Characterization of an extended receptive ligand repertoire of the human olfactory receptor OR17‐40 comprising structurally related compounds

Abstract Molecular properties of odorant compounds essential for activation of the human olfactory receptor hOR17‐40 were investigated using a collection of 23 variants of its cognate ligand helional. Coupling receptor activation to an optically detectable intracellular Ca 2+ ion flux allowed dose‐dependent screening of different odorant molecules in human embryonic kidney (HEK)293 cells. We found an extended collection of activating ligands and provide first evidence for hOR17‐40‐specific antagonists. The C‐terminal fusion of enhanced green fluorescent protein to the hOR17‐40 retained full receptor function and permitted the selection of cells with defined receptor expression levels, which was an essential step for optimizing our screening protocol. Interestingly, cells with a low EGFP fluorescence intensity exhibited efficient hOR17‐40 cell surface targeting and odorant‐evoked signal transduction; in contrast, highly fluorescent cells displayed mainly incorrectly targeted, intracellular receptors. Fluorescence‐activated cell sorting was used to separate hOR17‐40‐expressing cells on the basis of their endogenous EGFP fluorescence intensity, thereby increasing the fraction of odorant‐responsive cells to up to 80% of the total cell number.