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Cecilia M Giachelli - One of the best experts on this subject based on the ideXlab platform.
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the role of osteoprotegerin and tumor necrosis Factor related apoptosis inducing ligand in human microvascular endothelial cell survival
Molecular Biology of the Cell, 2004Co-Authors: L B Pritzker, Marta Scatena, Cecilia M GiachelliAbstract:Endothelial cell survival and antiapoptotic pathways, including those stimulated by extracellular matrix, are critical regulators of vasculogenesis, angiogenesis, endothelial repair, and shear-stress-induced endothelial activation. One of these pathways is mediated by αvβ3 integrin ligation, downstream activation of nuclear Factor-κB, and subsequent up-regulation of osteoprotegerin (OPG). In this study, the mechanism by which OPG protects endothelial cells from death was examined. Serum-starved human microvascular endothelial cells (HMECs) plated on the αvβ3 ligand osteopontin were protected from cell death. Immunoprecipitation experiments indicated that OPG formed a complex with tumor necrosis Factor-related apoptosis-inducing ligand (TRAIL) in HMECs under these conditions. Furthermore, inhibitors of TRAIL, including recombinant soluble TRAIL receptors and a neutralizing antibody against TRAIL, blocked apoptosis of serum-starved HMECs plated on the nonintegrin Attachment Factor poly-d-lysine. Whereas TRAIL was unable to induce apoptosis in HMECs plated on osteopontin, the addition of recombinant TRAIL did increase the percentage of apoptotic HMECs plated on poly-d-lysine. This evidence indicates that OPG blocks endothelial cell apoptosis through binding TRAIL and preventing its interaction with death-inducing TRAIL-receptors
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the role of osteoprotegerin and tumor necrosis Factor related apoptosis inducing ligand in human microvascular endothelial cell survival
Molecular Biology of the Cell, 2004Co-Authors: L B Pritzker, Marta Scatena, Cecilia M GiachelliAbstract:Endothelial cell survival and antiapoptotic pathways, including those stimulated by extracellular matrix, are critical regulators of vasculogenesis, angiogenesis, endothelial repair, and shear-stress-induced endothelial activation. One of these pathways is mediated by alpha(v)beta(3) integrin ligation, downstream activation of nuclear Factor-kappaB, and subsequent up-regulation of osteoprotegerin (OPG). In this study, the mechanism by which OPG protects endothelial cells from death was examined. Serum-starved human microvascular endothelial cells (HMECs) plated on the alpha(v)beta(3) ligand osteopontin were protected from cell death. Immunoprecipitation experiments indicated that OPG formed a complex with tumor necrosis Factor-related apoptosis-inducing ligand (TRAIL) in HMECs under these conditions. Furthermore, inhibitors of TRAIL, including recombinant soluble TRAIL receptors and a neutralizing antibody against TRAIL, blocked apoptosis of serum-starved HMECs plated on the nonintegrin Attachment Factor poly-d-lysine. Whereas TRAIL was unable to induce apoptosis in HMECs plated on osteopontin, the addition of recombinant TRAIL did increase the percentage of apoptotic HMECs plated on poly-d-lysine. This evidence indicates that OPG blocks endothelial cell apoptosis through binding TRAIL and preventing its interaction with death-inducing TRAIL-receptors
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osteoprotegerin is an αvβ3 induced nf κb dependent survival Factor for endothelial cells
Journal of Biological Chemistry, 2000Co-Authors: Uriel M Malyankar, Marta Scatena, Katherine L Suchland, Edward A Clark, Cecilia M GiachelliAbstract:Abstract Osteopontin protects endothelial cells from apoptosis induced by growth Factor withdrawal. This interaction is mediated by the αvβ3 integrin and is NF-κB-dependent (Scatena, M., Almeida, M., Chaisson, M. L., Fausto, N., Nicosia, R. F., and Giachelli, C. M. (1998) J. Cell Biol. 141, 1083–1093). In the present study we used differential cloning to identify osteopontin-induced, NF-κB-dependent genes in endothelial cells. One of the genes identified in this screen was osteoprotegerin, a member of the tumor necrosis Factor receptor superfamily. By Northern and Western blot analysis, osteoprotegerin mRNA and protein levels were very low in endothelial cells plated on the non-integrin cell Attachment Factor, poly-d-lysine. In contrast, osteoprotegerin mRNA and protein levels were induced 5–7-fold following αvβ3 ligation by osteopontin. Osteoprotegerin induction by osteopontin was time-dependent and observed as early as 3 h following treatment. NF-κB inactivation achieved by over expression of an IκB super repressor in endothelial cells completely inhibited osteoprotegerin induction by osteopontin. Finally, purified osteoprotegerin protected endothelial cells with inactive NF-κB from apoptosis induced by growth Factor deprivation. These data suggest that αvβ3-mediated endothelial survival depends on osteoprotegerin induction by NF-κB and indicate a new function for osteoprotegerin in endothelial cells.
