scholarly journals N-Cadherin Interacts with Axin and LRP5 To Negatively Regulate Wnt/β-Catenin Signaling, Osteoblast Function, and Bone Formation

2008 ◽  
Vol 29 (4) ◽  
pp. 953-964 ◽  
Author(s):  
Eric Haÿ ◽  
Emmanuel Laplantine ◽  
Valérie Geoffroy ◽  
Monique Frain ◽  
Thomas Kohler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Transgenic Mice ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Adhesion Molecule ◽  
Molecular Complex ◽  
Tail Domain ◽  
Osteoblast Function ◽  
Canonical Wnt

ABSTRACT Wnt signaling plays an important role in the regulation of bone formation and bone mass. The mechanisms that regulate canonical Wnt signaling in osteoblasts are not fully understood. We show here a novel mechanism by which the adhesion molecule N-cadherin interacts with the Wnt coreceptor LRP5 and regulates canonical Wnt/β-catenin signaling in osteoblasts. We demonstrate that N-cadherin, besides associating with β-catenin at the membrane, forms a molecular complex with axin and LRP5 involving the LRP5 cytoplasmic tail domain. N-cadherin overexpression in osteoblasts increases N-cadherin-LRP5 interaction, causing increased β-catenin degradation and altered TCF/LEF transcription in response to Wnt3a. This mechanism results in decreased osteoblast gene expression and osteogenesis in basal conditions and in response to Wnt3a. Consistent with a functional mechanism, silencing N-cadherin expression in control cells increases TCF/LEF transcription and enhances the response to Wnt3a. Using N-cadherin transgenic mice, we show that increased N-cadherin-LRP5 interaction resulting from targeted overexpression of N-cadherin in osteoblasts causes increased β-catenin ubiquitination and results in cell-autonomous defective osteoblast function, reduced bone formation, and delayed bone mass acquisition. These data indicate that a previously unrecognized N-cadherin-axin-LRP5 interaction negatively regulates Wnt/β-catenin signaling and is critical in the regulation of osteoblast function, bone formation, and bone mass.

scholarly journals R-spondin 3 deletion favors Erk phosphorylation to enhance Wnt signaling and bone formation

2021 ◽  
Author(s):  
Kenichi Nagano ◽  
Kei Yamana ◽  
Hiroaki Saito ◽  
Riku Kiviranta ◽  
Ana Clara Pedroni ◽  
...  
Keyword(s):  
Bone Density ◽  
Bone Formation ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Erk Signaling ◽  
Canonical Wnt Signaling ◽  
Erk Phosphorylation ◽  
High Bone ◽  
Canonical Wnt

Abstract Activation of Wnt signaling leads to high bone density. The R-spondin family of four secreted glycoproteins (Rspo1-4) amplifies Wnt signaling. In humans, RSPO3 variants are strongly associated with bone density, but how RSPO3 affects skeletal homeostasis is not fully understood. Here we show that in mice Rspo3 haplo-insufficiency or its targeted deletion in osteoprogenitors lead to an increase in bone formation and bone mass. Contrary to expectations, Rspo3 haplo-insufficiency results in canonical Wnt signaling activation. Using mouse embryonic fibroblasts we show that Rspo3 deficiency leads to activation of Erk signaling, stabilizing β-catenin. Furthermore, Rspo3 haplo-insufficiency impairs Dkk1 efficacy in blocking canonical Wnt signaling and prevents the in vivo inhibition of bone formation and bone mass induced by osteoblast-targeted expression of Dkk1. We conclude that Rspo3 haplo-insufficiency/deficiency boosts canonical Wnt signaling by activating Erk signaling and impairing Dkk1’s inhibitory activity, which in turn lead to increased bone formation and bone mass.

scholarly journals R-spondin 3 deletion favors Erk phosphorylation to enhance Wnt signaling and bone formation

2021 ◽  
Author(s):  
Kenichi Nagano ◽  
Kei Yamana ◽  
Hiroaki Saito ◽  
Riku Kiviranta ◽  
Ana Clara Pedroni ◽  
...  
Keyword(s):  
Bone Density ◽  
Bone Formation ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Erk Signaling ◽  
Canonical Wnt Signaling ◽  
Erk Phosphorylation ◽  
High Bone ◽  
Canonical Wnt

Abstract Activation of Wnt signaling leads to high bone density. The R-spondin family of four secreted glycoproteins (Rspo1-4) amplifies Wnt signaling. In humans, RSPO3 variants are strongly associated with bone density, but how RSPO3 affects skeletal homeostasis is not fully understood. Here we show that in mice Rspo3 haplo-insufficiency or its targeted deletion in osteoprogenitors lead to an increase in bone formation and bone mass. Contrary to expectations, Rspo3 haplo-insufficiency results in canonical Wnt signaling activation. Using mouse embryonic fibroblasts we show that Rspo3 deficiency leads to activation of Erk signaling, stabilizing β-catenin. Furthermore, Rspo3 haplo-insufficiency impairs Dkk1 efficacy in blocking canonical Wnt signaling and prevents the in vivo inhibition of bone formation and bone mass induced by osteoblast-targeted expression of Dkk1. We conclude that Rspo3 haplo-insufficiency/deficiency boosts canonical Wnt signaling by activating Erk signaling and impairing Dkk1’s inhibitory activity, which in turn lead to increased bone formation and bone mass.

