P56LCK A LYMPHOCYTE-SPECIFIC PROTEIN-TYROSINE KINASE - ACTIVATION, REGULATION AND SIGNAL-TRANSDUCTION

p56lck, a src family protein tyrosine kinase interacts with several T cell receptors, like: CD4, CD8, CD2 and the beta-chain of the IL2, the reby receptors devoided of kinase activity may transduce signals via t yr phosphorylation. Tyr 192 and ser 194, located in the SH2 domain of p56lck is phosphorylated upon CD3 triggering, which can change interac tions of tyr-P proteins with this SH2 domain. Upon activation through the CD2 or the CD45 receptors the kinase activity of p56lck is tempora rely increased. By immunofluorescent and confocal microscopy we observ ed that a significant proportion of p56lck and CD2 receptors are local ized in endosomal vesicles after stimulation. By Western blot we showe d a parallel recruitment of the PTK p70-ZAP in this vesicles. The role of p56lck away from the plasma membrane localized in vesicles is unde r study.