Regulation of cytoplasmic division of Xenopus embryo by rho p21 and its inhibitory GDP/GTP exchange protein (rho GDI).

Abstract

Abstract. Evidence is accumulating that the rho family, a member of the ms p21-related small GTPbinding protein superfamily, regulates cell morphology, cell motility, and smooth muscle contraction through the actomyosin system. The actomyosin system is also known to be essential for cytoplasmic division of cells (cytokinesis). In this study, we examined the action of rho p21, its inhibitory GDP/GTP exchange protein, named rho GDI, its stimulatory GDP/GTP exchange protein, named smg GDS, and botulinum ADP-ribosyltransferase C3, known to selectively ADP-ribosylate rho p21 and to impair its function, in the cytoplasmic division using Xenopus embryos. The sperm-induced cytoplasmic division of Xenopus embryos was not affected by microinjection into the embryos of either smg GDS or the guanosine-5'-(3-O-thio)triphosphate (GTP'yS)-bound form of rhoA p21, one member of the rho family, but completely inhibited by microinjection of rho GDI or C3. Under these conditions, nuclear division occurred normally but the furrow formation, which was induced by the contractile ring consisting of actomyosin just beneath the plasma membrane, was impaired. Comicroinjection of rho GDI with the GTP'yS-bound form of rhoA p21 prevented the rho GDI action. Moreover, the sperm-induced cytoplasmic division of Xenopus embryos was inhibited by microinjection into the embryos of the rhoA p21 pre-ADP-ribosylated by C3 which might serve as a dominant negative inhibitor of endogenous rho p21. These results indicate that rho p21 together with its regulatory proteins regulates the cytoplasmic division through the actomyosin system.

Specific accumulation of Rho-associated kinase at the cleavage furrow during cytokinesis: cleavage furrow-specific phosphorylation of intermediate filaments

“…The small GTPase Rho (Van Aelst and D'Souza-Schorey, 1997;Hall, 1998) is known to play a critical role in cytokinesis (Kishi et al, 1993;Mabuchi et al, 1993;Drechsel et al, 1997) and localize to the cleavage furrow (Takaishi et al, 1995). In the present study, we found that Rho-kinase also localized to the cleavage furrow, suggesting that Rhokinase binds to Rho in vivo and phosphorylates several proteins during cytokinesis.…”

Rho GTPase activity zones and transient contractile arrays

“…(19)(20)(21)(22)(23) Rho activity zones are typically spatially confined to regions with widths on the order of microns, while the linear dimension of the cells in which they form ranges from hundreds of microns (Xenopus oocytes, echinoderm zygotes) to tens of microns (echinoderm blastomeres, cultured mammalian cells). Rho itself was shown to be required for cytokinesis long ago, (1) but these findings, and the demonstration that active Rho dynamically senses microtubule perturbation, (18) imply that Rho zones are part of the long-sought link between microtubule geometry and stimulation of cytokinetic furrowing. It remains to be seen whether Cdc42 and/or Rac activity zones also participate in cytokinesis, but this is consistent with several findings.…”

Dissecting the Role of Rho-mediated Signaling in Contractile Ring Formation

“…A contribution of Rho in contractile ring formation has been reported previously (Kishi et al, 1993;Mabuchi et al, 1993). However, in fluorescence resonance energy transfer (FRET)-based analysis, it has been concluded that Rho activation is not required for contractile ring formation (Yoshizaki et al, 2003).…”