, Stefani FD, Cáceres A, Bisbal M. Dual spatio-temporal regulation of axon growth and microtubule dynamics by RhoA signaling pathways. J Cell Sci 2024; 137:jcs261970. [PMID: 38910449 DOI: 10.1242/jcs.261970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 06/17/2024] [Indexed: 06/25/2024] Open
Abstract
RhoA plays a crucial role in neuronal polarization, where its action restraining axon outgrowth has been thoroughly studied. We now report that RhoA has not only an inhibitory but also a stimulatory effect on axon development depending on when and where exerts its action and the downstream effectors involved. In cultured hippocampal neurons, FRET imaging revealed that RhoA activity selectively localized in growth cones of undifferentiated neurites, whereas in developing axons it displayed a biphasic pattern, being low in nascent axons and high in elongating ones. RhoA-Rho kinase (ROCK) signaling prevented axon initiation but had no effect on elongation, whereas formin inhibition reduced axon extension without significantly altering initial outgrowth. In addition, RhoA-mDia signaling promoted axon elongation by stimulating growth cone microtubule stability and assembly, as opposed to RhoA-ROCK signaling, which restrained growth cone microtubule assembly and protrusion.
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Affiliation(s)
- José Wojnacki
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba 5016, Argentina
| | - Gonzalo Quassollo
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba 5016, Argentina
| | - Martín D Bordenave
- Centro de Investigaciones en Bionanociencias (CIBION), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2390, Ciudad Autónoma de Buenos Aires C1425FQD, Argentina
| | - Nicolás Unsain
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba 5016, Argentina
- Instituto Universitario Ciencias Biomédicas de Córdoba (IUCBC), Córdoba 5016, Argentina
| | - Gaby F Martínez
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba 5016, Argentina
| | - Alan M Szalai
- Centro de Investigaciones en Bionanociencias (CIBION), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2390, Ciudad Autónoma de Buenos Aires C1425FQD, Argentina
| | - Olivier Pertz
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, Bern 3012, Switzerland
| | - Gregg G Gundersen
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Francesca Bartolini
- Department of Pathology and Cell Biology, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
| | - Fernando D Stefani
- Centro de Investigaciones en Bionanociencias (CIBION), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Godoy Cruz 2390, Ciudad Autónoma de Buenos Aires C1425FQD, Argentina
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Güiraldes 2620, Ciudad Autónoma de Buenos Aires C1428EHA, Argentina
| | - Alfredo Cáceres
- Centro Investigación Medicina Traslacional Severo R Amuchástegui (CIMETSA), Instituto Universitario Ciencias Biomédicas Córdoba (IUCBC), Av. Naciones Unidas 440, Córdoba 5016, Argentina
| | - Mariano Bisbal
- Instituto de Investigación Médica Mercedes y Martín Ferreyra (INIMEC), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Córdoba, Córdoba 5016, Argentina
- Instituto Universitario Ciencias Biomédicas de Córdoba (IUCBC), Córdoba 5016, Argentina
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3
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Fox S, Gaudreau-LaPierre A, Reshke R, Podinic I, Gibbings DJ, Trinkle-Mulcahy L, Copeland JW. Identification of an FMNL2 Interactome by Quantitative Mass Spectrometry. Int J Mol Sci 2024; 25:5686. [PMID: 38891874 PMCID: PMC11171801 DOI: 10.3390/ijms25115686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 05/14/2024] [Accepted: 05/16/2024] [Indexed: 06/21/2024] Open
Abstract
Formin Homology Proteins (Formins) are a highly conserved family of cytoskeletal regulatory proteins that participate in a diverse range of cellular processes. FMNL2 is a member of the Diaphanous-Related Formin sub-group, and previous reports suggest FMNL2's role in filopodia assembly, force generation at lamellipodia, subcellular trafficking, cell-cell junction assembly, and focal adhesion formation. How FMNL2 is recruited to these sites of action is not well understood. To shed light on how FMNL2 activity is partitioned between subcellular locations, we used biotin proximity labeling and proteomic analysis to identify an FMNL2 interactome. The interactome identified known and new FMNL2 interacting proteins with functions related to previously described FMNL2 activities. In addition, our interactome predicts a novel connection between FMNL2 and extracellular vesicle assembly. We show directly that FMNL2 protein is present in exosomes.
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Affiliation(s)
| | | | | | | | | | | | - John W. Copeland
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada; (S.F.)
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4
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Srapyan S, Tran DP, Loo JA, Grintsevich EE. Mapping Molecular Interaction Interface Between Diaphanous Formin-2 and Neuron-Specific Drebrin A. J Mol Biol 2023; 435:168334. [PMID: 37898384 DOI: 10.1016/j.jmb.2023.168334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/13/2023] [Accepted: 10/23/2023] [Indexed: 10/30/2023]
Abstract
Actin cytoskeleton is critical for neuronal shape and function. Drebrin and formins are key regulators of neuronal actin networks. Neuron-specific drebrin A is highly enriched in dendritic spines (postsynaptic terminals) of mature excitatory neurons. Decreased levels of drebrin in dendritic spines is a hallmark of Alzheimer's disease, epilepsy, and other complex disorders, which calls for better understanding of its regulatory functions. Drebrin A was previously shown to inhibit actin nucleation and bundling by the diaphanous formin-2 (mDia2) - an actin nucleator that is involved in the initiation of dendritic spines. Characterization of the molecular binding interface between mDia2 and drebrin is necessary to better understand the functional consequences of this interaction and its biological relevance. Prior work suggested a multi-pronged interface between mDia2 and drebrin, which involves both N-terminal and C-terminal regions of the drebrin molecule. Here we used mass spectrometry analysis, deletion mutagenesis, and an array of synthetic peptides of neuronal drebrin A to map its formin-binding interface. The mDia2-interacting interface on drebrin was narrowed down to three highly conserved 9-16 residue sequences that were used to identify some of the key residues involved in this interaction. Deletion of the C-terminal region of drebrin greatly reduces its binding to mDia2 and the extent of its inhibition of formin-driven actin assembly. Moreover, our experiments with formins from different subfamilies showed that drebrin is a specific rather than general inhibitor of these proteins. This work contributes to a molecular level understanding of the formin-drebrin interaction and will help to unravel its biological significance.
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Affiliation(s)
- Sargis Srapyan
- Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA 90840, USA
| | - Denise P Tran
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA; Sydney Mass Spectrometry, The University of Sydney (USyd), Sydney, New South Wales 2006, Australia
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Elena E Grintsevich
- Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA 90840, USA.
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5
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Gazsó-Gerhát G, Gombos R, Tóth K, Kaltenecker P, Szikora S, Bíró J, Csapó E, Asztalos Z, Mihály J. FRL and DAAM are required for lateral adhesion of interommatidial cells and patterning of the retinal floor. Development 2023; 150:dev201713. [PMID: 37997920 PMCID: PMC10690107 DOI: 10.1242/dev.201713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 10/17/2023] [Indexed: 11/25/2023]
Abstract
Optical insulation of the unit eyes (ommatidia) is an important prerequisite of precise sight with compound eyes. Separation of the ommatidia is ensured by pigment cells that organize into a hexagonal lattice in the Drosophila eye, forming thin walls between the facets. Cell adhesion, mediated by apically and latero-basally located junctional complexes, is crucial for stable attachment of these cells to each other and the basal lamina. Whereas former studies have focused on the formation and remodelling of the cellular connections at the apical region, here, we report a specific alteration of the lateral adhesion of the lattice cells, leaving the apical junctions largely unaffected. We found that DAAM and FRL, two formin-type cytoskeleton regulatory proteins, play redundant roles in lateral adhesion of the interommatidial cells and patterning of the retinal floor. We show that formin-dependent cortical actin assembly is crucial for latero-basal sealing of the ommatidial lattice. We expect that the investigation of these previously unreported eye phenotypes will pave the way toward a better understanding of the three-dimensional aspects of compound eye development.
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Affiliation(s)
- Gabriella Gazsó-Gerhát
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
- Doctoral School in Biology, Faculty of Science and Informatics, University of Szeged, Szeged H-6726, Hungary
| | - Rita Gombos
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Krisztina Tóth
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Péter Kaltenecker
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Szilárd Szikora
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
| | - Judit Bíró
- Aktogen Hungary Ltd., Szeged H-6726, Hungary
| | - Enikő Csapó
- Aktogen Hungary Ltd., Szeged H-6726, Hungary
| | - Zoltán Asztalos
- Institute of Biochemistry, HUN-REN Biological Research Centre, Szeged H-6726, Hungary
| | - József Mihály
- Institute of Genetics, HUN-REN Biological Research Centre, Temesvári krt. 62, Szeged H-6726, Hungary
- Department of Genetics, University of Szeged, Szeged H-6726, Hungary
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6
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Antoku S, Schwartz TU, Gundersen GG. FHODs: Nuclear tethered formins for nuclear mechanotransduction. Front Cell Dev Biol 2023; 11:1160219. [PMID: 37215084 PMCID: PMC10192571 DOI: 10.3389/fcell.2023.1160219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 03/28/2023] [Indexed: 05/24/2023] Open
Abstract
In this review, we discuss FHOD formins with a focus on recent studies that reveal a new role for them as critical links for nuclear mechanotransduction. The FHOD family in vertebrates comprises two structurally related proteins, FHOD1 and FHOD3. Their similar biochemical properties suggest overlapping and redundant functions. FHOD1 is widely expressed, FHOD3 less so, with highest expression in skeletal (FHOD1) and cardiac (FHOD3) muscle where specific splice isoforms are expressed. Unlike other formins, FHODs have strong F-actin bundling activity and relatively weak actin polymerization activity. These activities are regulated by phosphorylation by ROCK and Src kinases; bundling is additionally regulated by ERK1/2 kinases. FHODs are unique among formins in their association with the nuclear envelope through direct, high affinity binding to the outer nuclear membrane proteins nesprin-1G and nesprin-2G. Recent crystallographic structures reveal an interaction between a conserved motif in one of the spectrin repeats (SRs) of nesprin-1G/2G and a site adjacent to the regulatory domain in the amino terminus of FHODs. Nesprins are components of the LINC (linker of nucleoskeleton and cytoskeleton) complex that spans both nuclear membranes and mediates bidirectional transmission of mechanical forces between the nucleus and the cytoskeleton. FHODs interact near the actin-binding calponin homology (CH) domains of nesprin-1G/2G enabling a branched connection to actin filaments that presumably strengthens the interaction. At the cellular level, the tethering of FHODs to the outer nuclear membrane mechanically couples perinuclear actin arrays to the nucleus to move and position it in fibroblasts, cardiomyocytes, and potentially other cells. FHODs also function in adhesion maturation during cell migration and in the generation of sarcomeres, activities distant from the nucleus but that are still influenced by it. Human genetic studies have identified multiple FHOD3 variants linked to dilated and hypertrophic cardiomyopathies, with many mutations mapping to "hot spots" in FHOD3 domains. We discuss how FHOD1/3's role in reinforcing the LINC complex and connecting to perinuclear actin contributes to functions of mechanically active tissues such as striated muscle.
