title: Notch-dependent VEGFR3 upregulation allows angiogenesis without VEGF-VEGFR2 signalling.
abstract: Developing tissues and growing tumours produce vascular endothelial growth factors (VEGFs), leading to the activation of the corresponding receptors in endothelial cells. The resultant angiogenic expansion of the local vasculature can promote physiological and pathological growth processes. Previous work has uncovered that the VEGF and Notch pathways are tightly linked. Signalling triggered by VEGF-A (also known as VEGF) has been shown to induce expression of the Notch ligand DLL4 in angiogenic vessels and, most prominently, in the tip of endothelial sprouts. DLL4 activates Notch in adjacent cells, which suppresses the expression of VEGF receptors and thereby restrains endothelial sprouting and proliferation. Here we show, by using inducible loss-of-function genetics in combination with inhibitors in vivo, that DLL4 protein expression in retinal tip cells is only weakly modulated by VEGFR2 signalling. Surprisingly, Notch inhibition also had no significant impact on VEGFR2 expression and induced deregulated endothelial sprouting and proliferation even in the absence of VEGFR2, which is the most important VEGF-A receptor and is considered to be indispensable for these processes. By contrast, VEGFR3, the main receptor for VEGF-C, was strongly modulated by Notch. VEGFR3 kinase-activity inhibitors but not ligand-blocking antibodies suppressed the sprouting of endothelial cells that had low Notch signalling activity. Our results establish that VEGFR2 and VEGFR3 are regulated in a highly differential manner by Notch. We propose that successful anti-angiogenic targeting of these receptors and their ligands will strongly depend on the status of endothelial Notch signalling.
authors.affiliation: Max Planck Institute for Molecular Biomedicine, Department of Tissue Morphogenesis, D-48149 Münster, Germany. rui.benedito@mpi-muenster.mpg.de
authors.forename: Rui
authors.initials: R
authors.lastname: Benedito
authors.forename: Susana F
authors.initials: SF
authors.lastname: Rocha
authors.forename: Marina
authors.initials: M
authors.lastname: Woeste
authors.forename: Martin
authors.initials: M
authors.lastname: Zamykal
authors.forename: Freddy
authors.initials: F
authors.lastname: Radtke
authors.forename: Oriol
authors.initials: O
authors.lastname: Casanovas
authors.forename: Antonio
authors.initials: A
authors.lastname: Duarte
authors.forename: Bronislaw
authors.initials: B
authors.lastname: Pytowski
authors.forename: Ralf H
authors.initials: RH
authors.lastname: Adams
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002135:Calcium-Binding Proteins; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051880:Receptors, Notch / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D040321:Vascular Endothelial Growth Factor Receptor-3 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D051880:Receptors, Notch; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D040321:Vascular Endothelial Growth Factor Receptor-3