Participation of mitogen-activated protein kinase in luteinizing hormone-induced differential regulation of steroidogenesis and steroidogenic gene expression in mural and cumulus granulosa cells of mouse preovulatory follicles.
The LH surge induces the terminal differentiation and onset of luteinization in granulosa cells of preovulatory follicles, a process that involves the differential expression of genes essential for steroidogenesis and appears to be mediated by complex signaling pathways. The objective of this study was to investigate whether these processes that commonly occur in mural granulosa cells (MGCs) also occur in cumulus cells, and whether they are mediated by the mitogen-activated protein kinase (MAPK), specifically MAPK3/1 (also commonly known as extracellular signal-regulated kinase 1&2, ERK1/2). The standard superovulation model for premature female mice was used to obtain MGCs and cumulus-oocyte complexes (COCs), and sensitive real-time RT-PCR was used to simultaneously detect the expression levels of transcripts encoding key steroidogenic enzymes in the same sample. We observed significant downregulation of Cyp19a1 and upregulation of Star and Cyp11a1 mRNA expression in both COCs and MGCs after in vivo administration of hCG or in vitro treatment with gonadotropins or 8-Br-cAMP. This differential pattern of steroidogenic gene expression was correlated with the ultimate changes of circulating estradiol (E(2)) and progesterone (P(4)) levels after administration of hCG. In vitro, when MGCs and COCs were treated with U0126 - a specific inhibitor of MAPK3/1 activation - gonadotropin-induced P(4) production, 8-Br-cAMP-induced P(4) production, and expression of Star and Cyp11a1 mRNA were significantly downregulated, whereas the levels of E(2) and Cyp19a1 mRNA in the same samples were significantly upregulated. We conclude that the surge of preovulatory LH induces the differential expression of transcripts encoding key steroidogenic enzymes essential for E(2) and P(4) synthesis in both cumulus and MGCs, and this process is mediated by the MAPK3/1-dependent pathway.
Su
You-Qiang
YQ
Department of Obstetrics and Gynecology, Stanford University, Stanford, California 94305, USA.
Nyegaard
Mette
M
Overgaard
Michael Toft
MT
Qiao
Jie
J
Giudice
Linda C
LC
D000818:Animals; D001141:Aromatase / Q000235:genetics; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005498:Follicular Phase / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006107:Granulosa Cells / Q000166:cytology / Q000201:enzymology*; D007986:Luteinizing Hormone / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D006080:Ovarian Follicle / Q000166:cytology / Q000201:enzymology*; D011374:Progesterone / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D006063:Chorionic Gonadotropin; D012333:RNA, Messenger; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D001141:Aromatase; D002786:Cholesterol Side-Chain Cleavage Enzyme; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3