NOTCH3 signalling controls human trophoblast stem cell expansion and differentiation.

Failures in growth and differentiation of the early human placenta are associated with severe pregnancy disorders such as pre-eclampsia and fetal growth restriction. However, regulatory mechanisms controlling development of placental epithelial cells, the trophoblasts, remain poorly elucidated. Using trophoblast stem cells (TSCs), trophoblast organoids (TB-ORGs) and primary cytotrophoblasts (CTBs) of early pregnancy, we herein show that autocrine NOTCH3 signalling controls human placental expansion and differentiation. The NOTCH3 receptor was specifically expressed in proliferative CTB progenitors and its active form, the nuclear NOTCH3 intracellular domain (NOTCH3-ICD), interacted with the transcriptional co-activator mastermind-like 1 (MAML1). Doxycycline-inducible expression of dominant-negative MAML1 in TSC lines provoked cell fusion and upregulation of genes specific for multinucleated syncytiotrophoblasts, which are the differentiated hormone-producing cells of the placenta. However, progenitor expansion and markers of trophoblast stemness and proliferation were suppressed. Accordingly, inhibition of NOTCH3 signalling diminished growth of TB-ORGs, whereas overexpression of NOTCH3-ICD in primary CTBs and TSCs showed opposite effects. In conclusion, the data suggest that canonical NOTCH3 signalling plays a key role in human placental development by promoting self-renewal of CTB progenitors.

Notch signalling drives synovial fibroblast identity and arthritis pathology.

The synovium is a mesenchymal tissue composed mainly of fibroblasts, with a lining and sublining that surround the joints. In rheumatoid arthritis the synovial tissue undergoes marked hyperplasia, becomes inflamed and invasive, and destroys the joint1,2. It has recently been shown that a subset of fibroblasts in the sublining undergoes a major expansion in rheumatoid arthritis that is linked to disease activity3-5; however, the molecular mechanism by which these fibroblasts differentiate and expand is unknown. Here we identify a critical role for NOTCH3 signalling in the differentiation of perivascular and sublining fibroblasts that express CD90 (encoded by THY1). Using single-cell RNA sequencing and synovial tissue organoids, we found that NOTCH3 signalling drives both transcriptional and spatial gradients-emanating from vascular endothelial cells outwards-in fibroblasts. In active rheumatoid arthritis, NOTCH3 and Notch target genes are markedly upregulated in synovial fibroblasts. In mice, the genetic deletion of Notch3 or the blockade of NOTCH3 signalling attenuates inflammation and prevents joint damage in inflammatory arthritis. Our results indicate that synovial fibroblasts exhibit a positional identity that is regulated by endothelium-derived Notch signalling, and that this stromal crosstalk pathway underlies inflammation and pathology in inflammatory arthritis.

Human blood vessel organoids as a model of diabetic vasculopathy.

The increasing prevalence of diabetes has resulted in a global epidemic1. Diabetes is a major cause of blindness, kidney failure, heart attacks, stroke and amputation of lower limbs. These are often caused by changes in blood vessels, such as the expansion of the basement membrane and a loss of vascular cells2-4. Diabetes also impairs the functions of endothelial cells5 and disturbs the communication between endothelial cells and pericytes6. How dysfunction of endothelial cells and/or pericytes leads to diabetic vasculopathy remains largely unknown. Here we report the development of self-organizing three-dimensional human blood vessel organoids from pluripotent stem cells. These human blood vessel organoids contain endothelial cells and pericytes that self-assemble into capillary networks that are enveloped by a basement membrane. Human blood vessel organoids transplanted into mice form a stable, perfused vascular tree, including arteries, arterioles and venules. Exposure of blood vessel organoids to hyperglycaemia and inflammatory cytokines in vitro induces thickening of the vascular basement membrane. Human blood vessels, exposed in vivo to a diabetic milieu in mice, also mimic the microvascular changes found in patients with diabetes. DLL4 and NOTCH3 were identified as key drivers of diabetic vasculopathy in human blood vessels. Therefore, organoids derived from human stem cells faithfully recapitulate the structure and function of human blood vessels and are amenable systems for modelling and identifying the regulators of diabetic vasculopathy, a disease that affects hundreds of millions of patients worldwide.

