ROCKs: multifunctional kinases in cell behaviour

Abstract
Rho effectors include two serine/threonine kinases that are known as ROCK I and ROCK II. ROCKs phosphorylate various substrates, including myosin light chain phosphatase, myosin light chain, ezrin–radixin–moesin proteins and LIM (for Lin11, Isl1 and Mec3) kinases, and mediate the formation of actin stress fibres and focal adhesions in various cell types. In smooth muscle, ROCKs are involved in agonist-induced Ca2+-sensitization in muscle contraction, possibly by phosphorylating the myosin-binding subunit of myosin light chain phosphatase, and thereby inhibiting the phosphatase activity. ROCKs have an important role in cell migration by enhancing cell contractility. They are required for tail retraction of monocytes and cancer cells, and a ROCK inhibitor has been used to reduce tumour-cell dissemination in vivo. ROCKs also have a role in other cellular responses that require actomyosin contractility, such as axonal growth and cytokinesis. Recently, ROCKs have been linked to the control of cell size and regulation of distance between the two centrioles.