Kainate receptors, or kainic acid receptors (KARs), are ionotropic receptors that respond to the neurotransmitter glutamate. They were first identified as a distinct receptor type through their selective activation by the agonist kainate, a drug first isolated from the algae Digenea simplex. They have been traditionally classified as a non-NMDA-type receptor, along with the AMPA receptor. KARs are less understood than AMPA and NMDA receptors, the other ionotropic glutamate receptors. Postsynaptic kainate receptors are involved in excitatory neurotransmission. Presynaptic kainate receptors have been implicated in inhibitory neurotransmission by modulating release of the inhibitory neurotransmitter GABA through a presynaptic mechanism. The ion channel formed by kainate receptors is permeable to sodium and potassium ions. The single channel conductance of kainate receptor channels is similar to that of AMPA channels, at about 20 pS. However, rise and decay times for postsynaptic potentials generated by KARs are slower than for AMPA postsynaptic potentials. Their permeability to Ca2+ is usually very slight but varies with subunits and RNA editing at the tip of the p-loop. Many kainate receptors appear to exist as heteromers. The 'high-affinity' subunits GluK4 and GluK5 can only form functional channels as heteromers with 'low-affinity' subunits (GluK1-3). Recent investigation through voltage clamping has shown that kainate receptors have more than just an ionotropic (or directly changing a membrane's conductivity) role in neurons. The metabotropic (or indirect through secondary protein pathways) effect has been verified through many accessory proteins and sustained current through G-protein cascades. Here you can see the rat GluK2 kainate receptor in partially-open conformation, as determined by cryoEM (PDB code: 8GC4)

#molecularart ... #kainate ... #receptor ... #cascade ... #voltage ... #clamping ... #cryoem

Structure rendered with @proteinimaging and depicted with @corelphotopaint