Deconstructing voltage sensor function and pharmacology in sodium channels

Article metrics


Voltage-activated sodium (Nav) channels are crucial for the generation and propagation of nerve impulses, and as such are widely targeted by toxins and drugs. The four voltage sensors in Nav channels have distinct amino acid sequences, raising fundamental questions about their relative contributions to the function and pharmacology of the channel. Here we use four-fold symmetric voltage-activated potassium (Kv) channels as reporters to examine the contributions of individual S3b–S4 paddle motifs within Nav channel voltage sensors to the kinetics of voltage sensor activation and to forming toxin receptors. Our results uncover binding sites for toxins from tarantula and scorpion venom on each of the four paddle motifs in Nav channels, and reveal how paddle-specific interactions can be used to reshape Nav channel activity. One paddle motif is unique in that it slows voltage sensor activation, and toxins selectively targeting this motif impede Nav channel inactivation. This reporter approach and the principles that emerge will be useful in developing new drugs for treating pain and Nav channelopathies.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Transfer of the voltage sensor paddle motifs from rNa v 1.2a to K v 2.1.
Figure 2: Sensitivity of rNa v 1.2a paddle chimaeras to extracellular toxins.
Figure 3: Scanning mutagenesis of Na v channel paddle motifs.
Figure 4: Reconstitution of paddle mutants into rNa v 1.2a and their effects on toxin–channel interactions.
Figure 5: Kinetics of opening and closing for rNa v 1.2a/K v 2.1 chimaeras.
Figure 6: Identifying a tarantula toxin selective for the paddle motif in domain IV.


  1. 1

    Catterall, W. A. From ionic currents to molecular mechanisms: The structure and function of voltage-gated sodium channels. Neuron 26, 13–25 (2000)

  2. 2

    Cannon, S. C. Pathomechanisms in channelopathies of skeletal muscle and brain. Annu. Rev. Neurosci. 29, 387–415 (2006)

  3. 3

    George, A. L. Inherited disorders of voltage-gated sodium channels. J. Clin. Invest. 115, 1990–1999 (2005)

  4. 4

    Cox, J. J. et al. An SCN9A channelopathy causes congenital inability to experience pain. Nature 444, 894–898 (2006)

  5. 5

    Fertleman, C. R. et al. SCN9A mutations in paroxysmal extreme pain disorder: Allelic variants underlie distinct channel defects and phenotypes. Neuron 52, 767–774 (2006)

  6. 6

    Kaczorowski, G. J., McManus, O. B., Priest, B. T. & Garcia, M. L. Ion channels as drug targets: The next GPCRs. J. Gen. Physiol. 131, 399–405 (2008)

  7. 7

    Horn, R., Ding, S. & Gruber, H. J. Immobilizing the moving parts of voltage-gated ion channels. J. Gen. Physiol. 116, 461–476 (2000)

  8. 8

    Sheets, M. F., Kyle, J. W., Kallen, R. G. & Hanck, D. A. The Na channel voltage sensor associated with inactivation is localized to the external charged residues of domain IV, S4. Biophys. J. 77, 747–757 (1999)

  9. 9

    Yang, N. & Horn, R. Evidence for voltage-dependent S4 movement in sodium channels. Neuron 15, 213–218 (1995)

  10. 10

    Chanda, B. & Bezanilla, F. Tracking voltage-dependent conformational changes in skeletal muscle sodium channel during activation. J. Gen. Physiol. 120, 629–645 (2002)

  11. 11

    Catterall, W. A. et al. Voltage-gated ion channels and gating modifier toxins. Toxicon 49, 124–141 (2007)

  12. 12

    Alabi, A. A., Bahamonde, M. I., Jung, H. J., Kim, J. I. & Swartz, K. J. Portability of paddle motif function and pharmacology in voltage sensors. Nature 450, 370–375 (2007)

  13. 13

    Chakrapani, S., Cuello, L. G., Cortes, D. M. & Perozo, E. Structural dynamics of an isolated voltage-sensor domain in a lipid bilayer. Structure 16, 398–409 (2008)

