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Nuclear Factor of Activated T Cells-5 Regulates Notochord Lumenogenesis in Chordate Larval Development. Int J Mol Sci 2022; 23:ijms232214407. [PMID: 36430885 PMCID: PMC9698811 DOI: 10.3390/ijms232214407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 11/22/2022] Open
Abstract
Osmoregulation is essential for organisms to adapt to the exterior environment and plays an important role in embryonic organogenesis. Tubular organ formation usually involves a hyperosmotic lumen environment. The mechanisms of how the cells respond and regulate lumen formation remain largely unknown. Here, we reported that the nuclear factor of activated T cells-5 (NFAT5), the only transcription factor in the NFAT family involved in the cellular responses to hypertonic stress, regulated notochord lumen formation in chordate Ciona. Ciona NFAT5 (Ci-NFAT5) was expressed in notochord, and its expression level increased during notochord lumen formation and expansion. Knockout and expression of the dominant negative of NFAT5 in Ciona embryos resulted in the failure of notochord lumen expansion. We further demonstrated that the Ci-NFAT5 transferred from the cytoplasm into nuclei in HeLa cells under the hyperosmotic medium, indicating Ci-NFAT5 can respond the hypertonicity. To reveal the underly mechanisms, we predicted potential downstream genes of Ci-NFAT5 and further validated Ci-NFAT5-interacted genes by the luciferase assay. The results showed that Ci-NFAT5 promoted SLC26A6 expression. Furthermore, expression of a transport inactivity mutant of SLC26A6 (L421P) in notochord led to the failure of lumen expansion, phenocopying that of Ci-NFAT5 knockout. These results suggest that Ci-NFAT5 regulates notochord lumen expansion via the SLC26A6 axis. Taken together, our results reveal that the chordate NFAT5 responds to hypertonic stress and regulates lumen osmotic pressure via an ion channel pathway on luminal organ formation.
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Koç Ş. A possible follow-up method for diabetic heart failure patients. Int J Clin Pract 2021; 75:e14794. [PMID: 34482595 DOI: 10.1111/ijcp.14794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/02/2021] [Indexed: 11/30/2022] Open
Abstract
INTRODUCTION Plasma osmolarity is maintained through various mechanisms. The osmolarity of the aqueous humor around the crystalline lens is correlated with plasma osmolarity. A vacuole can be formed in the lens upon changes in osmolarity. The sodium-glucose cotransporter 2 inhibitors (SGLT2i) are new in the treatment of heart failure. They can cause osmotic diuresis but do not affect plasma osmolarity. OBJECTIVE It is unclear if the presence or absence of lens vacuole changes can monitor diabetic heart failure and SGLT2i treatment efficacy. METHODS Web of Science, PubMed and Scopus databases were searched for relevant articles about osmolarity, diabetes, transient receptor potential vanilloid channel, diabetic heart failure, lens vacuoles up to May 2021. MAIN MESSAGE The effect of SGLT2i on osmosis underlies its benefit to heart failure, but this in turn affects many other mechanisms. Failure to experience osmolarity changes will reduce the negative changes in terms of heart failure affected by osmolarity. A practical observable method is needed. CONCLUSIONS There is a possibility of using lens vacuoles in the follow-up of diabetic heart failure patients.
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Affiliation(s)
- Şahbender Koç
- University of Health Sciences, Keçiören Education and Training Hospital, Ankara, Turkey
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Cen L, Xing F, Xu L, Cao Y. Potential Role of Gene Regulator NFAT5 in the Pathogenesis of Diabetes Mellitus. J Diabetes Res 2020; 2020:6927429. [PMID: 33015193 PMCID: PMC7512074 DOI: 10.1155/2020/6927429] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 07/15/2020] [Accepted: 08/31/2020] [Indexed: 02/05/2023] Open
Abstract
Nuclear factor of activated T cells 5 (NFAT5), a Rel/nuclear factor- (NF-) κB family member, is the only known gene regulator of the mammalian adaptive response to osmotic stress. Exposure to elevated glucose increases the expression and nuclear translocation of NFAT5, as well as NFAT5-driven transcriptional activity in vivo and in vitro. Increased expression of NFAT5 is closely correlated with the progression of diabetes in patients. The distinct structure of NFAT5 governs its physiological and pathogenic roles, indicating its opposing functions. The ability of NFAT5 to maintain cell homeostasis and proliferation is impaired in patients with diabetes. NFAT5 promotes the formation of aldose reductase, pathogenesis of diabetic vascular complications, and insulin resistance. Additionally, NFAT5 activates inflammation at a very early stage of diabetes and induces persistent inflammation. Recent studies revealed that NFAT5 is an effective therapeutic target for diabetes. Here, we describe the current knowledge about NFAT5 and its relationship with diabetes, focusing on its diverse regulatory functions, and highlight the importance of this protein as a potential therapeutic target in patients with diabetes.
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Affiliation(s)
- Lusha Cen
- Department of Ophthalmology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Fengling Xing
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, China
| | - Liying Xu
- Department of Emergency, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Yi Cao
- Department of Dermatology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Youdian Rd. 54th, Hangzhou 310006, China
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Dayang W, Dongbo P. Osmolyte taurine induction in UVA exposed human retinal pigment epithelial cells. Cutan Ocul Toxicol 2018; 37:338-343. [PMID: 29658345 DOI: 10.1080/15569527.2018.1465078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
AIM To explore the osmolytes expression in ultraviolet (UVA) stressed human retinal pigment epithelial cells. METHODS Osmolyte transporters and vascular endothelial growth factor (VEGF) messenger RNA (mRNA) were determined by real time polymerase chain reaction (PCR). Osmolyte uptake was measured by radioimmunoassay. VEGF concentrations were determined by immunoassay and enzyme-linked immunosorbent assay (ELISA). Osmolyte taurine transporter (TAUT) were silenced by siRNA technology. RESULTS Hypertonicity accelerated osmolyte betaine uptake, myoinositol uptake, and taurine uptake, compared to normotonic stress. UVA irradiation also accelerated osmolyte transporters expression and osmolytes uptake. Especially, osmolyte taurine remarkably inhibited VEGF release induced by UVA irradiation. VEGF in the UVA stressed retinal pigment epithelial cell supernatant was accumulated slow after taurine preincubation. VEGF expression increased significantly in UVA-stressed cells after TAUT silencing. Moreover, taurine reduced the VEGF level in human ocular aqueous humor. CONCLUSION The inhibition of VEGF by osmolyte taurine plays the crucial role in retina adaption to UVA irradiation.
