title: Ligation of CD40 receptor in human B lymphocytes triggers the 5-lipoxygenase pathway to produce reactive oxygen species and activate p38 MAPK.
abstract: Previously, we reported that CD40-induced production of reactive oxygen species (ROS) by NADPH oxidase requires the TNF receptor-associated factor (TRAF) 3, as well as the activities of phosphatidylinositol 3-kinase (PI3K) and Rac1. Here we investigated the possible mechanisms of the production of ROS after CD40 ligation in B cells. We describe an alternative ROS production pathway that is triggered by CD40 ligation, involves 5-lipoxygenase (5-LO), and results in activation of p38 MAPK. Our studies in Raji human B lymphomas revealed that CD40-induced ROS production by 5-LO also requires the activities of PI3K and Rac1. In contrast to the NADPH oxidase pathway, however, TRAF molecules are not required for the CD40-induced ROS production by 5-LO. The association of CD40 with 5-LO is dependent on CD40 ligation in Raji B cells, and co-immunoprecipitation experiments using epitope- tagged proteins transiently expressed in human embryonic kidney 293T cells revealed the role of the regulatory subunit of PI3K, p85, in this association. Collectively, these data suggest a separate pathway for the CD40-induced ROS production in B cells and demonstrate that this pathway requires 5-LO via direct association of p85 with both CD40 and 5-LO.
authors.affiliation: Division of Life and Pharmaceutical Sciences, Department of Life Science, College of Natural Sciences, Center for Cell Signaling and Drug Discovery Research, Ewha Womans University, Seoul, Korea.
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Ha
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Seul
authors.forename: Jong Ran
authors.initials: JR
authors.lastname: Lee
mesh_terms: D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D019013:CD40 Antigens / Q000378:metabolism*; D023201:CD40 Ligand / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D019013:CD40 Antigens; D017382:Reactive Oxygen Species; D023201:CD40 Ligand; D001094:Arachidonate 5-Lipoxygenase; D019869:Phosphatidylinositol 3-Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020744:rac GTP-Binding Proteins