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Guan D, Bae H, Zhou D, Chen Y, Jiang C, La CM, Xiao Y, Zhu K, Hu W, Trinh TM, Liu P, Xiong Y, Cai B, Jang C, Lazar MA. Hepatocyte SREBP signaling mediates clock communication within the liver. J Clin Invest 2023; 133:e163018. [PMID: 37066875 PMCID: PMC10104893 DOI: 10.1172/jci163018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 02/23/2023] [Indexed: 04/18/2023] Open
Abstract
Rhythmic intraorgan communication coordinates environmental signals and the cell-intrinsic clock to maintain organ homeostasis. Hepatocyte-specific KO of core components of the molecular clock Rev-erbα and -β (Reverb-hDKO) alters cholesterol and lipid metabolism in hepatocytes as well as rhythmic gene expression in nonparenchymal cells (NPCs) of the liver. Here, we report that in fatty liver caused by diet-induced obesity (DIO), hepatocyte SREBP cleavage-activating protein (SCAP) was required for Reverb-hDKO-induced diurnal rhythmic remodeling and epigenomic reprogramming in liver macrophages (LMs). Integrative analyses of isolated hepatocytes and LMs revealed that SCAP-dependent lipidomic changes in REV-ERB-depleted hepatocytes led to the enhancement of LM metabolic rhythms. Hepatocytic loss of REV-ERBα and β (REV-ERBs) also attenuated LM rhythms via SCAP-independent polypeptide secretion. These results shed light on the signaling mechanisms by which hepatocytes regulate diurnal rhythms in NPCs in fatty liver disease caused by DIO.
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Affiliation(s)
- Dongyin Guan
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Hosung Bae
- Department of Biological Chemistry, University of California Irvine, Irvine, California, USA
| | - Dishu Zhou
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Ying Chen
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Chunjie Jiang
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Cam Mong La
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Yang Xiao
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Kun Zhu
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wenxiang Hu
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Basic Research, Guangzhou Laboratory, Guangdong, China
| | - Trang Minh Trinh
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Panpan Liu
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, Texas, USA
| | - Ying Xiong
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Bishuang Cai
- Division of Liver Diseases, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Cholsoon Jang
- Department of Biological Chemistry, University of California Irvine, Irvine, California, USA
| | - Mitchell A. Lazar
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine and
- Department of Genetics, the University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
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Fu L, Fei J, Tan ZX, Chen YH, Hu B, Xiang HX, Zhao H, Xu DX. Low Vitamin D Status Is Associated with Inflammation in Patients with Chronic Obstructive Pulmonary Disease. THE JOURNAL OF IMMUNOLOGY 2020; 206:515-523. [PMID: 33361208 DOI: 10.4049/jimmunol.2000964] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 11/11/2020] [Indexed: 02/06/2023]
Abstract
Vitamin D deficiency is associated with increased risks of chronic obstructive pulmonary disease (COPD). Nevertheless, the mechanisms remain unknown. This study analyzed the correlations between vitamin D levels and inflammation in COPD patients. One hundred and one patients with COPD and 202 control subjects were enrolled. Serum 25(OH)D level and inflammatory cytokines were detected. Serum 25(OH)D was decreased and inflammatory cytokines were increased in COPD patients. According to forced expiratory volume in 1 s, COPD patients were divided into three grades. Furthermore, serum 25(OH)D was gradually decreased in COPD patients ranging from grade 1-2 to 4. Serum 25(OH)D was inversely associated with inflammatory cytokines in COPD patients. Further analysis found that NF-κB and AP-1 signaling were activated in COPD patients. Besides, inflammatory signaling was gradually increased in parallel with the severity of COPD. By contrast, pulmonary nuclear vitamin D receptor was decreased in COPD patients. In vitro experiments showed that 1,25(OH)2D3 inhibited LPS-activated inflammatory signaling in A549 cells (human lung adenocarcinoma cell). Mechanically, 1,25(OH)2D3 reinforced physical interactions between vitamin D receptor with NF-κB p65 and c-Jun. Our results indicate that vitamin D is inversely correlated with inflammatory signaling in COPD patients. Inflammation may be a vital mediator of COPD progress in patients with low vitamin D levels.
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Affiliation(s)
- Lin Fu
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China.,Department of Toxicology, Anhui Medical University, Hefei 230032, China; and
| | - Jun Fei
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China
| | - Zhu-Xia Tan
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China
| | - Yuan-Hua Chen
- Department of Toxicology, Anhui Medical University, Hefei 230032, China; and.,Department of Histology and Embryology, Anhui Medical University, Hefei 230032, China
| | - Biao Hu
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China
| | - Hui-Xiang Xiang
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China
| | - Hui Zhao
- The Second Affiliated Hospital, Anhui Medical University, Hefei 230032, China;
| | - De-Xiang Xu
- Department of Toxicology, Anhui Medical University, Hefei 230032, China; and
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Shirvani-Farsani Z, Behmanesh M, Mohammadi SM, Naser Moghadasi A. Vitamin D levels in multiple sclerosis patients: Association with TGF-β2, TGF-βRI, and TGF-βRII expression. Life Sci 2015; 134:63-7. [PMID: 26037400 DOI: 10.1016/j.lfs.2015.05.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 05/09/2015] [Accepted: 05/11/2015] [Indexed: 01/09/2023]
Abstract
AIM A variety of evidence suggests that vitamin D can prevent the development of multiple sclerosis (MS). TGF-β pathway genes also play important roles in MS. Here, we aim to study whether vitamin D affects TGF-β pathway gene expression and Expanded Disability Status Scale (EDSS) scores in MS patients. MAIN METHODS A randomized clinical trial was conducted on 31 relapsing-remitting (RR) MS patients. Using real-time RT-PCR, we tested the levels of TGF-β2, TGF-βRI and TGF-βRII mRNAs in the RRMS patients before and after 8 weeks of supplementation with vitamin D. KEY FINDINGS Expression of TGF-β2 mRNA increased 2.84-fold, while TGF-βRI and TGF-βRII mRNA levels did not change after vitamin D treatment. In addition, these results revealed no correlation between the normalized expression of TGF-β2, TGF-βRI, or TGF-βRII and EDSS scores. SIGNIFICANCE Here, we demonstrate new evidence for the complex role of vitamin D in the pathogenesis, activity and progression of MS through the TGF-β signaling pathway.
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Affiliation(s)
- Zeinab Shirvani-Farsani
- Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
| | - Mehrdad Behmanesh
- Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran.
| | - Seyed Mahdi Mohammadi
- Department of Genetics, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
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4
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Yang Z, Tan S, Shen Y, Chen R, Wu C, Xu Y, Song Z, Fu Q. Inhibition of FSS-induced actin cytoskeleton reorganization by silencing LIMK2 gene increases the mechanosensitivity of primary osteoblasts. Bone 2015; 74:182-90. [PMID: 25549868 DOI: 10.1016/j.bone.2014.12.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Revised: 12/21/2014] [Accepted: 12/22/2014] [Indexed: 01/05/2023]
Abstract
Mechanical stimulation plays an important role in bone cell metabolic activity. However, bone cells lose their mechanosensitivity upon continuous mechanical stimulation (desensitization) and they can recover the sensitivity with insertion of appropriate rest period into the mechanical loading profiles. The concrete molecular mechanism behind the regulation of cell mechanosensitivity still remains unclear. As one kind of mechanosensitive cell to react to the mechanical stimulation, osteoblasts respond to fluid shear stress (FSS) with actin cytoskeleton reorganization, and the remodeling of actin cytoskeleton is closely associated with the alteration of cell mechanosensitivity. In order to find out whether inhibiting the actin cytoskeleton reorganization by silencing LIM-kinase 2 (LIMK2) gene would increase the mechanosensitivity of primary osteoblasts, we attenuated the formation of actin stress fiber under FSS in a more specific way: inhibiting the LIMK2 expression by RNA interference. We found that inhibition of LIMK2 expression by RNA interference attenuated the formation of FSS-induced actin stress fiber, and simultaneously maintained the integrity of actin cytoskeleton in primary osteoblasts. We confirmed that the decreased actin cytoskeleton reorganization in response to LIMK2 inhibition during FSS increased the mechanosensitivity of the osteoblasts, based on the increased c-Fos and COX-2 expression as well as the enhanced proliferative activity in response to FSS. These data suggest that osteoblasts can increase their mechanosensitivity under continuous mechanical stimulation by reducing the actin stress fiber formation through inhibiting the LIMK2 expression. This study provides us with a new and more specific method to regulate the osteoblast mechanosensitivity, and also a new therapeutic target to cure bone related diseases, which is of importance in maintaining bone mass and promoting osteogenesis.
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Affiliation(s)
- Zhi Yang
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China
| | - Shuyi Tan
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China
| | - Yun Shen
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai 200072, PR China
| | - Rui Chen
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Guangdong No. 2 Provincial People's Hospital, Guangzhou, Guangdong 510317, PR China
| | - Changjing Wu
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Guangzhou Hospital of Integrated Traditional and West Medicine, Guangzhou, Guangdong 510800, PR China
| | - Yajuan Xu
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China; Huizhou Stomatological Hospital Zhong Kai Branch, Huizhou, Guangdong 516006, PR China
| | - Zijun Song
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China
| | - Qiang Fu
- Department of Prosthodontics Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong 510055, PR China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, Guangdong 510055, PR China.
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Dimitrov V, Salehi-Tabar R, An BS, White JH. Non-classical mechanisms of transcriptional regulation by the vitamin D receptor: insights into calcium homeostasis, immune system regulation and cancer chemoprevention. J Steroid Biochem Mol Biol 2014; 144 Pt A:74-80. [PMID: 23911725 DOI: 10.1016/j.jsbmb.2013.07.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Accepted: 07/22/2013] [Indexed: 12/15/2022]
Abstract
Hormonal 1,25-dihydroxyvitamin D [1,25(OH)2D] signals through the nuclear vitamin D receptor (VDR), a ligand-regulated transcription factor. Gene expression profiling studies have revealed that 1,25(OH)2D signaling through the VDR can lead to activation or repression of target gene transcription in roughly equal proportions. Classically, transcriptional regulation by the VDR, similar to other nuclear receptors, has been characterized by its capacity to recognize high affinity cognate vitamin D response elements (VDREs), located in the regulatory regions of target genes. Several biochemical studies revealed that the VDRE-bound receptor recruits a series of coregulatory proteins, leading to transactivation of adjacent target genes. However, genome-wide and other analyses of VDR binding have revealed that a subset of VDR binding sites does not contain VDREs, and that VDREs are not associated with transcriptionally repressed VDR target genes. Work over the last ∼20 years and in particular recent findings have revealed a diverse array of mechanisms by which VDR can form complexes with several other classes of transcriptional activators, leading to repression of gene transcription. Moreover, these efforts have led to several insights into the molecular basis for the physiological regulation of calcium homeostasis, immune system function and cancer chemoprevention by 1,25(OH)2D/VDR signaling. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.
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Affiliation(s)
- Vassil Dimitrov
- Department of Physiology, McGill University, Montreal, QC, Canada
| | | | - Beum-Soo An
- Department of Physiology, McGill University, Montreal, QC, Canada; Department of Biomaterial Science, College of Natural Resources and Life Science, Pusan National University, Gyeongsangnam-do 627-706, Republic of Korea
| | - John H White
- Department of Physiology, McGill University, Montreal, QC, Canada; Department of Medicine, McGill University, Montreal, QC, Canada.
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6
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Genomic Binding Sites and Biological Effects of the Vitamin D: VDR Complex in Multiple Sclerosis. Neuromolecular Med 2014; 16:265-79. [DOI: 10.1007/s12017-014-8301-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Accepted: 03/29/2014] [Indexed: 01/14/2023]
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7
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Lee KN, Jang WG, Kim EJ, Oh SH, Son HJ, Kim SH, Franceschi R, Zhang XK, Lee SE, Koh JT. Orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) protein negatively regulates bone morphogenetic protein 2-induced osteoblast differentiation through suppressing runt-related gene 2 (Runx2) activity. J Biol Chem 2012; 287:18888-99. [PMID: 22493443 DOI: 10.1074/jbc.m111.311878] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan nuclear receptor of the steroid-thyroid hormone receptor superfamily. COUP-TFII is widely expressed in multiple tissues and organs throughout embryonic development and has been shown to regulate cellular growth, differentiation, and organ development. However, the role of COUP-TFII in osteoblast differentiation has not been systematically evaluated. In the present study, COUP-TFII was strongly expressed in multipotential mesenchymal cells, and the endogenous expression level decreased during osteoblast differentiation. Overexpression of COUP-TFII inhibited bone morphogenetic protein 2 (BMP2)-induced osteoblastic gene expression. The results of alkaline phosphatase, Alizarin Red staining, and osteocalcin production assay showed that COUP-TFII overexpression blocks BMP2-induced osteoblast differentiation. In contrast, the down-regulation of COUP-TFII synergistically induced the expression of BMP2-induced osteoblastic genes and osteoblast differentiation. Furthermore, the immunoprecipitation assay showed that COUP-TFII and Runx2 physically interacted and COUP-TFII significantly impaired the Runx2-dependent activation of the osteocalcin promoter. From the ChIP assay, we found that COUP-TFII repressed DNA binding of Runx2 to the osteocalcin gene, whereas Runx2 inhibited COUP-TFII expression via direct binding to the COUP-TFII promoter. Taken together, these findings demonstrate that COUP-TFII negatively regulates osteoblast differentiation via interaction with Runx2, and during the differentiation state, BMP2-induced Runx2 represses COUP-TFII expression and promotes osteoblast differentiation.
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Affiliation(s)
- Kkot-Nim Lee
- Dental Science Research Institute and the BK21 Project, Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju 500-757, Republic of Korea
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8
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Yang S, Xu H, Yu S, Cao H, Fan J, Ge C, Fransceschi RT, Dong HH, Xiao G. Foxo1 mediates insulin-like growth factor 1 (IGF1)/insulin regulation of osteocalcin expression by antagonizing Runx2 in osteoblasts. J Biol Chem 2011; 286:19149-58. [PMID: 21471200 DOI: 10.1074/jbc.m110.197905] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In this study, we determined the molecular mechanisms whereby forkhead transcription factor Foxo1, a key downstream signaling molecule of insulin-like growth factor 1 (IGF1)/insulin actions, regulates Runx2 activity and expression of the mouse osteocalcin gene 2 (Bglap2) in osteoblasts in vitro. We showed that Foxo1 inhibited Runx2-dependent transcriptional activity and osteocalcin mRNA expression and Bglap2 promoter activity in MC-4 preosteoblasts. Co-immunoprecipitation assay showed that Foxo1 physically interacted with Runx2 via its C-terminal region in osteoblasts or when co-expressed in COS-7 cells. Electrophoretic mobility shift assay demonstrated that Foxo1 suppressed Runx2 binding to its cognate site within the Bglap2 promoter. IGF1 and insulin prevented Foxo1 from inhibiting Runx2 activity by promoting Foxo1 phosphorylation and nuclear exclusion. In contrast, a neutralizing anti-IGF1 antibody decreased Runx2 activity and osteocalcin expression in osteoblasts. Chromatin immunoprecipitation assay revealed that IGF1 increased Runx2 interaction with a chromatin fragment of the proximal Bglap2 promoter in a PI3K/AKT-dependent manner. Conversely, knockdown of Foxo1 increased Runx2 interaction with the promoter. This study establishes that Foxo1 is a novel negative regulator of osteoblast-specific transcription factor Runx2 and modulates IGF1/insulin-dependent regulation of osteocalcin expression in osteoblasts.
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Affiliation(s)
- Shengyong Yang
- Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15240, USA
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9
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Chi Y, Hong Y, Zong H, Wang Y, Zou W, Yang J, Kong X, Yun X, Gu J. CDK11p58 represses vitamin D receptor-mediated transcriptional activation through promoting its ubiquitin-proteasome degradation. Biochem Biophys Res Commun 2009; 386:493-8. [PMID: 19538938 DOI: 10.1016/j.bbrc.2009.06.061] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 06/11/2009] [Indexed: 10/20/2022]
Abstract
Vitamin D receptor (VDR) is a member of the nuclear receptor superfamily and regulates transcription of target genes. In this study, we identified CDK11(p58) as a novel protein involved in the regulation of VDR. CDK11(p58), a member of the large family of p34cdc2-related kinases, is associated with cell cycle progression, tumorigenesis, and apoptotic signaling. Our study demonstrated that CDK11(p58) interacted with VDR and repressed VDR-dependent transcriptional activation. Furthermore, overexpression of CDK11(p58) decreased the stability of VDR through promoting its ubiquitin-proteasome-mediated degradation. Taken together, these results suggest that CDK11(p58) is involved in the negative regulation of VDR.
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Affiliation(s)
- Yayun Chi
- Gene Research Center, Shanghai Medical College and Institutes of Biomedical, Shanghai 200032, People's Republic of China
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10
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Akhouayri O, St-Arnaud R. Differential mechanisms of transcriptional regulation of the mouse osteocalcin gene by Jun family members. Calcif Tissue Int 2007; 80:123-31. [PMID: 17308994 DOI: 10.1007/s00223-006-0102-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Accepted: 10/11/2006] [Indexed: 01/08/2023]
Abstract
The osteocalcin gene encodes an osteoblast-specific protein that is induced with the onset of mineralization at late stages of differentiation. Several transcriptional regulators have been characterized that control the transcription of osteocalcin, including activator protein 1 (AP-1) family members such as the Fra2/JunD heterodimer. We have previously shown that the c-Jun homodimer activates transcription from the murine osteocalcin proximal promoter and that this response is potentiated by the alpha chain of the nascent polypeptide-associated complex (alphaNAC) transcriptional coactivator. We now further explore the mechanisms involved and show that c-Jun binds two cryptic AP-1 sites within the proximal promoter of osteocalcin and that this binding is strictly alphaNAC-dependent. Chromatin immunoprecipitation (ChIP) confirmed that c-Jun occupies its binding sites within the osteocalcin 5'-flanking region in living osteoblasts. Interestingly, the ChIP assay revealed that both JunB and JunD also bind the osteocalcin promoter. JunD, but not JunB, stimulated osteocalcin gene transcription in transient transfection assays, but this effect was not potentiated by alphaNAC. Thus, the c-Jun and JunD family members utilize distinct mechanisms that implicate differential interaction with transcriptional coactivators to regulate osteocalcin expression.
