Gonadotropin-stimulated epidermal growth factor receptor expression in human ovarian surface epithelial cells: involvement of cyclic AMP-dependent exchange protein activated by cAMP pathway.
In addition to their critical roles in folliculogenesis and ovarian granulosa cell steroidogenesis, gonadotropins have been implicated as potential risk factors in ovarian epithelial carcinomas, most of which are derived from ovarian surface epithelium (OSE). However, the molecular mechanism underlying the effects of FSH and LH in OSE and its neoplastic counterpart is not well understood. We previously demonstrated that gonadotropins promote the growth of OSE cells by regulating the levels of epidermal growth factor receptor (EGFR) via the activation of ERK1/2 and PI3K pathways in immortalized human OSE (IOSE) cells. In this study, we investigated whether cAMP and its novel binding target, named exchange protein activated by cAMP (Epac), are involved in the gonadotropin-induced EGFR expression in OSE cells. Gonadotropins elevated intracellular cAMP levels in both IOSE and granulosa cells, and this increase was attenuated by SQ22536, an inhibitor of adenylyl cyclase (AC). The activation of the ERK1/2 and Akt pathways as well as the expression of EGFR was stimulated by reagents that elevate intracellular cAMP levels, via cAMP analog 8-bromo-cAMP and AC activator forskolin. A similar increase was observed when the cells were treated with a novel cAMP analog, 8-(4-chlorophenylthio)-2'-O-methyl adenosine-3',5'-cyclic monophosphate (8-CPT-2ME-cAMP), which activates Epac specifically but not PKA. Moreover, the gonadotropin-induced EGFR expression and ERK1/2 and Akt activation were abolished by overexpression of dominant negative Epac. Taken together, these results indicate that the AC/cAMP/Epac signaling pathway may mediate the up-regulation of EGFR by gonadotropins via ERK1/2 and Akt activation.
Choi
Jung-Hye
JH
Department of Obstetrics and Gynecology, University of British Columbia, 2H-30, Vancouver, British Columbia, Canada V6H 3V5.
Chen
Chien-Lin
CL
Poon
Song Ling
SL
Wang
Hsin-Shih
HS
Leung
Peter C K
PC
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism* / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D007986:Luteinizing Hormone / Q000378:metabolism* / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D006080:Ovarian Follicle / Q000166:cytology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D020662:Guanine Nucleotide Exchange Factors; C116122:RAPGEF3 protein, human; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3