1
|
Huang B, Zhao W, Cai X, Zhu Y, Lu Y, Zhao J, Xiang N, Wang X, Deng H, Tang X, Liu L, Zhao Y, Shi Y. Expression and Activity of the Transcription Factor CCAAT/Enhancer-Binding Protein β (C/EBPβ) Is Regulated by Specific Pulse-Modulated Radio Frequencies in Oligodendroglial Cells. Int J Mol Sci 2023; 24:11131. [PMID: 37446309 DOI: 10.3390/ijms241311131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/27/2023] [Accepted: 06/27/2023] [Indexed: 07/15/2023] Open
Abstract
The rapid growth of wireless electronic devices has raised concerns about the harmful effects of leaked electromagnetic radiation (EMR) on human health. Even though numerous studies have been carried out to explore the biological effects of EMR, no clear conclusions have been drawn about the effect of radio frequency (RF) EMR on oligodendrocytes. To this end, we exposed oligodendroglia and three other types of brain cells to 2.4 GHz EMR for 6 or 48 h at an average input power of 1 W in either a continuous wave (CW-RF) or a pulse-modulated wave (PW-RF, 50 Hz pulse frequency, 1/3 duty cycle) pattern. RNA sequencing, RT-qPCR, and Western blot were used to examine the expression of C/EBPβ and its related genes. Multiple reaction monitoring (MRM) was used to examine the levels of expression of C/EBPβ-interacting proteins. Our results showed that PW-RF EMR significantly increased the mRNA level of C/EBPβ in oligodendroglia but not in other types of cells. In addition, the expression of three isoforms and several interacting proteins and targeted genes of C/EBPβ were markedly changed after 6-h PW-RF but not CW-RF. Our results indicated that RF EMR regulated the expression and functions of C/EBPβ in a waveform- and cell-type-dependent manner.
Collapse
Affiliation(s)
- Bing Huang
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Xihu District, Hangzhou 310024, China
- Brain Function and Disease Laboratory, Department of Pharmacology, Shantou University Medical College, Xin-Ling Road #22, Shantou 515041, China
- Institute of Biology, Westlake Institute for Advanced Study, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Weihao Zhao
- Program in Computational Biology and Bioinformatics, Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Xue Cai
- iMarker Lab, Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Yumin Zhu
- MOE Key Laboratory of Population Health Across Life Cycle, Anhui Provincial Key Laboratory of Population Health and Aristogenics, Department of Maternal & Child and Adolescent Health, School of Public Health, Anhui Medical University, Hefei 230032, China
| | - Yingxian Lu
- Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Junli Zhao
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Xihu District, Hangzhou 310024, China
- Institute of Biology, Westlake Institute for Advanced Study, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Nan Xiang
- iMarker Lab, Westlake Laboratory of Life Sciences and Biomedicine, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Xiaofei Wang
- Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Hu Deng
- Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Xiaping Tang
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Xihu District, Hangzhou 310024, China
- Institute of Biology, Westlake Institute for Advanced Study, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Lingyu Liu
- Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Yanyu Zhao
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Xihu District, Hangzhou 310024, China
- Institute of Biology, Westlake Institute for Advanced Study, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
| | - Yigong Shi
- Zhejiang Provincial Laboratory of Life Sciences and Biomedicine, Xihu District, Hangzhou 310024, China
- Institute of Biology, Westlake Institute for Advanced Study, Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou 310024, China
- Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China
| |
Collapse
|
2
|
Geng L, Zhang J, Mu W, Wu X, Zhou Z, Wang X, Ye B, Ma L. Replacing fishmeal protein with blended alternatives alters growth, feed utilization, protein deposition and gut micromorphology of humpback grouper, Cromileptes altivelis. Anim Feed Sci Technol 2022. [DOI: 10.1016/j.anifeedsci.2022.115434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
3
|
Li X, Gracilla D, Cai L, Zhang M, Yu X, Chen X, Zhang J, Long X, Ding HF, Yan C. ATF3 promotes the serine synthesis pathway and tumor growth under dietary serine restriction. Cell Rep 2021; 36:109706. [PMID: 34551291 PMCID: PMC8491098 DOI: 10.1016/j.celrep.2021.109706] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 07/23/2021] [Accepted: 08/23/2021] [Indexed: 11/24/2022] Open
Abstract
The serine synthesis pathway (SSP) involving metabolic enzymes phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH) drives intracellular serine biosynthesis and is indispensable for cancer cells to grow in serine-limiting environments. However, how SSP is regulated is not well understood. Here, we report that activating transcription factor 3 (ATF3) is crucial for transcriptional activation of SSP upon serine deprivation. ATF3 is rapidly induced by serine deprivation via a mechanism dependent on ATF4, which in turn binds to ATF4 and increases the stability of this master regulator of SSP. ATF3 also binds to the enhancers/promoters of PHGDH, PSAT1, and PSPH and recruits p300 to promote expression of these SSP genes. As a result, loss of ATF3 expression impairs serine biosynthesis and the growth of cancer cells in the serine-deprived medium or in mice fed with a serine/glycine-free diet. Interestingly, ATF3 expression positively correlates with PHGDH expression in a subset of TCGA cancer samples. Activation of the serine synthesis pathway is important for cancer cell growth, but how this pathway is regulated is not well understood. Li et al. report that ATF3 is an important regulator of this pathway and can promote serine biosynthesis and tumor growth under serine-limiting conditions.
Collapse
Affiliation(s)
- Xingyao Li
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA
| | - Daniel Gracilla
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA
| | - Lun Cai
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA
| | - Mingyi Zhang
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA; Institute of Materia Medica, Peking Union Medical College, Beijing 100050, China
| | - Xiaolin Yu
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA
| | - Xiaoguang Chen
- Institute of Materia Medica, Peking Union Medical College, Beijing 100050, China
| | - Junran Zhang
- Department of Radiation Oncology, Ohio State University James Comprehensive Cancer Center and College of Medicine, Columbus, OH 43210, USA
| | - Xiaochun Long
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Han-Fei Ding
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA; Department of Pathology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Chunhong Yan
- Georgia Cancer Center, Augusta University, Augusta, GA 30912, USA; Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA.
| |
Collapse
|
4
|
Kakadia JH, Jain BB, Biggar K, Sutherland A, Nygard K, Li C, Nathanielsz PW, Jansson T, Gupta MB. Hyperphosphorylation of fetal liver IGFBP-1 precedes slowing of fetal growth in nutrient-restricted baboons and may be a mechanism underlying IUGR. Am J Physiol Endocrinol Metab 2020; 319:E614-E628. [PMID: 32744097 PMCID: PMC7642856 DOI: 10.1152/ajpendo.00220.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In cultured fetal liver cells, insulin-like growth factor (IGF) binding protein (IGFBP)-1 hyperphosphorylation in response to hypoxia and amino acid deprivation is mediated by inhibition of mechanistic target of rapamycin (mTOR) and activation of amino acid response (AAR) signaling and casein kinase (CK)2. We hypothesized that fetal liver mTOR inhibition, activation of AAR and CK2, and IGFBP-1 hyperphosphorylation occur before development of intrauterine growth restriction (IUGR). Pregnant baboons were fed a control (C) or a maternal nutrient restriction (MNR; 70% calories of control) diet starting at gestational day (GD) 30 (term GD 185). Umbilical blood and fetal liver tissue were obtained at GD 120 (C, n = 7; MNR, n = 10) and 165 (C, n = 7; MNR, n = 8). Fetal weights were unchanged at GD 120 but decreased at GD 165 in the MNR group (-13%, P = 0.03). IGFBP-1 phosphorylation, as determined by parallel reaction monitoring mass spectrometry (PRM-MS), immunohistochemistry, and/or Western blot, was enhanced in MNR fetal liver and umbilical plasma at GD 120 and 165. IGF-I receptor autophosphorylationTyr1135 (-64%, P = 0.05) was reduced in MNR fetal liver at GD 120. Furthermore, fetal liver CK2 (α/α'/β) expression, CK2β colocalization, proximity with IGFBP-1, and CK2 autophosphorylationTyr182 were greater at GD 120 and 165 in MNR vs. C. Additionally, mTOR complex (mTORC)1 (p-P70S6KThr389, -52%, P = 0.05) and mTORC2 (p-AktSer473, -56%, P < 0.001) activity were decreased and AAR was activated (p-GCN2Thr898, +117%, P = 0.02; p-eIF2αSer51, +294%, P = 0.002; p-ERKThr202, +111%, P = 0.03) in MNR liver at GD 120. Our data suggest that fetal liver IGFBP-1 hyperphosphorylation, mediated by mTOR inhibition and both AAR and CK2 activation, is a key link between restricted nutrient and oxygen availability and the development of IUGR.
