TSC1 regulates osteoclast podosome organization and bone resorption through mTORC1 and Rac1/Cdc42.
Ontology highlight
ABSTRACT:
SUBMITTER: Xu S
PROVIDER: S-EPMC6143527 | biostudies-literature | 2018 Sep
REPOSITORIES: biostudies-literature
Publications
TSC1 regulates osteoclast podosome organization and bone resorption through mTORC1 and Rac1/Cdc42.
Xu Song S Zhang Yue Y Wang Jian J Li Kai K Tan Kang K Liang Kangyan K Shen Junhui J Cai Daozhang D Jin Dadi D Li Mangmang M Xiao Guozhi G Xu Jiake J Jiang Yu Y Bai Xiaochun X
Cell death and differentiation 20180122 9
Reorganization of the podosome into the sealing zone is crucial for osteoclasts (OCLs) to resorb bone, but the underlying mechanisms are unclear. Here, we show that tuberous sclerosis complex 1 (TSC1) functions centrally in OCLs to promote podosome organization and bone resorption through mechanistic target of rapamycin complex 1 (mTORC1) and the small GTPases Rac1/Cdc42. During osteoclastogenesis, enhanced expression of TSC1 downregulates mTORC1 activity. TSC1 deletion in OCLs reduced podosome ...[more]
Similar Datasets
Project description:Tuberous sclerosis complex 1 (Tsc1) is a tumor suppressor that functions together with Tsc2 to negatively regulate the mechanistic target of rapamycin complex 1 (mTORC1) activity. Here, we show that Tsc1 has a critical role in the tight junction (TJ) formation of epithelium, independent of its role in Tsc2 and mTORC1 regulation. When an epithelial cell establishes contact with neighboring cells, Tsc1, but not Tsc2, migrates from the cytoplasm to junctional membranes, in which it binds myosin 6 to anchor the perijunctional actin cytoskeleton to β-catenin and ZO-1. In its absence, perijunctional actin cytoskeleton fails to form. In mice, intestine-specific or inducible, whole-body Tsc1 ablation disrupts adherens junction/TJ structures in intestine or skin epithelia, respectively, causing Crohn's disease-like symptoms in the intestine or psoriasis-like phenotypes on the skin. In patients with Crohn's disease or psoriasis, junctional Tsc1 levels in epithelial tissues are markedly reduced, concomitant with the TJ structure impairment, suggesting that Tsc1 deficiency may underlie TJ-related diseases. These findings establish an essential role of Tsc1 in the formation of cell junctions and underpin its association with TJ-related human diseases.
| S-EPMC8325158 | biostudies-literature
Project description:Hypoxia and the hypoxia-inducible factor (HIF) transcription factor regulate angiogenic-osteogenic coupling and osteoclast-mediated bone resorption. To determine how HIF might coordinate osteoclast and osteoblast function, we studied angiopoietin-like 4 (ANGPTL4), the top HIF target gene in an Illumina HumanWG-6 v3.0 48k array of normoxic vs. hypoxic osteoclasts differentiated from human CD14(+) monocytes (14.3-fold induction, P<0.0004). ANGPTL4 mRNA and protein were induced by 24 h at 2% O(2) in human primary osteoclasts, monocytes, and osteoblasts. ANGPTL4 protein was observed by immunofluorescence in osteoclasts and osteoblasts in vivo. Normoxic inducers of HIF (CoCl(2), desferrioxamine, and l-mimosine) and 100 ng/ml ANGPTL4 stimulated osteoclastic resorption 2- to 3-fold in assays of lacunar dentine resorption, without affecting osteoclast viability. Isoform-specific HIF-1? small interfering RNA ablated hypoxic induction of ANGPTL4 and of resorption, which was rescued by addition of exogenous ANGPTL4 (P<0.001). In the osteoblastic Saos2 cell line, ANGPTL4 caused a dose-dependent increase in proliferation (P<0.01, 100 ng/ml) and, at lower doses (1-25 ng/ml), mineralization. These results demonstrate that HIF is sufficient to enhance osteoclast-mediated bone resorption and that ANGPTL4 can compensate for HIF-1? deficiency with respect to stimulation of osteoclast activity and also augments osteoblast proliferation and differentiation.
