The work in our lab uses the tools of synthetic medicinal chemistry and chemical biology to develop new tools for studying therapeutically important protein-protein interactions. Our work currently focuses on two classes of protein-protein interactions: the nuclear receptor/steroid receptor coactivator interaction and the Keap1/Nrf2 interaction.
Nuclear Receptor/Steroid Receptor Coactivator
The nuclear receptor family of transcription factors comprises 48 members and, together, they make up one of the most important classes of drug targets, particularly with respect to targeted cancer therapy. Binding of coregulators to nuclear receptors is a molecular event that modulates the expression of genes under the control of the transcription factor.
We are developing cell-permeable, peptidic molecular probes that inhibit the interactions between nuclear receptors and coactivators, and we study these interactions using fluorescence-based assays. The interaction between many of the nuclear receptors and coactivators occurs over two turns of an α-helix, using an ILXXLL motif (I = isoleucine, L = leucine, and X = any amino acid) from the coactivator.
The major transcription factor in the adaptive stress response is called Nrf2; its negative regulator is Keap1, a substrate adaptor protein for a ubiquitin-ligase complex that aids in constantly degrading Nrf2. In times of electrophilic or oxidative stress, reactive cysteine residues are modified so that Nrf2 is no longer degraded. Excess Nrf2 then translocates into the nucleus and effects transcription of cytoprotective genes, especially those involved in Phase II metabolism.
There are a number of activators of Nrf2 that are known, but they are electrophilic in nature: they react with Keap1’s reactive sensor cysteines to keep Nrf2 from being degraded. We are preparing molecules that directly inhibit the interaction between Nrf2 and Keap1 as probes that can interrogate this mechanism of Nrf2 activation.