miR-34a/ATG9A/TFEB Signaling Modulates Autophagy in Cochlear Hair Cells and Correlates with Age-related Hearing Loss.

Our previous studies revealed that miR-34a suppresses autophagy in the ageing cochlea, which correlates with cochlear hair cell loss and age-related hearing loss (AHL). However, the mechanisms underlying miR-34a regulation of autophagy in the cochlea remain unclear. Here, we show that nuclear translocation of transcription factor EB (TFEB), a master regulator of autophagy, was regulated by miR-34a in HEI-OC1 cells. Moreover, ATG9A, one of the main targets of miR-34a, was shown to interact with TFEB and thus promote its nuclear translocation in HEI-OC1 cells. Rapamycin rescued the inhibition of TFEB nuclear translocation induced by miR-34a/ATG9A activation, restored autophagic flux and consequently prevented HEI-OC1 cell death. Long-term supplementation with rapamycin attenuated outer hair cells (OHCs) and inner hair cell synaptic ribbons, and delayed AHL in C57BL/6 mice. Most importantly, rapamycin partially restored TFEB's nuclear localization and autophagic flux in OHCs of the ageing cochlea. These findings open new avenues for protection against AHL through miR-34a/ATG9a/TFEB modulation of autophagy.