GRIK4 encodes a kainate-type ionotropic glutamate receptor subunit that functions as a ligand-gated cation channel. The protein cannot form functional channels independently but assembles with other kainate receptor subunits (GRIK1, GRIK2, GRIK3) to create active complexes that mediate fast synaptic transmission and regulate neuronal excitability. GRIK4 is expressed early in human fetal brain development and localizes to specific neuronal populations in the hippocampus, cerebellum, and cortex, where it plays roles in synaptic plasticity and circuit function 1. A deletion variant in GRIK4 is associated with reduced bipolar disorder risk and correlates with increased KA1 protein abundance in hippocampal and cortical neurons 2. Conversely, forebrain overexpression of GRIK4 in mice causes an imbalance between excitatory and inhibitory synaptic activity, producing behavioral abnormalities including social impairment, anxiety, and depression that resemble autism spectrum disorder features 34. Genetic variants in GRIK4 (rs1954787, rs6589847, rs56275759) associate with antidepressant treatment response to venlafaxine in depressed patients, with the C allele at rs1954787 predicting better treatment outcomes 56. Kainate receptor antagonists including selurampanel and tezampanel represent therapeutic approaches targeting this pathway in seizure disorders and neuropsychiatric conditions.