Brevetoxin and Conotoxin Interactions with Single-Domain Voltage-Gated Sodium Channels from a Diatom and Coccolithophore

The recently characterized single-domain voltage-gated ion channels from eukaryotic protists (EukCats) provide an array of novel channel proteins upon which to test the pharmacology of both clinically and environmentally relevant marine toxins. Here, we examined the effects of the hydrophilic µ-CTx PIIIA and the lipophilic brevetoxins PbTx-2 and PbTx-3 on heterologously expressed EukCat ion channels from a marine diatom and coccolithophore. Surprisingly, none of the toxins inhibited the peak currents evoked by the two EukCats tested. The lack of homology in the outer pore elements of the channel may disrupt the binding of µ-CTx PIIIA, while major structural differences between mammalian sodium channels and the C-terminal domains of the EukCats may diminish interactions with the brevetoxins. However, all three toxins produced significant negative shifts in the voltage dependence of activation and steady state inactivation, suggesting alternative and state-dependent binding conformations that potentially lead to changes in the excitability of the phytoplankton themselves.

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Voltage gating of ion channels

Quarterly Reviews of Biophysics ◽

10.1017/s0033583500002894 ◽

1994 ◽

Vol 27 (1) ◽

pp. 1-40 ◽

Cited By ~ 283

Author(s):

F. J. Sigworth

Keyword(s):

Ion Channels ◽

Action Potential ◽

Sodium Channels ◽

Calcium Ions ◽

Neurotransmitter Release ◽

Voltage Gating ◽

Voltage Gated ◽

Voltage Gated Calcium Channels ◽

Voltage Gated Sodium Channels ◽

Voltage Gated Ion Channels

Voltage-gated ion channels are membrane proteins that play a central role in the propagation and transduction of cellular signals (Hille, 1992). Calcium ions entering cells through voltage-gated calcium channels serve as the trigger for neurotransmitter release, muscle contraction, and the release of hormones. Voltage-gated sodium channels initiate the nerve action potential and provide for its rapid propagation because the ion fluxes through these channels regeneratively cause more channels to open.

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Comparisons of voltage-gated sodium channel structures with open and closed gates and implications for state-dependent drug design

Biochemical Society Transactions ◽

10.1042/bst20180295 ◽

2018 ◽

Vol 46 (6) ◽

pp. 1567-1575 ◽

Cited By ~ 3

Author(s):

Giulia Montini ◽

Jennifer Booker ◽

Altin Sula ◽

B.A. Wallace

Keyword(s):

Drug Design ◽

Sodium Channels ◽

Rational Drug Design ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

State Dependent ◽

Rational Drug ◽

Sequence Homologies ◽

Arcobacter Butzleri ◽

Functional Consequences

Voltage-gated sodium channels (Navs) are responsible for the initiation of the action potential in excitable cells. Several prokaryotic sodium channels, most notably NavMs from Magnetococcus marinus and NavAb from Arcobacter butzleri, have been shown to be good models for human sodium channels based on their sequence homologies and high levels of functional similarities, including ion flux, and functional consequences of critical mutations. The complete full-length crystal structures of these prokaryotic sodium channels captured in different functional states have now revealed the molecular natures of changes associated with the gating process. These include the structures of the intracellular gate, the selectivity filter, the voltage sensors, the intra-membrane fenestrations, and the transmembrane (TM) pore. Here we have identified for the first time how changes in the fenestrations in the hydrophobic TM region associated with the opening of the intracellular gate could modulate the state-dependent ingress and binding of drugs in the TM cavity, in a way that could be exploited for rational drug design.

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Inhibition of Nav1.7 and Nav1.4 Sodium Channels by Trifluoperazine Involves the Local Anesthetic Receptor

Journal of Neurophysiology ◽

10.1152/jn.00354.2006 ◽

2006 ◽

Vol 96 (4) ◽

pp. 1848-1859 ◽

Cited By ~ 13

Author(s):

Patrick L. Sheets ◽

Peter Gerner ◽

Chi-Fei Wang ◽

Sho-Ya Wang ◽

Ging Kuo Wang ◽

...

