title: Syk regulation of phosphoinositide 3-kinase-dependent NK cell function.
abstract: Emerging evidence suggests that NK-activatory receptors use KARAP/DAP12, CD3zeta, and FcepsilonRIgamma adaptors that contain immunoreceptor tyrosine-based activatory motifs to mediate NK direct lysis of tumor cells via Syk tyrosine kinase. NK cells may also use DAP10 to drive natural cytotoxicity through phosphoinositide 3-kinase (PI3K). In contrast to our recently identified PI3K pathway controlling NK cytotoxicity, the signaling mechanism by which Syk associates with downstream effectors to drive NK lytic function has not been clearly defined. In NK92 cells, which express DAP12 but little DAP10/NKG2D, we now show that Syk acts upstream of PI3K, subsequently leading to the specific signaling of the PI3K-->Rac1-->PAK1-->mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase-->ERK cascade that we earlier described. Tumor cell ligation stimulated DAP12 tyrosine phosphorylation and its association with Syk in NK92 cells; Syk tyrosine phosphorylation and activation were also observed. Inhibition of Syk function by kinase-deficient Syk or piceatannol blocked target cell-induced PI3K, Rac1, PAK1, mitogen-activated protein/ERK kinase, and ERK activation, perforin movement, as well as NK cytotoxicity, indicating that Syk is upstream of all these signaling events. Confirming that Syk does not act downstream of PI3K, constitutively active PI3K reactivated all the downstream effectors as well as NK cytotoxicity suppressed in Syk-impaired NK cells. Our results are the first report documenting the instrumental role of Syk in control of PI3K-dependent natural cytotoxicity.
authors.affiliation: Immunology Program, H. Lee Moffitt Cancer Center, Department of Interdisciplinary Oncology, University of South Florida College of Medicine, Tampa, FL 33612, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Jiang
authors.forename: Bin
authors.initials: B
authors.lastname: Zhong
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Gilvary
authors.forename: Brian C
authors.initials: BC
authors.lastname: Corliss
authors.forename: Eric
authors.initials: E
authors.lastname: Vivier
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hong-Geller
authors.forename: Sheng
authors.initials: S
authors.lastname: Wei
authors.forename: Julie Y
authors.initials: JY
authors.lastname: Djeu
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000276:immunology / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D020014:K562 Cells; D007694:Killer Cells, Natural / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D008024:Ligands; D048728:MAP Kinase Kinase Kinase 1; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D054353:Perforin; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism* / Q000502:physiology; D052899:Pore Forming Cytotoxic Proteins; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D021381:Protein Transport / Q000276:immunology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D011971:Receptors, Immunologic / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D013267:Stilbenes / Q000494:pharmacology; D000072377:Syk Kinase; D014407:Tumor Cells, Cultured; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D007166:Immunosuppressive Agents; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D048728:MAP Kinase Kinase Kinase 1; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases; D054353:Perforin; D019869:Phosphatidylinositol 3-Kinases; D052899:Pore Forming Cytotoxic Proteins; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011971:Receptors, Immunologic; D013267:Stilbenes; D000072377:Syk Kinase; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein; C110546:TYROBP protein, human; C041525:3,3',4,5'-tetrahydroxystilbene; C000606896:SYK protein, human; C515903:PAK1 protein, human; C482576:MAP3K1 protein, human