A midposition NOTCH3 truncation in inherited cerebral small vessel disease may affect the protein interactome.

Mutations in NOTCH3 underlie cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), the most common inherited cerebral small vessel disease. Two cleavages of NOTCH3 protein, at Asp80 and Asp121, were previously described in CADASIL pathological samples. Using monoclonal antibodies developed against a NOTCH3 neoepitope, we identified a third cleavage at Asp964 between an Asp-Pro sequence. We characterized the structural requirements for proteolysis at Asp964 and the vascular distribution of the cleavage event. A proteome-wide analysis was performed to find proteins that interact with the cleavage product. Finally, we investigated the biochemical determinants of this third cleavage event. Cleavage at Asp964 was critically dependent on the proline adjacent to the aspartate residue. In addition, the cleavage product was highly enriched in CADASIL brain tissue and localized to the media of degenerating arteries, where it deposited with the two additional NOTCH3 cleavage products. Recombinant NOTCH3 terminating at Asp964 was used to probe protein microarrays. We identified multiple molecules that bound to the cleaved NOTCH3 more than to uncleaved protein, suggesting that cleavage may alter the local protein interactome within disease-affected blood vessels. The cleavage of purified NOTCH3 protein at Asp964 in vitro was activated by reducing agents and NOTCH3 protein; cleavage was inhibited by specific dicarboxylic acids, as seen with cleavage at Asp80 and Asp121. Overall, we propose homologous redox-driven Asp-Pro cleavages and alterations in protein interactions as potential mechanisms in inherited small vessel disease; similarities in protein cleavage characteristics may indicate common biochemical modulators of pathological NOTCH3 processing.

The role of Niemann-Pick type C2 in zebrafish embryonic development.

Niemann-Pick disease type C (NPC) is a rare, fatal, neurodegenerative lysosomal disease caused by mutations of either NPC1 or NPC2. NPC2 is a soluble lysosomal protein that functions in coordination with NPC1 to efflux cholesterol from the lysosomal compartment. Mutations of either gene result in the accumulation of unesterified cholesterol and other lipids in the late endosome/lysosome, and reduction of cellular cholesterol bioavailability. Zygotic null npc2m/m zebrafish showed significant unesterified cholesterol accumulation at larval stages, a reduction in body size, and motor and balance defects in adulthood. However, the phenotype at embryonic stages was milder than expected, suggesting a possible role of maternal Npc2 in embryonic development. Maternal-zygotic npc2m/m zebrafish exhibited significant developmental defects, including defective otic vesicle development/absent otoliths, abnormal head/brain development, curved/twisted body axes and no circulating blood cells, and died by 72 hpf. RNA-seq analysis conducted on 30 hpf npc2+/m and MZnpc2m/m embryos revealed a significant reduction in the expression of notch3 and other downstream genes in the Notch signaling pathway, suggesting that impaired Notch3 signaling underlies aspects of the developmental defects observed in MZnpc2m/m zebrafish.

Inhibition of Notch3/Hey1 ameliorates peribiliary hypoxia by preventing hypertrophic hepatic arteriopathy in biliary atresia progression.

Emerging evidence indicates the presence of vascular abnormalities and ischemia in biliary atresia (BA), although specific mechanisms remain undefined. This study examined both human and experimental BA. Structural and hemodynamic features of hepatic arteries were investigated by Doppler ultrasound, indocyanine green angiography, microscopic histology, and invasive arterial pressure measurement. Opal multiplex immunohistochemistry, western blot, and RT-PCR were applied to assess Notch3 expression and the phenotype of hepatic arterial smooth muscle cells (HASMCs). We established animal models of Notch3 inhibition, overexpression, and knockout to evaluate the differences in overall survival, hepatic artery morphology, peribiliary hypoxia, and HASMC phenotype. Hypertrophic hepatic arteriopathy was evidenced by an increased wall-to-lumen ratio and clinically manifested as hepatic arterial hypertension, decreased hepatic artery perfusion, and formation of hepatic subcapsular vascular plexuses (HSVPs). We observed a correlation between overactivation of Notch3 and phenotypic disruption of HASMCs with the exacerbation of peribiliary hypoxia. Notch3 signaling mediated the phenotype alteration of HASMCs, resulting in arterial wall thickening and impaired oxygen supply in the portal microenvironment. Inhibition of Notch3/Hey1 ameliorates portal hypoxia by restoring the balance of contractile/synthetic HASMCs, thereby preventing hypertrophic arteriopathy in BA.

A NOTCH3-CXCL12-driven myeloma-tumor niche signaling axis promotes chemoresistance in multiple myeloma.

Multiple myeloma (MM) remains incurable due to disease relapse and drug resistance. Notch signals from the tumor microenvironment (TME) confer chemoresistance, but the cellular and molecular mechanisms are not entirely understood. Using clinical and transcriptomic datasets, we found that NOTCH3 is upregulated in CD138+ cells from newly diagnosed MM (NDMM) patients compared to healthy individuals and increased in progression/relapsed MM (PRMM) patients. Further, NDMM patients with high NOTCH3 expression exhibited worse responses to bortezomib (BOR)-based therapies. Cells of the TME, including osteocytes, upregulated NOTCH3 in MM cells and protected them from apoptosis induced by BOR. NOTCH3 activation (NOTCH3OE) in MM cells decreased BOR anti-MM efficacy and its ability to improve survival in in vivo myeloma models. Molecular analyses revealed that NDMM and PRMM patients with high NOTCH3 exhibit CXCL12 upregulation. TME cells upregulated CXCL12 and activated the CXCR4 pathway in MM cells in a NOTCH3-dependent manner. Moreover, genetic or pharmacologic inhibition of CXCL12 in NOTCH3OE MM cells restored sensitivity to BOR regimes in vitro and in human bones bearing NOTCH3OE MM tumors cultured ex vivo. Our clinical and preclinical data unravel a novel NOTCH3-CXCL12 pro-survival signaling axis in the TME and suggest that osteocytes transmit chemoresistance signals to MM cells.

NRN1 interacts with Notch to increase oncogenic STAT3 signaling in melanoma.

BACKGROUND: Melanoma is a highly heterogeneous cancer, in which frequent changes in activation of signaling pathways lead to a high adaptability to ever changing tumor microenvironments. The elucidation of cancer specific signaling pathways is of great importance, as demonstrated by the inhibitor of the common BrafV600E mutation PLX4032 in melanoma treatment. We therefore investigated signaling pathways that were influenced by neurotrophin NRN1, which has been shown to be upregulated in melanoma. METHODS: Using a cell culture model system with an NRN1 overexpression, we investigated the influence of NRN1 on melanoma cells' functionality and signaling. We employed real time cell analysis and spheroid formation assays, while for investigation of molecular mechanisms we used a kinase phosphorylation kit as well as promotor activity analysis followed by mRNA and protein analysis. RESULTS: We revealed that NRN1 interacts directly with the cleaved intracellular domain (NICD) of Notch1 and Notch3, causing a potential retention of NICD in the cytoplasm and thereby reducing the expression of its direct downstream target Hes1. This leads to decreased sequestration of JAK and STAT3 in a Hes1-driven phosphorylation complex. Consequently, our data shows less phosphorylation of STAT3 while presenting an accumulation of total protein levels of STAT3 in association with NRN1 overexpression. The potential of the STAT3 signaling pathway to act in both a tumor suppressive and oncogenic manner led us to investigate specific downstream targets - namely Vegf A, Mdr1, cMet - which were found to be upregulated under oncogenic levels of NRN1. CONCLUSIONS: In summary, we were able to show that NRN1 links oncogenic signaling events between Notch and STAT3 in melanoma. We also suggest that in future research more attention should be payed to cellular regulation of signaling molecules outside of the classically known phosphorylation events.

