Figure 2. Channel activity is altered in the TRPV5 W583 mutants.

(a–c) Representative traces of the whole-cell Na⁺ currents at the voltage step to −100 mV of HEK293 cells expressing either wild type (WT) TRPV5 or the indicated mutants (W583L and W583F) in nominally DVF (nDVF) and divalent-free (DVF) solutions. (d) Representative current-voltage relationship of wild type (WT) TRPV5 (circle), W583F (triangle), and W583L (square) measured from a voltage step protocol of −100 to + 40 mV in the whole cell configuration in DVF solution and current is depicted as percentage of the maximal current at −100 mV (%I_max). (e) Histogram showing the average open probability at −80 mV for wild type (WT) TRPV5, W583F, and W583L. Values are shown as mean ± SEM (N > 7 per condition). Asterisk indicates statistical significance (p < 0.05) compared to WT. (f–h) Cell-attached single channel recordings were measured during a 10 s step to −80 mV (holding potential 0 mV) in wild type (WT) TRPV5 (f), W583F (g), and W583L (h). Bottom panels show the amplitude histograms with a Gaussian fit function corresponding to the closed and open states in the upper panels. (i) The dwell time constants (τ) are extracted via a three-state model of one open (o) and two closed states (C1 and C2). Average τ values of wild type (WT) TRPV5, W583F, and W583L were derived by two-exponential fit of the model-based distribution of dwell times, obtained from single channel recordings (N > 7). Values are shown as mean ± SEM. Asterisk indicates statistical significance (p < 0.05) compared to WT.