TRPM7 is a non-selective cation channel which permeates Ca2+ and Mg2+ and plays important roles in fundamental cellular functions, including Mg2+ homeostasis, proliferation, migration, and viability. In various cell types, it has been reported that during whole-cell patch-clamp recordings, low [Mg2+]i conditions induced activation of cationic currents called magnesium inhibited cation (MIC) currents, which is considered to be endogenous TRPM7 currents. We previously demonstrated that MIC currents were activated by lowering [Mg2+]i under the whole cell recordings and inhibited by hydrogen peroxide in white adipocytes isolated from mice (ref.1). In the present study, we investigated whether or not hetelorogously overexpressed murine TRPM7 is inhibited by oxidative stress as endogenous MIC currents. First, to clarify if the molecular identity of MIC channel was TRPM7, shRNAs for human TRPM7 were introduced to HEK293T cells which express MIC currents similar to that in white adipocytes. Introduction of shRNAs for human TRPM7 reduced both the expression of MIC currents and TRPM7 mRNA to ~30% of control cells. Thus TRPM7 might be responsible for MIC currents. Next murine TRPM7 variants 1 and 2 were cloned from mouse white adipose tissue and then tetracycline-inducible HEK293 cell lines for each variants were established. Under the whole-cell recordings, both veriant 1 or 2 of TRPM7 showed similar properties to endogenous MIC currents in white adipocytes and HEK293T cells; outward rectification in the presence of extracellular divalent cations, liner I-V relationships in the absence of extracellular divalent cations, and inhibition by 2-aminoethoxydiphenil borate (100 or 200μM) and N-methyl maleimide (100 μM). On the other hand, hydrogen peroxide (500 μM) could not inhibit TRPM7 currents when Mg2+ was eliminated from intracellular solutions in both of variants of TRPM7. However when [Mg2+]i was added to the intracellular solution, TRPM7 currents were inhibited by hydrogen peroxide concentration dependently. The inhibition was irreversible during whole-cell recordings. From these results, it is suggested that oxidation of TRPM7 or its regulatory proteins by hydrogen peroxide inactivate TRPM7, possibly by sensitizing it to intracellular Mg2+.