Progesterone-stimulated meiotic cell division in Xenopus oocytes. Induction by regulatory subunit and inhibition by catalytic subunit of adenosine 3':5'-monophosphate-dependent protein kinase

Abstract

Ripe Xenopus oocytes in first meiotic prophase when incubated with progesterone in vitro progress synchronously in 3 to 5 h without interphase to second meiotic metaphase where they remain until fertilization or activation. Using highly purified preparations of regulatory and catalytic subunits of adenosine 3':5'-monophosphate-dependent protein kinase from muscle, this progesterone-stimulated cell division sequence was found to be inhibited by microinjection of the catalytic subunit and induced directly in the absence of progesterone after microinjection of regulatory subunit. Dose-response curves revealed that half-maximal effects of regulatory and catalytic subunits occurred at an internal concentration of approximately 0.1 muM. These results indicate that the catalytic subunit is necessary and sufficient to block progesterone-stimulated meiotic cell division. Other experiments revealed that the catalytic subunit was inhibitory only during the first hour after progesterone exposure, suggesting that initial steps in meiotic cell division are affected. Control experiments demonstrate that the muscle cAMP-dependent protein kinase subunits may interact with the endogenous oocyte protein kinase. The results support a model in which meiotic cell division is regulated by a phosphoprotein subject to control by cAMP-dependent protein kinase.