title: A role for Ras signaling in coreceptor regulation during differentiation of a double-positive thymocyte cell line.
abstract: Evidence suggests that the Ras/mitogen-activated protein kinase signaling pathway is required for positive selection of thymocytes. We have asked whether Ras activation is also sufficient to mediate changes in gene expression that are associated with positive selection. To accomplish this, we expressed a constitutively active form of Ras in the immature CD4+ 8+ DPK thymocyte cell line. DPK cells that express active Ras have reduced levels of CD8alpha and CD8beta at the level of cell surface protein and mRNA. These data provide evidence of a direct link between Ras signaling pathways and coreceptor regulation during positive selection. They also suggest that a sustained or potent Ras signal may play a critical role in directing thymocytes into the CD4 lineage. DPK cells that express active Ras, however, were not fully differentiated, indicating that Ras signaling provides only a partial signal for double-positive thymocyte differentiation.
authors.affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: H
authors.initials: H
authors.lastname: Shao
authors.forename: E M
authors.initials: EM
authors.lastname: Rubin
authors.forename: L Y
authors.initials: LY
authors.lastname: Chen
authors.forename: J
authors.initials: J
authors.lastname: Kaye
mesh_terms: D000818:Animals; D015704:CD4 Antigens / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology; D002460:Cell Line; D015536:Down-Regulation / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D018631:ras Proteins / Q000502:physiology*
chemical_list: D015704:CD4 Antigens; D016827:CD8 Antigens; D011948:Receptors, Antigen, T-Cell; D018631:ras Proteins