Role of the Menkes Copper-Transporting ATPase in NMDA Receptor-Mediated Neuronal Toxicity

• Published in: Proceedings of the National Academy of Sciences - PNAS 2006-10, Vol.103 (40), p.14919-14924
• Main Authors: Schlief, Michelle L., West, Tim, Craig, Ann Marie, Holtzman, David M., Gitlin, Jonathan D.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - metabolism; Animals; Apoptosis; Biological Sciences; Calpain - metabolism; Caspase 3; Caspases - metabolism; Cation Transport Proteins - metabolism; Cell death; Cells, Cultured; Chelation therapy; Copper; Copper - metabolism; Copper - pharmacology; Copper-transporting ATPases; Culture Media, Conditioned; Enzyme Activation - drug effects; Female; Humans; Hypoxia; Insults; Male; Menkes kinky hair syndrome; Menkes Kinky Hair Syndrome - pathology; Mice; Mice, Inbred C57BL; N methyl D aspartate receptors; Neurological disorders; Neurons; Neurons - cytology; Neurons - drug effects; Neurons - pathology; Neuroprotective Agents - pharmacology; Neuroscience; Nitric Oxide - biosynthesis; Oxides; Protein Transport - drug effects; Rats; Receptors, N-Methyl-D-Aspartate - metabolism; Rodents; Viability
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0605390103

Menkes disease, a fatal neurodegenerative disorder resulting in seizures, hypotonia, and failure to thrive, is due to inherited loss-of-function mutations in the gene encoding a copper-transporting ATPase (Atp7a) on the X chromosome. Although affected patients exhibit signs and symptoms of copper deficiency, the mechanisms resulting in neurologic disease remain unknown. We recently discovered that Atp7a is required for the production of an NMDA receptor-dependent releasable copper pool within hippocampal neurons, a finding that suggests a role for copper in activity-dependent modulation of synaptic activity. In support of this hypothesis, we now demonstrate that copper chelation exacerbates NMDA-mediated excitotoxic cell death in primary hippocampal neurons, whereas the addition of copper is specifically protective and results in a significant decrease in cytoplasmic$Ca^{2+}$levels after NMDA receptor activation. Consistent with the known neuroprotective effect of NMDA receptor nitrosylation, we show here that this protective effect of copper depends on endogenous nitric oxide production in hippocampal neurons, demonstrating in vivo links among neuroprotection, copper metabolism, and nitrosylation. Atp7a is required for these copper-dependent effects: Hippocampal neurons isolated from newborn$Mo^{br}$mice reveal a marked sensitivity to endogenous glutamate-mediated NMDA receptor-dependent excitotoxicity in vitro, and mild hypoxic/ischemic insult to these mice in vivo results in significantly increased caspase 3 activation and neuronal injury. Taken together, these data reveal a unique connection between copper homeostasis and NMDA receptor activity that is of broad relevance to the processes of synaptic plasticity and excitotoxic cell death.