1
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Ma L, Kuhn J, Chang YT, Elnatan D, Luxton GWG, Starr DA. FLN-2 functions in parallel to linker of nucleoskeleton and cytoskeleton complexes and CDC-42/actin pathways during P-cell nuclear migration through constricted spaces in Caenorhabditis elegans. Genetics 2024:iyae071. [PMID: 38797871 DOI: 10.1093/genetics/iyae071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 04/24/2024] [Indexed: 05/29/2024] Open
Abstract
Nuclear migration through narrow constrictions is important for development, metastasis, and proinflammatory responses. Studies performed in tissue culture cells have implicated linker of nucleoskeleton and cytoskeleton (LINC) complexes, microtubule motors, the actin cytoskeleton, and nuclear envelope repair machinery as important mediators of nuclear movements through constricted spaces. However, little is understood about how these mechanisms operate to move nuclei in vivo. In Caenorhabditis elegans larvae, six pairs of hypodermal P cells migrate from lateral to ventral positions through a constricted space between the body wall muscles and the cuticle. P-cell nuclear migration is mediated in part by LINC complexes using a microtubule-based pathway and by an independent CDC-42/actin-based pathway. However, when both LINC complex and actin-based pathways are knocked out, many nuclei still migrate, suggesting the existence of additional pathways. Here, we show that FLN-2 functions in a third pathway to mediate P-cell nuclear migration. The predicted N-terminal actin-binding domain in FLN-2 that is found in canonical filamins is dispensable for FLN-2 function; this and structural predictions suggest that FLN-2 does not function as a filamin. The immunoglobulin-like repeats 4-8 of FLN-2 were necessary for P-cell nuclear migration. Furthermore, in the absence of the LINC complex component unc-84, fln-2 mutants had an increase in P-cell nuclear rupture. We conclude that FLN-2 functions to maintain the integrity of the nuclear envelope in parallel with the LINC complex and CDC-42/actin-based pathways to move P-cell nuclei through constricted spaces.
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Affiliation(s)
- Linda Ma
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Jonathan Kuhn
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Yu-Tai Chang
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Daniel Elnatan
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - G W Gant Luxton
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, 1 Shields Ave, Davis, CA 95616, USA
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2
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Schiller NR, Almuhanna SA, Hoppe PE. UNC-82/NUAK kinase is required by myosin A, but not myosin B, to assemble and function in the thick filament arms of C. elegans striated muscle. Cytoskeleton (Hoboken) 2023. [PMID: 37983932 DOI: 10.1002/cm.21807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/10/2023] [Accepted: 10/27/2023] [Indexed: 11/22/2023]
Abstract
The mechanisms that ensure proper assembly, activity, and turnover of myosin II filaments are fundamental to a diverse range of cellular processes. In Caenorhabditis elegans striated muscle, thick filaments contain two myosins that are functionally distinct and spatially segregated. Using transgenic double mutants, we demonstrate that the ability of increased myosin A expression to restore muscle structure and movement in myosin B mutants requires UNC-82/NUAK kinase activity. Myosin B function appears unaffected in the kinase-impaired unc-82(e1220) mutant: the recessive antimorphic effects on early assembly of paramyosin and myosin A in this mutant are counteracted by increased myosin B expression and exacerbated by loss of myosin B. Using chimeric myosins and motility assays, we mapped the region of myosin A that requires UNC-82 activity to a 531-amino-acid region of the coiled-coil rod. This region includes the 264-amino-acid Region 1, which is sufficient in chimeric myosins to rescue the essential filament-initiation function of myosin A, as well as two sites that interact with myosin head domains in the Interacting Heads Motif. A specific physical interaction between myosin A and UNC-82::GFP is supported by GFP labeling of ectopic myosin A filaments but not thin filaments. We hypothesize that UNC-82 regulates assembly competence of myosin A during parallel assembly in the filament arms.
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Affiliation(s)
- NaTasha R Schiller
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan, USA
- Biology Department, Wingate University, Wingate, North Carolina, USA
| | - Sarah A Almuhanna
- Clinical Laboratory Sciences, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia
| | - Pamela E Hoppe
- Department of Biological Sciences, Western Michigan University, Kalamazoo, Michigan, USA
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3
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Ma L, Kuhn J, Chang YT, Elnatan D, Luxton GWG, Starr DA. FLN-2 functions in parallel to LINC complexes and Cdc42/actin pathways during P-cell nuclear migration through constricted spaces in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.04.552041. [PMID: 37577634 PMCID: PMC10418278 DOI: 10.1101/2023.08.04.552041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Nuclear migration through narrow constrictions is important for development, metastasis, and pro-inflammatory responses. Studies performed in tissue culture cells have implicated LINC (linker of nucleoskeleton and cytoskeleton) complexes, microtubule motors, the actin cytoskeleton, and nuclear envelope repair machinery as important mediators of nuclear movements through constricted spaces. However, little is understood about how these mechanisms operate to move nuclei in vivo. In C. elegans larvae, 6 pairs of hypodermal P cells migrate from lateral to ventral positions through a constricted space between the body wall muscles and the cuticle. P-cell nuclear migration is mediated in part by LINC complexes using a microtubule-based pathway and by an independent CDC-42/actin-based pathway. However, when both LINC complex and actin-based pathways are knocked out, many nuclei still migrate, suggesting the existence of additional pathways. Here we show that FLN-2 functions in a third pathway to mediate P-cell nuclear migration. The predicted N-terminal actin binding domain in FLN-2 that is found in canonical filamins is dispensable for FLN-2 function, this and structural predictions suggest that FLN-2 is not a divergent filamin. The immunoglobulin (Ig)-like repeats 4-8 of FLN-2 were necessary for P-cell nuclear migration. Furthermore, in the absence of the LINC complex component unc-84, fln-2 mutants had an increase in P-cell nuclear rupture. We conclude that FLN-2 functions to maintain the integrity of the nuclear envelope in parallel with the LINC complex and CDC-42/actin-based pathways to move P-cell nuclei through constricted spaces.
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Affiliation(s)
- Linda Ma
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Jonathan Kuhn
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Yu-Tai Chang
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Daniel Elnatan
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - G W Gant Luxton
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Daniel A Starr
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
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4
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Miyazaki S, Kawano T, Yanagisawa M, Hayashi Y. Intracellular Ca2+ dynamics in the ALA neuron reflect sleep pressure and regulate sleep in Caenorhabditis elegans. iScience 2022; 25:104452. [PMID: 35707721 PMCID: PMC9189131 DOI: 10.1016/j.isci.2022.104452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 04/03/2022] [Accepted: 05/17/2022] [Indexed: 11/30/2022] Open
Abstract
The mechanisms underlying sleep homeostasis are poorly understood. The nematode Caenorhabditis elegans exhibits 2 types of sleep: lethargus, or developmentally timed, and stress-induced sleep. Lethargus is characterized by alternating cycles of sleep and motion bouts. Sleep bouts are homeostatically regulated, i.e., prolonged active bouts lead to prolonged sleep bouts. Here we reveal that the interneuron ALA is crucial for homeostatic regulation during lethargus. Intracellular Ca2+ in ALA gradually increased during active bouts and rapidly decayed upon transitions to sleep bouts. Longer active bouts were accompanied by higher intracellular Ca2+ peaks. Optogenetic activation of ALA during active bouts caused transitions to sleep bouts. Dysfunction of CEH-17, which is an LIM homeodomain transcription factor selectively expressed in ALA, impaired the characteristic patterns of ALA intracellular Ca2+ and abolished the homeostatic regulation of sleep bouts. These findings indicate that ALA encodes sleep pressure and contributes to sleep homeostasis. ALA gradually increases its activity during motion bouts during lethargus in C. elegans Dysfunction or artificial activation of ALA perturbs the sleep structure ALA plays a crucial role in homeostatic sleep regulation
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Affiliation(s)
- Shinichi Miyazaki
