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Warnhoff K, Bhattacharya S, Snoozy J, Breen PC, Ruvkun G. Hypoxia-inducible factor induces cysteine dioxygenase and promotes cysteine homeostasis in Caenorhabditis elegans. eLife 2024; 12:RP89173. [PMID: 38349720 PMCID: PMC10942545 DOI: 10.7554/elife.89173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2024] Open
Abstract
Dedicated genetic pathways regulate cysteine homeostasis. For example, high levels of cysteine activate cysteine dioxygenase, a key enzyme in cysteine catabolism in most animal and many fungal species. The mechanism by which cysteine dioxygenase is regulated is largely unknown. In an unbiased genetic screen for mutations that activate cysteine dioxygenase (cdo-1) in the nematode Caenorhabditis elegans, we isolated loss-of-function mutations in rhy-1 and egl-9, which encode proteins that negatively regulate the stability or activity of the oxygen-sensing hypoxia inducible transcription factor (hif-1). EGL-9 and HIF-1 are core members of the conserved eukaryotic hypoxia response. However, we demonstrate that the mechanism of HIF-1-mediated induction of cdo-1 is largely independent of EGL-9 prolyl hydroxylase activity and the von Hippel-Lindau E3 ubiquitin ligase, the classical hypoxia signaling pathway components. We demonstrate that C. elegans cdo-1 is transcriptionally activated by high levels of cysteine and hif-1. hif-1-dependent activation of cdo-1 occurs downstream of an H2S-sensing pathway that includes rhy-1, cysl-1, and egl-9. cdo-1 transcription is primarily activated in the hypodermis where it is also sufficient to drive sulfur amino acid metabolism. Thus, the regulation of cdo-1 by hif-1 reveals a negative feedback loop that maintains cysteine homeostasis. High levels of cysteine stimulate the production of an H2S signal. H2S then acts through the rhy-1/cysl-1/egl-9 signaling pathway to increase HIF-1-mediated transcription of cdo-1, promoting degradation of cysteine via CDO-1.
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Affiliation(s)
- Kurt Warnhoff
- Pediatrics and Rare Diseases Group, Sanford ResearchSioux FallsUnited States
- Department of Pediatrics, Sanford School of Medicine, University of South DakotaSioux FallsUnited States
| | | | - Jennifer Snoozy
- Pediatrics and Rare Diseases Group, Sanford ResearchSioux FallsUnited States
| | - Peter C Breen
- Department of Molecular Biology, Massachusetts General HospitalBostonUnited States
| | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General HospitalBostonUnited States
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Warnhoff K, Bhattacharya S, Snoozy J, Breen PC, Ruvkun G. Hypoxia-inducible factor induces cysteine dioxygenase and promotes cysteine homeostasis in Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.04.538701. [PMID: 37205365 PMCID: PMC10187278 DOI: 10.1101/2023.05.04.538701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Dedicated genetic pathways regulate cysteine homeostasis. For example, high levels of cysteine activate cysteine dioxygenase, a key enzyme in cysteine catabolism in most animal and many fungal species. The mechanism by which cysteine dioxygenase is regulated is largely unknown. In an unbiased genetic screen for mutations that activate cysteine dioxygenase (cdo-1) in the nematode C. elegans, we isolated loss-of-function mutations in rhy-1 and egl-9, which encode proteins that negatively regulate the stability or activity of the oxygen-sensing hypoxia inducible transcription factor (hif-1). EGL-9 and HIF-1 are core members of the conserved eukaryotic hypoxia response. However, we demonstrate that the mechanism of HIF-1-mediated induction of cdo-1 is largely independent of EGL-9 prolyl hydroxylase activity and the von Hippel-Lindau E3 ubiquitin ligase, the classical hypoxia signaling pathway components. We demonstrate that C. elegans cdo-1 is transcriptionally activated by high levels of cysteine and hif-1. hif-1-dependent activation of cdo-1 occurs downstream of an H2S-sensing pathway that includes rhy-1, cysl-1, and egl-9. cdo-1 transcription is primarily activated in the hypodermis where it is also sufficient to drive sulfur amino acid metabolism. Thus, the regulation of cdo-1 by hif-1 reveals a negative feedback loop that maintains cysteine homeostasis. High levels of cysteine stimulate the production of an H2S signal. H2S then acts through the rhy-1/cysl-1/egl-9 signaling pathway to increase HIF-1-mediated transcription of cdo-1, promoting degradation of cysteine via CDO-1.
