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Gilchrist JM, Yang ND, Jiang V, Moyer BD. Pharmacologic Characterization of LTGO-33, a Selective Small Molecule Inhibitor of the Voltage-Gated Sodium Channel Na V1.8 with a Unique Mechanism of Action. Mol Pharmacol 2024; 105:233-249. [PMID: 38195157 DOI: 10.1124/molpharm.123.000789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/28/2023] [Accepted: 01/02/2024] [Indexed: 01/11/2024] Open
Abstract
Discovery and development of new molecules directed against validated pain targets is required to advance the treatment of pain disorders. Voltage-gated sodium channels (NaVs) are responsible for action potential initiation and transmission of pain signals. NaV1.8 is specifically expressed in peripheral nociceptors and has been genetically and pharmacologically validated as a human pain target. Selective inhibition of NaV1.8 can ameliorate pain while minimizing effects on other NaV isoforms essential for cardiac, respiratory, and central nervous system physiology. Here we present the pharmacology, interaction site, and mechanism of action of LTGO-33, a novel NaV1.8 small molecule inhibitor. LTGO-33 inhibited NaV1.8 in the nM potency range and exhibited over 600-fold selectivity against human NaV1.1-NaV1.7 and NaV1.9. Unlike prior reported NaV1.8 inhibitors that preferentially interacted with an inactivated state via the pore region, LTGO-33 was state-independent with similar potencies against closed and inactivated channels. LTGO-33 displayed species specificity for primate NaV1.8 over dog and rodent NaV1.8 and inhibited action potential firing in human dorsal root ganglia neurons. Using chimeras combined with mutagenesis, the extracellular cleft of the second voltage-sensing domain was identified as the key site required for channel inhibition. Biophysical mechanism of action studies demonstrated that LTGO-33 inhibition was relieved by membrane depolarization, suggesting the molecule stabilized the deactivated state to prevent channel opening. LTGO-33 equally inhibited wild-type and multiple NaV1.8 variants associated with human pain disorders. These collective results illustrate LTGO-33 inhibition via both a novel interaction site and mechanism of action previously undescribed in NaV1.8 small molecule pharmacologic space. SIGNIFICANCE STATEMENT: NaV1.8 sodium channels primarily expressed in peripheral pain-sensing neurons represent a validated target for the development of novel analgesics. Here we present the selective small molecule NaV1.8 inhibitor LTGO-33 that interdicts a distinct site in a voltage-sensor domain to inhibit channel opening. These results inform the development of new analgesics for pain disorders.
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Affiliation(s)
| | - Nien-Du Yang
- Latigo Biotherapeutics, Inc., Thousand Oaks, California
| | | | - Bryan D Moyer
- Latigo Biotherapeutics, Inc., Thousand Oaks, California
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Ahern CA, Payandeh J, Bosmans F, Chanda B. The hitchhiker's guide to the voltage-gated sodium channel galaxy. ACTA ACUST UNITED AC 2016; 147:1-24. [PMID: 26712848 PMCID: PMC4692491 DOI: 10.1085/jgp.201511492] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
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.
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Affiliation(s)
- Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242
| | - Jian Payandeh
- Department of Structural Biology, Genentech, Inc., South San Francisco, CA 94080
| | - Frank Bosmans
- Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205 Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
| | - Baron Chanda
- Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705 Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705
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Salari A, Vega BS, Milescu LS, Milescu M. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels. Sci Rep 2016; 6:23894. [PMID: 27045173 PMCID: PMC4820701 DOI: 10.1038/srep23894] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 03/16/2016] [Indexed: 01/26/2023] Open
Abstract
Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b–S4 “paddle motif,” which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple toxin binding sites. We show here that the S3–S4 segments within Cav3.1 can be transplanted into Kv2.1 to examine their individual contributions to voltage sensing and pharmacology. With these results, we now have a more complete picture of the conserved nature of the paddle motif in all three major voltage-gated ion channel types (Kv, Nav, and Cav). When screened with tarantula toxins, the four paddle sequences display distinct toxin binding properties, demonstrating that gating-modifier toxins can bind to Cav channels in a domain specific fashion. Domain III was the most commonly and strongly targeted, and mutagenesis revealed an acidic residue that is important for toxin binding. We also measured the lipid partitioning strength of all toxins tested and observed a positive correlation with their inhibition of Cav3.1, suggesting a key role for membrane partitioning.
