Regulation of granulosa cell-derived insulin-like growth factor binding proteins (IGFBPs): role for protein kinase-C in the pre- and posttranslational modulation of IGFBP-4 and IGFBP-5.
A growing body of information suggests antigonadotropic and atretogenic roles for granulosa cell-derived insulin-like growth factor binding proteins (IGFBPs) 4 and 5 during ovarian folliculogenesis. Activation of protein kinase-A (PKA) in rat granulosa cells has been shown to modulate the relative expression of IGFBP-4 and -5 transcripts and proteins. In this article, we assess the role of protein kinase-C (PKC) in this regard. Provision of granulosa cells with phorbol 12-myristate 13-acetate (PMA) (but not 4alphaPMA, an inert analogue), a tumor-promoting phorbol ester and an established activator of PKC, was without significant effect on the expression of IGFBP-4 transcripts but resulted in biphasic dose-dependent alterations in IGFBP-5 transcripts and in the accumulation of the IGFBP-4 and -5 proteins. Comparable effects were noted for GnRH, an established PKC agonist. Provision of staurosporine, a potent inhibitor of the catalytic subunit of PKC, produced significant dose-dependent decrements in the relative expression of IGFBP-5 transcripts. Treatment with FSH (presumptively PKA-mediated) markedly attenuated the ability of PMA or GnRH to upregulate the accumulation of the IGFBP-5 (but not IGFBP-4) protein. Taken together, our present findings indicate that the modulation of rat ovarian IGFBP-4 and -5 is PKC as well as PKA dependent and that these two signaling pathways interact in a diametrically opposed and antagonistic fashion.
Chamoun
Diran
D
Department of Obstetrics and Gynecology, Sungkyunkwan University, School of Medicine, Samsung Medical Center, Seoul, Korea.
Choi
DooSeok
D
Tavares
Adriano B
AB
Udoff
Laurence C
LC
Levitas
Eliahu
E
Resnick
Carol E
CE
Rosenfeld
Ron G
RG
Adashi
Eli Y
EY
D000818:Animals; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D005786:Gene Expression Regulation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006107:Granulosa Cells / Q000201:enzymology / Q000378:metabolism*; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics* / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000235:genetics* / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D005640:Follicle Stimulating Hormone; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate