Choi You-Jin, Nam Yoon Ah, Hyun Ji Ye, Yu Jihyeon, Mun Yewon, Yun Sung Ho, Lee Wonseok, Park Cheon Jun, Han Byung Woo, Lee Byung-Hoon
College of Pharmacy, Daegu Catholic University, Gyeongsan, Gyeongsangbuk-do, Republic of Korea.
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, Republic of Korea.
Autophagy. 2025 Apr;21(4):827-839. doi: 10.1080/15548627.2024.2435234. Epub 2024 Dec 8.
SORT1 (sortilin 1), a member of the the Vps10 (vacuolar protein sorting 10) family, is involved in hepatic lipid metabolism by regulating very low-density lipoprotein (VLDL) secretion and facilitating the lysosomal degradation of CES1 (carboxylesterase 1), crucial for triglyceride (TG) breakdown in the liver. This study explores whether SORT1 is targeted for degradation by chaperone-mediated autophagy (CMA), a selective protein degradation pathway that directs proteins containing KFERQ-like motifs to lysosomes via LAMP2A (lysosomal-associated membrane protein 2A). Silencing LAMP2A or HSPA8/Hsc70 with siRNA increased cytosolic SORT1 protein levels. Leupeptin treatment induced lysosomal accumulation of SORT1, unaffected by si co-treatment, indicating CMA-dependent degradation. Human SORT1 contains five KFERQ-like motifs (VVTKQ, VREVK, VKDLK, KDLKK, and DLKKK), crucial for HSPA8 recognition; mutating any single amino acid within these motifs decreased HSPA8 binding. Furthermore, compromised CMA activity resulted in elevated SORT1-mediated degradation of CES1, contributing to increased lipid accumulation in hepatocytes. Consistent with findings, LAMP2A knockdown in mice exacerbated high-fructose diet-induced fatty liver, marked by increased SORT1 and decreased CES1 levels. Conversely, LAMP2A overexpression promoted SORT1 degradation and CES1D accumulation, counteracting fasting-induced CES1D suppression through CMA activation. Our findings reveal that SORT1 is a substrate of CMA, highlighting its crucial role in directing CES1 to lysosomes. Consequently, disrupting CMA-mediated SORT1 degradation significantly affects CES1-dependent TG hydrolysis, thereby affecting hepatic lipid homeostasis.: APOB: apolipoprotein B; CES1: carboxylesterase 1; CMA: chaperone-mediated autophagy; HSPA8/Hsc70: heat shock protein family A (Hsp70) member 8; LAMP2A: lysosomal associated membrane protein 2A; LDL-C: low-density lipoprotein-cholesterol; PLIN: perilipin; SORT1: sortilin 1; TG: triglyceride; VLDL: very low-density lipoprotein; Vps10: vacuolar protein sorting 10.
SORT1（sortilin 1）是Vps10（液泡蛋白分选10）家族的成员，通过调节极低密度脂蛋白（VLDL）的分泌以及促进CES1（羧酸酯酶1）的溶酶体降解来参与肝脏脂质代谢，而CES1对肝脏中甘油三酯（TG）的分解至关重要。本研究探讨了SORT1是否通过伴侣介导的自噬（CMA）被靶向降解，CMA是一种选择性蛋白质降解途径，它通过LAMP2A（溶酶体相关膜蛋白2A）将含有KFERQ样基序的蛋白质导向溶酶体。用小干扰RNA（siRNA）沉默LAMP2A或HSPA8/Hsc70可增加胞质SORT1蛋白水平。亮肽素处理诱导SORT1在溶酶体中积累，联合小干扰RNA处理对此无影响，表明这是依赖CMA的降解。人类SORT1含有五个KFERQ样基序（VVTKQ、VREVK、VKDLK、KDLKK和DLKKK），这对HSPA8的识别至关重要；这些基序内的任何单个氨基酸发生突变都会降低HSPA8的结合。此外，CMA活性受损导致CES1的SORT1介导的降解增加，促使肝细胞中脂质积累增加。与这些发现一致，在小鼠中敲低LAMP2A会加剧高果糖饮食诱导的脂肪肝，其特征是SORT1水平升高和CES1水平降低。相反，LAMP2A过表达促进SORT1降解和CES1D积累，通过激活CMA抵消禁食诱导的CES1D抑制。我们的发现揭示SORT1是CMA的底物，突出了其在将CES1导向溶酶体中的关键作用。因此，破坏CMA介导的SORT1降解会显著影响CES1依赖的TG水解，从而影响肝脏脂质稳态。：APOB：载脂蛋白B；CES1：羧酸酯酶1；CMA：伴侣介导的自噬；HSPA8/Hsc70：热休克蛋白家族A（Hsp70）成员8；LAMP2A：溶酶体相关膜蛋白2A；LDL-C：低密度脂蛋白胆固醇；PLIN：围脂滴蛋白；SORT1：sortilin 1；TG：甘油三酯；VLDL：极低密度脂蛋白；Vps10：液泡蛋白分选10