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Affiliation(s)
- Autoosa Salari
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Benjamin S Vega
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Lorin S Milescu
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
| | - Mirela Milescu
- University of Missouri, Division of Biological Sciences, Columbia, 65211, USA
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Xiao Y, Blumenthal K, Cummins TR. Gating-pore currents demonstrate selective and specific modulation of individual sodium channel voltage-sensors by biological toxins. Mol Pharmacol 2014; 86:159-67. [PMID: 24898004 DOI: 10.1124/mol.114.092338] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Voltage-gated sodium channels are critical determinants of nerve and muscle excitability. Although numerous toxins and small molecules target sodium channels, identifying the mechanisms of action is challenging. Here we used gating-pore currents selectively generated in each of the voltage-sensors from the four α-subunit domains (DI-DIV) to monitor the activity of individual voltage-sensors and to investigate the molecular determinants of sodium channel pharmacology. The tarantula toxin huwentoxin-IV (HWTX-IV), which inhibits sodium channel current, exclusively enhanced inward gating-pore currents through the DII voltage-sensor. By contrast, the tarantula toxin ProTx-II, which also inhibits sodium channel currents, altered the gating-pore currents in multiple voltage-sensors in a complex manner. Thus, whereas HWTX-IV inhibits central-pore currents by selectively trapping the DII voltage-sensor in the resting configuration, ProTx-II seems to inhibit central-pore currents by differentially altering the configuration of multiple voltage-sensors. The sea anemone toxin anthopleurin B, which impairs open-channel inactivation, exclusively enhanced inward gating-pore currents through the DIV voltage-sensor. This indicates that trapping the DIV voltage-sensor in the resting configuration selectively impairs open-channel inactivation. Furthermore, these data indicate that although activation of all four voltage-sensors is not required for central-pore current generation, activation of the DII voltage-sensor is crucial. Overall, our data demonstrate that gating-pore currents can determine the mechanism of action for sodium channel gating modifiers with high precision. We propose this approach could be adapted to identify the molecular mechanisms of action for gating modifiers of various voltage-gated ion channels.
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Affiliation(s)
- Yucheng Xiao
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana (Y.X., T.R.C.); Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York (K.B.)
| | - Kenneth Blumenthal
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana (Y.X., T.R.C.); Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York (K.B.)
| | - Theodore R Cummins
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana (Y.X., T.R.C.); Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York (K.B.)
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Abstract
Voltage-gated sodium (Nav) channels are essential contributors to neuronal excitability, making them the most commonly targeted ion channel family by toxins found in animal venoms. These molecules can be used to probe the functional aspects of Nav channels on a molecular level and to explore their physiological role in normal and diseased tissues. This chapter summarizes our existing knowledge of the mechanisms by which animal toxins influence Nav channels as well as their potential application in designing therapeutic drugs.
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Park JH, Carlin KP, Wu G, Ilyin VI, Kyle DJ. Cysteine racemization during the Fmoc solid phase peptide synthesis of the Nav1.7-selective peptide - protoxin II. J Pept Sci 2012; 18:442-8. [DOI: 10.1002/psc.2407] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Revised: 02/01/2012] [Accepted: 02/17/2012] [Indexed: 12/16/2022]
Affiliation(s)
- Jae H. Park
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Kevin P. Carlin
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Gang Wu
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Victor I. Ilyin
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
| | - Donald J. Kyle
- Discovery Research; Purdue Pharma LP. 6 Cedar Brook Drive Cranbury NJ 08512 USA
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Palmitoylation influences the function and pharmacology of sodium channels. Proc Natl Acad Sci U S A 2011; 108:20213-8. [PMID: 22123950 DOI: 10.1073/pnas.1108497108] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Palmitoylation is a common lipid modification known to regulate the functional properties of various proteins and is a vital step in the biosynthesis of voltage-activated sodium (Nav) channels. We discovered a mutation in an intracellular loop of rNav1.2a (G1079C), which results in a higher apparent affinity for externally applied PaurTx3 and ProTx-II, two voltage sensor toxins isolated from tarantula venom. To explore whether palmitoylation of the introduced cysteine underlies this observation, we compared channel susceptibility to a range of animal toxins in the absence and presence of 2-Br-palmitate, a palmitate analog that prevents palmitate incorporation into proteins, and found that palmitoylation contributes to the increased affinity of PaurTx3 and ProTx-II for G1079C. Further investigations with 2-Br-palmitate revealed that palmitoylation can regulate the gating and pharmacology of wild-type (wt) rNav1.2a. To identify rNav1.2a palmitoylation sites contributing to these phenomena, we substituted three endogenous cysteines predicted to be palmitoylated and found that the gating behavior of this triple cysteine mutant is similar to wt rNav1.2a treated with 2-Br-palmitate. As with chemically depalmitoylated rNav1.2a channels, this mutant also exhibits an increased susceptibility for PaurTx3. Additional mutagenesis experiments showed that palmitoylation of one cysteine in particular (C1182) primarily influences PaurTx3 sensitivity and may enhance the inactivation process of wt rNav1.2a. Overall, our results demonstrate that lipid modifications are capable of altering the gating and pharmacological properties of rNav1.2a.
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Edgerton GB, Blumenthal KM, Hanck DA. Inhibition of the activation pathway of the T-type calcium channel Ca(V)3.1 by ProTxII. Toxicon 2010; 56:624-36. [PMID: 20600227 DOI: 10.1016/j.toxicon.2010.06.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 06/12/2010] [Accepted: 06/15/2010] [Indexed: 11/18/2022]
Abstract
Toxins have been used extensively to probe the gating mechanisms of voltage-gated ion channels. Relatively few such tools are available to study the low-voltage activated T-type Ca channels, which underlie thalamic neuron firing and affect sleep, resistance to seizures, and weight gain. Here we show that ProTxII, a peptide toxin recently isolated from the venom of the tarantula spider Thrixopelma pruriens, dose-dependently inhibited Ca(V)3.1 causing a decrease in current (81.6% +/- 3.1% at -30 mV in 5 microM toxin) and a positive shift in the voltage range of activation (+34.5 mV +/- 4.4 mV). Toxin-modified currents were slower to activate and faster to deactivate and they displayed a longer lag in the onset of current, i.e. the Cole-Moore shift, consistent with the inhibition of gating transitions along the activation pathway, particularly the final opening transition. Single-channel current amplitude and total gating charge were unaffected by toxin, ruling out a change in ion flux or channel dropout as mechanisms for the decrease in macroscopic conductance. A positive shift in the voltage range of gating charge movement (+30.6 mV +/- 2.6 mV shift in the voltage of half maximal charge movement in the presence of 5 microM toxin) confirmed that ProTxII-induced gating perturbations in this channel occur at the level of the voltage sensors, and kinetic modeling based on these findings suggested that reductions in current magnitude could be largely accounted for by kinetic perturbations of activation.
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Affiliation(s)
- Gabrielle B Edgerton
- Committee on Neurobiology, University of Chicago, 5841 S. Maryland Avenue, MC6094, Chicago, IL 60637, USA
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Lampert A, O'Reilly AO, Reeh P, Leffler A. Sodium channelopathies and pain. Pflugers Arch 2010; 460:249-63. [PMID: 20101409 DOI: 10.1007/s00424-009-0779-3] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 12/13/2009] [Accepted: 12/18/2009] [Indexed: 12/19/2022]
Abstract
Chronic pain often represents a severe, debilitating condition. Up to 10% of the worldwide population are affected, and many patients are poorly responsive to current treatment strategies. Nociceptors detect noxious conditions to produce the sensation of pain, and this signal is conveyed to the CNS by means of action potentials. The fast upstroke of action potentials is mediated by voltage-gated sodium channels, of which nine pore-forming alpha-subunits (Nav1.1-1.9) have been identified. Heterogeneous functional properties and distinct expression patterns denote specialized functions of each subunit. The Nav1.7 and Nav1.8 subunits have emerged as key molecules involved in peripheral pain processing and in the development of an increased pain sensitivity associated with inflammation and tissue injury. Several mutations in the SCN9A gene encoding for Nav1.7 have been identified as important cellular substrates for different heritable pain syndromes. This review aims to cover recent progress on our understanding of how biophysical properties of mutant Nav1.7 translate into an aberrant electrogenesis of nociceptors. We also recapitulate the role of Nav1.8 for peripheral pain processing and of additional sodium channelopathies which have been linked to disorders with pain as a significant component.
