A PIKfyve Modulator Combined with an Integrated Stress Response Inhibitor to treat Lysosomal Storage Diseases

Lysosomal degradation pathways coordinate the clearance of superfluous and damaged cellular components. Compromised lysosomal degradation is a hallmark of many degenerative diseases, including lysosomal storage diseases, which are caused by loss-of-function mutations within both alleles of a lysosomal hydrolase, leading to lysosomal substrate accumulation. Gaucher’s disease, characterized by <15% of normal glucocerebrosidase function, is the most common lysosomal storage disease and is a prominent risk factor for developing Parkinson’s disease. Here, we show that either of two structurally distinct small molecules that modulate PIKfyve activity, discovered from a high-throughput cellular lipid droplet clearance screen, can improve glucocerebrosidase function in Gaucher patient–derived fibroblasts through an MiT/TFE transcription factor that promotes lysosomal gene translation. An ISR antagonist used in combination with a PIKfyve modulator further improves cellular glucocerebrosidase activity, likely because integrated stress response (ISR) signaling appears to also be slightly activated by treatment by either small molecule at the higher doses employed, This strategy of combining a PIKfyve modulator with an integrated stress response inhibitor improves mutant lysosomal hydrolase function in cellular models of additional lysosomal storage diseases.