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Dimeloe S, Gubser P, Loeliger J, Frick C, Develioglu L, Fischer M, Marquardsen F, Bantug GR, Thommen D, Lecoultre Y, Zippelius A, Langenkamp A, Hess C. Tumor-derived TGF-β inhibits mitochondrial respiration to suppress IFN-γ production by human CD4 + T cells. Sci Signal 2019; 12:12/599/eaav3334. [PMID: 31530731 DOI: 10.1126/scisignal.aav3334] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transforming growth factor-β (TGF-β) is produced by tumors, and increased amounts of this cytokine in the tumor microenvironment and serum are associated with poor patient survival. TGF-β-mediated suppression of antitumor T cell responses contributes to tumor growth and survival. However, TGF-β also has tumor-suppressive activity; thus, dissecting cell type-specific molecular effects may inform therapeutic strategies targeting this cytokine. Here, using human peripheral and tumor-associated lymphocytes, we investigated how tumor-derived TGF-β suppresses a key antitumor function of CD4+ T cells, interferon-γ (IFN-γ) production. Suppression required the expression and phosphorylation of Smad proteins in the TGF-β signaling pathway, but not their nuclear translocation, and depended on oxygen availability, suggesting a metabolic basis for these effects. Smad proteins were detected in the mitochondria of CD4+ T cells, where they were phosphorylated upon treatment with TGF-β. Phosphorylated Smad proteins were also detected in the mitochondria of isolated tumor-associated lymphocytes. TGF-β substantially impaired the ATP-coupled respiration of CD4+ T cells and specifically inhibited mitochondrial complex V (ATP synthase) activity. Last, inhibition of ATP synthase alone was sufficient to impair IFN-γ production by CD4+ T cells. These results, which have implications for human antitumor immunity, suggest that TGF-β targets T cell metabolism directly, thus diminishing T cell function through metabolic paralysis.
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Affiliation(s)
- Sarah Dimeloe
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland. .,Institute of Immunology and Immunotherapy and Institute of Metabolism and Systems Research, University of Birmingham, Birmingham B15 2TT, UK
| | - Patrick Gubser
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Jordan Loeliger
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Corina Frick
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Leyla Develioglu
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Marco Fischer
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Florian Marquardsen
- Immunodeficiency Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Glenn R Bantug
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Daniela Thommen
- Cancer Immunology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Yannic Lecoultre
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | - Alfred Zippelius
- Cancer Immunology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland
| | | | - Christoph Hess
- Immunobiology Laboratory, Department of Biomedicine, University of Basel, 4031 Basel, Switzerland. .,Department of Medicine, University of Cambridge, Cambridge CB2 0AW, UK
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Abstract
SMADs are essential transcriptional effectors of transforming growth factor-β (TGFβ)/TGFβ-related signaling that underlies embryonic development and adult homeostasis. A recent study by Fang et al. in Cell Research adds to this biological complexity by demonstrating an atypical cytoplasmic role for SMAD5 in modulating the bioenergetic homeostasis (i.e., glycolysis and mitochondrial respiration) of cells in response to fluctuations in intracellular pH that is independent of receptor signaling.
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3
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Lee SJ, Jeong JY, Oh CJ, Park S, Kim JY, Kim HJ, Doo Kim N, Choi YK, Do JY, Go Y, Ha CM, Ha CM, Choi JY, Huh S, Ho Jeoung N, Lee KU, Choi HS, Wang Y, Park KG, Harris RA, Lee IK. Pyruvate Dehydrogenase Kinase 4 Promotes Vascular Calcification via SMAD1/5/8 Phosphorylation. Sci Rep 2015; 5:16577. [PMID: 26560812 PMCID: PMC4642318 DOI: 10.1038/srep16577] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 10/12/2015] [Indexed: 01/07/2023] Open
Abstract
Vascular calcification, a pathologic response to defective calcium and phosphate homeostasis, is strongly associated with cardiovascular mortality and morbidity. In this study, we have observed that pyruvate dehydrogenase kinase 4 (PDK4) is upregulated and pyruvate dehydrogenase complex phosphorylation is increased in calcifying vascular smooth muscle cells (VSMCs) and in calcified vessels of patients with atherosclerosis, suggesting that PDK4 plays an important role in vascular calcification. Both genetic and pharmacological inhibition of PDK4 ameliorated the calcification in phosphate-treated VSMCs and aortic rings and in vitamin D3-treated mice. PDK4 augmented the osteogenic differentiation of VSMCs by phosphorylating SMAD1/5/8 via direct interaction, which enhances BMP2 signaling. Furthermore, increased expression of PDK4 in phosphate-treated VSMCs induced mitochondrial dysfunction followed by apoptosis. Taken together, our results show that upregulation of PDK4 promotes vascular calcification by increasing osteogenic markers with no adverse effect on bone formation, demonstrating that PDK4 is a therapeutic target for vascular calcification.
