title: Urokinase-type plasminogen activator receptor (uPAR) ligation induces a raft-localized integrin signaling switch that mediates the hypermotile phenotype of fibrotic fibroblasts.
abstract: The urokinase-type plasminogen activator receptor (uPAR) is a glycosylphosphatidylinositol-linked membrane protein with no cytosolic domain that localizes to lipid raft microdomains. Our laboratory and others have documented that lung fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibit a hypermotile phenotype. This study was undertaken to elucidate the molecular mechanism whereby uPAR ligation with its cognate ligand, urokinase, induces a motile phenotype in human lung fibroblasts. We found that uPAR ligation with the urokinase receptor binding domain (amino-terminal fragment) leads to enhanced migration of fibroblasts on fibronectin in a protease-independent, lipid raft-dependent manner. Ligation of uPAR with the amino-terminal fragment recruited α5β1 integrin and the acylated form of the Src family kinase, Fyn, to lipid rafts. The biological consequences of this translocation were an increase in fibroblast motility and a switch of the integrin-initiated signal pathway for migration away from the lipid raft-independent focal adhesion kinase pathway and toward a lipid raft-dependent caveolin-Fyn-Shc pathway. Furthermore, an integrin homologous peptide as well as an antibody that competes with β1 for uPAR binding have the ability to block this effect. In addition, its relative insensitivity to cholesterol depletion suggests that the interactions of α5β1 integrin and uPAR drive the translocation of α5β1 integrin-acylated Fyn signaling complexes into lipid rafts upon uPAR ligation through protein-protein interactions. This signal switch is a novel pathway leading to the hypermotile phenotype of IPF patient-derived fibroblasts, seen with uPAR ligation. This uPAR dependent, fibrotic matrix-selective, and profibrotic fibroblast phenotype may be amenable to targeted therapeutics designed to ameliorate IPF.
authors.affiliation: From the Departments of Pathobiology and.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Grove
authors.forename: Brian D
authors.initials: BD
authors.lastname: Southern
authors.forename: Tong H
authors.initials: TH
authors.lastname: Jin
authors.forename: Kimberly E
authors.initials: KE
authors.lastname: White
authors.forename: Sailaja
authors.initials: S
authors.lastname: Paruchuri
authors.forename: Efrat
authors.initials: E
authors.lastname: Harel
authors.forename: Ying
authors.initials: Y
authors.lastname: Wei
authors.forename: Shaik O
authors.initials: SO
authors.lastname: Rahaman
authors.forename: Candece L
authors.initials: CL
authors.lastname: Gladson
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ding
authors.forename: Charles S
authors.initials: CS
authors.lastname: Craik
authors.forename: Harold A
authors.initials: HA
authors.lastname: Chapman
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Olman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D022461:Caveolins / Q000235:genetics / Q000378:metabolism; D002465:Cell Movement; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000097:blood / Q000378:metabolism / Q000473:pathology; D039081:Integrin alpha5beta1 / Q000235:genetics / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D011485:Protein Binding; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D055293:Receptors, Urokinase Plasminogen Activator / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D012720:Severity of Illness Index; D055765:Shc Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism
chemical_list: D022461:Caveolins; D005353:Fibronectins; D039081:Integrin alpha5beta1; D055293:Receptors, Urokinase Plasminogen Activator; D055765:Shc Signaling Adaptor Proteins; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn; D014568:Urokinase-Type Plasminogen Activator
keywords: Fibroblast; Fibrosis; Integrin; Lipid Raft; Urokinase Receptor