Collapse
Affiliation(s)
- Jenica H Kakadia
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Bhawani B Jain
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Kyle Biggar
- Institute of Biochemistry, Carleton University, Ottawa, Ontario, Canada
| | - Austen Sutherland
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
| | - Karen Nygard
- Biotron Integrated Microscopy Facility, University of Western Ontario, London, Ontario, Canada
| | - Cun Li
- University of Wyoming, Laramie, Wyoming
- Southwest National Primate Research Center, San Antonio, Texas
| | - Peter W Nathanielsz
- University of Wyoming, Laramie, Wyoming
- Southwest National Primate Research Center, San Antonio, Texas
| | - Thomas Jansson
- Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado
| | - Madhulika B Gupta
- Department of Biochemistry, University of Western Ontario, London, Ontario, Canada
- Department of Pediatrics, University of Western Ontario, London, Ontario, Canada
- Children's Health Research Institute, London, Ontario, Canada
| |
Collapse
|
5
|
Song DG, Kim D, Jung JW, Nam SH, Kim JE, Kim HJ, Kim JH, Lee SJ, Pan CH, Kim S, Lee JW. Glutamyl‐prolyl‐tRNA synthetase induces fibrotic extracellular matrix
via
both transcriptional and translational mechanisms. FASEB J 2018; 33:4341-4354. [DOI: 10.1096/fj.201801344rr] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Dae-Geun Song
- Department of PharmacyResearch Institute of Pharmaceutical SciencesCollege of PharmacySeoul National University Seoul Republic of Korea
- Systems Biotechnology Research CenterKorea Institute of Science and Technology (KIST) Gangneung-si Republic of Korea
| | - Doyeun Kim
- Medicinal Bioconvergence Research CenterSeoul National University Seoul Republic of Korea
| | - Jae Woo Jung
- Interdisciplinary Program in Genetic EngineeringSeoul National University Seoul Republic of Korea
| | - Seo Hee Nam
- Department of PharmacyResearch Institute of Pharmaceutical SciencesCollege of PharmacySeoul National University Seoul Republic of Korea
| | - Ji Eon Kim
- Department of PharmacyResearch Institute of Pharmaceutical SciencesCollege of PharmacySeoul National University Seoul Republic of Korea
| | - Hye-Jin Kim
- Department of PharmacyResearch Institute of Pharmaceutical SciencesCollege of PharmacySeoul National University Seoul Republic of Korea
| | - Jong Hyun Kim
- Medicinal Bioconvergence Research CenterSeoul National University Seoul Republic of Korea
| | - Seo-Jin Lee
- Department of Life Science and BiotechnologyShingyeong University Gyeonggi-do Republic of Korea
| | - Cheol-Ho Pan
- Systems Biotechnology Research CenterKorea Institute of Science and Technology (KIST) Gangneung-si Republic of Korea
| | - Sunghoon Kim
- Medicinal Bioconvergence Research CenterSeoul National University Seoul Republic of Korea
| | - Jung Weon Lee
- Department of PharmacyResearch Institute of Pharmaceutical SciencesCollege of PharmacySeoul National University Seoul Republic of Korea
- Medicinal Bioconvergence Research CenterSeoul National University Seoul Republic of Korea
- Interdisciplinary Program in Genetic EngineeringSeoul National University Seoul Republic of Korea
| |
Collapse
|
6
|
Kalfalah F, Janke L, Schiavi A, Tigges J, Ix A, Ventura N, Boege F, Reinke H. Crosstalk of clock gene expression and autophagy in aging. Aging (Albany NY) 2017; 8:1876-1895. [PMID: 27574892 PMCID: PMC5076443 DOI: 10.18632/aging.101018] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 08/18/2016] [Indexed: 01/13/2023]
Abstract
Autophagy and the circadian clock counteract tissue degeneration and support longevity in many organisms. Accumulating evidence indicates that aging compromises both the circadian clock and autophagy but the mechanisms involved are unknown. Here we show that the expression levels of transcriptional repressor components of the circadian oscillator, most prominently the human Period homologue PER2, are strongly reduced in primary dermal fibroblasts from aged humans, while raising the expression of PER2 in the same cells partially restores diminished autophagy levels. The link between clock gene expression and autophagy is corroborated by the finding that the circadian clock drives cell-autonomous, rhythmic autophagy levels in immortalized murine fibroblasts, and that siRNA-mediated downregulation of PER2 decreases autophagy levels while leaving core clock oscillations intact. Moreover, the Period homologue lin-42 regulates autophagy and life span in the nematode Caenorhabditis elegans, suggesting an evolutionarily conserved role for Period proteins in autophagy control and aging. Taken together, this study identifies circadian clock proteins as set-point regulators of autophagy and puts forward a model, in which age-related changes of clock gene expression promote declining autophagy levels.
Collapse
Affiliation(s)
- Faiza Kalfalah
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany
| | - Linda Janke
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany.,IUF-Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany
| | - Alfonso Schiavi
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany.,IUF-Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany
| | - Julia Tigges
- IUF-Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany
| | - Alexander Ix
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany
| | - Natascia Ventura
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany.,IUF-Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany
| | - Fritz Boege
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany
| | - Hans Reinke
- University of Düsseldorf, Medical Faculty, Institute of Clinical Chemistry and Laboratory Diagnostics, 40225 Düsseldorf, Germany.,IUF-Leibniz Research Institute for Environmental Medicine, 40225 Düsseldorf, Germany
| |
Collapse
|
7
|
Pan S, Jia Y, Yang X, Cai D, Liu Z, Song H, Zhao R. Amino acid starvation-induced autophagy is involved in reduced subcutaneous fat deposition in weaning piglets derived from sows fed low-protein diet during gestation and lactation : Autophagy is involved in reduced fat deposition in maternal low-protein piglets. Eur J Nutr 2017; 57:991-1001. [PMID: 28233111 DOI: 10.1007/s00394-017-1383-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 01/24/2017] [Indexed: 02/08/2023]
Abstract
PURPOSE The study aimed to determine the effects of maternal low-protein (LP) diet on subcutaneous fat deposition of weaning piglets and the potential mechanism. METHODS Sows were fed either a standard protein (SP, 15 and 18% crude protein) or a LP diet (50% protein levels of SP) throughout pregnancy and lactation. Subcutaneous fat and blood were sampled from male piglets at 28 days of age. Serum biochemical metabolites and hormone concentrations were detected with the enzymatic colorimetric methods. Serum-free amino acid (FAA) levels were measured by amino acid auto-analyzer. The mRNA and protein were measured by qRT-PCR and Western blot. RESULTS Body weight, back fat thickness, triglycerides concentrations in subcutaneous fat tissue, and serum, as well as FFA concentrations were significantly reduced in LP piglets when compared with SP piglets. Further studies showed that mRNA and protein expression of acetyl-CoA carboxylase and fatty acid synthetase, two key enzymes of de novo lipogenesis, were significantly reduced in LP piglets, while mRNA expression and the lipolytic enzymes activities of lipolysis genes, adipose triglyceride lipase and hormone-sensitive lipase, were significantly increased. Furthermore, expression of autophagy-related gene 7 and autophagy maker gene microtubule-associated protein 1A/1B-light chain 3 (LC 3) as well as the conversion of LC3I to LC3II were significantly elevated, along with the expression of activating transcription factor-4 and eukaryotic translation initiation factor-2a. CONCLUSION These results indicate that amino acid starvation-induced autophagy is involved in reduced subcutaneous fat deposition in maternal LP weaning piglets, demonstrating links between maternal protein restriction and offspring fat deposition.
Collapse
Affiliation(s)
- Shifeng Pan
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.,College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, People's Republic of China
| | - Yimin Jia
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China
| | - Xiaojing Yang
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China
| | - Demin Cai
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China
| | - Zhiqing Liu
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China
| | - Haogang Song
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China
| | - Ruqian Zhao
- Key Laboratory of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. .,Jiangsu Collaborative Innovation Center of Meat Production and Processing, Quality and Safety Control, Nanjing, 210095, People's Republic of China.
| |
Collapse
|
8
|
Shan J, Zhang F, Sharkey J, Tang TA, Örd T, Kilberg MS. The C/ebp-Atf response element (CARE) location reveals two distinct Atf4-dependent, elongation-mediated mechanisms for transcriptional induction of aminoacyl-tRNA synthetase genes in response to amino acid limitation. Nucleic Acids Res 2016; 44:9719-9732. [PMID: 27471030 PMCID: PMC5175342 DOI: 10.1093/nar/gkw667] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 07/19/2016] [Accepted: 07/20/2016] [Indexed: 12/13/2022] Open
Abstract
The response to amino acid (AA) limitation of the entire aminoacyl-tRNA synthetase (ARS) gene family revealed that 16/20 of the genes encoding cytoplasmic-localized enzymes are transcriptionally induced by activating transcription factor 4 (Atf4) via C/ebp-Atf-Response-Element (CARE) enhancers. In contrast, only 4/19 of the genes encoding mitochondrial-localized ARSs were weakly induced. Most of the activated genes have a functional CARE near the transcription start site (TSS), but for others the CARE is downstream. Regardless of the location of CARE enhancer, for all ARS genes there was constitutive association of RNA polymerase II (Pol II) and the general transcription machinery near the TSS. However, for those genes with a downstream CARE, Atf4, C/ebp-homology protein (Chop), Pol II and TATA-binding protein exhibited enhanced recruitment to the CARE during AA limitation. Increased Atf4 binding regulated the association of elongation factors at both the promoter and the enhancer regions, and inhibition of cyclin-dependent kinase 9 (CDK9), that regulates these elongation factors, blocked induction of the AA-responsive ARS genes. Protein pull-down assays indicated that Atf4 directly interacts with CDK9 and its associated protein cyclin T1. The results demonstrate that AA availability modulates the ARS gene family through modulation of transcription elongation.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Fan Zhang
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Jason Sharkey
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Tiffany A Tang
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, FL 32610, USA
| | - Tönis Örd
- Estonian Biocentre, Riia 23, Tartu, 51010, Estonia
| | - Michael S Kilberg
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, FL 32610, USA
| |
Collapse
|
9
|
Huggins CJ, Mayekar MK, Martin N, Saylor KL, Gonit M, Jailwala P, Kasoji M, Haines DC, Quiñones OA, Johnson PF. C/EBPγ Is a Critical Regulator of Cellular Stress Response Networks through Heterodimerization with ATF4. Mol Cell Biol 2015; 36:693-713. [PMID: 26667036 PMCID: PMC4760225 DOI: 10.1128/mcb.00911-15] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 10/30/2015] [Accepted: 12/07/2015] [Indexed: 12/24/2022] Open
Abstract
The integrated stress response (ISR) controls cellular adaptations to nutrient deprivation, redox imbalances, and endoplasmic reticulum (ER) stress. ISR genes are upregulated in stressed cells, primarily by the bZIP transcription factor ATF4 through its recruitment to cis-regulatory C/EBP:ATF response elements (CAREs) together with a dimeric partner of uncertain identity. Here, we show that C/EBPγ:ATF4 heterodimers, but not C/EBPβ:ATF4 dimers, are the predominant CARE-binding species in stressed cells. C/EBPγ and ATF4 associate with genomic CAREs in a mutually dependent manner and coregulate many ISR genes. In contrast, the C/EBP family members C/EBPβ and C/EBP homologous protein (CHOP) were largely dispensable for induction of stress genes. Cebpg(-/-) mouse embryonic fibroblasts (MEFs) proliferate poorly and exhibit oxidative stress due to reduced glutathione levels and impaired expression of several glutathione biosynthesis pathway genes. Cebpg(-/-) mice (C57BL/6 background) display reduced body size and microphthalmia, similar to ATF4-null animals. In addition, C/EBPγ-deficient newborns die from atelectasis and respiratory failure, which can be mitigated by in utero exposure to the antioxidant, N-acetyl-cysteine. Cebpg(-/-) mice on a mixed strain background showed improved viability but, upon aging, developed significantly fewer malignant solid tumors than WT animals. Our findings identify C/EBPγ as a novel antioxidant regulator and an obligatory ATF4 partner that controls redox homeostasis in normal and cancerous cells.