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Affiliation(s)
- Sun Joo Lee
- Department of Biomedical Science, Graduate School of Medicine, Kyungpook National University
| | - Ji Yun Jeong
- Department of Internal Medicine, Kyungpook National University.,Department of Internal Medicine, Soonchunhyang University Gumi Hospital, Gumi, Republic of Korea
| | - Chang Joo Oh
- Department of Internal Medicine, Kyungpook National University
| | - Sungmi Park
- Leading-edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University
| | - Joon-Young Kim
- Department of Internal Medicine, Kyungpook National University.,GIST College, Gwangju Institute of Science and Technology
| | - Han-Jong Kim
- Department of Internal Medicine, Kyungpook National University.,Research Institute of Clinical Medicine, Chonnam National University Hwasun Hospital, Gwangju, Republic of Korea
| | - Nam Doo Kim
- New Drug Development Center, Daegu-Gyeongbuk Medical Innovation Foundation
| | - Young-Keun Choi
- Department of Internal Medicine, Kyungpook National University
| | - Ji-Yeon Do
- Leading-edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University
| | - Younghoon Go
- Department of Internal Medicine, Kyungpook National University
| | | | - Chae-Myung Ha
- Department of Internal Medicine, Kyungpook National University
| | - Je-Yong Choi
- Department of Biochemistry and Cell Biology, Kyungpook National University.,BK21 plus KNU Biomedical Convergence Programs at Kyungpook National University, Daegu, Republic of Korea
| | - Seung Huh
- Department of Surgery, Kyungpook National University, Daegu, Republic of Korea
| | - Nam Ho Jeoung
- Department of Fundamental Medical and Pharmaceutical Sciences, Catholic University of Daegu, Gyeongsan, Republic of Korea
| | - Ki-Up Lee
- Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Hueng-Sik Choi
- National Creative Research Initiatives Center for Nuclear Receptor Signals and Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Yu Wang
- State Key Laboratory of Pharmaceutical Biotechnology and Department of Pharmacology and Pharmacy, The University of Hong Kong, Hong Kong, China
| | - Keun-Gyu Park
- Department of Internal Medicine, Kyungpook National University.,Leading-edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University
| | - Robert A Harris
- Roudebush VA Medical Center and the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - In-Kyu Lee
- Department of Internal Medicine, Kyungpook National University.,Leading-edge Research Center for Drug Discovery and Development for Diabetes and Metabolic Disease, Kyungpook National University.,BK21 plus KNU Biomedical Convergence Programs at Kyungpook National University, Daegu, Republic of Korea
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4
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Hou J, Lü AL, Liu BW, Xing YJ, Da J, Hou ZL, Ai SY. Combination of BMP-2 and 5-AZA is advantageous in rat bone marrow-derived mesenchymal stem cells differentiation into cardiomyocytes. Cell Biol Int 2013; 37:1291-9. [PMID: 23881855 DOI: 10.1002/cbin.10161] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Accepted: 07/08/2013] [Indexed: 12/31/2022]
Abstract
Bone morphogenetic protein-2 (BMP-2) has a crucial role in the development of cardiogenesis, and is used in inducing bone marrow mesenchymal stem cells (BMMSCs) to differentiate into cardiomyocytes. We have examined a combination of BMP-2 and 5-azacytidine (5-AZA) in inducing these differentiation effects. BMMSCs were collected and purified from bone marrow of 4-week-old Sprague-Dawley (SD) rats by density-gradient centrifugation and differential attachment. The fourth passage subculture of BMMSCs, selected by cytometry for purity and identification, was divided into four groups: a control group, BMP-2 treated, 5-AZA treated, and a combination of BMP-2 and 5-AZA treatment. Expression of cardiac Troponin I (cTnI) and Connexin 43 (CX-43) in BMMSCs after induction were detected by immunofluorescence and Western blot. Flow cytometry analysis was used for differentiation rates and apoptosis of induced BMMSCs, through the expression of cardiac Troponin T (cTnT) and Annexin V-FITC & PI kit, respectively. BMP-2 can ameliorate apoptosis of BMMSCs caused by 5-AZA and promote the differentiation of BMMSCs into cardiomyocyte-like cells. Thus a combination of BMP-2 and 5-AZA can significantly improve the cardiac differentiation with fewer cell damage effects, making it a safe and effective method of induction in vitro.
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Affiliation(s)
- Jing Hou
- Department of Cardiology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi, 710032, China
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5
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IHG-1 must be localised to mitochondria to decrease Smad7 expression and amplify TGF-β1-induced fibrotic responses. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1969-78. [PMID: 23567938 DOI: 10.1016/j.bbamcr.2013.03.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 02/28/2013] [Accepted: 03/26/2013] [Indexed: 01/15/2023]
Abstract
TGF-β1 is a prototypic profibrotic cytokine and major driver of fibrosis in the kidney and other organs. Induced in high glucose-1 (IHG-1) is a mitochondrial protein which we have recently reported to be associated with renal disease. IHG-1 amplifies responses to TGF-β1 and regulates mitochondrial biogenesis by stabilising the transcriptional co-activator peroxisome proliferator-activated receptor gamma coactivator-1-alpha. Here we report that the mitochondrial localisation of IHG-1 is pivotal in the amplification of TGF-β1 signalling. We demonstrate that IHG-1 expression is associated with repression of the endogenous TGF-β1 inhibitor Smad7. Intriguingly, expression of a non-mitochondrial deletion mutant of IHG-1 (Δmts-IHG-1) repressed TGF-β1 fibrotic signalling in renal epithelial cells. In cells expressing Δmts-IHG-1 fibrotic responses including CCN2/connective tissue growth factor, fibronectin and jagged-1 expression were reduced following stimulation with TGF-β1. Δmts-IHG-1 modulation of TGF-β1 signalling was associated with increased Smad7 protein expression. Δmts-IHG-1 modulated TGF-β1 activity by increasing Smad7 protein expression as it failed to inhibit TGF-β1 transcriptional responses when endogenous Smad7 expression was knocked down. These data indicate that mitochondria modulate TGF-β1 signal transduction and that IHG-1 is a key player in this modulation.
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6
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Casalena G, Daehn I, Bottinger E. Transforming growth factor-β, bioenergetics, and mitochondria in renal disease. Semin Nephrol 2012; 32:295-303. [PMID: 22835461 DOI: 10.1016/j.semnephrol.2012.04.009] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The transforming growth factor-β (TGF-β) family comprises more than 30 family members that are structurally related secreted dimeric cytokines, including TGF-β, activins, and bone morphogenetic proteins/growth and differentiation factors. TGF-β are pluripotent regulators of cell proliferation, differentiation, apoptosis, migration, and adhesion of many different cell types. TGF-β pathways are highly evolutionarily conserved and control embryogenesis, tissue repair, and tissue homeostasis in invertebrates and vertebrates. Aberrations in TGF-β activity and signaling underlie a broad spectrum of developmental disorders and major pathologies in human beings, including cancer, fibrosis, and autoimmune diseases. Recent observations have indicated an emerging role for TGF-β in the regulation of mitochondrial bioenergetics and oxidative stress responses characteristic of chronic degenerative diseases and aging. Conversely, energy and metabolic sensory pathways cross-regulate mediators of TGF-β signaling. Here, we review TGF-β and regulation of bioenergetic and mitochondrial functions, including energy and oxidant metabolism and apoptotic cell death, as well as their emerging relevance in renal biology and disease.
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Affiliation(s)
- Gabriella Casalena
- Department of Medicine, Mount Sinai School of Medicine, New York, NY 10029, USA
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7
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Dhillon S, Hellings JA, Butler MG. Genetics and mitochondrial abnormalities in autism spectrum disorders: a review. Curr Genomics 2012; 12:322-32. [PMID: 22294875 PMCID: PMC3145262 DOI: 10.2174/138920211796429745] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 05/24/2011] [Accepted: 05/25/2011] [Indexed: 02/08/2023] Open
Abstract
We review the current status of the role and function of the mitochondrial DNA (mtDNA) in the etiology of autism spectrum disorders (ASD) and the interaction of nuclear and mitochondrial genes. High lactate levels reported in about one in five children with ASD may indicate involvement of the mitochondria in energy metabolism and brain development. Mitochondrial disturbances include depletion, decreased quantity or mutations of mtDNA producing defects in biochemical reactions within the mitochondria. A subset of individuals with ASD manifests copy number variation or small DNA deletions/duplications, but fewer than 20 percent are diagnosed with a single gene condition such as fragile X syndrome. The remaining individuals with ASD have chromosomal abnormalities (e.g., 15q11-q13 duplications), other genetic or multigenic causes or epigenetic defects. Next generation DNA sequencing techniques will enable better characterization of genetic and molecular anomalies in ASD, including defects in the mitochondrial genome particularly in younger children.
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Affiliation(s)
- Sukhbir Dhillon
- Departments of Psychiatry & Behavioral Sciences and Pediatrics, Kansas University Medical Center, Kansas City, Kansas 66160, USA
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Pang L, Qiu T, Cao X, Wan M. Apoptotic role of TGF-β mediated by Smad4 mitochondria translocation and cytochrome c oxidase subunit II interaction. Exp Cell Res 2011; 317:1608-20. [PMID: 21324314 DOI: 10.1016/j.yexcr.2011.02.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 11/29/2022]
Abstract
Smad4, originally isolated from the human chromosome 18q21, is a key factor in transducing the signals of the TGF-β superfamily of growth hormones and plays a pivotal role in mediating antimitogenic and proapoptotic effects of TGF-β, but the mechanisms by which Smad4 induces apoptosis are elusive. Here we report that Smad4 directly translocates to the mitochondria of apoptotic cells. Smad4 gene silencing by siRNA inhibits TGF-β-induced apoptosis in Hep3B cells and UV-induced apoptosis in PANC-1 cells. Cell fractionation assays demonstrated that a fraction of Smad4 translocates to mitochondria after long time TGF-β treatment or UV exposure, during which the cells were under apoptosis. Smad4 mitochondria translocation during apoptosis was also confirmed by fluorescence observation of Smad4 colocalization with MitoTracker Red. We searched for mitochondria proteins that have physical interactions with Smad4 using yeast two-hybrid screening approach. DNA sequence analysis identified 34 positive clones, five of which encoded subunits in mitochondria complex IV, i.e., one clone encoded cytochrome c oxidase COXII, three clones encoded COXIII and one clone encoded COXVb. Strong interaction between Smad4 with COXII, an important apoptosis regulator, was verified in yeast by β-gal activity assays and in mammalian cells by immunoprecipitation assays. Further, mitochondrial portion of cells was isolated and the interaction between COXII and Smad4 in mitochondria upon TGF-β treatment or UV exposure was confirmed. Importantly, targeting Smad4 to mitochondria using import leader fusions enhanced TGF-β-induced apoptosis. Collectively, the results suggest that Smad4 promote apoptosis of the cells through its mitochondrial translocation and association with mitochondria protein COXII.
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Affiliation(s)
- Lijuan Pang
- The Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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9
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Arcucci A, Montagnani S, Gionti E. Expression and intracellular localization of Pyk2 in normal and v-src transformed chicken epiphyseal chondrocytes. Biochimie 2005; 88:77-84. [PMID: 16040187 DOI: 10.1016/j.biochi.2005.06.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2005] [Accepted: 06/20/2005] [Indexed: 11/24/2022]
Abstract
The expression and localization of prolin-rich tyrosine kinase 2 (Pyk2) were studied in chick embryo epiphyseal chondrocytes. Two immunoreactive bands were detected in chondrocytes, a major band with an apparent Mr of 123 kDa and a minor band with an apparent Mr of 68 kDa. The major band appears to migrate as a doublet with apparent Mr of 116/123 kDa. Increased levels of the three forms of Pyk2 were observed in v-src transformed chondrocytes as compared to control uninfected chondrocytes. Immunofluorescent staining shows that Pyk2 is clearly visible in the cytosol and in the perinuclear region of control and v-src-chondrocytes and displays a pattern very similar to the distribution of the mitochondrial marker Mito Tracker. More, immunofluorescent staining shows that Pyk2 is nuclear in most chondrocytes. By subcellular fractionation, the p116/123 Pyk2 doublet, was found to be accumulated mainly in the cytoplasm while the p68 Pyk2 form, was found to be accumulated exclusively in the nucleus. The differential nuclear/cytoplasmic distribution of the Pyk2 forms remains unchanged after v-Src-induced transformation. The p68 Pyk2 form could no longer be detected by using a N-terminus domain-specific anti-Pyk2 antibody. Consistently, Pyk2 immunoreactivity was restricted to the cytoplasm of control and v-src transformed chondrocytes. Thus it appears that the p68 Pyk2 form that accumulates in the nucleus has a deletion in the N-terminus region.
