Inhibitory Role of beta-Casein on the alpha-Synuclein Aggregation Associated with Parkinson's Disease In Vitro

摘要

Large soluble oligomeric species are observed as probable intermediates during fibril formation in aggregations of Parkinson's disease (PD). Fibrillar deposits occur in PD. Amyloid forms alpha-Synuclein is one of the main compounds aggregations. beta-Casein, a member of the Casein family, has been demonstrated to inhibit alpha-Synuclein aggregation by chaperone-like activity. In this study, we investigated the effect of chaperone activity of beta-Casein in preventing the aggregation of alpha-Synuclein protein. We have examined the effect of beta-Casein in preventing alpha-Synuclein aggregation by using from Thioflavin T-binding assay, transmission electron microscopy, ANS-binding assay, circular dichroism spectroscopy and FTIR spectroscopy. Results from the ThT binding assay demonstrated an increase in the ThT fluorescence intensity of alpha-Synuclein incubated in absence of beta-Casein but in its presence fluorescence intensity is decreased. Electron microscopy data also indicated that beta-Casein decreased the aggregation content of alpha-Synuclein. ANS results also showed that beta-Casein significantly decreased the the hydrophobic area in alpha-Synuclein incubated. Circular dichroism spectroscopy (CD) results also showed that beta-sheet structures of alpha-Synuclein incubated change to structural alpha-helical and beta-turn in presence of beta-Casein. FTIR spectroscopy indicates the presence of beta-sheet structures in alpha-Synuclein incubated in absence of beta-Casein and beta-sheet structures decreased in its presence. Thus, our results suggest that in vitro, beta-Casein interacts with alpha-Synuclein fibrils, changes the alpha-Synuclein structure and prevents amyloid fibril formation. This means that beta-Casein could be essential for therapies inhibiting aggregation and to be an important therapeutic drug against PD.