1
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Kimmich MJ, Sundaramurthy S, Geary MA, Lesanpezeshki L, Yingling CV, Vanapalli SA, Littlefield RS, Pruyne D. FHOD-1/profilin-mediated actin assembly protects sarcomeres against contraction-induced deformation in C. elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.29.582848. [PMID: 38559004 PMCID: PMC10979920 DOI: 10.1101/2024.02.29.582848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Formin HOmology Domain 2-containing (FHOD) proteins are a subfamily of actin-organizing formins important for striated muscle development in many animals. We showed previously that absence of the sole FHOD protein, FHOD-1, from C. elegans results in thin body-wall muscles with misshapen dense bodies that serve as sarcomere Z-lines. We demonstrate here that actin polymerization by FHOD-1 is required for its function in muscle development, and that FHOD-1 cooperates with profilin PFN-3 for dense body morphogenesis, and profilins PFN-2 and PFN-3 to promote body-wall muscle growth. We further demonstrate dense bodies in fhod-1 and pfn-3 mutants are less stable than in wild type animals, having a higher proportion of dynamic protein, and becoming distorted by prolonged muscle contraction. We also observe accumulation of actin depolymerization factor/cofilin homolog UNC-60B in body-wall muscle of these mutants. Such accumulations may indicate targeted disassembly of thin filaments dislodged from unstable dense bodies, and may account for the abnormally slow growth and reduced strength of body-wall muscle in fhod-1 mutants. Overall, these results show the importance of FHOD protein-mediated actin assembly to forming stable sarcomere Z-lines, and identify profilin as a new contributor to FHOD activity in striated muscle development.
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Affiliation(s)
- Michael J. Kimmich
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Sumana Sundaramurthy
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Meaghan A. Geary
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Leila Lesanpezeshki
- Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409
| | - Curtis V. Yingling
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
| | - Siva A. Vanapalli
- Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409
| | | | - David Pruyne
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY 13210
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2
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Farkas D, Szikora S, Jijumon AS, Polgár TF, Patai R, Tóth MÁ, Bugyi B, Gajdos T, Bíró P, Novák T, Erdélyi M, Mihály J. Peripheral thickening of the sarcomeres and pointed end elongation of the thin filaments are both promoted by SALS and its formin interaction partners. PLoS Genet 2024; 20:e1011117. [PMID: 38198522 PMCID: PMC10805286 DOI: 10.1371/journal.pgen.1011117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 01/23/2024] [Accepted: 12/27/2023] [Indexed: 01/12/2024] Open
Abstract
During striated muscle development the first periodically repeated units appear in the premyofibrils, consisting of immature sarcomeres that must undergo a substantial growth both in length and width, to reach their final size. Here we report that, beyond its well established role in sarcomere elongation, the Sarcomere length short (SALS) protein is involved in Z-disc formation and peripheral growth of the sarcomeres. Our protein localization data and loss-of-function studies in the Drosophila indirect flight muscle strongly suggest that radial growth of the sarcomeres is initiated at the Z-disc. As to thin filament elongation, we used a powerful nanoscopy approach to reveal that SALS is subject to a major conformational change during sarcomere development, which might be critical to stop pointed end elongation in the adult muscles. In addition, we demonstrate that the roles of SALS in sarcomere elongation and radial growth are both dependent on formin type of actin assembly factors. Unexpectedly, when SALS is present in excess amounts, it promotes the formation of actin aggregates highly resembling the ones described in nemaline myopathy patients. Collectively, these findings helped to shed light on the complex mechanisms of SALS during the coordinated elongation and thickening of the sarcomeres, and resulted in the discovery of a potential nemaline myopathy model, suitable for the identification of genetic and small molecule inhibitors.
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Affiliation(s)
- Dávid Farkas
- Institute of Genetics, Biological Research Centre, Szeged, Hungary
| | - Szilárd Szikora
- Institute of Genetics, Biological Research Centre, Szeged, Hungary
| | - A S Jijumon
- Institute of Genetics, Biological Research Centre, Szeged, Hungary
| | - Tamás F Polgár
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary
- Doctoral School of Theoretical Medicine, University of Szeged, Szeged, Hungary
| | - Roland Patai
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary
| | - Mónika Ágnes Tóth
- University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
| | - Beáta Bugyi
- University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
| | - Tamás Gajdos
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Péter Bíró
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Tibor Novák
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - Miklós Erdélyi
- Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary
| | - József Mihály
- Institute of Genetics, Biological Research Centre, Szeged, Hungary
- University of Szeged, Department of Genetics, Szeged, Hungary
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3
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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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4
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Costache V, Prigent Garcia S, Plancke CN, Li J, Begnaud S, Suman SK, Reymann AC, Kim T, Robin FB. Rapid assembly of a polar network architecture drives efficient actomyosin contractility. Cell Rep 2022; 39:110868. [PMID: 35649363 PMCID: PMC9210446 DOI: 10.1016/j.celrep.2022.110868] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 03/13/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022] Open
Abstract
Actin network architecture and dynamics play a central role in cell contractility and tissue morphogenesis. RhoA-driven pulsed contractions are a generic mode of actomyosin contractility, but the mechanisms underlying how their specific architecture emerges and how this architecture supports the contractile function of the network remain unclear. Here we show that, during pulsed contractions, the actin network is assembled by two subpopulations of formins: a functionally inactive population (recruited) and formins actively participating in actin filament elongation (elongating). We then show that elongating formins assemble a polar actin network, with barbed ends pointing out of the pulse. Numerical simulations demonstrate that this geometry favors rapid network contraction. Our results show that formins convert a local RhoA activity gradient into a polar network architecture, causing efficient network contractility, underlying the key function of kinetic controls in the assembly and mechanics of cortical network architectures. RhoA-driven actomyosin contractility plays a key role in driving cell and tissue contractility during morphogenesis. Tracking individual formins, Costache et al. show that the network assembled downstream of RhoA displays a polar architecture, barbed ends pointing outward, a feature that supports efficient contractility and force transmission during pulsed contractions.
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Affiliation(s)
- Vlad Costache
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France
| | - Serena Prigent Garcia
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France
| | - Camille N Plancke
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France
| | - Jing Li
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA
| | - Simon Begnaud
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France
| | - Shashi Kumar Suman
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France
| | - Anne-Cécile Reymann
- IGBMC, CNRS UMR7104, INSERM U1258, and Université de Strasbourg, Illkirch, France
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, USA.
| | - François B Robin
- Sorbonne Université, CNRS, INSERM, Institut de Biologie Paris-Seine IBPS, Laboratoire de Biologie du Développement, Paris, France.
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5
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The Mechanisms of Thin Filament Assembly and Length Regulation in Muscles. Int J Mol Sci 2022; 23:ijms23105306. [PMID: 35628117 PMCID: PMC9140763 DOI: 10.3390/ijms23105306] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
The actin containing tropomyosin and troponin decorated thin filaments form one of the crucial components of the contractile apparatus in muscles. The thin filaments are organized into densely packed lattices interdigitated with myosin-based thick filaments. The crossbridge interactions between these myofilaments drive muscle contraction, and the degree of myofilament overlap is a key factor of contractile force determination. As such, the optimal length of the thin filaments is critical for efficient activity, therefore, this parameter is precisely controlled according to the workload of a given muscle. Thin filament length is thought to be regulated by two major, but only partially understood mechanisms: it is set by (i) factors that mediate the assembly of filaments from monomers and catalyze their elongation, and (ii) by factors that specify their length and uniformity. Mutations affecting these factors can alter the length of thin filaments, and in human cases, many of them are linked to debilitating diseases such as nemaline myopathy and dilated cardiomyopathy.
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6
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Li Y, Munro E. Filament-guided filament assembly provides structural memory of filament alignment during cytokinesis. Dev Cell 2021; 56:2486-2500.e6. [PMID: 34480876 DOI: 10.1016/j.devcel.2021.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 05/30/2021] [Accepted: 08/13/2021] [Indexed: 10/24/2022]
Abstract
During cytokinesis, animal cells rapidly remodel the equatorial cortex to build an aligned array of actin filaments called the contractile ring. Local reorientation of filaments by active equatorial compression is thought to underlie the emergence of filament alignment during ring assembly. Here, combining single molecule analysis and modeling in one-cell C. elegans embryos, we show that filaments turnover is far too fast for reorientation of individual filaments by equatorial compression to explain the observed alignment, even if favorably oriented filaments are selectively stabilized. By tracking single formin/CYK-1::GFP particles to monitor local filament assembly, we identify a mechanism that we call filament-guided filament assembly (FGFA), in which existing filaments serve as templates to orient the growth of new filaments. FGFA sharply increases the effective lifetime of filament orientation, providing structural memory that allows cells to build highly aligned filament arrays in response to equatorial compression, despite rapid turnover of individual filaments.
