Fellowship Veronique Hermann / Structural Characterization of Exon 1 of Huntingtin, an Emerging Drug Target

The aim of this postdoctoral research project is to characterize the conformational properties of exon 1 of huntingtin. an emerging drug target. Exon I contains the polyglutamine tract responsible for aggregation. The polyglutamine tra( was previously thought to be random coil but emerging evidence suggests a non-random structure to which a drug could be designed. A drug which prevents aggregation of the polyglutamine region of exon I should prevent disease pathogenesis, providing a route to disease therapy. Individual sections of exon 1 will be compared to the whole exon 1< determine the role of each part in the conformation of exon 1, a goal which could not be accomplished by examining the entire exon 1 alone. This project will be carried out in collaboration with Prof. Ronald Wetzel of the University 01 Tennessee. In order to achieve the goal of determining the conformational properties of exon I in solution, we will examine by circular dichroism (CD) the secondary structure of exon 1 components both separately and with neighboring components: 1) the polyglutamine region, for which we will examine various lengths reflecting disease and non-disease states, 2) the N-terminal sequence, 3) the polyproline sequence, 4) the proline/glutamine-rich region, 5) the C-terminal region and 6) the entire exon 1 region. Specific residues of interest will be examined by substitution and/or deletion as appropriate. Preliminary studies on the polyglutamine and polyproline sections indicate that this pair of neighbors have a dramatic structural effect on each other, so we wish to investigate other combinations of neighbor pairs. Preliminary data indicates the presence of a limited number of well-defined conformations in the polyglutamine peptidt constructs, contrary to the prevailing view that polyglutamine is a random coil. We will use NMR to examine in greatel detail the different conformations with the aim of identifying common points where a drug could bind. Findings from the experimental approach outlined here will allow the generation of a set of model structures for exon 1 of huntingtin. These structures will allow us to devise a strategy for rational drug design which would form a key part oj an integrated therapy program. Lay Summary: Huntington's disease patients possess a longer sequence of glutamines in the protein huntingtin than normal patients. This expanded polyglutamine sequence is known to aggregate, whereas normal length polyglutamine does not. Polyglutamine aggregation in neuronal cells is thought to cause neuronal death, thereby causing disease pathogenesis, characterized by neurological symptoms. The goal of this research project is to find a new route to Huntington's disease therapy by preventing aggregation of th, polyglutamine sequence. If a drug could be designed to bind to this region, aggregation would be prevented, providing a route to disease therapy. In order to devise a successful rational drug design strategy, more experimental knowledge of the structural properties of this region (exon I) of huntingtin is needed. Exon 1 comprises the first -100 residues of this large (> 3000 residue) protein. This exon contains the polyglutamine sequence as well as some other motifs of which little is known structurally. Exon 1 was previously thought to be unstructured, but new evidence is replacing that view with a discrete set of defined structures. In this new light, exon I can be regarded as an emerging drug target. We will examine the conformational properties of various regions of exon I in solution by circular dichroism and NMR. The effects of disease-length and normal lengths of polyglutamine will be examined. Findings from the experimental approach outlined here will allow the generation of a set of model structures for exon I of huntingtin. These structures will allow us to devise a strategy for rational drug design which would form a key part of an integrated therapy program.