Keyword(s):

Sodium Channels ◽

Local Anesthetic ◽

Receptor Site ◽

Inhibitory Peptide ◽

Sensory Blockade ◽

Voltage Gated Sodium Channels ◽

State Dependent ◽

Steady State Inactivation ◽

Channel Interactions

The calmodulin (CaM) inhibitor trifluoperazine (TFP) can produce analgesia when given intrathecally to rats; however, the mechanism is not known. We asked whether TFP could modulate the Nav1.7 sodium channel, which is highly expressed in the peripheral nervous system and plays an important role in nociception. We show that 500 nM and 2 μM TFP induce major decreases in Nav1.7 and Nav1.4 current amplitudes and that 2 μM TFP causes hyperpolarizing shifts in the steady-state inactivation of Nav1.7 and Nav1.4. CaM can bind to the C-termini of voltage-gated sodium channels and modulate their functional properties; therefore we investigated if TFP modulation of sodium channels was due to CaM inhibition. However, the TFP inhibition was not replicated by whole cell dialysis of a calmodulin inhibitory peptide, indicating that major effects of TFP do not involve a disruption of CaM-channel interactions. Rather, our data show that TFP inhibition is state dependent and that the majority of the TFP inhibition depends on specific amino-acid residues in the local anesthetic receptor site in sodium channels. TFP was also effective in vivo in causing motor and sensory blockade after subfascial injection to the rat sciatic nerve. The state-dependent block of Nav1.7 channels with nanomolar concentrations of TFP raises the possibility that TFP, or TFP analogues, might be useful for regional anesthesia and pain management and could be more potent than traditional local anesthetics.

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

Toxins ◽

10.3390/toxins10100408 ◽

2018 ◽

Vol 10 (10) ◽

pp. 408 ◽

Cited By ~ 1

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.

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Optical electrophysiology for probing function and pharmacology of voltage-gated ion channels

eLife ◽

10.7554/elife.15202 ◽

2016 ◽

Vol 5 ◽

Cited By ~ 24

Author(s):

Hongkang Zhang ◽

Elaine Reichert ◽

Adam E Cohen

Keyword(s):

Ion Channels ◽

Voltage Clamp ◽

High Throughput Screening ◽

Drug Targets ◽

Inhibitory Effect ◽

Optical Measurements ◽

Voltage Gated ◽

State Dependent ◽

Voltage Gated Ion Channels ◽

Gated Ion Channels

Voltage-gated ion channels mediate electrical dynamics in excitable tissues and are an important class of drug targets. Channels can gate in sub-millisecond timescales, show complex manifolds of conformational states, and often show state-dependent pharmacology. Mechanistic studies of ion channels typically involve sophisticated voltage-clamp protocols applied through manual or automated electrophysiology. Here, we develop all-optical electrophysiology techniques to study activity-dependent modulation of ion channels, in a format compatible with high-throughput screening. Using optical electrophysiology, we recapitulate many voltage-clamp protocols and apply to Nav1.7, a channel implicated in pain. Optical measurements reveal that a sustained depolarization strongly potentiates the inhibitory effect of PF-04856264, a Nav1.7-specific blocker. In a pilot screen, we stratify a library of 320 FDA-approved compounds by binding mechanism and kinetics, and find close concordance with patch clamp measurements. Optical electrophysiology provides a favorable tradeoff between throughput and information content for studies of NaV channels, and possibly other voltage-gated channels.

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Role of the Local Anesthetic Receptor in the State-Dependent Inhibition of Voltage-Gated Sodium Channels by the Insecticide Metaflumizone

Molecular Pharmacology ◽

10.1124/mol.111.075283 ◽

2011 ◽

Vol 81 (3) ◽

pp. 366-374 ◽

Cited By ~ 11

Author(s):

Richard T. von Stein ◽

David M. Soderlund

Keyword(s):

Sodium Channels ◽

Local Anesthetic ◽

The State ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

State Dependent ◽

Dependent Inhibition

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Opening TRPP2 (PKD2L1) requires the transfer of gating charges

