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P3‐342: Amyloid‐mediated NCX3 cleavage by calpain is an early and toxic event
Author(s) -
Noble Wendy,
Garwood Claire,
Hanger Diane P.,
Anderton Brian H.
Publication year - 2008
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2008.05.1911
Subject(s) - calpain , calcium , cleavage (geology) , neurotoxicity , calcium in biology , chemistry , voltage dependent calcium channel , blot , microbiology and biotechnology , neurodegeneration , biochemistry , biology , medicine , toxicity , enzyme , organic chemistry , gene , disease , paleontology , fracture (geology)
Background: amyloid activates calpain and there are sustained increases in calpain activation early in AD, suggesting that this may be a primary neurotoxic event. Since a tonic level of calpain activation is physiologically important, it is essential to determine what causes increased intraneuronal calcium concentrations and calpain over-activation in disease. Calpain was recently shown to cleave and thus inactivate the sodium/calcium exchanger 3 (NCX3), preventing calcium extrusion from neurons and causing neurotoxicity. Methods: We have used primary neuronal cultures to determine the effects of -amyloid treatment on calpain activation and NCX3 cleavage in vitro. Mechanisms have been explored using specific inhibitors of calcium channels, intraneuronal calcium release and NCX3 reverse-mode antagonists. Calpain-mediated protein cleavage has been examined in postmortem human AD and control brain by western blotting. Finally, the effects of -amyloid on neuronal calcium sensors, downstream of NCX3, have been assessed by western blotting and immunofluorescence. Results: We find that A induces NCX3 cleavage in minutes in primary neuronal cultures and that this cleavage can be blocked by calpain inhibition and is variably modulated by regulating calcium influx and the release of calcium from intraneuronal stores. We find calpain inhibition is protective against A -induced neurotoxicity in vitro, suggesting that NCX3 cleavage may be an early pathogenic effect of A . These effects are, at least partially, mediated by altered expression and localisation of neuronal calcium sensors in response to A . Finally, analysis of AD brain reveals significantly increased calpain activation and NCX3 cleavage compared to control brain. Increased NCX3 cleavage was not found in other tauopathies lacking amyloid pathology, suggesting that cleavage of NCX3 in AD is amyloid-mediated. Conclusions: These findings illustrate a novel and important mechanism of calpain activation and show the impact of calpain cleavage of a specific sodium/ calcium exchanger (NCX3) during A -induced neurodegeneration. NCX3 may thus represent a potential novel therapeutic target for the treatment of AD and related amyloidopathies.