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William P Schiemann

Publications and source records attributed to William P Schiemann.

At least 19 recordsLinked to original sources
PubMed2006

Apoptotic cells, through transforming growth factor-beta, coordinately induce anti-inflammatory and suppress pro-inflammatory eicosanoid and NO synthesis in murine macrophages.

Apoptotic cells are rapidly engulfed by adjacent tissue cells or macrophages before they can release pro-inflammatory/proimmunogenic intracellular contents. In addition, recognition of the apoptotic cells is actively anti-inflammatory and anti-immunogenic with generation of anti-inflammatory mediators such as transforming growth factor-beta (TGF-beta) and anti-inflammatory eicosanoids. Here, we have investigated the role played by the induction of TGF-beta in the coordinate expression of anti-inflammatory eicosanoids or peroxisome proliferator-activated receptor-gamma and in the suppression of pro-inflammatory lipid mediators and nitric oxide (NO). By use of a dominant negative TGFbetaII receptor, TGF-beta signaling was blocked, and its participation in the consequences of apoptotic cell stimulation was determined. The induction of TGF-beta itself could be attributed to exposed phosphatidylserine on the apoptotic cells, which therefore appears to drive the balanced inflammatory mediator responses. Arachidonic acid release, COX-2, and prostaglandin synthase expression were shown to be significantly dependent on the TGF-beta production. On the other hand, a requirement for TGF-beta was also shown in the inhibition of thromboxane synthase and thromboxanes, of 5-lipoxygenase and sulfidopeptide leukotrienes, as well as of inducible nitric-oxide synthase and NO. TGF-beta-dependent induction of arginase was also found and would further limit the NO generation. Finally, apoptotic cells stimulated production of 15-lipoxygenase and 15-hydroxyeicosatetraenoic acid, a potentially anti-inflammatory pathway acting through peroxisome proliferator-activated receptor-gamma, and lipoxin A(4) production, which were also up-regulated by a TGF-beta-dependent pathway in this system. These results strongly suggest that the apoptotic cell inhibition of pro-inflammatory mediator production is pleiotropic and significantly dependent on the stimulation of TGF-beta production.

Animals↗
PubMed2006

Fibulins 3 and 5 antagonize tumor angiogenesis in vivo.

Lethal tumor growth and progression cannot occur without angiogenesis, which facilitates cancer cell proliferation, survival, and dissemination. Fibulins (FBLN) 5 and 3 are widely expressed extracellular matrix proteins that regulate cell proliferation in a context-specific manner. Reduced FBLN-5 expression has been associated with cancer formation and progression in humans, whereas its constitutive expression antagonizes endothelial cell angiogenic sprouting in vitro. Thus, FBLN-5 may suppress tumorigenesis by preventing tumor angiogenesis. FBLN-3 is homologous to FBLN-5 and expressed in endothelial cells, yet its role in tumorigenesis and angiogenesis is unknown. We find FBLN-3 expression to be altered in some human tumors and that its constitutive expression in endothelial cells inhibited their proliferation, invasion, and angiogenic sprouting, as well as their response to vascular endothelial growth factor as measured by p38 mitogen-activated protein kinase activation. In endothelial cells, both FBLNs (a) reduced angiogenic sprouting stimulated by basic fibroblast growth factor (bFGF); (b) inhibited matrix metalloproteinase expression and activity; and (c) stimulated tissue inhibitor of metalloproteinase expression. More importantly, both FBLNs prevented angiogenesis and vessel infiltration into bFGF-supplemented Matrigel plugs implanted in genetically normal mice, as well as decreased the growth and blood vessel density in tumors produced by MCA102 fibrosarcoma cells implanted s.c. into syngeneic mice. Our findings establish FBLN-3 and FBLN-5 as novel angiostatic agents capable of reducing tumor angiogenesis and, consequently, tumor growth in vivo and suggest that these angiostatic activities may one day be exploited to combat tumor angiogenesis and metastasis in cancer patients.

Amino Acid Sequence↗
PubMed2006

Beta3 integrin and Src facilitate transforming growth factor-beta mediated induction of epithelial-mesenchymal transition in mammary epithelial cells.

