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未折叠蛋白反应传感器 IRE1α 促进足细胞中的网质体自噬。

The unfolded protein response transducer IRE1α promotes reticulophagy in podocytes.

机构信息

Department of Medicine, McGill University Health Centre, McGill University, Montreal, Canada.

Department of Life Science, Kanazawa Medical University, Uchinada, Japan.

出版信息

Biochim Biophys Acta Mol Basis Dis. 2022 Jun 1;1868(6):166391. doi: 10.1016/j.bbadis.2022.166391. Epub 2022 Mar 15.

Abstract

Glomerular diseases involving podocyte/glomerular epithelial cell (GEC) injury feature protein misfolding and endoplasmic reticulum (ER) stress. Inositol-requiring enzyme 1α (IRE1α) mediates chaperone production and autophagy during ER stress. We examined the role of IRE1α in selective autophagy of the ER (reticulophagy). Control and IRE1α knockout (KO) GECs were incubated with tunicamycin to induce ER stress and subjected to proteomic analysis. This showed IRE1α-dependent upregulation of secretory pathway mediators, including the coat protein complex II component Sec23B. Tunicamycin enhanced expression of Sec23B and the reticulophagy adaptor reticulon-3-long (RTN3L) in control, but not IRE1α KO GECs. Knockdown of Sec23B reduced autophagosome formation in response to ER stress. Tunicamycin stimulated colocalization of autophagosomes with Sec23B and RTN3L in an IRE1α-dependent manner. Similarly, during ER stress, glomerular α5 collagen IV colocalized with RTN3L and autophagosomes. Degradation of RTN3L and collagen IV increased in response to tunicamycin, and the turnover was blocked by deletion of IRE1α; thus, the IRE1α pathway promotes RTN3L-mediated reticulophagy and collagen IV may be an IRE1α-dependent reticulophagy substrate. In experimental glomerulonephritis, expression of Sec23B, RTN3L, and LC3-II increased in glomeruli of control mice, but not in podocyte-specific IRE1α KO littermates. In conclusion, during ER stress, IRE1α redirects a subset of Sec23B-positive vesicles to deliver RTN3L-coated ER fragments to autophagosomes. Reticulophagy is a novel outcome of the IRE1α pathway in podocytes and may play a cytoprotective role in glomerular diseases.

摘要

涉及足细胞/肾小球上皮细胞 (GEC) 损伤的肾小球疾病的特征是蛋白质错误折叠和内质网 (ER) 应激。肌醇需求酶 1α (IRE1α) 在 ER 应激过程中介导伴侣蛋白的产生和自噬。我们研究了 IRE1α 在 ER 选择性自噬 (网质体自噬) 中的作用。用衣霉素孵育对照和 IRE1α 敲除 (KO) GEC 以诱导 ER 应激,并进行蛋白质组学分析。结果显示,IRE1α 依赖性上调分泌途径介质,包括衣壳蛋白复合物 II 成分 Sec23B。衣霉素增强了 Sec23B 和网质体自噬衔接蛋白 reticulon-3-long (RTN3L) 在对照中的表达,但在 IRE1α KO GEC 中没有。Sec23B 的敲低减少了 ER 应激时自噬体的形成。衣霉素以 IRE1α 依赖的方式刺激自噬体与 Sec23B 和 RTN3L 的共定位。同样,在 ER 应激期间,肾小球 α5 胶原 IV 与 RTN3L 和自噬体共定位。衣霉素处理后,RTN3L 和胶原 IV 的降解增加,而 IRE1α 的缺失阻断了这一过程;因此,IRE1α 途径促进 RTN3L 介导的网质体自噬,胶原 IV 可能是 IRE1α 依赖的网质体自噬底物。在实验性肾小球肾炎中,Sec23B、RTN3L 和 LC3-II 的表达在对照小鼠的肾小球中增加,但在足细胞特异性 IRE1α KO 同窝仔鼠中没有增加。总之,在 ER 应激期间,IRE1α 将一部分 Sec23B 阳性囊泡重定向到自噬体,以递送 RTN3L 包被的 ER 片段。网质体自噬是 IRE1α 途径在足细胞中的一种新的结果,可能在肾小球疾病中发挥细胞保护作用。

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