RT Journal Article
SR Electronic
T1 Crystal Structures of the Kainate Receptor GluR5 Ligand Binding Core Dimer with Novel GluR5-Selective Antagonists
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 2852
OP 2861
DO 10.1523/JNEUROSCI.0123-06.2005
VO 26
IS 11
A1 Mark L. Mayer
A1 Alokesh Ghosal
A1 Nigel P. Dolman
A1 David E. Jane
YR 2006
UL http://www.jneurosci.org/content/26/11/2852.abstract
AB Glutamate receptor (GluR) ion channels mediate fast synaptic transmission in the mammalian CNS. Numerous crystallographic studies, the majority on the GluR2-subtype AMPA receptor, have revealed the structural basis for binding of subtype-specific agonists. In contrast, because there are far fewer antagonist-bound structures, the mechanisms for antagonist binding are much less well understood, particularly for kainate receptors that exist as multiple subtypes with a distinct biology encoded by the GluR5–7, KA1, and KA2 genes. We describe here high-resolution crystal structures for the GluR5 ligand-binding core complex with UBP302 and UBP310, novel GluR5-selective antagonists. The crystal structures reveal the structural basis for the high selectivity for GluR5 observed in radiolabel displacement assays for the isolated ligand binding cores of the GluR2, GluR5, and GluR6 subunits and during inhibition of glutamate-activated currents in studies on full-length ion channels. The antagonists bind via a novel mechanism and do not form direct contacts with the E723 side chain as occurs in all previously solved AMPA and kainate receptor agonist and antagonist complexes. This results from a hyperextension of the ligand binding core compared with previously solved structures. As a result, in dimer assemblies, there is a 22 Å extension of the ion channel linkers in the transition from antagonist- to glutamate-bound forms. This large conformational change is substantially different from that described for AMPA receptors, was not possible to predict from previous work, and suggests that glutamate receptors are capable of much larger movements than previously thought.