Association of Notch signaling pathway expression in liposarcomas with outcome, and targeting with gamma-secretase inhibitors

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 10526-10526
Author(s):  
R. D. Meng ◽  
L. Qin ◽  
C. C. Shelton ◽  
Y. Li ◽  
R. G. Maki ◽  
...  
Keyword(s):  
Notch Signaling ◽  
Empirical Bayes ◽  
Cox Regression ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Gamma Secretase ◽  
Fat Tissue ◽  
Fat Cell ◽  
Dapi Staining ◽  
Notch 3

10526 Background: The Notch pathway directs normal fat cell development, but its aberrant activation may promote the development of sarcomas. The expression of the Notch pathway in liposarcoma (LPS), however, is unknown. We examined Notch signaling components in LPS's and suppressed Notch activation with drug targeting in LPS cell lines. Methods: RNA was isolated from 18 normal fat and 140 LPS tissue samples from five LPS subtypes: well-differentiated (33%), de-differentiated DD (25%), myxoid (12%), round cell (6%), and pleomorphic (13%), and were hybridized to Affymetrix U133A arrays. Microarray data were normalized with the RMA method. Correlation analysis identified genes expressed between sample classes, using Empirical Bayes t-test, and genes associated with survival, using Cox regression. The Notch pathway in two LPS lines, DDLS and LS141, was suppressed with a novel gamma-secretase inhibitor (GSI) or with siRNA to Notch receptors. Viability was assessed by colony formation, apoptosis by DAPI staining, and Notch expression by immunoblotting. Results: Expression of Notch-3 and its targets, Hes-1, Hey-1, and survivin, was increased in LPS subtypes, compared to fat tissue (p<0.001). Inhibition of Notch signaling with GSI's or siRNA to Notch-1 suppressed the viability of both DD LPS lines (p<0.05), inducing a G1/S arrest followed by apoptosis. Transfection of siRNA to each Notch receptor, especially Notch-3, also suppressed the viability of DD LPS's (p<0.05). Expression of Notch-3 (p=0.027, HR=2.64), Notch-4 (p=0.026, HR=2.70), the ligand JAG-2 (p=0.049, HR=2.32), and Hey-1 (p=0.001, HR=4.25) was associated with reduced distant recurrence free survival in patients with DD LPS's. Expression of the negative Notch regulator Fbxw7 was associated with improved overall survival in patients with LPS (p=0.008, HR=-1.42). Conclusions: Elements of the Notch pathway (receptors, ligands, targets, and modifiers) are overexpressed in LPS's compared to normal fat tissue and associate with outcome. Suppression of Notch signaling decreased DD LPS cell line viability and induced apoptosis. Notch inhibition may represent a new therapeutic strategy for patients with LPS's and deserves further validation in a clinical trial. No significant financial relationships to disclose.

scholarly journals Notch Signaling Regulation in HCC: From Hepatitis Virus to Non-Coding RNAs

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 521
Author(s):  
Catia Giovannini ◽  
Francesca Fornari ◽  
Fabio Piscaglia ◽  
Laura Gramantieri
Keyword(s):  
Notch Signaling ◽  
Cell Fate ◽  
Hepatitis Virus ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Gamma Secretase ◽  
Stem Cell Maintenance ◽  
Pathway Activation ◽  
Promising Therapeutic Approach ◽  
Conserved Genes

The Notch family includes evolutionary conserved genes that encode for single-pass transmembrane receptors involved in stem cell maintenance, development and cell fate determination of many cell lineages. Upon activation by different ligands, and depending on the cell type, Notch signaling plays pleomorphic roles in hepatocellular carcinoma (HCC) affecting neoplastic growth, invasion capability and stem like properties. A specific knowledge of the deregulated expression of each Notch receptor and ligand, coupled with resultant phenotypic changes, is still lacking in HCC. Therefore, while interfering with Notch signaling might represent a promising therapeutic approach, the complexity of Notch/ligands interactions and the variable consequences of their modulations raises concerns when performed in undefined molecular background. The gamma-secretase inhibitors (GSIs), representing the most utilized approach for Notch inhibition in clinical trials, are characterized by important adverse effects due to the non-specific nature of GSIs themselves and to the lack of molecular criteria guiding patient selection. In this review, we briefly summarize the mechanisms involved in Notch pathway activation in HCC supporting the development of alternatives to the γ-secretase pan-inhibitor for HCC therapy.