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Affiliation(s)
- Wu Dayang
- a Department of Ophthalmology , The First Affiliated Hospital of Jinzhou Medical University , Jinzhou , P.R. China
| | - Pang Dongbo
- a Department of Ophthalmology , The First Affiliated Hospital of Jinzhou Medical University , Jinzhou , P.R. China
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Dayang W, Dongbo P. Taurine reduces blue light-induced retinal neuronal cell apoptosis in vitro. Cutan Ocul Toxicol 2018; 37:240-244. [PMID: 29417844 DOI: 10.1080/15569527.2018.1434665] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND The massive uptake of organic compatible osmolytes is a self-protective response to multiple stressors. OBJECTIVE This study aimed to determine the protective effects of the osmolyte taurine against blue light-induced apoptosis in retinal neuronal cells in vitro. METHODS Real-time PCR was used to measure osmolyte transport. Radioimmunoassays were performed to measure osmolyte uptake. Cell Counting Kit-8 assays were conducted to measure cellular viability. Flow cytometry analysis was used to measure apoptosis. RESULTS Compared with normotonic stress, hypertonic stress-induced uptake of osmolytes, including betaine, myoinositol, and taurine, into the retinal neuronal cells. Blue light increased osmolyte transporter mRNA expression together with osmolyte uptake. Furthermore, taurine significantly suppressed blue light-induced retinal neuronal cell apoptosis. CONCLUSION The compatible osmolyte taurine may have an important role in cell resistance to blue light and cell survival.
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Affiliation(s)
- Wu Dayang
- a Department of Ophthalmology , The First Affiliated Hospital of Jinzhou Medical University , Jinzhou , PR China
| | - Pang Dongbo
- a Department of Ophthalmology , The First Affiliated Hospital of Jinzhou Medical University , Jinzhou , PR China
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Dayang W, Dongbo P. Taurine Protects Lens Epithelial Cells Against Ultraviolet B-Induced Apoptosis. Curr Eye Res 2017; 42:1407-1411. [PMID: 28708005 DOI: 10.1080/02713683.2016.1255759] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Wu Dayang
- Department of Ophthalmology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, P.R. China
| | - Pang Dongbo
- Department of Ophthalmology, The First Affiliated Hospital of Jinzhou Medical University, Jinzhou, P.R. China
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Chung I, Hah YS, Ju S, Kim JH, Yoo WS, Cho HY, Yoo JM, Seo SW, Choi WS, Kim SJ. Ultraviolet B Radiation Stimulates the Interaction between Nuclear Factor of Activated T Cells 5 (NFAT5) and Nuclear Factor-Kappa B (NF-κB) in Human Lens Epithelial Cells. Curr Eye Res 2017. [PMID: 28632030 DOI: 10.1080/02713683.2016.1270327] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
PURPOSE Nuclear factor-kappa B (NF-κB) has been proposed as a therapeutic target for the treatment of cataracts. The authors investigated the relationship between nuclear factor of activated T cells 5 (NFAT5) and NF-κB in ultraviolet B (UVB)-irradiated human lens epithelial (HLE) cells. METHODS Human lens epithelial B-3 (HLE-B3) cells were exposed to UVB light at a dose of 10 mJ/cm2 and then incubated for 24 h. Cell viability was assessed by using the Cell Counting Kit-8 (CCK-8) assay. Gene expression level of NFAT5 was determined using real-time quantitative polymerase chain reaction (qPCR). Protein expression levels of NFAT5, NF-κB p65, and α-smooth muscle actin (α-SMA) and the association of NFAT5 with the NF-κB p65 subunit were measured by Western blot analysis and a co-immunoprecipitation assay, respectively. The cellular distribution of NFAT5 and NF-κB p65 was examined by triple immunofluorescence staining. RESULTS At 24 h after UVB exposure, cell viability significantly decreased in a dose-dependent manner, and UVB light (15 and 20 mJ/cm2) significantly increased the ROS generation. UVB irradiation increased NFAT5 mRNA and protein levels and increased phosphorylation of NF-κB in HLE-B3 cells. α-SMA protein levels were increased in the irradiated cells. In addition, NFAT5 and NF-κB translocated from the cytoplasm to the nucleus, and binding between the p65 subunit and NFAT5 was increased. CONCLUSIONS Exposure to UVB radiation induces nuclear translocation and stimulates binding between NFAT5 and NF-κB proteins in HLE-B3 cells. These interactions may form part of the biochemical mechanism of cataractogenesis in UVB-irradiated HLECs.
