Cryo-EM structures of hIAPP fibrils seeded by patient-extracted fibrils reveal new polymorphs and conserved fibril cores

Amyloidosis of human islet amyloid polypeptide (hIAPP) is a pathological hallmark of type II diabetes (T2D), an epidemic afflicting nearly 10% of the world's population. To visualize disease-relevant hIAPP fibrils, we extracted amyloid fibrils from islet cells of a T2D donor and amplified their quantity by seeding synthetic hIAPP. Cryo-EM studies revealed four fibril polymorphic atomic structures. Their resemblance to four unseeded hIAPP fibrils varies from nearly identical (TW3) to non-existent (TW2). The diverse repertoire of hIAPP polymorphs appears to arise from three distinct protofilament cores entwined in different combinations. The structural distinctiveness of TW1, TW2 and TW4 suggests they may be faithful replications of the pathogenic seeds. If so, the structures determined here provide the most direct view yet of hIAPP amyloid fibrils formed during T2D. Human islet amyloid polypeptide (hIAPP) is a protein commonly forming aggregates in islet cells of those afflicted by type II diabetes. New structures of fibrils seeded with patient-derived material reveal a diverse repertoire of structures, some of which may resemble those appearing in vivo.

Automated summary

Human islet amyloid polypeptide (hIAPP) is commonly aggregated in the islet cells of individuals with type II diabetes. New structures of fibrils seeded with patient-derived material show a diverse repertoire of structures, some of which may resemble those appearing in vivo.