Differential regulation of oocyte maturation and cumulus expansion in the mouse oocyte-cumulus cell complex by site-selective analogs of cyclic adenosine monophosphate.
In the present study, we have examined how differential distribution of cyclic adenosine 5'-monophosphate (cAMP)-dependent protein kinase isozymes within the mouse oocyte-cumulus cell complex might influence the physiological response of the complex to cAMP, by determining the actions 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-aminohexylamino-cAMP, which binds to site 1 on the type I regulatory subunit (RI) of PKA; N6-monobutyryl cAMP, which binds to site 2 on either RI or RII; and 8-piperidino-cAMP, which binds to either site 1 on RII or site 2 on RI. These analogs were tested alone or in paired combinations that synergistically activate either the type I or type II PKA isozyme. When tested alone, analogs that can bind to, and presumably activate, type I PKA were the most potent inhibitors of germinal vesicle breakdown (GVB) in both cumulus cell-enclosed and denuded oocytes. Consistent with this result was the finding that paired combinations of analogs that selectively activate type I PKA were also most effective in preventing 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 combinations thereof that presumably stimulate type I PKA was less effective. Cumulus expansion in response to PKA stimulation showed similar selectivity in that type II PKA-stimulating treatments were considerably more effective in provoking expansion than type I PKA-stimulating treatments. 8-N3-[32P]cAMP photoaffinity labeling of PKA regulatory subunits revealed that only RI was present in oocyte extracts, while extracts from oocyte-cumulus cell complexes contained both RI and RII. These results support the hypothesis that type II PKA mediates cAMP-stimulated cumulus expansion and resumption of meiotic maturation, while direct elevation of type I PKA within the oocyte is instrumental in maintaining meiotic arrest.
Downs
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SM
Biology Department, Marquette University, Milwaukee, Wisconsin 53233, USA.
Hunzicker-Dunn
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D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D008540:Meiosis / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013329:Structure-Activity Relationship
D000345:Affinity Labels; D001386:Azides; D015124:8-Bromo Cyclic Adenosine Monophosphate; C017042:8-azidoadenosine-3',5'-monophosphate; D000242:Cyclic AMP; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases