Notch signaling is impaired during inflammation in a Lunatic Fringe-dependent manner

The elimination of the cancer stem cell (CSC) population may be required to achieve better outcomes of cancer therapy. We evaluated stearoyl-CoA desaturase 1 (SCD1) as a novel target for CSC-selective elimination in colon cancer. CSCs expressed more SCD1 than bulk cultured cells (BCCs), and blocking SCD1 expression or function revealed an essential role for SCD1 in the survival of CSCs, but not BCCs. The CSC potential selectively decreased after treatment with the SCD1 inhibitor in vitro and in vivo. The CSC-selective suppression was mediated through the induction of apoptosis. The mechanism leading to selective CSC death was investigated by performing a quantitative RT-PCR analysis of 14 CSC-specific signaling and marker genes after 24 and 48 h of treatment with two concentrations of an inhibitor. The decrease in the expression of Notch1 and AXIN2 preceded changes in the expression of all other genes, at 24 h of treatment in a dose-dependent manner, followed by the downregulation of most Wnt- and NOTCH-signaling genes. Collectively, we showed that not only Wnt but also NOTCH signaling is a primary target of suppression by SCD1 inhibition in CSCs, suggesting the possibility of targeting SCD1 against colon cancer in clinical settings.

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Abstract 3380: Acetylation-dependent Regulation Of Notch1 Signaling In Endothelial Cells

Circulation ◽

10.1161/circ.118.suppl_18.s_415-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Virginia Guarani ◽

Franck Dequiedt ◽

Andreas M Zeiher ◽

Stefanie Dimmeler ◽

Michael Potente

Keyword(s):

Endothelial Cells ◽

Notch Signaling ◽

Cell Fate ◽

Molecular Mechanisms ◽

Trichostatin A ◽

Notch Pathway ◽

Dependent Manner ◽

Class Iii ◽

Cell Fate Decisions ◽

Knock Down

The Notch signaling pathway is a versatile regulator of cell fate decisions and plays an essential role for embryonic and postnatal vascular development. As only modest differences in Notch pathway activity suffice to determine dramatic differences in blood vessel development, this pathway is tightly regulated by a variety of molecular mechanisms. Reversible acetylation has emerged as an important post-translational modification of several non-histone proteins, which are targeted by histone deacetylases (HDACs). Here, we report that specifically the Notch1 intracellular domain (NICD) is itself an acetylated protein and that its acetylation level is tightly regulated by the SIRT1 deacetylase, which we have previously identified as a key regulator of endothelial angiogenic functions during vascular growth. Coexpression of NICD with histone acetyltransferases such as p300 or PCAF induced a dose- and time-dependent acetylation of NICD. Blocking HDAC activity using the class III HDAC inhibitor nicotinamid (NAM), but not the class I/II HDAC inhibior trichostatin A, resulted in a significant increase of NICD acetylation suggesting that NICD is targetd by class III HDACs for deacetylation. Among the class III HDACs with deacetylase activity (SIRT1, 2, 3, 5), knock down of specifically SIRT1 resulted in enhanced acetylation of NICD. Moreover, wild type SIRT1, but not a catalytically inactive mutant catalyzed the deacetylation of NICD in a nicotinamid-dependent manner. SIRT1, but SIRT2, SIRT3 or SIRT5, associated with NICD through its catalytic domain demonstrating that SIRT1 is a direct NICD deacetylase. Enhancing NICD acetylation by either overexpression of p300 or inhibition of SIRT1 activity using NAM or RNAi-mediated knock down resulted in enhanced NICD protein stability by blocking its ubiquitin-mediated degradation. Consistent with these results, loss of SIRT1 amplified Notch target gene expression in endothelial cells in response to NICD overexpression or treatment with the Notch ligand Dll4. In summary, our results identify reversible acetylation of NICD as a novel molecular mechanism to control Notch signaling and suggest that deacetylation of NICD by SIRT1 plays a key role in the dynamic regulation of Notch signaling in endothelial cells.

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The retromer complex safeguards against neural progenitor-derived tumorigenesis by regulating Notch receptor trafficking

eLife ◽

10.7554/elife.38181 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 5

Author(s):

Bo Li ◽

Chouin Wong ◽

Shihong Max Gao ◽

Rulan Zhang ◽

Rongbo Sun ◽

...

