title: Regulation of EphA2 receptor endocytosis by SHIP2 lipid phosphatase via phosphatidylinositol 3-Kinase-dependent Rac1 activation.
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.
authors.affiliation: Department of Cancer Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: Guanglei
authors.initials: G
authors.lastname: Zhuang
authors.forename: Sonja
authors.initials: S
authors.lastname: Hunter
authors.forename: Yoonha
authors.initials: Y
authors.lastname: Hwang
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D015536:Down-Regulation; D004705:Endocytosis; D000072181:Inositol Polyphosphate 5-Phosphatases; D051379:Mice; D009479:Neuropeptides / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D034622:RNA Interference; D036104:Receptor, EphA2 / Q000378:metabolism*; D015398:Signal Transduction; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein
chemical_list: D000072181:Inositol Polyphosphate 5-Phosphatases; D009479:Neuropeptides; D019869:Phosphatidylinositol 3-Kinases; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases; D036104:Receptor, EphA2; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; C484602:Rac1 protein, mouse; C000606435:Inppl1 protein, mouse