| S-EPMC2992372 | biostudies-literature
Project description:Coupling is the process that links bone resorption to bone formation in a temporally and spatially coordinated manner within the remodeling cycle. Several lines of evidence point to the critical roles of osteoclast-derived coupling factors in the regulation of osteoblast performance. Here, we used a fractionated secretomic approach and identified the axon-guidance molecule SLIT3 as a clastokine that stimulated osteoblast migration and proliferation by activating ?-catenin. SLIT3 also inhibited bone resorption by suppressing osteoclast differentiation in an autocrine manner. Mice deficient in Slit3 or its receptor, Robo1, exhibited osteopenic phenotypes due to a decrease in bone formation and increase in bone resorption. Mice lacking Slit3 specifically in osteoclasts had low bone mass, whereas mice with either neuron-specific Slit3 deletion or osteoblast-specific Slit3 deletion had normal bone mass, thereby indicating the importance of SLIT3 as a local determinant of bone metabolism. In postmenopausal women, higher circulating SLIT3 levels were associated with increased bone mass. Notably, injection of a truncated recombinant SLIT3 markedly rescued bone loss after an ovariectomy. Thus, these results indicate that SLIT3 plays an osteoprotective role by synchronously stimulating bone formation and inhibiting bone resorption, making it a potential therapeutic target for metabolic bone diseases.
| S-EPMC5873876 | biostudies-literature
Project description:RNA interference (RNAi) is a sequence-specific post-transcriptional gene silencing technique developed with dramatically increasing utility for both scientific and therapeutic purposes. Short interfering RNA (siRNA) is currently exploited to regulate protein expression relevant to many therapeutic applications, and commonly used as a tool for elucidating disease-associated genes. Osteoporosis and their associated osteoporotic fragility fractures in both men and women are rapidly becoming a global healthcare crisis as average life expectancy increases worldwide. New therapeutics are needed for this increasing patient population. This review describes the diversity of molecular targets suitable for RNAi-based gene knock down in osteoclasts to control osteoclast-mediated excessive bone resorption. We identify strategies for developing targeted siRNA delivery and efficient gene silencing, and describe opportunities and challenges of introducing siRNA as a therapeutic approach to hard and connective tissue disorders.
| S-EPMC3293106 | biostudies-literature
Project description:ObjectiveAutoantibodies are detected in most patients with rheumatoid arthritis (RA) and can be of the IgM, IgG or IgA subclass. Correlations between IgA autoantibodies and more severe disease activity have been previously reported, but the functional role of IgA autoantibodies in the pathogenesis of RA is ill understood. In this study, we explored the effect of IgA immune complexes on osteoclast mediated bone resorption.MethodsAnti-citrullinated peptide antibody (ACPA) and anti-carbamylated protein (anti-CarP) antibody levels of the IgA and IgG isotype and rheumatoid factor (RF) IgA were determined in synovial fluid (SF) of RA patients. Monocytes, neutrophils, and osteoclasts were stimulated with precipitated immune complexes from SF of RA patients or IgA- and IgG-coated beads. Activation was determined by neutrophil extracellular trap (NET) release, cytokine secretion, and bone resorption.ResultsNET formation by neutrophils was enhanced by SF immune complexes compared to immune complexes from healthy or RA serum. Monocytes stimulated with isolated SF immune complexes released IL-6 and IL-8, which correlated with the levels of ACPA IgA levels in SF. Osteoclasts cultured in the presence of supernatant of IgA-activated monocytes resorbed significantly more bone compared to osteoclasts that were cultured in supernatant of IgG-activated monocytes (p=0.0233). Osteoclasts expressed the Fc receptor for IgA (FcαRI; CD89) and Fc gamma receptors. IgA-activated osteoclasts however produced significantly increased levels of IL-6 (p<0.0001) and IL-8 (p=0.0007) compared to IgG-activated osteoclasts. Both IL-6 (p=0.03) and IL-8 (p=0.0054) significantly enhanced bone resorption by osteoclasts.ConclusionIgA autoantibodies induce release of IL-6 and IL-8 by immune cells as well as osteoclasts, which enhances bone resorption by osteoclasts. We anticipate that this will result in more severe disease activity in RA patients. Targeting IgA-FcαRI interactions therefore represents a promising novel therapeutic strategy for RA patients with IgA autoantibodies.
