Functional characterization of a potassium-selective prokaryotic glutamate receptor. Sun, Y. Mechanism of glutamate receptor desensitization. Xia, X. Mechanism of calcium gating in small-conductance calcium-activated potassium channels.
Schumacher, M. Sigworth, F. Voltage gating of ion channels. Noda, M. Primary structure of Electrophorus electricus sodium channel deduced from cDNA sequence. Seoh, S. Aggarwal, S. Tiwari-Woodruff, S. Islas, L. Electrostatics and the gating pore of Shaker potassium channels.
Yang, N. Molecular basis of charge movement in voltage-gated sodium channels. Larsson, H. Durell, S. Monks, S. Li-Smerin, Y. Hong, K. Guy, H. Molecular model of the action potential sodium channel. USA 83 , — Catterall, W. Voltage-dependent gating of sodium channels: correlating structure and function. Trends Neurosci. Glauner, K. Spectroscopic mapping of voltage sensor movement in the Shaker potassium channel. Cha, A. Atomic scale movement of the voltage-sensing region in a potassium channel measured via spectroscopy.
Elinder, F. S4 charges move close to residues in the pore domain during activation in a K channel. Tristani-Firouzi, M. Heginbotham, L. Ren, D. A prokaryotic voltage-gated sodium channel. Kreusch, A. Crystal structure of the tetramerization domain of the Shaker potassium channel.
Shen, N. Neuron 14 , — Holmes, T. Association of Src tyrosine kinase with a human potassium channel mediated by SH3 domain. Crystal structures of a complexed and peptide-free membrane protein-binding domain: molecular basis of peptide recognition by PDZ.
Cell 85 , — Wallner, M. USA 93 , — Morais, C. Cell 95 , — Knaus, H. Identification of the site of incorporation and implications for channel topology. Tapper, A. Jr Location and orientation of minK within the I Ks potassium channel complex. Download references. I would like to thank members of my laboratory and B.
Bean for many discussions and for suggestions about the manuscript, and R. MacKinnon for advice about timing. My research was supported by the National Institutes of Health.
You can also search for this author in PubMed Google Scholar. Correspondence to Gary Yellen. Reprints and Permissions.
Gating modifier toxins from spiders such as hanatoxin may interact with the voltage sensor to increase the stability of the closed state, causing rightward shift of the voltage dependence curve for channel activation. Figure 7. The pore domain of potassium channels. EC: extracellular; IC: intracellular. The voltage dependence of K V channel activation[1, 6] derives from their voltage sensor domains [].
As shown in Fig. The voltage sensor domain of one subunit interacts with the pore domain of a neighboring subunit in a domain swap configuration, and within a voltage sensor the positively charged arginine residues on S4 may interact with negatively charged acidic residues in neighboring helices Fig. Figure 8. The voltage sensor domain of voltage-gated potassium channels. Figure 9. Contacts between the pore domain and the voltage sensor domain of K V channels.
The contacts on the intracellular side involve the interaction of the S4-S5 linker with S6, and the contacts on the extracellular side involve the interaction between S1 and the pore helix [23]. Lipids yellow surrounding the channel and in between the pore domain and the voltage sensor domain are detectable in the crystal structure. Channelopathies linked to Voltage-gated potassium channels Voltage-gated potassium channels are broadly expressed in a variety of tissues. In neurons, they are targeted to various subcellular compartments [3, 26] Fig.
Mutations of K V channel genes may cause neurological diseases such as episodic ataxia and epilepsies, heart diseases, and deafness []. Evolutionary conservation of K V channel function is evident, for example, from the similar movement disorders caused by mutation of K V 1 orthologs in human, mouse, and the fruit fly [10]. Figure Subcellular distribution of voltage-gated potassium channels.
The schematic on the top left depicts a K V 4 channel with two different auxiliary subunits. Subcellular localization of various K V channels in mammalian central neurons is indicated in the middle box [3]. References and notes 1. Hille, B. Gonzalez, C. Compr Physiol, Vacher, H. Mohapatra, and J. Trimmer, Localization and targeting of voltage-dependent ion channels in mammalian central neurons.
Physiol Rev, Jegla, T. Comb Chem High Throughput Screen, Cang, C. Cell, Hodgkin, A. Huxley, Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo. J Physiol, Rosenthal, J. Liu, and W. J Neurosci, Young, J. Neuron, Jan, L. Jan, Voltage-gated potassium channels and the diversity of electrical signalling. Johnston, J. Forsythe, and C.
Kopp-Scheinpflug, Going native: voltage-gated potassium channels controlling neuronal excitability. Bocksteins, E. J Gen Physiol, Wulff, H. Castle, and L. Pardo, Voltage-gated potassium channels as therapeutic targets. Nat Rev Drug Discov, Patients carrying such mutations show signs of cardiac dysfunction diagnosed as long QT syndrome.
