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Cofilin phosphorylation by LIM-kinase 1 and its role in Rac-mediated actin reorganization


Rac is a small GTPase of the Rho family that mediates stimulus-induced actin cytoskeletal reorganization to generate lamellipodia1,2,3,4,5. 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 dynamics6,7,8,9,10, and its ability to bind and depolymerize actin is abolished by phosphorylation of serine residue at 3 (refs 11, 12); 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 domains13,14,15,16, 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.

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Figure 1: LIMK-1 binds to F-actin and induces actin reorganization.
Figure 2: Phosphorylation of cofilin by LIMK-1.
Figure 3: Involvement of LIMK-1 in Rac signalling.
Figure 4: Involvement of LIMK-1 in insulin-induced formation of membrane ruffling.

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We thank S. Kuroda, K. Kaibuchi and K. Ito for plasmids of Rho, Rac and Cdc42; T.Amano and A. Miyata for technical assistance; and Y. Fujiki, H. Matsuo, C. Ikebe, M. Ohara and K.Toyoshima for comments. This work was supported by grants from the Ministry of Education, Science, Sports and Culture of Japan and the Japan Science and Technology Corporation (to K.M.).

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Correspondence to Kensaku Mizuno.

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Yang, N., Higuchi, O., Ohashi, K. et al. Cofilin phosphorylation by LIM-kinase 1 and its role in Rac-mediated actin reorganization. Nature 393, 809–812 (1998).

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