The Experts below are selected from a list of 7515 Experts worldwide ranked by ideXlab platform
Thomas D Mueller - One of the best experts on this subject based on the ideXlab platform.
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anti Sclerostin antibody inhibits internalization of Sclerostin and Sclerostin mediated antagonism of wnt lrp6 signaling
PLOS ONE, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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Anti-Sclerostin Antibody Inhibits Internalization of Sclerostin and Sclerostin-Mediated Antagonism of Wnt/LRP6 Signaling
PloS one, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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distinct modes of inhibition by Sclerostin on bone morphogenetic protein and wnt signaling pathways
Journal of Biological Chemistry, 2010Co-Authors: Carola Krause, Stella E Weidauer, David J J De Gorter, Thomas D Mueller, Rutger L Van Bezooijen, Olexandr Korchynskyi, Karien E De Rooij, Sarah Hatsell, Aris N Economides, Clemens W G M LowikAbstract:Sclerostin is expressed by osteocytes and has catabolic effects on bone. It has been shown to antagonize bone morphogenetic protein (BMP) and/or Wnt activity, although at present the underlying mechanisms are unclear. Consistent with previous findings, Sclerostin opposed direct Wnt3a-induced but not direct BMP7-induced responses when both ligand and antagonist were provided exogenously to cells. However, we found that when both proteins are expressed in the same cell, Sclerostin can antagonize BMP signaling directly by inhibiting BMP7 secretion. Sclerostin interacts with both the BMP7 mature domain and pro-domain, leading to intracellular retention and proteasomal degradation of BMP7. Analysis of Sclerostin knock-out mice revealed an inhibitory action of Sclerostin on Wnt signaling in both osteoblasts and osteocytes in cortical and cancellous bones. BMP7 signaling was predominantly inhibited by Sclerostin in osteocytes of the calcaneus and the cortical bone of the tibia. Our results suggest that Sclerostin exerts its potent bone catabolic effects by antagonizing Wnt signaling in a paracrine and autocrine manner and antagonizing BMP signaling selectively in the osteocytes that synthesize simultaneously both Sclerostin and BMP7 proteins.
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NMR structure of the Wnt modulator protein Sclerostin
Biochemical and biophysical research communications, 2009Co-Authors: Stella E Weidauer, Peter Schmieder, Monika Beerbaum, Werner Schmitz, Hartmut Oschkinat, Thomas D MuellerAbstract:Sclerostin has been identified as a negative regulator of bone growth. Initially it was considered that Sclerostin performs its regulatory function via acting as a modulator of bone morphogenetic proteins (BMPs) similar to known examples such as Noggin, Chordin, and members of the DAN family. Recent findings, however, show that Sclerostin interferes with the Wnt signaling pathway due to binding to the Wnt co-receptor LRP5 thereby modulating bone growth. As Sclerostin is exclusively produced by osteocytes located in bones, neutralization of its bone-inhibiting functions makes it a highly interesting target for an osteoanabolic therapeutic approach in diseases characterized by bone loss, such as osteoporosis. Despite the huge interest in Sclerostin inhibitors the molecular basis of its function and its interaction with components of the Wnt signaling cascade has remained unclear. Here, we present the NMR structure of murine Sclerostin providing the first insights how Sclerostin might bind to LRP5.
Stella E Weidauer - One of the best experts on this subject based on the ideXlab platform.
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The Sclerostin-neutralizing antibody AbD09097 recognizes an epitope adjacent to Sclerostin's binding site for the Wnt co-receptor LRP6
Open biology, 2016Co-Authors: Verena Boschert, Stella E Weidauer, Evamaria Muth, Achim Knappik, Christian Frisch, Peter Schmieder, Monika Beerbaum, J. W. Back, K. Van Pee, Peter TimmermanAbstract:The glycoprotein Sclerostin has been identified as a negative regulator of bone growth. It exerts its function by interacting with the Wnt co-receptor LRP5/6, blocks the binding of Wnt factors and thereby inhibits Wnt signalling. Neutralizing anti-Sclerostin antibodies are able to restore Wnt activity and enhance bone growth thereby presenting a new osteoanabolic therapy approach for diseases such as osteoporosis. We have generated various Fab antibodies against human and murine Sclerostin using a phage display set-up. Biochemical analyses have identified one Fab developed against murine Sclerostin, AbD09097 that efficiently neutralizes Sclerostin's Wnt inhibitory activity. In vitro interaction analysis using Sclerostin variants revealed that this neutralizing Fab binds to Sclerostin's flexible second loop, which has been shown to harbour the LRP5/6 binding motif. Affinity maturation was then applied to AbD09097, providing a set of improved neutralizing Fab antibodies which particularly bind human Sclerostin with enhanced affinity. Determining the crystal structure of AbD09097 provides first insights into how this antibody might recognize and neutralize Sclerostin. Together with the structure-function relationship derived from affinity maturation these new data will foster the rational design of new and highly efficient anti-Sclerostin antibodies for the therapy of bone loss diseases such as osteoporosis.
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anti Sclerostin antibody inhibits internalization of Sclerostin and Sclerostin mediated antagonism of wnt lrp6 signaling
PLOS ONE, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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Anti-Sclerostin Antibody Inhibits Internalization of Sclerostin and Sclerostin-Mediated Antagonism of Wnt/LRP6 Signaling
PloS one, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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distinct modes of inhibition by Sclerostin on bone morphogenetic protein and wnt signaling pathways
Journal of Biological Chemistry, 2010Co-Authors: Carola Krause, Stella E Weidauer, David J J De Gorter, Thomas D Mueller, Rutger L Van Bezooijen, Olexandr Korchynskyi, Karien E De Rooij, Sarah Hatsell, Aris N Economides, Clemens W G M LowikAbstract:Sclerostin is expressed by osteocytes and has catabolic effects on bone. It has been shown to antagonize bone morphogenetic protein (BMP) and/or Wnt activity, although at present the underlying mechanisms are unclear. Consistent with previous findings, Sclerostin opposed direct Wnt3a-induced but not direct BMP7-induced responses when both ligand and antagonist were provided exogenously to cells. However, we found that when both proteins are expressed in the same cell, Sclerostin can antagonize BMP signaling directly by inhibiting BMP7 secretion. Sclerostin interacts with both the BMP7 mature domain and pro-domain, leading to intracellular retention and proteasomal degradation of BMP7. Analysis of Sclerostin knock-out mice revealed an inhibitory action of Sclerostin on Wnt signaling in both osteoblasts and osteocytes in cortical and cancellous bones. BMP7 signaling was predominantly inhibited by Sclerostin in osteocytes of the calcaneus and the cortical bone of the tibia. Our results suggest that Sclerostin exerts its potent bone catabolic effects by antagonizing Wnt signaling in a paracrine and autocrine manner and antagonizing BMP signaling selectively in the osteocytes that synthesize simultaneously both Sclerostin and BMP7 proteins.
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NMR structure of the Wnt modulator protein Sclerostin
Biochemical and biophysical research communications, 2009Co-Authors: Stella E Weidauer, Peter Schmieder, Monika Beerbaum, Werner Schmitz, Hartmut Oschkinat, Thomas D MuellerAbstract:Sclerostin has been identified as a negative regulator of bone growth. Initially it was considered that Sclerostin performs its regulatory function via acting as a modulator of bone morphogenetic proteins (BMPs) similar to known examples such as Noggin, Chordin, and members of the DAN family. Recent findings, however, show that Sclerostin interferes with the Wnt signaling pathway due to binding to the Wnt co-receptor LRP5 thereby modulating bone growth. As Sclerostin is exclusively produced by osteocytes located in bones, neutralization of its bone-inhibiting functions makes it a highly interesting target for an osteoanabolic therapeutic approach in diseases characterized by bone loss, such as osteoporosis. Despite the huge interest in Sclerostin inhibitors the molecular basis of its function and its interaction with components of the Wnt signaling cascade has remained unclear. Here, we present the NMR structure of murine Sclerostin providing the first insights how Sclerostin might bind to LRP5.
Jesus Delgado-calle - One of the best experts on this subject based on the ideXlab platform.
