Cell Biology

Oocyte Maturation and G Beta and Gamma Subunits

Science's STKE  27 Mar 2001:
Vol. 2001, Issue 75, pp. tw7
DOI: 10.1126/stke.2001.75.tw7

The molecular details of progesterone-dependent Xenopus oocyte maturation are not well defined, but adenylyl cyclase activity is inhibited and cyclic AMP (cAMP) concentrations decrease. Maturation does not appear to involve Gαi activity; however, Sheng et al. found that Gβγ subunits are involved in arresting oocyte meiosis. maturation was induced by overexpressing in oocytes Gβγ scavengers, such as the α subunit of bovine transducin (Gαt) or a membrane-localized COOH-terminal bovine β-adrenergic receptor kinase (βARK-CCAAX) fragment, both of which sequester Gβγ subunits. βARK-CCAAX coprecipitated with Gβ in oocyte lysates, suggesting that Gβ-dependent inhibition was perturbed by direct association. Xenopus mitogen-activated protein kinase (xMAPK) was activated, an essential step in maturation, as a consequence of Gβ sequestration. Finally, overexpression of Gβγ in oocytes expressing βARK-CCAAX inhibited maturation and resulted in increased production of cAMP. These data suggest that Gβγ may influence oocyte maturation arrest and that progesterone may prevent the activation of a heterotrimeric G protein and the consequent release of Gβγ.

Y. Sheng, M. Tiberi, R. A. Booth, C. Ma, X. J. Liu, Regulation of Xenopus oocyte meiosis arrest by G protein βγ subunits. Curr. Biol. 11, 405-416 (2001). [Online Journal]