Increased expression of alpha(q) family G-proteins during oocyte maturation and early development of Xenopus laevis

G-proteins of the alpha(q) family link extracellular stimulation of plasma membrane receptors to phospholipase C and consequently to intracellular Ca2+ release. Because they might function in initiating Ca2+ release at fertilization, we examined G alpha(q) family proteins in oocytes and eggs of Xenopus laevis. Three members of this protein family were identified by immunoblotting and antisense depletion. These proteins are barely detectable in the immature oocyte, but undergo a 6-fold increase in amount during oocyte maturation. This increase in G alpha(q) family protein expression correlates with the acquisition, during oocyte maturation, of the ability to release Ca2+ at fertilization (Schlichter and Elinson, 1981, Dev. Biol. 83, 33-41). In contrast, amounts of G alpha(s) and G alpha(i3) are constant during maturation. We also examined the amounts of G alpha(q), G alpha(s), and G alpha(i3) proteins during early development. While amounts of G alpha(s) and G alpha(i3) show little or no change, G alpha(q) family protein expression increases 27-fold between the egg and neurula stages, suggesting that these proteins may be important in initiating Ca2+ release during early development. (C) 1996 Academic Press, Inc.