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Inactivation of Osteoblast PKC Signaling Reduces Cortical Bone Mass and Density and Aggravates Renal Osteodystrophy in Mice with Chronic Kidney Disease on High Phosphate Diet. Int J Mol Sci 2022; 23:ijms23126404. [PMID: 35742850 PMCID: PMC9223847 DOI: 10.3390/ijms23126404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/01/2022] [Accepted: 06/06/2022] [Indexed: 02/05/2023] Open
Abstract
Chronic kidney disease (CKD) frequently leads to hyperphosphatemia and hyperparathyroidism, mineral bone disorder (CKD-MBD), ectopic calcifications and cardiovascular mortality. PTH activates the osteoanabolic Gαs/PKA and the Gαq/11/PKC pathways in osteoblasts, the specific impact of the latter in CKD-MBD is unknown. We generated osteoblast specific Gαq/11 knockout (KO) mice and established CKD-MBD by subtotal nephrectomy and dietary phosphate load. Bone morphology was assessed by micro-CT, osteoblast function by bone planar scintigraphy at week 10 and 22 and by histomorphometry. Osteoblasts isolated from Gαq/11 KO mice increased cAMP but not IP3 in response to PTH 1-34, demonstrating the specific KO of the PKC signaling pathway. Osteoblast specific Gαq/11 KO mice exhibited increased serum calcium and reduced bone cortical thickness and mineral density at 24 weeks. CKD Gαq/11 KO mice had similar bone morphology compared to WT, while CKD Gαq/11-KO on high phosphate diet developed decreased metaphyseal and diaphyseal cortical thickness and area, as well as a reduction in trabecular number. Gαq/11-KO increased bone scintigraphic tracer uptake at week 10 and mitigated tracer uptake in CKD mice at week 22. Histological bone parameters indicated similar trends. Gαq/11-KO in osteoblast modulates calcium homeostasis, bone formation rate, bone morphometry, and bone mineral density. In CKD and high dietary phosphate intake, osteoblast Gαq/11/PKC KO further aggravates mineral bone disease.
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Yu W, Zhong L, Yao L, Wei Y, Gui T, Li Z, Kim H, Holdreith N, Jiang X, Tong W, Dyment N, Liu XS, Yang S, Choi Y, Ahn J, Qin L. Bone marrow adipogenic lineage precursors promote osteoclastogenesis in bone remodeling and pathologic bone loss. J Clin Invest 2021; 131:140214. [PMID: 33206630 DOI: 10.1172/jci140214] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 10/29/2020] [Indexed: 02/06/2023] Open
Abstract
Bone is maintained by coupled activities of bone-forming osteoblasts/osteocytes and bone-resorbing osteoclasts. Alterations in this relationship can lead to pathologic bone loss such as osteoporosis. It is well known that osteogenic cells support osteoclastogenesis via production of RANKL. Interestingly, our recently identified bone marrow mesenchymal cell population-marrow adipogenic lineage precursors (MALPs) that form a multidimensional cell network in bone-was computationally demonstrated to be the most interactive with monocyte-macrophage lineage cells through high and specific expression of several osteoclast regulatory factors, including RANKL. Using an adipocyte-specific Adipoq-Cre to label MALPs, we demonstrated that mice with RANKL deficiency in MALPs have a drastic increase in trabecular bone mass in long bones and vertebrae starting from 1 month of age, while their cortical bone appears normal. This phenotype was accompanied by diminished osteoclast number and attenuated bone formation at the trabecular bone surface. Reduced RANKL signaling in calvarial MALPs abolished osteolytic lesions after LPS injections. Furthermore, in ovariectomized mice, elevated bone resorption was partially attenuated by RANKL deficiency in MALPs. In summary, our studies identified MALPs as a critical player in controlling bone remodeling during normal bone metabolism and pathological bone loss in a RANKL-dependent fashion.
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Affiliation(s)
- Wei Yu
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Leilei Zhong
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Lutian Yao
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Yulong Wei
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Tao Gui
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Bone and Joint Surgery, Institute of Orthopedic Diseases, The First Affiliated Hospital, Jinan University, Guangzhou, Guangdong, China
| | - Ziqing Li
- Department of Basic & Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Hyunsoo Kim
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nicholas Holdreith
- Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.,Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Xi Jiang
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wei Tong
- Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.,Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nathaniel Dyment
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - X Sherry Liu
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Shuying Yang
- Department of Basic & Translational Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Yongwon Choi
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jaimo Ahn
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ling Qin
- Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Sahbani K, Cardozo CP, Bauman WA, Tawfeek HA. Abaloparatide exhibits greater osteoanabolic response and higher cAMP stimulation and β-arrestin recruitment than teriparatide. Physiol Rep 2019; 7:e14225. [PMID: 31565870 PMCID: PMC6766518 DOI: 10.14814/phy2.14225] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 08/16/2019] [Indexed: 12/26/2022] Open
Abstract
Teriparatide and abaloparatide are parathyroid hormone receptor 1 (PTHR1) analogs with unexplained differential efficacy for the treatment of osteoporosis. Therefore, we compared the effects of abaloparatide and teriparatide on bone structure, turnover, and levels of receptor activator of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG). Wild-type (WT) female mice were injected daily with vehicle or 20-80 µg/kg/day of teriparatide or abaloparatide for 30 days. Femurs and spines were examined by microcomputed tomography scanning and serum levels of bone turnover markers, RANKL, and OPG, were measured by ELISA. Both analogs similarly increased the distal femoral fractional trabecular bone volume, connectivity, and number, and reduced the structure model index (SMI) at 20-80 µg/kg/day doses. However, only abaloparatide exhibited a significant increase (13%) in trabecular thickness at 20 µg/kg/day dose. Femoral cortical evaluation showed that abaloparatide caused a greater dose-dependent increase in cortical thickness than teriparatide. Both teriparatide and abaloparatide increased lumbar 5 vertebral trabecular connectivity but had no or modest effect on other indices. Biochemical analysis demonstrated that abaloparatide promoted greater elevation of procollagen type 1 intact N-terminal propeptide, a bone formation marker, and tartrate-resistant acid phosphatase 5b levels, a bone resorption marker, and lowered the RANKL/OPG ratio. Furthermore, PTHR1 signaling was compared in cells treated with 0-100 nmol/L analog. Interestingly, abaloparatide had a markedly lower EC50 for cAMP formation (2.3-fold) and β-arrestin recruitment (1.6-fold) than teriparatide. Therefore, abaloparatide-improved efficacy can be attributed to enhanced bone formation and cortical structure, reduced RANKL/OPG ratio, and amplified Gs-cAMP and β-arrestin signaling.
