DIFFERENTIAL REGULATION OF OOCYTE MATURATION AND CUMULUS EXPANSION INTHE MOUSE OOCYTE-CUMULUS CELL COMPLEX BY SITE-SELECTIVE ANALOGS OF CYCLIC ADENOSINE-MONOPHOSPHATE

In the present study, we have examined how differential distribution o f cyclic adenosine 5'-monophosphate (cAMP)-dependent protein kinase is ozymes within the mouse oocyte-cumulus cell complex might influence th e physiological response of the complex to cAMP, by determining the ac tions of site-selective cAMP analogs on oocyte maturation and cumulus expansion. Five different analogs of cAMP were utilized: 8-thiomethyl- cAMP and 8-bromo-cAMP, which bind to site 1 on the type II regulatory subunit (RII) of cAMP-dependent protein kinase A (PKA); 8-aminohexylam ino-cAMP, which binds to site 1 on the type I regulatory subunit (pi) of PKA; N-6-monobutyryl cAMP, which binds to site 2 on either RI or RI I; and 8-piperidino-cAMP, which binds to either site 1 on RII or site 2 on KI. These analogs were tested alone or in paired combinations tha t synergistically activate either the type I or type II PKA isozyme. W hen tested alone, analogs that can bind to, and presumably activate, t ype I PKA were the most potent inhibitors of germinal vesicle breakdow n (GVB) in both cumulus cell-enclosed and denuded oocytes. Consistent with this result was the finding that paired combinations of analogs t hat selectively activate type I PKA were also most effective in preven ting GVB. On the other hand, pulsing meiotically arrested cumulus cell -enclosed oocytes with high concentrations of analogs that bind to PKA II, or with paired combinations of analogs that selectively activate type II PKA, led to induction of GVB; stimulation with analogs or comb inations thereof that presumably stimulate type I PKA was less effecti ve. Cumulus expansion in response to PKA stimulation showed similar se lectivity in that type II PKA-stimulating treatments were considerably more effective in provoking expansion than type I PKA-stimulating tre atments. 8-N-3-[P-32]cAMP photoaffinity labeling of PKA regulatory sub units revealed that only RI was present in oocyte extracts, while extr acts from oocyte-cumulus cell complexes contained both RI and RII. The se results support the hypothesis that type II PKA mediates cAMP-stimu lated cumulus expansion and resumption of meiotic maturation, while di rect elevation of type I PKA within the oocyte is instrumental in main taining meiotic arrest. (C) 1995 Academic Press, Inc.