title: Structural basis of kainate subtype glutamate receptor desensitization.
abstract: Glutamate receptors are ligand-gated tetrameric ion channels that mediate synaptic transmission in the central nervous system. They are instrumental in vertebrate cognition and their dysfunction underlies diverse diseases. In both the resting and desensitized states of AMPA and kainate receptor subtypes, the ion channels are closed, whereas the ligand-binding domains, which are physically coupled to the channels, adopt markedly different conformations. Without an atomic model for the desensitized state, it is not possible to address a central problem in receptor gating: how the resting and desensitized receptor states both display closed ion channels, although they have major differences in the quaternary structure of the ligand-binding domain. Here, by determining the structure of the kainate receptor GluK2 subtype in its desensitized state by cryo-electron microscopy (cryo-EM) at 3.8 Å resolution, we show that desensitization is characterized by the establishment of a ring-like structure in the ligand-binding domain layer of the receptor. Formation of this 'desensitization ring' is mediated by staggered helix contacts between adjacent subunits, which leads to a pseudo-four-fold symmetric arrangement of the ligand-binding domains, illustrating subtle changes in symmetry that are important for the gating mechanism. Disruption of the desensitization ring is probably the key switch that enables restoration of the receptor to its resting state, thereby completing the gating cycle.
authors: Laboratory of Cell Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA.
authors: Joel R
authors: JR
authors: Meyerson
authors: Laboratory of Cell Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA.|Laboratory of Cellular and Molecular Neurophysiology, Porter Neuroscience Research Center, NICHD, NIH, Bethesda, Maryland 20892, USA.
authors: Sagar
authors: S
authors: Chittori
authors: Laboratory of Cell Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA.
authors: Alan
authors: A
authors: Merk
authors: Laboratory of Cell Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA.
authors: Prashant
authors: P
authors: Rao
authors: Program in Cellular Regulation and Metabolism, NICHD, NIH, Bethesda, Maryland 20892, USA.
authors: Tae Hee
authors: TH
authors: Han
authors: Program in Cellular Regulation and Metabolism, NICHD, NIH, Bethesda, Maryland 20892, USA.
authors: Mihaela
authors: M
authors: Serpe
authors: Laboratory of Cellular and Molecular Neurophysiology, Porter Neuroscience Research Center, NICHD, NIH, Bethesda, Maryland 20892, USA.
authors: Mark L
authors: ML
authors: Mayer
authors: Laboratory of Cell Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA.
authors: Sriram
authors: S
authors: Subramaniam
mesh_terms: D000818:Animals; D001665:Binding Sites; D020285:Cryoelectron Microscopy; D015536:Down-Regulation; D015640:Ion Channel Gating; D008024:Ligands; D008958:Models, Molecular; D000072417:Protein Domains; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D018092:Kainic Acid Receptors / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure*; D000097806:GluK2 Kainate Receptor
chemical_list: D008024:Ligands; D021122:Protein Subunits; D018092:Kainic Acid Receptors; D000097806:GluK2 Kainate Receptor