PTH activates c-Src kinase via G-proteins in rat enterocytes

GENTILI CLAUDIA; MORELLI SUSANA; RUSSO DE BOLAND ANA

Iguazú, Misiones

Congreso; XL Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. (SAIBBM); 2004

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular. (SAIBBM)

Parathyroid hormone (PTH) is an essential regulator of calcium homeostasis. PTH interacts in target tissues with a G protein-coupled receptor(GPCR) but the mechanism by which G proteins activate tyrosine kinases is not completely understood. In this work we demonstrated that PTH rapidly increases the activity of tyrosine kinase c-Src in rat enterocytes. The response is biphasic, the early phase is transient, peaking at 30 sec. while the second phase is maximal at 5 min.of treatment with PTH. To evaluate whether G-proteins are required for PTH-induced c-Src activation, the enterocytes were treated with PTH (10-8 M, 30 sec-5 min) and c-Src was co-immunoprecipitated with anti-cSrc and resolved by Western blotting with anti-Gb, anti-Gas or anti-Gai antibodies. In basal condition the three subunits are associated with c-Src and this association increases with different temporal profile, in cells treated with PTH. In addition, the hormone activates c-Src in enterocytes through changes in the tyrosine phosphorylation of  the enzyme. We demonstrate that the first event in the activation of c-Src is the dephosphorylation of Y527 followed by a second event of activation with phosphorylation at Y416. Futhermore, preincubation with anti-Gb antibody inhibited the PTH-mediated increase in the phosphorylation at Y416. These results suggest that G protein stimulation of c-Src can cause conformational changes and can modulate the phosphorylation of tyrosine residues of the enzyme via Gbg. <!--[if !supportEmptyParas]--> <!--[endif]-->