Angiotensin II-induced mitogen-activated protein kinase phosphatase-1 expression in bovine adrenal glomerulosa cells: implications in mineralocorticoid biosynthesis.
Angiotensin II (AngII) stimulates aldosterone biosynthesis in the zona glomerulosa of the adrenal cortex. AngII also triggers the MAPK pathways (ERK1/2 and p38). Because ERK1/2 phosphorylation is a transient process, phosphatases could play a crucial role in the acute steroidogenic response. Here we show that the dual specificity (threonine/tyrosine) MAPK phosphatase-1 (MKP-1) is present in bovine adrenal glomerulosa cells in primary culture and that AngII markedly increases its expression in a time- and concentration-dependent manner (IC(50) = 1 nm), a maximum of 548 +/- 10% of controls being reached with 10 nm AngII after 3 h (n = 3, P < 0.01). This effect is completely abolished by losartan, a blocker of the AT(1) receptor subtype. Moreover, this AngII-induced MKP-1 expression is reduced to 250 +/- 35% of controls (n = 3, P < 0.01) in the presence of U0126, an inhibitor of ERK1/2 phosphorylation, suggesting an involvement of the ERK1/2 MAPK pathway in MKP-1 induction. Indeed, shortly after AngII-induced phosphorylation of ERK1/2 (220% of controls at 30 min), MKP-1 protein expression starts to increase. This increase is associated with a reduction in ERK1/2 phosphorylation, which returns to control values after 3 h of AngII challenge. Enhanced MKP-1 expression is essentially due to a stabilization of MKP-1 mRNA. AngII treatment leads to a 53-fold increase in phosphorylated MKP-1 levels and a doubling of MKP-1 phosphatase activity. Overexpression of MKP-1 results in decreased phosphorylation of ERK1/2 and aldosterone production in response to AngII stimulation. These results strongly suggest that MKP-1 is the specific phosphatase induced by AngII and involved in the negative feedback mechanism ensuring adequate ERK1/2-mediated aldosterone production in response to the hormone.
Casal
Andrés J
AJ
Division of Endocrinology, Diabetology and Nutrition, University Hospital, 24 rue Micheli-du-Crest, CH-1211, Geneva 14, Switzerland.
Ryser
Stéphane
S
Capponi
Alessandro M
AM
Wang-Buholzer
Carine F
CF
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics*; D025461:Feedback, Physiological / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D008901:Mineralocorticoids / Q000096:biosynthesis*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D015384:Zona Glomerulosa / Q000187:drug effects* / Q000378:metabolism
D008901:Mineralocorticoids; D012333:RNA, Messenger; D000804:Angiotensin II; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054638:Dual Specificity Phosphatase 1