Frank O Fackelmayer - One of the best experts on this subject based on the ideXlab platform.
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arginine methylation of scaffold Attachment Factor a by heterogeneous nuclear ribonucleoprotein particle associated prmt1
Journal of Biological Chemistry, 2004Co-Authors: Frank Herrmann, Maike Bossert, Andrea Schwander, Ercan Akgun, Frank O FackelmayerAbstract:Components of the heterogeneous nuclear ribonucleoprotein (hnRNP) complex and other nucleic acid-binding proteins are subject to methylation on specific arginine residues by the catalytic activity of arginine methyltransferases. The methylation has been implicated in transcriptional regulation and RNA and protein trafficking and signal transduction, but the mechanism by which these functions are achieved has remained undetermined. We show here that the predominant arginine methyltransferase in human cells, protein arginine methyltransferase 1 (PRMT1), is associated with hnRNP complexes, dependent on the methylation status of the cell, and that it methylates its preferred substrates in situ. Binding of PRMT1 occurs through physical interaction with scaffold Attachment Factor A (SAF-A), also known as hnRNP-U, which is quantitatively methylated by PRMT1 in all investigated cell lines as determined by a novel, highly specific, methylation-sensitive antibody.
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scaffold Attachment Factor a saf a is concentrated in inactive x chromosome territories through its rgg domain
Chromosoma, 2003Co-Authors: Roger Helbig, Frank O FackelmayerAbstract:Female mammalian cells inactivate transcription from one of their X chromosomes to equalize gene expression of X-linked genes between males and females. Inactivation is a multistep process that involves a large non-coding RNA termed XIST, a variety of epigenetic modifications of chromatin, and alterations in protein composition such as enrichment of the histone variant macroH2A. We show here that inactive X chromosomes are also enriched in a well-characterized protein component of the nuclear scaffold, SAF-A. This protein has been implicated in chromatin organization, owing to its high specificity for scaffold-associated region (SAR)-DNA, in transcriptional regulation, e.g. of hormone-regulated genes, owing to its functional interaction with steroid receptors, and in RNA processing, owing to its interaction with RNA and heterogeneous nuclear ribonucleoprotein (hnRNP) particles. After near complete removal of DNA and associated chromatin proteins such as macroH2A, SAF-A remains with the “nuclear matrix”, still highlighting the former position of inactive X chromosomes. Interestingly, the enrichment of SAF-A in the inactive X chromosome depends on the RNA binding domain of the protein, the RGG box, raising the possibility that interaction of SAF-A with XIST RNA may contribute to the silencing of X-linked genes by local changes in nuclear architecture.
