Cleavage of the plasma membrane Na+/Ca2+ exchanger in excitotoxicity.
In brain ischemia, gating of postsynaptic glutamate receptors and other membrane channels triggers intracellular Ca2+ overload and cell death. In excitotoxic settings, the initial Ca2+ influx through glutamate receptors is followed by a second uncontrolled Ca2+ increase that leads to neuronal demise. Here we report that the major plasma membrane Ca2+ extruding system, the Na+/Ca2+ exchanger (NCX), is cleaved during brain ischemia and in neurons undergoing excitotoxicity. Inhibition of Ca2+-activated proteases (calpains) by overexpressing their endogenous inhibitor protein, calpastatin or the expression of an NCX isoform not cleaved by calpains, prevented Ca2+ overload and rescued neurons from excitotoxic death. Conversely, down-regulation of NCX by siRNA compromised neuronal Ca2+ handling, transforming the Ca2+ transient elicited by non-excitotoxic glutamate concentrations into a lethal Ca2+overload. Thus, proteolytic inactivation of NCX-driven neuronal Ca2+ extrusion is responsible for the delayed excitotoxic Ca2+ deregulation and neuronal death.
Bano
Daniele
D
MRC Toxicology Unit, University of Leicester, Hodgkin Building, Lancaster Road LE1 9HN, Leicester, United Kingdom.
Young
Kenneth W
KW
Guerin
Christopher J
CJ
Lefeuvre
Ros
R
Rothwell
Nancy J
NJ
Naldini
Luigi
L
Rizzuto
Rosario
R
Carafoli
Ernesto
E
Nicotera
Pierluigi
P
D000595:Amino Acid Sequence; D000818:Animals; D002545:Brain Ischemia / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D015853:Cysteine Proteinase Inhibitors; D026901:Membrane Transport Proteins; D017470:Receptors, Glutamate; C491102:Slc8a3 protein, rat; D019831:Sodium-Calcium Exchanger; C033668:calpastatin; D002154:Calpain; D002118:Calcium