PKCθ cooperates with atypical PKCζ and PKCι in NF-κB transactivation of T lymphocytes

Using yeast two-hybrid, we isolated atypical PKC zeta as a PKC theta-interacting kinase and demonstrated that it selectively interacted with, and was phosphorylated by, PKC theta. Importantly, however, both atypical PKC zeta and PKC iota were functionally required in TCR/CD28-mediated activation of NF-kappa B downstream of PKC theta in Jurkat T cells albeit, activation responses of PKC zeta-deficient CD3(+) T cells were comparable with wildtype controls. This normal activation thresholds of PKC zeta(-/-) T cells suggested that PKC iota, the closest structural relative, might play a compensatory role in TCR/CD28-induced signalling. Consistently, both PKC zeta and PKC iota resided in the plasma membrane lipid raft microdomains of Jurkat as well as primary mouse CD3(+) T cells. Thus, PKC theta, the established constituent of the immunological synapse, physically and functionally interacted with PKC zeta and PKC iota. Together, these data demonstrate that atypical PKC zeta/iota h isotypes serve as direct downstream targets of PKC theta in the signalling pathway leading to NF-kappa B activation in T lymphocytes. (C) 2007 Elsevier Ltd. All rights reserved.