TRPM5 is specifically expressed in brush cells of the respiratory system. Detection of solitary TRPM5-expressing cells in the mouse respiratory epithelium of nose (indicated by arrows in (A)), trachea (B) and bronchus (C). Overlays of TRPM5 fluorescence with the corresponding DIC images are shown. The inset in (C) shows the fluorescent image of a TRPM5-positive cell with a basolateral extension (indicated by the arrow). (D-L) TRPM5-expressing cells express brush cell-specific marker proteins. Confocal images of TRPM5-specific signals (left panels), villin or CK18 (middle panels) and their overlays with corresponding DIC images (right panel) are shown. Note the co-localization of TRPM5 with villin (D-F) and CK18 (G-H) in rat trachea and TRPM5 with villin in rat alveolar epithelium (J-L). Scale bars are 20 μm.