On-Pathway Oligomer of Human Islet Amyloid Polypeptide Induced and Stabilized by Mechanical Rotation during Magic Angle Spinning Nuclear Magnetic Resonance

Intermediatesalong the fibrillation pathway are generallyconsideredto be the toxic species responsible for the pathologies of amyloiddiseases. However, structural studies of these species have been hamperedby heterogeneity and poor stability under standard aqueous conditions.Here, we report a novel methodology for producing stable, on-pathwayoligomers of the human type-2 diabetes-associated islet amyloid polypeptide(hIAPP or amylin) using the mechanical forces associated with magicangle spinning (MAS). The species were a heterogeneous mixture ofglobular and short rod-like species with significant & beta;-sheetcontent and the capability of seeding hIAPP fibrillation. We usedMAS nuclear magnetic resonance to demonstrate that the nature of thespecies was sensitive to sample conditions, including peptide concentration,ionic strength, and buffer. The methodology should be suitable forstudies of other aggregating systems.

Automated summary

We developed a new method using magic angle spinning (MAS) to produce stable intermediates of the islet amyloid polypeptide associated with type-2 diabetes. These intermediates were a heterogeneous mixture of globular and rod-like species with beta-sheet structure and the ability to seed fibrillation. Our findings suggest that this methodology can be applied to studying other aggregating systems.