Family with sequence similarity 134 member B-mediated reticulophagy ameliorates hepatocyte apoptosis induced by dithiothreitol

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 Ca^(2+) levels were evaluated by the co-localization of intracellular Ca^(2+)-tracker and Mitotracker.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 FAM134Bmediated ER-phagy in attenuating hepatocyte apoptosis.