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- PhD Program in Humanics, School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Taizo Kawano
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Masashi Yanagisawa
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Life Science Center for Survival Dynamics (TARA), University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
- R&D Center for Frontiers of Mirai in Policy and Technology (F-MIRAI), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
| | - Yu Hayashi
- International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan
- Department of Human Health Sciences, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 603-8363, Japan
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- Corresponding author
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5
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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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6
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Kelley CA, De Henau S, Bell L, Dansen TB, Cram EJ. Redox signaling modulates Rho activity and tissue contractility in the Caenorhabditis elegans spermatheca. Mol Biol Cell 2020; 31:1486-1497. [PMID: 32374641 PMCID: PMC7359568 DOI: 10.1091/mbc.e20-04-0236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Actomyosin-based contractility in smooth muscle and nonmuscle cells is regulated by signaling through the small GTPase Rho and by calcium-activated pathways. We use the myoepithelial cells of the Caenorhabditis elegans spermatheca to study the mechanisms of coordinated myosin activation in vivo. Here, we show that redox signaling modulates RHO-1/Rho activity in this contractile tissue. Exogenously added as well as endogenously generated hydrogen peroxide decreases spermathecal contractility by inhibition of RHO-1, which depends on a conserved cysteine in its nucleotide binding site (C20). Further, we identify an endogenous gradient of H2O2 across the spermathecal tissue, which depends on the activity of cytosolic superoxide dismutase, SOD-1. Collectively, we show that SOD-1-mediated H2O2 production regulates the redox environment and fine tunes Rho activity across the spermatheca through oxidation of RHO-1 C20.
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Affiliation(s)
| | - Sasha De Henau
- Center for Molecular Medicine, Molecular Cancer Research Section, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands
| | - Liam Bell
- Department of Biology, Northeastern University, Boston, MA 02115
| | - Tobias B Dansen
- Center for Molecular Medicine, Molecular Cancer Research Section, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands
| | - Erin J Cram
- Department of Biology, Northeastern University, Boston, MA 02115
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7
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Zhao Y, Wang H, Poole RJ, Gems D. A fln-2 mutation affects lethal pathology and lifespan in C. elegans. Nat Commun 2019; 10:5087. [PMID: 31704915 PMCID: PMC6841690 DOI: 10.1038/s41467-019-13062-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 10/15/2019] [Indexed: 12/12/2022] Open
Abstract
Differences in genetic background in model organisms can have complex effects on phenotypes of interest. We previously reported a difference in hermaphrodite lifespan between two wild-type lines widely used by C. elegans researchers (N2 hermaphrodite and male stocks). Here, using pathology-based approaches and genome sequencing, we identify the cause of this difference as a nonsense mutation in the filamin gene fln-2 in the male stock, which reduces early mortality caused by pharyngeal infection. We show how fln-2 variation explains previous discrepancies involving effects of sir-2.1 (sirtuin deacetylase) on ageing, and show that in a fln-2(+) background, sir-2.1 over-expression causes an FUDR (DNA synthesis inhibitor)-dependent reduction in pharyngeal infection and increase in lifespan. In addition we show how fln-2 variation confounds effects on lifespan of daf-2 (insulin/IGF-1 signalling), daf-12 (steroid hormone signalling), and eat-2 (putative dietary restriction). These findings underscore the importance of identifying and controlling genetic background variation.
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Affiliation(s)
- Yuan Zhao
- Institute of Healthy Ageing, Department of Genetics, Evolution and Environment, University College London, London, WC1E 6BT, UK
| | - Hongyuan Wang
- Institute of Healthy Ageing, Department of Genetics, Evolution and Environment, University College London, London, WC1E 6BT, UK
- School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, China
| | - Richard J Poole
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
| | - David Gems
- Institute of Healthy Ageing, Department of Genetics, Evolution and Environment, University College London, London, WC1E 6BT, UK.
