The Juvenile Myoclonic Epilepsy GABAA Receptor 1 Subunit Mutation A322D Produces Asymmetrical, Subunit Position-Dependent Reduction of Heterozygous Receptor Currents and 1 Subunit Protein Expression

摘要: Individuals with autosomal dominant juvenile myoclonic epilepsy are heterozygous for a GABAA receptor α1 subunit mutation (α1A322D). αβγ subunits arranged around the pore in β-α-β-α-γ sequence (counterclockwise from synaptic cleft). Therefore, each has different adjacent subunits, and expression of α1(A322D), β, γ could produce receptors four arrangements: β-α1-β-α1-γ (wild type); β-α1(A322D)-β-α1-γ (Hetβαβ); β-α1-β-α1(A322D)-γ (Hetβαγ);β-α1(A322D)-β-α1(A322D)-γ (homozygous). Expression 1:1 mixture wild-type andα1(A322D) β2S γ2S (heterozygous transfection) produced smaller currents than wild type much larger homozygous mutant transfections. Western blot biotinylation assays demonstrated that amount total surface transfections was also intermediate between those α1(A322D) mutations were then made covalently tethered triplet (γ2S-β2S-α1) tandem (β2S-α1) concatamers to target selectively asymmetric subunits. Coexpression resulted either Hetβαβ or Hetβαγ receptors. currents. Furthermore, contained less β-α concatamer but more both Thus, whole-cell protein α1(A322D)β2Sγ2S depended on position subunit, individuals likely result primarily little contribution