University of Pittsburgh, Department of Immunology, BST E-1056, 200 Lothrop Street, Pittsburgh, PA 15261, United States.
University of Pittsburgh, Department of Immunology, BST E-1056, 200 Lothrop Street, Pittsburgh, PA 15261, United States; Graduate Program in Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States.
Mol Immunol. 2014 May;59(1):110-6. doi: 10.1016/j.molimm.2014.01.011. Epub 2014 Feb 16.
Previous studies from our group and others have shown that the Akt kinase can contribute to induction of NF-κB by antigen receptor signaling. However, the direct targets of Akt in this pathway are not known. Here we show that Akt-mediated NF-κB activation is mediated at least in part through direct phosphorylation of the adaptor protein Carma1, which we previously demonstrated could interact with Akt in a TCR ligation-dependent manner. The putative Akt phosphorylation sites in Carma1 are distinct from known PKC consensus sites. Mutation of S551, S637 and S645 in Carma1 to non-phosphorylatable residues decreased phosphorylation of GST-Carma1-linker construct by Akt in vitro. In addition, Carma1 S637A/S645A mutants were significantly impaired in their ability to restore TCR-mediated NF-κB activation and IL-2 expression in Carma1-deficient T cells. Thus, our data reveal Carma1 as a novel target for Akt phosphorylation and suggest that Akt-mediated phosphorylation of Carma1 is an additional regulatory mechanism tuning the NF-κB response downstream of antigen receptor and co-stimulatory signaling.
先前我们团队和其他团队的研究表明，Akt 激酶可以促进抗原受体信号诱导 NF-κB。然而，Akt 在该途径中的直接靶标尚不清楚。在这里，我们表明 Akt 介导的 NF-κB 激活至少部分是通过衔接蛋白 Carma1 的直接磷酸化介导的，我们之前证明 Carma1 可以以 TCR 连接依赖性的方式与 Akt 相互作用。Carma1 中的假定 Akt 磷酸化位点与已知的 PKC 共有序列位点不同。Carma1 中的 S551、S637 和 S645 突变为非磷酸化残基可降低 GST-Carma1 连接子构建体在体外的 Akt 磷酸化。此外，Carma1 S637A/S645A 突变体在恢复 Carma1 缺陷 T 细胞中 TCR 介导的 NF-κB 激活和 IL-2 表达的能力方面受到严重损害。因此，我们的数据揭示了 Carma1 是 Akt 磷酸化的新靶标，并表明 Akt 介导的 Carma1 磷酸化是调节抗原受体和共刺激信号下游 NF-κB 反应的另一种调节机制。