Keyword(s):

Notch Signaling ◽

Molecular Mechanisms ◽

Neural Progenitor ◽

Tumor Formation ◽

Neural Progenitors ◽

Notch Receptor ◽

Dependent Manner ◽

Cell Fate Decisions ◽

Retromer Complex ◽

Signaling Activation

The correct establishment and maintenance of unidirectional Notch signaling are critical for the homeostasis of various stem cell lineages. However, the molecular mechanisms that prevent cell-autonomous ectopic Notch signaling activation and deleterious cell fate decisions remain unclear. Here we show that the retromer complex directly and specifically regulates Notch receptor retrograde trafficking in Drosophila neuroblast lineages to ensure the unidirectional Notch signaling from neural progenitors to neuroblasts. Notch polyubiquitination mediated by E3 ubiquitin ligase Itch/Su(dx) is inherently inefficient within neural progenitors, relying on retromer-mediated trafficking to avoid aberrant endosomal accumulation of Notch and cell-autonomous signaling activation. Upon retromer dysfunction, hypo-ubiquitinated Notch accumulates in Rab7+ enlarged endosomes, where it is ectopically processed and activated in a ligand-dependent manner, causing progenitor-originated tumorigenesis. Our results therefore unveil a safeguard mechanism whereby retromer retrieves potentially harmful Notch receptors in a timely manner to prevent aberrant Notch activation-induced neural progenitor dedifferentiation and brain tumor formation.

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Lunatic Fringe-mediated Notch signaling is required for lung alveogenesis

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.90550.2008 ◽

2010 ◽

Vol 298 (1) ◽

pp. L45-L56 ◽

Cited By ~ 52

Author(s):

Keli Xu ◽

Erica Nieuwenhuis ◽

Brenda L. Cohen ◽

Wei Wang ◽

Angelo J. Canty ◽

...

Keyword(s):

Notch Signaling ◽

Lung Development ◽

Smooth Muscle Actin ◽

Mutant Mice ◽

Myofibroblast Differentiation ◽

Lunatic Fringe ◽

Notch Receptors ◽

Distal Lung

Distal lung development occurs through coordinated induction of myofibroblasts, epithelial cells, and capillaries. Lunatic Fringe ( Lfng) is a β1–3 N-acetylglucosamine transferase that modifies Notch receptors to facilitate their activation by Delta-like (Dll1/4) ligands. Lfng is expressed in the distal lung during saccular development, and deletion of this gene impairs myofibroblast differentiation and alveogenesis in this context. A similar defect was observed in Notch2 β-geo/+ Notch3 β-geo/β-geo compound mutant mice but not in Notch2 β-geo/+ or Notch3 β-geo/β-geo single mutants. Finally, to directly test for the role of Notch signaling in myofibroblast differentiation in vivo, we used ROSA26-rtTA/+; tetO-CRE/+; RBPJκflox/flox inducible mutant mice to show that disruption of canonical Notch signaling during late embryonic development prevents induction of smooth muscle actin in mesenchymal cells of the distal lung. In sum, these results demonstrate that Lfng functions to enhance Notch signaling in myofibroblast precursor cells and thereby to coordinate differentiation and mobilization of myofibroblasts required for alveolar septation.

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Binding of Delta1, Jagged1, and Jagged2 to Notch2 Rapidly Induces Cleavage, Nuclear Translocation, and Hyperphosphorylation of Notch2

Molecular and Cellular Biology ◽

10.1128/mcb.20.18.6913-6922.2000 ◽

2000 ◽

Vol 20 (18) ◽

pp. 6913-6922 ◽

Cited By ~ 122

Author(s):

Kiyoshi Shimizu ◽

Shigeru Chiba ◽

Noriko Hosoya ◽

Keiki Kumano ◽

Toshiki Saito ◽

...

Keyword(s):

Ligand Binding ◽

Notch Signaling ◽

Time Course ◽

Nuclear Translocation ◽

Reporter Genes ◽

Time Dependent ◽

Dependent Manner ◽

Notch Receptors ◽

Notch Protein ◽

Membrane Spanning

ABSTRACT Delta1, Jagged1, and Jagged2, commonly designated Delta/Serrate/LAG-2 (DSL) proteins, are known to be ligands for Notch1. However, it has been less understood whether they are ligands for Notch receptors other than Notch1. Meanwhile, ligand-induced cleavage and nuclear translocation of the Notch protein are considered to be fundamental for Notch signaling, yet direct observation of the behavior of the Notch molecule after ligand binding, including cleavage and nuclear translocation, has been lacking. In this report, we investigated these issues for Notch2. All of the three DSL proteins bound to endogenous Notch2 on the surface of BaF3 cells, although characteristics of Jagged2 for binding to Notch2 apparently differed from that of Delta1 and Jagged1. After binding, the three DSL proteins induced cleavage of the membrane-spanning subunit of Notch2 (Notch2TM), which occurred within 15 min. In a simultaneous time course, the cleaved fragment of Notch2TMwas translocated into the nucleus. Interestingly, the cleaved Notch2 fragment was hyperphosphorylated also in a time-dependent manner. Finally, binding of DSL proteins to Notch2 also activated the transcription of reporter genes driven by the RBP-Jκ-responsive promoter. Together, these data indicate that all of these DSL proteins function as ligands for Notch2. Moreover, the findings of rapid cleavage, nuclear translocation, and phosphorylation of Notch2 after ligand binding facilitate the understanding of the Notch signaling.

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