title: Exploring the structure of the voltage-gated Na+ channel by an engineered drug access pathway to the receptor site for local anesthetics.
abstract: Despite the availability of several crystal structures of bacterial voltage-gated Na(+) channels, the structure of eukaryotic Na(+) channels is still undefined. We used predictions from available homology models and crystal structures to modulate an external access pathway for the membrane-impermeant local anesthetic derivative QX-222 into the internal vestibule of the mammalian rNaV1.4 channel. Potassium channel-based homology models predict amino acid Ile-1575 in domain IV segment 6 to be in close proximity to Lys-1237 of the domain III pore-loop selectivity filter. The mutation K1237E has been shown previously to increase the diameter of the selectivity filter. We found that an access pathway for external QX-222 created by mutations of Ile-1575 was abolished by the additional mutation K1237E, supporting the notion of a close spatial relationship between sites 1237 and 1575. Crystal structures of bacterial voltage-gated Na(+) channels predict that the side chain of rNaV1.4 Trp-1531 of the domain IV pore-loop projects into the space between domain IV segment 6 and domain III pore-loop and, therefore, should obstruct the putative external access pathway. Indeed, mutations W1531A and W1531G allowed for exceptionally rapid access of QX-222. In addition, W1531G created a second non-selective ion-conducting pore, bypassing the outer vestibule but probably merging into the internal vestibule, allowing for control by the activation gate. These data suggest a strong structural similarity between bacterial and eukaryotic voltage-gated Na(+) channels.
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Peter
authors.initials: P
authors.lastname: Lukacs
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Vaibhavkumar S
authors.initials: VS
authors.lastname: Gawali
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Rene
authors.initials: R
authors.lastname: Cervenka
authors.affiliation: Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, UZA 2, A-1090 Vienna, Austria.
authors.forename: Song
authors.initials: S
authors.lastname: Ke
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Xaver
authors.initials: X
authors.lastname: Koenig
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Lena
authors.initials: L
authors.lastname: Rubi
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Touran
authors.initials: T
authors.lastname: Zarrabi
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and.
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Hilber
authors.affiliation: Department of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, UZA 2, A-1090 Vienna, Austria.
authors.forename: Anna
authors.initials: A
authors.lastname: Stary-Weinzinger
authors.affiliation: From the Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria and hannes.todt@meduniwien.ac.at.
authors.forename: Hannes
authors.initials: H
authors.lastname: Todt
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D015640:Ion Channel Gating; D056004:Molecular Dynamics Simulation; D016297:Mutagenesis, Site-Directed; D018408:Patch-Clamp Techniques; D011487:Protein Conformation; D015222:Sodium Channels / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics; D014982:Xenopus laevis
chemical_list: D000779:Anesthetics, Local; D015222:Sodium Channels
keywords: Anesthetic; Docking; Molecular Modeling; Molecular Pharmacology; Mutagenesis; Patch Clamp Electrophysiology; Permeability; Protein Design; Protein Structure; Sodium Channel