Fig. 2
From: TMC4 is a novel chloride channel involved in high-concentration salt taste sensation
TMC4 functions as a novel anion channel. A Representative current–voltage (I-V) relationship of the currents by step pulses with KCl (left) or N-Methyl-d-glucamine (NMDG)-Cl (centre) pipette solution in human embryonic kidney (HEK) 293T cells expressing mouse TMC4. Right panel shows the response of mock cells as a negative control. Open and filled arrowheads show the points of data selection from raw trace shown below. B Representative I–V relationship of the currents by step pulses under different bath solutions in cation. The current observed is not affected by the bath application of NMDG-Cl, NaCl, or amiloride (epithelial sodium channel inhibitor), but is significantly reduced by the anion channel inhibitor, 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB). C Effect of several anion channel inhibitors. Relative inhibition ratio calculated using the formula Iblocker/Icontrol at + 60 mV. Ca2+-activated chloride channel inhibitor (CaCC inh)-A01: ANO1/2 inhibitor, tannic acid: cystic fibrosis transmembrane conductance regulator (CFTR) and CaCC inh, niflumic acid: CaCC inh, and 4,4′-diisothiocyanatostilbene-2, 2′-disulfonic (DIDS): anion exchanger inhibitor. Different letters show significant differences, detected by Tukey–Kramer test (n = 4 or more for each, p < 0.05). D Representative I–V curves by step pulses with different extracellular Cl− concentrations through replacement with gluconate. E Representative I–V curves by step pulses with bath solution that has completely replaced a chloride ion with an organic anion. F Effects of increase in intracellular Ca2+ concentrations by ionomycin on mTMC4 (upper) or mANO1 (lower) -mediated currents. Open arrow heads indicate the starting point for perfusion of the bath solution containing ionomycin. Bath and pipette solution components and calculation procedures are shown in the Materials and methods section, Additional file 1: Table S1 and Table S2