Phosphatases are enzymes responsible for the dephosphorylation of tyrosine, serine, and threonine residues of proteins. Their counterparts, kinases, are responsible for the phosphorylation of these residues. Through balancing of phosphorylation states, these enzymes work in concert to maintain organismal homeostasis by regulating signal transduction pathways. Accordingly, the dysregulation of phosphatases or kinases can result in cognitive and neurological disorders, and specific diseases such as cancer, diabetes and obesity. As such, it is necessary to develop methods to inhibit, or in certain cases, activate these enzymes to treat and prevent these disorders and diseases. There has been success in developing small molecules that inhibit kinases. On the other hand, developing modulators of phosphatases has proven far more challenging given that they lack a pocket for a small molecule and prefer negatively charged compounds, which have poor cell permeability and bioavailability. Given the therapeutic importance of phosphatases, novel and general strategies to target them are warranted.
Fragment-based drug discovery is a newly emerging strategy for the development of therapeutics. We hypothesize that developing fragments that would be biased toward the enzymatic activity of phosphatase would provide useful starting points for further optimization. We propose that small molecules with the phosphonic acid moiety will successfully bind to phosphatases, with binding affinity changing based on the structural “linker” accompanying the acid. A group of 6 phosphonic acids were found to stabilize a phosphatase involved in the survival of Mycobacterium tuberculosis using differential scanning fluorimetry. Validation experiments were conducted using Isothermal Titration Calorimetry (ITC) to measure the equilibrium dissociation constants (Kd).
This study demonstrates that biased fragments can serve as a basis for generating weak binders to phosphatases that may be further optimized by fragment growing.
PROJECT: Using phosphonic acid fragments to target phosphatases
The Summer Research Program in Genomics has been my best research experience to date. I was allowed to conduct research in my field of interest, organic chemistry, while getting experience in related fields such as chemical biology and genomics. Although the Broad is a place that conducts truly amazing science, its most salient feature is its uniquely collaborative environment. Challenging problems are tackled from multiple angles, encouraging burgeoning scientists like me to think deeply and broadly about research. This summer has played an instrumental role in my scientific development and I am exceedingly grateful to be a lifetime member of the Broad community.