Enhancement of BKCa channel activity induced by hydrogen peroxide: Involvement of lipid phosphatase activity of PTEN

Large-conductance calcium and voltage-dependent potassium (BK_Ca) channel is an important determinant of vascular tone. It is activated by hydrogen peroxide (H₂O₂) which occurs in various physiological and pathological processes. However, the regulation mechanism is not fully understood. In the present study, the mSlo in the presence or absence of hβ1 were cotransfected with the PTEN_wt, PTEN_C124S, PTEN_G129E in HEK 293 cells. Typical BK_Ca channel currents could be recorded in cell-attached configurations. We found that PTEN_wt reduced the H₂O₂-induced BK_Ca channel activation during the initial 10 min treatment. In contrast, coexpression with catalytically inactive PTEN_C124S/PTEN_G129E mutants that lack lipid phosphatase activity produced no regulation on the H₂O₂-induced BK_Ca channel activation. These results demonstrated that PTEN regulated the H₂O₂-induced BK_Ca channel activation through phosphatidylinositol 3-phosphatse. However, the inhibitory effect of PTEN on the H₂O₂-induced BK_Ca channel activation was attenuated when cells were treated with H₂O₂ at concentrations higher than 100 μM or at 100 μM for long-term treatment. In addition, the p-AKT expression level in PTEN_wt overexpressing cells was lower than that in control cells, and the increase of cytoplasmic free calcium concentration (Ca²⁺]_i) induced by H₂O₂ was also inhibited. These findings may elucidate a new mechanism for H₂O₂-induced BK_Ca channel activation and provide some evidences for the role of PTEN on vasodilation induced by H₂O₂.