title: Binding of islet amyloid polypeptide to supported lipid bilayers and amyloid aggregation at the membranes.
abstract: Amyloid deposition of human islet amyloid polypeptide (hIAPP) in the islets of Langerhans is closely associated with the pathogenesis of type II diabetes mellitus. Despite substantial evidence linking amyloidogenic hIAPP to loss of β-cell mass and decreased pancreatic function, the molecular mechanism of hIAPP cytotoxicity is poorly understood. We here investigated the binding of hIAPP and nonamyloidogenic rat IAPP to substrate-supported planar bilayers and examined the membrane-mediated amyloid aggregation. The membrane binding of IAPP in soluble and fibrillar states was characterized using quartz crystal microbalance with dissipation monitoring, revealing significant differences in the binding abilities among different species and conformational states of IAPP. Patterned model membranes composed of polymerized and fluid lipid bilayer domains were used to microscopically observe the amyloid aggregation of hIAPP in its membrane-bound state. The results have important implications for lipid-mediated aggregation following the penetration of hIAPP into fluid membranes. Using the fluorescence recovery after photobleaching method, we show that the processes of membrane binding and subsequent amyloid aggregation are accompanied by substantial changes in membrane fluidity and morphology. Additionally, we show that the fibrillar hIAPP has a potential ability to perturb the membrane structure in experiments of the fibril-mediated aggregation of lipid vesicles. The results obtained in this study using model membranes reveal that membrane-bound hIAPP species display a pronounced membrane perturbation ability and suggest the potential involvement of the oligomeic forms of hAPP in membrane dysfunction.
authors.affiliation: Division of Structural Biology (G-COE), Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan. sasahara@med.kobe-u.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Sasahara
authors.forename: Kenichi
authors.initials: K
authors.lastname: Morigaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Okazaki
authors.forename: Daizo
authors.initials: D
authors.lastname: Hamada
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D050417:Insulin-Secreting Cells / Q000737:chemistry / Q000378:metabolism; D058228:Islet Amyloid Polypeptide / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008560:Membrane Fluidity; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D058525:Quartz Crystal Microbalance Techniques; D051381:Rats; D016415:Sequence Alignment; D012995:Solubility
chemical_list: D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D008051:Lipid Bilayers