The majority of these mutations disrupt fast sodium channel inactivation, impairing the ability of the channel to close completely and thereby generating persistent sodium currents and a prolongation of the ventricular action potential.
Altered cardiac action potentials lead to ventricular arrhythmias and in extreme cases to Brugada syndrome, in which fibrillation may lead to death. These drugs act as frequency-dependent inhibitors of cardiac sodium channels. Drug-induced channel block accumulates with increasing firing frequencies during tachyarrhythmias, thereby slowing the rate of action potential generation in the cardiac myocyte and dampening excitability in the heart. In summary, the risks of cardiac Na v 1.
Therefore, unless the goal is development of novel antiarrhythmics, activity on Na v 1. Cough is a symptom of a number of diseases that affect the respiratory system, and the use of Na v inhibitors to treat cough has emerged as a very promising therapy. The cough reflex in mammalian airways is regulated by vagal sensory neurons expressing Na v channels. Local anesthetics are effective antitussive agents in humans and animals when applied locally, presumably by inhibiting action potentials of airway afferent neurons.
However, the effect is short-lasting and of little use for the treatment of pathological cough. Studies in the guinea pig have shown that the vagal cough receptors and neurons innervating the respiratory tract express Na v 1.
Using the gene silencing technique small hairpin RNA to knock down Na v 1. Importantly, selective inhibition of Na v 1.
Ion channels such as Na v s play an important control function in a range of cellular processes involved in metastasis and angiogenesis. Na v channel function and expression are regulated by hormones, growth factors, cytokines, and hypoxia, and the channels control cancer cell invasiveness by regulating cell motility and the secretion of proteolytic enzymes. The pathological upregulation of Na v channels can make cancer cells highly invasive.
In fact, evidence exists that the levels of Na v expression are correlated with invasiveness and metastatic potential in several types of cancer.
For example, the overexpression of Na v 1. Another therapeutic avenue to be explored is the diagnostic use of Na v channel expression patterns observed in tumor tissues as cancer biomarkers. A number of research articles have revealed a potential role for Na v channels in treating a variety of neuronal medical conditions, such as diabetic neuropathy, cognitive dysfunction, autism, and multiple sclerosis, where there may be opportunities for developing novel treatments.
Diabetes mellitus is commonly associated with painful peripheral neuropathy, and it has traditionally been thought that pathological changes during diabetes may be the cause of neuropathy. Recently Hoeijmakers and co-workers came up with the intriguing hypothesis that painful neuropathy is not a complication of diabetes but rather occurs as a result of Na v 1. It has been suggested that dysfunction of Na v 1. Impaired cognitive performance associated with reduced expression of Na v 1.
As a consequence, Na v 1. The function of Na v subtypes Na v 1. Thus, Na v 1. Furthermore, the upregulation of Na v 1. Consistently, MS-like deficits observed in the mouse model could be partially reversed with the Na v 1.
In summary, we have illustrated the important role of Na v channels in physiological processes and the consequences of Na v channel dysfunction, often caused by mutations, leading to a broad spectrum of diseases associated with various genetic phenotypes.
Because of their key role in neuronal conduction and muscle contraction, Na v channels have been successfully targeted for decades by antiepileptic and antiarrhythmic agents and by local anesthetics.
However, currently available Na v channel modulators are not selective and often suffer from a limited therapeutic index. Genetic studies in recent years have pinpointed the role of specific Na v channel subtypes in certain disease phenotypes and hence identified novel, genetically validated drug targets.
The Na v arena holds promise, and research investment from academics, biotech, and the pharmaceutical industry is substantial. The key to success for any novel therapeutic Na v channel modulators will be increased potency and selectivity that can improve efficacy and safety margins relative to existing nonselective treatment options.
Natural Products and Their Derivatives. Throughout history, envenoming by animal and plant toxins has fascinated humans. By producing toxins that target Na v channels, venomous animals and poisonous plants exploit the excitatory and inhibitory action of toxins to incapacitate prey or defend against predators Figure 3. Not only do toxins from scorpions, sea anemones, spiders, cone snails, insects, and plant extracts serve as important chemical tools for understanding Na v channel structure, pharmacology and physiology, but they also provide extraordinary leads for developing novel subtype-selective agents that have therapeutic potential.
They serve as an important reminder of the vital role of natural products in drug discovery research. TTX inhibits Na v 1. TTX has a rigid structure comprised of a atom carbon—oxygen cage and a fused 6-membered guanidinium ring. It is present mainly in marine species such as puffer fish, blue ringed octopus, and some worms, shellfish, and crustaceans, although it can also be found in terrestrial animals such as some amphibians and in bacteria. Whether TTX accumulates after dietary administration or is biosynthesized in each of the above species still remains to be clarified.
On the other hand, it is well-known that STX is produced by single-celled dinoflagellate algae and freshwater cyanobacteria, although it is most commonly associated with oceanic red tides and shellfish poisoning. STX is an unusual tricyclic bisguanidinium compound with functional activity equivalent to that of TTX. When occupied, the guanidinium toxic binding site resembles a conical hole plugged by a stopper.