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Affiliation(s)
- Younan Li
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Edwin Munro
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA; Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
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7
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Drewnik ED, Wiesenfahrt T, Smit RB, Park YJ, Pallotto LM, Mains PE. Tissue-specific regulation of epidermal contraction during C. elegans embryonic morphogenesis. G3-GENES GENOMES GENETICS 2021; 11:6273666. [PMID: 33974063 PMCID: PMC8495928 DOI: 10.1093/g3journal/jkab164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Accepted: 05/05/2021] [Indexed: 11/17/2022]
Abstract
Actin and myosin mediate the epidermal cell contractions that elongate the Caenorhabditis elegans embryo from an ovoid to a tubular-shaped worm. Contraction occurs mainly in the lateral epidermal cells, while the dorsoventral epidermis plays a more passive role. Two parallel pathways trigger actinomyosin contraction, one mediated by LET-502/Rho kinase and the other by PAK-1/p21 activated kinase. A number of genes mediating morphogenesis have been shown to be sufficient when expressed either laterally or dorsoventrally. Additional genes show either lateral or dorsoventral phenotypes. This led us to a model where contractile genes have discrete functions in one or the other cell type. We tested this by examining several genes for either lateral or dorsoventral sufficiency. LET-502 expression in the lateral cells was sufficient to drive elongation. MEL-11/Myosin phosphatase, which antagonizes contraction, and PAK-1 were expected to function dorsoventrally, but we could not detect tissue-specific sufficiency. Double mutants of lethal alleles predicted to decrease lateral contraction with those thought to increase dorsoventral force were previously shown to be viable. We hypothesized that these mutant combinations shifted the contractile force from the lateral to the dorsoventral cells and so the embryos would elongate with less lateral cell contraction. This was tested by examining 10 single and double mutant strains. In most cases, elongation proceeded without a noticeable alteration in lateral contraction. We suggest that many embryonic elongation genes likely act in both lateral and dorsoventral cells, even though they may have their primary focus in one or the other cell type.
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Affiliation(s)
- Elizabeth D Drewnik
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Tobias Wiesenfahrt
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Ryan B Smit
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Ye-Jean Park
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Linda M Pallotto
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Paul E Mains
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
- Corresponding author: Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada.
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8
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CYK-1/Formin activation in cortical RhoA signaling centers promotes organismal left-right symmetry breaking. Proc Natl Acad Sci U S A 2021; 118:2021814118. [PMID: 33972425 PMCID: PMC8157923 DOI: 10.1073/pnas.2021814118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Proper left-right symmetry breaking is essential for animal development, and in many cases, this process is actomyosin-dependent. In Caenorhabditis elegans embryos active torque generation in the actomyosin layer promotes left-right symmetry breaking by driving chiral counterrotating cortical flows. While both Formins and Myosins have been implicated in left-right symmetry breaking and both can rotate actin filaments in vitro, it remains unclear whether active torques in the actomyosin cortex are generated by Formins, Myosins, or both. We combined the strength of C. elegans genetics with quantitative imaging and thin film, chiral active fluid theory to show that, while Non-Muscle Myosin II activity drives cortical actomyosin flows, it is permissive for chiral counterrotation and dispensable for chiral symmetry breaking of cortical flows. Instead, we find that CYK-1/Formin activation in RhoA foci is instructive for chiral counterrotation and promotes in-plane, active torque generation in the actomyosin cortex. Notably, we observe that artificially generated large active RhoA patches undergo rotations with consistent handedness in a CYK-1/Formin-dependent manner. Altogether, we conclude that CYK-1/Formin-dependent active torque generation facilitates chiral symmetry breaking of actomyosin flows and drives organismal left-right symmetry breaking in the nematode worm.
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9
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Yingling CV, Pruyne D. FHOD formin and SRF promote post-embryonic striated muscle growth through separate pathways in C. elegans. Exp Cell Res 2021; 398:112388. [PMID: 33221314 PMCID: PMC7750259 DOI: 10.1016/j.yexcr.2020.112388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 11/13/2020] [Accepted: 11/16/2020] [Indexed: 11/28/2022]
Abstract
Previous work with cultured cells has shown transcription of muscle genes by serum response factor (SRF) can be stimulated by actin polymerization driven by proteins of the formin family. However, it is not clear if endogenous formins similarly promote SRF-dependent transcription during muscle development in vivo. We tested whether formin activity promotes SRF-dependent transcription in striated muscle in the simple animal model, Caenorhabditis elegans. Our lab has shown FHOD-1 is the only formin that directly promotes sarcomere formation in the worm's striated muscle. We show here FHOD-1 and SRF homolog UNC-120 both support muscle growth and also muscle myosin II heavy chain A expression. However, while a hypomorphic unc-120 allele blunts expression of a set of striated muscle genes, these genes are largely upregulated or unchanged by absence of FHOD-1. Instead, pharmacological inhibition of the proteasome restores myosin protein levels in worms lacking FHOD-1, suggesting elevated proteolysis accounts for their myosin deficit. Interestingly, proteasome inhibition does not restore normal muscle growth to fhod-1(Δ) mutants, suggesting formin contributes to muscle growth by some alternative mechanism. Overall, we find SRF does not depend on formin to promote muscle gene transcription in a simple in vivo system.
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Affiliation(s)
- Curtis V Yingling
- Department of Cell and Developmental Biology, 107 Weiskotten Hall, State University of New York Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13210, USA.
| | - David Pruyne
- Department of Cell and Developmental Biology, 107 Weiskotten Hall, State University of New York Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13210, USA.
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10
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Sundaramurthy S, Votra S, Laszlo A, Davies T, Pruyne D. FHOD-1 is the only formin in Caenorhabditis elegans that promotes striated muscle growth and Z-line organization in a cell autonomous manner. Cytoskeleton (Hoboken) 2020; 77:422-441. [PMID: 33103378 DOI: 10.1002/cm.21639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/21/2020] [Accepted: 10/22/2020] [Indexed: 11/06/2022]
Abstract
The striated body wall muscles of Caenorhabditis elegans are a simple model for sarcomere assembly. Previously, we observed deletion mutants for two formin genes, fhod-1 and cyk-1, develop thin muscles with abnormal dense bodies (the sarcomere Z-line analogs). However, this work left in question whether these formins work in a muscle cell autonomous manner, particularly since cyk-1(∆) deletion has pleiotropic effects on development. Using a fast acting temperature-sensitive cyk-1(ts) mutant, we show here that neither postembryonic loss nor acute loss of CYK-1 during embryonic sarcomerogenesis cause lasting muscle defects. Furthermore, mosaic expression of CYK-1 in cyk-1(∆) mutants is unable to rescue muscle defects in a cell autonomous manner, suggesting muscle phenotypes caused by cyk-1(∆) are likely indirect. Conversely, mosaic expression of FHOD-1 in fhod-1(Δ) mutants promotes muscle cell growth and proper dense body organization in a muscle cell autonomous manner. As we observe no effect of loss of any other formin on muscle development, we conclude FHOD-1 is the only worm formin that directly promotes striated muscle development, and the effects on formin loss in C. elegans are surprisingly modest compared to other systems.
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Affiliation(s)
- Sumana Sundaramurthy
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - SarahBeth Votra
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Arianna Laszlo
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
| | - Tim Davies
- Department of Pathology and Cell Biology, Columbia University, New York, New York, USA.,Department of Biosciences, Durham University, Durham, UK
| | - David Pruyne
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, USA
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11
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Kelley CA, Triplett O, Mallick S, Burkewitz K, Mair WB, Cram EJ. FLN-1/filamin is required to anchor the actomyosin cytoskeleton and for global organization of sub-cellular organelles in a contractile tissue. Cytoskeleton (Hoboken) 2020; 77:379-398. [PMID: 32969593 DOI: 10.1002/cm.21633] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/11/2020] [Accepted: 09/17/2020] [Indexed: 01/01/2023]
Abstract
Actomyosin networks are organized in space, direction, size, and connectivity to produce coordinated contractions across cells. We use the C. elegans spermatheca, a tube composed of contractile myoepithelial cells, to study how actomyosin structures are organized. FLN-1/filamin is required for the formation and stabilization of a regular array of parallel, contractile, actomyosin fibers in this tissue. Loss of fln-1 results in the detachment of actin fibers from the basal surface, which then accumulate along the cell junctions and are stabilized by spectrin. In addition, actin and myosin are captured at the nucleus by the linker of nucleoskeleton and cytoskeleton complex (LINC) complex, where they form large foci. Nuclear positioning and morphology, distribution of the endoplasmic reticulum and the mitochondrial network are also disrupted. These results demonstrate that filamin is required to prevent large actin bundle formation and detachment, to prevent excess nuclear localization of actin and myosin, and to ensure correct positioning of organelles.
