The aggregation of the 37-amino acid polypeptide human Islet Amyloid Polypeptide (hIAPP, amylin), as either insoluble amyloid or as small oligomers, appears to play a direct role in the death of pancreatic ?-islet cells in type 2 diabetes. While hIAPP is the primary component of type 2 diabetes amyloid, the molecular interactions responsible for this aggregation are not well understood. hIAPP is found as extracellular deposits of amyloid in approximately 90% of patients afflicted with type 2 diabetes. hIAPP has also been shown to be a toxic agent in vitro when added to mammalian cells. While it remains unclear how self-assembly of hIAPP leads to the development of disease, recent studies have suggested that the formation of lower order protein aggregates (two to ten self- assembled proteins) leads to cellular toxicity and ultimately to the progression of disease. Preventing the formation of these toxic oligomeric species may slow, if not prevent entirely, the progression of type 2 diabetes. We have identified a series of peptides capable of inhibiting hIAPP aggregation. We propose characterizing and optimizing these peptides to yield potent hIAPP aggregation inhibitors. We will then use these inhibitors to analyze and understand the unfolded protein response system in mammalian cells. We will use a combination of rational protein engineering and molecular screening to yield optimized hIAPP aggregation inhibitors. In this screen, the gene for hIAPP is genetically fused to the gene for enhanced green fluorescent protein (EGFP). When the hIAPP-EGFP fusion protein is expressed in E. coli the natural propensity of hIAPP to aggregate precludes EGFP from folding and fluorescing. However, in the presence of peptides that prevent amyloid aggregation, the fused EGFP can fold properly and fluoresce green. Using this screen and elements of rational protein engineering, we will identify potent inhibitors of hIAPP aggregation. We will use these aggregation inhibitors, to identify the relevant genes involved in the pancreatic unfolded protein response system.
The aggregation of the small peptide human Islet Amyloid Polypeptide (hIAPP, amylin) appears to be directly related to the loss of insulin-producing ?-cells and the progression of type 2 diabetes. Using naturally occurring peptides, recently identified in our laboratories as potent inhibitors of hIAPP aggregation, we propose to (i) characterize the molecular underpinnings of this inhibition (ii) optimize the inhibitor peptides and (iii) probe the natural response system of mammalian cells to amyloidogenic hIAPP. These experiments have the potential to characterize the root of hIAPP toxicity and identify novel therapeutic targets.