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Affiliation(s)
- Susumu Antoku
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
| | - Thomas U. Schwartz
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Gregg G. Gundersen
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States
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7
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Rajan S, Kudryashov DS, Reisler E. Actin Bundles Dynamics and Architecture. Biomolecules 2023; 13:450. [PMID: 36979385 PMCID: PMC10046292 DOI: 10.3390/biom13030450] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/16/2023] [Accepted: 02/20/2023] [Indexed: 03/04/2023] Open
Abstract
Cells use the actin cytoskeleton for many of their functions, including their division, adhesion, mechanosensing, endo- and phagocytosis, migration, and invasion. Actin bundles are the main constituent of actin-rich structures involved in these processes. An ever-increasing number of proteins that crosslink actin into bundles or regulate their morphology is being identified in cells. With recent advances in high-resolution microscopy and imaging techniques, the complex process of bundles formation and the multiple forms of physiological bundles are beginning to be better understood. Here, we review the physiochemical and biological properties of four families of highly conserved and abundant actin-bundling proteins, namely, α-actinin, fimbrin/plastin, fascin, and espin. We describe the similarities and differences between these proteins, their role in the formation of physiological actin bundles, and their properties-both related and unrelated to their bundling abilities. We also review some aspects of the general mechanism of actin bundles formation, which are known from the available information on the activity of the key actin partners involved in this process.
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Affiliation(s)
- Sudeepa Rajan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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8
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Silva AM, Chan FY, Norman MJ, Sobral AF, Zanin E, Gassmann R, Belmonte JM, Carvalho AX. β-heavy-spectrin stabilizes the constricting contractile ring during cytokinesis. J Cell Biol 2022; 222:213538. [PMID: 36219157 PMCID: PMC9559602 DOI: 10.1083/jcb.202202024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 08/17/2022] [Accepted: 09/20/2022] [Indexed: 11/22/2022] Open
Abstract
Cytokinesis requires the constriction of an actomyosin-based contractile ring and involves multiple F-actin crosslinkers. We show that partial depletion of the C. elegans cytokinetic formin generates contractile rings with low F-actin levels that constrict but are structurally fragile, and we use this background to investigate the roles of the crosslinkers plastin/PLST-1 and β-heavy-spectrin/SMA-1 during ring constriction. We show that the removal of PLST-1 or SMA-1 has opposite effects on the structural integrity of fragile rings. PLST-1 loss reduces cortical tension that resists ring constriction and makes fragile rings less prone to ruptures and regressions, whereas SMA-1 loss exacerbates structural defects, leading to frequent ruptures and cytokinesis failure. Fragile rings without SMA-1 or containing a shorter SMA-1, repeatedly rupture at the same site, and SMA-1::GFP accumulates at repair sites in fragile rings and in rings cut by laser microsurgery. These results establish that β-heavy-spectrin stabilizes the constricting ring and reveals the importance of β-heavy-spectrin size for network connectivity at low F-actin density.
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Affiliation(s)
- Ana Marta Silva
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal,IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Fung-Yi Chan
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal,IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Michael J. Norman
- Department of Physics, North Carolina State University, Raleigh, NC,Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC
| | - Ana Filipa Sobral
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal,IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Esther Zanin
- Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Reto Gassmann
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal,IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal
| | - Julio Monti Belmonte
- Department of Physics, North Carolina State University, Raleigh, NC,Quantitative and Computational Developmental Biology Cluster, North Carolina State University, Raleigh, NC
| | - Ana Xavier Carvalho
- i3S—Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal,IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal,Correspondence to Ana Xavier Carvalho:
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9
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Fung TS, Chakrabarti R, Kollasser J, Rottner K, Stradal TEB, Kage F, Higgs HN. Parallel kinase pathways stimulate actin polymerization at depolarized mitochondria. Curr Biol 2022; 32:1577-1592.e8. [PMID: 35290799 PMCID: PMC9078333 DOI: 10.1016/j.cub.2022.02.058] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 02/04/2022] [Accepted: 02/21/2022] [Indexed: 12/31/2022]
Abstract
Mitochondrial damage (MtD) represents a dramatic change in cellular homeostasis, necessitating metabolic changes and stimulating mitophagy. One rapid response to MtD is a rapid peri-mitochondrial actin polymerization termed ADA (acute damage-induced actin). The activation mechanism for ADA is unknown. Here, we use mitochondrial depolarization or the complex I inhibitor metformin to induce ADA. We show that two parallel signaling pathways are required for ADA. In one pathway, increased cytosolic calcium in turn activates PKC-β, Rac, WAVE regulatory complex, and Arp2/3 complex. In the other pathway, a drop in cellular ATP in turn activates AMPK (through LKB1), Cdc42, and FMNL formins. We also identify putative guanine nucleotide exchange factors for Rac and Cdc42, Trio and Fgd1, respectively, whose phosphorylation states increase upon mitochondrial depolarization and whose suppression inhibits ADA. The depolarization-induced calcium increase is dependent on the mitochondrial sodium-calcium exchanger NCLX, suggesting initial mitochondrial calcium efflux. We also show that ADA inhibition results in enhanced mitochondrial shape changes upon mitochondrial depolarization, suggesting that ADA inhibits these shape changes. These depolarization-induced shape changes are not fragmentation but a circularization of the inner mitochondrial membrane, which is dependent on the inner mitochondrial membrane protease Oma1. ADA inhibition increases the proteolytic processing of an Oma1 substrate, the dynamin GTPase Opa1. These results show that ADA requires the combined action of the Arp2/3 complex and formin proteins to polymerize a network of actin filaments around mitochondria and that the ADA network inhibits the rapid mitochondrial shape changes that occur upon mitochondrial depolarization.
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Affiliation(s)
- Tak Shun Fung
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Rajarshi Chakrabarti
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Jana Kollasser
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Klemens Rottner
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany; Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany
| | - Theresia E B Stradal
- Department of Cell Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Frieda Kage
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Henry N Higgs
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA.
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10
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Sherer LA, Courtemanche N. Cooperative bundling by fascin generates actin structures with architectures that depend on filament length. Front Cell Dev Biol 2022; 10:974047. [PMID: 36120572 PMCID: PMC9479110 DOI: 10.3389/fcell.2022.974047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 08/12/2022] [Indexed: 11/30/2022] Open
Abstract
The assembly of actin-based structures with precisely defined architectures supports essential cellular functions, including motility, intracellular transport, and division. The geometric arrangements of the filaments within actin structures are stabilized via the association of crosslinking proteins, which bind two filaments simultaneously. Because actin polymerization and crosslinking occur concurrently within the dynamic environment of the cell, these processes likely play interdependent roles in shaping the architectures of actin-based structures. To dissect the contribution of polymerization to the construction of higher-order actin structures, we investigated how filament elongation affects the formation of simple, polarized actin bundles by the crosslinking protein fascin. Using populations of actin filaments to represent distinct stages of elongation, we found that the rate of bundle assembly increases with filament length. Fascin assembles short filaments into discrete bundles, whereas bundles of long filaments merge with one another to form interconnected networks. Although filament elongation promotes bundle coalescence, many connections formed between elongating bundles are short-lived and are followed by filament breakage. Our data suggest that initiation of crosslinking early in elongation aligns growing filaments, creating a template for continued bundle assembly as elongation proceeds. This initial alignment promotes the assembly of bundles that are resistant to large changes in curvature that are required for coalescence into interconnected networks. As a result, bundles of short filaments remain straighter and more topologically discrete as elongation proceeds than bundles assembled from long filaments. Thus, uncoordinated filament elongation and crosslinking can alter the architecture of bundled actin networks, highlighting the importance of maintaining precise control over filament length during the assembly of specialized actin structures.
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11
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Grintsevich EE, Ahmed G, Ginosyan AA, Wu H, Rich SK, Reisler E, Terman JR. Profilin and Mical combine to impair F-actin assembly and promote disassembly and remodeling. Nat Commun 2021; 12:5542. [PMID: 34545088 PMCID: PMC8452626 DOI: 10.1038/s41467-021-25781-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 08/24/2021] [Indexed: 11/30/2022] Open
Abstract
Cellular events require the spatiotemporal interplay between actin assembly and actin disassembly. Yet, how different factors promote the integration of these two opposing processes is unclear. In particular, cellular monomeric (G)-actin is complexed with profilin, which inhibits spontaneous actin nucleation but fuels actin filament (F-actin) assembly by elongation-promoting factors (formins, Ena/VASP). In contrast, site-specific F-actin oxidation by Mical promotes F-actin disassembly and release of polymerization-impaired Mical-oxidized (Mox)-G-actin. Here we find that these two opposing processes connect with one another to orchestrate actin/cellular remodeling. Specifically, we find that profilin binds Mox-G-actin, yet these complexes do not fuel elongation factors’-mediated F-actin assembly, but instead inhibit polymerization and promote further Mox-F-actin disassembly. Using Drosophila as a model system, we show that similar profilin–Mical connections occur in vivo – where they underlie F-actin/cellular remodeling that accompanies Semaphorin–Plexin cellular/axon repulsion. Thus, profilin and Mical combine to impair F-actin assembly and promote F-actin disassembly, while concomitantly facilitating cellular remodeling and plasticity. Actin-based structures in cells and tissues are built and maintained through a poorly understood balance between assembly and disassembly. Here, our findings provide insights into how factors known to promote these opposing effects dynamically integrate to shape cells and tissue systems.