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8
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Ono K, Qin Z, Johnsen RC, Baillie DL, Ono S. Kettin, the large actin-binding protein with multiple immunoglobulin domains, is essential for sarcomeric actin assembly and larval development in Caenorhabditis elegans. FEBS J 2019; 287:659-670. [PMID: 31411810 DOI: 10.1111/febs.15039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 07/29/2019] [Accepted: 08/12/2019] [Indexed: 12/30/2022]
Abstract
Among many essential genes in the nematode Caenorhabditis elegans, let-330 is located on the left arm of chromosome V and was identified as the largest target of a mutagen in this region. However, let-330 gene has not been characterized at the molecular level. Here, we report that two sequenced let-330 alleles are nonsense mutations of ketn-1, a previously characterized gene encoding kettin. Kettin is a large actin-binding protein of 472 kDa with 31 immunoglobulin domains and is expressed in muscle cells in C. elegans. let-330/ketn-1 mutants are homozygous lethal at the first larval stage with mild defects in body elongation. These mutants have severe defects in sarcomeric actin and myosin assembly in striated muscle. However, α-actinin and vinculin, which are components of the dense bodies anchoring actin to the membranes, were not significantly disorganized by let-330/ketn-1 mutation. Kettin localizes to embryonic myofibrils before α-actinin is expressed, and α-actinin deficiency does not affect kettin localization in larval muscle. Depletion of vinculin minimally affects kettin localization but significantly reduces colocalization of actin with kettin in embryonic muscle cells. These results indicate that kettin is an essential protein for sarcomeric assembly of actin filaments in muscle cells.
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Affiliation(s)
- Kanako Ono
- Department of Pathology, Emory University, Atlanta, GA, USA.,Department of Cell Biology, Emory University, Atlanta, GA, USA.,Winship Cancer Institute, Emory University, Atlanta, GA, USA
| | - Zhaozhao Qin
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
| | - Robert C Johnsen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
| | - David L Baillie
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada
| | - Shoichiro Ono
- Department of Pathology, Emory University, Atlanta, GA, USA.,Department of Cell Biology, Emory University, Atlanta, GA, USA.,Winship Cancer Institute, Emory University, Atlanta, GA, USA
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9
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Regulation of Actin Dynamics in the C. elegans Somatic Gonad. J Dev Biol 2019; 7:jdb7010006. [PMID: 30897735 PMCID: PMC6473838 DOI: 10.3390/jdb7010006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2019] [Revised: 03/13/2019] [Accepted: 03/15/2019] [Indexed: 11/25/2022] Open
Abstract
The reproductive system of the hermaphroditic nematode C. elegans consists of a series of contractile cell types—including the gonadal sheath cells, the spermathecal cells and the spermatheca–uterine valve—that contract in a coordinated manner to regulate oocyte entry and exit of the fertilized embryo into the uterus. Contraction is driven by acto-myosin contraction and relies on the development and maintenance of specialized acto-myosin networks in each cell type. Study of this system has revealed insights into the regulation of acto-myosin network assembly and contractility in vivo.
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10
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Baudier J, Jenkins ZA, Robertson SP. The filamin-B–refilin axis – spatiotemporal regulators of the actin-cytoskeleton in development and disease. J Cell Sci 2018; 131:131/8/jcs213959. [DOI: 10.1242/jcs.213959] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
ABSTRACT
During development, cycles of spatiotemporal remodeling of higher-order networks of actin filaments contribute to control cell fate specification and differentiation. Programs for controlling these dynamics are hard-wired into actin-regulatory proteins. The filamin family of actin-binding proteins exert crucial mechanotransduction and signaling functions in tissue morphogenesis. Filamin-B (FLNB) is a key player in chondrocyte progenitor differentiation for endochondral ossification. Biallelic loss-of-function mutations or gain-of-function mutations in FLNB cause two groups of skeletal disorders that can be attributed to either the loss of repressive function on TGF-β signaling or a disruption in mechanosensory properties, respectively. In this Review, we highlight a unique family of vertebrate-specific short-lived filamin-binding proteins, the refilins (refilin-A and refilin-B), that modulate filamin-dependent actin crosslinking properties. Refilins are downstream TGF-β effectors in epithelial cells. Double knockout of both refilin-A and refilin-B in mice results in precocious ossification of some axial skeletal elements, leading to malformations that are similar to those seen in FLNB-deficient mice. Based on these findings, we present a model summarizing the role of refilins in regulating the mechanosensory functions of FLNB during skeletal development. We also discuss the possible contribution of refilins to FLNB-related skeletal pathologies that are associated with gain-of-function mutations.