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the scaffold matrix Attachment region binding protein hnrnp u saf a is directly bound to chromosomal dna in vivo a chemical cross linking study
Biochemistry, 1997Co-Authors: Frank Gohring, Frank O FackelmayerAbstract:The protein heterogeneous nuclear ribonucleoprotein U (hnRNP-U, also known as scaffold Attachment Factor A, SAF-A) is an abundant component of hnRNP particles and of the nuclear matrix. Previous experiments have demonstrated that, in vitro, hnRNP-U specifically binds to scaffold/matrix Attachment (S/MAR) region DNA elements and could thus be involved in higher order chromatin structure. In this paper we report on the use of chemical cross-linking to investigate whether the protein is also bound to DNA in vivo, which is a prerequisite for its presumed function in chromatin loop formation. We have improved published methods for cross-linking proteins to DNA with the aim to minimize unspecific fixation and possible contamination with RNA binding proteins. Our protocol is based on a limited cross-linking of living human cells with formaldehyde, followed by the purification of DNA/protein complexes by two consecutive cesium chloride density gradient centrifugations. Analysis of the protein constituents of thes...
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characterization of saf a a novel nuclear dna binding protein from hela cells with high affinity for nuclear matrix scaffold Attachment dna elements
The EMBO Journal, 1992Co-Authors: Helmut Romig, Frank O Fackelmayer, Andrea Renz, Uwe Ramsperger, Arndt RichterAbstract:We identified four proteins in nuclear extracts from HeLa cells which specifically bind to a scaffold Attachment region (SAR) element from the human genome. Of these four proteins, SAF-A (scaffold Attachment Factor A), shows the highest affinity for several homologous and heterologous SAR elements from vertebrate cells. SAF-A is an abundant nuclear protein and a constituent of the nuclear matrix and scaffold. The homogeneously purified protein is a novel double stranded DNA binding protein with an apparent molecular weight of 120 kDa. SAF-A binds at multiple sites to the human SAR element; competition studies with synthetic polynucleotides indicate that these sites most probably reside in the multitude of A/T-stretches which are distributed throughout this element. In addition we show by electron microscopy that the protein forms large aggregates and mediates the formation of looped DNA structures.
Stefan Pöhlmann - One of the best experts on this subject based on the ideXlab platform.
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analysis of the interaction of ebola virus glycoprotein with dc sign dendritic cell specific intercellular adhesion molecule 3 grabbing nonintegrin and its homologue dc signr
The Journal of Infectious Diseases, 2007Co-Authors: Andrea Marzi, Peggy Moller, Sheri L Hanna, Thomas Harrer, Jutta Eisemann, Alexander Steinkasserer, Stephan Becker, Frederic Baribaud, Stefan PöhlmannAbstract:Background. The lectin DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin) augments Ebola virus (EBOV) infection. However, it its unclear whether DC-SIGN promotes only EBOV Attachment (Attachment Factor function, nonessential) or actively facilitates EBOV entry (receptor function, essential). Methods. We investigated whether DC-SIGN on B cell lines and dendritic cells acts as an EBOV Attachment Factor or receptor. Results. Engineered DC-SIGN expression rendered some B cell lines susceptible to EBOV glycoprotein (EBOV GP)-driven infection, whereas others remained refractory, suggesting that cellular Factors other than DC-SIGN are also required for susceptibility to EBOV infection. Augmentation of entry was independent of efficient DC-SIGN internalization and might not involve lectin-mediated endocytic uptake of virions. Therefore, DC-SIGN is unlikely to function as an EBOV receptor on B cell lines; instead, it might concentrate virions onto cells, thereby allowing entry into cell lines expressing low levels of endogenous receptor(s). Indeed, artificial concentration of virions onto cells mirrored DC-SIGN expression, confirming that optimization of viral Attachment is sufficient for EBOV GP-driven entry into some B cell lines. Finally, EBOV infection of dendritic cells was only partially dependent on mannose-specific lectins, such as DC-SIGN, suggesting an important contribution of other Factors. Conclusions. Our results indicate that DC-SIGN is not an EBOV receptor but, rather, is an Attachment-promoting Factor that boosts entry into B cell lines susceptible to low levels of EBOV GP-mediated infection.