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1902917116 ◽

2019 ◽

Vol 116 (31) ◽

pp. 15540-15549 ◽

Cited By ~ 7

Author(s):

Leo C. T. Ng ◽

Thuy N. Vien ◽

Vladimir Yarov-Yarovoy ◽

Paul G. DeCaen

Keyword(s):

Ion Channels ◽

Transient Receptor Potential ◽

Trp Channels ◽

Receptor Potential ◽

Voltage Gated ◽

State Dependent ◽

Transient Receptor ◽

Voltage Gated Ion Channels ◽

Gating Charges ◽

Gated Ion Channels

The opening of voltage-gated ion channels is initiated by transfer of gating charges that sense the electric field across the membrane. Although transient receptor potential ion channels (TRP) are members of this family, their opening is not intrinsically linked to membrane potential, and they are generally not considered voltage gated. Here we demonstrate that TRPP2, a member of the polycystin subfamily of TRP channels encoded by the PKD2L1 gene, is an exception to this rule. TRPP2 borrows a biophysical riff from canonical voltage-gated ion channels, using 2 gating charges found in its fourth transmembrane segment (S4) to control its conductive state. Rosetta structural prediction demonstrates that the S4 undergoes ∼3- to 5-Å transitional and lateral movements during depolarization, which are coupled to opening of the channel pore. Here both gating charges form state-dependent cation–π interactions within the voltage sensor domain (VSD) during membrane depolarization. Our data demonstrate that the transfer of a single gating charge per channel subunit is requisite for voltage, temperature, and osmotic swell polymodal gating of TRPP2. Taken together, we find that irrespective of stimuli, TRPP2 channel opening is dependent on activation of its VSDs.

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V102862 (Co 102862): a potent, broad-spectrum state-dependent blocker of mammalian voltage-gated sodium channels

British Journal of Pharmacology ◽

10.1038/sj.bjp.0706058 ◽

2005 ◽

Vol 144 (6) ◽

pp. 801-812 ◽

Cited By ~ 21

Author(s):

Victor I Ilyin ◽

Dianne D Hodges ◽

Edward R Whittemore ◽

Richard B Carter ◽

Sui Xiong Cai ◽

...

Keyword(s):

Sodium Channels ◽

Broad Spectrum ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

State Dependent

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Domain–domain interactions determine the gating, permeation, pharmacology, and subunit modulation of the IKs ion channel

eLife ◽

10.7554/elife.03606 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 48

Author(s):

Mark A Zaydman ◽

Marina A Kasimova ◽

Kelli McFarland ◽

Zachary Beller ◽

Panpan Hou ◽

...

Keyword(s):

Ion Channels ◽

Physiological Role ◽

Specific Expression ◽

Electrical Currents ◽

Voltage Gated ◽

State Dependent ◽

Domain Interactions ◽

Voltage Gated Ion Channels ◽

Hormonal Release

Voltage-gated ion channels generate electrical currents that control muscle contraction, encode neuronal information, and trigger hormonal release. Tissue-specific expression of accessory (β) subunits causes these channels to generate currents with distinct properties. In the heart, KCNQ1 voltage-gated potassium channels coassemble with KCNE1 β-subunits to generate the IKs current (<xref ref-type="bibr" rid="bib3">Barhanin et al., 1996</xref>; <xref ref-type="bibr" rid="bib57">Sanguinetti et al., 1996</xref>), an important current for maintenance of stable heart rhythms. KCNE1 significantly modulates the gating, permeation, and pharmacology of KCNQ1 (<xref ref-type="bibr" rid="bib77">Wrobel et al., 2012</xref>; <xref ref-type="bibr" rid="bib66">Sun et al., 2012</xref>; <xref ref-type="bibr" rid="bib1">Abbott, 2014</xref>). These changes are essential for the physiological role of IKs (<xref ref-type="bibr" rid="bib62">Silva and Rudy, 2005</xref>); however, after 18 years of study, no coherent mechanism explaining how KCNE1 affects KCNQ1 has emerged. Here we provide evidence of such a mechanism, whereby, KCNE1 alters the state-dependent interactions that functionally couple the voltage-sensing domains (VSDs) to the pore.

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