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Madrigal A, Tan L, Zhao Y. Expression regulation and functional analysis of RGS2 and RGS4 in adipogenic and osteogenic differentiation of human mesenchymal stem cells. Biol Res 2017; 50:43. [PMID: 29279050 PMCID: PMC5742872 DOI: 10.1186/s40659-017-0148-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 12/14/2017] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Understanding the molecular basis underlying the formation of bone-forming osteocytes and lipid-storing adipocytes will help provide insights into the cause of disorders originating in stem/progenitor cells and develop therapeutic treatments for bone- or adipose-related diseases. In this study, the role of RGS2 and RGS4, two members of the regulators of G protein signaling (RGS) family, was investigated during adipogenenic and osteogenenic differentiation of human mesenchymal stem cells (hMSCs). RESULTS Expression of RGS2 and RGS4 were found to be inversely regulated during adipogenesis induced by dexamethasone (DEX) and 3-isobutyl-methylxanthine, regardless if insulin was present, with RGS2 up-regulated and RGS4 down-regulated in response to adipogenic induction. RGS2 expression was also up-regulated during osteogenesis at a level similar to that induced by treatment of DEX alone, a shared component of adipogenic and osteogenic differentiation inducing media, but significantly lower than the level induced by adipogenic inducing media. RGS4 expression was down-regulated during the first 48 h of osteogenesis but up-regulated afterwards, in both cases at levels similar to that induced by DEX alone. Expression knock-down using small interfering RNA against RGS2 resulted in decreased differentiation efficiency during both adipogenesis and osteogenesis. On the other hand, expression knock-down of RGS4 also resulted in decreased adipogenic differentiation but increased osteogenic differentiation. CONCLUSIONS RGS2 and RGS4 are differentially regulated during adipogenic and osteogenic differentiation of hMSCs. In addition, both RGS2 and RGS4 play positive roles during adipogenesis but opposing roles during osteogenesis, with RGS2 as a positive regulator and RGS4 as a negative regulator. These results imply that members of RGS proteins may play multifaceted roles during human adipogenesis and osteogenesis to balance or counterbalance each other's function during those processes.
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Affiliation(s)
- Alma Madrigal
- Biological Sciences Department, California State Polytechnic University at Pomona, 3801 W. Temple Ave., Pomona, CA, 91768, USA.,Center for Biomedicine and Genetics, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA, 91010, USA
| | - Lun Tan
- Biological Sciences Department, California State Polytechnic University at Pomona, 3801 W. Temple Ave., Pomona, CA, 91768, USA
| | - Yuanxiang Zhao
- Biological Sciences Department, California State Polytechnic University at Pomona, 3801 W. Temple Ave., Pomona, CA, 91768, USA.
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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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Nikitovic D, Kavasi RM, Berdiaki A, Papachristou DJ, Tsiaoussis J, Spandidos DA, Tsatsakis AM, Tzanakakis GN. Parathyroid hormone/parathyroid hormone-related peptide regulate osteosarcoma cell functions: Focus on the extracellular matrix (Review). Oncol Rep 2016; 36:1787-92. [PMID: 27499459 PMCID: PMC5022866 DOI: 10.3892/or.2016.4986] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 07/15/2016] [Indexed: 12/25/2022] Open
Abstract
Osteosarcoma (OS) is a primary bone tumor of mesenchymal origin mostly affecting children and adolescents. The OS extracellular matrix (ECM) is extensively altered as compared to physiological bone tissue. Indeed, the main characteristic of the most common osteoblastic subtype of OS is non-mineralized osteoid production. Parathyroid hormone (PTH) is a polypeptide hormone secreted by the chief cells of the parathyroid glands. The PTH-related peptide (PTHrP) may be comprised of 139, 141 or 173 amino acids and exhibits considerate N-terminal amino acid sequence homology with PTH. The function of PTH/PTHrP is executed through the activation of the PTH receptor 1 (PTHR1) and respective downstream intracellular pathways which regulate skeletal development, bone turnover and mineral ion homeostasis. Both PTHR1 and its PTH/PTHrP ligands have been shown to be expressed in OS and to affect the functions of these tumor cells. This review aims to highlight the less well known aspects of PTH/PTHrP functions in the progression of OS by focusing on ECM-dependent signaling.
