Discovery of a Celecoxib Binding Site on Prostaglandin E Synthase (PTGES) with a Cleavable Chelation-Assisted Biotin Probe

The
coxibs are a subset of nonsteroidal 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),
which is an enzyme downstream of COX-2 in the prostaglandin signaling
pathway, using a cleavable chelation-assisted biotin probe 6. Evaluation of the multifunctional 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 photoaffinity 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. Four binding sites to photo-celecoxib were mapped
by the probe 6, including a binding site with PTGES.
The binding interaction with PTGES was validated by competitive displacement
with celecoxib and licofelone, which is a known PTGES inhibitor, and
was used to generate a structural model of the interaction. The identification
of photo-celecoxib interactions with membrane proteins, including
the direct binding site on the membrane protein PTGES, will inform
further functional followup and the design of new selective inhibitors
of the prostaglandin signaling pathway.