Oshiro N, Fukata Y, Kaibuchi K
Division of Signal Transduction, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0101, Japan.
J Biol Chem. 1998 Dec 25;273(52):34663-6. doi: 10.1074/jbc.273.52.34663.
Rho-associated kinase (Rho-kinase), which is activated by the small GTPase Rho, phosphorylates moesin at Thr558 in vitro. Here, using a site- and phosphorylation state-specific antibody, we found that the expression of dominant active RhoA in COS7 cells induced moesin phosphorylation and the formation of microvilli-like structures at apical membranes where the Thr558-phosphorylated moesin accumulated, whereas the expression of dominant negative Rho-kinase inhibited both of these processes. The expression of dominant active Rho-kinase also induced moesin phosphorylation. When COS7 cells expressing moesin or moesinT558A (substitution of Thr by Ala) were cultured under serum-depleted conditions, there were few microvilli-like structures, whereas microvilli-like structures remained in the cells expressing moesinT558D (substitution of Thr by Asp). The expression of moesinT558A inhibited the dominant active RhoA-induced formation of microvilli-like structures. These results indicate that Rho-kinase regulates moesin phosphorylation downstream of Rho in vivo and that the phosphorylation of moesin by Rho-kinase plays a crucial role in the formation of microvilli-like structures.
Rho相关激酶（Rho激酶）由小GTP酶Rho激活，在体外可使埃兹蛋白在苏氨酸558位点发生磷酸化。在此，我们使用位点和磷酸化状态特异性抗体，发现COS7细胞中显性活性RhoA的表达诱导了埃兹蛋白磷酸化，并在顶端膜上形成了微绒毛样结构，苏氨酸558磷酸化的埃兹蛋白在该顶端膜上积累，而显性负性Rho激酶的表达则抑制了这两个过程。显性活性Rho激酶的表达也诱导了埃兹蛋白磷酸化。当在血清饥饿条件下培养表达埃兹蛋白或埃兹蛋白T558A（苏氨酸被丙氨酸取代）的COS7细胞时，几乎没有微绒毛样结构，而在表达埃兹蛋白T558D（苏氨酸被天冬氨酸取代）的细胞中仍保留微绒毛样结构。埃兹蛋白T558A的表达抑制了显性活性RhoA诱导的微绒毛样结构的形成。这些结果表明，Rho激酶在体内Rho的下游调节埃兹蛋白磷酸化，并且Rho激酶介导的埃兹蛋白磷酸化在微绒毛样结构的形成中起关键作用。
