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General Comment |
upstream of Hippo signaling
NCBI Summary:
This gene encodes a protein serine/threonine kinase that is activated when bound to the GTP-bound form of Rho. The small GTPase Rho regulates formation of focal adhesions and stress fibers of fibroblasts, as well as adhesion and aggregation of platelets and lymphocytes by shuttling between the inactive GDP-bound form and the active GTP-bound form. Rho is also essential in cytokinesis and plays a role in transcriptional activation by serum response factor. This protein, a downstream effector of Rho, phosphorylates and activates LIM kinase, which in turn, phosphorylates cofilin, inhibiting its actin-depolymerizing activity. [provided by RefSeq, Jul 2008]
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Comment |
The Rho-GTPase effector ROCK regulates meiotic maturation of the bovine oocyte via myosin light chain phosphorylation and cofilin phosphorylation. Lee SR et al. (2015) Oocyte meiosis involves a unique asymmetric division involving spindle movement from the central cytoplasm to the cortex, followed by polar body extrusion. ROCK is a Rho-GTPase effector involved in various cellular functions in somatic cells as well as oocyte meiosis. ROCK was previously shown to promote actin organization by phosphorylating several downstream targets, including LIM domain kinase (LIMK), phosphorylated cofilin (p-cofilin), and myosin light chain (MLC). In this study, we investigated the roles of ROCK and MLC during bovine oocyte meiosis. We found that ROCK was localized around the nucleus at the oocyte's germinal-vesicle (GV) stage, but spreads to the rest of the cytoplasm in later developmental stages. On the other hand, phosphorylated MLC (p-MLC) localized at the cortex, and its abundance decreased by the metaphase-II stage. Disrupting ROCK activity, via RNAi or the chemical inhibitor Y-27632, blocked both cell-cycle progression and polar body extrusion. ROCK inhibition also resulted in decreased cortical actin, p-cofilin, and p-MLC levels. Similar to the phenotype associated with inhibition of ROCK activity, inhibition of MLC kinase by the chemical inhibitor ML-7 caused defects in polar body extrusion. Collectively, our results suggest that the ROCK/MLC/actomyosin as well as ROCK/LIMK/cofilin pathways regulate meiotic spindle migration and cytokinesis during bovine oocyte maturation. This article is protected by copyright. All rights reserved.//////////////////
Rho-GTPase Effector ROCK Phosphorylates Cofilin in Actin-Meditated Cytokinesis During Mouse Oocyte Meiosis. Duan X 2014 et al.
During oocyte meiosis a spindle forms in the central cytoplasm and migrates to the cortex. Subsequently, the oocyte extrudes a small body and forms a highly polarized egg; this process is primarily regulated by actin. ROCK is a Rho-GTPase effector that is involved in various cellular functions, such as stress fiber formation, cell migration, tumor cell invasion, and cell motility. In this study, we investigated possible roles for ROCK in mouse oocyte meiosis. ROCK was localized around spindles after germinal vesicle breakdown (GVBD) and was co-localized with cytoplasmic actin and mitochondria. Disrupting ROCK activity by RNAi or an inhibitor resulted in cell cycle progression and polar body extrusion failure. Time lapse microscopy showed that this may have been due to spindle migration and cytokinesis defects, as chromosomes segregated, but failed to extrude a polar body, and then re-aligned. Actin expression at oocyte membranes and in cytoplasm was significantly decreased after these treatments. Actin caps were also disrupted, which was confirmed by a failure to form cortical granule-free domains (CGFDs). The mitochondrial distribution was also disrupted, which indicated that mitochondria involved into the ROCK-mediated actin assembly. In addition, the phosphorylation levels of Cofilin, a downstream molecule of ROCK, decreased after disrupting ROCK activity. Thus, our results indicated that a ROCK-Cofilin-actin pathway regulated meiotic spindle migration and cytokinesis during mouse oocyte maturation.
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RhoA/ROCK Signaling in the Cumulus Mediates Extracellular Matrix Assembly. Yodoi R et al. Cumulus cells surround the oocyte and regulate the production and assembly of the extracellular matrix (ECM) around the cumulus-oocyte complex for its timely interaction with sperm in the oviduct. We recently found that C-C chemokines such as CCL2, CCL7 and CCL9 are produced and stimulate integrin-mediated ECM assembly in the post-ovulatory cumulus to protect eggs, and that prostaglandin (PG) E2-EP2 signaling in the cumulus cells facilitates fertilization by suppressing this chemokine signaling, which otherwise results in fertilization failure by preventing sperm penetration through the cumulus ECM. However, it remains unknown as to what mechanisms underlie chemokine-induced cumulus ECM assembly. Here we report that inhibition of EP2 signaling or addition of CCL7 augments RhoA activation and induces the surface accumulation of integrin and the contraction of cumulus cells. Enhanced surface accumulation of integrin then stimulates the formation and assembly of fibronectin fibrils, as well as induces cumulus ECM resistance to hyaluronidase and sperm penetration. These changes in the cumulus ECM as well as cell contraction are relieved by the addition of Y27632 or blebbistatin. These results suggest that chemokines induce integrin engagement to the ECM and consequent ECM remodeling through the RhoA/ROCK/actomyosin pathway, making the cumulus ECM barrier resistant to sperm penetration. Based on these results, we propose that PGE2-EP2 signaling negatively regulates chemokine-induced Rho/ROCK signaling in cumulus cells for successful fertilization./////// ROCK inhibitor Y-27632 prevents porcine oocyte maturation. Zhang Y 2014 et al.
The inhibitor Y-27632 is a specific selective inhibitor of Rho-associated protein kinases (ROCKs), which are downstream effectors of Rho guanosine triphosphatease (GTPases) and regulate Rho-associated cellular functions, including actin cytoskeletal organization. Little is known regarding the effects of Y-27632 on mammalian oocyte maturation. In the present study, we investigated the effects of Y-27632 on porcine oocyte meiosis and possible regulatory mechanisms of ROCK during porcine oocyte maturation. We found that ROCK accumulated not only at spindles, but also at the cortex in porcine oocytes. Y-27632 treatment reduced ROCK expression, and inhibited porcine oocyte meiotic maturation, which might be because of the impairment of actin expression and actin-related spindle positioning. Y-27632 treatment also disrupted the formation of actin cap and cortical granule-free domain, which further confirmed a spindle positioning failure. Thus, Y-27632 has significant effects on the meiotic competence of mammalian oocytes by reducing ROCK expression, and the regulation is related to its effects on actin-mediated spindle positioning.
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