Hormone induction of luteinization and prostaglandin endoperoxide synthase-2 involves multiple cellular signaling pathways.
To determine the cellular signaling pathways involved in granulosa cell luteinization, known activators of protein kinase-A (LH and FSH) and protein kinase-C [GnRH and phorbol 12-myristate 13-acetate (PMA)] as well as inhibitors of tyrosine kinases (AG18 and genistein) were tested in an in vitro system using specific markers of luteinization (cell hypertrophy, side-chain cleavage cytochrome P450, and progesterone) and ovulation [prostaglandin endoperoxide synthase-2 (PGS-2)]. When preovulatory follicles were incubated in the presence of an ovulatory (500 ng/ml) dose of LH or high GnRH (1 microM), the granulosa cells harvested from these follicles assumed and maintained a stable luteal cell phenotype in vitro. Granulosa cells harvested from follicles incubated in subovulatory doses of LH (5 and 50 ng/ml), lower doses of GnRH (5, 50, and 500 nM), or PMA alone were unable to form a stable luteal cell phenotype. When PMA was combined with subovulatory doses of LH, granulosa cells luteinized, and PGS-2 protein was induced. AG18 (or genistein) blocked agonist induction of luteinization and of PGS-2 mRNA and protein when present during the first 2 h (0-2 h) of follicle incubation, but failed to block these events if added for the last 2 h (5-7 h of incubation). Combined, these results provide evidence to support a primary role for cAMP and protein kinase-A, a supportive but essential role for protein kinase-C, and an obligatory role for tyrosine kinases acting at an early stage in the cascade of events required for luteinization and ovulation.
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
J K
JK
Morris
J S
JS
Richards
D000818:Animals; D001597:Benzylidene Compounds / Q000008:administration & dosage / Q000494:pharmacology; D002478:Cells, Cultured; D003338:Corpus Luteum / Q000187:drug effects* / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D009570:Nitriles / Q000008:administration & dosage / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020032:Tyrphostins
D001597:Benzylidene Compounds; D009570:Nitriles; D012333:RNA, Messenger; D020032:Tyrphostins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D011451:Prostaglandin-Endoperoxide Synthases; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C060641:tyrphostin A23