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Affiliation(s)
- Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA, 90840, USA.
| | - Giasuddin Ahmed
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Anush A Ginosyan
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Heng Wu
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Shannon K Rich
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Molecular Biology Institute, UCLA, Los Angeles, CA, 90095, USA.
| | - Jonathan R Terman
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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12
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Homa KE, Zsolnay V, Anderson CA, O'Connell ME, Neidt EM, Voth GA, Bidone TC, Kovar DR. Formin Cdc12's specific actin assembly properties are tailored for cytokinesis in fission yeast. Biophys J 2021; 120:2984-2997. [PMID: 34214524 DOI: 10.1016/j.bpj.2021.06.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 06/07/2021] [Accepted: 06/16/2021] [Indexed: 11/16/2022] Open
Abstract
Formins generate unbranched actin filaments by a conserved, processive actin assembly mechanism. Most organisms express multiple formin isoforms that mediate distinct cellular processes and facilitate actin filament polymerization by significantly different rates, but how these actin assembly differences correlate to cellular activity is unclear. We used a computational model of fission yeast cytokinetic ring assembly to test the hypothesis that particular actin assembly properties help tailor formins for specific cellular roles. Simulations run in different actin filament nucleation and elongation conditions revealed that variations in formin's nucleation efficiency critically impact both the probability and timing of contractile ring formation. To probe the physiological importance of nucleation efficiency, we engineered fission yeast formin chimera strains in which the FH1-FH2 actin assembly domains of full-length cytokinesis formin Cdc12 were replaced with the FH1-FH2 domains from functionally and evolutionarily diverse formins with significantly different actin assembly properties. Although Cdc12 chimeras generally support life in fission yeast, quantitative live-cell imaging revealed a range of cytokinesis defects from mild to severe. In agreement with the computational model, chimeras whose nucleation efficiencies are least similar to Cdc12 exhibit more severe cytokinesis defects, specifically in the rate of contractile ring assembly. Together, our computational and experimental results suggest that fission yeast cytokinesis is ideally mediated by a formin with properly tailored actin assembly parameters.
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Affiliation(s)
- Kaitlin E Homa
- Department of Molecular Genetics and Cell Biology, Chicago, Illinois
| | - Vilmos Zsolnay
- Graduate Program in Biophysical Sciences, Chicago, Illinois
| | | | | | - Erin M Neidt
- Department of Molecular Genetics and Cell Biology, Chicago, Illinois
| | - Gregory A Voth
- Department of Chemistry, The James Franck Institute, Institute for Biophysical Dynamics and Computation Institute, Chicago, Illinois
| | - Tamara C Bidone
- Department of Biomedical Engineering, Salt Lake City, Utah; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah.
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, Chicago, Illinois; Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois.
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13
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Nishimura Y, Shi S, Zhang F, Liu R, Takagi Y, Bershadsky AD, Viasnoff V, Sellers JR. The formin inhibitor SMIFH2 inhibits members of the myosin superfamily. J Cell Sci 2021; 134:237818. [PMID: 33589498 PMCID: PMC8121067 DOI: 10.1242/jcs.253708] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 02/03/2021] [Indexed: 12/31/2022] Open
Abstract
The small molecular inhibitor of formin FH2 domains, SMIFH2, is widely used in cell biological studies. It inhibits formin-driven actin polymerization in vitro, but not polymerization of pure actin. It is active against several types of formin from different species. Here, we found that SMIFH2 inhibits retrograde flow of myosin 2 filaments and contraction of stress fibers. We further checked the effect of SMIFH2 on non-muscle myosin 2A and skeletal muscle myosin 2 in vitro, and found that SMIFH2 inhibits activity of myosin ATPase and the ability to translocate actin filaments in the gliding actin in vitro motility assay. Inhibition of non-muscle myosin 2A in vitro required a higher concentration of SMIFH2 compared with that needed to inhibit retrograde flow and stress fiber contraction in cells. We also found that SMIFH2 inhibits several other non-muscle myosin types, including bovine myosin 10, Drosophila myosin 7a and Drosophila myosin 5, more efficiently than it inhibits formins. These off-target inhibitions demand additional careful analysis in each case when solely SMIFH2 is used to probe formin functions. This article has an associated First Person interview with Yukako Nishimura, joint first author of the paper.
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Affiliation(s)
- Yukako Nishimura
- Mechanobiology Institute (MBI), National University of Singapore, Singapore 117411, Singapore
| | - Shidong Shi
- Mechanobiology Institute (MBI), National University of Singapore, Singapore 117411, Singapore
| | - Fang Zhang
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rong Liu
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Yasuharu Takagi
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexander D Bershadsky
- Mechanobiology Institute (MBI), National University of Singapore, Singapore 117411, Singapore.,Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Virgile Viasnoff
- Mechanobiology Institute (MBI), National University of Singapore, Singapore 117411, Singapore.,CNRS UMI 3639 BMC, Singapore 117411, Singapore.,Department of Biological Sciences, National university of Singapore, Singapore 117558, Singapore
| | - James R Sellers
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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14
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Betaine ameliorates schizophrenic traits by functionally compensating for KIF3-based CRMP2 transport. Cell Rep 2021; 35:108971. [PMID: 33852848 DOI: 10.1016/j.celrep.2021.108971] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 12/22/2020] [Accepted: 03/19/2021] [Indexed: 12/13/2022] Open
Abstract
In schizophrenia (SCZ), neurons in the brain tend to undergo gross morphological changes, but the related molecular mechanism remains largely elusive. Using Kif3b+/- mice as a model with SCZ-like behaviors, we found that a high-betaine diet can significantly alleviate schizophrenic traits related to neuronal morphogenesis and behaviors. According to a deficiency in the transport of collapsin response mediator protein 2 (CRMP2) by the KIF3 motor, we identified a significant reduction in lamellipodial dynamics in developing Kif3b+/- neurons as a cause of neurite hyperbranching. Betaine administration significantly decreases CRMP2 carbonylation, which enhances the F-actin bundling needed for proper lamellipodial dynamics and microtubule exclusion and may thus functionally compensate for KIF3 deficiency. Because the KIF3 expression levels tend to be downregulated in the human prefrontal cortex of the postmortem brains of SCZ patients, this mechanism may partly participate in human SCZ pathogenesis, which we hypothesize could be alleviated by betaine administration.
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15
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Effects of neuronal drebrin on actin dynamics. Biochem Soc Trans 2021; 49:685-692. [PMID: 33739391 DOI: 10.1042/bst20200577] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 02/14/2021] [Accepted: 02/23/2021] [Indexed: 11/17/2022]
Abstract
Drebrin is a key regulator of actin cytoskeleton in neuronal cells which is critical for synaptic plasticity, neuritogenesis, and neuronal migration. It is also known to orchestrate a cross-talk between actin and microtubules. Decreased level of drebrin is a hallmark of multiple neurodegenerative disorders such as Alzheimer's disease. Despite its established importance in health and disease, we still have a lot to learn about drebrin's interactome and its effects on cytoskeletal dynamics. This review aims to summarize the recently reported novel effects of drebrin on actin and its regulators. Here I will also reflect on the most recent progress made in understanding of the role of drebrin isoforms and posttranslational modifications on its functionality.
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16
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A M, Latario CJ, Pickrell LE, Higgs HN. Lysine acetylation of cytoskeletal proteins: Emergence of an actin code. J Biophys Biochem Cytol 2020; 219:211455. [PMID: 33044556 PMCID: PMC7555357 DOI: 10.1083/jcb.202006151] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/26/2020] [Accepted: 09/02/2020] [Indexed: 02/06/2023] Open
Abstract
Reversible lysine acetylation of nuclear proteins such as histones is a long-established important regulatory mechanism for chromatin remodeling and transcription. In the cytoplasm, acetylation of a number of cytoskeletal proteins, including tubulin, cortactin, and the formin mDia2, regulates both cytoskeletal assembly and stability. More recently, acetylation of actin itself was revealed to regulate cytoplasmic actin polymerization through the formin INF2, with downstream effects on ER-to-mitochondrial calcium transfer, mitochondrial fission, and vesicle transport. This finding raises the possibility that actin acetylation, along with other post-translational modifications to actin, might constitute an "actin code," similar to the "histone code" or "tubulin code," controlling functional shifts to these central cellular proteins. Given the multiple roles of actin in nuclear functions, its modifications might also have important roles in gene expression.
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17
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Thompson SB, Sandor AM, Lui V, Chung JW, Waldman MM, Long RA, Estin ML, Matsuda JL, Friedman RS, Jacobelli J. Formin-like 1 mediates effector T cell trafficking to inflammatory sites to enable T cell-mediated autoimmunity. eLife 2020; 9:58046. [PMID: 32510333 PMCID: PMC7308091 DOI: 10.7554/elife.58046] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 06/07/2020] [Indexed: 01/21/2023] Open
Abstract
Lymphocyte migration is essential for the function of the adaptive immune system, and regulation of T cell entry into tissues is an effective therapy in autoimmune diseases. Little is known about the specific role of cytoskeletal effectors that mediate mechanical forces and morphological changes essential for migration in complex environments. We developed a new Formin-like-1 (FMNL1) knock-out mouse model and determined that the cytoskeletal effector FMNL1 is selectively required for effector T cell trafficking to inflamed tissues, without affecting naïve T cell entry into secondary lymphoid organs. Here, we identify a FMNL1-dependent mechanism of actin polymerization at the back of the cell that enables migration of the rigid lymphocyte nucleus through restrictive barriers. Furthermore, FMNL1-deficiency impairs the ability of self-reactive effector T cells to induce autoimmune disease. Overall, our data suggest that FMNL1 may be a potential therapeutic target to specifically modulate T cell trafficking to inflammatory sites.
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Affiliation(s)
- Scott B Thompson
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Adam M Sandor
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Victor Lui
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Jeffrey W Chung
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States.,Barbara Davis Center, University of Colorado School of Medicine, Aurora, United States
| | - Monique M Waldman
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States.,Barbara Davis Center, University of Colorado School of Medicine, Aurora, United States
| | - Robert A Long
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Miriam L Estin
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Jennifer L Matsuda
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States
| | - Rachel S Friedman
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States.,Barbara Davis Center, University of Colorado School of Medicine, Aurora, United States
| | - Jordan Jacobelli
- Department of Biomedical Research, National Jewish Health, Denver, United States.,Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, United States.,Barbara Davis Center, University of Colorado School of Medicine, Aurora, United States
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18
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The podosome cap: past, present, perspective. Eur J Cell Biol 2020; 99:151087. [DOI: 10.1016/j.ejcb.2020.151087] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 05/04/2020] [Accepted: 05/16/2020] [Indexed: 12/22/2022] Open
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19
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van Gisbergen P, Wu SZ, Cheng X, Pattavina KA, Bezanilla M. In vivo analysis of formin dynamics in the moss P. patens reveals functional class diversification. J Cell Sci 2020; 133:jcs233791. [PMID: 31969472 PMCID: PMC10679510 DOI: 10.1242/jcs.233791] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 01/07/2020] [Indexed: 01/02/2023] Open
Abstract
Formins are actin regulators critical for diverse processes across eukaryotes. With many formins in plants and animals, it has been challenging to determine formin function in vivo We found that the phylogenetically distinct class I integral membrane formins (denoted For1) from the moss P.patens enrich at sites of membrane turnover, with For1D more tightly associated with the plasma membrane than For1A. To probe formin function, we generated formin-null lines with greatly reduced formin complexity. We found that For1A and For1D help to anchor actin near the cell apex, with For1A contributing to formation of cytosolic actin, while For1D contributes to plasma membrane-associated actin. At the cortex, For1A and For1D localized to motile puncta and differentially impacted actin dynamics. We found that class I cortical formin mobility depended on microtubules and only moderately on actin, whereas class II formin (denoted For2) mobility solely depended on actin. Moreover, cortical For2A tightly correlated with the puncta labeled by the endocytic membrane dye FM4-64, and null mutants in class I formins did not affect uptake of a similar dye, FM1-43, suggesting that class I and II formins are involved in distinct membrane trafficking pathways.
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Affiliation(s)
- Peter van Gisbergen
- Plant Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA
| | - Shu-Zon Wu
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Xiaohang Cheng
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Kelli A Pattavina
- Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA
| | - Magdalena Bezanilla
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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20
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Miller EW, Blystone SD. The carboxy-terminus of the formin FMNL1ɣ bundles actin to potentiate adenocarcinoma migration. J Cell Biochem 2019; 120:14383-14404. [PMID: 30977161 DOI: 10.1002/jcb.28694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 12/31/2022]
Abstract
The formin family of proteins contributes to spatiotemporal control of actin cytoskeletal rearrangements during motile cell activities. The FMNL subfamily exhibits multiple mechanisms of linear actin filament formation and organization. Here we report novel actin-modifying functions of FMNL1 in breast adenocarcinoma migration models. FMNL1 is required for efficient cell migration and its three isoforms exhibit distinct localization. Suppression of FMNL1 protein expression results in a significant impairment of cell adhesion, migration, and invasion. Overexpression of FMNL1ɣ, but not FMNL1β or FMNL1α, enhances cell adhesion independent of the FH2 domain and FMNL1ɣ rescues migration in cells depleted of all three endogenous isoforms. While FMNL1ɣ inhibits actin assembly in vitro, it facilitates bundling of filamentous actin independent of the FH2 domain. The unique interactions of FMNL1ɣ with filamentous actin provide a new understanding of formin domain functions and its effect on motility of diverse cell types suggest a broader role than previously realized.
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Affiliation(s)
- Eric W Miller
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - Scott D Blystone
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
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21
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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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22
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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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23
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Multiple roles of the actin and microtubule-regulating formins in the developing brain. Neurosci Res 2019; 138:59-69. [DOI: 10.1016/j.neures.2018.09.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 01/08/2023]
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24
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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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25
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Aydin F, Courtemanche N, Pollard TD, Voth GA. Gating mechanisms during actin filament elongation by formins. eLife 2018; 7:37342. [PMID: 30035712 PMCID: PMC6056239 DOI: 10.7554/elife.37342] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2018] [Accepted: 07/01/2018] [Indexed: 02/03/2023] Open
Abstract
Formins play an important role in the polymerization of unbranched actin filaments, and particular formins slow elongation by 5–95%. We studied the interactions between actin and the FH2 domains of formins Cdc12, Bni1 and mDia1 to understand the factors underlying their different rates of polymerization. All-atom molecular dynamics simulations revealed two factors that influence actin filament elongation and correlate with the rates of elongation. First, FH2 domains can sterically block the addition of new actin subunits. Second, FH2 domains flatten the helical twist of the terminal actin subunits, making the end less favorable for subunit addition. Coarse-grained simulations over longer time scales support these conclusions. The simulations show that filaments spend time in states that either allow or block elongation. The rate of elongation is a time-average of the degree to which the formin compromises subunit addition rather than the formin-actin complex literally being in ‘open’ or ‘closed’ states.
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Affiliation(s)
- Fikret Aydin
- Department of Chemistry, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States
| | - Naomi Courtemanche
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, United States.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States
| | - Thomas D Pollard
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, Chicago, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, United States.,James Franck Institute, The University of Chicago, Chicago, United States
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26
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Rottner K, Faix J, Bogdan S, Linder S, Kerkhoff E. Actin assembly mechanisms at a glance. J Cell Sci 2018; 130:3427-3435. [PMID: 29032357 DOI: 10.1242/jcs.206433] [Citation(s) in RCA: 195] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The actin cytoskeleton and associated motor proteins provide the driving forces for establishing the astonishing morphological diversity and dynamics of mammalian cells. Aside from functions in protruding and contracting cell membranes for motility, differentiation or cell division, the actin cytoskeleton provides forces to shape and move intracellular membranes of organelles and vesicles. To establish the many different actin assembly functions required in time and space, actin nucleators are targeted to specific subcellular compartments, thereby restricting the generation of specific actin filament structures to those sites. Recent research has revealed that targeting and activation of actin filament nucleators, elongators and myosin motors are tightly coordinated by conserved protein complexes to orchestrate force generation. In this Cell Science at a Glance article and the accompanying poster, we summarize and discuss the current knowledge on the corresponding protein complexes and their modes of action in actin nucleation, elongation and force generation.
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Affiliation(s)
- Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Jan Faix
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - Sven Bogdan
- Institute for Physiology and Pathophysiology, Department of Molecular Cell Physiology, Philipps-University of Marburg, 35032 Marburg, Germany
| | - Stefan Linder
- Institute for Medical Microbiology, Virology and Hygiene, University Medical Center Eppendorf, 20246 Hamburg, Germany
| | - Eugen Kerkhoff
- Department of Neurology, University Hospital Regensburg, 93053 Regensburg, Germany
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27
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NAA80 is actin's N-terminal acetyltransferase and regulates cytoskeleton assembly and cell motility. Proc Natl Acad Sci U S A 2018; 115:4399-4404. [PMID: 29581253 PMCID: PMC5924898 DOI: 10.1073/pnas.1718336115] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
More than 80% of human proteins are N-terminal (Nt)–acetylated during translation. In contrast, actin, the most abundant protein in the cytoplasm of animal cells, is Nt-acetylated posttranslationally and following a unique multistep mechanism that has remained poorly characterized. Here, we describe the discovery of actin’s N-terminal acetyltransferase (NAT), NAA80. We further demonstrate that actin Nt-acetylation plays essential roles in filament assembly, cytoskeleton organization, and cell motility, resulting in a net increase in the ratio of monomeric to filamentous actin and fewer lamellipodia and filopodia. These effects converge to reduce cell hypermotility. This work establishes the role of Nt-acetylation for the most abundant cytoskeletal protein in animals and reveals a NAT acting posttranslationally and on a single dedicated substrate. Actin, one of the most abundant proteins in nature, participates in countless cellular functions ranging from organelle trafficking and pathogen motility to cell migration and regulation of gene transcription. Actin’s cellular activities depend on the dynamic transition between its monomeric and filamentous forms, a process exquisitely regulated in cells by a large number of actin-binding and signaling proteins. Additionally, several posttranslational modifications control the cellular functions of actin, including most notably N-terminal (Nt)-acetylation, a prevalent modification throughout the animal kingdom. However, the biological role and mechanism of actin Nt-acetylation are poorly understood, and the identity of actin’s N-terminal acetyltransferase (NAT) has remained a mystery. Here, we reveal that NAA80, a suggested NAT enzyme whose substrate specificity had not been characterized, is Nt-acetylating actin. We further show that actin Nt-acetylation plays crucial roles in cytoskeletal assembly in vitro and in cells. The absence of Nt-acetylation leads to significant differences in the rates of actin filament depolymerization and elongation, including elongation driven by formins, whereas filament nucleation by the Arp2/3 complex is mostly unaffected. NAA80-knockout cells display severely altered cytoskeletal organization, including an increase in the ratio of filamentous to globular actin, increased filopodia and lamellipodia formation, and accelerated cell motility. Together, the results demonstrate NAA80’s role as actin’s NAT and reveal a crucial role for actin Nt-acetylation in the control of cytoskeleton structure and dynamics.
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Fernández-Barrera J, Bernabé-Rubio M, Casares-Arias J, Rangel L, Fernández-Martín L, Correas I, Alonso MA. The actin-MRTF-SRF transcriptional circuit controls tubulin acetylation via α-TAT1 gene expression. J Cell Biol 2018; 217:929-944. [PMID: 29321169 PMCID: PMC5839776 DOI: 10.1083/jcb.201702157] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 06/28/2017] [Accepted: 12/11/2017] [Indexed: 02/07/2023] Open
Abstract
The role of formins in microtubules is not well understood. In this study, we have investigated the mechanism by which INF2, a formin mutated in degenerative renal and neurological hereditary disorders, controls microtubule acetylation. We found that silencing of INF2 in epithelial RPE-1 cells produced a dramatic drop in tubulin acetylation, increased the G-actin/F-actin ratio, and impaired myocardin-related transcription factor (MRTF)/serum response factor (SRF)-dependent transcription, which is known to be repressed by increased levels of G-actin. The effect on tubulin acetylation was caused by the almost complete absence of α-tubulin acetyltransferase 1 (α-TAT1) messenger RNA (mRNA). Activation of the MRTF-SRF transcriptional complex restored α-TAT1 mRNA levels and tubulin acetylation. Several functional MRTF-SRF-responsive elements were consistently identified in the α-TAT1 gene. The effect of INF2 silencing on microtubule acetylation was also observed in epithelial ECV304 cells, but not in Jurkat T cells. Therefore, the actin-MRTF-SRF circuit controls α-TAT1 transcription. INF2 regulates the circuit, and hence microtubule acetylation, in cell types where it has a prominent role in actin polymerization.