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Affiliation(s)
- Inyoung Chung
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Young-Sool Hah
- b Biomedical Research Institute , Gyeongsang National University Hospital, Institute of Health Sciences , Jinju , Korea
| | - SunMi Ju
- c Division of Pulmonology and Allergy, Department of Internal Medicine , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Ji-Hye Kim
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Woong-Sun Yoo
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Hee-Young Cho
- b Biomedical Research Institute , Gyeongsang National University Hospital, Institute of Health Sciences , Jinju , Korea
| | - Ji-Myong Yoo
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Seong-Wook Seo
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
| | - Wan-Sung Choi
- d Department of Anatomy and Neurobiology, Institute of Health Sciences , Gyeongsang National University School of Medicine , Jinju , Korea
| | - Seong-Jae Kim
- a Department of Ophthalmology, Institute of Health Sciences , Gyeongsang National University School of Medicine, Gyeongsang National University Hospital , Jinju , Korea
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Zhang Y, Zhang X, Lu H. Aberrant activation of p53 due to loss of MDM2 or MDMX causes early lens dysmorphogenesis. Dev Biol 2014; 396:19-30. [PMID: 25263199 DOI: 10.1016/j.ydbio.2014.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/10/2014] [Accepted: 09/17/2014] [Indexed: 12/28/2022]
Abstract
Although forming a heterodimer or heterooligomer is essential for MDM2 and MDMX to fully control p53 during early embryogenesis, deletion of either MDM2 or MDMX in specific tissues using the loxp-Cre system reveals phenotypic diversity during organ morphogenesis, which can be completely rescued by loss of p53, suggesting the spatiotemporal independence and specificity of the regulation of p53 by MDM2 and MDMX. In this study, we investigated the role of the MDM2-MDMX-p53 pathway in the developing lens that is a relatively independent region integrating cell proliferation, differentiation and apoptosis. Using the mice expressing Cre recombinase specifically in the lens epithelial cells (LECs) beginning at E9.5, we demonstrated that deletion of either MDM2 or MDMX induces apoptosis of LEC and reduces cell proliferation, resulting in lens developmental defect that finally progresses into aphakia. Specifically, the lens defect caused by MDM2 deletion was evident at E10, occurring earlier than that caused by MDMX deletion. These lens defects were completely rescued by loss of two alleles of p53, but not one allele of p53. These results demonstrate that both MDM2 and MDMX are required for monitoring p53 activity during lens development, and they may function independently or synergistically to control p53 and maintain normal lens morphogenesis.
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Affiliation(s)
- Yiwei Zhang
- Department of Biochemistry & Molecular Biology and Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
| | - Xin Zhang
- Departments of Ophthalmology, Pathology & Cell Biology, Columbia University, 635 W. 165th Street, EI902A, New York, NY 10032, USA
| | - Hua Lu
- Department of Biochemistry & Molecular Biology and Tulane Cancer Center, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
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Dayang W, Jinsong Z. Taurine inhibits interleukin-6 expression and release induced by ultraviolet B exposure to human retinal pigment epithelium cells. Cutan Ocul Toxicol 2014; 34:189-94. [PMID: 25198400 DOI: 10.3109/15569527.2014.944649] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND The massive uptake of compatible osmolytes is a self-protective response shared by retina exposed to hypertonic stress and ultraviolet stress. OBJECTIVE This study aimed to investigate the protective effects of taurine against ultraviolet damage in human retinal pigment epithelium cells. METHODS Real-time PCR, radioimmunoassay, ELISA and immunoassay were used to measure osmolyte uptake and IL-6 expression. RESULTS Compared with normotonic stress, hypertonic stress led to an induction of osmolyte uptake including betaine, myoinositol and taurine. UVB exposure upregulated osmolyte transporter mRNA expression and increased osmolyte uptake respectively. Especially, taurine suppressed UVB-induced IL-6 mRNA expression significantly. The accumulation of IL-6 in UVB-exposed human retinal pigment epithelial cells supernatant was much slower when the cells were preincubated with taurine. Moreover, taurine suppressed IL-6 concentration in aqueous humour. CONCLUSION The effect of compatible osmolyte taurine on IL-6 expression and release may play an important role in cell resistance and adaption to UVB exposure.
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Affiliation(s)
- Wu Dayang
- Department of Ophthalmology, The First Affiliated Hospital of Liaoning Medical University , Jinzhou , P.R. China and
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10
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Identification and characterization of FGF2-dependent mRNA: microRNA networks during lens fiber cell differentiation. G3-GENES GENOMES GENETICS 2013; 3:2239-55. [PMID: 24142921 PMCID: PMC3852386 DOI: 10.1534/g3.113.008698] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
MicroRNAs (miRNAs) and fibroblast growth factor (FGF) signaling regulate a wide range of cellular functions, including cell specification, proliferation, migration, differentiation, and survival. In lens, both these systems control lens fiber cell differentiation; however, a possible link between these processes remains to be examined. Herein, the functional requirement for miRNAs in differentiating lens fiber cells was demonstrated via conditional inactivation of Dicer1 in mouse (Mus musculus) lens. To dissect the miRNA-dependent pathways during lens differentiation, we used a rat (Rattus norvegicus) lens epithelial explant system, induced by FGF2 to differentiate, followed by mRNA and miRNA expression profiling. Transcriptome and miRNome analysis identified extensive FGF2-regulated cellular responses that were both independent and dependent on miRNAs. We identified 131 FGF2-regulated miRNAs. Seventy-six of these miRNAs had at least two in silico predicted and inversely regulated target mRNAs. Genes modulated by the greatest number of FGF-regulated miRNAs include DNA-binding transcription factors Nfib, Nfat5/OREBP, c-Maf, Ets1, and N-Myc. Activated FGF signaling influenced bone morphogenetic factor/transforming growth factor-β, Notch, and Wnt signaling cascades implicated earlier in lens differentiation. Specific miRNA:mRNA interaction networks were predicted for c-Maf, N-Myc, and Nfib (DNA-binding transcription factors); Cnot6, Cpsf6, Dicer1, and Tnrc6b (RNA to miRNA processing); and Ash1l, Med1/PBP, and Kdm5b/Jarid1b/Plu1 (chromatin remodeling). Three miRNAs, including miR-143, miR-155, and miR-301a, down-regulated expression of c-Maf in the 3′-UTR luciferase reporter assays. These present studies demonstrate for the first time global impact of activated FGF signaling in lens cell culture system and predicted novel gene regulatory networks connected by multiple miRNAs that regulate lens differentiation.
