Human Islet Amyloid Polypeptide Assembly: The Key Role of the 8-20 Fragment

The aggregation of human islet amyloid polypeptide (hIAPP) has been closely associated with the pathogeny of type 2 diabetes mellitus (T2DM) and destruction of pancreatic islet β-cells. Several amyloidogenic domains within the hIAPP sequence capable of self-association have been identified. Among them is the 8–20 region of hIAPP, which has formed β-sheet fibrils despite being contained within an α-helical region of full-length hIAPP. To further understand the propensity of this region for self-assembly, two peptide fragments were compared, one consisting of the residues 8–20 (WT8–20) and a mutant fragment with a His18Pro substitution (H18P8–20). The conformational distribution and aggregation propensity of these peptides was determined using a combination of ion mobility mass spectrometry and atomic force microscopy. Our results reveal that the two peptide fragments have vastly differing assembly pathways. WT8–20 produces a wide range of oligomers up to decamer whereas the H18P8–20 mutant produces only lo...