Limits...
The biochemistry, ultrastructure, and subunit assembly mechanism of AMPA receptors.

Nakagawa T - Mol. Neurobiol. (2010)

Bottom Line: The AMPA-R proteomics studies continuously reveal a previously unexpected degree of molecular heterogeneity of the complex.The current ultrastructural data on the receptors and the receptor-expressing stable cell lines that were developed during the course of these studies are useful resources for high throughput drug screening and further drug designing.Moreover, we are getting closer to understanding the precise mechanisms of AMPA-R-mediated synaptic plasticity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. nakagawa@ucsd.edu

ABSTRACT
The AMPA-type ionotropic glutamate receptors (AMPA-Rs) are tetrameric ligand-gated ion channels that play crucial roles in synaptic transmission and plasticity. Our knowledge about the ultrastructure and subunit assembly mechanisms of intact AMPA-Rs was very limited. However, the new studies using single particle EM and X-ray crystallography are revealing important insights. For example, the tetrameric crystal structure of the GluA2cryst construct provided the atomic view of the intact receptor. In addition, the single particle EM structures of the subunit assembly intermediates revealed the conformational requirement for the dimer-to-tetramer transition during the maturation of AMPA-Rs. These new data in the field provide new models and interpretations. In the brain, the native AMPA-R complexes contain auxiliary subunits that influence subunit assembly, gating, and trafficking of the AMPA-Rs. Understanding the mechanisms of the auxiliary subunits will become increasingly important to precisely describe the function of AMPA-Rs in the brain. The AMPA-R proteomics studies continuously reveal a previously unexpected degree of molecular heterogeneity of the complex. Because the AMPA-Rs are important drug targets for treating various neurological and psychiatric diseases, it is likely that these new native complexes will require detailed mechanistic analysis in the future. The current ultrastructural data on the receptors and the receptor-expressing stable cell lines that were developed during the course of these studies are useful resources for high throughput drug screening and further drug designing. Moreover, we are getting closer to understanding the precise mechanisms of AMPA-R-mediated synaptic plasticity.

Show MeSH

Related in: MedlinePlus

Structures of the dimer intermediates and the subunit assembly pathway of AMPA-R. aTop—the EM structure of dimer intermediate of wild-type GluA2 is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). bTop—the EM structure of dimer intermediate of GluA2 L504Y is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). c Proposed AMPA-R subunit assembly pathways are shown. In the wild-type subunit dimers, the LBDs are not dimerized. We propose that the LBD dimers in wild-type subunits are formed during the dimer-to-tetramer transition. On the other hand, the LBDs in the L504Y mutant subunits form intra-dimer dimers that may prevent efficient dimer-to-tetramer transition. NTD—red and orange, LBD—blue and purple, TMD—yellow and green. The images were reproduced from [23]
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2992128&req=5

Fig7: Structures of the dimer intermediates and the subunit assembly pathway of AMPA-R. aTop—the EM structure of dimer intermediate of wild-type GluA2 is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). bTop—the EM structure of dimer intermediate of GluA2 L504Y is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). c Proposed AMPA-R subunit assembly pathways are shown. In the wild-type subunit dimers, the LBDs are not dimerized. We propose that the LBD dimers in wild-type subunits are formed during the dimer-to-tetramer transition. On the other hand, the LBDs in the L504Y mutant subunits form intra-dimer dimers that may prevent efficient dimer-to-tetramer transition. NTD—red and orange, LBD—blue and purple, TMD—yellow and green. The images were reproduced from [23]

Mentions: By controlling the timing of GluA2 expression using a DOX inducible expression system, a recent study showed that subunit dimers are the intermediate biosynthetic form of AMPA-Rs [23]. Comparison of the single particle EM structures of the dimeric and the tetrameric AMPA-R revealed the possible gross conformational changes that occur during AMPA-R maturation. Furthermore, the separation of the LBDs is required for maturation. The study also proposed a model for the connection between the individual domain in the tetrameric AMPA-R. The detail of this study is discussed in the later section (Figs. 6 and 7).


The biochemistry, ultrastructure, and subunit assembly mechanism of AMPA receptors.

