MAPK Phosphatase-1 (MKP-1) Expression Is

LAURA BRION, PAULA M. MALOBERTI, NATALIA V. GOMEZ, CECILIA PODEROSO ALEJANDRA B. GOROSTIZAGA, MARIA M. MORI SEQUEIROS GARCIA, ANDREA B. ACQUIER MARIANA COOKE, CARLOS F. MENDEZ, ERNESTO J. PODESTA, AND CRISTINA PAZ

ENDOCRINOLOGY

ENDOCRINE SOC

Año: 2011 vol. 152

0013-7227

MAPK, sch as ERK1/2, exert profound effects on a variety of physiological processes. In steroidogenic cells, ERK1/2 are involved in the expression and activation of steroidogenic acute regulatory protein, which plays a central role in the regulation of steroidogenesis. In MA-10 Leydig cells, LH and chorionic gonadotropin (CG) trigger transient ERK1/2 activation via protein kinase A, although the events that lead toERK1/2inactivation arenotfully described. Here,wedescribethehormonalregulation ofMAPK phosphatase-1 (MKP-1), an enzyme that inactivates MAPK, in MA-10 cells. In our experiments, human CG (hCG)/cAMP stimulation rapidly and transiently increased MKP-1 mRNA levels by a transcriptional action. This effect was accompanied by an increase in protein levels in both nuclear and mitochondrial compartments. In cells transiently expressing flag-MKP-1 protein, hCG/cAMP promoted the accumulation of the recombinant protein in a time-dependent manner (10-fold at 1 h). Moreover, hCG/cAMP triggered ERK1/2-dependent MKP-1 phosphorylation. The blockade of cAMP-induced MAPK kinase/ ERK activation abated MKP-1 phosphorylation but only partially reduced flag-MKP-1 protein accumulation. Together, these results suggest that hCG regulates MKP-1 at transcriptional and posttranslational level, protein phosphorylation being one of the mechanisms involved in this regulation. Our study also demonstrates that MKP-1 overexpression reduces the effects of cAMP on ERK1/2 phosphorylation, steroidogenic acute regulatory gene promoter activity, mRNA levels, and steroidogenesis, whereas MKP-1 down-regulation by small interferingRNAproduces opposite effects. In summary, our data demonstrate that hCG regulates MKP-1 expression at multiple stages as a negative feedback regulatory mechanism to modulate the hormonal action on ERK1/2 activity and steroidogenesis.