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Frank SJ. Classical and novel GH receptor signaling pathways. Mol Cell Endocrinol 2020; 518:110999. [PMID: 32835785 PMCID: PMC7799394 DOI: 10.1016/j.mce.2020.110999] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/12/2020] [Accepted: 08/17/2020] [Indexed: 12/16/2022]
Abstract
In this review, I summarize historical and recent features of the classical pathways activated by growth hormone (GH) through the cell surface GH receptor (GHR). GHR is a cytokine receptor superfamily member that signals by activating the non-receptor tyrosine kinase, JAK2, and members of the Src family kinases. Activation of the GHR engages STATs, PI3K, and ERK pathways, among others, and details of these now-classical pathways are presented. Modulating elements, including the SOCS proteins, phosphatases, and regulated GHR metalloproteolysis, are discussed. In addition, a novel physical and functional interaction of GHR with IGF-1R is summarized and discussed in terms of its mechanisms, consequences, and physiological and therapeutic implications.
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Affiliation(s)
- Stuart J Frank
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, 1720 2nd Avenue South, BDB 485, AL, 35294-0012, USA; Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL, 35233, USA.
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Insulin-Like Growth Factors Are Key Regulators of T Helper 17 Regulatory T Cell Balance in Autoimmunity. Immunity 2020; 52:650-667.e10. [PMID: 32294406 DOI: 10.1016/j.immuni.2020.03.013] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 12/17/2019] [Accepted: 03/19/2020] [Indexed: 12/14/2022]
Abstract
Appropriate balance of T helper 17 (Th17) and regulatory T (Treg) cells maintains immune tolerance and host defense. Disruption of Th17-Treg cell balance is implicated in a number of immune-mediated diseases, many of which display dysregulation of the insulin-like growth factor (IGF) system. Here, we show that, among effector T cell subsets, Th17 and Treg cells selectively expressed multiple components of the IGF system. Signaling through IGF receptor (IGF1R) activated the protein kinase B-mammalian target of rapamycin (AKT-mTOR) pathway, increased aerobic glycolysis, favored Th17 cell differentiation over that of Treg cells, and promoted a heightened pro-inflammatory gene expression signature. Group 3 innate lymphoid cells (ILC3s), but not ILC1s or ILC2s, were similarly responsive to IGF signaling. Mice with deficiency of IGF1R targeted to T cells failed to fully develop disease in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis. Thus, the IGF system represents a previously unappreciated pathway by which type 3 immunity is modulated and immune-mediated pathogenesis controlled.
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Zhang Y, Gc S, Patel SB, Liu Y, Paterson AJ, Kappes JC, Jiang J, Frank SJ. Growth hormone (GH) receptor (GHR)-specific inhibition of GH-Induced signaling by soluble IGF-1 receptor (sol IGF-1R). Mol Cell Endocrinol 2019; 492:110445. [PMID: 31100495 PMCID: PMC6613819 DOI: 10.1016/j.mce.2019.05.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/06/2019] [Accepted: 05/07/2019] [Indexed: 12/31/2022]
Abstract
Human growth hormone (GH) binds and activates GH receptor (GHR) and prolactin (PRL) receptor (PRLR). LNCaP human prostate cancer cells express only GHR. A soluble fragment of IGF-1 receptor (IGF-1R) extracellular domain (sol IGF-1R) interacts with GHR and blocks GH signaling. We now explore sol IGF-1R's specificity for inhibiting GH signaling via GHR vs. PRLR and test GHR and PRLR extracellular domain inhibition determinants. Although T47D human breast cancer cells express GHR and PRLR, GH signaling is largely PRLR-mediated. In T47D, sol IGF-1R inhibited neither GH- nor PRL-induced STAT5 activation. However, sol IGF-1R inhibited GH-induced STAT5 activation in T47D-shPRLR cells, which harbor reduced PRLR. In MIN6 mouse β-cells, bovine GH (bGH) activates mouse GHR, not PRLR, while human GH activates mouse GHR and PRLR. In MIN6, sol IGF-1R inhibited bGH-induced STAT5 activation, but partially inhibited human GH-induced STAT5 activation. These findings suggest sol IGF-1R's inhibition is GHR-specific. Using a cellular reconstitution system, we compared effects of sol IGF-1R on signaling through GHR, PRLR, or chimeras in which extracellular subdomains 2 (S2) of the receptors were swapped. Sol IGF-1R inhibited GH-induced STAT5 activation in GHR-expressing, not PRLR-expressing cells, consistent with GHR specificity of sol IGF-1R. Interestingly, we found that GHR S2 (which harbors the GHR-GHR dimer interface) was required, but not sufficient for sol IGF-1R inhibition of GHR signaling. These results suggest sol IGF-1R specifically inhibits GH-induced GHR-mediated signaling, possibly through interaction with GHR S1 and S2 domains. Our findings have implications for GH antagonist development.
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Affiliation(s)
- Yue Zhang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sajina Gc
- Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Sweta B Patel
- Department of Medicine, Division of Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Ying Liu
- School of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Andrew J Paterson
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - John C Kappes
- Department of Medicine, Division of Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Jing Jiang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA
| | - Stuart J Frank
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA; Endocrinology Section, Medical Service, Veterans Affairs Medical Center, Birmingham, AL, 35233, USA.
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Chesnokova V, Zonis S, Barrett RJ, Gleeson JP, Melmed S. Growth Hormone Induces Colon DNA Damage Independent of IGF-1. Endocrinology 2019; 160:1439-1447. [PMID: 31002310 PMCID: PMC6530523 DOI: 10.1210/en.2019-00132] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 04/13/2019] [Indexed: 12/13/2022]
Abstract
DNA damage occurs as a result of environmental insults and aging and, if unrepaired, may lead to chromosomal instability and tumorigenesis. Because GH suppresses ataxia-telangiectasia mutated kinase phosphorylation, decreases DNA repair, and increases DNA damage accumulation, we elucidated whether GH effects on DNA damage are mediated through induced IGF-1. In nontumorous human colon cells, GH, but not IGF-1, increased DNA damage. Stably disrupted IGF-1 receptor (IGF-1R) by lentivirus-expressing short hairpin RNA in vitro or treatment with the IGF-1R phosphorylation inhibitor picropodophyllotoxin (PPP) in vitro and in vivo led to markedly induced GH receptor (GHR) abundance, rendering cells more responsive to GH actions. Suppressing IGF-1R triggered DNA damage in both normal human colon cells and three-dimensional human intestinal organoids. DNA damage was further increased when cells with disrupted IGF-1R were treated with GH. Because GH induction of DNA damage accumulation appeared to be mediated not by IGF-1R but probably by more abundant GH receptor expression, we injected athymic mice with GH-secreting xenografts and then treated them with PPP. In these mice, high circulating GH levels were associated with increased colon DNA damage despite disrupted IGF-1R activity (P < 0.01), whereas GHR levels were also induced. Further confirming that GH effects on DNA damage are directly mediated by GHR signaling, GHR-/- mice injected with PPP did not show increased DNA damage, whereas wild-type mice with intact GHR exhibited increased colon DNA damage in the face of IGF-1 signaling suppression. The results indicate that GH directly induces DNA damage independent of IGF-1.