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Affiliation(s)
- Kurt Warnhoff
- Pediatrics and Rare Diseases Group, Sanford Research, Sioux Falls, SD 57104, USA
- Department of Pediatrics, Sanford School of Medicine, University of South Dakota, Sioux Falls, SD 57105 USA
| | - Sushila Bhattacharya
- Pediatrics and Rare Diseases Group, Sanford Research, Sioux Falls, SD 57104, USA
| | - Jennifer Snoozy
- Pediatrics and Rare Diseases Group, Sanford Research, Sioux Falls, SD 57104, USA
| | - Peter C. Breen
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
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Chen M, Zhu JY, Mu WJ, Guo L. Cysteine dioxygenase type 1 (CDO1): its functional role in physiological and pathophysiological processes. Genes Dis 2022. [DOI: 10.1016/j.gendis.2021.12.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Krijt J, Sokolová J, Šilhavý J, Mlejnek P, Kubovčiak J, Liška F, Malínská H, Hüttl M, Marková I, Křížková M, Stipanuk MH, Křížek T, Ditroi T, Nagy P, Kožich V, Pravenec M. High cysteine diet reduces insulin resistance in SHR-CRP rats. Physiol Res 2021; 70:687-700. [PMID: 34505526 PMCID: PMC8820534 DOI: 10.33549/physiolres.934736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 06/18/2021] [Indexed: 01/08/2023] Open
Abstract
Increased plasma total cysteine (tCys) has been associated with obesity and metabolic syndrome in human and some animal studies but the underlying mechanisms remain unclear. In this study, we aimed at evaluating the effects of high cysteine diet administered to SHR-CRP transgenic rats, a model of metabolic syndrome and inflammation. SHR-CRP rats were fed either standard (3.2 g cystine/kg diet) or high cysteine diet (HCD, enriched with additional 4 g L-cysteine/kg diet). After 4 weeks, urine, plasma and tissue samples were collected and parameters of metabolic syndrome, sulfur metabolites and hepatic gene expression were evaluated. Rats on HCD exhibited similar body weights and weights of fat depots, reduced levels of serum insulin, and reduced oxidative stress in the liver. The HCD did not change concentrations of tCys in tissues and body fluids while taurine in tissues and body fluids, and urinary sulfate were significantly increased. In contrast, betaine levels were significantly reduced possibly compensating for taurine elevation. In summary, increased Cys intake did not induce obesity while it ameliorated insulin resistance in the SHR-CRP rats, possibly due to beneficial effects of accumulating taurine.
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Affiliation(s)
- J Krijt
- Laboratory of Genetics of Model Diseases, Institute of Physiology of the Czech Academy of Sciences, Praha 4, Czech Republic. and Department of Pediatrics and Inherited Metabolic Disorders, Charles University-First Faculty of Medicine and General University Hospital in Prague, Praha 2, Czech Republic.
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Luo W, Qu F, Song P, Xiong D, Yin Y, Li J, Liu Z. Molecular characterization and taurine regulation of two novel CDOs (CDO1 and CDO2) from Carassius auratus. Comp Biochem Physiol B Biochem Mol Biol 2019; 235:54-61. [PMID: 31176866 DOI: 10.1016/j.cbpb.2019.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/26/2019] [Accepted: 06/03/2019] [Indexed: 10/26/2022]
Abstract
Cysteine oxygenase (CDO) is a mononuclear nonhemoglobin enzyme that catalyzes the production of taurine through the cysteine (Cys) pathway and plays a key role in the biosynthesis of taurine in mammals. However, the function of CDOs in bony fish remains poorly understood. In this study, we cloned CDO genes (CaCDO1 and CaCDO2) from Carassius auratus. The cDNA sequences of both CaCDO1 and CaCDO2 encoded putative proteins with 201 amino acids, which included structural features typical of the CDO protein family. Multiple sequence alignment and phylogenetic analysis showed that CaCDO1 and CaCDO2 shared high sequence identities and similarities with C. carpio homologs. Quantitative real-time polymerase chain reaction (qRT-PCR) results revealed that CaCDO1 and CaCDO2 were both broadly expressed in all selected tissues and developmental stages in C. auratus but had differing mRNA levels. In addition, compared to those of the taurine-free group, the in vivo mRNA expression levels of both CaCDO1 and CaCDO2 significantly decreased with increasing dietary taurine levels from 1.0 to 9.0 g/kg. Furthermore, in vitro taurine treatments showed similar inhibitory effects on the expression of CaCDO1 and CaCDO2 in the intestines of C. auratus. Our results also showed that the mRNA expression of CaCDO2 in the intestines was higher than that of CaCDO1 in response to in vivo and in vitro taurine supplementation. Overall, these data may provide new insights into the regulation of fish CDO expression and provide valuable knowledge for improving dietary formulas in aquaculture.
