NKG2D-mediated signaling requires a DAP10-bound Grb2-Vav1 intermediate and phosphatidylinositol-3-kinase in human natural killer cells.
NKG2D is an important immunosurveillance receptor that responds to stress-induced ligand expression on tumors and virus-infected cells. Human natural killer cells express NKG2D and require the transmembrane adaptor DAP10 to initiate their full cytotoxic activation. However, DAP10 has no immunoreceptor tyrosine-based activation motif and thus the mechanism of recruiting 'downstream' effector proteins is unclear. We show here that binding of the p85 subunit of phosphatidylinositol-3- kinase to DAP10 could not by itself trigger cell-mediated cytotoxicity and that binding of an intermediate consisting of the DAP10 binding partner Grb2 and the effector molecule Vav1 (Grb2-Vav1) to DAP10 was sufficient to initiate tyrosine-phosphorylation events. For full calcium release and cytotoxicity to occur, both Grb2-Vav1 and p85 had to bind to DAP10. These findings identify a previously unknown mechanism by which NKG2D-DAP10 mediates cytotoxicity and provides a framework for evaluating activation by other receptor complexes that lack immunoreceptor tyrosine-based activation motifs.
Department of Immunology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Jadee L
JL
Upshaw
Laura N
LN
Arneson
Renee A
RA
Schoon
Christopher J
CJ
Dick
Daniel D
DD
Billadeau
Paul J
PJ
Leibson
D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D003602:Cytotoxicity, Immunologic; D051380:GRB2 Adaptor Protein / Q000378:metabolism*; D006801:Humans; D007694:Killer Cells, Natural / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D055655:NK Cell Lectin-Like Receptor Subfamily K; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D055607:Receptors, Natural Killer Cell; D015398:Signal Transduction / Q000276:immunology
D000945:Antigens, Differentiation, T-Lymphocyte; C075005:GNLY protein, human; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C120528:HCST protein, human; C527085:KLRK1 protein, human; D008565:Membrane Proteins; D055655:NK Cell Lectin-Like Receptor Subfamily K; D051567:Proto-Oncogene Proteins c-vav; D011971:Receptors, Immunologic; D055607:Receptors, Natural Killer Cell; C496618:VAV1 protein, human; D019869:Phosphatidylinositol 3-Kinases; D002118:Calcium