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Affiliation(s)
- Vera Chesnokova
- Pituitary Center, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
| | - Svetlana Zonis
- Pituitary Center, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
| | - Robert J Barrett
- Department of Medicine, Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - John P Gleeson
- Department of Medicine, Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - Shlomo Melmed
- Pituitary Center, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California
- Correspondence: Shlomo Melmed, MD, Academic Affairs, Room 2015, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, California 90048. E-mail:
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Zhou Y, Zhang Z, Wang N, Chen J, Zhang X, Guo M, John Zhong L, Wang Q. Suppressor of cytokine signalling-2 limits IGF1R-mediated regulation of epithelial-mesenchymal transition in lung adenocarcinoma. Cell Death Dis 2018; 9:429. [PMID: 29559623 PMCID: PMC5861121 DOI: 10.1038/s41419-018-0457-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 02/19/2018] [Accepted: 02/22/2018] [Indexed: 01/30/2023]
Abstract
Non-small cell lung cancer (NSCLC), including adenocarcinoma and squamous cell carcinoma, is the leading cause of death from lung malignancies and has a poor prognosis due to metastasis. Suppressor of cytokine signalling-2 (SOCS2), a feedback inhibitor of cytokine signalling, has been shown to be involved in growth control. Here, we show that SOCS2 were significantly downregulated in tumour foci in NSCLC patients. The expression levels of SOCS2 significantly correlated with clinical stage, lymph node metastasis, histological subtype and survival time. In particular, the decreased expression of SOCS2 significantly associated with advanced pathological stage, lymph node metastasis and shorter overall survival in lung adenocarcinoma patients. In vivo animal results showed that overexpressed SOCS2 attenuated the metastatic characteristics of lung adenocarcinoma, including by inhibiting the epithelial-mesenchymal transition (EMT). Further functional studies indicated that insulin-like growth factor 1 (IGF1)-driven migratory and invasive behaviours of lung adenocarcinoma cells can be partially suppressed by exogenous SOCS2 expression. Investigations into the mechanism of action revealed that SOCS2 inhibits EMT by inactivating signal transducer and activator of transcription 3 (STAT3) and STAT5 via the competitive binding of SOCS2 to the STAT binding sites on IGF1R. Altogether, our results reveal an important role for SOCS2 dysregulation in the pathogenicity of lung adenocarcinoma, suggest its potential use as a biomarker for diagnosing lung adenocarcinoma, and paves the way to develop novel therapy targets as the axis of SOCS2-IGF1R-STAT in lung adenocarcinoma.
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Affiliation(s)
- Yue Zhou
- Department of Thoracic Surgery, First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Zhilei Zhang
- Jiangsu Province Key Lab of Human Functional Genomics, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, China
| | - Ning Wang
- Jiangsu Province Key Lab of Human Functional Genomics, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, China
| | - Jizheng Chen
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Xu Zhang
- Jiangsu Province Key Lab of Human Functional Genomics, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, China
| | - Min Guo
- State Key Laboratory of Natural Medicines, School of Life Science and Technology, China Pharmaceutical University, Nanjing, Jiangsu, 210009, China
| | - Li John Zhong
- Jiangsu Province Key Lab of Human Functional Genomics, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, China
| | - Qian Wang
- Jiangsu Province Key Lab of Human Functional Genomics, Department of Biochemistry and Molecular Biology, Nanjing Medical University, Nanjing, 210029, China.
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Alkharobi H, Alhodhodi A, Hawsawi Y, Alkafaji H, Devine D, El-Gendy R, Beattie J. IGFBP-2 and -3 co-ordinately regulate IGF1 induced matrix mineralisation of differentiating human dental pulp cells. Stem Cell Res 2016; 17:517-522. [PMID: 27776273 PMCID: PMC5153425 DOI: 10.1016/j.scr.2016.09.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 09/22/2016] [Accepted: 09/22/2016] [Indexed: 01/07/2023] Open
Abstract
Human dental pulp cells (DPCs), which are known to contain a subset of stem cells capable of reforming a dentin and pulp-like complex upon in vivo transplantation, were isolated from third molars of three healthy donors and differentiated to a matrix mineralisation phenotype using by culture in dexamethasone and l-ascorbic acid. qRT-PCR analysis of insulin-like growth factor ( IGF) axis gene expression indicated that all genes, except insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein-1 ( IGFBP-1), were expressed in DPCs. During differentiation upregulation of insulin-like growth factor binding protein-2 (IGFBP-2) and downregulation of insulin-like growth factor binding protein-3 (IGFBP-3) expression was observed. Changes in IGFBP-2 and IGFBP-3 mRNA expression were confirmed at the protein level by ELISA of DPC conditioned medium functional analysis indicated that IGF1 stimulated the differentiation of DPCs and that the activity of the growth factor was enhanced by pre-complexation with IGFBP-2 but inhibited by pre-complexation with IGFBP-3. Therefore changes in IGFBP-2 and -3 expression during differentiation form part of a co-ordinated functional response to enhance the pro-differentiative action of IGF1 and represent a novel mechanism for the regulation of DPC differentiation.
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Affiliation(s)
- Hanaa Alkharobi
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom
| | - Aishah Alhodhodi
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom
| | - Yousef Hawsawi
- Dept. of Medical Breast Oncology, MD Anderson Cancer Research Centre, University of Texas, Houston, United States
| | - Hasanain Alkafaji
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom
| | - Deirdre Devine
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom
| | - Reem El-Gendy
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom; Dept. of Oral Pathology, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt.
| | - James Beattie
- Division of Oral Biology, Leeds School of Dentistry, Level 7 Wellcome Trust Brenner Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, United Kingdom.
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A cost-effective method to enhance adenoviral transduction of primary murine osteoblasts and bone marrow stromal cells. Bone Res 2016; 4:16021. [PMID: 27547486 PMCID: PMC4977485 DOI: 10.1038/boneres.2016.21] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 03/18/2016] [Accepted: 05/26/2016] [Indexed: 02/06/2023] Open
Abstract
We report here a method for the use of poly-l-lysine (PLL) to markedly improve the adenoviral transduction efficiency of primary murine osteoblasts and bone marrow stromal cells (BMSCs) in culture and in situ, which are typically difficult to transduce. We show by fluorescence microscopy and flow cytometry that the addition of PLL to the viral-containing medium significantly increases the number of green fluorescence protein (GFP)-positive osteoblasts and BMSCs transduced with an enhanced GFP-expressing adenovirus. We also demonstrate that PLL can greatly enhance the adenoviral transduction of osteoblasts and osteocytes in situ in ex vivo tibia and calvaria, as well as in long bone fragments. In addition, we validate that PLL can improve routine adenoviral transduction studies by permitting the use of low multiplicities of infection to obtain the desired biologic effect. Ultimately, the use of PLL to facilitate adenoviral gene transfer in osteogenic cells can provide a cost-effective means of performing efficient gene transfer studies in the context of bone research.
