Identification of ERK and JNK as signaling mediators on protein kinase C activation in cultured granulosa cells.
PKC signaling is critical for follicular development and the induction of ovulatory genes including Pgr, Prkg2, and Cyp11a1 (SCC). We investigated PKC signaling mechanisms in the JC-410 porcine granulosa cell line stably expressing an SCC-luciferase reporter gene containing 2kb of the porcine SCC promoter. Addition of phorbol 12-myristate 13-acetate (PMA), which activates protein kinase C, induced the promoter approximately 6-fold over the basal levels in 4h. This effect was predominantly mediated by the PKC beta and delta isoforms. PMA-mediated induction of the SCC promoter was sensitive to inhibition of ERK1/2 or JNK. Inhibition of p38 MAP kinase or Src tyrosine kinase did not alter the PMA-mediated inducibility of the promoter. SCC promoter induction in response to PMA treatment required basal EGF-receptor activity, but did not involve ectodomain shedding. Western blot analyses using phospho-specific antibodies showed that PMA treatment of JC-410 cells induced phosphorylation of MEK1/2, ERK1/2, and its downstream target p90 RSK at 15min. We also documented the rapid phosphorylation of JNK1/2 in response to PMA treatment. Phosphorylation of ERK and JNK was robust and sustained in contrast to activation of PKA and EGF-receptor signaling in these cells. Pretreatment of JC-410 granulosa cells with IGF-1 had a synergistic effect on PMA-mediated induction of the SCC promoter. We demonstrated the importance of PMA activation of ERK signaling and the synergism with IGF-1 by showing similar responses for Prkg2 expression in primary granulosa cells. In conclusion, our studies demonstrated PMA activation of ERK and JNK signaling which is relevant in the regulation of gene expression during follicular development, ovulation, and luteinization.
Sriraman
Venkataraman
V
Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX 77555-1060, USA. venkataraman.sriraman@emdserono.com
Modi
Swati R
SR
Bodenburg
Yvonne
Y
Denner
Larry A
LA
Urban
Randall J
RJ
D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000096:biosynthesis / Q000235:genetics; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D005576:Colforsin; D007334:Insulin-Like Growth Factor I; D002786:Cholesterol Side-Chain Cleavage Enzyme; D066246:ErbB Receptors; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D013755:Tetradecanoylphorbol Acetate