Figure 3: Potassium and calcium permeability of hTPC1 channels.

(a) Representative traces of PI(3,5)P₂-mediated currents recorded at different voltages from −80 to 90 mV, in 10 mV voltage step, after perfusion of 100 mM KCl (replacing 100 mM NaCl) in the bath solution. Holding potential of −70 mV, tail voltage of −50 mV. Inset: magnification of inward currents recorded from +60 to +90 mV. (b) Current-voltage relationship in the presence of 100 mM KCl (n = 6) in the bath solution. Current amplitudes were normalized to the value obtained at +40 mV. Dashed lines indicate the 0 level current. (c) Whole-vacuole recordings before (top) and after (bottom) PI(3,5)P₂ bath perfusion. Pipette (luminal side) was filled with 50 mM CaCl₂ in the place of 100 mM NaCl. Currents were recorded at voltages ranging to −90 to +80 mV in 10 mV step. Holding and tail voltage at −80 mV. (d) Tail currents recorded in response to potentials (1 sec-long) ranging from +70 mV to −100 in −10 mV decrement after 500 ms pre-pulse to +50 mV. Holding voltage: −80 mV. Inset: expanded view of tail currents recorded from −40 to −80 mV. (e) Permeability ratios, based on reversal voltage measurements (see Supplementary Fig. 2), in the presence of 100 mM (left, n = 11) or 200 mM (right, n = 4) cytosolic NaCl.