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Affiliation(s)
- Charlotte A Kelley
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Olivia Triplett
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Samyukta Mallick
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Kristopher Burkewitz
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts, USA.,Department of Cell and Developmental Biology, Vanderbilt School of Medicine, Nashville, Tennessee, USA
| | - William B Mair
- Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | - Erin J Cram
- Department of Biology, Northeastern University, Boston, Massachusetts, USA
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12
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Maniscalco C, Hall AE, Nance J. An interphase contractile ring reshapes primordial germ cells to allow bulk cytoplasmic remodeling. J Cell Biol 2020; 219:132628. [PMID: 31819975 PMCID: PMC7041695 DOI: 10.1083/jcb.201906185] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 10/18/2019] [Accepted: 11/04/2019] [Indexed: 01/04/2023] Open
Abstract
Some cells discard undesired inherited components in bulk by forming large compartments that are subsequently eliminated. Caenorhabditis elegans primordial germ cells (PGCs) jettison mitochondria and cytoplasm by forming a large lobe that is cannibalized by intestinal cells. Although PGCs are nonmitotic, we find that lobe formation is driven by constriction of a contractile ring and requires the RhoGEF ECT-2, a RhoA activator also essential for cytokinesis. Whereas centralspindlin activates ECT-2 to promote cytokinetic contractile ring formation, we show that the ECT-2 regulator NOP-1, but not centralspindlin, is essential for PGC lobe formation. We propose that lobe contractile ring formation is locally inhibited by the PGC nucleus, which migrates to one side of the cell before the cytokinetic ring assembles on the opposite cortex. Our findings reveal how components of the cytokinetic contractile ring are reemployed during interphase to create compartments used for cellular remodeling, and they reveal differences in the spatial cues that dictate where the contractile ring will form.
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Affiliation(s)
- Chelsea Maniscalco
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY
| | - Allison E Hall
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY
| | - Jeremy Nance
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY.,Department of Cell Biology, New York University School of Medicine, New York, NY
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13
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Lardennois A, Pásti G, Ferraro T, Llense F, Mahou P, Pontabry J, Rodriguez D, Kim S, Ono S, Beaurepaire E, Gally C, Labouesse M. An actin-based viscoplastic lock ensures progressive body-axis elongation. Nature 2019; 573:266-270. [PMID: 31462781 DOI: 10.1038/s41586-019-1509-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 07/29/2019] [Indexed: 01/08/2023]
Abstract
Body-axis elongation constitutes a key step in animal development, laying out the final form of the entire animal. It relies on the interplay between intrinsic forces generated by molecular motors1-3, extrinsic forces exerted by adjacent cells4-7 and mechanical resistance forces due to tissue elasticity or friction8-10. Understanding how mechanical forces influence morphogenesis at the cellular and molecular level remains a challenge1. Recent work has outlined how small incremental steps power cell-autonomous epithelial shape changes1-3, which suggests the existence of specific mechanisms that stabilize cell shapes and counteract cell elasticity. Beyond the twofold stage, embryonic elongation in Caenorhabditis elegans is dependent on both muscle activity7 and the epidermis; the tension generated by muscle activity triggers a mechanotransduction pathway in the epidermis that promotes axis elongation7. Here we identify a network that stabilizes cell shapes in C. elegans embryos at a stage that involves non-autonomous mechanical interactions between epithelia and contractile cells. We searched for factors genetically or molecularly interacting with the p21-activating kinase homologue PAK-1 and acting in this pathway, thereby identifying the α-spectrin SPC-1. Combined absence of PAK-1 and SPC-1 induced complete axis retraction, owing to defective epidermal actin stress fibre. Modelling predicts that a mechanical viscoplastic deformation process can account for embryo shape stabilization. Molecular analysis suggests that the cellular basis for viscoplasticity originates from progressive shortening of epidermal microfilaments that are induced by muscle contractions relayed by actin-severing proteins and from formin homology 2 domain-containing protein 1 (FHOD-1) formin bundling. Our work thus identifies an essential molecular lock acting in a developmental ratchet-like process.
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Affiliation(s)
- Alicia Lardennois
- CNRS UMR7622, Institut de Biologie Paris-Seine (IBPS), Sorbonne Université, Paris, France
| | - Gabriella Pásti
- IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France
| | - Teresa Ferraro
- CNRS UMR7622, Institut de Biologie Paris-Seine (IBPS), Sorbonne Université, Paris, France
| | - Flora Llense
- CNRS UMR7622, Institut de Biologie Paris-Seine (IBPS), Sorbonne Université, Paris, France
| | - Pierre Mahou
- INSERM U1182 - CNRS/ UMR7645, Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Paris, France
| | - Julien Pontabry
- IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France.,RS2D, Mundolsheim, France
| | - David Rodriguez
- IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France
| | - Samantha Kim
- IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France
| | - Shoichiro Ono
- Departments of Pathology and Cell Biology, Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - Emmanuel Beaurepaire
- INSERM U1182 - CNRS/ UMR7645, Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Paris, France
| | - Christelle Gally
- IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France
| | - Michel Labouesse
- CNRS UMR7622, Institut de Biologie Paris-Seine (IBPS), Sorbonne Université, Paris, France. .,IGBMC -CNRS UMR 7104, INSERM U964, Development and Stem Cells Department, Université de Strasbourg, Illkirch, France.
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14
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Yamashiro S, Watanabe N. Quantitative high-precision imaging of myosin-dependent filamentous actin dynamics. J Muscle Res Cell Motil 2019; 41:163-173. [PMID: 31313218 DOI: 10.1007/s10974-019-09541-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 07/10/2019] [Indexed: 12/20/2022]
Abstract
Over recent decades, considerable effort has been made to understand how mechanical stress applied to the actin network alters actin assembly and disassembly dynamics. However, there are conflicting reports concerning the issue both in vitro and in cells. In this review, we discuss concerns regarding previous quantitative live-cell experiments that have attempted to evaluate myosin regulation of filamentous actin (F-actin) turnover. In particular, we highlight an error-generating mechanism in quantitative live-cell imaging, namely convection-induced misdistribution of actin-binding probes. Direct observation of actin turnover at the single-molecule level using our improved electroporation-based Single-Molecule Speckle (eSiMS) microscopy technique overcomes these concerns. We introduce our recent single-molecule analysis that unambiguously demonstrates myosin-dependent regulation of F-actin stability in live cells. We also discuss the possible application of eSiMS microscopy in the analysis of actin remodeling in striated muscle cells.
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Affiliation(s)
- Sawako Yamashiro
- Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan. .,Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
| | - Naoki Watanabe
- Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Yoshida Konoe-cho, Sakyo-ku, Kyoto, 606-8501, Japan.,Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto, Japan
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15
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Hegsted A, Votra S, Christophe AM, Yingling CV, Sundaramurthy S, Pruyne D. Functional importance of an inverted formin C-terminal tail at morphologically dynamic epithelial junctions. Cytoskeleton (Hoboken) 2019; 76:322-336. [PMID: 31215743 DOI: 10.1002/cm.21547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/30/2019] [Accepted: 06/09/2019] [Indexed: 11/10/2022]
Abstract
Epithelial cell-cell junctions have dual roles of accommodating morphological changes in an epithelium, while maintaining cohesion during those changes. An abundance of junction proteins has been identified, but many details on how intercellular junctions respond to morphological changes remain unclear. In Caenorhabditis elegans, the spermatheca is an epithelial sac that repeatedly dilates and constricts to allow ovulation. It is thought that the junctions between spermatheca epithelial cells undergo reversible partial unzipping to allow rapid dilation. Previously, we found that EXC-6, a C. elegans protein homolog of the human disease-associated formin INF2, is expressed in the spermatheca and promotes oocyte entry. We show here that EXC-6 localizes toward the apical aspect of the spermatheca epithelial junctions, and that the EXC-6-labeled junction domains "unzip" and dramatically flatten with oocyte entry into the spermatheca. We demonstrate that the C-terminal tail of EXC-6 is necessary and sufficient for junction localization. Moreover, expression of the tail alone worsens ovulation defects, suggesting this region not only mediates EXC-6 localization, but also interacts with other components important for junction remodeling.
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Affiliation(s)
- Anna Hegsted
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - SarahBeth Votra
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - Amylisa M Christophe
- Department of Clinical Laboratory Sciences, SUNY Upstate Medical University, Syracuse, New York
| | - Curtis V Yingling
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - Sumana Sundaramurthy
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York
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16
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Tissue-Specific Functions of fem-2/PP2c Phosphatase and fhod-1/formin During Caenorhabditis elegans Embryonic Morphogenesis. G3-GENES GENOMES GENETICS 2018; 8:2277-2290. [PMID: 29720391 PMCID: PMC6027879 DOI: 10.1534/g3.118.200274] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The cytoskeleton is the basic machinery that drives many morphogenetic events. Elongation of the C. elegans embryo from a spheroid into a long, thin larva initially results from actomyosin contractility, mainly in the lateral epidermal seam cells, while the corresponding dorsal and ventral epidermal cells play a more passive role. This is followed by a later elongation phase involving muscle contraction. Early elongation is mediated by parallel genetic pathways involving LET-502/Rho kinase and MEL-11/MYPT myosin phosphatase in one pathway and FEM-2/PP2c phosphatase and PAK-1/p21 activated kinase in another. While the LET-502/MEL-11 pathway appears to act primarily in the lateral epidermis, here we show that FEM-2 can mediate early elongation when expressed in the dorsal and ventral epidermis. We also investigated the early elongation function of FHOD-1, a member of the formin family of actin nucleators and bundlers. Previous work showed that FHOD-1 acts in the LET-502/MEL-11 branch of the early elongation pathway as well as in muscle for sarcomere organization. Consistent with this, we found that lateral epidermal cell-specific expression of FHOD-1 is sufficient for elongation, and FHOD-1 effects on elongation appear to be independent of its role in muscle. Also, we found that fhod-1 encodes long and short isoforms that differ in the presence of a predicted coiled-coil domain. Based on tissue-specific expression constructions and an isoform-specific CRISPR allele, the two FHOD-1 isoforms show partially specialized epidermal or muscle function. Although fhod-1 shows only impenetrant elongation phenotypes, we were unable to detect redundancy with other C. elegans formin genes.
