ACTH ACTIVATES THE PROTEIN TYROSINE PHOSPHATASES PTP1D AND PTP-PEST IN ADRENOCORTICAL CELLS

GOROSTIZAGA AB; BRION L.; NEUMAN I; CORNEJO MACIEL F; PAZ C

Villa Carlos Paz, Córdoba, Argentina

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

We have already demonstrated that ACTH activates protein tyrosine phosphatases of 80 and 115 kDa (PTP80, PTP115) in the cytosol of rat adrenal zona fasciculata (rZF). Since PTP activity exerts a crucial role in steroidogenic cells, the aim of this work was to identify/characterize these enzymes. An antibody against PTP1D, a 72 kDa PTP, revealed a protein of 80 kDa when proteins of rZF and Y1 adrenocortical cells were analyzed by Western blot. In-gel PTP assay of rZF proteins precipitated with the anti-PTP1D antibody revealed a band of activity corresponding to a 80 kDa protein, being the activity of the samples obtained from ACTH-treated rats higher than controls. Immunoprecipitation with anti-PTP1D antibody of in vitro PKA phosphorylated rZF cytosolic proteins rendered an 80 kDa phosphorylated protein, detected by autoradiography, and ingel assay of immunoprecipitates revelead a phosphorylationdependent increase of PTP activity. Regarding PTP115, an anti- PTP-PEST antibody recognized a 115 kDa protein in Y1 cells, in rZF and also in a partially purified sample of PTP115. This sample, that displayed only one band of activity (115 kDa) in the in-gel assay, showed changes in the kinetic parameters after in vitro PKA phosphorylation. We conclude that the ACTH-activated PTPs of 80 and 115 kDa are PTP1D and PTP-PEST and that both enzymes are regulated by PKA-mediated phosphorylation.