ACTION OF PROTEIN TYROSINE PHOSPHATASES (PTPs) ON StAR PROMOTER ACTIVITY

CORNEJO MACIEL, FABIANA, PODEROSO CECILIA, GOROSTIZAGA A/EJANDRA, BEY PAULA, PAZ CRISTINA, JEFCOATE COLIN, PODESTÁ ERNESTO J.

Villa Carlos Paz, Cordoba

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2002

SAIB

PreviousIy, we demonstrated that hormonal stimulation of steroidogenic cells increases protein tyrosine phosphatases (PTPs) activity through a PKA-dependent pathway. An oxidative agent like phenylarsine oxide (PAO) produces inhibition of tyrosine dephosphorylation in parallel to inhibition of the expression of Steroidogenic Acute Regulatory (StAR) protein in Leydig ceIls. In this work, we used PAO and benzylphosphoníc acid (BPA), a competitive PTP inhibitor, as a tool to study the mechanism of action of PTPs on StAR protein expression and steroid production. For this purpose, we detemined the cAMP stimulated-StAR promoter luciferase activity in Y 1 cells under PTP inhibition.. The results show that 8Br-cAMP activation is abolished by both PAO and BPA (control = 3.5±0.5, 8Br-cAMP = 11.9±0.3, 8Br-cAMP + BPA (0.2 mM) =3.9±0.2 arbitrary units). The fact that these compounds also inhibit stimulated-StAR protein expression and steroid production indicates that StAR transcription is at least one of .the points where the action of PTPs is exerted.