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17
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Sherwood DR, Plastino J. Invading, Leading and Navigating Cells in Caenorhabditis elegans: Insights into Cell Movement in Vivo. Genetics 2018; 208:53-78. [PMID: 29301948 PMCID: PMC5753875 DOI: 10.1534/genetics.117.300082] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 10/26/2017] [Indexed: 12/30/2022] Open
Abstract
Highly regulated cell migration events are crucial during animal tissue formation and the trafficking of cells to sites of infection and injury. Misregulation of cell movement underlies numerous human diseases, including cancer. Although originally studied primarily in two-dimensional in vitro assays, most cell migrations in vivo occur in complex three-dimensional tissue environments that are difficult to recapitulate in cell culture or ex vivo Further, it is now known that cells can mobilize a diverse repertoire of migration modes and subcellular structures to move through and around tissues. This review provides an overview of three distinct cellular movement events in Caenorhabditis elegans-cell invasion through basement membrane, leader cell migration during organ formation, and individual cell migration around tissues-which together illustrate powerful experimental models of diverse modes of movement in vivo We discuss new insights into migration that are emerging from these in vivo studies and important future directions toward understanding the remarkable and assorted ways that cells move in animals.
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Affiliation(s)
- David R Sherwood
- Department of Biology, Regeneration Next, Duke University, Durham, North Carolina 27705
| | - Julie Plastino
- Institut Curie, PSL Research University, CNRS, UMR 168, F-75005 Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 168, F-75005 Paris, France
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18
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Hegsted A, Yingling CV, Pruyne D. Inverted formins: A subfamily of atypical formins. Cytoskeleton (Hoboken) 2017; 74:405-419. [PMID: 28921928 DOI: 10.1002/cm.21409] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 08/22/2017] [Accepted: 08/31/2017] [Indexed: 12/25/2022]
Abstract
Formins are a family of regulators of actin and microtubule dynamics that are present in almost all eukaryotes. These proteins are involved in many cellular processes, including cytokinesis, stress fiber formation, and cell polarization. Here we review one subfamily of formins, the inverted formins. Inverted formins as a group break several formin stereotypes, having atypical biochemical properties and domain organization, and they have been linked to kidney disease and neuropathy in humans. In this review, we will explore recent research on members of the inverted formin sub-family in mammals, zebrafish, fruit flies, and worms.
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Affiliation(s)
- Anna Hegsted
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Curtis V Yingling
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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19
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Rochester JD, Tanner PC, Sharp CS, Andralojc KM, Updike DL. PQN-75 is expressed in the pharyngeal gland cells of Caenorhabditiselegans and is dispensable for germline development. Biol Open 2017; 6:1355-1363. [PMID: 28916707 PMCID: PMC5612245 DOI: 10.1242/bio.027987] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Caenorhabditis elegans, five pharyngeal gland cells reside in the terminal bulb of the pharynx and extend anterior processes to five contact points in the pharyngeal lumen. Pharyngeal gland cells secrete mucin-like proteins thought to facilitate digestion, hatching, molting and assembly of the surface coat of the cuticle, but supporting evidence has been sparse. Here we show pharyngeal gland cell expression of PQN-75, a unique protein containing an N-terminal signal peptide, nucleoporin (Nup)-like phenylalanine/glycine (FG) repeats, and an extensive polyproline repeat domain with similarities to human basic salivary proline-rich pre-protein PRB2. Imaging of C-terminal tagged PQN-75 shows localization throughout pharyngeal gland cell processes but not the pharyngeal lumen; instead, aggregates of PQN-75 are occasionally found throughout the pharynx, suggesting secretion from pharyngeal gland cells into the surrounding pharyngeal muscle. PQN-75 does not affect fertility and brood size in C. elegans but confers some degree of stress resistance and thermotolerance through unknown mechanisms. Summary: PQN-75 is expressed in pharyngeal gland cells and shares similarity with human basic salivary proline-rich protein PBR2, suggesting evolutionary conservation between gland cells in the upper digestive tract.
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Affiliation(s)
- Jesse D Rochester
- The Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA
| | - Paige C Tanner
- The Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA
| | - Catherine S Sharp
- The Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA
| | | | - Dustin L Updike
- The Mount Desert Island Biological Laboratory, Bar Harbor, ME 04672, USA
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20
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Panzica MT, Marin HC, Reymann AC, McNally FJ. F-actin prevents interaction between sperm DNA and the oocyte meiotic spindle in C. elegans. J Cell Biol 2017. [PMID: 28637747 PMCID: PMC5551714 DOI: 10.1083/jcb.201702020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
After fertilization, interactions between sperm and egg DNA must be prevented before the completion of female meiosis. Panzica et al. show that cortical tethering by F-actin prevents contact between the paternal DNA and the meiotic spindle. Fertilization occurs during female meiosis in most animals, which raises the question of what prevents the sperm DNA from interacting with the meiotic spindle. In this study, we find that Caenorhabditis elegans sperm DNA stays in a fixed position at the opposite end of the embryo from the meiotic spindle while yolk granules are transported throughout the embryo by kinesin-1. In the absence of F-actin, the sperm DNA, centrioles, and organelles were transported as a unit with the yolk granules, resulting in sperm DNA within 2 µm of the meiotic spindle. F-actin imaging revealed a cytoplasmic meshwork that might restrict transport in a size-dependent manner. However, increasing yolk granule size did not slow their velocity, and the F-actin moved with the yolk granules. Instead, sperm contents connect to the cortical F-actin to prevent interaction with the meiotic spindle.
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Affiliation(s)
- Michelle T Panzica
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
| | - Harold C Marin
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
| | | | - Francis J McNally
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA
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21
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Abstract
Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. © 2017 American Physiological Society. Compr Physiol 7:891-944, 2017.
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Affiliation(s)
- Christine A Henderson
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Christopher G Gomez
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Stefanie M Novak
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Lei Mi-Mi
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
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22
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Sanger JW, Wang J, Fan Y, White J, Mi-Mi L, Dube DK, Sanger JM, Pruyne D. Assembly and Maintenance of Myofibrils in Striated Muscle. Handb Exp Pharmacol 2017; 235:39-75. [PMID: 27832381 DOI: 10.1007/164_2016_53] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this chapter, we present the current knowledge on de novo assembly, growth, and dynamics of striated myofibrils, the functional architectural elements developed in skeletal and cardiac muscle. The data were obtained in studies of myofibrils formed in cultures of mouse skeletal and quail myotubes, in the somites of living zebrafish embryos, and in mouse neonatal and quail embryonic cardiac cells. The comparative view obtained revealed that the assembly of striated myofibrils is a three-step process progressing from premyofibrils to nascent myofibrils to mature myofibrils. This process is specified by the addition of new structural proteins, the arrangement of myofibrillar components like actin and myosin filaments with their companions into so-called sarcomeres, and in their precise alignment. Accompanying the formation of mature myofibrils is a decrease in the dynamic behavior of the assembling proteins. Proteins are most dynamic in the premyofibrils during the early phase and least dynamic in mature myofibrils in the final stage of myofibrillogenesis. This is probably due to increased interactions between proteins during the maturation process. The dynamic properties of myofibrillar proteins provide a mechanism for the exchange of older proteins or a change in isoforms to take place without disassembling the structural integrity needed for myofibril function. An important aspect of myofibril assembly is the role of actin-nucleating proteins in the formation, maintenance, and sarcomeric arrangement of the myofibrillar actin filaments. This is a very active field of research. We also report on several actin mutations that result in human muscle diseases.
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Affiliation(s)
- Joseph W Sanger
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA.
| | - Jushuo Wang
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - Yingli Fan
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - Jennifer White
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - Lei Mi-Mi
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - Dipak K Dube
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - Jean M Sanger
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, 766 Irving Avenue, Syracuse, NY, 13224, USA.
