Human islet amyloid polypeptide fibril binding to catalase: a transmission electron microscopy and microplate study.
The diabetes-associated human islet amyloid polypeptide (IAPP) is a 37-amino-acid peptide that forms fibrils in vitro and in vivo. Human IAPP fibrils are toxic in a similar manner to Alzheimer's amyloid-beta (A-beta) and prion protein (PrP) fibrils. Previous studies have shown that catalase binds to A-beta fibrils and appears to recognize a region containing the Gly-Ala-Ile-Ile sequence that is similar to the Gly-Ala-Ile-Leu sequence found in human IAPP residues 24-27. This study presents a transmission electron microscopy (TEM)-based analysis of fibril formation and the binding of human erythrocyte catalase to IAPP fibrils. The results show that human IAPP 1-37, 8-37, and 20-29 peptides form fibrils with diverse and polymorphic structures. All three forms of IAPP bound catalase, and complexes of IAPP 1-37 or 8-37 with catalase were identified by immunoassay. The binding of biotinylated IAPP to catalase was high affinity with a KD of 0.77 nM, and could be inhibited by either human or rat IAPP 1-37 and 8-37 forms. Fibrils formed by the PrP 118-135 peptide with a Gly-Ala-Val-Val sequence also bound catalase. These results suggest that catalase recognizes a Gly-Ala-Ile-Leu-like sequence in amyloid fibril-forming peptides. For IAPP 1-37 and 8-37, the catalase binding was primarily directed towards fibrillar rather than ribbon-like structures, suggesting differences in the accessibility of the human IAPP 24-27 Gly-Ala-Ile-Leu region. This suggests that catalase may be able to discriminate between different structural forms of IAPP fibrils. The ability of catalase to bind IAPP, A-beta, and PrP fibrils demonstrates the presence of similar accessible structural motifs that may be targets for antiamyloid therapeutic development.
Milton
Nathaniel G N
NG
1Department of Human and Health Sciences, School of Life Sciences, University of Westminster, London, U.K. n.milton@westminster.ac.uk
Harris
J Robin
JR
D000682:Amyloid / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D002374:Catalase / Q000097:blood / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D058228:Islet Amyloid Polypeptide; D046529:Microscopy, Electron, Transmission; D011485:Protein Binding; D051381:Rats
D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D002374:Catalase