Abstract
Although previous studies demonstrate that appropriate Notch signaling is required during angiogenesis and in vascular homeostasis, the mechanisms by which Notch regulates vascular function remain to be elucidated. Here, we show that activation of the Notch pathway by the ligand Jagged1 reduces the proliferation of endothelial cells. Notch activation inhibits proliferation of endothelial cells in a cell-autonomous manner by inhibiting phosphorylation of the retinoblastoma protein (Rb). During cell cycle entry, p21Cip1 is upregulated in endothelial cells. Activated Notch inhibits mitogen-induced upregulation of p21Cip1 and delays cyclin D-cdk4-mediated Rb phosphorylation. Notch-dependent repression of p21Cip1 prevents nuclear localization of cyclin D and cdk4. The necessity of p21Cip1 for nuclear translocation of cyclin D-cdk4 and S-phase entry in endothelial cells was demonstrated by targeted downregulation of p21Cip1 by using RNA interference. We further demonstrate that when endothelial cells reach confluence, Notch is activated and p21Cip1 is downregulated. Inhibition of the Notch pathway at confluence prevents p21Cip1 downregulation and induces Rb phosphorylation. We suggest that Notch activation contributes to contact inhibition of endothelial cells, in part through repression of p21Cip1 expression.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Active Transport, Cell Nucleus / physiology
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Animals
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Calcium-Binding Proteins
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Cell Cycle / physiology*
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell Line
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Cell Proliferation
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Contact Inhibition / physiology*
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Cyclin D
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Cyclin-Dependent Kinase 4
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclin-Dependent Kinases / metabolism
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Cyclins / metabolism
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Endothelial Cells / cytology
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Endothelial Cells / physiology*
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Endothelium, Vascular / cytology
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Humans
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Intercellular Signaling Peptides and Proteins
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Intracellular Signaling Peptides and Proteins
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Jagged-1 Protein
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Phosphorylation
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Proteins / genetics
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Proteins / metabolism
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Proto-Oncogene Proteins / genetics
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Proto-Oncogene Proteins / metabolism*
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RNA Interference
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Receptor, Notch1
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Receptor, Notch4
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism*
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Receptors, Notch
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Retinoblastoma Protein / metabolism
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Serrate-Jagged Proteins
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Signal Transduction / physiology*
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Transcription Factors / genetics
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Transcription Factors / metabolism*
Substances
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CDKN1A protein, human
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Calcium-Binding Proteins
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Cell Cycle Proteins
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Cyclin D
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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Intercellular Signaling Peptides and Proteins
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Intracellular Signaling Peptides and Proteins
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JAG1 protein, human
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Jagged-1 Protein
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Membrane Proteins
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NOTCH1 protein, human
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NOTCH4 protein, human
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Proteins
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Proto-Oncogene Proteins
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Receptor, Notch1
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Receptor, Notch4
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Receptors, Cell Surface
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Receptors, Notch
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Recombinant Fusion Proteins
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Retinoblastoma Protein
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Serrate-Jagged Proteins
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Transcription Factors
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delta protein
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CDK4 protein, human
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Cyclin-Dependent Kinase 4
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Cyclin-Dependent Kinases