Centre for Lipid Research & Chongqing Key Laboratory of Metabolism on Lipid and Glucose, Key Laboratory of Molecular Biology for Infectious Diseases (Ministry of Education), Institute for Viral Hepatitis, Department of Infectious Diseases, the Second Affiliated Hospital, Chongqing Medical University, Chongqing, China.
John Moorhead Research Laboratory, Centre for Nephrology, University College London Medical School, London, England, UK.
Autophagy. 2023 Sep;19(9):2504-2519. doi: 10.1080/15548627.2023.2196876. Epub 2023 Apr 23.
Macroautophagy/autophagy plays a protective role in sepsis-induced liver injury. As a member of class B scavenger receptors, CD36 plays important roles in various disorders, such as atherosclerosis and fatty liver disease. Here we found that the expression of CD36 in hepatocytes was increased in patients and a mouse model with sepsis, accompanied by impaired autophagy flux. Furthermore, hepatocyte knockout (-HKO) markedly improved liver injury and the impairment of autophagosome-lysosome fusion in lipopolysaccharide (LPS)-induced septic mice. (ubiquilin 1) overexpression (OE) in hepatocyte blocked the protective effect of -HKO on LPS-induced liver injury in mice. Mechanistically, with LPS stimulation, CD36 on the plasma membrane was depalmitoylated and distributed to the lysosome, where CD36 acted as a bridge molecule linking UBQLN1 to soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and hence promoting the proteasomal degradation of SNARE proteins, resulting in fusion impairment. Overall, our data reveal that CD36 is essential for modulating the proteasomal degradation of autophagic SNARE proteins in a UBQLN1-dependent manner. Targeting CD36 in hepatocytes is effective for improving autophagic flux in sepsis and therefore represents a promising therapeutic strategy for clinical treatment of septic liver injury. AAV8: adeno-associated virus 8; AOSC: acute obstructive suppurative cholangitis; ATP1A1: ATPase, Na+/K+ transporting, alpha 1 polypeptide; CASP3: caspase 3; CASP8: caspase 8; CCL2: chemokine (C-C motif) ligand 2; -HKO: hepatocyte-specific knockout; Co-IP: co-immunoprecipitation; CQ: chloroquine; Cys: cysteine; GOT1: glutamic-oxaloacetic transaminase 1, soluble; GPT: glutamic-pyruvic transaminase, soluble; IL1B: interleukin 1 beta; IL6: interleukin 6; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LDH, lactate dehydrogenase; LPS: lipopolysaccharide; LYPLA1: lysophospholipase 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; OE: overexpression; qPCR: quantitative polymerase chain reaction; SNAP29: synaptosome associated protein 29; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; STX17: syntaxin 17; TNF: tumor necrosis factor; TRIM: tripartite motif-containing; UBA: ubiquitin-associated; UBL: ubiquitin-like; UBQLN: ubiquilin; VAMP8: vesicle associated membrane protein 8; WT: wild-type.
自噬在脓毒症诱导的肝损伤中发挥保护作用。作为 B 族清道夫受体的一员，CD36 在各种疾病中发挥重要作用，如动脉粥样硬化和脂肪肝疾病。在这里，我们发现脓毒症患者和小鼠模型中肝细胞内 CD36 的表达增加，同时自噬流受损。此外，肝细胞特异性敲除（-HKO）明显改善了脂多糖（LPS）诱导的脓毒症小鼠的肝损伤和自噬体-溶酶体融合受损。肝细胞内泛素结合酶 1（ubiquilin 1）过表达（OE）阻断了 -HKO 对 LPS 诱导的小鼠肝损伤的保护作用。在机制上，LPS 刺激后，质膜上的 CD36 去棕榈酰化并分布到溶酶体中，CD36 在溶酶体中作为桥联分子将 UBQLN1 与可溶性 N-乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）蛋白连接，从而促进 SNARE 蛋白的蛋白酶体降解，导致融合受损。总的来说，我们的数据揭示了 CD36 是调节自噬 SNARE 蛋白蛋白酶体降解所必需的，这种调节作用依赖于 UBQLN1。在肝细胞中靶向 CD36 可有效改善脓毒症中的自噬流，因此代表了治疗脓毒症肝损伤的有前途的临床治疗策略。AAV8：腺相关病毒 8；AOSC：急性梗阻性化脓性胆管炎；ATP1A1：钠/钾转运 ATP 酶，α 1 多肽；CASP3：半胱天冬酶 3；CASP8：半胱天冬酶 8；CCL2：趋化因子（C-C 基序）配体 2；-HKO：肝细胞特异性敲除；Co-IP：免疫共沉淀；CQ：氯喹；Cys：半胱氨酸；GOT1：谷草转氨酶 1，可溶性；GPT：谷丙转氨酶，可溶性；IL1B：白细胞介素 1β；IL6：白细胞介素 6；KO：敲除；LAMP1：溶酶体相关膜蛋白 1；LDH，乳酸脱氢酶；LPS：脂多糖；LYPLA1：溶血磷脂酶 1；MAP1LC3/LC3：微管相关蛋白 1 轻链 3；OE：过表达；qPCR：定量聚合酶链反应；SNAP29：突触相关蛋白 29；SNARE：可溶性 N-乙基马来酰亚胺敏感因子附着蛋白受体；SQSTM1/p62：自噬相关蛋白 1；STX17：突触融合蛋白 17；TNF：肿瘤坏死因子；TRIM：三肽重复含；UBA：泛素结合；UBL：泛素样；UBQLN：泛素结合；VAMP8：囊泡相关膜蛋白 8；WT：野生型。