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Wang Q, Zhou Y, Rychahou P, Liu C, Weiss HL, Evers BM. NFAT5 represses canonical Wnt signaling via inhibition of β-catenin acetylation and participates in regulating intestinal cell differentiation. Cell Death Dis 2013; 4:e671. [PMID: 23764852 PMCID: PMC3702276 DOI: 10.1038/cddis.2013.202] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 05/07/2013] [Accepted: 05/08/2013] [Indexed: 01/05/2023]
Abstract
The intestinal mucosa undergoes a continual process of proliferation, differentiation, and apoptosis, which is regulated by multiple signaling pathways. The Wnt/β-catenin pathway has a critical role in this process. Previously, we have shown that the calcineurin-dependent nuclear factor of activated T cell (NFAT) is involved in the regulation of intestinal cell differentiation, as noted by the alteration of brush-border enzyme intestinal alkaline phosphatase (IAP) activity. Here, we show that calcineurin-independent NFAT5 interacts with β-catenin to repress Wnt signaling. We found that overexpression of NFAT5 inhibits, whereas knockdown of NFAT5 increases, TOPflash reporter activity and the expression of Wnt/β-catenin target genes, suggesting that NFAT5 inhibits Wnt signaling. In addition, we demonstrated that NFAT5 directly interacts with the C-terminal transactivation domain (TAD) of β-catenin, inhibits CBP interaction with β-catenin, and inhibits CBP-mediated β-catenin acetylation. Moreover, NFAT5 is expressed in the mucosa of human intestine, with the most pronounced staining in the most differentiated region near the epithelial surface. Knockdown of NFAT5 attenuated sodium butyrate (NaBT)-mediated induction of IAP and sucrase activities; overexpression of NFAT5 induced IAP promoter activity. In summary, we provide evidence showing that NFAT5 is a regulator of Wnt signaling. Importantly, our results suggest that NFAT5 regulation of intestinal cell differentiation may be through inhibition of Wnt/β-catenin signaling.
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Affiliation(s)
- Q Wang
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
| | - Y Zhou
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
| | - P Rychahou
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
| | - C Liu
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - H L Weiss
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Department of Surgery, University of Kentucky, Lexington, KY, USA
- Department of Biostatistics, University of Kentucky, Lexington, KY, USA
| | - B M Evers
- Department of Surgery, Markey Cancer Center, University of Kentucky, Lexington, KY, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY, USA
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Embryonic lethality in mice lacking the nuclear factor of activated T cells 5 protein due to impaired cardiac development and function. PLoS One 2011; 6:e19186. [PMID: 21765887 PMCID: PMC3134469 DOI: 10.1371/journal.pone.0019186] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Accepted: 03/22/2011] [Indexed: 12/29/2022] Open
Abstract
Nuclear factor of activated T cells 5 protein (NFAT5) is thought to be important for cellular adaptation to osmotic stress by regulating the transcription of genes responsible for the synthesis or transport of organic osmolytes. It is also thought to play a role in immune function, myogenesis and cancer invasion. To better understand the function of NFAT5, we developed NFAT5 gene knockout mice. Homozygous NFAT5 null (NFAT5−/−) mouse embryos failed to develop normally and died after 14.5 days of embryonic development (E14.5). The embryos showed peripheral edema, and abnormal heart development as indicated by thinner ventricular wall and reduced cell density at the compact and trabecular areas of myocardium. This is associated with reduced level of proliferating cell nuclear antigen and increased caspase-3 in these tissues. Cardiomyocytes from E14.5 NFAT5−/− embryos showed a significant reduction of beating rate and abnormal Ca2+ signaling profile as a consequence of reduced sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and ryanodine receptor (RyR) expressions. Expression of NFAT5 target genes, such as HSP 70 and SMIT were reduced in NFAT5−/− cardiomyocytes. Our findings demonstrated an essential role of NFAT5 in cardiac development and Ca2+ signaling. Cardiac failure is most likely responsible for the peripheral edema and death of NFAT5−/− embryos at E14.5 days.
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José-Edwards DS, Kerner P, Kugler JE, Deng W, Jiang D, Di Gregorio A. The identification of transcription factors expressed in the notochord of Ciona intestinalis adds new potential players to the brachyury gene regulatory network. Dev Dyn 2011; 240:1793-805. [PMID: 21594950 PMCID: PMC3685856 DOI: 10.1002/dvdy.22656] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2011] [Indexed: 11/07/2022] Open
Abstract
The notochord is the distinctive characteristic of chordates; however, the knowledge of the complement of transcription factors governing the development of this structure is still incomplete. Here we present the expression patterns of seven transcription factor genes detected in the notochord of the ascidian Ciona intestinalis at various stages of embryonic development. Four of these transcription factors, Fos-a, NFAT5, AFF and Klf15, have not been directly associated with the notochord in previous studies, while the others, including Spalt-like-a, Lmx-like, and STAT5/6-b, display evolutionarily conserved expression in this structure as well as in other domains. We examined the hierarchical relationships between these genes and the transcription factor Brachyury, which is necessary for notochord development in all chordates. We found that Ciona Brachyury regulates the expression of most, although not all, of these genes. These results shed light on the genetic regulatory program underlying notochord formation in Ciona and possibly other chordates.