Association of NOTCH3 With Elastic Fiber Dispersion in the Infrarenal Abdominal Aorta of Cynomolgus Monkeys.

BACKGROUND: The regional heterogeneity of vascular components and transcriptomes is an important determinant of aortic biology. This notion has been explored in multiple mouse studies. In the present study, we examined the regional heterogeneity of aortas in nonhuman primates. METHODS: Aortic samples were harvested from the ascending, descending thoracic, suprarenal, and infrarenal regions of young control monkeys and adult monkeys with high fructose consumption for 3 years. The regional heterogeneity of aortic structure and transcriptomes was examined by histological and bulk RNA sequencing analyses, respectively. RESULTS: Immunostaining of CD31 and αSMA (alpha-smooth muscle actin) revealed that endothelial and smooth muscle cells were distributed homogeneously across the aortic regions. In contrast, elastic fibers were less abundant and dispersed in the infrarenal aorta compared with other regions and associated with collagen deposition. Bulk RNA sequencing identified a distinct transcriptome related to the Notch signaling pathway in the infrarenal aorta with significantly increased NOTCH3 mRNA compared with other regions. Immunostaining revealed that NOTCH3 protein was increased in the media of the infrarenal aorta. The abundance of medial NOTCH3 was positively correlated with the dispersion of elastic fibers. Adult cynomolgus monkeys with high fructose consumption displayed vascular wall remodeling, such as smooth muscle cell loss and elastic fiber disruption, predominantly in the infrarenal region. The correlation between NOTCH3 and elastic fiber dispersion was enhanced in these monkeys. CONCLUSIONS: Aortas of young cynomolgus monkeys display regional heterogeneity of their transcriptome and the structure of elastin and collagens. Elastic fibers in the infrarenal aorta are dispersed along with upregulation of medial NOTCH3.

CBFB cooperates with p53 to maintain TAp73 expression and suppress breast cancer.

The CBFB gene is frequently mutated in several types of solid tumors. Emerging evidence suggests that CBFB is a tumor suppressor in breast cancer. However, our understanding of the tumor suppressive function of CBFB remains incomplete. Here, we analyze genetic interactions between mutations of CBFB and other highly mutated genes in human breast cancer datasets and find that CBFB and TP53 mutations are mutually exclusive, suggesting a functional association between CBFB and p53. Integrated genomic studies reveal that TAp73 is a common transcriptional target of CBFB and p53. CBFB cooperates with p53 to maintain TAp73 expression, as either CBFB or p53 loss leads to TAp73 depletion. TAp73 re-expression abrogates the tumorigenic effect of CBFB deletion. Although TAp73 loss alone is insufficient for tumorigenesis, it enhances the tumorigenic effect of NOTCH3 overexpression, a downstream event of CBFB loss. Immunohistochemistry shows that p73 loss is coupled with higher proliferation in xenografts. Moreover, TAp73 loss-of-expression is a frequent event in human breast cancer tumors and cell lines. Together, our results significantly advance our understanding of the tumor suppressive functions of CBFB and reveal a mechanism underlying the communication between the two tumor suppressors CBFB and p53.

NOTCH3 and Pulmonary Arterial Hypertension.

NOTCH3 receptor signaling has been linked to the regulation of smooth muscle cell proliferation and the maintenance of smooth muscle cells in an undifferentiated state. Pulmonary arterial hypertension (World Health Organization Group 1 idiopathic disease: PAH) is a fatal disease characterized clinically by elevated pulmonary vascular resistance caused by extensive vascular smooth muscle cell proliferation, perivascular inflammation, and asymmetric neointimal hyperplasia in precapillary pulmonary arteries. In this review, a detailed overview of the specific role of NOTCH3 signaling in PAH, including its mechanisms of activation by a select ligand, downstream signaling effectors, and physiologic effects within the pulmonary vascular tree, is provided. Animal models showing the importance of the NOTCH3 pathway in clinical PAH will be discussed. New drugs and biologics that inhibit NOTCH3 signaling and reverse this deadly disease are highlighted.

