title: A new concept: Aβ1-42 generates a hyperfunctional proteolytic NCX3 fragment that delays caspase-12 activation and neuronal death.
abstract: Although the amyloid-β(1-42) (Aβ(1-42)) peptide involved in Alzheimer's disease is known to cause a dysregulation of intracellular Ca(2+) homeostasis, its molecular mechanisms still remain unclear. We report that the extracellular-dependent early increase (30 min) in intracellular calcium concentration ([Ca(2+)](i)), following Aβ(1-42) exposure, caused the activation of calpain that in turn elicited a cleavage of the Na(+)/Ca(2+) exchanger isoform NCX3. This cleavage generated a hyperfunctional form of the antiporter and increased NCX currents (I(NCX)) in the reverse mode of operation. Interestingly, this NCX3 calpain-dependent cleavage was essential for the Aβ(1-42)-dependent I(NCX) increase. Indeed, the calpain inhibitor calpeptin and the removal of the calpain-cleavage recognition sequence, via site-directed mutagenesis, abolished this effect. Moreover, the enhanced NCX3 activity was paralleled by an increased Ca(2+) content in the endoplasmic reticulum (ER) stores. Remarkably, the silencing in PC-12 cells or the knocking-out in mice of the ncx3 gene prevented the enhancement of both I(NCX) and Ca(2+) content in ER stores, suggesting that NCX3 was involved in the increase of ER Ca(2+) content stimulated by Aβ(1-42). By contrast, in the late phase (72 h), when the NCX3 proteolytic cleavage abruptly ceased, the occurrence of a parallel reduction in ER Ca(2+) content triggered ER stress, as revealed by caspase-12 activation. Concomitantly, the late increase in [Ca(2+)](i) coincided with neuronal death. Interestingly, NCX3 silencing caused an earlier activation of Aβ(1-42)-induced caspase-12. Indeed, in NCX3-silenced neurons, Aβ(1-42) exposure hastened caspase-dependent apoptosis, thus reinforcing neuronal cell death. These results suggest that Aβ(1-42), through Ca(2+)-dependent calpain activation, generates a hyperfunctional form of NCX3 that, by increasing Ca(2+) content into ER, delays caspase-12 activation and thus neuronal death.
authors.affiliation: Division of Pharmacology, Department of Neuroscience, National Institute of Neuroscience, School of Medicine, "Federico II" University of Naples, 80131 Naples, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Pannaccione
authors.forename: Agnese
authors.initials: A
authors.lastname: Secondo
authors.forename: Pasquale
authors.initials: P
authors.lastname: Molinaro
authors.forename: Carla
authors.initials: C
authors.lastname: D'Avanzo
authors.forename: Maria
authors.initials: M
authors.lastname: Cantile
authors.forename: Alba
authors.initials: A
authors.lastname: Esposito
authors.forename: Francesca
authors.initials: F
authors.lastname: Boscia
authors.forename: Antonella
authors.initials: A
authors.lastname: Scorziello
authors.forename: Rossana
authors.initials: R
authors.lastname: Sirabella
authors.forename: Sophie
authors.initials: S
authors.lastname: Sokolow
authors.forename: André
authors.initials: A
authors.lastname: Herchuelz
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Di Renzo
authors.forename: Lucio
authors.initials: L
authors.lastname: Annunziato
mesh_terms: D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002154:Calpain / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D006224:Cricetinae; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D004622:Embryo, Mammalian; D004721:Endoplasmic Reticulum / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006624:Hippocampus / Q000166:cytology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010446:Peptide Fragments / Q000494:pharmacology*; D059748:Proteolysis / Q000187:drug effects*; D034622:RNA Interference / Q000502:physiology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D016229:Amyloid beta-Peptides; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D010446:Peptide Fragments; C491101:Slc8a3 protein, mouse; D019831:Sodium-Calcium Exchanger; C075222:amyloid beta-protein (1-42); C110374:sodium-calcium exchanger 1; D004533:Egtazic Acid; D020932:Nerve Growth Factor; D012964:Sodium; D002154:Calpain; D053148:Caspase 3; D002118:Calcium