Characterizing affinity epitopes between prion protein and β-amyloid using an epitope mapping immunoassay

Abstract

Cellular prion protein, a membrane protein, is expressed in all mammals. Prion protein is also found in human blood as an anchorless protein, and this protein form is one of the many potential sources of misfolded prion protein replication during transmission. Many studies have suggested that β-amyloid1–42 oligomer causes neurotoxicity associated with Alzheimer's disease, which is mediated by the prion protein that acts as a receptor and regulates the hippocampal potentiation. The prevention of the binding of these proteins has been proposed as a possible preventative treatment for Alzheimer's disease; therefore, a greater understanding of the binding hot-spots between the two molecules is necessary. In this study, the epitope mapping immunoassay was employed to characterize binding epitopes within the prion protein and complementary epitopes in β-amyloid. Residues 23–39 and 93–119 in the prion protein were involved in binding to β-amyloid1–40 and 1–42, and monomers of this protein interacted with prion protein residues 93–113 and 123–166. Furthermore, β-amyloid antibodies against the C-terminus detected bound β-amyloid1–42 at residues 23–40, 104–122 and 159–175. β-Amyloid epitopes necessary for the interaction with prion protein were not determined. In conclusion, charged clusters and hydrophobic regions of the prion protein were involved in binding to β-amyloid1–40 and 1–42. The 3D structure appears to be necessary for β-amyloid to interact with prion protein. In the future, these binding sites may be utilized for 3D structure modeling, as well as for the pharmaceutical intervention of Alzheimer's disease.

Structural details of amyloid beta oligomers in complex with human prion protein as revealed by solid-state MAS NMR spectroscopy

“…3). These findings suggest that the C-terminus of full-length huPrP(23-230) does not have a major impact on the conformation of the N-terminus and its interaction with Aβoligo, in line with previous results [28][29][30]33 . Second, the spectrum of fulllength huPrP complexed by Aβoligo displays additional resonances which are absent in the 9 spectrum of N-terminal huPrP in complex with Aβoligo.…”

“…Amino acid sequence of huPrP(23-230) 38 . The Aβ-binding regions K23 to K27 and T95 to K110 [28][29][30][31][32][33] and the five octarepeats are indicated above the sequence. b 3D structure of the natively folded prion domain (residues 125 to 228) of full-length huPrP(23-230) in solution.…”

“…Several in vitro studies on the Aβ-PrP interaction suggest that Aβoligos bind at two Lys-rich parts (residues 23 to 27 and ≈ 95 to 110) on PrP [28][29][30][31][32][33] , but an additional involvement of the Cterminus of PrP has also been suggested 14 . A structural study of insoluble PrP C -Aβoligo complexes described this as a "hydrogel", in which the A oligomers were rigid, while PrP still has high molecular mobility 34 .…”

Prion protein modulates iron transport in the anterior segment: Implications for ocular iron homeostasis and prion transmission

“…Widespread expression of PrP C in the anterior segment, predominance of β-cleaved PrP C in the ciliary epithelium, and a phenotype of relative iron deficiency in PrP −/− mice supports active participation of PrP C in iron transport as reported for outer retina and other cell types (Asthana et al, 2017; Haldar et al, 2015; Tripathi et al, 2015). Soluble PrP C in the AH and vitreous has significant clinical implications because of the known interaction between PrP C and amyloid-β (Hirsch et al, 2014; Kang et al, 2013; Lauren, 2014), and requires further exploration.…”

A d-enantiomeric peptide interferes with heteroassociation of amyloid-β oligomers and prion protein

“…This competition might also explain the suggested neuroprotective function of the naturally produced soluble N1 fragment (amino acids 23-110/111) of PrP (24), which contains both A␤ oligo -binding regions. The binding regions on A␤, however, have not been identified so far and might constitute a specific conformational epitope of A␤ oligo (21). All these data show that the A␤-PrP interaction is a promising point of intervention to prevent the toxic signaling in AD.…”