  14. 14

    Jiang, Y. et al. X-ray structure of a voltage-dependent K+ channel. Nature 423, 33–41 (2003)

  15. 15

    Jiang, Y., Ruta, V., Chen, J., Lee, A. & MacKinnon, R. The principle of gating charge movement in a voltage-dependent K+ channel. Nature 423, 42–48 (2003)

  16. 16

    Ruta, V., Chen, J. & MacKinnon, R. Calibrated measurement of gating-charge arginine displacement in the KvAP voltage-dependent K+ channel. Cell 123, 463–475 (2005)

  17. 17

    Swartz, K. J. & MacKinnon, R. Mapping the receptor site for hanatoxin, a gating modifier of voltage-dependent K+ channels. Neuron 18, 675–682 (1997)

  18. 18

    Swartz, K. J. & MacKinnon, R. Hanatoxin modifies the gating of a voltage-dependent K+ channel through multiple binding sites. Neuron 18, 665–673 (1997)

  19. 19

    Li-Smerin, Y. & Swartz, K. J. Gating modifier toxins reveal a conserved structural motif in voltage-gated Ca2+ and K+ channels. Proc. Natl Acad. Sci. USA 95, 8585–8589 (1998)

  20. 20

    Li-Smerin, Y. & Swartz, K. J. Localization and molecular determinants of the Hanatoxin receptors on the voltage-sensing domains of a K(+) channel. J. Gen. Physiol. 115, 673–684 (2000)

  21. 21

    Lee, H. C., Wang, J. M. & Swartz, K. J. Interaction between extracellular Hanatoxin and the resting conformation of the voltage-sensor paddle in Kv channels. Neuron 40, 527–536 (2003)

  22. 22

    Lee, S. Y. & MacKinnon, R. A membrane-access mechanism of ion channel inhibition by voltage sensor toxins from spider venom. Nature 430, 232–235 (2004)

  23. 23

    Milescu, M. et al. Tarantula toxins interact with voltage sensors within lipid membranes. J. Gen. Physiol. 130, 497–511 (2007)

  24. 24

    Phillips, L. R. et al. Voltage-sensor activation with a tarantula toxin as cargo. Nature 436, 857–860 (2005)

  25. 25

    Bosmans, F. et al. Four novel tarantula toxins as selective modulators of voltage-gated sodium channel subtypes. Mol. Pharmacol. 69, 419–429 (2006)

  26. 26

    Middleton, R. E. et al. Two tarantula peptides inhibit activation of multiple sodium channels. Biochemistry 41, 14734–14747 (2002)

  27. 27

    Smith, J. J., Cummins, T. R., Alphy, S. & Blumenthal, K. M. Molecular interactions of the gating modifier toxin ProTx-II with NaV 1.5: Implied existence of a novel toxin binding site coupled to activation. J. Biol. Chem. 282, 12687–12697 (2007)

  28. 28

    Sokolov, S., Kraus, R. L., Scheuer, T. & Catterall, W. A. Inhibition of sodium channel gating by trapping the domain II voltage sensor with protoxin II. Mol. Pharmacol. 73, 1020–1028 (2008)

  29. 29

    Cahalan, M. D. Modification of sodium channel gating in frog myelinated nerve fibres by Centruroides sculpturatus scorpion venom. J. Physiol. (Lond.) 244, 511–534 (1975)

  30. 30

    Koppenhofer, E. & Schmidt, H. Effect of scorpion venom on ionic currents of the node of Ranvier. II. Incomplete sodium inactivation. Pflugers Arch. 303, 150–161 (1968)

  31. 31

    Rogers, J. C., Qu, Y., Tanada, T. N., Scheuer, T. & Catterall, W. A. Molecular determinants of high affinity binding of alpha-scorpion toxin and sea anemone toxin in the S3-S4 extracellular loop in domain IV of the Na+ channel alpha subunit. J. Biol. Chem. 271, 15950–15962 (1996)

  32. 32

    Cestele, S. et al. Voltage sensor-trapping: Enhanced activation of sodium channels by beta-scorpion toxin bound to the S3-S4 loop in domain II. Neuron 21, 919–931 (1998)

