Article | Published:

Channel opening and gating mechanism in AMPA-subtype glutamate receptors

Nature volume 549, pages 6065 (07 September 2017) | Download Citation

Abstract

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid)-subtype ionotropic glutamate receptors mediate fast excitatory neurotransmission throughout the central nervous system. Gated by the neurotransmitter glutamate, AMPA receptors are critical for synaptic strength, and dysregulation of AMPA receptor-mediated signalling is linked to numerous neurological diseases. Here we use cryo-electron microscopy to solve the structures of AMPA receptor–auxiliary subunit complexes in the apo, antagonist- and agonist-bound states and determine the iris-like mechanism of ion channel opening. The ion channel selectivity filter is formed by the extended portions of the re-entrant M2 loops, while the helical portions of M2 contribute to extensive hydrophobic interfaces between AMPA receptor subunits in the ion channel. We show how the permeation pathway changes upon channel opening and identify conformational changes throughout the entire AMPA receptor that accompany activation and desensitization. Our findings provide a framework for understanding gating across the family of ionotropic glutamate receptors and the role of AMPA receptors in excitatory neurotransmission.

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Acknowledgements

We thank H. Kao for computational support, A. des Georges, I. S. Fernandez, M. Fislage and A. K. Singh for processing advice. E.C.T. is supported by National Institutes of Health (NIH) F31 NS093838. A.I.S. is supported by the NIH (R01 NS083660, R01 CA206573), the Pew Scholar Award in Biomedical Sciences, and the Irma T. Hirschl Career Scientist Award. J.F. is supported by the Howard Hughes Medical Institute and the NIH (R01 GM029169). Cryo-EM data were collected at the Columbia University Medical Center cryo-EM facility and at the Simons Electron Microscopy Center and National Resource for Automated Molecular Microscopy located at the New York Structural Biology Center, supported by grants from the Simons Foundation (349247), NYSTAR, and the NIH National Institute of General Medical Sciences (GM103310).

Author information

Affiliations

  1. Department of Biochemistry and Molecular Biophysics, Columbia University, 650 West 168th Street, New York, New York 10032, USA

    • Edward C. Twomey
    • , Maria V. Yelshanskaya
    • , Robert A. Grassucci
    • , Joachim Frank
    •  & Alexander I. Sobolevsky
  2. Integrated Program in Cellular, Molecular, and Biomedical Studies, Columbia University, 650 West 168th Street, New York, New York 10032, USA

    • Edward C. Twomey
  3. Howard Hughes Medical Institute, 650 West 168th Street, New York, New York 10032, USA

    • Robert A. Grassucci
    •  & Joachim Frank
  4. Department of Biological Sciences, Columbia University, 650 West 168th Street, New York, New York 10032, USA

    • Joachim Frank

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Contributions

E.C.T. designed the constructs, prepared the protein samples, carried out cryo-EM data collection and processing, built models, analysed data and wrote the manuscript. M.V.Y. carried out electrophysiology experiments, assisted in protein production and edited the manuscript. R.A.G. assisted in cryo-EM data collection. J.F. advised on the cryo-EM workflow and provided funding. A.I.S. supervised the project, built models, analysed data, wrote the manuscript and provided funding. E.C.T. and A.I.S. designed the project.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Alexander I. Sobolevsky.

Reviewer Information Nature thanks M. Mayer, S. Traynelis and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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    Conformational changes between GluA2 closed, open and desensitized states

    A morph between GluA2 closed, open and desensitized stated represented by the GluA2-GSG1LZK-1, GluA2-STZGlu-CTZ and GluA2-2xGSG1LQuis structures, respectively. The GluA2 subunits A and C are colored purple and B and D green. The agonists Glu are represented by space-filling models. Note, the pre-M4 helices in subunits A and C unfold during channel opening, while the entire TMD becomes wider. The receptor undergoes a corkscrew twist and becomes shorter while progressing from the closed to open to desensitized states.

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https://doi.org/10.1038/nature23479

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