Ionotropic glutamate receptor. L-glutamate acts as an excitatory neurotransmitter at many synapses in the central nervous system. Binding of the excitatory neurotransmitter L-glutamate induces a conformation change, leading to the opening of the cation channel, and thereby converts the chemical signal to an electrical impulse. The receptor then desensitizes rapidly and enters a transient inactive state, characterized by the presence of bound agonist. Modulates cell surface expression of NETO2. Independent of its ionotropic glutamate receptor activity, acts as a thermoreceptor conferring sensitivity to cold temperatures (By similarity). Functions in dorsal root ganglion neurons (By similarity). Cold receptor activity activated by temperatures between 10-19 degrees Celsius. Homotetramer or heterotetramer of pore-forming glutamate receptor subunits. Tetramers may be formed by the dimerization of dimers (Probable). Assembles into a kainate-gated homomeric channel that does not bind AMPA. GRIK2 associated to GRIK5 forms functional channels that can be gated by AMPA (By similarity). Interacts with DLG4 (By similarity). Interacts with NETO2 (By similarity). Interacts (via C-terminus) with KLHL17 (via kelch repeats); the interaction targets GRIK2 for degradation via ubiquitin-proteasome pathway (By similarity). Sumoylation mediates kainate receptor-mediated endocytosis and regulates synaptic transmission. Sumoylation is enhanced by PIAS3 and desumoylated by SENP1 (By similarity). Ubiquitinated. Ubiquitination regulates the GRIK2 levels at the synapse by leading kainate receptor degradation through proteasome (By similarity). Phosphorylated by PKC at Ser-868 upon agonist activation, this directly enhance sumoylation. The postsynaptic actions of Glu are mediated by a variety of receptors that are named according to their selective agonists. This receptor binds domoate > kainate > quisqualate > 6-cyano-7-nitroquinoxaline-2,3-dione > L-glutamate = 6,7-dinitroquinoxaline-2,3-dione > dihydrokainate (By similarity). Belongs to the glutamate-gated ion channel (TC 1.A.10.1) family. GRIK2 subfamily.