Mechanistic Studies and Inhibition of Islet Amyloid

A number of debilitating human diseases involve the association and aggregation of normally soluble proteins to form insoluble deposits known as amyloid. Amyloid, or the process of its formation is toxic and has been implicated in more than twenty human disorders ranging from neurodegenerative diseases such as Parkinson disease, Huntington?s disease, and Alzheimer?s disease to type-2 diabetes. The research outlined here focuses on a protein known as Islet Amyloid Polypeptide (IAPP, also known as Amylin). IAPP is a hormone which is released from the pancreatic beta-cells together with insulin. IAPP normally acts as a partner with insulin, but forms amyloid deposits in type-2 diabetes. The deposits are localized in the pancreases, are toxic to the insulin producing pancreatic beta-cells, and play a role in the pathology of the disease by killing beta-cells. There is growing evidence that amyloid formation by IAPP is also a critical factor in the failure of islet cell transplants. Type-2 diabetes is reaching epidemic proportions in the UK, but comparatively little is known about amyloid formation by IAPP. A combination of protein chemistry, biochemistry, cell biology and new biophysical approaches will be used to study amyloid formation by IAPP and its consequences. The work involves the application of new techniques for studying the intermediate steps in the process of amyloid formation. A key goal is to define the process in as much detail as possible since a detailed understanding of amyloid formation is critical for drug development. These studies will be complimented by the development of new inhibitors of IAPP amyloid formation and by the demonstration of new strategies for screening libraries of chemical compounds for potential inhibitors. IAPP is an important protein for study in its own right, but it is also an excellent model system for studies of amyloid formation by other proteins, including proteins involved in neurodegenerative disorders. Outreach to undergraduates, pre-university students, and the general public will involve lectures, lab visits (open days), and the hosting of ?lab experiences? for younger students.

Funding is requested to support a well developed research program on amyloid formation by islet amyloid polypeptide (IAPP, also known as amylin), the causative agent of amyloid formation in type-2 diabetes. IAPP is a 37 residue hormone which is responsible for pancreatic islet amyloid formation in type-2 diabetes. The polypeptide is processed in the beta cells of the pancreas, and cosecreted with insulin as a soluble monomer in response to the same stimuli that lead to insulin release. IAPP normally functions as an endocrine partner to insulin, but forms pancreatic islet amyloid in type-2 diabetes. Formation of islet amyloid plays a role in the pathology of the disease by promoting beta cell death, thereby contributing to the loss of beta cell mass. There is growing evidence that islet amyloid formation is also an important complicating factor in islet cell transplantation and we have shown that prevention of islet amyloid contributes significantly to graft survival.

The pathway of amyloid formation by IAPP will be defined at high resolution by the use of newly developed isotope edited two dimensional infrared methods in combination with studies of novel fluorescence analogs of IAPP. The conformation of the species responsible for cytotoxicity will be deduced using spectroscopic methods, antibody binding, electron and atomic force microscopy. A new class of inhibitors of islet amyloid formation will be developed and refined and their mode of action defined. A strategy for the development of inhibitors of amyloid formation that employs the rational combination of moderately effective inhibitors of amyloid in trans to lead to highly effective inhibition will be developed. A high through put version of this method will be implemented. The work outlined in the application focuses on studies of IAPP and islet amyloid, but the methods being developed can be directly applied to other amyloidogenic proteins including the A-beta peptide of Alzheimer?s disease and alpha-synuclein. The general principles which emerge, i.e. the nature of toxic species, mechanisms of amyloid formation, methods for screening inhibitors, will be applicable to a broad range of amyloidogenic systems. Thus, the results of the research are expected to have a significant impact beyond their application to IAPP.