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Affiliation(s)
- Karim Sahbani
- National Center for the Medical Consequences of Spinal Cord InjuryJames J. Peters Veterans Affairs Medical CenterBronxNew York
| | - Christopher P. Cardozo
- National Center for the Medical Consequences of Spinal Cord InjuryJames J. Peters Veterans Affairs Medical CenterBronxNew York
- Department of MedicineThe Icahn School of Medicine at Mount SinaiNew YorkNew York
- Department of Rehabilitation MedicineThe Icahn School of Medicine at Mount SinaiNew YorkNew York
- Department of Pharmacologic ScienceThe Icahn School of Medicine at Mount SinaiNew YorkNew York
| | - William A. Bauman
- National Center for the Medical Consequences of Spinal Cord InjuryJames J. Peters Veterans Affairs Medical CenterBronxNew York
- Department of MedicineThe Icahn School of Medicine at Mount SinaiNew YorkNew York
| | - Hesham A. Tawfeek
- National Center for the Medical Consequences of Spinal Cord InjuryJames J. Peters Veterans Affairs Medical CenterBronxNew York
- Department of MedicineThe Icahn School of Medicine at Mount SinaiNew YorkNew York
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Ebner JK, König GM, Kostenis E, Siegert P, Aktories K, Orth JHC. Activation of G q signaling by Pasteurella multocida toxin inhibits the osteoblastogenic-like actions of Activin A in C2C12 myoblasts, a cell model of fibrodysplasia ossificans progressiva. Bone 2019; 127:592-601. [PMID: 31376533 DOI: 10.1016/j.bone.2019.07.031] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 07/29/2019] [Accepted: 07/30/2019] [Indexed: 01/15/2023]
Abstract
The human disease fibrodysplasia ossificans progressiva (FOP) is a rare and highly disabling disorder of extensive heterotopic bone growth that is caused by a point mutation (R206H) in the activation domain of Alk2, a BMP (bone morphogenic protein) type 1 receptor. The mutation leads to extensive BMP-signaling induced by Activin A, which is normally an antagonist for wildtype receptors, resulting in excessive and uncontrolled bone formation. Here, we studied the effects of Pasteurella multocida toxin (PMT), which activates osteoclasts and inhibits osteoblast activity, in C2C12 myoblasts expressing the mutant Alk2(R206H) receptor as model of FOP. In our study, we mainly used alkaline phosphatase (ALP) activity as marker to determine osteoblast differentiation. BMP-4 stimulated an increase in ALP activity in C2C12-Alk2wt and C2C12-Alk2(R206H) cells. By contrast, Activin A only induced ALP activity in C2C12-Alk2(R206H) cells. In both cases, PMT acted as a potent inhibitor of ALP activity. PMT-induced inhibition of ALP activity was paralleled by a constitutive activation of the heterotrimeric Gq protein. Expression of a permanently active Gαq blocked Activin A/Alk2(R206H)-dependent increase in ALP activity. Inactivation of Gq by specific inhibitor FR900359 blocked the PMT effect. Similarly, canonical second messengers and effectors of Gαq (e.g. ionophore A23187-induced increase in intracellular Ca2+ and activation of PKC by PMA (phorbol 12-myristate 13-acetate)) inhibited Alk2(R206H)-mediated induction of ALP activity. Notably, Activin A-induced increase in ALP activity in C2C12-Alk2(R206H) cells was also inhibited by stimulation of the α1A-adrenoceptor, which couples to Gαq, by phenylephrine. PMT did not alter tail phosphorylation of the major downstream effectors of the Alk2 receptor, Smad1/5/9; neither did the toxin affect nuclear translocation of the Smad-complex. However, PMT diminished BMP responsive element-induced gene expression. The data indicate that PMT potently inhibits the induction of osteoblast markers in a FOP model via activation of G proteins. Moreover, our findings indicate that activation of G protein-coupled receptors and of G protein signaling might be a rationale for pharmacological therapy of FOP.
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Affiliation(s)
- Julia K Ebner
- Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, Albertstr. 25, 79104 Freiburg, Germany; Faculty of Biology, University of Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany; Spemann Graduate School for Biology and Medicine, University of Freiburg, Albertstr. 19A, 79104 Freiburg, Germany
| | - Gabriele M König
- Molecular, Cellular and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Evi Kostenis
- Molecular, Cellular and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Peter Siegert
- Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, Albertstr. 25, 79104 Freiburg, Germany
| | - Klaus Aktories
- Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, Albertstr. 25, 79104 Freiburg, Germany; Spemann Graduate School for Biology and Medicine, University of Freiburg, Albertstr. 19A, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestr. 18, 79104 Freiburg, Germany.
| | - Joachim H C Orth
- Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, University of Freiburg, Albertstr. 25, 79104 Freiburg, Germany
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6
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Suppression of osteogenic differentiation in mesenchymal stem cells from patients with ossification of the posterior longitudinal ligament by a histamine-2-receptor antagonist. Eur J Pharmacol 2017; 810:156-162. [PMID: 28690192 DOI: 10.1016/j.ejphar.2017.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 07/04/2017] [Accepted: 07/05/2017] [Indexed: 01/25/2023]
Abstract
Mesenchymal stem cells (MSCs) in ossification of the posterior longitudinal ligament (OPLL) patients have a high propensity toward osteogenesis. Histamine receptor H2 (H2R) antagonists (H2 blockers) like famotidine decrease ossification in patients, by an unclear mechanism. To confirm that MSCs express H2R and to clarify how H2 blockers suppress osteogenic differentiation, we used spinal-ligament MSCs from patients with OPLL or with cervical spondylotic myelopathy (CSM) (control). The MSCs were treated with 10, 30, or 100nM famotidine for 7 or 21 days. Flow cytometry revealed that cells from both groups expressed MSC surface markers CD44, CD90, and CD105 (> 97.5%) but not CD34 or CD45 (< 2.5%). Immunoblotting showed that the MSCs from both groups expressed H2R, but those from OPLL patients expressed it at higher levels. Real-time qPCR indicated the H2R expression was significantly suppressed by 30nM famotidine for 7 days or by 30 or 100nM for 21 days. However, histidine decarboxylase, a key enzyme in histamine production, did not change significantly after famotidine addition. Famotidine treatment at 100nM for 21 days significantly suppressed mRNA expression of the osteogenic markers osteocalcin (OCN), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (RUNX2) only in OPLL-derived MSCs. Immunoblots showed that famotidine suppressed BMP2 and OCN in the OPLL group and H2R and RUNX2 in both groups. These results suggest famotidine inhibits osteogenic differentiation in OPLL-derived MSCs by acting as an H2R antagonist, but also by decreasing H2R expression, and support the clinical use of famotidine to treat OPLL.
