The Experts below are selected from a list of 14760 Experts worldwide ranked by ideXlab platform
David D. Roberts - One of the best experts on this subject based on the ideXlab platform.
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THBS1 (Thrombospondin-1).
Atlas of genetics and cytogenetics in oncology and haematology, 2020Co-Authors: Jeffrey S. Isenberg, David D. RobertsAbstract:Thrombospondins are encoded in vertebrates by a family of 5 THBS genes. THBS1 is infrequently mutated in most cancers, but its expression is positively regulated by several tumor suppressor genes and negatively regulated by activated oncogenes and promoter hypermethylation. Consequently, Thrombospondin-1 expression is frequently lost during oncogenesis and is correlated with a poor prognosis for some cancers. Thrombospondin-1 is a secreted protein that acts in the tumor microenvironment to inhibit angiogenesis, regulate antitumor immunity, stimulate tumor cell migration, and regulate the activities of extracellular proteases and growth factors. Differential effects of Thrombospondin-1 on the sensitivity of normal versus malignant cells to ischemic and genotoxic stress also regulate the responses to tumors to therapeutic radiation and chemotherapy.
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Thrombospondin-1 interactions regulate eicosanoid metabolism and signaling in cancer-related inflammation
Cancer and Metastasis Reviews, 2018Co-Authors: Manuel U. Ramirez, David D. Roberts, Elizabeth R. Stirling, Nancy J. Emenaker, D R Soto-pantojaAbstract:The metabolism of arachidonic acid and other polyunsaturated fatty acids produces eicosanoids, a family of biologically active lipids that are implicated in homeostasis and in several pathologies that involve inflammation. Inflammatory processes mediated by eicosanoids promote carcinogenesis by exerting direct effects on cancer cells and by affecting the tumor microenvironment. Therefore, understanding how eicosanoids mediate cancer progression may lead to better approaches and chemopreventive strategies for the treatment of cancer. The matricellular protein Thrombospondin-1 is involved in processes that profoundly regulate inflammatory pathways that contribute to carcinogenesis and metastatic spread. This review focuses on interactions of Thrombospondin-1 and eicosanoids in the microenvironment that promote carcinogenesis and how the microenvironment can be targeted for cancer prevention to increase curative responses of cancer patients.
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Thrombospondins: Purification of human platelet Thrombospondin-1.
Methods in cell biology, 2017Co-Authors: John M Sipes, Joanne E. Murphy-ullrich, David D. RobertsAbstract:Abstract Thrombospondins are a family of five secreted proteins that have diverse roles in modulating cellular function. Thrombospondins-1 and 2 were identified as matricellular proteins based on their functional roles combined with their transient appearance or accumulation in extracellular matrix at specific times during development and in response to injury or stress in mature tissues. Thrombospondin-1 is a major component of platelet α-granules, which provides a convenient source for purification of the protein. Methods are described to prepare Thrombospondin-1 from human platelets in a biologically active form with minimal degradation or contamination with other platelet proteins. A nondenaturing method is described for removing bound transforming growth factor-β1.
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Dietary fat overcomes the protective activity of Thrombospondin-1 signaling in the Apc(Min/+) model of colon cancer.
Oncogenesis, 2016Co-Authors: D R Soto-pantoja, John M Sipes, G Martin-manso, N L Morris, A Ghosh, N J Emenaker, Brian M. Westwood, David D. RobertsAbstract:Thrombospondin 1 is a glycoprotein that regulates cellular phenotype through interactions with its cellular receptors and extracellular matrix-binding partners. Thrombospondin 1 locally regulates angiogenesis and inflammatory responses that contribute to colorectal carcinogenesis in Apc(Min/+) mice. The ability of Thrombospondin 1 to regulate responses of cells and tissues to a variety of stresses suggested that loss of Thrombospondin 1 may also have broader systemic effects on metabolism to modulate carcinogenesis. Apc(Min/+):Thbs1(-/-) mice exhibited decreased survival and higher tumor multiplicities in the small and large intestine relative to Apc(Min/+) mice when fed a low (5%) fat western diet. However, the protective effect of endogenous Thrombospondin 1 was lost when the mice were fed a western diet containing 21% fat. Biochemical profiles of liver tissue identified systemic metabolic changes accompanying the effects of Thrombospondin 1 and dietary lipid intake on tumorigenesis. A high-fat western diet differentially regulated elements of amino acid, energy and lipid metabolism in Apc(Min/+):Thbs1(-/-) mice relative to Apc(Min/+):Thbs1(+/+)mice. Metabolic changes in ketone body and tricarboxylic acid cycle intermediates indicate functional interactions between Apc and Thrombospondin 1 signaling that control mitochondrial function. The cumulative diet-dependent differential changes observed in Apc(Min/+):Thbs1(-/-) versus Apc(Min/+) mice include altered amino acid and lipid metabolism, mitochondrial dysfunction, eicosanoids and ketone body formation. This metabolic profile suggests that the protective role of Thrombospondin 1 to decrease adenoma formation in Apc(Min/+) mice results in part from improved mitochondrial function.
