Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Light-activated ion channels for remote control of neuronal firing

Abstract

Neurons have ion channels that are directly gated by voltage, ligands and temperature but not by light. Using structure-based design, we have developed a new chemical gate that confers light sensitivity to an ion channel. The gate includes a functional group for selective conjugation to an engineered K+ channel, a pore blocker and a photoisomerizable azobenzene. Long-wavelength light drives the azobenzene moiety into its extended trans configuration, allowing the blocker to reach the pore. Short-wavelength light generates the shorter cis configuration, retracting the blocker and allowing conduction. Exogenous expression of these channels in rat hippocampal neurons, followed by chemical modification with the photoswitchable gate, enables different wavelengths of light to switch action potential firing on and off. These synthetic photoisomerizable azobenzene-regulated K+ (SPARK) channels allow rapid, precise and reversible control over neuronal firing, with potential applications for dissecting neural circuits and controlling activity downstream from sites of neural damage or degeneration.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Photoisomerization of MAL-AZO-QA gates ionic currents through modified Shaker channels.
Figure 2: Photocontrol of MAL-AZO-QA-modified Shaker channels in X. laevis oocytes.
Figure 3: Absorbance and action spectra of MAL-AZO-QA.
Figure 4: Expression of light-activated channels confers light sensitivity on hippocampal pyramidal neurons.

References

  1. 1

    Nerbonne, J.M. Caged compounds: tools for illuminating neuronal responses and connections. Curr. Opin. Neurobiol. 6, 379–386 (1996).

    CAS  Article  Google Scholar 

  2. 2

    James, D.A., Burns, D.C. & Woolley, G.A. Kinetic characterization of ribonuclease S mutants containing photoisomerizable phenylazophenylalanine residues. Protein Eng. 14, 983–991 (2001).

    CAS  Article  Google Scholar 

  3. 3

    Flint, D.G., Kumita, J.R., Smart, O.S. & Woolley, G.A. Using an azobenzene cross-linker to either increase or decrease peptide helix content upon trans-to-cis photoisomerization. Chem. Biol. 9, 391–397 (2002).

    CAS  Article  Google Scholar 

  4. 4

    Lester, H.A., Krouse, M.E., Nass, M.M., Wassermann, N.H. & Erlanger, B.F. A covalently bound photoisomerizable agonist: comparison with reversibly bound agonists at Electrophorus electroplaques. J. Gen. Physiol. 75, 207–232 (1980).

    CAS  Article  Google Scholar 

  5. 5

    Katz, L.C. & Dalva, M.B. Scanning laser photostimulation: a new approach for analyzing brain circuits. J. Neurosci. Methods 54, 205–218 (1994).

    CAS  Article  Google Scholar 

  6. 6

    Callaway, E.M. Caged neurotransmitters. Shedding light on neural circuits. Curr. Biol. 4, 1010–1012 (1994).

    CAS  Article  Google Scholar 

  7. 7

    Nitabach, M., Blau, J. & Holmes, T. Electrical silencing of Drosophila pacemaker neurons stops the free-running circadian clock. Cell 109, 485–495 (2002).

    CAS  Article  Google Scholar 

  8. 8

    Johns, D., Marx, R., Mains, R., O'Rourke, B. & Marban, E. Inducible genetic suppression of neuronal excitability. J. Neurosci. 19, 1691–1697 (1999).

    CAS  Article  Google Scholar 

  9. 9

    White, B. et al. Targeted attenuation of electrical activity in Drosophila using a genetically modified K+ channel. Neuron 31, 699–711 (2001).

    CAS  Article  Google Scholar 

  10. 10

    Lechner, H., Lein, E. & Callaway, E. A genetic method for selective and quickly reversible silencing of mammalian neurons. J. Neurosci. 22, 5287–5290 (2002).

    CAS  Article  Google Scholar 

  11. 11

    Slimko, E., McKinney, S., Anderson, D., Davidson, N. & Lester, H. Selective electrical silencing of mammalian neurons in vitro by the use of invertebrate ligand-gated chloride channels. J. Neurosci. 22, 7373–7379 (2002).

    CAS  Article  Google Scholar 

  12. 12

    Zemelman, B.V., Lee, G.A., Ng, M. & Miesenbock, G. Selective photostimulation of genetically chARGed neurons. Neuron 33, 15–22 (2002).

    CAS  Article  Google Scholar 

  13. 13

    Sigworth, F. Voltage gating of ion channels. Q. Rev. Biophys. 27, 1–40 (1994).

    CAS  Article  Google Scholar 

  14. 14

    Yellen, G. The voltage-gated potassium channels and their relatives. Nature 419, 35–42 (2002).

