FIGURE 3.

Whole-cell SOCE currents in MDA-MB231 ER⁻ and MCF7 ER⁺ breast cancer cells. Wild-type MDA-MB231 cells (A) or wild-type MCF7 cells (C) were dialyzed with a pipette solution containing 12 mm BAPTA to induce store depletion and whole-cell currents were measured in the presence of 10 mm extracellular Ca²⁺. A small inwardly rectifying I_CRAC-like current developed in both cell types. B and D show the current/voltage (I/V) relationships of these Ca²⁺ currents in MDA-MB231 and MCF7 cells, respectively; the sweeps after break-in (black) and those when the current has developed (dark gray) were taken where shown by asterisks. The light gray sweep represents the subtraction of the “black” sweep from the “dark gray” sweep. For MCF7 (C), the trace depicted also shows amplification of the current by switching to a divalent-free (DVF) solution. Monovalent I_CRAC measured in MDA-MB231 cells (E) and MCF7 cells (G) under DVF conditions is shown. Monovalent I_CRAC currents measured from MDA-MB231 show substantial “depotentiation” in DVF solutions while those measured in MCF7 have a less pronounced depotentiation. Monovalent I_CRAC in MCF7 is potentiated by 2-APB and this is accompanied by a change in the I/V relationship of the current (left shift of reversal potential and outward component. H, in this case, background currents were not subtracted). The I/V curve of monovalent I_CRAC in MDA-MB231 is shown in F. Monovalent I_CRAC in MDA-MB231 is inhibited by Gd³⁺ (5 μm) and 2-APB (50 μm), and data are summarized in I (n = 5). J, data summary of monovalent I_CRAC current density in MCF7 cells before and after 2-APB (50 μm) potentiation (n = 7).