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Sclerostin: an Emerging Target for the Treatment of Cancer-Induced Bone Disease
Current Osteoporosis Reports, 2017Co-Authors: Michelle M. Mcdonald, Jesus Delgado-calleAbstract:Purpose of Review This review provides a summary of the current knowledge on Sost/Sclerostin in cancers targeting the bone, discusses novel observations regarding its potential as a therapeutic approach to treat cancer-induced bone loss, and proposes future research needed to fully understand the potential of therapeutic approaches that modulate Sclerostin function. Recent Findings Accumulating evidence shows that Sclerostin expression is dysregulated in a number of cancers that target the bone. Further, new findings demonstrate that pharmacological inhibition of Sclerostin in preclinical models of multiple myeloma results in a robust prevention of bone loss and preservation of bone strength, without apparent effects on tumor growth. These data raise the possibility of targeting Sclerostin for the treatment of cancer patients with bone metastasis. Summary Sclerostin is emerging as a valuable target to prevent the bone destruction that accompanies the growth of cancer cells in the bone. Further studies will focus on combining anti-Sclerostin therapy with tumor-targeted agents to achieve both beneficial skeletal outcomes and inhibition of tumor progression.
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Sclerostin: an Emerging Target for the Treatment of Cancer-Induced Bone Disease
Current osteoporosis reports, 2017Co-Authors: Michelle M. Mcdonald, Jesus Delgado-calleAbstract:This review provides a summary of the current knowledge on Sost/Sclerostin in cancers targeting the bone, discusses novel observations regarding its potential as a therapeutic approach to treat cancer-induced bone loss, and proposes future research needed to fully understand the potential of therapeutic approaches that modulate Sclerostin function. Accumulating evidence shows that Sclerostin expression is dysregulated in a number of cancers that target the bone. Further, new findings demonstrate that pharmacological inhibition of Sclerostin in preclinical models of multiple myeloma results in a robust prevention of bone loss and preservation of bone strength, without apparent effects on tumor growth. These data raise the possibility of targeting Sclerostin for the treatment of cancer patients with bone metastasis. Sclerostin is emerging as a valuable target to prevent the bone destruction that accompanies the growth of cancer cells in the bone. Further studies will focus on combining anti-Sclerostin therapy with tumor-targeted agents to achieve both beneficial skeletal outcomes and inhibition of tumor progression.
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Epigenetic Regulation of Sost/Sclerostin Expression
Current Molecular Biology Reports, 2017Co-Authors: Álvaro Real, José A. Riancho, Jesus Delgado-calleAbstract:Purpose of Review Sclerostin, encoded by the gene Sost, is a regulatory glycoprotein produced by mature osteocytes in bone. Findings in animals and humans revealed that Sost/Sclerostin deficiency results in increased bone density, and neutralizing antibodies to this protein are being investigated for treatment of postmenopausal osteoporosis. While it is clear that Sclerostin is a major regulator of skeletal homeostasis, the specific mechanisms that control its expression are not completely understood. Recent Findings Growing evidence suggest that epigenetic phenomena such as histone modification, DNA methylation, or microRNAs influence Sost/Sclerostin expression under physiologic and pathologic conditions. Furthermore, these epigenetic mechanisms control Sost/Sclerostin production in a time- and cell-context manner. Together with previous literature, these new findings indicate that Sost/Sclerostin regulation is complex and requires coordination of multiple mechanisms. Summary This review summarizes the current knowledge on the epigenetic regulation of Sost/Sclerostin expression and discusses future research needed to unravel the mechanisms by which Sost/Sclerostin expression is controlled in a cell-, time-, and space-specific manner.
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Role and mechanism of action of Sclerostin in bone
Bone, 2016Co-Authors: Jesus Delgado-calle, Amy Y. Sato, Teresita BellidoAbstract:After discovering that lack of Sost/Sclerostin expression is the cause of the high bone mass human syndromes Van Buchem disease and sclerosteosis, extensive animal experimentation and clinical studies demonstrated that Sclerostin plays a critical role in bone homeostasis and that its deficiency or pharmacological neutralization increases bone formation. Dysregulation of Sclerostin expression also underlies the pathophysiology of skeletal disorders characterized by loss of bone mass, as well as the damaging effects of some cancers in bone. Thus, Sclerostin has quickly become a promising molecular target for the treatment of osteoporosis and other skeletal diseases, and beneficial skeletal outcomes are observed in animal studies and clinical trials using neutralizing antibodies against Sclerostin. However, the anabolic effect of blocking Sclerostin decreases with time, bone mass accrual is also accompanied by anti-catabolic effects, and there is bone loss over time after therapy discontinuation. Further, the cellular source of Sclerostin in the bone/bone marrow microenvironment under physiological and pathological conditions, the pathways that regulate Sclerostin expression and the mechanisms by which Sclerostin modulates the activity of osteocytes, osteoblasts, and osteoclasts remain unclear. In this review, we highlight the current knowledge on the regulation of Sost/sclerotin expression and its mechanism(s) of action, discuss novel observations regarding its role in signaling pathways activated by hormones and mechanical stimuli in bone, and propose future research needed to understand the full potential of therapeutic interventions that modulate Sost/Sclerostin expression.
