Mo Jie, Su Chen, Li Pengcheng, Yang Zhenhua, Tao Ran, Liu Qiumeng, Yuan Chaoyi, Xu Lei, Ge Qianyun, Ning Deng, Liang Huifang, Zhu Haidan, Luo Yan, Chen Xiaoping, Chen Jin, Zhang Bixiang
Hepatic Surgery Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China.
Department of Plastic and Cosmetic Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China.
Autophagy. 2025 Apr;21(4):840-859. doi: 10.1080/15548627.2024.2435236. Epub 2024 Dec 17.
RETREG1/FAM134B is known for its role as a reticulophagy receptor. Our previous study established that RETREG1 is upregulated in hepatocellular carcinoma (HCC) and contributes to disease progression by activating the AKT signaling pathway. However, the specific mechanisms underlying the elevated expression of RETREG1 in HCC remain unclear. This study unveils the interaction of RETREG1 with CKAP4 and TRIM21. We demonstrated that TRIM21 ubiquitinates RETREG1 at K247 and K252, facilitating its proteasomal degradation. Conversely, CKAP4 shields RETREG1 from degradation by competitively binding to it, revealing a novel post-translational modification mechanism for RETREG1. By modulating RETREG1 expression, CKAP4, and TRIM21 intricately regulate reticulophagy. Additionally, we observed that stress-induced TRIM21 upregulation mitigates the function of RETREG1 to restore ER stress equilibrium. The oncogenic potential of CKAP4 in HCC was demonstrated using various animal models. Clinical sample analyses suggested that CKAP4 is a potential biomarker for HCC prognosis and diagnosis.: AKT: thymoma viral proto-oncogene; aa: amino acid; bp: base pair; CHX: cycloheximide; co-IP: co-Immunoprecipitation; CQ: chloroquine; CKAP4: cytoskeleton-associated protein 4; DKK1: dickkopf WNT signaling pathway inhibitor 1; DUBs: deubiquitinating enzymes; EBSS: Earle's balanced salt solution; EGFP: enhanced green fluorescent protein; ER: endoplasmic reticulum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HCC: hepatocellular carcinoma; HFD: high-fat diet; HiTV: hyperdynamic tail vein injection; IF: immunofluorescence; IHC: immunohistochemistry; IP-MS: immunoprecipitation-mass spectrometry; LIR: LC3-interacting region; mAbs: monoclonal antibodies; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; mCherry: monomeric cherry; oe: overexpression; PDX: patient-derived tumor xenograft; reticulophagy: endoplasmic reticulum selective autophagy; RETREG1: reticulophagy regulator 1; RHD: reticulon-homology domain; Tg: thapsigargin; Tm: tunicamycin; TRIM21: tripartite motif-containing 21; UB: ubiquitin; WT: wild-type.
RETREG1/FAM134B作为一种网织自噬受体而为人所知。我们之前的研究表明，RETREG1在肝细胞癌（HCC）中上调，并通过激活AKT信号通路促进疾病进展。然而，HCC中RETREG1表达升高的具体机制仍不清楚。本研究揭示了RETREG1与CKAP4和TRIM21之间的相互作用。我们证明，TRIM21在K247和K252位点使RETREG1发生泛素化，促进其蛋白酶体降解。相反，CKAP4通过竞争性结合来保护RETREG1不被降解，揭示了一种新的RETREG1翻译后修饰机制。通过调节RETREG1的表达，CKAP4和TRIM21复杂地调节网织自噬。此外，我们观察到应激诱导的TRIM21上调减轻了RETREG1恢复内质网应激平衡的功能。使用各种动物模型证明了CKAP4在HCC中的致癌潜力。临床样本分析表明，CKAP4是HCC预后和诊断的潜在生物标志物。：AKT：胸腺瘤病毒原癌基因；aa：氨基酸；bp：碱基对；CHX：放线菌酮；co-IP：免疫共沉淀；CQ：氯喹；CKAP4：细胞骨架相关蛋白4；DKK1：Dickkopf WNT信号通路抑制剂1；DUBs：去泛素化酶；EBSS：Earle平衡盐溶液；EGFP：增强型绿色荧光蛋白；ER：内质网；GAPDH：甘油醛-3-磷酸脱氢酶；GFP：绿色荧光蛋白；HCC：肝细胞癌；HFD：高脂饮食；HiTV：高动力尾静脉注射；IF：免疫荧光；IHC：免疫组织化学；IP-MS：免疫沉淀-质谱；LIR：LC3相互作用区域；mAbs：单克隆抗体；MAP1LC3B/LC3B：微管相关蛋白1轻链3β；mCherry：单体樱桃；oe：过表达；PDX：患者来源的肿瘤异种移植；网织自噬：内质网选择性自噬；RETREG1：网织自噬调节因子1；RHD：网织同源结构域；Tg：毒胡萝卜素；Tm：衣霉素；TRIM21：含三联基序的蛋白21；UB：泛素；WT：野生型
