Structural Analysis of IAPP Fibril Formation and Membrane Interaction

University Of Southern California, Los Angeles CA

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Abstract

DESCRIPTION (provided by applicant): Project Summary: The misfolding of IAPP (islet amyloid polypeptide) is thought to play an important role in type II diabetes and is analogous to that of other proteins involved in other age-related amyloid diseases, including Alzheimer and Parkinson disease. However, structural details of this misfolding process have been difficult to obtain. Recent work, largely from my group, demonstrates that site-directed spin labeling (SDSL) is a powerful approach for investigating the structures of amyloidogenic proteins. In this proposed study, we will use SDSL to provide detailed structural information on defined conformational states involved in IAPP misfolding, and we will try to determine how small molecule inhibitors can prevent those structures from forming. Specific Aim 1 is designed to generate a three-dimensional model of IAPP amyloid fibrils. Amyloid fibrils are the pathological hallmarks of amyloid diseases and represent the end product of a stepwise misfolding process. Understanding the molecular mechanism of amyloid protein misfolding will not be possible without detailed knowledge of the fibrillar structures. In Specific Aim 2, we propose to perform structural studies on ?-helical, membrane-bound IAPP in order to provide a mechanistic understanding of our previous finding that such membrane interactions can catalyze the misfolding of IAPP. In Specific Aim 3, we propose to provide detailed structural information on non-fibrillar, cytotoxic oligomers of IAPP. Importantly, these well-defined oligomers have been identified in vivo, and are thought to play an important role in amyloid diseases, including type II diabetes. In Specific Aim 4, we will utilize our SDSL approach, combined with the structural information from Specific Aims 1-3, to study how small molecule inhibitors interact with IAPP and prevent misfolding. Relevance: The structural and mechanistic information obtained from Specific Aims 1-4 should greatly facilitate the development of therapeutic agents for the treatment of type II diabetes and other amyloid diseases, including Alzheimer and Parkinson disease. In addition, our studies should make it possible to design mutants that selectively alter misfolding. Such mutants would provide powerful tools for studying the cellular targets and mechanisms of toxicity of misfolded amyloid proteins in vivo.