Department of Chemistry, University of Illinois, Chicago, IL 60607, USA.
J Biol Chem. 2012 Aug 31;287(36):30518-28. doi: 10.1074/jbc.M112.391557. Epub 2012 Jul 11.
Protein kinase Cθ (PKCθ) is a novel PKC that plays a key role in T lymphocyte activation. To understand how PKCθ is regulated in T cells, we investigated the properties of its N-terminal C2 domain that functions as an autoinhibitory domain. Our measurements show that a Tyr(P)-containing peptide derived from CDCP1 binds the C2 domain of PKCθ with high affinity and activates the enzyme activity of the intact protein. The Tyr(P) peptide also binds the C2 domain of PKCδ tightly, but no enzyme activation was observed with PKCδ. Mutations of PKCθ-C2 residues involved in Tyr(P) binding abrogated the enzyme activation and association of PKCθ with Tyr-phosphorylated full-length CDCP1 and severely inhibited the T cell receptor/CD28-mediated activation of a PKCθ-dependent reporter gene in T cells. Collectively, these studies establish the C2 domain of PKCθ as a Tyr(P)-binding domain and suggest that the domain may play a major role in PKCθ activation via its Tyr(P) binding.
蛋白激酶 Cθ（PKCθ）是一种新型的蛋白激酶，在 T 淋巴细胞激活中发挥关键作用。为了了解 PKCθ 在 T 细胞中的调控机制，我们研究了其作为自抑制结构域的 N 端 C2 结构域的特性。我们的测量结果表明，源自 CDCP1 的含有 Tyr(P)的肽与 PKCθ 的 C2 结构域具有高亲和力，并激活完整蛋白的酶活性。Tyr(P)肽也与 PKCδ 的 C2 结构域紧密结合，但未观察到 PKCδ 的酶激活。参与 Tyr(P)结合的 PKCθ-C2 残基的突变消除了酶激活以及 PKCθ 与 Tyr-磷酸化全长 CDCP1 的结合，并严重抑制了 T 细胞受体/CD28 介导的 T 细胞中依赖 PKCθ 的报告基因的激活。总之，这些研究确立了 PKCθ 的 C2 结构域为 Tyr(P)结合结构域，并表明该结构域可能通过其 Tyr(P)结合在 PKCθ 激活中发挥主要作用。