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23
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Hegsted A, Wright FA, Votra S, Pruyne D. INF2- and FHOD-related formins promote ovulation in the somatic gonad of C. elegans. Cytoskeleton (Hoboken) 2016; 73:712-728. [PMID: 27770600 PMCID: PMC5148669 DOI: 10.1002/cm.21341] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 10/16/2016] [Accepted: 10/18/2016] [Indexed: 11/06/2022]
Abstract
Formins are regulators of actin filament dynamics. We demonstrate here that two formins, FHOD-1 and EXC-6, are important in the nematode Caenorhabditis elegans for ovulation, during which actomyosin contractions push a maturing oocyte from the gonad arm into a distensible bag-like organ, the spermatheca. EXC-6, a homolog of the disease-associated mammalian formin INF2, is highly expressed in the spermatheca, where it localizes to cell-cell junctions and to circumferential actin filament bundles. Loss of EXC-6 does not noticeably affect the organization the actin filament bundles, and causes only a very modest increase in the population of junction-associated actin filaments. Despite absence of a strong cytoskeletal phenotype, approximately half of ovulations in exc-6 mutants exhibit extreme defects, including failure of the oocyte to enter the spermatheca, or breakage of the oocyte as the distal spermatheca entrance constricts during ovulation. Loss of FHOD-1 alone has little effect, and we cannot detect FHOD-1 in the spermatheca. However, combined loss of these formins in double fhod-1;exc-6 mutants results in profound ovulation defects, with significant slowing of the entry of oocytes into the spermatheca, and failure of nearly 80% of ovulations. We suggest that EXC-6 plays a role directly in the spermatheca, perhaps by modulating the ability of the spermatheca wall to rapidly accommodate an incoming oocyte, while FHOD-1 may play an indirect role relating to its known importance in the growth and function of the egg-laying muscles. © 2016 The Authors. Cytoskeleton Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Anna Hegsted
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, 13210
| | - Forrest A Wright
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, New York, 13210
| | - SarahBeth Votra
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, 13210
| | - David Pruyne
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York, 13210
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24
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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: 29] [Impact Index Per Article: 3.6] [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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25
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Shaye DD, Greenwald I. A network of conserved formins, regulated by the guanine exchange factor EXC-5 and the GTPase CDC-42, modulates tubulogenesis in vivo. Development 2016; 143:4173-4181. [PMID: 27697907 DOI: 10.1242/dev.141861] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 09/20/2016] [Indexed: 12/20/2022]
Abstract
The C. elegans excretory cell (EC) is a powerful model for tubulogenesis, a conserved process that requires precise cytoskeletal regulation. EXC-6, an ortholog of the disease-associated formin INF2, coordinates cell outgrowth and lumen formation during EC tubulogenesis by regulating F-actin at the tip of the growing canal and the dynamics of basolateral microtubules. EXC-6 functions in parallel with EXC-5/FGD, a predicted activator of the Rho GTPase Cdc42. Here, we identify the parallel pathway: EXC-5 functions through CDC-42 to regulate two other formins: INFT-2, another INF2 ortholog, and CYK-1, the sole ortholog of the mammalian diaphanous (mDia) family of formins. We show that INFT-2 promotes F-actin accumulation in the EC, and that CYK-1 inhibits INFT-2 to regulate F-actin levels and EXC-6-promoted outgrowth. As INF2 and mDia physically interact and cross-regulate in cultured cells, our work indicates that a conserved EXC-5-CDC-42 pathway modulates this regulatory interaction and that it is functionally important in vivo during tubulogenesis.
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Affiliation(s)
- Daniel D Shaye
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA .,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Iva Greenwald
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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Revisiting the Phylogeny of the Animal Formins: Two New Subtypes, Relationships with Multiple Wing Hairs Proteins, and a Lost Human Formin. PLoS One 2016; 11:e0164067. [PMID: 27695129 PMCID: PMC5047451 DOI: 10.1371/journal.pone.0164067] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 09/19/2016] [Indexed: 11/23/2022] Open
Abstract
Formins are a widespread family of eukaryotic cytoskeleton-organizing proteins. Many species encode multiple formin isoforms, and for animals, much of this reflects the presence of multiple conserved subtypes. Earlier phylogenetic analyses identified seven major formin subtypes in animals (DAAM, DIAPH, FHOD, FMN, FMNL, INF, and GRID2IP/delphilin), but left a handful of formins, particularly from nematodes, unassigned. In this new analysis drawing from genomic data from a wider range of taxa, nine formin subtypes are identified that encompass all the animal formins analyzed here. Included in this analysis are Multiple Wing Hairs proteins (MWH), which bear homology to formin N-terminal domains. Originally identified in Drosophila melanogaster and other arthropods, MWH-related proteins are also identified here in some nematodes (including Caenorhabditis elegans), and are shown to be related to a novel MWH-related formin (MWHF) subtype. One surprising result of this work is the discovery that a family of pleckstrin homology domain-containing formins (PHCFs) is represented in many vertebrates, but is strikingly absent from placental mammals. Consistent with a relatively recent loss of this formin, the human genome retains fragments of a defunct homologous formin gene.
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27
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Single-molecule visualization of a formin-capping protein 'decision complex' at the actin filament barbed end. Nat Commun 2015; 6:8707. [PMID: 26566078 PMCID: PMC4660045 DOI: 10.1038/ncomms9707] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 09/22/2015] [Indexed: 01/01/2023] Open
Abstract
Precise control of actin filament length is essential to many cellular processes. Formins processively elongate filaments, whereas capping protein (CP) binds to barbed ends and arrests polymerization. While genetic and biochemical evidence has indicated that these two proteins function antagonistically, the mechanism underlying the antagonism has remained unresolved. Here we use multi-wavelength single-molecule fluorescence microscopy to observe the fully reversible formation of a long-lived 'decision complex' in which a CP dimer and a dimer of the formin mDia1 simultaneously bind the barbed end. Further, mDia1 displaced from the barbed end by CP can randomly slide along the filament and later return to the barbed end to re-form the complex. Quantitative kinetic analysis reveals that the CP-mDia1 antagonism that we observe in vitro occurs through the decision complex. Our observations suggest new molecular mechanisms for the control of actin filament length and for the capture of filament barbed ends in cells.
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Abstract
Eukaryotic cells have evolved a variety of actin-binding proteins to regulate the architecture and the dynamics of the actin cytoskeleton in time and space. The Diaphanous-related formins (DRF) represent a diverse group of Rho-GTPase-regulated actin regulators that control a range of actin structures composed of tightly-bundled, unbranched actin filaments as found in stress fibers and in filopodia. Under resting conditions, DRFs are auto-inhibited by an intra-molecular interaction between the C-terminal and the N-terminal domains. The auto-inhibition is thought to be released by binding of an activated RhoGTPase to the N-terminal GTPase-binding domain (GBD). However, there is growing evidence for more sophisticated variations from this simplified linear activation model. In this review we focus on the formin homology domain-containing proteins (FHOD), an unconventional group of DRFs. Recent findings on the molecular control and cellular functions of FHOD proteins in vivo are discussed in the light of the phylogeny of FHOD proteins.
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Key Words
- AML-1B, acute myeloid leukemia transcription factor
- DAD, diaphanous auto-regulatory domain
- DID, diaphanous inhibitory domain
- DRF, Diaphanous-related formins
- Dia, Diaphanous related formin
- FH1, formin homology 1
- FH2, formin homology 2
- FH3, formin homology 3
- FHOD
- FHOD, FH1/FH2 domain-containing protein
- GBD, GTPase-binding domain
- RhoGTPases
- SRE, serum response element
- actin
- cell migration
- formins
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Affiliation(s)
- Meike Bechtold
- a Institut für Neurobiologie ; Universität Münster ; Münster , Germany
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29
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Mangio RS, Votra S, Pruyne D. The canonical eIF4E isoform of C. elegans regulates growth, embryogenesis, and germline sex-determination. Biol Open 2015; 4:843-51. [PMID: 25979704 PMCID: PMC4571089 DOI: 10.1242/bio.011585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
eIF4E plays a conserved role in initiating protein synthesis, but with multiple eIF4E isoforms present in many organisms, these proteins also adopt specialized functions. Previous RNAi studies showed that ife-3, encoding the sole canonical eIF4E isoform of Caenorhabditis elegans, is essential for viability. Using ife-3 gene mutations, we show here that it is maternal ife-3 function that is essential for embryogenesis, but ife-3 null progeny of heterozygous animals are viable. We find that zygotic ife-3 function promotes body growth and regulates germline development in hermaphrodite worms. Specifically, the normal transition from spermatogenesis to oogenesis in the hermaphrodite germline fails in ife-3 mutants. This failure to switch is reversed by inhibiting expression of the key masculinizing gene, fem-3, suggesting ife-3 resembles a growing number of genes that promote the sperm/oocyte switch by acting genetically as upstream inhibitors of fem-3.