INTRODUCTION: Transforming growth factor (TGF)-beta suppresses breast cancer formation by preventing cell cycle progression in mammary epithelial cells (MECs). During the course of mammary tumorigenesis, genetic and epigenetic changes negate the cytostatic actions of TGF-beta, thus enabling TGF-beta to promote the acquisition and development of metastatic phenotypes. The molecular mechanisms underlying this conversion of TGF-beta function remain poorly understood but may involve signaling inputs from integrins. METHODS: beta3 Integrin expression or function in MECs was manipulated by retroviral transduction of active or inactive beta3 integrins, or by transient transfection of small interfering RNA (siRNA) against beta3 integrin. Altered proliferation, invasion, and epithelial-mesenchymal transition (EMT) stimulated by TGF-beta in control and beta3 integrin manipulated MECs was determined. Src involvement in beta3 integrin mediated alterations in TGF-beta signaling was assessed by performing Src protein kinase assays, and by interdicting Src function pharmacologically and genetically. RESULTS: TGF-beta stimulation induced alphavbeta3 integrin expression in a manner that coincided with EMT in MECs. Introduction of siRNA against beta3 integrin blocked its induction by TGF-beta and prevented TGF-beta stimulation of EMT in MECs. beta3 integrin interacted physically with the TGF-beta receptor (TbetaR) type II, thereby enhancing TGF-beta stimulation of mitogen-activated protein kinases (MAPKs), and of Smad2/3-mediated gene transcription in MECs. Formation of beta3 integrin:TbetaR-II complexes blocked TGF-beta mediated growth arrest and increased TGF-beta mediated invasion and EMT. Dual beta3 integrin:TbetaR-II activation induced tyrosine phosphorylation of TbetaR-II, a phosphotransferase reaction mediated by Src in vitro. Inhibiting Src activity in MECs prevented the ability of beta3 integrin to induce TbetaR-II tyrosine phosphorylation, MAPK activation, and EMT stimulated by TGF-beta. Lastly, wild-type and D119A beta3 integrin expression enhanced and abolished, respectively, TGF-beta stimulation of invasion in human breast cancer cells. CONCLUSION: We show that beta3 integrin alters TGF-beta signaling in MECs via Src-mediated TbetaR-II tyrosine phosphorylation, which significantly enhanced the ability of TGF-beta to induce EMT and invasion. Our findings suggest that beta3 integrin interdiction strategies may represent an innovative approach to re-establishing TGF-beta mediated tumor suppression in progressing human breast cancers.

Animals↗
PubMed2006

Role of transforming growth factor-beta in cancer progression.

Invasion and metastasis are the most lethal characteristics of cancer and the leading causes of cancer-related death. Transforming growth factor (TGF)-beta is a multifunctional cytokine that normally functions to prevent the uncontrolled proliferation of epithelial, endothelial and hematopoietic cells. Quite dichotomously, however, aberrant genetic or epigenetic events often negate the cytostatic function of TGF-beta in these cells, leading to tumor formation. Once freed from the growth-inhibitory effects of TGF-beta, cancer cells acquire the ability to proliferate, invade and metastasize when stimulated by TGF-beta. A thorough understanding of the molecular mechanisms underlying these paradoxical functions of TGF-beta remains elusive. Here, the authors review the tumor-suppressing and -promoting activities of TGF-beta and discuss the potential use and targeting of the TGF-beta-signaling system to prevent the progression and acquisition of metastatic phenotypes by human malignancies.

Antineoplastic Agents↗
PubMed2005

The use of cystatin C to inhibit epithelial-mesenchymal transition and morphological transformation stimulated by transforming growth factor-beta.

INTRODUCTION: Transforming growth factor-beta (TGF-beta) is a potent suppressor of mammary epithelial cell (MEC) proliferation and is thus an inhibitor of mammary tumor formation. Malignant MECs typically evolve resistance to TGF-beta-mediated growth arrest, enhancing their proliferation, invasion, and metastasis when stimulated by TGF-beta. Recent findings suggest that therapeutics designed to antagonize TGF-beta signaling may alleviate breast cancer progression, thereby improving the prognosis and treatment of breast cancer patients. We identified the cysteine protease inhibitor cystatin C (CystC) as a novel TGF-beta type II receptor antagonist that inhibits TGF-beta binding and signaling in normal and cancer cells. We hypothesized that the oncogenic activities of TGF-beta, particularly its stimulation of mammary epithelial-mesenchymal transition (EMT), can be prevented by CystC. METHOD: Retroviral infection was used to constitutively express CystC or a CystC mutant impaired in its ability to inhibit cathepsin protease activity (namely Delta14CystC) in murine NMuMG MECs and in normal rat kidney (NRK) fibroblasts. The effect of recombinant CystC administration or CystC expression on TGF-beta stimulation of NMuMG cell EMT in vitro was determined with immunofluorescence to monitor rearrangements of actin cytoskeletal architecture and E-cadherin expression. Soft-agar growth assays were performed to determine the effectiveness of CystC in preventing TGF-beta stimulation of morphological transformation and anchorage-independent growth in NRK fibroblasts. Matrigel invasion assays were performed to determine the ability of CystC to inhibit NMuMG and NRK motility stimulated by TGF-beta. RESULTS: CystC and Delta14CystC both inhibited NMuMG cell EMT and invasion stimulated by TGF-beta by preventing actin cytoskeletal rearrangements and E-cadherin downregulation. Moreover, both CystC molecules completely antagonized TGF-beta-mediated morphological transformation and anchorage-independent growth of NRK cells, and inhibited their invasion through synthetic basement membranes. Both CystC and Delta14CystC also inhibited TGF-beta signaling in two tumorigenic human breast cancer cell lines. CONCLUSION: Our findings show that TGF-beta stimulation of initiating metastatic events, including decreased cell polarization, reduced cell-cell contact, and elevated cell invasion and migration, are prevented by CystC treatment. Our findings also suggest that the future development of CystC or its peptide mimetics hold the potential to improve the therapeutic response of human breast cancers regulated by TGF-beta.

Animals↗
PubMed2005

Fibulin-5 function during tumorigenesis.

Tumorigenesis is the process by which normal cells evolve the capacity to evade and overcome the constraints normally placed upon their growth and survival. During cancer progression, indolent tumors experience an array of genetic and epigenetic events that ultimately coordinate the development of tumor metastasis, which is the most lethal facet of cancer and the leading cause of cancer-related death. The therapeutic necessity to combat tumor metastasis continues to drive investigations aimed at identifying novel regulators of this deadly process. Fibulin-5 is a newly described extracellular matrix protein that is important for normal embryonic development and organogenesis. Fibulin-5 expression may also be associated with the suppression of tumor formation through its control of cell proliferation, motility and angiogenic sprouting. Here, the tumor suppressing activities of fibulin-5 are reviewed, and the potential use and targeting of fibulin-5 to combat growth and metastasis of human malignancies is discussed.

Amino Acid Sequence↗
PubMed2004

Identification and characterization of regulator of G protein signaling 4 (RGS4) as a novel inhibitor of tubulogenesis: RGS4 inhibits mitogen-activated protein kinases and vascular endothelial growth factor signaling.

Tubulogenesis by epithelial cells regulates kidney, lung, and mammary development, whereas that by endothelial cells regulates vascular development. Although functionally dissimilar, the processes necessary for tubulation by epithelial and endothelial cells are very similar. We performed microarray analysis to further our understanding of tubulogenesis and observed a robust induction of regulator of G protein signaling 4 (RGS4) mRNA expression solely in tubulating cells, thereby implicating RGS4 as a potential regulator of tubulogenesis. Accordingly, RGS4 overexpression delayed and altered lung epithelial cell tubulation by selectively inhibiting G protein-mediated p38 MAPK activation, and, consequently, by reducing epithelial cell proliferation, migration, and expression of vascular endothelial growth factor (VEGF). The tubulogenic defects imparted by RGS4 in epithelial cells, including its reduction in VEGF expression, were rescued by overexpression of constitutively active MKK6, an activator of p38 MAPK. Similarly, RGS4 overexpression abrogated endothelial cell angiogenic sprouting by inhibiting their synthesis of DNA and invasion through synthetic basement membranes. We further show that RGS4 expression antagonized VEGF stimulation of DNA synthesis and extracellular signal-regulated kinase (ERK)1/ERK2 and p38 MAPK activation as well as ERK1/ERK2 activation stimulated by endothelin-1 and angiotensin II. RGS4 had no effect on the phosphorylation of Smad1 and Smad2 by bone morphogenic protein-7 and transforming growth factor-beta, respectively, indicating that RGS4 selectively inhibits G protein and VEGF signaling in endothelial cells. Finally, we found that RGS4 reduced endothelial cell response to VEGF by decreasing VEGF receptor-2 (KDR) expression. We therefore propose RGS4 as a novel antagonist of epithelial and endothelial cell tubulogenesis that selectively antagonizes intracellular signaling by G proteins and VEGF, thereby inhibiting cell proliferation, migration, and invasion, and VEGF and KDR expression.

