期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：11
页码：3523-3528
DOI：10.1073/pnas.1415126112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceStatus epilepticus (SE) is defined as a state of continuous unremitting seizures that often exhibits underlying deficits in neuronal inhibition mediated by GABAA receptors. The efficacy of neuronal inhibition is critically dependent on the activity of the K+/Cl- cotransporter KCC2, which allows neurons to maintain low intracellular Cl- levels. KCC2 activity is enhanced by phosphorylation of residue serine 940, and here we show that SE leads to rapid dephosphorylation of this key regulatory residue. Moreover, we demonstrate that deficits in S940 phosphorylation directly contribute to the onset and severity of SE. Collectively, our results suggest that deficits in KCC2 activity directly contribute to the pathophysiology of SE. The K+/Cl- cotransporter (KCC2) allows adult neurons to maintain low intracellular Cl- levels, which are a prerequisite for efficient synaptic inhibition upon activation of {gamma}-aminobutyric acid receptors. Deficits in KCC2 activity are implicated in epileptogenesis, but how increased neuronal activity leads to transporter inactivation is ill defined. In vitro, the activity of KCC2 is potentiated via phosphorylation of serine 940 (S940). Here we have examined the role this putative regulatory process plays in determining KCC2 activity during status epilepticus (SE) using knockin mice in which S940 is mutated to an alanine (S940A). In wild-type mice, SE induced by kainate resulted in dephosphorylation of S940 and KCC2 internalization. S940A homozygotes were viable and exhibited comparable basal levels of KCC2 expression and activity relative to WT mice. However, exposure of S940A mice to kainate induced lethality within 30 min of kainate injection and subsequent entrance into SE. We assessed the effect of the S940A mutation in cultured hippocampal neurons to explore the mechanisms underlying this phenotype. Under basal conditions, the mutation had no effect on neuronal Cl- extrusion. However, a selective deficit in KCC2 activity was seen in S940A neurons upon transient exposure to glutamate. Significantly, whereas the effects of glutamate on KCC2 function could be ameliorated in WT neurons with agents that enhance S940 phosphorylation, this positive modulation was lost in S940A neurons. Collectively our results suggest that phosphorylation of S940 plays a critical role in potentiating KCC2 activity to limit the development of SE.
