title: Signal transduction events involved in TPA downregulation of SP-A gene expression.
abstract: Surfactant protein A (SP-A), the most abundant pulmonary surfactant protein, plays a role in innate host defense and blocks the inhibitory effects of serum proteins on surfactant surface tension-lowering properties. SP-A mRNA and protein are downregulated by phorbol esters (TPA) via inhibition of gene transcription. We evaluated the TPA signaling pathways involved in SP-A inhibition in a lung cell line, H441 cells. TPA caused sustained phosphorylation of p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, and c-Jun-NH(2)-terminal kinase. An inhibitor of conventional and novel isoforms of protein kinase C (PKC) and two inhibitors of p44/42 MAPK kinase partially or completely blocked the inhibitory effects of TPA on SP-A mRNA levels. In contrast, inhibitors of conventional PKC-alpha and -beta, stress-activated protein kinases, protein phosphatases, protein kinase A, and the phosphatidylinositol 3-kinase pathway had no effect on the TPA-mediated inhibition of SP-A mRNA. TPA also stimulated the synthesis of c-Jun mRNA and protein in a time-dependent manner. Inhibitors of the p44/42 MAPK signaling pathway and PKC blocked the TPA-mediated phosphorylation of p44/42 MAPK and the increase in c-Jun mRNA. We conclude that TPA inhibits SP-A gene expression via novel isoforms of PKC, the p44/42 MAPK pathway, and the activator protein-1 complex.
authors.affiliation: Department of Anatomy and Cell Biology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, 51 Newton Rd., 1-550 BSB, Iowa City, IA 52242-1109, USA.
authors.forename: Olga L
authors.initials: OL
authors.lastname: Miakotina
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Snyder
mesh_terms: D002273:Carcinogens / Q000494:pharmacology*; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D020545:Respiratory Mucosa / Q000166:cytology / Q000201:enzymology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002273:Carcinogens; D004791:Enzyme Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D037662:Pulmonary Surfactant-Associated Protein A; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D013755:Tetradecanoylphorbol Acetate