Abstract
The alpha-chain of the IL-15R (IL-15Ralpha) serves as the specific, high-affinity receptor for IL-15. It is expressed by lymphoid and nonlymphoid cells, including B cell lymphoma lines. In this study, we have further explored IL-15Ralpha-mediated signaling in activated primary B cells and in Raji cells, a human B-lymphoblastoid cell line which expresses the IL-15Ralpha and IL-2Rgamma chains, but lacks the IL-2Rbeta chain. Stimulation of Raji cells with IL-15 induces their proliferation and rescues them from C2-ceramide-induced apoptosis. By immunoprecipitation and Western blotting, we show that treatment of Raji cells and activated primary B cells with IL-15 induces coprecipitation of Syk kinase with the IL-15Ralpha chain. Upon association, the activated Syk kinase phosphorylates the IL-15Ralpha chain as well as phospholipase Cgamma, which coprecipitates with Syk. Furthermore, transfection of Raji cells with stem-loop Syk antisense oligonucleotides prevents IL-15Ralpha and phospholipase Cgamma phosphorylation as well as the inhibition of apoptosis by IL-15. Mutation of a defined region of the intracellular signaling portion of IL-15Ralpha (Tyr227) abrogates both the IL-15Ralpha/Syk association and IL-15Ralpha phosphorylation. Taken together, this suggests that Syk kinase physically and functionally associates with the IL-15Ralpha chain in B cells and that Syk plays a key role in mediating IL-15-induced signal transduction, thus accounting for the distinct functional consequences of IL-15 vs IL-2 binding to B cells.
Publication types
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Research Support, Non-U.S. Gov't
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Retracted Publication
MeSH terms
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Apoptosis / drug effects
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Apoptosis / genetics
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Apoptosis / immunology
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B-Lymphocyte Subsets / drug effects
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B-Lymphocyte Subsets / enzymology
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B-Lymphocyte Subsets / immunology*
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B-Lymphocyte Subsets / metabolism*
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Calcium / antagonists & inhibitors
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Calcium Signaling / genetics
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Calcium Signaling / immunology
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Cell Division / drug effects
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Cell Division / immunology
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Enzyme Activation / immunology
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Enzyme Precursors / antagonists & inhibitors
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Enzyme Precursors / genetics
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Enzyme Precursors / metabolism*
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Enzyme Precursors / physiology
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Humans
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Interleukin-15 / antagonists & inhibitors
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Interleukin-15 / metabolism*
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Interleukin-15 / physiology
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Intracellular Signaling Peptides and Proteins
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Isoenzymes / antagonists & inhibitors
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Isoenzymes / metabolism
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Jurkat Cells
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K562 Cells
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Lymphocyte Activation
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Mutagenesis, Site-Directed
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Oligonucleotides, Antisense / pharmacology
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Phospholipase C gamma
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Phosphorylation
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / genetics
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Protein-Tyrosine Kinases / metabolism*
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Protein-Tyrosine Kinases / physiology
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Receptors, Interleukin-15
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Receptors, Interleukin-2 / antagonists & inhibitors
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Receptors, Interleukin-2 / biosynthesis
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Receptors, Interleukin-2 / metabolism
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Receptors, Interleukin-2 / physiology*
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Signal Transduction / genetics
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Signal Transduction / immunology*
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Sphingosine / analogs & derivatives*
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Sphingosine / pharmacology
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Syk Kinase
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T-Lymphocyte Subsets / enzymology
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T-Lymphocyte Subsets / immunology
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T-Lymphocyte Subsets / metabolism
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Tumor Cells, Cultured
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Type C Phospholipases / antagonists & inhibitors
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Type C Phospholipases / metabolism
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src Homology Domains / immunology
Substances
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Enzyme Precursors
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IL15RA protein, human
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Interleukin-15
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Intracellular Signaling Peptides and Proteins
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Isoenzymes
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N-acetylsphingosine
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Oligonucleotides, Antisense
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Receptors, Interleukin-15
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Receptors, Interleukin-2
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Protein-Tyrosine Kinases
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SYK protein, human
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Syk Kinase
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Type C Phospholipases
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Phospholipase C gamma
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Sphingosine
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Calcium