In this site, named Site 1 Figure 4 , negatively charged carboxylate groups of acidic amino acid residues form two charged rings at the outer pore of the Na v channel. Chen and Chung examined the inhibition of the Na v 1. Interestingly, it was observed that the guanidinium group of TTX adopts a lateral orientation, as opposed to protruding into the SF as previously thought. Despite its close structural similarity to TTX, metabolite 4 is a Na v 1.
One exception is the recently isolated deoxy-analogue 5 6-deoxy-TTX, Figure 6 , which EC 50 was found to be three times greater than that of TTX in a mouse neuroblastoma cell-based assay. Figure 6. Structure of guanidinium-based nonpeptidic toxins. CTXs are found on dead coral surfaces and bottom-dwelling algae, and PbTxs are responsible for the red tides off the Florida coast and Gulf of Mexico that cause massive fish kills and mortalities in birds, marine mammals, and other marine species.
These toxins accumulate in tissues of fish that eat the algae and bioaccumulate through the food chain, where they are oxidized to more toxic metabolites before being ingested by humans.
Interestingly, the Na v 1. Type B brevetoxin PbTx-3 shows tissue selectivity in humans and rats, binding to the heart tissue with a significantly lower affinity than to skeletal muscle and brain tissues. Figure 7. Brevetoxins and ciguatoxins. Ciguatera fish poisoning CFP is caused by consuming ciguateric reef fish. The initial symptoms consist of gastrointestinal effects nausea, diarrhea, and abdominal pain and usually disappear within 2 days to 1 week.
The neurological signs, which develop after 2—5 days and can last for months or even 1 year, include paresthesias, painful dysesthesias, ataxia, and cold allodynia. Trying to understand how brain neuron and astrocyte signals underlie the mechanism of ciguatera poisoning, Li and co-workers isolated CTX-1 from the viscera of moray eels and administered it orally or cerebroventricularly to rats.
They showed that CTX-1 elicited neuronal hyperexcitability, facilitating synaptic transmission and blocking the induction of long-term potentiation in the anterior cingulate cortex. Between and cases of CFP are reported each year, and these numbers are expected to grow because of global warming, 89 so a major effort is currently underway to develop better detection and quantification technologies and methods to attenuate the neurotoxic effect of these toxins.
Batrachotoxin BTX, 11 , Figures 3 B and 8 is a complex steroidal alkaloid isolated from the skin secretion of frogs of the genus Phyllobates found in South and Central America. One frog has enough poison to prepare around 50 hunting darts.
Because Phyllobates frogs in captivity are entirely free of BTX, it is believed that this toxin has a dietary origin. The presence of BTX in these birds has been linked to the consumption of small beetles of the melyrid family. Unfortunately, SAR and pharmacology studies of BTX and their analogues have been limited by difficulties in obtaining BTX, either from natural sources or synthetically.
Veratridine VTD, 13 , Figure 8 is another steroidal alkaloid neurotoxin isolated from the seeds of the Central America and Mexican plant sabadilla lily.
Marine macrocyclic natural products form another class of nonpeptidic Na v ligands. Although this class of compounds has not received much attention, antillatoxin 15 , Figure 8 , 97 a natural product isolated from a marine cyanobacteria, is a potent Na v agonist that binds at Site 2. During millions of years of evolution, natural selection has favored animals whose venoms contain peptides neurotoxins that block or modify the function of ion channels.
Millions of unique disulfide-rich peptides from venomous spiders, scorpions, and mollusks, some of them known but the vast majority remaining undiscovered, serve as a tremendous, invaluable pool of novel agonists and antagonists with superb selectivity and potency against specific Na v subtypes.
Proteomic and transcriptomic analyses have revealed that individual spider and cone snail venoms can comprise more than distinct peptides, and scorpion venoms often contain as many as several hundred components. To facilitate the search for new therapeutic leads, several technologies have recently been developed to identify, isolate, and synthesize those peptides present in the enormous diversity of venom-derived neurotoxins. In this section, we summarize recent findings in the major venomous species already mentioned, with emphasis on peptides that possess the highest potency and subtype-selectivity at mammalian Na v s.
Cone snails, slow moving and unable to swim, are unique among the venomous species for their ability to deliver via a harpoon a diverse array of small disulfide-bridged conopeptides or conotoxins for prey capture. At present, only about 0. There are a number of cone snail venom peptide families that act on VGICs, ligand-gated ion channels, G protein-coupled receptors GPCRs , and neurotransmitter transporters. Importantly, these families of conotoxins provide some of the most subtype-selective Na v modulators, especially for Na v 1.
They consist of 16—26 residues, with six cysteine amino acids forming three conserved disulfide bonds that stabilize their three-dimensional structure. By stepwise replacement of the three cysteine residues with alanine in GIIIA, Sato and co-workers have demonstrated that all three disulfide bridges are essential for stabilizing the specific conformation of GIIIA needed for biological activity.