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Affiliation(s)
- Angelika Lampert
- Department of Physiology and Pathophysiology, Friedrich-Alexander University Erlangen-Nuremberg, Universitätsstrasse 17, 91054, Erlangen, Germany.
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Targeting voltage sensors in sodium channels with spider toxins. Trends Pharmacol Sci 2010; 31:175-82. [PMID: 20097434 DOI: 10.1016/j.tips.2009.12.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 12/15/2009] [Accepted: 12/17/2009] [Indexed: 12/19/2022]
Abstract
Voltage-activated sodium (Nav) channels are essential in generating and propagating nerve impulses, placing them amongst the most widely targeted ion channels by toxins from venomous organisms. An increasing number of spider toxins have been shown to interfere with the voltage-driven activation process of mammalian Nav channels, possibly by interacting with one or more of their voltage sensors. This review focuses on our existing knowledge of the mechanism by which spider toxins affect Nav channel gating and the possible applications of these toxins in the drug discovery process.
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Redaelli E, Cassulini RR, Silva DF, Clement H, Schiavon E, Zamudio FZ, Odell G, Arcangeli A, Clare JJ, Alagón A, de la Vega RCR, Possani LD, Wanke E. Target promiscuity and heterogeneous effects of tarantula venom peptides affecting Na+ and K+ ion channels. J Biol Chem 2009; 285:4130-4142. [PMID: 19955179 DOI: 10.1074/jbc.m109.054718] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Venom-derived peptide modulators of ion channel gating are regarded as essential tools for understanding the molecular motions that occur during the opening and closing of ion channels. In this study, we present the characterization of five spider toxins on 12 human voltage-gated ion channels, following observations about the target promiscuity of some spider toxins and the ongoing revision of their "canonical" gating-modifying mode of action. The peptides were purified de novo from the venom of Grammostola rosea tarantulas, and their sequences were confirmed by Edman degradation and mass spectrometry analysis. Their effects on seven tetrodotoxin-sensitive Na(+) channels, the three human ether-à-go-go (hERG)-related K(+) channels, and two human Shaker-related K(+) channels were extensively characterized by electrophysiological techniques. All the peptides inhibited ion conduction through all the Na(+) channels tested, although with distinctive patterns. The peptides also affected the three pharmaceutically relevant hERG isoforms differently. At higher concentrations, all peptides also modified the gating of the Na(+) channels by shifting the activation to more positive potentials, whereas more complex effects were recorded on hERG channels. No effects were evident on the two Shaker-related K(+) channels at concentrations well above the IC(50) value for the affected channels. Given the sequence diversity of the tested peptides, we propose that tarantula toxins should be considered both as multimode and target-promiscuous ion channel modulators; both features should not be ignored when extracting mechanistic interpretations about ion channel gating. Our observations could also aid in future structure-function studies and might help the development of novel ion channel-specific drugs.
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Affiliation(s)
- Elisa Redaelli
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy
| | - Rita Restano Cassulini
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy; the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Deyanira Fuentes Silva
- the Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán DF 04510, México
| | - Herlinda Clement
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Emanuele Schiavon
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy
| | - Fernando Z Zamudio
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - George Odell
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Annarosa Arcangeli
- the Dipartimento di Patologia e Oncologia Sperimentali, Università di Firenze, Viale Morgagni 50, 50134 Firenze, Italy
| | - Jeffrey J Clare
- Gene Expression and Protein Biochemistry, GlaxoSmithKline, Medicines Research Centre, Gunnels Wood Road, Stevenage, Herts SG1 2NY, United Kingdom, and
| | - Alejandro Alagón
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Ricardo C Rodríguez de la Vega
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México; the Structural and Computational Biology/Genome Biology Units, European Molecular Biology Laboratory, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Lourival D Possani
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Enzo Wanke
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy.
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