NKG2D

NKG2D is a transmembrane protein belonging to the CD94/NKG2 family of C-type lectin-like receptors. NKG2D is encoded by KLRK1 gene which is located in the NK-gene complex (NKC) situated on chromosome 6 in mice and chromosome 12 in humans. In mice, it is expressed by NK cells, NK1.1⁺ T cells, γδ T cells, activated CD8⁺ αβ T cells and activated macrophages. In humans, it is expressed by NK cells, γδ T cells and CD8⁺ αβ T cells. NKG2D recognizes induced-self proteins from MIC and RAET1/ULBP families which appear on the surface of stressed, malignant transformed, and infected cells.

Structure

Human NKG2D receptor complex assembles into a hexameric structure. NKG2D itself forms a homodimer whose ectodomains serve for ligand binding. Each NKG2D monomer is associated with DAP10 dimer. This association is maintained by ionic interaction of a positively charged arginine present in a transmembrane segment of NKG2D and negatively charged aspartic acids within both transmembrane regions of DAP10 dimer.DAP10 functions as an adaptor protein and transduces the signal after the ligand binding by recruiting the p85 subunit of PI3K and Grb2-Vav1 complex which are responsible for subsequent downstream events.