scholarly journals Structures of closed and open states of a voltage-gated sodium channel

2017 ◽  
Vol 114 (15) ◽  
pp. E3051-E3060 ◽  
Author(s):  
Michael J. Lenaeus ◽  
Tamer M. Gamal El-Din ◽  
Christopher Ing ◽  
Karthik Ramanadane ◽  
Régis Pomès ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Full Range ◽  
Structural Basis ◽  
Ion Permeation ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Gating Mechanism ◽  
Activation Gate ◽  
Open States

Bacterial voltage-gated sodium channels (BacNavs) serve as models of their vertebrate counterparts. BacNavs contain conserved voltage-sensing and pore-forming domains, but they are homotetramers of four identical subunits, rather than pseudotetramers of four homologous domains. Here, we present structures of two NaVAb mutants that capture tightly closed and open states at a resolution of 2.8–3.2 Å. Introduction of two humanizing mutations in the S6 segment (NaVAb/FY: T206F and V213Y) generates a persistently closed form of the activation gate in which the intracellular ends of the four S6 segments are drawn tightly together to block ion permeation completely. This construct also revealed the complete structure of the four-helix bundle that forms the C-terminal domain. In contrast, truncation of the C-terminal 40 residues in NavAb/1–226 captures the activation gate in an open conformation, revealing the open state of a BacNav with intact voltage sensors. Comparing these structures illustrates the full range of motion of the activation gate, from closed with its orifice fully occluded to open with an orifice of ∼10 Å. Molecular dynamics and free-energy simulations confirm designation of NaVAb/1–226 as an open state that allows permeation of hydrated Na+, and these results also support a hydrophobic gating mechanism for control of ion permeation. These two structures allow completion of a closed–open–inactivated conformational cycle in a single voltage-gated sodium channel and give insight into the structural basis for state-dependent binding of sodium channel-blocking drugs.

scholarly journals Tracking S4 movement by gating pore currents in the bacterial sodium channel NaChBac

2014 ◽  
Vol 144 (2) ◽  
pp. 147-157 ◽  
Author(s):  
Tamer M. Gamal El-Din ◽  
Todd Scheuer ◽  
William A. Catterall
Keyword(s):  
Membrane Potential ◽  
Sodium Channel ◽  
Sodium Channels ◽  
Voltage Dependence ◽  
Periodic Paralysis ◽  
Membrane Potentials ◽  
Structural Basis ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Gating Charges

Voltage-gated sodium channels mediate the initiation and propagation of action potentials in excitable cells. Transmembrane segment S4 of voltage-gated sodium channels resides in a gating pore where it senses the membrane potential and controls channel gating. Substitution of individual S4 arginine gating charges (R1–R3) with smaller amino acids allows ionic currents to flow through the mutant gating pore, and these gating pore currents are pathogenic in some skeletal muscle periodic paralysis syndromes. The voltage dependence of gating pore currents provides information about the transmembrane position of the gating charges as S4 moves in response to membrane potential. Here we studied gating pore current in mutants of the homotetrameric bacterial sodium channel NaChBac in which individual arginine gating charges were replaced by cysteine. Gating pore current was observed for each mutant channel, but with different voltage-dependent properties. Mutating the first (R1C) or second (R2C) arginine to cysteine resulted in gating pore current at hyperpolarized membrane potentials, where the channels are in resting states, but not at depolarized potentials, where the channels are activated. Conversely, the R3C gating pore is closed at hyperpolarized membrane potentials and opens with channel activation. Negative conditioning pulses revealed time-dependent deactivation of the R3C gating pore at the most hyperpolarized potentials. Our results show sequential voltage dependence of activation of gating pore current from R1 to R3 and support stepwise outward movement of the substituted cysteines through the narrow portion of the gating pore that is sealed by the arginine side chains in the wild-type channel. This pattern of voltage dependence of gating pore current is consistent with a sliding movement of the S4 helix through the gating pore. Through comparison with high-resolution models of the voltage sensor of bacterial sodium channels, these results shed light on the structural basis for pathogenic gating pore currents in periodic paralysis syndromes.

scholarly journals Assessing the Structural Basis of μ-Conotoxin KIIIA Inhibition of the Voltage-Gated Sodium Channel Nav1.7

2018 ◽  
Vol 114 (3) ◽  
pp. 635a ◽  
Author(s):  
Ian H. Kimball ◽  
Phuong T. Nguyen ◽  
Jon T. Sack ◽  
Vladimir Yarov-Yarovoy
Keyword(s):  
Sodium Channel ◽  
Structural Basis ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated

scholarly journals Fluorine-19 NMR and computational quantification of isoflurane binding to the voltage-gated sodium channel NaChBac

2016 ◽  
Vol 113 (48) ◽  
pp. 13762-13767 ◽  
Author(s):  
Monica N. Kinde ◽  
Vasyl Bondarenko ◽  
Daniele Granata ◽  
Weiming Bu ◽  
Kimberly C. Grasty ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Binding Sites ◽  
Ion Selectivity ◽  
Selectivity Filter ◽  
Inactivation Kinetics ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Binding Data ◽  
Quantitative Analyses

Voltage-gated sodium channels (NaV) play an important role in general anesthesia. Electrophysiology measurements suggest that volatile anesthetics such as isoflurane inhibit NaVby stabilizing the inactivated state or altering the inactivation kinetics. Recent computational studies suggested the existence of multiple isoflurane binding sites in NaV, but experimental binding data are lacking. Here we use site-directed placement of19F probes in NMR experiments to quantify isoflurane binding to the bacterial voltage-gated sodium channel NaChBac.19F probes were introduced individually to S129 and L150 near the S4–S5 linker, L179 and S208 at the extracellular surface, T189 in the ion selectivity filter, and all phenylalanine residues. Quantitative analyses of19F NMR saturation transfer difference (STD) spectroscopy showed a strong interaction of isoflurane with S129, T189, and S208; relatively weakly with L150; and almost undetectable with L179 and phenylalanine residues. An orientation preference was observed for isoflurane bound to T189 and S208, but not to S129 and L150. We conclude that isoflurane inhibits NaChBac by two distinct mechanisms: (i) as a channel blocker at the base of the selectivity filter, and (ii) as a modulator to restrict the pivot motion at the S4–S5 linker and at a critical hinge that controls the gating and inactivation motion of S6.

scholarly journals Resting-State Structure and Gating Mechanism of a Voltage-Gated Sodium Channel

Cell ◽  
2019 ◽  
Vol 178 (4) ◽  
pp. 993-1003.e12 ◽  
Author(s):  
Goragot Wisedchaisri ◽  
Lige Tonggu ◽  
Eedann McCord ◽  
Tamer M. Gamal El-Din ◽  
Liguo Wang ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Resting State ◽  
State Structure ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Gating Mechanism

scholarly journals Nedd4-2 (NEDD4L) controls intracellular Na+-mediated activity of voltage-gated sodium channels in primary cortical neurons

2013 ◽  
Vol 457 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Jenny A. Ekberg ◽  
Natasha A. Boase ◽  
Grigori Rychkov ◽  
Jantina Manning ◽  
Philip Poronnik ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Ubiquitin Ligase ◽  
Cortical Neurons ◽  
Channel Activity ◽  
Primary Cortical Neurons ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
First Time

The study shows for the first time that the ubiquitin ligase Nedd4-2 regulates voltage-gated sodium channel activity in cortical neurons, specifically in response to elevated intracellular Na+ concentration.

scholarly journals Structural basis of ion permeation gating in Slo2.1 K+ channels

2013 ◽  
Vol 142 (5) ◽  
pp. 523-542 ◽  
Author(s):  
Priyanka Garg ◽  
Alison Gardner ◽  
Vivek Garg ◽  
Michael C. Sanguinetti
Keyword(s):  
Selectivity Filter ◽  
Structural Basis ◽  
K Channel ◽  
Xenopus Laevis Oocytes ◽  
Ion Permeation ◽  
Channel Activation ◽  
K Channels ◽  
Voltage Gated ◽  
Channel Function ◽  
Activation Gate