Collapse
Affiliation(s)
- Christopher J Huggins
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Manasi K Mayekar
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Nancy Martin
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Karen L Saylor
- Laboratory Animal Sciences Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Mesfin Gonit
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Parthav Jailwala
- Advanced Biomedical Computing Center, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Manjula Kasoji
- Advanced Biomedical Computing Center, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Diana C Haines
- Pathology/Histotechnology Laboratory, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Octavio A Quiñones
- DMS, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
| | - Peter F Johnson
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| |
Collapse
|
10
|
Gowen BG, Chim B, Marceau CD, Greene TT, Burr P, Gonzalez JR, Hesser CR, Dietzen PA, Russell T, Iannello A, Coscoy L, Sentman CL, Carette JE, Muljo SA, Raulet DH. A forward genetic screen reveals novel independent regulators of ULBP1, an activating ligand for natural killer cells. eLife 2015; 4. [PMID: 26565589 PMCID: PMC4629278 DOI: 10.7554/elife.08474] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 08/28/2015] [Indexed: 02/07/2023] Open
Abstract
Recognition and elimination of tumor cells by the immune system is crucial for limiting tumor growth. Natural killer (NK) cells become activated when the receptor NKG2D is engaged by ligands that are frequently upregulated in primary tumors and on cancer cell lines. However, the molecular mechanisms driving NKG2D ligand expression on tumor cells are not well defined. Using a forward genetic screen in a tumor-derived human cell line, we identified several novel factors supporting expression of the NKG2D ligand ULBP1. Our results show stepwise contributions of independent pathways working at multiple stages of ULBP1 biogenesis. Deeper investigation of selected hits from the screen showed that the transcription factor ATF4 drives ULBP1 gene expression in cancer cell lines, while the RNA-binding protein RBM4 supports ULBP1 expression by suppressing a novel alternatively spliced isoform of ULBP1 mRNA. These findings offer insight into the stress pathways that alert the immune system to danger. DOI:http://dx.doi.org/10.7554/eLife.08474.001 Cancer is caused by a series of mutations that result in uncontrolled cell growth and division. Yet, the body's immune system can often detect and destroy abnormal cells before they cause tumors and disease. Natural killer cells are part of the immune system and have receptors on their surface that allow them to tell the difference between healthy host cells and host cells that are stressed or abnormal. Some of these receptors activate the natural killer cells when they bind to their target molecules. Other receptors have the opposite effect and inhibit the natural killer cells. Activation occurs when the signaling from the activating receptors is stronger than the signals from the inhibitory receptors. One of the well-studied activating receptors recognizes a number of proteins and molecules that are produced by abnormal or tumor cells, including a protein called ULBP1. This protein is absent from the surface of healthy cells but is found in abundance on tumor cells. However, it is still not clear what drives tumor cells to produce ULBP1 (or other molecules) that are recognized by natural killer cell receptors. Now, Gowen et al. report on a genetic screen that has revealed numerous genes that regulate the levels of ULBP1 in human cells. Many of these genes had independent effects that when added together accounted for most of the ULBP1 present on the cell surface. Gowen et al. then explored some of the ‘regulators’ encoded by these genes in more detail. One called ATF4, which had previously been linked to stress responses, was shown to increase the expression of the gene for ULBP1 in cancer cells. Another regulator called RBM4 instead acted in a different way and at a later stage in ULBP1 production. All together, these findings offer insight into the stress pathways that alert the immune system to abnormal cells. The next challenge will be investigating how these pathways might be exploited for cancer immunotherapy. DOI:http://dx.doi.org/10.7554/eLife.08474.002
Collapse
Affiliation(s)
- Benjamin G Gowen
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Bryan Chim
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - Caleb D Marceau
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Trever T Greene
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Patrick Burr
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - Jeanmarie R Gonzalez
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Charles R Hesser
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Peter A Dietzen
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Teal Russell
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Alexandre Iannello
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Laurent Coscoy
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| | - Charles L Sentman
- Center for Synthetic Immunity, Department of Microbiology and Immunology, Dartmouth Geisel School of Medicine, Lebanon, United States
| | - Jan E Carette
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, United States
| | - Stefan A Muljo
- Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, Bethesda, United States
| | - David H Raulet
- Department of Molecular and Cell Biology, Cancer Research Laboratory, University of California, Berkeley, Berkeley, United States
| |
Collapse
|
11
|
Malkani N, Jansson T, Gupta MB. IGFBP-1 hyperphosphorylation in response to leucine deprivation is mediated by the AAR pathway. Mol Cell Endocrinol 2015; 412:182-95. [PMID: 25957086 PMCID: PMC5563670 DOI: 10.1016/j.mce.2015.04.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 04/28/2015] [Accepted: 04/30/2015] [Indexed: 02/07/2023]
Abstract
Insulin-like growth factor-1 (IGF-I) is the key regulator of fetal growth. IGF-I bioavailability is markedly diminished by IGF binding protein-1 (IGFBP-1) phosphorylation. Leucine deprivation strongly induces IGFBP-1 hyperphosphorylation, and plays an important role in fetal growth restriction (FGR). FGR is characterized by decreased amino acid availability, which activates the amino acid response (AAR) and inhibits the mechanistic target of rapamycin (mTOR) pathway. We investigated the role of AAR and mTOR in mediating IGFBP-1 secretion and phosphorylation in HepG2 cells in leucine deprivation. mTOR inhibition (rapamycin or raptor + rictor siRNA), or activation (DEPTOR siRNA) demonstrated a role of mTOR in leucine deprivation-induced IGFBP-1 secretion but not phosphorylation. When the AAR was blocked (U0126, or ERK/GCN2 siRNA), both IGFBP-1 secretion and hyperphosphorylation (pSer101/pSer119/pSer169) due to leucine deprivation were prevented. CK2 inhibition by TBB also attenuated IGFBP-1 phosphorylation in leucine deprivation. These results suggest that the AAR and mTOR independently regulate IGFBP-1 secretion and phosphorylation in response to decreased amino acid availability.
Collapse
Affiliation(s)
- Niyati Malkani
- Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Thomas Jansson
- Department of Obstetrics & Gynecology, University of Colorado, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Madhulika B Gupta
- Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada; Department of Pediatrics, University of Western Ontario, London, Canada; Children's Health Research Institute, University of Western Ontario, London, ON, Canada.
| |
Collapse
|
12
|
Shan J, Donelan W, Hayner JN, Zhang F, Dudenhausen EE, Kilberg MS. MAPK signaling triggers transcriptional induction of cFOS during amino acid limitation of HepG2 cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:539-48. [PMID: 25523140 DOI: 10.1016/j.bbamcr.2014.12.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 11/19/2014] [Accepted: 12/10/2014] [Indexed: 12/17/2022]
Abstract
Amino acid (AA) deprivation in mammalian cells activates a collection of signaling cascades known as the AA response (AAR), which is characterized by transcriptional induction of stress-related genes, including FBJ murine osteosarcoma viral oncogene homolog (cFOS). The present study established that the signaling mechanism underlying the AA-dependent transcriptional regulation of the cFOS gene in HepG2 human hepatocellular carcinoma cells is independent of the classic GCN2-eIF2-ATF4 pathway. Instead, a RAS-RAF-MEK-ERK cascade mediates AAR signaling to the cFOS gene. Increased cFOS transcription is observed from 4-24 h after AAR-activation, exhibiting little or no overlap with the rapid and transient increase triggered by the well-known serum response. Furthermore, serum is not required for the AA-responsiveness of the cFOS gene and no phosphorylation of promoter-bound serum response factor (SRF) is observed. The ERK-phosphorylated transcription factor E-twenty six-like (p-ELK1) is increased in its association with the cFOS promoter after activation of the AAR. This research identified cFOS as a target of the AAR and further highlights the importance of AA-responsive MAPK signaling in HepG2 cells.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610
| | - William Donelan
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Jaclyn N Hayner
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Fan Zhang
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Elizabeth E Dudenhausen
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Michael S Kilberg
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida 32610.
| |
Collapse
|
13
|
Anand S, Ebner J, Warren CB, Raam MS, Piliang M, Billings SD, Maytin EV. C/EBP transcription factors in human squamous cell carcinoma: selective changes in expression of isoforms correlate with the neoplastic state. PLoS One 2014; 9:e112073. [PMID: 25402211 PMCID: PMC4234316 DOI: 10.1371/journal.pone.0112073] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 10/13/2014] [Indexed: 12/28/2022] Open
Abstract
The CCAAT/Enhancer Binding Proteins (C/EBPs) are a family of leucine-zipper transcription factors that regulate physiological processes such as energy metabolism, inflammation, cell cycle, and the development and differentiation of several tissues including skin. Recently, a role for C/EBPs in tumor cell proliferation and differentiation has been proposed, but the incomplete characterization in the literature of multiple translational isoforms of these proteins has made interpretation of these roles difficult. Therefore, we have carefully reexamined C/EBP isoform expression in human non-melanoma skin cancers. C/EBPα, C/EBPβ, and C/EBPδ were analyzed histologically in squamous cell carcinomas (SCC). The individual isoforms of C/EBPα and C/EBPβ were examined by immunofluorescent digital imaging, western blotting and DNA binding activity (electrophoretic mobility shift analysis). Expression of all C/EBP family proteins was decreased in SCC tumors. Suppression was greatest for C/EBPα, less for C/EBPβ, and least for C/EBPδ. Western analyses confirmed that C/EBPα p42 and p30 isoforms were decreased. For C/EBPβ, only the abundant full-length isoform (C/EBPβ−1, LAP*, 55 kD) was reduced, whereas the smaller isoforms, C/EBPβ−2 (LAP, 48 kD) and C/EBPβ−3 (LIP, 20 kD), which are predominantly nuclear, were significantly increased in well- and moderately-differentiated SCC (up to 14-fold for C/EBPβ−3). These elevations correlated with increases in PCNA, a marker of proliferation. Although C/EBPβ displayed increased post-translational modifications in SCC, phosphorylation of C/EBPβ−1 (Thr 235) was not altered. C/EBP-specific DNA binding activity in nuclear and whole-cell extracts of cultured cells and tumors was predominantly attributable to C/EBPβ. In summary, two short C/EBPβ isoforms, C/EBPβ−2 and C/EBPβ−3, represent strong candidate markers for epithelial skin malignancy, due to their preferential expression in carcinoma versus normal skin, and their strong correlation with tumor proliferation.
