Fig. 1.

TRPM5 is a transmembrane protein and a calcium-activated cation channel. (A) Northern blot analysis of HEK-293 cells stably transfected with pcDNA3-TRPM5 and pcDNA3. (B) Confocal laser microscopic analysis of HEK-293 cells expressing the EGFP-TRPM5 fusion protein showing significant amounts of the protein in the plasma membrane. (C) Average TRPM5 currents at -80 mV or +80 mV in HEK-293 cells perfused with intracellular solutions buffered to the indicated levels of [Ca²⁺]_i (n = 5–20). (D) Typical I/V curve of TRPM5 currents measured 10 s or 40 s after establishment of whole-cell configuration with 500 nM [Ca²⁺]_i. (E) Concentration–response curve of TRPM5 currents (left axis, filled circles; n = 5–20). The fit represents the product of two Boltzmann functions with an apparent EC₅₀ for activation of 840 nM (Hill coefficient, 5). The right axis shows the dose dependence of TRPM4 currents evoked by different concentrations of intracellular [Ca²⁺]_i (data recalculated by webmaxc, see Methods). The fit to these data yields an EC₅₀ of 885 nM (Hill coefficient, 3.6).