Structural basis of α-scorpion toxin action on Nav channels

Science ◽  
2019 ◽  
Vol 363 (6433) ◽  
pp. eaav8573 ◽  
Author(s):  
Thomas Clairfeuille ◽  
Alexander Cloake ◽  
Daniel T. Infield ◽  
José P. Llongueras ◽  
Christopher P. Arthur ◽  
...  
Keyword(s):  
Electromechanical Coupling ◽  
Receptor Site ◽  
Scorpion Toxin ◽  
Structural Basis ◽  
Fast Inactivation ◽  
Gating Charge ◽  
Nav Channels ◽  
Fast Activation ◽  
Electrical Signaling ◽  
Voltage Sensing Domain

Fast inactivation of voltage-gated sodium (Nav) channels is essential for electrical signaling, but its mechanism remains poorly understood. Here we determined the structures of a eukaryotic Nav channel alone and in complex with a lethal α-scorpion toxin, AaH2, by electron microscopy, both at 3.5-angstrom resolution. AaH2 wedges into voltage-sensing domain IV (VSD4) to impede fast activation by trapping a deactivated state in which gating charge interactions bridge to the acidic intracellular carboxyl-terminal domain. In the absence of AaH2, the S4 helix of VSD4 undergoes a ~13-angstrom translation to unlatch the intracellular fast-inactivation gating machinery. Highlighting the polypharmacology of α-scorpion toxins, AaH2 also targets an unanticipated receptor site on VSD1 and a pore glycan adjacent to VSD4. Overall, this work provides key insights into fast inactivation, electromechanical coupling, and pathogenic mutations in Nav channels.

scholarly journals Structural basis for voltage-sensor trapping of the cardiac sodium channel by a deathstalker scorpion toxin

2020 ◽  
Author(s):  
Daohua Jiang ◽  
Lige Tonggu ◽  
Tamer M. Gamal El-Din ◽  
Richard Banh ◽  
Régis Pomès ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Voltage Sensor ◽  
Structural Basis ◽  
Fast Inactivation ◽  
Toxin Binding ◽  
Cardiac Sodium Channel ◽  
Activated State ◽  
Nav Channels ◽  
Gating Modifier ◽  
Voltage Sensing Domain

AbstractVoltage-gated sodium (NaV) channels initiate action potentials in excitable cells, and their function is altered by potent gating-modifier toxins. The α-toxin LqhIII from the deathstalker scorpion inhibits fast inactivation of cardiac NaV1.5 channels with IC50=11.4 nM. Here we reveal the structure of LqhIII bound to NaV1.5 at 3.3 Å resolution by cryo-EM. LqhIII anchors on top of voltage-sensing domain IV, wedged between the S1-S2 and S3-S4 linkers, which traps the gating charges of the S4 segment in a unique intermediate-activated state stabilized by four ion-pairs. This conformational change is propagated inward to weaken binding of the fast inactivation gate and favor opening the activation gate. However, these changes do not permit Na+ permeation, revealing why LqhIII slows inactivation of NaV channels but does not open them. Our results provide important insights into the structural basis for gating-modifier toxin binding, voltage-sensor trapping, and fast inactivation of NaV channels.

scholarly journals α-Scorpion Toxin Impairs a Conformational Change that Leads to Fast Inactivation of Muscle Sodium Channels

2008 ◽  
Vol 132 (2) ◽  
pp. 251-263 ◽  
Author(s):  
Fabiana V. Campos ◽  
Baron Chanda ◽  
Paulo S.L. Beirão ◽  
Francisco Bezanilla
Keyword(s):  
Sodium Channels ◽  
Slow Component ◽  
Scorpion Toxin ◽  
Fast Inactivation ◽  
Gating Current ◽  
Voltage Sensors ◽  
Current Decay ◽  
Fluorescence Measurements ◽  
Gating Charge ◽  
Domain Iii

α-Scorpion toxins bind in a voltage-dependent way to site 3 of the sodium channels, which is partially formed by the loop connecting S3 and S4 segments of domain IV, slowing down fast inactivation. We have used Ts3, an α-scorpion toxin from the Brazilian scorpion Tityus serrulatus, to analyze the effects of this family of toxins on the muscle sodium channels expressed in Xenopus oocytes. In the presence of Ts3 the total gating charge was reduced by 30% compared with control conditions. Ts3 accelerated the gating current kinetics, decreasing the contribution of the slow component to the ON gating current decay, indicating that S4-DIV was specifically inhibited by the toxin. In addition, Ts3 accelerated and decreased the fraction of charge in the slow component of the OFF gating current decay, which reflects an acceleration in the recovery from the fast inactivation. Site-specific fluorescence measurements indicate that Ts3 binding to the voltage-gated sodium channel eliminates one of the components of the fluorescent signal from S4-DIV. We also measured the fluorescent signals produced by the movement of the first three voltage sensors to test whether the bound Ts3 affects the movement of the other voltage sensors. While the fluorescence–voltage (F-V) relationship of domain II was only slightly affected and the F-V of domain III remained unaffected in the presence of Ts3, the toxin significantly shifted the F-V of domain I to more positive potentials, which agrees with previous studies showing a strong coupling between domains I and IV. These results are consistent with the proposed model, in which Ts3 specifically impairs the fraction of the movement of the S4-DIV that allows fast inactivation to occur at normal rates.

scholarly journals Structural basis for voltage-sensor trapping of the cardiac sodium channel by a deathstalker scorpion toxin

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Daohua Jiang ◽  
Lige Tonggu ◽  
Tamer M. Gamal El-Din ◽  
Richard Banh ◽  
Régis Pomès ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Voltage Sensor ◽  
Structural Basis ◽  
Fast Inactivation ◽  
Excitable Cells ◽  
Toxin Binding ◽  
Cardiac Sodium Channel ◽  
Activated State ◽  
Gating Modifier ◽  
Voltage Sensing Domain

AbstractVoltage-gated sodium (NaV) channels initiate action potentials in excitable cells, and their function is altered by potent gating-modifier toxins. The α-toxin LqhIII from the deathstalker scorpion inhibits fast inactivation of cardiac NaV1.5 channels with IC50 = 11.4 nM. Here we reveal the structure of LqhIII bound to NaV1.5 at 3.3 Å resolution by cryo-EM. LqhIII anchors on top of voltage-sensing domain IV, wedged between the S1-S2 and S3-S4 linkers, which traps the gating charges of the S4 segment in a unique intermediate-activated state stabilized by four ion-pairs. This conformational change is propagated inward to weaken binding of the fast inactivation gate and favor opening the activation gate. However, these changes do not permit Na+ permeation, revealing why LqhIII slows inactivation of NaV channels but does not open them. Our results provide important insights into the structural basis for gating-modifier toxin binding, voltage-sensor trapping, and fast inactivation of NaV channels.

scholarly journals Regulation of Na+ channel inactivation by the DIII and DIV voltage-sensing domains

2017 ◽  
Vol 149 (3) ◽  
pp. 389-403 ◽  
Author(s):  
Eric J. Hsu ◽  
Wandi Zhu ◽  
Angela R. Schubert ◽  
Taylor Voelker ◽  
Zoltan Varga ◽  
...  
Keyword(s):  
Na Channel ◽  
Fast Inactivation ◽  
Voltage Sensing ◽  
Channel Inactivation ◽  
Recovery From Inactivation ◽  
Nav Channels ◽  
Rate Of Recovery ◽  
Membrane Spanning ◽  
Voltage Sensing Domain ◽  
Gating Process

Functional eukaryotic voltage-gated Na+ (NaV) channels comprise four domains (DI–DIV), each containing six membrane-spanning segments (S1–S6). Voltage sensing is accomplished by the first four membrane-spanning segments (S1–S4), which together form a voltage-sensing domain (VSD). A critical NaV channel gating process, inactivation, has previously been linked to activation of the VSDs in DIII and DIV. Here, we probe this interaction by using voltage-clamp fluorometry to observe VSD kinetics in the presence of mutations at locations that have been shown to impair NaV channel inactivation. These locations include the DIII–DIV linker, the DIII S4–S5 linker, and the DIV S4-S5 linker. Our results show that, within the 10-ms timeframe of fast inactivation, the DIV-VSD is the primary regulator of inactivation. However, after longer 100-ms pulses, the DIII–DIV linker slows DIII-VSD deactivation, and the rate of DIII deactivation correlates strongly with the rate of recovery from inactivation. Our results imply that, over the course of an action potential, DIV-VSDs regulate the onset of fast inactivation while DIII-VSDs determine its recovery.

scholarly journals Cryo-EM structure of the complete and ligand-saturated insulin receptor ectodomain

