Bridging Chemistry and Biology for New Classes of Imaging Probes and Protein Degraders

The overarching goal for my research is to develop new tools for advancing biological research and new therapies for improving human health at the interface of chemistry and biology. My group has made major contributions in the areas of ratiometric redox probes and small molecule drugs. Glutathione (GSH) is the most abundant non-protein thiol in eukaryotic cells. Together with its oxidized partner (GSSG), GSH maintains cellular redox homeostasis, regulates protein functions through S‑glutathionylation, and acts as a signaling molecule to directly activate gene expression. Currently, the concentration of intracellular GSH is derived from either cell lysates or GSH-S-transferase (GST) dependent probes. These approaches, however, cannot provide information about the real-time dynamics of GSH concentration changes. We developed a fluorescent probe that can reversibly react with GSH and quantitatively monitor the real-time GSH dynamics in living cells for the first time. This new GSH probe enables unprecedented opportunities to study GSH spatiotemporal dynamics, which will revolutionize our understanding of its physiological and pathological roles in living cells. On the other hand, we also developed a dual functional Bruton’s Tyrosine Kinase (BTK) inhibitor and degrader. Current efforts in the proteolysis targeting chimera (PROTAC) field mostly focus on choosing an appropriate E3 ligase for the target protein, improving the binding affinities towards the target protein and the E3 ligase, and optimizing the PROTAC linker. However, due to the large molecular weights of PROTACs, their cellular uptake remains an issue. Through comparing how different warhead chemistry affects the degradation of BTK, we serendipitously discover that cyano-acrylamide-based reversible covalent chemistry can significantly enhance the intracellular accumulation and target engagement of PROTACs and develop RC-1 as a reversible covalent BTK PROTAC with a high target occupancy as its corresponding kinase inhibitor and effectiveness as a dual functional inhibitor and degrader, a different mechanism-of-action for PROTACs. Importantly, this reversible covalent strategy is generalizable to improve other PROTACs, opening a path to enhance PROTAC efficacy.