Gipc3 Mutation Might Cause Sensorineural Hearing Loss by Inhibiting Mitophagy in Inner Ear Hair Cells

Sensorineural hearing loss (SNHL) has a high degree of genetic heterogeneity, with numerous mutated genes that contribute to deafness. GIPC3 gene is one of the mutated genes that can cause congenital hearing loss, which has been identified in recent years; however, the exact mechanism behind this condition remains unclear. Mitophagy is the process of selectively encapsulating and lysing damaged or dysfunctional mitochondria in order to prevent the accumulation of damaged mitochondria from damaging the cells and is of great importance in the maintenance of homeostasis in the inner ear. This paper aims to investigate the potential mechanism of sensorineural hearing loss brought on by Gipc3 mutations by observing the impact of Gipc3 expression on mitochondrial metabolism and autophagy in inner ear hair cells. In this study, The House Ear Institute Organ of Corti 1(HEI-OC1) cells and cochlear explants were cultured to change the expression level of Gipc3 by transfection, and the knockdown efficiency was examined by quantitative polymerase chain reaction (qPCR) and Western blot. Knockdown of Gipc3 inhibited cell viability and its proliferation ability. When tert-butyl hydroperoxide (t-BHP) was used to induce oxidative stress injury and knockdown of Gipc3, inner ear hair cells had a weakened ability to resist oxidative stress injury, mitochondrial metabolism was altered, and there was an accumulation of reactive oxygen species (ROS) and a reduction of mitochondrial membrane potential. Immunofluorescence and Western blot techniques demonstrated autophagy abnormalities in the mitophagy-related proteins LC3B and p62. Early endosome-dependent mitophagy is mediated by a PH domain and leucine zipper motif 1 (APPL1), and mitophagy is hampered by APPL1 deletion. We discovered that there is probably co-localization between Gipc3 and APPL1 by confocal microscopy imaging and that their trends show a positive association. In summary, Gipc3 mutations may lead to decreased mitochondrial function by inhibiting the APPL1-mediated mitophagy process. This may lead to a reduction in oxidative metabolism in hair cells, which is one potential mechanism via which Gipc3 mutations suppress mitophagy.