Figure 1.

Functional expression of bitter taste receptors and their downstream signaling effectors. A) Immunohistochemistry images showed that bitter taste receptor TAS2R10 and its downstream signaling effectors GNAT3 (B) and TRPM5 (C) were highly expressed on airway epithelial cells in mice. Scale bar: 100 μm. D) Western blot showed that bitter taste receptor TAS2R4 and GNAT3 were expressed on A549 cells. E) In vitro experiments showed that 1 mM denatonium triggered Ca²⁺ oscillations in A549 human epithelial cells. A549 cells were stained with Fluo-4 to visualize intracellular free Ca²⁺. Red arrow points to the region of interest (ROI) in an A549 cell. F) Ca²⁺ oscillations started immediately after denatonium application and lasted for a few cell cycles.