Receptor protein tyrosine phosphatase beta/zeta is a functional binding partner for vascular endothelial growth factor

Mol Cancer. 2015 Feb 3;14(1):19. doi: 10.1186/s12943-015-0287-3.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cell Line
  • Cell Movement / genetics
  • Cricetulus
  • Down-Regulation / genetics
  • Glioma
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Integrins / genetics
  • Integrins / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation / genetics
  • Protein Binding / genetics*
  • Protein Interaction Maps / genetics
  • RNA, Small Interfering / genetics
  • Receptor-Like Protein Tyrosine Phosphatases, Class 5 / genetics
  • Receptor-Like Protein Tyrosine Phosphatases, Class 5 / metabolism*
  • Vascular Endothelial Growth Factor A / genetics
  • Vascular Endothelial Growth Factor A / metabolism*

Substances

  • Integrins
  • RNA, Small Interfering
  • Vascular Endothelial Growth Factor A
  • Phosphatidylinositol 3-Kinases
  • Receptor-Like Protein Tyrosine Phosphatases, Class 5