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Affiliation(s)
- Richard S Mangio
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - SarahBeth Votra
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - David Pruyne
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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Dwyer J, Pluess M, Iskratsch T, Dos Remedios CG, Ehler E. The formin FHOD1 in cardiomyocytes. Anat Rec (Hoboken) 2015; 297:1560-70. [PMID: 25125170 DOI: 10.1002/ar.22984] [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] [Received: 11/12/2013] [Accepted: 05/30/2014] [Indexed: 12/20/2022]
Abstract
Members of the formin family are known to be involved in the regulation of the actin cytoskeleton. We have recently identified a muscle specific splice variant of the formin FHOD3 and demonstrated its role in the maintenance of the contractile filaments of cardiomyocytes. Here, we characterize the expression and subcellular localization of FHOD3's closest relative, FHOD1, in the heart. Confocal microscopy shows that FHOD1 is mainly located at the intercalated disc, the special type of cell-cell contact between cardiomyocytes, but also partially associated with the myofibrils. Subcellular targeting of FHOD1 is probably mediated by its N-terminal domain, since expression constructs lacking this domain show aberrant localization in primary cultures of neonatal rat cardiomyocytes. Finally, we show that in contrast to FHOD3, FHOD1 shows increased expression levels in dilated cardiomyopathy, suggesting that the two formins play distinct roles and are differentially regulated in cardiomyocytes.
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Affiliation(s)
- Joseph Dwyer
- Randall Division of Cell and Molecular Biophysics and Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, SE1 1UL, United Kingdom
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31
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Ono S. Regulation of structure and function of sarcomeric actin filaments in striated muscle of the nematode Caenorhabditis elegans. Anat Rec (Hoboken) 2015; 297:1548-59. [PMID: 25125169 DOI: 10.1002/ar.22965] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Revised: 02/26/2014] [Accepted: 02/26/2014] [Indexed: 02/01/2023]
Abstract
The nematode Caenorhabditis elegans has been used as a valuable system to study structure and function of striated muscle. The body wall muscle of C. elegans is obliquely striated muscle with highly organized sarcomeric assembly of actin, myosin, and other accessory proteins. Genetic and molecular biological studies in C. elegans have identified a number of genes encoding structural and regulatory components for the muscle contractile apparatuses, and many of them have counterparts in mammalian cardiac and skeletal muscles or striated muscles in other invertebrates. Applicability of genetics, cell biology, and biochemistry has made C. elegans an excellent system to study mechanisms of muscle contractility and assembly and maintenance of myofibrils. This review focuses on the regulatory mechanisms of structure and function of actin filaments in the C. elegans body wall muscle. Sarcomeric actin filaments in C. elegans muscle are associated with the troponin-tropomyosin system that regulates the actin-myosin interaction. Proteins that bind to the side and ends of actin filaments support ordered assembly of thin filaments. Furthermore, regulators of actin dynamics play important roles in initial assembly, growth, and maintenance of sarcomeres. The knowledge acquired in C. elegans can serve as bases to understand the basic mechanisms of muscle structure and function.
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Affiliation(s)
- Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, Georgia; Department of Cell Biology, Emory University, Atlanta, Georgia
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32
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Shaye DD, Greenwald I. The disease-associated formin INF2/EXC-6 organizes lumen and cell outgrowth during tubulogenesis by regulating F-actin and microtubule cytoskeletons. Dev Cell 2015; 32:743-55. [PMID: 25771894 DOI: 10.1016/j.devcel.2015.01.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 12/02/2014] [Accepted: 01/13/2015] [Indexed: 10/23/2022]
Abstract
We investigate how outgrowth at the basolateral cell membrane is coordinated with apical lumen formation in the development of a biological tube by characterizing exc-6, a gene required for C. elegans excretory cell (EC) tubulogenesis. We show that EXC-6 is orthologous to the human formin INF2, which polymerizes filamentous actin (F-actin) and binds microtubules (MTs) in vitro. Dominant INF2 mutations cause focal segmental glomerulosclerosis (FSGS), a kidney disease, and FSGS+Charcot-Marie-Tooth neuropathy. We show that activated INF2 can substitute for EXC-6 in C. elegans and that disease-associated mutations cause constitutive activity. Using genetic analysis and live imaging, we show that exc-6 regulates MT and F-actin accumulation at EC tips and dynamics of basolateral-localized MTs, indicating that EXC-6 organizes F-actin and MT cytoskeletons during tubulogenesis. The pathology associated with INF2 mutations is believed to reflect misregulation of F-actin, but our results suggest alternative or additional mechanisms via effects on MT dynamics.
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Affiliation(s)
- Daniel D Shaye
- Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
| | - Iva Greenwald
- Howard Hughes Medical Institute, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA; Department of Genetics and Development, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
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33
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Mi-Mi L, Pruyne D. Loss of Sarcomere-associated Formins Disrupts Z-line Organization, but does not Prevent Thin Filament Assembly in Caenorhabditis elegans Muscle. ACTA ACUST UNITED AC 2015; 6. [PMID: 26161293 DOI: 10.4172/2157-7099.1000318] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Members of the formin family of actin filament nucleation factors have been implicated in sarcomere formation, but precisely how these proteins affect sarcomere structure remains poorly understood. Of six formins in the simple nematode Caenorhabditis elegans, only FHOD-1 and CYK-1 contribute to sarcomere assembly in the worm's obliquely striated body-wall muscles. We analyze here the ultrastructure of body-wall muscle sarcomeres in worms with putative null fhod-1 and cyk-1 gene mutations. Contrary to a simple model that formins nucleate actin for thin filament assembly, formin mutant sarcomeres contain thin filaments. Rather, formin mutant sarcomeres are narrower and have deformed thin filament-anchoring Z-line structures. Thus, formins affect multiple aspects of sarcomere structure.
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Affiliation(s)
- Lei Mi-Mi
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, 766 Irving Avenue, Syracuse, NY 13210, USA
| | - David Pruyne
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, 766 Irving Avenue, Syracuse, NY 13210, USA
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34
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Al Haj A, Mazur AJ, Radaszkiewicz K, Radaszkiewicz T, Makowiecka A, Stopschinski BE, Schönichen A, Geyer M, Mannherz HG. Distribution of formins in cardiac muscle: FHOD1 is a component of intercalated discs and costameres. Eur J Cell Biol 2014; 94:101-13. [PMID: 25555464 DOI: 10.1016/j.ejcb.2014.11.003] [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: 06/06/2014] [Revised: 11/21/2014] [Accepted: 11/26/2014] [Indexed: 10/24/2022] Open
Abstract
The formin homology domain-containing protein1 (FHOD1) suppresses actin polymerization by inhibiting nucleation, but bundles actin filaments and caps filament barbed ends. Two polyclonal antibodies against FHOD1 were generated against (i) its N-terminal sequence (residues 1-339) and (ii) a peptide corresponding the sequence from position 358-371, which is unique for FHOD1 and does not occur in its close relative FHOD3. After affinity purification both antibodies specifically stain purified full length FHOD1 and a band of similar molecular mass in homogenates of cardiac muscle. The antibody against the N-terminus of FHOD1 was used for immunostaining cells of established lines, primary neonatal (NRC) and adult (ARC) rat cardiomyocytes and demonstrated the presence of FHOD1 in HeLa and fibroblastic cells along stress fibers and within presumed lamellipodia and actin arcs. In NRCs and ARCs we observed a prominent staining of presumed intercalated discs (ICD). Immunostaining of sections of hearts with both anti-FHOD1 antibodies confirmed the presence of FHOD1 in ICDs and double immunostaining demonstrated its colocalisation with cadherin, plakoglobin and a probably slightly shifted localization to connexin43. Similarly, immunostaining of isolated mouse or pig ICDs corroborated the presence of FHOD1 and its colocalisation with the mentioned cell junctional components. Anti-FHOD1 immunoblots of isolated ICDs demonstrated the presence of an immunoreactive band comigrating with purified FHOD1. Conversely, an anti-peptide antibody specific for FHOD3 with no cross-reactivity against FHOD1 immunostained on sections of cardiac muscle and ARCs the myofibrils in a cross-striated pattern but not the ICDs. In addition, the anti-peptide-FHOD1 antibody stained the lateral sarcolemma of ARCs in a banded pattern. Double immunostaining with anti-cadherin and -integrin-ß1 indicated the additional localization of FHOD1 in costameres. Immunostaining of cardiac muscle sections or ARCs with antibodies against mDia3-FH2-domain showed colocalisation with cadherin along the lateral border of cardiomyocytes suggesting also its presence in costameres.
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Affiliation(s)
- Abdulatif Al Haj
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany
| | - Antonina J Mazur
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany; Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Poland
| | - Katarzyna Radaszkiewicz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany; Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Poland
| | - Tomasz Radaszkiewicz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany; Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Poland
| | - Aleksandra Makowiecka
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany; Department of Cell Pathology, Faculty of Biotechnology, University of Wroclaw, Poland
| | - Barbara E Stopschinski
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany; Department of Physical Biochemistry, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany
| | - André Schönichen
- Department of Physical Biochemistry, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany
| | - Matthias Geyer
- Department of Physical Biochemistry, Max-Planck-Institute of Molecular Physiology, Dortmund, Germany; Center of Advanced European Studies and Research (CAESAR), Bonn, Germany
| | - Hans Georg Mannherz
- Department of Anatomy and Molecular Embryology, Ruhr-University, Bochum, Germany.
