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.

Deciphering N6‐Methyladenosine‐Related Genes Signature to Predict Survival in Lung Adenocarcinoma

“…Proteins of HNRNPC are thought to be the potential m 6 A-selective binding proteins to affect mRNA localization and transport [8,23]. Some studies have confirmed the interaction between HNRNPC and the urokinase receptor (uPAR) mRNA in lung-derived epithelial cells, which could contribute to the pathogenesis of lung neoplasia [25,26]. In other cases, overexpressing HNRNPC in gastric cancer cells promotes chemoresistance [27].…”

Ribonucleotide Reductase Subunit M2 Predicts Survival in Subgroups of Patients with Non-Small Cell Lung Carcinoma: Effects of Gender and Smoking Status

“…RRM2 functioned downstream of β-catenin to inhibit Wnt signaling but phosphorylation on serine 20 of RRM2 countered this effect [ 43 ]. Shetty et al found RRM2 was a binding protein for urokinase-type plasminogen activator (uPA) mRNA 3'UTR in pulmonary epithelial cells [ 44 ], so RRM2 could affect a range of functions in lung inflammation and repair related to uPA. Therefore prognostic relevance in cancer survival could also be separate from ribonucleotide reductase activity.…”

Role of p53–fibrinolytic system cross-talk in the regulation of quartz-induced lung injury

“…Defective fibrinolysis associated with lung injuries has been attributed to loss of uPA activity caused by disproportionate increase in the expression of uPA inhibitor, PAI-1. uPA increases lung epithelial cell viability through induction of its own as well as its receptor, uPAR expression (Shetty et al, 2002(Shetty et al, , 2012a. These changes occur via suppression of p53, which inhibits both uPA and uPAR and promotes PAI-1 expression (Shetty et al, 2007;P.…”