Sustained Inhibition of GABA-AT by OV329 Enhances Neuronal Inhibition and Prevents Development of Benzodiazepine Refractory Seizures.

γ-Aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the adult brain which mediates its rapid effects on neuronal excitability via ionotropic GABA receptors. GABA levels in the brain are critically dependent upon GABA-aminotransferase (GABA-AT) which promotes its degradation. Vigabatrin, a low-affinity GABA-AT inhibitor, exhibits anticonvulsant efficacy, but its use is limited due to cumulative ocular toxicity.

Direct activation of KCC2 arrests benzodiazepine refractory status epilepticus and limits the subsequent neuronal injury in mice.

Hyperpolarizing GABAR currents, the unitary events that underlie synaptic inhibition, are dependent upon efficient Cl extrusion, a process that is facilitated by the neuronal specific K/Cl co-transporter KCC2. Its activity is also a determinant of the anticonvulsant efficacy of the canonical GABAR-positive allosteric: benzodiazepines (BDZs). Compromised KCC2 activity is implicated in the pathophysiology of status epilepticus (SE), a medical emergency that rapidly becomes refractory to BDZ (BDZ-RSE).

Spectrin-beta 2 facilitates the selective accumulation of GABA receptors at somatodendritic synapses.

Fast synaptic inhibition is dependent on targeting specific GABAR subtypes to dendritic and axon initial segment (AIS) synapses. Synaptic GABARs are typically assembled from α1-3, β and γ subunits. Here, we isolate distinct GABARs from the brain and interrogate their composition using quantitative proteomics.

KCC2 is required for the survival of mature neurons but not for their development.

The K/Cl cotransporter KCC2 (SLC12A5) allows mature neurons in the CNS to maintain low intracellular Cl levels that are critical in mediating fast hyperpolarizing synaptic inhibition via type A γ-aminobutyric acid receptors (GABARs). In accordance with this, compromised KCC2 activity results in seizures, but whether such deficits directly contribute to the subsequent changes in neuronal structure and viability that lead to epileptogenesis remains to be assessed. Canonical hyperpolarizing GABAR currents develop postnatally, which reflect a progressive increase in KCC2 expression levels and activity.

Calcium currents are enhanced by α2δ-1 lacking its membrane anchor.

The accessory α(2)δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α(2) and δ. All α(2)δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α(2)δ subunits, we have now examined the properties of α(2)δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α(2)δ-1ΔC-term).