The Rho kinases I and II regulate different aspects of myosin II activity.

Research output: Contribution to journalJournal articleResearchpeer-review

The homologous mammalian rho kinases (ROCK I and II) are assumed to be functionally redundant, based largely on kinase construct overexpression. As downstream effectors of Rho GTPases, their major substrates are myosin light chain and myosin phosphatase. Both kinases are implicated in microfilament bundle assembly and smooth muscle contractility. Here, analysis of fibroblast adhesion to fibronectin revealed that although ROCK II was more abundant, its activity was always lower than ROCK I. Specific reduction of ROCK I by siRNA resulted in loss of stress fibers and focal adhesions, despite persistent ROCK II and guanine triphosphate-bound RhoA. In contrast, the microfilament cytoskeleton was enhanced by ROCK II down-regulation. Phagocytic uptake of fibronectin-coated beads was strongly down-regulated in ROCK II-depleted cells but not those lacking ROCK I. These effects originated in part from distinct lipid-binding preferences of ROCK pleckstrin homology domains. ROCK II bound phosphatidylinositol 3,4,5P(3) and was sensitive to its levels, properties not shared by ROCK I. Therefore, endogenous ROCKs are distinctly regulated and in turn are involved with different myosin compartments.
Original languageEnglish
JournalJournal of Cell Biology
Issue number3
Pages (from-to)443-53
Number of pages10
Publication statusPublished - 2005

Bibliographical note

Keywords: 1-Phosphatidylinositol 3-Kinase; Animals; Cardiac Myosins; Cell Adhesion; Cells, Cultured; Cercopithecus aethiops; Fibroblasts; Fibronectins; Focal Adhesions; Guanosine Triphosphate; Humans; Intracellular Signaling Peptides and Proteins; Microfilaments; Myosin Light Chains; Myosin Type II; Phagocytosis; Phosphatidylinositol Phosphates; Phosphorylation; Protein-Serine-Threonine Kinases; RNA, Small Interfering; Rats; Stress Fibers; rho-Associated Kinases

ID: 5160894