Basic Study
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 21, 2022; 28(23): 2569-2581
Published online Jun 21, 2022. doi: 10.3748/wjg.v28.i23.2569
Family with sequence similarity 134 member B-mediated reticulophagy ameliorates hepatocyte apoptosis induced by dithiothreitol
Yi-Xin Guo, Bing Han, Ting Yang, Yu-Si Chen, Yi Yang, Jia-Yao Li, Qin Yang, Ru-Jia Xie
Yi-Xin Guo, Jia-Yao Li, Department of Pathophysiology, Guizhou Provincial Key Laboratory of Pathogenesis and Drug Research on Common Chronic Diseases, Guizhou Medical University, Guiyang 550025, Guizhou Province, China
Bing Han, Ting Yang, Yu-Si Chen, Yi Yang, Qin Yang, Ru-Jia Xie, Department of Pathophysiology, College of Basic Medical Sciences, Guizhou Medical University, Guiyang 550025, Guizhou Province, China
Author contributions: Yang Q and Xie RJ designed and coordinated the study; Guo YX, Han B and Yang T performed the experiments and acquired data; Chen YS, Yang Y and Li JY analyzed and interpreted data; Guo YX and Xie RJ drafted the manuscript; all authors approved the final version of the article.
Supported by National Natural Science Foundation of China, No. 81560105; Science and Technology Foundation of Guizhou Province, No. Qiankehe Jichu-ZK[2021]365, and No. Qiankehe Pingtai Rencai[2019]5801; and National Natural Science Foundation Cultivation Project of Guizhou Medical University, No. 20NSP016.
Institutional review board statement: This study did not involve human subjects or living animals.
Institutional animal care and use committee statement: This study did not involve human subjects or living animals.
Conflict-of-interest statement: The authors declare no conflicts of interest.
Data sharing statement: The data used to support the findings of this study are available from the corresponding author at 592153968@qq.com upon request.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Ru-Jia Xie, MD, Academic Research, Department of Pathophysiology, College of Basic Medical Sciences, Guizhou Medical University, Dongqing Road, Guiyang 550025, Guizhou Province, China. 592153968@qq.com
Received: January 5, 2022
Peer-review started: January 5, 2022
First decision: March 9, 2022
Revised: March 23, 2022
Accepted: April 29, 2022
Article in press: April 29, 2022
Published online: June 21, 2022
Processing time: 162 Days and 7.6 Hours
Abstract
BACKGROUND

Endoplasmic reticulum (ER) stress-related hepatocyte apoptosis is responsible for multiple hepatic diseases. Previous studies have revealed that endoplasmic reticulophagy (ER-phagy) promotes the selective clearance of damaged ER fragments during ER stress, playing a crucial role in maintaining ER homeostasis and inhibiting apoptosis. Family with sequence similarity 134 member B (FAM134B) is a receptor involved in ER-phagy that can form a complex with calnexin (CNX) and microtubule-associated protein 1 light chain 3 (LC3). The complex can mediate the selective isolation of ER fragments to attenuate hepatocyte apoptosis. However, the precise regulatory mechanisms remain unclear.

AIM

To elucidate the effect of FAM134B-mediated ER-phagy on ER stress-induced apoptosis in buffalo rat liver 3A (BRL-3A) rat hepatocytes and the potential regulatory mechanisms.

METHODS

ER stress-related hepatocyte apoptosis was induced using dithiothreitol (DTT). Proteins related to ER stress and autophagy were measured with western blotting. Protein complex interactions with FAM134B were isolated by co-immunoprecipitation. ER-phagy was evaluated in immunofluorescence experiments. Cell cycle distribution and apoptosis were measured by flow cytometry. Mitochondrial Ca2+ levels were evaluated by the co-localization of intracellular Ca2+-tracker and Mito-tracker. The small interfering RNA against FAM134B was used to knockdown FAM134B in BRL-3A cells.

RESULTS

ER stress-related and autophagy-related proteins in BRL-3A cells were elevated by both short and long-term DTT treatment. Furthermore, co-immunoprecipitation confirmed an interaction between FAM134B, CNX, FAM134B, and LC3 in BRL-3A cells. Immunofluorescence assays revealed that autolysosomes significantly decreased following short-term DTT treatment, but increased after long-term treatment. Mitochondrial Ca2+ levels and apoptotic rates were dramatically elevated, and more cells were arrested in the G1 stage after short-term DTT treatment; however, these decreased 48 h later. Moreover, FAM134B downregulation accelerated mitochondrial apoptotic pathway activation and aggravated hepatocyte apoptosis under ER stress.

CONCLUSION

FAM134B-mediated ER-phagy attenuates hepatocyte apoptosis by suppressing the mitochondrial apoptotic pathway. Our findings provide new evidence highlighting the importance of FAM134B-mediated ER-phagy in attenuating hepatocyte apoptosis.

Keywords: Hepatocytes; Reticulophagy; Family with sequence similarity 134 member B; Apoptosis; Endoplasmic reticulum stress; Endoplasmic reticulum homeostasis

Core Tip: We show that family with sequence similarity 134 member B (FAM134B)-mediated reticulophagy maintains the endoplasmic reticulum (ER) homeostasis in ER-stressed hepatocytes via the clearance of damaged ER fragments. Thereby FAM134B-mediated reticulophagy ameliorates dithiothreitol-induced hepatocyte apoptosis. Our findings provide emerging evidence of the prominence of ER-phagy in ER stress-related hepatocyte apoptosis. FAM134B may represent a potential therapeutic target for liver disease treatment.