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.
Morris
J K
JK
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Richards
J S
JS
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