title: The dual specificity phosphatase transcriptome of the murine thymus.
abstract: Properly regulated mitogen-activated protein (MAP) kinase activity is critical for normal thymocyte development. MAP kinases are activated by phosphorylation of tyrosine and threonine, and dual specificity phosphatases (DUSPs) can inactivate MAP kinases by dephosphorylating both tyrosine and threonine. However, a role for DUSPs in thymocyte development has not been described. In this study, we have defined the subset of DUSP genes expressed in the murine thymus, and how their expression varies in different thymocyte subsets. Of the murine DUSP genes screened that could potentially dephosphorylate MAP kinases, we found 10 transcribed in the thymus. Seven of these 10 thymic DUSPs are true MAP kinase phosphatases based on the presence of a MAP kinase binding domain and demonstrated phosphatase activity against MAP kinases. Six of the seven thymic MAP kinase phosphatases have been shown to dephosphorylate extracellular regulated kinase (ERK). Quantitative PCR analysis of thymocyte populations isolated from different developmental stages revealed significant changes in DUSP expression as thymocytes progressed through development. Specifically, DUSPs 1, 4, and 5 significantly increase in expression as cells go from small, resting CD4/CD8 double positive cells to the CD4 single positive stage. Additionally, in vitro experiments showed that DUSPs could respond to TCR signaling, as anti-CD3 stimulation of thymocytes transiently increased transcription of six of the 10 thymic DUSP genes within 30 min. Notably, the ERK-specific phosphatase DUSP5 was upregulated 43-fold within 30 min, and returned to baseline within 24 h. Overall, we have identified a subset of DUSPs that could potentially regulate ERK activation in response to TCR signals in thymocytes.
authors.affiliation: Graduate Program in Immunology and Molecular Pathogenesis, Emory University School of Medicine, 7311 WMB, 101 Woodruff Circle, Atlanta, GA 30322, USA.
authors.forename: Melinda B
authors.initials: MB
authors.lastname: Tanzola
authors.forename: Gilbert J
authors.initials: GJ
authors.lastname: Kersh
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D018797:Cell Cycle Proteins / Q000235:genetics; D054638:Dual Specificity Phosphatase 1; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017874:Immediate-Early Proteins / Q000235:genetics; D051379:Mice; D008806:Mice, Inbred AKR; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000235:genetics*; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000166:cytology; D013950:Thymus Gland / Q000166:cytology* / Q000201:enzymology; D014158:Transcription, Genetic
chemical_list: D018797:Cell Cycle Proteins; D017874:Immediate-Early Proteins; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases