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 pl asma membrane receptors to phospholipase C and consequently to intrace llular Ca2+ release. Because they might function in initiating Ca2+ re lease at fertilization, we examined G alpha(q) family proteins in oocy tes and eggs of Xenopus laevis. Three members of this protein family w ere identified by immunoblotting and antisense depletion. These protei ns 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 o ocyte maturation, of the ability to release Ca2+ at fertilization (Sch lichter 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) prote ins during early development. While amounts of G alpha(s) and G alpha( i3) show little or no change, G alpha(q) family protein expression inc reases 27-fold between the egg and neurula stages, suggesting that the se proteins may be important in initiating Ca2+ release during early d evelopment. (C) 1996 Academic Press, Inc.