Structure-Based Small Molecule Modulation of a Pre-Amyloid State: Pharmacological Enhancement of IAPP Membrane-Binding and Toxicity.

Islet amyloid polypeptide (IAPP) is a peptide hormone whose pathological self-assembly is a hallmark of the progression of type II diabetes. IAPP-membrane interactions catalyze its higher-order self-assembly and also underlie its toxic effects toward cells. While there is great interest in developing small molecule reagents capable of altering the structure and behavior of oligomeric, membrane-bound IAPP, the dynamic and heterogeneous nature of this ensemble makes it recalcitrant to traditional approaches. Here, we build on recent insights into the nature of membrane-bound states and develop a combined computational and experimental strategy to address this problem. The generalized structural approach efficiently identified diverse compounds from large commercial libraries with previously unrecognized activities toward the gain-of-function behaviors of IAPP. The use of appropriate computational prescreening reduced the experimental burden by orders of magnitude relative to unbiased high-throughput screening. We found that rationally targeting experimentally derived models of membrane-bound dimers identified several compounds that demonstrate the remarkable ability to enhance IAPP-membrane binding and one compound that enhances IAPP-mediated cytotoxicity. Taken together, these findings imply that membrane binding per se is insufficient to generate cytotoxicity; instead, enhanced sampling of rare states within the membrane-bound ensemble may potentiate IAPP's toxic effects.