A Point Mutation in the Glutamate Binding Site Blocks Desensitization of AMPA Receptors

Stern‐Bach, Yael; Russo, Sebastian G.; Neuman, Menahem; Rosenmund, Christian

doi:10.1016/s0896-6273(00)80605-4

Cited by 229 publications

(221 citation statements)

References 49 publications

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“…Indeed, mutagenesis experiments on AMPA receptors have localized structural determinants responsible for the rapid desensitization and its modulation by allosteric ligands exclusively in the S1 and S2 segments (27)(28)(29). Our present results do not exclude the possibility that the X domain can participate in the fine-tuning of channel responses, as shown by the minor difference in desensitization rates observed between the ⌬402 and full-length GluR-D constructs.…”

Section: Discussioncontrasting

confidence: 79%

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Channels Lacking the N-terminal Domain

Pasternack¹,

Coleman²,

Jouppila³

et al. 2002

Journal of Biological Chemistry

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Ionotropic glutamate receptor (iGluR) subunits contain a ϳ400-residue extracellular N-terminal domain ("X domain"), which is sequence-related to bacterial amino acid-binding proteins and to class C G-protein-coupled receptors. The X domain has been implicated in the assembly, transport to the cell surface, allosteric ligand binding, and desensitization in various members of the iGluR family, but its actual role in these events is poorly characterized. We have studied the properties of homomeric ␣-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA)-selective GluR-D glutamate receptors carrying N-terminal deletions. Our analysis indicates that, surprisingly, transport to the cell surface, ligand binding properties, agonist-triggered channel activation, rapid desensitization, and allosteric potentiation by cyclothiazide can occur normally in the complete absence of the X domain (residues 22-402). The relatively intact ligand-gated channel function of a homomeric AMPA receptor in the absence of the X domain indirectly suggests more subtle roles for this domain in AMPA receptors, e.g. in the assembly of heteromeric receptors and in synaptic protein interactions.

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Section: Discussioncontrasting

confidence: 79%

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Channels Lacking the N-terminal Domain

Pasternack¹,

Coleman²,

Jouppila³

et al. 2002

Journal of Biological Chemistry

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“…Their model of receptor activation predicted that mutations that stabilize the dimer will reduce or eliminate desensitization, whereas those that destabilize it will accelerate desensitization. This has been found largely to be the case in GluR2 (31,32).…”

Section: Resultsmentioning

confidence: 88%

“…We predict that GluR6 desensitizes, because Y521 is held in a strong interaction with K525. In support of this hypothesis, mutation of the GluR3 homologue of GluR6 K525 (E511) to lysine increases desensitization of the GluR3 L507Y mutant (32).…”

Section: Resultsmentioning

confidence: 92%

“…In GluR2, there is a good correlation between stability of the dimer (measured by equilibrium centrifugation) and the degree of desensitization, leading Sun et al (31) to propose a model where rearrangement of the dimer is required for the receptor to desensitize (31). They showed that L483Y, the GluR2 homologue of the nondesensitizing GluR3 mutant L507Y (32), increased the stability of the dimer through an intersubunit contact (31). Further, they showed that cyclothiazide, which blocks desensitization in AMPA receptors, binds to a site in the dimer interface.…”

Section: Resultsmentioning

confidence: 99%

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Structure of the kainate receptor subunit GluR6 agonist-binding domain complexed with domoic acid

Nanao

Green

Stern‐Bach

et al. 2005

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

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We report the crystal structure of the glycosylated ligand-binding (S1S2) domain of the kainate receptor subunit GluR6, in complex with the agonist domoate. The structure shows the expected overall homology with AMPA and NMDA receptor subunit structures but reveals an unexpected binding mode for the side chain of domoate, in which contact is made to the larger lobe only (lobe I). In common with the AMPA receptor subunit GluR2, the GluR6 S1S2 domain associates as a dimer, with many of the interdimer contacts being conserved. Subtle differences in these contacts provide a structural explanation for why GluR2 L483Y and GluR3 L507Y are nondesensitizing, but GluR6, which has a tyrosine at that site, is not. The structure incorporates native glycosylation, which has not previously been described for ionotropic glutamate receptors. The position of the sugars near the subunit interface rules out their direct involvement in subunit association but leaves open the possibility of indirect modulation. Finally, we observed several tetrameric assemblies that satisfy topological constraints with respect to connection to the receptor pore, and which are therefore candidates for the native quaternary structure.crystal structure ͉ domoate ͉ glutamate receptor I onotropic glutamate receptors (iGluRs) are major mediators of rapid excitatory neurotransmission in the mammalian CNS and in consequence are involved in a wide range of physiological and pathological neural processes (1). There are three main iGluR subfamilies: AMPA, NMDA, and kainate receptors. The functional importance of both AMPA and NMDA receptors in synaptic transmission and plasticity has long been recognized. It is only recently, however, that the physiological roles of kainate receptors have begun to be delineated. Studies using selective ligands and gene ablation in mice have shown that kainate receptors are involved in the regulation of synaptic transmission and plasticity in several brain regions (2).All iGluRs are thought to share a similar overall structure, with four homologous subunits arranged around a central cationselective pore. The subunits themselves share a common membrane topology (Fig. 1A), with three transmembrane domains (termed M1, M3, and M4) and a reentrant loop similar to the P loop found in potassium channels (termed M2). This leaves two large polypeptide domains on the extracellular (synaptic) side of the membrane: the Ϸ530-aa N terminus and the domain between M3 and M4. Studies of chimeric receptors and recombinant constructs identified the Ϸ120-aa preceding M1 (termed S1) and the Ϸ140-aa M3-M4 loop (S2) as forming the agonist-binding domain (3, 4). The S1S2 domain can be expressed as a soluble polypeptide independently of the membrane-spanning domains, making it amenable to crystallization and structure determination by x-ray diffraction. In this way, structures for the S1S2 domains for the AMPA-selective subunit GluR2 (5-7) and the NMDA subunit NR1 (8) have been determined, with both proteins sharing a bilobate structure. Although no str...

