Structural basis of α-synuclein and DJ-1 complex.

The structure of α-synuclein is predominantly α-helical when bound to cellular membranes. However, under pathological or destabilizing conditions, this α-helical structure transitions into β-sheet-rich conformations, promoting protein aggregation and formation of Lewy bodies (LBs) in neurodegenerative disorders such as Parkinson's disease dementia (PDD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and Alzheimer's disease (AD). DJ-1 is a multifunctional brain protein acting as a chaperone or protease under oxidative stress and associating with abnormal protein aggregates. Although previous studies suggested DJ-1 inhibits α-synuclein aggregation, the structural basis remained elusive. Here, we elucidate the direct interaction between α-synuclein and DJ-1 using size-exclusion chromatography (SEC), fluorescence spectroscopy, and multi-angle light scattering (MALS), and determined their crystal structure by X-ray diffraction. The interaction interface was mapped to residues Q24, E28, A29, and N65 of α-synuclein and K148, N173, and Q180 of DJ-1, with Q180 forming strong hydrogen bonds (2.60-2.97 Å) with α-synuclein. Transmission electron microscopy (TEM) demonstrated DJ-1 suppresses α-synuclein fibril formation. Based on the structure, we designed a DJ-1-derived peptide (173-180) that significantly inhibited α-synuclein aggregation in TEM and ELISA assays, suggesting its potential as a therapeutic candidate for α-synucleinopathies.