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Affiliation(s)
- Wenjie Luo
- Hunan International Joint Laboratory of Animal Intestinal Ecology and Health, Hunan Normal University, Changsha 410081, China
| | - Fufa Qu
- Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Environmental Engineering, Changsha University, Changsha 410022, China
| | - Peng Song
- Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Environmental Engineering, Changsha University, Changsha 410022, China
| | - Ding Xiong
- Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Environmental Engineering, Changsha University, Changsha 410022, China
| | - Yulong Yin
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, China
| | - Jianzhong Li
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, China.
| | - Zhen Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, China; Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Environmental Engineering, Changsha University, Changsha 410022, China.
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Jurkowska H, Niewiadomski J, Hirschberger LL, Roman HB, Mazor KM, Liu X, Locasale JW, Park E, Stipanuk MH. Downregulation of hepatic betaine:homocysteine methyltransferase (BHMT) expression in taurine-deficient mice is reversed by taurine supplementation in vivo. Amino Acids 2015; 48:665-676. [PMID: 26481005 DOI: 10.1007/s00726-015-2108-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 09/26/2015] [Indexed: 01/25/2023]
Abstract
The cysteine dioxygenase (Cdo1)-null and the cysteine sulfinic acid decarboxylase (Csad)-null mouse are not able to synthesize hypotaurine/taurine by the cysteine/cysteine sulfinate pathway and have very low tissue taurine levels. These mice provide excellent models for studying the effects of taurine on biological processes. Using these mouse models, we identified betaine:homocysteine methyltransferase (BHMT) as a protein whose in vivo expression is robustly regulated by taurine. BHMT levels are low in liver of both Cdo1-null and Csad-null mice, but are restored to wild-type levels by dietary taurine supplementation. A lack of BHMT activity was indicated by an increase in the hepatic betaine level. In contrast to observations in liver of Cdo1-null and Csad-null mice, BHMT was not affected by taurine supplementation of primary hepatocytes from these mice. Likewise, CSAD abundance was not affected by taurine supplementation of primary hepatocytes, although it was robustly upregulated in liver of Cdo1-null and Csad-null mice and lowered to wild-type levels by dietary taurine supplementation. The mechanism by which taurine status affects hepatic CSAD and BHMT expression appears to be complex and to require factors outside of hepatocytes. Within the liver, mRNA abundance for both CSAD and BHMT was upregulated in parallel with protein levels, indicating regulation of BHMT and CSAD mRNA synthesis or degradation.
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Affiliation(s)
- Halina Jurkowska
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA.,Chair of Medical Biochemistry, Jagiellonian University Medical College, Kraków, Poland
| | - Julie Niewiadomski
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | | | - Heather B Roman
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Kevin M Mazor
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Xiaojing Liu
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Jason W Locasale
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Eunkyue Park
- New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY, USA
| | - Martha H Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA.
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Yin J, Ren W, Yang G, Duan J, Huang X, Fang R, Li C, Li T, Yin Y, Hou Y, Kim SW, Wu G. L-Cysteine metabolism and its nutritional implications. Mol Nutr Food Res 2015; 60:134-46. [PMID: 25929483 DOI: 10.1002/mnfr.201500031] [Citation(s) in RCA: 205] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 04/08/2015] [Accepted: 04/23/2015] [Indexed: 01/17/2023]
Abstract
L-Cysteine is a nutritionally semiessential amino acid and is present mainly in the form of L-cystine in the extracellular space. With the help of a transport system, extracellular L-cystine crosses the plasma membrane and is reduced to L-cysteine within cells by thioredoxin and reduced glutathione (GSH). Intracellular L-cysteine plays an important role in cellular homeostasis as a precursor for protein synthesis, and for production of GSH, hydrogen sulfide (H(2)S), and taurine. L-Cysteine-dependent synthesis of GSH has been investigated in many pathological conditions, while the pathway for L-cysteine metabolism to form H(2)S has received little attention with regard to prevention and treatment of disease in humans. The main objective of this review is to highlight the metabolic pathways of L-cysteine catabolism to GSH, H(2)S, and taurine, with special emphasis on therapeutic and nutritional use of L-cysteine to improve the health and well-being of animals and humans.