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Affiliation(s)
- O Akhouayri
- Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec, Canada H3G 1A6
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11
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Marcinkowska E, Garay E, Gocek E, Chrobak A, Wang X, Studzinski GP. Regulation of C/EBPbeta isoforms by MAPK pathways in HL60 cells induced to differentiate by 1,25-dihydroxyvitamin D3. Exp Cell Res 2006; 312:2054-65. [PMID: 16624284 PMCID: PMC2814412 DOI: 10.1016/j.yexcr.2006.03.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 03/06/2006] [Accepted: 03/08/2006] [Indexed: 01/30/2023]
Abstract
C/EBPbeta is known to be important for monocytic differentiation and macrophage function. Here, we found that expression of all three C/EBPbeta isoforms induced in HL60 cells by 1,25-dihydroxyvitamin D3 (1,25D) was upregulated in a sustained manner that correlates with the appearance of monocytic phenotype and with the G1 phase cell cycle arrest. In 1,25D-resistant HL60-40AF cells, isoforms beta-1 and beta-3 were expressed at levels comparable to 1,25D-sensitive HL60-G cells, but isoform beta-2 was difficult to detect. Treatment of sensitive HL60 cells with 1,25D resulted in predominantly nuclear localization of C/EBP isoforms beta-2 and beta-3, while a large proportion of C/EBPbeta-1 remained in the cytoplasm. Attenuation of the MEK-ERK MAPK pathway by the inhibitor PD98059 markedly reduced the expression, 1,25D-induced phosphorylation and nuclear localization of C/EBPbeta-2 and C/EBPbeta-3. Interestingly, only the lower molecular mass isoforms of C/EBPbeta phosphorylated on Thr235 were found in the nuclei, while C/EBPbeta-1 was constitutively phosphorylated and was detected principally in the cytoplasmic fraction. Although the role of C/EBPbeta isoforms in 1,25D-induced differentiation is complex, our results taken together strongly suggest that the phosphorylation of C/EBPbeta isoforms on Thr235 takes place mainly via the MEK-ERK pathway and that C/EBPbeta-2 is the principal transcription factor in this cell system.
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Affiliation(s)
- Ewa Marcinkowska
- Institute of Biochemistry and Molecular Biology, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland
| | - Edward Garay
- Department of Pathology and Laboratory Medicine, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA
| | - Elzbieta Gocek
- Institute of Biochemistry and Molecular Biology, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland
| | - Agnieszka Chrobak
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolf Weigl St. 12, 53-114 Wroclaw, Poland
| | - Xuening Wang
- Department of Pathology and Laboratory Medicine, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA
| | - George P. Studzinski
- Department of Pathology and Laboratory Medicine, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA
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12
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Lian JB, Stein GS, Javed A, van Wijnen AJ, Stein JL, Montecino M, Hassan MQ, Gaur T, Lengner CJ, Young DW. Networks and hubs for the transcriptional control of osteoblastogenesis. Rev Endocr Metab Disord 2006; 7:1-16. [PMID: 17051438 DOI: 10.1007/s11154-006-9001-5] [Citation(s) in RCA: 340] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We present an overview of the concepts of tissue-specific transcriptional control mechanisms essential for development of the bone cell phenotype. BMP2 induced transcription factors constitute a network of activities and molecular switches for bone development and osteoblast differentiation. Among these regulators are Runx2 (Cbfa1/AML3), the principal osteogenic master gene for bone formation, as well as homeodomain proteins and osterix. Runx2 has multiple regulatory activities, including activation or repression of gene expression, and integration of biological signals from developmental cues, such as BMP/TGFbeta, Wnt and Src signaling pathways. Runx2 provides a new paradigm for transcriptional control by functioning as a principal scaffolding protein in nuclear microenvironments to control gene expression in response to physiologic signals (growth factors, cytokines and hormones). The protein serves as a hub for the coordination of activities essential for the expansion and differentiation of osteogenic lineage cells through the formation of co-regulatory protein complexes organized in subnuclear domains. Mechanisms by which Runx2 supports commitment to osteogenesis and determines cell fate involve its retention on mitotic chromosomes. Disruption of a unique protein module, the subnuclear targeting signal of Runx2, has profound effects on osteoblast differentiation and metastasis of cancer cells in the bone microenvironment. Runx2 target genes include regulators of cell growth control, components of the bone extracellular matrix, angiogenesis, and signaling proteins for development of the osteoblast phenotype and bone turnover. The specificity of Runx2 regulatory activities provides a basis for novel therapeutic strategies to correct bone disorders.
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Affiliation(s)
- Jane B Lian
- Department of Cell Biology and Cancer Center, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA.
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13
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Fretz JA, Zella LA, Kim S, Shevde NK, Pike JW. 1,25-Dihydroxyvitamin D3 regulates the expression of low-density lipoprotein receptor-related protein 5 via deoxyribonucleic acid sequence elements located downstream of the start site of transcription. Mol Endocrinol 2006; 20:2215-30. [PMID: 16613987 DOI: 10.1210/me.2006-0102] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The skeleton is a direct target of vitamin D action, where the hormone modulates the proliferation of osteoblast precursors, their differentiation into mature osteoblasts, and their functional activity. Some of these effects of vitamin D are reminiscent of those orchestrated by the Wnt signaling pathway wherein stimulation of the membrane receptor Frizzled and its coreceptor LRP5 leads to activation of beta-catenin and subsequent transcription-mediated changes in osteoblast biology. Indeed, LRP5 is now known to play a particularly important role in bone formation such that the loss of this component results in a reduction in osteoblast number, a delay in mineralization, and a reduction in peak bone mineral density. Interestingly, we discovered during the course of a vitamin D receptor (VDR) chromatin immunoprecipitation/DNA microarray analysis that 1,25-(OH)2D3 could induce binding of the VDR to sites within the Lrp5 gene locus. VDR and retinoid X receptor binding was evident both in primary osteoblasts as well as in osteoblasts of cell line origin. Importantly, this interaction between 1,25-(OH)2D3-activated VDR and the Lrp5 gene led to both a modification in chromatin structure within the Lrp5 locus and the induction of Lrp5 mRNA transcripts in vivo as well as in vitro. One of these sites within the Lrp5 locus was discovered to confer vitamin D response to a heterologous promoter when introduced into osteoblastic cells, permitting both the identification and characterization of the vitamin D response element located within. Interestingly, additional studies revealed that whereas the regulatory region in the mouse Lrp5 gene was highly conserved in the human genome, the vitamin D response element was not. Our studies show that 1,25-(OH)2D3 can enhance the expression of a critical component of the Wnt signaling pathway that is known to impact osteogenesis.
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Affiliation(s)
- Jackie A Fretz
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin 53706, USA
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14
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Jian Y, Yan J, Wang H, Chen C, Sun M, Jiang J, Lu J, Yang Y, Gu J. Cyclin D3 interacts with vitamin D receptor and regulates its transcription activity. Biochem Biophys Res Commun 2005; 335:739-48. [PMID: 16105657 DOI: 10.1016/j.bbrc.2005.07.141] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Accepted: 07/23/2005] [Indexed: 11/26/2022]
Abstract
D-type cyclins are essential for the progression through the G1 phase of the cell cycle. Besides serving as cell cycle regulators, D-type cyclins were recently reported to have transcription regulation functions. Here, we report that cyclin D3 is a new interacting partner of vitamin D receptor (VDR), a member of the superfamily of nuclear receptors for steroid hormones, thyroid hormone, and the fat-soluble vitamins A and D. The interaction was confirmed with methods of yeast two-hybrid system, in vitro binding analysis and in vivo co-immunoprecipitation. Cyclin D3 interacted with VDR in a ligand-independent manner, but treatment of the ligand, 1,25-dihydroxyvitamin D3, strengthened the interaction. Confocal microscopy analysis showed that ligand-activated VDR led to an accumulation of cyclin D3 in the nuclear region. Cyclin D3 up-regulated transcriptional activity of VDR and this effect was counteracted by overexpression of CDK4 and CDK6. These findings provide us a new clue to understand the transcription regulation functions of D-type cyclins.
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Affiliation(s)
- Yongzhi Jian
- State Key Laboratory of Genetic Engineering and Gene Research Center, Shanghai Medical College of Fudan University, Shanghai 200032, PR China
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15
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Xiao G, Jiang D, Ge C, Zhao Z, Lai Y, Boules H, Phimphilai M, Yang X, Karsenty G, Franceschi RT. Cooperative interactions between activating transcription factor 4 and Runx2/Cbfa1 stimulate osteoblast-specific osteocalcin gene expression. J Biol Chem 2005; 280:30689-96. [PMID: 16000305 DOI: 10.1074/jbc.m500750200] [Citation(s) in RCA: 185] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The role of ATF4 (activating transcription factor 4) in osteoblast differentiation and bone formation was recently described using ATF4-deficient mice (Yang, X., Matsuda, K., Bialek, P., Jacquot, S., Masuoka, H. C., Schinke, T., Li, L., Brancorsini, S., Sassone-Corsi, P., Townes, T. M., Hanauer, A., and Karsenty, G. (2004) Cell 117, 387-398). However, the mechanisms of ATF4 in bone cells are still not clear. In this study, we determined the molecular mechanisms through which ATF4 activates the mouse osteocalcin (Ocn) gene 2 (mOG2) expression and mOG2 promoter activity. ATF4 increased the levels of Ocn mRNA and mOG2 promoter activity in Runx2-containing osteoblasts but not in non-osteoblastic cells that lack detectable Runx2 protein. However, ATF4 increased Ocn mRNA and mOG2 promoter activity in non-osteoblastic cells when Runx2 was co-expressed. Mutational analysis of the OSE1 (ATF4-binding site) and the two OSE2s (Runx2-binding sites) in the 657-bp mOG2 promoter demonstrated that ATF4 and Runx2 activate Ocn via cooperative interactions with these sites. Pull-down assays using nuclear extracts from osteoblasts or COS-7 cells overexpressing ATF4 and Runx2 showed that both factors are present in either anti-ATF4 and anti-Runx2 immunoprecipitates. In contrast, pull-down assays using purified glutathione S-transferase fusion proteins were unable to demonstrate a direct physical interaction between ATF4 and Runx2. Thus, accessory factors are likely involved in stabilizing interactions between these two molecules. Regions within Runx2 required for ATF4 complex formation and activation were identified. Deletion analysis showed that the leucine zipper domain of ATF4 is critical for Runx2 activation. This study is the first demonstration that cooperative interactions between ATF4 and Runx2/Cbfa1 stimulate osteoblast-specific Ocn expression and suggests that this regulation may represent a novel intramolecular mechanism regulating Runx2 activity and, thereby, osteoblast differentiation and bone formation.
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Affiliation(s)
- Guozhi Xiao
- Department of Periodontics, Prevention, and Geriatrics, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109-1078, USA.
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16
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Akhouayri O, Quélo I, St-Arnaud R. Sequence-specific DNA binding by the alphaNAC coactivator is required for potentiation of c-Jun-dependent transcription of the osteocalcin gene. Mol Cell Biol 2005; 25:3452-60. [PMID: 15831452 PMCID: PMC1084295 DOI: 10.1128/mcb.25.9.3452-3460.2005] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Revised: 10/14/2004] [Accepted: 01/11/2005] [Indexed: 11/20/2022] Open
Abstract
Since the c-Jun coactivator alphaNAC was initially identified in a differential screen for genes expressed in differentiated osteoblasts, we examined whether the osteocalcin gene, a specific marker of terminal osteoblastic differentiation, could be a natural target for the coactivating function of alphaNAC. We had also previously shown that alphaNAC can specifically bind DNA in vitro, but it remained unclear whether the DNA-binding function of alphaNAC is expressed in vivo or if it is required for coactivation. We have identified an alphaNAC binding site within the murine osteocalcin gene proximal promoter region and demonstrated that recombinant alphaNAC or alphaNAC from ROS17/2.8 nuclear extracts can specifically bind this element. Using transient transfection assays, we have shown that alphaNAC specifically potentiated the c-Jun-dependent transcription of the osteocalcin promoter and that this activity specifically required the DNA-binding domain of alphaNAC. Chromatin immunoprecipitation confirmed that alphaNAC occupies its binding site on the osteocalcin promoter in living osteoblastic cells expressing osteocalcin. Inhibition of the expression of endogenous alphaNAC in osteoblastic cells by use of RNA interference provoked a decrease in osteocalcin gene transcription. Our results show that the osteocalcin gene is a target for the alphaNAC coactivating function, and we propose that alphaNAC is specifically targeted to the osteocalcin promoter through its DNA-binding activity as a means to achieve increased specificity in gene transcription.