2019 ◽  
Author(s):  
Theresia Gutmann ◽  
Ingmar Schäfer ◽  
Chetan Poojari ◽  
Beate Brankatschk ◽  
Ilpo Vattulainen ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Binding Sites ◽  
Structural Model ◽  
Receptor Site ◽  
Insulin Binding ◽  
Proximal Region ◽  
Dynamics Simulation ◽  
Structural Basis ◽  
Structure Based Drug Design ◽  
Receptor Interactions

AbstractGlucose homeostasis and growth essentially depend on the peptide hormone insulin engaging its receptor. Despite biochemical and structural advances, a fundamental contradiction has persisted in the current understanding of insulin ligand–receptor interactions. While biochemistry predicts two distinct insulin binding sites, 1 and 2, recent structural analyses have only resolved site 1. Using a combined approach of cryo-EM and atomistic molecular dynamics simulation, we determined the structure of the entire dimeric insulin receptor ectodomain saturated with four insulin molecules. Complementing the previously described insulin–site 1 interaction, we present the first view of insulin bound to the discrete insulin receptor site 2. Insulin binding stabilizes the receptor ectodomain in a T-shaped conformation wherein the membrane-proximal domains converge and contact each other. These findings expand the current models of insulin binding to its receptor and of its regulation. In summary, we provide the structural basis enabling a comprehensive description of ligand–receptor interactions that ultimately will inform new approaches to structure-based drug design.In briefA cryo-EM structure of the complete insulin receptor ectodomain saturated with four insulin ligands is reported. The structural model of the insulin–insulin receptor complex adopts a T-shaped conformation, reveals two additional insulin-binding sites potentially involved in the initial interaction of insulin with its receptor, and resolves the membrane proximal region.

scholarly journals Bot IT2 : a new scorpion toxin to study receptor site on insect sodium channels

FEBS Letters ◽  
1997 ◽  
Vol 405 (1) ◽  
pp. 77-80 ◽  
Author(s):  
Sandrine Cestèle ◽  
Lamia Borchani ◽  
Mohamed El Ayeb ◽  
Hervé Rochat
Keyword(s):  
Sodium Channels ◽  
Receptor Site ◽  
Scorpion Toxin

Reconstitution of High-Affinity Binding of a β-Scorpion Toxin to Neurotoxin Receptor Site 4 on Purified Sodium Channels

2002 ◽  
Vol 65 (3) ◽  
pp. 1358-1364 ◽  
Author(s):  
William Thomsen ◽  
M. F. Martin-Eauclaire ◽  
Hervé Rochat ◽  
William A. Catterall
Keyword(s):  
Sodium Channels ◽  
Receptor Site ◽  
Scorpion Toxin ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity

scholarly journals The hitchhiker’s guide to the voltage-gated sodium channel galaxy

2015 ◽  
Vol 147 (1) ◽  
pp. 1-24 ◽  
Author(s):  
Christopher A. Ahern ◽  
Jian Payandeh ◽  
Frank Bosmans ◽  
Baron Chanda
Keyword(s):  
Ion Selectivity ◽  
Current Understanding ◽  
Voltage Gated ◽  
Accessory Subunits ◽  
Genes Encoding ◽  
Nav Channels ◽  
Functional Symmetry ◽  
Electrical Signaling ◽  
And Behavior ◽  
Inherited Mutations

Eukaryotic voltage-gated sodium (Nav) channels contribute to the rising phase of action potentials and served as an early muse for biophysicists laying the foundation for our current understanding of electrical signaling. Given their central role in electrical excitability, it is not surprising that (a) inherited mutations in genes encoding for Nav channels and their accessory subunits have been linked to excitability disorders in brain, muscle, and heart; and (b) Nav channels are targeted by various drugs and naturally occurring toxins. Although the overall architecture and behavior of these channels are likely to be similar to the more well-studied voltage-gated potassium channels, eukaryotic Nav channels lack structural and functional symmetry, a notable difference that has implications for gating and selectivity. Activation of voltage-sensing modules of the first three domains in Nav channels is sufficient to open the channel pore, whereas movement of the domain IV voltage sensor is correlated with inactivation. Also, structure–function studies of eukaryotic Nav channels show that a set of amino acids in the selectivity filter, referred to as DEKA locus, is essential for Na+ selectivity. Structures of prokaryotic Nav channels have also shed new light on mechanisms of drug block. These structures exhibit lateral fenestrations that are large enough to allow drugs or lipophilic molecules to gain access into the inner vestibule, suggesting that this might be the passage for drug entry into a closed channel. In this Review, we will synthesize our current understanding of Nav channel gating mechanisms, ion selectivity and permeation, and modulation by therapeutics and toxins in light of the new structures of the prokaryotic Nav channels that, for the time being, serve as structural models of their eukaryotic counterparts.

