title: Regulation of urokinase expression at the posttranscription level by lung epithelial cells.
abstract: Urokinase-type plasminogen activator (uPA) is expressed by lung epithelial cells and regulates fibrin turnover and epithelial cell viability. PMA, LPS, and TNF-alpha, as well as uPA itself, induce uPA expression in lung epithelial cells. PMA, LPS, and TNF-alpha induce uPA expression through increased synthesis as well as stabilization of uPA mRNA, while uPA increases its own expression solely through uPA mRNA stabilization. The mechanism by which lung epithelial cells regulate uPA expression at the level of mRNA stability is unclear. To elucidate this process, we sought to characterize protein-uPA mRNA interactions that regulate uPA expression. Regulation of uPA at the level of mRNA stability involves the interaction of a ~40 kDa cytoplasmic-nuclear shuttling protein with a 66 nt uPA mRNA 3'UTR sequence. We purified the uPA mRNA 3'UTR binding protein and identified it as ribonucleotide reductase M2 (RRM2). We expressed recombinant RRM2 and confirmed its interaction with a specific 66 nt uPA 3'UTR sequence. Immunoprecipitation of cell lysates with anti-RRM2 antibody and RT-PCR for uPA mRNA confirmed that RRM2 binds to uPA mRNA. Treatment of Beas2B cells with uPA or LPS attenuated RRM2-endogenous uPA mRNA interactions, while overexpression of RRM2 inhibited uPA protein and mRNA expression through destabilization of uPA mRNA. LPS exposure of lung epithelial cells translocates RRM2 from the cytoplasm to the nucleus in a time-dependent manner, leading to stabilization of uPA mRNA. This newly recognized pathway could influence uPA expression and a broad range of uPA-dependent functions in lung epithelial cells in the context of lung inflammation and repair.
authors.affiliation: Texas Lung Injury Institute, The University of Texas Health Science Center, Tyler, Texas 75708, United States.
authors.forename: Shwetha K
authors.initials: SK
authors.lastname: Shetty
authors.forename: Amarnath S
authors.initials: AS
authors.lastname: Marudamuthu
authors.forename: Daniel
authors.initials: D
authors.lastname: Abernathy
authors.forename: Rashmi S
authors.initials: RS
authors.lastname: Shetty
authors.forename: Praveenkumar
authors.initials: P
authors.lastname: Shetty
authors.forename: Jian
authors.initials: J
authors.lastname: Fu
authors.forename: Steven
authors.initials: S
authors.lastname: Idell
authors.forename: Yashodhar P
authors.initials: YP
authors.lastname: Bhandary
authors.forename: Honglong
authors.initials: H
authors.lastname: Ji
authors.forename: Ming-Cheh
authors.initials: MC
authors.lastname: Liu
authors.forename: Sreerama
authors.initials: S
authors.lastname: Shetty
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004795:Enzyme Stability / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D020871:RNA Stability / Q000187:drug effects / Q000235:genetics; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D012262:Ribonucleoside Diphosphate Reductase / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D008070:Lipopolysaccharides; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C093713:ribonucleotide reductase M2; D012262:Ribonucleoside Diphosphate Reductase; D014568:Urokinase-Type Plasminogen Activator