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First published online 7 August 2007
doi: 10.1242/jcs.013516

Journal of Cell Science 120, 3022-3033 (2007)
Published by The Company of Biologists 2007
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Research Article

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

Sawako Yamashiro1, Mario Gimona2 and Shoichiro Ono1,*

1 Department of Pathology, Emory University, Atlanta, GA 30322, USA
2 Unit of Actin Cytoskeleton Regulation, Consorzio Mario Negri Sud, Department of Cell Biology and Oncology, Via Nazionale 8a, 66030 Santa Maria, Imbaro, Italy

* Author for correspondence (e-mail: sono{at}emory.edu)

Accepted 26 June 2007

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.

Key words: Actin dynamics, ADF/cofilin, Calponin, Tropomyosin


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UNC-87 stabilises actin with a CLIK

JCS 2007 120: 1704. [Full Text]  





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