title: Selection for nonamyloidogenic mutants of islet amyloid polypeptide (IAPP) identifies an extended region for amyloidogenicity.
abstract: The aggregation of the 37-residue protein, islet amyloid polypeptide (IAPP), as either insoluble amyloid or as small oligomers, appears to play a direct role in the death of pancreatic beta-islet cells in type II diabetes. While IAPP has been known to be the primary component of type II diabetes amyloid, the molecular interactions responsible for this aggregation have not been identified. To identify the aggregation-prone region(s), we constructed a library of randomly generated point mutants of IAPP. This mutant IAPP library was expressed in Escherichia coli as genetic fusions to the reporter protein enhanced green fluorescent protein (EGFP). Because IAPP aggregates rapidly, both independently and when fused to EGFP, the fusion protein does not yield a functional, fluorescent EGFP. However, mutations of IAPP that result in nonamyloidogenic sequences remain soluble and allow EGFP to fold and fluoresce. Using this screen, we identified 22 single mutations, 4 double mutations, and 2 triple mutations of IAPP that appear to be less amyloidogenic than wild-type human IAPP. A comparison of these sequences suggests residues 13 and 15-17 comprise an additional aggregation-prone region outside of the main amyloidogenic region of IAPP.
authors.affiliation: Department of Chemistry and Biochemistry, Loyola Marymount University, 1 LMU Drive, Los Angeles, California 90045, USA.
authors.forename: Ayano
authors.initials: A
authors.lastname: Fox
authors.forename: Thibaut
authors.initials: T
authors.lastname: Snollaerts
authors.forename: Camille
authors.initials: C
authors.lastname: Errecart Casanova
authors.forename: Anastasia
authors.initials: A
authors.lastname: Calciano
authors.forename: Luiza A
authors.initials: LA
authors.lastname: Nogaj
authors.forename: David A
authors.initials: DA
authors.lastname: Moffet
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D058228:Islet Amyloid Polypeptide; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D009154:Mutation; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D049452:Green Fluorescent Proteins