Pharmacology

Biography

Biography: J Amin

Abstract

Anesthetic molecules act on synaptic transmission via the allosteric modulation of ligand-gated chloride channels, such as hetero-oligomeric α₁β₂γ₂ GABA_A receptors. To elucidate the overall activation paradigm via allosteric versus orthosteric sites, we used highly homologous, but homooligomeric, ρ₁ receptors that are contrastingly insensitive to anesthetics and respond partially to several full GABA α₁β₂γ₂ receptor agonists. Here, we co-expressed varying ratios of RNAs encoding the wild-type and the mutated ρ₁ subunits, which are anesthetic-sensitive and respond with full efficacy to partial GABA agonists, to generate distinct ensembles of receptors containing five, four, three, two, one, or zero mutated subunits. Using these experiments, we then demonstrate that, in the pentamer, three anesthetic-sensitive ρ₁ subunits are needed to impart full efficacy to the partial GABA agonists. By contrast, five anesthetic-sensitive subunits are required for direct activation by anesthetics alone, and only one anesthetic-sensitive subunit is sufficient to confer the anesthetic-dependent potentiation to the GABA current. In conclusion, our data indicate that GABA and anesthetics holistically activate the GABA_A ρ₁ receptor through distinct subunit level rearrangements and suggest that in contrast to the global impact of GABA via orthosteric sites, the force of anesthetics through allosteric sites may not propagate to the neighboring subunits and, thus, may have only a local and limited effect on the ρ₁ GABA_A receptor model system.