Cryo-EM exposes diverse polymorphism in IAPP mutants to guide rational design of novel therapeutics

28 March 2025, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

In the pursuit of potential therapeutic agents for type 2 diabetes, non-amyloidogenic forms of the human Islet Amyloid Polypeptide (hIAPP) containing site-specific mutations are of significant interest. In the present study, we dissect the three proline mutations present in the core region of the non-amyloidogenic rat IAPP into single-point mutations at A25P, S28P, and S29P sites. We apply high-resolution cryo-electron microscopy and solve the structures of 6 polymorphs formed by these mutants, revealing the peptide's self-assembly patterns and identifying critical interactions that reinforce these structures in the presence of the β-sheet breaker. A unique trimeric aggregate with C3 symmetry was identified in the A25P mutant, which we resolved with a 3.05 Å resolution, while asymmetric trimeric assemblies were observed in the other mutants. Guided by the high-resolution structural models of A25P and S28P fibrils obtained in our study, we successfully designed novel non-amyloidogenic mutants of IAPP with potential therapeutic value. Our findings demonstrate the immense potential of structure-based approaches in developing effective therapeutics against amyloid diseases.

Keywords

Amyloid
hIAPP
Cryo-EM
Type 2 Diabetes

Supplementary materials

Title
Description
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Title
Cryo-EM exposes diverse polymorphism in IAPP mutants to guide rational design of novel therapeutics: Supplementary Information
Description
Sequences of hIAPP wildtype, rat IAPP, Pram- lintide, Cagrilintide, and the mutants used in this study. Aggregation kinetics of A25P, S28P, and S29P. LCMS of the synthesized peptides. Nega- tive staining of A25P, S28P and S29P. Cryo-EM data processing workflow, FSC, schematic repre- sentation of the mutants and Cryo-EM maps. Map of the low resolution A25P-P2. ZipperDB analysis of the mutants.
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