Affiliations: [a] Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada | [b] Research and Development Area, Instituto Grifols S.A., Parets del Vallès, Barcelona, Spain | [c] Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
Correspondence:
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Correspondence to: Prof. Giuseppe Melacini, Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4M1, Canada. Tel.: +1 905 525 9140, Ext: 26959; Fax: +1 905 522 2509; E-mail: melacin@mcmaster.ca.
Abstract: Background:A promising approach for treating Alzheimer’s disease relies on the net efflux of the amyloid-β (Aβ) peptide from the brain to peripheral plasma, as a result of plasma Aβ clearance promoted by plasma removal and therapeutic albumin replacement. Objective:To assess the binding of therapeutic albumin (Albutein®, Grifols) to monomeric and aggregated Aβ according to methods previously tested on the interactions between Aβ and research-grade albumin. Methods:Albumin integrity and the interactions with albumin stabilizers (octanoic acid and N-Ac-Trp) were assessed through one-dimensional (1D) 1H-NMR and saturation transfer difference (STD) NMR spectra. The interactions between monomeric Aβ1-40 and albumin were probed by 2D 1H-15 N HSQC spectra of labeled Aβ1-40. The formation of cross-β structured Aβ1-42 assemblies was monitored by ThT fluorescence. The interactions between self-assembled Aβ1-42 and albumin were probed by Trp fluorescence. Results:NMR spectra indicated that both therapeutic and research-grade albumin are similarly well-folded proteins. No significant changes in either HSQC peak position or intensity were observed upon addition of albumin to 15N-labeled Aβ1-40, which rules out binding of albumin to monomeric Aβ with dissociation constant in the µM or lower range. When aggregated Aβ1-42 was added to albumin, quenching of Trp fluorescence was observed, which indicates albumin binding to Aβ1-42 aggregates. The relative potency of therapeutic albumin as an Aβ self-association inhibitor was in the same order of magnitude as research-grade albumin. Conclusions:Albutein® inhibited Aβ self-association by selectively binding Aβ aggregates rather than monomers and by preventing further growth of the Aβ assemblies.
Keywords: Alzheimer's disease, amyloid, amyloid-β peptide, NMR, oligomers, therapeutic albumin