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Divergent modulation of normal and neoplastic stem cells by Thrombospondin-1 and CD47 signaling.
The international journal of biochemistry & cell biology, 2016Co-Authors: Sukhbir Kaur, David D. RobertsAbstract:Thrombospondin-1 is a secreted matricellular protein that regulates the differentiation and function of many cell types. Thrombospondin-1 is not required for embryonic development, but studies using lineage-committed adult stem cells have identified positive and negative effects of Thrombospondin-1 on stem cell differentiation and self-renewal and identified several Thrombospondin-1 receptors that mediate these responses. Genetic studies in mice reveal a broad inhibitory role of Thrombospondin-1 mediated by its receptor CD47. Cells and tissues lacking Thrombospondin-1 or CD47 exhibit an increased capacity for self-renewal associated with increased expression of the stem cell transcription factors c-Myc, Sox2, Klf4, and Oct4. Thrombospondin-1 inhibits expression of these transcription factors in a CD47-dependent manner. However, this regulation differs in some neoplastic cells. Tumor initiating/cancer stem cells express high levels of CD47, but in contrast to nontransformed stem cells CD47 signaling supports cancer stem cells. Suppression of CD47 expression in cancer stem cells or ligation of CD47 by function blocking antibodies or Thrombospondin-1 results in loss of self-renewal. Therefore, the therapeutic CD47 antagonists that are in clinical development for stimulating innate anti-tumor immunity may also inhibit tumor growth by suppressing cancer stem cells. These and other therapeutic modulators of Thrombospondin-1 and CD47 signaling may also have applications in regenerative medicine to enhance the function of normal stem cells.
Jeff S. Isenberg - One of the best experts on this subject based on the ideXlab platform.
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differential interactions of Thrombospondin 1 2 and 4 with cd47 and effects on cgmp signaling and ischemic injury responses
Journal of Biological Chemistry, 2009Co-Authors: Jeff S. Isenberg, Deane F. Mosher, Douglas S Annis, Michael L. Pendrak, William A. Frazier, Malgorzata Ptaszynska, David D. RobertsAbstract:Thrombospondin-1 regulates nitric oxide (NO) signaling in vascular cells via CD47. Because CD47 binding motifs are conserved in the C-terminal signature domains of all five Thrombospondins and indirect evidence has implied CD47 interactions with other family members, we compared activities of recombinant signature domains of Thrombospondin-1, -2, and -4 to interact with CD47 and modulate cGMP signaling. Signature domains of Thrombospondin-2 and -4 were less active than that of Thrombospondin-1 for inhibiting binding of radiolabeled signature domain of Thrombospondin-1 or SIRPα (signal-regulatory protein) to cells expressing CD47. Consistent with this binding selectivity, the signature domain of Thrombospondin-1 was more potent than those of Thrombospondin-2 or -4 for inhibiting NO-stimulated cGMP synthesis in vascular smooth muscle cells and downstream effects on cell adhesion. In contrast to Thrombospondin-1- and CD47-null cells, primary vascular cells from Thrombospondin-2-null mice lack enhanced basal and NO-stimulated cGMP signaling. Effects of endogenous Thrombospondin-2 on NO/cGMP signaling could be detected only in Thrombospondin-1-null cells. Furthermore, tissue survival of ischemic injury and acute recovery of blood flow in Thrombospondin-2-nulls resembles that of wild type mice. Therefore, Thrombospondin-1 is the dominant regulator of NO/cGMP signaling via CD47, and its limiting role in acute ischemic injury responses is not shared by Thrombospondin-2.
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Enhancing Cardiovascular Dynamics by Inhibition of Thrombospondin- 1/CD47 Signaling
Current drug targets, 2008Co-Authors: Jeff S. Isenberg, David A. Wink, Murali C. Krishna, William A. Frazier, David D. RobertsAbstract:Activation of soluble guanylate cyclase by nitric oxide (NO) controls signaling pathways that play critical roles in normal vascular physiology and in the pathogenesis of cardiovascular disease. We have identified the secreted protein Thrombospondin-1 as a key regulator of NO signaling. Thrombospondin-1 limits the angiogenic activity of NO in endothelial cells, its vasodilator activity in vascular smooth muscle, and its antithrombotic activity in platelets. Loss of either Thrombospondin-1 or its receptor CD47 in transgenic mice results in hyperdynamic responses to NO and reveals the importance of this pathway in normal physiology. Thrombospondin-1 and CD47 null mice show improved abilities to respond to ischemic stress, suggesting that therapeutic targeting of this pathway could benefit patients with a variety of ischemic conditions. We review the preclinical development of therapeutics targeting Thrombospondin-1 or CD47 for improving survival of fixed ischemia, ischemia due to aging and peripheral vascular disease, and skin grafting.
