PROTEIN PHOSPHATASE ACTIVITY IN STEROIDOGENIC CELLS: ITS REGULATION AND PARTICIPATION IN THE STIMULATION OF STEROIDOGENESIS

CORNEJO MACIEL, FABIANA; PODEROSO, CECILIA; GOROSTIZAGA, ALEJANDRA; BEY, PAULA; MALOBERTI, PAULA; STOCCO, DOUGLAS; PAZ, CRISTINA AND PODESTÁ, ERNESTO

Villa Carlos Paz, Cordoba, Argentina

Congreso; XXXVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2001

Previously, we demostrated that hormonal activation of testicular and adrenal steroidogenesis depends on the activity of tyrosine (PTP) and serine/threonine (PP) acting between PKA activation and cholesterol transport across the inner mitochondrial membrane. We also proved that ACTH increases PTP activity in rat adrenal gland through a PKA-dependent pathway. 8Br-cAMP stimulation (1mM) of MA-10 cells resulted in a rapid and transient increase on PTP activity (Control=230 +/-12, 8Br-cAMP, 10 min=320+/-15 mU/mg protein) involving activation of, at least, two PTPs (110 and 50 kDa). The kinetic profile of the activity of PP2A, A Ser/Thr phosphatase, also showed modulation of this enzyme by 8Br-cAMP. Since the intramitochondrial transport of cholesterol is absolutely dependent on hormone-triggered induction of StAR protein, it may be suggested that protein phosphatases act at this level. Even when the effect of PPs inhibition upon this process remains to be tested in MA-10 cells, we provd that PTP inhibition abrogated the effect of both hCG and 8Br-cAMP on StAR levels. We then conclude that StAR induction occurs through a PTP-dependent pathway and supports the universal role proposed for these enzymes in the steroidogenic cascade.