The cytotoxicity receptor CRACC (CS-1) recruits EAT-2 and activates the PI3K and phospholipase Cgamma signaling pathways in human NK cells.
The CD2-like receptor-activating cytotoxic cell (CRACC) is a cell surface receptor of the CD2 family that triggers NK cell-mediated cytotoxicity through an undefined signaling pathway. CRACC contains cytoplasmic tyrosine-based motifs, immunoreceptor tyrosine-based switch motifs, which resemble those found in the NK cell receptor 2B4. In 2B4, these motifs recruit the adaptor signaling lymphocytic activation molecule-associated protein (SAP), which initiates a signaling cascade mediating cytotoxicity. However, CRACC does not recruit SAP. In this study, we demonstrate that, upon activation, CRACC associates with a homolog of SAP, Ewing's sarcoma's/FLI1-activated transcript 2 (EAT-2), in human NK cells. We show that association of EAT-2 induces the phosphorylation of CRACC and that this process is partially reduced by a pharmacological inhibitor of Src kinases. We identify PLCgamma1, PLCgamma2, and PI3K as the major signaling mediators downstream of CRACC/EAT-2 implicated in NK cell-mediated cytotoxicity. Moreover, EAT-2 also associates with 2B4 predominantly in resting NK cells, whereas SAP preferentially binds 2B4 upon activation. These results outline a new signaling pathway that triggers CRACC-mediated cytotoxicity and modulates 2B4-mediated activation.
Tassi
Ilaria
I
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Colonna
Marco
M
D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D004789:Enzyme Activation; D006801:Humans; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation; D021381:Protein Transport; D011971:Receptors, Immunologic / Q000378:metabolism*; D015398:Signal Transduction; D000071176:Signaling Lymphocytic Activation Molecule Family; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D011971:Receptors, Immunologic; C103572:SH2D1B protein, human; C448987:SLAMF7 protein, human; D000071176:Signaling Lymphocytic Activation Molecule Family; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D051966:Phospholipase C gamma