Deciphering the Molecular Dance: Exploring the Dynamic Interplay Between Mouse Insulin B9–23 Peptides and their Variants

Type 1 diabetes results from the autoimmune destruction of pancreatic insulin-producing β-cells, primarily targeted by autoreactive T cells that recognize insulin B9–23 peptides as antigens. Using drift tube ion mobility spectrometry-mass spectrometry, transmission electron microscopy, and two-dimensional infrared spectroscopy, we characterized mouse insulin 1 B9–23 (Ins1 B9–23), insulin 2 B9–23 (Ins2 B9–23), along with two of their mutants, Ins2 B9–23 Y16A and Ins2 B9–23 C19S. Our findings indicate that Ins1 B9–23 and the Ins2 Y16A mutant exhibit rapid fibril formation, whereas Ins2 B9–23 and the Ins2 C19S mutant show slower fibrillization and a structural rearrangement from globular protofibrils to fibrillar aggregates. These differences in aggregation behaviors also manifest in interactions with (−)epigallocatechin gallate (EGCG), a canonical amyloid inhibitor. EGCG effectively disrupts the fibrils formed by Ins1 B9–23 and the Y16A mutant. However, it proves ineffective in preventing fibril formation of Ins2 B9–23 and the C19S mutant. These results establish a strong correlation between the aggregation behaviors of these peptides and their divergent effects on anti-islet autoimmunity.