FAM134B alleviates cisplatin-induced spiral ganglion neurons (SGNs) damage by mediating ER-phagy

Abstract Aims FAM134B, the first endoplasmic reticulum autophagy (ER-phagy) receptor identified, regulates certain ER-phagy-related processes. The present study was designed to determine whether FAM134B is expressed in cochlear spiral ganglion neurons (SGNs) of C57BL /6 mice and, if so, to explore the underlying mechanisms of FAM134B in cisplatin-induced SGNs damage in vitro. Methods SGNs were treated with 30 µm cisplatin for 24 h. The expression of FAM134B, morphological changes of SGNs, and the colocalization of endoplasmic reticulum segments and lysosomes were measured by immunofluorescence. Apoptosis was measured by TUNEL staining. The expression of FAM134B, phosphorylated-inositol-requiring endoribonuclease 1α (P-IRE1α), LC3B, Bcl-2, cleaved caspase-3, and caspase-12 was detected by western blot. The reactive oxygen species (ROS) levels were evaluated by MitoSOX and 2',7'-D chlorodihydrofluorescein diacetate (DCFH-DA) probe. Results We found that FAM134B expressed in the cytoplasm of SGNs, especially in the fourth postnatal day mice. Cisplatin resulted in a decrease in the number of SGNs and FAM134B expression, as well as increases in ROS levels, ER stress, ER-phagy, and apoptosis. Interestingly, we observed an increase in FAM134B expression, ER stress, and apoptosis when autophagy was inhibited, while, the opposite changes were observed when autophagy was activated. Additionally, co-treatment with the ROS scavenger, N-Acetyl-L-Cysteine (NAC), alleviated ER stress, ER-phagy, and apoptosis, but increased FAM134B expression. Conclusions The present study provides the first evidence of FAM134B expression in the SGNs. Importantly, FAM134B possesses the protective effect against cisplatin ototoxicity in SGNs by mediating ER-phagy, thereby providing new therapeutic targets and directions for sensorineural hearing loss.