" ROLE OF PTPALPHA IN 1a,25(OH)2D3¡V DEPENDENT Src ACTIVATION IN SKELETAL MUSCLE CELLS

BUITRAGO C; BOLAND R

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2007

C-Src is a member of a tyrosine kinase family involved in ERK 1/2 and p38 MAPK activation in several tissues. Dephosphorylation of c-Src in Tyr 527 residues allows it to become activated, so c-Src has been reported as a substrate for the protein tyrosine phosphatase alpha (PTPa) which can be in turn activated by PKC. We have previously shown that the steroid hormone 1a,25-dihydroxy-vitamin D3 [1a,25(OH)2D3] -dependent ERK 1/2 and p38 MAPK activation occur with c-Src participation in the skeletal muscle cell line C2C12. In addition, we observed that 1a,25(OH)2D3 modulates Src activation in a PKC-dependent manner. Now, we have studied the role of PTPa in Src activation which is involved in modulation of MAPK cascades in these cells. Our results demonstrate that 1a,25(OH)2D3 promotes Tyr 789 phosphorylation of  PTPa, which is necessary to activate c-Src by tyrosine dephosphorylation. An acute augment in PTPa phosphatase activity is observed at 60 minutes of hormone stimulation. Moreover, there is a co-localization between PTPa and c-Src promoted by the hormone that is blocked with the specific PKC inhibitor Ro 318220. Finally, we corroborated the physical association of PTPa-c-Src by co-immunoprecipitation assays after 1a,25(OH)2D3 and TPA treatments. We conclude that 1a,25(OH)2D3 activates PKC which induces Src kinase activity via activation of  PTPa, events upstream to MAPKs activation.