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Affiliation(s)
- Diana S. José-Edwards
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, Box 60, New York, NY 10065, U.S.A
| | - Pierre Kerner
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, Box 60, New York, NY 10065, U.S.A
| | - Jamie E. Kugler
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, Box 60, New York, NY 10065, U.S.A
| | - Wei Deng
- Sars International Centre for Marine Molecular Biology, Thormøhlensgt. 55, N-5008 Bergen, Norway
| | - Di Jiang
- Sars International Centre for Marine Molecular Biology, Thormøhlensgt. 55, N-5008 Bergen, Norway
| | - Anna Di Gregorio
- Department of Cell and Developmental Biology, Weill Medical College of Cornell University, 1300 York Avenue, Box 60, New York, NY 10065, U.S.A
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Wang WL, Li Q, Xu J, Cvekl A. Lens fiber cell differentiation and denucleation are disrupted through expression of the N-terminal nuclear receptor box of NCOA6 and result in p53-dependent and p53-independent apoptosis. Mol Biol Cell 2010; 21:2453-68. [PMID: 20484573 PMCID: PMC2903674 DOI: 10.1091/mbc.e09-12-1031] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Nuclear receptor coactivator 6 (NCOA6) is a multifunctional protein implicated in embryonic development, cell survival, and homeostasis. An 81-amino acid fragment, dnNCOA6, containing the N-terminal nuclear receptor box (LXXLL motif) of NCOA6, acts as a dominant-negative (dn) inhibitor of NCOA6. Here, we expressed dnNCOA6 in postmitotic transgenic mouse lens fiber cells. The transgenic lenses showed reduced growth; a wide spectrum of lens fiber cell differentiation defects, including reduced expression of gamma-crystallins; and cataract formation. Those lens fiber cells entered an alternate proapoptotic pathway, and the denucleation (karyolysis) process was stalled. Activation of caspase-3 at embryonic day (E)13.5 was followed by double-strand breaks (DSBs) formation monitored via a biomarker, gamma-H2AX. Intense terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) signals were found at E16.5. Thus, a window of approximately 72 h between these events suggested prolonged though incomplete apoptosis in the lens fiber cell compartment that preserved nuclei in its cells. Genetic experiments showed that the apoptotic-like processes in the transgenic lens were both p53-dependent and p53-independent. Lens-specific deletion of Ncoa6 also resulted in disrupted lens fiber cell differentiation. Our data demonstrate a cell-autonomous role of Ncoa6 in lens fiber cell differentiation and suggest novel insights into the process of lens fiber cell denucleation and apoptosis.
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Affiliation(s)
- Wei-Lin Wang
- Department of Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Tong EHY, Guo JJ, Xu SX, Mak K, Chung SK, Chung SSM, Huang AL, Ko BCB. Inducible nucleosome depletion at OREBP-binding-sites by hypertonic stress. PLoS One 2009; 4:e8435. [PMID: 20041176 PMCID: PMC2793017 DOI: 10.1371/journal.pone.0008435] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 11/22/2009] [Indexed: 01/01/2023] Open
Abstract
Background Osmotic Response Element-Binding Protein (OREBP), also known as TonEBP or NFAT5, is a unique transcription factor. It is hitherto the only known mammalian transcription factor that regulates hypertonic stress-induced gene transcription. In addition, unlike other monomeric members of the NFAT family, OREBP exists as a homodimer and it is the only transcription factor known to bind naked DNA targets by complete encirclement in vitro. Nevertheless, how OREBP interacts with target DNA, also known as ORE/TonE, and how it elicits gene transcription in vivo, remains unknown. Methodology Using hypertonic induction of the aldose reductase (AR) gene activation as a model, we showed that OREs contained dynamic nucleosomes. Hypertonic stress induced a rapid and reversible loss of nucleosome(s) around the OREs. The loss of nucleosome(s) was found to be initiated by an OREBP-independent mechanism, but was significantly potentiated in the presence of OREBP. Furthermore, hypertonic induction of AR gene was associated with an OREBP-dependent hyperacetylation of histones that spanned the 5′ upstream sequences and at least some exons of the gene. Nevertheless, nucleosome loss was not regulated by the acetylation status of histone. Significance Our findings offer novel insights into the mechanism of OREBP-dependent transcriptional regulation and provide a basis for understanding how histone eviction and transcription factor recruitment are coupled.
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Affiliation(s)
- Edith H. Y. Tong
- Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Hong Kong, China
- State Key Laboratory in Oncology in South China, The Chinese University of Hong Kong, Hong Kong, China
- Department of Physiology, The University of Hong Kong, Hong Kong, China
| | - Jin-Jun Guo
- Key Laboratory of Molecular Biology on Infectious Diseases, Ministry of Education, Institute of Viral Hepatitis, Chongqing University of Medical Sciences, Chong Qing, China
| | - Song-Xiao Xu
- Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Hong Kong, China
- State Key Laboratory in Oncology in South China, The Chinese University of Hong Kong, Hong Kong, China
| | - Keri Mak
- Department of Anatomy, The University of Hong Kong, Hong Kong, China
| | - Sookja K. Chung
- Department of Anatomy, The University of Hong Kong, Hong Kong, China
| | | | - Ali-Long Huang
- Key Laboratory of Molecular Biology on Infectious Diseases, Ministry of Education, Institute of Viral Hepatitis, Chongqing University of Medical Sciences, Chong Qing, China
| | - Ben C. B. Ko
- Department of Anatomical and Cellular Pathology, The Chinese University of Hong Kong, Hong Kong, China
- State Key Laboratory in Oncology in South China, The Chinese University of Hong Kong, Hong Kong, China
- * E-mail:
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The transcription factor NFAT5 is required for cyclin expression and cell cycle progression in cells exposed to hypertonic stress. PLoS One 2009; 4:e5245. [PMID: 19381288 PMCID: PMC2667631 DOI: 10.1371/journal.pone.0005245] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Accepted: 03/19/2009] [Indexed: 11/20/2022] Open
Abstract
Background Hypertonicity can perturb cellular functions, induce DNA damage-like responses and inhibit proliferation. The transcription factor NFAT5 induces osmoprotective gene products that allow cells to adapt to sustained hypertonic conditions. Although it is known that NFAT5-deficient lymphocytes and renal medullary cells have reduced proliferative capacity and viability under hypertonic stress, less is understood about the contribution of this factor to DNA damage responses and cell cycle regulation. Methodology/Principal Findings We have generated conditional knockout mice to obtain NFAT5−/− T lymphocytes, which we used as a model of proliferating cells to study NFAT5-dependent responses. We show that hypertonicity triggered an early, NFAT5-independent, genotoxic stress-like response with induction of p53, p21 and GADD45, downregulation of cyclins, and cell cycle arrest. This was followed by an NFAT5-dependent adaptive phase in wild-type cells, which induced an osmoprotective gene expression program, downregulated stress markers, resumed cyclin expression and proliferation, and displayed enhanced NFAT5 transcriptional activity in S and G2/M. In contrast, NFAT5−/− cells failed to induce osmoprotective genes and exhibited poorer viability. Although surviving NFAT5−/− cells downregulated genotoxic stress markers, they underwent cell cycle arrest in G1/S and G2/M, which was associated with reduced expression of cyclins E1, A2 and B1. We also show that pathologic hypertonicity levels, as occurring in plasma of patients and animal models of osmoregulatory disorders, inhibited the induction of cyclins and aurora B kinase in response to T cell receptor stimulation in fresh NFAT5−/− lymphocytes. Conclusions/Significance We conclude that NFAT5 facilitates cell proliferation under hypertonic conditions by inducing an osmoadaptive response that enables cells to express fundamental regulators needed for cell cycle progression.
