Point substitution in the central hydrophobic cluster of a human beta-amyloid congener disrupts peptide folding and abolishes plaque competence.
Alzheimer's disease (AD) is pathologically characterized by the presence of numerous insoluble amyloid plaques in the brain composed primarily of a 40-43 amino acid peptide, the human beta-amyloid peptide (A beta). The process of A beta deposition can be modeled in vitro by deposition of physiological concentrations of radiolabeled A beta onto preexisting amyloid in preparations of unfixed AD cerebral cortex. Using this model system, it has been shown that A beta deposition is biochemically distinct from A beta aggregation and occurs readily at physiological A beta concentrations, but which regions and conformations of A beta are essential to A beta deposition is poorly understood. We report here that an active congener, A beta (10-35)-NH2, displays time dependence, pH-activity profile, and kinetic order of deposition similar to A beta (1-40), and is sufficiently soluble for NMR spectroscopy in water under conditions where it actively deposits. To examine the importance of the central hydrophobic cluster of A beta (LVFFA, residues 17-21) for in vitro A beta deposition, an A beta (10-35)-NH2 analog with a single point substitution (F19T) in this region was synthesized and examined. Unlike A beta (10-35)-NH2, the F19T analog was plaque growth incompetent, and NMR analysis indicated that the mutant peptide was significantly less folded than wild-type A beta. These results support previous studies suggesting that the plaque competence of A beta correlates with peptide folding. Since compounds that alter A beta folding may reduce amyloid deposition, the central hydrophobic cluster of A beta will be a tempting target for structure-based drug design when high-resolution structural information becomes available.
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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Esler
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Stimson
J R
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Ghilardi
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Lu
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Felix
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Vinters
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Mantyh
J P
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Lee
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Maggio
D000544:Alzheimer Disease / Q000209:etiology / Q000378:metabolism; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016874:Neurofibrillary Tangles / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D017510:Protein Folding; D012995:Solubility
D016229:Amyloid beta-Peptides; D010446:Peptide Fragments