Abstract
A 39-43-amino acid residue-long fragment (beta-peptide) from the amyloid precursor protein is the predominant component of amyloid deposits in the brain of individuals with Alzheimer's disease. Serum amyloid P component (SAP) is present in all types of amyloid, including that of Alzheimer's disease. We have used an in vitro model to study the effects of purified SAP on the fibril formation of synthetic Alzheimer beta-peptide 1-42. SAP was found to inhibit fibril formation and to increase the solubility of the peptide in a dose-dependent manner. At a 5:1 molar ratio of A beta 1-42 peptide to SAP, fibril formation was completely inhibited, and approximately 80% of the peptide remained in solution even after 4 days of incubation. At lower SAP concentrations, e.g. at peptide to SAP ratio of 1000:1, short fibrillar like structures, lacking amyloid characteristics, were formed. These structures frequently contained associated SAP molecules, suggesting that SAP binds to the polymerizing peptide in a reaction which prevented further fibril formation.
Highlights
Sulfated groups are involved [5,6,7,8]
The predominant component of amyloid deposits in the brain of individuals with Alzheimer’s disease (AD) is a 39 – 43-amino acid-long peptide (A-peptide) which is a proteolytic product of the amyloid precursor protein [15, 16]
To examine the effect of Serum amyloid P component (SAP) on A1– 42 fibril formation, an in vitro model was used in which the Alzheimer A1– 42 peptide spontaneously adopts a-pleated sheet conformation and forms elongated, approximately 7– 8 nm thick, fibrils
Summary
Sulfated groups are involved [5,6,7,8]. After calcium-dependent self-aggregation, or when bound to chromatin, SAP may trigger complement activation (9 –11). SAP binds to preformed amyloid fibrils and to Alzheimer A1– 40 peptide in vitro in a calcium-dependent reaction [23, 24]. We wish to report that SAP inhibits amyloid fibril formation from the Alzheimer A1– 42 peptide in an in vitro model.
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