Role of Conformational Dynamics in α-Amino-3-hydroxy-5-methylisoxazole-4-propionic Acid (AMPA) Receptor Partial Agonism

Ramaswamy, Swarna S.; Cooper, David R.; Poddar, Nitesh Kumar; MacLean, David M.; Rambhadran, Anu; Taylor, Joshua P.; Uhm, Heui; Landes, Christy F.; Jayaraman, Vasanthi

doi:10.1074/jbc.m112.371815

Cited by 41 publications

(58 citation statements)

References 53 publications

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“…A similar situation occurs with the LBD of AMPA receptors where single molecule FRET (smFRET) studies show that the LBD samples a spectrum of open-and closedcleft conformations in both apo-and agonist-bound states (33,34), with the agonist-bound forms on average being more closed. Similar NMR and smFRET studies such as those performed on the AMPA receptor LBD may be able to provide insight into the role of such dynamics in zinc modulation of the receptor function (33)(34)(35)(36).…”

Section: Tablementioning

confidence: 93%

Amino-terminal Domain Tetramer Organization and Structural Effects of Zinc Binding in the N-Methyl-d-aspartate (NMDA) Receptor

Sirrieh¹,

MacLean²,

Jayaraman

2013

Journal of Biological Chemistry

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Background: NMDA receptors are ion channels activated by glutamate and glycine and inhibited by zinc. Results: Zinc binding causes a decrease in distance between the amino-terminal domain lower and upper lobes without affecting intersubunit distances. Conclusion: Zinc induces cleft closure in the amino-terminal domain without causing large scale rearrangements in the upper lobe of the ATD tetramer. Significance: This work demonstrates zinc-induced conformational changes in a functional NMDA receptor.

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Section: Tablementioning

confidence: 93%

Amino-terminal Domain Tetramer Organization and Structural Effects of Zinc Binding in the N-Methyl-d-aspartate (NMDA) Receptor

Sirrieh¹,

MacLean²,

Jayaraman

2013

Journal of Biological Chemistry

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“…FRET has previously been applied to AMPARs to characterize the clamshell-closure motions within the LBDs (21,53,54) and the role of interfaces during desensitization (20). However, these studies relied on labeling of engineered cysteine residues, requiring removal of endogenous cysteines, either by mutation or truncation of the receptor (20,41,53,55).…”

Section: Discussionmentioning

confidence: 99%

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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“…1, inset) (24,25), which in turn opens the ion channel in the full-length protein (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). The average distance of the isolated LBD cleft closure has been shown to directly correlate to channel transport efficiency for multiple glutamate receptor types (18,(35)(36)(37), allowing the isolated LBD to be used as a model for further conformational analysis and prediction of channel transport efficiencies.…”

Section: Introductionmentioning

confidence: 96%

Conformational Transitions in the Glycine-Bound GluN1 NMDA Receptor LBD via Single-Molecule FRET

Cooper

Dolino

Jaurich

et al. 2015

Biophysical Journal

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The N-methyl-D-aspartate receptor (NMDAR) is a member of the glutamate receptor family of proteins and is responsible for excitatory transmission. Activation of the receptor is thought to be controlled by conformational changes in the ligand binding domain (LBD); however, glutamate receptor LBDs can occupy multiple conformations even in the activated form. This work probes equilibrium transitions among NMDAR LBD conformations by monitoring the distance across the glycine-bound LBD cleft using single-molecule Förster resonance energy transfer (smFRET). Recent improvements in photoprotection solutions allowed us to monitor transitions among the multiple conformations. Also, we applied a recently developed model-free algorithm called "step transition and state identification" to identify the number of states, their smFRET efficiencies, and their interstate kinetics. Reversible interstate conversions, corresponding to transitions among a wide range of cleft widths, were identified in the glycine-bound LBD, on much longer timescales compared to channel opening. These transitions were confirmed to be equilibrium in nature by shifting the distribution reversibly via denaturant. We found that the NMDAR LBD proceeds primarily from one adjacent smFRET state to the next under equilibrium conditions, consistent with a cleft-opening/closing mechanism. Overall, by analyzing the state-to-state transition dynamics and distributions, we achieve insight into specifics of long-lived LBD equilibrium structural dynamics, as well as obtain a more general description of equilibrium folding/unfolding in a conformationally dynamic protein. The relationship between such long-lived LBD dynamics and channel function in the full receptor remains an open and interesting question.

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Role of Conformational Dynamics in α-Amino-3-hydroxy-5-methylisoxazole-4-propionic Acid (AMPA) Receptor Partial Agonism

Cited by 41 publications

References 53 publications

Amino-terminal Domain Tetramer Organization and Structural Effects of Zinc Binding in the N-Methyl-d-aspartate (NMDA) Receptor

Amino-terminal Domain Tetramer Organization and Structural Effects of Zinc Binding in the N-Methyl-d-aspartate (NMDA) Receptor

Structural rearrangement of the intracellular domains during AMPA receptor activation

Conformational Transitions in the Glycine-Bound GluN1 NMDA Receptor LBD via Single-Molecule FRET

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