Glutamate receptor desensitization is mediated by changes in quaternary structure of the ligand binding domain.

Published

Journal Article

Glutamate receptor ion channels are membrane proteins that mediate excitatory synaptic transmission in the central nervous system of vertebrates. Insight into molecular mechanisms underlying glutamate receptor gating is limited by lack of structural information for receptors trapped in different conformational states. Here, we report the use of single-particle cryoelectron tomography to determine the structures, at ∼21 Å resolution, of full-length GluK2 kainate receptors trapped in antagonist-bound resting and agonist-bound desensitized states. The resting state, stabilized by the competitive antagonist LY466195, closely resembles the crystal structure of the AMPA receptor GluA2, with well-resolved proximal and distal subunits exhibiting cross-over between the twofold symmetric amino terminal domain and a twofold symmetric ligand binding domain (LBD) dimer of dimers assembly. In the desensitized state, the LBD undergoes a major rearrangement, resulting in a separation of the four subunits by ∼25 Å. However, the amino terminal domain, transmembrane, and cytoplasmic regions of the receptor have similar conformations in the resting and desensitized states. The LBD rearrangement was not anticipated in prior models based on crystal structures for soluble LBD dimer assemblies, and we speculate that subunit separation allows a better match to the fourfold symmetric ion channel domain. From fits of the amino terminal domain and LBD domains into the density map of the desensitized state we have derived a structural model for differences in quaternary conformation between the resting and desensitized states.

Full Text

Duke Authors

Cited Authors

  • Schauder, DM; Kuybeda, O; Zhang, J; Klymko, K; Bartesaghi, A; Borgnia, MJ; Mayer, ML; Subramaniam, S

Published Date

  • April 2013

Published In

Volume / Issue

  • 110 / 15

Start / End Page

  • 5921 - 5926

PubMed ID

  • 23530186

Pubmed Central ID

  • 23530186

Electronic International Standard Serial Number (EISSN)

  • 1091-6490

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.1217549110

Language

  • eng