scholarly journals Structural basis for the modulation of voltage-gated sodium channels by animal toxins

Science ◽  
2018 ◽  
Vol 362 (6412) ◽  
pp. eaau2596 ◽  
Author(s):  
Huaizong Shen ◽  
Zhangqiang Li ◽  
Yan Jiang ◽  
Xiaojing Pan ◽  
Jianping Wu ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Structural Basis ◽  
Shellfish Poisoning ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Puffer Fish ◽  
Gating Modifier ◽  
Extracellular Side ◽  
Fish And Shellfish ◽  
Shed Light

Animal toxins that modulate the activity of voltage-gated sodium (Nav) channels are broadly divided into two categories—pore blockers and gating modifiers. The pore blockers tetrodotoxin (TTX) and saxitoxin (STX) are responsible for puffer fish and shellfish poisoning in humans, respectively. Here, we present structures of the insect Navchannel NavPaS bound to a gating modifier toxin Dc1a at 2.8 angstrom-resolution and in the presence of TTX or STX at 2.6-Å and 3.2-Å resolution, respectively. Dc1a inserts into the cleft between VSDIIand the pore of NavPaS, making key contacts with both domains. The structures with bound TTX or STX reveal the molecular details for the specific blockade of Na+access to the selectivity filter from the extracellular side by these guanidinium toxins. The structures shed light on structure-based development of Navchannel drugs.

scholarly journals Purification and Characterization of JZTx-14, a Potent Antagonist of Mammalian and Prokaryotic Voltage-Gated Sodium Channels

Toxins ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 408 ◽  
Author(s):  
Jie Zhang ◽  
Dongfang Tang ◽  
Shuangyu Liu ◽  
Haoliang Hu ◽  
Songping Liang ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Resting State ◽  
Purification And Characterization ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Steady State Inactivation ◽  
Ic50 Values ◽  
Gating Modifier ◽  
Potent Antagonist

Exploring the interaction of ligands with voltage-gated sodium channels (NaVs) has advanced our understanding of their pharmacology. Herein, we report the purification and characterization of a novel non-selective mammalian and bacterial NaVs toxin, JZTx-14, from the venom of the spider Chilobrachys jingzhao. This toxin potently inhibited the peak currents of mammalian NaV1.2–1.8 channels and the bacterial NaChBac channel with low IC50 values (<1 µM), and it mainly inhibited the fast inactivation of the NaV1.9 channel. Analysis of NaV1.5/NaV1.9 chimeric channel showed that the NaV1.5 domain II S3–4 loop is involved in toxin association. Kinetics data obtained from studying toxin–NaV1.2 channel interaction showed that JZTx-14 was a gating modifier that possibly trapped the channel in resting state; however, it differed from site 4 toxin HNTx-III by irreversibly blocking NaV currents and showing state-independent binding with the channel. JZTx-14 might stably bind to a conserved toxin pocket deep within the NaV1.2–1.8 domain II voltage sensor regardless of channel conformation change, and its effect on NaVs requires the toxin to trap the S3–4 loop in its resting state. For the NaChBac channel, JZTx-14 positively shifted its conductance-voltage (G–V) and steady-state inactivation relationships. An alanine scan analysis of the NaChBac S3–4 loop revealed that the 108th phenylalanine (F108) was the key residue determining the JZTx-14–NaChBac interaction. In summary, this study provided JZTx-14 with potent but promiscuous inhibitory activity on both the ancestor bacterial NaVs and the highly evolved descendant mammalian NaVs, and it is a useful probe to understand the pharmacology of NaVs.

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 Gating modifier toxins isolated from spider venom: Modulation of voltage-gated sodium channels and the role of lipid membranes

2018 ◽  
Vol 293 (23) ◽  
pp. 9041-9052 ◽  
Author(s):  
Akello J. Agwa ◽  
Steve Peigneur ◽  
Chun Yuen Chow ◽  
Nicole Lawrence ◽  
David J. Craik ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Lipid Membranes ◽  
Spider Venom ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Gating Modifier

scholarly journals Structural Basis for the Inhibition of Voltage-gated Sodium Channels by Conotoxin μO§-GVIIJ

2016 ◽  
Vol 291 (13) ◽  
pp. 7205-7220 ◽  
Author(s):  
Brad R. Green ◽  
Joanna Gajewiak ◽  
Sandeep Chhabra ◽  
Jack J. Skalicky ◽  
Min-Min Zhang ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Structural Basis ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels

scholarly journals Molecular Determinants of Brevetoxin Binding to Voltage-Gated Sodium Channels