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7
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Bastepe M, Turan S, He Q. Heterotrimeric G proteins in the control of parathyroid hormone actions. J Mol Endocrinol 2017; 58:R203-R224. [PMID: 28363951 PMCID: PMC5650080 DOI: 10.1530/jme-16-0221] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 02/17/2017] [Indexed: 12/17/2022]
Abstract
Parathyroid hormone (PTH) is a key regulator of skeletal physiology and calcium and phosphate homeostasis. It acts on bone and kidney to stimulate bone turnover, increase the circulating levels of 1,25 dihydroxyvitamin D and calcium and inhibit the reabsorption of phosphate from the glomerular filtrate. Dysregulated PTH actions contribute to or are the cause of several endocrine disorders. This calciotropic hormone exerts its actions via binding to the PTH/PTH-related peptide receptor (PTH1R), which couples to multiple heterotrimeric G proteins, including Gs and Gq/11 Genetic mutations affecting the activity or expression of the alpha-subunit of Gs, encoded by the GNAS complex locus, are responsible for several human diseases for which the clinical findings result, at least partly, from aberrant PTH signaling. Here, we review the bone and renal actions of PTH with respect to the different signaling pathways downstream of these G proteins, as well as the disorders caused by GNAS mutations.
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Affiliation(s)
- Murat Bastepe
- Endocrine UnitDepartment of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Serap Turan
- Department of Pediatric EndocrinologyMarmara University School of Medicine, Istanbul, Turkey
| | - Qing He
- Endocrine UnitDepartment of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Roszko KL, Bi R, Gorvin CM, Bräuner-Osborne H, Xiong XF, Inoue A, Thakker RV, Strømgaard K, Gardella T, Mannstadt M. Knockin mouse with mutant G α11 mimics human inherited hypocalcemia and is rescued by pharmacologic inhibitors. JCI Insight 2017; 2:e91079. [PMID: 28194446 PMCID: PMC5291736 DOI: 10.1172/jci.insight.91079] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G proteins play critical roles in transducing extracellular signals generated by 7-transmembrane domain receptors. Somatic gain-of-function mutations in G protein α subunits are associated with a variety of diseases. Recently, we identified gain-of-function mutations in Gα11 in patients with autosomal-dominant hypocalcemia type 2 (ADH2), an inherited disorder of hypocalcemia, low parathyroid hormone (PTH), and hyperphosphatemia. We have generated knockin mice harboring the point mutation GNA11 c.C178T (p.Arg60Cys) identified in ADH2 patients. The mutant mice faithfully replicated human ADH2. They also exhibited low bone mineral density and increased skin pigmentation. Treatment with NPS 2143, a negative allosteric modulator of the calcium-sensing receptor (CASR), increased PTH and calcium concentrations in WT and mutant mice, suggesting that the gain-of-function effect of GNA11R6OC is partly dependent on coupling to the CASR. Treatment with the Gα11/q-specific inhibitor YM-254890 increased blood calcium in heterozygous but not in homozygous GNA11R60C mice, consistent with published crystal structure data showing that Arg60 forms a critical contact with YM-254890. This animal model of ADH2 provides insights into molecular mechanism of this G protein-related disease and potential paths toward new lines of therapy.
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Affiliation(s)
- Kelly L Roszko
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Ruiye Bi
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
- West China School of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Caroline M Gorvin
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, England, United Kingdom
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Xiao-Feng Xiong
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
- Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), Kawaguchi, Saitama, Japan
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, England, United Kingdom
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Gardella
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Michael Mannstadt
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Bo Z, Bin G, Jing W, Cuifang W, Liping A, Jinglin M, Jin J, Xiaoyi T, Cong C, Ning D, Yayi X. Fluid shear stress promotes osteoblast proliferation via the Gαq-ERK5 signaling pathway. Connect Tissue Res 2016; 57:299-306. [PMID: 27115838 DOI: 10.1080/03008207.2016.1181063] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Fluid shear stress (FSS) is a ubiquitous mechanical stimulus that potently promotes osteoblast proliferation. Previously, we reported that extracellular signal-regulated kinase 5 (ERK5) is essential for FSS-induced osteoblast proliferation. However, the precise mechanism by which FSS promotes osteoblast proliferation via ERK5 activation is poorly understood. The aim of this study was to determine the critical role of Gαq in FSS-induced ERK5 phosphorylation and osteoblast proliferation, as well as the downstream targets of the Gαq-ERK5 pathway. MC3T3-E1 cells were transfected with 50 nM Gαq siRNA, treated with 5 mM XMD8-92 (a highly selective inhibitor of ERK5 activity), and/or exposed to FSS (12 dyn/cm(2)). Cell proliferation was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The protein expression levels of Gαq, P-ERK5, ERK5, Cyclin B1, and CDK1 were analyzed by Western blot. Physiological FSS exposure for 60 min remarkably promoted MC3T3-E1 cell proliferation, however, this effect was suppressed by siRNA-mediated Gαq knockdown or inhibition of ERK5 activity by XMD8-92 treatment, suggesting that Gαq and ERK5 might modulate FSS-increased osteoblast proliferation. Furthermore, ERK5 phosphorylation was dramatically inhibited by Gαq siRNA. In addition, our study further revealed that FSS treatment of MC3T3-E1 cells for 60 min markedly upregulated the protein expression levels of Cyclin B1 and CDK1, and this increased expression was predominantly blocked by Gαq siRNA or XMD8-92 treatment. We propose that FSS acts on the Gαq-ERK5 signaling pathway to upregulate Cyclin B1 and CDK1 expression, thereby resulting in MC3T3-E1 cell proliferation. Thus, the Gαq-ERK5 signaling pathway may provide useful information regarding the treatment of bone metabolic disease.
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Affiliation(s)
- Zhang Bo
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Geng Bin
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Wang Jing
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Wang Cuifang
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - An Liping
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Ma Jinglin
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Jiang Jin
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Tan Xiaoyi
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Chen Cong
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Ding Ning
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
| | - Xia Yayi
- a Department of Orthopedics , The Second Hospital of Lanzhou University , Lanzhou , China.,b Key Laboratory of Orthopedics of Gansu Province, The Second Hospital of Lanzhou University , Lanzhou , China
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Dela Cruz A, Grynpas MD, Mitchell J. Elevated Gα11 expression in osteoblast lineage cells promotes osteoclastogenesis and leads to enhanced trabecular bone accrual in response to pamidronate. Am J Physiol Endocrinol Metab 2016; 310:E811-20. [PMID: 27006198 DOI: 10.1152/ajpendo.00049.2016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 03/15/2016] [Indexed: 11/22/2022]
Abstract
Osteoblastic cells indirectly induce osteoclastogenesis in the bone microenvironment by expressing paracrine factors such as RANKL and M-CSF, leading to increased bone resorption. These cytokines can be regulated by a variety of intracellular pathways, which include G protein-coupled receptor signaling. To explore how enhanced signaling of the Gαq/11 pathway in osteoblast lineage cells may mediate osteoclast formation, we cocultured wild-type (WT) preosteoclasts with BMSCs derived from either WT or transgenic mice with osteoblast-specific overexpression of Gα11 (G11-Tg). G11-Tg cocultures had elevated osteoclast numbers with greater resorptive capacity and increased expression of Rankl, Rankl:Opg (osteoprotegerin), and M-csf compared with cocultures with WT BMSCs. As well, cocultures with G11-Tg BMSCs required a higher concentration of OPG to inhibit osteoclast formation and less angiotensin II to increase osteoclast size. These indicate that G11-Tg osteoblasts drive the increased osteoclast formation and osteopenia seen in G11-Tg mice. Pamidronate treatment of G11-Tg mice restored the trabecular bone loss phenotype, as bone mineral density, bone volume, trabecular number, separation, and expressions of osteoblastic and osteoclastic genes were comparable with WT parameters. These changes were characterized by enhanced accumulation of calcified cartilage in trabecular bone, demonstrating that resorption of the cartilaginous intermediate by osteoclasts is more affected by bisphosphonate treatment in G11-Tg mice. In conclusion, overexpression of Gα11 in osteoblastic cells promotes osteoclastogenesis by upregulation of Rankl and M-csf and bone loss by increased osteoclast resorption of the trabecular bone and cartilaginous matrix.
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Affiliation(s)
- Ariana Dela Cruz
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario Canada
| | - Marc D Grynpas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada; and Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Jane Mitchell
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario Canada;
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Li D, Opas EE, Tuluc F, Metzger DL, Hou C, Hakonarson H, Levine MA. Autosomal dominant hypoparathyroidism caused by germline mutation in GNA11: phenotypic and molecular characterization. J Clin Endocrinol Metab 2014; 99:E1774-83. [PMID: 24823460 PMCID: PMC4154081 DOI: 10.1210/jc.2014-1029] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
CONTEXT Most cases of autosomal dominant hypoparathyroidism (ADH) are caused by gain-of-function mutations in CASR or dominant inhibitor mutations in GCM2 or PTH. OBJECTIVE Our objectives were to identify the genetic basis for ADH in a multigenerational family and define the underlying disease mechanism. SUBJECTS Here we evaluated a multigenerational family with ADH in which affected subjects had normal sequences in these genes and were shorter than unaffected family members. METHODS We collected clinical and biochemical data from 6 of 11 affected subjects and performed whole-exome sequence analysis on DNA from two affected sisters and their affected father. Functional studies were performed after expression of wild-type and mutant Gα11 proteins in human embryonic kidney-293-CaR cells that stably express calcium-sensing receptors. RESULTS Whole-exome-sequencing followed by Sanger sequencing revealed a heterozygous mutation, c.179G>T; p.R60L, in GNA11, which encodes the α-subunit of G11, the principal heterotrimeric G protein that couples calcium-sensing receptors to signal activation in parathyroid cells. Functional studies of Gα11 R60L showed increased accumulation of intracellular concentration of free calcium in response to extracellular concentration of free calcium with a significantly decreased EC50 compared with wild-type Gα11. By contrast, R60L was significantly less effective than the oncogenic Q209L form of Gα11 as an activator of the MAPK pathway. Compared to subjects with CASR mutations, patients with GNA11 mutations lacked hypercalciuria and had normal serum magnesium levels. CONCLUSIONS Our findings indicate that the germline gain-of-function mutation of GNA11 is a cause of ADH and implicate a novel role for GNA11 in skeletal growth.