scholarly journals TAMI-11. IMPACT OF oHSV ACTIVATED NOTCH SIGNALING IN TUMOR MICROENVIRONMENT, AND ITS IMPACT ON ANTI-TUMOR IMMUNITY

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii215-ii215
Author(s):  
Yoshihiro Otani ◽  
Ji Young Yoo ◽  
Samantha Chao ◽  
Toshihiko Shimizu ◽  
Cole Lewis ◽  
...  
Keyword(s):  
Tumor Microenvironment ◽  
Notch Signaling ◽  
Tumor Immunity ◽  
Cell Communication ◽  
Notch Signaling Pathway ◽  
Therapeutic Benefit ◽  
Notch Receptor ◽  
Negative Regulator ◽  
Gamma Secretase ◽  
The Impact

Abstract NOTCH signaling is a method of cell-cell communication where membrane bound NOTCH ligands on signal-sending cells can bind to and initiate cleavage of the NOTCH receptor, releasing NICD which can initiate signal transduction in adjacent “signal-receiving” cells. We have recently shown that oHSV treatment of GBM cells induces NICD cleavage and NOTCH activation in adjacent uninfected glioma cells. RNA sequencing of GBM cells post-infection also uncovered Gene Ontology NOTCH signaling pathway to be significantly upregulated. This activation was induced by viral miRNA-H16, which represses FIH-1 expression. FIH-1 was found to be a negative regulator of Mib1, a ubiquitin ligase, which activates NOTCH ligand-mediated activation of adjacent signal-receiving cells bearing the NOTCH receptor (Otani et al Clin. Can. Res. 2020). Here we have investigated the impact of oHSV-induced NOTCH signaling on the tumor microenvironment. Treatment of brain tumors in immune competent mice with oHSV and NOTCH blocking gamma secretase inhibitor (GSI) induced an anti-tumor memory immune response. Long term survivors in mice treated with the combination also completely rejected subsequent tumor re-challenge in the other hemisphere. UMAP of flow cytometry of tumor-bearing hemispheres and functional analysis of isolated cellular fractions from treated mice showed a significant influx of MDSC cells after oHSV treatment that was rescued in mice treated with oHSV and GSI. Ongoing mechanistic studies are uncovering a significant induction of NOTCH in tumor associated macrophages that aids in recruitment of MDSC cells. Overall these studies have uncovered a significant impact of oHSV therapy on GBM tumor microenvironment and presents opportunities for combination therapies that can help improve therapeutic benefit and anti-tumor immunity.

scholarly journals An RBPJ-Drosophila Model Reveals Dependence of RBPJ Protein Stability on the Formation of Transcription–Regulator Complexes

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1252 ◽  
Author(s):  
Gahr ◽  
Brändle ◽  
Zimmermann ◽  
Nagel
Keyword(s):  
Protein Stability ◽  
Notch Signaling ◽  
Genome Engineering ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Model Systems ◽  
Congenital Diseases ◽  
Murine Homologue ◽  
Pathway Regulation ◽  
Signaling Activity

Notch signaling activity governs widespread cellular differentiation in higher animals, including humans, and is involved in several congenital diseases and different forms of cancer. Notch signals are mediated by the transcriptional regulator RBPJ in a complex with activated Notch (NICD). Analysis of Notch pathway regulation in humans is hampered by a partial redundancy of the four Notch receptor copies, yet RBPJ is solitary, allowing its study in model systems. In Drosophila melanogaster, the RBPJ orthologue is encoded by Suppressor of Hairless [Su(H)]. Using genome engineering, we replaced Su(H) by murine RBPJ in order to study its function in the fly. In fact, RBPJ largely substitutes for Su(H)’s function, yet subtle phenotypes reflect increased Notch signaling activity. Accordingly, the binding of RBPJ to Hairless (H) protein, the general Notch antagonist in Drosophila, was considerably reduced compared to that of Su(H). An H-binding defective RBPJLLL mutant matched the respective Su(H)LLL allele: homozygotes were lethal due to extensive Notch hyperactivity. Moreover, RBPJLLL protein accumulated at lower levels than wild type RBPJ, except in the presence of NICD. Apparently, RBPJ protein stability depends on protein complex formation with either H or NICD, similar to Su(H), demonstrating that the murine homologue underlies the same regulatory mechanisms as Su(H) in Drosophila. These results underscore the importance of regulating the availability of RBPJ protein to correctly mediate Notch signaling activity in the fly.

