In drug development, attention typically focuses compounds that bind to the main functional site, which is termed the protein active or orthosteric site. Orthosteric sites are often the most highly conserved region of a protein family making targeting of one protein family member problematic. Allosteric sites are distal from the orthosteric site and are of particular interest in drug development as they may present opportunities for improved specificity. In our lab we have developed as suite of approaches that has allowed us to discover and exploit allosteric sites in biomedically important proteases. We focus much of our attention on the caspase proteases, which initiate and induce apoptotic cell death.
A common theme in neurodeneration and aging is that cells required for health die by caspase-mediated apoptosis. In addition, caspase-6 cleaves Tau, the protein that aggregates to form the neurofibrilary tangles that are hallmarks of an Alzheimer’s diseased brain. Thus there is great interest in controlling caspase function in a number of contexts, however specific inhibition of individual caspases is required. Work from our lab has shown that caspase-6 is capable of attaining a unique, helical structure that can not be achieved by any other caspase. This structure is naturally inactive. Identifying small molecules that can lock caspase-6 into this unique helical conformation may prove to be an effective caspase-6-directed therapy. We also exploit the embedded record of evolved regulatory sites that can be triggered by phosphorylation and other post-translational modification or binding of zinc to identify additional allosteric sites in caspases. We combine biochemical and cell-based assays with structure determination by x-ray crystallography to determine the mechanisms of allosteric inhibition. In addition to identifying naturally-occuring allosteric sites, we also design caspases with properties that make them potentially attractive drugs themselves. Activating apoptosis induces proliferating cancer cells to die without activating the death response in adjacent cells and tissues. Today, many of the most effective cancer therapies work via this mechanism. We work collaboratively to develop new methods for targeted delivery of active and handcuffed caspases to selectively kill cancer cells. We have recently expanded our focus to discover and exploit allosteric sites in other proteases. We have developed a method that has allowed us to identify a new allosteric site in the protease from Dengue virus, which causes Dengue fever. Small molecules bound at this allosteric site function by blocking mobility of the NS2B 120’s loop.
Learn more at people.chem.umass.edu/jhardy/
- BS/MS Utah State University, 1994
- PhD University of California at Berkeley, 2000
- NIH Postdoctoral Fellowship, 2002-2005, Sunesis Pharmaceuticals