THE PROTEIN-TYROSINE KINASE P59(FYN) IS ASSOCIATED WITH PROLACTIN (PRL) RECEPTOR AND IS ACTIVATED BY PRL STIMULATION OF T-LYMPHOCYTES

The clonal expansion of antigen-stimulated T-lymphocytes during an immune response is mediated by several lymphokines. Strong evidence now exists that the neuroendocrine hormone PRL is necessary, but not sufficient, for T-cell proliferation. Little is known, however, of the signal transduction mechanisms of the PRL receptor (PRLR) within T-cells. We demonstrate here that PRL stimulation of the T-cell line Nb2 induced the concentration- and time-dependent activation of the protein tyrosine kinase p59(fyn), but not of four other src family protein tyrosine kinases. activation of fyn was also observed in Concanavalin-A-primed peripheral blood lymphocytes stimulated with PRL and in Nb2 cells incubated with anti-PRLR antibodies. The activation of fyn by PRL stimulation correlated with Nb2 cell proliferation. Immunoblot analysis of anti-fyn and anti-PRLR immune complexes revealed an association between each PRLR isoform and p59(fyn). These studies demonstrate for the first time an association between the PRLR and a src family protein tyrosine kinase affiliated with signal transduction.