Small molecule modulator of neuronal lysosome positioning and function resolves Alzheimer’s Disease-linked pathologies in cultured human neurons

Abnormal increase in axonal lysosome abundance is associated with multiple neurodegenerative diseases including Alzheimer’s disease. However, the underlying mechanisms and disease relevance are not fully understood. We have recently identified RH1115 as a small molecule modulator of the autophagy-lysosomal pathway that regulates lysosome positioning in neurons. This allowed us to manipulate neuronal lysosome distribution including in axons and interrogate its contribution to both optimal neuronal functioning and to disease pathology. We demonstrate that the small molecule not only rescues aberrant buildup of both axonal autophagic and lysosomal intermediates but also reduces secreted Aβ42 levels in human iPSC-derived neurons lacking the lysosomal adaptor, JIP3. We thus demonstrate that restoring efficient axonal lysosome transport has an anti-amyloidogenic effect in human neurons and is a promising therapeutic strategy for Alzheimer’s disease. Furthermore, we show that the small molecule enhances neuronal lysosome degradation, requires the lysosomal adaptor JIP4 to rescue the axonal lysosome pathology in the JIP3 KO neurons and increases levels of the JIP4-interacting lysosomal membrane protein, TMEM55B. Lastly, treatment with the small molecule led to a striking rescue of locomotor defects in JIP3 KO zebrafish larvae. Thus, we have identified a small molecule which can be impactful in neurodegenerative diseases that have a lysosomal pathology and have determined its molecular targets in modulating axonal lysosome abundance.