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35
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Randall TS, Ehler E. A formin-g role during development and disease. Eur J Cell Biol 2014; 93:205-11. [PMID: 24342720 DOI: 10.1016/j.ejcb.2013.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/15/2013] [Accepted: 11/18/2013] [Indexed: 11/22/2022] Open
Abstract
Several different protein families were shown to be involved in the regulation of actin filament formation and have been studied extensively in processes such as cell migration. Among them are members of the formin family, which tend to promote the formation of linear actin filaments. Studies in recent years, often using loss of function animal models, have indicated that formin family members play roles beyond cell motility in vitro and are involved in processes ranging from tissue morphogenesis and cell differentiation to diseases such as cancer and cardiomyopathy. Therefore the aim of this review is to discuss these findings and to start putting them into a subcellular context.
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Affiliation(s)
- Thomas S Randall
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom
| | - Elisabeth Ehler
- Randall Division of Cell and Molecular Biophysics, Cardiovascular Division, British Heart Foundation Centre of Research Excellence, King's College London, London SE1 1UL, United Kingdom.
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36
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Rubenstein PA, Wen KK. Insights into the effects of disease-causing mutations in human actins. Cytoskeleton (Hoboken) 2014; 71:211-29. [PMID: 24574087 DOI: 10.1002/cm.21169] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 02/13/2013] [Accepted: 02/19/2014] [Indexed: 01/04/2023]
Abstract
Mutations in all six actins in humans have now been shown to cause diseases. However, a number of factors have made it difficult to gain insight into how the changes in actin functions brought about by these pathogenic mutations result in the disease phenotype. These include the presence of multiple actins in the same cell, limited accessibility to pure mutant material, and complexities associated with the structures and their component cells that manifest the diseases. To try to circumvent these difficulties, investigators have turned to the use of model systems. This review describes these various approaches, the initial results obtained using them, and the insight they have provided into allosteric mechanisms that govern actin function. Although results so far have not explained a particular disease phenotype at the molecular level, they have provided valuable insight into actin function at the mechanistic level which can be utilized in the future to delineate the molecular bases of these different actinopathies.
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Affiliation(s)
- Peter A Rubenstein
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, Iowa
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37
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Molnár I, Migh E, Szikora S, Kalmár T, Végh AG, Deák F, Barkó S, Bugyi B, Orfanos Z, Kovács J, Juhász G, Váró G, Nyitrai M, Sparrow J, Mihály J. DAAM is required for thin filament formation and Sarcomerogenesis during muscle development in Drosophila. PLoS Genet 2014; 10:e1004166. [PMID: 24586196 PMCID: PMC3937221 DOI: 10.1371/journal.pgen.1004166] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 12/23/2013] [Indexed: 11/19/2022] Open
Abstract
During muscle development, myosin and actin containing filaments assemble into the highly organized sarcomeric structure critical for muscle function. Although sarcomerogenesis clearly involves the de novo formation of actin filaments, this process remained poorly understood. Here we show that mouse and Drosophila members of the DAAM formin family are sarcomere-associated actin assembly factors enriched at the Z-disc and M-band. Analysis of dDAAM mutants revealed a pivotal role in myofibrillogenesis of larval somatic muscles, indirect flight muscles and the heart. We found that loss of dDAAM function results in multiple defects in sarcomere development including thin and thick filament disorganization, Z-disc and M-band formation, and a near complete absence of the myofibrillar lattice. Collectively, our data suggest that dDAAM is required for the initial assembly of thin filaments, and subsequently it promotes filament elongation by assembling short actin polymers that anneal to the pointed end of the growing filaments, and by antagonizing the capping protein Tropomodulin.
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Affiliation(s)
- Imre Molnár
- Institute of Genetics, Biological Research Centre HAS, Szeged, Hungary
| | - Ede Migh
- Institute of Genetics, Biological Research Centre HAS, Szeged, Hungary
| | - Szilárd Szikora
- Institute of Genetics, Biological Research Centre HAS, Szeged, Hungary
| | - Tibor Kalmár
- Institute of Genetics, Biological Research Centre HAS, Szeged, Hungary
| | - Attila G. Végh
- Institute of Biophysics, Biological Research Centre HAS, Szeged, Hungary
| | - Ferenc Deák
- Institute of Biochemistry, Biological Research Centre HAS, Szeged, Hungary
| | - Szilvia Barkó
- University of Pécs, Department of Biophysics, Pécs, Hungary
| | - Beáta Bugyi
- University of Pécs, Department of Biophysics, Pécs, Hungary
| | | | - János Kovács
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Budapest, Hungary
| | - György Váró
- Institute of Biophysics, Biological Research Centre HAS, Szeged, Hungary
| | - Miklós Nyitrai
- University of Pécs, Department of Biophysics, Pécs, Hungary
- Hungarian Academy of Sciences, Office for Subsidized Research Units, Budapest, Hungary
| | - John Sparrow
- Department of Biology, University of York, York, United Kingdom
| | - József Mihály
- Institute of Genetics, Biological Research Centre HAS, Szeged, Hungary
- * E-mail:
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38
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Lammel U, Bechtold M, Risse B, Berh D, Fleige A, Bunse I, Jiang X, Klämbt C, Bogdan S. The Drosophila FHOD1-like formin Knittrig acts through Rok to promote stress fiber formation and directed macrophage migration during the cellular immune response. Development 2014; 141:1366-80. [PMID: 24553290 DOI: 10.1242/dev.101352] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A tight spatiotemporal control of actin polymerization is important for many cellular processes that shape cells into a multicellular organism. The formation of unbranched F-actin is induced by several members of the formin family. Drosophila encodes six formin genes, representing six of the seven known mammalian subclasses. Knittrig, the Drosophila homolog of mammalian FHOD1, is specifically expressed in the developing central nervous system midline glia, the trachea, the wing and in macrophages. knittrig mutants exhibit mild tracheal defects but survive until late pupal stages and mainly die as pharate adult flies. knittrig mutant macrophages are smaller and show reduced cell spreading and cell migration in in vivo wounding experiments. Rescue experiments further demonstrate a cell-autonomous function of Knittrig in regulating actin dynamics and cell migration. Knittrig localizes at the rear of migrating macrophages in vivo, suggesting a cellular requirement of Knittrig in the retraction of the trailing edge. Supporting this notion, we found that Knittrig is a target of the Rho-dependent kinase Rok. Co-expression with Rok or expression of an activated form of Knittrig induces actin stress fibers in macrophages and in epithelial tissues. Thus, we propose a model in which Rok-induced phosphorylation of residues within the basic region mediates the activation of Knittrig in controlling macrophage migration.
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Affiliation(s)
- Uwe Lammel
- Institute for Neurobiology, University of Münster, 48149 Münster, Germany
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39
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Yamashiro S, Mizuno H, Smith MB, Ryan GL, Kiuchi T, Vavylonis D, Watanabe N. New single-molecule speckle microscopy reveals modification of the retrograde actin flow by focal adhesions at nanometer scales. Mol Biol Cell 2014; 25:1010-24. [PMID: 24501425 PMCID: PMC3967967 DOI: 10.1091/mbc.e13-03-0162] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
This paper introduces a new, easy-to-use method of fluorescence single-molecule speckle microscopy for actin with nanometer-scale accuracy. This new method reveals that actin flows in front of mature focal adhesions (FAs) are fast and biased toward FAs, suggesting that mature FAs are actively engaged in pulling and remodeling the local actin network. Speckle microscopy directly visualizes the retrograde actin flow, which is believed to promote cell-edge protrusion when linked to focal adhesions (FAs). However, it has been argued that, due to rapid actin turnover, the use of green fluorescent protein–actin, the lack of appropriate analysis algorithms, and technical difficulties, speckle microscopy does not necessarily report the flow velocities of entire actin populations. In this study, we developed a new, user-friendly single-molecule speckle (SiMS) microscopy using DyLight dye-labeled actin. Our new SiMS method enables in vivo nanometer-scale displacement analysis with a low localization error of ±8–8.5 nm, allowing accurate flow-velocity measurement for actin speckles with lifetime <5 s. In lamellipodia, both short- and long-lived F-actin molecules flow with the same speed, indicating they are part of a single actin network. These results do not support coexistence of F-actin populations with different flow speeds, which is referred to as the lamella hypothesis. Mature FAs, but not nascent adhesions, locally obstruct the retrograde flow. Interestingly, the actin flow in front of mature FAs is fast and biased toward FAs, suggesting that mature FAs attract the flow in front and actively remodel the local actin network.