Collapse
Affiliation(s)
- Sanjay Anand
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - John Ebner
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Christine B. Warren
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Manu S. Raam
- Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Melissa Piliang
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Anatomic Pathology, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Steven D. Billings
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Anatomic Pathology, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Edward V. Maytin
- Department of Dermatology, Cleveland Clinic, Cleveland, Ohio, United States of America
- Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, United States of America
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
14
|
Shan J, Balasubramanian MN, Donelan W, Fu L, Hayner J, Lopez MC, Baker HV, Kilberg MS. A mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-dependent transcriptional program controls activation of the early growth response 1 (EGR1) gene during amino acid limitation. J Biol Chem 2014; 289:24665-79. [PMID: 25028509 DOI: 10.1074/jbc.m114.565028] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Amino acid (AA) limitation in mammalian cells triggers a collection of signaling cascades jointly referred to as the AA response (AAR). In human HepG2 hepatocellular carcinoma, the early growth response 1 (EGR1) gene was induced by either AA deprivation or endoplasmic reticulum stress. AAR-dependent EGR1 activation was discovered to be independent of the well characterized GCN2-ATF4 pathway and instead dependent on MEK-ERK signaling, one of the MAPK pathways. ChIP showed that constitutively bound ELK1 at the EGR1 proximal promoter region was phosphorylated after AAR activation. Increased p-ELK1 binding was associated with increased de novo recruitment of RNA polymerase II to the EGR1 promoter. EGR1 transcription was not induced in HEK293T cells lacking endogenous MEK activity, but overexpression of exogenous constitutively active MEK in HEK293T cells resulted in increased basal and AAR-induced EGR1 expression. ChIP analysis of the human vascular endothelial growth factor A (VEGF-A) gene, a known EGR1-responsive gene, revealed moderate increases in AAR-induced EGR1 binding within the proximal promoter and highly inducible binding to a site within the first intron. Collectively, these data document a novel AA-activated MEK-ERK-ELK1 signaling mechanism.
Collapse
Affiliation(s)
- Jixiu Shan
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| | - Mukundh N Balasubramanian
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| | - William Donelan
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| | - Lingchen Fu
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| | - Jaclyn Hayner
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| | - Maria-Cecilia Lopez
- the Department of Molecular Genetics and Microbiology, Genetics Institute, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Henry V Baker
- the Department of Molecular Genetics and Microbiology, Genetics Institute, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Michael S Kilberg
- From the Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences and
| |
Collapse
|
15
|
Xu X, Hu J, McGrath BC, Cavener DR. GCN2 regulates the CCAAT enhancer binding protein beta and hepatic gluconeogenesis. Am J Physiol Endocrinol Metab 2013; 305:E1007-17. [PMID: 23900421 PMCID: PMC3798698 DOI: 10.1152/ajpendo.00063.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mice deficient for general control nondepressible-2 (Gcn2) either globally or specifically in the liver display reduced capacity to maintain glucose homeostasis during fasting, suggesting the hypothesis that GCN2 may regulate gluconeogenesis (GNG), which normally plays a key role maintaining peripheral glucose homeostasis. Gcn2-deficient mice exhibit normal insulin sensitivity and plasma insulin but show reduced GNG when administered pyruvate, a gluconeogenic substrate. The basal expression of phosphoenolpyruvate carboxykinase, a rate-limiting enzyme in GNG, is abnormally elevated in Gcn2 knockout (KO) mice in the fed state but fails to be further induced during fasting. The level of tricarboxylic acid cycle intermediates, including malate and oxaloacetate, and the NADH-to-NAD(+) ratio are perturbed in the liver of Gcn2 KO mice either in the fed or fasted state, which may directly impinge upon GNG. Additionally, the expression of the CCAAT enhancer-binding protein-β (C/EBPβ) in the liver fails to be induced in Gcn2 KO mice after 24 h fasting, and the liver-specific Cebpβ KO mice show reduced fasting GNG similar to that seen in Gcn2-deficient mice. Our study demonstrates that GCN2 is important in maintaining GNG in the liver, which is likely to be mediated through regulation of C/EBPβ.
Collapse
Affiliation(s)
- Xu Xu
- Department of Biology, Center for Cellular Dynamics, Pennsylvania State University, University Park, Pennsylvania
| | | | | | | |
Collapse
|
16
|
Yu J, Xiao F, Zhang Q, Liu B, Guo Y, Lv Z, Xia T, Chen S, Li K, Du Y, Guo F. PRLR regulates hepatic insulin sensitivity in mice via STAT5. Diabetes 2013; 62:3103-13. [PMID: 23775766 PMCID: PMC3749345 DOI: 10.2337/db13-0182] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Insulin resistance is one of the major contributing factors in the development of metabolic diseases. The mechanisms responsible for insulin resistance, however, remain poorly understood. Although numerous functions of the prolactin receptor (PRLR) have been identified, a direct effect on insulin sensitivity has not been previously described. The aim of our current study is to investigate this possibility and elucidate underlying mechanisms. Here we show that insulin sensitivity is improved or impaired in mice injected with adenovirus that overexpress or knock down PRLR expression, respectively. Similar observations were obtained in in vitro studies. In addition, we discovered that the signal transducer and activator of transcription-5 pathway are required for regulating insulin sensitivity by PRLR. Moreover, we observed that PRLR expression is decreased or increased under insulin-resistant (db/db mice) or insulin-sensitive (leucine deprivation) conditions, respectively, and found that altering PRLR expression significantly reverses insulin sensitivity under both conditions. Finally, we found that PRLR expression levels are increased under leucine deprivation via a general control nonderepressible 2/mammalian target of rapamycin/ribosomal protein S6 kinase-1-dependent pathway. These results demonstrate a novel function for hepatic PRLR in the regulation of insulin sensitivity and provide important insights concerning the nutritional regulation of PRLR expression.
Collapse
|
17
|
Shan J, Hamazaki T, Tang TA, Terada N, Kilberg MS. Activation of the amino acid response modulates lineage specification during differentiation of murine embryonic stem cells. Am J Physiol Endocrinol Metab 2013; 305:E325-35. [PMID: 23736538 PMCID: PMC4116408 DOI: 10.1152/ajpendo.00136.2013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In somatic cells, a collection of signaling pathways activated by amino acid limitation have been identified and referred to as the amino acid response (AAR). Despite the importance of possible detrimental effects of nutrient limitation during in vitro culture, the AAR has not been investigated in embryonic stem cells (ESC). AAR activation caused the expected increase in transcription factors that mediate specific AAR pathways, as well as the induction of asparagine synthetase, a terminal AAR target gene. Neither AAR activation nor stable knockdown of activating transcription factor (Atf) 4, a transcriptional mediator of the AAR, adversely affected ESC self-renewal or pluripotency. Low-level induction of the AAR over a 12-day period of embryoid body differentiation did alter lineage specification such that the primitive endodermal, visceral endodermal, and endodermal lineages were favored, whereas mesodermal and certain ectodermal lineages were suppressed. Knockdown of Atf4 further enhanced the AAR-induced increase in endodermal formation, suggesting that this phenomenon is mediated by an Atf4-independent mechanism. Collectively, the results indicate that, during differentiation of mouse embryoid bodies in culture, the availability of nutrients, such as amino acids, can influence the formation of specific cell lineages.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology, McKnight Brain Institute, Shands Cancer Center, and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida, USA
| | | | | | | | | |
Collapse
|
18
|
Hensen SMM, Heldens L, van Genesen ST, Pruijn GJM, Lubsen NH. A delayed antioxidant response in heat-stressed cells expressing a non-DNA binding HSF1 mutant. Cell Stress Chaperones 2013; 18:455-73. [PMID: 23321918 PMCID: PMC3682012 DOI: 10.1007/s12192-012-0400-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 12/20/2012] [Accepted: 12/21/2012] [Indexed: 12/30/2022] Open
Abstract
To assess the consequences of inactivation of heat shock factor 1 (HSF1) during aging, we analyzed the effect of HSF1 K80Q, a mutant unable to bind DNA, and of dnHSF1, a mutant lacking the activation domain, on the transcriptome of cells 6 and 24 h after heat shock. The primary response to heat shock (6 h recovery), of which 30 % was HSF1-dependent, had decayed 24 h after heat shock in control cells but was extended in HSF1 K80Q and dnHSF1 cells. Comparison with literature data showed that even the HSF1 dependent primary stress response is largely cell specific. HSF1 K80Q, but not HSF1 siRNA-treated, cells showed a delayed stress response: an increase in transcript levels of HSF1 target genes 24 h after heat stress. Knockdown of NRF2, but not of ATF4, c-Fos or FosB, inhibited this delayed stress response. EEF1D_L siRNA inhibited both the delayed and the extended primary stress responses, but had off target effects. In control cells an antioxidant response (ARE binding, HMOX1 mRNA levels) was detected 6 h after heat shock; in HSF1 K80Q cells this response was delayed to 24 h and the ARE complex had a different mobility. Inactivation of HSF1 thus affects the timing and nature of the antioxidant response and NRF2 can activate at least some HSF1 target genes in the absence of HSF1 activity.
