title: Opposing roles of serine/threonine kinases MEKK1 and LOK in regulating the CD28 responsive element in T-cells.
abstract: T-cell activation requires signals from both the T-cell receptor (TcR) and other co-stimulatory molecules such as CD28. TcR- and CD28-mediated signals are integrated during T-cell activation resulting in the expression of cytokine genes such as interleukin-2 (IL-2). An enhancer element (CD28RE) of the IL-2 gene specifically responsive to CD28 signals has been previously identified and characterized. This response element and an adjacent Activated Protein-1 (nuclear factor-interleukin-2B) site together (RE/AP1) were shown to complex with c-rel, AP-1 and other factors. However, details of the signal transduction pathways leading from CD28 to the composite response element remain poorly understood. We present data showing that overexpression of the serine threonine kinase, mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase kinase-1 (MEKK1), but not nuclear factor-kappa B inducing kinase, or MAP kinase/ERK kinase-1 (MEK1), can significantly increase the level of CD28RE/AP1-driven luciferase (Luc) reporter gene expression in Jurkat E6-1 cells. A MEKK1 dominant negative mutant blocked such activation induced by stimulation with Raji B cells and the superantigen staphylococcus enterotoxin E (SEE), as well as via CD3/CD28. Mutations in either site of the RE/AP1 element abolished MEKK1-induced Luc expression. Calcineurin inhibitors, CsA and FK520, or inhibitors of p38 kinase (SB 203580), or MEK1 (PD 098059), did not affect MEKK1-induced reporter activation. These results directly implicate MEKK1 in the CD28 signalling pathway that activates the CD28 response element. Co-expression of the lymphocyte-oriented kinase (LOK) kinase attenuated Raji/SEE-induced IL-2 production in Jurkat cells, as well as MEKK1 and Raji/SEE-induced reporter gene activation. These data suggest that MEKK1 and LOK may have opposing roles in regulating the CD28RE/AP1 element.
authors.affiliation: R. W. Johnson Pharmaceutical Research Institute, Drug Discovery Research, Raritan, NJ 08869, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tao
authors.forename: Scott
authors.initials: S
authors.lastname: Wadsworth
authors.forename: Jason
authors.initials: J
authors.lastname: Mercer
authors.forename: Cynthia
authors.initials: C
authors.lastname: Mueller
authors.forename: Kirsten
authors.initials: K
authors.lastname: Lynn
authors.forename: John
authors.initials: J
authors.lastname: Siekierka
authors.forename: Avery
authors.initials: A
authors.lastname: August
mesh_terms: D018106:CD28 Antigens / Q000096:biosynthesis* / Q000378:metabolism; D019703:Calcineurin / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D004789:Enzyme Activation; D005799:Genes, Dominant; D017930:Genes, Reporter; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D008156:Luciferases / Q000378:metabolism; D008213:Lymphocyte Activation; D048728:MAP Kinase Kinase Kinase 1; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism* / Q000502:physiology*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology*; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D018106:CD28 Antigens; D018076:DNA, Complementary; D007376:Interleukin-2; D016328:NF-kappa B; D016755:Proto-Oncogene Proteins c-jun; D020569:Proto-Oncogene Proteins c-rel; D004247:DNA; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; C108145:Stk10 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse; D019703:Calcineurin