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The conversion of the β-amyloid (Aβ) peptide into pathogenic aggregates is linked to the onset and progression of Alzheimer's disease. Although this observation has prompted an extensive search for therapeutic agents to modulate the concentration of Aβ or inhibit its aggregation, all clinical trials with these objectives have so far failed, at least in part because of a lack of understanding of the molecular mechanisms underlying the process of aggregation and its inhibition. To address this problem, we describe a chemical kinetics approach for rational drug discovery, in which the effects of small molecules on the rates of specific microscopic steps in the self-assembly of Aβ42, the most aggregation-prone variant of Aβ, are analyzed quantitatively. By applying this approach, we report that bexarotene, an anticancer drug approved by the U.S. Food and Drug Administration, selectively targets the primary nucleation step in Aβ42 aggregation, delays the formation of toxic species in neuroblastoma cells, and completely suppresses Aβ42 deposition and its consequences in a Caenorhabditis elegans model of Aβ42-mediated toxicity. These results suggest that the prevention of the primary nucleation of Aβ42 by compounds such as bexarotene could potentially reduce the risk of onset of Alzheimer's disease and, more generally, that our strategy provides a general framework for the rational identification of a range of candidate drugs directed against neurodegenerative disorders.

Among the various hereditary mutants of amyloid β (Aβ) in familial Alzheimer's disease (AD), the A21G Flemish-type mutant has unique properties showing a low aggregation propensity but progressive deposition in vascular walls. Moreover, in contrast to other familial AD cases that show extensive Aβ1-42 deposition in the brain, patients with Flemish AD predominantly exhibit the deposition of the Aβ1-40 isoform. Here we report the structural characterization of the Flemish-type mutant (A21G) in comparison with the wild-type Aβ1-40 peptide to examine the possible effects of the A21G mutation on the conformation of the Aβ1-40 isoform. The kinetic analysis of the aggregation of the peptides monitored by thioflavin T fluorescence measurement indicates that the mutation precludes the initial nucleation process of amyloid fibril formation by Aβ1-40. Spectroscopic data indicate that the Flemish-type mutant bound to aqueous micelles composed of lyso-GM1, in which the mobile N-terminal segment is tethered through the C-terminal helical segment, has reduced α-helical structure compared to the wild-type peptide. Our findings suggest that the mutational perturbation to the membrane binding properties is coupled with the changes in nucleation behavior of Aβ during its fibril formation.

Despite well-organized peptide-loading mechanisms within the endoplasmic reticulum, major histocompatibility complex class I (MHC-I) molecules can be displayed on cell surfaces in peptide-free forms. Although these empty MHC-I (eMHC-I) molecules are presumably involved in physiological and pathological processes, little is known about their structures and functions due to their instability. Using bacterially expressed HLA-Cw*07:02 heavy chain and β2 microglobulin molecules, we successfully established an in vitro refolding method to prepare eMHC-I molecules in sufficient quantities for detailed structural analyses. NMR spectroscopy in conjunction with subunit-specific ¹⁵N-labeling techniques revealed that the peptide-binding domains and the adjacent regions were unstructured in the peptide-free form, while the remaining regions maintained their structural integrity. Consistent with our spectroscopic data, the eMHC-I complex could interact with leukocyte Ig-like receptor B1, but not with killer cell Ig-like receptor 2DL3. Thus, eMHC-I molecules have a mosaic nature in terms of their three-dimensional structure and binding to immunologically relevant molecules., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Here we report an NMR study on the substrate interaction modes of GroEL using amyloid β (Aβ) as a model ligand. We found that GroEL could suppress Aβ(1-40) amyloid formation by interacting with its two hydrophobic segments Leu17-Ala21 and Ala30-Val36, which involve key residues in fibril formation. The binding site of Aβ(1-40) was mapped on a pair of α-helices located in the GroEL apical domain. These results provide insights into chaperonin recognition of amyloidogenic proteins of pathological interest., (Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Gangliosides are targets for a variety of pathologically relevant proteins, including amyloid beta (Abeta), an important component implicated in Alzheimer's disease (AD). To provide a structural basis for this pathogenic interaction associated with AD, we conducted NMR analyses of the Abeta interactions with gangliosides using lyso-GM1 micelles as a model system. Our NMR data revealed that the sugar-lipid interface is primarily perturbed upon binding of Abeta to the micelles, underscoring the importance of the inner part of the ganglioside cluster for accommodating Abeta in comparison with the outer carbohydrate branches that provide microbial toxin- and virus-binding sites., (Copyright 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)