Human olfactory receptor responses to odorants

Abstract

Although the human olfactory system is capable of discriminating a vast number of odors, we do not currently understand what chemical features are encoded by olfactory receptors. In large part this is due to a paucity of data in a search space covering the interactions of hundreds of receptors with billions of odorous molecules. Of the approximately 400 intact human odorant receptors, only 10% have a published ligand. Here we used a heterologous luciferase assay to screen 73 odorants against a clone library of 511 human olfactory receptors. This dataset will allow other researchers to interrogate the combinatorial nature of olfactory coding.

Figure 1. Outline of the screening procedure.

This figure was reprinted from our previous publication, where it was included as Supplementary Figure 1.

Figure 2. Normalized dose-response curves of the receptor encoded by the most common functional allele for 25 receptors.

The responses of cells transfected with either a plasmid encoding the indicated odorant receptor or an empty vector to the indicated odorants. Responses have been normalized such that each receptor has a minimum response of zero and a maximum response of one. Error bars, s.e.m. over three replicates. Abbreviations for the odorants are as follows: +CAR are shown, (+)-carvone; LIN, linalool; GA, geranyl acetate; COUM, coumarin; OTHI, octanethiol; C3HEX, cis-3-hexen-1-ol; EUG, eugenol; EUGME, eugenol methyl ether; ANIS, anisaldehyde; ANDI, 4,16-androstadien-3-one; AND, 5α-androst-16-en-3-one; DMHDMF, caramel furanone; +MEN, (+)-menthol; 3PPP, 3-phenyl propyl propionate; VAN, vanillin; LYR, lyral; 2EF, 2-ethyl fenchol; IVA, isovaleric acid; APA, allyl phenyl acetate. This figure was modified from our previous publication, where it was included as Figure 1.

Figure 3. Dose-response curves of the receptor encoded by the most common functional allele for 25 receptors.

The responses of cells transfected with either a plasmid encoding the indicated odorant receptor or an empty vector to the indicated odorants. Error bars, s.e.m. over three replicates. Abbreviations for the odorants are as follows: +CAR are shown, (+)-carvone; LIN, linalool; GA, geranyl acetate; COUM, coumarin; OTHI, octanethiol; C3HEX, cis-3-hexen-1-ol; EUG, eugenol; EUGME, eugenol methyl ether; ANIS, anisaldehyde; ANDI, 4,16-androstadien-3-one; AND, 5α-androst-16-en-3-one; DMHDMF, caramel furanone; +MEN, (+)-menthol; 3PPP, 3-phenyl propyl propionate; VAN, vanillin; LYR, lyral; 2EF, 2-ethyl fenchol; IVA, isovaleric acid; APA, allyl phenyl acetate. This figure was modified from our previous publication, where it was included as Figure 1.

Figure 4. Plate layout for the primary screen.

Screens were set up with a master transfection plate for each day. The master transfection plate was used to transfect twelve plates. Each plate was then stimulated with a different odor. Eleven wells were reserved for broadly tuned receptors and a standard to validate the protocol.

Figure 5. Validation of the screen.

An ROC curve indicates that (a) the primary screen predicts odor/receptor pairs that pass the secondary screen, (b) the primary screen predicts odor/receptor pairs that pass the dose response filter, and (c) the secondary screen predicts odor/receptor pairs that pass the dose response filter.