title: Protein Phosphatase 1 Beta is Modulated by Chronic Hypoxia and Involved in the Angiogenic Endothelial Cell Migration.
abstract: OBJECTIVE
  Endothelial cell migration is required for physiological angiogenesis, but also contributes to various pathological conditions, including tumour vascularization. The mRNA expression of PP1cβ, the beta isoform of the catalytic PP1 subunit, was shown to be upregulated in chronic hypoxia. Since hypoxia is a major regulator of angiogenesis, the potential role of PP1cβ in angiogenesis was investigated.
  
  
  METHODS
  We examined PP1cβ protein level in pediatric heart following chronic hypoxia and found PP1cβ upregulation in cyanotic compared with acyanotic myocardium. By treating HUVEC cells with hypoxia mimicking agent, PP1cβ protein level increased with maximum at 8 hours. The effect of PP1cβ pharmacological inhibition, knockdown and overexpression, on endothelial cell migration and morphogenesis, was examined using in vitro wound healing scratch assay and endothelial tube formation assay. The PP1cβ knockdown effects on F-actin reorganization (phalloidin staining), focal adhesion formation (vinculin) and focal adhesion kinases (FAK) activation, were evaluated by immunocytochemical staining and immunoblotting with specific antibodies.
  
  
  RESULTS
  PP1cβ knockdown significantly reduces endothelial cell migration, but does not have any significant effect on endothelial tube formation. Endothelial cell migration in the knockdown group is restored to the control level upon consecutive transfection with PP1cβ cDNA. PP1cβ overexpression does not significantly affect endothelial cell migration. Furthermore, PP1cβ knockdown induces profound cytoskeletal reorganization, loss of focal adhesion sites and impairment of focal adhesion kinases (FAK) activation.
  
  
  CONCLUSIONS
  PP1cβ is regulator of endothelial cell migration, which is critical in the angiogenic process. PP1cβ inhibition reduces endothelial cell migration through focal adhesion turnover and actin polymerization pathways.
authors.affiliation: Bristol Heart Institute, University of Bristol, Bristol, UK.
authors.forename: Dominga
authors.initials: D
authors.lastname: Iacobazzi
authors.forename: Indira
authors.initials: I
authors.lastname: Garaeva
authors.forename: Ambra
authors.initials: A
authors.lastname: Albertario
authors.forename: Myriam
authors.initials: M
authors.lastname: Cherif
authors.forename: Gianni D
authors.initials: GD
authors.lastname: Angelini
authors.forename: Massimo
authors.initials: M
authors.lastname: Caputo
authors.forename: Mohamed T
authors.initials: MT
authors.lastname: Ghorbel
mesh_terms: D015687:Cell Hypoxia; D002465:Cell Movement / Q000187:drug effects; D003035:Cobalt / Q000494:pharmacology*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013771:Tetralogy of Fallot / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D015854:Up-Regulation
chemical_list: D003035:Cobalt; D051416:Focal Adhesion Protein-Tyrosine Kinases; C517188:PPP1CB protein, human; D054645:Protein Phosphatase 1; C018021:cobaltous chloride