Fig. 5.

The ATD of hT1R2 is required for hT1R2-hT1R3 to respond to MCL. (A) Representative ratiometric images of MCL (100 nM)-preincubated cells that were transfected with four different combinations of human and mouse T1R2-T1R3 together with G15Gi3 in response to acidic buffer (pH 5.0). The Upper and Lower rows show the representative cell images obtained 2 and 30 s after acidic buffer application, respectively. The color scale indicates the F₃₄₀/F₃₈₀ ratio as a pseudocolor. (Scale bar, 50 μm.) (B) Responses of the cells expressing hT1R2-hT1R3, mT1R2-mT1R3, hT1R2-mT1R3, and mT1R2-hT1R3, together with G15Gi3. Cells expressing mT1R2-hT1R3 did not respond to any sweetener. Without MCL preincubation, few responses were observed after acidic buffer application when each combination of T1R2-T1R3 was expressed [see buffer (pH 5.0)]. Data are expressed as the mean ± SE (n = 3) numbers of responding cells. (C) Responses of the cells expressing each human/mouse chimeric T1R2 together with mT1R3 and G15Gi3. Data are expressed as the mean ± SE (n = 3) numbers of responding cells.