title: FAK regulates Cdk2 in EGF-stimulated primary cultures of hepatocytes.
abstract: In this study, we report a novel role of FAK as a regulator of Cdk2 in anchorage-dependent primary cultured hepatocytes. In response to EGF, we found that S-phase entry was reduced upon FAK inhibition. This correlated with decreased protein expression and nuclear accumulation of the G1/S-phase regulator Cdk2. Further, nuclear accumulation of the Cdk2 partner cyclinE, was reduced, but not its protein level. Also, protein levels of Cdk2 were inversely linked with increased expression of the Cdk2 inhibitor p27, known to be degraded in a Cdk2-dependent manner. Also, cyclinD1 was regulated by FAK, but to a lesser extent than Cdk2. To assess the mechanism in which FAK mediates Cdk2-regulation, FAK mutants were used: FAKY397F, mutated at its integrin-regulated site, and two others mutated at docking sites for Grb2-ERK-activation (FAKY925F) and for p130Cas-Rac1-activation (FAKY861F). All three sites were central for EGF-induced ERK-activity and Cdk2 expression. In addition, FAK was important for HGF-mediated proliferation, suggesting a general mechanism for anchorage-dependent growth. Moreover, growth factor-induced cell spreading, but not survival, required FAK. Hence, integrins and growth factors cooperate in anchorage-dependent signaling events leading to proliferation and motility. In conclusion, our data suggest that FAK acts as a central coordinator of integrin and growth factor-mediated S-phase entry by its ability to regulate Cdk2.
authors.affiliation: Laboratory for Toxicopathology, Institute of Pathology, Oslo University Hospital, University of Oslo, Oslo, Norway.
authors.forename: Liv Ingrid
authors.initials: LI
authors.lastname: Flinder
authors.forename: Lene
authors.initials: L
authors.lastname: Wierød
authors.forename: Carola M
authors.initials: CM
authors.lastname: Rosseland
authors.forename: Henrik S
authors.initials: HS
authors.lastname: Huitfeldt
authors.forename: Ellen
authors.initials: E
authors.lastname: Skarpen
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D017209:Apoptosis; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D048430:Cell Shape; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D061251:Primary Cell Culture; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017208:Rats, Wistar; D059807:S Phase Cell Cycle Checkpoints; D015398:Signal Transduction; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: C530106:Ccnd1 protein, rat; C493962:Cdkn1b protein, rat; D019927:Cyclin E; D047428:Protein Kinase Inhibitors; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004815:Epidermal Growth Factor; D017228:Hepatocyte Growth Factor; D051417:Focal Adhesion Kinase 1; C496052:Ptk2 protein, rat; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases