title: Metalloproteinase/Presenilin1 processing of ephrinB regulates EphB-induced Src phosphorylation and signaling.
abstract: Bidirectional signaling triggered by interacting ephrinB receptors (EphB) and ephrinB ligands is crucial for development and function of the vascular and nervous systems. A signaling cascade triggered by this interaction involves activation of Src kinase and phosphorylation of ephrinB. The mechanism, however, by which EphB activates Src in the ephrinB-expressing cells is unknown. Here we show that EphB stimulates a metalloproteinase cleavage of ephrinB2, producing a carboxy-terminal fragment that is further processed by PS1/gamma-secretase to produce intracellular peptide ephrinB2/CTF2. This peptide binds Src and inhibits its association with inhibitory kinase Csk, allowing autophosphorylation of Src at residue tyr418. EphrinB2/CTF2-activated Src phosphorylates ephrinB2 and inhibits its processing by gamma-secretase. These data show that the PS1/gamma-secretase system controls Src activation and ephrinB phosphorylation by regulating production of Src activator ephrinB2/CTF2. Accordingly, gamma-secretase inhibitors prevented the EphB-induced sprouting of endothelial cells and the recruitment of Grb4 to ephrinB. PS1 FAD and gamma-secretase dominant-negative mutants inhibited the EphB-induced cleavage of ephrinB2 and Src autophosphorylation, raising the possibility that FAD mutants interfere with the functions of Src and ephrinB2 in the CNS.
authors.affiliation: Department of Psychiatry, Mount Sinai School of Medicine, NYU, New York, NY 10029, USA.
authors.forename: Anastasios
authors.initials: A
authors.lastname: Georgakopoulos
authors.forename: Claudia
authors.initials: C
authors.lastname: Litterst
authors.forename: Enrico
authors.initials: E
authors.lastname: Ghersi
authors.forename: Lia
authors.initials: L
authors.lastname: Baki
authors.forename: ChiJie
authors.initials: C
authors.lastname: Xu
authors.forename: Geo
authors.initials: G
authors.lastname: Serban
authors.forename: Nikolaos K
authors.initials: NK
authors.lastname: Robakis
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D036388:Ephrin-B2 / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D045726:Metalloproteases / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D053764:Presenilin-1; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D036183:Receptor, EphB2 / Q000378:metabolism*; D015398:Signal Transduction; D019061:src-Family Kinases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D036388:Ephrin-B2; D008565:Membrane Proteins; C485544:NCK2 protein, human; D015513:Oncogene Proteins; C508853:PSEN1 protein, human; D053764:Presenilin-1; D011518:Proto-Oncogene Proteins; D010770:Phosphotransferases; D011505:Protein-Tyrosine Kinases; D036183:Receptor, EphB2; D000081247:CSK Tyrosine-Protein Kinase; D016392:Proto-Oncogene Proteins pp60(c-src); D019061:src-Family Kinases; C000631346:CSK protein, human; D045726:Metalloproteases