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J. Cell Biol.,
Volume 143, Number 5, November 30, 1998 1249-1258


* Laboratory of Biochemistry, Aichi Cancer Center Research Institute, Chikusa-ku, Nagoya 464-0021, Japan; Rho-associated kinase (Rho-kinase), which
is activated by the small GTPase Rho, regulates formation of stress fibers and focal adhesions, myosin fiber
organization, and neurite retraction through the phosphorylation of cytoskeletal proteins, including myosin light chain, the ERM family proteins (ezrin, radixin,
and moesin) and adducin. Rho-kinase was found to
phosphorylate a type III intermediate filament (IF)
protein, glial fibrillary acidic protein (GFAP), exclusively at the cleavage furrow during cytokinesis. In the
present study, we examined the roles of Rho-kinase in
cytokinesis, in particular organization of glial filaments
during cytokinesis. Expression of the dominant-negative form of Rho-kinase inhibited the cytokinesis of Xenopus embryo and mammalian cells, the result being
production of multinuclei. We then constructed a series of mutant GFAPs, where Rho-kinase phosphorylation
sites were variously mutated, and expressed them in
type III IF-negative cells. The mutations induced impaired segregation of glial filament (GFAP filament)
into postmitotic daughter cells. As a result, an unusually long bridge-like cytoplasmic structure formed between the unseparated daughter cells. Alteration of
other sites, including the cdc2 kinase phosphorylation
site, led to no remarkable defect in glial filament separation. These results suggest that Rho-kinase is essential not only for actomyosin regulation but also for segregation of glial filaments into daughter cells which in
turn ensures correct cytokinetic processes.
Division of Signal
Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan; § Department of Tumor Genetics and Biology,
Kumamoto University School of Medicine, 2-2-1, Honjo, Kumamoto 860-0811, Japan
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