Hypoxia-inducible factor-1α and poly [ADP ribose] polymerase 1 cooperatively regulate Notch3 expression under hypoxia via a noncanonical mechanism.

Upregulation of Notch3 expression has been reported in many cancers and is considered a marker for poor prognosis. Hypoxia is a driving factor of the Notch3 signaling pathway; however, the induction mechanism and role of hypoxia-inducible factor-1α (HIF-1α) in the Notch3 response are still unclear. In this study, we found that HIF-1α and poly [ADP-ribose] polymerase 1 (PARP-1) regulate Notch3 induction under hypoxia via a noncanonical mechanism. In the analyzed cancer cell lines, Notch3 expression was increased during hypoxia at both the mRNA and protein levels. HIF-1α knockdown and Notch3 promoter reporter analyses indicated that the induction of Notch3 by hypoxia requires HIF-1α and also another molecule that binds the Notch3 promoter's guanine-rich region, which lacks the canonical hypoxia response element. Therefore, using mass spectrometry analysis to identify the binding proteins of the Notch3 promoter, we found that PARP-1 specifically binds to the Notch3 promoter. Interestingly, analyses of the Notch3 promoter reporter and knockdown of PARP-1 revealed that PARP-1 plays an important role in Notch3 regulation. Furthermore, we demonstrate that PARP inhibitors, including an inhibitor specific for PARP-1, attenuated the induction of Notch3 by hypoxia. These results uncover a novel mechanism in which HIF-1α associates with PARP-1 on the Notch3 promoter in a hypoxia response element-independent manner, thereby inducing Notch3 expression during hypoxia. Further studies on this mechanism could facilitate a better understanding of the broader functions of HIF-1α, the roles of Notch3 in cancer formation, and the insights into novel therapeutic strategies.

HIV-1 subtype B Tat enhances NOTCH3 signaling in astrocytes to mediate oxidative stress, inflammatory response, and neuronal apoptosis.

NOTCH receptors are relevant to multiple neurodegenerative diseases. However, the roles and mechanisms of NOTCH receptors in HIV-associated neurocognitive disorder (HAND) remain largely unclear. Transactivator of transcription (Tat) induces oxidative stress and inflammatory response in astrocytes, thereby leading to neuronal apoptosis in the central nervous system. We determined that NOTCH3 expression was upregulated during subtype B or C Tat expression in HEB astroglial cells. Moreover, bioinformatics analysis of the Gene Expression Omnibus (GEO) dataset revealed that NOTCH3 mRNA expression in the frontal cortex tissues of HIV encephalitis patients was higher than that of HIV control patients. Of note, subtype B Tat, rather than subtype C Tat, interacted with the extracellular domain of the NOTCH3 receptor, thus activating NOTCH3 signaling. Downregulation of NOTCH3 attenuated subtype B Tat-induced oxidative stress and reactive oxygen species generation. In addition, we demonstrated that NOTCH3 signaling facilitated subtype B Tat-activated NF-κB signaling pathway, thereby mediating pro-inflammatory cytokines IL-6 and TNF-α production. Furthermore, downregulation of NOTCH3 in HEB astroglial cells protected SH-SY5Y neuronal cells from astrocyte-mediated subtype B Tat neurotoxicity. Taken together, our study clarifies the potential role of NOTCH3 in subtype B Tat-induced oxidative stress and inflammatory response in astrocytes, which could be a novel therapeutic target for the relief of HAND.

Regulation of Hepatocytes in G0 and G1 Phases by NOTCH3 mRNA, miR-369-3p, and rno-Rmdn2_0006 during the Initial Stage of Rat Liver Regeneration.

