マツイ　タケシ   Takeshi Matsui   松井　毅    所属   応用生物学部 応用生物学科    職種   教授
言語種別	英語
発行・発表の年月	2002/06
形態種別	学術論文
査読	査読あり
標題	Rho-dependent and-independent activation mechanisms of ezrin/radixin/moesin proteins: an essential role for polyphosphoinositides in vivo
執筆形態	共著
掲載誌名	Journal of Cell Biology
掲載区分	国外
出版社・発行元	The Company of Biologists
巻・号・頁	115,pp.2569-2580
著者・共著者	Shigenobu Yonemura, Takeshi Matsui, Shoichiro Tsukita, Sachiko Tsukita
概要	Ezrin/radixin/moesin (ERM) proteins crosslink actin filaments to plasma membranes and are involved in the organization of the cortical cytoskeleton, especially in the formation of microvilli. ERM proteins are reported to be activated as crosslinkers in a Rho-dependent manner and are stabilized when phosphorylated at their C-terminal threonine residue to create C-terminal threonine-phosphorylated ERM proteins (CPERMs). Using a CPERM-specific mAb, we have shown, in vivo, that treatment with C3 transferase (a Rho inactivator) or staurosporine (a protein kinase inhibitor) leads to the dephosphorylation of CPERMs, the translocation of ERM proteins from plasma membranes to the cytoplasm and microvillar breakdown. We further elucidated that ERM protein activation does not require C-terminal phosphorylation in A431 cells stimulated with epidermal growth factor. In certain types of kidney-derived cells such as MDCK cells, however, ERM proteins appear to be activated in the absence of Rho activation and remain active without C-terminal phosphorylation. Interestingly, microinjection of an aminoglycoside antibiotic, neomycin, which binds to polyphosphoinositides, such as phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P(2)], affected the activation of ERM proteins regardless of cell type. These findings not only indicate the existence of a Rho-independent activation mechanism of ERM proteins but also suggest that both Rho-dependent and -independent activation of ERM proteins require a local elevation of PtdIns(4,5)P(2) concentration in vivo.