Fig. 3.

Relationship between halide-induced inhibition of TRPM7 and intracellular Mg·ATP, extracellular divalent-free- or acidic pH conditions. Whole-cell patch clamp experiments were performed in tetHEKTRPM7 cells. Voltage ramps were from −100 to +100 mV over 50 ms and acquired at 0.5 Hz. TRPM7 current amplitudes were assessed at +80 mV, averaged and normalized to cell size (in pF). Error bar indicates SEM. For detailed solution composition see “Methods”. a Dose–response curves of TRPM7 established as a function of increasing intracellular chloride concentrations and at various fixed intracellular Mg·AT P. Each dose–response curve was calculated as in Fig. 1e and normalized to 1 by dividing with Y_max (n = 4–8). All the Hill coefficients of the dose–response curves were fixed to −3. b Dose–response curves of TRPM7 plotted as a function of intracellular bromide concentration at various fixed Mg·ATP. Each dose–response curve was calculated as in Fig. 1e and normalized to 1 by dividing with Y_max (n = 4–8). Hill coefficients were fixed to −3. c Comparison of dose–response curves as a function of iodide concentrations at different fixed Mg·ATP. Each dose–response curve was calculated as in Fig. 1e and normalized to 1 by dividing with Y_max (n = 4–8). Best-fit Hill coefficients approximated −5 and were therefore fixed to −5. d Effects of external acidic solution (pH 4.0) on TRPM7 inward currents when perfusing cells with intracellular solution containing either 14 mM (open circles) or 154 mM (solid circles) Cl⁻. Intracellular Mg²⁺ was chelated to zero mM by adding 10 mM EDTA (n = 6–8). The black bar indicates application time from 200 to 300 s. e Effects of external acidification (pH 4.0) on TRPM7 inward current while perfusing cells with internal solution containing 14 mM (open circles) or 154 mM (solid circles) Cl⁻. Intracellular Mg²⁺ was clamped to 800 μM (n = 6–8). f Application of divalent-free external solution (DVF) on fully developed TRPM7 currents assessed at −80 mV and cells perfused with internal solution containing either 14 mM (open circles) or 154 mM (solid circles) Cl⁻. Intracellular Mg²⁺ was chelated to close to 0 mM by adding 10 mM EDTA (n = 6–8). g Application of a DVF solution on TRPM7 inward currents assessed at −80 mV where cells were perfused with internal solution containing either 14 or 154 mM Cl⁻. Intracellular Mg2+ was clamped to 800 μM (n = 6–8). h Representative I/V relationships for TRPM7 currents assessed in the presence of intracellular 14 mM (black trace) Cl⁻ or 154 mM (red trace) Cl⁻ in response to acidic pH as shown in panel e. All I/V curves were extracted at 210 s into the experiment. g Representative I/V curves for TRPM7 in the presence of intracellular 14 mM (black trace) Cl⁻ and 154 mM (red trace) Cl⁻ in response to DVF conditions as described in panel g. All I/V curves were extracted at 210 s into the experiment