H ₂ O ₂ inhibited mouse and human TRPM7 current in a [Mg ²⁺ ] _i -dependent manner without affecting expression on the plasma membrane . (A) Time course of whole-cell currents in the presence of various [Mg²⁺]_i in full-length mTRPM7-overexpressing HEK293 cells. Each symbol represents the mean ± SEM of recordings at [Mg²⁺]_i, which are shown on the right. The currents at 2 min (control; black vertical dashed line) and 6 min (H₂O₂; red vertical dashed line) relative to the mean current at 2 min in the absence of Mg²⁺ are plotted in Fig. 1 D. Each symbol represents the mean ± SEM (vertical bar) of 14, 11, 9, 6, 8, 10, 18, 4, and 6 observations in the absence or presence of 2.8 µM, 7.4 µM, 20.9 µM 0.2 mM, 0.5 mM, 1.0 mM, 2.0 mM, and 5.0 mM [Mg²⁺]_i, respectively. (B) Localization of TRPM7 in full-length mTRPM7-wt–overexpressing HEK293 cells. Control conditions (left), 5-min treatment with H₂O₂ (500 µM; middle), or NMM (100 µM; right). Confocal images show the localization of TRPM7 (green) and nuclei (blue). Scale bar, 20 µm. (C) The effect of oxidative stress induced by H₂O₂ on the hTRPM7 current. Representative traces of whole-cell currents showing the time course of the current inhibition by H₂O₂ (500 µM) in the absence (open circles) or presence (closed circles) of 0.2 mM [Mg²⁺]_i in hTRPM7-expressing HEK293 cells. (D) H₂O₂ (500 µM) inhibited the hTRPM7 current in the presence of 0.2 mM [Mg²⁺]_i (n = 6), but not in the absence of intracellular Mg²⁺ (n = 5). Each bar represents the mean ± SEM (vertical bar). *, P = 0.00040 versus control. (E) NMM (100 µM) inhibited the hTRPM7 current in the presence of 0.2 mM [Mg²⁺]_i (n = 5), but not in the absence of intracellular Mg²⁺ (n = 4). Each bar represents the mean ± SEM (vertical bar). *, P = 0.031 versus control.