Early changes in KCC2 phosphorylation in response to neuronal stress result in functional downregulation
Early changes in KCC2 phosphorylation in response to neuronal stress result in functional downregulation
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DOI：
10.1523/jneurosci.3104-06.2007
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发表时间：
2007-02-14
影响因子：
5.3
通讯作者：
Nabekura, Junichi
中科院分区：
文献类型：
--
作者：
Wake, Hiroaki;Watanabe, Miho;Nabekura, Junichi
K+ Cl-协同转运蛋白KCC 2在氯离子稳态和离子型GABA和甘氨酸受体介导的神经元反应中起重要作用。神经元中KCC 2的表达水平决定了神经递质反应是抑制性还是兴奋性。KCC 2表达在发育中的神经元中减少，以及对各种神经元损伤和癫痫模型的响应。我们研究了是否也有直接调制KCC 2活性的磷酸化的变化，在这样的神经元应激。我们研究了在体外神经元应激的不同条件下大鼠海马神经元中KCC 2的酪氨酸磷酸化和酪氨酸磷酸化变化的功能后果。氧化应激（H2 O2）和诱导癫痫发作活动（BDNF）和过度兴奋（0 Mg 2+）导致KCC 2的快速去磷酸化，在KCC 2蛋白或mRNA表达的减少之前。KCC 2的去磷酸化与转运活性的降低和[Cl-]（i）的减少以及KCC 2表面表达的减少相关。操纵KCC 2酪氨酸磷酸化导致神经元活力改变，在体外氧化应激反应。在持续的神经元应激期间，发生功能性KCC 2下调的第二阶段，其对应于KCC 2蛋白表达水平的降低。我们认为，神经元应激诱导KCC 2酪氨酸磷酸化的快速丧失，导致蛋白质的易位和运输活性的功能丧失。对所涉及的机制的进一步理解可能提供用于操纵由不同神经元应激源引起的不可逆损伤的程度的手段。
The K+ Cl- cotransporter KCC2 plays an important role in chloride homeostasis and in neuronal responses mediated by ionotropic GABA and glycine receptors. The expression levels of KCC2 in neurons determine whether neurotransmitter responses are inhibitory or excitatory. KCC2 expression is decreased in developing neurons, as well as in response to various models of neuronal injury and epilepsy. We investigated whether there is also direct modulation of KCC2 activity by changes in phosphorylation during such neuronal stressors. We examined tyrosine phosphorylation of KCC2 in rat hippocampal neurons under different conditions of in vitro neuronal stress and the functional consequences of changes in tyrosine phosphorylation. Oxidative stress (H2O2) and the induction of seizure activity (BDNF) and hyperexcitability (0 Mg2+) resulted in a rapid dephosphorylation of KCC2 that preceded the decreases in KCC2 protein or mRNA expression. Dephosphorylation of KCC2 is correlated with a reduction of transport activity and a decrease in [Cl-](i), as well as a reduction in KCC2 surface expression. Manipulation of KCC2 tyrosine phosphorylation resulted in altered neuronal viability in response to in vitro oxidative stress. During continued neuronal stress, a second phase of functional KCC2 downregulation occurs that corresponds to decreases in KCC2 protein expression levels. We propose that neuronal stress induces a rapid loss of tyrosine phosphorylation of KCC2 that results in translocation of the protein and functional loss of transport activity. Additional understanding of the mechanisms involved may provide means for manipulating the extent of irreversible injury resulting from different neuronal stressors.