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Attachment Factor and receptor engagement of sars coronavirus and human coronavirus nl63
Advances in Experimental Medicine and Biology, 2006Co-Authors: Heike Hofmann, Lia Van Der Hoek, Krzysztof Pyrc, Ben Berkhout, Thomas Gramberg, Andrea Marzi, Martina Geier, Stefan PöhlmannAbstract:The cellular membrane constitutes a physical barrier against viral infection. Enveloped viruses developed specialized proteins to overcome this barrier. These proteins, which are often extensively glycosylated, are inserted into the viral membrane and mediate both recognition of target cells and fusion of the viral membrane with a host cell membrane. The latter process allows introduction of the viral genome and associated viral proteins into the host cell lumen and is therefore critical for establishment of productive infection. which in the case of coronaviruses (CoV) are termed spike (S) proteins, are attractive targets for inhibitors and vaccines. Enveloped viruses evolved two prototypes of glycoproteins to enter target cells, termed class I and class II fusion proteins. 4 Class I fusion proteins are found in, e.g., retroviruses and paramyxoviruses, while, e.g., flaviviruses and alphaviruses encode class II fusion proteins. Both types of fusion proteins exhibit a distinct functional organization, which is reflected by their different spatial orientations. Thus, class I fusion proteins are oriented perpendicular to the cellular membrane and are visible as spikes in electron micrographs, while class II proteins are oriented horizontally relative to the cellular membrane and are well ordered on the virion surface. Viral class I fusion proteins are organized into a globular surface unit (SU), which interacts with cellular receptors, and a transmembrane unit (TM), which harbors highly conserved sequence elements required for membrane fusion. Membrane fusion is initiated by binding of SU to cellular receptor(s) or by exposure of the glycoprotein to low pH, which triggers conformational changes in the glycoprotein that activate TM. TM-driven membrane fusion is initiated by insertion of a N-terminal fusion peptide into the target cell membrane, followed by
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dc signr a dc sign homologue expressed in endothelial cells binds to human and simian immunodeficiency viruses and activates infection in trans
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Stefan Pöhlmann, Frederic Baribaud, Elizabeth J Soilleux, George J Leslie, Lesley S Morris, John Trowsdale, Benhur Lee, Nicholas Coleman, Robert W DomsAbstract:DC-SIGN, a C-type lectin expressed on the surface of dendritic cells (DCs), efficiently binds and transmits HIVs and simian immunodeficiency viruses to susceptible cells in trans. A DC-SIGN homologue, termed DC-SIGNR, has recently been described. Herein we show that DC-SIGNR, like DC-SIGN, can bind to multiple strains of HIV-1, HIV-2, and simian immunodeficiency virus and transmit these viruses to both T cell lines and human peripheral blood mononuclear cells. Binding of virus to DC-SIGNR was dependent on carbohydrate recognition. Immunostaining with a DC-SIGNR-specific antiserum showed that DC-SIGNR was expressed on sinusoidal endothelial cells in the liver and on endothelial cells in lymph node sinuses and placental villi. The presence of this efficient virus Attachment Factor on multiple endothelial cell types indicates that DC-SIGNR could play a role in the vertical transmission of primate lentiviruses, in the enabling of HIV to traverse the capillary endothelium in some organs, and in the presentation of virus to CD4-positive cells in multiple locations including lymph nodes.
Steffi Oesterreich - One of the best experts on this subject based on the ideXlab platform.