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17
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Ito T, Fujio Y, Schaffer SW, Azuma J. Involvement of transcriptional factor TonEBP in the regulation of the taurine transporter in the cardiomyocyte. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 643:523-32. [PMID: 19239184 DOI: 10.1007/978-0-387-75681-3_54] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Taurine is found in high concentrations in heart where it exerts several actions that could potentially benefit the diseased heart. The taurine transporter (TauT) is crucial for the maintenance of high taurine levels in the heart. Although cardiac taurine content is altered in various pathological conditions, little is known about the regulatory mechanisms governing TauT expression in cardiac myocytes. In the present study, we found that treatment with the antineoplastic drug doxorubicin (DOX), which is also known as a cardiotoxic agent, decreases the expression of the TauT gene in cultured cardiomyocytes isolated from the neonatal rat heart. Based on data obtained using a luciferase assay, DOX significantly reduced transcriptional activity driven by the TauT promoter, while deletion or mutation of a tonicity-response element (TonE) in this promoter eliminated the change of promoter activity. The protein level of the TonE-binding protein (TonEBP) was reduced by DOX treatment. In addition, the reduction in TonEBP protein content was suppressed by proteasome inhibitors. In conclusion, the DOX-enhanced degradation of TonEBP resulting in reduced TauT expression in the cardiomyocyte.
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Affiliation(s)
- Takashi Ito
- Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, Japan.
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18
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Xu S, Wong CCL, Tong EHY, Chung SSM, Yates JR, Yin Y, Ko BCB. Phosphorylation by casein kinase 1 regulates tonicity-induced osmotic response element-binding protein/tonicity enhancer-binding protein nucleocytoplasmic trafficking. J Biol Chem 2008; 283:17624-34. [PMID: 18411282 DOI: 10.1074/jbc.m800281200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The osmotic response element-binding protein (OREBP), also known as tonicity enhancer-binding protein (TonEBP) or NFAT5, is the only known osmo-sensitive transcription factor that mediates cellular adaptations to extracellular hypertonic stress. Although it is well documented that the subcellular localization and transactivation activity of OREBP/TonEBP are tightly regulated by extracellular tonicity, the molecular mechanisms involved remain elusive. Here we show that nucleocytoplasmic trafficking of OREBP/TonEBP is regulated by the dual phosphorylation of Ser-155 and Ser-158. Alanine scanning mutagenesis revealed that Ser-155 is an essential residue that regulates OREBP/TonEBP nucleocytoplasmic trafficking. Tandem mass spectrometry revealed that Ser-155 and Ser-158 of OREBP/TonEBP are both phosphorylated in living cells under hypotonic conditions. In vitro phosphorylation assays further suggest that phosphorylation of the two serine residues proceeds in a hierarchical manner with phosphorylation of Ser-155 priming the phosphorylation of Ser-158 and that these phosphorylations are essential for nucleocytoplasmic trafficking of the transcription factor. Finally, we have shown that the pharmacological inhibition of casein kinase 1 (CK1) abolishes the phosphorylation of Ser-158 and impedes OREBP/TonEBP nuclear export and that recombinant CK1 phosphorylates Ser-158. Knockdown of CK1alpha1L, a novel isoform of CK1, inhibits hypotonicity-induced OREBP/TonEBP nuclear export. Together these data highlight the importance of Ser-155 and Ser-158 in the nucleocytoplasmic trafficking of OREBP/TonEBP and indicate that CK1 plays a major role in regulating this process.
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Affiliation(s)
- SongXiao Xu
- The State Key Laboratory in Oncology in South China, Chinese University of Hong Kong, Hong Kong, China
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19
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Abstract
Cells in the renal inner medulla are normally exposed to extraordinarily high levels of NaCl and urea. The osmotic stress causes numerous perturbations because of the hypertonic effect of high NaCl and the direct denaturation of cellular macromolecules by high urea. High NaCl and urea elevate reactive oxygen species, cause cytoskeletal rearrangement, inhibit DNA replication and transcription, inhibit translation, depolarize mitochondria, and damage DNA and proteins. Nevertheless, cells can accommodate by changes that include accumulation of organic osmolytes and increased expression of heat shock proteins. Failure to accommodate results in cell death by apoptosis. Although the adapted cells survive and function, many of the original perturbations persist, and even contribute to signaling the adaptive responses. This review addresses both the perturbing effects of high NaCl and urea and the adaptive responses. We speculate on the sensors of osmolality and document the multiple pathways that signal activation of the transcription factor TonEBP/OREBP, which directs many aspects of adaptation. The facts that numerous cellular functions are altered by hyperosmolality and remain so, even after adaptation, indicate that both the effects of hyperosmolality and adaptation to it involve profound alterations of the state of the cells.
