Ionotropic glutamate receptors (iGluRs) mediate the majority of fast excitatory synaptic neurotransmission in the central nervous system. The selective assembly of iGluRs into AMPA, kainate, and N-methyl-D-aspartic acid (NMDA) receptor subtypes is regulated by their extracellular amino-terminal domains (ATDs)¹.

Kainate receptors (KARs) are tetramers classified into low-affinity receptor families (GluK1–GluK3) and high-affinity receptor families (GluK4–GluK5) based on their affinity for the neurotoxin kainic acid. KARs share a similar architecture with other ionotropic glutamate receptors; the subunits have a large extracellular domain composed of an amino-terminal domain (ATD) and a ligand binding domain (LBD) and an intracellular carboxy-terminal region².

KARs are expressed in neurons and glial cells throughout the CNS. GluK3 is poorly expressed, appearing in layer IV of the neocortex and dentate gyrus in the hippocampus³.

KARs serve a crucial role as modulators of synaptic transmission and plasticity and their dysfunction has been linked to several disease states such as epilepsy, chronic pain and neurodegenerative diseases⁴. Alteration in the extracellular domain of GluK3, is in linkage disequilibrium with recurrent major depressive disorder patients⁵ and subjects with schizophrenia⁶.