Details

Autor(en) / Beteiligte

• Soh, Ming S
• Estrada-Mondragon, Argel
• Durisic, Nela
• Keramidas, Angelo
• Lynch, Joseph W

Titel

Probing the Structural Mechanism of Partial Agonism in Glycine Receptors Using the Fluorescent Artificial Amino Acid, ANAP

Ist Teil von

• ACS chemical biology, 2017-03, Vol.12 (3), p.805-813

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2017

Quelle

MEDLINE

Beschreibungen/Notizen

• The efficacy of an agonist at a pentameric ligand-gated ion channel is determined by the rate at which it induces a conformational change from the resting closed state to a preopen (“flip”) state. If the ability of an agonist to promote this isomerization is sufficiently low, then it becomes a partial agonist. As partial agonists at pentameric ligand-gated ion channels show considerable promise as therapeutics, understanding the structural basis of the resting-flip-state isomerization may provide insight into therapeutic design. Accordingly, we sought to identify structural correlates of the resting-flip conformational change in the glycine receptor chloride channel. We used nonsense suppression to introduce the small, fluorescent amino acid, 3-(6-acetylnaphthalen-2-ylamino)-2-aminopropanoic acid (ANAP), into specific sites in the extracellular and transmembrane domains. Then, under voltage-clamp conditions in Xenopus oocytes, we simultaneously quantified current and fluorescence responses induced by structurally similar agonists with high, medium, and low efficacies (glycine, β-alanine, and taurine, respectively). Analyzing results from nine ANAP-incorporated sites, we show that glycine receptor activation by agonists with graded efficacies manifests structurally as correspondingly graded movements of the β1−β2 loop, the β8−β9 loop, and the Cys-loop from the extracellular domain and the TM2–TM3 linker in the transmembrane domain. We infer that the resting-flip transition involves an efficacy-dependent molecular reorganization at the extracellular-transmembrane domain interface that primes receptors for efficacious opening.