The key event of liver regeneration initiation (LRI) is the switch of hepatocytes from the G0 phase to the G1 phase. This study aimed to use the data from large-scale quantitatively detecting and analyzing (LQDA) to reveal the regulation of hepatocytes in the G0 or G1 phase by competing endogenous RNAs (ceRNAs) during LRI. The hepatocytes of the rat liver right lobe were isolated 0, 6, and 24 h after partial hepatectomy. Their ceRNA expression level was measured using LQDA, and the correlation among their expression, interaction, and role was revealed by ceRNA comprehensive analysis. The expression of neurogenic loci notch homologous protein 3 (NOTCH3) mRNA was upregulated in 0 h, but the expression of miR-369-3p and rno-Rmdn2_0006 of hepatocytes did not change significantly. Meanwhile, the expression of the G0 phase-related gene CDKN1c was promoted by NOTCH3 upregulation, and the expression of the G1 phase-related gene PSEN2 was inhibited by NOTCH3 downregulation. On the contrary, the expression of NOTCH3 mRNA and rno-Rmdn2_0006 was upregulated at 6 h, but the expression of miR-136-3p was downregulated. The expression of the G1 phase-related genes CHUK, DDX24, HES1, NET1, and STAT3 was promoted by NOTCH3 upregulation, and the expression of the G0 phase-related gene CDKN1a was inhibited by NOTCH3 downregulation. These results suggested that the ceRNAs and the NOTCH3-regulated G0 phase- and G1 phase-related genes showed a correlation in expression, interaction, and role. They together regulated the hepatocytes in the G0 phase at 0 h and in the G1 phase at 6 h. These findings might help understand the mechanism by which ceRNA together regulated the hepatocytes in the G0 or G1 phase.

Notch1 and Notch3 coordinate for pericyte-induced stabilization of vasculature.

The Notch pathway regulates complex patterning events in many species and is critical for the proper formation and function of the vasculature. Despite this importance, how the various components of the Notch pathway work in concert is still not well understood. For example, NOTCH1 stabilizes homotypic endothelial junctions, but the role of NOTCH1 in heterotypic interactions is not entirely clear. NOTCH3, on the other hand, is essential for heterotypic interactions of pericytes with the endothelium, but how NOTCH3 signaling in pericytes impacts the endothelium remains elusive. Here, we use in vitro vascular models to investigate whether pericyte-induced stabilization of the vasculature requires the cooperation of NOTCH1 and NOTCH3. We observe that both pericyte NOTCH3 and endothelial NOTCH1 are required for the stabilization of the endothelium. Loss of either NOTCH3 or NOTCH1 decreases the accumulation of VE-cadherin at endothelial adherens junctions and increases the frequency of wider, more motile junctions. We found that DLL4 was the key ligand for simulating NOTCH1 activation in endothelial cells and observed that DLL4 expression in pericytes is dependent on NOTCH3. Altogether, these data suggest that an interplay between pericyte NOTCH3 and endothelial NOTCH1 is critical for pericyte-induced vascular stabilization.

Activation of Notch3 in osteoblasts/osteocytes causes compartment-specific changes in bone remodeling.

Notch receptors maintain skeletal homeostasis. NOTCH1 and 2 have been studied for their effects on bone remodeling. Although NOTCH3 plays a significant role in vascular physiology, knowledge about its function in other cellular environments, including bone, is limited. The present study was conducted to establish the function of NOTCH3 in skeletal cells using models of Notch3 misexpression. Microcomputed tomography demonstrated that Notch3 null mice did not have appreciable bone phenotypes. To study the effects of the NOTCH3 activation in the osteoblast lineage, BGLAP-Cre or Dmp1-Cre transgenics were crossed with RosaNotch3 mice, where the NOTCH3 intracellular domain is expressed following the removal of a loxP-flanked STOP cassette. Microcomputed tomography demonstrated that BGLAP-Cre;RosaNotch3 and Dmp1-Cre;RosaNotch3 mice of both sexes exhibited an increase in trabecular bone and in connectivity, with a decrease in cortical bone and increased cortical porosity. Histological analysis revealed a decrease in osteoclast number and bone resorption in trabecular bone and an increase in osteoclast number and void or pore area in cortical bone of RosaNotch3 mice. Bone formation was either decreased or could not be determined in Cre;RosaNotch3 mice. NOTCH3 activation in osteoblasts inhibited Alpl (alkaline phosphatase) and Bglap (osteocalcin) and induced Tnfsf11 (RANKL) and Tnfrsf11b (osteoprotegerin) mRNA, possibly explaining the trabecular bone phenotype. However, NOTCH3 induced Tnfsf11 and suppressed Tnfrsf11b in osteocytes, possibly explaining the cortical porosity. In conclusion, basal NOTCH3 is dispensable for skeletal homeostasis, whereas activation of NOTCH3 in osteoblasts/osteocytes inhibits osteoclastogenesis and bone resorption in cancellous bone but increases intracortical remodeling and causes cortical porosity.

