Title:	3D Helical Reconstruction of Amyloid Fibrils formed by the human Islet Amyloid Polypeptide and its mutants
DNr:	Berzelius-2023-77
Project Type:	LiU Berzelius
Principal Investigator:	Michal Maj <michal.maj@kemi.uu.se>
Affiliation:	Uppsala universitet
Duration:	2023-03-22 – 2023-10-01
Classification:	10601
Homepage:	https://www.majgroup.net
Keywords:

Abstract

Aggregation of the human Islet Amyloid Polypeptide (hIAPP) is associated with the loss of insulin-producing β-cells in type 2 diabetes. Formation of amyloid fibrils by IAPP is one of the critical factors in pathogenesis of the disease, but non-amyloidogenic forms of IAPP are also common in nature. The rat IAPP does not form amyloid fibrils because of three proline mutations which disrupt the β-sheet structure in the most amyloidogenic part of the peptide sequence. Introduction of such mutations has been the basis for the development of many IAPP-based drugs for type 2 diabetes. In the present study, we break down the proline residues present in the rat IAPP and synthesize 3 mutant peptides containing prolines at positions Ala25, Ser28, and Ser29, respectively. We show that single prolines are incapable of arresting the growth of amyloid fibrils, but the location of point mutation has a great effect on the morphology and three-dimensional structure of the fibrils. We apply cryo-EM to solve the high-resolution structure of the amyloid fibrils formed by these mutants and identify the most important interactions responsible for their drastically different polymorphism. The results will deliver information on the mode of action of peptide-based therapeutics in type 2 diabetes. The project is part of Uppsala's BAG application for SciLifeLab Cryo-EM beamtime