Ray Truant/McMaster: Navigator Coalition Proposal Summary 2001

Analysis of the Huntingtin Nuclear Export Signal

My laboratory is predominantly interested in how some proteins are regulated in human cells to enter and exit from the nucleus. The disease model we have decided to focus on is Huntington’s disease (HD).

We have recently discovered the presence of a highly conserved nuclear export signal (NES) in huntingtin. This is the only functional domain of the huntingtin protein described to date. The presence of this NES has lead us to a functional model of huntingtin neurotoxicity based on the ratio of nuclear import and export signals in a huntingtin protein complex.

Protein sequence alignment has revealed the presence of a strictly conserved serine residue next to a critical leucine involved in the huntingtin NES function. Serines are frequently important targets of protein kinases involved in the regulation of protein activity. Kinase inhibitors are often effective drugs against a variety of diseases. We will be conducting experiments to determine the possible role of phosphorylation on the activity of the huntingtin NES.

In addition, by the use of a unique reagent, a huntingtin molecule labeled in two different colours at each end of the protein, we propose to do time course microscopic analysis of huntingtin in living neurons.

The goal of these experiments is to ask the question of what the effect is of excluding huntingtin from the nucleus on cell toxicity and HD. Should excluding huntingtin from entering the nucleus at the molecular level prove effective against cell toxicity in culture and in HD mouse models, we will have determined an excellent target for future therapeutic agents.