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Affiliation(s)
- Alessandro Arcucci
- Dipartimento di Scienze Biomorfologiche e Funzionali, Università di Napoli Federico II, via S. Pansini n. 5, 80131 Napoli, Italy
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Schuh RA, Kristián T, Fiskum G. Calcium-dependent dephosphorylation of brain mitochondrial calcium/cAMP response element binding protein (CREB). J Neurochem 2005; 92:388-94. [PMID: 15663486 PMCID: PMC2572760 DOI: 10.1111/j.1471-4159.2004.02873.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Calcium-mediated signaling regulates nuclear gene transcription by calcium/cAMP response element binding protein (CREB) via calcium-dependent kinases and phosphatases. This study tested the hypothesis that CREB is also present in mitochondria and subject to dynamic calcium-dependent modulation of its phosphorylation state. Antibodies to CREB and phosphorylated CREB (pCREB) were used to demonstrate the presence of both forms in isolated mitochondria and mitoplasts from rat brain. When energized mitochondria were exposed to increasing concentrations of Ca2+ in the physiological range, pCREB was lost while total CREB remained constant. In the presence of Ru360, an inhibitor of the mitochondrial Ca2+ uptake uniporter, calcium-dependent loss of pCREB levels was attenuated, suggesting that intramitochondrial calcium plays an important role in pCREB dephosphorylation. pCREB dephosphorylation was not, however, inhibited by the phosphatase inhibitors okadaic acid and Tacrolimus. In the absence of Ca2+, CREB phosphorylation was elevated by the addition of ATP to the mitochondrial suspension. Exposure of mitochondria to the pore-forming molecule alamethicin that causes osmotic swelling and release of intermembrane proteins enriched mitochondrial pCREB immunoreactivity. These results further suggest that mitochondrial CREB is located in the matrix or inner membrane and that a kinase and a calcium-dependent phosphatase regulate its phosphorylation state.
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Affiliation(s)
- Rosemary A. Schuh
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Toxicology Program, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Tibor Kristián
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Gary Fiskum
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Toxicology Program, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Sun Y, Zhou J, Liao X, Lü Y, Deng C, Huang P, Chen Q, Yang X. Disruption of Smad5 gene induces mitochondria-dependent apoptosis in cardiomyocytes. Exp Cell Res 2005; 306:85-93. [PMID: 15878335 DOI: 10.1016/j.yexcr.2005.02.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 02/03/2005] [Accepted: 02/14/2005] [Indexed: 10/25/2022]
Abstract
Our previous studies have shown that SMAD5, an important intracellular mediator of transforming growth factor beta (TGF-beta) family, is required for normal development of the cardiovascular system in vivo. In the current study, we reported that the lack of the Smad5 gene resulted in apoptosis of cardiac myocytes in vivo. To further investigate the mechanism of the Smad5 gene in cardiomyocyte apoptosis, the embryonic stem (ES) cell differentiation system was employed. We found that the myotubes that differentiated from the homozygous Smad5ex6/ex6 mutant ES cells underwent collapse and degeneration during the late stages of in vitro differentiation, mimicking the in vivo observation. By electron microscopy, abnormal swollen mitochondria were observed in cardiomyocytes both from Smad5-deficient embryos and from ES-differentiated cells. There was also a significant reduction in mitochondrial membrane potential (Deltapsi m) and a leakage of cytochrome c from mitochondria into the cytosol of myocytes differentiated from Smad5 mutant ES cells. The expression of p53 and p21 was found to be elevated in the differentiated Smad5 mutant myocytes, and this was accompanied by an up-regulation in caspase 3 expression. These results suggest that the Smad5-mediated TGF-beta signals may protect cardiomyocytes from apoptosis by maintaining the integrity of the mitochondria, probably through suppression of p53 mediated pathways.
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MESH Headings
- Animals
- Apoptosis/genetics
- Apoptosis/physiology
- Caspase 3
- Caspases/metabolism
- Cell Differentiation/genetics
- Cell Differentiation/physiology
- Cells, Cultured
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/physiology
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Embryo, Mammalian/ultrastructure
- Gene Expression Regulation, Developmental
- Mice
- Mice, Knockout
- Microscopy, Electron
- Mitochondria/metabolism
- Mitochondria/pathology
- Mitochondria/physiology
- Myocardium/metabolism
- Myocardium/pathology
- Myocardium/ultrastructure
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/physiology
- Myocytes, Cardiac/ultrastructure
- Phosphoproteins/genetics
- Phosphoproteins/physiology
- Smad5 Protein
- Trans-Activators/genetics
- Trans-Activators/physiology
- Tumor Suppressor Protein p53/genetics
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Affiliation(s)
- Yanxun Sun
- Genetic Laboratory of Development and Diseases, Institute of Biotechnology, 20 Dongdajie, Fengtai, Beijing 100071, PR China.
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