title: Cbl enforces an SLP76-dependent signaling pathway for T cell differentiation.
abstract: A signaling pathway involving ZAP-70, LAT, and SLP76 has been regarded as essential for receptor-driven T cell development and activation. Consistent with this model, mice deficient in SLP76 have a complete block at the double negative 3 stage of T cell development. Recently, however, it has been reported that inactivation of Cbl, a ubiquitin-protein isopeptide ligase, partially rescues T cell development in SLP76-deficient mice. To probe the influence of Cbl on domain-specific SLP76 functions, we reconstituted SLP76(-/-) Cbl(-/-) mice with Slp76 transgenes bearing mutations in each of three functional domains of SLP76 as follows: Y3F, in which the amino-terminal tyrosine residues of SLP76 were mutated, eliminating sites of SLP76 interaction with Vav, Nck, and Itk; Delta20, in which 20 amino acids in the proline-rich region of SLP76 were deleted, removing a binding site for Gads; and RK, in which arginine 448 of SLP76 was replaced by lysine, abolishing function of the Src homology 2 domain. Although each of these transgenes has been shown to partially rescue T cell development in SLP76(-/-) mice, we report here that Cbl inactivation completely reverses the severe double negative 3 developmental block that occurs in SLP76-deficient mice expressing the Y3F transgene (Y3F mice) and partially rescues the defect in positive selection in T cell receptor transgenic Y3F mice, but in contrast fails to rescue thymic development of SLP76-deficient mice expressing the Delta20 or RK transgene. Rescue in SLP76(-/-)Cbl(-/-)Y3F double-positive thymocytes is associated with enhanced tyrosine phosphorylation of signaling molecules, including Lck, Vav, PLC-gamma1, and ERKs, but not Itk, in response to T cell receptor stimulation. Thus, our data demonstrate that Cbl suppresses activation of a bypass signaling pathway and thereby enforces SLP76 dependence of early T cell development.
authors.affiliation: Experimental Immunology Branch, NCI, and NIA, National Institutes of Health, Bethesda, Maryland 20892, USA. chiangj@mail.nih.gov
authors.forename: Y Jeffrey
authors.initials: YJ
authors.lastname: Chiang
authors.forename: Martha S
authors.initials: MS
authors.lastname: Jordan
authors.forename: Reiko
authors.initials: R
authors.lastname: Horai
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Schwartzberg
authors.forename: Gary A
authors.initials: GA
authors.lastname: Koretzky
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Hodes
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D008213:Lymphocyte Activation / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D015513:Oncogene Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C491734:Lat protein, mouse; D008565:Membrane Proteins; C078332:Nck protein; D015513:Oncogene Proteins; D010750:Phosphoproteins; D051567:Proto-Oncogene Proteins c-vav; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; D050721:Proto-Oncogene Proteins c-cbl; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497262:Zap70 protein, mouse; C080813:emt protein-tyrosine kinase; C493849:Cbl protein, mouse