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Structure and different conformational states of native AMPA receptor complexes

Abstract

Ionotropic glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system1,2. Their modulation is believed to affect learning and memory, and their dysfunction has been implicated in the pathogenesis of neurological and psychiatric diseases1,2. Despite a wealth of functional data, little is known about the intact, three-dimensional structure of these ligand-gated ion channels. Here, we present the structure of native AMPA receptors (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid; AMPA-Rs) purified from rat brain, as determined by single-particle electron microscopy. Unlike the homotetrameric recombinant GluR2 (ref. 3), the native heterotetrameric AMPA-R adopted various conformations, which reflect primarily a variable separation of the two dimeric extracellular amino-terminal domains. Members of the stargazin/TARP family of transmembrane proteins co-purified with AMPA-Rs and contributed to the density representing the transmembrane region of the complex. Glutamate and cyclothiazide markedly altered the conformational equilibrium of the channel complex, suggesting that desensitization is related to separation of the N-terminal domains. These data provide a glimpse of the conformational changes of an important ligand-gated ion channel of the brain.

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Figure 1: Negative staining and Fab decoration of AMPA-Rs.
Figure 2: Three-dimensional reconstruction of AMPA-Rs and placement of crystal structures into the density map.
Figure 3: TARP contributes to the density of the transmembrane domain.
Figure 4: Ligand-dependent conformational change of AMPA receptors.

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Acknowledgements

This work was supported by an NIH grant (to T.W.). M.S. is an investigator of the Howard Hughes Medical Institute.

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Correspondence to Morgan Sheng or Thomas Walz.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Data

This file contains Supplementary Methods and legends for Supplementary Figures 1-5 and Table 1. (DOC 47 kb)

Supplementary Figure 1

Purification of AMPA-Rs. (JPG 99 kb)

Supplementary Figure 2

Plot of the angle distributions and comparison of reprojections from 3D models with the corresponding raw particle images. (JPG 150 kb)

Supplementary Figure 3

3D density map of AMPA-R in the type I conformation filtered to 42 Å (FSC = 0.5 criterion) or 31 Å (FSC = 0.142 criterion). (JPG 87 kb)

Supplementary Figure 4

ClustalW alignment of mGluR1 (extracellular domain), LIVBP, and GluR2-NTD. (JPG 163 kb)

Supplementary Figure 5

Class averages of particles obtained under different drug treatments. (JPG 378 kb)

Supplementary Table 1

Peptides and corresponding proteins identified by LC/MS/MS tandem mass spectrometry analysis of the bands indicated by asterisks in Fig. 3a. (XLS 15 kb)

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Nakagawa, T., Cheng, Y., Ramm, E. et al. Structure and different conformational states of native AMPA receptor complexes. Nature 433, 545–549 (2005). https://doi.org/10.1038/nature03328

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