Animals↗
PubMed2004

Pigment epithelium-derived factor in idiopathic pulmonary fibrosis: a role in aberrant angiogenesis.

Pigment epithelium-derived factor (PEDF) is a 50-kD protein with angiostatic and neurotrophic activities that regulates vascular development within the eye. PEDF expression was increased in the lungs of patients with idiopathic pulmonary fibrosis (IPF) based on microarray analyses. Angiogenesis has been implicated in the pathogenesis of fibrotic lung diseases, we therefore hypothesized that regional abnormalities in vascularization occur in IPF as a result of an imbalance between PEDF and vascular endothelial growth factor. We demonstrated that vascular density is regionally decreased in IPF within the fibroblastic foci, and that within these areas PEDF was increased, whereas vascular endothelial growth factor was decreased. PEDF colocalized with the fibrogenic cytokine, transforming growth factor (TGF)-beta 1, particularly within the fibrotic interstitium and the fibroblastic focus, and prominently within the epithelium directly overlying the fibroblastic focus. This suggested that TGF-beta 1 might regulate PEDF expression. Using 3T3-L1 fibroblasts and human lung fibroblasts, we showed that PEDF was indeed a TGF-beta 1 target gene. Collectively, our findings implicate PEDF as a regulator of pulmonary angiogenesis and an important mediator in IPF.

Biopsy↗
PubMed2004

Cloning of a novel signaling molecule, AMSH-2, that potentiates transforming growth factor beta signaling.

BACKGROUND: Transforming growth factor-betas (TGF-betas), bone morphogenetic proteins (BMPs) and activins are important regulators of developmental cell growth and differentiation. Signaling by these factors is mediated chiefly by the Smad family of latent transcription factors. RESULTS: There are a large number of uncharacterized cDNA clones that code for novel proteins with homology to known signaling molecules. We have identified a novel molecule from the HUGE database that is related to a previously known molecule, AMSH (associated molecule with the SH3 domain of STAM), an adapter shown to be involved in BMP signaling. Both of these molecules contain a coiled-coil domain located within the amino-terminus region and a JAB (Domain in Jun kinase activation domain binding protein and proteasomal subunits) domain at the carboxy-terminus. We show that this novel molecule, which we have designated AMSH-2, is widely expressed and its overexpression potentiates activation of TGF-beta-dependent promoters. Coimmunoprecipitation studies indicated that Smad7 and Smad2, but not Smad3 or 4, interact with AMSH-2. We show that overexpression of AMSH-2 decreases the inhibitory effect of Smad7 on TGF-beta signaling. Finally, we demonstrate that knocking down AMSH-2 expression by RNA interference decreases the activation of 3TP-lux reporter in response to TGF-beta. CONCLUSIONS: This report implicates AMSH and AMSH-2 as a novel family of molecules that positively regulate the TGF-beta signaling pathway. Our results suggest that this effect could be partially explained by AMSH-2 mediated decrease of the action of Smad7 on TGF-beta signaling pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Transforming growth factor-beta (TGF-beta)-resistant B cells from chronic lymphocytic leukemia patients contain recurrent mutations in the signal sequence of the type I TGF-beta receptor.

B cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in western societies, and is currently incurable. B cells of some B-CLL patients are resistant to the anti-proliferative effects of transforming growth factor-beta (TGF-beta). Herein, we identified two mutations within the putative signal sequence of TGF-beta type I receptor (TbetaR-I) gene of TGF-beta-resistant B-CLL patients (i.e., a Leu12Gln substitution together with an in-frame single Ala deletion). Although TbetaR-I mutants were expressed to the cell surface and interacted normally with TGF-beta-bound TbetaR-II, their expression significantly reduced gene transcription stimulated by TGF-beta, suggesting a causal relationship in the development of TGF-beta-resistant B-CLL. Screening of additional B-CLL patients solely for the presence of TbetaR-I signal sequence mutations showed that these mutations correlated with and predicted for B-CLL patient insensitivity to TGF-beta. Our results demonstrate that TGF-beta-resistant B-CLL is linked to signal sequence mutations within the TbetaR-I gene, and may eventually be employed as a prognostic indicator in B-CLL.

B-Lymphocytes↗
PubMed2004

Fibulin-5 promotes wound healing in vivo.

BACKGROUND: Fibulin-5 is a recently discovered multifunctional extracellular matrix protein that mediates endothelial cell adhesion through integrin ligation, regulates cell growth and motility in a context-specific manner, and prevents elastinopathy in vivo. Because fibulin-5 expression is induced dramatically in endothelial and smooth muscle cells in response to mechanical injury, my colleagues and I studied its role in dermal wound healing. STUDY DESIGN: We have used a gene therapy approach that used retroviral gene transfer to deliver fibulin-5 to the dermal wound milieu. Surgical generation of rabbit ear full-thickness dermal ulcers was performed in six female New Zealand white rabbits (6 months old). Wounds were injected with retrovirus containing either sense or antisense fibulin-5 or control vectors. Wounds were harvested on postwounding day 8 and analyzed by confocal microscopy, in situ hybridization, and histology. RESULTS: We report that fibulin-5 promotes wound healing in vivo. Wounds infected with fibulin-5 showed a considerable net increase (approximately 50%) in both newly formed granulation tissue volume and wound closure. Fibulin-5 expression stimulated substantial expression of collagen in dermal wounds. CONCLUSIONS: Taken together, our findings provide the first known example of overexpression of one extracellular matrix protein (fibulin-5) enhancing expression of another (type I collagen) in vivo. Our findings also demonstrate a novel role for fibulin-5 and suggest that altering extracellular matrix protein production through gene therapy may provide a novel means to promote wound healing.

Animals↗
PubMed2004

Fibulin-5 antagonizes vascular endothelial growth factor (VEGF) signaling and angiogenic sprouting by endothelial cells.

Fibulin-5 (FBLN-5) is a widely expressed, integrin-binding extracellular matrix protein that mediates endothelial cell adhesion and scaffolds cells to elastic fibers. It is also a gene target of TGF-beta in fibroblasts and endothelial cells that regulates cell proliferation and motility in a context-specific manner. Whereas FBLN-5 expression is low in adult vasculature, its expression is high in developing and injured vasculature, implicating FBLN-5 in regulating angiogenesis and endothelial cell function. We show here that TGF-beta stimulates FBLN-5 expression in endothelial cells, and that this response was inhibited by coadministration of the proangiogenic factor, VEGF. FBLN-5 expression was downregulated significantly during endothelial cell tubulogenesis, implying that FBLN-5 expression antagonizes angiogenesis. Accordingly, FBLN-5 overexpression in or recombinant FBLN-5 treatment of endothelial cells abrogated their ability to undergo angiogenic sprouting, doing so by inhibiting endothelial cell proliferation and invasion through Matrigel matrices. Moreover, FBLN-5 antagonized VEGF signaling in endothelial cells, as well as enhanced their expression of the antiangiogenic factor, thrombospondin-1. Finally, the ability of FBLN-5 to antagonize angiogenic processes was determined to be independent of its integrin-binding RGD motif. Collectively, our findings establish FBLN-5 as a novel antagonist of angiogenesis and endothelial cell activities, and offer new insights into why tumorigenesis downregulates FBLN-5 expression.

Angiogenesis Inhibitors↗
PubMed2004

Fibulin-2 and fibulin-5 alterations in tsk mice associated with disorganized hypodermal elastic fibers and skin tethering.

The Tight skin (Tsk) mouse is an important model of skin fibrosis that occurs in systemic sclerosis. These mice develop skin tethering and thickening associated with expression of a mutant fibrillin-1 gene. We show that Tsk fibrillin-1 leads to marked alterations in elastic fibers of the hypodermis of Tsk animals. In Tsk mice, a prominent elastic fiber layer found normally at the interface between hypodermal muscle and connective tissue was absent from an early age. The lack of elastic fibers at the hypodermal muscle-connective tissue (M-CT) interface was associated with a loss of staining for fibulin-5 in the same region. These mice also formed disorganized elastic fibers throughout hypodermal connective tissue as they aged. The increased elastic fibers in Tsk hypodermal connective tissue was associated with increased fibrillin-1 and fibulin-2 matrices. These results suggest that Tsk fibrillin-1 causes skin tethering by altering matrix protein composition in Tsk hypodermal connective tissues. The closely parallel alterations in elastogenesis associated with increased fibulin-2 in hypodermal connective tissues and decreased fibulin-5 at the hypodermal M-CT interface suggest that these proteins mediate the effect of Tsk-fibrillin-1 on elastogenesis.

Animals↗
PubMed2004

Cystatin C antagonizes transforming growth factor beta signaling in normal and cancer cells.

Cystatin C (CystC) is a secreted cysteine protease inhibitor that regulates bone resorption, neutrophil chemotaxis, and tissue inflammation, as well as resistance to bacterial and viral infections. CystC is ubiquitously expressed and present in most bodily fluids where it inhibits the activities of cathepsins, a family of cysteine proteases that can promote cancer cell invasion and metastasis. Transforming growth factor beta (TGF-beta) is a multifunctional cytokine endowed with both tumor-suppressing and tumor-promoting activities. We show herein that TGF-beta treatment up-regulated CystC transcript and protein in murine 3T3-L1 fibroblasts. Moreover, CystC mRNA expression was down-regulated in approximately 50% of human malignancies, particularly cancers of the stomach, uterus, colon, and kidney. Overexpression of CystC in human HT1080 fibrosarcoma cells antagonized their invasion through synthetic basement membranes in part via a cathepsin-dependent pathway. Independent of effects on cathepsin activity, CystC also reduced HT1080 cell gene expression stimulated by TGF-beta. Invasion of 3T3-L1 cells occurred through both cathepsin- and TGF-beta-dependent pathways. Both pathways were blocked by CystC, but only the TGF-beta-dependent pathway was blocked by a CystC mutant (i.e., delta14CystC) that is impaired in its ability to inhibit cathepsin activity. Moreover, CystC and delta14CystC both inhibited 3T3-L1 cell gene expression stimulated by TGF-beta. We further show that CystC antagonized TGF-beta binding to its cell surface receptors, doing so by interacting physically with the TGF-beta type II receptor and antagonizing its binding of TGF-beta. Collectively, our findings have identified CystC as a novel TGF-beta receptor antagonist, as well as a novel CystC-mediated feedback loop that inhibits TGF-beta signaling.

3T3-L1 Cells↗
PubMed2003

SPARC inhibits epithelial cell proliferation in part through stimulation of the transforming growth factor-beta-signaling system.

