MKP-3 is induced by hCG and cAMP in MA-10 Leydig cells

MORI SEQUEIROS GARCÍA M; BRION L; GOMEZ N; ACQUIER A; CASTILLO AF; MENDEZ CF; PAZ C.

Tucumán, Argentina

Congreso; XLV Reunión Anual - Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

MKP-3 is a dual activity phosphatase specifically involved in the regulation of MAP kinases ERK1/2. In steroidogenic cells, trophic hormones activate steroid production and promote also cell proliferation. In the testis, lutheinizing hormone (LH) exerts these effects by a mechanism that involves PKA and ERK1/2 transient activation. Given that MKP-3 is induced by proliferative signals, we analyzed the effect of hCG (gonadotrophin hormone, an agonist of LH receptor) on MKP-3 expression in MA-10 Leydig cells. Semi-quantitative RT-PCR analysis showed that hCG (10 ng/ml) transiently increases MKP-3 mRNA levels. This effect reaches its maximum (2 fold) after 3 hs of stimulation and is mimicked by cAMP (0.75 mM 8Br-cAMP). The fact that a MEK inhibitor reduces the effect of hCG and of cAMP on MKP-3 mRNA levels, suggests that ERK1/2 participates in MKP-3 induction. In order to establish whether hCG/cAMP also induces MKP-3 by post translational modification, a Flag-MKP-3 chimera was over-expressed by transient transfection in MA-10 cells. Western blot analysis using an anti-Flag antibody, demonstrates that hCG and cAMP increase protein levels. Together, the present data indicates that in Leydig cells, MKP-3 is up-regulated by hCG/cAMP by a mechanism that includes actions at transcriptional and post translational levels.Supported by UBACyT, ANPCyT and CONICET.