Because of its small size, selectivity profile, and analgesic efficacy in vivo, KIIIA presents an attractive starting point for the design of peptidomimetics. With the aim of improving potency and, most importantly, subtype-selectivity, a number of KIIIA peptidomimetics have been recently synthesized. In all cases, the toxin—channel complex was stabilized by three or four salt bridges.
Despite intense interest in Na v 1. Similarly, it would be useful to identify a conotoxin that selectively interacts with the Na v 1. Relatively little is known about the other four families of conotoxins that interact with Na v s.
Scorpions use a cocktail of toxins to immobilize their prey and to defend against predators. Scorpion venom consists of a complex mixture of peptides, enzymes, lipids, nucleotides, mucopolysaccharides, and biogenic amines. Within these cocktails, only a small set of peptides are responsible for the toxicity in humans and other mammals. Among these, long-chain peptides 61—70 amino acids interfere with Na v channel voltage-sensing function, increasing the depolarization of the membrane and the release of neurotransmitters by affecting activation or inactivation states.
These neurotoxins consist of small basic proteins with a single chain of 61—70 amino acids, some of which are strictly conserved. They share the same general location for eight cysteine residues that form four similar disulfide bridges so that they share a similar three-dimensional structure.
Both toxins impair fast inactivation of Na v 1. Neither Na v 1. Unfortunately, only a few structure—function studies with scorpion toxins have been undertaken because of the challenges of obtaining multimilligram quantities of these complex structures via isolation from natural sources or chemical synthesis. We envision that with the number of technological advances in the synthesis and isolation of structurally complex peptides, a new era of research in this fascinating field is just beginning.
More than species of spiders have been described and an even greater number remain to be characterized, making them the largest group of terrestrial predators.
Spider venoms are complex chemical cocktails that contain disulfide-rich peptides that modulate the activity of vertebrate Na v channels. Because a single venom can contain as many as peptides, it has been conservatively estimated that more than 10 million bioactive peptides are likely to be present in the venoms of spiders, of which only 0. It is remarkable that two such taxonomically diverse animals, one confined to marine environments and the other a terrestrial predator, have evolved such similar molecular scaffolds for targeting the Na v channels of their prey.
The mechanism by which NaSpTxs interact with mammalian Na v s is multifaceted, having three distinct effects on Na v channel function: inhibiting channel opening, delaying fast activation, and facilitating channel opening. There are 12 different families named Family 1—12 of NaSpTxs based on the specific spider species where the toxin is found.
NaSpTxs are useful therapeutic leads for the development of Na v -targeting analgesics. NaSpTxs contain an inhibitor cystine knot ICK motif that provides them with tremendous chemical, thermal, and biological stability. Notably, an ICK scaffold forms the core of the analgesic drug zinconotide Prialt , a peptidic toxin derived from the cone snail Conus magus.
The drug targets calcium channels and is approved in the U. Because NaSpTxs are gating modifiers rather than pore blockers, NaSpTxs are more likely to display superior subtype selectivity compared with small compounds that bind in the highly conserved pore of the channel.
Huwentoxins HWTXs are a group of neurotoxin peptides found in the venom of the Chinese bird tarantula Haplopelma huwena. Recently, Yi and co-workers have reported that another huwentoxin, HWTX-IV, shows antinociceptive effects in various mouse and rat models of inflammatory and neuropathic pain. Substitution of three C-terminal residues resulted in a severe reduction of toxin binding affinities 10—fold for TTX-sensitive Na v s from DRG neurons, a result suggesting that these three residues may have critical interactions with TTX-sensitive Na v s.
ProTx-II achieves Na v 1. Interestingly, some peptidic toxins have been observed to access their respective receptor sites and gain most of their binding affinity by partitioning into the lipid membrane. This seems to be the case for ProTx-II based on its demonstrated ability to bind to liposomes. Centipedes form another class of ancient extant terrestrial arthropods that use venom to capture prey. Sea anemone venoms contain toxins such as anthopleurin B Ap-B, Figure 3 C a that are known to bind to Site 3 of Na v s Figure 4 and can inhibit fast inactivation at nanomolar concentrations.
Most of the biologically active peptides in sea anemones remain unexplored. Although a number of mutagenic and pharmacological studies have been performed with anemone toxins such as Ap-A, Ap-B, and ATX-II, b research on this area is progressing slowly.
Zoanthids, marine animals found mainly in coral reefs and the deep sea, have been poorly studied and only some low-molecular-weight compounds with anti-inflammatory and antiparasitic activity have been isolated.
Although there have recently been major technological advances that facilitate high-throughput screening of venoms, as well as structural and functional characterization of venom components, many natural toxins remain to be discovered. In particular, the vast number of peptidic toxins represent an invaluable source for exploring how Na v subtype selectivity, a major challenge in this field, can be achieved.