Reinhard Gruber - One of the best experts on this subject based on the ideXlab platform.
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Dental and periodontal phenotype in Sclerostin knockout mice
International Journal of Oral Science, 2014Co-Authors: Ulrike Kuchler, Uwe Yacine Schwarze, Toni Dobsak, Patrick Heimel, Dieter D. Bosshardt, Michaela Kneissel, Reinhard GruberAbstract:Sclerostin is a Wnt signalling antagonist that controls bone metabolism. Sclerostin is expressed by osteocytes and cementocytes; however, its role in the formation of dental structures remains unclear. Here, we analysed the mandibles of Sclerostin knockout mice to determine the influence of Sclerostin on dental structures and dimensions using histomorphometry and micro-computed tomography (μCT) imaging. μCT and histomorphometric analyses were performed on the first lower molar and its surrounding structures in mice lacking a functional Sclerostin gene and in wild-type controls. μCT on six animals in each group revealed that the dimension of the basal bone as well as the coronal and apical part of alveolar part increased in the Sclerostin knockout mice. No significant differences were observed for the tooth and pulp chamber volume. Descriptive histomorphometric analyses of four wild-type and three Sclerostin knockout mice demonstrated an increased width of the cementum and a concomitant moderate decrease in the periodontal space width. Taken together, these results suggest that the lack of Sclerostin mainly alters the bone and cementum phenotypes rather than producing abnormalities in tooth structures such as dentin. A protein that alters bone and dental support structures does not affect tooth development, which has been reported by researchers in Austria and Switzerland. A team led by Reinhard Gruber, from both the Medical University of Vienna, Austria, and the University of Bern, Switzerland, analysed the lower jaws of mice engineered to lack a functioning copy of a gene called Sost . This gene encodes the protein Sclerostin, which inhibits bone formation. Scientists knew that Sclerostin was expressed by bone-resorbing cells called osteocytes and cementocytes, which form the modified bone found around the root of teeth. Gruber and colleagues found abnormalities in the structures surrounding the first molars of the mice lacking Sclerostin. However, they found no significant defects in tooth dimensions. The work has implications for periodontal regeneration, implant dentistry and dentin formation.
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Dental and periodontal phenotype in Sclerostin knockout mice.
International journal of oral science, 2014Co-Authors: Ulrike Kuchler, Uwe Yacine Schwarze, Toni Dobsak, Patrick Heimel, Dieter D. Bosshardt, Michaela Kneissel, Reinhard GruberAbstract:Sclerostin is a Wnt signalling antagonist that controls bone metabolism. Sclerostin is expressed by osteocytes and cementocytes; however, its role in the formation of dental structures remains unclear. Here, we analysed the mandibles of Sclerostin knockout mice to determine the influence of Sclerostin on dental structures and dimensions using histomorphometry and micro-computed tomography (μCT) imaging. μCT and histomorphometric analyses were performed on the first lower molar and its surrounding structures in mice lacking a functional Sclerostin gene and in wild-type controls. μCT on six animals in each group revealed that the dimension of the basal bone as well as the coronal and apical part of alveolar part increased in the Sclerostin knockout mice. No significant differences were observed for the tooth and pulp chamber volume. Descriptive histomorphometric analyses of four wild-type and three Sclerostin knockout mice demonstrated an increased width of the cementum and a concomitant moderate decrease in the periodontal space width. Taken together, these results suggest that the lack of Sclerostin mainly alters the bone and cementum phenotypes rather than producing abnormalities in tooth structures such as dentin.
David J J De Gorter - One of the best experts on this subject based on the ideXlab platform.
