title: Effects of an aminosteroid inhibitor of phospholipase C-dependent processes on the TCR-mediated signal transduction pathway in human T cells.
abstract: Phospholipase C (PLC) is a key enzyme in the T cell antigen receptor (TCR)-mediated signal transduction pathway in human T cells. Agonist-induced PLC activation leads to a cascade of intracellular events that ultimately regulate gene transcription and T cell activation. We studied the effects of U-73122, a putative inhibitor of PLC-dependent events, on TCR/CD3 complex-mediated early and late events in human T cells. Both anti-CD3 monoclonal antibody-induced 1,4,5-inositol trisphosphate (IP3) and free intracytoplasmic calcium [Ca2+]i increases were inhibited by U-73122 (0.05-0.1 microM), but not by the related inactive analog, U-73343. U-73122 did not affect thapsigargin-evoked [Ca2+]i increase in T cells, indicating a specific mode of inhibition of CD3 signaling. Late events in T cell activation like CD3-mediated T cell proliferation and mitogen-induced interleukin 2 receptor (IL2-R) expression were also inhibited by this agent. T cell proliferation induced by a combination of a phorbol ester and ionomycin was not affected by U-73122. Although an agonist effect on basal IP3 and [Ca2+]i levels was observed with high concentrations of U-73122, the inhibitor alone did not induce any proliferative effect or IL2-R expression in T cells. Our results demonstrate for the first time that U-73122 is a specific inhibitor of PLC-dependent processes in human T cells and could serve as a valuable tool for studying T cell signal transduction pathways.
authors.affiliation: Department of Clinical Investigation, Walter Reed Army Medical Center, Washington, DC, USA.
authors.forename: D
authors.initials: D
authors.lastname: Vassilopoulos
authors.forename: R C
authors.initials: RC
authors.lastname: Smallridge
authors.forename: G C
authors.initials: GC
authors.lastname: Tsokos
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology; D017252:CD3 Complex / Q000502:physiology; D002118:Calcium / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004963:Estrenes / Q000494:pharmacology*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology*; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects*; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
chemical_list: D000276:Adjuvants, Immunologic; D017252:CD3 Complex; D004791:Enzyme Inhibitors; D004963:Estrenes; D007476:Ionophores; D011760:Pyrrolidinones; D015375:Receptors, Interleukin-2; D013729:Terpenes; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D015759:Ionomycin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium