A scintillation proximity assay for fatty acid amide hydrolase compatible with inhibitor screening

Scintillation proximity assay (SPA) is a homogenous and versatile technology for the simple and sensitive detection of the interaction of protein targets with their ligands. Herein, we described a SPA assay developed to identify compounds that bind to human fatty acid amide hydrolase (FAAH). This SPA assay utilizes the specific binding of [(3)H]-R(+)-methanandamide ((3)H-MAEA), a competitive nonhydrolyzed FAAH inhibitor, to FAAH expressing microsomes and evaluates its displacement by FAAH inhibitors. In contrast to the classical SPA radioligand binding assay which detects bound ligand, in our assay the released radiolabel is detected through its interaction with the SPA beads. This novel SPA assay has been validated and demonstrated to be simple, sensitive, and amenable to high-throughput screening.