title: Mechanism of amylin fibrillization enhancement by heparin.
abstract: We characterized the interaction of amylin with heparin fragments of defined length, which model the glycosaminoglycan chains associated with amyloid deposits found in type 2 diabetes. Binding of heparin fragments to the positively charged N-terminal half of monomeric amylin depends on the concentration of negatively charged saccharides but is independent of oligosaccharide length. By contrast, amylin fibrillogenesis has a sigmoidal dependence on heparin fragment length, with an enhancement observed for oligosaccharides longer than four monomers and a leveling off of effects beyond 12 monomers. The length dependence suggests that the negatively charged helical structure of heparin electrostatically complements the positively charged surface of the fibrillar amylin cross-β structure. Fluorescence resonance energy transfer and total internal reflection fluorescence microscopy experiments indicate that heparin associates with amylin fibrils, rather than enhancing fibrillogenesis catalytically. Short heparin fragments containing two- or eight-saccharide monomers protect against amylin cytotoxicity toward a MIN6 mouse cell model of pancreatic β-cells.
authors.affiliation: Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269-3125, USA.
authors.forename: Suman
authors.initials: S
authors.lastname: Jha
authors.forename: Sharadrao M
authors.initials: SM
authors.lastname: Patil
authors.forename: Jason
authors.initials: J
authors.lastname: Gibson
authors.forename: Craig E
authors.initials: CE
authors.lastname: Nelson
authors.forename: Nathan N
authors.initials: NN
authors.lastname: Alder
authors.forename: Andrei T
authors.initials: AT
authors.lastname: Alexandrescu
mesh_terms: D000818:Animals; D002460:Cell Line; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000737:chemistry / Q000378:metabolism*; D058228:Islet Amyloid Polypeptide / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary
chemical_list: D058228:Islet Amyloid Polypeptide; D009844:Oligosaccharides; D006493:Heparin