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Zhang Y, Wang X, Loesch K, May LA, Davis GE, Jiang J, Frank SJ. TIMP3 Modulates GHR Abundance and GH Sensitivity. Mol Endocrinol 2016; 30:587-99. [PMID: 27075707 DOI: 10.1210/me.2015-1302] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH receptor (GHR) binds GH at the cell surface via its extracellular domain and initiates intracellular signal transduction, resulting in important anabolic and metabolic actions. GH signaling is subject to dynamic regulation, which in part is exerted by modulation of cell surface GHR levels. Constitutive and inducible metalloprotease-mediated cleavage of GHR regulate GHR abundance and thereby modulate GH action. We previously demonstrated that GHR proteolysis is catalyzed by the TNF-α converting enzyme (TACE; ADAM17). Tissue inhibitors of metalloproteases-3 (TIMP3) is a natural specific inhibitor of TACE, although mechanisms underlying this inhibition are not yet fully understood. In the current study, we use two model cell lines to examine the relationships between cellular TACE, TIMP3 expression, GHR metalloproteolysis, and GH sensitivity. These two cell lines exhibited markedly different sensitivity to inducible GHR proteolysis, which correlated directly to their relative levels of mature TACE vs unprocessed TACE precursor and indirectly to their levels of cellular TIMP3. Our results implicate TIMP3 as a modulator of cell surface GHR abundance and the ability of GH to promote cellular signaling; these modulatory effects may be conferred by endogenous TIMP3 expression as well as exogenous TIMP3 exposure. Furthermore, our analysis suggests that TIMP3, in addition to regulating the activity of TACE, may also modulate the maturation of TACE, thereby affecting the abundance of the active form of the enzyme.
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Affiliation(s)
- Yue Zhang
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Xiangdong Wang
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Kimberly Loesch
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Larry A May
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - George E Davis
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Jing Jiang
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
| | - Stuart J Frank
- Department of Medicine (Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; The Institute of Cell Biology (X.W.), Shandong University School of Medicine, Jinan 250012, China; Department of Biochemistry and Biophysics (K.L.), Texas A&M University, College Station, Texas 77843; Department of Surgery (L.A.M.), University of Tennessee College of Medicine Chattanooga, Chattanooga, Tennessee 37403; Department of Medical Pharmacology and Physiology (G.E.D.), University of Missouri School of Medicine, Columbia, Missouri 65212; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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Luna-Acosta JL, Alba-Betancourt C, Martínez-Moreno CG, Ramírez C, Carranza M, Luna M, Arámburo C. Direct antiapoptotic effects of growth hormone are mediated by PI3K/Akt pathway in the chicken bursa of Fabricius. Gen Comp Endocrinol 2015; 224:148-59. [PMID: 26231908 DOI: 10.1016/j.ygcen.2015.07.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Revised: 07/26/2015] [Accepted: 07/28/2015] [Indexed: 10/23/2022]
Abstract
Growth hormone (GH) is expressed in several extra-pituitary tissues, including the primary and secondary lymphoid organs of the immune system. In birds, GH mRNA and protein expression show a specific developmental distribution pattern in the bursa of Fabricius (BF), particularly in epithelial and B cells. Changes in the bursal concentration and distribution of locally produced GH during ontogeny suggest it is involved in B cell differentiation and maturation, as well as in a functional survival role in this organ, which may be mediated by paracrine/autocrine mechanisms. Here, we analyzed the anti-apoptotic effect of GH in BF and the intracellular signaling pathways involved in this activity. Also, we studied if this effect was exerted directly by GH or mediated indirectly by IGF-I. Bursal cell cultures showed an important loss of their viability after 4h of incubation and a significant increase in apoptosis. However, treatment with 10nM GH or 40 nM IGF-I significantly increased B cell viability (16.7 ± 0.67% and 13.4 ± 1.12%, respectively) when compared with the untreated controls. In addition, the presence of apoptotic bodies (TUNEL) dramatically decreased (5.5-fold) after GH and IGF-I treatments, whereas co-incubation with anti-GH or anti-IGF-I, respectively, blocked their anti-apoptotic effect. Likewise, both GH and IGF-I significantly inhibited caspase-3 activity (by 40 ± 2.0%) in these cultures. However, the use of anti-IGF-I could not reverse the GH anti-apoptotic effects, thus indicating that these were exerted directly. The addition of 100 nM wortmannin (a PI3K/Akt inhibitor) blocked the GH protective effects. Also, GH stimulated (3-fold) the phosphorylation of Akt in bursal cells, and adding wortmannin or an anti-GH antibody inhibited this effect. Furthermore, GH was capable to stimulate (7-fold) the expression of Bcl-2. Taken together, these results indicate that the direct anti-apoptotic activity of GH observed in the chicken bursal B cell cultures might be mediated through the PI3K/Akt pathway.
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Affiliation(s)
- José Luis Luna-Acosta
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico
| | - Clara Alba-Betancourt
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico; Departamento de Farmacia, Universidad de Guanajuato, Guanajuato 36050, Mexico
| | - Carlos G Martínez-Moreno
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico
| | - Candy Ramírez
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico
| | - Martha Carranza
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico
| | - Maricela Luna
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico
| | - Carlos Arámburo
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico.
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Liu Z, Kennedy OD, Cardoso L, Basta-Pljakic J, Partridge NC, Schaffler MB, Rosen CJ, Yakar S. DMP-1-mediated Ghr gene recombination compromises skeletal development and impairs skeletal response to intermittent PTH. FASEB J 2015; 30:635-52. [PMID: 26481310 DOI: 10.1096/fj.15-275859] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 09/28/2015] [Indexed: 12/20/2022]
Abstract
Bone minerals are acquired during growth and are key determinants of adult skeletal health. During puberty, the serum levels of growth hormone (GH) and its downstream effector IGF-1 increase and play critical roles in bone acquisition. The goal of the current study was to determine how bone cells integrate signals from the GH/IGF-1 to enhance skeletal mineralization and strength during pubertal growth. Osteocytes, the most abundant bone cells, were shown to orchestrate bone modeling during growth. We used dentin matrix protein (Dmp)-1-mediated Ghr knockout (DMP-GHRKO) mice to address the role of the GH/IGF axis in osteocytes. We found that DMP-GHRKO did not affect linear growth but compromised overall bone accrual. DMP-GHRKO mice exhibited reduced serum inorganic phosphate and parathyroid hormone (PTH) levels and decreased bone formation indices and were associated with an impaired response to intermittent PTH treatment. Using an osteocyte-like cell line along with in vivo studies, we found that PTH sensitized the response of bone to GH by increasing Janus kinase-2 and IGF-1R protein levels. We concluded that endogenously secreted PTH and GHR signaling in bone are necessary to establish radial bone growth and optimize mineral acquisition during growth.
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Affiliation(s)
- Zhongbo Liu
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Oran D Kennedy
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Luis Cardoso
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Jelena Basta-Pljakic
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Nicola C Partridge
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Mitchell B Schaffler
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Clifford J Rosen
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
| | - Shoshana Yakar
- *Department of Basic Science and Craniofacial Biology, David B. Kriser Dental Center, New York University College of Dentistry, New York, New York, USA; Department of Biomedical Engineering, City College of New York, New York, New York, USA; and Maine Medical Center Research Institute, Scarborough, Maine, USA
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11
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Dobie R, Ahmed SF, Staines KA, Pass C, Jasim S, MacRae VE, Farquharson C. Increased linear bone growth by GH in the absence of SOCS2 is independent of IGF-1. J Cell Physiol 2015; 230:2796-806. [PMID: 25833299 PMCID: PMC4949688 DOI: 10.1002/jcp.25006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 03/30/2015] [Indexed: 11/12/2022]
Abstract
Growth hormone (GH) signaling is essential for postnatal linear bone growth, but the relative importance of GHs actions on the liver and/or growth plate cartilage remains unclear. The importance of liver derived insulin like‐growth factor‐1 (IGF‐1) for endochondral growth has recently been challenged. Here, we investigate linear growth in Suppressor of Cytokine Signaling‐2 (SOCS2) knockout mice, which have enhanced growth despite normal systemic GH/IGF‐1 levels. Wild‐type embryonic ex vivo metatarsals failed to exhibit increased linear growth in response to GH, but displayed increased Socs2 transcript levels (P < 0.01). In the absence of SOCS2, GH treatment enhanced metatarsal linear growth over a 12 day period. Despite this increase, IGF‐1 transcript and protein levels were not increased in response to GH. In accordance with these data, IGF‐1 levels were unchanged in GH‐challenged postnatal Socs2‐/‐ conditioned medium despite metatarsals showing enhanced linear growth. Growth‐plate Igf1 mRNA levels were not elevated in juvenile Socs2‐/‐ mice. GH did however elevate IGF‐binding protein 3 levels in conditioned medium from GH challenged metatarsals and this was more apparent in Socs2‐/‐ metatarsals. GH did not enhance the growth of Socs2‐/‐ metatarsals when the IGF receptor was inhibited, suggesting that IGF receptor mediated mechanisms are required. IGF‐2 may be responsible as IGF‐2 promoted metatarsal growth and Igf2 expression was elevated in Socs2‐/‐ (but not WT) metatarsals in response to GH. These studies emphasise the critical importance of SOCS2 in regulating GHs ability to promote bone growth. Also, GH appears to act directly on the metatarsals of Socs2‐/‐ mice, promoting growth via a mechanism that is independent of IGF‐1. J. Cell. Physiol. 9999: 2796–2806, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Ross Dobie
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Syed F Ahmed
- Developmental Endocrinology Research Group, School of Medicine, University of Glasgow, Yorkhill, Glasgow, Scotland, UK
| | - Katherine A Staines
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Chloe Pass
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Seema Jasim
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Vicky E MacRae
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
| | - Colin Farquharson
- The Roslin Institute and R(D)SVS, University of Edinburgh, Easter Bush, Midlothian, UK
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12
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Gan Y, Buckels A, Liu Y, Zhang Y, Paterson AJ, Jiang J, Zinn KR, Frank SJ. Human GH receptor-IGF-1 receptor interaction: implications for GH signaling. Mol Endocrinol 2014; 28:1841-54. [PMID: 25211187 DOI: 10.1210/me.2014-1174] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
GH signaling yields multiple anabolic and metabolic effects. GH binds the transmembrane GH receptor (GHR) to activate the intracellular GHR-associated tyrosine kinase, Janus kinase 2 (JAK2), and downstream signals, including signal transducer and activator of transcription 5 (STAT5) activation and IGF-1 gene expression. Some GH effects are partly mediated by GH-induced IGF-1 via IGF-1 receptor (IGF-1R), a tyrosine kinase receptor. We previously demonstrated in non-human cells that GH causes formation of a GHR-JAK2-IGF-1R complex and that presence of IGF-1R (even without IGF-1 binding) augments proximal GH signaling. In this study, we use human LNCaP prostate cancer cells as a model system to further study the IGF-1R's role in GH signaling. GH promoted JAK2 and GHR tyrosine phosphorylation and STAT5 activation in LNCaP cells. By coimmunoprecipitation and a new split luciferase complementation assay, we find that GH augments GHR/IGF-1R complex formation, which is inhibited by a Fab of an antagonistic anti-GHR monoclonal antibody. Short hairpin RNA-mediated IGF-1R silencing in LNCaP cells reduced GH-induced GHR, JAK2, and STAT5 phosphorylation. Similarly, a soluble IGF-1R extracellular domain fragment (sol IGF-1R) interacts with GHR in response to GH and blunts GH signaling. Sol IGF-1R also markedly inhibits GH-induced IGF-1 gene expression in both LNCaP cells and mouse primary osteoblast cells. On the basis of these and other findings, we propose a model in which IGF-1R augments GH signaling by allowing a putative IGF-1R-associated molecule that regulates GH signaling to access the activated GHR/JAK2 complex and envision sol IGF-1R as a dominant-negative inhibitor of this IGF-1R-mediated augmentation. Physiological implications of this new model are discussed.
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Affiliation(s)
- Yujun Gan
- Department of Medicine (Y.G., A.B., Y.L., Y.Z., A.J.P., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Departments of Radiology (K.R.Z.) and Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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13
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Chia DJ. Minireview: mechanisms of growth hormone-mediated gene regulation. Mol Endocrinol 2014; 28:1012-25. [PMID: 24825400 DOI: 10.1210/me.2014-1099] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH exerts a diverse array of physiological actions that include prominent roles in growth and metabolism, with a major contribution via stimulating IGF-1 synthesis. GH achieves its effects by influencing gene expression profiles, and Igf1 is a key transcriptional target of GH signaling in liver and other tissues. This review examines the mechanisms of GH-mediated gene regulation that begin with signal transduction pathways activated downstream of the GH receptor and continue with chromatin events at target genes and additionally encompasses the topics of negative regulation and cross talk with other cellular inputs. The transcription factor, signal transducer and activator of transcription 5b, is regarded as the major signaling pathway by which GH achieves its physiological effects, including in stimulating Igf1 gene transcription in liver. Recent studies exploring the mechanisms of how activated signal transducer and activator of transcription 5b accomplishes this are highlighted, which begin to characterize epigenetic features at regulatory domains of the Igf1 locus. Further research in this field offers promise to better understand the GH-IGF-1 axis in normal physiology and disease and to identify strategies to manipulate the axis to improve human health.
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Affiliation(s)
- Dennis J Chia
- Department of Pediatrics, Icahn School of Medicine at Mt Sinai, New York, New York 10029
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14
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Dieudonne FX, Sévère N, Biosse-Duplan M, Weng JJ, Su Y, Marie PJ. Promotion of osteoblast differentiation in mesenchymal cells through Cbl-mediated control of STAT5 activity. Stem Cells 2014; 31:1340-9. [PMID: 23533197 DOI: 10.1002/stem.1380] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 02/28/2013] [Indexed: 02/02/2023]
Abstract
The identification of the molecular mechanisms controlling the degradation of regulatory proteins in mesenchymal stromal cells (MSC) may provide clues to promote MSC osteogenic differentiation and bone regeneration. Ubiquitin ligase-dependent degradation of proteins is an important process governing cell fate. In this study, we investigated the role of the E3 ubiquitin ligase c-Cbl in MSC osteoblast differentiation and identified the mechanisms involved in this effect. Using distinct shRNA targeting c-Cbl, we showed that c-Cbl silencing promotes osteoblast differentiation in murine and human MSC, as demonstrated by increased alkaline phosphatase activity, expression of phenotypic osteoblast marker genes (RUNX2, ALP, type 1 collagen), and matrix mineralization in vitro. Coimmunoprecipitation analyses showed that c-Cbl interacts with the transcription factor STAT5, and that STAT5 forms a complex with RUNX2, a master transcription factor controlling osteoblastogenesis. Silencing c-Cbl decreased c-Cbl-mediated STAT5 ubiquitination, increased STAT5 protein level and phosphorylation, and enhanced STAT5 and RUNX2 transcriptional activity. The expression of insulin like growth factor-1 (IGF-1), a target gene of STAT5, was increased by c-Cbl silencing in MSC and in bone marrow stromal cells isolated from c-Cbl deficient mice, suggesting that IGF-1 contributes to osteoblast differentiation induced by c-Cbl silencing in MSC. Consistent with these findings, pharmacological inhibition of STAT5 activity, or neutralization of IGF-1 activity, abrogated the positive effect of c-Cbl knockdown on MSC osteogenic differentiation. Taken together, the data provide a novel functional mechanism by which the ubiquitin ligase c-Cbl regulates the osteoblastic differentiation program in mesenchymal cells by controlling Cbl-mediated STAT5 degradation and activity.
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15
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Al-Kharobi H, El-Gendy R, Devine DA, Beattie J. The role of the insulin‑like growth factor (IGF) axis in osteogenic and odontogenic differentiation. Cell Mol Life Sci 2014; 71:1469-76. [PMID: 24232361 PMCID: PMC11113200 DOI: 10.1007/s00018-013-1508-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 10/25/2013] [Indexed: 11/28/2022]
Abstract
The insulin-like growth factor (IGF) axis is a multicomponent molecular network which has important biological functions in the development and maintenance of differentiated tissue function(s). One of the most important functions of the IGF axis is the control of skeletal tissue metabolism by the finely tuned regulation of the process of osteogenesis. To achieve this, the IGF axis controls the activity of several cell types—osteoprogenitor cells, osteoblasts, osteocytes and osteoclasts to achieve the co-ordinated development of appropriate hard tissue structure and associated matrix deposition. In addition, there is an increasing awareness that the IGF axis also plays a role in the process of odontogenesis (tooth formation). In this review, we highlight some of the key findings in both of these areas. A further understanding of the role of the IGF axis in hard tissue biology may contribute to tissue regeneration strategies in cases of skeletal tissue trauma.
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Affiliation(s)
- H. Al-Kharobi
- Leeds University School of Dentistry, University of Leeds, Clarendon Way, Leeds, LS2 9LU UK
| | - R. El-Gendy
- Leeds University School of Dentistry, University of Leeds, Clarendon Way, Leeds, LS2 9LU UK
| | - D. A. Devine
- Leeds University School of Dentistry, University of Leeds, Clarendon Way, Leeds, LS2 9LU UK
| | - J. Beattie
- Leeds University School of Dentistry, University of Leeds, Clarendon Way, Leeds, LS2 9LU UK
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16
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Gan Y, Paterson AJ, Zhang Y, Jiang J, Frank SJ. Functional collaboration of insulin-like growth factor-1 receptor (IGF-1R), but not insulin receptor (IR), with acute GH signaling in mouse calvarial cells. Endocrinology 2014; 155:1000-9. [PMID: 24302626 PMCID: PMC3929739 DOI: 10.1210/en.2013-1732] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
GH signals through the GH receptor (GHR), a cytokine receptor linked to Janus kinase 2 (JAK2). GH activates signal transducer and activator of transcription 5 (STAT5), causing expression of genes including IGF-I. IGF-I binds IGF-I receptor (IGF-IR), a heterotetrameric (α2-β2) tyrosine kinase growth factor receptor similar to insulin receptor (IR). In addition to this GH -> GHR -> IGF-I -> IGF-IR pathway, GH induces a complex including GHR, JAK2, and IGF-IR and deletion of floxed IGF-1R in primary murine calvarial cells with Cre-recombinase-expressing adenovirus (Ad-Cre) desensitizes cells to GH for STAT5 activation and IGF-I mRNA accumulation. Diminished GH-induced STAT5 phosphorylation in Ad-Cre-treated cells is rescued by adenoviruses encoding either IGF-IR or IGF-IR lacking the β-chain intracellular domain. Reasoning that IGF-IR's extracellular portion (α or extracellular β) mediates functional interaction with GH signaling, we pursued reconstitution studies. Although structurally related to IGF-IR, IR expressed adenovirally did not rescue GH-induced STAT5 phosphorylation in Ad-Cre-treated cells. We thus created chimeras, swapping homologous IR extracellular regions into IGF-IR. IR and IGF-IR possess N-terminal L1, cysteine-rich (CR), and L2 α-chain domains. We created Ad-IGF-IR/IR-L1 and Ad-IGF-IR/IR-L1-CR-L2, in which L1 alone or L1, CR, and L2 of IR replace corresponding IGF-IR regions, respectively. Ad-IGF-IR/IR-L1, but not Ad-IGF-IR/IR-L1-CR-L2, rescued GH-induced STAT5 phosphorylation in Ad-Cre-treated cells. Additionally, medium containing a soluble IGF-IR (including only L1-CR-L2) dampened GH-induced STAT5 phosphorylation in calvarial cells and two other GH-responsive cell lines. Thus, an extracellular determinant(s), likely in CR-L2, specifically allows IGF-IR to collaborate with GHR and JAK2 for robust GH-induced acute STAT5 phosphorylation.
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Affiliation(s)
- Yujun Gan
- Department of Medicine (Y.G., A.J.P., Y.Z., J.J., S.J.F.), Division of Endocrinology, Diabetes, and Metabolism, and Department of Cell, Developmental, and Integrative Biology (S.J.F.), University of Alabama at Birmingham, Birmingham, Alabama 35294; and Endocrinology Section (S.J.F.), Medical Service, Veterans Affairs Medical Center, Birmingham, Alabama 35233
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17
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Kennedy OD, Sun H, Wu Y, Courtland HW, Williams GA, Cardoso L, Basta-Pljakic J, Schaffler MB, Yakar S. Skeletal response of male mice to anabolic hormone therapy in the absence of the Igfals gene. Endocrinology 2014; 155:987-99. [PMID: 24424061 PMCID: PMC3929729 DOI: 10.1210/en.2013-1819] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IGF-I is a critical regulator of skeletal acquisition, which acts in endocrine and autocrine/paracrine modes. In serum, IGF-I is carried by the IGF-binding proteins in binary complexes. Further stabilization of these complexes is achieved by binding to the acid labile subunit (ALS) in a ternary complex (of IGF-I-IGF-binding protein 3/5-ALS). Ablation of the Igfals gene in humans (ALS deficiency) and mice (ALS knockout [ALSKO]) leads to markedly decreased serum IGF-I levels, growth retardation, and impaired skeletal acquisition. To investigate whether hormonal replacement therapy would improve the skeletal phenotype in cases of Igfals gene ablation, we treated male ALSKO mice with GH, IGF-I, or a combination of both. Treatments were administered to animals between 4 and 16 weeks of age or from 8 to 16 weeks of age. Although all treatment groups showed an increase (20%) in serum IGF-I levels, there was no increase in body weight, weight gain, or bone length in either age group. Despite the blunted linear growth in response to hormone therapy, ALSKO mice treated with GH showed radial bone growth, which contributed to bone strength tested by 4-point bending. We found that ALSKO mice treated with GH showed increased total cross-sectional area, cortical bone area, and cortical thickness by microtomography. Dynamic histomorphometry showed that although GH and double treatment groups resulted in trends towards increased bone formation parameters, these did not reach significance. However, bone resorption parameters were significantly increased in all treatment groups. ALSKO mice treated between 4 and 16 weeks of age showed minor differences in bone traits compared with vehicle-treated mice. In conclusion, treatment with GH and IGF-I do not work synergistically to rescue the stunted growth found in mice lacking the Igfals gene. Although GH alone appears to increase bone parameters slightly, it does not affect body weight or linear growth.
