EAAC1 gene deletion alters zinc homeostasis and exacerbates neuronal injury after transient cerebral ischemia.

EAAC1 is a neuronal glutamate and cysteine transporter. EAAC1 uptake of cysteine provides substrate for neuronal glutathione synthesis, which plays a key role in both antioxidant defenses and intracellular zinc binding. Here we evaluated the role of EAAC1 in neuronal resistance to ischemia. EAAC1(-/-) mice subjected to transient cerebral ischemia exhibited twice as much hippocampal neuronal death as wild-type mice and a corresponding increase in microglial activation. EAAC1(-/-) mice also had elevated vesicular and cytosolic zinc concentrations in hippocampal CA1 neurons and an increased zinc translocation to postsynaptic neurons after ischemia. Treatment of the EAAC1(-/-) mice with N-acetyl cysteine restored neuronal glutathione concentrations and normalized basal zinc levels in the EAAC1(-/-) mice. Treatment of the EAAC1(-/-) mice with either N-acetyl cysteine or with zinc chelators reduced ischemia-induced zinc translocation, superoxide production, and neuron death. These findings suggest that cysteine uptake by EAAC1 is important for zinc homeostasis and neuronal antioxidant function under ischemic conditions.