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Affiliation(s)
- Omar Akhouayri
- Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montréal, Québec, Canada H3G 1A6
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17
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Gutierrez S, Liu J, Javed A, Montecino M, Stein GS, Lian JB, Stein JL. The Vitamin D Response Element in the Distal Osteocalcin Promoter Contributes to Chromatin Organization of the Proximal Regulatory Domain. J Biol Chem 2004; 279:43581-8. [PMID: 15299011 DOI: 10.1074/jbc.m408335200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vitamin D receptor (VDR) and Runx2 are key regulators of tissue-specific gene transcription. Using the bone-related osteocalcin (OC) gene, we have previously shown that Runx2 is required for the extensive chromatin remodeling that accompanies gene activation. Here, we have addressed the direct contribution of the VDR to chromatin remodeling events necessary for regulation of OC transcription using mutational analysis. Our studies demonstrate that both the distal and proximal DNase I-hypersensitive sites characteristic of the transcriptionally active OC promoter are not enhanced in the absence of a functional vitamin D response element (VDRE). Furthermore, restriction enzyme accessibility studies reveal that nucleosomal reorganization of the proximal promoter occurs in response to vitamin D and this reorganization is abrogated by mutation of the VDRE. These findings indicate that binding of liganded VDR in the distal promoter directly impacts the chromatin structure of the proximal promoter. We find that, in the absence of functional Runx sites, the VDR cannot be recruited to the OC promoter and, therefore, the VDRE is not competent to mediate vitamin D responsiveness. On the other hand, chromatin immunoprecipitation assays show that Runx2 association with the OC promoter is not significantly impaired when the VDRE is mutated. Chromatin immunoprecipitation assays also demonstrate that basal levels of histone acetylation occur in the absence of Runx2 binding but that the VDRE and vitamin D are required for enhanced acetylation of histones H3 and H4 downstream of the VDRE. Together our results support a stepwise model for chromatin remodeling of the OC promoter and show that binding of the liganded VDR.retinoid X receptor directly impacts both the distal and proximal regulatory domains.
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Affiliation(s)
- Soraya Gutierrez
- Department of Cell Biology, University of Massachusetts Medical School, Worcester 01655, USA
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18
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Kenner L, Hoebertz A, Beil FT, Beil T, Keon N, Karreth F, Eferl R, Scheuch H, Szremska A, Amling M, Schorpp-Kistner M, Angel P, Wagner EF. Mice lacking JunB are osteopenic due to cell-autonomous osteoblast and osteoclast defects. ACTA ACUST UNITED AC 2004; 164:613-23. [PMID: 14769860 PMCID: PMC2171977 DOI: 10.1083/jcb.200308155] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Because JunB is an essential gene for placentation, it was conditionally deleted in the embryo proper. JunBΔ/Δ mice are born viable, but develop severe low turnover osteopenia caused by apparent cell-autonomous osteoblast and osteoclast defects before a chronic myeloid leukemia-like disease. Although JunB was reported to be a negative regulator of cell proliferation, junBΔ/Δ osteoclast precursors and osteoblasts show reduced proliferation along with a differentiation defect in vivo and in vitro. Mutant osteoblasts express elevated p16INK4a levels, but exhibit decreased cyclin D1 and cyclin A expression. Runx2 is transiently increased during osteoblast differentiation in vitro, whereas mature osteoblast markers such as osteocalcin and bone sialoprotein are strongly reduced. To support a cell-autonomous function of JunB in osteoclasts, junB was inactivated specifically in the macrophage–osteoclast lineage. Mutant mice develop an osteopetrosis-like phenotype with increased bone mass and reduced numbers of osteoclasts. Thus, these data reveal a novel function of JunB as a positive regulator controlling primarily osteoblast as well as osteoclast activity.
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Affiliation(s)
- Lukas Kenner
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria
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19
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Jiang D, Franceschi RT, Boules H, Xiao G. Parathyroid hormone induction of the osteocalcin gene. Requirement for an osteoblast-specific element 1 sequence in the promoter and involvement of multiple-signaling pathways. J Biol Chem 2003; 279:5329-37. [PMID: 14634012 DOI: 10.1074/jbc.m311547200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Parathyroid hormone (PTH) is an important peptide hormone regulator of bone formation and osteoblast activity. However, its mechanism of action in bone cells is largely unknown. This study examined the effect of PTH on mouse osteocalcin gene expression in MC3T3-E1 preosteoblastic cells and primary cultures of bone marrow stromal cells. PTH increased the levels of osteocalcin mRNA 4-5-fold in both cell types. PTH also stimulated transcriptional activity of a 1.3-kb fragment of the mouse osteocalcin gene 2 (mOG2) promoter. Inhibitor studies revealed a requirement for protein kinase A, protein kinase C, and mitogen-activated protein kinase pathways in the PTH response. Deletion of the mOG2 promoter sequence from -1316 to -116 caused no loss in PTH responsiveness whereas deletion from -116 to -34 completely prevented PTH stimulation. Interestingly, this promoter region does not contain the RUNX2 binding site shown to be necessary for PTH responsiveness in other systems. Nuclear extracts from PTH-treated MC3T3-E1 cells exhibited increased binding to OSE1, a previously described osteoblast-specific enhancer in the mOG2 promoter. Furthermore, mutation of OSE1 in DNA transfection assays established the requirement for this element in the PTH response. Collectively, these studies establish that actions of PTH on the osteocalcin gene are mediated by multiple signaling pathways and require OSE1 and associated nuclear proteins.