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Kosuge K, Chuang AI, Uematsu S, Tan KP, Ohashi K, Ko BCB, Ito S. Discovery of Osmosensitive Transcriptional Regulation of Human Cytochrome P450 3As by the Tonicity-Responsive Enhancer Binding Protein (Nuclear Factor of Activated T Cells 5). Mol Pharmacol 2007; 72:826-37. [PMID: 17600221 DOI: 10.1124/mol.107.034504] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We report the discovery of an osmosensitive transcriptional control of human CYP3A4, CYP3A7, and CYP3A5. Ambient hypertonicity (350-450 mOsmol/kg) increased mRNA expressions of the CYP3A by approximately 10- to 20-fold in human-intestinal C(2)bbe1 cells, followed by an increase of CYP3A protein. Hypotonicity, on the other hand, suppressed CYP3A mRNA levels, indicating that physiological isotonic conditions may regulate the basal expression of CYP3A. Similar responses to ambient tonicity were observed in other human-derived cell lines (intestinal LS180 and hepatic HepG2) and human primary colonic cells. The 11-base pair tonicity-responsive enhancer (TonE) is an osmosensitive regulator that is activated by the transcription factor, the nuclear factor of activated T-cells 5 (NFAT5). Luciferase-based reporter assays of 13 consensus TonE motifs within +/-10 kilobases (kb) from the transcription start sites of CYP3A showed that only the CYP3A7 intron 2 region ( approximately 5 kb downstream from the transcription start site), which contains two TonE motifs (+5076/+5086 and + 5417/+5427), was responsive to hypertonicity stimuli. This observation was confirmed upon cotransfection with an NFAT5 expression vector, small interfering RNA, or dominant-negative NFAT5. Deletion and mutation analyses suggested that the TonE (+5417/+5427) is indispensable for the enhancer activity. NFAT5 binding to the CYP3A7 intron 2 TonE motif was demonstrated with electrophoretic mobility shift assay and in a native cell context by chromatin immunoprecipitation. We conclude that transcription of human CYP3A is influenced by ambient tonicity. The physiological significance of the tonic regulation of CYP3A enzymes remains to be determined.
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Affiliation(s)
- Kazuhiro Kosuge
- Division of Clinical Pharmacology and Toxicology, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada
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21
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Ito T, Asakura K, Tougou K, Fukuda T, Kubota R, Nonen S, Fujio Y, Azuma J. Regulation of Cytochrome P450 2E1 under Hypertonic Environment through TonEBP in Human Hepatocytes. Mol Pharmacol 2007; 72:173-81. [PMID: 17440116 DOI: 10.1124/mol.106.033480] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whereas the liver as well as the other organs are continually exposed to the change of osmotic status, it has never been investigated whether activities and gene expressions of drug-metabolizing enzymes, including cytochromes P450, are dependent on osmotic change in the liver. In the present study, we determined that CYP2E1 is induced under hypertonic environments at a transcriptional level in human primary hepatocytes, as assessed by cDNA microarray and real time-reverse transcription-polymerase chain reaction analyses. Both a protein level and the catalytic activity of CYP2E1 were consistently increased in response to hypertonic conditions. In promoter-reporter assay, it was demonstrated that -586 to -566 in the CYP2E1 5'-flanking region was necessary for 2E1 promoter activation by hypertonic stimulation. It is noteworthy that tonicity-response element (TonE) consensus sequence was found at -578 to -568 in human CYP2E1 5'-flanking region, and electrophoretic mobility shift assay demonstrated the interaction of TonE binding protein (TonEBP) with TonE motif of CYP2E1 promoter. Furthermore, cotransfection of a CYP2E1 promoter construct with wild-type TonEBP expression vector enhanced promoter activity under both isotonic and hypertonic conditions, whereas dominant-negative TonEBP suppressed an induction of CYP2E1 promoter activity. These results indicate that the level of CYP2E1 is induced by hypertonic condition via TonEBP transactivation. The present study suggests that osmotic status may influence individual responses to the substrate of CYP2E1.
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Affiliation(s)
- Takashi Ito
- Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka, 565-0871, Japan
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O'Connor RS, Mills ST, Jones KA, Ho SN, Pavlath GK. A combinatorial role for NFAT5 in both myoblast migration and differentiation during skeletal muscle myogenesis. J Cell Sci 2006; 120:149-59. [PMID: 17164296 DOI: 10.1242/jcs.03307] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Skeletal muscle regeneration depends on myoblast migration, differentiation and myofiber formation. Isoforms of the nuclear factor of activated T cells (NFAT) family of transcription factors display nonredundant roles in skeletal muscle. NFAT5, a new isoform of NFAT, displays many differences from NFATc1-c4. Here, we examine the role of NFAT5 in myogenesis. NFAT5+/- mice displayed a defect in muscle regeneration with fewer myofibers formed at early times after injury. NFAT5 has a muscle-intrinsic function because inhibition of NFAT5 transcriptional activity caused both a migratory and differentiation defect in cultured myoblasts. We identified Cyr61 as a target of NFAT5 signaling in skeletal muscle cells. Addition of Cyr61 to cells expressing inhibitory forms of NFAT5 rescued the migratory phenotype. These results demonstrate a role for NFAT5 in skeletal muscle cell migration and differentiation. Furthermore, as cell-cell interactions are crucial for myoblast differentiation, these data suggest that myoblast migration and differentiation are coupled and that NFAT5 is a key regulator.
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Affiliation(s)
- Roddy S O'Connor
- Graduate Program in Molecular and Systems Pharmacology, Emory University, Atlanta, GA 30322, USA
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Ito T, Fujio Y, Takahashi K, Azuma J. Degradation of NFAT5, a transcriptional regulator of osmotic stress-related genes, is a critical event for doxorubicin-induced cytotoxicity in cardiac myocytes. J Biol Chem 2006; 282:1152-60. [PMID: 17105721 DOI: 10.1074/jbc.m609547200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Nuclear factor-activated T cell 5 (NFAT5), a novel member of the NFAT family of proteins, was originally identified as a transcriptional factor responsible for adaptation to hyperosmotic stress. Though NFAT5 is ubiquitously expressed, the biological functions of NFAT5 remain to be clarified, especially in the tissues that are not exposed to hypertonicity, including hearts. In the present study, we focused on the cardioprotective roles of NFAT5 against the cardiotoxic anti-tumor agent doxorubicin (Dox). In cultured cardiomyocytes, transcripts of the hypertonicity-inducible genes, such as taurine transporter (TauT) and sodium/myo-inositol transporter, were down-regulated by Dox. Interestingly, NFAT5 protein, but not mRNA, was decreased in cardiomyocytes exposed to Dox. Treatment of proteasome inhibitors, MG-132 or proteasome-specific inhibitor 1, prevented the Dox-mediated decrease of NFAT5 protein. Further, ubiquitin-conjugated NFAT5 was not detected in cultured cardiomyocytes treated with MG-132 and/or Dox, as assessed by immunoprecipitation assay, suggesting Dox-induced degradation through ubiquitin-independent proteasome pathway. Importantly, inhibition of NFAT5 with overexpression of dominant-negative NFAT5 decreased cell viability and increased creatine kinase leakage into culture medium. Consistently, small interfering RNA targeting NFAT5 gene enhanced myocyte death. These findings suggest that Dox promoted the degradation of NFAT5 protein, reducing cell viability in cardiomyocytes. This is the first demonstration that NFAT5 is a positive regulator of cardiomyocyte survival.
