Figure 1.

Cytoplasmic (A) and mitochondrial (B) Ca²⁺ homeostasis in control and Bcl-2–overexpressing HeLa cells. Parallel batches of HeLa cells were either cotransfected with the appropriate AEQ chimera (cytAEQ and mtAEQ for monitoring the cytoplasm and the mitochondria, respectively) and Bcl-2 (Bcl-2), or transfected with the AEQ chimera alone (control). 36 h after transfection, the measurement of AEQ luminescence was carried out and calibrated into [Ca²⁺] values, as described in Materials and Methods. Where indicated, the cells, perfused with KRB, were challenged with 100 μM ATP added to the same buffer. These and the following traces are representative of ten experiments that gave similar results.