scholarly journals Notch pathway activation targets AML-initiating cell homeostasis and differentiation

2013 ◽  
Vol 210 (2) ◽  
pp. 301-319 ◽  
Author(s):  
Camille Lobry ◽  
Panagiotis Ntziachristos ◽  
Delphine Ndiaye-Lobry ◽  
Philmo Oh ◽  
Luisa Cimmino ◽  
...  
Keyword(s):  
Tumor Suppressor ◽  
Notch Signaling ◽  
Myeloproliferative Neoplasms ◽  
Notch Pathway ◽  
Notch Signaling Pathway ◽  
Notch Receptor ◽  
Pathway Activation ◽  
Function Models

Notch signaling pathway activation is known to contribute to the pathogenesis of a spectrum of human malignancies, including T cell leukemia. However, recent studies have implicated the Notch pathway as a tumor suppressor in myeloproliferative neoplasms and several solid tumors. Here we report a novel tumor suppressor role for Notch signaling in acute myeloid leukemia (AML) and demonstrate that Notch pathway activation could represent a therapeutic strategy in this disease. We show that Notch signaling is silenced in human AML samples, as well as in AML-initiating cells in an animal model of the disease. In vivo activation of Notch signaling using genetic Notch gain of function models or in vitro using synthetic Notch ligand induces rapid cell cycle arrest, differentiation, and apoptosis of AML-initiating cells. Moreover, we demonstrate that Notch inactivation cooperates in vivo with loss of the myeloid tumor suppressor Tet2 to induce AML-like disease. These data demonstrate a novel tumor suppressor role for Notch signaling in AML and elucidate the potential therapeutic use of Notch receptor agonists in the treatment of this devastating leukemia.

scholarly journals Targeting Notch signaling in autoimmune and lymphoproliferative disease

Blood ◽  
2008 ◽  
Vol 111 (2) ◽  
pp. 705-714 ◽  
Author(s):  
David T. Teachey ◽  
Alix E. Seif ◽  
Valerie I. Brown ◽  
Marlo Bruno ◽  
Ralph M. Bunte ◽  
...  
Keyword(s):  
T Cell ◽  
Notch Signaling ◽  
T Cell Activation ◽  
Cell Activation ◽  
Butyl Ester ◽  
Notch Pathway ◽  
Response To Treatment ◽  
Systemic Lupus Erythematosis ◽  
Gamma Secretase ◽  
Cell Functions

Patients with autoimmune lymphoproliferative syndrome (ALPS) and systemic lupus erythematosis (SLE) have T-cell dysregulation and produce abnormal, activated T lymphocytes and an atypical peripheral T-cell population, termed double negative T cells (DNTs). T-cell functions, including DNT transition in T-cell development and T-cell activation, are critically dependent on Notch signaling. We hypothesized that inhibiting Notch signaling would be effective in ALPS and SLE by reducing the production of abnormal DNTs and by blocking aberrant T-cell activation. We tested this hypothesis using murine models of ALPS and SLE. Mice were randomized to treatment with the notch pathway inhibitor (gamma-secretase inhibitor), N-S-phenyl-glycine-t-butyl ester (DAPT), or vehicle control. Response to treatment was assessed by measurement of DNTs in blood and lymphoid tissue, by monitoring lymph node and spleen size with ultrasound, by quantifying cytokines by bead-array, by ELISA for total IgG and anti–double-stranded DNA (dsDNA) specific antibodies, and by histopathologic assessment for nephritis. We found a profound and statistically significant decrease in all disease parameters, comparing DAPT-treated mice to controls. Using a novel dosing schema, we avoided the reported toxicities of gamma-secretase inhibitors. Inhibiting the Notch signaling pathway may thus present an effective, novel, and well-tolerated treatment for autoimmune and lymphoproliferative diseases.

Notch Signaling Is Necessary and Sufficient for Runx1-Dependent Stem Cell Induction in the Embryonic Aorta-Gonad-Mesonephros (AGM) Region.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4161-4161
Author(s):  
Caroline Erter Burns ◽  
Leonard I. Zon
Keyword(s):  
Stem Cell ◽  
Notch Signaling ◽  
Cell Fate ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Dorsal Aorta ◽  
Loss Of Function ◽  
Cardinal Vein ◽  
Hematopoietic Stem

