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 continuation study (final stages), 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 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. In the on-going and future studies, we aim at identifying protocols for propagating physiologically relevant hIAPP polymorphs and attempting at explaining the cellular origins of fibril polymorphism. We look at the interactions between hIAPP and not fully processed proIAPP(1-48) under different conditions. Additionally, we aggregate hIAPP in cell secretome media under proteolytic inhibition conditions and fibrils extracted from INS1-E cell lines. The INS1-E cells are designed to over-express hIAPP at elevated glucose concentrations. We will use cryo-EM to analyze the polymorphism and polymorphic distribution across different conditions. Additional project being currently run on Tetralith is related to developing DeepMD potentials for spectral simulations with particular focus on 2DIR spectroscopy. The project is part of Uppsala's BAG application for SciLifeLab Cryo-EM beamtime