Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

69-POS Board 69 Molecular Insights into Kv1.2 Channel Modulation by General Anesthetic Sevoflurane

Leticia Stock , Juliana Hosoume, Werner Treptow. Universidade de Brasilia, Brasilia, DF, Brazil.

Anesthetics have been routinely used in medical procedures for almost two centuries. Every year millions of people undergo surgery with anesthesia, attesting to its irrevocable importance to modern medicine. Dispite its role in health and relatively safe administration, the molecular mechanism leading to endpoint of anesthesia remains unknown. Early propositions argued anesthetics would act by altering cellular membranes’ physicochemical properties. Nonetheless, studies favoring allosteric modulation of multiple proteins targets are now challenging the indirect membrane-mediated hypothesis. One such target, evidenced by electrophysiolgy and in vivo experiments, is voltage-gated channel Kv1.2. Investigations on sevoflurane, a major general anesthetic, suggest it potentiates Kv1.2 by binding to multiple independent sites, causing a left- shift to the conductance-per-voltage (GV) curve, while also increasing its maximum conductance. We wish to identify Kv1.2 sevoflurane binding sites and quantify to what extent can macroscopically measured channel potentiation be recovered from direct modulation. For that, we’ve developed a theoretical framework to investigate small ligand concentration-dependent interaction to multiple saturable binding sites which allow for thorough calculation of the functional impact of such biding to equilibrium between well-known conformational states, i.e. open and closed Kv1.2 structures. Local anesthetic distribution and binding affinities are evaluated by a combination of docking and free-energy-perturbation calculations. We find that sevoflurane binds Kv1.2 in a conformation-depend manner. Also, the calculated open-conformation stabilization effected by the ligand agrees with experimental measurements. Our results successfully recover GV leftward shift from microscopic data alone. Key binding sites identified by the docking-FEP strategy are found to be in close proximity to residues identified as relevant by recent photolabeling and mutagenesis experiments. Altogether, results support the direct modulation hypothesis and contributes to understanding sevoflurane effects from a molecular standpoint. The theory is also general and could be applied to various ligand- receptor systems.

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