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Affiliation(s)
- Sawako Yamashiro
- Laboratory of Single-Molecule Cell Biology, Tohoku University Graduate School of Life Sciences, Sendai, Miyagi 980-8578, Japan Department of Physics, Lehigh University, Bethlehem, PA 18015
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Araki K, Kawauchi K, Hirata H, Yamamoto M, Taya Y. Cytoplasmic translocation of the retinoblastoma protein disrupts sarcomeric organization. eLife 2013; 2:e01228. [PMID: 24302570 PMCID: PMC3843810 DOI: 10.7554/elife.01228] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Skeletal muscle degeneration is a complication arising from a variety of chronic diseases including advanced cancer. Pro-inflammatory cytokine TNF-α plays a pivotal role in mediating cancer-related skeletal muscle degeneration. Here, we show a novel function for retinoblastoma protein (Rb), where Rb causes sarcomeric disorganization. In human skeletal muscle myotubes (HSMMs), up-regulation of cyclin-dependent kinase 4 (CDK4) and concomitant phosphorylation of Rb was induced by TNF-α treatment, resulting in the translocation of phosphorylated Rb to the cytoplasm. Moreover, induced expression of the nuclear exporting signal (NES)-fused form of Rb caused disruption of sarcomeric organization. We identified mammalian diaphanous-related formin 1 (mDia1), a potent actin nucleation factor, as a binding partner of cytoplasmic Rb and found that mDia1 helps maintain the structural integrity of the sarcomere. These results reveal a novel non-nuclear function for Rb and suggest a potential mechanism of TNF-α-induced disruption of sarcomeric organization. DOI:http://dx.doi.org/10.7554/eLife.01228.001 Skeletal muscles, such as the biceps and calves, are one of three main muscle groups in the body, and a range of chronic diseases—including cancer, heart disease and AIDS—can cause wasting and a loss of strength in these muscles. Many different cellular processes are known to be involved in the degeneration of skeletal muscle during illness. For example, in people suffering from cancer, the immune response produces large numbers of molecules called inflammatory cytokines to combat the cancer cells, and these molecules are thought to have a role in the breakdown of skeletal muscle. A cytokine called tumour necrosis factor alpha, or TNF-α for short, is thought to cause muscle damage, but the details of this process are not fully understood. One possibility is that TNF-α interacts with a protein called Rb—short for retinoblastoma protein—that suppresses the proliferation of cells that leads to cancer. However, if this protein is modified by a chemical process called phosphorylation, the Rb molecules will not be able to suppress the genes that lead to excessive cell growth. The hyperphosphorylation of Rb has been observed in many cancer cells, and it has been shown that high levels of TNF-α in cells results in Rb not working properly, but it has not been clear if faulty Rb also leads to the breakdown of skeletal muscle. Now Araki et al. provide evidence that the phosphorylation of Rb by TNF-α leads to skeletal muscle degeneration. Araki et al. found that in muscle cells that contain high concentrations of TNF-α, the Rb molecules move from the nuclei of the cells, where they interact with genes, to the cytoplasm, where they disrupt the formation of structural fibres. This means that Rb inhibits the ability of muscle cells to slide over one during contractions and relaxation, as happens in normal muscle tissue. If confirmed by further experiments, these results could lead to the development of new approaches for the treatment of skeletal muscle degeneration. DOI:http://dx.doi.org/10.7554/eLife.01228.002
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Affiliation(s)
- Keigo Araki
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
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Abstract
Cachexia, a condition that kills about one-fifth of cancer patients, may be linked to Rb—a protein that is already linked to various cancers—moving from the cell nucleus to the cytoplasm.
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Affiliation(s)
- Giulio Cossu
- Giulio Cossu is an eLife reviewing editor and is at the Institute of Inflammation and Repair, University of Manchester, Manchester, United Kingdom
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Vanneste CA, Pruyne D, Mains PE. The role of the formin gene fhod-1 in C. elegans embryonic morphogenesis. WORM 2013; 2:e25040. [PMID: 24778933 PMCID: PMC3875645 DOI: 10.4161/worm.25040] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/10/2013] [Accepted: 05/14/2013] [Indexed: 01/20/2023]
Abstract
During the second half of embryogenesis, the ellipsoidal Caenorhabditis elegans embryo elongates into a long, thin worm. This elongation requires a highly organized cytoskeleton composed of actin microfilaments, microtubules and intermediate filaments throughout the epidermis of the embryo. This architecture allows the embryonic epidermal cells to undergo a smooth muscle-like actin/myosin-based contraction that is redundantly controlled by LET- 502/Rho kinase and MEL-11/myosin phosphatase in one pathway and FEM-2/PP2c phosphatase and PAK-1/p21-activated kinase in a parallel pathway(s). Although actin microfilaments surround the embryo, the force for contraction is generated mainly in the lateral (seam) epidermal cells whose actin microfilaments appear qualitatively different from those in their dorsal/ventral neighbors. We have identified FHOD-1, a formin family actin nucleator, which acts in the lateral epidermis. fhod-1 mutants show microfilament defects in the embryonic lateral epidermal cells and FHOD-1 protein is detected only in those cells. fhod-1 genetic interactions with let-502, mel-11, fem-2 and pak-1 indicate that fhod-1 preferentially regulates those microfilaments acting with let-502 and mel-11, and in parallel to fem-2 and pak-1. Thus, FHOD-1 may contribute to the qualitative differences in microfilaments found in the contractile lateral epidermal cells and their non-contractile dorsal and ventral neighbors. Different microfilament populations may be involved in the different contractile pathways.
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Affiliation(s)
- Chrisotpher A Vanneste
- Department of Biochemistry and Molecular Biology; Alberta Children's Hospital Research Institute; University of Calgary; Calgary, AB Canada
| | - David Pruyne
- Department of Cell and Developmental Biology; State University of New York Upstate Medical University; Syracuse, NY USA
| | - Paul E Mains
- Department of Biochemistry and Molecular Biology; Alberta Children's Hospital Research Institute; University of Calgary; Calgary, AB Canada
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Schönichen A, Mannherz HG, Behrmann E, Mazur AJ, Kühn S, Silván U, Schoenenberger CA, Fackler OT, Raunser S, Dehmelt L, Geyer M. FHOD1 is a combined actin filament capping and bundling factor that selectively associates with actin arcs and stress fibers. J Cell Sci 2013; 126:1891-901. [PMID: 23444374 DOI: 10.1242/jcs.126706] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Formins are actin polymerization factors that are known to nucleate and elongate actin filaments at the barbed end. In the present study we show that human FHOD1 lacks actin nucleation and elongation capacity, but acts as an actin bundling factor with capping activity toward the filament barbed end. Constitutively active FHOD1 associates with actin filaments in filopodia and lamellipodia at the leading edge, where it moves with the actin retrograde flow. At the base of lamellipodia, FHOD1 is enriched in nascent, bundled actin arcs as well as in more mature stress fibers. This function requires actin-binding domains located N-terminally to the canonical FH1-FH2 element. The bundling phenotype is maintained in the presence of tropomyosin, confirmed by electron microscopy showing assembly of 5 to 10 actin filaments into parallel, closely spaced filament bundles. Taken together, our data suggest a model in which FHOD1 stabilizes actin filaments by protecting barbed ends from depolymerization with its dimeric FH2 domain, whereas the region N-terminal to the FH1 domain mediates F-actin bundling by simultaneously binding to the sides of adjacent F-actin filaments.
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Affiliation(s)
- André Schönichen
- Department of Physical Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany.
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Maiden SL, Harrison N, Keegan J, Cain B, Lynch AM, Pettitt J, Hardin J. Specific conserved C-terminal amino acids of Caenorhabditis elegans HMP-1/α-catenin modulate F-actin binding independently of vinculin. J Biol Chem 2012; 288:5694-706. [PMID: 23271732 DOI: 10.1074/jbc.m112.438093] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Stable intercellular adhesions formed through the cadherin-catenin complex are important determinants of proper tissue architecture and help maintain tissue integrity during morphogenetic movements in developing embryos. A key regulator of this stability is α-catenin, which connects the cadherin-catenin complex to the actin cytoskeleton. Although the C-terminal F-actin-binding domain of α-catenin has been shown to be crucial for its function, a more detailed in vivo analysis of discrete regions and residues required for actin binding has not been performed. Using Caenorhabditis elegans as a model system, we have characterized mutations in hmp-1/α-catenin that identify HMP-1 residues 687-742 and 826-927, as well as amino acid 802, as critical to the localization of junctional proximal actin during epidermal morphogenesis. We also find that the S823F transition in a hypomorphic allele, hmp-1(fe4), decreases actin binding in vitro. Using hmp-1(fe4) animals in a mutagenesis screen, we were then able to identify 11 intragenic suppressors of hmp-1(fe4) that revert actin binding to wild-type levels. Using homology modeling, we show that these amino acids are positioned at key conserved sites within predicted α-helices in the C terminus. Through the use of transgenic animals, we also demonstrate that HMP-1 residues 315-494, which correspond to a putative mechanotransduction domain that binds vinculin in vertebrate αE-catenin, are not required during epidermal morphogenesis but may aid efficient recruitment of HMP-1 to the junction. Our studies are the first to identify key conserved amino acids in the C terminus of α-catenin that modulate F-actin binding in living embryos of a simple metazoan.
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Affiliation(s)
- Stephanie L Maiden
- Department of Zoology, University of Wisconsin, Madison, Wisconsin 53706, USA
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Short B. Formin’ muscle sarcomeres. J Biophys Biochem Cytol 2012. [PMCID: PMC3392931 DOI: 10.1083/jcb.1981iti3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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