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Affiliation(s)
- Jie Yin
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Wenkai Ren
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Guan Yang
- Department of Animal Science, University of Florida, Gainesville, FL, USA
| | - Jielin Duan
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xingguo Huang
- Department of Animal Science, Hunan Agriculture University, Changsha, China
| | - Rejun Fang
- Department of Animal Science, Hunan Agriculture University, Changsha, China
| | - Chongyong Li
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
| | - Tiejun Li
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
| | - Yulong Yin
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
- School of Life Sciences, Hunan Normal University, Changsha, China
| | - Yongqing Hou
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan Polytechnic University, Wuhan, China
| | - Sung Woo Kim
- Department of Animal Science, North Carolina State University, Raleigh, NC, USA
| | - Guoyao Wu
- Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center of Healthy Livestock, Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan, China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety, Wuhan Polytechnic University, Wuhan, China
- Department of Animal Science, Texas A&M University, College Station, TX, USA
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Kabil O, Motl N, Banerjee R. H2S and its role in redox signaling. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1844:1355-66. [PMID: 24418393 PMCID: PMC4048824 DOI: 10.1016/j.bbapap.2014.01.002] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/19/2013] [Accepted: 01/02/2014] [Indexed: 02/08/2023]
Abstract
Hydrogen sulfide (H2S) has emerged as an important gaseous signaling molecule that is produced endogenously by enzymes in the sulfur metabolic network. H2S exerts its effects on multiple physiological processes important under both normal and pathological conditions. These functions include neuromodulation, regulation of blood pressure and cardiac function, inflammation, cellular energetics and apoptosis. Despite the recognition of its biological importance and its beneficial effects, the mechanism of H2S action and the regulation of its tissue levels remain unclear in part owing to its chemical and physical properties that render handling and analysis challenging. Furthermore, the multitude of potential H2S effects has made it difficult to dissect its signaling mechanism and to identify specific targets. In this review, we focus on H2S metabolism and provide an overview of the recent literature that sheds some light on its mechanism of action in cellular redox signaling in health and disease. This article is part of a Special Issue entitled: Thiol-Based Redox Processes.
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Affiliation(s)
- Omer Kabil
- University of Michigan Medical School, Ann Arbor, MI 48109-0600, USA
| | - Nicole Motl
- University of Michigan Medical School, Ann Arbor, MI 48109-0600, USA
| | - Ruma Banerjee
- University of Michigan Medical School, Ann Arbor, MI 48109-0600, USA.
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Hagiwara A, Ishizaki S, Takehana K, Fujitani S, Sonaka I, Satsu H, Shimizu M. Branched-chain amino acids inhibit the TGF-beta-induced down-regulation of taurine biosynthetic enzyme cysteine dioxygenase in HepG2 cells. Amino Acids 2014; 46:1275-83. [PMID: 24553827 PMCID: PMC3984414 DOI: 10.1007/s00726-014-1693-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 02/04/2014] [Indexed: 11/30/2022]
Abstract
Taurine deficiency has been suggested to contribute to the pathogenesis and complications of advanced hepatic diseases. The molecular basis for a low level of taurine associated with hepatic failure is largely unknown. Using carbon tetrachloride (CCl4)-induced cirrhotic rat model, we found that the activity and expression of cysteine dioxygenase (CDO), a rate-limiting enzyme in taurine synthesis, were significantly decreased in the liver of these rats. To investigate the underlying mechanisms for the suppression, we examined the effects of pathological cytokines on CDO expression in human hepatoma HepG2 cells. Among the several cytokines, transforming growth factor-β (TGF-β), one of the key mediators of fibrogenesis, suppressed Cdo1 gene transcription through the MEK/ERK pathway. Finally, we further examined potential effects of branched-chain amino acids (BCAA) on CDO expression, as it has been reported that oral BCAA supplementation increased plasma taurine level in the patients with liver cirrhosis. BCAA, especially leucine, promoted Cdo1 gene transcription, and attenuated TGF-β-mediated suppression of Cdo1 gene expression. These results indicate that the low plasma level of taurine in advanced hepatic disease is due to decreased hepatic CDO expression, which can be partly attributed to suppressive effect of TGF-β on Cdo1 gene transcription. Furthermore, our observation that BCAA promotes Cdo1 expression suggests that BCAA may be therapeutically useful to improve hepatic taurine metabolism and further suppress dysfunctions associated with low level of taurine in hepatic diseases.