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novel role of the ret finger protein in estrogen receptor mediated transcription in mcf 7 cells
Biochemical and Biophysical Research Communications, 2006Co-Authors: Steven M Townson, Kaiyan Kang, Steffi OesterreichAbstract:Abstract The Scaffold Attachment Factor B1 (SAFB1) is an estrogen receptor (ESR1) repressor that has been proposed to inhibit breast tumorigenesis. To obtain insight into the functions of SAFB1 we utilized a yeast two-hybrid screen and identified the Ret finger protein (RFP) as interacting with the SAFB1 C-terminus. RFP is a member of the trimotif (TRIM) family of proteins, which we found widely expressed in a series of breast cancer cell lines. We confirmed the interaction between SAFB1 and RFP through in vitro (GST-pull-down) and in vivo (coimmunoprecipitations) assays. We hypothesized that SAFB1 functions as a scaffolding protein to recruit proteins such as RFP into proximity with ESR1. Consequently, we asked whether RFP would modulate ESR1 activity and we discovered that RFP was important for the ESR1-dependent expression of cyclin D1 (CCND1) and the progesterone receptor (PR), but not IRS1 or MYC. Although RFP did not interact with ESR1 directly, it does coimmunoprecipitate with ESR1, demonstrating that RFP is found within the same protein complex. Chromatin immunoprecipitation assays (ChIP) located RFP to the TFF1 promoter, a known ESR1-regulated gene. Taken together, our study provides further evidence that coactivation and corepression are integrally linked processes and that RFP is a component of an ESR1 regulatory complex.
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disruption of scaffold Attachment Factor b1 leads to tbx2 up regulation lack of p19arf induction lack of senescence and cell immortalization
Cancer Research, 2006Co-Authors: Klaudia M Dobrzycka, Shiming Jiang, Rene Meyer, Kaiyan Kang, Adrian V Lee, Pulivarthi H Rao, Steffi OesterreichAbstract:Scaffold Attachment Factor B1 (SAFB1) is a multifunctional protein, which has previously been implicated in breast cancer. Here, we show that genetic deletion of SAFB1 in mouse embryonic fibroblasts (MEF) leads to spontaneous immortalization and altered expression of two proteins involved in immortalization and escape from senescence: low levels of p19ARF and high levels of TBX2. Inactivation of TBX2 using a dominant-negative TBX2 resulted in up-regulation of p19ARF in SAFB1 knockout MEFs. SAFB1 loss also caused lack of contact inhibition, increased foci formation, and increased oncogene-induced anchorage-independent growth. These findings suggest that SAFB1 is a novel player in cellular immortalization and transformation. (Cancer Res 2006; 66(16): 7859-63)
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scaffold Attachment Factor safb1 suppresses estrogen receptor α mediated transcription in part via interaction with nuclear receptor corepressor
Molecular Endocrinology, 2006Co-Authors: Shiming Jiang, Rene Meyer, Kaiyan Kang, Kent C Osborne, Jiemin Wong, Steffi OesterreichAbstract:Activity of the estrogen receptor (ER) is regulated through interaction with coactivators and corepressors. These proteins are present in large complexes, suggesting functional interactions among various coFactors. Scaffold Attachment Factors B1 and B2 (SAFB1/2) and nuclear receptor corepressor (N-CoR) function as ERα corepressors—they directly interact with ERα, and repress transcription via repression domains. We asked the question whether SAFB1/2 and N-CoR could directly interact with each other, and whether this interaction results in altered repressive activities. Employing coimmunoprecipitation, cofractionation, and colocalization experiments, we have shown that SAFB1/2 interact with the nuclear receptor corepressor N-CoR. This interaction was direct, and was mediated in vitro and in vivo through the C-terminal region of SAFB1 (amino acids 600–915 and the N-terminal region of N-CoR (amino acids 1–373). Decrease of SAFB1 or N-CoR expression by small interfering RNA resulted in an increase of the estr...
