The Role of Autophagy Dysfunction and Mitochondrial Depolarization in Neuronal Death in hiPSC-derived Niemann-Pick Type C1 Neurons (P1.302)

Objective: Our studies seek to innovate therapies for Niemann Pick type C1 (NPC1) through the repurposing of FDA-approved compounds in stem cell derived human neurons. Background: NPC1 is a lysosome storage disease that results in neurodegeneration, cognitive impairment, and death. NPC1 has no cure or treatment and shares features with Alzheimer’s disease, suggesting common pathological mechanisms. NPC1 is caused by a mutation in the NPC1 gene and is characterized by cholesterol accumulation in lysosomes. Design/Methods: Using human induced pluripotent stem cell (hiPSC) lines derived from patients carrying NPC1 disease-causing mutations, we investigated phenotypes related to autophagy flow, mitochondrial dysfunction, and cholesterol storage. After identifying pathological phenotypes, our group developed a drug screen in NPC1 neurons to identify potential therapeutics that revert mitochondrial dysfunction and preserve bulk autophagy. We tested compounds using two approaches: a hypothesis-driven screen using mito-protective compounds, and an unbiased screen using compounds with known central nervous system activity from the NIH Clinical Collection. To validate these compounds for clinical trials, we are testing them in CRISPR-engineered hiPSC-derived NPC1 knock-out lines and in a mouse model of NPC1 carrying the most common human mutation. Results: Our patient-derived hiPSC lines showed that lysosomal cholesterol sequestration activates the autophagy pathway. Autophagy acts as a back-up pathway that releases lysosomal cholesterol allowing short-term benefit. However, persistent autophagy leads to mitochondrial dysfunction and neuronal death. Additionally, the drug screen identified several compounds that improve mitochondria polarity and reduce neurodegeneration, thus representing a novel class of potential NPC1 therapies. The most promising compounds cross the blood-brain barrier and are FDA-approved for use in humans. Conclusions: Our observations suggest that lysosomal cholesterol sequestration does not directly cause neuronal failure, but rather a downstream effect of hyperactivity of the autophagy pathway caused by cholesterol accumulation. Additionally, we found that regulators of mitochondria fission rescue mitochondria dysfunction and improve neuronal viability. Disclosure: Dr. Wu has nothing to disclose. Dr. Ordonez has nothing to disclose. Dr. Steele has nothing to disclose. Dr. Goldstein has nothing to disclose.