PIM-induced phosphorylation of Notch3 promotes breast cancer tumorigenicity in a CSL-independent fashion.

Dysregulation of the developmentally important Notch signaling pathway is implicated in several types of cancer, including breast cancer. However, the specific roles and regulation of the four different Notch receptors have remained elusive. We have previously reported that the oncogenic PIM kinases phosphorylate Notch1 and Notch3. Phosphorylation of Notch1 within the second nuclear localization sequence of its intracellular domain (ICD) enhances its transcriptional activity and tumorigenicity. In this study, we analyzed Notch3 phosphorylation and its functional impact. Unexpectedly, we observed that the PIM target sites are not conserved between Notch1 and Notch3. Notch3 ICD (N3ICD) is phosphorylated within a domain, which is essential for formation of a transcriptionally active complex with the DNA-binding protein CSL. Through molecular modeling, X-ray crystallography, and isothermal titration calorimetry, we demonstrate that phosphorylation of N3ICD sterically hinders its interaction with CSL and thereby inhibits its CSL-dependent transcriptional activity. Surprisingly however, phosphorylated N3ICD still maintains tumorigenic potential in breast cancer cells under estrogenic conditions, which support PIM expression. Taken together, our data indicate that PIM kinases modulate the signaling output of different Notch paralogs by targeting distinct protein domains and thereby promote breast cancer tumorigenesis via both CSL-dependent and CSL-independent mechanisms.

S1P induces proliferation of pulmonary artery smooth muscle cells by promoting YAP-induced Notch3 expression and activation.

Sphingosine-1-phosphate (S1P), a natural multifunctional phospholipid, is highly increased in plasma from patients with pulmonary arterial hypertension and mediates proliferation of pulmonary artery smooth muscle cells (PASMCs) by activating the Notch3 signaling pathway. However, the mechanisms underpinning S1P-mediated induction of PASMCs proliferation remain unclear. In this study, using biochemical and molecular biology approaches, RNA interference and gene expression analyses, 5'-ethynyl-2'-deoxyuridine incorporation assay, and 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, we demonstrated that S1P promoted the activation of signal transducers and activators of transcription 3 (STAT3) through sphingosine-1-phosphate receptor 2 (S1PR2), and subsequently upregulated the expression of the microRNA miR-135b, which further reduced the expression of E3 ubiquitin ligase ß-transduction repeat-containing protein and led to a reduction in yes-associated protein (YAP) ubiquitinated degradation in PASMCs. YAP is the core effector of the Hippo pathway and mediates the expression of particular genes. The accumulation of YAP further increased the expression and activation of Notch3 and ultimately promoted the proliferation of PASMCs. In addition, we showed that preblocking S1PR2, prior silencing of STAT3, miR-135b, or YAP, and prior inhibition of Notch3 all attenuated S1P-induced PASMCs proliferation. Taken together, our study indicates that S1P stimulates PASMCs proliferation by activation of the S1PR2/STAT3/miR-135b/ß-transduction repeat-containing protein/YAP/Notch3 pathway, and our data suggest that targeting this cascade might have potential value in ameliorating PASMCs hyperproliferation and benefit pulmonary arterial hypertension.

Nidogen-2 Maintains the Contractile Phenotype of Vascular Smooth Muscle Cells and Prevents Neointima Formation via Bridging Jagged1-Notch3 Signaling.

