Inhibitory Effect of β-Casein on the Amyloid Fibril Formation of Aβ1–40 Associated with Alzheimer’s Disease
Alzheimer’s disease is associated with the fibril formation of β-amyloid peptide in extracellular plaque. β-Casein is a milk protein that has shown a remarkable ability to stabilize proteins by inhibiting their protein aggregation and precipitation. The aim of this study was to test in vitro the ability of β-casein to bind the Aβ1–40, change the structure and inhibit the formation of amyloid fibrils in Aβ1–40. Results from the ThT binding assay indicated that incubation of Aβ1–40 with β-casein retarded amyloid fibril formation of Aβ1–40 in a concentration dependent manner such that at a ratio of 1:1 (w:w) led to a significant reduction in the amount of fluorescent intensity. The results from transmission electron microscopy (TEM) also showed that β-casein significantly reduced the number and size of the Aβ1–40 fibrils, suggesting that the chaperone bound to the Aβ1–40 fibrils and/or interacted with the fibrils in some way. ANS results also showed that β-casein significantly decreased the exposed hydrophobic surface in Aβ1–40. Following an ANS binding assay, CD spectroscopy results also showed that incubation of Aβ1–40 resulted in a structural transition to a β-sheet. In the presence of β-casein, however, α-helical conformation was observed which indicated stabilization of the protein. These results reveal the highly efficacious chaperone action of β-casein against amyloid fibril formation of Aβ1–40. These results suggest that in vitro, β-casein binds to the Aβ1–40 fibrils, alters the Aβ1–40 structure and prevents amyloid fibril formation. This approach may result in the identification of a chaperone mechanism for the treatment of neurological diseases.
KeywordsAlzheimer Amyloid fibril Chaperone β-Casein Inhibition
This article does not contain any studies with human and animal subjects performed by any of the authors. All authors (Ghahghaei A, Shahraki S) declare that they have no conflict of interest. The authors are thankful to the university of Sistan and Baluchestan for providing the necessary facilities.
- Jarrett JT, Berger EP, LansburyP T Jr (1993) The C-terminus of the beta protein is critical in amyloidogenesis. Ann NY Acad Sci 695(14):4–148Google Scholar
- Nichols MR, Moss MA, Reed DK, Lin WL, Mukhopadhyay R, Hoh JH et al (2002) Growth of β-amyloid(1-40) protofibrils by monomer elongation and lateral association. Characterization of distinct products by light scattering and atomic force microscopy. Biochemistry 41:6115–6127CrossRefPubMedGoogle Scholar
- Shin RW, Ogino K (1997) Amyloid b-protein Aβ1–40 but not Aβ1–42 contributes to the experimental formation of Alzheimer disease amyloid fibrils in rat brain. J Neurosci 1:8187–8193Google Scholar