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 γ-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.F ast synaptic inhibition in the adult brain is largely mediated via the activation of γ-aminobutyric acid receptors (GABA A Rs). The ability of neurons to maintain low intracellular Cl -is dependent upon the activity of the K + /Cl -cotransporter KCC2. KCC2 expression in the rodent brain is developmentally regulated with low levels evident before birth that then dramatically increase from postnatal day 7 (P7) onwards and correlate with the appearance of hyperpolarizing GABA A R currents (1). KCC2 null mice die shortly after birth, exhibit high levels of intracellular Cl -and anomalous excitatory actions of GABA and glycine, highlighting the vital role of KCC2 (2). In addition to regulating Cl -transport, KCC2 exhibits transporter-independent properties that affect glutamate receptors and dendritic spines (3-6).Status epilepticus (SE) is a state of continuous seizures that is highly lethal and leads to long-term neurological deficits in survivors. A key feature of SE is impaired GABAergic inhibition (7) that manifests clinically as resistance to the GABA A modulator diazepam (8). The prevailing hypothesis of impaired GABAergic signaling during SE is displacement of GABA A receptors from the synapse and a reduction in the number of receptors on the cell surface (9). However, an additional component that could contribute to the compromised inhibition during SE is a buildup of intracellular C...
SummaryLimited availability of human neurons poses a significant barrier to progress in biological and preclinical studies of the human nervous system. Current stem cell-based approaches of neuron generation are still hindered by prolonged culture requirements, protocol complexity, and variability in neuronal differentiation. Here we establish stable human induced neural stem cell (hiNSC) lines through the direct reprogramming of neonatal fibroblasts and adult adipose-derived stem cells. These hiNSCs can be passaged indefinitely and cryopreserved as colonies. Independently of media composition, hiNSCs robustly differentiate into TUJ1-positive neurons within 4 days, making them ideal for innervated co-cultures. In vivo, hiNSCs migrate, engraft, and contribute to both central and peripheral nervous systems. Lastly, we demonstrate utility of hiNSCs in a 3D human brain model. This method provides a valuable interdisciplinary tool that could be used to develop drug screening applications as well as patient-specific disease models related to disorders of innervation and the brain.
GABA A receptors form ClϪ permeable channels that mediate the majority of fast synaptic inhibition in the brain. The K ϩ /Cl Ϫ cotransporter KCC2 is the main mechanism by which neurons establish low intracellular Cl Ϫ levels, which is thought to enable GABAergic inhibitory control of neuronal activity. However, the widely used KCC2 inhibitor furosemide is nonselective with antiseizure efficacy in slices and in vivo, leading to a conflicting scheme of how KCC2 influences GABAergic control of neuronal synchronization. Here we used the selective KCC2 inhibitor VU0463271 [N-cyclopropyl-N-(4-methyl-2-thiazolyl)-2-[(6-phenyl-3-pyridazinyl)thio]acetamide] to investigate the influence of KCC2 function. Application of VU0463271 caused a reversible depolarizing shift in E GABA values and increased spiking of cultured hippocampal neurons. Application of VU0463271 to mouse hippocampal slices under low-Mg 2ϩ conditions induced unremitting recurrent epileptiform discharges. Finally, microinfusion of VU0463271 alone directly into the mouse dorsal hippocampus rapidly caused epileptiform discharges. Our findings indicated that KCC2 function was a critical inhibitory factor ex vivo and in vivo.
Mesial temporal lobe epilepsy (mTLE) is the most common form of epilepsy, believed to arise in part from compromised GABAergic inhibition. The neuronal specific K+/Cl− co-transporter 2 (KCC2) is a critical determinant of the efficacy of GABAergic inhibition and deficits in its activity are observed in mTLE patients and animal models of epilepsy. To test if reductions of KCC2 activity directly contribute to the pathophysiology of mTLE, we locally ablated KCC2 expression in a subset of principal neurons within the adult hippocampus. Deletion of KCC2 resulted in compromised GABAergic inhibition and the development of spontaneous, recurrent generalized seizures. Moreover, local ablation of KCC2 activity resulted in hippocampal sclerosis, a key pathological change seen in mTLE. Collectively, our results demonstrate that local deficits in KCC2 activity within the hippocampus are sufficient to precipitate mTLE.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.