Receptor for glutamate. L-glutamate acts as an excitatory neurotransmitter at many synapses in the central nervous system. The postsynaptic actions of Glu are mediated by a variety of receptors that are named according to their selective agonists. This receptor binds kainate > quisqualate > glutamate >> AMPA (By similarity). Forms a heteromeric channel with GRIK1 or GRIK3. Belongs to the glutamate-gated ion channel (TC 1.A.10.1) family. GRIK4 subfamily.