Coexpression and characterization of the human large-conductance Ca(2+)-activated K (+) channel alpha + beta1 subunits in HEK293 cells.

Large-conductance Ca(2+)-activated K(+) channel is formed by a tetramer of the pore-forming alpha-subunit and distinct accessory beta-subunits (beta1-beta4) which contribute to BK(Ca) channel molecular diversity. Accumulative evidences indicate that not only alpha-subunit alone but also the alpha + beta subunit complex and/or beta-subunit might play an important role in modulating various physiological functions in most mammalian cells. To evaluate the detailed pharmacological and biophysical properties of alpha + beta1 subunit complex or beta1-subunit in BK(Ca) channel, we established an expression system that reliably coexpress hSloalpha + beta1 subunit complex in HEK293 cells. The coexpression of hSloalpha + beta1 subunit complex was evaluated by western blotting and immunolocalization, and then the single-channel kinetics and pharmacological properties of expressed hSloalpha + beta1 subunit complex were investigated by cell-attached and outside-out patches, respectively. The results in this study showed that the expressed hSloalpha + beta1 subunit complex demonstrated to be fully functional for its typical single-channel traces, Ca(2+)-sensitivity, voltage-dependency, high conductance (151 +/- 7 pS), and its pharmacological activation and inhibition.