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Affiliation(s)
- Dragana Nikitovic
- Department of Anatomy‑Histology‑Embryology, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Rafaela-Maria Kavasi
- Department of Anatomy‑Histology‑Embryology, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Aikaterini Berdiaki
- Department of Anatomy‑Histology‑Embryology, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Dionysios J Papachristou
- Department of Anatomy‑Histology‑Embryology, Unit of Bone and Soft Tissue Studies, School of Medicine, University of Patras, Patras 26504, Greece
| | - John Tsiaoussis
- Department of Anatomy‑Histology‑Embryology, School of Medicine, University of Crete, Heraklion 71003, Greece
| | - Demetrios A Spandidos
- Laboratory of Clinical Virology, Medical School, University of Crete, Heraklion 71003, Greece
| | - Aristides M Tsatsakis
- Laboratory of Toxicology, Medical School, University of Crete, Heraklion 71003, Greece
| | - George N Tzanakakis
- Department of Anatomy‑Histology‑Embryology, School of Medicine, University of Crete, Heraklion 71003, Greece
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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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Thompson MD, Hendy GN, Percy ME, Bichet DG, Cole DEC. G protein-coupled receptor mutations and human genetic disease. Methods Mol Biol 2015; 1175:153-87. [PMID: 25150870 DOI: 10.1007/978-1-4939-0956-8_8] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Genetic variations in G protein-coupled receptor genes (GPCRs) disrupt GPCR function in a wide variety of human genetic diseases. In vitro strategies and animal models have been used to identify the molecular pathologies underlying naturally occurring GPCR mutations. Inactive, overactive, or constitutively active receptors have been identified that result in pathology. These receptor variants may alter ligand binding, G protein coupling, receptor desensitization and receptor recycling. Receptor systems discussed include rhodopsin, thyrotropin, parathyroid hormone, melanocortin, follicle-stimulating hormone (FSH), luteinizing hormone, gonadotropin-releasing hormone (GNRHR), adrenocorticotropic hormone, vasopressin, endothelin-β, purinergic, and the G protein associated with asthma (GPRA or neuropeptide S receptor 1 (NPSR1)). The role of activating and inactivating calcium-sensing receptor (CaSR) mutations is discussed in detail with respect to familial hypocalciuric hypercalcemia (FHH) and autosomal dominant hypocalemia (ADH). The CASR mutations have been associated with epilepsy. Diseases caused by the genetic disruption of GPCR functions are discussed in the context of their potential to be selectively targeted by drugs that rescue altered receptors. Examples of drugs developed as a result of targeting GPCRs mutated in disease include: calcimimetics and calcilytics, therapeutics targeting melanocortin receptors in obesity, interventions that alter GNRHR loss from the cell surface in idiopathic hypogonadotropic hypogonadism and novel drugs that might rescue the P2RY12 receptor congenital bleeding phenotype. De-orphanization projects have identified novel disease-associated receptors, such as NPSR1 and GPR35. The identification of variants in these receptors provides genetic reagents useful in drug screens. Discussion of the variety of GPCRs that are disrupted in monogenic Mendelian disorders provides the basis for examining the significance of common pharmacogenetic variants.
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Affiliation(s)
- Miles D Thompson
- Department of Pharmacology, University of Toronto, 1 King's College Circle, Toronto, ON, Canada, M5S 1A8,
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Erbach GT, Biggers JD, Manning PC, Nowak RA. Localization of parathyroid hormone-related protein in the preimplantation mouse embryo is associated with events of blastocyst hatching. J Assist Reprod Genet 2014; 30:1009-15. [PMID: 24052330 DOI: 10.1007/s10815-013-0094-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To determine the pattern of expression of parathyroid hormone-related protein (PTHrP) and its receptor, parathyroid hormone receptor 1 (PTHR1), in mouse embryos in different stages of preimplantation development. METHODS Embryos were cultured from the pronuclear zygote stage and harvested as 2-cell, 4-cell and 8-cell embryos, morulae and blastocysts. RT-PCR was carried out on mRNAs of these and of trophoblast outgrowths for detection of PTHrP and PTHR1. Whole mounted embryos intact or stripped of zonae pellucidae were immunofluorescently stained for PTHrP and PTH receptor and observed with confocal microscopy. RESULTS PTHrP mRNA was present in the pronuclear zygote, not present in 2-cell, 4-cell and uncompacted 8-cell embryos, present in the 8-cell compacting embryo, and not detected in 16-cell morulae or blastocysts. The mRNA was present in trophoblasts growing on fibronectin beds. mRNA for PTHR1 was detected in the pronuclear zygote, then undetected until the compacted 8-cell stage and thereafter. PTH receptor protein was observed in 2-cell embryos, morulae and in the inner cell mass and trophectoderm of blastocysts. PTHrP was observed dispersed in the cytoplasm of 2-cell, 4-cell and uncompacted 8-cell embryos, and in distinct foci near the nuclei of morulae. In blastocysts, PTHrP appeared on the apical surface of only trophoblast cells which had extruded from the zona pellucida. Fully hatched blastocysts expressed the protein on the apical side of all trophoblasts. When morulae were prematurely stripped of their zonae, PTHrP was observed on the embryos' outer surface. CONCLUSIONS PTHrP protein is expressed throughout early embryo development, and its receptor PTHR1 is expressed from the morula stage. Embryo hatching is associated with translocation of PTHrP to the apical plasma membrane of trophoblasts. PTHrP may thus have autocrine effects on the developing blastocyst.
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Affiliation(s)
- Gregory T Erbach
- Department of Animal Sciences, University of Illinois, 310 Animal Science Laboratory, 1207 W. Gregory Drive, Urbana, IL, 61801, USA
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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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Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations. Int J Mol Sci 2013; 14:5036-129. [PMID: 23455471 PMCID: PMC3634480 DOI: 10.3390/ijms14035036] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 01/24/2013] [Accepted: 01/25/2013] [Indexed: 02/08/2023] Open
Abstract
The present review aims to systematically and critically analyze the current knowledge on phospholipases and their role in physiological and pathological mineralization undertaken by mineralization competent cells. Cellular lipid metabolism plays an important role in biological mineralization. The physiological mechanisms of mineralization are likely to take place in tissues other than in bones and teeth under specific pathological conditions. For instance, vascular calcification in arteries of patients with renal failure, diabetes mellitus or atherosclerosis recapitulates the mechanisms of bone formation. Osteoporosis—a bone resorbing disease—and rheumatoid arthritis originating from the inflammation in the synovium are also affected by cellular lipid metabolism. The focus is on the lipid metabolism due to the effects of dietary lipids on bone health. These and other phenomena indicate that phospholipases may participate in bone remodelling as evidenced by their expression in smooth muscle cells, in bone forming osteoblasts, chondrocytes and in bone resorbing osteoclasts. Among various enzymes involved, phospholipases A1 or A2, phospholipase C, phospholipase D, autotaxin and sphingomyelinase are engaged in membrane lipid remodelling during early stages of mineralization and cell maturation in mineralization-competent cells. Numerous experimental evidences suggested that phospholipases exert their action at various stages of mineralization by affecting intracellular signaling and cell differentiation. The lipid metabolites—such as arachidonic acid, lysophospholipids, and sphingosine-1-phosphate are involved in cell signaling and inflammation reactions. Phospholipases are also important members of the cellular machinery engaged in matrix vesicle (MV) biogenesis and exocytosis. They may favour mineral formation inside MVs, may catalyse MV membrane breakdown necessary for the release of mineral deposits into extracellular matrix (ECM), or participate in hydrolysis of ECM. The biological functions of phospholipases are discussed from the perspective of animal and cellular knockout models, as well as disease implications, development of potent inhibitors and therapeutic interventions.
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Kopic S, Geibel JP. Gastric acid, calcium absorption, and their impact on bone health. Physiol Rev 2013; 93:189-268. [PMID: 23303909 DOI: 10.1152/physrev.00015.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.
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Affiliation(s)
- Sascha Kopic
- Department of Surgery and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut, USA
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Lai LP, Mitchell J. Parathyroid hormone inhibits phosphorylation of mitogen-activated protein kinase (MAPK) ERK1/2 through inhibition of c-Raf and activation of MKP-1 in osteoblastic cells. Cell Biochem Funct 2009; 27:269-75. [PMID: 19384851 DOI: 10.1002/cbf.1568] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Parathyroid hormone (PTH) regulation of mitogen-activated protein kinases (MAPK) ERK1/2 contributes to PTH regulation of osteoblast growth and apoptosis. We investigated the mechanisms by which PTH inhibits ERK1/2 activity in osteoblastic UMR 106-01 cells. Treatment with PTH significantly inhibited phosphorylated ERK1/2 between 5 and 60 min. Transient transfection of cells with a cDNA encoding MAPK phosphatase-1 (MKP-1) resulted in 30-40% inhibition of pERK1/2; however MKP-1 protein levels were only significantly stimulated by PTH after 30 mins, suggesting another mechanism for the early phase of pERK1/2 inhibition. The active upstream kinase c-Raf phosphorylation at serine 338 (ser(338)) was significantly inhibited by PTH treatment within 5 min and transfection of the cells with constitutively-active c-Raf blocked PTH inhibition of pERK1/2. Inhibition of pERK1/2 and phosphor-c-Raf were seen when cells were treated with PTH(1-34) or PTH(1-31) analogues that stimulate cAMP, but not with PTH(3-34), PTH(7-34) or PTH(18-48) that do not stimulate cAMP. Stimulation of the cells with forskolin or 8BrcAMP also inhibited pERK1/2 and c-Raf.p338. Our results suggest that rapid PTH inhibition of ERK1/2 activity is mediated by PKA dependent inhibition of c-Raf activity and that stimulation of MKP-1 may contribute to maintaining pERK1/2 inhibition over prolonged time.
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Affiliation(s)
- Lick Pui Lai
- Department of Pharmacology and Toxicology, University of Toronto, 1 King's College Circle, Room 4342, Toronto, Ontario, Canada M5S 1A8, Canada
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Hömme M, Schaefer F, Mehls O, Schmitt CP. Differential regulation of RGS-2 by constant and oscillating PTH concentrations. Calcif Tissue Int 2009; 84:305-12. [PMID: 19225708 DOI: 10.1007/s00223-009-9222-1] [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: 10/02/2008] [Accepted: 01/18/2009] [Indexed: 02/07/2023]
Abstract
PTH has diverse effects on bone metabolism: anabolic when given intermittently, catabolic when given continuously. The cellular mechanisms underlying the varying target cell response are not clear yet. PTH induces RGS-2, a member of the Regulator of G-protein Signaling protein family, via cAMP/PKA, and inactivates PKC-mediated signaling. To investigate intracellular signaling pathways with different PTH concentration-time patterns, we treated UMR 106-01 osteoblast-like cells in a perfusion system. PTH was administered intermittently (4 min/h, 10(-7) M) or continuously at an equivalent cumulative dose (6.6 x 10(-9) M). cAMP was measured using radioimmunoassay, mRNA levels using real-time rtPCR and ribonuclease protection assay, and protein levels using Western immunoblotting. A single PTH pulse transiently increased cAMP levels by 2000% +/- 1200%. In contrast to continuous PTH exposure, cAMP induction remained unchanged with intermittent PTH, ruling out desensitization of the PTH receptor. In continuously perfused cells, RGS-2 abundance was three to five times higher than in cells intermittently exposed to PTH for up to 12 h. MKP-1 and -3 were significantly less induced with pulsatile PTH; exposure-mode-dependent differences in MMP-13 and IGFBP-5 were small. Pulsatile but not continuous PTH administration prevents PTHrP receptor desensitization and accumulation of RGS-2 in osteoblasts, which should preserve PKC-dependent signaling.
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Affiliation(s)
- M Hömme
- Division of Pediatric Nephrology, University Hospital for Pediatric and Adolescent Medicine, Im Neuenheimer Feld 153, 69120, Heidelberg, Germany.
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Intermittent PTH administration: A novel therapy method for periodontitis-associated alveolar bone loss. Med Hypotheses 2009; 72:294-6. [DOI: 10.1016/j.mehy.2008.10.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2008] [Revised: 09/27/2008] [Accepted: 10/02/2008] [Indexed: 11/22/2022]
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Wheeler D, Garrido JL, Bisello A, Kim YK, Friedman PA, Romero G. Regulation of parathyroid hormone type 1 receptor dynamics, traffic, and signaling by the Na+/H+ exchanger regulatory factor-1 in rat osteosarcoma ROS 17/2.8 cells. Mol Endocrinol 2008; 22:1163-70. [PMID: 18202147 DOI: 10.1210/me.2007-0461] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The effects of the expression of the Na+/H+ exchanger regulatory factor-1 (NHERF1) on the distribution, dynamics, and signaling properties of the PTH type 1 receptor (PTH1R) were studied in rat osteosarcoma cells ROS 17/2.8. NHERF1 had a dramatic effect on the subcellular distribution of PTH1R, promoting a substantial relocation of the receptor to regions of the plasma membrane located in very close proximity to cytoskeletal fibers. Direct interactions of NHERF1 with the PTH1R and the cytoskeleton were required for these effects, because they were abolished by 1) PTH1R mutations that impair NHERF1 binding, and 2) NHERF1 mutations that impair binding to the PTH1R or the cytoskeleton. NHERF1 reduced significantly the diffusion of the PTH1R by a mechanism that was also dependent on a direct association of NHERF1 with the PTH1R and the cytoskeleton. NHERF1 increased ligand-dependent production of cAMP and induced ligand-dependent rises in intracellular calcium. These effects on calcium were due to increased calcium uptake, as they were blocked by calcium channel inhibitors and by the addition of EGTA to the medium. These calcium effects were abolished by protein kinase A inhibition but phospholipase C inhibition was without effect. Based on these analyses, we propose that, in ROS cells, the presence of NHERF1 induces PTH-dependent calcium signaling by a cAMP-mediated mechanism that involves local protein kinase A-dependent activation of calcium channels.
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Affiliation(s)
- David Wheeler
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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Mannello F, Tonti GAM, Bagnara GP, Papa S. Role and function of matrix metalloproteinases in the differentiation and biological characterization of mesenchymal stem cells. Stem Cells 2005; 24:475-81. [PMID: 16150919 DOI: 10.1634/stemcells.2005-0333] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Matrix metalloproteinases (MMPs), known as matrixins, are Ca- and Zn-dependent endoproteinases involved in a wide variety of developmental and disease-associated processes, proving to be crucial protagonists in many physiological and pathological mechanisms. The ability of MMPs to alter, by limited proteolysis and through the fine control of tissue inhibitors of metalloproteinases, the activity or function of numerous proteins, enzymes, and receptors suggests that they are also involved in various important cellular functions during development. In this review, we focus on the differentiation of mesenchymal stem cells (including those of the myoblastic, osteoblastic, chondroblastic, neural, and apidoblastic lineages) and the possible, if unexpected, biological significance of MMPs in its regulation. The MMP system has been implicated in several differentiation events that suggests that it mediates the proliferative and prodifferentiating effect of the matrixin proteolytic cascade. We summarize these regulatory effects of MMPs on the differentiation of mesenchymal stem cells and hypothesize on the function of MMPs in the stem cell differentiation processes.
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Affiliation(s)
- Ferdinando Mannello
- Institute of Histology and Laboratory Analysis, Center of Cytometry, University Carlo Bo of Urbino, Italy.
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