UNC-87, a calponin-related protein in C. elegans, antagonizes ADF/cofilin-mediated actin filament dynamics

• Type of Material: Article
• Authors: Sawako Yamashiro, Emory University; Mario Gimona, Consorzio Mario Negri Sud; Shoichiro Ono, Emory University
• Language: English
• Date: 2007-09-01
• Publisher: Company of Biologists
• Publication Version: Final Published Version
• Copyright Statement: © The Company of Biologists Limited 2007
• Final Published Version (URL): http://jcs.biologists.org/content/120/17/3022.long
• Title of Journal or Parent Work: Journal of Cell Science
• ISSN: 0021-9533
• Volume: 120
• Issue: Pt 17
• Start Page: 3022
• End Page: 3033
• Grant/Funding Information: This work was supported by a Marie Curie Excellence Grant (MEXT-CT-2003–002573) of the European Union to M.G. and an NIH grant (R01 AR48615) to S.O.
• Keywords: ADF/cofilin; Tropomyosin; Calponin; Actin dynamics
• Research Categories: Biology, Cell; Health Sciences, Pathology

Abstract

Summary Stabilization of actin filaments is critical for supporting actomyosin-based contractility and for maintaining stable cellular structures. Tropomyosin is a well-characterized ubiquitous actin stabilizer that inhibits ADF/cofilin-dependent actin depolymerization. Here, we show that UNC-87, a calponin-related Caenorhabditis elegans protein with seven calponin-like repeats, competes with ADF/cofilin for binding to actin filaments and inhibits ADF/cofilin-dependent filament severing and depolymerization in vitro. Mutations in the unc-87 gene suppress the disorganized actin phenotype in an ADF/cofilin mutant in the C. elegans body wall muscle, supporting their antagonistic roles in regulating actin stability in vivo. UNC-87 and tropomyosin exhibit synergistic effects in stabilizing actin filaments against ADF/cofilin, and direct comparison reveals that UNC-87 effectively stabilizes actin filaments at much lower concentrations than tropomyosin. However, the in vivo functions of UNC-87 and tropomyosin appear different, suggesting their distinct roles in the regulation of actomyosin assembly and cellular contractility. Our results demonstrate that actin binding via calponin-like repeats competes with ADF/cofilin-driven cytoskeletal turnover, and is critical for providing the spatiotemporal regulation of actin filament stability.