Regulation of ovarian steroidogenesis in vitro by gonadotropin in common carp Cyprinus carpio: interaction between calcium- and adenylate cyclase-dependent pathways and involvement of ERK signaling cascade.
Multiple signal transduction pathways mediating gonadotropin-induced testosterone and 17β-estradiol (E(2)) production were identified in carp ovarian theca and granulosa cells in short-term co-incubation. Inhibitors of voltage-sensitive calcium channels (VSCCs) and calmodulin attenuated human chorionic gonadotropin (HCG)-induced steroid production, whereas modulators of adenylate cyclase and protein kinase A (PKA) increased their production, indicating that both calcium- and PKA-dependent pathways are involved in the regulation of gonadotropin-induced steroidogenesis in carp ovary. Interactions between these two pathways are evident from the positive effect of elevated intracellular calcium on HCG-induced steroid production and the reduction of forskolin (FK)- and dibutyryl cAMP (dbcAMP)-induced steroidogenesis by inhibitors of VSCCs and calmodulin. In this study, we found the involvement of a third signaling pathway, a mitogen-activated protein kinase (MAP kinase), in the regulation of gonadal steroidogenesis in this fish. An antagonist of mitogen-activated protein kinase kinases 1/2 (MEK1/2; also known as MAP2K1/MAP2K2) markedly attenuated HCG-induced steroid production. Cells treated with HCG stimulated MEK1/2-dependent phosphorylation of extracellular signal-regulated protein kinases 1/2 (ERKs1/2) in a concentration and time-dependent manner. Moreover, ERK1/2 activation in cells was mimicked by FK and dbcAMP suggesting that ERK1/2 transduce signal downstream of PKA in HCG-induced ovarian steroidogenesis. Evidence for presence of cross talk between calcium-dependent pathways and this MAP kinase cascade has been shown by demonstrating the inhibitory effects of verapamil and calmodulin on ERK1/2 activation after HCG stimulation. Our results suggest that activation of ERK1/2 by HCG as well as other agents may be a key mechanism for the modulation of gonadotropin-induced steroidogenesis in carp ovary.
Paul
Sudipta
S
Endocrinology Laboratory, Department of Zoology, University of Kalyani, Kalyani, West Bengal, India.
Kundu
Sourav
S
Pramanick
Kousik
K
Bandyopadhyay
Arun
A
Mukherjee
Dilip
D
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002347:Carps / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008954:Models, Biological; D010053:Ovary / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D013256:Steroids / Q000096:biosynthesis*; D013997:Time Factors
D000067956:Adenylyl Cyclase Inhibitors; D015220:Calcium Channels; D002147:Calmodulin; D006062:Gonadotropins; D047428:Protein Kinase Inhibitors; D013256:Steroids; D005576:Colforsin; D000001:Calcimycin; D003994:Bucladesine; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D000262:Adenylyl Cyclases; D002118:Calcium