title: Endoglin promotes endothelial cell proliferation and TGF-beta/ALK1 signal transduction.
abstract: Endoglin is a transmembrane accessory receptor for transforming growth factor-beta (TGF-beta) that is predominantly expressed on proliferating endothelial cells in culture and on angiogenic blood vessels in vivo. Endoglin, as well as other TGF-beta signalling components, is essential during angiogenesis. Mutations in endoglin and activin receptor-like kinase 1 (ALK1), an endothelial specific TGF-beta type I receptor, have been linked to the vascular disorder, hereditary haemorrhagic telangiectasia. However, the function of endoglin in TGF-beta/ALK signalling has remained unclear. Here we report that endoglin is required for efficient TGF-beta/ALK1 signalling, which indirectly inhibits TGF-beta/ALK5 signalling. Endothelial cells lacking endoglin do not grow because TGF-beta/ALK1 signalling is reduced and TGF-beta/ALK5 signalling is increased. Surviving cells adapt to this imbalance by downregulating ALK5 expression in order to proliferate. The ability of endoglin to promote ALK1 signalling also explains why ectopic endoglin expression in endothelial cells promotes proliferation and blocks TGF-beta-induced growth arrest by indirectly reducing TGF-beta/ALK5 signalling. Our results indicate a pivotal role for endoglin in the balance of ALK1 and ALK5 signalling to regulate endothelial cell proliferation.
authors.affiliation: Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan, Amsterdam, The Netherlands.
authors.forename: Franck
authors.initials: F
authors.lastname: Lebrin
authors.forename: Marie-José
authors.initials: MJ
authors.lastname: Goumans
authors.forename: Leon
authors.initials: L
authors.lastname: Jonker
authors.forename: Rita L C
authors.initials: RL
authors.lastname: Carvalho
authors.forename: Gudrun
authors.initials: G
authors.lastname: Valdimarsdottir
authors.forename: Midory
authors.initials: M
authors.lastname: Thorikay
authors.forename: Christine
authors.initials: C
authors.lastname: Mummery
authors.forename: Helen M
authors.initials: HM
authors.lastname: Arthur
authors.forename: Peter
authors.initials: P
authors.lastname: ten Dijke
mesh_terms: D030201:Activin Receptors, Type I / Q000378:metabolism*; D030301:Activin Receptors, Type II; D000818:Animals; D015703:Antigens, CD; D015153:Blotting, Western; D002455:Cell Division; D002461:Cell Line, Transformed; D002465:Cell Movement; D002472:Cell Transformation, Viral; D015536:Down-Regulation; D004622:Embryo, Mammalian; D000071063:Endoglin; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D017930:Genes, Reporter; D007150:Immunohistochemistry; D051379:Mice; D008954:Models, Biological; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D019010:Vascular Cell Adhesion Molecule-1; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D030301:Activin Receptors, Type II; C498931:Acvrl1 protein, mouse; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse