Signal transduction by a CD16/CD7/Jak2 fusion protein.
The addition of interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) to hormone-dependent cells induces tyrosine phosphorylation of Janus protein kinase 2 (Jak2) and activates its in vitro kinase activity. To explore the role of Jak2 in IL-3/GM-CSF-mediated signal transduction, we constructed a CD16/CD7/Jak2 (CD16/Jak2) fusion gene containing the external domain of CD16 and the entire Jak2 molecule and expressed this fusion protein using a recombinant vaccinia virus. The clustering of CD16/Jak2 fusion protein by cross-linking with an anti-CD16 antibody induced autophosphorylation of the fusion protein but did not induce the phosphorylation of either the endogenous Jak2 or the beta chain. Cross-linking of CD16/Jak2 stimulates the tyrosine phosphorylation of a large group of proteins that are also phosphorylated after the addition of IL-3 or GM-CSF and include proteins of 145, 97, 67, 52, and 42 kDa. Closer analysis demonstrated that the CD16/Jak2 phosphorylates Shc, a 52-kDa protein, and the 145-kDa protein associated tightly with Shc, as well as mitogen-associated protein kinase (pp42). Electrophoretic mobility shift assays demonstrate that CD16/Jak2 activates the ability of signal transduction and activation of transcription (STAT) proteins to bind to an interferon-gamma-activated sequence oligonucleotide in a manner similar to that seen after IL-3 treatment. Cross-linking of the CD16/Jak2 protein stimulated increases in c-fos and junB similar to IL-3 but did not cause major changes in the levels of the c-myc message, which normally increases after IL-3 treatment. Thus, a transmembrane CD16/Jak2 fusion is capable of activating protein phosphorylation and mRNA transcription in a manner similar but not identical to hematopoietic growth factors.
Sakai
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Department of Medicine, University of Alabama, Birmingham 35223.
Nabell
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Kraft
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D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D019011:Antigens, CD7; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D003432:Cross-Linking Reagents; D004789:Enzyme Activation; D006412:Hematopoietic Stem Cells; D053614:Janus Kinase 2; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000096:biosynthesis; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic
D015703:Antigens, CD; D019011:Antigens, CD7; D000945:Antigens, Differentiation, T-Lymphocyte; D003432:Cross-Linking Reagents; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases