title: Activated Notch4 inhibits angiogenesis: role of beta 1-integrin activation.
abstract: Notch4 is a member of the Notch family of transmembrane receptors that is expressed primarily on endothelial cells. Activation of Notch in various cell systems has been shown to regulate cell fate decisions. The sprouting of endothelial cells from microvessels, or angiogenesis, involves the modulation of the endothelial cell phenotype. Based on the function of other Notch family members and the expression pattern of Notch4, we postulated that Notch4 activation would modulate angiogenesis. Using an in vitro endothelial-sprouting assay, we show that expression of constitutively active Notch4 in human dermal microvascular endothelial cells (HMEC-1) inhibits endothelial sprouting. We also show that activated Notch4 inhibits vascular endothelial growth factor (VEGF)-induced angiogenesis in the chick chorioallantoic membrane in vivo. Activated Notch4 does not inhibit HMEC-1 proliferation or migration through fibrinogen. However, migration through collagen is inhibited. Our data show that Notch4 cells exhibit increased beta1-integrin-mediated adhesion to collagen. HMEC-1 expressing activated Notch4 do not have increased surface expression of beta 1-integrins. Rather, we demonstrate that Notch4-expressing cells display beta1-integrin in an active, high-affinity conformation. Furthermore, using function-activating beta 1-integrin antibodies, we demonstrate that activation of beta1-integrins is sufficient to inhibit VEGF-induced endothelial sprouting in vitro and angiogenesis in vivo. Our findings suggest that constitutive Notch4 activation in endothelial cells inhibits angiogenesis in part by promoting beta 1-integrin-mediated adhesion to the underlying matrix.
authors.affiliation: Department of Experimental Medicine, University of British Columbia and British Columbia Cancer Agency, Vancouver, British Columbia V5Z 1L3, Canada.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Leong
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Hu
authors.forename: Linheng
authors.initials: L
authors.lastname: Li
authors.forename: Michela
authors.initials: M
authors.lastname: Noseda
authors.forename: Bruno
authors.initials: B
authors.lastname: Larrivée
authors.forename: Christopher
authors.initials: C
authors.lastname: Hull
authors.forename: Leroy
authors.initials: L
authors.lastname: Hood
authors.forename: Fred
authors.initials: F
authors.lastname: Wong
authors.forename: Aly
authors.initials: A
authors.lastname: Karsan
mesh_terms: D000482:Allantois / Q000098:blood supply; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D002642:Chick Embryo; D002823:Chorion / Q000098:blood supply; D003094:Collagen / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D005340:Fibrinogen / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D019012:Integrin beta1 / Q000502:physiology*; D018919:Neovascularization, Physiologic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D000074562:Receptor, Notch4; D011956:Receptors, Cell Surface; D051880:Receptors, Notch
chemical_list: D019012:Integrin beta1; C106075:NOTCH4 protein, human; D011518:Proto-Oncogene Proteins; D000074562:Receptor, Notch4; D011956:Receptors, Cell Surface; D051880:Receptors, Notch; D005340:Fibrinogen; D003094:Collagen