The carboxyl terminus controls ligand-dependent activation of VEGFR-2 and its signaling.
Vascular endothelial growth factor receptor-2 (VEGFR-2/FLK-1) is a receptor tyrosine kinase whose activation stimulates angiogenesis. We recently generated a chimeric VEGFR-2 in which the extracellular domain of VEGFR-2 was replaced with the extracellular domain of human colony stimulating factor-1 receptor and expressed in endothelial cells. To study the contribution of the carboxyl terminus to activation of VEGFR-2, we created a panel of truncated receptors in which the carboxyl terminus of VEGFR-2 was progressively deleted. Removal of the entire carboxyl terminus eliminated activation of VEGFR-2, its ability to activate signaling proteins, and its ability to stimulate cell proliferation. The carboxyl terminus-deleted VEGFR-2 exhibited impaired ligand-dependent down-regulation and inhibited the activation of wild-type receptor in a dominant-negative fashion. Furthermore, introducing the carboxyl terminus of another receptor, i.e., VEGFR-1, restored the ligand-dependent activation of the carboxyl terminus-deleted VEGFR-2 and its ability to stimulate cell proliferation. Our findings suggest that the carboxyl terminus of VEGFR-2 plays a critical role in VEGFR-2 activation, its ability to activate signaling proteins, and its ability to induce biological responses. The presence of at least 57 amino acids at the carboxyl terminus of VEGFR-2 are required for VEGFR-2 activation. Thus, we propose that the carboxyl terminus is required for activation of VEGFR-2, and absence of the carboxyl terminus renders VEGFR-2 inactive.
Department of Ophthalmology, School of Medicine, Boston University, Boston, Massachusetts 02118, USA.
Rosana D
RD
Meyer
Amrik J
AJ
Singh
Nader
N
Rahimi
D000818:Animals; D001011:Aorta; D001483:Base Sequence; D002455:Cell Division; D017931:DNA Primers; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000502:physiology*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013552:Swine; D015854:Up-Regulation; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000737:chemistry / Q000502:physiology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000737:chemistry* / Q000502:physiology*
D017931:DNA Primers; D011993:Recombinant Fusion Proteins; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2