Collapse
Affiliation(s)
- Sanne M. M. Hensen
- 271 Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Lonneke Heldens
- 271 Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Siebe T. van Genesen
- 271 Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Ger J. M. Pruijn
- 271 Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Nicolette H. Lubsen
- 271 Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| |
Collapse
|
19
|
Bickford JS, Beachy DE, Newsom KJ, Barilovits SJ, Herlihy JDH, Qiu X, Walters JN, Li N, Nick HS. A distal enhancer controls cytokine-dependent human cPLA2α gene expression. J Lipid Res 2013; 54:1915-26. [PMID: 23549331 DOI: 10.1194/jlr.m037382] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Specific control of group IVA cytosolic phospholipase A2 (cPLA2α or PLA2G4A) expression modulates arachidonic acid production, thus tightly regulating the downstream effects of pro- and anti-inflammatory eicosanoids. The significance of this pathway in human disease is apparent in a range of pathologies from inflammation to tumorigenesis. While much of the regulation of cPLA2α has focused on posttranslational phosphorylation of the protein, studies on transcriptional regulation of this gene have focused only on proximal promoter regions. We have identified a DNase I hypersensitive site encompassing a 5' distal enhancer element containing a highly conserved consensus AP-1 site involved in transcriptional activation of cPLA2α by interleukin (IL)-1β. Chromatin immunoprecipitation (ChIP), knockdown, knockout, and overexpression analyses have shown that c-Jun acts both in a negative and positive regulatory role. Transcriptional activation of cPLA2α occurs through the phosphorylation of c-Jun in conjunction with increased association of C/EBPβ with the distal novel enhancer. The association of C/EBPβ with the transcriptional activation complex does not require an obvious DNA binding site. These data provide new and important contributions to the understanding of cPLA2α regulation at the transcriptional level, with implications for eicosanoid metabolism, cellular signaling, and disease pathogenesis.
Collapse
Affiliation(s)
- Justin S Bickford
- Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Fu L, Kilberg MS. Elevated cJUN expression and an ATF/CRE site within the ATF3 promoter contribute to activation of ATF3 transcription by the amino acid response. Physiol Genomics 2013; 45:127-37. [PMID: 23269699 PMCID: PMC3568878 DOI: 10.1152/physiolgenomics.00160.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 12/21/2012] [Indexed: 01/03/2023] Open
Abstract
Mammalian cells respond to amino acid deprivation through multiple signaling pathways referred to as the amino acid response (AAR). Transcription factors mediate the AAR after their activation by several mechanisms; examples include translational control (activating transcription factor 4, ATF4), phosphorylation (p-cJUN), and transcriptional control (ATF3). ATF4 induces ATF3 transcription through a promoter-localized C/EBP-ATF response element (CARE). The present report characterizes an ATF/CRE site upstream of the CARE that also contributes to AAR-induced ATF3 transcription. ATF4 binds to the ATF/CRE and CARE sequences and both are required for a maximal response to ATF4 induction. ATF3, which antagonizes ATF4 and represses its own gene, also exhibited binding activity to the ATF/CRE and CARE sequences. The AAR resulted in elevated total cJUN and p-cJUN protein levels and both forms exhibited binding activity to the ATF/CRE and CARE ATF3 sequences. Knockdown of AAR-enhanced cJUN expression blocked induction of the ATF3 gene and mutation of either the ATF/CRE or the CARE site prevented the cJUN-dependent increase in ATF3-driven luciferase activity. The results indicate that both increased cJUN and the cis-acting ATF/CRE sequence within the ATF3 promoter contribute to the transcriptional activation of the gene during the AAR.
Collapse
Affiliation(s)
- Lingchen Fu
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center, and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida, USA
| | | |
Collapse
|
21
|
Hensen SMM, Heldens L, van Enckevort CMW, van Genesen ST, Pruijn GJM, Lubsen NH. Activation of the antioxidant response in methionine deprived human cells results in an HSF1-independent increase in HSPA1A mRNA levels. Biochimie 2013; 95:1245-51. [PMID: 23395854 DOI: 10.1016/j.biochi.2013.01.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 01/29/2013] [Indexed: 12/30/2022]
Abstract
In cells starved for leucine, lysine or glutamine heat shock factor 1 (HSF1) is inactivated and the level of the transcripts of the HSF1 target genes HSPA1A (Hsp70) and DNAJB1 (Hsp40) drops. We show here that in HEK293 cells deprived of methionine HSF1 was similarly inactivated but that the level of HSPA1A and DNAJB1 mRNA increased. This increase was also seen in cells expressing a dominant negative HSF1 mutant (HSF379 or HSF1-K80Q), confirming that the increase is HSF1 independent. The antioxidant N-acetylcysteine completely inhibited the increase in HSPA1A and DNAJB1 mRNA levels upon methionine starvation, indicating that this increase is a response to oxidative stress resulting from a lack of methionine. Cells starved for methionine contained higher levels of c-Fos and FosB mRNA, but knockdown of these transcription factors had no effect on the HSPA1A or DNAJB1 mRNA level. Knockdown of NRF2 mRNA resulted in the inhibition of the increase in the HSPA1A mRNA, but not the DNAJB1 mRNA, level in methionine starved cells. We conclude that methionine deprivation results in both the amino acid deprivation response and an antioxidant response mediated at least in part by NRF2. This antioxidant response includes an HSF1 independent increase in the levels of HSPA1A and DNAJB1 mRNA.
Collapse
Affiliation(s)
- Sanne M M Hensen
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, NL-6500 HB Nijmegen, The Netherlands
| | | | | | | | | | | |
Collapse
|
22
|
Dynamic changes in genomic histone association and modification during activation of the ASNS and ATF3 genes by amino acid limitation. Biochem J 2013; 449:219-29. [PMID: 22978410 DOI: 10.1042/bj20120958] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Amino acid deprivation of mammalian cells triggers several signalling pathways, the AAR (amino acid response), that results in transcriptional activation. For the ASNS (asparagine synthetase) and ATF3 (activating transcription factor 3) genes, increased transcription occurs in conjunction with recruitment of ATF4 to the gene. In HepG2 cells, analysis of the ASNS and ATF3 genes during AAR activation revealed increases in histone H3K4me3 (histone 3 trimethylated Lys4) and H4Ac (acetylated histone 4) levels, marks associated with active transcription, but a concurrent loss of total H3 protein near the promoter. The dynamic nature of AAR-regulated transcription was illustrated by a decline in ASNS transcription activity within minutes after removal of the AAR stress and a return to basal levels by 2 h. Reversal of ASNS transcription occurred in parallel with decreased promoter-associated H4Ac and ATF4 binding. However, the reduction in histone H3 and increase in H3K4me3 were not reversed. In yeast, persistence of H3K4me3 has been proposed to be a 'memory' mark of gene activity that alters the responsiveness of the gene, but the time course and magnitude of ASNS induction was unaffected when cells were challenged with a second round of AAR activation. The results of the present study document changes in gene-associated nucleosome abundance and histone modifications in response to amino-acid-dependent transcription.
Collapse
|
23
|
Hensen SMM, Heldens L, van Enckevort CMW, van Genesen ST, Pruijn GJM, Lubsen NH. Heat shock factor 1 is inactivated by amino acid deprivation. Cell Stress Chaperones 2012; 17:743-55. [PMID: 22797943 PMCID: PMC3468675 DOI: 10.1007/s12192-012-0347-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/18/2012] [Accepted: 06/20/2012] [Indexed: 11/14/2022] Open
Abstract
Mammalian cells respond to a lack of amino acids by activating a transcriptional program with the transcription factor ATF4 as one of the main actors. When cells are faced with cytoplasmic proteotoxic stress, a quite different transcriptional response is mounted, the heat shock response, which is mediated by HSF1. Here, we show that amino acid deprivation results in the inactivation of HSF1. In amino acid deprived cells, active HSF1 loses its DNA binding activity as demonstrated by EMSA and ChIP. A sharp decrease in the transcript level of HSF1 target genes such as HSPA1A (Hsp70), DNAJB1 (Hsp40), and HSP90AA1 is also seen. HSPA1A mRNA, but not DNAJB1 mRNA, was also destabilized. In cells cultured with limiting leucine, HSF1 activity also declined. Lack of amino acids thus could lead to a lower chaperoning capacity and cellular frailty. We show that the nutrient sensing response unit of the ASNS gene contains an HSF1 binding site, but we could not detect binding of HSF1 to this site in vivo. Expression of either an HSF1 mutant lacking the activation domain (HSF379) or an HSF1 mutant unable to bind DNA (K80Q) had only a minor effect on the transcript levels of amino acid deprivation responsive genes.
