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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
113
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.