scholarly journals cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss

2018 ◽  
Vol 238 (3) ◽  
pp. 203-219 ◽  
Author(s):  
Ghania Ramdani ◽  
Nadine Schall ◽  
Hema Kalyanaraman ◽  
Nisreen Wahwah ◽  
Sahar Moheize ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Bone Loss ◽  
Bone Formation ◽  
Transgenic Mice ◽  
Bone Mass ◽  
Related Gene ◽  
Dependent Protein Kinase ◽  
Cgmp Dependent Protein Kinase ◽  
Dependent Protein

NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2 R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.

scholarly journals Chromatin-associated APC regulates gene expression in collaboration with canonical WNT signaling and AP-1

Oncotarget ◽  
2018 ◽  
Vol 9 (58) ◽  
pp. 31214-31230 ◽  
Author(s):  
William Hankey ◽  
Zhong Chen ◽  
Maxwell J. Bergman ◽  
Max O. Fernandez ◽  
Baris Hancioglu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Wnt Signaling ◽  
Canonical Wnt Signaling ◽  
Canonical Wnt

scholarly journals Prolyl Hydroxylase Domain-Containing Protein 3 Gene Expression in Chondrocytes Is Not Essential for Bone Development in Mice

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2200
Author(s):  
Weirong Xing ◽  
Sheila Pourteymoor ◽  
Gustavo A. Gomez ◽  
Yian Chen ◽  
Subburaman Mohan
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Bone Mass ◽  
Trabecular Bone ◽  
Bone Volume ◽  
Endochondral Bone Formation ◽  
Chondrocyte Differentiation ◽  
Trabecular Bone Volume ◽  
Endochondral Bone ◽  
Trabecular Bone Mass

We previously showed that conditional disruption of the Phd2 gene in chondrocytes led to a massive increase in long bone trabecular bone mass. Loss of Phd2 gene expression or inhibition of PHD2 activity by a specific inhibitor resulted in a several-fold compensatory increase in Phd3 expression in chondrocytes. To determine if expression of PHD3 plays a role in endochondral bone formation, we conditionally disrupted the Phd3 gene in chondrocytes by crossing Phd3 floxed (Phd3flox/flox) mice with Col2α1-Cre mice. Loss of Phd3 expression in the chondrocytes of Cre+; Phd3flox/flox conditional knockout (cKO) mice was confirmed by real time PCR. At 16 weeks of age, neither body weight nor body length was significantly different in the Phd3 cKO mice compared to Cre−; Phd3flox/flox wild-type (WT) mice. Areal BMD measurements of total body as well as femur, tibia, and lumbar skeletal sites were not significantly different between the cKO and WT mice at 16 weeks of age. Micro-CT measurements revealed significant gender differences in the trabecular bone volume adjusted for tissue volume at the secondary spongiosa of the femur and the tibia for both genotypes, but no genotype difference was found for any of the trabecular bone measurements of either the femur or the tibia. Trabecular bone volume of distal femur epiphysis was not different between cKO and WT mice. Histology analyses revealed Phd3 cKO mice exhibited a comparable chondrocyte differentiation and proliferation, as evidenced by no changes in cartilage thickness and area in the cKO mice as compared to WT littermates. Consistent with the in vivo data, lentiviral shRNA-mediated knockdown of Phd3 expression in chondrocytes did not affect the expression of markers of chondrocyte differentiation (Col2, Col10, Acan, Sox9). Our study found that Phd2 but not Phd3 expressed in chondrocytes regulates endochondral bone formation, and the compensatory increase in Phd3 expression in the chondrocytes of Phd2 cKO mice is not the cause for increased trabecular bone mass in Phd2 cKO mice.

scholarly journals Cellular FLIP Inhibits β-Catenin Ubiquitylation and Enhances Wnt Signaling

2004 ◽  
Vol 24 (19) ◽  
pp. 8418-8427 ◽  
Author(s):  
Mikihiko Naito ◽  
Ryohei Katayama ◽  
Toshiyasu Ishioka ◽  
Akiko Suga ◽  
Kohei Takubo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Immune Responses ◽  
Wnt Signaling ◽  
Axis Formation ◽  
Caspase Activity ◽  
Additional Mechanism ◽  
Long Form ◽  
Fas Signaling ◽  
Canonical Wnt ◽  
Cellular Flip

ABSTRACT Cellular FLIP (cFLIP) is a close homologue of caspase 8 without caspase activity that inhibits Fas signaling. The cFLIP protein is often expressed in human tumors and is believed to suppress antitumor immune responses involving the Fas system. Here, we report that a long form of cFLIP (cFLIP-L) inhibits β-catenin ubiquitylation and increases endogenous cytosolic β-catenin, which results in translocation of β-catenin into nuclei and induction of β-catenin-dependent gene expression in cFLIP-L-expressing cells. When cells stably expressing cFLIP-L were stimulated with Wnt3a, enhanced Wnt signaling was observed compared with the control cells. Conversely, depletion of endogenous cFLIP results in reduced Wnt signaling. Furthermore, cFLIP-L increases secondary-body axis formation when coinjected with suboptimal doses of β-catenin into early Xenopus embryos. Down-regulation of FADD by RNA-mediated interference abolishes the β-catenin-dependent gene expression induced by cFLIP-L. These results indicate that cFLIP-L, in cooperation with FADD, enhances canonical Wnt signaling by inhibiting proteasomal degradation of β-catenin, thus suggesting an additional mechanism involved with tumorgenesis, in addition to inhibiting Fas signaling.

scholarly journals Lrp5-independent activation of Wnt signaling by lithium chloride increases bone formation and bone mass in mice

2005 ◽  
Vol 102 (48) ◽  
pp. 17406-17411 ◽  
Author(s):  
P. Clement-Lacroix ◽  
M. Ai ◽  
F. Morvan ◽  
S. Roman-Roman ◽  
B. Vayssiere ◽  
...  
Keyword(s):  
Bone Formation ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Lithium Chloride

scholarly journals Reduced Affinity to and Inhibition by DKK1 Form a Common Mechanism by Which High Bone Mass-Associated Missense Mutations in LRP5 Affect Canonical Wnt Signaling

2005 ◽  
Vol 25 (12) ◽  
pp. 4946-4955 ◽  
Author(s):  
Minrong Ai ◽  
Sheri L. Holmen ◽  
Wim Van Hul ◽  
Bart O. Williams ◽  
Matthew L. Warman
Keyword(s):  
Cell Surface ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Common Mechanism ◽  
Missense Mutations ◽  
Canonical Wnt Signaling ◽  
High Bone Mass ◽  
Mutant Proteins ◽  
High Bone ◽  
Canonical Wnt

ABSTRACT The low-density-lipoprotein receptor-related protein 5 (LRP5), a coreceptor in the canonical Wnt signaling pathway, has been implicated in human disorders of low and high bone mass. Loss-of-function mutations cause the autosomal recessive osteoporosis-pseudoglioma syndrome, and heterozygous missense mutations in families segregating autosomal dominant high bone mass (HBM) phenotypes have been identified. We expressed seven different HBM-LRP5 missense mutations to delineate the mechanism by which they alter Wnt signaling. None of the mutations caused activation of the receptor in the absence of ligand. Each mutant receptor was able to reach the cell surface, albeit at differing amounts, and transduce exogenously supplied Wnt1 and Wnt3a signal. All HBM mutant proteins had reduced physical interaction with and reduced inhibition by DKK1. These data suggest that HBM mutant proteins can transit to the cell surface in sufficient quantity to transduce Wnt signal and that the likely mechanism for the HBM mutations' physiologic effects is via reduced affinity to and inhibition by DKK1.

scholarly journals The Microphthalmia-Associated Transcription Factor Mitf Interacts with β-Catenin To Determine Target Gene Expression

2006 ◽  
Vol 26 (23) ◽  
pp. 8914-8927 ◽  
Author(s):  
Alexander Schepsky ◽  
Katja Bruser ◽  
Gunnar J. Gunnarsson ◽  
Jane Goodall ◽  
Jón H. Hallsson ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Wnt Signaling ◽  
Signaling Pathway ◽  
Critical Role ◽  
Wnt Signaling Pathway ◽  
Feedback Mechanism ◽  
Canonical Wnt Signaling ◽  
Melanocyte Stem Cells ◽  
Canonical Wnt

ABSTRACT Commitment to the melanocyte lineage is characterized by the onset of expression of the microphthalmia-associated transcription factor (Mitf). This transcription factor plays a fundamental role in melanocyte development and maintenance and seems to be crucial for the survival of malignant melanocytes. Furthermore, Mitf has been shown to be involved in cell cycle regulation and to play important functions in self-renewal and maintenance of melanocyte stem cells. Although little is known about how Mitf regulates these various processes, one possibility is that Mitf interacts with other regulators. Here we show that Mitf can interact directly with β-catenin, the key mediator of the canonical Wnt signaling pathway. The Wnt signaling pathway plays a critical role in melanocyte development and is intimately involved in triggering melanocyte stem cell proliferation. Significantly, constitutive activation of this pathway is a feature of a number of cancers including malignant melanoma. Here we show that Mitf can redirect β-catenin transcriptional activity away from canonical Wnt signaling-regulated genes toward Mitf-specific target promoters to activate transcription. Thus, by a feedback mechanism, Mitf can diversify the output of canonical Wnt signaling to enhance the repertoire of genes regulated by β-catenin. Our results reveal a novel mechanism by which Wnt signaling and β-catenin activate gene expression, with significant implications for our understanding of both melanocyte development and melanoma.

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