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Báo cáo khoa học: hhLIM is a novel F-actin binding protein involved in actin cytoskeleton remodeling
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Human heart LIM protein (hhLIM) is a newly cloned protein.In vitro analyses showed that green fluorescent protein (GFP)-tagged hhLIM pro-tein accumulated in the cytoplasm of C2C12 cells and colocalized with F-actin, indicating that hhLIM is an actin-binding protein in C2C12 cells. | ễFEBS Journal hhLIM is a novel F-actin binding protein involved in actin cytoskeleton remodeling Bin Zheng Jin-kun Wen and Mei Han Department of Biochemistry and Molecular Biology Hebei MedicalUniversity Shijiazhuang China Keywords actin-binding protein cytoskeleton F-actin hhLIM LIM domain Correspondence M. Han Department of Biochemistry and Molecular Biology Hebei Medical University No. 361 Zhongshan East Road Shijiazhuang 050017 China Fax 86 311 8669 6826 Tel 86 311 8626 5563 E-mail hanmei@hebmu.edu.cn Received 21 November 2007 revised 15 January 2008 accepted 30 January 2008 doi 10.1111 j.1742-4658.2008.06315.x Human heart LIM protein hhLIM is a newly cloned protein. In vitro analyses showed that green fluorescent protein GFP -tagged hhLIM protein accumulated in the cytoplasm of C2C12 cells and colocalized with F-actin indicating that hhLIM is an actin-binding protein in C2C12 cells. Overexpression of hhLIM-GFP in C2C12 cells significantly stabilized actin filaments and delayed depolymerization of the actin cytoskeleton induced by cytochalasin B treatment. Expression of hhLIM-GFP in C2C12 cells also induced significant changes in the organization of the actin cytoskeleton specifically fewer and thicker actin bundles than in control cells suggesting that hhLIM functions as an actin-bundling protein. This hypothesis was confirmed using low-speed co-sedimentation assays and direct observation of F-actin bundles that formed in vitro in the presence of hhLIM. hhLIM has two LIM domains. To identify the essential regions and sites for association a series of truncated mutants was constructed which showed that LIM domain 2 has the same activity as full-length hhLIM. To further characterize the binding sites the LIM domain was functionally destructed by replacing cysteine with serine in domain 2 and results showed that the second LIM domain plays a central role in bundling of F-actin. Taken together these data identify hhLIM as an actin-binding protein that increases .