Heterologous functional expression system for odorant receptors

Heterologous functional expression system for odorant receptors (ORs) is essential for investigating the structure–activity relationship (SAR) of various ligands. Different systems that coexpressed ORs with different G-protein α subunits (Gα) demonstrated inconsistent effects on weak agonists and antagonists, but retained original relative sensitivities to potent agonists. In order to maintain the binding specificity of Gα to ORs, we constructed a chimeric Gα15_olf, which contained the Gα15 sequence with the conserved C-terminal region of Gαolf. The Ca2+ responses of the HEK293 cells that coexpressed OR-S6 with Gα15_olf were more robust and reproducible compared to those of cells that coexpressed OR-S6 with Gα15. Furthermore, Gα15 sometimes induced unstable Ca2+ responses that limited the accuracy of quantitative comparison of peak responses. Our results showed that a heterologous expression system that coexpressed ORs with Gα15_olf and receptor transporting proteins was suitable for SAR analysis of various ligands.