Collapse
Affiliation(s)
- Sanne M. M. Hensen
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Lonneke Heldens
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Chrissy M. W. van Enckevort
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Siebe T. van Genesen
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Ger J. M. Pruijn
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Nicolette H. Lubsen
- Department of Biomolecular Chemistry, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| |
Collapse
|
24
|
Xue H, Slavov D, Wischmeyer PE. Glutamine-mediated dual regulation of heat shock transcription factor-1 activation and expression. J Biol Chem 2012; 287:40400-13. [PMID: 23055521 DOI: 10.1074/jbc.m112.410712] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Regulation of transcriptional activity of heat shock factor-1 (HSF1) is widely thought to be the main point of control for heat shock protein (Hsp) expression. RESULTS Glutamine increases Hsf1 gene transcription in a C/EBPβ-dependent manner and up-regulates HSF1 activity. CONCLUSION Glutamine is an activator for both HSF1 expression and transactivation. SIGNIFICANCE Glutamine-induced HSF1 expression provides a novel mechanistic frame for HSF1-Hsp axis regulation. Heat shock transcription factor-1 (HSF1) is the master regulator for cytoprotective heat shock protein (Hsp) expression. It is widely thought that HSF1 expression is non-inducible, and thus the key control point of Hsp expression is regulation of the transactivation activity of HSF1. How HSF1 expression is regulated remains unknown. Herein we demonstrate that glutamine (Gln), a preferred fuel substrate for the gut, enhanced Hsp expression both in rat colonic epithelium in vivo and in cultured non-transformed young adult mouse colonic epithelial cells. This was associated with up-regulation of the transactivation activity of HSF1 via increased HSF1 trimerization, nuclear localization, DNA binding, and relative abundance of activating phosphorylation at Ser-230 of HSF1. More intriguingly, Gln enhanced HSF1 protein and mRNA expression and Hsf1 gene promoter activity. Within the -281/-200 region of the Hsf1 promoter, deletion of the putative CCAAT enhancer-binding protein (C/EBP) binding site abolished the HSF1 response to Gln. C/EBPβ was further shown to bind to this 82-bp sequence both in vitro and in vivo. Gln availability strikingly altered the ratio of C/EBPβ inhibitory and active isoforms, i.e. liver-enriched inhibitory protein and liver-enriched activating protein. Liver-enriched inhibitory protein and liver-enriched activating protein were further shown to be an independent repressor and activator, respectively, for Hsf1 gene transcription, and the relative abundance of these two C/EBPβ isoforms was demonstrated to determine Hsf1 transcription. We show for the first time that Gln not only enhances the transactivation of HSF1 but also induces Hsf1 expression by activating its transcription in a C/EBPβ-dependent manner.
Collapse
Affiliation(s)
- Hongyu Xue
- Department of Anesthesiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO 80045, USA.
| | | | | |
Collapse
|
25
|
Shan J, Fu L, Balasubramanian MN, Anthony T, Kilberg MS. ATF4-dependent regulation of the JMJD3 gene during amino acid deprivation can be rescued in Atf4-deficient cells by inhibition of deacetylation. J Biol Chem 2012; 287:36393-403. [PMID: 22955275 DOI: 10.1074/jbc.m112.399600] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Following amino acid deprivation, the amino acid response (AAR) induces transcription from specific genes through a collection of signaling mechanisms, including the GCN2-eIF2-ATF4 pathway. The present report documents that the histone demethylase JMJD3 is an activating transcription factor 4 (ATF4)-dependent target gene. The JMJD3 gene contains two AAR-induced promoter activities and chromatin immunoprecipitation (ChIP) analysis showed that the AAR leads to enhanced ATF4 recruitment to the C/EBP-ATF response element (CARE) upstream of Promoter-1. AAR-induced histone modifications across the JMJD3 gene locus occur upon ATF4 binding. Jmjd3 transcription is not induced in Atf4-knock-out cells, but the AAR-dependent activation was rescued by inhibition of histone deacetylation with trichostatin A (TSA). The TSA rescue of AAR activation in the absence of Atf4 also occurred for the Atf3 and C/EBP homology protein (Chop) genes, but not for the asparagine synthetase gene. ChIP analysis of the Jmjd3, Atf3, and Chop genes in Atf4 knock-out cells documented that activation of the AAR in the presence of TSA led to specific changes in acetylation of histone H4. The results suggest that a primary function of ATF4 is to recruit histone acetyltransferase activity to a sub-set of AAR target genes. Thus, absolute binding of ATF4 to these particular genes is not required and no ATF4 interaction with the general transcription machinery is necessary. The data are consistent with the hypothesis that ATF4 functions as a pioneer factor to alter chromatin structure and thus, enhance transcription in a gene-specific manner.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center, University of Florida College of Medicine, Gainesville, Florida 32610, USA
| | | | | | | | | |
Collapse
|
26
|
Cronin KR, Mangan TP, Carew JA. Upregulation of the coagulation factor VII gene during glucose deprivation is mediated by activating transcription factor 4. PLoS One 2012; 7:e40994. [PMID: 22848420 PMCID: PMC3407153 DOI: 10.1371/journal.pone.0040994] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 06/15/2012] [Indexed: 12/20/2022] Open
Abstract
Background Constitutive production of blood coagulation proteins by hepatocytes is necessary for hemostasis. Stressful conditions trigger adaptive cellular responses and delay processing of most proteins, potentially affecting plasma levels of proteins secreted exclusively by hepatocytes. We examined the effect of glucose deprivation on expression of coagulation proteins by the human hepatoma cell line, HepG2. Methodology/Principal Findings Expression of coagulation factor VII, which is required for initiation of blood coagulation, was elevated by glucose deprivation, while expression of other coagulation proteins decreased. Realtime PCR and ELISA demonstrated that the relative percentage expression +/− SD of steady-state F7 mRNA and secreted factor VII antigen were significantly increased (from 100+/−15% to 188+/−27% and 100+/−8.8% to 176.3+/−17.3% respectively, p<0.001) at 24 hr of treatment. The integrated stress response was induced, as indicated by upregulation of transcription factor ATF4 and of additional stress-responsive genes. Small interfering RNAs directed against ATF4 potently reduced basal F7 expression, and prevented F7 upregulation by glucose deprivation. The response of the endogenous F7 gene was replicated in reporter gene assays, which further indicated that ATF4 effects were mediated via interaction with an amino acid response element in the F7 promoter. Conclusions/Significance Our data indicated that glucose deprivation enhanced F7 expression in a mechanism reliant on prior ATF4 upregulation primarily due to increased transcription from the ATF4 gene. Of five coagulation protein genes examined, only F7 was upregulated, suggesting that its functions may be important in a systemic response to glucose deprivation stress.
Collapse
Affiliation(s)
- Katherine R. Cronin
- Department of Research, VA Boston Healthcare System, West Roxbury, Massachusetts, United States of America
| | - Thomas P. Mangan
- Department of Research, VA Boston Healthcare System, West Roxbury, Massachusetts, United States of America
| | - Josephine A. Carew
- Department of Research, VA Boston Healthcare System, West Roxbury, Massachusetts, United States of America
- Department of Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
27
|
Kilberg MS, Balasubramanian M, Fu L, Shan J. The transcription factor network associated with the amino acid response in mammalian cells. Adv Nutr 2012; 3:295-306. [PMID: 22585903 PMCID: PMC3649461 DOI: 10.3945/an.112.001891] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mammals exhibit multiple adaptive mechanisms that sense and respond to fluctuations in dietary nutrients. Consumption of reduced total dietary protein or a protein diet that is deficient in 1 or more of the essential amino acids triggers wide-ranging changes in feeding behavior and gene expression. At the level of individual cells, dietary protein deficiency is manifested as amino acid (AA) deprivation, which activates the AA response (AAR). The AAR is composed of a collection of signal transduction pathways that terminate in specific transcriptional programs designed to catalyze adaptation to the nutrient stress or, ultimately, undergo apoptosis. Independently of the AAR, endoplasmic reticulum stress activates 3 signaling pathways, collectively referred to as the unfolded protein response. The transcription factor activating transcription factor 4 is one of the terminal transcriptional mediators for both the AAR and the unfolded protein response, leading to a significant degree of overlap with regard to the target genes for these stress pathways. Over the past 5 y, research has revealed that the basic leucine zipper superfamily of transcription factors plays the central role in the AAR. Formation of both homo- and heterodimers among the activating transcription factor, CCAAT enhancer-binding protein, and FOS/JUN families of basic leucine zipper proteins forms the nucleus of a highly integrated transcription factor network that determines the initiation, magnitude, and duration of the cellular response to dietary protein or AA limitation.
Collapse
|
28
|
Zhou D, Pan YX. Gestational low protein diet selectively induces the amino acid response pathway target genes in the liver of offspring rats through transcription factor binding and histone modifications. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1809:549-56. [DOI: 10.1016/j.bbagrm.2011.07.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 06/27/2011] [Accepted: 07/06/2011] [Indexed: 12/19/2022]
|
29
|
Fu L, Balasubramanian M, Shan J, Dudenhausen EE, Kilberg MS. Auto-activation of c-JUN gene by amino acid deprivation of hepatocellular carcinoma cells reveals a novel c-JUN-mediated signaling pathway. J Biol Chem 2011; 286:36724-38. [PMID: 21862593 DOI: 10.1074/jbc.m111.277673] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mammalian cells respond to protein or amino acid (AA) limitation by activating a number of signaling pathways, collectively referred to as the AA response (AAR), that modulate a range of cellular functions, including transcriptional induction of target genes. This study demonstrates that in hepatocellular carcinoma cells, expression of c-JUN, JUN-B, c-FOS, and FOS-B was induced by the AAR, whereas JUN-D, FRA-1, and FRA-2 were not. Of the four activated FOS/JUN members, c-JUN made the largest contribution to the induction of several known AAR target genes. For several human liver, prostate, and ovarian cell lines, the AAR-induced increase in c-JUN expression was greater in transformed cells compared with nontransformed counterparts, an effect independent of cell growth rate. Thus far, the best characterized AA-responsive genes are all transcriptionally activated by ATF4, but the AAR-dependent induction of c-JUN transcription was ATF4-independent. The increased expression of c-JUN was dependent on ATF2 and on activation of the MEK-ERK and JNK arms of the MAPK signaling pathways. Formation of c-JUN-ATF2-activated heterodimers was increased after AA limitation, and c-JUN or ATF2 knockdown suppressed the induction of c-JUN and other AAR target genes. AA deprivation triggers a feed-forward process that involves phosphorylation of existing c-JUN protein by JNK and subsequent auto-activation of the c-JUN gene by recruitment of c-JUN and ATF2 to two AP-1 sites within the proximal promoter. The results document the novel observation that AP-1 sequences within the c-JUN gene can function as transcriptional amino acid-response elements.
