Screening of a Designed Combinatorial Peptide Library for Inhibitors of IAPP Aggregation
Authors:Paola Cota, Christina Cunha
Mentor:David Moffet, Associate Professor of Chemistry and Biochemistry, Loyola Marymount University
Islet amyloid polypeptide (IAPP) is 37-amino acids in length and is secreted from the pancreas in conjunction with insulin. Similar to other amyloid proteins, IAPP has the ability to misfold and aggregate forming large plaques in the pancreas. It is closely associated with Type II diabetes. IAPP aggregates have been found in the pancreas of over 90% of individuals afflicted with Type II diabetes. Our research involves finding small peptides that can inhibit the aggregation of IAPP in an attempt to slow the progression or eliminate completely the disease. A protein library was constructed targeted to bind to the aggregation-prone region of IAPP, but simultaneously block additional IAPP sequences from binding. This library has a theoretical size of over 663,000 peptides. The peptide library has been screened using an IAPP-EGFP screen developed in our laboratory. This involves the fusing of the genes for IAPP and enhanced green fluorescent protein (EGFP). In E. coli the IAPP-EGFP fusion protein does not fluoresce. This lack of fluorescence is due to the aggregation of the IAPP which prevents proper folding and fluorescing of the fused EGFP. When an inhibitor of amyloid aggregation is present, the fused EGFP can fold properly and fluoresce green. Using this method, we have screened and identified several peptides with IAPP inhibitory potential.