Centre of Reproduction, Development and Aging, Faculty of Health Sciences, University of Macau, Taipa, Macau, China.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Autophagy. 2023 Jan;19(1):241-255. doi: 10.1080/15548627.2022.2071381. Epub 2022 May 6.
Macroautophagy/autophagy, an evolutionarily conserved degradation system, serves to clear intracellular components through the lysosomal pathway. Mounting evidence has revealed cytoprotective roles of autophagy; however, the intracellular causes of overactivated autophagy, which has cytotoxic effects, remain elusive. Here we show that sustained proteotoxic stress induced by loss of the NG and lch repeat-containing protein C53A5.6/RIKE-1 induces sequestration of LET-363/MTOR complex and overactivation of autophagy, and consequently impairs epithelial integrity in . In C53A5.6/RIKE-1-deficient animals, blocking autophagosome formation effectively prevents excessive endosomal degradation, mitigates mislocalization of intestinal membrane components and restores intestinal lumen morphology. However, autophagy inhibition does not affect LET-363/MTOR aggregation in animals with compromised C53A5.6/RIKE-1 function. Improving proteostasis capacity by reducing DAF-2 insulin/IGF1 signaling markedly relieves the aggregation of LET-363/MTOR and alleviates autophagy overactivation, which in turn reverses derailed endosomal trafficking and rescues epithelial morphogenesis defects in C53A5.6/RIKE-1-deficient animals. Hence, our studies reveal that C53A5.6/RIKE-1-mediated proteostasis is critical for maintaining the basal level of autophagy and epithelial integrity. ACT-5: actin 5; ACTB: actin beta; ALs: autolysosomes; APs: autophagosomes; AJM-1: apical junction molecule; ATG: autophagy related; C. elegans: Caenorhabditis elegans; CPL-1: cathepsin L family; DAF: abnormal dauer formation; DLG-1: Drosophila discs large homolog; ERM-1: ezrin/radixin/moesin; EPG: ectopic P granule; GFP: freen fluorescent protein; HLH-30: helix loop helix; HSP: heat shock protein; LAAT-1: lysosome associated amino acid transporter; LET: lethal; LGG-1: LC3, GABARAP and GATE-16 family; LMP-1: LAMP (lysosome-associated membrane protein) homolog; MTOR: mechanistic target of rapamycin kinase; NUC-1: abnormal nuclease; PEPT-1/OPT-2: Peptide transporter family; PGP-1: P-glycoprotein related; RAB: RAB family; RIKE-1: RING and Kelch repeat-containing protein; SLCF-1: solute carrier family; SQST-1: sequestosome related; SPTL-1: serine palmitoyl transferase family.
自噬，一种进化上保守的降解系统，通过溶酶体途径清除细胞内成分。越来越多的证据表明自噬具有细胞保护作用；然而，导致细胞毒性的过度激活自噬的细胞内原因仍不清楚。在这里，我们表明，NG 和 lch 重复蛋白 C53A5.6/RIKE-1 的缺失引起的持续蛋白毒性应激诱导 LET-363/MTOR 复合物的隔离和自噬的过度激活，从而损害了 的上皮完整性。在 C53A5.6/RIKE-1 缺陷动物中，阻断自噬体的形成可有效防止内体过度降解，减轻肠道膜成分的定位错误，并恢复肠道腔形态。然而，自噬抑制并不影响 LET-363/MTOR 在 C53A5.6/RIKE-1 功能受损动物中的聚集。通过降低 DAF-2 胰岛素/IGF1 信号来提高蛋白质稳定性，显著缓解 LET-363/MTOR 的聚集，并减轻自噬的过度激活，从而逆转错误的内体运输，并挽救 C53A5.6/RIKE-1 缺陷动物的上皮形态发生缺陷。因此，我们的研究表明，C53A5.6/RIKE-1 介导的蛋白质稳定性对于维持自噬和上皮完整性的基础水平至关重要。ACT-5：肌动蛋白 5；ACTB：肌动蛋白β；ALs：自噬溶酶体；APs：自噬体；AJM-1：顶连接分子；ATG：自噬相关；C. elegans：秀丽隐杆线虫；CPL-1：组织蛋白酶 L 家族；DAF：异常 dauer 形成；DLG-1：果蝇盘状大同源物；ERM-1：埃兹林/雷迪辛/莫斯因；EPG：异位 P 颗粒；GFP：自由荧光蛋白；HLH-30：螺旋环螺旋；HSP：热休克蛋白；LAAT-1：溶酶体相关氨基酸转运蛋白；LET：致死；LGG-1：LC3、GABARAP 和 GATE-16 家族；LMP-1：LAMP（溶酶体相关膜蛋白）同源物；MTOR：雷帕霉素靶蛋白激酶；NUC-1：异常核酸酶；PEPT-1/OPT-2：肽转运蛋白家族；PGP-1：P-糖蛋白相关；RAB：RAB 家族；RIKE-1：环和 Kelch 重复蛋白；SLCF-1：溶质载体家族；SQST-1：自噬相关；SPTL-1：丝氨酸棕榈酰转移酶家族。
