Piezoelectric olfactory biosensor: ligand specificity and dose-dependence of an olfactory receptor expressed in a heterologous cell system

An olfactory receptor protein of rats, 17, was expressed on the surface of human embryonic kidney (HEK)-293 cells. For targeting and detecting the protein, rho-tag import sequence was fused with the 17 protein. The olfactory receptor was expressed on the plasma membrane of HEK-293 cells, and stable cell lines regulated by an inducer were obtained. The expression on the cell surface was confirmed by immunocytochemical and Western blotting methods, and the binding of specific odorant molecules to the olfactory receptor was measured using quartz crystal microbalance (QCM). The results for QCM coated with cells containing the olfactory receptor showed that the expressed protein 17 strongly interacted with octyl aldehyde (octanal), which is an odorant specific to the 17 protein. Several other odorants were tested, and the results showed that 17 interacted differently with them. The QCM response to the serial concentrations of octyl aldehyde showed that the response is dose dependent. All these results indicate that the 17 receptor protein expressed on the surface of the heterologous cell system is sensitive to the specific odorant and can be used for the quantitative measurement of the odorant. (C) 2004 Elsevier B.V. All rights reserved.