Inhibitory Role of β-Casein on the α-Synuclein Aggregation Associated with Parkinson’s Disease In Vitro

Abstract

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 α-Synuclein is one of the main compounds aggregations. β-Casein, a member of the Casein family, has been demonstrated to inhibit α-Synuclein aggregation by chaperone-like activity. In this study, we investigated the effect of chaperone activity of β-Casein in preventing the aggregation of α-Synuclein protein. We have examined the effect of β-Casein in preventing α-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 α-Synuclein incubated in absence of β-Casein but in its presence fluorescence intensity is decreased. Electron microscopy data also indicated that β-Casein decreased the aggregation content of α-Synuclein. ANS results also showed that β-Casein significantly decreased the the hydrophobic area in α-Synuclein incubated. Circular dichroism spectroscopy (CD) results also showed that β-sheet structures of α-Synuclein incubated change to structural α-helical and β-turn in presence of β-Casein. FTIR spectroscopy indicates the presence of β-sheet structures in α-Synuclein incubated in absence of β-Casein and β-sheet structures decreased in its presence. Thus, our results suggest that in vitro, β-Casein interacts with α-Synuclein fibrils, changes the α-Synuclein structure and prevents amyloid fibril formation. This means that β-Casein could be essential for therapies inhibiting aggregation and to be an important therapeutic drug against PD.