TTYH3 regulates a lysosomal chloride conductance and controls lysosomal fusion, autophagy and senescence.

Chloride is the most abundant anion within lysosomes and plays a pivotal role in regulating lysosomal physiology and function. However, the mechanisms governing lysosomal chloride homeostasis remain largely elusive. Here, we identified TTYH3 as a regulator of lysosomal chloride permeability. TTYH3 mediates chloride efflux from the lysosomal lumen and enhances TRPML1-mediated lysosomal calcium release. Overexpression of TTYH3 results in markedly enlarged lysosomes by promoting lysosomal fusion via the Ca2+/CaM and HSP90 pathways. Moreover, TTYH3 enhances autophagy by inhibiting the AKT/mTOR signaling pathway and alleviates cellular senescence via activation of the ERK pathway. Notably, TTYH3 expression mitigates cellular phenotypes associated with lysosomal storage diseases caused by deficiencies in another lysosomal chloride channel CLN7. Collectively, our findings demonstrate that TTYH3 mediates a lysosomal chloride conductance and regulates lysosomal physiology and autophagy, and may serve as a potential therapeutic target for interventions in aging and lysosome-related diseases.