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Affiliation(s)
- Jacques Baudier
- Aix Marseille Université, CNRS, IBDM, 13284 Marseille Cedex 07, France
- Institut de Biologie du Développement de Marseille-UMR CNRS 7288, Campus de Luminy-Case 907, 13288 Marseille Cedex 9, France
| | - Zandra A. Jenkins
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Stephen P. Robertson
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
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11
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Pavone LM, Norris RA. Distinct signaling pathways activated by "extracellular" and "intracellular" serotonin in heart valve development and disease. Cell Biochem Biophys 2014; 67:819-28. [PMID: 23605455 DOI: 10.1007/s12013-013-9606-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cardiac valve diseases are often due to developmental anomalies that progressively lead to the abnormal distribution and organization of extracellular matrix proteins overtime. Whereas mechanisms underlying adult valvulopathies are unknown, previous work has shown a critical involvement of the monoamine serotonin in disease pathogenesis. In particular, the interaction of serotonin with its receptors can activate transforming growth factor-β1 (TGF-β1) signaling, which in turn promotes extracellular matrix gene expression. Elevated levels of circulating serotonin can lead to aberrant TGF-β1 signaling with significant effects on cardiac valve structure and function. Additional functions of serotonin have recently been reported in which internalization of serotonin, through the serotonin transporter SERT, can exert important cytoskeletal functions in lieu of simply being degraded. Recent findings demonstrate that intracellular serotonin regulates cardiac valve remodeling, and perturbation of this pathway can also lead to heart valve defects. Thus, both extracellular and intracellular mechanisms of serotonin action appear to be operative in heart valve development, functionality, and disease. This review summarizes some of the salient aspects of serotonin activity during cardiac valve development and disease pathogenesis with an understanding that further elaboration of intracellular and extracellular serotonin pathways may lead to beneficial treatments for heart valve disease.
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Affiliation(s)
- Luigi Michele Pavone
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Via S. Pansini 5, Naples, 80131, Italy,
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12
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Kovacevic I, Cram EJ. Filamin and Phospholipase C-ε are required for calcium signaling in the Caenorhabditis elegans Spermatheca. WORM 2013; 2:e25717. [PMID: 24778940 PMCID: PMC3875652 DOI: 10.4161/worm.25717] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/10/2013] [Indexed: 11/23/2022]
Abstract
Mechanical properties of the microenvironment are fundamental in orchestrating normal tissue function, disease progression, and organismal development. Studies of mechanotransduction in cultured cells on artificial substrates have revealed underlying principles, but the in vivo roles of mechanotransduction remain unclear. We recently reported that the Caenorhabditis elegans spermatheca—a myoepithelial tube composed of a cell monolayer—may be mechanosensitive. Live imaging with the genetically encoded calcium indicator GCaMP revealed that oocyte-induced stretching of the spermatheca resulted in calcium oscillations and constriction of the tube. FLN-1/filamin, a mechanosensitive cytoskeletal scaffolding protein, is required to correctly trigger the calcium transients. PLC-1/phospholipase C-epsilon and ITR-1/IP3 receptor are required to produce the calcium transients, and may function downstream of filamin. In addition to providing important insights into the biology of C. elegans, our studies offer a novel and genetically tractable model for studying mechanotransduction in a myoepithelial tissue.
