Targeting of CH25H to boost p62-dependent autophagic degradation of α-synuclein in cell and mouse models of Parkinson's disease.
Insufficient understanding of α-synuclein turnover mechanisms has impeded successful clinical translation for Parkinson's disease (PD). Here, we pinpointed cholesterol 25-hydroxylase (CH25H) as a pivotal regulator of α-synuclein degradation. Through bulk RNA sequencing of substantia nigra tissue from the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD, along with reanalysis of published datasets from induced pluripotent stem cell-derived astrocytes of patients with PD, we observed an elevated CH25H expression in PD-associated astrocytes. This finding was validated by combined fluorescence in situ hybridization for Ch25h and immunofluorescence staining for GFAP in mouse substantia nigra sections. Conditional knockout or knockdown of astrocytic Ch25h alleviated PD-like motor deficits and reduced dopaminergic neuronal loss in MPTP and α-synuclein preformed fibril (PFF) mouse models. Using 4D label-free proteomics and molecular docking approaches, we uncovered a shared binding domain on p62 where both CH25H and α-synuclein interact. Proximity ligation assays in cultured astrocytes showed that Ch25h overexpression promoted formation of p62/CH25H complex, whereas it inhibited p62/α-synuclein interaction. Conversely, Ch25h knockdown enhanced p62/α-synuclein complex formation and facilitated α-synuclein degradation. 25-Hydroxycholesterol, the enzymatic by-product of CH25H, did not affect the expression of α-synuclein in astrocytes, suggesting an activity-independent influence of CH25H on α-synuclein clearance. In addition, treatment with a p62 polypeptide (60 to 90 amino acids) effectively facilitated α-synuclein clearance by sequestering free CH25H in both cultured astrocytes and mice in the PFF model. Collectively, our study provides insights into the mechanisms underlying α-synuclein turnover and suggests promising avenues for disease-modifying interventions in synucleinopathies.