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An intracellular P2X receptor required for osmoregulation in Dictyostelium discoideum


P2X receptors are membrane ion channels gated by extracellular ATP1,2 that are found widely in vertebrates, but not previously in microbes. Here we identify a weakly related gene in the genome of the social amoeba Dictyostelium discoideum, and show, with the use of heterologous expression in human embryonic kidney cells, that it encodes a membrane ion channel activated by ATP (30–100 μM). Site-directed mutagenesis revealed essential conservation of structure–function relations with P2X receptors of higher organisms. The receptor was insensitive to the usual P2X antagonists3 but was blocked by nanomolar concentrations of Cu2+ ions. In D. discoideum, the receptor was found on intracellular membranes, with prominent localization to an osmoregulatory organelle, the contractile vacuole. Targeted disruption of the gene in D. discoideum resulted in cells that were unable to regulate cell volume in hypotonic conditions. Cell swelling in these mutant cells was accompanied by a marked inhibition of contractile vacuole emptying. These findings demonstrate a new functional role for P2X receptors on intracellular organelles, in this case in osmoregulation.

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Figure 1: Dd P2X receptor is an ATP-gated ion channel.
Figure 2: Properties of Dd P2X receptors.
Figure 3: Dd P2X receptors are localized to the contractile vacuole and are required for cell volume regulation and contractile vacuole voiding.


  1. North, R. A. Molecular physiology of P2X receptors. Physiol. Rev. 82, 1013–1067 (2002)

    CAS  Article  Google Scholar 

  2. Khakh, B. S. & North, R. A. P2X receptors as cell-surface ATP sensors in health and disease. Nature 442, 527–532 (2006)

    ADS  CAS  Article  Google Scholar 

  3. Gever, J. R., Cockayne, D. A., Dillon, M. P., Burnstock, G. & Ford, A. P. Pharmacology of P2X channels. Pflügers Arch. 452, 513–537 (2006)

    CAS  Article  Google Scholar 

  4. Nicke, A. et al. P2X1 and P2X3 receptors form stable trimers: a novel structural motif of ligand-gated ion channels. EMBO J. 17, 3016–3028 (1998)

    CAS  Article  Google Scholar 

  5. Barrera, N. P., Ormond, S. J., Henderson, R. M., Murrell-Lagnado, R. D. & Edwardson, J. M. Atomic force microscopy imaging demonstrates that P2X2 receptors are trimers but that P2X6 receptor subunits do not oligomerize. J. Biol. Chem. 280, 10759–10765 (2005)

    CAS  Article  Google Scholar 

  6. Coddou, C. et al. Histidine 140 plays a key role in the inhibitory modulation of the P2X4 nucleotide receptor by copper but not zinc. J. Biol. Chem. 278, 36777–36785 (2003)

    CAS  Article  Google Scholar 

  7. Virginio, C., Church, D., North, R. A. & Surprenant, A. Effects of divalent cations, protons and calmidazolium at the rat P2X7 receptor. Neuropharmacology 36, 1285–1294 (1997)

    CAS  Article  Google Scholar 

  8. Roberts, J. A. et al. Molecular properties of P2X receptors. Pflügers Arch. 452, 486–500 (2006)

    CAS  Article  Google Scholar 

  9. Vial, C., Roberts, J. A. & Evans, R. J. Molecular properties of ATP-gated P2X receptor ion channels. Trends Pharmacol. Sci. 25, 487–493 (2004)

    CAS  Article  Google Scholar 

  10. Chaumont, S., Jiang, L. H., Penna, A., North, R. A. & Rassendren, F. Identification of a trafficking motif involved in the stabilization and polarization of P2X receptors. J. Biol. Chem. 279, 29628–29638 (2004)

    CAS  Article  Google Scholar 

  11. Allen, R. D. The contractile vacuole and its membrane dynamics. BioEssays 22, 1035–1042 (2000)

    CAS  Article  Google Scholar 

  12. Zhu, Q. & Clarke, M. Association of calmodulin and an unconventional myosin with the contractile vacuole complex of Dictyostelium discoideum. J. Cell Biol. 118, 347–358 (1992)

    CAS  Article  Google Scholar 

  13. Heuser, J. Evidence for recycling of contractile vacuole membrane during osmoregulation in Dictyostelium amoebae. Eur. J. Cell Biol. 85, 859–871 (2006)

    CAS  Article  Google Scholar 

  14. Allen, R. D. & Naitoh, Y. Osmoregulation and contractile vacuoles of protozoa. Int. Rev. Cytol. 215, 351–394 (2002)

    CAS  Article  Google Scholar 

  15. Gerald, N. J., Sianom, M. & De Lozanne, A. The Dictyostelium LvsA protein is localized on the contractile vacuole and is required for osmoregulation. Traffic 3, 50–60 (2002)

    Article  Google Scholar 

  16. Wu, W. I., Yajnik, J., Siano, M. & De Lozanne, A. Structure–function analysis of the BEACH protein LvsA. Traffic 5, 346–355 (2004)

    CAS  Article  Google Scholar 

  17. Jentsch, T. J., Hubner, C. A. & Fuhrmann, J. C. Ion channels: function unravelled by dysfunction. Nature Cell Biol. 6, 1039–1047 (2004)

    CAS  Article  Google Scholar 

  18. Masse, K., Eason, R., Bhamra, S., Dale, N. & Jones, E. A. Comparative genomic and expression analysis of the conserved NTPDase gene family in Xenopus. Genomics 87, 366–381 (2006)

    CAS  Article  Google Scholar 

  19. Ramjeesingh, M., Huan, L. J., Garami, E. & Bear, C. E. Novel method for evaluation of the oligomeric structure of membrane proteins. Biochem. J. 342, 119–123 (1999)

    CAS  Article  Google Scholar 

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We thank H. Broomhead, L. Almond, K. Dossi and N. Aldren for their technical expertise during this study, and A. Mueller-Taubenberger for the gift of the pDEX 27 GFP vector. This work was supported by the Wellcome Trust, the Medical Research Council and the Lister Institute of Preventive Medicine.

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Correspondence to Christopher R. L. Thompson or R. Alan North.

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Fountain, S., Parkinson, K., Young, M. et al. An intracellular P2X receptor required for osmoregulation in Dictyostelium discoideum. Nature 448, 200–203 (2007).

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