  33. 33

    Cestele, S. et al. Structure and function of the voltage sensor of sodium channels probed by a beta-scorpion toxin. J. Biol. Chem. 281, 21332–21344 (2006)

  34. 34

    Cohen, L. et al. Direct evidence that receptor site-4 of sodium channel gating modifiers is not dipped in the phospholipid bilayer of neuronal membranes. J. Biol. Chem. 281, 20673–20679 (2006)

  35. 35

    Tejedor, F. J. & Catterall, W. A. Site of covalent attachment of alpha-scorpion toxin derivatives in domain I of the sodium channel alpha subunit. Proc. Natl Acad. Sci. USA 85, 8742–8746 (1988)

  36. 36

    Marcotte, P., Chen, L. Q., Kallen, R. G. & Chahine, M. Effects of Tityus serrulatus scorpion toxin gamma on voltage-gated Na+ channels. Circ. Res. 80, 363–369 (1997)

  37. 37

    Campos, F. V., Chanda, B., Beirao, P. S. & Bezanilla, F. Beta-scorpion toxin modifies gating transitions in all four voltage sensors of the sodium channel. J. Gen. Physiol. 130, 257–268 (2007)

  38. 38

    Campos, F. V., Chanda, B., Beirao, P. S. & Bezanilla, F. Alpha-scorpion toxin impairs a conformational change that leads to fast inactivation of muscle sodium channels. J. Gen. Physiol. 132, 251–263 (2008)

  39. 39

    Cha, A., Ruben, P. C., George, A. L., Fujimoto, E. & Bezanilla, F. Voltage sensors in domains III and IV, but not I and II, are immobilized by Na+ channel fast inactivation. Neuron 22, 73–87 (1999)

  40. 40

    Sheets, M. F., Kyle, J. W. & Hanck, D. A. The role of the putative inactivation lid in sodium channel gating current immobilization. J. Gen. Physiol. 115, 609–620 (2000)

  41. 41

    Banerjee, A. & MacKinnon, R. Inferred motions of the S3a helix during voltage-dependent K+ channel gating. J. Mol. Biol. 381, 569–580 (2008)

  42. 42

    Ruta, V., Jiang, Y., Lee, A., Chen, J. & MacKinnon, R. Functional analysis of an archaebacterial voltage-dependent K+ channel. Nature 422, 180–185 (2003)

  43. 43

    Herrington, J. et al. Blockers of the delayed-rectifier potassium current in pancreatic beta-cells enhance glucose-dependent insulin secretion. Diabetes 55, 1034–1042 (2006)

  44. 44

    Lee, C. W. et al. Solution structure and functional characterization of SGTx1, a modifier of Kv2.1 channel gating. Biochemistry 43, 890–897 (2004)

  45. 45

    Armstrong, C. M. Na channel inactivation from open and closed states. Proc. Natl Acad. Sci. USA 103, 17991–17996 (2006)

  46. 46

    Chanda, B., Asamoah, O. K. & Bezanilla, F. Coupling interactions between voltage sensors of the sodium channel as revealed by site-specific measurements. J. Gen. Physiol. 123, 217–230 (2004)

  47. 47

    Wan, X., Chen, S., Sadeghpour, A., Wang, Q. & Kirsch, G. E. Accelerated inactivation in a mutant Na(+) channel associated with idiopathic ventricular fibrillation. Am. J. Physiol. Heart Circ. Physiol. 280, H354–H360 (2001)

  48. 48

    Bennett, P. B., Yazawa, K., Makita, N. & George, A. L. Molecular mechanism for an inherited cardiac arrhythmia. Nature 376, 683–685 (1995)

  49. 49

    Spampanato, J., Escayg, A., Meisler, M. H. & Goldin, A. L. Generalized epilepsy with febrile seizures plus type 2 mutation W1204R alters voltage-dependent gating of Na(v)1.1 sodium channels. Neuroscience 116, 37–48 (2003)

  50. 50

    Bendahhou, S., Cummins, T. R., Tawil, R., Waxman, S. G. & Ptacek, L. J. Activation and inactivation of the voltage-gated sodium channel: Role of segment S5 revealed by a novel hyperkalaemic periodic paralysis mutation. J. Neurosci. 19, 4762–4771 (1999)

