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On the Origin of Ion Selectivity in the Cys-Loop Receptor Family

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Abstract

Agonist binding to Cys-loop receptors promotes a large transmembrane ion flux of several million cations or anions per second. To investigate structural bases for the rapid and charge-selective flux, we used all atom molecular dynamics (MD) simulations, X-ray crystallography, and single channel recording. MD simulations of the muscle nicotinic receptor, imbedded in a lipid bilayer with an applied transmembrane potential, reveal single cation translocation events during transient periods of channel hydration. During the simulation trajectory, cations paused for prolonged periods near several rings of anionic residues projecting from the lumen of the extracellular domain of the receptor, but subsequently the cation moved rapidly through the hydrophobic transmembrane region as the constituent alpha-helices exhibited back and forth rocking motions. Cocrystallization of acetylcholine binding protein with sulfate ions revealed coordination of five sulfates with residues from one of these charged rings; in cation-selective Cys-loop receptors this ring contains negatively charged residues, whereas in anion-selective receptors it contains positively charged residues. In the muscle nicotinic receptor, charge reversal of residues of this ring decreases unitary conductance by up to 80%. Thus in Cys-loop receptors, a series of charged rings along the ion translocation pathway concentrates hydrated ions relative to bulk solution, giving rise to charge selectivity, and then subtle motions of the hydrophobic transmembrane, coupled with transient periods of water filling, enable rapid ion flux.

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References

  • Beckstein, O., Tai, K., & Sansom, M. S. (2004). Not ions alone: Barriers to ion permeation in nanopores and channels. Journal of the American Chemical Society, 126, 14694–14695.

    Article  CAS  PubMed  Google Scholar 

  • Bocquet, N., Nury, H., Baaden, M., Le Poupon, C., Changeux, J. P., Delarue, M., et al. (2009). X-ray structure of a pentameric ligand-gated ion channel in an apparently open conformation. Nature, 457, 111–114.

    Article  CAS  PubMed  Google Scholar 

  • Cymes, G., Ni, Y., & Grosman, C. (2005). Probing ion channel pores one proton at a time. Nature, 438, 975–980.

    Article  CAS  PubMed  Google Scholar 

  • Doyle, D. A., Morais Cabral, J., Pfuetzner, R. A., Kuo, A., Gulbis, J. M., Cohen, S. L., et al. (1998). The structure of the potassium channel: Molecular basis of K+ conduction and selectivity. Science, 280, 69–77.

    Article  CAS  PubMed  Google Scholar 

  • Dutzler, R., Campbell, E. B., Cadene, M., Chait, B. T., & MacKinnon, R. (2002). Gating the selectivity filter in ClC chloride channels. Nature, 415, 287–294.

    Article  CAS  PubMed  Google Scholar 

  • Hansen, S. B., Talley, T. T., Radic, Z., & Taylor, P. (2004). Structural and ligand recognition characteristics of an acetylcholine binding protein from Aplysia californica. Journal of Biological Chemistry, 279, 24197–24202.

    Article  CAS  PubMed  Google Scholar 

  • Hansen, S. B., Sulzenbacher, G., Huxford, T., Marchot, P., Taylor, P., & Bourne, Y. (2005). Structural characterization of agonist and antagonist-bound acetylcholine-binding protein from Aplysia californica. European Molecular Biology Organization Journal, 24, 3635–3646.

    CAS  Google Scholar 

  • Hansen, S. B., Wang, H.-L., Taylor, P., & Sine, S. M. (2008). An ion selectivity filter in the extracellular domain of Cys-loop receptors reveals determinants of ion conductance. Journal of Biological Chemistry, 283, 36066–36070.

    Article  CAS  PubMed  Google Scholar 

  • Hilf, R. J., & Dutzler, R. (2008). X-ray structure of a prokaryotic pentameric ligand-gated ion channel. Nature, 452, 375–379.

    Article  CAS  PubMed  Google Scholar 

  • Hilf, R., & Dutzler, R. (2009). Structure of a potentially open state of a proton-activated pentameric ligand-gated ion channel. Nature, 457, 115–118.

    Article  CAS  PubMed  Google Scholar 

  • Hummer, G., Rasaiah, J. C., & Noworyta, J. P. (2001). Water conduction through the hydrophobic channel of a carbon nanotube. Nature, 414, 188–190.

    Article  CAS  PubMed  Google Scholar 

  • Imoto, K., Busch, C., Sakmann, B., Mishina, M., Konno, T., et al. (1988). Rings of negatively charged amino acids determine the acetylcholine receptor channel conductance. Nature, 335, 645–648.

    Article  CAS  PubMed  Google Scholar 

  • Kehoe, J., & McIntosh, J. M. (1998). Two distinct nicotinic receptors, one pharmacologically similar to the vertebrate alpha7-containing receptor, mediate Cl currents in aplysia neurons. Journal of Neuroscience, 18, 8198–8213.

    CAS  PubMed  Google Scholar 

  • Kelley, S. P., Dunlop, J. I., Kirkness, E. F., Lambert, J. J., & Peters, J. A. (2003). A cytoplasmic region determines single-channel conductance in 5-HT3 receptors. Nature, 424, 321–324.

    Article  CAS  PubMed  Google Scholar 

  • Lewis, C. A., & Stevens, C. F. (1983). Acetylcholine receptor channel ionic selectivity: ions experience an aqueous environment. Proceedings of the National Academy of Sciences of the United States of America, 80, 6110–6113.

    Article  CAS  PubMed  Google Scholar 

  • Miller, C., & Hughes, H. (1992). Hunting for the pore of voltage-gated channels. Current Biology, 2, 573–575.

    Article  CAS  PubMed  Google Scholar 

  • Miyazawa, A., Fujiyoshi, Y., & Unwin, N. (2003). Structure and gating mechanism of the acetylcholine receptor pore. Nature, 423, 949–955.

    Article  CAS  PubMed  Google Scholar 

  • Reeves, P. J., Callewaert, N., Contreras, R., & Khorana, H. G. (2002). Structure and function in rhodopsin: High-level expression of rhodopsin with restricted and homogeneous N-glycosylation by a tetracycline-inducible N-acetylglucosaminyltransferase I-negative HEK293S stable mammalian cell line. Proceedings of the National Academy of Sciences of the United States of America, 99, 13419–13424.

    Article  CAS  PubMed  Google Scholar 

  • Smart, O. S., Neduvelil, J. G., Wang, X., Wallace, B. A., & Sansom, M. S. (1996). HOLE: A program for the analysis of the pore dimensions of ion channel structural models. Journal of Molecular Graphics, 14(354–360), 376.

    CAS  Google Scholar 

  • Spronk, S. A., Elmore, D. E., & Dougherty, D. A. (2006). Voltage-dependent hydration and conduction properties of the hydrophobic pore of the mechanosensitive channel of small conductance. Biophysical Journal, 90, 3555–3569.

    Article  CAS  PubMed  Google Scholar 

  • Sotomayor, M., van der Straaten, T. A., Ravaioli, U., & Schulten, K. (2006). Electrostatic properties of the mechanosensitive channel of small conductance MscS. Biophysical Journal, 90, 3496–3510.

    Article  CAS  PubMed  Google Scholar 

  • Sotomayor, M., Vasquez, V., Perozo, E., & Schulten, K. (2007). Ion conduction through MscS as determined by electrophysiology and simulation. Biophysical Journal, 92, 886–902.

    Article  CAS  PubMed  Google Scholar 

  • Tasneem, A., Iyer, L., Jakobsson, E., & Aravand, L. (2005). Identification of the prokaryotic ligand-gated ion channels and their implications for the mechanisms and origins of animal Cys-loop receptors. Genome Biology, 6, R4.

  • Unwin, N. (2005). Refined structure of the nicotinic acetylcholine receptor at 4 Å resolution. Journal of Molecular Biology, 346, 967–989.

    Article  CAS  PubMed  Google Scholar 

  • Wang, H. L., Cheng, X., Taylor, P., McCammon, J. A., & Sine, S. M. (2008). Control of ion permeation through the nicotinic receptor channel. PLoS Comput Biol, 4, e41.

    Article  PubMed  Google Scholar 

  • Zhou, Y., Morais-Cabral, J. H., Kaufman, A., & MacKinnon, R. (2001). Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 Å resolution. Nature, 414, 43–48.

    Article  CAS  PubMed  Google Scholar 

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Acknowledgements

Work in our laboratories was supported by NIH grants to S.M. Sine (NS031744) and P. Taylor (R37-GM18360/U01-DA019372).

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Correspondence to Steven M. Sine.

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Proceedings of the XIII International Symposium on Cholinergic Mechanisms

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Sine, S.M., Wang, HL., Hansen, S. et al. On the Origin of Ion Selectivity in the Cys-Loop Receptor Family. J Mol Neurosci 40, 70–76 (2010). https://doi.org/10.1007/s12031-009-9260-1

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  • DOI: https://doi.org/10.1007/s12031-009-9260-1

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