Journal
JOURNAL OF NEUROSCIENCE
Volume 25, Issue 48, Pages 11184-11193Publisher
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.3370-05.2005
Keywords
channel; epilepsy; hypoxia; ion channels; hippocampus; neurons; neuroprotection
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Funding
- NCI NIH HHS [P01 CA095616] Funding Source: Medline
- NCRR NIH HHS [C06 RR-12088-01, C06 RR012088] Funding Source: Medline
- NINDS NIH HHS [R01 NS042225, NS42225] Funding Source: Medline
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Ischemic stroke is often accompanied by neuronal hyperexcitability (i.e., seizures), which aggravates brain damage. Therefore, suppressing stroke- induced hyperexcitability and associated excitoxicity is a major focus of treatment for ischemic insults. Both ATP-dependent and Ca2+-activated K+ channels have been implicated in protective mechanisms to suppress ischemia-induced hyperexcitability. Here we provide evidence that the localization and function of Kv2.1, the major somatodendritic delayed rectifier voltage-dependent K+ channel in central neurons, is regulated by hypoxia/ ischemia-induced changes in metabolic state and intracellular Ca2(+) levels. Hypoxia/ischemia in rat brain induced a dramatic dephosphorylation of Kv2.1 and the translocation of surface Kv2.1 from clusters to a uniform localization. In cultured rat hippocampal neurons, chemical ischemia (CI) elicited a similar dephosphorylation and translocation of Kv2.1. These events were reversible and were mediated by Ca2(+) release from intracellular stores and calcineurin-mediated Kv2.1 dephosphorylation. CI also induced a hyperpolarizing shift in the voltage-dependent activation of neuronal delayed rectifier currents (I-K), leading to enhanced IK and suppressed neuronal excitability. The IK blocker tetraethylammonium reversed the ischemia-induced suppression of excitability and aggravated ischemic neuronal damage. Our results show that Kv2.1 can act as a novel Ca2(+)-and metabolic state-sensitive K+ channel and suggest that dynamic modulation of I-K/Kv2.1 in response to hypoxia/ischemia suppresses neuronal excitability and could confer neuroprotection in response to brief ischemic insults.
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