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Affiliation(s)
- Di Jiang
- Department of Periodontics, Prevention, and Geriatrics, School of Dentistry, University of Michigan, Ann Arbor, Michigan 48109-1078, USA
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20
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Sierra J, Villagra A, Paredes R, Cruzat F, Gutierrez S, Javed A, Arriagada G, Olate J, Imschenetzky M, Van Wijnen AJ, Lian JB, Stein GS, Stein JL, Montecino M. Regulation of the bone-specific osteocalcin gene by p300 requires Runx2/Cbfa1 and the vitamin D3 receptor but not p300 intrinsic histone acetyltransferase activity. Mol Cell Biol 2003; 23:3339-51. [PMID: 12697832 PMCID: PMC153185 DOI: 10.1128/mcb.23.9.3339-3351.2003] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
p300 is a multifunctional transcriptional coactivator that serves as an adapter for several transcription factors including nuclear steroid hormone receptors. p300 possesses an intrinsic histone acetyltransferase (HAT) activity that may be critical for promoting steroid-dependent transcriptional activation. In osteoblastic cells, transcription of the bone-specific osteocalcin (OC) gene is principally regulated by the Runx2/Cbfa1 transcription factor and is stimulated in response to vitamin D(3) via the vitamin D(3) receptor complex. Therefore, we addressed p300 control of basal and vitamin D(3)-enhanced activity of the OC promoter. We find that transient overexpression of p300 results in a significant dose-dependent increase of both basal and vitamin D(3)-stimulated OC gene activity. This stimulatory effect requires intact Runx2/Cbfa1 binding sites and the vitamin D-responsive element. In addition, by coimmunoprecipitation, we show that the endogenous Runx2/Cbfa1 and p300 proteins are components of the same complexes within osteoblastic cells under physiological concentrations. We also demonstrate by chromatin immunoprecipitation assays that p300, Runx2/Cbfa1, and 1alpha,25-dihydroxyvitamin D(3) receptor interact with the OC promoter in intact osteoblastic cells expressing this gene. The effect of p300 on the OC promoter is independent of its intrinsic HAT activity, as a HAT-deficient p300 mutant protein up-regulates expression and cooperates with P/CAF to the same extent as the wild-type p300. On the basis of these results, we propose that p300 interacts with key transcriptional regulators of the OC gene and bridges distal and proximal OC promoter sequences to facilitate responsiveness to vitamin D(3).
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Affiliation(s)
- Jose Sierra
- Departamento de Biologia Molecular, Facultad de Ciencias Biologicas, Universidad de Concepcion, Concepcion, Chile
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21
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Zambotti A, Makhluf H, Shen J, Ducy P. Characterization of an osteoblast-specific enhancer element in the CBFA1 gene. J Biol Chem 2002; 277:41497-506. [PMID: 12186862 DOI: 10.1074/jbc.m204271200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cbfa1 is a critical regulator of cell differentiation expressed only in the osteochondrogenic lineage. To define the molecular basis of this cell-specific expression we analyzed the murine Cbfa1 promoter. Here we show that the first 976 bp of this promoter are specifically active in osteoblastic cells. Within this region DNase I footprinting delineated a 40-bp area (CE1) protected differently by nuclear extracts from osteoblastic cells and from non-osteoblastic cells. When multimerized, CE1 conferred an osteoblast-specific activity to a heterologous promoter in DNA transfection experiments; this enhancing ability was conserved between mouse, rat, and human CE1 present in the respective Cbfa1 promoters. CE1 site-specific mutagenesis determined that it binds NF1- and AP1-like activities. Further analyses revealed that the NF1 site acts as a repressor in non-osteoblastic cells due to the binding of NF1-A, a NF1 isoform not expressed in osteoblastic cells. In contrast, the AP1 site mediates an osteoblast-specific activation caused by the preferential binding of FosB to CE1 in osteoblastic cells. In summary, this study identified an osteoblast-specific enhancer in the Cbfa1 promoter whose activity is achieved by the combination of an inhibitory and an activatory mechanism.
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Affiliation(s)
- Adriana Zambotti
- Departments of Molecular and Human Genetics and Medicine, Baylor College of Medicine, Houston, Texas 77030, USA
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22
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Willis DM, Loewy AP, Charlton-Kachigian N, Shao JS, Ornitz DM, Towler DA. Regulation of osteocalcin gene expression by a novel Ku antigen transcription factor complex. J Biol Chem 2002; 277:37280-91. [PMID: 12145306 DOI: 10.1074/jbc.m206482200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously described an osteocalcin (OC) fibroblast growth factor (FGF) response element (FRE) DNA binding activity as a target of Msx2 transcriptional regulation. We now identify Ku70, Ku80, and Tbdn100, a variant of Tubedown-1, as constituents of the purified OCFRE-binding complex. Northern and Western blot analyses demonstrate expression of Ku and Tbdn100 in MC3T3E1 osteoblasts. FGF2 treatment regulates Ku, but not Tbdn100, protein accumulation. Gel supershift studies confirm sequence-specific DNA binding of Ku in the OCFRE complex; chromatin immunoprecipitation assays confirm association of Ku and Tbdn100 with the endogenous OC promoter. In the promoter region -154 to -113, the OCFRE is juxtaposed to OSE2, an osteoblast-specific element that binds Runx2 (Osf2, Cbfa1). Expression of the Ku.Tbdn100 complex up-regulates both the basal and Runx2-dependent transcription driven by this 42-bp OC promoter element, reconstituted in CV-1 cells. Synergistic transactivation occurs in the presence of activated FGF receptor 2 signaling. Msx2 suppresses Ku- and Runx2-dependent transcription; suppression is dependent upon the Msx2 homeodomain NH(2)-terminal arm and extension. Pull-down assays confirm physical interactions between Ku and these co-regulatory transcription factors, consistent with the functional interactions identified. Finally, cultured Ku70 -/- calvarial cells exhibit a profound, selective deficiency in OC expression as compared with wild-type calvarial cells, confirming the biochemical data showing a role for Ku in OC transcription. In toto, these data indicate that a novel Ku antigen complex assembles on the OC promoter, functioning in concert with Msx2 and Runx2 to regulate OC gene expression.
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Affiliation(s)
- David M Willis
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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23
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Hansen CM, Rohde L, Madsen MW, Hansen D, Colston KW, Pirianov G, Holm PK, Binderup L. MCF-7/VD(R): a new vitamin D resistant cell line. J Cell Biochem 2001; 82:422-36. [PMID: 11500919 DOI: 10.1002/jcb.1162] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Several in vitro and in vivo experiments have demonstrated potent cell regulatory effects of vitamin D compounds in cancer cells. Moreover, a promising phase I study with the vitamin D analogue Seocalcitol (EB 1089) in patients with advanced breast and colon cancer has already been carried out and more clinical trials evaluating the clinical effectiveness of EB 1089 in other cancer types are in progress (Mørk Hansen et al. [2000a]). However, only little is known about the mechanisms underlying the actions of vitamin D or about the possible development of drug resistance in the patients. Therefore, in an attempt to gain more insight into these aspects, we have developed the MCF-7/VD(R) cell line, a stable subclone of the human MCF-7 breast cancer cell line, which is resistant to the growth inhibitory and apoptosis inducing effects of 1alpha,25(OH)(2)D(3). Despite this characteristic, receptor studies on the VDR have clearly demonstrated that the MCF-7/VD(R) cells contain fully functional VDRs, although in a lower number than seen with the parental MCF-7 cells. The regulation of the 24-hydroxylase enzyme appeared to be intact in the MCF-7/VD(R) cells and no differences with regard to growth rate and morphological appearance between the MCF-7/VD(R) cells and the parental MCF-7 cells were observed. Interestingly, however, the sensitivity of the MCF-7/VD(R) cells to the pure anti-estrogen ICI 182,780 was found to be increased. The MCF-7/VD(R) cell line shows characteristics different from those of previously described vitamin D resistant breast cancer cell lines but also some similarities. Together such vitamin D resistant cell lines therefore serve as a useful tool for studying the exact mechanism of action of vitamin D and the development of vitamin D resistance.
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Affiliation(s)
- C M Hansen
- Department of Biochemistry, Leo Pharmaceutical Products, DK-2750 Ballerup, Denmark.
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24
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Subramaniam N, Leong GM, Cock TA, Flanagan JL, Fong C, Eisman JA, Kouzmenko AP. Cross-talk between 1,25-dihydroxyvitamin D3 and transforming growth factor-beta signaling requires binding of VDR and Smad3 proteins to their cognate DNA recognition elements. J Biol Chem 2001; 276:15741-6. [PMID: 11278818 DOI: 10.1074/jbc.m011033200] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
1,25-Dihydroxyvitamin D(3) (vitamin D) and transforming growth factor-beta (TGF-beta) regulate diverse biological processes including cell proliferation and differentiation through modulation of the expression of target genes. Members of the Smad family of proteins function as effectors of TGF-beta signaling pathways whereas the vitamin D receptor (VDR) confers vitamin D signaling. We investigated the molecular mechanisms by which TGF-beta and vitamin D signaling pathways interact in the regulation of the human osteocalcin promoter. Synergistic activation of the osteocalcin gene promoter by TGF-beta and vitamin D was observed in transient transfection experiments. However, in contrast to a previous report by Yanagisawa, J., Yanagi, Y., Masuhiro, Y., Suzawa, M., Watanabe, M., Kashiwagi, K., Toriyabe, T., Kawabata, M., Miyazono, K., and Kato, S. (1999) Science, 283, 1317-1321, synergistic activation was not detectable when the osteocalcin vitamin D response element (VDRE) alone was linked to a heterologous promoter. Inclusion of the Smad binding elements (SBEs) with the VDRE in the heterologous promoter restored synergistic activation. Furthermore, this synergy was dependent on the spacing between VDRE and SBEs. The Smad3-Smad4 heterodimer was found to bind in gel shift assay to two distinct DNA segments of the osteocalcin promoter: -1030 to -989 (SBE3) and -418 to -349 (SBE1). Deletion of SBE1, which is proximal to the VDRE, but not the distal SBE3 in this promoter reporter abolished TGF-beta responsiveness and eliminated synergistic co-activation with vitamin D. Thus the molecular mechanism, whereby Smad3 and VDR mediate cross-talk between the TGF-beta and vitamin D signaling pathways, requires both a VDRE and a SBE located in close proximity to the target promoter.
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Affiliation(s)
- N Subramaniam
- Bone and Mineral Research Program, The Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia.
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25
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Prince M, Banerjee C, Javed A, Green J, Lian JB, Stein GS, Bodine PV, Komm BS. Expression and regulation of Runx2/Cbfa1 and osteoblast phenotypic markers during the growth and differentiation of human osteoblasts. J Cell Biochem 2001; 80:424-40. [PMID: 11135373 DOI: 10.1002/1097-4644(20010301)80:3<424::aid-jcb160>3.0.co;2-6] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The runt family transcription factor (AML-3/PEBP2alphaA1/Cbfa1/RUNX2) plays a crucial role in formation of the mineralized skeleton during embryogenesis and regulates maturation of the osteoblast phenotype. Because steroid hormones and growth factors significantly influence growth and differentiation properties of osteoblasts, we addressed Cbfa1 as a target gene for regulation by dexamethasone (Dex), 1,25(OH)D(3) (vitamin D(3)), 17beta-estradiol, and transforming growth factor-beta1 (TGF-beta1). The representation of functional protein levels by Western blot analyses and gel mobility shift assays was examined during the growth and mineralization of several conditionally immortalized human osteoblast cell lines HOB 04-T8, 03-CE6, and 03-CE10, each representing different stages of maturation. In situ immunofluorescence demonstrates Cbfa1 is associated with nuclear matrix in punctate domains, some of which are transcriptionally active, colocalizing with phosphorylated RNA polymerase II. Although each of the cell lines exhibited different responses to the steroid hormones and to TGF-beta1, all cell lines showed a similar increase in Cbfa1 protein and DNA binding activity induced only by Dex. On the other hand, Cbfa1 mRNA levels were not altered by Dex treatment. This regulation of Cbfa1 by steroid hormones in human osteoblasts contrasts to modifications in Cbfa1 expression in primary rat calvarial osteoblasts and the mouse MC3T3-E1 osteoblast cell line. Thus, these results reveal multiple levels of regulation of Cbfa1 expression and activity in osteoblasts. Moreover, the data suggest that in committed human osteoblasts, constitutive expression of Cbfa1 may be required to sustain the osteoblast phenotype.
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Affiliation(s)
- M Prince
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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