Abstract Vertebrate hematopoiesis can be divided into two embryonic phases: a short primitive wave predominantly generating erythrocytes and a definitive (fetal/adult) wave producing long-term hematopoietic stem cells (HSCs). The definitive wave occurs in the embryonic aorta-gonad-mesonephros (AGM) region through the asymmetric induction of HSCs from the ventral, but not dorsal, aortic endothelial wall. Since Notch signaling is critical for orchestrating a variety of developmental cell fate choices from invertebrates to humans and has been implicated in affecting the differentiation of some hematopoietic lineages, we analyzed whether the Notch pathway regulates definitive HSC induction in vivo. The zebrafish mutant mindbomb harbors a mutation in an essential E3 ligase that ubiquitylates Delta, which in turn allows the Notch intercellular domain to be released and activate downstream target gene transcription. Thus, in the absence of Mindbomb function Notch signaling does not occur. We found that although mindbomb mutants show normal primitive hematopoiesis, definitive c-myb and runx1 HSC expression is lacking. Since embryos injected with synthetic morpholinos designed to inhibit proper splicing of runx1 RNA ( runx morphants) show the same hematopoietic phenotype as mindbomb mutants, we next addressed the epistatic relationship between notch and runx1 using classic gain-of-function and loss-of-function analyses. In runx1 morphants expression of a notch receptor, notch3, and a delta ligand, deltaC, in the developing dorsal aorta was normal. Moreover, injection of runx1 RNA rescued HSCs in the AGM of mindbomb mutants. Together, these results suggest that Runx1 functions downstream of Notch in promoting HSC fate. We next analyzed whether a constitutively activated form of Notch (NICD) is sufficient for HSC specification in the AGM using an inducible binary transgenic system. Zebrafish carrying the heat-shock promoter driving the activator gal4 were mated to animals carrying 6 gal4 -responsive tandem upstream activating sequences (UAS) driving NICD. At the 10 somite-stage the embryos were heat-shocked at 37°C for 1 hour to activate NICD throughout the double transgenic animals. Surprisingly, expression of both HSC markers, c-myb and runx1, were expanded from their normal restricted domain in the ventral endothelium to the entire circumference of the dorsal aorta. Most interestingly, the presence of ectopic c-myb and runx1 transcripts were observed in the developing post-cardinal vein, a vessel that normally does not produce HSCs. These data imply that activation of the Notch pathway generates increased numbers of HSCs in vivo. When runx1 RNA is injected into wild-type embryos a similar expansion of c-myb transcripts is seen throughout the entire dorsal aorta and post-cardinal vein, further indicating that Runx1 functions downstream of Notch in HSC induction. In summary, discovery of the molecular programs essential and sufficient for fetal/adult hematopoietic ontogeny will lead to a further understanding of the physiologic and pathologic processes regulating stem cell homeostasis and translate into more effective therapies for blood disorders.

Quantitative Proteomic Studies of gamma-Secretase Inhibition in Hodgkin Lymphoma Cells Reveal Novel Insights into Notch Signaling.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 963-963
Author(s):  
Jeremy C. Wallentine ◽  
David K. Crockett ◽  
Kojo S.J. Elenitoba-Johnson ◽  
Megan S. Lim
Keyword(s):  
Mass Spectrometry ◽  
Notch Signaling ◽  
Hodgkin Lymphoma ◽  
Butyl Ester ◽  
Proteolytic Cleavage ◽  
Notch Receptor ◽  
Differentially Expressed ◽  
Gamma Secretase ◽  
Differentially Expressed Proteins ◽  
Proteomic Approach