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Affiliation(s)
- Asami Hagiwara
- Research Institute, Ajinomoto Pharmaceuticals Co. Ltd., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki, 210-8681, Japan
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Stipanuk MH, Ueki I. Dealing with methionine/homocysteine sulfur: cysteine metabolism to taurine and inorganic sulfur. J Inherit Metab Dis 2011; 34:17-32. [PMID: 20162368 PMCID: PMC2901774 DOI: 10.1007/s10545-009-9006-9] [Citation(s) in RCA: 305] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/22/2009] [Accepted: 09/24/2009] [Indexed: 11/30/2022]
Abstract
Synthesis of cysteine as a product of the transsulfuration pathway can be viewed as part of methionine or homocysteine degradation, with cysteine being the vehicle for sulfur conversion to end products (sulfate, taurine) that can be excreted in the urine. Transsulfuration is regulated by stimulation of cystathionine β-synthase and inhibition of methylene tetrahydrofolate reductase in response to changes in the level of S-adenosylmethionine, and this promotes homocysteine degradation when methionine availability is high. Cysteine is catabolized by several desulfuration reactions that release sulfur in a reduced oxidation state, generating sulfane sulfur or hydrogen sulfide (H₂S), which can be further oxidized to sulfate. Cysteine desulfuration is accomplished by alternate reactions catalyzed by cystathionine β-synthase and cystathionine γ-lyase. Cysteine is also catabolized by pathways that require the initial oxidation of the cysteine thiol by cysteine dioxygenase to form cysteinesulfinate. The oxidative pathway leads to production of taurine and sulfate in a ratio of approximately 2:1. Relative metabolism of cysteine by desulfuration versus oxidative pathways is influenced by cysteine dioxygenase activity, which is low in animals fed low-protein diets and high in animals fed excess sulfur amino acids. Thus, desulfuration reactions dominate when cysteine is deficient, whereas oxidative catabolism dominates when cysteine is in excess. In rats consuming a diet with an adequate level of sulfur amino acids, about two thirds of cysteine catabolism occurs by oxidative pathways and one third by desulfuration pathways. Cysteine dioxygenase is robustly regulated in response to cysteine availability and may function to provide a pathway to siphon cysteine to less toxic metabolites than those produced by cysteine desulfuration reactions.
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Affiliation(s)
- Martha H. Stipanuk
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Iori Ueki
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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11
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Stipanuk MH, Ueki I, Dominy JE, Simmons CR, Hirschberger LL. Cysteine dioxygenase: a robust system for regulation of cellular cysteine levels. Amino Acids 2008; 37:55-63. [PMID: 19011731 DOI: 10.1007/s00726-008-0202-y] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 10/07/2008] [Indexed: 11/26/2022]
Abstract
Cysteine catabolism in mammals is dependent upon cysteine dioxygenase (CDO), an enzyme that adds molecular oxygen to the sulfur of cysteine, converting the thiol to a sulfinic acid known as cysteinesulfinic acid (3-sulfinoalanine). CDO is one of the most highly regulated metabolic enzymes responding to diet that is known. It undergoes up to 45-fold changes in concentration and up to 10-fold changes in catalytic efficiency. This provides a remarkable responsiveness of the cell to changes in sulfur amino acid availability: the ability to decrease CDO activity and conserve cysteine when cysteine is scarce and to rapidly increase CDO activity and catabolize cysteine to prevent cytotoxicity when cysteine supply is abundant. CDO in both liver and adipose tissues responds to changes in dietary intakes of protein and/or sulfur amino acids over a range that encompasses the requirement level, suggesting that cysteine homeostasis is very important to the living organism.
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Affiliation(s)
- M H Stipanuk
- Division of Nutritional Sciences, Cornell University, 227 Savage Hall, Ithaca, NY 14853, USA.
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