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Affiliation(s)
- Dong Li
- Center for Applied Genomics (D.L., C.H., H.H.), Division of Endocrinology and Diabetes (E.E.O., M.A.L.), Division of Allergy and Immunology (F.T.), Division of Pulmonary Medicine (H.H.), and Center for Bone Health (M.A.L.), The Children's Hospital of Philadelphia; and Department of Pediatrics (H.H., M.A.L.), University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104; and Endocrinology and Diabetes Unit (D.L.M.), British Columbia Children's Hospital, and Department of Pediatrics (D.L.M.), University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4
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12
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Dela Cruz A, Mattocks M, Sugamori KS, Grynpas MD, Mitchell J. Reduced trabecular bone mass and strength in mice overexpressing Gα11 protein in cells of the osteoblast lineage. Bone 2014; 59:211-22. [PMID: 24308950 DOI: 10.1016/j.bone.2013.11.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 11/19/2013] [Accepted: 11/20/2013] [Indexed: 01/10/2023]
Abstract
G protein-coupled receptors (GPCRs) require G proteins for intracellular signaling to regulate a variety of growth and maintenance processes, including osteogenesis and bone turnover. Bone maintenance events may be altered by changes in the activity or level of G proteins, which then modify signaling in bone cells such as osteoblasts. We have previously reported increased levels of Gα11 protein and signaling to phospholipase C/protein kinase C pathways in response to dexamethasone in osteoblastic UMR 106-01 cells. Here we generated pOBCol3.6-GNA11 transgenic mice that overexpress Gα11 protein in cells of the osteoblast lineage (G11-Tg mice). G11-Tg mice exhibit an osteopenic phenotype characterized by significant reductions in trabecular bone mineral density, thickness, number and strength. The numbers of osteoblasts and osteocytes were unchanged in G11-Tg bone, but early markers of osteoblast differentiation, Alp and Bsp, were increased while the late stage differentiation marker Ocn was not changed suggesting reduced osteoblast maturation in G11-Tg trabecular bone which was accompanied by a decreased bone formation rate. Furthermore, in vitro cultures of G11-Tg primary osteoblasts show delayed osteoblast differentiation and mineralization. Histological analyses also revealed increased osteoclast parameters, accompanied by elevated mRNA expression of Trap and Ctsk. mRNA levels of Rankl and M-csf were elevated in vitro in bone marrow stromal cells undergoing osteogenesis and in trabecular bone in vivo. Together, these findings demonstrate that increasing Gα11 protein expression in osteoblasts can alter gene expression and result in a dual mechanism of trabecular bone loss.
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Affiliation(s)
- Ariana Dela Cruz
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Michael Mattocks
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Kim S Sugamori
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Marc D Grynpas
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Lunenfeld-Tanenbaum Research Institute of Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
| | - Jane Mitchell
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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Siegert P, Schmidt G, Papatheodorou P, Wieland T, Aktories K, Orth JHC. Pasteurella multocida toxin prevents osteoblast differentiation by transactivation of the MAP-kinase cascade via the Gα(q/11)--p63RhoGEF--RhoA axis. PLoS Pathog 2013; 9:e1003385. [PMID: 23696743 PMCID: PMC3656108 DOI: 10.1371/journal.ppat.1003385] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/11/2013] [Indexed: 11/19/2022] Open
Abstract
The 146-kDa Pasteurella multocida toxin (PMT) is the main virulence factor to induce P. multocida-associated progressive atrophic rhinitis in various animals. PMT leads to a destruction of nasal turbinate bones implicating an effect of the toxin on osteoblasts and/or osteoclasts. The toxin induces constitutive activation of Gα proteins of the Gq/11-, G12/13- and Gi-family by deamidating an essential glutamine residue. To study the PMT effect on bone cells, we used primary osteoblasts derived from rat calvariae and stromal ST-2 cells as differentiation model. As marker of functional osteoblasts the expression and activity of alkaline phosphatase, formation of mineralization nodules or expression of specific transcription factors as osterix was determined. Here, we show that the toxin inhibits differentiation and/or function of osteoblasts by activation of Gαq/11. Subsequently, Gαq/11 activates RhoA via p63RhoGEF, which specifically interacts with Gαq/11 but not with other G proteins like Gα12/13 and Gαi. Activated RhoA transactivates the mitogen-activated protein (MAP) kinase cascade via Rho kinase, involving Ras, MEK and ERK, resulting in inhibition of osteoblast differentiation. PMT-induced inhibition of differentiation was selective for the osteoblast lineage as adipocyte-like differentiation of ST-2 cells was not hampered. The present work provides novel insights, how the bacterial toxin PMT can control osteoblastic development by activating heterotrimeric G proteins of the Gαq/11-family and is a molecular pathogenetic basis for understanding the role of the toxin in bone loss during progressive atrophic rhinitis induced by Pasteurella multocida. Pasteurella multocida causes as a facultative pathogen various diseases in men and animals. One induced syndrome is atrophic rhinitis, which is a form of osteopenia, mainly characterized by facial distortion due to degradation of nasal turbinate bones. Strains, which especially affect bone tissue, produce the protein toxin P. multocida toxin (PMT). Importantly, PMT alone is capable to induce all symptoms of atrophic rhinitis. To cause osteopenia PMT influences the development and/or activity of specialized bone cells like osteoblasts and osteoclasts. Recently, we could identify the molecular mechanism of PMT. The toxin constitutively activates certain heterotrimeric G proteins by deamidation. Here, we studied the effect of PMT on the differentiation of osteoblasts. We demonstrate the direct action of PMT on osteoblasts and osteoblast-like cells and as a consequence inhibition of osteoblastic differentiation. Moreover, we revealed the underlying signal transduction pathway to impair proper osteoblast development. We show that PMT activates small GTPases in a Gαq/11 dependent manner via a non-ubiquitously expressed RhoGEF. In turn the mitogen-activated protein kinase pathway is transactivated leading to inhibition of osteoblastogenesis. Our findings present a mechanism how PMT hijacks host cell signaling pathways to hinder osteoblast development, which contributes to the syndrome of atrophic rhinitis.
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Affiliation(s)
- Peter Siegert
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Hermann–Staudinger–Graduiertenschule Universität Freiburg, Freiburg, Germany
| | - Gudula Schmidt
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Panagiotis Papatheodorou
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Thomas Wieland
- Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Klaus Aktories
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, Universität Freiburg, Freiburg, Germany
- * E-mail: (KA); (JO)
| | - Joachim H. C. Orth
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- * E-mail: (KA); (JO)
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14
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Tobar-Rubin R, Sultan D, Janevska D, Turcic K, Carroll J, Ooms L, Pals-Rylaarsdam R. Intragenic suppression of a constitutively active allele of Gsα associated with McCune-Albright syndrome. J Mol Endocrinol 2013; 50:193-201. [PMID: 23288949 PMCID: PMC3836019 DOI: 10.1530/jme-12-0087] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
McCune-Albright syndrome (MAS) is a human genetic disorder caused by a mutation that constitutively activates the G(s)α subunit by abolishing GTP hydrolysis. MAS patients suffer from a range of endocrinopathies as well as polyostotic fibrous dysplasia of bone. We previously identified an intragenic suppressor of the MAS mutation in a yeast system, which substituted two residues in the GTP-binding site of Gpa1: L318P and D319V to suppress the constitutive activity of an R297H mutation, corresponding to the human F222P, D223V, and R201H mutations respectively. To extend these studies, the human GNAS gene was subjected to site-directed mutagenesis. Constructs expressing the MAS mutation (R201H), the MAS mutation plus the mutations homologous to the yeast suppressors (R201H, F222P/D223V), or the yeast suppressor mutation alone (F222P/D223V) were transfected into HEK293 cells, and basal and receptor-stimulated cAMP levels were measured. Expression of R201H increased the basal cAMP levels and decreased the EC(50) for hormone-stimulated cAMP production. These effects were dependent on the amount of R201H protein expressed. R201H, F222P/D223V abolished the constitutive activity of the MAS mutation and caused responses to hormone that were not different from those measured in cells expressing WT G(s)α. Interestingly, F222P/D223V behaved similar to R201H in causing increases in basal cAMP production, thus demonstrating constitutive activity. Substitution of another acidic (E) or polar (N, T, and G) amino acid at position 223 caused no suppression of R201H activity, while substitution of a second nonpolar amino acid (A) at this position partially suppressed, and the larger polar I residue completely suppressed the effects of R201H.