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Affiliation(s)
- Jaime Fernández-Barrera
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel Bernabé-Rubio
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Javier Casares-Arias
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Laura Rangel
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain.,Department of Molecular Biology, Universidad Autónoma de Madrid, Madrid, Spain
| | - Laura Fernández-Martín
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
| | - Isabel Correas
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain.,Department of Molecular Biology, Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel A Alonso
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Madrid, Spain
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Dvorak KM, Pettee KM, Rubinic-Minotti K, Su R, Nestor-Kalinoski A, Eisenmann KM. Carcinoma associated fibroblasts (CAFs) promote breast cancer motility by suppressing mammalian Diaphanous-related formin-2 (mDia2). PLoS One 2018; 13:e0195278. [PMID: 29596520 PMCID: PMC5875872 DOI: 10.1371/journal.pone.0195278] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 03/19/2018] [Indexed: 12/21/2022] Open
Abstract
The tumor microenvironment (TME) promotes tumor cell invasion and metastasis. An important step in the shift to a pro-cancerous microenvironment is the transformation of normal stromal fibroblasts to carcinoma-associated fibroblasts (CAFs). CAFs are present in a majority of solid tumors and can directly promote tumor cell motility via cytokine, chemokine and growth factor secretion into the TME. The exact effects that the TME has upon cytoskeletal regulation in motile tumor cells remain enigmatic. The conserved formin family of cytoskeleton regulating proteins plays an essential role in the assembly and/or bundling of unbranched actin filaments. Mammalian Diaphanous-related formin 2 (mDia2/DIAPH3/Drf3/Dia) assembles a dynamic F-actin cytoskeleton that underlies tumor cell migration and invasion. We therefore sought to understand whether CAF-derived chemokines impact breast tumor cell motility through modification of the formin-assembled F-actin cytoskeleton. In MDA-MB-231 cells, conditioned media (CM) from WS19T CAFs, a human breast tumor-adjacent CAF line, significantly and robustly increased wound closure and invasion relative to normal human mammary fibroblast (HMF)-CM. WS19T-CM also promoted proteasome-mediated mDia2 degradation in MDA-MB-231 cells relative to control HMF-CM and WS21T CAF-CM, a breast CAF cell line that failed to promote robust MDA-MB-231 migration. Cytokine array analysis of CM identified up-regulated secreted factors in WS19T relative to control WS21T CM. We identified CXCL12 as a CM factor influencing loss of mDia2 protein while increasing MDA-MB-231 cell migration. Our data suggest a mechanism whereby CAFs promote tumor cell migration and invasion through CXCL12 secretion to regulate the mDia2-directed cytoskeleton in breast tumor cells.
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Affiliation(s)
- Kaitlyn M. Dvorak
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
| | - Krista M. Pettee
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
| | - Kaitlin Rubinic-Minotti
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
| | - Robin Su
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
| | - Andrea Nestor-Kalinoski
- Department of Surgery, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
| | - Kathryn M. Eisenmann
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, Ohio, United States of America
- * E-mail:
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30
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Silkworth WT, Kunes KL, Nickel GC, Phillips ML, Quinlan ME, Vizcarra CL. The neuron-specific formin Delphilin nucleates nonmuscle actin but does not enhance elongation. Mol Biol Cell 2017; 29:610-621. [PMID: 29282276 PMCID: PMC6004577 DOI: 10.1091/mbc.e17-06-0363] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 12/06/2017] [Accepted: 12/22/2017] [Indexed: 12/11/2022] Open
Abstract
The formin Delphilin binds the glutamate receptor, GluRδ2, in dendritic spines of Purkinje cells. Both proteins play a role in learning. To understand how Delphilin functions in neurons, we studied the actin assembly properties of this formin. Formins have a conserved formin homology 2 domain, which nucleates and associates with the fast-growing end of actin filaments, influencing filament growth together with the formin homology 1 (FH1) domain. The strength of nucleation and elongation varies widely across formins. Additionally, most formins have conserved domains that regulate actin assembly through an intramolecular interaction. Delphilin is distinct from other formins in several ways: its expression is limited to Purkinje cells, it lacks classical autoinhibitory domains, and its FH1 domain has minimal proline-rich sequence. We found that Delphilin is an actin nucleator that does not accelerate elongation, although it binds to the barbed end of filaments. In addition, Delphilin exhibits a preference for actin isoforms, nucleating nonmuscle actin but not muscle actin, which has not been described or systematically studied in other formins. Finally, Delphilin is the first formin studied that is not regulated by intramolecular interactions. We speculate how the activity we observe is consistent with its localization in the small dendritic spines.
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Affiliation(s)
- William T Silkworth
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Kristina L Kunes
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Grace C Nickel
- Department of Chemistry, Barnard College, New York, NY 10027
| | - Martin L Phillips
- 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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31
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Pfisterer SG, Gateva G, Horvath P, Pirhonen J, Salo VT, Karhinen L, Varjosalo M, Ryhänen SJ, Lappalainen P, Ikonen E. Role for formin-like 1-dependent acto-myosin assembly in lipid droplet dynamics and lipid storage. Nat Commun 2017; 8:14858. [PMID: 28361956 PMCID: PMC5380971 DOI: 10.1038/ncomms14858] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 02/01/2017] [Indexed: 11/10/2022] Open
Abstract
Lipid droplets (LDs) are cellular organelles specialized in triacylglycerol (TG) storage undergoing homotypic clustering and fusion. In non-adipocytic cells with numerous LDs this is balanced by poorly understood droplet dissociation mechanisms. We identify non-muscle myosin IIa (NMIIa/MYH-9) and formin-like 1 (FMNL1) in the LD proteome. NMIIa and actin filaments concentrate around LDs, and form transient foci between dissociating LDs. NMIIa depletion results in decreased LD dissociations, enlarged LDs, decreased hydrolysis and increased storage of TGs. FMNL1 is required for actin assembly on LDs in vitro and for NMIIa recruitment to LDs in cells. We propose a novel acto-myosin structure regulating lipid storage: FMNL1-dependent assembly of myosin II-functionalized actin filaments on LDs facilitates their dissociation, thereby affecting LD surface-to-volume ratio and enzyme accessibility to TGs. In neutrophilic leucocytes from MYH9-related disease patients NMIIa inclusions are accompanied by increased lipid storage in droplets, suggesting that NMIIa dysfunction may contribute to lipid imbalance in man.
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Affiliation(s)
- Simon G. Pfisterer
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland
- Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland
| | - Gergana Gateva
- Institute of Biotechnology, University of Helsinki, Helsinki 00790, Finland
| | - Peter Horvath
- Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki 00290, Finland
- Synthetic and Systems Biology Unit, Hungarian Academy of Sciences, BRC, Szeged H-6726, Hungary
| | - Juho Pirhonen
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland
- Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland
| | - Veijo T. Salo
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland
- Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland
| | - Leena Karhinen
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland
| | - Markku Varjosalo
- Institute of Biotechnology, University of Helsinki, Helsinki 00790, Finland
| | - Samppa J. Ryhänen
- Division of Hematology-Oncology and Stem Cell Transplantation, Children's Hospital, Helsinki University Central Hospital and University of Helsinki, Helsinki 00290, Finland
| | - Pekka Lappalainen
- Institute of Biotechnology, University of Helsinki, Helsinki 00790, Finland
| | - Elina Ikonen
- Department of Anatomy and Research Programs Unit, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland
- Minerva Foundation Institute for Medical Research, Helsinki 00290, Finland
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32
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Miller MR, Miller EW, Blystone SD. Non-canonical activity of the podosomal formin FMNL1γ supports immune cell migration. J Cell Sci 2017; 130:1730-1739. [PMID: 28348104 DOI: 10.1242/jcs.195099] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 03/16/2017] [Indexed: 12/14/2022] Open
Abstract
Having previously located the formin FMNL1 in macrophage podosomes, we developed an in vivo model to assess the role of FMNL1 in the migration activities of primary macrophages. Deletion of FMNL1 in mice was genetically lethal; however, targeted deletion in macrophages was achieved by employing macrophage-specific Cre. Unchallenged FMNL1-deficient mice exhibited an unexpected reduction in tissue-resident macrophages despite normal blood monocyte numbers. Upon immune stimulus, the absence of FMNL1 resulted in reduced macrophage recruitment in vivo, decreased migration in two-dimensional in vitro culture and a decrease in the number of macrophages exhibiting podosomes. Of the three described isoforms of FMNL1 - α, β and γ - only FMNL1γ rescued macrophage migration when expressed exogenously in depleted macrophages. Surprisingly, mutation of residues in the FH2 domain of FMNL1γ that disrupt barbed-end actin binding did not limit rescue of macrophage migration and podosome numbers. These observations suggest that FMNL1 contributes to macrophage migration activity by stabilizing the lifespan of podosomes without interaction of fast-growing actin termini.
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Affiliation(s)
- Matthew R Miller
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, NY 13210, USA
| | - Eric W Miller
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, NY 13210, USA
| | - Scott D Blystone
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, NY 13210, USA
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33
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Dimchev G, Steffen A, Kage F, Dimchev V, Pernier J, Carlier MF, Rottner K. Efficiency of lamellipodia protrusion is determined by the extent of cytosolic actin assembly. Mol Biol Cell 2017; 28:1311-1325. [PMID: 28331069 PMCID: PMC5426846 DOI: 10.1091/mbc.e16-05-0334] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 02/10/2017] [Accepted: 03/17/2017] [Indexed: 11/26/2022] Open
Abstract
Lamellipodia protrusion requires actin network formation driven by the Arp2/3 complex and its upstream regulators WAVE complex and Rac. Actin assembly factors of the formin and Ena/VASP families can influence protrusion, in particular by maintaining a balance between lamellipodial and cytosolic actin filament assembly. Cell migration and cell–cell communication involve the protrusion of actin-rich cell surface projections such as lamellipodia and filopodia. Lamellipodia are networks of actin filaments generated and turned over by filament branching through the Arp2/3 complex. Inhibition of branching is commonly agreed to eliminate formation and maintenance of lamellipodial actin networks, but the regulation of nucleation or elongation of Arp2/3-independent filament populations within the network by, for example, formins or Ena/VASP family members and its influence on the effectiveness of protrusion have been unclear. Here we analyzed the effects of a set of distinct formin fragments and VASP on site-specific, lamellipodial versus cytosolic actin assembly and resulting consequences on protrusion. Surprisingly, expression of formin variants but not VASP reduced lamellipodial protrusion in B16-F1 cells, albeit to variable extents. The rates of actin network polymerization followed a similar trend. Unexpectedly, the degree of inhibition of both parameters depended on the extent of cytosolic but not lamellipodial actin assembly. Indeed, excess cytosolic actin assembly prevented actin monomer from rapid translocation to and efficient incorporation into lamellipodia. Thus, as opposed to sole regulation by actin polymerases operating at their tips, the protrusion efficiency of lamellipodia is determined by a finely tuned balance between lamellipodial and cytosolic actin assembly.