    CAS  Article  Google Scholar 

  15. 15

    MacKinnon, R. & Yellen, G. Mutations affecting TEA blockade and ion permeation in voltage-activated K+ channels. Science 250, 276–279 (1990).

    CAS  Article  Google Scholar 

  16. 16

    Heginbotham, L. & MacKinnon, R. The aromatic binding site for tetraethylammonium ion on potassium channels. Neuron 8, 483–491 (1992).

    CAS  Article  Google Scholar 

  17. 17

    Blaustein, R., Cole, P., Williams, C. & Miller, C. Tethered blockers as molecular 'tape measures' for a voltage-gated K+ channel. Nat. Struct. Biol. 7, 309–311 (2000).

    CAS  Article  Google Scholar 

  18. 18

    Doyle, D. et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280, 69–77 (1998).

    CAS  Article  Google Scholar 

  19. 19

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

    CAS  Article  Google Scholar 

  20. 20

    Knoll, H. Photoisomerism of azobenzenes. in CRC Handbook of Organic Photochemistry and Photobiology edn. 2 (eds. Horspool, W. & Lenci, F.) 89.1–89.16 (CRC Press, Boca Raton, Florida, USA, 2004).

    Google Scholar 

  21. 21

    Choi, K., Aldrich, R. & Yellen, G. Tetraethylammonium blockade distinguishes two inactivation mechanisms in voltage-activated K+ channels. Proc. Natl. Acad. Sci. USA 88, 5092–5095 (1991).

    CAS  Article  Google Scholar 

  22. 22

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

    CAS  Article  Google Scholar 

  23. 23

    Lopez-Barneo, J., Hoshi, T., Heinemann, S. & Aldrich, R. Effects of external cations and mutations in the pore region on C-type inactivation of Shaker potassium channels. Receptors Channels 1, 61–71 (1993).

    CAS  PubMed  PubMed Central  Google Scholar 

  24. 24

    Lopez, G., Jan, Y. & Jan, L. Hydrophobic substitution mutations in the S4 sequence alter voltage-dependent gating in Shaker K+ channels. Neuron 7, 327–336 (1991).

    CAS  Article  Google Scholar 

  25. 25

    Blaustein, R. Kinetics of tethering quaternary ammonium compounds to K+ channels. J. Gen. Physiol. 120, 203–216 (2002).

    CAS  Article  Google Scholar 

  26. 26

    Griffin, B.A., Adams, S.R. & Tsien, R.Y. Specific covalent labeling of recombinant protein molecules inside live cells. Science 281, 269–272 (1998).

    CAS  Article  Google Scholar 

  27. 27

    Sutherland, M.L. et al. Overexpression of a Shaker-type potassium channel in mammalian central nervous system dysregulates native potassium channel gene expression. Proc. Natl. Acad. Sci. USA 96, 2451–2455 (1999).

    CAS  Article  Google Scholar 

  28. 28

    Gu, C., Jan, Y.N. & Jan, L.Y. A conserved domain in axonal targeting of Kv1 (Shaker) voltage-gated potassium channels. Science 301, 646–649 (2003).

    CAS  Article  Google Scholar 

  29. 29

    Karschin, A., Aiyar, J., Gouin, A., Davidson, N. & Lester, H.A. K+ channel expression in primary cell cultures mediated by vaccinia virus. FEBS Lett. 278, 229–233 (1991).

    CAS  Article  Google Scholar 

  30. 30

    Djurisic, M. et al. Optical monitoring of neural activity using voltage-sensitive dyes. Methods Enzymol. 361, 423–451 (2003).

    CAS  Article  Google Scholar 

  31. 31

    Jiang, Y. et al. The open pore conformation of potassium channels. Nature 417, 523–526 (2002).

    CAS  Article  Google Scholar 

Download references

Acknowledgements

We thank S. Ahituv for technical support, R. Fredrick and J. Harvey for contributing to the chemical synthesis, I. Hafez and C. Nam for help with cell culture, F. Tombola for advice and C. Luetje for comments on the manuscript. This work was supported by a Fight-for-Sight grant to R.H.K. and funds from the Lawrence Berkeley National Laboratory to D.T. K.B. was supported by a Howard Hughes Medical Institute predoctoral fellowship.

Author information

Affiliations

Authors

Corresponding authors

Correspondence to Dirk Trauner or Richard H Kramer.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Banghart, M., Borges, K., Isacoff, E. et al. Light-activated ion channels for remote control of neuronal firing. Nat Neurosci 7, 1381–1386 (2004). https://doi.org/10.1038/nn1356

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing