The β-amyloid precursor protein controls a store-operated Ca2+ entry in cortical neurons

A polyclonal antibody (APP‐Ab) raised against the extracellular domain of the beta‐amyloid precursor protein (APP) triggers a marked neuronal cell death preceded by activation of Ca2+‐dependent enzymes, neurite degeneration, oxidative stress and nuclear condensation [Mbebi et al. (2002) J. Biol. Chem., 277, 20979–20990]. We have investigated whether activation of APP by this antibody could promote cell death through cellular Ca2+ homeostasis alteration. We carried out time‐lapse recordings of intracellular Ca2+ signals in cultured mice cortical neurons by means of a scanning confocal microscope. When applied in the presence of 2 mm external Ca2+, APP‐Ab elicited a long‐lasting elevation of the intracellular concentration of Ca2+ ([Ca2+]i). Experiments performed in the absence of external Ca2+ showed that APP‐Ab triggers the release of Ca2+ from intracellular stores. The re‐admission of external Ca2+ provides an additional rise of Ca2+ most likely through store‐operated channels. A pretreatment of the cells with pertussis toxin, to inhibit the activity of Gi/Go proteins, or with the phospholipase C inhibitor, 3‐nitrocoumarin, prevented both the APP‐dependent elevation of Ca2+ as well as the APP‐Ab‐mediated cell death. Similarly, the store‐operated channel inhibitors, 2‐APB or SKF‐96365 block both the APP‐Ab‐dependent Ca2+ entry and the APP‐Ab‐mediated cell death. Altogether, our data provide functional evidence that APP can perturb intracellular Ca2+ homeostasis by emptying intracellular Ca2+ stores and triggering Ca2+ entry through store‐operated channels. In response to APP activation, the long‐lasting elevation of [Ca2+]i due to an entry of Ca2+ via store‐operated channels appears as a major event that leads to neuronal cell death.