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Affiliation(s)
- Georgi Dimchev
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Anika Steffen
- Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Frieda Kage
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Vanessa Dimchev
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany.,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
| | - Julien Pernier
- Cytoskeleton Dynamics and Motility, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette, France
| | - Marie-France Carlier
- Cytoskeleton Dynamics and Motility, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette, France
| | - Klemens Rottner
- Division of Molecular Cell Biology, Zoological Institute, Technische Universität Braunschweig, 38106 Braunschweig, Germany .,Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany
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34
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Formin like 1 expression is increased on CD4+ T lymphocytes in spontaneous autoimmune uveitis. J Proteomics 2017; 154:102-108. [DOI: 10.1016/j.jprot.2016.12.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 12/22/2016] [Accepted: 12/27/2016] [Indexed: 12/27/2022]
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35
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Johnson S, Rahmani R, Drew DR, Williams MJ, Wilkinson M, Tan YH, Huang JX, Tonkin CJ, Beeson JG, Baum J, Smith BJ, Baell JB. Truncated Latrunculins as Actin Inhibitors Targeting Plasmodium falciparum Motility and Host Cell Invasion. J Med Chem 2016; 59:10994-11005. [PMID: 28002959 DOI: 10.1021/acs.jmedchem.6b01109] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Polymerization of the cytosolic protein actin is critical to cell movement and host cell invasion by the malaria parasite, Plasmodium falciparum. Any disruption to actin polymerization dynamics will render the parasite incapable of invading a host cell and thereby unable to cause infection. Here, we explore the potential of using truncated latrunculins as potential chemotherapeutics for the treatment of malaria. Exploration of the binding interactions of the natural actin inhibitor latrunculins with actin revealed how a truncated core of the inhibitor could retain its key interaction features with actin. This truncated core was synthesized and subjected to preliminary structure-activity relationship studies to generate a focused set of analogues. Biochemical analyses of these analogues demonstrate their 6-fold increased activity compared with that of latrunculin B against P. falciparum and a 16-fold improved selectivity ex vivo. These data establish the latrunculin core as a potential focus for future structure-based drug design of chemotherapeutics against malaria.
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Affiliation(s)
- Swapna Johnson
- La Trobe Institute for Molecular Science, La Trobe University , Melbourne, Victoria 3086, Australia.,Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, Victoria 3052, Australia
| | - Raphaël Rahmani
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, Victoria 3052, Australia
| | - Damien R Drew
- Burnet Institute , 85 Commercial Rd, Melbourne Victoria 3004, Australia.,Central Clinical School and Department of Microbiology, Monash University , Melbourne, Victoria 3004, Australia
| | - Melanie J Williams
- Walter and Eliza Hall Institute , 1G Royal Parade, Parkville, Victoria 3052, Australia.,The Department of Medical Biology, The University of Melbourne , Melbourne, Victoria 3010, Australia
| | - Mark Wilkinson
- Department of Life Sciences, Imperial College London , South Kensington SW7 2AZ, United Kingdom
| | - Yan Hong Tan
- Walter and Eliza Hall Institute , 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Life Sciences, Imperial College London , South Kensington SW7 2AZ, United Kingdom
| | - Johnny X Huang
- Institute for Molecular Bioscience, The University of Queensland , St Lucia, Queensland 4072, Australia
| | - Christopher J Tonkin
- Walter and Eliza Hall Institute , 1G Royal Parade, Parkville, Victoria 3052, Australia.,The Department of Medical Biology, The University of Melbourne , Melbourne, Victoria 3010, Australia
| | - James G Beeson
- Burnet Institute , 85 Commercial Rd, Melbourne Victoria 3004, Australia.,Central Clinical School and Department of Microbiology, Monash University , Melbourne, Victoria 3004, Australia
| | - Jake Baum
- Walter and Eliza Hall Institute , 1G Royal Parade, Parkville, Victoria 3052, Australia.,Department of Life Sciences, Imperial College London , South Kensington SW7 2AZ, United Kingdom
| | - Brian J Smith
- La Trobe Institute for Molecular Science, La Trobe University , Melbourne, Victoria 3086, Australia
| | - Jonathan B Baell
- Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, Victoria 3052, Australia
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36
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Shwartz A, Dhanyasi N, Schejter ED, Shilo BZ. The Drosophila formin Fhos is a primary mediator of sarcomeric thin-filament array assembly. eLife 2016; 5. [PMID: 27731794 PMCID: PMC5061545 DOI: 10.7554/elife.16540] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 09/15/2016] [Indexed: 01/26/2023] Open
Abstract
Actin-based thin filament arrays constitute a fundamental core component of muscle sarcomeres. We have used formation of the Drosophila indirect flight musculature for studying the assembly and maturation of thin-filament arrays in a skeletal muscle model system. Employing GFP-tagged actin monomer incorporation, we identify several distinct phases in the dynamic construction of thin-filament arrays. This sequence includes assembly of nascent arrays after an initial period of intensive microfilament synthesis, followed by array elongation, primarily from filament pointed-ends, radial growth of the arrays via recruitment of peripheral filaments and continuous barbed-end turnover. Using genetic approaches we have identified Fhos, the single Drosophila homolog of the FHOD sub-family of formins, as a primary and versatile mediator of IFM thin-filament organization. Localization of Fhos to the barbed-ends of the arrays, achieved via a novel N-terminal domain, appears to be a critical aspect of its sarcomeric roles. DOI:http://dx.doi.org/10.7554/eLife.16540.001 Muscles owe their ability to contract to structural units called sarcomeres, and a single muscle fiber can contain many thousands of these structures, aligned one next to the other. Each mature sarcomere is made up of precisely arranged and intertwined thin filaments of actin and thicker bundles of motor proteins, surrounded by other proteins. Sliding the motors along the filaments provides the force needed to contract the muscle. However, it was far from clear how sarcomeres, especially the arrays of thin-filaments, are assembled from scratch in developing muscles. When the fruit fly Drosophila transforms from a larva into an adult, it needs to build muscles to move its newly forming wings. While smaller in size, these flight muscles closely resemble the skeletal muscles of animals with backbones, and therefore serve as a good model for muscle formation in general. New muscles require new sarcomeres too, and now Shwartz et al. have observed and monitored sarcomeres assembling in developing flight muscles of fruit flies, a process that takes about three days. The analysis made use of genetically engineered flies in which the gene for a fluorescently labeled version of actin, the building block of the thin filaments, could be switched on at specific points in time. Looking at how these green-glowing proteins become incorporated into the growing sarcomere revealed that the assembly process involves four different phases. First, a large store of unorganized and newly-made thin filaments is generated for future use. These filaments are then assembled into rudimentary structures in which the filaments are roughly aligned. Once these core structures are formed, the existing filaments are elongated, while additional filaments are brought in to expand the structure further. Finally, actin proteins are continuously added and removed at the part of the sarcomere where the thin filaments are anchored. Shwartz et al. went on to identify a protein termed Fhos as the chief player in the process. Fhos is a member of a family of proteins that are known to elongate and organize actin filaments in many different settings. Without Fhos, the thin-filament arrays cannot properly begin to assemble, and the subsequent steps of growth and expansion are blocked as well. The next challenges will be to understand what guides the initial stages in the assembly of the thin-filament array, and how the coordination between assembly of actin filament arrays and motor proteins is executed. It will also be important to determine how sarcomeres are maintained throughout the life of the organism when defective actin filaments are replaced, and which proteins are responsible for carrying out this process. DOI:http://dx.doi.org/10.7554/eLife.16540.002
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Affiliation(s)
- Arkadi Shwartz
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Nagaraju Dhanyasi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Eyal D Schejter
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Ben-Zion Shilo
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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37
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Van Audenhove I, Denert M, Boucherie C, Pieters L, Cornelissen M, Gettemans J. Fascin Rigidity and L-plastin Flexibility Cooperate in Cancer Cell Invadopodia and Filopodia. J Biol Chem 2016; 291:9148-60. [PMID: 26945069 DOI: 10.1074/jbc.m115.706937] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Indexed: 01/15/2023] Open
Abstract
Invadopodia and filopodia are dynamic, actin-based protrusions contributing to cancer cell migration, invasion, and metastasis. The force of actin bundles is essential for their protrusive activity. The bundling protein fascin is known to play a role in both invadopodia and filopodia. As it is more and more acknowledged that functionally related proteins cooperate, it is unlikely that only fascin bundles actin in these protrusions. Another interesting candidate is L-plastin, normally expressed in hematopoietic cells, but considered a common marker of many cancer types. We identified L-plastin as a new component of invadopodia, where it contributes to degradation and invasiveness. By means of specific, high-affinity nanobodies inhibiting bundling of fascin or L-plastin, we further unraveled their cooperative mode of action. We show that the bundlers cannot compensate for each other due to strikingly different bundling characteristics: L-plastin bundles are much thinner and less tightly packed. Composite bundles adopt an intermediate phenotype, with fascin delivering the rigidity and strength for protrusive force and structural stability, whereas L-plastin accounts for the flexibility needed for elongation. Consistent with this, elevated L-plastin expression promotes elongation and reduces protrusion density in cells with relatively lower L-plastin than fascin levels.
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Affiliation(s)
| | | | | | - Leen Pieters
- Basic Medical Science, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Maria Cornelissen
- Basic Medical Science, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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Sahasrabudhe A, Ghate K, Mutalik S, Jacob A, Ghose A. Formin 2 regulates the stabilization of filopodial tip adhesions in growth cones and affects neuronal outgrowth and pathfinding in vivo. Development 2015; 143:449-60. [PMID: 26718007 DOI: 10.1242/dev.130104] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/23/2015] [Indexed: 12/28/2022]
Abstract
Growth cone filopodia are actin-based mechanosensory structures that are essential for chemoreception and the generation of contractile forces necessary for directional motility. However, little is known about the influence of filopodial actin structures on substrate adhesion and filopodial contractility. Formin 2 (Fmn2) localizes along filopodial actin bundles and its depletion does not affect filopodia initiation or elongation. However, Fmn2 activity is required for filopodial tip adhesion maturation and the ability of filopodia to generate traction forces. Dysregulation of filopodia in Fmn2-depleted neurons leads to compromised growth cone motility. Additionally, in mouse fibroblasts, Fmn2 regulates ventral stress fiber assembly and affects the stability of focal adhesions. In the developing chick spinal cord, Fmn2 activity is required cell-autonomously for the outgrowth and pathfinding of spinal commissural neurons. Our results reveal an unanticipated function for Fmn2 in neural development. Fmn2 regulates structurally diverse bundled actin structures, parallel filopodial bundles in growth cones and anti-parallel stress fibers in fibroblasts, in turn modulating the stability of substrate adhesions. We propose Fmn2 as a mediator of actin bundle integrity, enabling efficient force transmission to the adhesion sites.