Despite the tedious nature of purifying neurotoxins from complex venom mixtures, researchers have been successful in identifying peptides with the potential to treat various human diseases.
There are currently six FDA-approved drugs derived from venom peptides or proteins: zinconotide, a selective Ca v 2. Clinical Update. Most of the hundreds of ongoing clinical studies are evaluating new indications using first-generation Na v subtype-nonselective inhibitors that are already on the market, such as phenytoin, lidocaine, carbamazepine, bupivacaine, lamotrigine, oxcarbazepine, and eslicarbazepine, that bind at the local anesthetic site where amino acid residues are highly conserved among the different Na v subtypes Figure 5 A.
Two patent application reviews regarding Na v inhibitors have recently been published. After identification and characterization of 16 Figure 9 56 as a selective Na v 1. In addition, a benzimidazole series of potent Na v 1. Figure 9. Pfizer Na v inhibitors. Convergence, a company strongly focused on ion channels for the treatment of chronic pain, is developing CNV structure not disclosed as a potent, and selective state-dependent Na v 1. CNV has received orphan-drug designation by the FDA and is being developed for the treatment of trigeminal neuralgia, a very severe form of facial pain.
Results of a phase II study to evaluate the efficacy of CNV for treating trigeminal neuralgia showed that this compound reduced the pain severity and the number of paroxysms in all primary and secondary outcomes at a dose of mg tid. Notably, this study demonstrated for the first time the efficacy of a selective state-dependent Na v 1. This drug was well tolerated and showed no serious adverse events. Furthermore, recent results of a second phase II proof-of-concept study with CNV at a dose of mg bid in subjects with neuropathic pain from lumbosacral radiculopathy sciatica , showed a statistically significant reduction in pain.
In addition to drugs for chronic pain, Convergence is developing CNV structure not disclosed , b a highly potent and selective state-dependent Na v 1. There has been no disclosure of the chemical structure of any of these four Na v inhibitors, but based on a recent patent search they may be related to structures 24 , 25 , 26 , and 27 Figure Figure Convergence Pharmaceuticals Na v inhibitors.
Another clinical trial to evaluate XEN in the topical treatment of primary OA of a single knee is currently recruiting patients, and it is estimated that it will be completed by June Representative examples of recently published Na v 1.
A second product candidate, GDC structure not disclosed , is being developed in collaboration with Genentech for the treatment of pain.
Other Na v inhibitors. Nektar, a company specializing in water-soluble drug—polymer conjugates, is evaluating NKTR in phase I trials. Additionally, at efficacious doses of analgesia, NKTR exhibited a significantly reduced CNS penetration versus currently approved Na v inhibitors without showing major side effects such as impairment of motor coordination.
In preclinical in vitro studies, NKTR preferentially blocked abnormal rapidly firing neurons associated with neuropathic pain without affecting normal nerves, suggesting a frequency-dependent blockade of inactivated Na v s. WEX has two ongoing clinical studies to develop the marine natural product TTX, a phase III clinical study for the treatment of moderate to severe inadequately controlled cancer-related pain and a phase II clinical study to treat chemotherapy-induced neuropathic pain in cancer patients.
In both studies, TTX is administered via subcutaneous injection twice a day for 4 days. GlaxoSmithKline is developing GSK structure not disclosed but possibly related to 35 , Figure 12 , a broad-spectrum Na v inhibitor that is being evaluated in phase II clinical trials for the attenuation of cough by inhalation delivery in patients with chronic idiopathic cough. Gilead is developing GS structure not disclosed but possibly related to structure 36 , Figure 12 , a potent and selective inhibitor of the late sodium current of cardiac subtype Na v 1.
An oral dose 10—60 mg over 12 h of GS led to a shortening of the QTc interval in patients with long QT-3 syndrome without showing any safety concern. Because of extensive recent research and discoveries in the field of Na v channels, today we have a substantial body of information available on channel structure, physiological roles of Na v subtypes, and the impact of channel dysfunction on physiology leading to a variety of disorders.
A huge number of publications underscores a high interest in this field which undoubtedly offers an enormous potential for discovering new therapies. Many attempts have been made to identify novel Na v channel modulators, establishing a rich set of pharmacological tools to study channel structure and function and the effects of channel modulation in diseases.
The vigor of the current stream of research on Na v inhibitors is also highlighted by the hundreds of clinical studies currently underway to evaluate treatments for cardiovascular and respiratory diseases, epilepsy, and pain. The interest and need for novel pain therapies is particularly obvious. The current standard of care for moderate to severe chronic pain includes nonsteroidal anti-inflammatory drugs NSAIDs , tricyclic antidepressants, gabapentinoids, and opioids.
NSAIDs, as a widely prescribed option for OA, often suffer from minimal efficacy and potentially serious gastrointestinal and cardiovascular adverse effects. Gabapentinoids, such as gabapentin Neurontin and pregabalin Lyrica and tricyclic antidepressants show variable efficacy in pain patients and cause adverse effects, such as drowsiness, dizziness, and weight gain. Opioids can cause serious side effects such as constipation, nausea, sedation, dizziness, vomiting, and respiratory depression and may present a risk for addiction and tolerance in some patients.
