Signal transduction in avian granulosa cells: effects of protein kinase C inhibitors.
We evaluated the effects of two protein kinase C (PKC) inhibitors, staurosporine (ST) and H-7, on LH-activated phospholipase C and adenylate cyclase activity by measuring the production of inositol phosphates (IP) and cAMP in freshly dispersed granulosa cells from mature preovulatory follicles of laying hens. ST and H-7 dose-dependently potentiated LH-stimulated IP generation, whereas a protein kinase A (PKA) inhibitor (H-8) had no effect. The PKC activator, phorbol ester TPA (50 nM), significantly inhibited LH-stimulated IP production, which was completely prevented by ST. Both ST and H-7, while having no effect on basal cAMP levels, significantly and dose-dependently potentiated LH-stimulated, but not forskolin-stimulated cAMP production. However, progesterone production in response to LH, forskolin, and 8-Br-cAMP was inhibited in granulosa cells preincubated for 30 min with H-7 or ST. H-7 and ST had no effect on 25-hydroxycholesterol- and pregnenolone-supported progesterone production. These results support a negative feedback role for PKC in LH-initiated signal transduction in avian granulosa cells. PKC blockade removes the inhibitory effect on LH-stimulated phospholipase C and adenylate cyclase activity. The inhibitory effect of H-7 and ST on progesterone synthesis could be attributed to inhibition of PKA and/or steps proximal to cholesterol side-chain cleavage.
Jamaluddin
M
M
Department of Obstetrics and Gynecology, St. Louis University School of Medicine, Missouri 63110.
Molnár
M
M
Marrone
B L
BL
Hertelendy
F
F
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004357:Drug Synergism; D005260:Female; D006107:Granulosa Cells / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011374:Progesterone / Q000096:biosynthesis; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D015398:Signal Transduction; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D007295:Inositol Phosphates; D007546:Isoquinolines; D010879:Piperazines; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D011374:Progesterone; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate