TY - JOUR

T1 - Structure and affinity of two bicyclic glutamate analogues at AMPA and kainate receptors

AU - Møllerud, Stine

AU - Pinto, Andrea

AU - Marconi, Laura

AU - Frydenvang, Karla Andrea

AU - Thorsen, Thor Seneca

AU - Laulumaa, Saara Kaisa

AU - Venskutonyte, Raminta

AU - Winther, Nikolaj

AU - Cunado Moral, Ana Maria

AU - Tamborini, Lucia

AU - Conti, Paola

AU - Pickering, Darryl S

AU - Kastrup, Jette Sandholm Jensen

PY - 2017

Y1 - 2017

N2 - Ionotropic glutamate receptors (iGluRs) are involved in most of the fast excitatory synaptic transmission in the central nervous system. These receptors are important for learning and memory formation, but are also involved in the development of diseases such as Alzheimer’s disease, epilepsy and depression. In order to understand the function of different types of iGluRs, selective agonists are invaluable as pharmacological tool compounds. Here, we report binding affinities of two bicyclic, conformationally restricted analogues of glutamate (CIP-AS and LM-12b) at AMPA (GluA2 and GluA3) and kainate receptor subunits (GluK1-3 and GluK5). Both CIP-AS and LM-12b were found to be GluK3-preferring agonists, with Ki of 6 and 22 nM, respectively, at recombinant GluK3 receptors. The detailed binding mode of CIP-AS and LM-12b in the ligand-binding domains of the AMPA receptor subunit GluA2 (GluA2-LBD) and the kainate receptor subunits GluK1 (GluK1-LBD) and GluK3 (GluK3-LBD) was investigated by X-ray crystallography. CIP-AS stabilized all three receptor constructs in conformations similar to those with kainate. Remarkably, whereas LM-12b bound in a similar manner to CIP-AS in GluA2-LBD and GluK3-LBD, it introduced full closure of the ligand-binding domain in GluK1-LBD and formation of a D1-D2 interlobe hydrogen bond between Glu441 and Ser721, as also observed with glutamate. As the binding affinity of LM-12b at GluK1 is ~8-fold better than for CIP-AS (Ki of 85 and 656 nM, respectively), it shows that small changes in agonist structure can lead to prominent differences in structure and function.

AB - Ionotropic glutamate receptors (iGluRs) are involved in most of the fast excitatory synaptic transmission in the central nervous system. These receptors are important for learning and memory formation, but are also involved in the development of diseases such as Alzheimer’s disease, epilepsy and depression. In order to understand the function of different types of iGluRs, selective agonists are invaluable as pharmacological tool compounds. Here, we report binding affinities of two bicyclic, conformationally restricted analogues of glutamate (CIP-AS and LM-12b) at AMPA (GluA2 and GluA3) and kainate receptor subunits (GluK1-3 and GluK5). Both CIP-AS and LM-12b were found to be GluK3-preferring agonists, with Ki of 6 and 22 nM, respectively, at recombinant GluK3 receptors. The detailed binding mode of CIP-AS and LM-12b in the ligand-binding domains of the AMPA receptor subunit GluA2 (GluA2-LBD) and the kainate receptor subunits GluK1 (GluK1-LBD) and GluK3 (GluK3-LBD) was investigated by X-ray crystallography. CIP-AS stabilized all three receptor constructs in conformations similar to those with kainate. Remarkably, whereas LM-12b bound in a similar manner to CIP-AS in GluA2-LBD and GluK3-LBD, it introduced full closure of the ligand-binding domain in GluK1-LBD and formation of a D1-D2 interlobe hydrogen bond between Glu441 and Ser721, as also observed with glutamate. As the binding affinity of LM-12b at GluK1 is ~8-fold better than for CIP-AS (Ki of 85 and 656 nM, respectively), it shows that small changes in agonist structure can lead to prominent differences in structure and function.

U2 - 10.1021/acschemneuro.7b00201

DO - 10.1021/acschemneuro.7b00201

M3 - Journal article

C2 - 28691798

VL - 8

SP - 2056

EP - 2064

JO - ACS Chemical Neuroscience

JF - ACS Chemical Neuroscience

SN - 1948-7193

IS - 9

ER -