Nakagawa T - Mol. Neurobiol. (2010)

Structures of the dimer intermediates and the subunit assembly pathway of AMPA-R. aTop—the EM structure of dimer intermediate of wild-type GluA2 is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). bTop—the EM structure of dimer intermediate of GluA2 L504Y is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). c Proposed AMPA-R subunit assembly pathways are shown. In the wild-type subunit dimers, the LBDs are not dimerized. We propose that the LBD dimers in wild-type subunits are formed during the dimer-to-tetramer transition. On the other hand, the LBDs in the L504Y mutant subunits form intra-dimer dimers that may prevent efficient dimer-to-tetramer transition. NTD—red and orange, LBD—blue and purple, TMD—yellow and green. The images were reproduced from [23]
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2992128&req=5

Fig7: Structures of the dimer intermediates and the subunit assembly pathway of AMPA-R. aTop—the EM structure of dimer intermediate of wild-type GluA2 is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). bTop—the EM structure of dimer intermediate of GluA2 L504Y is shown from two different views. Bottom—placement of known crystal structures into the EM density map. Red, ligand binding domain of GluA2 (PDB:3H5W); blue, ligand binding domain of GluR2 S1S2 wild-type (PDB:1FTJ). c Proposed AMPA-R subunit assembly pathways are shown. In the wild-type subunit dimers, the LBDs are not dimerized. We propose that the LBD dimers in wild-type subunits are formed during the dimer-to-tetramer transition. On the other hand, the LBDs in the L504Y mutant subunits form intra-dimer dimers that may prevent efficient dimer-to-tetramer transition. NTD—red and orange, LBD—blue and purple, TMD—yellow and green. The images were reproduced from [23]
Mentions: By controlling the timing of GluA2 expression using a DOX inducible expression system, a recent study showed that subunit dimers are the intermediate biosynthetic form of AMPA-Rs [23]. Comparison of the single particle EM structures of the dimeric and the tetrameric AMPA-R revealed the possible gross conformational changes that occur during AMPA-R maturation. Furthermore, the separation of the LBDs is required for maturation. The study also proposed a model for the connection between the individual domain in the tetrameric AMPA-R. The detail of this study is discussed in the later section (Figs. 6 and 7).

Bottom Line: The AMPA-R proteomics studies continuously reveal a previously unexpected degree of molecular heterogeneity of the complex.The current ultrastructural data on the receptors and the receptor-expressing stable cell lines that were developed during the course of these studies are useful resources for high throughput drug screening and further drug designing.Moreover, we are getting closer to understanding the precise mechanisms of AMPA-R-mediated synaptic plasticity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA. nakagawa@ucsd.edu

ABSTRACT
The AMPA-type ionotropic glutamate receptors (AMPA-Rs) are tetrameric ligand-gated ion channels that play crucial roles in synaptic transmission and plasticity. Our knowledge about the ultrastructure and subunit assembly mechanisms of intact AMPA-Rs was very limited. However, the new studies using single particle EM and X-ray crystallography are revealing important insights. For example, the tetrameric crystal structure of the GluA2cryst construct provided the atomic view of the intact receptor. In addition, the single particle EM structures of the subunit assembly intermediates revealed the conformational requirement for the dimer-to-tetramer transition during the maturation of AMPA-Rs. These new data in the field provide new models and interpretations. In the brain, the native AMPA-R complexes contain auxiliary subunits that influence subunit assembly, gating, and trafficking of the AMPA-Rs. Understanding the mechanisms of the auxiliary subunits will become increasingly important to precisely describe the function of AMPA-Rs in the brain. The AMPA-R proteomics studies continuously reveal a previously unexpected degree of molecular heterogeneity of the complex. Because the AMPA-Rs are important drug targets for treating various neurological and psychiatric diseases, it is likely that these new native complexes will require detailed mechanistic analysis in the future. The current ultrastructural data on the receptors and the receptor-expressing stable cell lines that were developed during the course of these studies are useful resources for high throughput drug screening and further drug designing. Moreover, we are getting closer to understanding the precise mechanisms of AMPA-R-mediated synaptic plasticity.

Show MeSH
Related in: MedlinePlus