title: A single amino acid substitution in the activation loop defines the decoy characteristic of VEGFR-1/FLT-1.
abstract: VEGFR-1 is a kinase-defective receptor tyrosine kinase (RTK) and negatively modulates angiogenesis by acting as a decoy receptor. The decoy characteristic of VEGFR-1 is required for normal development and angiogenesis. To date, there is no molecular explanation for this unusual characteristic of VEGFR-1. Here we show that the molecular mechanisms underlying the decoy characteristic of VEGFR-1 is linked to the replacement of a highly conserved amino acid residue in the activation loop. This amino acid is highly conserved among all the type III RTKs and corresponds to aspartic acid, but in VEGFR-1 it is substituted to asparagine. Mutation of asparagine (Asn(1050)) within the activation loop to aspartic acid promoted enhanced ligand-dependent tyrosine autophosphorylation and kinase activation in vivo and in vitro. The mutant VEGFR-1 (Asp(1050)) promoted endothelial cell proliferation but not tubulogenesis. It also displayed an oncogenic phenotype as its expression in fibroblast cells elicited transformation and colony growth. Furthermore, mutation of the invariable aspartic acid to asparagine in VEGFR-2 lowered the autophosphorylation of activation loop tyrosines 1052 and 1057. We propose that the conserved aspartic acid in the activation loop favors the transphosphorylation of the activation loop tyrosines, and its absence renders RTK to a less potent enzyme by disfavoring transphosphorylation of activation loop tyrosines.
authors.affiliation: Department of Ophthalmology, School of Medicine, Boston University, MA 02118, USA.
authors.forename: Rosana D
authors.initials: RD
authors.lastname: Meyer
authors.forename: Moosa
authors.initials: M
authors.lastname: Mohammadi
authors.forename: Nader
authors.initials: N
authors.lastname: Rahimi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001216:Asparagine / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D016895:Culture Media, Serum-Free / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D009389:Neovascularization, Pathologic; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013936:Thymidine / Q000737:chemistry; D013997:Time Factors; D014443:Tyrosine / Q000737:chemistry; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000737:chemistry* / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000737:chemistry
chemical_list: D016895:Culture Media, Serum-Free; D008024:Ligands; D011993:Recombinant Fusion Proteins; D001224:Aspartic Acid; D014443:Tyrosine; D001216:Asparagine; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2; D013936:Thymidine