  51. 51

    Frech, G. C., VanDongen, A. M., Schuster, G., Brown, A. M. & Joho, R. H. A novel potassium channel with delayed rectifier properties isolated from rat brain by expression cloning. Nature 340, 642–645 (1989)

  52. 52

    Stuhmer, W. et al. Molecular basis of functional diversity of voltage-gated potassium channels in mammalian brain. EMBO J. 8, 3235–3244 (1989)

  53. 53

    Tempel, B. L., Papazian, D. M., Schwarz, T. L., Jan, Y. N. & Jan, L. Y. Sequence of a probable potassium channel component encoded at Shaker locus of Drosophila. Science 237, 770–775 (1987)

  54. 54

    Auld, V. J. et al. A rat brain Na+ channel alpha subunit with novel gating properties. Neuron 1, 449–461 (1988)

  55. 55

    Trimmer, J. S. et al. Primary structure and functional expression of a mammalian skeletal muscle sodium channel. Neuron 3, 33–49 (1989)

  56. 56

    Garcia, M. L., Garcia-Calvo, M., Hidalgo, P., Lee, A. & MacKinnon, R. Purification and characterization of three inhibitors of voltage-dependent K+ channels from Leiurus quinquestriatus var. hebraeus venom. Biochemistry 33, 6834–6839 (1994)

  57. 57

    Hoshi, T., Zagotta, W. N. & Aldrich, R. W. Biophysical and molecular mechanisms of Shaker potassium channel inactivation. Science 250, 533–538 (1990)

  58. 58

    Swartz, K. J. & MacKinnon, R. An inhibitor of the Kv2.1 potassium channel isolated from the venom of a Chilean tarantula. Neuron 15, 941–949 (1995)

  59. 59

    Jung, H. J. et al. Solution structure and lipid membrane partitioning of VSTx1, an inhibitor of the KvAP potassium channel. Biochemistry 44, 6015–6023 (2005)

  60. 60

    Ceard, B., De Lima, M. E., Bougis, P. E. & Martin-Eauclaire, M. F. Purification of the main beta-toxin from Tityus serrulatus scorpion venom using high-performance liquid chromatography. Toxicon 30, 105–110 (1992)

  61. 61

    Martin, M. F., Rochat, H., Marchot, P. & Bougis, P. E. Use of high performance liquid chromatography to demonstrate quantitative variation in components of venom from the scorpion Androctonus australis hector . Toxicon 25, 569–573 (1987)

  62. 62

    Wang, G. K., Quan, C., Seaver, M. & Wang, S. Y. Modification of wild-type and batrachotoxin-resistant muscle mu1 Na+ channels by veratridine. Pflugers Arch. 439, 705–713 (2000)

Download references


We thank J. W. Kyle, D. A. Hanck and A. L. Goldin for the rNav1.2a, rNav1.4 and β1 clones, C. Deutsch for Kv1.3, M. M. Smith for GxTx-1E, K. M. Blumenthal and J. B. Herrington for ProTx-II, L. D. Possani for a sample of TsVII, the NINDS DNA sequencing facility for DNA sequencing, and the NINDS protein sequencing facility for mass spectrometry and peptide sequencing. We thank A. A. Alabi for helping with Kv and Nav channel alignments and T.-H. Chang for assistance with Nav channel mutants. We also thank A. A. Alabi, M. Holmgren, M. Mayer, M. Milescu, J. Mindell, A. Plested, S. Silberberg and members of the Swartz laboratory for discussions. This work was supported by the Intramural Research Program of the NINDS, NIH (K.J.S.) and by an NIH-FWO postdoctoral fellowship (F.B.).

Author information

Correspondence to Kenton J. Swartz.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-5 with Legends and Supplementary Tables 1-7. (PDF 4665 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bosmans, F., Martin-Eauclaire, M. & Swartz, K. Deconstructing voltage sensor function and pharmacology in sodium channels. Nature 456, 202–208 (2008) doi:10.1038/nature07473

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.