Discovery of a celecoxib binding site on PTGES with a cleavable chelation-assisted biotin probe

Abstract

The coxibs are a subset of non-steroidal anti-inflammatory drugs (NSAIDs) that primarily target cyclooxygenase-2 (COX-2) to inhibit prostaglandin signaling and reduce inflammation. However, mechanisms to inhibit other members of the prostaglandin signaling pathway may improve selectivity and reduce off-target toxicity. Here, we report a novel binding site for celecoxib on prostaglandin E synthase (PTGES), an enzyme downstream of COX-2 in the prostaglandin signaling pathway, using a cleavable chelation-assisted biotin probe 6. Evaluation of the multi-functional probe 6 revealed significantly improved tagging efficiencies attributable to the embedded picolyl functional group. Application of the probe 6 within the small molecule interactome mapping by photo-affinity labeling (SIM-PAL) platform using photo-celecoxib as a reporter for celecoxib identified PTGES and other membrane proteins in the top eight enriched proteins from A549 cells. Carbonic anhydrase 12, a known protein target of celecoxib, was also enriched. Four binding sites to photo-celecoxib were additionally mapped by the probe 6, including a binding site with PTGES. The binding interaction with PTGES was validated by competitive displacement with celecoxib and known PTGES inhibitor licofelone. The binding site of photo-celecoxib on PTGES enabled the development of a structural model of the interaction and will inform the design of new selective inhibitors of the prostaglandin signaling pathway.