Enhancement of BK(Ca) 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 (H(2)O(2)) 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 hbeta1 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 H(2)O(2)-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 H(2)O(2)-induced BK(Ca) channel activation. These results demonstrated that PTEN regulated the H(2)O(2)-induced BK(Ca) channel activation through phosphatidylinositol 3-phosphatse. However, the inhibitory effect of PTEN on the H(2)O(2)-induced BK(Ca) channel activation was attenuated when cells were treated with H(2)O(2) at concentrations higher than 100 microM or at 100 microM 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 ([Ca(2+)](i)) induced by H(2)O(2) was also inhibited. These findings may elucidate a new mechanism for H(2)O(2)-induced BK(Ca) channel activation and provide some evidences for the role of PTEN on vasodilation induced by H(2)O(2).