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

FAM134B-mediated ER-phagy alleviates alcohol-related liver fibrosis by reducing endoplasmic reticulum stress

BACKGROUND

Alcohol-related liver fibrosis (ALF), a severe stage of alcohol-related liver disease (ALD), currently lacks effective treatments. Endoplasmic reticulum (ER) stress is a key pathological feature of ALF. FAM134B (JK-1, RETREG1), an ER-phagy receptor, mediates ER-phagy to alleviate ER stress and restore ER homeostasis. However, the molecular mechanisms linking ER stress to ALF remain unclear.

AIMS

This study aimed to investigate the role and molecular mechanisms of FAM134B in ALF, specifically whether FAM134B-mediated ER-phagy reduces ER stress to mitigate ALF.

METHODS

We developed a FAM134B overexpression mouse model using tail vein injection of AAV-8-TBG-m-FAM134B and monitored disease progression in ALF mice. Fibrosis markers (α-SMA, COL1A1), ER stress indicators (GRP78, CHOP, IRE1-α, ATF6), and ER-phagy markers (LC3, p62, VAPB, CANX, Climp63, REEP5) were analyzed. Additionally, further in vitro experiments were carried out to explore whether FAM134B-mediated ER-phagy attenuates ALF by alleviating hepatocyte ER stress.

RESULTS

FAM134B overexpression increased ER-phagy, reduced ER stress, and ameliorated liver fibrosis. In vitro, FAM134B overexpression promoted autophagy, decreased cytokine secretion, and inhibited hepatic stellate cell (JS-1) and macrophage activation (RAW264.7).

CONCLUSION

These findings suggest that FAM134B-mediated ER-phagy mitigates ALF by alleviating ER stress, providing new targets and intervention strategies for ALF.

TRIM13 Reduces Damage to Alveolar Epithelial Cells in COPD by Inhibiting Endoplasmic Reticulum Stress-Induced ER-Phagy

PURPOSE

Tripartite motif-containing protein 13 (TRIM13) directly or indirectly participates in autophagy and apoptosis. However, it remains unclear whether TRIM13 participates in chronic obstructive pulmonary disease (COPD) progression. This study aimed to reveal the molecular mechanisms through which TRIM13 regulates alveolar epithelial cell injury in COPD to provide new molecular targets for COPD treatment.

METHODS

The TRIM13 expression levels were determined in clinical COPD patients and a rat emphysema model. A cigarette smoke-induced model of endoplasmic reticulum stress (ERS) and endoplasmic reticulum autophagy (ER-phagy) was developed using A549 cells, and the effects of TRIM13 gene overexpression/knockdown on ERS, ER-phagy, and cell apoptosis were assessed in these cells.

RESULTS

TRIM13 expression was significantly decreased in the lung tissues of COPD patients and rats with emphysema. Moreover, the apoptosis level was significantly increased in the lung tissues of rats with emphysema. TRIM13 gene overexpression reduced the expression levels of ERS-related molecules (GRP78, GRP94, XBP-1, and eIF2a) in the COPD model; it also lowered the ER-phagy level, as evidenced by decreased number of autolysosomes observed by transmission electron microscopy, improved endoplasmic reticulum structure, reduced LC3-II/LC3-I and Beclin1 expression levels, and increased expression level of the autophagy inhibitory molecule Bcl-2. TRIM13 gene knockdown, however, led to opposite results.

CONCLUSION

TRIM13 expression attenuated alveolar epithelial cell injury in COPD by inhibiting ERS-induced ER-phagy.

Autophagy: Regulator of cell death

Autophagy is the process by which cells degrade and recycle proteins and organelles to maintain intracellular homeostasis. Generally, autophagy plays a protective role in cells, but disruption of autophagy mechanisms or excessive autophagic flux usually leads to cell death. Despite recent progress in the study of the regulation and underlying molecular mechanisms of autophagy, numerous questions remain to be answered. How does autophagy regulate cell death? What are the fine-tuned regulatory mechanisms underlying autophagy-dependent cell death (ADCD) and autophagy-mediated cell death (AMCD)? In this article, we highlight the different roles of autophagy in cell death and discuss six of the main autophagy-related cell death modalities, with a focus on the metabolic changes caused by excessive endoplasmic reticulum-phagy (ER-phagy)-induced cell death and the role of mitophagy in autophagy-mediated ferroptosis. Finally, we discuss autophagy enhancement in the treatment of diseases and offer a new perspective based on the use of autophagy for different functional conversions (including the conversion of autophagy and that of different autophagy-mediated cell death modalities) for the clinical treatment of tumors.