Cell Biology Oocyte Maturation and G Beta and Gamma Subunits

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 Gα_i activity; however, Sheng et al. found that Gβ subunits are involved in arresting oocyte meiosis. maturation was induced by overexpressing in oocytes Gβ scavengers, such as the α subunit of bovine transducin (Gα_t) or a membrane-localized COOH-terminal bovine β-adrenergic receptor kinase (βARK-C_CAAX) fragment, both of which sequester Gβ subunits. βARK-C_CAAX 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 Gβ in oocytes expressing βARK-C_CAAX inhibited maturation and resulted in increased production of cAMP. These data suggest that Gβ may influence oocyte maturation arrest and that progesterone may prevent the activation of a heterotrimeric G protein and the consequent release of Gβ.

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

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Nancy R. Gough (4 September 2007)
Sci. STKE 2007 (402), tw319. [DOI: 10.1126/stke.4022007tw319]
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