Abstract Notch signaling has been implicated in the regulation of Hodgkin lymphoma (HL) survival via NF-kappaB. Notch signaling is dependent on the interaction of ligands with the transmembrane notch receptor. Ligand binding triggers proteolytic cleavage of the intracellular notch domain with subsequent translocation to the nucleus and activation of transcription factors. Gamma-secretase which catalyzes the proteolytic cleavage and release of the notch intracellular domain is critical in the mediation of notch signaling. Inhibition of gamma-secretase using 7{N-[N-(3,5-difluorophenyl)-L-alanyl]-s-phenyl-glycine t-butyl ester} (DAPT) in rat fetal thymocytes significantly reduces the expression of notch target genes. We identified proteins released by HL-derived cells into conditioned media including multiple upstream and downstream components of the notch signaling cascade, specifically: notch1, notch2, jagged1, jagged2, HES2, Hes4, GATA2 and GATA5. A proteomic analysis of the differentially expressed proteins among DAPT treated and untreated cells will reveal potential novel downstream mediators of notch signaling, increasing our understanding of HL pathogenesis. We sought to identify the proteomic consequences of notch signaling inhibition in L428 HL cells using a mass spectrometry-based proteomic approach. Treatment of L428 HL cells with DAPT (50μM) resulted in decreased cell proliferation as measured by the MTT assay which was associated with induction of p27Kip1. We utilized an endoproteinase catalyzed O16/O18 differential isotopic strategy to quantitatively determine the global proteomic changes following inhibition of the notch signaling pathway using DAPT. Proteins were collected from the cell lysate of treated and non-treated L428 cells, subjected to O16/O18 labeling and then analyzed by reverse-phase liquid chromatography coupled with electrospray ionization tandem mass spectrometry. A total of 156 proteins with 2 or more unique peptides were identified as being differentially expressed between treated and non-treated L428 cells. Proteins of diverse location and function were identified. Importantly a large number of proteins involved in transcription (12%; RelB, TRRAP, RB-associated protein, NCOR1), and located in the nucleus (27%; H2AO, FUSE binding protein 1, ANC5, SMYD1) were identified. Other important functional categories of the identified proteins included signaling activity (28%), and catalytic activity (41%). Several known proteins regulated by notch and involved with the regulation of notch activity such as (Histone acetyltransferase PCAF, RelB, N-COR1) were identified and found to be under expressed in treated cells. In addition, novel proteins with transcriptional and cell signaling activities have been identified, representing unique pathways that may be directly or indirectly affected by notch signaling. Our study represents the first comprehensive analysis of differentially expressed proteins following the inhibition of notch signaling. These results provide novel insights into our understanding of the pathogenesis and the role of notch signaling in HL

scholarly journals The zebrafish reveals dependence of the mast cell lineage on Notch signaling in vivo

Blood ◽  
2012 ◽  
Vol 119 (15) ◽  
pp. 3585-3594 ◽  
Author(s):  
Sahar I. Da'as ◽  
Andrew J. Coombs ◽  
Tugce B. Balci ◽  
Chloe A. Grondin ◽  
Adolfo A. Ferrando ◽  
...  
Keyword(s):  
Mast Cell ◽  
Notch Signaling ◽  
Notch Pathway ◽  
Cell Development ◽  
Notch Receptor ◽  
Receptor Expression ◽  
Specific Marker ◽  
Dependent Manner ◽  
Hematopoietic Stem

We used the opportunities afforded by the zebrafish to determine upstream pathways regulating mast cell development in vivo and identify their cellular origin. Colocalization studies demonstrated zebrafish notch receptor expression in cells expressing carboxypeptidase A5 (cpa5), a zebrafish mast cell-specific marker. Inhibition of the Notch pathway resulted in decreased cpa5 expression in mindbomb mutants and wild-type embryos treated with the γ-secretase inhibitor, Compound E. A series of morpholino knockdown studies specifically identified notch1b and gata2 as the critical factors regulating mast cell fate. Moreover, hsp70::GAL4;UAS::nicd1a transgenic embryos overexpressing an activated form of notch1, nicd1a, displayed increased cpa5, gata2, and pu.1 expression. This increase in cpa5 expression could be reversed and reduced below baseline levels in a dose-dependent manner using Compound E. Finally, evidence that cpa5 expression colocalizes with lmo2 in the absence of hematopoietic stem cells revealed that definitive mast cells initially delineate from erythromyeloid progenitors. These studies identify a master role for Notch signaling in vertebrate mast cell development and establish developmental origins of this lineage. Moreover, these findings postulate targeting the Notch pathway as a therapeutic strategy in mast cell diseases.

scholarly journals A computational guided, functional validation of a novel therapeutic antibody proposes Notch signaling as a clinical relevant and druggable target in glioma

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dayana Herrera-Rios ◽  
Guanzhang Li ◽  
Dilaware Khan ◽  
Julia Tsiampali ◽  
Ann-Christin Nickel ◽  
...  
Keyword(s):  
Stem Cell ◽  
Cell Signaling ◽  
Notch Signaling ◽  
Notch Pathway ◽  
Therapy Resistance ◽  
Drug Candidate ◽  
Severe Toxicity ◽  
Gamma Secretase ◽  
Signaling Activity ◽  
Notch1 Receptor