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Thrombospondin-1 and CD47 limit cell and tissue survival of radiation injury.
The American journal of pathology, 2008Co-Authors: Jeff S. Isenberg, Fuminori Hyodo, Maria Tsokos, David A. Wink, Justin B. Maxhimer, Michael L. Pendrak, Lisa A. Ridnour, William Degraff, David D. RobertsAbstract:Radiation, a primary mode of cancer therapy, acutely damages cellular macromolecules and DNA and elicits stress responses that lead to cell death. The known cytoprotective activity of nitric oxide (NO) is blocked by Thrombospondin-1, a potent antagonist of NO/cGMP signaling in ischemic soft tissues, suggesting that Thrombospondin-1 signaling via its receptor CD47 could correspondingly increase radiosensitivity. We show here that soft tissues in Thrombospondin-1-null mice are remarkably resistant to radiation injury. Twelve hours after 25-Gy hindlimb irradiation, Thrombospondin-1-null mice showed significantly less cell death in both muscle and bone marrow. Two months after irradiation, skin and muscle units in null mice showed minimal histological evidence of radiation injury and near full retention of mitochondrial function. Additionally, both tissue perfusion and acute vascular responses to NO were preserved in irradiated Thrombospondin-1-null hindlimbs. The role of Thrombospondin-1 in radiosensitization is specific because Thrombospondin-2-null mice were not protected. However, mice lacking CD47 showed radioresistance similar to Thrombospondin-1-null mice. Both Thrombospondin-1- and CD47-dependent radiosensitization is cell autonomous because vascular cells isolated from the respective null mice showed dramatically increased survival and improved proliferative capacity after irradiation in vitro. Therefore, Thrombospondin-1/CD47 antagonists may have selective radioprotective activity for normal tissues.
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Thrombospondin 1 stimulates platelet aggregation by blocking the antithrombotic activity of nitric oxide cgmp signaling
Blood, 2008Co-Authors: Jeff S. Isenberg, Martin J. Romeo, David A. Wink, William A. Frazier, Khauh Nghiem, Jude Monsale, Margaret E. Rick, David D. RobertsAbstract:Platelet α-granules constitute the major rapidly releasable reservoir of Thrombospondin-1 in higher animals. Although some fragments and peptides derived from Thrombospondin-1 stimulate or inhibit platelet aggregation, its physiologic function in platelets has remained elusive. We now show that endogenous Thrombospondin-1 is necessary for platelet aggregation in vitro in the presence of physiologic levels of nitric oxide (NO). Exogenous NO or elevation of cGMP delays thrombin-induced platelet aggregation under high shear and static conditions, and exogenous Thrombospondin-1 reverses this delay. Thrombospondin-1–null murine platelets fail to aggregate in response to thrombin in the presence of exogenous NO or 8Br-cGMP. At physiologic concentrations of the NO synthase substrate arginine, Thrombospondin-1–null platelets have elevated basal cGMP. Ligation of CD36 or CD47 is sufficient to block NO-induced cGMP accumulation and mimic the effect of Thrombospondin-1 on aggregation. Exogenous Thrombospondin-1 also reverses the suppression by NO of αIIb/β3 integrin–mediated platelet adhesion on immobilized fibrinogen, mediated in part by increased GTP loading of Rap1. Thrombospondin-1 also inhibits cGMP-mediated activation of cGMP-dependent protein kinase and thereby prevents phosphorylation of VASP. Thus, release of Thrombospondin-1 from α-granules during activation provides positive feedback to promote efficient platelet aggregation and adhesion by overcoming the antithrombotic activity of physiologic NO.
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Thrombospondin-1: a physiological regulator of nitric oxide signaling.
Cellular and molecular life sciences : CMLS, 2008Co-Authors: Jeff S. Isenberg, William A. Frazier, David D. RobertsAbstract:Thrombospondin-1 is secreted protein that modulates vascular cell behavior via several cell surface receptors. In vitro, nanomolar concentrations of Thrombospondin-1 are required to alter endothelial and vascular smooth muscle cell adhesion, proliferation, motility, and survival. Yet, much lower levels of Thrombospondin-1 are clearly functional in vivo. This discrepancy was explained with the discovery that the potency of Thrombospondin-1 increases more than 100-fold in the presence of physiological levels of NO. Thrombospondin-1 binding to CD47 inhibits NO signaling by preventing cGMP synthesis and activation of its target cGMP-dependent protein kinase. This potent antagonism of NO signaling allows Thrombospondin-1 to acutely constrict blood vessels, accelerate platelet aggregation and, if sustained, inhibit angiogenic responses. Acute antagonism of NO signaling by Thrombospondin-1 is important for hemostasis but becomes detrimental for tissue survival of ischemic injuries. New therapeutic approaches targeting Thrombospondin-1 or CD47 can improve recovery from ischemic injuries and overcome a deficit in NO-responsiveness in aging.