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Affiliation(s)
- Takashi Ito
- Department of Clinical Pharmacology and Pharmacogenomics, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan
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Tsai TT, Danielson KG, Guttapalli A, Oguz E, Albert TJ, Shapiro IM, Risbud MV. TonEBP/OREBP Is a Regulator of Nucleus Pulposus Cell Function and Survival in the Intervertebral Disc. J Biol Chem 2006; 281:25416-24. [PMID: 16772300 DOI: 10.1074/jbc.m601969200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nucleus pulposus is an aggrecan-rich hydrated tissue that permits the intervertebral disc to resist compressive loads. Adaptation to loading is achieved through an elevation in disc osmolarity mediated by the numerous charged glycosoaminoglycan side chains of the aggrecan molecule. The goal of this investigation was to determine the functional role of the osmo-regulatory protein, TonEBP, in cells of the nucleus pulposus. We found that TonEBP and its downstream target genes were robustly expressed in the tissues of the disc. Above 330 mosmol/kg, cultured nucleus pulposus cells up-regulated target genes TauT, BGT-1, and SMIT; above 450 mosmol/kg, there was raised expression of HSP-70. In hypertonic media there was activation of TauT and heat shock protein-70 (HSP-70) reporter activity and increased binding of TonEBP to the TonE motif. When cells were transfected with the dominant-negative form of TonEBP (DN-TonEBP) there was suppression of TauT and HSP-70 reporter gene expression; pTonEBP enhanced reporter gene expression. Moreover, in hypertonic media, forced expression of DN-TonEBP induced apoptosis. We suppressed TonEBP using small interfering RNA technique and noted a decrease in TauT reporter activity in isotonic as well as hyperosmolar media. Finally, we report that the aggrecan promoter contains two conserved TonE motifs. To evaluate the importance of these motifs, we overexpressed DN-TonEBP and partially silenced TonEBP using small interfering RNA. Both approaches resulted in suppression of aggrecan promoter activity. It is concluded that TonEBP permits the disc cells to adapt to the hyperosmotic milieu while autoregulating the expression of molecules that generate the unique extracellular environment.
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Affiliation(s)
- Tsung-Ting Tsai
- Department of Orthopaedic Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Aramburu J, Drews-Elger K, Estrada-Gelonch A, Minguillón J, Morancho B, Santiago V, López-Rodríguez C. Regulation of the hypertonic stress response and other cellular functions by the Rel-like transcription factor NFAT5. Biochem Pharmacol 2006; 72:1597-604. [PMID: 16904650 DOI: 10.1016/j.bcp.2006.07.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Revised: 06/29/2006] [Accepted: 07/08/2006] [Indexed: 11/28/2022]
Abstract
Stress, be it from environmental factors or intrinsic to the cell as result of growth and metabolism, can be harmful to cells. Mammalian cells have developed numerous mechanisms to respond to diverse forms of stress. These mechanisms combine signaling cascades and activation of gene expression programs to orchestrate an adaptive response that will allow the cell to survive and resume its normal functioning. In this review we will focus on the transcription factor NFAT5, a fundamental regulator of the response to osmotic stress in mammalian cells. Identified in 1999, NFAT5 is the latest addition to the Rel family, which comprises the NF-kappaB and NFATc proteins. Though in some of its structural and functional features NFAT5 is a hybrid between these two major groups of Rel proteins, it has unique characteristics that make it stand on its own as a third type of Rel transcription factor. Since its discovery, NFAT5 has been studied mostly in the context of the hypertonicity stress response. The advent of mouse models deficient in NFAT5 and other recent advances have confirmed a fundamental osmoprotective role for this factor in mammals, but also revealed features that suggest it may have a wider range of functions.
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Affiliation(s)
- José Aramburu
- Molecular Immunopathology Unit, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Carrer Dr. Aiguader 80, E-08003 Barcelona, Spain.
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Jeon US, Kim JA, Sheen MR, Kwon HM. How tonicity regulates genes: story of TonEBP transcriptional activator. Acta Physiol (Oxf) 2006; 187:241-7. [PMID: 16734761 DOI: 10.1111/j.1748-1716.2006.01551.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
TonEBP stimulates genes whose products drive cellular accumulation of organic osmolytes and HSP70, which protect cells from the deleterious effects of hypertonicity and urea, respectively. Mice deficient in the TonEBP gene display severe atrophy of the renal medulla because cells failed to adapt to the hyperosmolality. Emerging data suggest that TonEBP plays a key role in the urinary concentrating mechanism by stimulating the UT-A urea transporters and possibly AQP2 water channel. Thus, TonEBP is an essential regulator in the urinary concentrating mechanism. Studies on structural basis of TonEBP function have revealed the structure of the DNA binding domain, and defined the transactivation domains. Molecular mechanisms underlying the nucleocytoplasmic trafficking, transactivation, and phosphorylation in response to changes in tonicity need to be understood in molecular detail. Such knowledge is needed for the identification of the sensor that detects changes in ambient tonicity and signals to TonEBP.
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Affiliation(s)
- U S Jeon
- Department of Medicine, University of Maryland, Baltimore, MD 21201, USA
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