BACKGROUND: How the extracellular matrix (ECM) microenvironment modulates the contractile phenotype of vascular smooth muscle cells (VSMCs) and confers vascular homeostasis remains elusive. METHODS: To explore the key ECM proteins in the maintenance of the contractile phenotype of VSMCs, we applied protein-protein interaction network analysis to explore novel ECM proteins associated with the VSMC phenotype. By combining in vitro and in vivo genetic mice vascular injury models, we identified nidogen-2, a basement membrane glycoprotein, as a key ECM protein for maintenance of vascular smooth muscle cell identity. RESULTS: We collected a VSMC phenotype-related gene dataset by using Gene Ontology annotation combined with a literature search. A computational analysis of protein-protein interactions between ECM protein genes and the genes from the VSMC phenotype-related gene dataset revealed the candidate gene nidogen-2, a basement membrane glycoprotein involved in regulation of the VSMC phenotype. Indeed, nidogen-2-deficient VSMCs exhibited loss of contractile phenotype in vitro, and compared with wild-type mice, nidogen-2-/- mice showed aggravated post-wire injury neointima formation of carotid arteries. Further bioinformatics analysis, coimmunoprecipitation assays, and luciferase assays revealed that nidogen-2 specifically interacted with Jagged1, a conventional Notch ligand. Nidogen-2 maintained the VSMC contractile phenotype via Jagged1-Notch3 signaling but not Notch1 or Notch2 signaling. Nidogen-2 enhanced Jagged1 and Notch3 interaction and subsequent Notch3 activation. Reciprocally, Jagged1 and Notch3 interaction, signaling activation, and Jagged1-triggered VSMC differentiation were significantly repressed in nidogen-2-deficient VSMCs. In accordance, the suppressive effect of Jagged1 overexpression on neointima formation was attenuated in nidogen-2-/- mice compared with wild-type mice. CONCLUSIONS: Nidogen-2 maintains the contractile phenotype of VSMCs through Jagged1-Notch3 signaling in vitro and in vivo. Nidogen-2 is required for Jagged1-Notch3 signaling.

Omega-3 fatty acids impair miR-1-3p-dependent Notch3 down-regulation and alleviate sepsis-induced intestinal injury.

BACKGROUND: Sepsis is a troublesome syndrome that can cause intestinal injury and even high mortality rates. Omega-3 fatty acids (FAs) are known to protect against intestinal damage. Accordingly, the current study set out to explore if omega-3 FAs could affect sepsis-induced intestinal injury with the involvement of the microRNA (miR)-1-3p/Notch3-Smad axis. METHODS: First, cecal ligation and perforation (CLP) was performed to establish septic mouse models in C57BL/6J mice, and mouse intestinal epithelial MODE-K cells were induced by lipopolysaccharide (LPS) to establish sepsis cell models. The CLP-induced septic mice or LPS-exposed cells were subjected to treatment with Omega-3 FAs and activin (Smad signaling activator), miR-1-3p inhibitor and over-expressed/short hairpin RNA (oe-/sh)-Notch3 to explore their roles in inflammation, intestinal oxidative stress and cell apoptosis. A dual-luciferase reporter gene assay was further performed to verify the regulatory relationship between miR-1-3p and Notch3. RESULTS: Omega-3 FAs inhibited CLP-induced intestinal injury and ameliorated LPS-induced intestinal epithelial cell injury by down-regulating miR-1-3p, as evidenced by decreased levels of tumor necrosis factor-α, interleukin-1ß (IL-1ß) and IL-6, in addition to diminished levels of reactive oxygen species, malondialdehyde levels and superoxide dismutase activity. Furthermore, miR-1-3p could down-regulate Notch3, which inactivated the Smad pathway. CONCLUSION: Collectively, our findings indicated that omega-3 FAs elevate the expression of Notch3 by down-regulating miR-1-3p, and then blocking the Smad pathway to alleviate intestinal epithelial inflammation and oxidative stress injury caused by sepsis.