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Affiliation(s)
- Abhishek Sahasrabudhe
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ketakee Ghate
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Sampada Mutalik
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ajesh Jacob
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Aurnab Ghose
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
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Young LE, Heimsath EG, Higgs HN. Cell type-dependent mechanisms for formin-mediated assembly of filopodia. Mol Biol Cell 2015; 26:4646-59. [PMID: 26446836 PMCID: PMC4678021 DOI: 10.1091/mbc.e15-09-0626] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 10/01/2015] [Indexed: 11/11/2022] Open
Abstract
Filopodia are finger-like protrusions from the plasma membrane and are of fundamental importance to cellular physiology, but the mechanisms governing their assembly are still in question. One model, called convergent elongation, proposes that filopodia arise from Arp2/3 complex-nucleated dendritic actin networks, with factors such as formins elongating these filaments into filopodia. We test this model using constitutively active constructs of two formins, FMNL3 and mDia2. Surprisingly, filopodial assembly requirements differ between suspension and adherent cells. In suspension cells, Arp2/3 complex is required for filopodial assembly through either formin. In contrast, a subset of filopodia remains after Arp2/3 complex inhibition in adherent cells. In adherent cells only, mDia1 and VASP also contribute to filopodial assembly, and filopodia are disproportionately associated with focal adhesions. We propose an extension of the existing models for filopodial assembly in which any cluster of actin filament barbed ends in proximity to the plasma membrane, either Arp2/3 complex dependent or independent, can initiate filopodial assembly by specific formins.
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Affiliation(s)
- Lorna E Young
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Ernest G Heimsath
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Henry N Higgs
- Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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Addepalli B, Lesner NP, Limbach PA. Detection of RNA nucleoside modifications with the uridine-specific ribonuclease MC1 from Momordica charantia. RNA (NEW YORK, N.Y.) 2015; 21:1746-1756. [PMID: 26221047 PMCID: PMC4574751 DOI: 10.1261/rna.052472.115] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 06/28/2015] [Indexed: 06/06/2023]
Abstract
A codon-optimized recombinant ribonuclease, MC1 is characterized for its uridine-specific cleavage ability to map nucleoside modifications in RNA. The published MC1 amino acid sequence, as noted in a previous study, was used as a template to construct a synthetic gene with a natural codon bias favoring expression in Escherichia coli. Following optimization of various expression conditions, the active recombinant ribonuclease was successfully purified as a C-terminal His-tag fusion protein from E. coli [Rosetta 2(DE3)] cells. The isolated protein was tested for its ribonuclease activity against oligoribonucleotides and commercially available E. coli tRNA(Tyr I). Analysis of MC1 digestion products by ion-pairing reverse phase liquid-chromatography coupled with mass spectrometry (IP-RP-LC-MS) revealed enzymatic cleavage of RNA at the 5'-termini of uridine and pseudouridine, but cleavage was absent if the uridine was chemically modified or preceded by a nucleoside with a bulky modification. Furthermore, the utility of this enzyme to generate complementary digestion products to other common endonucleases, such as RNase T1, which enables the unambiguous mapping of modified residues in RNA is demonstrated.
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Affiliation(s)
- Balasubrahmanym Addepalli
- Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, USA
| | - Nicholas P Lesner
- Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, USA Department of Chemistry, The College of Wooster, Wooster, Ohio 44691-2393, USA
| | - Patrick A Limbach
- Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221-0172, USA
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The Formin DAAM Functions as Molecular Effector of the Planar Cell Polarity Pathway during Axonal Development in Drosophila. J Neurosci 2015; 35:10154-67. [PMID: 26180192 DOI: 10.1523/jneurosci.3708-14.2015] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent studies established that the planar cell polarity (PCP) pathway is critical for various aspects of nervous system development and function, including axonal guidance. Although it seems clear that PCP signaling regulates actin dynamics, the mechanisms through which this occurs remain elusive. Here, we establish a functional link between the PCP system and one specific actin regulator, the formin DAAM, which has previously been shown to be required for embryonic axonal morphogenesis and filopodia formation in the growth cone. We show that dDAAM also plays a pivotal role during axonal growth and guidance in the adult Drosophila mushroom body, a brain center for learning and memory. By using a combination of genetic and biochemical assays, we demonstrate that Wnt5 and the PCP signaling proteins Frizzled, Strabismus, and Dishevelled act in concert with the small GTPase Rac1 to activate the actin assembly functions of dDAAM essential for correct targeting of mushroom body axons. Collectively, these data suggest that dDAAM is used as a major molecular effector of the PCP guidance pathway. By uncovering a signaling system from the Wnt5 guidance cue to an actin assembly factor, we propose that the Wnt5/PCP navigation system is linked by dDAAM to the regulation of the growth cone actin cytoskeleton, and thereby growth cone behavior, in a direct way.
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Arden JD, Lavik KI, Rubinic KA, Chiaia N, Khuder SA, Howard MJ, Nestor-Kalinoski AL, Alberts AS, Eisenmann KM. Small-molecule agonists of mammalian Diaphanous-related (mDia) formins reveal an effective glioblastoma anti-invasion strategy. Mol Biol Cell 2015; 26:3704-18. [PMID: 26354425 PMCID: PMC4626057 DOI: 10.1091/mbc.e14-11-1502] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 09/04/2015] [Indexed: 12/26/2022] Open
Abstract
Formin agonists impede the most dangerous aspect of glioblastoma—tumor spread into surrounding healthy tissue. Formin activation impairs a novel aspect of the transformed cell and informs the development of antitumor strategies for a cancer needing a more effective therapy. The extensive invasive capacity of glioblastoma (GBM) makes it resistant to surgery, radiotherapy, and chemotherapy and thus makes it lethal. In vivo, GBM invasion is mediated by Rho GTPases through unidentified downstream effectors. Mammalian Diaphanous (mDia) family formins are Rho-directed effectors that regulate the F-actin cytoskeleton to support tumor cell motility. Historically, anti-invasion strategies focused upon mDia inhibition, whereas activation remained unexplored. The recent development of small molecules directly inhibiting or activating mDia-driven F-actin assembly that supports motility allows for exploration of their role in GBM. We used the formin inhibitor SMIFH2 and mDia agonists IMM-01/-02 and mDia2-DAD peptides, which disrupt autoinhibition, to examine the roles of mDia inactivation versus activation in GBM cell migration and invasion in vitro and in an ex vivo brain slice invasion model. Inhibiting mDia suppressed directional migration and spheroid invasion while preserving intrinsic random migration. mDia agonism abrogated both random intrinsic and directional migration and halted U87 spheroid invasion in ex vivo brain slices. Thus mDia agonism is a superior GBM anti-invasion strategy. We conclude that formin agonism impedes the most dangerous GBM component—tumor spread into surrounding healthy tissue. Formin activation impairs novel aspects of transformed cells and informs the development of anti-GBM invasion strategies.
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Affiliation(s)
- Jessica D Arden
- Department of Biochemistry and Cancer Biology, University of Toledo Health Science Campus, Toledo, OH 43614
| | - Kari I Lavik
- Department of Biochemistry and Cancer Biology, University of Toledo Health Science Campus, Toledo, OH 43614
| | - Kaitlin A Rubinic
- Department of Biochemistry and Cancer Biology, University of Toledo Health Science Campus, Toledo, OH 43614
| | - Nicolas Chiaia
- Department of Neurosciences, University of Toledo Health Science Campus, Toledo, OH 43614
| | - Sadik A Khuder
- Departments of Medicine and Public Health and Homeland Security, University of Toledo Health Science Campus, Toledo, OH 43614
| | - Marthe J Howard
- Department of Neurosciences, University of Toledo Health Science Campus, Toledo, OH 43614
| | | | - Arthur S Alberts
- Laboratory of Cell Structure and Signal Integration, Van Andel Research Institute, Grand Rapids, MI 49503
| | - Kathryn M Eisenmann
- Department of Biochemistry and Cancer Biology, University of Toledo Health Science Campus, Toledo, OH 43614 )
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Miller MR, Blystone SD. Reliable and inexpensive expression of large, tagged, exogenous proteins in murine bone marrow-derived macrophages using a second generation lentiviral system. J Biol Methods 2015; 2:e23. [PMID: 26457319 DOI: 10.14440/jbm.2015.66] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Over the past two decades, researchers have struggled to efficiently express foreign DNA in primary macrophages, impeding research progress. The applications of lipofection, electroporation, microinjection, and viral-mediated transfer typically result in disruptions in macrophage differentiation and function, low expression levels of exogenous proteins, limited efficiency and high cell mortality. In this report, after extensive optimization, we present a method of expressing large tagged proteins at high efficiency, consistency, and low cost using lentiviral infection. This method utilizes laboratory-propagated second generation plasmids to produce efficient virus that can be stored for later use. The expression of proteins up to 150 kDa in size is achieved in 30-70% of cells while maintaining normal macrophage differentiation and morphology as determined by fluorescence microscopy and Western blot analysis. This manuscript delineates the reagents and methods used to produce lentivirus to express exogenous DNA in murine bone marrow-derived macrophages sufficient for single cell microscopy as well as functional assays requiring large numbers of murine bone marrow-derived macrophages.
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Affiliation(s)
- Matthew R Miller
- Department of Cell & Developmental Biology, SUNY Upstate Medical University, 750 East Adams St. Syracuse, NY 13210, USA
| | - Scott D Blystone
- Department of Cell & Developmental Biology, SUNY Upstate Medical University, 750 East Adams St. Syracuse, NY 13210, USA
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Qu Z, Silvan U, Jockusch BM, Aebi U, Schoenenberger CA, Mannherz HG. Distinct actin oligomers modulate differently the activity of actin nucleators. FEBS J 2015. [DOI: 10.1111/febs.13381] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Zheng Qu
- Department of Anatomy and Molecular Embryology; Ruhr-University; Bochum Germany
| | - Unai Silvan
- Institute for Biomechanics; Balgrist University Hospital; ETH and University of Zürich; Switzerland
| | - Brigitte M. Jockusch
- Department of Cell Biology; Institute of Zoology; Technical University; Braunschweig Germany
| | - Ueli Aebi
- Focal Area Structural Biology and Biophysics; Biozentrum; University of Basel; Switzerland
| | | | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology; Ruhr-University; Bochum Germany
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45
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Lu Q, Schafer DA, Adler PN. The Drosophila planar polarity gene multiple wing hairs directly regulates the actin cytoskeleton. Development 2015; 142:2478-86. [PMID: 26153232 DOI: 10.1242/dev.122119] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/29/2015] [Indexed: 01/18/2023]
Abstract
The evolutionarily conserved frizzled/starry night (fz/stan) pathway regulates planar cell polarity (PCP) in vertebrates and invertebrates. This pathway has been extensively studied in the Drosophila wing, where it is manifested by an array of distally pointing cuticular hairs. Using in vivo imaging we found that, early in hair growth, cells have multiple actin bundles and hairs that subsequently fuse into a single growing hair. The downstream PCP gene multiple wing hairs (mwh) plays a key role in this process and acts to antagonize the actin cytoskeleton. In mwh mutants hair initiation is not limited to a small region at the distal edge of pupal wing cells as in wild type, resulting in multiple hairs with aberrant polarity. Extra actin bundles/hairs are formed and do not completely fuse, in contrast to wild type. As development proceeded additional hairs continued to form, further increasing hair number. We identified a fragment of Mwh with in vivo rescue activity and that bound and bundled F-actin filaments and inhibited actin polymerization in in vitro actin assays. The loss of these activities can explain the mwh mutant phenotype. Our data suggest a model whereby, prior to hair initiation, proximally localized Mwh inhibits actin polymerization resulting in polarized activation of the cytoskeleton and hair formation on the distal side of wing cells. During hair growth Mwh is found in growing hairs, where we suggest it functions to promote the fusion of actin bundles and inhibit the formation of additional actin bundles that could lead to extra hairs.