Notably, pain has emerged as a very promising therapeutic indication for Na v inhibitors selectively targeting Na v 1. In particular, Na v 1. However, all currently approved Na v blockers in the clinic, such as local anesthetics, have limited clinical utility due to the lack of selectivity among the distinct Na v subtypes. The development of novel suitable therapeutic agents for selectively targeting Na v s presents a number of challenges: 1 Na v s are very complex molecular structures that rapidly transition through different states closed, open, or inactivated.
A more detailed perspective on the molecular structure of Na v will help to overcome some of the above listed challenges. Several bacterial Na v crystal structures have been elucidated to date, providing a way to visualize these channels. We anticipate that eukaryotic Na v crystal structures containing bound ligands at different channel states will be solved in the near future. Combined with recent advances in molecular dynamics simulations, this will enable the development of improved homology models for structure-based drug design.
Additionally, the recent generation of stable cell lines overexpressing specific Na v subtypes, and the advancements in functional ion-channel screening technologies, such as high throughput automated patch clamp assay, have spurred the development of in vitro assays for the detection and characterization of selective state-dependent and state-independent channel modulators.
Author Information. The authors declare no competing financial interest. Voltage gated sodium channels Handb. Springer GmbH. Voltage-gated sodium channels VGSCs are present in many tissue types within the human body including both cardiac and neuronal tissues. Like other channels, VGSCs activate, deactivate, and inactivate in response to changes in membrane potential. VGSCs also have a similar structure to other channels: 24 transmembrane segments arranged into four domains that surround a central pore.
The structure and elec. Because of their distribution throughout the body, VGSCs are implicated in a variety of diseases including epilepsy, cardiac arrhythmias, and neuropathic pain. As such the study of these channels is essential. This brief review will introduce sodium channel structure, physiol. Advances in targeting voltage-gated sodium channels with small molecules ChemMedChem , 7 , 1 — 30 Google Scholar There is no corresponding record for this reference. A quantitative description of membrane current and its application to conduction and excitation in nerve J.
Purification of the tetrodotoxin-binding component associated with the voltage-sensitive sodium channel from Electrophorus electricus electroplax membrane Proc. Society for Neuroscience. We generated Nav2 gene-deficient mice by inserting the lacZ gene. Besides in the lung, heart, dorsal root ganglia, and Schwann cells in the peripheral nervous system, Nav2 was expressed in neurons and ependymal cells in restricted areas of the CNS, particularly in the circumventricular organs, which are involved in body-fluid homeostasis.
Under water-depleted conditions, c-fos expression was markedly elevated in neurons in the subfornical organ and organum vasculosum laminae terminalis compared with wild-type animals, suggesting a hyperactive state in the Nav2-null mice. Moreover, the null mutants showed abnormal intakes of hypertonic saline under both water- and salt-depleted conditions. These findings suggest that the Nav2 channel plays an important role in the central sensing of body-fluid sodium level and regulation of salt intake behavior.
International Union of Pharmacology. Nomenclature and structure—function relationships of voltage-gated sodium channels Pharmacol. Diversity of mammalian voltage-gated sodium channels Ann. New York Academy of Sciences. A review, with refs. A variety of different isoforms of mammalian voltage-gated sodium channels have been identified.
These channels can be classified into 3 different types. All of these channels have been expressed in exogenous systems, and all of the genes have been mapped.
Three type 2 isoforms have been identified in heart, uterus, and muscle. These channels diverge from the type 1 channels in crit.
A single isoform identified in the PNS may represent a 3rd class of channels, in that it diverges from both type 1 and 2 channels. The type 3 channel has not been functionally expressed. Molecular mechanisms of neurotoxin action on voltage-gated sodium channels Biochimie , 82 9—10 — Google Scholar There is no corresponding record for this reference. Google Scholar There is no corresponding record for this reference. Covalent labeling of protein components of the sodium channel with a photoactivable derivative of a scorpion toxin Proc.
Purification of the saxitoxin receptor of the sodium channel from rat brain Proc. The saxitoxin receptor of the sodium channel from rat brain.
The crystal structure of a voltage-gated sodium channel Nature , — [ Crossref ], [ PubMed ], [ CAS ], Google Scholar 9 The crystal structure of a voltage-gated sodium channel. Nature Publishing Group.
Voltage-gated sodium NaV channels initiate elec. The arginine gating charges make multiple hydrophilic interactions within the voltage sensor, including unanticipated hydrogen bonds to the protein backbone.
Comparisons to previous open-pore potassium channel structures indicate that the voltage-sensor domains and the S4-S5 linkers dilate the central pore by pivoting together around a hinge at the base of the pore module. Fenestrations in the sides of the pore module are unexpectedly penetrated by fatty acyl chains that extend into the central cavity, and these portals are large enough for the entry of small, hydrophobic pore-blocking drugs. This structure provides the template for understanding elec.