Collapse
Affiliation(s)
- Lingchen Fu
- Department of Biochemistry and Molecular Biology, Shands Cancer Center, University of Florida College of Medicine, Gainesville, Florida 32610, USA
| | | | | | | | | |
Collapse
|
30
|
Carraro V, Maurin AC, Lambert-Langlais S, Averous J, Chaveroux C, Parry L, Jousse C, Örd D, Örd T, Fafournoux P, Bruhat A. Amino acid availability controls TRB3 transcription in liver through the GCN2/eIF2α/ATF4 pathway. PLoS One 2010; 5:e15716. [PMID: 21203563 PMCID: PMC3006201 DOI: 10.1371/journal.pone.0015716] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2010] [Accepted: 11/23/2010] [Indexed: 11/20/2022] Open
Abstract
In mammals, plasma amino acid concentrations are markedly affected by dietary or pathological conditions. It has been well established that amino acids are involved in the control of gene expression. Up to now, all the information concerning the molecular mechanisms involved in the regulation of gene transcription by amino acid availability has been obtained in cultured cell lines. The present study aims to investigate the mechanisms involved in transcriptional activation of the TRB3 gene following amino acid limitation in mice liver. The results show that TRB3 is up-regulated in the liver of mice fed a leucine-deficient diet and that this induction is quickly reversible. Using transient transfection and chromatin immunoprecipitation approaches in hepatoma cells, we report the characterization of a functional Amino Acid Response Element (AARE) in the TRB3 promoter and the binding of ATF4, ATF2 and C/EBPβ to this AARE sequence. We also provide evidence that only the binding of ATF4 to the AARE plays a crucial role in the amino acid-regulated transcription of TRB3. In mouse liver, we demonstrate that the GCN2/eIF2α/ATF4 pathway is essential for the induction of the TRB3 gene transcription in response to a leucine-deficient diet. Therefore, this work establishes for the first time that the molecular mechanisms involved in the regulation of gene transcription by amino acid availability are functional in mouse liver.
Collapse
Affiliation(s)
- Valérie Carraro
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | - Anne-Catherine Maurin
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | - Sarah Lambert-Langlais
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | - Julien Averous
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | | | - Laurent Parry
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | - Céline Jousse
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
| | | | | | - Pierre Fafournoux
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
- * E-mail: (PF); (AB)
| | - Alain Bruhat
- INRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France
- Université Clermont 1, UFR Médecine, UMR 1019 Nutrition Humaine, Clermont-Ferrand, France
- * E-mail: (PF); (AB)
| |
Collapse
|
31
|
Shan J, Lopez MC, Baker HV, Kilberg MS. Expression profiling after activation of amino acid deprivation response in HepG2 human hepatoma cells. Physiol Genomics 2010; 41:315-27. [PMID: 20215415 DOI: 10.1152/physiolgenomics.00217.2009] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dietary protein malnutrition is manifested as amino acid deprivation of individual cells, which activates an amino acid response (AAR) that alters cellular functions, in part, by regulating transcriptional and posttranscriptional mechanisms. The AAR was activated in HepG2 human hepatoma cells, and the changes in mRNA content were analyzed by microarray expression profiling. The results documented that 1,507 genes were differentially regulated by P < 0.001 and by more than twofold in response to the AAR, 250 downregulated and 1,257 upregulated. The spectrum of altered genes reveals that amino acid deprivation has far-reaching implications for gene expression and cellular function. Among those cellular functions with the largest numbers of altered genes were cell growth and proliferation, cell cycle, gene expression, cell death, and development. Potential biological relationships between the differentially expressed genes were analyzed by computer software that generates gene networks. Proteins that were central to the most significant of these networks included c-myc, polycomb group proteins, transforming growth factor β1, nuclear factor (erythroid-derived 2)-like 2-related factor 2, FOS/JUN family members, and many members of the basic leucine zipper superfamily of transcription factors. Although most of these networks contained some genes that were known to be amino acid responsive, many new relationships were identified that underscored the broad impact that amino acid stress has on cellular function.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology and
| | | | | | | |
Collapse
|
32
|
Lee SH, Krisanapun C, Baek SJ. NSAID-activated gene-1 as a molecular target for capsaicin-induced apoptosis through a novel molecular mechanism involving GSK3beta, C/EBPbeta and ATF3. Carcinogenesis 2010; 31:719-28. [PMID: 20110283 DOI: 10.1093/carcin/bgq016] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Capsaicin, a natural product of the Capsicum species of red peppers, is known to induce apoptosis and suppress growth. Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) is a cytokine associated with pro-apoptotic and antitumorigenic property in colorectal and lung cancer. Our data demonstrate that capsaicin leads to induction of apoptosis and up-regulates NAG-1 gene expression at the transcriptional level. Overexpression of CCAAT/enhancer binding protein beta (C/EBPbeta) caused a significant increase of basal and capsaicin-induced NAG-1 promoter activity. We subsequently identified C/EBPbeta binding sites in the NAG-1 promoter responsible for capsaicin-induced NAG-1 transactivation. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirmed binding of C/EBPbeta to the NAG-1 promoter. Capsaicin treatment resulted in an increase of phosphorylated serine/threonine residues on C/EBPbeta, and the immunoprecipitation study showed that capsaicin enhanced binding of C/EBPbeta with glycogen synthase kinase 3beta (GSK3beta) and activating transcription factor 3 (ATF3). The phosphorylation and interaction of C/EBPbeta with GSK3beta and ATF3 are decreased by the inhibition of the GSK3beta and Protein Kinase C pathways. Knockdown of C/EBPbeta, GSK3beta or ATF3 ameliorates NAG-1 expression induced by capsaicin treatment. These data indicate that C/EBPbeta phosphorylation through GSK3beta may mediate capsaicin-induced expression of NAG-1 and apoptosis through cooperation with ATF3 in human colorectal cancer cells.
Collapse
Affiliation(s)
- Seong-Ho Lee
- Laboratory of Environmental Carcinogenesis, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA
| | | | | |
Collapse
|
33
|
Kilberg MS, Shan J, Su N. ATF4-dependent transcription mediates signaling of amino acid limitation. Trends Endocrinol Metab 2009; 20:436-43. [PMID: 19800252 PMCID: PMC3587693 DOI: 10.1016/j.tem.2009.05.008] [Citation(s) in RCA: 430] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Revised: 05/18/2009] [Accepted: 05/19/2009] [Indexed: 01/28/2023]
Abstract
Mammals respond to dietary nutrient fluctuations; for example, deficiency of dietary protein or an imbalance of essential amino acids activates an amino acid response (AAR) signal transduction pathway, consisting of detection of uncharged tRNA by the GCN2 kinase, eIF2alpha phosphorylation and ATF4 expression. In concert with heterodimerization partners, ATF4 activates specific genes via a CCAAT-enhancer binding protein-activating transcription factor response element (CARE). This review outlines the ATF4-dependent transcriptional mechanisms associated with the AAR, focusing on progress during the past 5 years. Recent evidence suggests that maternal nutrient deprivation not only has immediate metabolic effects on the fetus, but also triggers gene expression changes in adulthood, possibly through epigenetic mechanisms. Therefore, understanding the transcriptional programs initiated by amino acid limitation is crucial and timely.
Collapse
Affiliation(s)
- Michael S Kilberg
- Department of Biochemistry and Molecular Biology, Box 100245, University of Florida, Gainesville, Florida 32610-0245, USA.
| | | | | |
Collapse
|
34
|
Stow LR, Gumz ML, Lynch IJ, Greenlee MM, Rudin A, Cain BD, Wingo CS. Aldosterone modulates steroid receptor binding to the endothelin-1 gene (edn1). J Biol Chem 2009; 284:30087-96. [PMID: 19638349 DOI: 10.1074/jbc.m109.030718] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aldosterone and endothelin-1 (ET-1) act on collecting duct cells of the kidney and are important regulators of renal sodium transport and cardiovascular physiology. We recently identified the ET-1 gene (edn1) as a novel aldosterone-induced transcript. However, aldosterone action on edn1 has not been characterized at the present time. In this report, we show that aldosterone stimulated edn1 mRNA in acutely isolated rat inner medullary collecting duct cells ex vivo and ET-1 peptide in rat inner medulla in vivo. Aldosterone induction of edn1 mRNA occurred in cortical, outer medullary, and inner medullary collecting duct cells in vitro. Inspection of the edn1 promoter revealed two putative hormone response elements. Levels of heterogeneous nuclear RNA synthesis demonstrated that edn1 mRNA stimulation occurred at the level of transcription. RNA knockdowns corroborated pharmacological studies and demonstrated both mineralocorticoid receptor and glucocorticoid receptor participated in this response. Aldosterone resulted in dose-dependent nuclear translocation and binding of mineralocorticoid receptor and glucocorticoid receptor to the edn1 hormone response elements. Hormone receptors mediated the association of chromatin remodeling complexes, histone modification, and RNA polymerase II at the edn1 promoter. Direct interaction between aldosterone and ET-1 has important implications for renal and cardiovascular function.
Collapse
Affiliation(s)
- Lisa R Stow
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida 32610, USA
| | | | | | | | | | | | | |
Collapse
|
35
|
Su N, Thiaville MM, Awad K, Gjymishka A, Brant JO, Yang TP, Kilberg MS. Protein or amino acid deprivation differentially regulates the hepatic forkhead box protein A (FOXA) genes through an activating transcription factor-4-independent pathway. Hepatology 2009; 50:282-90. [PMID: 19415718 PMCID: PMC3594789 DOI: 10.1002/hep.22971] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The FOXA (forkhead box A) proteins (FOXA1, FOXA2, and FOXA3) play a critical role in the development of the liver, and they also regulate metabolism in adult hepatic tissue. The liver responds to changes in nutrient availability by initiating a number of stress signaling pathways. The present studies demonstrated that in mouse dams fed a low-protein diet hepatic expression of FOXA2 and FOXA3 messenger RNA, but not FOXA1, was induced. Conversely, fetal liver did not exhibit this regulation. Amino acid deprivation of HepG2 hepatoma cells also enhanced transcription from the FOXA2 and FOXA3 genes. In contrast, endoplasmic reticulum stress inhibited the expression of FOXA1, only slightly induced FOXA2, and had no effect on FOXA3. The FOXA2 and FOXA3 messenger RNA induction by amino acid deprivation did not require activating transcription factor 4, a critical component of the conventional amino acid response (AAR) pathway, but their induction was partially dependent on CCAAT/enhancer-binding protein beta. Simultaneous knockdown of both FOXA2 and FOXA3 by small interfering RNA did not affect the activation of other amino acid responsive genes, suggesting that the FOXA proteins are not required for the known AAR pathway. Collectively, the results document that the hepatic FOXA family of genes are differentially regulated by amino acid availability.