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Affiliation(s)
- Raquel Tobar-Rubin
- Department of Biological Science, Benedictine University, Lisle, Illinois 60532, USA
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15
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Yamamoto K, Hojo H, Koshima I, Chung UI, Ohba S. Famotidine suppresses osteogenic differentiation of tendon cells in vitro and pathological calcification of tendon in vivo. J Orthop Res 2012; 30:1958-62. [PMID: 22592911 DOI: 10.1002/jor.22146] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 04/26/2012] [Indexed: 02/04/2023]
Abstract
Heterotopic ossification or calcification follows any type of musculoskeletal trauma and is known to occur after arthroplasties of hip, knee, shoulder, or elbow; fractures; joint dislocations; or tendon ruptures. Histamine receptor H2 (Hrh2) has been shown to be effective for reducing pain and decreasing calcification in patients with calcifying tendinitis, which suggested that H2 blockers were effective for the treatment of tendon ossification or calcification. However, the detailed mechanisms of its action on tendon remain to be clarified. We investigated the mechanisms underlying H2 blocker-mediated suppression of tendon calcification, with a focus on the direct action of the drug on tendon cells. Famotidine treatment suppressed the mRNA expressions of Col10a1 and osteocalcin, ossification markers, in a tendon-derived cell line TT-D6, as well as a preosteoblastic one MC3T3-E1. Both of the cell lines expressed Hrh2; histamine treatment induced osteocalcin expression in these cells. Famotidine administration suppressed calcification in the Achilles tendon of ttw mice, a mouse model of ectopic ossification. These data suggest that famotidine inhibits osteogenic differentiation of tendon cells in vitro, and this inhibition may underlie the anti-calcification effects of the drug in vivo. This study points to the use of H2 blockers as a promising strategy for treating heterotopic ossification or calcification in tendon, and provides evidence in support of the clinical use of famotidine.
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Affiliation(s)
- Kenichi Yamamoto
- Center for Disease Biology and Integrative Medicine, Division of Clinical Biotechnology, The University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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16
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Swine atrophic rhinitis caused by pasteurella multocida toxin and bordetella dermonecrotic toxin. Curr Top Microbiol Immunol 2012; 361:113-29. [PMID: 22411430 DOI: 10.1007/82_2012_206] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Atrophic rhinitis is a widespread and economically important swine disease caused by Pasteurella multocida and Bordetella bronchiseptica. The disease is characterized by atrophy of the nasal turbinate bones, which results in a shortened and deformed snout in severe cases. P. multocida toxin and B. bronchiseptica dermonecrotic toxin have been considered to independently or cooperatively disturb the osteogenesis of the turbinate bone by inhibiting osteoblastic differentiation and/or stimulating bone resorption by osteoclasts. Recently, the intracellular targets and molecular actions of both toxins have been clarified, enabling speculation on the intracellular signals leading to the inhibition of osteogenesis.
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17
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Xiong J, Onal M, Jilka RL, Weinstein RS, Manolagas SC, O'Brien CA. Matrix-embedded cells control osteoclast formation. Nat Med 2011; 17:1235-41. [PMID: 21909103 PMCID: PMC3192296 DOI: 10.1038/nm.2448] [Citation(s) in RCA: 939] [Impact Index Per Article: 72.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 07/20/2011] [Indexed: 02/08/2023]
Abstract
Osteoclasts resorb the mineralized matrices formed by chondrocytes or osteoblasts. The cytokine receptor activator of nuclear factor-κB ligand (RANKL) is essential for osteoclast formation and thought to be supplied by osteoblasts or their precursors, thereby linking bone formation to resorption. However, RANKL is expressed by a variety of cell types, and it is unclear which of them are essential sources for osteoclast formation. Here we have used a mouse strain in which RANKL can be conditionally deleted and a series of Cre-deleter strains to demonstrate that hypertrophic chondrocytes and osteocytes, both of which are embedded in matrix, are essential sources of the RANKL that controls mineralized cartilage resorption and bone remodeling, respectively. Moreover, osteocyte RANKL is responsible for the bone loss associated with unloading. Contrary to the current paradigm, RANKL produced by osteoblasts or their progenitors does not contribute to adult bone remodeling. These results suggest that the rate-limiting step of matrix resorption is controlled by cells embedded within the matrix itself.
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Affiliation(s)
- Jinhu Xiong
- Center for Osteoporosis and Metabolic Bone Diseases, University of Arkansas for Medical Sciences (UAMS), Little Rock, Arkansas, USA
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18
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Nakura A, Higuchi C, Yoshida K, Yoshikawa H. PKCα suppresses osteoblastic differentiation. Bone 2011; 48:476-84. [PMID: 20951242 DOI: 10.1016/j.bone.2010.09.238] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 09/08/2010] [Accepted: 09/29/2010] [Indexed: 11/30/2022]
Abstract
Protein kinase C (PKC) plays an essential role in cellular signal transduction for mediating a variety of biological functions. There are 11 PKC isoforms and these isoforms are believed to play distinct roles in cells. Although the role of individual isoforms of PKC has been investigated in many fields, little is known about the role of PKC in osteoblastic differentiation. Here, we investigated which isoforms of PKC are involved in osteoblastic differentiation of the mouse preosteoblastic cell line MC3T3-E1. Treatment with Gö6976, an inhibitor of PKCα and PKCβI, increased alkaline phosphatase (ALP) activity as well as gene expression of ALP and Osteocalcin (OCN), and enhanced calcification of the extracellular matrix. Concurrently, osteoblastic cell proliferation decreased at a concentration of 1.0 μM. In contrast, a PKCβ inhibitor, which inhibits PKCβI and PKCβII, did not significantly affect osteoblastic differentiation or cell proliferation. Knockdown of PKCα using MC3T3-E1 cells transfected with siRNA also induced an increase in ALP activity and in gene expression of ALP and OCN. In contrast, overexpression of wild-type PKCα decreased ALP activity and attenuated osteoblastic differentiation markers including ALP and OCN, but promoted cell proliferation. Taken together, our results indicate that PKCα suppresses osteoblastic differentiation, but promotes osteoblastic cell proliferation. These results imply that PKCα may have a pivotal role in cell signaling that modulates the differentiation and proliferation of osteoblasts.
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Affiliation(s)
- Akio Nakura
- Department of Orthopaedic Surgery, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
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19
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Ogata N, Shinoda Y, Wettschureck N, Offermanns S, Takeda S, Nakamura K, Segre GV, Chung UI, Kawaguchi H. G alpha(q) signal in osteoblasts is inhibitory to the osteoanabolic action of parathyroid hormone. J Biol Chem 2011; 286:13733-40. [PMID: 21345793 DOI: 10.1074/jbc.m110.200196] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
This study examined the role of the Gα(q) signal constituted by Gα(q) and Gα(11) (encoded by Gnα(q) and Gnα(11), respectively), a major intracellular pathway of parathyroid hormone (PTH), in the PTH osteoanabolic action by the gain- and loss-of-function analyses. Transgenic mice with osteoblast-specific overexpression of the constitutively active Gnα(q) gene under the control of 2.3-kb type I collagen α1 chain (Col1a1) promoter exhibited osteopenia with decreased bone formation parameters and did not respond to the daily PTH treatment. We then established osteoblast-specific Gnα(q) and Gnα(11) double-knock-out (cDKO) mice by crossing the 2.3-kb Col1a1 promoter-Cre recombinase transgenic mice and those with Gnα(q) gene flanked with loxP and global ablation of Gnα(11) (Col1a1-Cre(+/-);Gna(q)(fl/fl);Gna(11)(-/-)) and found that the cDKO and single knock-out littermates of Gnα(q) or Gnα(11) exhibited normal bone volume and turnover under physiological conditions. With a daily injection of PTH, however, the cDKO mice, but not the single knock-out mice, showed higher bone volume and turnover than the wild-type littermates. Cultures of primary osteoblasts derived from cDKO and wild-type littermates confirmed enhancement of the PTH osteoanabolic action by the Gα(q) signal deficiency in a cell-autonomous mechanism, in association with the membrane translocation of protein kinase Cδ. This enhancement was reproduced by overexpression of regulator of G protein signaling-2, a Gα(q) signal inhibitor, in osteoblastic MC3T3-E1 cells. Hence, the Gα(q) signal plays an inhibitory role in the PTH osteoanabolic action, suggesting that its suppression may lead to a novel treatment in combination with PTH against osteoporosis.
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Affiliation(s)
- Naoshi Ogata
- Department of Bone and Cartilage Regenerative Medicine, University of Tokyo, Tokyo 113-8655, Japan
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Hisa I, Inoue Y, Hendy GN, Canaff L, Kitazawa R, Kitazawa S, Komori T, Sugimoto T, Seino S, Kaji H. Parathyroid hormone-responsive Smad3-related factor, Tmem119, promotes osteoblast differentiation and interacts with the bone morphogenetic protein-Runx2 pathway. J Biol Chem 2011; 286:9787-96. [PMID: 21239498 DOI: 10.1074/jbc.m110.179127] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanisms whereby the parathyroid hormone (PTH) exerts its anabolic action on bone are incompletely understood. We previously showed that inhibition of ERK1/2 enhanced Smad3-induced bone anabolic action in osteoblasts. These findings suggested the hypothesis that changes in gene expression associated with the altered Smad3-induced signaling brought about by an ERK1/2 inhibitor would identify novel bone anabolic factors in osteoblasts. We therefore performed a comparative DNA microarray analysis between empty vector-transfected mouse osteoblastic MC3T3-E1 cells and PD98059-treated stable Smad3-overexpressing MC3T3-E1 cells. Among the novel factors, Tmem119 was selected on the basis of its rapid induction by PTH independent of later increases in endogenous TGF-β. The levels of Tmem119 increased with time in cultures of MC3T3-E1 cells and mouse mesenchymal ST-2 cells committed to the osteoblast lineage by BMP-2. PTH stimulated Tmem119 levels within 1 h as determined by Western blot analysis and immunocytochemistry in MC3T3-E1 cells. MC3T3-E1 cells stably overexpressing Tmem119 exhibited elevated levels of Runx2, osteocalcin, alkaline phosphatase, and β-catenin, whereas Tmem119 augmented BMP-2-induced Runx2 levels in mesenchymal cells. Tmem119 interacted with Runx2, Smad1, and Smad5 in C2C12 cells. In conclusion, we identified a Smad3-related factor, Tmem119, that is induced by PTH and promotes differentiation in mouse osteoblastic cells. Tmem119 is an important molecule in the pathway downstream of PTH and Smad3 signaling in osteoblasts.