Crystal structure of a voltage-gated sodium channel in two potentially inactivated states Nature , — [ Crossref ], [ PubMed ], [ CAS ], Google Scholar 10 Crystal structure of a voltage-gated sodium channel in two potentially inactivated states. In excitable cells, voltage-gated sodium NaV channels activate to initiate action potentials and then undergo fast and slow inactivation processes that terminate their ionic conductance. Inactivation is a hallmark of NaV channel function and is crit.
Here we report crystallog. Compared to previous structures of NaVAb channels with cysteine mutations in the pore-lining S6 helixes, the S6 helixes and the intracellular activation gate have undergone significant rearrangements: one pair of S6 helixes has collapsed towards the central pore axis and the other S6 pair has moved outward to produce a striking dimer-of-dimers configuration.
An increase in global structural asymmetry is obsd. The voltage-sensing domains have also shifted around the perimeter of the pore module in wild-type NaVAb, compared to the mutant channel, and local structural changes identify a conserved interaction network that connects distant mol. These potential inactivated-state structures provide new insights into NaV channel gating and novel avenues to drug development and therapy for a range of debilitating NaV channelopathies. Crystal structure of an orthologue of the NaChBac voltage-gated sodium channel Nature , — Google Scholar There is no corresponding record for this reference.
Structure of a bacterial voltage-gated sodium channel pore reveals mechanisms of opening and closing Nature Commun. Nature communications , 3 , ISSN:. Voltage-gated sodium channels are vital membrane proteins essential for electrical signalling; in humans, they are key targets for the development of pharmaceutical drugs.
Here we report the crystal structure of an open-channel conformation of NavMs, the bacterial channel pore from the marine bacterium Magnetococcus sp.
This produces an open activation gate of sufficient diameter to allow hydrated sodium ions to pass through. Comparison of the open and closed structures provides new insight into the features of the functional states present in the activation cycles of sodium channels and the mechanism of channel opening and closing.
Structure and function of voltage-gated sodium channels at atomic resolution Exp. A review. What is the topic of this review. The central goal of the research reviewed here is to understand the functional properties of voltage-gated sodium channels at the level of high-resoln.
What advances does it highlight. The key functional properties of voltage-gated sodium channels, including voltage-dependent activation. Sodium conductance and selectivity, block by local anesthetics and related drugs, and both fast and slow inactivation, are now understood at the level of protein structure with high resoln.
These emerging high-resoln. Voltage-gated sodium channels initiate action potentials in nerve, muscle and other excitable cells. Early physiol. This review article follows the topics of my Sharpey-Schafer Prize Lecture and gives an overview of research using a combination of biochem.
Structural models for voltage-dependent activation, sodium selectivity and conductance, drug block and both fast and slow inactivation are discussed. A perspective for the future envisions new advances in understanding the structural basis for sodium channel function and the opportunity for structure-based discovery of novel therapeutics. Prokaryotic Na v Ms channel as a structural and functional model for eukaryotic sodium channel antagonism Proc.
Molecular dynamics of ion transport through the open conformation of a bacterial voltage-gated sodium channel Proc. Two alternative conformations of a voltage-gated sodium channel J. Ion conduction and conformational flexibility of a bacterial voltage-gated sodium channel Proc.
Sodium channel selectivity and conduction: prokaryotes have devised their own molecular strategy J. Role of the C-terminal domain in the structure and function of tetrameric sodium channels Nature Commun. Nature Communications , 4 , , 10 pp. Voltage-gated sodium channels have essential roles in elec. Prokaryotic sodium channels are tetramers consisting of transmembrane TM voltage-sensing and pore domains, and a cytoplasmic carboxy-terminal domain.
Previous crystal structures of bacterial sodium channels revealed the nature of their TM domains but not their C-terminal domains CTDs. Functional analyses demonstrate that the coiled-coil domain couples inactivation with channel opening, and is enabled by neg. A mechanism for gating is proposed based on the structure, whereby splaying of the bottom of the pore is possible without requiring unravelling of the coiled-coil.
Asymmetric functional contributions of acidic and aromatic side chains in sodium channel voltage-sensor domains J. Investigating the size and dynamics of voltage-gated sodium channel fenestrations Channels , 8 3 — Google Scholar There is no corresponding record for this reference. Voltage-gated sodium channel Na v protein dissection creates a set of functional pore-only proteins Proc. Structure of a prokaryotic sodium channel pore reveals essential gating elements and an outer ion binding site common to eukaryotic channels J.
Calcium channel characteristics conferred on the sodium channel by single mutations Nature , , — [ Crossref ], [ PubMed ], [ CAS ], Google Scholar 19 Calcium channel characteristics conferred on the sodium channel by single mutations. Heinemann, Stefan H. This selectivity presumably reflects a distinct structure of its ion-conducting pore.
