title: Focal adhesion kinase (FAK)-related non-kinase inhibits myofibroblast differentiation through differential MAPK activation in a FAK-dependent manner.
abstract: Transforming growth factor (TGF)-beta1 induces fibroblast transdifferentiation to myofibroblasts, a process that requires the involvement of integrin-mediated signaling and focal adhesion kinase (FAK). FAK-related non-kinase (FRNK) is known for its role in inhibiting integrin-mediated cell migration; however, its role in myofibroblast differentiation has not been defined. Here, we report that FRNK abrogates TGF-beta1-induced myofibroblast differentiation in vitro and in vivo. TGF-beta1 can induce alpha-smooth muscle actin (alpha-SMA) expression in the presence or absence of FAK; however, TGF-beta1-induced alpha-SMA expression is reduced (approximately 73%) in FAK-deficient fibroblasts. Although both ERK and p38 MAPK activation is required for maximal TGF-beta1-induced alpha-SMA expression, ERK is the major signaling intermediate in cells that express FAK. In contrast, p38 MAPK is the dominant mediator of TGF-beta1-induced alpha-SMA expression in FAK-deficient cells. FRNK overexpression blocks TGF-beta1-induced ERK or p38 MAPK activation in the presence, and surprisingly, in the absence of FAK. The loss of FRNK was tested in vivo during experimentally induced pulmonary fibrosis in mice. FRNK knock-out mice have a greater increase in alpha-SMA-expressing cells in response to a pulmonary fibrotic stimulus in vivo, as compared with congenic wild type mice. This is the first time that FRNK loss has been shown to modify the pathobiology in any animal disease model. Together, the data demonstrate that FRNK negatively regulates myofibroblast differentiation in vitro and in vivo. These data further suggest that modulation FRNK expression may be a novel avenue for therapeutic intervention in tissue fibrosis.
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA. qding@uab.edu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ding
authors.forename: Candece L
authors.initials: CL
authors.lastname: Gladson
authors.forename: Hongju
authors.initials: H
authors.lastname: Wu
authors.forename: Haurko
authors.initials: H
authors.lastname: Hayasaka
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Olman
mesh_terms: D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology*; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D032446:Myoblasts / Q000201:enzymology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011658:Pulmonary Fibrosis / Q000201:enzymology* / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D053773:Transforming Growth Factor beta1; C113183:FAK-related nonkinase; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases