Elevated Notch ligands in serum are associated with HIV/TB coinfection

Cell-cell interactions mediated by Notch and its ligands are known to effect many cell fate decisions in both invertebrates and vertebrates. However, the mechanisms involved in ligand induced Notch activation are unknown. Recently it was shown that, in at least some cases, endocytosis of the extracellular domain of Notch and ligand by the signaling cell is required for signal induction in the receptive cell. These results imply that soluble ligands (ligand extracellular domains) although capable of binding Notch would be unlikely to activate it. To test the potential activity of soluble Notch ligands, we generated monomeric and dimeric forms of the Notch ligand Delta-1 by fusing the extracellular domain to either a series of myc epitopes (Delta-1(ext-myc)) or to the Fc portion of human IgG-1 (Delta-1(ext-IgG)), respectively. Notch activation, assayed by inhibition of differentiation in C2 myoblasts and by HES1 transactivation in U20S cells, occurred when either Delta-1(ext-myc) or Delta-1(ext-IgG) were first immobilized on the plastic surface. However, Notch was not activated by either monomeric or dimeric ligand in solution (non-immobilized). Furthermore, both non-immobilized Delta-1(ext-myc) and Delta-1(ext-IgG) blocked the effect of immobilized Delta. These results indicate that Delta-1 extracellular domain must be immobilized to induce Notch activation in C2 or U20S cells and that non-immobilized Delta-1 extracellular domain is inhibitory to Notch function. These results imply that ligand stabilization may be essential for Notch activation.

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Abstract 1680: Notch Signaling Directly Targets Msx2: Possible Role of Notch Signaling in Osteogenic Conversion of Vascular Smooth Muscle Cells and Vascular Calcification

Circulation ◽

10.1161/circ.118.suppl_18.s_368-a ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Takehisa Shimizu ◽

Toru Tanaka ◽

Tatsuya Iso ◽

Masahiko Kurabayashi

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Notch Signaling ◽

Vascular Calcification ◽

Transcriptional Activity ◽

Muscle Cells ◽

Matrix Mineralization ◽

Cardiovascular Morbidity And Mortality ◽

Notch Ligands

Vascular calcification is a prominent feature of atherosclerosis and closely correlated with cardiovascular morbidity and mortality. In this study, we hypothesize that Notch signaling plays an important role in osteogenic conversion of smooth muscle cells (SMCs) and vascular calcification. <Methods and Results> Either Notch ligand-expressing cells or overexpression of Notch intracellular domains (NICDs) induced expression of Msx2, a key regulator of osteogenic conversion, in human aortic SMCs (HASMCs). In addition, overexpression of Notch1 intracellular domain (N1-ICD) markedly upregulated alkaline phosphatase (ALP) activity and matrix mineralization of HASMCs. A knockdown experiment with a small interfering RNA confirmed that Msx2, but not Runx2/Cbfa1, another key osteogenic transcription factor, is responsible for Notch1-induced osteogenic conversion of HASMCs. Furthermore, this Notch1-Msx2 pathway was independent of bone morphogenetic protein-2 (BMP-2), an osteogenic morphogen upstream of Msx2. The transcriptional activity of the Msx2 promoter was significantly enhanced by Notch ligands stimulation, whereas it was abrogated by a specific Notch signaling inhibitor. The RBP-Jk binding element within the Msx2 promoter was critical to Notch1-induced Msx2 gene expression, and correspondingly, neither N1-ICD overexpression nor Notch ligands stimulation increase the Msx2 expression or transcriptional activity of the Msx2 promoter, respectively, in RBP-Jk-deficient fibroblasts. Immunohistochemistry of human artery specimens revealed colocalization of Notch1 and Msx2 within atherosclerotic plaques, indicating a role of Notch1-Msx2 pathway in vascular calcification in vivo. These results suggest that Notch signaling directly targets Msx2, thus accelerating osteogenic conversion of HASMCs and, as a result, a formation of vascular calcification.

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Interactions among Delta, Serrate and Fringe modulate Notch activity during Drosophila wing development

Development ◽

10.1242/dev.125.15.2951 ◽

1998 ◽

Vol 125 (15) ◽

pp. 2951-2962 ◽

Cited By ~ 10

Author(s):

T. Klein ◽

A.M. Arias

Keyword(s):

Notch Signalling ◽

Dominant Negative ◽

Wing Development ◽

Notch Signalling Pathway ◽

Notch Ligand ◽

Drosophila Wing ◽

Signalling Molecule ◽

Dorsoventral Boundary ◽

Notch Ligands ◽

Specific Nuclear Protein

The Notch signalling pathway plays an important role during the development of the wing primordium, especially of the wing blade and margin. In these processes, the activity of Notch is controlled by the activity of the dorsal specific nuclear protein Apterous, which regulates the expression of the Notch ligand, Serrate, and the Fringe signalling molecule. The other Notch ligand, Delta, also plays a role in the development and patterning of the wing. It has been proposed that Fringe modulates the ability of Serrate and Delta to signal through Notch and thereby restricts Notch signalling to the dorsoventral boundary of the developing wing blade. Here we report the results of experiments aimed at establishing the relationships between Fringe, Serrate and Delta during wing development. We find that Serrate is not required for the initiation of wing development but rather for the expansion and early patterning of the wing primordium. We provide evidence that, at the onset of wing development, Delta is under the control of apterous and might be the Notch ligand in this process. In addition, we find that Fringe function requires Su(H). Our results suggest that Notch signalling during wing development relies on careful balances between positive and dominant negative interactions between Notch ligands, some of which are mediated by Fringe.

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Endothelial Upregulation of Mechanosensitive Channel Piezo1 in Pulmonary Hypertension

AJP Cell Physiology ◽

10.1152/ajpcell.00147.2021 ◽

2021 ◽

Author(s):

Ziyi Wang ◽

Jiyuan Chen ◽

Aleksandra Babicheva ◽

Pritesh P. Jain ◽

Marisela Rodriguez ◽

...

Keyword(s):

Pulmonary Hypertension ◽

Cyclic Stretch ◽

Mechanosensitive Channel ◽

Pathogenic Role ◽

Membrane Stretch ◽

Mrna And Protein Expression ◽

Resultant Increase ◽

Pulmonary Arterial ◽

Arterial Endothelial Cells ◽

Notch Ligands

Piezo is a mechanosensitive cation channel responsible for stretch-mediated Ca2+ and Na+ influx in multiple types of cells. Little is known about the functional role of Piezo1 in the lung vasculature and its potential pathogenic role in pulmonary arterial hypertension (PAH). Pulmonary arterial endothelial cells (PAECs) are constantly under mechanic stretch and shear stress that are sufficient to activate Piezo channels. Here we report that Piezo1 is significantly upregulated in PAECs from patients with idiopathic PAH and animals with experimental pulmonary hypertension (PH) compared to normal controls. Membrane stretch by decreasing extracellular osmotic pressure or by cyclic stretch (18% CS) increases Ca2+-dependent phosphorylation (p) of AKT and ERK, and subsequently upregulates expression of Notch ligands, Jagged1/2 (Jag1 and Jag-2), and Delta like-4 (DLL4) in PAECs. siRNA-mediated downregulation of Piezo1 significantly inhibited the stretch-mediated pAKT increase and Jag-1 upregulation, while downregulation of AKT by siRNA markedly attenuated the stretch-mediated Jag1 upregulation in human PAECs. Furthermore, the mRNA and protein expression level of Piezo1 in the isolated pulmonary artery, which mainly contains pulmonary arterial smooth muscle cells (PASMCs), from animals with severe PH was also significantly higher than that from control animals. Taken together, our study suggests that membrane stretch-mediated Ca2+ influx through Piezo1 is an important trigger for pAKT-mediated upregulation of Jag-1 in PAECs. Upregulation of the mechanosensitive channel Piezo1 and the resultant increase in the Notch ligands (Jag-1/2 and DLL4) in PAECs may play a critical pathogenic role in the development of pulmonary vascular remodeling in PAH and PH.

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The NHR1 Domain of Neuralized Binds Delta and Mediates Delta Trafficking and Notch Signaling

Molecular Biology of the Cell ◽

10.1091/mbc.e06-08-0753 ◽

2007 ◽

Vol 18 (1) ◽

pp. 1-13 ◽

Cited By ~ 26

Author(s):

Cosimo Commisso ◽

Gabrielle L. Boulianne

Keyword(s):

Plasma Membrane ◽

Notch Signaling ◽

Ubiquitin Ligase ◽

Protein Interactions ◽

Neural Development ◽

Ring Domain ◽

Protein Protein Interactions ◽

Necessary And Sufficient ◽

Conserved Residue ◽

Notch Ligands

Notch signaling, which is crucial to metazoan development, requires endocytosis of Notch ligands, such as Delta and Serrate. Neuralized is a plasma membrane-associated ubiquitin ligase that is required for neural development and Delta internalization. Neuralized is comprised of three domains that include a C-terminal RING domain and two neuralized homology repeat (NHR) domains. All three domains are conserved between organisms, suggesting that these regions of Neuralized are functionally important. Although the Neuralized RING domain has been shown to be required for Delta ubiquitination, the function of the NHR domains remains elusive. Here we show that neuralized1, a well-characterized neurogenic allele, exhibits a mutation in a conserved residue of the NHR1 domain that results in mislocalization of Neuralized and defects in Delta binding and internalization. Furthermore, we describe a novel isoform of Neuralized and show that it is recruited to the plasma membrane by Delta and that this is mediated by the NHR1 domain. Finally, we show that the NHR1 domain of Neuralized is both necessary and sufficient to bind Delta. Altogether, our data demonstrate that NHR domains can function in facilitating protein–protein interactions and in the case of Neuralized, mediate binding to its ubiquitination target, Delta.

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