Lipid domain boundary triggers membrane damage and protein folding of human islet amyloid polypeptide in the early pathogenesis of amyloid diseases

The misfolding and self-aggregation of human Islet Amyloid Polypeptide (hIAPP) are linked to the onset of type 2 diabetes (T2D). However, the mechanism of how the disordered hIAPP aggregates trigger membrane damage leading to the loss of Islet cells in T2D is unknown. Using coarse-grained (CG) and all-atom (AA) molecular dynamics simulations, we have investigated the membrane-disruption behaviors of hIAPP oligomers on the phase-separated lipid nanodomains that mimic the highly heterogeneous lipid raft structures of cell membranes. Our results revealed that hIAPP oligomers preferentially bind to the liquid-ordered and liquid-disordered domain boundary around two hydrophobic residues at L16 and I26, and lipid acyl chain order disruption and beta-sheet formation occur upon hIAPP binding to the membrane surface. We propose that the lipid order disruption and surface-induced beta-sheet formation on the lipid domain boundary represent the early molecular events of membrane damage associated with the early pathogenesis of T2D.