Functional association of cytokine-induced SH2 protein and protein kinase C in activated T cells.

TCR signaling is mediated by intracellular signaling molecules and nuclear transcription factors, which are tightly regulated by interaction with regulatory proteins such as Grb2 and SLAP. We reported recently that TCR stimulation induces the expression of cytokine-induced SH2 protein (CIS). The expression of CIS promotes TCR-mediated activation. We have now found specific interactions between CIS and activated protein kinase C (PKC) alpha, beta and theta in TCR-stimulated T cells. CIS was shown by in vitro kinase assay to associate with activated PKC. In CIS-expressing T cells isolated from CIS-transgenic mice, the amount of activated PKC associated with CIS was found to increase following TCR stimulation. By immunohistochemical analysis, CIS was also found to co-localize with PKCtheta at the plasma membrane of activated T cells. In addition to the interaction and intracellular co-localization of the CIS and PKC, an increase in the activation of AP-1 and NF-kappaB was noted in CIS-expressing T cells, after stimulation by either anti-CD3/CD28 or phorbol myristate acetate + ionomycin. These results suggest that CIS regulates PKC activation, and that this may be important for the activation of both the AP-1 and NF-kappaB pathways in TCR signaling.