Design of peptide-based inhibitors of human islet amyloid polypeptide fibrillogenesis.
Human islet amyloid polypeptide (IAPP) is the major component of amyloid deposits found in the pancreas of over 90% of all cases of type-2 diabetes. We have generated a series of overlapping hexapeptides to target an amyloidogenic region of IAPP (residues 20-29) and examined their effects on fibril assembly. Peptide fragments corresponding to SNNFGA (residues 20-25) and GAILSST (residues 24-29) were strong inhibitors of the beta-sheet transition and amyloid aggregation. Circular dichroism indicated that even at 1:1 molar ratios, these peptides maintained full-length IAPP (1-37) in a largely random coil conformation. Negative stain electron microscopy revealed that co-incubation of these peptides with IAPP resulted in the formation of only semi-fibrous aggregates and loss of the typical high density and morphology of IAPP fibrils. This inhibitory activity, particularly for the SNNFGA sequence, also correlated with a reduction in IAPP-induced cytotoxicity as determined by cell culture studies. In contrast, the peptide NFGAIL (residues 22-27) enhanced IAPP fibril formation. Conversion to the amyloidogenic beta-sheet was immediate and the accompanying fibrils were more dense and complex than IAPP alone. The remaining peptide fragments either had no detectable effects or were only weakly inhibitory. Specificity of peptide activity was illustrated by the fragments, SSNNFG and AILSST. These differed from the most active inhibitors by only a single amino acid residue but delayed the random-to-beta conformational change only when used at higher molar ratios. This study has identified internal IAPP peptide fragments which can regulate fibrillogenesis and may be of therapeutic use for the treatment of type-2 diabetes.
Scrocchi
Louise A
LA
Centre for Research in Neurodegenerative Diseases, University of Toronto, Tanz Neuroscience Building, 6 Queen's Park Crescent West, Toronto, Ontario, Canada M5S 3H2. l.scrocchi@utoronto.ca
Chen
Yan
Y
Waschuk
Stefko
S
Wang
Feng
F
Cheung
Sindy
S
Darabie
Audrey A
AA
McLaurin
JoAnne
J
Fraser
Paul E
PE
D000595:Amino Acid Sequence; D000682:Amyloid / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000648:ultrastructure; D002460:Cell Line; D002942:Circular Dichroism; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism; D015195:Drug Design; D006801:Humans; D066298:In Vitro Techniques; D058228:Islet Amyloid Polypeptide; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D011487:Protein Conformation
D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D009842:Oligopeptides