Regulation of EphA2 receptor endocytosis by SHIP2 lipid phosphatase via phosphatidylinositol 3-Kinase-dependent Rac1 activation

J Biol Chem. 2007 Jan 26;282(4):2683-94. doi: 10.1074/jbc.M608509200. Epub 2006 Nov 29.

Abstract

Endocytosis of Eph receptors is critical for a number of biological processes, including modulating axon growth cone collapse response and regulating cell surface levels of receptor in epithelial cells. In particular, ephrin-A ligand stimulation of tumor cells induces EphA2 receptor internalization and degradation, a process that has been explored as a means to reduce tumor malignancy. However, the mechanism and regulation of ligand-induced Eph receptor internalization are not well understood. Here we show that SHIP2 (Src homology 2 domain-containing phosphoinositide 5-phosphatase 2) is recruited to activated EphA2 via a heterotypic sterile alpha motif (SAM)-SAM domain interaction, leading to regulation of EphA2 internalization. Overexpression of SHIP2 inhibits EphA2 receptor endocytosis, whereas suppression of SHIP2 expression by small interfering RNA-mediated gene silencing promotes ligand-induced EphA2 internalization and degradation. SHIP2 regulates EphA2 endocytosis via phosphatidylinositol 3-kinase-dependent Rac1 activation. Phosphatidylinositol 3,4,5-trisphosphate levels are significantly elevated in SHIP2 knockdown cells, phosphatidylinositol 3-kinase inhibitor decreases phosphatidylinositol 3,4,5-trisphosphate levels and suppresses increased EphA2 endocytosis. Ephrin-A1 stimulation activates Rac1 GTPase, and the Rac1-GTP levels are further increased in SHIP2 knockdown cells. A dominant negative Rac1 GTPase effectively inhibited ephrin-A1-induced EphA2 endocytosis. Together, our findings provide evidence that recruitment of SHIP2 to EphA2 attenuates a positive signal to receptor endocytosis mediated by phosphatidylinositol 3-kinase and Rac1 GTPase.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Down-Regulation
  • Endocytosis*
  • Inositol Polyphosphate 5-Phosphatases
  • Mice
  • Neuropeptides / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphoric Monoester Hydrolases / metabolism*
  • Phosphorylation
  • Protein Binding
  • RNA Interference
  • Receptor, EphA2 / metabolism*
  • Signal Transduction*
  • rac GTP-Binding Proteins / metabolism*
  • rac1 GTP-Binding Protein

Substances

  • Neuropeptides
  • Phosphoinositide-3 Kinase Inhibitors
  • Rac1 protein, mouse
  • Receptor, EphA2
  • Phosphoric Monoester Hydrolases
  • Inositol Polyphosphate 5-Phosphatases
  • Inppl1 protein, mouse
  • Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
  • rac GTP-Binding Proteins
  • rac1 GTP-Binding Protein