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Affiliation(s)
- Itoko Hisa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
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Hsiao EC, Boudignon BM, Halloran BP, Nissenson RA, Conklin BR. Gs G protein-coupled receptor signaling in osteoblasts elicits age-dependent effects on bone formation. J Bone Miner Res 2010; 25:584-93. [PMID: 20200944 PMCID: PMC3153396 DOI: 10.1002/jbmr.3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Age-dependent changes in skeletal growth are important for regulating skeletal expansion and determining peak bone mass. However, how G protein-coupled receptors (GPCRs) regulate these changes is poorly understood. Previously, we described a mouse model expressing Rs1, an engineered receptor with high basal G(s) activity. Rs1 expression in osteoblasts induced a dramatic age-dependent increase in trabecular bone with features resembling fibrous dysplasia. To further investigate how activation of the G(s)-GPCR pathway affects bone formation at different ages, we used the tetracycline-inducible system in the ColI(2.3)(+)/Rs1(+) mouse model to control the timing of Rs1 expression. We found that the Rs1 phenotype developed rapidly between postnatal days 4 and 6, that delayed Rs1 expression resulted in attenuation of the Rs1 phenotype, and that the Rs1-induced bone growth and deformities were markedly reversed when Rs1 expression was suppressed in adult mice. These findings suggest a distinct window of increased osteoblast responsiveness to G(s) signaling during the early postnatal period. In addition, adult bones encode information about their normal shape and structure independently from mechanisms regulating bone expansion. Finally, our model provides a powerful tool for investigating the effects of continuous G(s)-GPCR signaling on dynamic bone growth and remodeling.
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Affiliation(s)
- Edward C Hsiao
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA.
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Hsiao EC, Millard SM, Louie A, Huang Y, Conklin BR, Nissenson RA. Ligand-mediated activation of an engineered gs g protein-coupled receptor in osteoblasts increases trabecular bone formation. Mol Endocrinol 2010; 24:621-31. [PMID: 20150184 DOI: 10.1210/me.2009-0424] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Age-dependent changes in skeletal growth play important roles in regulating skeletal expansion and in the course of many diseases affecting bone. How G protein-coupled receptor (GPCR) signaling affects these changes is poorly understood. Previously, we described a mouse model expressing Rs1, an engineered receptor with constitutive G(s) activity. Rs1 expression in osteoblasts from gestation induced a dramatic age-dependent increase in trabecular bone with features resembling fibrous dysplasia; however, these changes were greatly minimized if Rs1 expression was delayed until after puberty. To further investigate whether ligand-induced activation of the G(s)-GPCR pathway affects bone formation in adult mice, we activated Rs1 in adult mice with the synthetic ligand RS67333 delivered continuously via an osmotic pump or intermittently by daily injections. We found that osteoblasts from adult animals can be stimulated to form large amounts of bone, indicating that adult mice are sensitive to the dramatic bone- forming actions of G(s) signaling in osteoblasts. In addition, our results show that intermittent and continuous activation of Rs1 led to structurally similar but quantitatively different degrees of trabecular bone formation. These results indicate that activation of a G(s)-coupled receptor in osteoblasts of adult animals by either intermittent or continuous ligand administration can increase trabecular bone formation. In addition, osteoblasts located at the bone epiphyses may be more responsive to G(s) signaling than osteoblasts at the bone diaphysis. This model provides a powerful tool for investigating the effects of ligand-activated G(s)-GPCR signaling on dynamic bone growth and remodeling.
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Affiliation(s)
- Edward C Hsiao
- Gladstone Institute of Cardiovascular Disease, 1650 Owens Street, San Francisco, California 94158, USA.
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23
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Murrills RJ, Andrews JL, Samuel RL, Coleburn VE, Bhat BM, Bhat RA, Bex FJ, Bodine PVN. Parathyroid hormone synergizes with non-cyclic AMP pathways to activate the cyclic AMP response element. J Cell Biochem 2009; 106:887-95. [PMID: 19180574 DOI: 10.1002/jcb.22057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Parathyroid hormone (PTH) activates multiple signaling pathways following binding to the PTH1 receptor in osteoblasts. Previous work revealed a discrepancy between cAMP stimulation and CRE reporter activation of truncated PTH peptides, suggesting that additional signaling pathways contribute to activation of the CRE. Using a CRE-Luciferase reporter containing multiple copies of the CRE stably transfected into the osteoblastic cell line Saos-2, we tested the ability of modulators of alternative pathways to activate the CRE or block the PTH-induced activation of the CRE. Activators of non-cyclic AMP pathways, that is, EGF (Akt, MAPK, JAK/STAT pathways); thapsigargin (intracellular calcium pathway); phorbol myristate acetate (protein kinase C, PKC pathway) induced minor increases in CRE-luciferase activity alone but induced dramatic synergistic effects in combination with PTH. The protein kinase A (PKA) inhibitor H-89 (10 microM) almost completely blocked PTH-induced activation of the CRE-reporter. Adenylate cyclase inhibitors SQ 22536 and DDA had profound and time-dependent biphasic effects on the CRE response. The MAPK inhibitor PD 98059 partially inhibited basal and PTH-induced CRE activity to the same degree, while the PKC inhibitor bisindolylmaleimide (BIS) had variable effects. The calmodulin kinase II inhibitor KN-93 had no significant effect on the response to PTH. We conclude that non-cAMP pathways (EGF pathway, calcium pathway, PKC pathway) converge on, and have synergistic effects on, the response of a CRE reporter to PTH.
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Affiliation(s)
- Richard J Murrills
- Department of Osteoporosis & Frailty, Women's Health & Musculoskeletal Biology, Wyeth Research, Collegeville, Pennsylvania 19426, USA.
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Osteoblast expression of an engineered Gs-coupled receptor dramatically increases bone mass. Proc Natl Acad Sci U S A 2008; 105:1209-14. [PMID: 18212126 DOI: 10.1073/pnas.0707457105] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Osteoblasts are essential for maintaining bone mass, avoiding osteoporosis, and repairing injured bone. Activation of osteoblast G protein-coupled receptors (GPCRs), such as the parathyroid hormone receptor, can increase bone mass; however, the anabolic mechanisms are poorly understood. Here we use "Rs1," an engineered GPCR with constitutive G(s) signaling, to evaluate the temporal and skeletal effects of G(s) signaling in murine osteoblasts. In vivo, Rs1 expression induces a dramatic anabolic skeletal response, with midfemur girth increasing 1,200% and femur mass increasing 380% in 9-week-old mice. Bone volume, cellularity, areal bone mineral density, osteoblast gene markers, and serum bone turnover markers were also elevated. No such phenotype developed when Rs1 was expressed after the first 4 weeks of postnatal life, indicating an exquisite temporal sensitivity of osteoblasts to Rs1 expression. This pathway may represent an important determinant of bone mass and may open future avenues for enhancing bone repair and treating metabolic bone diseases.
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