FIGURE 2.
Activities of single calcium channels in HEK293 cells transfected with STIM1 siRNA or control siRNA. Recordings were made in the cell-attached patch clamp configuration at a membrane potential of −70 mV. In all experiments, the pipette solution contained 105 mm Ba2+ as a charge carrier. Representative fragments of the recordings are shown. A, average current-voltage relationships of Imin (dotted line solid line), INS (solid line), and Imax (dashed line) channels in control HEK293 cells. The fit to the data points yielded single-channel conductances of 1.2 pS for Imin, 5 pS for INS, and 17 pS for Imax. B and C, bath application of 1 μm Tg to cell-attached patches induced (B) Imax channel and (C) INS channel activity in HEK293 cells transfected with nonspecific siRNA (Control). D, Imin channel activity in STIM1 siRNA-transfected HEK293 cells (STIM1 siRNA) induced by bath application of 1 μm Tg and subsequent addition of 100 μm UTP. A fragment of the recording on an expanded time scale is shown at the bottom. E, the same as in D for control cells. F, occurrence frequencies of Imin, Imax, and INS channels in HEK293 and STIM1 siRNA cells. The cells were stimulated with Tg in cell-attached patches.