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structure function analysis of the estrogen receptor α corepressor scaffold Attachment Factor b1 identification of a potent transcriptional repression domain
Journal of Biological Chemistry, 2004Co-Authors: Steven M Townson, Kaiyan Kang, Adrian V Lee, Steffi OesterreichAbstract:Abstract Scaffold Attachment Factor-B1 (SAFB1) is a nuclear matrix protein that has been proposed to couple chromatin structure, transcription, and RNA processing. We have previously shown that SAFB1 can repress estrogen receptor (ERα)-mediated transactivation. Here we present a structure-function study showing that transactivation is mediated via an intrinsic and transferable C-terminal repression domain (RD). A similar C-terminal RD was found in the family member SAFB2. Removal of the RD from SAFB1 resulted in a dominant-negative SAFB1 protein that increased ligand-dependent and -independent ERα activity. SAFB1RD-mediated repression was partly blocked by histone deacetylase inhibitors; however, no histone deacetylase inhibitors were identified in a yeast two-hybrid screen using the RD as bait. Instead, SAFB1RD was found to interact with TAFII68, a member of the basal transcription machinery. We propose a model in which SAFB1 represses ERα activity via indirect association with histone deacetylation and interaction with the basal transcription machinery.
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tamoxifen bound estrogen receptor er strongly interacts with the nuclear matrix protein het saf b a novel inhibitor of er mediated transactivation
Molecular Endocrinology, 2000Co-Authors: Steffi Oesterreich, Kent C Osborne, Qingping Zhang, Torsten A Hopp, Suzanne A W Fuqua, Marten Michaelis, Holly Hong Zhao, James R Davie, Adrian V LeeAbstract:The estrogen receptor (ER) is a ligand-dependent transcription Factor that acts in a cell- and promoter-specific manner. Evidence suggests that the activity of the ER can be regulated by a number of other stimuli (e.g. growth Factors) and that the effects of the ER are modulated by nuclear Factors termed coregulators. While the interplay among these Factors may in part explain the pleiotropic effects elicited by the ER, there are several other less well described mechanisms of control, such as interactions with the nuclear matrix. Here we report that the nuclear matrix protein/scaffold Attachment Factor HET/SAF-B is an ER-interacting protein. ER and HET/SAF-B interact in in vitro binding assays, with HET binding to both the ER DNA-binding domain and the hinge region. Coimmunoprecipitation experiments reveal that HET/SAF-B and ER associate in cell lines in the presence or absence of estradiol, but binding is increased by the antiestrogen tamoxifen. HET/SAF-B enhances tamoxifen antagonism of estrogen-induced ER-mediated transactivation, but at high concentrations can inhibit both estrogen and tamoxifen-induced ER activity. HET/SAF-B-mediated repression of ER activity is dependent upon interaction with the ER-DBD. While the existence of high-affinity binding sites for the ER in the nuclear matrix has been known for some time, we now provide evidence of a specific nuclear matrix protein binding to the ER. Furthermore, our data showing that HET/SAF-B binds to ER particularly strongly in the presence of tamoxifen suggests that it may be important for the antagonist effect of tamoxifen.
Marta Scatena - One of the best experts on this subject based on the ideXlab platform.