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anti Sclerostin antibody inhibits internalization of Sclerostin and Sclerostin mediated antagonism of wnt lrp6 signaling
PLOS ONE, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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Anti-Sclerostin Antibody Inhibits Internalization of Sclerostin and Sclerostin-Mediated Antagonism of Wnt/LRP6 Signaling
PloS one, 2013Co-Authors: Maarten Van Dinther, Juan Zhang, Stella E Weidauer, Verena Boschert, Evamaria Muth, Achim Knappik, David J J De Gorter, Puck B Van Kasteren, Christian Frisch, Thomas D MuellerAbstract:Sclerosteosis is a rare high bone mass disease that is caused by inactivating mutations in the SOST gene. Its gene product, Sclerostin, is a key negative regulator of bone formation and might therefore serve as a target for the anabolic treatment of osteoporosis. The exact molecular mechanism by which Sclerostin exerts its antagonistic effects on Wnt signaling in bone forming osteoblasts remains unclear. Here we show that Wnt3a-induced transcriptional responses and induction of alkaline phosphatase activity, an early marker of osteoblast differentiation, require the Wnt co-receptors LRP5 and LRP6. Unlike Dickkopf1 (DKK1), Sclerostin does not inhibit Wnt-3a-induced phosphorylation of LRP5 at serine 1503 or LRP6 at serine 1490. Affinity labeling of cell surface proteins with [125I]Sclerostin identified LRP6 as the main specific Sclerostin receptor in multiple mesenchymal cell lines. When cells were challenged with Sclerostin fused to recombinant green fluorescent protein (GFP) this was internalized, likely via a Clathrin-dependent process, and subsequently degraded in a temperature and proteasome-dependent manner. Ectopic expression of LRP6 greatly enhanced binding and cellular uptake of Sclerostin-GFP, which was reduced by the addition of an excess of non-GFP-fused Sclerostin. Finally, an anti-Sclerostin antibody inhibited the internalization of Sclerostin-GFP and binding of Sclerostin to LRP6. Moreover, this antibody attenuated the antagonistic activity of Sclerostin on canonical Wnt-induced responses.
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distinct modes of inhibition by Sclerostin on bone morphogenetic protein and wnt signaling pathways
Journal of Biological Chemistry, 2010Co-Authors: Carola Krause, Stella E Weidauer, David J J De Gorter, Thomas D Mueller, Rutger L Van Bezooijen, Olexandr Korchynskyi, Karien E De Rooij, Sarah Hatsell, Aris N Economides, Clemens W G M LowikAbstract:Sclerostin is expressed by osteocytes and has catabolic effects on bone. It has been shown to antagonize bone morphogenetic protein (BMP) and/or Wnt activity, although at present the underlying mechanisms are unclear. Consistent with previous findings, Sclerostin opposed direct Wnt3a-induced but not direct BMP7-induced responses when both ligand and antagonist were provided exogenously to cells. However, we found that when both proteins are expressed in the same cell, Sclerostin can antagonize BMP signaling directly by inhibiting BMP7 secretion. Sclerostin interacts with both the BMP7 mature domain and pro-domain, leading to intracellular retention and proteasomal degradation of BMP7. Analysis of Sclerostin knock-out mice revealed an inhibitory action of Sclerostin on Wnt signaling in both osteoblasts and osteocytes in cortical and cancellous bones. BMP7 signaling was predominantly inhibited by Sclerostin in osteocytes of the calcaneus and the cortical bone of the tibia. Our results suggest that Sclerostin exerts its potent bone catabolic effects by antagonizing Wnt signaling in a paracrine and autocrine manner and antagonizing BMP signaling selectively in the osteocytes that synthesize simultaneously both Sclerostin and BMP7 proteins.
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osteocyte derived Sclerostin inhibits bone formation its role in bone morphogenetic protein and wnt signaling
Journal of Bone and Joint Surgery American Volume, 2008Co-Authors: Peter Ten Dijke, David J J De Gorter, Carola Krause, Clemens W G M Lowik, Rutger L Van BezooijenAbstract:Sclerosteosis and Van Buchem disease are rare, high-bone-mass disorders that have been linked to deficiency in the SOST gene, encoding Sclerostin. Sclerostin belongs to the DAN family of glycoproteins, of which multiple family members have been shown to antagonize bone morphogenetic protein (BMP) and/or Wnt activity. Sclerostin is specifically expressed by osteocytes and inhibits BMP-induced osteoblast differentiation and ectopic bone formation. Sclerostin binds only weakly to BMPs and does not inhibit direct BMP-induced responses. Instead, Sclerostin antagonizes canonical Wnt signaling by binding to Wnt coreceptors, low-density lipoprotein receptor-related protein 5 and 6. Several lipoprotein receptor-related protein-5 mutants that cause the high-bone-mass trait are defective in Sclerostin binding. Thus, high bone mass in sclerosteosis and Van Buchem disease may result from increased Wnt signaling due to the absence of or insensitivity to Sclerostin.
