Phosphatase Holoenzyme PP1/GADD34 Negatively Regulates TLR Response by Inhibiting TAK1 Serine 412 Phosphorylation
Phosphatase Holoenzyme PP1/GADD34 Negatively Regulates TLR Response by Inhibiting TAK1 Serine 412 Phosphorylation
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磷酸酶全酶 PP1/GADD34 通过抑制 TAK1 丝氨酸 412 磷酸化负调节 TLR 反应
DOI：
10.4049/jimmunol.1302537
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发表时间：
2014-03-15
影响因子：
4.4
通讯作者：
Wang, Xiaojian
中科院分区：
文献类型：
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作者：
Gu, Meidi;Ouyang, Chuan;Wang, Xiaojian
需要充分阐明微调 TLR 反应的分子机制。蛋白磷酸酶-1 (PP1) 已被证明在细胞死亡和分化中很重要。然而，PP1 在 TLR 触发的免疫反应中的作用仍不清楚。在本研究中，我们证明PP1以磷酸酶依赖性方式抑制TLR3、TLR4和TLR9触发的MAPK和NF-κB通路的激活以及巨噬细胞中TNF-α、IL-6的产生。相反，PP1 敲低会增加 TLR 触发的信号传导和促炎细胞因子的产生。 Tautomycetin 是 PP1 的特异性抑制剂，会加重 LPS 诱导的小鼠内毒素休克。我们进一步证明，PP1 通过靶向 TGF-β 激活激酶 1 (TAK1) 丝氨酸 412 (Ser412) 磷酸化来负调节 TLR 触发的信号传导，这是激活 TAK1 介导的 IL-1R 和 TLR 信号传导所必需的。 TAK1 丝氨酸 412 突变为丙氨酸 (S412A) 可显着抑制 TLR/IL-1R 触发的 NF-κB 和 MAPK 激活以及巨噬细胞和小鼠胚胎成纤维细胞中促炎细胞因子的诱导。 DNA 损伤诱导蛋白 34 (GADD34) 指定 PP1 在 Ser412 位点使 TAK1 去磷酸化。 GADD34 缺失消除了 TAK1 和 PP1 之间的相互作用，并且缓解了 PP1 过表达诱导的 TLR 信号传导和促炎细胞因子产生的抑制。此外，敲低 GADD34 显着促进 TLR 诱导的 TAK1 Ser412 磷酸化、下游 NF-κB 和 MAPK 激活以及促炎细胞因子的产生。因此，PP1作为一种生理抑制剂，与其调节亚基GADD34一起严格控制TLR诱导的TAK1 Ser412磷酸化，防止TLR过度激活并保护宿主免受炎症免疫反应的破坏。
The molecular mechanisms that fine tune TLRs responses need to be fully elucidated. Protein phosphatase-1 (PP1) has been shown to be important in cell death and differentiation. However, the roles of PP1 in TLR-triggered immune response remain unclear. In this study, we demonstrate that PP1 inhibits the activation of the MAPK and NF-κB pathway and the production of TNF-α, IL-6 in macrophages triggered by TLR3, TLR4, and TLR9 in a phosphatase-dependent manner. Conversely, PP1 knockdown increases TLRs-triggered signaling and proinflammatory cytokine production. Tautomycetin, a specific inhibitor of PP1, aggravates LPS-induced endotoxin shock in mice. We further demonstrate that PP1 negatively regulates TLR-triggered signaling by targeting TGF-β–activated kinase 1 (TAK1) serine 412 (Ser412) phosphorylation, which is required for activation of TAK1-mediated IL-1R and TLR signaling. Mutation of TAK1 Serine 412 to alanine (S412A) significantly inhibits TLR/IL-1R–triggered NF-κB and MAPK activation and induction of proinflammatory cytokines in macrophage and murine embryonic fibroblast cells. DNA damage-inducible protein 34 (GADD34) specifies PP1 to dephosphorylate TAK1 at Ser412. GADD34 depletion abolished the interaction between TAK1 and PP1, and it relieved PP1 overexpression-induced inhibition of TLRs signaling and proinflammatory cytokine production. In addition, knockdown of GADD34 significantly promotes TLR-induced TAK1 Ser412 phosphorylation, downstream NF-κB and MAPK activation, and proinflammatory cytokine production. Therefore, PP1, as a physiologic inhibitor, together with its regulatory subunit GADD34, tightly controls TLR-induced TAK1 Ser412 phosphorylation, preventing excessive activation of TLRs and protecting the host from overwhelmed inflammatory immune responses.