Autophagy-dependent PELI3 degradation inhibits proinflammatory IL1B expression
Autophagy-dependent PELI3 degradation inhibits proinflammatory IL1B expression
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DOI：
10.4161/auto.32178
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发表时间：
2014-11-01
期刊：
影响因子：
13.3
通讯作者：
von Knethen, Andreas
中科院分区：
文献类型：
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作者：
Giegerich, Annika Klara;Kuchler, Laura;von Knethen, Andreas
脂多糖(LPS)诱导TLR4(Toll样受体4)的激活之后是随后的压倒性炎症反应，这是脓毒症第一阶段的标志。因此，通过自噬来对抗过度的先天免疫对于炎症的终止具有重要意义。然而，这种相互作用的确切分子细节还知之甚少。在这里，我们发现PELI3/Pellino3(Pellino E3泛素蛋白连接酶家族成员3)是一种E3泛素连接酶，也是TLR4信号转导的支架蛋白，受到内毒素刺激后巨噬细胞自噬(M Phi)的影响。我们注意到，在Peli3基因敲除的小鼠M Phi中，内毒素处理后，促炎因子IL1b(白介素1)的mRNA表达减弱。自噬适配蛋白SQSTM1/p62(隔离小体1)是TLR4信号通路中潜在的PELI3结合伙伴。针对Sqstm1和ATG7(自噬相关的7)的siRNA、Wortmannin对自噬的药理抑制以及巴菲霉素A(1)阻断溶酶体空泡型H+-ATPase使PELI3蛋白水平升高，而对蛋白酶体的抑制作用不明显。一致地，通过MTOR(雷帕霉素的机械靶点(丝氨酸/苏氨酸激酶))抑制或饥饿诱导自噬的治疗促进了PELI3的降解并减少了促炎性IL1b的表达。发现PELI3在脂多糖刺激下被泛素化，PELI3-赖氨酸残基316位点突变(Lys316Arg)减弱了对Torin2依赖的PELI3的降解。免疫荧光分析表明，PELI3与典型的自噬标记MAP1LC3B/LC3B(微管相关蛋白1轻链3)和LAMP2(溶酶体相关膜蛋白2)共定位。我们的观察表明，自噬在TLR4信号转导过程中导致PELI3降解，从而损害脓毒症期间的高炎性阶段。
Lipopolysaccharide (LPS)-induced activation of TLR4 (toll-like receptor 4) is followed by a subsequent overwhelming inflammatory response, a hallmark of the first phase of sepsis. Therefore, counteracting excessive innate immunity by autophagy is important to contribute to the termination of inflammation. However, the exact molecular details of this interplay are only poorly understood. Here, we show that PELI3/Pellino3 (pellino E3 ubiquitin protein ligase family member 3), which is an E3 ubiquitin ligase and scaffold protein in TLR4-signaling, is impacted by autophagy in macrophages (M phi) after LPS stimulation. We noticed an attenuated mRNA expression of proinflammatory Il1b (interleukin 1, ) in Peli3 knockdown murine M phi in response to LPS treatment. The autophagy adaptor protein SQSTM1/p62 (sequestosome 1) emerged as a potential PELI3 binding partner in TLR4-signaling. siRNA targeting Sqstm1 and Atg7 (autophagy related 7), pharmacological inhibition of autophagy by wortmannin as well as blocking the lysosomal vacuolar-type H+-ATPase by bafilomycin A(1) augmented PELI3 protein levels, while inhibition of the proteasome had no effect. Consistently, treatment to induce autophagy by MTOR (mechanistic target of rapamycin (serine/threonine kinase)) inhibition or starvation enhanced PELI3 degradation and reduced proinflammatory Il1b expression. PELI3 was found to be ubiquitinated upon LPS stimulation and point mutation of PELI3-lysine residue 316 (Lys316Arg) attenuated Torin2-dependent degradation of PELI3. Immunofluorescence analysis revealed that PELI3 colocalized with the typical autophagy markers MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 ) and LAMP2 (lysosomal-associated membrane protein 2). Our observations suggest that autophagy causes PELI3 degradation during TLR4-signaling, thereby impairing the hyperinflammatory phase during sepsis.