title: Combinatorial activation of FAK and AKT by transforming growth factor-beta1 confers an anoikis-resistant phenotype to myofibroblasts.
abstract: Transforming growth factor-beta (TGF-beta) is a prototypical tumour-suppressor cytokine with cytostatic and pro-apoptotic effects on most target cells; however, mechanisms of its pro-survival/anti-apoptotic signalling in certain cell types and contexts remain unclear. In human lung fibroblasts, TGF-beta1 is known to induce myofibroblast differentiation in association with the delayed activation of focal adhesion kinase (FAK) and protein kinase B (PKB/AKT). Here, we demonstrate that FAK and AKT are independently regulated by early activation of SMAD3 and p38 MAPK, respectively. Pharmacologic or genetic approaches that disrupt SMAD3 signalling block TGF-beta1-induced activation of FAK, but not AKT; in contrast, disruption of early p38 MAPK signalling abrogates AKT activation, but does not alter FAK activation. TGF-beta1 is able to activate AKT in cells expressing mutant FAK or in cells treated with an RGD-containing peptide that interferes with integrin signalling, inhibits FAK activation and induces anoikis (apoptosis induced by loss of adhesion signalling). TGF-beta1 protects myofibroblasts from anoikis, in part, by activation of the PI3K-AKT pathway. Thus, TGF-beta1 co-ordinately and independently activates the FAK and AKT protein kinase pathways to confer an anoikis-resistant phenotype to myofibroblasts. Activation of these pro-survival/anti-anoikis pathways in myofibroblasts likely contributes to essential roles of TGF-beta1 in tissue fibrosis and tumour-promotion.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical Center, 6301 MSRB III, Ann Arbor, MI 48109, USA.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Horowitz
authors.forename: David S
authors.initials: DS
authors.lastname: Rogers
authors.forename: Vishal
authors.initials: V
authors.lastname: Sharma
authors.forename: Ragini
authors.initials: R
authors.lastname: Vittal
authors.forename: Eric S
authors.initials: ES
authors.lastname: White
authors.forename: Zongbin
authors.initials: Z
authors.lastname: Cui
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Thannickal
mesh_terms: D000818:Animals; D023102:Anoikis / Q000187:drug effects*; D002448:Cell Adhesion / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D009842:Oligopeptides / Q000494:pharmacology; D010641:Phenotype; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000378:metabolism; D013552:Swine; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D009842:Oligopeptides; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; C047981:arginyl-glycyl-aspartic acid; D051417:Focal Adhesion Kinase 1; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases