UL16-binding proteins, novel MHC class I-related proteins, bind to NKG2D and activate multiple signaling pathways in primary NK cells.
The UL16-binding proteins (ULBPs) are a novel family of MHC class I-related molecules that were identified as targets of the human CMV glycoprotein, UL16. We have previously shown that ULBP expression renders a relatively resistant target cell sensitive to NK cytotoxicity, presumably by engaging NKG2D, an activating receptor expressed by NK and other immune effector cells. In this study we show that NKG2D is the ULBP counterstructure on primary NK cells and that its expression is up-regulated by IL-15 stimulation. Soluble forms of ULBPs induce marked protein tyrosine phosphorylation, and activation of the Janus kinase 2, STAT5, extracellular signal-regulated kinase, mitogen-activated protein kinase, and phosphatidylinositol 3-kinase (PI 3-kinase)/Akt signal transduction pathways. ULBP-induced activation of Akt and extracellular signal-regulated kinase and ULBP-induced IFN-gamma production are blocked by inhibitors of PI 3-kinase, consistent with the known binding of PI 3-kinase to DAP10, the membrane-bound signal-transducing subunit of the NKG2D receptor. While all three ULBPs activate the same signaling pathways, ULBP3 was found to bind weakly and to induce the weakest signal. In summary, we have shown that NKG2D is the ULBP counterstructure on primary NK cells and for the first time have identified signaling pathways that are activated by NKG2D ligands. These results increase our understanding of the mechanisms by which NKG2D activates immune effector cells and may have implications for immune surveillance against pathogens and tumors.
Sutherland
Claire L
CL
Department of Molecular Biology, Immunex, Seattle, WA 98101, USA. sutherlandc@immunex.com
Chalupny
N Jan
NJ
Schooley
Kenneth
K
VandenBos
Tim
T
Kubin
Marek
M
Cosman
David
D
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D018925:Chemokines / Q000096:biosynthesis; D016207:Cytokines / Q000096:biosynthesis; D003587:Cytomegalovirus / Q000276:immunology / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic; D004268:DNA-Binding Proteins / Q000378:metabolism; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D007694:Killer Cells, Natural / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D008213:Lymphocyte Activation; D020935:MAP Kinase Signaling System / Q000276:immunology; D008565:Membrane Proteins; D008894:Milk Proteins; D055655:NK Cell Lectin-Like Receptor Subfamily K; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011971:Receptors, Immunologic / Q000276:immunology / Q000378:metabolism*; D055607:Receptors, Natural Killer Cell; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000276:immunology*; D015534:Trans-Activators / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D018925:Chemokines; D016207:Cytokines; D004268:DNA-Binding Proteins; D058851:GPI-Linked Proteins; D015395:Histocompatibility Antigens Class I; D007141:Immunoglobulin Fc Fragments; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D008565:Membrane Proteins; D008894:Milk Proteins; D055655:NK Cell Lectin-Like Receptor Subfamily K; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011971:Receptors, Immunologic; D055607:Receptors, Natural Killer Cell; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D014443:Tyrosine; C527085:KLRK1 protein, human; C423231:ULBP1 protein, human; C423230:ULBP2 protein, human; C423229:ULBP3 protein, human; C507924:JAK2 protein, human; C494918:AKT1 protein, human