Regulation of PKC-θ function by phosphorylation in T cell receptor signaling

Protein kinase C (PKC)-theta is a serine/threonine kinase belonging to the calcium-independent novel PKC subfamily; its expression is restricted to certain tissues and cell types, including T cells. The signals delivered from T cell receptor (TCR) and CD28 costimulatory molecules trigger PKC-theta catalytic activation and membrane translocation to the immunological synapse, leading to activation of NE-kappa B, AP-1, and NE-AT. These transcription factors are important for T cell survival, activation, and differentiation. Phosphorylation of PKC-theta at multiple Ser/Thr/Tyr residues is induced in T cells during TCR signaling. Some phosphorylation sites play critical roles in the regulation of PKC-theta function and downstream signaling. The regulation mechanisms for PKC-theta phosphorylation sites are now being revealed. In this review, we discuss the current understanding of the regulation of PKC-theta function by phosphorylation during TCR signaling.