title: EGF-induced ERK-activation downstream of FAK requires rac1-NADPH oxidase.
abstract: Reactive oxygen species (ROS) function as signaling molecules mainly by reversible oxidation of redox-sensitive target proteins. ROS can be produced in response to integrin ligation and growth factor stimulation through Rac1 and its effector protein NADPH oxidase. One of the central roles of Rac1-NADPH oxidase is actin cytoskeletal rearrangement, which is essential for cell spreading and migration. Another important regulator of cell spread is focal adhesion kinase (FAK), a coordinator of integrin and growth factor signaling. Here, we propose a novel role for NADPH oxidase as a modulator of the FAK autophosphorylation site. We found that Rac1-NADPH oxidase enhanced the phosphorylation of FAK at Y397. This site regulates FAK's ability to act as a scaffold for EGF-mediated signaling, including activation of ERK. Accordingly, we found that EGF-induced activation of FAK at Y925, the following activation of ERK, and phosphorylation of FAK at the ERK-regulated S910-site depended upon NADPH oxidase. Furthermore, the inhibition of NADPH oxidase caused excessive focal adhesions, which is in accordance with ERK and FAK being modulators of focal adhesion dissociation. Our data suggest that Rac1 through NADPH oxidase is part of the signaling pathway constituted by FAK, Rac1, and ERK that regulates focal adhesion disassembly during cell spreading.
authors.affiliation: Laboratory for Toxicopathology, Institute of Pathology, Rikshospitalet University Hospital, University of Oslo, Oslo, Norway.
authors.forename: Liv Ingrid
authors.initials: LI
authors.lastname: Flinder
authors.forename: Olga A
authors.initials: OA
authors.lastname: Timofeeva
authors.forename: Carola M
authors.initials: CM
authors.lastname: Rosseland
authors.forename: Lene
authors.initials: L
authors.lastname: Wierød
authors.forename: Henrik S
authors.initials: HS
authors.lastname: Huitfeldt
authors.forename: Ellen
authors.initials: E
authors.lastname: Skarpen
mesh_terms: D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D022001:Focal Adhesions / Q000187:drug effects / Q000201:enzymology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D008297:Male; D051379:Mice; D008954:Models, Biological; D019255:NADPH Oxidases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D010768:Phosphoserine; D004815:Epidermal Growth Factor; D019255:NADPH Oxidases; D066246:ErbB Receptors; D051416:Focal Adhesion Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020830:rac1 GTP-Binding Protein