Different mitogen-activated protein kinase signaling pathways cooperate toregulate tumor necrosis factor a gene expression in T lymphocytes

Tumor necrosis factor a (TNF-alpha) is a potent proinflammatory cytokine an d plays a crucial role in early events of inflammation. TNF-alpha is primar ily produced by monocytes and T lymphocytes, In particular, T-cell-derived TNF-alpha plays a critical role in autoimmune inflammation and superantigen -induced septic shock. However, little is known about the intracellular sig naling pathways that regulate TNF expression in T cells. Here we show that extracellular signal-regulated kinase (ERK), c-dun N-terminal kinase (JNK), and p38-mitogen-activated protein kinase (MaPK) pathways control the trans cription and synthesis of TNF-alpha in A3.01 T cells that produce the cytok ine upon T cell activation by costimulation with 12-O-tetradecanoylphorbol- 13-acetate (TPA) and ionomycin, Selective activation of each if the distinc t MaPK pathways by expression of constitutively active kinases is sufficien t for TNF-alpha promoter induction. Furthermore, blockage of all three path ways almost abolishes TPA/ionomycin-induced transcriptional activation of t he TNF-alpha promoter. Selective inhibition of one or more MATH pathways im pairs TNF-alpha induction by TPA/ionomycin, indicating a cooperation betwee n these signal transduction pathways. Our approach revealed that the MAPK k inase 6 (MKK6)/p38 pathway is involved in both transcriptional and posttran scriptional regulation of TNF expression. Moreover, analysis of the progres sive 5' deletion mutants of the TNF-cr promoter indicates that distinct pro moter regions are targeted by either ERK-, JNK-, or p38-activating pathways . Thus, unlike what has been reported for other TNF-alpha-producing cells, all three MAPK pathways are critical and cooperate to regulate transcriptio n of the TNF-alpha gene in T lymphocytes, suggesting a T-cell-specific regu lation of the cytokine.