Rho-kinase-mediated contraction of isolated stress fibers

Kazuo Katoh, Yumiko Kano, Mutsuki Amano, Hirofumi Onishi, Kozo Kaibuchi, Keigi Fujiwara

Research output: Contribution to journalArticlepeer-review

271 Citations (Scopus)


It is widely accepted that actin filaments and the conventional double-headed myosin interact to generate force for many types of nonmuscle cell motility, and that this interaction occurs when the myosin regulatory light chain (MLC) is phosphorylated by MLC kinase (MLCK) together with calmodulin and Ca2+. However, recent studies indicate that Rho-kinase is also involved in regulating the smooth muscle and nonmuscle cell contractility. We have recently isolated reactivatable stress fibers from cultured cells and established them as a model system for actomyosin-based contraction in nonmuscle cells. Here, using isolated stress fibers, we show that Rho-kinase mediates MLC phosphorylation and their contraction in the absence of Ca2+. More rapid and extensive stress fiber contraction was induced by MLCK than was by Rho-kinase. When the activity of Rho-kinase but not MLCK was inhibited, cells not only lost their stress fibers and focal adhesions but also appeared to lose cytoplasmic tension. Our study suggests that actomyosin-based nonmuscle contractility is regulated by two kinase systems: the Ca2+-dependent MLCK and the Rho-kinase systems. We propose that Ca2+ is used to generate rapid contraction, whereas Rho-kinase plays a major role in maintaining sustained contraction in cells.

Original languageEnglish
Pages (from-to)569-583
Number of pages15
JournalJournal of Cell Biology
Issue number3
Publication statusPublished - 05-02-2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Cell Biology


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