Copper-Induced Amyloidosis Studied by Mass Spectrometry

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DESCRIPTION (provided by applicant): Several human proteins are known to form amyloid fibrils, and these fibrils are associated with several devastating diseases, including Alzheimer's, Parkinson's, type II diabetes, and dialysis-related amyloidosis (DRA). One of these proteins, human beta-2- microglobulin (beta2m), can form amyloid fibrils in the presence of Cu(II). The fibrils formed by beta2m are the main pathogenic process underlying DRA. Like other amyloid systems, beta2m fibril formation proceeds by partial protein unfolding, subsequent oligomerization, and eventual elongation to form mature fibrils. While many general aspects of amyloid formation are understood, molecular-level information for the early stages of almost all amyloid forming reactions is only starting to emerge. This information, though, is critical for the rational development of therapeutics against amyloid diseases like DRA. We intend to obtain amino acid-level information about the unfolding and oligomerization of beta2m that precedes its fibril formation, with a particular emphasis on the unique role that Cu(II) plays in inducing this reaction. We will also investigate the molecular basis of several inhibitors that show promise for disrupting beta2m amyloid formation. To obtain the desired insight, we have three main aims. First, we will explore a combination of covalent labeling and hydrogen/deuterium exchange with mass spectrometric detection to obtain a detailed picture of the structural changes that betam and its oligomers undergo prior to amyloid formation. Second, we will develop and apply new labeling methods in conjunction with mass spectrometry to study metal-protein interactions with the goal of understanding the unique role that Cu(II) plays in beta2m amyloid formation. Third, our new labeling approaches will be applied to understand the molecular basis of three inhibitors of beta2m amyloid formation. Our prior work has revealed that Cu(II) destabilizes beta2m, allowing it to form oligomers prior to amyloid fibrils. We hypothesize that Cu(II) initiate the amyloid reaction by repositioning several regions of the protein and that Cu(II)'s coordination chemistry enables these structural and oligomeric changes in a way that is unique among transition metals. Our mass spectrometry-based methods will allow us to test this hypothesis, and along with the proposed inhibitor studies, we will obtain a deeper understanding of beta2m amyloid formation, which will facilitate the design of better therapeutics against DRA. Moreover, we expect that the techniques developed here will be applicable to other amyloid systems.