David A. Wink - One of the best experts on this subject based on the ideXlab platform.
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Enhancing Cardiovascular Dynamics by Inhibition of Thrombospondin- 1/CD47 Signaling
Current drug targets, 2008Co-Authors: Jeff S. Isenberg, David A. Wink, Murali C. Krishna, William A. Frazier, David D. RobertsAbstract:Activation of soluble guanylate cyclase by nitric oxide (NO) controls signaling pathways that play critical roles in normal vascular physiology and in the pathogenesis of cardiovascular disease. We have identified the secreted protein Thrombospondin-1 as a key regulator of NO signaling. Thrombospondin-1 limits the angiogenic activity of NO in endothelial cells, its vasodilator activity in vascular smooth muscle, and its antithrombotic activity in platelets. Loss of either Thrombospondin-1 or its receptor CD47 in transgenic mice results in hyperdynamic responses to NO and reveals the importance of this pathway in normal physiology. Thrombospondin-1 and CD47 null mice show improved abilities to respond to ischemic stress, suggesting that therapeutic targeting of this pathway could benefit patients with a variety of ischemic conditions. We review the preclinical development of therapeutics targeting Thrombospondin-1 or CD47 for improving survival of fixed ischemia, ischemia due to aging and peripheral vascular disease, and skin grafting.
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Thrombospondin-1 and CD47 limit cell and tissue survival of radiation injury.
The American journal of pathology, 2008Co-Authors: Jeff S. Isenberg, Fuminori Hyodo, Maria Tsokos, David A. Wink, Justin B. Maxhimer, Michael L. Pendrak, Lisa A. Ridnour, William Degraff, David D. RobertsAbstract:Radiation, a primary mode of cancer therapy, acutely damages cellular macromolecules and DNA and elicits stress responses that lead to cell death. The known cytoprotective activity of nitric oxide (NO) is blocked by Thrombospondin-1, a potent antagonist of NO/cGMP signaling in ischemic soft tissues, suggesting that Thrombospondin-1 signaling via its receptor CD47 could correspondingly increase radiosensitivity. We show here that soft tissues in Thrombospondin-1-null mice are remarkably resistant to radiation injury. Twelve hours after 25-Gy hindlimb irradiation, Thrombospondin-1-null mice showed significantly less cell death in both muscle and bone marrow. Two months after irradiation, skin and muscle units in null mice showed minimal histological evidence of radiation injury and near full retention of mitochondrial function. Additionally, both tissue perfusion and acute vascular responses to NO were preserved in irradiated Thrombospondin-1-null hindlimbs. The role of Thrombospondin-1 in radiosensitization is specific because Thrombospondin-2-null mice were not protected. However, mice lacking CD47 showed radioresistance similar to Thrombospondin-1-null mice. Both Thrombospondin-1- and CD47-dependent radiosensitization is cell autonomous because vascular cells isolated from the respective null mice showed dramatically increased survival and improved proliferative capacity after irradiation in vitro. Therefore, Thrombospondin-1/CD47 antagonists may have selective radioprotective activity for normal tissues.
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Thrombospondin 1 stimulates platelet aggregation by blocking the antithrombotic activity of nitric oxide cgmp signaling
Blood, 2008Co-Authors: Jeff S. Isenberg, Martin J. Romeo, David A. Wink, William A. Frazier, Khauh Nghiem, Jude Monsale, Margaret E. Rick, David D. RobertsAbstract:Platelet α-granules constitute the major rapidly releasable reservoir of Thrombospondin-1 in higher animals. Although some fragments and peptides derived from Thrombospondin-1 stimulate or inhibit platelet aggregation, its physiologic function in platelets has remained elusive. We now show that endogenous Thrombospondin-1 is necessary for platelet aggregation in vitro in the presence of physiologic levels of nitric oxide (NO). Exogenous NO or elevation of cGMP delays thrombin-induced platelet aggregation under high shear and static conditions, and exogenous Thrombospondin-1 reverses this delay. Thrombospondin-1–null murine platelets fail to aggregate in response to thrombin in the presence of exogenous NO or 8Br-cGMP. At physiologic concentrations of the NO synthase substrate arginine, Thrombospondin-1–null platelets have elevated basal cGMP. Ligation of CD36 or CD47 is sufficient to block NO-induced cGMP accumulation and mimic the effect of Thrombospondin-1 on aggregation. Exogenous Thrombospondin-1 also reverses the suppression by NO of αIIb/β3 integrin–mediated platelet adhesion on immobilized fibrinogen, mediated in part by increased GTP loading of Rap1. Thrombospondin-1 also inhibits cGMP-mediated activation of cGMP-dependent protein kinase and thereby prevents phosphorylation of VASP. Thus, release of Thrombospondin-1 from α-granules during activation provides positive feedback to promote efficient platelet aggregation and adhesion by overcoming the antithrombotic activity of physiologic NO.
