title: Tyrosine 769 of the keratinocyte growth factor receptor is required for receptor signaling but not endocytosis.
abstract: Keratinocyte growth factor receptor (KGFR) is a receptor tyrosine kinase expressed on epithelial cells which belongs to the family of fibroblast growth factor receptors (FGFRs). Following ligand binding, KGFR is rapidly autophosphorylated on specific tyrosine residues in the intracellular domain, recruits substrate proteins, and is rapidly internalized by clathrin-mediated endocytosis. The role of different autophosphorylation sites in FGFRs, and in particular the role of the tyrosine 766 in FGFR1, first identified as PLCgamma binding site, has been extensively studied. We analyzed here the possible role of the tyrosine 769 in KGFR, corresponding to tyrosine 766 in FGFR1, in the regulation of KGFR signal transduction and MAPK activation as well as in the control of the endocytic process of KGFR. A mutant KGFR in which tyrosine 769 was substituted by phenylalanine was generated and transfected in NIH3T3 and HeLa cells. Our results indicate that tyrosine 769 is required for the binding to KGFR and tyrosine phosphorylation of PLCgamma as well as for the full activation of MAPKs and for cell proliferation through the regulation of FRS2 tyrosine phosphorylation, suggesting that this residue represents a key regulator of KGFR signal transduction. Our data also show that tyrosine 769 is not involved in the regulation of the endocytic process of KGFR.
authors.affiliation: Dipartimento di Medicina Sperimentale e Patologia, Università di Roma La Sapienza, Rome, Italy. mara.ceridono@uniroma1.it <mara.ceridono@uniroma1.it>
authors.forename: Mara
authors.initials: M
authors.lastname: Ceridono
authors.forename: Francesca
authors.initials: F
authors.lastname: Belleudi
authors.forename: Simona
authors.initials: S
authors.lastname: Ceccarelli
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Torrisi
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004705:Endocytosis; D051523:Fibroblast Growth Factor 7; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D009154:Mutation / Q000235:genetics; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D051497:Receptor, Fibroblast Growth Factor, Type 2; D017468:Receptors, Fibroblast Growth Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism*
chemical_list: C496453:FGF7 protein, human; C496454:Fgf7 protein, mouse; D010750:Phosphoproteins; D017468:Receptors, Fibroblast Growth Factor; D051523:Fibroblast Growth Factor 7; D019000:Phosphotyrosine; D014443:Tyrosine; D005346:Fibroblast Growth Factors; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor; D010738:Type C Phospholipases; D051966:Phospholipase C gamma