Secreted protein, acidic and rich in cysteine (SPARC) is a multifunctional secreted protein that regulates cell-cell and cell-matrix interactions, leading to alterations in cell adhesion, motility, and proliferation. Although SPARC is expressed in epithelial cells, its ability to regulate epithelial cell growth remains largely unknown. We show herein that SPARC strongly inhibited DNA synthesis in transforming growth factor (TGF)-beta-sensitive Mv1Lu cells, whereas moderately inhibiting that in TGF-beta-insensitive Mv1Lu cells (i.e., R1B cells). Overexpression of dominant-negative Smad3 in Mv1Lu cells, which abrogated growth arrest by TGF-beta, also attenuated growth arrest stimulated by SPARC. Moreover, the extracellular calcium-binding domain of SPARC (i.e., SPARC-EC) was sufficient to inhibit Mv1Lu cell proliferation but not that of R1B cells. Similar to TGF-beta and thrombospondin-1, treatment of Mv1Lu cells with SPARC or SPARC-EC stimulated Smad2 phosphorylation and Smad2/3 nuclear translocation: the latter response to all agonists was abrogated in R1B cells or by pretreatment of Mv1Lu cells with neutralizing TGF-beta antibodies. SPARC also stimulated Smad2 phosphorylation in MB114 endothelial cells but had no effect on bone morphogenetic protein-regulated Smad1 phosphorylation in either Mv1Lu or MB114 cells. Finally, SPARC and SPARC-EC stimulated TGF-beta-responsive reporter gene expression through a TGF-beta receptor- and Smad2/3-dependent pathway in Mv1Lu cells. Collectively, our findings identify a novel mechanism whereby SPARC inhibits epithelial cell proliferation by selectively commandeering the TGF-beta signaling system, doing so through coupling of SPARC-EC to a TGF-beta receptor- and Smad2/3-dependent pathway.

Animals↗
PubMed2003

Development of human protein reference database as an initial platform for approaching systems biology in humans.

Human Protein Reference Database (HPRD) is an object database that integrates a wealth of information relevant to the function of human proteins in health and disease. Data pertaining to thousands of protein-protein interactions, posttranslational modifications, enzyme/substrate relationships, disease associations, tissue expression, and subcellular localization were extracted from the literature for a nonredundant set of 2750 human proteins. Almost all the information was obtained manually by biologists who read and interpreted >300,000 published articles during the annotation process. This database, which has an intuitive query interface allowing easy access to all the features of proteins, was built by using open source technologies and will be freely available at http://www.hprd.org to the academic community. This unified bioinformatics platform will be useful in cataloging and mining the large number of proteomic interactions and alterations that will be discovered in the postgenomic era.

BRCA1 Protein↗
PubMed2002

Context-specific effects of fibulin-5 (DANCE/EVEC) on cell proliferation, motility, and invasion. Fibulin-5 is induced by transforming growth factor-beta and affects protein kinase cascades.

Fibulin-5 (FBLN-5; also known as DANCE or EVEC) is an integrin-binding extracellular matrix protein that mediates endothelial cell adhesion; it is also a calcium-dependent elastin-binding protein that scaffolds cells to elastic fibers, thereby preventing elastinopathy in the skin, lung, and vasculature. Transforming growth factor-beta (TGF-beta) regulates the production of cytokines, growth factors, and extracellular matrix proteins by a variety of cell types and tissues. We show here that TGF-beta stimulates murine 3T3-L1 fibroblasts to synthesize FBLN-5 transcript and protein through a Smad3-independent pathway. Overexpression of FBLN-5 in 3T3-L1 cells increased DNA synthesis and enhanced basal and TGF-beta-stimulated activation of ERK1/ERK2 and p38 mitogen-activated protein kinase (MAPK). FBLN-5 overexpression also augmented the tumorigenicity of human HT1080 fibrosarcoma cells by increasing their DNA synthesis, migration toward fibronectin, and invasion through synthetic basement membranes. In stark contrast, FBLN-5 expression was down-regulated in the majority of metastatic human malignancies, particularly in cancers of the kidney, breast, ovary, and colon. Unlike its proliferative response in fibroblasts, FBLN-5 overexpression in mink lung Mv1Lu epithelial cells resulted in an antiproliferative response, reducing their DNA synthesis and cyclin A expression. Moreover, FBLN-5 synergizes with TGF-beta in stimulating AP-1 activity in Mv1Lu cells, an effect that was abrogated by overexpression of dominant-negative versions of either MKK1 or p38 MAPKalpha. Accordingly, both the stimulation and duration of ERK1/ERK2 and p38 MAPK by TGF-beta was enhanced in Mv1Lu cells expressing FBLN-5. Our findings identify FBLN-5 as a novel TGF-beta-inducible target gene that regulates cell growth and motility in a context-specific manner and affects protein kinase activation by TGF-beta. Our findings also indicate that aberrant FBLN-5 expression likely contributes to tumor development in humans.

3T3 Cells↗