title: Tissue-type plasminogen activator acts as a cytokine that triggers intracellular signal transduction and induces matrix metalloproteinase-9 gene expression.
abstract: Tissue-type plasminogen activator (tPA), a serine protease well known for generating plasmin, has been demonstrated to induce matrix metalloproteinase-9 (MMP-9) gene expression and protein secretion in renal interstitial fibroblasts. However, exactly how tPA transduces its signal into the nucleus to control gene expression is unknown. This study investigated the mechanism by which tPA induces MMP-9 gene expression. Both wild-type and non-enzymatic mutant tPA were found to induce MMP-9 expression in rat kidney interstitial fibroblasts (NRK-49F), indicating that the actions of tPA are independent of its proteolytic activity. tPA bound to the low density lipoprotein receptor-related protein-1 (LRP-1) in NRK-49F cells, and this binding was competitively abrogated by the LRP-1 antagonist, the receptor-associated protein. In mouse embryonic fibroblasts (PEA-13) lacking LRP-1, tPA failed to induce MMP-9 expression. Furthermore, tPA induced rapid tyrosine phosphorylation on the beta subunit of LRP-1, which was followed by the activation of Mek1 and its downstream Erk-1 and -2. Blockade of Erk-1/2 activation by the Mek1 inhibitor abolished MMP-9 induction by tPA in NRK-49F cells. Conversely, overexpression of constitutively activated Mek1 induced Erk-1/2 phosphorylation and MMP-9 expression. In mouse obstructed kidney, tPA, LRP-1, and MMP-9 were concomitantly induced in the renal interstitium. Collectively, these results suggest that besides its classical proteolytic activity, tPA acts as a cytokine that binds to the cell membrane receptor LRP-1, induces its tyrosine phosphorylation, and triggers intracellular signal transduction, thereby inducing specific gene expression in renal interstitial fibroblasts.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, S-405 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15261, USA.
authors.forename: Kebin
authors.initials: K
authors.lastname: Hu
authors.forename: Junwei
authors.initials: J
authors.lastname: Yang
authors.forename: Sakae
authors.initials: S
authors.lastname: Tanaka
authors.forename: Steven L
authors.initials: SL
authors.lastname: Gonias
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Mars
authors.forename: Youhua
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001667:Binding, Competitive; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005780:Gelatin / Q000737:chemistry; D005786:Gene Expression Regulation; D006720:Homozygote; D047468:Immunoprecipitation; D007668:Kidney / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D051379:Mice; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D011973:Receptors, LDL / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D010959:Tissue Plasminogen Activator / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry
chemical_list: D016207:Cytokines; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D011973:Receptors, LDL; D025521:Tumor Suppressor Proteins; D014443:Tyrosine; D005780:Gelatin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D010959:Tissue Plasminogen Activator; D020780:Matrix Metalloproteinase 9