Novel biochemical pathways of endoglin in vascular cell physiology

19 p.-3 fig.The broad role of the transforming growth factor beta (TGFβ) signaling pathway in vascular development, homeostasis, and repair is well appreciated. Endoglin is emerging as a novel, complex, and poorly understood regulatory component of the TGFβ receptor complex, whose importance is underscored by its recognition as the site of mutations causing hereditary hemorrhagic telangiectasia (HHT) [McAllister et al., 1994]. Extensive analyses of endoglin function in normal developmental mouse models [Bourdeau et al., 1999; Li et al., 1999; Arthur et al., 2000] and in HHT animal models [Bourdeau et al., 2000; Torsney et al., 2003] exemplify the importance of understanding endoglin's biochemical functions. However, novel mechanisms underlying the regulation of these pathways continue to emerge. These mechanisms include modification of TGFβ receptor signaling at the ligand and receptor activation level, direct effects of endoglin on cell adhesion and migration, and emerging roles for endoglin in the determination of stem cell fate and tissue patterning. The purpose of this review is to highlight the cellular and molecular studies that underscore the central role of endoglin in vascular development and diseaseC.P.H.V. was supported by NIH grants RR15555 from the COBRE program of the National Center for Research Resources, R01-HL083151 from the NIH National Heart, Lung and Blood Institute, and the Maine Cancer Foundation. The research work of C.B. was supported by grants from the Ministerio de Educación y Ciencia (SAF2004-01390) and the Instituto de Salud Carlos III (ISCIII-CIBER CB/06/07/0038) of SpainPeer reviewe

Functional blockade of Smad4 leads to a decrease in β-catenin levels and signaling activity in human pancreatic carcinoma cells

El pdf del artículo es la versión de autor.In the last several years, many laboratories have tried to unravel the complex signaling mechanisms activated by TGF-β1 in transformed cells. Smad proteins are the principal mediators of the transforming growth factor β (TGF-β) response, but this factor can also activate Smad-independent pathways in different cell types. Our previous studies in murine keratinocytes led to the identification of a cooperation between oncogenic Ras and Smad4 inactivation during malignant progression. We further investigated the function of Smad4 in human pancreatic cancer, in which loss-of-function mutations affecting Smad4 occur with a 50% frequency. Expression of a dominant-negative Smad4 construct in the adenocarcinoma cell line PANC-1 led to increased ubiquitination and proteasomal degradation of β-catenin. Moreover, loss of Smad4 abrogated β-catenin-signaling activity and was associated with a reduction of the tumorigenic potential of PANC-1 cells in scid mice. Although the expression of the dominant-negative Smad4 blocked TGF-β1/Smad2,3-signaling activity, the above-mentioned effects of Smad4 on β-catenin stability were independent of the TGF-β1/Smad2,3-signaling pathway. These findings provide evidence for a cross talk between Smad4 and the Wnt/β-catenin pathway in pancreatic carcinoma cells, suggesting a new role for Smad4 as an attenuator of β-catenin proteasomal degradation. © The Author 2008. Published by Oxford University Press. All rights reserved.Ministerio de Ciencia y Tecnologia (SAF2004-04902) to M.Q.; fellowship for Training and Specialization of Postgraduates from Centro Superior de Investigaciones Cientificas to D.R.Peer Reviewe

Notch signal integration in the vasculature during remodeling.

Notch signaling plays many important roles in homeostasis and remodeling in the vessel wall, and serves a critical role in the communication between endothelial cells and smooth muscle cells. Within blood vessels, Notch signaling integrates with multiple pathways by mechanisms including direct protein–protein interaction, cooperative or synergistic regulation of signal cascades, and co-regulation of transcriptional targets. After establishment of the mature blood vessel, the spectrum and intensity of Notch signaling change during phases of active remodeling or disease progression. These changes can be mediated by regulation via microRNAs and protein stability or signaling, and corresponding changes in complementary signaling pathways. Notch also affects endothelial cells on a system level by regulating key metabolic components. This review will outline the most recent findings of Notch activity in blood vessels, with a focus on how Notch signals integrate with other molecular signaling pathways controlling vascular phenotype

Functional blockade of Smad4 leads to a decrease in β-catenin levels and signaling activity in human pancreatic carcinoma cells

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Cryptic collagen IV promotes cell migration and adhesion in myeloid leukemia.

Previously, we showed that discoidin domain receptor 1 (DDR1), a class of collagen-activated receptor tyrosine kinase (RTK) was highly upregulated on bone marrow (BM)-derived CD33+ leukemic blasts of acute myeloid leukemia (AML) patients. Herein as DDR1 is a class of collagen-activated RTK, we attempt to understand the role of native and remodeled collagen IV in BM microenvironment and its functional significance in leukemic cells. Exposure to denatured collagen IV significantly increased the migration and adhesion of K562 cells, which also resulted in increased activation of DDR1 and AKT. Further, levels of MMP9 were increased in conditioned media (CM) of denatured collagen IV exposed cells. Mass spectrometric liquid chromatography/tandem mass spectrometry QSTAR proteomic analysis revealed exclusive presence of Secretogranin 3 and InaD-like protein in the denatured collagen IV CM. Importantly, BM samples of AML patients exhibited increased levels of remodeled collagen IV compared to native as analyzed via anti-HUIV26 antibody. Taken together, for the first time, we demonstrate that remodeled collagen IV is a potent activator of DDR1 and AKT that also modulates both migration and adhesion of myeloid leukemia cells. Additionally, high levels of the HUIV26 cryptic collagen IV epitope are expressed in BM of AML patients. Further understanding of this phenomenon may lead to the development of therapeutic agents that directly modulate the BM microenvironment and attenuate leukemogenesis

AHNAK2 participates in the stress-induced nonclassical FGF1 secretion pathway.

FGF1 is a nonclassically released growth factor that regulates carcinogenesis, angiogenesis, and inflammation. In vitro and in vivo, FGF1 export is stimulated by cell stress. Upon stress, FGF1 is transported to the plasma membrane where it localizes prior to transmembrane translocation. To determine which proteins participate in the submembrane localization of FGF1 and its export, we used immunoprecipitation mass spectrometry to identify novel proteins that associate with FGF1 during heat shock. The heat shock-dependent association of FGF1 with the large protein AHNAK2 was observed. Heat shock induced the translocation of FGF1 and AHNAK2 to the cytoskeletal fraction. In heat-shocked cells, FGF1 and the C-terminal fragment of AHNAK2 colocalized with F-actin in the vicinity of the cell membrane. Depletion of AHNAK2 resulted in a drastic decrease of stress-induced FGF1 export but did not affect spontaneous FGF2 export and FGF1 release induced by the inhibition of Notch signaling. Thus, AHNAK2 is an important element of the FGF1 nonclassical export pathway

Mechanisms of TGF-β-induced differentiation in human vascular smooth muscle cells.

BACKGROUND: Transforming growth factor-β (TGF-β) plays an important role in vascular homeostasis through effects on vascular smooth muscle cells (SMC). Fine-tuning of TGF-β signaling occurs at the level of ALK receptors or Smads, and is regulated with cell type specificity. METHODS: Our goal was to understand TGF-β signaling in regulating SMC differentiation marker expression in human SMC. Activation of Smads was characterized, and loss- and gain-of-function reagents used to define ALK pathways. In addition, Smad-independent mechanisms were determined. RESULTS: TGF-β type I receptors, ALK1 and ALK5, are expressed in human SMC, and TGF-β1 phosphorylates Smad1/5/8 and Smad2/3 in a time- and dosage-dependent pattern. ALK5 activity, not bone morphogenetic protein type I receptors, is required for Smad phosphorylation. Endoglin, a TGF-β type III receptor, is a TGF-β1 target in SMC, yet endoglin does not modify TGF-β1 responsiveness. ALK5, not ALK1, is required for TGF-β1-induction of SMC differentiation markers, and ALK5 signals through an ALK5/Smad3- and MAP kinase-dependent pathway. CONCLUSION: The definition of the specific signaling downstream of TGF-β regulating SMC differentiation markers will contribute to a better understanding of vascular disorders involving changes in SMC phenotype

Cancer incidence in patients with hereditary hemorrhagic telangiectasia.

PURPOSE: Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by deficiency in endoglin, an angiogenic protein. We previously showed that HHT, in which systemic endoglin expression is reduced, was associated with better survival outcomes in cancer patients (Duarte et al. in Cancer Epidemiol Biomarkers Prev 23:117-125, 2014). Here, we evaluated whether HHT was associated with reduced cancer incidence. METHODS: A matched case-control analysis using SEER Medicare was conducted to evaluate the effect of HHT on diagnosis with breast, colorectal, lung, or prostate cancer between 2000 and 2007 (n = 633,162). Cancer and non-cancer patients were matched on age, sex, SEER registry region, and length of the ascertainment period for HHT. We assessed crude association using a McNemar\u27s test and then adjusted for demographic variables, cancer type, cancer stage, comorbidities, and ascertainment period with a conditional logistic regression model for cancer incidence. RESULTS: The McNemar\u27s test showed no significant association between HHT and cancer incidence (p = 0.74). Adjusting for covariates with the conditional logistic regression model did not change the result [HHT odds ratio 0.978; 95 % CI (0.795, 1.204)]. The lack of association between HHT and cancer incidence is unexpected given the previously discovered significant association between HHT and improved survival outcomes (Duarte et al. in Cancer Epidemiol Biomarkers Prev 23:117-125, 2014). CONCLUSIONS: We conclude that the protective effect of reduced systemic endoglin expression in cancer is specific to cancer progression through its effect on vascularization and other stromal effects but does not extend to cancer initiation