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Affiliation(s)
- Oran D Kennedy
- Department of Biomedical Engineering (O.D.K., L.C., J.B.-P., M.B.S.), City College of New York, New York 10031; David B. Kriser Dental Center (H.S., Y.W., G.A.W., S.Y.), Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York 10010-4086; and Division of Endocrinology (H.-W.C., S.Y.), Diabetes and Bone Disease, Mount Sinai School of Medicine, New York, New York 10029-6547
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18
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Huang Y, Chang Y. Regulation of pancreatic islet beta-cell mass by growth factor and hormone signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 121:321-49. [PMID: 24373242 DOI: 10.1016/b978-0-12-800101-1.00010-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Dysfunction and destruction of pancreatic islet beta cells is a hallmark of diabetes. Better understanding of cellular signals in beta cells will allow development of therapeutic strategies for diabetes, such as preservation and expansion of beta-cell mass and improvement of beta-cell function. During the past several decades, the number of studies analyzing the molecular mechanisms, including growth factor/hormone signaling pathways that impact islet beta-cell mass and function, has increased exponentially. Notably, somatolactogenic hormones including growth hormone (GH), prolactin (PRL), and insulin-like growth factor-1 (IGF-1) and their receptors (GHR, PRLR, and IGF-1R) are critically involved in beta-cell growth, survival, differentiation, and insulin secretion. In this chapter, we focus more narrowly on GH, PRL, and IGF-1 signaling, and GH-IGF-1 cross talk. We also discuss how these signaling aspects contribute to the regulation of beta-cell proliferation and apoptosis. In particular, our novel findings of GH-induced formation of GHR-JAK2-IGF-1R protein complex and synergistic effects of GH and IGF-1 on beta-cell signaling, proliferation, and antiapoptosis lead to a new concept that IGF-1R may serve as a proximal component of GH/GHR signaling.
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Affiliation(s)
- Yao Huang
- Department of Obstetrics and Gynecology, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
| | - Yongchang Chang
- Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA
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19
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Wang Y, Bikle DD, Chang W. Autocrine and Paracrine Actions of IGF-I Signaling in Skeletal Development. Bone Res 2013; 1:249-59. [PMID: 26273506 DOI: 10.4248/br201303003] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 06/29/2013] [Indexed: 11/10/2022] Open
Abstract
Insulin-like growth factor-I (IGF-I) regulates cell growth, survival, and differentiation by acting on the IGF-I receptor, (IGF-IR)-a tyrosine kinase receptor, which elicits diverse intracellular signaling responses. All skeletal cells express IGF-I and IGF-IR. Recent studies using tissue/cell-specific gene knockout mouse models and cell culture techniques have clearly demonstrated that locally produced IGF-I is more critical than the systemic IGF-I in supporting embryonic and postnatal skeletal development and bone remodeling. Local IGF-I/IGF-IR signaling promotes the growth, survival and differentiation of chondrocytes and osteoblasts, directly and indirectly, by altering other autocrine/paracrine signaling pathways in cartilage and bone, and by enhancing interactions among these skeletal cells through hormonal and physical means. Moreover, local IGF-I/IGF-IR signaling is critical for the anabolic bone actions of growth hormone and parathyroid hormone. Herein, we review evidence supporting the actions of local IGF-I/IGF-IR in the above aspects of skeletal development and remodeling.
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Affiliation(s)
- Yongmei Wang
- Endocrine Unit, University of California, San Francisco, Veterans Affairs Medical Center , San Francisco, CA, USA
| | - Daniel D Bikle
- Endocrine Unit, University of California, San Francisco, Veterans Affairs Medical Center , San Francisco, CA, USA
| | - Wenhan Chang
- Endocrine Unit, University of California, San Francisco, Veterans Affairs Medical Center , San Francisco, CA, USA
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20
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Gan Y, Zhang Y, Buckels A, Paterson AJ, Jiang J, Clemens TL, Zhang ZY, Du K, Chang Y, Frank SJ. IGF-1R modulation of acute GH-induced STAT5 signaling: role of protein tyrosine phosphatase activity. Mol Endocrinol 2013; 27:1969-79. [PMID: 24030252 DOI: 10.1210/me.2013-1178] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH is a potent anabolic and metabolic factor that binds its cell surface receptor (GHR), activating the GHR-associated tyrosine kinase, Janus kinase 2, which phosphorylates and activates the latent transcription factor, signal transducer and activator of transcription 5 (STAT5). Some GH actions are mediated by the elaboration of IGF-1, which exerts effects by binding and activating the heterotetrameric tyrosine kinase growth factor receptor, IGF-1R. In addition to this GH-GHR-IGF-1-IGF-1R scheme, we have demonstrated in primary osteoblasts and in islet β-cells that then deletion or silencing of IGF-1R results in diminished GH-induced STAT5 phosphorylation, suggesting that the presence of IGF-1R may facilitate GH signaling. In this study, we explore potential roles for protein tyrosine phosphatase activity in modulating GH-induced signaling, comparing conditions in which IGF-1R is present or diminished. We confirm that in mouse primary osteoblasts harboring loxP sites flanking the IGF-1R gene, infection with an adenovirus that expresses the Cre recombinase results in IGF-1R deletion and diminished acute GH-induced STAT5 phosphorylation. Furthermore, we present a new model of IGF-1R silencing, in which expression of short hairpin RNA directed at IGF-1R greatly reduces IGF-1R abundance in LNCaP human prostate cancer cells. In both models, treatment with a chemical inhibitor of protein tyrosine phosphatase-1B (PTP-1B), but not one of src homology region 2 domain-containing phosphotase-1 (SHP-1) and SHP-2, reverses the loss of GH-induced STAT5 phosphorylation in cells lacking IGF-1R but has no effect in cells with intact IGF-1R. Furthermore, expression of either a dominant-negative PTP-1B or the PTP-1B-interacting inhibitory protein, constitutive photomorphogenesis 1, also rescues acute GH-induced STAT5 signaling in IGF-1R-deficient cells but has no effect in IGF-1R replete cells. By expressing a substrate-trapping mutant PTP-1B, we demonstrate that tyrosine phosphorylated Janus kinase-2 is a PTP-1B substrate only in cells lacking IGF-1R. Collectively, our data suggest that IGF-1R positively regulates acute GH signaling by preventing access of PTP-1B activity to Janus kinase 2 and thereby preventing PTP-1B-mediated suppression of GH-induced STAT5 activation.
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Affiliation(s)
- Yujun Gan
- MD, University of Alabama at Birmingham, 1530 Third Avenue South, BDB 720, Birmingham, Alabama 35294-0012.
