title: Growth arrest-specific 6 regulates thrombin-induced expression of vascular cell adhesion molecule-1 through forkhead box O1 in endothelial cells.
abstract: BACKGROUND
  Growth arrest-specific 6 (Gas6)-deficient mice are protected against venous thromboembolism (VTE), suggesting a role for Gas6 in this disorder. We previously demonstrated that Gas6 induces forkhead box O1 (FoxO-1) phosphorylation through the phosphoinositide 3-kinase-Akt pathway. FoxO-1 regulates the expression of vascular cell adhesion molecule-1 (VCAM-1), a molecule that has been implicated in VTE.
  
  
  OBJECTIVE
  To assess the role of FoxO-1 in Gas6-dependent VCAM-1 expression.
  
  
  METHODS
  Thrombin was used to stimulate endothelial cells (ECs). Wild-type (WT) and Gas6(-/-) ECs were transfected with small interfering RNA targeting Axl or FoxO-1, a luciferase-coupled plasmid containing the FoxO-1 consensus sequence, and a phosphorylation-resistant FoxO-1 mutant, or treated with an Akt inhibitor. VCAM-1 mRNA expression was measured by real time-qPCR. VCAM-1 protein expression and FoxO-1 and Akt phosphorylation were assessed by western blot analysis. FoxO-1 localization was assessed by immunofluorescence. Adhesion of bone marrow mononuclear cells (BM-MCs) on ECs was assessed by fluorescence.
  
  
  CONCLUSIONS
  Thrombin induces both VCAM-1 expression and FoxO-1 phosphorylation and nuclear exclusion in WT ECs only. Silencing of FoxO-1 enhances VCAM-1 expression in both WT and Gas6(-/-) ECs. Inhibition of Akt or FoxO-1 phosphorylation prevents VCAM-1 expression in WT ECs. These data show that Gas6 induces FoxO-1 phosphorylation, leading to derepression of VCAM-1 expression. BM-MC-EC adhesion is increased by thrombin in WT ECs. BM-MC-EC adhesion is further increased when FoxO-1 is silenced, but decreased when FoxO-1 phosphorylation is inhibited. These results demonstrate that the Gas6-FoxO-1 signaling axis plays an important role in VCAM-1 expression in the context of VTE by promoting BM-MC-EC adhesion.
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.
authors.forename: F R
authors.initials: FR
authors.lastname: Bertin
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.|Department of Medicine, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
authors.forename: C A
authors.initials: CA
authors.lastname: Lemarié
authors.affiliation: The Royal Victoria Hospital, McGill University Health Center, McGill University, Montreal, Quebec, Canada.
authors.forename: R S
authors.initials: RS
authors.lastname: Robins
authors.affiliation: Lady Davis Institute for Medical Research, McGill University, Montreal, Quebec, Canada.|Department of Medicine, Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
authors.forename: M D
authors.initials: MD
authors.lastname: Blostein
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D002448:Cell Adhesion; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D005838:Genotype; D036341:Intercellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D054556:Venous Thromboembolism / Q000235:genetics / Q000378:metabolism; D000099255:Growth Arrest-Specific Protein 6
chemical_list: D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D036341:Intercellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D013917:Thrombin; D019010:Vascular Cell Adhesion Molecule-1; D000099255:Growth Arrest-Specific Protein 6; C085126:FOXO1 protein, human
keywords: FoxO1 protein, mouse; VCAM-1; endothelial cells; growth arrest-specific protein 6; thromboembolism