Toxins ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 513 ◽  
Author(s):  
Keiichi Konoki ◽  
Daniel G. Baden ◽  
Todd Scheuer ◽  
William A. Catterall
Keyword(s):  
Sodium Channels ◽  
Red Tides ◽  
Shellfish Poisoning ◽  
Alanine Scanning Mutagenesis ◽  
Α Subunit ◽  
Voltage Gated ◽  
Transmembrane Segments ◽  
Voltage Gated Sodium Channels ◽  
Fold Reduction ◽  
Molecular Determinants

Brevetoxins are produced by dinoflagellates such as Karenia brevis in warm-water red tides and cause neurotoxic shellfish poisoning. They bind to voltage-gated sodium channels at neurotoxin receptor 5, making the channels more active by shifting the voltage-dependence of activation to more negative potentials and by slowing the inactivation process. Previous work using photoaffinity labeling identified binding to the IS6 and IVS5 transmembrane segments of the channel α subunit. We used alanine-scanning mutagenesis to identify molecular determinants for brevetoxin binding in these regions as well as adjacent regions IVS5-SS1 and IVS6. Most of the mutant channels containing single alanine substitutions expressed functional protein in tsA-201 cells and bound to the radioligand [42-3H]-PbTx3. Binding affinity for the great majority of mutant channels was indistinguishable from wild type. However, transmembrane segments IS6, IVS5 and IVS6 each contained 2 to 4 amino acid positions where alanine substitution resulted in a 2–3-fold reduction in brevetoxin affinity, and additional mutations caused a similar increase in brevetoxin affinity. These findings are consistent with a model in which brevetoxin binds to a protein cleft comprising transmembrane segments IS6, IVS5 and IVS6 and makes multiple distributed interactions with these α helices. Determination of brevetoxin affinity for Nav1.2, Nav1.4 and Nav1.5 channels showed that Nav1.5 channels had a characteristic 5-fold reduction in affinity for brevetoxin relative to the other channel isoforms, suggesting the interaction with sodium channels is specific despite the distributed binding determinants.

scholarly journals Propofol is a Potent Gating Modifier of Voltage-Gated Sodium Channels

2017 ◽  
Vol 112 (3) ◽  
pp. 105a-106a
Author(s):  
Elaine Yang ◽  
Daniele Granata ◽  
Roderic Eckenhoff ◽  
Vincenzo Carnevale ◽  
Manuel Covarrubias
Keyword(s):  
Sodium Channels ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Gating Modifier

scholarly journals Mapping of voltage sensor positions in resting and inactivated mammalian sodium channels by LRET

2017 ◽  
Vol 114 (10) ◽  
pp. E1857-E1865 ◽  
Author(s):  
Tomoya Kubota ◽  
Thomas Durek ◽  
Bobo Dang ◽  
Rocio K. Finol-Urdaneta ◽  
David J. Craik ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Structural Changes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Voltage Sensor ◽  
Structural Basis ◽  
Excitable Cells ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Voltage Dependent

Voltage-gated sodium channels (Navs) play crucial roles in excitable cells. Although vertebrate Nav function has been extensively studied, the detailed structural basis for voltage-dependent gating mechanisms remain obscure. We have assessed the structural changes of the Nav voltage sensor domain using lanthanide-based resonance energy transfer (LRET) between the rat skeletal muscle voltage-gated sodium channel (Nav1.4) and fluorescently labeled Nav1.4-targeting toxins. We generated donor constructs with genetically encoded lanthanide-binding tags (LBTs) inserted at the extracellular end of the S4 segment of each domain (with a single LBT per construct). Three different Bodipy-labeled, Nav1.4-targeting toxins were synthesized as acceptors: β-scorpion toxin (Ts1)-Bodipy, KIIIA-Bodipy, and GIIIA-Bodipy analogs. Functional Nav-LBT channels expressed inXenopusoocytes were voltage-clamped, and distinct LRET signals were obtained in the resting and slow inactivated states. Intramolecular distances computed from the LRET signals define a geometrical map of Nav1.4 with the bound toxins, and reveal voltage-dependent structural changes related to channel gating.

Sign in / Sign up

Export Citation Format

Share Document