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21
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Felice DL, El-Shennawy L, Zhao S, Lantvit DL, Shen Q, Unterman TG, Swanson SM, Frasor J. Growth hormone potentiates 17β-estradiol-dependent breast cancer cell proliferation independently of IGF-I receptor signaling. Endocrinology 2013; 154:3219-27. [PMID: 23782942 PMCID: PMC3749474 DOI: 10.1210/en.2012-2208] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Estrogen action in mammary gland development and breast cancer progression is tightly linked to the GH/IGF-I axis. Although many of the effects of GH on mammary gland growth and development require IGF-I, the extent to which GH action in breast cancer depends on IGF-I is not known. We examined GH action in a panel of estrogen receptor-positive breast cancer cell lines and found that T47D cells express significant levels of GH receptor and that GH significantly enhances 17β-estradiol (E2)-stimulated proliferation in these cells. GH action in the T47D cells was independent of changes in IGF-I and IGF-I receptor (IGF-IR) expression and IGF-IR signaling, suggesting that GH can exert direct effects on breast cancer cells. Although E2-dependent proliferation required IGF-IR signaling, the combination of GH+E2 overcame inhibition of IGF-IR activity to restore proliferation. In contrast, GH required both Janus kinase 2 and epidermal growth factor receptor signaling for subsequent ERK activation and potentiation of E2-dependent proliferation. Downstream of these pathways, we identified a number of immediate early-response genes associated with proliferation that are rapidly and robustly up-regulated by GH. These findings demonstrate that GH can have important effects in breast cancer cells that are distinct from IGF-IR activity, suggesting that novel drugs or improved combination therapies targeting estrogen receptor and the GH/IGF axis may be beneficial for breast cancer patients.
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Affiliation(s)
- Dana L Felice
- Department of Physiology and Biophysics, University of Illinois at Chicago, 835 South Wolcott Avenue, MC 901, Chicago, Illinois 60612, USA
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JOUNG YOUNHEE, LIM EUNJOUNG, DARVIN PRAMOD, JANG JUWOONG, PARK KYUNGDO, LEE HAKKYO, KIM HEUISOO, CHO BYUNGWOOK, PARK TAEKYU, CHUNG SUMI, PARK JONGHWAN, YANG YOUNGMOK. Hwanggeumchal sorghum extract enhances BMP7 and GH signaling through the activation of Jak2/STAT5B in MC3T3-E1 osteoblastic cells. Mol Med Rep 2013; 8:891-6. [DOI: 10.3892/mmr.2013.1593] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 07/11/2013] [Indexed: 11/06/2022] Open
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Beck P, Urbano FJ, Williams DK, Garcia-Rill E. Effects of leptin on pedunculopontine nucleus (PPN) neurons. J Neural Transm (Vienna) 2013; 120:1027-38. [PMID: 23263542 PMCID: PMC3618992 DOI: 10.1007/s00702-012-0957-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/10/2012] [Indexed: 12/24/2022]
Abstract
Leptin, a hormone that regulates appetite and energy expenditure, is increased in obese individuals, although these individuals often exhibit leptin resistance. Obesity is characterized by sleep/wake disturbances, such as excessive daytime sleepiness, increased REM sleep, increased nighttime arousals, and decreased percentage of total sleep time. Several studies have shown that short sleep duration is highly correlated with decreased leptin levels in both animal and human models. Arousal and rapid eye movement (REM) sleep are regulated by the cholinergic arm of the reticular activating system, the pedunculopontine nucleus (PPN). The goal of this project was to determine the role of leptin in the PPN, and thus in obesity-related sleep disorders. Whole-cell patch-clamp recordings were conducted on PPN neurons in 9- to 17-day-old rat brainstem slices. Leptin decreased action potential (AP) amplitude, AP frequency, and h-current (I(H)). These findings suggest that leptin causes a blockade of Na⁺ channels. Therefore, we conducted an experiment to test the effects of leptin on Na⁺ conductance. To determine the average voltage dependence of this conductance, results from each cell were equally weighted by expressing conductance as a fraction of the maximum conductance in each cell. I Na amplitude was decreased in a dose-dependent manner, suggesting a direct effect of leptin on these channels. The average decrease in Na⁺ conductance by leptin was ~40 %. We hypothesize that leptin normally decreases activity in the PPN by reducing I(H) and I(Na) currents, and that in states of leptin dysregulation (i.e., leptin resistance) this effect may be blunted, therefore causing increased arousal and REM sleep drive, and ultimately leading to sleep-related disorders.
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Affiliation(s)
- Paige Beck
- Center for Translational Neuroscience, Dept. Neurobiology & Dev. Sci., University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | | | - D. Keith Williams
- Center for Translational Neuroscience, Dept. Neurobiology & Dev. Sci., University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Edgar Garcia-Rill
- Center for Translational Neuroscience, Dept. Neurobiology & Dev. Sci., University of Arkansas for Medical Sciences, Little Rock, AR, USA
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Darvin P, Joung YH, Yang YM. JAK2-STAT5B pathway and osteoblast differentiation. JAKSTAT 2013; 2:e24931. [PMID: 24470975 PMCID: PMC3894232 DOI: 10.4161/jkst.24931] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 05/03/2013] [Accepted: 05/03/2013] [Indexed: 12/31/2022] Open
Abstract
Osteoblast differentiation is a critical step in the maintenance of bone homeostasis. Osteoblast differentiation is generally maintained by growth hormone (GH) and various other endocrine and autocrine/paracrine factors. JAK2-STAT5B pathway is a central axis in the mechanism of GH signaling. Similarly, the autocrine/paracrine signaling factor IGF-1 also mediates its effects through this pathway. Analysis on JAK2-STAT5B pathway showed its importance in the IGF-1/IGF-1R mediated regulation of gene expression and osteoblast differentiation. Persistent activation of STAT5B and inhibition of STAT5B degradation showed increased osteoblastic differentiation and STAT5B/Runx-2 activities. Conditional gene silencing studies showed the importance of the JAK2-STAT5B pathway in stimulation of other transcription factors and expression of various differentiation markers.
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Affiliation(s)
- Pramod Darvin
- Department of Pathology; School of Medicine; and Institute of Biomedical Science and Technology; Konkuk University; Seoul, Republic of Korea
| | - Youn Hee Joung
- Department of Pathology; School of Medicine; and Institute of Biomedical Science and Technology; Konkuk University; Seoul, Republic of Korea
| | - Young Mok Yang
- Department of Pathology; School of Medicine; and Institute of Biomedical Science and Technology; Konkuk University; Seoul, Republic of Korea
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Joung YH, Lim EJ, Darvin P, Chung SC, Jang JW, Do Park K, Lee HK, Kim HS, Park T, Yang YM. MSM enhances GH signaling via the Jak2/STAT5b pathway in osteoblast-like cells and osteoblast differentiation through the activation of STAT5b in MSCs. PLoS One 2012; 7:e47477. [PMID: 23071812 PMCID: PMC3469535 DOI: 10.1371/journal.pone.0047477] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 09/17/2012] [Indexed: 01/27/2023] Open
Abstract
Methylsulfonylmethane (MSM) is a naturally occurring sulfur compound with well-known anti-oxidant properties and anti-inflammatory activities. But, its effects on bone are unknown. Growth hormone (GH) is regulator of bone growth and bone metabolism. GH activates several signaling pathways such as the Janus kinase (Jak)/signal transducers and activators of transcription (STAT) pathway, thereby regulating expression of genes including insulin-like growth factor (IGF)-1. GH exerts effects both directly and via IGF-1, which signals by activating the IGF-1 receptor (IGF-1R). In this study, we investigated the effects of MSM on the GH signaling via the Jak/STAT pathway in osteoblasts and the differentiation of primary bone marrow mesenchymal stem cells (MSCs). MSM was not toxic to osteoblastic cells and MSCs. MSM increased the expression of GH-related proteins including IGF-1R, p-IGF-1R, STAT5b, p-STAT5b, and Jak2 in osteoblastic cells and MSCs. MSM increased IGF-1R and GHR mRNA expression in osteoblastic cells. The expression of MSM-induced IGF-1R and GHR was inhibited by AG490, a Jak2 kinase inhibitor. MSM induced binding of STAT5 to the IGF-1R and increased IGF-1 and IGF-1R promoter activities. Analysis of cell extracts by immunoprecipitation and Western blot showed that MSM enhanced GH-induced activation of Jak2/STAT5b. We found that MSM and GH, separately or in combination, activated GH signaling via the Jak2/STAT5b pathway in UMR-106 cells. Using siRNA analysis, we found that STAT5b plays an essential role in GH signaling activation in C3H10T1/2 cells. Osteogenic marker genes (ALP, ON, OCN, BSP, OSX, and Runx2) were activated by MSM, and siRNA-mediated STAT5b knockdown inhibited MSM-induced expression of osteogenic markers. Furthermore, MSM increased ALP activity and the mineralization of MSCs. Taken together, these results indicated that MSM can promote osteogenic differentiation of MSCs through activation of STAT5b.
