title: Receptor protein tyrosine phosphatase beta/zeta is a functional binding partner for vascular endothelial growth factor.
abstract: BACKGROUND
  Receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ) is a chondroitin sulphate (CS) transmembrane protein tyrosine phosphatase and is a receptor for pleiotrophin (PTN). RPTPβ/ζ interacts with ανβ₃ on the cell surface and upon binding of PTN leads to c-Src dephosphorylation at Tyr530, β₃ Tyr773 phosphorylation, cell surface nucleolin (NCL) localization and stimulation of cell migration. c-Src-mediated β₃ Tyr773 phosphorylation is also observed after vascular endothelial growth factor 165 (VEGF₁₆₅) stimulation of endothelial cells and is essential for VEGF receptor type 2 (VEGFR2) - ανβ₃ integrin association and subsequent signaling. In the present work, we studied whether RPTPβ/ζ mediates angiogenic actions of VEGF.
  
  
  METHODS
  Human umbilical vein endothelial, human glioma U87MG and stably transfected Chinese hamster ovary cells expressing different β₃ subunits were used. Protein-protein interactions were studied by a combination of immunoprecipitation/Western blot, immunofluorescence and proximity ligation assays, properly quantified as needed. RPTPβ/ζ expression was down-regulated using small interference RNA technology. Migration assays were performed in 24-well microchemotaxis chambers, using uncoated polycarbonate membranes with 8 μm pores.
  
  
  RESULTS
  RPTPβ/ζ mediates VEGF₁₆₅-induced c-Src-dependent β₃ Tyr773 phosphorylation, which is required for VEGFR2-ανβ₃ interaction and the downstream activation of phosphatidylinositol 3-kinase (PI3K) and cell surface NCL localization. RPTPβ/ζ directly interacts with VEGF165, and this interaction is not affected by bevacizumab, while it is interrupted by both CS-E and PTN. Down-regulation of RPTPβ/ζ by siRNA or administration of exogenous CS-E abolishes VEGF₁₆₅-induced endothelial cell migration, while PTN inhibits the migratory effect of VEGF₁₆₅ to the levels of its own effect.
  
  
  CONCLUSIONS
  These data identify RPTPβ/ζ as a cell membrane binding partner for VEGF that regulates angiogenic functions of endothelial cells and suggest that it warrants further validation as a potential target for development of additive or alternative anti-VEGF therapies.
authors: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR, 26504, Patras, Greece. mkoutsioumpa@upatras.gr.|Current address: Center for Systems Biomedicine, Division of Digestive Diseases, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA. mkoutsioumpa@upatras.gr.
authors: Marina
authors: M
authors: Koutsioumpa
authors: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR, 26504, Patras, Greece. evipoi@yahoo.com.
authors: Evangelia
authors: E
authors: Poimenidi
authors: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR, 26504, Patras, Greece. eva.pantazaka@cantab.net.
authors: Evangelia
authors: E
authors: Pantazaka
authors: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR, 26504, Patras, Greece. theodoropoulou.pharmacy@gmail.com.
authors: Christina
authors: C
authors: Theodoropoulou
authors: Computer Engineering and Informatics Department, University of Patras, GR 26504, Patras, Greece. skoura@ceid.upatras.gr.
authors: Angeliki
authors: A
authors: Skoura
authors: Computer Engineering and Informatics Department, University of Patras, GR 26504, Patras, Greece. vasilis@ceid.upatras.gr.
authors: Vasileios
authors: V
authors: Megalooikonomou
authors: Sino-French Research Centre for Life Sciences and Genomics, CNRS/LIA124, Rui Jin Hospital, Jiao Tong University Medical School, Shanghai, China. kieffer.nelly@gmail.com.
authors: Nelly
authors: N
authors: Kieffer
authors: Laboratoire CRRET, Universite Paris Est Creteil Val de Marne, Paris, France. courty@u-pec.fr.
authors: Jose
authors: J
authors: Courty
authors: Proteoglycan Signaling and Therapeutics Research Group, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan. mizumoto@meijo-u.ac.jp.|Current address: Department of Pathobiochemistry, Faculty of Pharmacy, Meijo University, Nagoya, 463-8503, Japan. mizumoto@meijo-u.ac.jp.
authors: Shuji
authors: S
authors: Mizumoto
authors: Proteoglycan Signaling and Therapeutics Research Group, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan. k-sugar@sci.hokudai.ac.jp.
authors: Kazuyuki
authors: K
authors: Sugahara
authors: Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, GR, 26504, Patras, Greece. epapad@upatras.gr.
authors: Evangelia
authors: E
authors: Papadimitriou
mesh_terms: D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics; D003412:Cricetulus; D015536:Down-Regulation / Q000235:genetics; D005910:Glioma; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D016023:Integrins / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D011485:Protein Binding / Q000235:genetics*; D060066:Protein Interaction Maps / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5 / Q000235:genetics / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D016023:Integrins; D034741:RNA, Small Interfering; D042461:Vascular Endothelial Growth Factor A; D019869:Phosphatidylinositol 3-Kinases; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5
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