Structural mechanism of glutamate receptor activation and desensitization

Meyerson, Joel R.; Kumar, Janesh; Chittori, Sagar; Rao, Prashant; Pierson, Jason; Bartesaghi, Alberto; Mayer, Mark L.; Subramaniam, Sriram

doi:10.1038/nature13603

Cited by 212 publications

(296 citation statements)

References 53 publications

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“…Structures of AMPARs captured in various functional states using X-ray crystallography and cryoelectron microscopy have recently become available (5)(6)(7)(8)(9). Overall, the structures confirm three distinct structural layers (Fig.…”

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confidence: 73%

Structural rearrangement of the intracellular domains during AMPA receptor activation

Zachariassen

Katchan

Jensen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are ligand-gated ion channels that mediate the majority of fast excitatory neurotransmission in the central nervous system. Despite recent advances in structural studies of AMPARs, information about the specific conformational changes that underlie receptor function is lacking. Here, we used single and dual insertion of GFP variants at various positions in AMPAR subunits to enable measurements of conformational changes using fluorescence resonance energy transfer (FRET) in live cells. We produced dual CFP/ YFP-tagged GluA2 subunit constructs that had normal activity and displayed intrareceptor FRET. We used fluorescence lifetime imaging microscopy (FLIM) in live HEK293 cells to determine distinct steady-state FRET efficiencies in the presence of different ligands, suggesting a dynamic picture of the resting state. Patch-clamp fluorometry of the double-and single-insert constructs showed that both the intracellular C-terminal domain (CTD) and the loop region between the M1 and M2 helices move during activation and the CTD is detached from the membrane. Our time-resolved measurements revealed unexpectedly complex fluorescence changes within these intracellular domains, providing clues as to how posttranslational modifications and receptor function interact.T he α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type ionotropic glutamate receptors (iGluRs) reside in postsynaptic membranes in the central nervous system (1). Like the other major iGluR subtypes, the N-methyl-Daspartate receptors (NMDARs) and kainate receptors, AMPARs are ligand-gated cation channels formed by hetero-or homotetrameric assembly of the GluA1 to GluA4 subunits into a membranespanning receptor with an integral ion channel. The energy from binding of the excitatory neurotransmitter glutamate at extracellular sites triggers AMPARs to passage through functional states that can include ion channel activation, deactivation, and desensitization. The timing and interplay between the necessarily distinct conformations of these states determine both basal transmission and short-term plasticity of the postsynapse (2-4).Structures of AMPARs captured in various functional states using X-ray crystallography and cryoelectron microscopy have recently become available (5-9). Overall, the structures confirm three distinct structural layers (Fig. 1). The amino-terminal domain (ATD) and the ligand-binding domain (LBD), both distal to the membrane, and the transmembrane ion channel are each formed from four copies of the respective domain from each subunit. However, a fourth region of the receptor extends from the intracellular side of the membrane. This part of the receptor includes intracellular loops between the transmembrane helices and the variable C-terminal domain (CTD), and remains entirely unresolved in the presently available AMPAR structures.The GluA2 structures and previous results from biochemical, biophysical, and crystallographic studies of isolated subunits and fu...

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confidence: 73%

Structural rearrangement of the intracellular domains during AMPA receptor activation

Zachariassen

Katchan

Jensen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…However, it has been previously shown that reduction of GluD2 LC activity by D-Ser results from conformational changes at the LBD dimer interface (Hansen et al, 2009). Interestingly, conformational changes at the LBD dimer interface reflect desensitization of AMPA and kainate receptors (Armstrong et al, 2006;Plested and Mayer, 2009;Daniels et al, 2013;Schauder et al, 2013;Durr et al, 2014;Meyerson et al, 2014), and the extent of desensitization of AMPA receptors is correlated with the degree of domain closure (Jin and Gouaux, 2003). That is, ligands that induce full domain closure desensitize AMPA receptors to a higher extent than ligands that induce less closure.…”

Section: Resultsmentioning

confidence: 99%

Pharmacology and Structural Analysis of Ligand Binding to the Orthosteric Site of Glutamate-Like GluD2 Receptors

et al. 2015

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The GluD2 receptor is a fundamental component of postsynaptic sites in Purkinje neurons, and is required for normal cerebellar function. GluD2 and the closely related GluD1 are classified as members of the ionotropic glutamate receptor (iGluR) superfamily on the basis of sequence similarity, but do not bind L-glutamate. The amino acid neurotransmitter D-Ser is a GluD2 receptor ligand, and endogenous D-Ser signaling through GluD2 has recently been shown to regulate endocytosis of a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type iGluRs during synaptic plasticity in the cerebellum, such as long-term depression. Here, we investigate the pharmacology of the orthosteric binding site in GluD2 by examining the activity of analogs of D-Ser and GluN1 glycine site competitive antagonists at GluD2

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“…Since the first crystal structure for a nearfull-length AMPA receptor in antagonist-bound form was first presented in 2009 (3), more than a dozen such structures covering both AMPA and NMDA receptors have been published (4,(24)(25)(26)(27)(28). Some of these structures are bound with full agonists along with positive allosteric modulators.…”

Section: Introductionmentioning

confidence: 99%

Semiclosed Conformations of the Ligand-Binding Domains of NMDA Receptors during Stationary Gating

Dai

Zhou

2016

Biophysical Journal

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NMDA receptors are tetrameric ligand-gated ion channels. In the continuous presence of saturating agonists, NMDA receptors undergo stationary gating, in which the channel stochastically switches between an open state that permits ion conductance and a closed state that prevents permeation. The ligand-binding domains (LBDs) of the four subunits are expected to have closed clefts in the channel-open state. On the other hand, there is little knowledge about the conformational status of the LBDs in the channel-closed state during stationary gating. To probe the latter conformational status, Kussius and Popescu engineered interlobe disulfide cross-links in NMDA receptors and found that the cross-linking produced stationary gating kinetics that differed only subtly from that produced by agonist binding. These authors assumed that the cross-linking immobilized the LBDs in cleft-closed conformations, and consequently concluded that throughout stationary gating, agonistbound LBDs also stayed predominantly in cleft-closed conformations and made only infrequent excursions to cleft-open conformations. Here, by calculating the conformational free energies of cross-linked and agonist-bound LBDs, we assess whether cross-linking actually traps the LBDs in cleft-closed conformations and delineate semiclosed conformations of agonist-bound LBDs that may potentially be thermodynamically and kinetically important during stationary gating. Our free-energy results show that the cross-linked LBDs are not locked in the fully closed form; rather, they sample semiclosed conformations almost as readily as the agonist-bound LBDs. Several lines of reasoning suggest that LBDs are semiclosed in the channel-closed state during stationary gating. Our free-energy simulations suggest possible structural details of such semiclosed LBD conformations, including intra-and intermolecular interactions that serve as alternatives to those in the cleft-closed conformations.

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Structural mechanism of glutamate receptor activation and desensitization

Cited by 212 publications

References 53 publications

Structural rearrangement of the intracellular domains during AMPA receptor activation

Structural rearrangement of the intracellular domains during AMPA receptor activation

Pharmacology and Structural Analysis of Ligand Binding to the Orthosteric Site of Glutamate-Like GluD2 Receptors

Semiclosed Conformations of the Ligand-Binding Domains of NMDA Receptors during Stationary Gating

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