Phenotypic screening in Parkinson's iPSC-dopamine neurons identifies the FASN-SREBP1 axis as a potential therapeutic target
Parkinson's disease (PD) remains highly challenging to model in vitro, particularly when seeking robust functional phenotypes for target discovery. Patient-derived induced pluripotent stem cell dopaminergic neurons (iPSC-DANs) offer a promising platform to address this challenge. Because calcium dyshomeostasis is well-described in PD pathophysiology, it offers a platform for phenotypic screening. We have previously shown that GBA-N370S iPSC-DANs display impaired intracellular calcium release. Here, we used this disease-relevant phenotype to undertake a 4,108-compound phenotypic screen in GBA-N370S (GBA-NS) iPSC-DANs. This screen identified fatty acid synthase (FASN) as the most enriched protein target. The ability of compounds to rescue calcium release correlated with biochemical potency against FASN across multiple chemical series. We confirmed that FASN knockdown increased intracellular calcium release, supporting an on-target effect. Untargeted lipidomics demonstrated broad remodelling of the neuronal lipidome after FASN inhibition, confirming target engagement. FASN inhibition also increased active a-glucocerebrosidase (GCase), reduced extracellular a-synuclein release and ER stress, and altered RASGRF1 expression. Mechanistically, FASN inhibition activated sterol regulatory element-binding protein 1 (SREBP1), and SREBP1 overexpression alone was sufficient to increase intracellular calcium release, identifying a FASN-SREBP1-calcium homeostasis axis in human neurons. Finally, the FASN inhibitor BI 99179 achieved brain exposure and reduced brain fatty acid levels while inducing an SRE-associated transcriptional response in a Parkinson's mouse model, providing evidence of in vivo target engagement. These findings establish patient iPSC-neuron functional screening as a tractable discovery platform to identify targets which can be taken in vivo and nominate the FASN-SREBP1 axis as a candidate therapeutic pathway in PD.