Abstract The Notch signaling network determines stemness in various tissues and targeting signaling activity in malignant brain cancers by gamma-secretase inhibitors (GSI) has shown promising preclinical success. However, the clinical translation remains challenging due to severe toxicity side effects and emergence of therapy resistance. Better anti-Notch directed therapies, specifically directed against the tumor promoting Notch receptor 1 signaling framework, and biomarkers predicting response to such therapy are of highest clinical need. We assessed multiple patient datasets to probe the clinical relevance Notch1 activation and possible differential distribution amongst molecular subtypes in brain cancers. We functionally assessed the biological effects of the first-in-human tested blocking antibody against Notch1 receptor (brontictuzumab, BRON) in a collection of glioma stem-like cell (GSC) models and compared its effects to genetic Notch1 inhibition as well as classical pharmacological Notch inhibitor treatment using gamma-secretase inhibitor MRK003. We also assess effects on Wingless (WNT) stem cell signaling activation, which includes the interrogation of genetic WNT inhibition models. Our computed transcriptional Notch pathway activation score is upregulated in neural stem cells, as compared to astrocytes; as well as in GSCs, as compared to differentiated glioblastoma cells. Moreover, the Notch signature is clinical predictive in our glioblastoma patient discovery and validation cohort. Notch signature is significantly increased in tumors with mutant IDH1 genome and tumors without 1p and 19q co-deletion. In GSCs with elevated Notch1 expression, BRON treatment blocks transcription of Notch pathway target genes Hes1/Hey1, significantly reduced the amount of cleaved Notch1 receptor protein and caused significantly impairment of cellular invasion. Benchmarking this phenotype to those observed with genetic Notch1 inhibition in corresponding cell models did result in higher reduction of cell invasion under chemotherapy. BRON treatment caused signs of upregulation of Wingless (WNT) stem cell signaling activity, and vice versa, blockage of WNT signaling caused induction of Notch target gene expression in our models. We extend the list of evidences that elevated Notch signal expression is a biomarker signature declaring stem cell prevalence and useful for predicting negative clinical course in glioblastoma. By using functional assays, we validated a first in man tested Notch1 receptor specific antibody as a promising drug candidate in the context of neuro oncology and propose biomarker panel to predict resistance and therapy success of this treatment option. We note that the observed phenotype seems only in part due to Notch1 blockage and the drug candidate leads to activation of off target signals. Further studies addressing a possible emergence of therapy resistance due to WNT activation need to be conducted. We further validated our 3D disease modeling technology to be of benefit for drug development projects.

scholarly journals The Drosophila melanogaster Suppressor of deltex Gene, a Regulator of the Notch Receptor Signaling Pathway, Is an E3 Class Ubiquitin Ligase

Genetics ◽  
1999 ◽  
Vol 152 (2) ◽  
pp. 567-576 ◽  
Author(s):  
M Cornell ◽  
D A P Evans ◽  
R Mann ◽  
M Fostier ◽  
M Flasza ◽  
...  
Keyword(s):  
Notch Signaling ◽  
Signaling Pathway ◽  
Cell Fate ◽  
Ubiquitin Ligase ◽  
Notch Pathway ◽  
Notch Receptor ◽  
Negative Regulator ◽  
Loss Of Function ◽  
Wing Vein ◽  
Cell Fate Decisions

Abstract During development, the Notch receptor regulates many cell fate decisions by a signaling pathway that has been conserved during evolution. One positive regulator of Notch is Deltex, a cytoplasmic, zinc finger domain protein, which binds to the intracellular domain of Notch. Phenotypes resulting from mutations in deltex resemble loss-of-function Notch phenotypes and are suppressed by the mutation Suppressor of deltex [Su(dx)]. Homozygous Su(dx) mutations result in wing-vein phenotypes and interact genetically with Notch pathway genes. We have previously defined Su(dx) genetically as a negative regulator of Notch signaling. Here we present the molecular identification of the Su(dx) gene product. Su(dx) belongs to a family of E3 ubiquitin ligase proteins containing membrane-targeting C2 domains and WW domains that mediate protein-protein interactions through recognition of proline-rich peptide sequences. We have identified a seven-codon deletion in a Su(dx) mutant allele and we show that expression of Su(dx) cDNA rescues Su(dx) mutant phenotypes. Overexpression of Su(dx) also results in ectopic vein differentiation, wing margin loss, and wing growth phenotypes and enhances the phenotypes of loss-of-function mutations in Notch, evidence that supports the conclusion that Su(dx) has a role in the downregulation of Notch signaling.

Sign in / Sign up

Export Citation Format

Share Document