| S-EPMC8281931 | biostudies-literature
Project description:ObjectiveWhile phosphoinositide 3-kinases (PI3Ks) are involved in various intracellular signal transduction processes, the specific functions of the different PI3K isoforms are poorly understood. We have previously shown that the PI3K? isoform is required for arthritis development in the K/BxN serum-transfer model. Since osteoclasts play a critical role in pathologic bone loss during inflammatory arthritis and other diseases, we undertook this study to test the role of PI3K? in osteoclast development and function using a combined genetic and pharmacologic approach.MethodsThe role of PI3K? in primary human and murine osteoclast cultures was tested with the PI3K?-selective inhibitor TGX221 and by using PI3K?(-/-) mice. The trabecular bone architecture of PI3K?(-/-) mice was evaluated using micro-computed tomography and histomorphometric analyses.ResultsThe expression of PI3K? was strongly and specifically up-regulated during in vitro osteoclast differentiation. In vitro development of large multinucleated osteoclasts from human or murine progenitors and their resorption capacity were strongly reduced by the PI3K? inhibitor TGX221 or by the genetic deficiency of PI3K?. This was likely due to defective cytoskeletal reorganization and vesicular trafficking, since PI3K?(-/-) mouse multinucleated cells failed to form actin rings and retained intracellular acidic vesicles and cathepsin K. In contrast, osteoclast-specific gene expression and the survival and apoptosis of osteoclasts were not affected. PI3K?(-/-) mice had significantly increased trabecular bone volume and showed abnormal osteoclast morphology with defective resorption pit formation.ConclusionPI3K? plays an important role in osteoclast development and function and is required for in vivo bone homeostasis.
| S-EPMC4314683 | biostudies-literature
Project description:Lysosomal trafficking and protease exocytosis in osteoclasts are essential for ruffled border formation and bone resorption. Yet the mechanism underlying lysosomal trafficking and the related process of exocytosis remains largely unknown. We found ATP6ap1 (Ac45), an accessory subunit of vacuolar-type H(+)-ATPases (V-ATPases), to be highly induced by receptor activator for nuclear factor kappa B ligand (RANKL) in osteoclast differentiation. Ac45 knockdown osteoclasts formed normal actin rings, but had severely impaired extracellular acidification and bone resorption. Ac45 knockdown significantly reduced osteoclast formation. The decrease in the number of osteoclasts does not result from abnormal apoptosis; rather, it results from decreased osteoclast precursor cell proliferation and fusion, which may be partially due to the downregulation of extracellular signal-regulated kinase (ERK) phosphorylation and FBJ osteosarcoma oncogene (c-fos), nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), and "transmembrane 7 superfamily member 4" (Tm7sf4) expression. Notably, Ac45 knockdown osteoclasts exhibited impaired lysosomal trafficking and exocytosis, as indicated by the absence of lysosomal trafficking to the ruffled border and a lack of cathepsin K exocytosis into the resorption lacuna. Our data revealed that the impaired exocytosis is specifically due to Ac45 deficiency, and not the general consequence of a defective V-ATPase. Together, our results demonstrate the essential role of Ac45 in osteoclast-mediated extracellular acidification and protease exocytosis, as well as the ability of Ac45 to guide lysosomal intracellular trafficking to the ruffled border, potentially through its interaction with the small guanosine-5'-triphosphatase (GTPase) Rab7. Our work indicates that Ac45 may be a novel therapeutic target for osteolytic disease.
| S-EPMC3951719 | biostudies-literature
Project description:BackgroundOsteomyelitis (OM) is an inflammatory condition of bone characterized by cortical bone devascularization and necrosis. Dysregulation of bone remodelling is triggered by OM. Bone remodelling is precisely coordinated by bone resorption and formation via a reversal phase. However, the cellular and molecular mechanisms underlying bone remodelling failure after osteomyelitis remain elusive.MethodsTo elucidate the cellular and molecular mechanism underlying bone healing after osteomyelitis, we employed single-cell RNA sequencing (scRNA-seq) to depict the atlas of human cortical bone in normal, infected and reconstructed states. Dimensionality reduction by t-stochastic neighbourhood embedding (t-SNE) and graph-based clustering were applied to analyse the detailed clusters of osteoclast lineages. After trajectory analysis of osteoclast lineages over pseudotime, real-time PCR and immunofluorescence (IF) staining were applied to identify marker gene expression of various osteoclast lineages in the osteoclast induction model and human bone sections, respectively. The potential function and communication of osteoclasts were analysed via gene set enrichment analysis (GSEA) and CellChat. The chemotactic ability of mesenchymal stem cells (MSCs) and osteoclast lineage cells in various differentiation states was determined