Misfolding and aggregation of polyglutamine sequences in neurodegenerative diseases

U.S. National Inst Diabetes/Digst/Kidney, Bethesda MD

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Abstract

? DESCRIPTION (provided by applicant): The formation of accumulated, abnormally folded proteins is associated with more than twenty different clinical syndromes, each of which is associated with a distinct `misfolding' protein. These misfolded proteins aggregate and form the hallmarks of many neurodegenerative diseases, termed amyloids. Amyloid formation is associated with neurodegenerative disseases such as Alzheimer's, Parkinson's, and Huntington's disease, as well as localized diseases such as Type II Diabetes. Of the amyloid-related diseases, polyglutamine (polyQ) diseases represent a set of heritable neurological disorders, comprising at least nine diseases. In polyQ diseases like Huntington's disease (HD), our knowledge of how and why an expanded tract of polyQ leads to aggregation and amyloid formation is largely hampered by the fact that there is little high-resolution structural and dynamic insight into this process. Furthermore, the ability of a polyQ protein misfolded species to engage in aberrant protein interactions has become increasingly studied. Particularly, the interactions of polyQ proteins with molecular chaperones and their resistance to proteolysis are poorly understood. Challenges posed by polyQ proteins are manifold and, therefore, new biochemical and biophysical approaches developed to tackle such problems would greatly aid our understanding of polyQ diseases. To accomplish this goal, this application seeks to further investigate the aggregative properties of polyQ proteins at high-resolution, namely the N- terminal fragment of the huntingtin protein (implicated in the progression of HD), by using by nuclear magnetic resonance (NMR) spectroscopy. Newly developed NMR methods, such as dark-state exchange saturation transfer (DEST) and lifetime line broadening, offer the capability to achieve atomic resolution on the dynamic exchange occurring in the self-assembly of polyQ proteins, in addition to their interactions with molecular chaperones such as Hsp70 and Hsp40. While this proposal will focus on the development and application of new NMR methodologies to such challenging systems, the study will be extended for investigation using a variety of other biophysical techniques, including electron paramagnetic resonance (EPR), fluorescence spectroscopy, and calorimetry. The outcome of the proposed studies on amyloid formation by polyQ proteins will significantly advance our understanding of HD and other polyQ diseases, in general, by achieving structural and dynamic insights with atomic-level resolution and will aid in the development of therapeutic strategies for such diseases.