Requirement for ERK1/2 activation in the regulation of progesterone production in human granulosa-lutein cells is stimulus specific.
This study was conducted to determine whether the ERK1/2 family of MAPKs can be modulated by physiological regulators of the human corpus luteum, and whether this activation is important for progesterone secretion in human granulosa-lutein (hGL) cells. Human LH (hLH), hCG, and agents that indirectly elevate cAMP [cholera toxin, forskolin, (Bu)(2)cAMP], time- and dose-dependently activated ERK1/2 in hGL cells. ERK1/2 activation was reduced by preincubation with PKA inhibitors, including myristoylated PKI, suggesting that cAMP mediates ERK1/2 activation. Two structurally distinct inhibitors of MAPK kinase (MEK), PD 98059 and U 0126, abrogated hLH/hCG-induced ERK1/2 activation, but had no effect on hLH-, hCG-, or 22R-hydroxycholesterol-stimulated progesterone secretion. In contrast, both inhibitors blocked cholera toxin-, forskolin-, and (Bu)(2)cAMP-induced ERK1/2 phosphorylation concomitant with a reduction in progesterone secretion. The known luteotropin, PGE(2), promoted MEK- and cAMP-dependent activation of ERK1/2, and inhibitors of either MEK or PKA decreased PGE(2)-induced progesterone synthesis. Our findings demonstrate that the requirement for ERK1/2 activation as a regulator of progesterone synthesis in hGL cells is stimulus dependent, and that the MEK inhibitor-sensitive step is distal to cAMP generation, but proximal to the conversion of cholesterol to pregnenolone.
Dewi
D A
DA
Department of Veterinary Basic Sciences, Royal Veterinary College, London, United Kingdom NW1 0TU.
Abayasekara
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DR
Wheeler-Jones
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CP
D002469:Cell Separation; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D002784:Cholesterol / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006062:Gonadotropins / Q000494:pharmacology; D006107:Granulosa Cells / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D015151:Immunoblotting; D007202:Indicators and Reagents; D008184:Luteal Cells / Q000187:drug effects / Q000201:enzymology*; D007986:Luteinizing Hormone / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011284:Pregnenolone / Q000378:metabolism; D011374:Progesterone / Q000096:biosynthesis*
D004791:Enzyme Inhibitors; D006062:Gonadotropins; D007202:Indicators and Reagents; D005576:Colforsin; D011374:Progesterone; D011284:Pregnenolone; D007986:Luteinizing Hormone; D002772:Cholera Toxin; D002784:Cholesterol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases