title: NACP, the precursor protein of the non-amyloid beta/A4 protein (A beta) component of Alzheimer disease amyloid, binds A beta and stimulates A beta aggregation.
abstract: NACP, a 140-amino acid presynaptic protein, is the precursor of NAC [the non-amyloid beta/A4 protein (A beta) component of Alzheimer disease (AD) amyloid], a peptide isolated from and immunologically localized to brain amyloid of patients afflicted with AD. NACP produced in Escherichia coli bound to A beta peptides, the major component of AD amyloid. NACP bound to A beta 1-38 and A beta 25-35 immobilized on nitrocellulose but did not bind to A beta 1-28 on the filter under the same conditions. NACP binding to A beta 1-38 was abolished by addition of A beta 25-35 but not by A beta 1-28, suggesting that the hydrophobic region of the A beta peptide is critical to this binding. NACP-112, a shorter splice variant of NACP containing the NAC sequence, bound to A beta, but NACP delta, a deletion mutant of NACP lacking the NAC domain, did not bind A beta 1-38. Furthermore, binding between NACP-112 and A beta 1-38 was decreased by addition of peptide Y, a peptide that covers the last 15 residues of NAC. In an aqueous solution, A beta 1-38 aggregation was observed when NACP was also present in an incubation mixture at a ratio of 1:125 (NACP/A beta), whereas A beta 1-38 alone or NACP alone did not aggregate under the same conditions, suggesting that the formation of a complex between A beta and NACP may promote aggregation of A beta. Thus, NACP can bind A beta peptides through the specific sequence and can promote A beta aggregation, raising the possibility that NACP may play a role in the development of AD amyloid.
authors.affiliation: Department of Neurosciences, University of California at San Diego, La Jolla 92093-0624, USA.
authors.forename: M
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: A
authors.initials: A
authors.lastname: Iwai
authors.forename: D
authors.initials: D
authors.lastname: Kang
authors.forename: D A
authors.initials: DA
authors.lastname: Otero
authors.forename: Y
authors.initials: Y
authors.lastname: Xia
authors.forename: T
authors.initials: T
authors.lastname: Saitoh
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D003001:Cloning, Molecular; D004926:Escherichia coli; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D051843:Synucleins
chemical_list: D000682:Amyloid; D016229:Amyloid beta-Peptides; D009419:Nerve Tissue Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; D051843:Synucleins