scholarly journals Domain IV voltage-sensor movement is both sufficient and rate limiting for fast inactivation in sodium channels

2013 ◽  
Vol 142 (2) ◽  
pp. 101-112 ◽  
Author(s):  
Deborah L. Capes ◽  
Marcel P. Goldschen-Ohm ◽  
Manoel Arcisio-Miranda ◽  
Francisco Bezanilla ◽  
Baron Chanda
Keyword(s):  
Sodium Channels ◽  
Voltage Sensor ◽  
Fast Inactivation ◽  
Voltage Range ◽  
Voltage Gated Sodium Channels ◽  
Channel Opening ◽  
The Individual ◽  
Electrical Impulses ◽  
Voltage Sensing Domain ◽  
Rate Limiting

Voltage-gated sodium channels are critical for the generation and propagation of electrical signals in most excitable cells. Activation of Na+ channels initiates an action potential, and fast inactivation facilitates repolarization of the membrane by the outward K+ current. Fast inactivation is also the main determinant of the refractory period between successive electrical impulses. Although the voltage sensor of domain IV (DIV) has been implicated in fast inactivation, it remains unclear whether the activation of DIV alone is sufficient for fast inactivation to occur. Here, we functionally neutralize each specific voltage sensor by mutating several critical arginines in the S4 segment to glutamines. We assess the individual role of each voltage-sensing domain in the voltage dependence and kinetics of fast inactivation upon its specific inhibition. We show that movement of the DIV voltage sensor is the rate-limiting step for both development and recovery from fast inactivation. Our data suggest that activation of the DIV voltage sensor alone is sufficient for fast inactivation to occur, and that activation of DIV before channel opening is the molecular mechanism for closed-state inactivation. We propose a kinetic model of sodium channel gating that can account for our major findings over a wide voltage range by postulating that DIV movement is both necessary and sufficient for fast inactivation.

scholarly journals Scorpion β-toxin interference with NaV channel voltage sensor gives rise to excitatory and depressant modes

2012 ◽  
Vol 139 (4) ◽  
pp. 305-319 ◽  
Author(s):  
Enrico Leipold ◽  
Adolfo Borges ◽  
Stefan H. Heinemann
Keyword(s):  
Voltage Sensor ◽  
Dependent Manner ◽  
Gating Charge ◽  
Whole Cell Patch Clamp ◽  
Channel Opening ◽  
Arginine Residues ◽  
Equivalent Residue ◽  
Nav Channels ◽  
Excitatory Action ◽  
Gating Modification

Scorpion β toxins, peptides of ∼70 residues, specifically target voltage-gated sodium (NaV) channels to cause use-dependent subthreshold channel openings via a voltage–sensor trapping mechanism. This excitatory action is often overlaid by a not yet understood depressant mode in which NaV channel activity is inhibited. Here, we analyzed these two modes of gating modification by β-toxin Tz1 from Tityus zulianus on heterologously expressed NaV1.4 and NaV1.5 channels using the whole cell patch-clamp method. Tz1 facilitated the opening of NaV1.4 in a use-dependent manner and inhibited channel opening with a reversed use dependence. In contrast, the opening of NaV1.5 was exclusively inhibited without noticeable use dependence. Using chimeras of NaV1.4 and NaV1.5 channels, we demonstrated that gating modification by Tz1 depends on the specific structure of the voltage sensor in domain 2. Although residue G658 in NaV1.4 promotes the use-dependent transitions between Tz1 modification phenotypes, the equivalent residue in NaV1.5, N803, abolishes them. Gating charge neutralizations in the NaV1.4 domain 2 voltage sensor identified arginine residues at positions 663 and 669 as crucial for the outward and inward movement of this sensor, respectively. Our data support a model in which Tz1 can stabilize two conformations of the domain 2 voltage sensor: a preactivated outward position leading to NaV channels that open at subthreshold potentials, and a deactivated inward position preventing channels from opening. The results are best explained by a two-state voltage–sensor trapping model in that bound scorpion β toxin slows the activation as well as the deactivation kinetics of the voltage sensor in domain 2.

Sign in / Sign up

Export Citation Format

Share Document