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the role of osteoprotegerin and tumor necrosis Factor related apoptosis inducing ligand in human microvascular endothelial cell survival
Molecular Biology of the Cell, 2004Co-Authors: L B Pritzker, Marta Scatena, Cecilia M GiachelliAbstract:Endothelial cell survival and antiapoptotic pathways, including those stimulated by extracellular matrix, are critical regulators of vasculogenesis, angiogenesis, endothelial repair, and shear-stress-induced endothelial activation. One of these pathways is mediated by αvβ3 integrin ligation, downstream activation of nuclear Factor-κB, and subsequent up-regulation of osteoprotegerin (OPG). In this study, the mechanism by which OPG protects endothelial cells from death was examined. Serum-starved human microvascular endothelial cells (HMECs) plated on the αvβ3 ligand osteopontin were protected from cell death. Immunoprecipitation experiments indicated that OPG formed a complex with tumor necrosis Factor-related apoptosis-inducing ligand (TRAIL) in HMECs under these conditions. Furthermore, inhibitors of TRAIL, including recombinant soluble TRAIL receptors and a neutralizing antibody against TRAIL, blocked apoptosis of serum-starved HMECs plated on the nonintegrin Attachment Factor poly-d-lysine. Whereas TRAIL was unable to induce apoptosis in HMECs plated on osteopontin, the addition of recombinant TRAIL did increase the percentage of apoptotic HMECs plated on poly-d-lysine. This evidence indicates that OPG blocks endothelial cell apoptosis through binding TRAIL and preventing its interaction with death-inducing TRAIL-receptors
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the role of osteoprotegerin and tumor necrosis Factor related apoptosis inducing ligand in human microvascular endothelial cell survival
Molecular Biology of the Cell, 2004Co-Authors: L B Pritzker, Marta Scatena, Cecilia M GiachelliAbstract:Endothelial cell survival and antiapoptotic pathways, including those stimulated by extracellular matrix, are critical regulators of vasculogenesis, angiogenesis, endothelial repair, and shear-stress-induced endothelial activation. One of these pathways is mediated by alpha(v)beta(3) integrin ligation, downstream activation of nuclear Factor-kappaB, and subsequent up-regulation of osteoprotegerin (OPG). In this study, the mechanism by which OPG protects endothelial cells from death was examined. Serum-starved human microvascular endothelial cells (HMECs) plated on the alpha(v)beta(3) ligand osteopontin were protected from cell death. Immunoprecipitation experiments indicated that OPG formed a complex with tumor necrosis Factor-related apoptosis-inducing ligand (TRAIL) in HMECs under these conditions. Furthermore, inhibitors of TRAIL, including recombinant soluble TRAIL receptors and a neutralizing antibody against TRAIL, blocked apoptosis of serum-starved HMECs plated on the nonintegrin Attachment Factor poly-d-lysine. Whereas TRAIL was unable to induce apoptosis in HMECs plated on osteopontin, the addition of recombinant TRAIL did increase the percentage of apoptotic HMECs plated on poly-d-lysine. This evidence indicates that OPG blocks endothelial cell apoptosis through binding TRAIL and preventing its interaction with death-inducing TRAIL-receptors
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osteoprotegerin is an αvβ3 induced nf κb dependent survival Factor for endothelial cells
Journal of Biological Chemistry, 2000Co-Authors: Uriel M Malyankar, Marta Scatena, Katherine L Suchland, Edward A Clark, Cecilia M GiachelliAbstract:Abstract Osteopontin protects endothelial cells from apoptosis induced by growth Factor withdrawal. This interaction is mediated by the αvβ3 integrin and is NF-κB-dependent (Scatena, M., Almeida, M., Chaisson, M. L., Fausto, N., Nicosia, R. F., and Giachelli, C. M. (1998) J. Cell Biol. 141, 1083–1093). In the present study we used differential cloning to identify osteopontin-induced, NF-κB-dependent genes in endothelial cells. One of the genes identified in this screen was osteoprotegerin, a member of the tumor necrosis Factor receptor superfamily. By Northern and Western blot analysis, osteoprotegerin mRNA and protein levels were very low in endothelial cells plated on the non-integrin cell Attachment Factor, poly-d-lysine. In contrast, osteoprotegerin mRNA and protein levels were induced 5–7-fold following αvβ3 ligation by osteopontin. Osteoprotegerin induction by osteopontin was time-dependent and observed as early as 3 h following treatment. NF-κB inactivation achieved by over expression of an IκB super repressor in endothelial cells completely inhibited osteoprotegerin induction by osteopontin. Finally, purified osteoprotegerin protected endothelial cells with inactive NF-κB from apoptosis induced by growth Factor deprivation. These data suggest that αvβ3-mediated endothelial survival depends on osteoprotegerin induction by NF-κB and indicate a new function for osteoprotegerin in endothelial cells.