T cell expressed PKC theta demonstrates cell-type selective function

T lymphocyte stimulation leading to interleukin-2 (IL-2) expression require s activation of protein kinase C (PKC); however, the relevant PKC isoform(s ) have not yet been systematically defined. Here we examine seven major T c ell expressed PKC isoforms (PKC alpha, delta, epsilon, xi, eta, theta and l ) and identify PKC theta to be essential for IL-2 expression (via the criti cal NF-AT and NF-kappaB enhancer) in Jurkat T cells. Employing a conditiona lly activated PKC theta estrogen-receptor fusion mutant, a de novo synthesi s-independent transactivation of JNK2 was established. Based on mRNA in sit u hybridization to mouse whole body sections, PKC theta was found to be hig hly expressed in lymphoid organs but also skeletal muscle and the nervous s ystem. PKC theta function appears to be cell-type specific, since its isoen zyme-selective function was not observed in ectopic expression studies, emp loying COS-I or NIH3T3 cells. These results confirm PKC theta to be the pri me target for the activating effect of phorbol ester in T cell signaling an d suggest that gene expression as well as gene function of PKC theta is str ictly controlled by the cell type.