title: Phospholipase D1 plays a key role in TNF-alpha signaling.
abstract: The primary characteristic features of any inflammatory or infectious lesions are immune cell infiltration, cellular proliferation, and the generation of proinflammatory mediators. TNF-alpha is a potent proinflammatory and immuno-regulatory cytokine. Decades of research have been focused on the physiological/pathophysiological events triggered by TNF-alpha. However, the signaling network initiated by TNF-alpha in human leukocytes is still poorly understood. In this study, we report that TNF-alpha activates phospholipase D1 (PLD1), in a dose-dependent manner, and PLD1 is required for the activation of sphingosine kinase and cytosolic calcium signals. PLD1 is also required for NFkappaB and ERK1/2 activation in human monocytic cells. Using antisense oligonucleotides to reduce specifically the expression of PLD isozymes showed PLD1, but not PLD2, to be coupled to TNF-alpha signaling and that PLD1 is required to mediate receptor activation of sphingosine kinase and calcium transients. In addition, the coupling of TNF-alpha to activation of the phosphorylation of ERK1/2 and the activation of NFkappaB were inhibited by pretreating cells with antisense to PLD1, but not to PLD2; thus, demonstrating a specific requirement for PLD1. Furthermore, use of antisense oligonucleotides to reduce expression of PLD1 or PLD2 demonstrated that PLD1 is required for TNF-alpha-induced production of several important cytokines, such as IL-1beta, IL-5, IL-6, and IL-13, in human monocytes. These studies demonstrate the critical role of PLD1 in the intracellular signaling cascades initiated by TNF-alpha and its functional role for coordinating the signals to inflammatory responses.
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Swaminathan
authors.initials: S
authors.lastname: Sethu
authors.forename: Grecia
authors.initials: G
authors.lastname: Mendez-Corao
authors.forename: Alirio J
authors.initials: AJ
authors.lastname: Melendez
mesh_terms: D020013:Calcium Signaling / Q000187:drug effects / Q000276:immunology*; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000201:enzymology / Q000276:immunology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism; D009000:Monocytes / Q000201:enzymology / Q000276:immunology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000276:immunology / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000494:pharmacology*; D020298:U937 Cells; D000099157:Sphingosine Kinase
chemical_list: D016207:Cytokines; D007527:Isoenzymes; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016376:Oligonucleotides, Antisense; D010739:Phospholipase D; D017853:Phosphotransferases (Alcohol Group Acceptor); D014409:Tumor Necrosis Factor-alpha; D000099157:Sphingosine Kinase; C105606:phospholipase D2; C106801:phospholipase D1