Two clusters of predominantly neg. All site-directed mutations reducing net neg. These amino-acid substitutions, unlike other substitutions in the adjacent regions, alter ion-selection properties of the sodium channel to resemble those of calcium channels. This result indicates that lysine 1, and alanine 1, are crit. Analysis of the selectivity filter of the voltage-gated sodium channel Na v Rh Cell Res. NaChBac is a bacterial voltage-gated sodium Nav channel that shows sequence similarity to voltage-gated calcium channels.
To understand the ion-permeation mechanism of Nav channels, we combined mol. In addn. From ionic currents to molecular mechanisms: the structure and function of voltage-gated sodium channels Neuron , 26 , 13 — 25 [ Crossref ], [ PubMed ], [ CAS ], Google Scholar 22 From ionic currents to molecular mechanisms: the structure and function of voltage-gated sodium channels.
Cell Press. Molecular architecture of a sodium channel S6 helix J. Deletion mutation of sodium channel Na v 1. Evolutionarily conserved intracellular gate of voltage-dependent sodium channels Nature Commun.
Nature communications , 5 , ISSN:. Members of the voltage-gated ion channel superfamily VGIC regulate ion flux and generate electrical signals in excitable cells by opening and closing pore gates. The location of the gate in voltage-gated sodium channels, a founding member of this superfamily, remains unresolved. Here we explore the chemical modification rates of introduced cysteines along the S6 helix of domain IV in an inactivation-removed background.
We find that state-dependent accessibility is demarcated by an S6 hydrophobic residue; substituted cysteines above this site are not modified by charged thiol reagents when the channel is closed. These accessibilities are consistent with those inferred from open- and closed-state structures of prokaryotic sodium channels.
Our findings suggest that an intracellular gate composed of a ring of hydrophobic residues is not only responsible for regulating access to the pore of sodium channels, but is also a conserved feature within canonical members of the VGIC superfamily. Proton sensors in the pore domain of the cardiac voltage-gated sodium channel J.
Frontiers Research Foundation. As such, they may prove useful in disease diagnosis and therapy. The fibroblast growth factor voltage-gated sodium channel complex is a new target of glycogen synthase kinase 3 GSK3 J.
Neurological perspectives on voltage-gated sodium channels Brain , , — [ Crossref ], [ PubMed ], [ CAS ], Google Scholar 31 Neurological perspectives on voltage-gated sodium channels.
The activity of voltage-gated sodium channels has long been linked to disorders of neuronal excitability such as epilepsy and chronic pain. Recent genetic studies have now expanded the role of sodium channels in health and disease, to include autism, migraine, multiple sclerosis, cancer as well as muscle and immune system disorders.
Transgenic mouse models have proved useful in understanding the physiological role of individual sodium channels, and there has been significant progress in the development of subtype selective inhibitors of sodium channels. This review will outline the functions and roles of specific sodium channels in electrical signalling and disease, focusing on neurological aspects.
We also discuss recent advances in the development of selective sodium channel inhibitors. Altered sodium channel gating as molecular basis for pain: contribution of activation, inactivation, and resurgent currents Handb. Mutations in voltage-gated sodium channels, esp. Functional anal. The mutations are distributed over the whole channel protein, but nevertheless induce similar changes for each pain syndrome.
In this review we focus on their impact on sodium channel gating, which may be conferred via modulation of 1 conformation affecting all gating characteristics ; 2 the amt. Understanding the mol. Human voltage-gated sodium channel mutations that cause inherited neuronal and muscle channelopathies increase resurgent sodium currents J.
Tetrodotoxin-resistant sodium channels in sensory neurons generate slow resurgent currents that are enhanced by inflammatory mediators J. Resurgent sodium currents contribute to the regeneration of action potentials and enhanced neuronal excitability.
Tetrodotoxin-sensitive TTX-S resurgent currents have been described in many different neuron populations, including cerebellar and dorsal root ganglia DRG neurons. In most cases, sodium channel Nav1. However, the TTX-R resurgent currents exhibit much slower kinetics, occur at more depolarized voltages, and are sensitive to the Nav1. Moreover, coimmunopptn. We propose that these slow TTX-R resurgent currents contribute to the membrane excitability of nociceptive DRG neurons under normal conditions and that enhancement of both types of resurgent currents by inflammatory mediators could contribute to sensory neuronal hyperexcitability assocd.
Pathophysiological role of omega pore current in channelopathies Front. Biophysics, pathophysiology, and pharmacology of ion channel gating pores Front. Noncanonical roles of voltage-gated sodium channels Neuron , 80 2 — Google Scholar There is no corresponding record for this reference. De novo mutations revealed by whole-exome sequencing are strongly associated with autism Nature , — Google Scholar There is no corresponding record for this reference. Regulation of cough and action potentials by voltage-gated Na channels Pulm.
Elsevier Ltd. The classical role ascribed to voltage-gated Na channels is the conduction of action potentials.
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