NKG2D type II integral membrane protein (NKG2D)

The NKG2D type II integral membrane protein, encoded by the KLRK1 gene on chromosome 12p12.3-p13.1, is a homodimeric activating receptor expressed on NK cells, CD8+ T cells, γδ T cells, and other immune cells, functioning in immunosurveillance by recognizing stress-inducible ligands such as MICA, MICB, and ULBPs on infected, transformed, or senescent cells.[2][3][9] It lacks signaling motifs in its short cytoplasmic tail and associates via transmembrane interactions with the adaptor protein DAP10 (in humans) to form a hexameric complex, recruiting PI3K through the YXXM motif to trigger cytotoxicity, cytokine secretion like IFN-γ, and co-stimulatory signals enhancing immune cell activation.[1][3][5] Unlike other NKG2 family members that heterodimerize with CD94, NKG2D operates independently with only 21% homology to them, featuring a C-type lectin-like extracellular domain that binds diverse MHC class I-like ligands induced by cellular stress.[1][5][7] In disease, upregulated NKG2D ligands on tumor cells like hepatocellular carcinoma promote NK-mediated killing, while soluble ligands or genetic polymorphisms can dampen receptor function, contributing to immune evasion in cancer and infections.[2][3][7] NKG2D thus serves as a key sensor of "missing self" and danger signals, with therapeutic potential in CAR-T/CAR-NK therapies targeting its pathway, though no approved small-molecule drugs directly interact with it yet.[1][3]

Other names

KLRK1CD314D12S2489Ekiller cell lectin-like receptor K1