title: Angiopoietin-1/Tie2 signal augments basal Notch signal controlling vascular quiescence by inducing delta-like 4 expression through AKT-mediated activation of beta-catenin.
abstract: Angiopoietin-1 (Ang1) regulates both vascular quiescence and angiogenesis through the receptor tyrosine kinase Tie2. We and another group previously showed that Ang1 and Tie2 form distinct signaling complexes at cell-cell and cell-matrix contacts. We further demonstrated that the former up-regulates Notch ligand delta-like 4 (Dll4) only in the presence of cell-cell contacts. Because Dll4/Notch signal restricts sprouting angiogenesis and promotes vascular stabilization, we investigated the mechanism of how the Ang1/Tie2 signal induces Dll4 expression to clarify the role of the Dll4/Notch signal in Ang1/Tie2 signal-mediated vascular quiescence. Under confluent endothelial cells, the basal Notch signal was observed. Ang1, moreover, induced Dll4 expression and production of the Notch intracellular domain (NICD). Ang1 stimulated transcriptional activity of β-catenin through phosphoinositide 3-kinase (PI3K)/AKT-mediated phosphorylation of glycogen synthase kinase 3β (GSK3β). Correspondingly, the GSK3β inhibitor up-regulated Dll4, whereas depletion of β-catenin by siRNA blocked Ang1-induced Dll4 expression, indicating the indispensability of β-catenin in Ang1-mediated up-regulation of Dll4. In addition, Dll4 expression by the GSK3β inhibitor was only observed in confluent cells, and was impeded by DAPT, a γ-secretase inhibitor, implying requirement of the Notch signal in β-catenin-dependent Dll4 expression. Consistently, we found that either Ang1 or NICD up-regulates Dll4 through the RBP-J binding site within intron 3 of the DLL4 gene and that β-catenin forms a complex with NICD/RBP-J to enhance Dll4 expression. Ang1 induced the deposition of extracellular matrix that is preferable for basement membrane formation through Dll4/Notch signaling. Collectively, the Ang1/Tie2 signal potentiates basal Notch signal controlling vascular quiescence by up-regulating Dll4 through AKT-mediated activation of β-catenin.
authors.affiliation: From the Department of Cell Biology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan.
authors.forename: Jianghui
authors.initials: J
authors.lastname: Zhang
authors.affiliation: From the Department of Cell Biology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan,. Electronic address: fuku@ri.ncvc.go.jp.
authors.forename: Shigetomo
authors.initials: S
authors.lastname: Fukuhara
authors.affiliation: From the Department of Cell Biology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sako
authors.affiliation: the Transgenic Animal Research Center, National Institute of Agrobiological Sciences, Ibaraki 305-8634, Japan,; the Laboratory for Chemistry and Metabolism, Tokyo Metropolitan Institute for Neuroscience, Tokyo 183-8526, Japan.
authors.forename: Takato
authors.initials: T
authors.lastname: Takenouchi
authors.affiliation: the Transgenic Animal Research Center, National Institute of Agrobiological Sciences, Ibaraki 305-8634, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitani
authors.affiliation: the Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, Illinois 60611, and.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kume
authors.affiliation: the Biomedical Research Center and Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Guseong-dong, Daejeon 305-701, Korea.
authors.forename: Gou Young
authors.initials: GY
authors.lastname: Koh
authors.affiliation: From the Department of Cell Biology, National Cerebral and Cardiovascular Center Research Institute, Fujishirodai 5-7-1, Suita, Osaka 565-8565, Japan,. Electronic address: nmochizu@ri.ncvc.go.jp.
authors.forename: Naoki
authors.initials: N
authors.lastname: Mochizuki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D042683:Angiopoietin-1 / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D018919:Neovascularization, Physiologic / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism*; D051176:beta Catenin / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D042683:Angiopoietin-1; D002135:Calcium-Binding Proteins; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D036341:Intercellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020794:Receptor Protein-Tyrosine Kinases; D051880:Receptors, Notch; D051176:beta Catenin; C467630:ANGPT1 protein, human; C424126:DLL4 protein, human; C000605506:GSK3B protein, human