Zhuang, H. and Matsunami, H.
Notes: To explore the role that accessory proteins may play in successfully expressing odorant receptors (ORs) on the cell surface of heterologous cells, the authors explored cotransfecting receptor-transporting proteins RTP1S, Ric8b and Gαolf with an N-terminally tagged OR to generate a functional and ligand-specific expression system. Three tags (Rho, FLAG or HA) were inserted into the NheI and EcoRI sites of the pCI Mammalian Expression Vector. Amplified OR orfs were cloned into the MluI and NotI sites of the tagged pCI Mammalian Expression Vector. The accessory proteins were subcloned into HA-pCI (RTP1S) or pCI (RTP1S, Ric8b, Hsc70t and Gαolf). For cotransfection, the N-terminal tagged OR vectors (0.8µg) and the assessory proteins (individually or in combination; 0.8µg) were transfected into HEK293T or Hana3A cells. The transfected cells were then subjected to immunocytochemistry, live-cell surface staining, permeabilized staining or FACS analysis. The Dual-Glo™ Luciferase Assay System was used to assess OR activation via CRE elements on a firefly luciferase vector. pRL-SV40 Vector was the internal control for cell viability and transfection efficiency. HEK293T or Hana3A cells were plated on 96-well plates, transfected with 1µg of CRE-Luc vector, 1µg of pRL-SV40 Vector, 5µg of OR and 1µg total for all accessory proteins (0.25µg each protein with pCI Mammalian Expression Vector to keep amount of plasmid constant). Twenty-four hours posttransfection, the medium was changed to CD293 chemically defined medium, incubated for 30 minutes at 37°C then replaced with 25µl of odorant solution in CD293 for a second incubation of 4 hours at 4°C. Then the reporter protein expression levels were measured by luminescence. (3687)