The ability to visualize enzyme activity in a cell, tissue, or living organism can be transformative in enhancing our understanding of the biological roles of that enzyme. We are developing a toolkit of fluorogenic phosphatase activity probes with the goal of ultimately being able to investigate any phosphatase of interest with a targeted probe. From small molecule fluorophores to genetically encodable fluorescent proteins, our enzyme-responsive tools provide facile means for visualizing phosphatase activity in living cells in real time.

Protein phosphatases and kinases play critical roles in cellular signaling, and misregulated protein phosphorylation is a characteristic of many human diseases including cancer, metabolic disorders, autoimmunity, and neurodegeneration. Researchers in the Barrios lab are developing tools for studying individual protein phosphatase enzymes with the goal of understanding their biological activity.

For example, our approach to visualizing CD45 activity directly in living cells allows us to better understand the regulation of this key signaling enzyme in immune function and autoimmune disorders. Targeted inhibitors are helping us to elucidate the roles of the LAR subfamily of protein tyrosine phosphatases in neurological development. The tools developed and validated in our lab are providing key insights into phosphatase biology and enabling novel approaches to phosphatase targeted drug discovery.

Very little is known about the roles played by histidine phosphorylation in mammalian systems. However, it is becoming clear that this poorly studied post translational modification is critical in controlling some key cellular processes including DNA regulation, cellular signaling, and fatty acid catabolism. We are studying the enzymes involved in histidine phosphorylation with a particular emphasis on the mammalian protein histidine phosphatase PHPT1.

We identified the first inhibitors of PHPT1 activity and are working to optimize and improve upon them. We are developing PHPT1-selective fluorogenic substrates for monitoring PHPT1 activity in vitro and in cells. And we have been working with collaborators to elucidate the mechanisms by which PHPT1 activity is regulated in vivo, with an emphasis on understanding the impacts that post-translational modifications have on the enzyme’s activity.