Phosphotyrosine-dependent interaction between the kinases PKC? and Zap70 promotes proximal TCR signaling.

ABSTRACT: Protein kinase C-? (PKC?) is an important component of proximal T cell receptor (TCR) signaling. We previously identified the amino-terminal C2 domain of PKC? as a phosphotyrosine (pTyr)-binding domain. Using a mutant form of PKC? that cannot bind pTyr (PKC?HR2A), we showed that pTyr binding by PKC? was required for TCR-induced T cell activation, proliferation, and TH2 cell differentiation but not for T cell development. Using tandem mass spectrometry and coimmunoprecipitation, we identified the kinase ?-associated protein kinase of 70 kDa (Zap70) as a binding partner of the PKC? pTyr-binding pocket. Tyr126 of Zap70 directly bound to PKC?, and the interdomain B residues Tyr315 and Tyr319 were indirectly required for binding to PKC?, reflecting their role in promoting the open conformation of Zap70. PKC?HR2A-expressing CD4+ T cells displayed defects not only in known PKC?-dependent signaling events, such as nuclear factor ?B (NF-?B) activation and TH2 cell differentiation, but also in full activation of Zap70 itself and in the activating phosphorylation of linker of activation of T cells (LAT) and phospholipase C-?1 (PLC?1), signaling proteins that are traditionally considered to be activated independently of PKC. These findings demonstrate that PKC? plays an important role in a positive feedback regulatory loop that modulates TCR-proximal signaling and, moreover, provide a mechanistic explanation for earlier reports that documented an important role for PKC? in T cell Ca2+ signaling. This PKC?-Zap70 interaction could potentially serve as a promising and highly selective immunosuppressive drug target in autoimmunity and organ transplantation.

SUBMITTER: Xie J 

PROVIDER: S-EPMC7195849 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature