Figure 1

Akt-modulation of the Ca²⁺ signal in COS7, but not in SH-SY 5Y cells. (a) IP₃R levels in COS7, HeLa and SH-SY 5Y cells. HeLa cells were used as reference because they possess both type I and III IP₃Rs; the increment of p-Akt S473 levels reflects an effective Akt activation after m/p-Akt overexpression. (b) ER Ca²⁺ measurements in mock-transfected and m/p-Akt-overexpressing COS7 cells. To induce Ca²⁺ release from ER, cells were challenged with ATP, an agonist that, through interaction with G-protein-coupled receptors, evokes a rapid discharge from IP₃Rs. Akt activation markedly modulates ER Ca²⁺ kinetics (red trace), diminishing the amount of Ca²⁺ released, quantified after analysis of maximum rate of calcium release during agonist stimulation (see bars inside the dotted circle). (c) Experiments analogous to b were carried out in SH-SY 5Y cells. In these cells, the agonist used is Cch. (d) Mitochondrial Ca²⁺ homeostasis modulation after Akt activation in COS7 cells and (e) in SH-SY 5Y cells. (f) Cytosolic Ca²⁺ homeostasis in control and m/p-Akt-overexpressing COS7 and (g) SH-SY 5Y cells. Where indicated, cells were stimulated with 100 μM ATP or 500 μM Cch. The bars in d–g indicate the levels of Ca²⁺ uptake, expressed in percentage, control assumed as 100%. All traces are from single representative experiments and [Ca²⁺] are presented as means of at least 20 experiments (±S.E.)