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blockade of Thrombospondin 1 cd47 interactions prevents necrosis of full thickness skin grafts
Annals of Surgery, 2008Co-Authors: Jeff S. Isenberg, Martin J. Romeo, Maria Tsokos, David A. Wink, William A. Frazier, Mones Abuasab, Loretta K Pappan, David D. RobertsAbstract:Thrombospondin-1 is a potent physiologic regulator of nitric oxide driven blood flow and angiogenesis. This regulation requires the cell receptor CD47. In a murine model of skin graft survival we demonstrate that endogenous Thrombospondin-1 limits graft survival via CD47 and targeting CD47 with antibodies or suppressing CD47 with a morpholino oligonucleotide enhances graft survival by blocking this pathway. Background Skin graft survival and healing requires rapid restoration of blood flow to the avascular graft. Failure or delay in the process of graft vascularization is a significant source of morbidity and mortality. One of the primary regulators of blood flow and vessel growth is nitric oxide (NO). The secreted protein Thrombospondin-1 (TSP1) limits NO-stimulated blood flow and growth and composite tissue survival to ischemia. We herein demonstrate a role for TSP1 in regulating full thickness skin graft survival.
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Thrombospondin-1 stimulates platelet aggregation by blocking the antithrombotic activity of nitric oxide/cGMP signaling.
Blood, 2007Co-Authors: Jeff S. Isenberg, Martin J. Romeo, David A. Wink, William A. Frazier, Khauh Nghiem, Jude Monsale, Margaret E. Rick, David D. RobertsAbstract:Platelet α-granules constitute the major rapidly releasable reservoir of Thrombospondin-1 in higher animals. Although some fragments and peptides derived from Thrombospondin-1 stimulate or inhibit platelet aggregation, its physiologic function in platelets has remained elusive. We now show that endogenous Thrombospondin-1 is necessary for platelet aggregation in vitro in the presence of physiologic levels of nitric oxide (NO). Exogenous NO or elevation of cGMP delays thrombin-induced platelet aggregation under high shear and static conditions, and exogenous Thrombospondin-1 reverses this delay. Thrombospondin-1–null murine platelets fail to aggregate in response to thrombin in the presence of exogenous NO or 8Br-cGMP. At physiologic concentrations of the NO synthase substrate arginine, Thrombospondin-1–null platelets have elevated basal cGMP. Ligation of CD36 or CD47 is sufficient to block NO-induced cGMP accumulation and mimic the effect of Thrombospondin-1 on aggregation. Exogenous Thrombospondin-1 also reverses the suppression by NO of αIIb/β3 integrin–mediated platelet adhesion on immobilized fibrinogen, mediated in part by increased GTP loading of Rap1. Thrombospondin-1 also inhibits cGMP-mediated activation of cGMP-dependent protein kinase and thereby prevents phosphorylation of VASP. Thus, release of Thrombospondin-1 from α-granules during activation provides positive feedback to promote efficient platelet aggregation and adhesion by overcoming the antithrombotic activity of physiologic NO.
Deane F. Mosher - One of the best experts on this subject based on the ideXlab platform.
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Thrombospondin-1 (TSP1) Contributes to the Development of Vascular Inflammation by Regulating Monocytic Cell Motility in Mouse Models of Abdominal Aortic Aneurysm
Circulation research, 2015Co-Authors: Zhenjie Liu, Deane F. Mosher, Douglas S Annis, Jing Zhang, Stephanie Morgan, Jun Ren, Qiwei Wang, Christine M. Sorenson, Nader Sheibani, Bo LiuAbstract:Rationale:Histological examination of abdominal aortic aneurysm (AAA) tissues demonstrates extracellular matrix destruction and infiltration of inflammatory cells. Previous work with mouse models of AAA has shown that anti-inflammatory strategies can effectively attenuate aneurysm formation. Thrombospondin-1 is a matricellular protein involved in the maintenance of vascular structure and homeostasis through the regulation of biological functions, such as cell proliferation, apoptosis, and adhesion. Expression levels of Thrombospondin-1 correlate with vascular disease conditions. Objective:To use Thrombospondin-1–deficient (Thbs1−/−) mice to test the hypothesis that Thrombospondin-1 contributes to pathogenesis of AAAs. Methods and Results:Mouse experimental AAA was induced through perivascular treatment with calcium phosphate, intraluminal perfusion with porcine elastase, or systemic administration of angiotensin II. Induction of AAA increased Thrombospondin-1 expression in aortas of C57BL/6 or apoE−/− mic...
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differential interactions of Thrombospondin 1 2 and 4 with cd47 and effects on cgmp signaling and ischemic injury responses
Journal of Biological Chemistry, 2009Co-Authors: Jeff S. Isenberg, Deane F. Mosher, Douglas S Annis, Michael L. Pendrak, William A. Frazier, Malgorzata Ptaszynska, David D. RobertsAbstract:Thrombospondin-1 regulates nitric oxide (NO) signaling in vascular cells via CD47. Because CD47 binding motifs are conserved in the C-terminal signature domains of all five Thrombospondins and indirect evidence has implied CD47 interactions with other family members, we compared activities of recombinant signature domains of Thrombospondin-1, -2, and -4 to interact with CD47 and modulate cGMP signaling. Signature domains of Thrombospondin-2 and -4 were less active than that of Thrombospondin-1 for inhibiting binding of radiolabeled signature domain of Thrombospondin-1 or SIRPα (signal-regulatory protein) to cells expressing CD47. Consistent with this binding selectivity, the signature domain of Thrombospondin-1 was more potent than those of Thrombospondin-2 or -4 for inhibiting NO-stimulated cGMP synthesis in vascular smooth muscle cells and downstream effects on cell adhesion. In contrast to Thrombospondin-1- and CD47-null cells, primary vascular cells from Thrombospondin-2-null mice lack enhanced basal and NO-stimulated cGMP signaling. Effects of endogenous Thrombospondin-2 on NO/cGMP signaling could be detected only in Thrombospondin-1-null cells. Furthermore, tissue survival of ischemic injury and acute recovery of blood flow in Thrombospondin-2-nulls resembles that of wild type mice. Therefore, Thrombospondin-1 is the dominant regulator of NO/cGMP signaling via CD47, and its limiting role in acute ischemic injury responses is not shared by Thrombospondin-2.
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Secreted Thrombospondin-1 controls platelet sensitivity to NO
Blood, 2008Co-Authors: Deane F. Mosher, Lisa M. Maurer, C. Britt CarlsonAbstract:Many functions have been suggested for the large amounts of Thrombospondin-1 that are stored in α-granules of platelets. Isenberg et al describe a new role whereby Thrombospondin-1 counteracts NO and allows platelet activation to take place in situations in which NO is being generated.
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fibroblast growth factor 2 binding to the Thrombospondin 1 type iii repeats a novel antiangiogenic domain
The International Journal of Biochemistry & Cell Biology, 2008Co-Authors: Barbara Margosio, Douglas S Annis, Marco Rusnati, Katiuscia Bonezzi, Blue Leaf A Cordes, Chiara Urbinati, Raffaella Giavazzi, Marco Presta, Domenico Ribatti, Deane F. MosherAbstract:Thrombospondin-1, an antiangiogenic matricellular protein, binds with high affinity to the angiogenic fibroblast growth factor-2, affecting its bioavailability and activity. The present work aimed at further locating the fibroblast growth factor-2 binding site of Thrombospondin-1 and investigating its activity, using recombinant Thrombospondin-1 proteins. Only recombinant constructs containing the Thrombospondin-1 type III repeats bound fibroblast growth factor-2, whereas other domains, including the known anti-angiogenic type I repeats, were inactive. Binding was specific and inhibited by the anti Thrombospondin-1 monoclonal antibody B5.2. Surface plasmon resonance analysis on BIAcore revealed a binding affinity (Kd) of 310 nM for the type III repeats and 11 nM for intact Thrombospondin-1. Since the type III repeats bind calcium, the effect of calcium on Thrombospondin-1 binding to fibroblast growth factor-2 was investigated. Binding was modulated by calcium, as Thrombospondin-1 or the type III repeats bound to fibroblast growth factor-2 only in calcium concentrations <0.3 mM. The type III repeats inhibited binding of fibroblast growth factor-2 to endothelial cells, fibroblast growth factor-2-induced endothelial cell proliferation in vitro and angiogenesis in the chorioallantoic membrane assay in vivo, thus indicating the antiangiogenic activity of the domain. In conclusion, this study demonstrates that the fibroblast growth factor-2 binding site of Thrombospondin-1 is located in the type III repeats. The finding that this domain is active in inhibiting angiogenesis indicates that the type III repeats represent a novel antiangiogenic domain of Thrombospondin-1.
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Calcium indirectly regulates immunochemical reactivity and functional activities of the N-domain of Thrombospondin-1.
Matrix biology : journal of the International Society for Matrix Biology, 2007Co-Authors: Maria J Calzada, John M Sipes, Deane F. Mosher, Douglas S Annis, Svetlana A. Kuznetsova, Rui G. Rodrigues, Jo Anne Cashel, David D. RobertsAbstract:Conformational changes induced in Thrombospondin-1 by removal of calcium regulate interactions with some ligands of its N-modules. Because calcium binds primarily to elements of the C-terminal signature domain of Thrombospondin-1, which are distant from the N-modules, such regulation was unexpected. To clarify the mechanism for this regulation, we compared ligand binding to the N-modules of Thrombospondin-1 in the full-length protein and recombinant trimeric Thrombospondin-1 truncated prior to the signature domain. Three monoclonal antibodies were identified that recognize the N-modules, two of which exhibit calcium-dependent binding to native Thrombospondin-1 but not to the truncated trimeric protein. These antibodies or calcium selectively modulate interactions of fibronectin, heparin, sulfatide, α3β1 integrin, tumor necrosis factor-α-stimulated gene-6 protein, and, to a lesser extent, α4β1 integrin with native Thrombospondin-1 but not with the truncated protein. These results indicate connectivity between calcium binding sites in the C-terminal signature domain and the N-modules of Thrombospondin-1 that regulates ligand binding and functional activities of the N-modules.
William A. Frazier - One of the best experts on this subject based on the ideXlab platform.
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Thrombospondin-1 and CD47 regulate blood pressure and cardiac responses to vasoactive stress.
Matrix biology : journal of the International Society for Matrix Biology, 2009Co-Authors: Jeffrey S. Isenberg, John M Sipes, Justin B. Maxhimer, William A. Frazier, Yan Qin, Daryl Despres, Jurgen Schnermann, David D. RobertsAbstract:Nitric oxide (NO) locally regulates vascular resistance and blood pressure by modulating blood vessel tone. Thrombospondin-1 signaling via its receptor CD47 locally limits the ability of NO to relax vascular smooth muscle cells and increase regional blood flow in ischemic tissues. To determine whether Thrombospondin-1 plays a broader role in central cardiovascular physiology, we examined vasoactive stress responses in mice lacking Thrombospondin-1 or CD47. Mice lacking Thrombospondin-1 exhibit activity-associated increases in heart rate, central diastolic and mean arterial blood pressure and a constant decrease in pulse pressure. CD47-deficient mice have normal central pulse pressure but elevated resting peripheral blood pressure. Both null mice show exaggerated decreases in peripheral blood pressure and increased cardiac output and ejection fraction in response to NO. Autonomic blockade also induces exaggerated hypotensive responses in awake Thrombospondin-1 null and CD47 null mice. Both null mice exhibit a greater hypotensive response to isoflurane, and autonomic blockage under isoflurane anesthesia leads to premature death of Thrombospondin-1 null mice. Conversely, the hypertensive response to epinephrine is attenuated in Thrombospondin-1 null mice. Thus, the matricellular protein Thrombospondin-1 and its receptor CD47 serve as acute physiological regulators of blood pressure and exert a vasopressor activity to maintain global hemodynamics under stress.
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differential interactions of Thrombospondin 1 2 and 4 with cd47 and effects on cgmp signaling and ischemic injury responses
Journal of Biological Chemistry, 2009Co-Authors: Jeff S. Isenberg, Deane F. Mosher, Douglas S Annis, Michael L. Pendrak, William A. Frazier, Malgorzata Ptaszynska, David D. RobertsAbstract:Thrombospondin-1 regulates nitric oxide (NO) signaling in vascular cells via CD47. Because CD47 binding motifs are conserved in the C-terminal signature domains of all five Thrombospondins and indirect evidence has implied CD47 interactions with other family members, we compared activities of recombinant signature domains of Thrombospondin-1, -2, and -4 to interact with CD47 and modulate cGMP signaling. Signature domains of Thrombospondin-2 and -4 were less active than that of Thrombospondin-1 for inhibiting binding of radiolabeled signature domain of Thrombospondin-1 or SIRPα (signal-regulatory protein) to cells expressing CD47. Consistent with this binding selectivity, the signature domain of Thrombospondin-1 was more potent than those of Thrombospondin-2 or -4 for inhibiting NO-stimulated cGMP synthesis in vascular smooth muscle cells and downstream effects on cell adhesion. In contrast to Thrombospondin-1- and CD47-null cells, primary vascular cells from Thrombospondin-2-null mice lack enhanced basal and NO-stimulated cGMP signaling. Effects of endogenous Thrombospondin-2 on NO/cGMP signaling could be detected only in Thrombospondin-1-null cells. Furthermore, tissue survival of ischemic injury and acute recovery of blood flow in Thrombospondin-2-nulls resembles that of wild type mice. Therefore, Thrombospondin-1 is the dominant regulator of NO/cGMP signaling via CD47, and its limiting role in acute ischemic injury responses is not shared by Thrombospondin-2.
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Enhancing Cardiovascular Dynamics by Inhibition of Thrombospondin- 1/CD47 Signaling
Current drug targets, 2008Co-Authors: Jeff S. Isenberg, David A. Wink, Murali C. Krishna, William A. Frazier, David D. RobertsAbstract:Activation of soluble guanylate cyclase by nitric oxide (NO) controls signaling pathways that play critical roles in normal vascular physiology and in the pathogenesis of cardiovascular disease. We have identified the secreted protein Thrombospondin-1 as a key regulator of NO signaling. Thrombospondin-1 limits the angiogenic activity of NO in endothelial cells, its vasodilator activity in vascular smooth muscle, and its antithrombotic activity in platelets. Loss of either Thrombospondin-1 or its receptor CD47 in transgenic mice results in hyperdynamic responses to NO and reveals the importance of this pathway in normal physiology. Thrombospondin-1 and CD47 null mice show improved abilities to respond to ischemic stress, suggesting that therapeutic targeting of this pathway could benefit patients with a variety of ischemic conditions. We review the preclinical development of therapeutics targeting Thrombospondin-1 or CD47 for improving survival of fixed ischemia, ischemia due to aging and peripheral vascular disease, and skin grafting.
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Thrombospondin 1 stimulates platelet aggregation by blocking the antithrombotic activity of nitric oxide cgmp signaling
Blood, 2008Co-Authors: Jeff S. Isenberg, Martin J. Romeo, David A. Wink, William A. Frazier, Khauh Nghiem, Jude Monsale, Margaret E. Rick, David D. RobertsAbstract:Platelet α-granules constitute the major rapidly releasable reservoir of Thrombospondin-1 in higher animals. Although some fragments and peptides derived from Thrombospondin-1 stimulate or inhibit platelet aggregation, its physiologic function in platelets has remained elusive. We now show that endogenous Thrombospondin-1 is necessary for platelet aggregation in vitro in the presence of physiologic levels of nitric oxide (NO). Exogenous NO or elevation of cGMP delays thrombin-induced platelet aggregation under high shear and static conditions, and exogenous Thrombospondin-1 reverses this delay. Thrombospondin-1–null murine platelets fail to aggregate in response to thrombin in the presence of exogenous NO or 8Br-cGMP. At physiologic concentrations of the NO synthase substrate arginine, Thrombospondin-1–null platelets have elevated basal cGMP. Ligation of CD36 or CD47 is sufficient to block NO-induced cGMP accumulation and mimic the effect of Thrombospondin-1 on aggregation. Exogenous Thrombospondin-1 also reverses the suppression by NO of αIIb/β3 integrin–mediated platelet adhesion on immobilized fibrinogen, mediated in part by increased GTP loading of Rap1. Thrombospondin-1 also inhibits cGMP-mediated activation of cGMP-dependent protein kinase and thereby prevents phosphorylation of VASP. Thus, release of Thrombospondin-1 from α-granules during activation provides positive feedback to promote efficient platelet aggregation and adhesion by overcoming the antithrombotic activity of physiologic NO.
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Thrombospondin-1: a physiological regulator of nitric oxide signaling.
Cellular and molecular life sciences : CMLS, 2008Co-Authors: Jeff S. Isenberg, William A. Frazier, David D. RobertsAbstract:Thrombospondin-1 is secreted protein that modulates vascular cell behavior via several cell surface receptors. In vitro, nanomolar concentrations of Thrombospondin-1 are required to alter endothelial and vascular smooth muscle cell adhesion, proliferation, motility, and survival. Yet, much lower levels of Thrombospondin-1 are clearly functional in vivo. This discrepancy was explained with the discovery that the potency of Thrombospondin-1 increases more than 100-fold in the presence of physiological levels of NO. Thrombospondin-1 binding to CD47 inhibits NO signaling by preventing cGMP synthesis and activation of its target cGMP-dependent protein kinase. This potent antagonism of NO signaling allows Thrombospondin-1 to acutely constrict blood vessels, accelerate platelet aggregation and, if sustained, inhibit angiogenic responses. Acute antagonism of NO signaling by Thrombospondin-1 is important for hemostasis but becomes detrimental for tissue survival of ischemic injuries. New therapeutic approaches targeting Thrombospondin-1 or CD47 can improve recovery from ischemic injuries and overcome a deficit in NO-responsiveness in aging.