Rho-associated coiled-coil containing kinases (ROCK)

Abstract

In humans, ROCK1 and ROCK2 both contain 33 exons and are located on chromosome 18 (18q11.1) and 2 (2p24) respectively. The ROCK1 open reading frame encodes 1354 amino acids, whereas ROCK2 encodes 1388 amino acids. ROCK2 also has a reported splice variant, preferentially expressed in skeletal muscle, which results in the inclusion of 57 additional amino acids. 7 The two ROCK homologs shares 64% identity in their primary amino acid sequences, with the highest homology (92%) within the kinase domains and the coiled-coil domains being the most diverse (55%). 5 The kinase domains of ROCK are closely related to many homologous domains in this family, including dystrophia myotonica protein kinase (DMPK), myotonic dystrophy kinase related-Cdc42 related kinases (MRCK) α and β, and citron Rho-interacting kinase (CRIK) . To date, the crystal structures of the kinase domains from ROCK1, 8 ROCK2, 9 MRCKβ, 10 and DMPK 11 have been determined, which has highlighted the high degree of tertiary as well as primary similarity. N-terminal and carboxyl-terminal extensions of the ROCK kinase domains are essential for catalytic activity. 4,8,9 The ROCK kinase domains are located in the N-terminal region, which is followed by a central ~600 amino acid long amphipathic α-helix forming a coiledcoil region (Fig. 1).12 At the carboxyl-terminal region, there is a split pleckstrin homology (PH) domain, which is bisected by an internal cysteine-rich zinc finger-like motif domain (CRD). The two separate PH portions assemble together to form a typical PH domain that is attached by two short linkers to a separate CRD. 13The canonical Rho binding domain (RBD) forms a parallel coiled coil dimer, as revealed by crystal structure determinations, and binds exclusively to the switch I and switch II regions of GTP-bound active RhoA and RhoC.14,15 Two additional Rhointeracting domains were identified that can tightly interact with RhoA, which may cooperatively contribute to binding. 16 Crystal structure studies revealed that ROCK has two dimerization domains: the ~70 residue N-terminal dimerization region 8,9 and the coiled-coil helical regions.12 Charged residues in the coiled-coil might function as a hinge that allows the N-terminal kinase domains to interact with C-terminal inhibitory regions. Structural determination of full-length ROCK protein crystals will ultimately reveal how the various domains interact and the mechanism of auto-inhibition. Regulation of ROCK ActivityAlthough ROCK1 and ROCK2 have highly related functional domains and significant amino acid identity, they are regulated both by common means as well as mechanisms unique to ROCK1 or ROCK2.

HIF-3α Promotes Metastatic Phenotypes in Pancreatic Cancer by Transcriptional Regulation of the RhoC–ROCK1 Signaling Pathway

“…Although RhoA and RhoB expression levels were not significantly associated with patient clinicopathologic findings, RhoC overexpression has been shown to play a role in tumor invasion and correlates with a poor patient prognosis (31). The RhoC-ROCK1 signaling pathway plays a pivotal role in actin cytoskeleton organization and is involved in many key processes, including cell adhesion, vesicular trafficking, proliferation, cell survival, cell morphology, and cell-matrix interactions (32)(33)(34)(35)(36)(37). Inhibition of ROCK1 expression blocks LIMK2/cofilin phosphorylation and subsequent stress fiber formation (38,39).…”

Rho GTPases: Regulation and roles in cancer cell biology

“…ROCK acts by increasing the phosphorylation of myosin light chain, which increases the interaction of myosin II with actin filaments. 76 The consistently high cortical tension results in blebbing, which contributes to cancer cell motility. 76,77 Cells using lamellipodium-driven cell migration have an elongated morphology that depends on cell adhesion dynamics and traction forces between both poles of the cell.…”

“…76 The consistently high cortical tension results in blebbing, which contributes to cancer cell motility. 76,77 Cells using lamellipodium-driven cell migration have an elongated morphology that depends on cell adhesion dynamics and traction forces between both poles of the cell. Lamellipodia drive protrusion of the plasma membrane at the Figure 4.…”

Cytoskeleton Rearrangements during the Execution Phase of Apoptosis

“…Actinomyosin contraction is activated via the Rho/Rhokinase (ROCK) signalling pathway which ends up with the phosphorylation of myosin light chain II (MLC-II) [32]. Rho-kinases are effectors of Rho-GTPase proteins, being RhoA and RhoC the most well characterized ROCK regulators [33]. Active GTP-bound Rho proteins activate ROCK by binding to their C-terminal portion of the coiled coil.…”