title: Epitope-specific engagement of the protein tyrosine phosphatase CD45 induces tumor necrosis factor-alpha gene expression via transcriptional mechanisms.
abstract: The common leukocyte antigen CD45 plays a central role in T cell activation in coupling the T cell receptor (TCR) to the phosphatidylinositol pathway via interactions with TCR-associated protein tyrosine kinases lck and fyn. We here demonstrate that engagement of CD45 by monoclonal antibodies (mAb) on activated T cells induces tumor necrosis factor (TNF)-alpha as well as TNF-beta, interleukin (IL)-2 and IL-3 gene expression. When human alloreactive T cells are stimulated with mAb 4B2, which recognizes a determinant common to all CD45 isoforms, a vigorous production of TNF-alpha mRNA was detected, which peaked 2 h later. Anti-CD45 mAb cross-linking was required. In contrast, neither mAb 10G10, which recognizes an epitope distinct from the one recognized by mAb 4B2, nor mAb UCHL-1, a CD45RO-specific antibody, induced any significant increase in TNF-alpha transcription. Nuclear run-on transcription assays demonstrated that CD45 cross-linking caused transcriptional activation of the TNF-alpha gene. De novo protein synthesis was not required, since incubation with cycloheximide (CHX) did not block transcriptional activation. CHX in contrast up-regulated TNF-alpha gene expression and increased transcript half-life, an effect that was under control of post-transcriptional mechanisms. Engagement of CD45 by itself did not affect transcript stability. CD45 ligation resulted in TNF-alpha secretion. These results indicate that in addition to its role in TCR/CD3-mediated T cell activation, CD45, in an epitope-specific manner, may act as a primary signaling molecule, leading to the transcriptional regulation and secretion of a major pro-inflammatory cytokine.
authors.affiliation: Department of Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors.forename: O
authors.initials: O
authors.lastname: Estoppey
authors.forename: A
authors.initials: A
authors.lastname: Sauty
authors.forename: E
authors.initials: E
authors.lastname: Espel
authors.forename: Z
authors.initials: Z
authors.lastname: Menoud
authors.forename: P C
authors.initials: PC
authors.lastname: Frei
authors.forename: F
authors.initials: F
authors.lastname: Spertini
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000939:Epitopes / Q000276:immunology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D017493:Leukocyte Common Antigens / Q000276:immunology*; D008213:Lymphocyte Activation; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017027:Protein Tyrosine Phosphatases / Q000276:immunology*; D012333:RNA, Messenger / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014158:Transcription, Genetic / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases