• Identified four iGluR subunits in lampreys, including Lr-GRIK1, and confirmed their conserved structural features with jawed vertebrates.
• Lr-GRIK1 is highly expressed in kidney tissue, suggesting a role beyond neurotransmission.
• Silencing Lr-GRIK1 in lampreys altered expression of genes involved in immune response pathways, indicating a negative regulatory role in immunity.
• This study provides the first functional evidence of KARs in jawless vertebrates, expanding understanding of iGluR evolution and immune function.