Rapid Alpha-Synuclein Toxicity in a Neural Cell Model and Its Rescue by a Stearoyl-CoA Desaturase Inhibitor

Genetic and biochemical evidence attributes neuronal loss in Parkinson's disease (PD) and related brain diseases to dyshomeostasis of the 14 kDa protein alpha-synuclein (alpha S). There is no consensus on how alpha S exerts toxicity. Explanations range from disturbed vesicle biology to proteotoxicity caused by fibrillar aggregates. To probe these mechanisms further, robust cellular toxicity models are needed, but their availability is limited. We previously reported that a shift from dynamic multimers to monomers is an early event in alpha S dyshomeostasis, as caused by familial PD (fPD)-linked mutants such as E46K. Excess monomers accumulate in round, lipid-rich inclusions. Engineered alpha S '3K' (E35K+E46K+E61K) amplifies E46K, causing a PD-like, L-DOPA-responsive motor phenotype in transgenic mice. Here, we present a cellular model of alpha S neurotoxicity after transducing human neuroblastoma cells to express yellow fluorescent protein (YFP)-tagged alpha S 3K in a doxycycline-dependent manner. alpha S-3K::YFP induction causes pronounced growth defects that accord with cell death. We tested candidate compounds for their ability to restore growth, and stearoyl-CoA desaturase (SCD) inhibitors emerged as a molecule class with growth-restoring capacity, but the therapeutic window varied among compounds. The SCD inhibitor MF-438 fully restored growth while exerting no apparent cytotoxicity. Our alpha S bioassay will be useful for elucidating compound mechanisms, for pharmacokinetic studies, and for compound/genetic screens.