The activation gate of ion channels controls the transmembrane flux of permeant ions. In voltage-gated K+ channels, the aperture formed by the S6 bundle crossing can widen to open or narrow to close the ion permeation pathway, whereas the selectivity filter gates ion flux in cyclic-nucleotide gated (CNG) and Slo1 channels. Here we explore the structural basis of the activation gate for Slo2.1, a weakly voltage-dependent K+ channel that is activated by intracellular Na+ and Cl−. Slo2.1 channels were heterologously expressed in Xenopus laevis oocytes and activated by elevated [NaCl]i or extracellular application of niflumic acid. In contrast to other voltage-gated channels, Slo2.1 was blocked by verapamil in an activation-independent manner, implying that the S6 bundle crossing does not gate the access of verapamil to its central cavity binding site. The structural basis of Slo2.1 activation was probed by Ala scanning mutagenesis of the S6 segment and by mutation of selected residues in the pore helix and S5 segment. Mutation to Ala of three S6 residues caused reduced trafficking of channels to the cell surface and partial (K256A, I263A, Q273A) or complete loss (E275A) of channel function. P271A Slo2.1 channels trafficked normally, but were nonfunctional. Further mutagenesis and intragenic rescue by second site mutations suggest that Pro271 and Glu275 maintain the inner pore in an open configuration by preventing formation of a tight S6 bundle crossing. Mutation of several residues in S6 and S5 predicted by homology modeling to contact residues in the pore helix induced a gain of channel function. Substitution of the pore helix residue Phe240 with polar residues induced constitutive channel activation. Together these findings suggest that (1) the selectivity filter and not the bundle crossing gates ion permeation and (2) dynamic coupling between the pore helix and the S5 and S6 segments mediates Slo2.1 channel activation.

scholarly journals Solution Structure and Alanine Scan of a Spider Toxin That Affects the Activation of Mammalian Voltage-gated Sodium Channels

2006 ◽  
Vol 282 (7) ◽  
pp. 4643-4652 ◽  
Author(s):  
Gerardo Corzo ◽  
Jennifer K. Sabo ◽  
Frank Bosmans ◽  
Bert Billen ◽  
Elba Villegas ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Solution Structure ◽  
Receptor Site ◽  
Amino Acid Sequences ◽  
Structural Motif ◽  
Dimensional Structure ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels

Magi 5, from the hexathelid spider Macrothele gigas, is a 29-residue polypeptide containing three disulfide bridges. It binds specifically to receptor site 4 on mammalian voltage-gated sodium channels and competes with scorpion β-toxins, such as Css IV from Centruroides suffusus suffusus. As a consequence, Magi 5 shifts the activation voltage of the mammalian rNav1.2a channel to more hyperpolarized voltages, whereas the insect channel, DmNav1, is not affected. To gain insight into toxin-channel interactions, Magi 5 and 23 analogues were synthesized. The three-dimensional structure of Magi 5 in aqueous solution was determined, and its voltage-gated sodium channel-binding surfaces were mapped onto this structure using data from electrophysiological measurements on a series of Ala-substituted analogues. The structure clearly resembles the inhibitor cystine knot structural motif, although the triple-stranded β-sheet typically found in that motif is partially distorted in Magi 5. The interactive surface of Magi 5 toward voltage-gated sodium channels resembles in some respects the Janus-faced atracotoxins, with functionally important charged residues on one face of the toxin and hydrophobic residues on the other. Magi 5 also resembles the scorpion β-toxin Css IV, which has distinct nonpolar and charged surfaces that are critical for channel binding and has a key Glu involved in voltage sensor trapping. These two distinct classes of toxin, with different amino acid sequences and different structures, may utilize similar groups of residues on their surface to achieve the common end of modifying voltage-gated sodium channel function.

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