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Effect of Pressure on Islet Amyloid Polypeptide Aggregation: Revealing the Polymorphic Nature of the Fibrillation Process

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: Diana Radovan, Vytautas Smirnovas, Roland Winter

Editorial: Biochemistry, 47 (24), p.6352 - 60, 2008.


Type II diabetes mellitus is a disease which is characterized by peripheral insulin resistance coupled with a progressive loss of insulin secretion that is associated with a decrease in pancreatic islet beta-cell mass and the deposition of amyloid in the extracellular matrix of beta cells, which lead to islet cell death. The principal component of the islet amyloid is a pancreatic hormone called islet amyloid polypeptide(IAPP). High-pressure coupled with FT-IR spectroscopic and AFM studies were carried out to elucidate further information about the aggregation pathway as well as the aggregate structures of IAPP.To this
end,a comparative fibrillation study of IAPP fragments was carried out as well.As high hydrostatic pressure (HHP) is acting to weaken or even prevent hydrophobic self-organization and electrostatic interactions, application of HHP has been used as a measure to reveal the importance of these
interactions in the fibrillation process of IAPP and its fragments.IAPP preformed fibrils exhibit a strong polymorphism with heterogeneous structures, a large population of which are rather sensitive to high hydrostatic pressure, thus indicating a high percentage of ionic and hydrophobic interactions and loose packing of these species. Conversely, fragments 1-19 and 1-29 are resistant to pressure treatment, suggesting more densely packed aggregate structures with less void volume and strong cooperative hydrogen bonding.Furthermore, the
FT-IR data indicate that fragment 1-29 has intermolecular beta-sheet conformational properties different
from those of fragment 1-19, the latter exhibiting polymorphic behavior with more disordered structures and less strongly hydrogen bonded fibrillar assemblies.The data also suggest that hydrophobic interactions and/or less efficient packing of amino acids 30-37 region leads to the marked pressure sensitivity observed for full-length IAPP.

Cuvinte cheie: IAPP, islet amyloid polypeptide, IAPP fragments, packing properties, FT-IR spectroscopy, atomic force microscopy, type II diabetes mellitus, protein/peptide aggregation, polymorphism, fibrils, amyloid, high hydrostatic pressure