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Affiliation(s)
- Qiuheng Lu
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Dorothy A Schafer
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Paul N Adler
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, VA 22904, USA
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46
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Wang F, Zhang L, Duan X, Zhang GL, Wang ZB, Wang Q, Xiong B, Sun SC. RhoA-mediated FMNL1 regulates GM130 for actin assembly and phosphorylates MAPK for spindle formation in mouse oocyte meiosis. Cell Cycle 2015; 14:2835-43. [PMID: 26083584 DOI: 10.1080/15384101.2015.1031438] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Formin-like 1 (FMNL1) is a member of Formin family proteins which are the actin nucleators. Although FMNL1 activities have been shown to be essential for cell adhesion, cytokinesis, cell polarization and migration in mitosis, the functional roles of mammalian FMNL1 during oocyte meiosis remain uncertain. In this study, we investigated the functions of FMNL1 in mouse oocytes using specific morpholino (MO) microinjection and live cell imaging. Immunofluorescent staining showed that in addition to its cytoplasmic distribution, FMNL1 was primarily localized at the spindle poles after germinal vesicle breakdown (GVBD). FMNL1 knockdown caused the low rate of polar body extrusion and resulted in large polar bodies. Time-lapse microscopic and immunofluorescence intensity analysis indicated that this might be due to the aberrant actin expression levels. Cortical polarity was disrupted as shown by a loss of actin cap and cortical granule free domain (CGFD) formation, which was confirmed by a failure of meiotic spindle positioning. And this might be the reason for the large polar body formation. Spindle formation was also disrupted, which might be due to the abnormal localization of p-MAPK. These results indicated that FMNL1 affected both actin dynamics and spindle formation for the oocyte polar body extrusion. Moreover, FMNL1 depletion resulted in aberrant localization and expression patterns of a cis-Golgi marker protein, GM130. Finally, we found that the small GTPase RhoA might be the upstream regulator of FMNL1. Taken together, our data indicate that FMNL1 is required for spindle organization and actin assembly through a RhoA-FMNL1-GM130 pathway during mouse oocyte meiosis.
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Affiliation(s)
- Fei Wang
- a College of Animal Science and Technology; Nanjing Agricultural University ; Nanjing , China
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47
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Miller MR, Blystone SD. Human Macrophages Utilize the Podosome Formin FMNL1 for Adhesion and Migration. ACTA ACUST UNITED AC 2015; 4:1-11. [PMID: 26942206 DOI: 10.4236/cellbio.2015.41001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Macrophages play a crucial role in detecting, regulating, and resolving immune crises, requiring migration through complex extracellular matrices. Unwarranted macrophage inflammatory activity potentiates kidney disease, rheumatoid arthritis, and transplant rejection. Proper remodeling of the actin cytoskeleton, especially at adhesion structures, is essential to the translocation of macrophages. Macrophages form actin-rich adhesions termed "podosomes", giving them the capacity to make contacts with the substratum for traction through interstitial tissues. Macrophages express multiple formins, including FMNL1, Dia1, and Fhod1, with potential to impact actin remodeling involved in migration. Formins are a family of proteins that are best known for modifying the actin cytoskeleton via nucleation, elongation, bundling, and/or severing actin filaments. In this study we demonstrate that the formin FMNL1 is a key regulator of podosomes and is required for normal macrophage migration. Additionally, this is the first study to demonstrate defects in primary human cell migration resulting from specific formin silencing. Pharmacologic inhibition of all formin activity results in a significant decrease in podosome formation and normal macrophage migration. Furthermore, targeted suppression of FMNL1 results in decreases in macrophage migration similar to inhibition of all expressed macrophage formins. These novel findings suggest FMNL1 as a possible chemotherapeutic target to hinder macrophage migration, which could offer an innovative method for limiting unnecessary macrophage-mediated inflammation. We hypothesize that formins are required in podosome actin dynamics to support macrophage migration.
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Affiliation(s)
- Matthew R Miller
- Department of Cell & Developmental Biology, SUNY Upstate Medical University, New York, USA
| | - Scott D Blystone
- Department of Cell & Developmental Biology, SUNY Upstate Medical University, New York, USA
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Lu Q, Adler PN. The diaphanous gene of Drosophila interacts antagonistically with multiple wing hairs and plays a key role in wing hair morphogenesis. PLoS One 2015; 10:e0115623. [PMID: 25730111 PMCID: PMC4346269 DOI: 10.1371/journal.pone.0115623] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 11/25/2014] [Indexed: 11/18/2022] Open
Abstract
The Drosophila wing is covered by an array of distally pointing hairs that has served as a key model system for studying planar cell polarity (PCP). The adult cuticular hairs are formed in the pupae from cell extensions that contain extensive actin filaments and microtubules. The importance of the actin cytoskeleton for hair growth and morphogenesis is clear from the wide range of phenotypes seen in mutations in well-known actin regulators. Formin proteins promote the formation of long actin filaments of the sort thought to be important for hair growth. We report here that the formin encoding diaphanous (dia) gene plays a key role in hair morphogenesis. Both loss of function mutations and the expression of a constitutively active Dia led to cells forming both morphologically abnormal hairs and multiple hairs. The conserved frizzled (fz)/starry night (stan) PCP pathway functions to restrict hair initiation and activation of the cytoskeleton to the distal most part of wing cells. It also ensures the formation of a single hair per cell. Our data suggest that the localized inhibition of Dia activity may be part of this mechanism. We found the expression of constitutively active Dia greatly expands the region for activation of the cytoskeleton and that dia functions antagonistically with multiple wing hairs (mwh), the most downstream member of the fz/stan pathway. Further we established that purified fragments of Dia and Mwh could be co-immunoprecipitated suggesting the genetic interaction could reflect a direct physical interaction.
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Affiliation(s)
- Qiuheng Lu
- Biology Department, University of Virginia, Charlottesville, Virginia, United States of America
| | - Paul N. Adler
- Biology Department, University of Virginia, Charlottesville, Virginia, United States of America
- Cell Biology Department, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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49
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Zhang Y, Wang F, Niu YJ, Liu HL, Rui R, Cui XS, Kim NH, Sun SC. Formin mDia1, a downstream molecule of FMNL1, regulates Profilin1 for actin assembly and spindle organization during mouse oocyte meiosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:317-27. [PMID: 25447542 DOI: 10.1016/j.bbamcr.2014.11.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 10/06/2014] [Accepted: 11/04/2014] [Indexed: 02/07/2023]
Abstract
Mammalian diaphanous1 (mDia1) is a homologue of Drosophila diaphanous and belongs to the Formin-homology family of proteins that catalyze actin nucleation and polymerization. Although Formin family proteins, such as Drosophila diaphanous, have been shown to be essential for cytokinesis, whether and how mDia1 functions during meiosis remain uncertain. In this study, we explored possible roles and the signaling pathway involved for mDia1 using a mouse oocyte model. mDia1 depletion reduced polar body extrusion, which may have been due to reduced cortical actin assembly. mDia1 and Profilin1 had similar localization patterns in mouse oocytes and mDia1 knockdown resulted in reduced Profilin1 expression. Depleting FMNL1, another Formin family member, resulted in reduced mDia1 expression, while RhoA inhibition did not alter mDia1 expression, which indicated that there was a FMNL1-mDia1-Profilin1 signaling pathway in mouse oocytes. Additionally, mDia1 knockdown resulted in disrupting oocyte spindle morphology, which was confirmed by aberrant p-MAPK localization. Thus, these results demonstrated indispensable roles for mDia1 in regulating mouse oocyte meiotic maturation through its effects on actin assembly and spindle organization.
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Affiliation(s)
- Yu Zhang
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Fei Wang
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Ying-Jie Niu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Hong-Lin Liu
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
| | - Rong Rui
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
| | - Xiang-Shun Cui
- Department of Animal Sciences, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea
| | - Nam-Hyung Kim
- Department of Animal Sciences, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea
| | - Shao-Chen Sun
- College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
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50
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Vattepu R, Yadav R, Beck MR. Actin-induced dimerization of palladin promotes actin-bundling. Protein Sci 2014; 24:70-80. [PMID: 25307943 DOI: 10.1002/pro.2588] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 10/09/2014] [Indexed: 12/12/2022]
Abstract
A subset of actin binding proteins is able to form crosslinks between two or more actin filaments, thus producing structures of parallel or networked bundles. These actin crosslinking proteins interact with actin through either bivalent binding or dimerization. We recently identified two binding sites within the actin binding domain of palladin, an actin crosslinking protein that plays an important role in normal cell adhesion and motility during wound healing and embryonic development. In this study, we show that actin induces dimerization of palladin. Furthermore, the extent of dimerization reflects earlier comparisons of actin binding and bundling between different domains of palladin. On the basis of these results we hypothesized that actin binding may promote a conformational change that results in dimerization of palladin, which in turn may drive the crosslinking of actin filaments. The proximal distance between two actin binding sites on crosslinking proteins determines the ultrastructural properties of the filament network, therefore we also explored interdomain interactions using a combination of chemical crosslinking experiments and actin cosedimentation assays. Limited proteolysis data reveals that palladin is less susceptible to enzyme digestion after actin binding. Our results suggest that domain movements in palladin are necessary for interactions with actin and are induced by interactions with actin filaments. Accordingly, we put forth a model linking the structural changes to functional dynamics.
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Affiliation(s)
- Ravi Vattepu
- Chemistry Department, Wichita State University, Wichita, Kansas, 67260
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