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Antidepressant specificity of serotonin transporter suggested by three LeuT–SSRI structures

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Abstract

Sertraline and fluoxetine are selective serotonin re-uptake inhibitors (SSRIs) that are widely prescribed to treat depression. They exert their effects by inhibiting the presynaptic plasma membrane serotonin transporter (SERT). All SSRIs possess halogen atoms at specific positions, which are key determinants for the drugs' specificity for SERT. For the SERT protein, however, the structural basis of its specificity for SSRIs is poorly understood. Here we report the crystal structures of LeuT, a bacterial SERT homolog, in complex with sertraline, R-fluoxetine or S-fluoxetine. The SSRI halogens all bind to exactly the same pocket within LeuT. Mutation at this halogen-binding pocket (HBP) in SERT markedly reduces the transporter's affinity for SSRIs but not for tricyclic antidepressants. Conversely, when the only nonconserved HBP residue in both norepinephrine and dopamine transporters is mutated into that found in SERT, their affinities for all the three SSRIs increase uniformly. Thus, the specificity of SERT for SSRIs is dependent largely on interaction of the drug halogens with the protein's HBP.

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Figure 1: Interaction of three SSRIs with LeuT and the crystal structures of their complexes.
Figure 2: Comparison of common features of SSRI binding to LeuT and key determinants for specificity for SSRIs.
Figure 3: HBP in SERT and its critical importance in the protein's specificity for antidepressants.

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Protein Data Bank

Change history

  • 18 May 2009

    In the version of this article initially published online, “Cl-“ was incorrectly referred to as “Cl“ on the fifth page in the section entitled “SSRI halogens and HBP”. The error has been corrected for the print, PDF and HTML versions of this article.

References

  1. Chang, A.S. et al. Cloning and expression of the mouse serotonin transporter. Brain Res. Mol. Brain Res. 43, 185–192 (1996).

    Article  CAS  Google Scholar 

  2. Baldessarini, R.J. Drug therapy of depression and anxiety disorders. in Goodman and Gilman's the Pharmacological Basis of Therapeutics (eds. Brunton, L.L., Lazoskip, J.S. & Parker, K.L.) 429–459 (McGraw-Hill, Columbus, OH, 2005).

    Google Scholar 

  3. Tatsumi, M., Groshan, K., Blakely, R.D. & Richelson, E. Pharmacological profile of antidepressants and related compounds at human monoamine transporters. Eur. J. Pharmacol. 340, 249–258 (1997).

    Article  CAS  Google Scholar 

  4. Eshleman, A.J. et al. Characteristics of drug interactions with recombinant biogenic amine transporters expressed in the same cell type. J. Pharmacol. Exp. Ther. 289, 877–885 (1999).

    CAS  Google Scholar 

  5. Wong, D.T. & Bymaster, F.P. Development of antidepressant drugs. Fluoxetine (Prozac) and other selective serotonin uptake inhibitors. Adv. Exp. Med. Biol. 363, 77–95 (1995).

    Article  CAS  Google Scholar 

  6. Wong, D.T., Bymaster, F.P. & Engleman, E.A. Prozac (fluoxetine, Lilly 110140), the first selective serotonin uptake inhibitor and an antidepressant drug: twenty years since its first publication. Life Sci. 57, 411–441 (1995).

    Article  CAS  Google Scholar 

  7. Eildal, J.N. et al. From the selective serotonin transporter inhibitor citalopram to the selective norepinephrine transporter inhibitor talopram: synthesis and structure-activity relationship studies. J. Med. Chem. 51, 3045–3048 (2008).

    Article  CAS  Google Scholar 

  8. Pinder, R.M. & Wieringa, J.H. Third-generation antidepressants. Med. Res. Rev. 13, 259–325 (1993).

    Article  CAS  Google Scholar 

  9. Roman, D.L., Walline, C.C., Rodriguez, G.J. & Barker, E.L. Interactions of antidepressants with the serotonin transporter: a contemporary molecular analysis. Eur. J. Pharmacol. 479, 53–63 (2003).

    Article  CAS  Google Scholar 

  10. Welch, W.M., Kraska, A.R., Sarges, R. & Koe, B.K. Nontricyclic antidepressant agents derived from cis- and trans-1-amino-4-aryltetralins. J. Med. Chem. 27, 1508–1515 (1984).

    Article  CAS  Google Scholar 

  11. Iversen, L. Neurotransmitter transporters and their impact on the development of psychopharmacology. Br. J. Pharmacol. 147, S82–S88 (2006).

    Article  CAS  Google Scholar 

  12. Rudnick, G. Mechanisms of biogenic amine neurotransmitter transporters. in Neurotransmitter Transporters: Structure, Function, and Regulation (ed. Reith, M.E.A.) 25–52 (Humana Press, Totowa, NJ, 2002).

    Chapter  Google Scholar 

  13. Torres, G.E., Gainetdinov, R.R. & Caron, M.G. Plasma membrane monoamine transporters: structure, regulation and function. Nat. Rev. Neurosci. 4, 13–25 (2003).

    Article  CAS  Google Scholar 

  14. Kanner, B.I. & Zomot, E. Sodium-coupled neurotransmitter transporters. Chem. Rev. 108, 1654–1668 (2008).

    Article  CAS  Google Scholar 

  15. Androutsellis-Theotokis, A. et al. Characterization of a functional bacterial homologue of sodium-dependent neurotransmitter transporters. J. Biol. Chem. 278, 12703–12709 (2003).

    Article  CAS  Google Scholar 

  16. Yamashita, A., Singh, S.K., Kawate, T., Jin, Y. & Gouaux, E. Crystal structure of a bacterial homologue of Na+/Cl-dependent neurotransmitter transporters. Nature 437, 215–223 (2005).

    Article  CAS  Google Scholar 

  17. Henry, L.K., Defelice, L.J. & Blakely, R.D. Getting the message across: a recent transporter structure shows the way. Neuron 49, 791–796 (2006).

    Article  CAS  Google Scholar 

  18. Forrest, L.R., Tavoulari, A., Zhang, Y.W., Rudnick, G. & Honig, B. Identification of a chloride ion binding site in Na+/Cl-dependent transporters. Proc. Natl. Acad. Sci. USA 104, 12761–12766 (2007).

    Article  CAS  Google Scholar 

  19. Zomot, E. et al. Mechanism of chloride interaction with neurotransmitter:sodium symporters. Nature 449, 726–730 (2007).

    Article  CAS  Google Scholar 

  20. Ravna, A.W., Sylte, I. & Dahl, S.G. Structure and localisation of drug binding sites on neurotransmitter transporters. J. Mol. Model. Published online, doi:10.1007/s00894-009-0478-1 (24 February 2009).

  21. Zhou, Z. et al. LeuT-desipramine structure reveals how antidepressants block neurotransmitter reuptake. Science 317, 1390–1393 (2007).

    Article  CAS  Google Scholar 

  22. Singh, S.K., Yamashita, A. & Gouaux, E. Antidepressant binding site in a bacterial homologue of neurotransmitter transporters. Nature 448, 952–956 (2007).

    Article  CAS  Google Scholar 

  23. Singh, S.K., Piscitelli, C.L., Yamashita, A. & Gouaux, E. A competitive inhibitor traps LeuT in an open-to-out conformation. Science 322, 1655–1661 (2008).

    Article  CAS  Google Scholar 

  24. Caruso, F., Besmer, A. & Rossi, M. The absolute configuration of sertraline (Zoloft) hydrochloride. Acta Crystallogr. C 55, 1712–1714 (1999).

    Article  Google Scholar 

  25. Robertson, D.W., Jones, N.D., Swartzendruber, J.K., Yang, K.S. & Wong, D.T. Molecular structure of fluoxetine hydrochloride, a highly selective serotonin-uptake inhibitor. J. Med. Chem. 31, 185–189 (1988).

    Article  CAS  Google Scholar 

  26. Barker, E.L. & Blakely, R.D. Identification of a single amino acid, phenylalanine 586, that is responsible for high affinity interactions of tricyclic antidepressants with the human serotonin transporter. Mol. Pharmacol. 50, 957–965 (1996).

    CAS  Google Scholar 

  27. Henry, L.K. et al. Tyr-95 and Ile-172 in transmembrane segments 1 and 3 of human serotonin transporters interact to establish high affinity recognition of antidepressants. J. Biol. Chem. 281, 2012–2023 (2006).

    Article  CAS  Google Scholar 

  28. Walline, C.C., Nichols, D.E., Carroll, F.I. & Barker, E.L. Comparative molecular field analysis using selectivity fields reveals residues in the third transmembrane helix of the serotonin transporter associated with substrate and antagonist recognition. J. Pharmacol. Exp. Ther. 325, 791–800 (2008).

    Article  CAS  Google Scholar 

  29. Plenge, P. & Wiborg, O. High- and low-affinity binding of S-citalopram to the human serotonin transporter mutated at 20 putatively important amino acid positions. Neurosci. Lett. 383, 203–208 (2005).

    Article  CAS  Google Scholar 

  30. Owens, M.J., Knight, D.L. & Nemeroff, C.B. Second-generation SSRIs: human monoamine transporter binding profile of escitalopram and R-fluoxetine. Biol. Psychiatry 50, 345–350 (2001).

    Article  CAS  Google Scholar 

  31. Shi, L., Quick, M., Zhao, Y., Weinstein, H. & Javitch, J.A. The mechanism of a neurotransmitter:sodium symporter–inward release of Na+ and substrate is triggered by substrate in a second binding site. Mol. Cell 30, 667–677 (2008).

    Article  CAS  Google Scholar 

  32. Quick, M. et al. Binding of an octylglucoside detergent molecule in the second substrate (S2) site of LeuT establishes an inhibitor-bound conformation. Proc. Natl. Acad. Sci. USA 106, 5563–5568 (2009).

    Article  CAS  Google Scholar 

  33. Müller, K., Faeh, C. & Diederich, F. Fluorine in pharmaceuticals: looking beyond intuition. Science 317, 1881–1886 (2007).

    Article  Google Scholar 

  34. Iversen, L. Antidepressants. in Burger's Medical Chemistry and Drug Discovery Vol. 6 (ed. Abraham, D.J.) 483–524 (Wiley, San Francisco, 2003).

    Google Scholar 

  35. Heal, D.J. et al. Sibutramine: a novel anti-obesity drug. A review of the pharmacological evidence to differentiate it from d-amphetamine and d-fenfluramine. Int. J. Obes. Relat. Metab. Disord. 22, S18–S28 (1998).

    CAS  Google Scholar 

  36. Sánchez, C. & Hyttel, J. Comparison of the effects of antidepressants and their metabolites on reuptake of biogenic amines and on receptor binding. Cell. Mol. Neurobiol. 19, 467–489 (1999).

    Article  Google Scholar 

  37. Pearce, R.K. et al. The monoamine reuptake blocker brasofensine reverses akinesia without dyskinesia in MPTP-treated and levodopa-primed common marmosets. Mov. Disord. 17, 877–886 (2002).

    Article  Google Scholar 

  38. Lehr, T. et al. Population pharmacokinetic modelling of NS2330 (tesofensine) and its major metabolite in patients with Alzheimer's disease. Br. J. Clin. Pharmacol. 64, 36–48 (2007).

    Article  CAS  Google Scholar 

  39. Rothman, R.B. et al. Neurochemical neutralization of methamphetamine with high-affinity nonselective inhibitors of biogenic amine transporters: a pharmacological strategy for treating stimulant abuse. Synapse 35, 222–227 (2000).

    Article  CAS  Google Scholar 

  40. Skolnick, P., Popik, P., Janowsky, A., Beer, B. & Lippa, A.S. Antidepressant-like actions of DOV 21,947: a “triple” reuptake inhibitor. Eur. J. Pharmacol. 461, 99–104 (2003).

    Article  CAS  Google Scholar 

  41. Quick, M. & Javitch, J. Monitoring the function of membrane transport proteins in detergent-solubilized form. Proc. Natl. Acad. Sci. USA 104, 3603–3608 (2007).

    Article  CAS  Google Scholar 

  42. Fann, M.C., Busch, A. & Maloney, P.C. Functional characterization of cysteine residues in GlpT, the glycerol 3-phosphate transporter of Escherichia coli . J. Bacteriol. 185, 3863–3870 (2003).

    Article  CAS  Google Scholar 

  43. Law, C.J. et al. Salt-bridge dynamics control substrate-induced conformational change in the membrane transporter GlpT. J. Mol. Biol. 378, 828–839 (2008).

    Article  Google Scholar 

  44. Otwinowski, Z. & Minor, W. Processing of X-ray diffraction data collected in oscillation mode. Methods Enzymol. 276, 307–326 (1997).

    Article  CAS  Google Scholar 

  45. Collaborative Computational Project Number 4. The CCP4 Suite: programs for protein crystallography. Acta Crystallogr. D Biol. Crystallogr. 50, 760–763 (1994).

  46. Emsley, P. & Cowtan, K. Coot: model-building tools for molecular graphics. Acta Crystallogr. D Biol. Crystallogr. 60, 2126–2132 (2004).

    Article  Google Scholar 

  47. Brünger, A.T. et al. Crystallography & NMR system: a new software suite for macromolecular structure determination. Acta Crystallogr. D Biol. Crystallogr. 54, 905–921 (1998).

    Article  Google Scholar 

  48. Chen, N., Rickey, J., Berfield, J.L. & Reith, M.E. Aspartate 345 of the dopamine transporter is critical for conformational changes in substrate translocation and cocaine binding. J. Biol. Chem. 279, 5508–5519 (2004).

    Article  CAS  Google Scholar 

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Acknowledgements

We thank the staff of the X12B, X25 and X29 beamlines at the National Synchrotron Light Source in Brookhaven National Laboratory for assistance in X-ray diffraction data collection. We are grateful to L.R. Forrest and B. Honig of Columbia University for providing the coordinates of the human SERT homology model, and to B. Czyzewski, M.R. Li, I. Parrington and J. Wu for assistance and helpful discussions. N.K.K. thanks the American Heart Association and the US National Institutes of Health (NIH) for postdoctoral fellowships. This work was financially supported by the NIH Roadmap (GM075936 to D.N.W.) and NIH grants (MH083840 to D.-N.W. and M.E.A.R., DA019676 and DA013261 to M.E.A.R.).

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Contributions

Z.Z. crystallized the LeuT–SSRI complexes, generated mutants and solved the crystal structures with help from N.K.K; J.Z. measured SSRIs binding to LeuT as well as binding to and uptake by human neurotransmitter transporters; N.K.K. performed docking calculations and prepared structural figures; Z.Z and C.J.L. measured LeuT transport in proteoliposomes. All authors discussed the results and commented on the manuscript.

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Correspondence to Maarten E A Reith or Da-Neng Wang.

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Zhou, Z., Zhen, J., Karpowich, N. et al. Antidepressant specificity of serotonin transporter suggested by three LeuT–SSRI structures. Nat Struct Mol Biol 16, 652–657 (2009). https://doi.org/10.1038/nsmb.1602

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