by transwell assays and coculture assays. The effects of various osteoclast lineages on the osteogenic differentiation potential of MSCs were also determined by using this coculture system. A normal mouse tibia fracture model and an osteomyelitis-related tibia fracture model were generated via injection of luciferase-labelled Staphylococcus aureus to verify the relationships between a novel osteoclast lineage and MSCs. Then, the infection was detected by a bioluminescence imaging system. Finally, immunofluorescence staining was used to detect the expression of markers of MSCs and novel osteoclast lineages in different remodelling phases in normal and infected bone remodelling models.ResultsIn this study, we constructed a cell atlas encompassing normal, infected, and reconstructed cortical bone. Then, we identified a novel subset at the earlier stage of the osteoclast lineage that exhibited increased expression of IDO1, CCL3, and CCL4. These IDO1highCCL3highCCL4high cells, termed osteostaticytes (OSCs), were further regarded as the reservoir of osteoclasts in the reversal phase. Notably, OSCs exhibited the highest chemotactic activity, surpassing other lineage subsets. We also discovered that cells at the earlier stage of the osteoclast lineage play a significant role in recruiting mesenchymal stem cells (MSCs). Finally, the data revealed that OSCs might be positively related to the occurrence of bone MSCs and the contribution of bone remodelling.ConclusionCollectively, our findings revealed a novel stage (OSC) within the osteoclast lineage, potentially representing elusive bone reversal cells due to its increased chemotactic ability towards MSCs and potential contribution to bone remodelling. This study provides valuable insights into the intricate mechanisms of the reversal phase during bone remodelling and unveils potential therapeutic strategies for diseases associated with bone uncoupling.Translational potential of this articleThis study identified a new subset, referred to as IDO1(plus symbol) CCL3(plus symbol) CCL4(plus symbol) osteostaticytes which displayed the highest chemotactic activity among all osteoclast lineages and may serve as reversal cells in bone remodelling. These findings offer new insights and insights for understanding bone reversal-related diseases and may serve as novel therapeutic targets for conditions such as osteomyelitis and delayed bone healing.
| S-EPMC11254843 | biostudies-literature
Project description:Vav1 is a Rho/Rac guanine nucleotide exchange factor primarily expressed in hematopoietic cells. In this study, we investigated the potential role of Vav1 in osteoclast (OC) differentiation by comparing the ability of bone marrow mononuclear cells (BMMCs) obtained from Vav1-deficient (Vav1-/-) and wild-type (WT) mice to differentiate into mature OCs upon stimulation with macrophage colony stimulating factor and receptor activator of nuclear kappa B ligand in vitro. Our results suggested that Vav1 deficiency promoted the differentiation of BMMCs into OCs, as indicated by the increased expression of tartrate-resistant acid phosphatase, cathepsin K, and calcitonin receptor. Therefore, Vav1 may play a negative role in OC differentiation. This hypothesis was supported by the observation of more OCs in the femurs of Vav1-/- mice than in WT mice. Furthermore, the bone status of Vav1-/- mice was analyzed in situ and the femurs of Vav1-/- mice appeared abnormal, with poor bone density and fewer number of trabeculae. In addition, Vav1-deficient OCs showed stronger adhesion to vitronectin, an ?v?3 integrin ligand important in bone resorption. Thus, Vav1 may inhibit OC differentiation and protect against bone resorption. [BMB Reports 2019; 52(11): 659-664].
| S-EPMC6889896 | biostudies-literature
Project description:Osteogenesis is an orchestrated process regulated by osteoclastogenesis and osteoblastogenesis. Excessive osteoclastogenesis causes bone diseases, such as osteoporosis. Although a few drugs are effective in osteoporosis treatment, these drugs lead to side effects, including cellulitis, flatulence, and hypocalcemia. In this study, we reported a 2-(N-Phenylmethylsulfonamido)-N-(2-(phenylthio)phenyl)propanamide (PSTP) compound, PSTP-3,5-Me, as a potential therapeutic agent for osteoporosis. Mouse bone marrow-derived macrophages (BMMs) were differentiated into osteoclasts by receptor activator of nuclear factor kappa B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) in the presence of PSTP-3,5-Me. PSTP-3,5-Me inhibited osteoclast differentiation by reduced tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, and suppressed the expression of osteoclast marker genes, such as cathepsin K (Ctsk) and TRAP (Acp5). We investigated signaling pathways mediated by RANKL and its receptor, RANK, and found that PSTP-3,5-Me inhibits nucleus translocation of nuclear factor of activated T cell cytoplasmic-1 (NFATc1). Moreover, PSTP-3,5-Me inhibited F-actin ring formation and mineral resorption. Overall, our data suggests that PSTP-3,5-Me attenuates osteoclast differentiation by blocking the activation of NFATc1.
| S-EPMC6767254 | biostudies-literature