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	1999/11
形態種別	学術論文
査読	査読あり
標題	Activation of ERM proteins in vivo by Rho involves phosphatidyl-inositol 4-phosphate 5-kinase and not ROCK kinases
執筆形態	共著
掲載誌名	Current Biology
掲載区分	国外
出版社・発行元	CellPress
巻・号・頁	9(21),pp.1259-1262
総ページ数	4
担当区分	筆頭著者
著者・共著者	Takeshi Matsui, Shigenobu Yonemura, Shoichiro Tsukita, Sachiko Tsukita
概要	When activated, ERM (ezrin, radixin, moesin) proteins are recruited to the plasma membrane, with concomitant carboxy-terminal threonine phosphorylation, where they crosslink actin filaments to the plasma membrane to form microvilli. Here, we report that, when NIH3T3 or HeLa cells were transfected with a constitutively active mutant of the small GTPase RhoA (V14RhoA), microvilli were induced and the level of carboxy-terminal threonine-phosphorylated ERM proteins (CPERM) increased ∼30-fold. This increase was not observed following transfection of constitutively active forms of two other Rho-family GTPases, Rac1 and Cdc42, or of a direct effector of Rho, Rho-kinase (also known as ROKα or ROCK-II). The V14RhoA-induced phosphorylation of ERM proteins was not suppressed by Y-27632, a specific inhibitor of ROCK kinases including Rho-kinase. Overexpression of another direct effector of Rho, phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) type Iα, but not a kinase-inactive mutant, increased ∼sixfold the level of CPERM, and induced microvilli. Together with the previous finding that the PI4P5K product phosphatidylinositol 4,5-bisphosphate (PIP2) activates ERM proteins in vitro, our data suggest that PIP2, and not ROCK kinases, is involved in the RhoA-dependent activation of ERM proteins in vivo. The active state of ERM proteins is maintained through threonine phosphorylation by as yet undetermined kinases, leading to microvillus formation.