Parkin regulates neuronal lipid homeostasis through SREBP2-lipoprotein lipase pathway-implications for Parkinson's disease

Abnormal lipid homeostasis has been observed in the brain of Parkinson's disease (PD) patients and experimental models, although the mechanism underlying this phenomenon is unclear. Notably, previous studies have reported that the PD-linked protein Parkin functionally interacts with important lipid regulators, including Sterol Regulatory Element Binding Proteins (SREBPs) and Cluster of differentiation 36 (CD36). Here, we demonstrate a functional relationship between Parkin and Lipoprotein Lipase (LPL), a triglyceride Lipase that is widely expressed in the brain. Using a human neuroblastoma cell line and a Parkin knockout (KO) mouse model, we demonstrate that Parkin expression level positively correlates with neuronal LPL protein level and activity. Importantly, our study identified SREBP2, a major regulator of sterol and fatty acid synthesis, as a potential mediator between Parkin and LPL. Supporting this, SREBP2 genetic ablation abolished Parkin effect on LPL expression. We further demonstrate that Parkin-LPL pathway regulates the formation of intracellular lipid droplets, and that this pathway is upregulated upon exposure to PD-linked oxidative stress induced by rotenone. Finally, we show that inhibition of either LPL or SREBP2 exacerbates rotenone-induced cell death. Taken together, our findings reveal a novel pathway linking Parkin, SREBP2, and LPL in neuronal lipid homeostasis that may be relevant to the pathogenesis of PD.