Involvement of G-proteins and adenylate cyclase in the action of gonad-stimulating substance on starfish ovarian follicle cells.

Gonad-stimulating substance (GSS) secreted from radial nerves induces meiotic maturation of starfish oocytes by stimulating production of 1-methyladenine (1-MeAde) in ovarian follicle cells. We have previously shown that cAMP mediates the action of GSS on 1-MeAde synthesis by starfish ovarian follicle cells. The present study examines the possible involvement of guanine nucleotide-binding regulatory proteins (G-proteins) and adenylate cyclase in the action of GSS on 1-MeAde production by starfish (Asterina pectinifera) follicle cells. GSS slightly stimulated adenylate cyclase activity in crude membrane preparations of follicle cells. GTP markedly enhanced this action of GSS in a dose-dependent manner. Nonhydrolyzable GTP analogs such as guanosine 5'-O-(3-thiotriphosphate) and 5'-guanylylimidodiphosphate, NaF, and forskolin also stimulated adenylate cyclase activity. In addition, chorela toxin (CT) stimulated adenylate cyclase activity in membrane preparations in the presence of NAD and GTP. Unlike adenylate cyclase, phosphodiesterase activity was not influenced by GSS. When crude membranes of follicle cells were incubated with [alpha-32P]NAD in the presence of CT and pertussis toxin, 45-kDa and 41-kDa proteins were ADP-ribosylated, respectively, suggesting the presence of two types (stimulatory and inhibitory) of G-proteins. It is concluded that G-proteins and adenylate cyclase play an important role in the action of GSS on 1-MeAde production by starfish ovarian follicle cells.