PKC-θ is required for TCR-induced NF-κB activation in mature but not immature T lymphocytes

Productive interaction of a T lymphocyte with an antigen-presenting cell results in the clustering of the T-cell antigen receptor (TCR) and the recruitment of a large signalling complex to the site of cell–cell contact1,2. Subsequent signal transduction resulting in cytokine gene expression requires the activation of one or more of the multiple isoenzymes of serine/threonine-specific protein kinase C (PKC)3. Among the several PKC isoenzymes expressed in T cells, PKC-θ is unique in being rapidly recruited to the site of TCR clustering4. Here we show that PKC-θ is essential for TCR-mediated T-cell activation, but is dispensable during TCR-dependent thymocyte development. TCR-initiated NF-κB activation was absent from PKC-θ-/- mature T lymphocytes, but was intact in thymocytes. Activation of NF-κB by tumour-necrosis factor α and interleukin-1 was unaffected in the mutant mice. Although studies in T-cell lines had suggested that PKC-θ regulates activation of the JNK signalling pathway5,6, induction of JNK was normal in T cells from mutant mice. These results indicate that PKC-θ functions in a unique pathway that links the TCR signalling complex to the activation of NF-κB in mature T lymphocytes.