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Affiliation(s)
- Ismar Kovacevic
- Department of Biology; Northeastern University; Boston, MA USA
| | - Erin J Cram
- Department of Biology; Northeastern University; Boston, MA USA
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13
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Filamin and phospholipase C-ε are required for calcium signaling in the Caenorhabditis elegans spermatheca. PLoS Genet 2013; 9:e1003510. [PMID: 23671426 PMCID: PMC3650001 DOI: 10.1371/journal.pgen.1003510] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 03/30/2013] [Indexed: 12/05/2022] Open
Abstract
The Caenorhabditis elegans spermatheca is a myoepithelial tube that stores sperm and undergoes cycles of stretching and constriction as oocytes enter, are fertilized, and exit into the uterus. FLN-1/filamin, a stretch-sensitive structural and signaling scaffold, and PLC-1/phospholipase C-ε, an enzyme that generates the second messenger IP3, are required for embryos to exit normally after fertilization. Using GCaMP, a genetically encoded calcium indicator, we show that entry of an oocyte into the spermatheca initiates a distinctive series of IP3-dependent calcium oscillations that propagate across the tissue via gap junctions and lead to constriction of the spermatheca. PLC-1 is required for the calcium release mechanism triggered by oocyte entry, and FLN-1 is required for timely initiation of the calcium oscillations. INX-12, a gap junction subunit, coordinates propagation of the calcium transients across the spermatheca. Gain-of-function mutations in ITR-1/IP3R, an IP3-dependent calcium channel, and loss-of-function mutations in LFE-2, a negative regulator of IP3 signaling, increase calcium release and suppress the exit defect in filamin-deficient animals. We further demonstrate that a regulatory cassette consisting of MEL-11/myosin phosphatase and NMY-1/non-muscle myosin is required for coordinated contraction of the spermatheca. In summary, this study answers long-standing questions concerning calcium signaling dynamics in the C. elegans spermatheca and suggests FLN-1 is needed in response to oocyte entry to trigger calcium release and coordinated contraction of the spermathecal tissue. During organism development and normal physiological function cells sense, integrate, and respond to a variety of cues or signals including biochemical and mechanical stimuli. In this study we used Caenorhabditis elegans, a small transparent worm, to study filamin (FLN-1), a structural protein that may act as a molecular strain gauge. The C. elegans spermatheca is a contractile tube that is stretched during normal function, making it an ideal candidate for study of how cells respond to stretch. Oocytes are ovulated into the spermatheca, fertilized, and then pushed into the uterus by constriction of the spermatheca. The ability of the spermatheca to constrict depends on inositol 1,4,5-triphosphate (IP3), a signaling molecule produced by the enzyme phospholipase C (PLC-1) that triggers calcium release within cells. In animals with mutated FLN-1 or PLC-1 the spermathecal cells fail to constrict. Using genetic analysis and a calcium-sensitive fluorescent protein, we show that FLN-1 functions with PLC-1 to regulate IP3 production, calcium release, and contraction of the spermatheca. Filamin may function to sense stretch caused by entering oocytes and to trigger constriction. These findings establish a link between filamin and calcium signaling that may apply to similar signaling pathways in other systems.
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14
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Abstract
Filamins are essential, evolutionarily conserved, modular, multidomain, actin-binding proteins that organize the actin cytoskeleton and maintain extracellular matrix connections by anchoring actin filaments to transmembrane receptors. By cross-linking and anchoring actin filaments, filamins stabilize the plasma membrane, provide cellular cortical rigidity, and contribute to the mechanical stability of the plasma membrane and the cell cortex. In addition to binding actin, filamins interact with more than 90 other binding partners including intracellular signaling molecules, receptors, ion channels, transcription factors, and cytoskeletal and adhesion proteins. Thus, filamins scaffold a wide range of signaling pathways and are implicated in the regulation of a diverse array of cellular functions including motility, maintenance of cell shape, and differentiation. Here, we review emerging structural and functional evidence that filamins are mechanosensors and/or mechanotransducers playing essential roles in helping cells detect and respond to physical forces in their local environment.
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Affiliation(s)
- Ziba Razinia
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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