PROLACTIN AND INTERLEUKIN-2 RECEPTORS IN T-LYMPHOCYTES SIGNAL THROUGHA MGF-STAT5-LIKE TRANSCRIPTION FACTOR

The cell surface receptors for PRL and interleukin-2 (IL-2) are struct urally distinct, but share regulatory tasks in T lymphocytes. They can stimulate proliferation and activate transcription of overlapping set s of genes of T cells. PRL and IL-2 receptor activation are both linke d to the Jak/Stat (signal transducer and activator of transcription) p athway. We investigated the ability of PRL and IL-2 to activate Stat p roteins in different T cell lines. The DNA binding specificities, the reactivities toward Stat-specific antisera, and the mol wt of IL-2- an d PRL-induced DNA-binding proteins in Nb2 and Cl96 T cell lines were i nvestigated. A comparison with the Stat proteins induced by interferon -gamma, PRL, and IL-6 in T47D mammary tumor cells was made. We found t hat these parameters were indistinguishable for one of the PRL- and IL -2-induced factors. A transcription factor closely related to mammary gland factor-Stat5 is rapidly activated upon interaction of IL-2 and P RL with their respective receptors. Activation of a second protein rel ated to Stat1 was also observed. Our results emphasize the role of PRL as a regulator of the immune response and indicate that the Stat fact ors mammary gland factor-Stat5 and Stat1 play a role in the regulation of gene expression during T cell development.