Collapse
Affiliation(s)
- Nan Su
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, FL 32610-0245, USA
| | | | | | | | | | | | | |
Collapse
|
36
|
Shan J, Ord D, Ord T, Kilberg MS. Elevated ATF4 expression, in the absence of other signals, is sufficient for transcriptional induction via CCAAT enhancer-binding protein-activating transcription factor response elements. J Biol Chem 2009; 284:21241-8. [PMID: 19509279 DOI: 10.1074/jbc.m109.011338] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein limitation in vivo or amino acid deprivation of cells in culture causes a signal transduction cascade consisting of activation of the kinase GCN2 (general control nonderepressible 2), phosphorylation of eukaryotic initiation factor 2, and increased synthesis of activating transcription factor (ATF) 4 by a translational control mechanism. In a self-limiting transcriptional program, ATF4 transiently activates a wide range of downstream target genes involved in transport, cellular metabolism, and other cell functions. Simultaneous activation of other signal transduction pathways by amino acid deprivation led to the question of whether or not the increased abundance of ATF4 alone was sufficient to trigger the transcriptional control mechanisms. Using 293 cells that ectopically express ATF4 in a tetracycline-inducible manner showed that ATF4 target genes were activated in the absence of amino acid deprivation. Ectopic expression of ATF4 alone resulted in effective recruitment of the general transcription machinery, but some reduction in histone modification was observed. These data document that ATF4 alone is sufficient to trigger the amino acid-responsive transcriptional control program. However, the absolute amount of ectopic ATF4 required to achieve the same degree of transcriptional activation observed after amino acid limitation was greater, suggesting that other factors may serve to enhance ATF4 function.
Collapse
Affiliation(s)
- Jixiu Shan
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida, USA
| | | | | | | |
Collapse
|
37
|
Du K, Ding J. Insulin regulates TRB3 and other stress-responsive gene expression through induction of C/EBPbeta. Mol Endocrinol 2009; 23:475-85. [PMID: 19164449 DOI: 10.1210/me.2008-0284] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Pseudokinase TRB3 is an inducible gene whose expression is regulated by stress response and insulin and associated with insulin resistance and metabolic syndrome. In this report, we have investigated the mechanism under which insulin regulates TRB3 gene expression and demonstrated that insulin induces TRB3 expression via C/EBPbeta. We found that in Fao hepatoma and 3T3-L1 adipocytes, C/EBPbeta expression induced by insulin preceded that of TRB3 and that mutation of the C/EBPbeta binding site in TRB3 promoter abolished the responsiveness of the TRB3 gene to insulin. We further showed that ectopic expression of C/EBPbeta augmented, whereas knockdown of C/EBPbeta reduced, TRB3 expression induced by insulin. In addition, we presented data to show that insulin, through a similar mechanism under which insulin induces TRB3 expression, promotes the expression of genes such as ANAS, ATF3, BIP, and CHOP, which are typical stress-responsive genes. We also examined the impact of C/EBPbeta expression on Akt activation and found that inaction of C/EBPbeta not only augmented Akt activation but also obliterated the suppression of Akt activation due to prolonged insulin stimulation. We suggest, through induction of C/EBPbeta in hepatic cells and adipocytes, that insulin induces the expression of stress-responsive genes, which may represent a novel insulin action.
Collapse
Affiliation(s)
- Keyong Du
- Molecular Oncology Research Institute, Tufts Medical Center, Boston, Massachusetts 02111, USA.
| | | |
Collapse
|
38
|
Su N, Kilberg MS. C/EBP homology protein (CHOP) interacts with activating transcription factor 4 (ATF4) and negatively regulates the stress-dependent induction of the asparagine synthetase gene. J Biol Chem 2008; 283:35106-17. [PMID: 18940792 DOI: 10.1074/jbc.m806874200] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C/EBP homology protein (CHOP), a stress-induced transcription factor, is involved in transcriptional regulation, cell cycle, and apoptosis. The present studies identified CHOP as an interacting partner of activating transcription factor (ATF) 4 in a yeast two-hybrid screen and confirmed their interaction in HEK293T cells. CHOP protein levels rose modestly and transiently during amino acid deprivation, whereas endoplasmic reticulum stress caused a much higher and sustained expression of CHOP protein. Exogenous CHOP expression enhanced the TRB3 gene induction by amino acid deprivation. Conversely, CHOP suppressed the induction of the endogenous asparagine synthetase (ASNS) gene and inhibited transcription from a reporter gene driven by the ASNS promoter following activation by ATF4 or amino acid deprivation. Short interfering RNA-mediated knockdown of CHOP further enhanced the induction of ASNS by either amino acid deprivation or endoplasmic reticulum stress. The CHOP-dependent repression of the ASNS gene required the entire CHOP protein, arguing against the possibility of simple sequestration of ATF4 by the CHOP leucine zipper domain, and chromatin immunoprecipitation analysis showed association of CHOP with the ASNS and TRB3 promoters. Interestingly, chromatin immunoprecipitation also showed that CHOP was associated with the C/EBP-ATF composite site regions of the SNAT2, VEGF, and CAT-1 genes, despite no significant effect on their expression after exogenous CHOP overexpression. Collectively, the results document that CHOP is a member of the transcription factor network that controls the stress-induced regulation of specific C/EBP-ATF-containing genes, such as ASNS.
Collapse
Affiliation(s)
- Nan Su
- Department of Biochemistry and Molecular Biology, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610, USA
| | | |
Collapse
|
39
|
Gjymishka A, Palii SS, Shan J, Kilberg MS. Despite increased ATF4 binding at the C/EBP-ATF composite site following activation of the unfolded protein response, system A transporter 2 (SNAT2) transcription activity is repressed in HepG2 cells. J Biol Chem 2008; 283:27736-27747. [PMID: 18697751 PMCID: PMC2562058 DOI: 10.1074/jbc.m803781200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/16/2008] [Indexed: 12/20/2022] Open
Abstract
The activated amino acid response (AAR) and unfolded protein response (UPR) stress signaling pathways converge at the phosphorylation of translation initiation factor eIF2alpha. This eIF2alpha modification suppresses global protein synthesis but enhances translation of selected mRNAs such as that for activating transcription factor 4 (ATF4). An ATF4 target gene, SNAT2 (system A sodium-dependent neutral amino acid transporter 2), contains a C/EBP-ATF site that binds ATF4 and triggers increased transcription during the AAR. However, the present studies show that despite increased ATF4 binding to the SNAT2 gene during UPR activation in HepG2 human hepatoma cells, transcription activity was not enhanced. Hyperacetylation of histone H3 and recruitment of the general transcription factors at the HepG2 SNAT2 promoter occurred in response to the AAR but not the UPR. In contrast, the UPR did enhance transcription from a plasmid-based reporter gene driven by a SNAT2 genomic fragment containing the C/EBP-ATF site. Simultaneous activation of the AAR and the UPR pathways revealed that the UPR actually suppressed the increased SNAT2 transcription by the AAR pathway, demonstrating that the UPR pathway generates a repressive signal that acts downstream of ATF4 binding.
Collapse
Affiliation(s)
- Altin Gjymishka
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Stela S Palii
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Jixiu Shan
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610
| | - Michael S Kilberg
- Department of Biochemistry and Molecular Biology, Genetics Institute, Shands Cancer Center and Center for Nutritional Sciences, University of Florida College of Medicine, Gainesville, Florida 32610.
| |
Collapse
|
40
|
Li Y, Bevilacqua E, Chiribau CB, Majumder M, Wang C, Croniger CM, Snider MD, Johnson PF, Hatzoglou M. Differential control of the CCAAT/enhancer-binding protein beta (C/EBPbeta) products liver-enriched transcriptional activating protein (LAP) and liver-enriched transcriptional inhibitory protein (LIP) and the regulation of gene expression during the response to endoplasmic reticulum stress. J Biol Chem 2008; 283:22443-56. [PMID: 18550528 DOI: 10.1074/jbc.m801046200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The accumulation of unfolded proteins in the endoplasmic reticulum (ER) triggers a stress response program that protects cells early in the response and can lead to apoptosis during prolonged stress. The basic leucine zipper transcription factor, CCAAT/enhancer-binding protein beta (C/EBPbeta), is one of the genes with increased expression during ER stress. Translation of the C/EBPbeta mRNA from different initiation codons leads to the synthesis of two transcriptional activators (LAP-1 and -2) and a transcriptional repressor (LIP). The LIP/LAP ratio is a critical factor in C/EBPbeta-mediated gene transcription. It is shown here that the LIP/LAP ratio decreased by 5-fold during the early phase of ER stress and increased by 20-fold during the late phase, mostly because of changes in LIP levels. The early decrease in LIP required degradation via the proteasome pathway and phosphorylation of the translation initiation factor, eIF2alpha. The increased LIP levels during the late phase were due to increased synthesis and increased stability of the protein. It is proposed that regulation of synthesis and degradation rates during ER stress controls the LIP/LAP ratio. The importance of C/EBPbeta in the ER-stress response program was demonstrated using C/EBPbeta-deficient mouse embryonic fibroblasts. It is shown that C/EBPbeta attenuates expression of pro-survival ATF4 target genes in late ER stress and enhances expression of cell death-associated genes downstream of CHOP. The inhibitory effect of LIP on ATF4-induced transcription was demonstrated for the cat-1 amino acid transporter gene. We conclude that regulation of LIP/LAP ratios during ER stress is a novel mechanism for modulating the cellular stress response.
Collapse
Affiliation(s)
- Yi Li
- Department of Nutrition, School of Medicine, Case Western University, Cleveland, Ohio 44106-4954, USA
| | | | | | | | | | | | | | | | | |
Collapse
|