Abstract
Chemoproteomic approaches to identify ligand-receptor interactions have gained popularity however, identifying trans-membrane receptors remains challenging. A new tri-functional probe to aid the non-biased identification of such receptors was developed and synthesized using a convenient 7-step synthesis. This probe contained three functional groups: (1) an NHS-ester for ligand-coupling through free amines; (2) a diazirine moiety to capture the receptor of interest upon irradiation with UV-light; and (3) a biotin group which allowed affinity purification of the final adduct using streptavidin. The interaction between the G protein-coupled tachykinin NK1 receptor, expressed in an inducible manner using the Flp-InTM T-RExTM system, and the peptidic ligand substance P was employed as a test system. Liquid chromatography - mass spectrometry analysis confirmed successful coupling of the probe to substance P, while inositol monophosphate accumulation assays demonstrated that coupling of the probe did not interfere substantially with the substance P-NK1 receptor interaction. Confocal microscopy and western blotting provided evidence of the formation of a covalent bond between the probe and the NK1 receptor upon UV activation. As proof of concept, the probe was used in full ligand-based receptor capture experiments to identify the substance P-binding receptor via LC-MS/MS, resulting in the successful identification only of the NK1 receptor. This provides proof-of-concept towards general utilization of this probe to define interactions between ligands and previously unidentified plasma-membrane receptors.
- The American Society for Pharmacology and Experimental Therapeutics