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Affiliation(s)
- Youn Hee Joung
- Department of Pathology, School of Medicine, Institute of Biomedical Science and Technology, Konkuk University, Seoul, Republic of Korea
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26
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Ma F, Wei Z, Shi C, Gan Y, Lu J, Frank SJ, Balducci J, Huang Y. Signaling cross talk between growth hormone (GH) and insulin-like growth factor-I (IGF-I) in pancreatic islet β-cells. Mol Endocrinol 2011; 25:2119-33. [PMID: 22034225 DOI: 10.1210/me.2011-1052] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Dysfunction and destruction of pancreatic islet β-cells is a hallmark of diabetes. Better understanding of cell signals regulating β-cell growth and antiapoptosis will allow development of therapeutic strategies for diabetes by preservation and expansion of β-cell mass. GH and IGF-I share a complicated physiological relationship and have both been implicated in β-cell function. GH and IGF-I exert their biological effects through binding to respective receptors (GHR and IGF-IR) and subsequently engaging downstream signaling pathways. However, their collaborative roles in modulation of β-cell mass and the underlying molecular mechanisms remain poorly understood. In this study, we demonstrate that cultured β-cells are appealing systems for investigating potential GH-IGF-I signaling cross talk. We uncover that GH specifically promotes formation of a protein complex containing GHR, Janus kinase 2 (a nonreceptor kinase coupled to GH/GHR signaling), and IGF-IR. More importantly, GH and IGF-I synergistically activate both signal transducer and activator of transcription 5 and Akt pathways. Concomitantly, β-cells proliferate more robustly and are better protected from serum deprivation-induced apoptosis when exposed to GH and IGF-I in combination vs. GH or IGF-I alone. The augmented proliferative effects by GH and IGF-I are confirmed in isolated islets. Taken together, our findings strongly suggest that there exists a novel signaling relationship between GH/GHR and IGF-I/IGF-IR systems in β-cells, i.e. IGF-IR may serve as a proximal component of GH/GHR signaling, contributing to enhancement of β-cell mass and function. In support of this, IGF-IR knockdown in β-cells resulted in the desensitization of acute GH-induced signal transducer and activator of transcription 5 activation.
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Affiliation(s)
- Fanxin Ma
- Laboratory of Signal Transduction, Department of Obstetrics and Gynecology, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona 85004, USA
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27
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Xu J, Zhang Y, Berry PA, Jiang J, Lobie PE, Langenheim JF, Chen WY, Frank SJ. Growth hormone signaling in human T47D breast cancer cells: potential role for a growth hormone receptor-prolactin receptor complex. Mol Endocrinol 2011; 25:597-610. [PMID: 21310852 DOI: 10.1210/me.2010-0255] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
GH receptor (GHR) and prolactin (PRL) receptor (PRLR) are structurally similar cytokine receptor superfamily members that are highly conserved among species. GH has growth-promoting and metabolic effects in various tissues in vertebrates, including humans. PRL is essential for regulation of lactation in mammals. Recent studies indicate that breast tissue bears GHR and PRLR and that both GH and PRL may impact development or behavior of breast cancer cells. An important facet of human GH (hGH) and human PRL (hPRL) biology is that although hPRL interacts only with hPRLR, hGH binds well to both hGHR and hPRLR. Presently, we investigated potential signaling effects of both hormones in the estrogen receptor- and progesterone receptor-positive human T47D breast cancer cell line. We found that this cell type expresses ample GHR and PRLR and responds well to both hGH and hPRL, as evidenced by activation of the Janus kinase 2/signal transducer and activator of transcription 5 pathway. Immunoprecipitation studies revealed specific GHR-PRLR association in these cells that was acutely enhanced by GH treatment. Although GH caused formation of disulfide-linked and chemically cross-linked GHR dimers in T47D cells, GH preferentially induced tyrosine phosphorylation of PRLR rather than GHR. Notably, both a GHR-specific ligand antagonist (B2036) and a GHR-specific antagonist monoclonal antibody (anti-GHR(ext-mAb)) failed to inhibit GH-induced signal transducer and activator of transcription 5 activation. In contrast, although the non-GHR-specific GH antagonist (G120R) and the PRL antagonist (G129R) individually only partially inhibited GH-induced activation, combined treatment with these two antagonists conferred greater inhibition than either alone. These data indicate that endogenous GHR and PRLR associate (possibly as a GHR-PRLR heterodimer) in human breast cancer cells and that GH signaling in these cells is largely mediated by the PRLR in the context of both PRLR-PRLR homodimers and GHR-PRLR heterodimers, broadening our understanding of how these related hormones and their related receptors may function in physiology and pathophysiology.
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Affiliation(s)
- Jie Xu
- Department of Medicine, University of Alabama at Birmingham, Alabama 35294-0012, USA
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Li X, Huang Y, Jiang J, Frank SJ. Synergy in ERK activation by cytokine receptors and tyrosine kinase growth factor receptors. Cell Signal 2010; 23:417-24. [PMID: 20946955 DOI: 10.1016/j.cellsig.2010.10.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 10/01/2010] [Indexed: 10/19/2022]
Abstract
Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) signal through EGF and PDGF receptors, which are important receptor tyrosine kinases (RTKs). Growth hormone (GH) and prolactin (PRL) are four helical bundle peptide hormones that signal via GHR and PRLR, members of the cytokine receptor superfamily. In this study, we examine crosstalk between signaling pathways emanating from these disparate receptor groups (RTKs and cytokine receptors). We find that GH and EGF specifically synergize for activation of ERK in murine preadipocytes. The locus of this synergy resides at the level of MEK activation, but not above this level (i.e., not at the level of EGFR, SHC, or Raf activation). Furthermore, dephosphorylation of the scaffold protein, KSR, at a critical serine residue is also synergistically promoted by GH and EGF, suggesting that GH sensitizes these cells to EGF-induced ERK activation by augmenting the actions of KSR in facilitating MEK-ERK activation. Similarly specific synergy in ERK activation is also detected in human T47D breast cancer cells by cotreatment with PRL and PDGF. This synergy also resides at the level of MEK activation. Consistent with this synergy, PRL and PDGF also synergized for c-fos-dependent transactivation of a luciferase reporter gene in T47D cells, indicating that events downstream of ERK activation reflect this signaling synergy. Important conceptual and physiological implications of these findings are discussed.
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Affiliation(s)
- Xin Li
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, AL 35294-0012, USA
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