Yang N, Higuchi O, Ohashi K, Nagata K, Wada A, Kangawa K, Nishida E, Mizuno K
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
Nature. 1998 Jun 25;393(6687):809-12. doi: 10.1038/31735.
Rac is a small GTPase of the Rho family that mediates stimulus-induced actin cytoskeletal reorganization to generate lamellipodia. Little is known about the signalling pathways that link Rac activation to changes in actin filament dynamics. Cofilin is known to be a potent regulator of actin filament dynamics, and its ability to bind and depolymerize actin is abolished by phosphorylation of serine residue at 3; however, the kinases responsible for this phosphorylation have not been identified. Here we show that LIM-kinase 1 (LIMK-1), a serine/threonine kinase containing LIM and PDZ domains, phosphorylates cofilin at Ser 3, both in vitro and in vivo. When expressed in cultured cells, LIMK-1 induces actin reorganization and reverses cofilin-induced actin depolymerization. Expression of an inactive form of LIMK-1 suppresses lamellipodium formation induced by Rac or insulin. Furthermore, insulin and an active form of Rac increase the activity of LIMK-1. Taken together, our results indicate that LIMK-1 participates in Rac-mediated actin cytoskeletal reorganization, probably by phosphorylating cofilin.
Rac是Rho家族的一种小GTP酶，它介导刺激诱导的肌动蛋白细胞骨架重组以产生片状伪足。关于将Rac激活与肌动蛋白丝动力学变化联系起来的信号通路，人们了解甚少。已知丝切蛋白是肌动蛋白丝动力学的有效调节剂，其结合和解聚肌动蛋白的能力会因丝氨酸残基在3位的磷酸化而丧失；然而，负责这种磷酸化的激酶尚未被鉴定出来。在此我们表明，LIM激酶1（LIMK-1），一种含有LIM和PDZ结构域的丝氨酸/苏氨酸激酶，在体外和体内均能使丝切蛋白在丝氨酸3位磷酸化。当在培养细胞中表达时，LIMK-1诱导肌动蛋白重组并逆转丝切蛋白诱导的肌动蛋白解聚。无活性形式的LIMK-1的表达抑制了由Rac或胰岛素诱导的片状伪足形成。此外，胰岛素和活性形式的Rac增加了LIMK-1的活性。综上所述，我们的结果表明LIMK-1可能通过使丝切蛋白磷酸化而参与Rac介导的肌动蛋白细胞骨架重组。