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“…For practical reasons (see "Experimental Procedures") these substitutions were made on the backbone of R3(R6S1), a GluR3 subunit having S1 from GluR6. This subunit is identical to GluR3 except for an increased affinity to some agonists (5) and a complete loss of receptor desensitization (29). The terminology used to describe the resulting intra-NTD chimeras is N(XXXX), where X stands for either "3" or "6," representing a GluR3 or a GluR6 sequence in the corresponding N1-N4 regions.…”

Section: Glur3/glur6mentioning

confidence: 99%

Two Regions in the N-terminal Domain of Ionotropic Glutamate Receptor 3 Form the Subunit Oligomerization Interfaces That Control Subtype-specific Receptor Assembly

Ayalon¹,

Segev²,

Elgavish

et al. 2005

Journal of Biological Chemistry

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The N-terminal domain (NTD) of ␣-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and kainate glutamate receptors plays an important role in controlling subtype specific receptor assembly. To identify NTD subdomains involved in this process we generated AMPA glutamate receptor 3 (GluR3) mutants having intra-NTD substitutions with the corresponding regions of the kainate receptor GluR6 and tested their ability to form functional heteromers with wild-type subunits. The chimeric design was based on the homology of the NTD to the NTD of the metabotropic GluR1, shown to form two globular lobes and to assemble in dimers. Accordingly, the NTD was divided into four regions, termed here N1-N4, of which N1 and N3 correspond to the regions forming lobe-1 and N2 and N4 to those forming lobe-2. Substituting N1 or N3 impaired functional heteromerization but allowed protein-protein interactions. Conversely, exchanging N2 or N4 preserved functional heteromerization, although it significantly decreased homomeric activity, indicating a role in subunit folding. Moreover, a deletion in GluR3 corresponding to the hotfoot mouse mutation of the glutamate receptor ␦2, covering part of N2, N3, and N4, impaired both homomeric and heteromeric oligomerization, thus explaining the null-like mouse phenotype. Finally, computer modeling suggested that the dimer interface, largely formed by N1, is highly hydrophobic in GluR3, whereas in GluR6 it contains electrostatic interactions, hence offering an explanation for the subtype assembly specificity conferred by this region. N3, however, is positioned perpendicular to the dimer interface and therefore may be involved in secondary interactions between dimers in the assembled tetrameric receptor.Glutamate, the major excitatory neurotransmitter, activates two receptor families: metabotropic glutamate receptors (mGluRs), 1 which are coupled to G-proteins, and ionotropic glutamate receptors (iGluRs), which form cation selective ion channels. The iGluRs are further divided into three subtypes: AMPA, kainate, and NMDA receptors, originally named after their most selective agonist (1). Each subtype, in turn, consists of several subunits that assemble as tetramers in various combinations to form channels with distinct properties (2). Of the cloned subunits, GluR1-4 form the AMPA receptors, GluR5-7 and KA1-2 form the kainate receptors, and NR1, NR2A-D, and NR3A-B form the NMDA receptors. The ␦1-2 subunits constitute an orphan group of iGluRs, and their relation to the three principal subtypes is unclear.Overall, all iGluR subunits have a common domain organization (3). Each subunit contains four membrane regions (M1-M4), of which M1, M3, and M4 traverse the plasma membrane and M2 is a reentrant loop aligning the channel pore. The N terminus is extracellular and comprises an ϳ400-residue Nterminal domain (NTD; also termed "X domain"), which is homologous to bacterial periplasmic amino acid-binding proteins and to the N-terminal domain of mGluRs (4). Following the NTD is S1, an ϳ150-residue segment, which ...

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A Point Mutation in the Glutamate Binding Site Blocks Desensitization of AMPA Receptors

Cited by 229 publications

References 49 publications

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Channels Lacking the N-terminal Domain

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Channels Lacking the N-terminal Domain

Structure of the kainate receptor subunit GluR6 agonist-binding domain complexed with domoic acid

Two Regions in the N-terminal Domain of Ionotropic Glutamate Receptor 3 Form the Subunit Oligomerization Interfaces That Control Subtype-specific Receptor Assembly

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