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Chen J, Ji X, Gao J, Huang J, Ren J. gys1 regulates maternal glycogen reserve essential for embryonic development in zebrafish. Heliyon 2024; 10:e31149. [PMID: 38803914 PMCID: PMC11128933 DOI: 10.1016/j.heliyon.2024.e31149] [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: 08/10/2023] [Revised: 05/10/2024] [Accepted: 05/10/2024] [Indexed: 05/29/2024] Open
Abstract
The reserve of glycogen is essential for embryonic development. In oviparous fish, egg is an isolated system after egg laying with all the required energy deposits by their mothers. However, the key regulated factor mediates the storage of maternal glycogen reserve which support for embryogenesis in the offspring is largely unknown. Glycogen synthase (GYS) is a central enzyme for glycogen synthesis. In our previous study, we generated a gys1 knockout zebrafish line, showed an embryonic developmental defect in F3 generation. In this study, firstly we determined that the gys1 was maternal origin by backcrossing the F2 mutant with wildtype lines. PAS staining and glycogen content measurement showed that glycogen reserve was reduced both in ovaries and embryos in the mutant group compared to wildtypes. Free glucose measurement analysis showed a 50 % of reduction in gys1 mutant embryos compared to wildtype embryos at 24 hpf; showed an approximal 50 % of reduction in gys1 mutant adults compared to wildtypes. Microinjection of 2-NBDG in embryos and comparison of fluorescent signal demonstrated that glucose uptake ability was decreased in the mutant embryos, indicating an impaired glucose metabolism. Untargeted metabolomics analysis then was employed and revealed that key modified metabolites enriched into vitamin B pathway, carbohydrate and unsaturated fatty acid pathways. These results demonstrated that gys1 played a role on glycogen metabolism, involved into the maternal glycogen reserve which essentially contribute to embryonic development.
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Affiliation(s)
- Jie Chen
- International Research Center for Marine Biosciences, Ministry of Science and Technology and National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
- CCMAR/CIMAR Centro de Ciências do Mar do Algarve, Universidade do Algarve, Campus de Gambelas, 8005-139, Faro, Portugal
| | - Xiao Ji
- International Research Center for Marine Biosciences, Ministry of Science and Technology and National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
| | - Jing Gao
- International Research Center for Marine Biosciences, Ministry of Science and Technology and National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
| | - Jiao Huang
- International Research Center for Marine Biosciences, Ministry of Science and Technology and National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
| | - Jianfeng Ren
- International Research Center for Marine Biosciences, Ministry of Science and Technology and National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
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Zhuo S, Bai M, Wang Z, Chen L, Li Z, Zhu X, Chen J, Ye X, Guo C, Chen Y. Glycogen synthesis is required for adaptive thermogenesis in beige adipose tissue and affects diet-induced obesity. Am J Physiol Endocrinol Metab 2024; 326:E696-E708. [PMID: 38568151 DOI: 10.1152/ajpendo.00074.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/18/2024] [Accepted: 03/22/2024] [Indexed: 05/15/2024]
Abstract
Glycogen is a form of energy storage for glucose in different tissues such as liver and skeletal muscle. It remains incompletely understood how glycogen impacts on adipose tissue functionality. Cold exposure elevated the expression of Gys1 that encodes glycogen synthase 1 in brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT). The in vivo function of Gys1 was analyzed using a mouse model in which Gys1 was deleted specifically in adipose tissues. Under normal chow conditions, Gys1 deletion caused little changes to body weight and glucose metabolism. Deletion of Gys1 abrogated upregulation of UCP1 and other thermogenesis-related genes in iWAT upon prolonged cold exposure or treatment with β3-adrenergic receptor agonist CL-316,243. Stimulation of UCP1 by CL-316,243 in adipose-derived stromal cells (stromal vascular fractions, SVFs) was also reduced by Gys1 deletion. Both the basal glycogen content and CL-316,243-stimulated glycogen accumulation in adipose tissues were reduced by Gys1 deletion. High-fat diet-induced obesity and insulin resistance were aggravated in Gys1-deleted mice. The loss of body weight upon CL-316,243 treatment was also abrogated by the loss of Gys1. In conclusion, our results underscore the pivotal role of glycogen synthesis in adaptive thermogenesis in beige adipose tissue and its impact on diet-induced obesity in mice.NEW & NOTEWORTHY Glycogen is one of major types of fuel reserve in the body and its classical function is to maintain blood glucose level. This study uncovers that glycogen synthesis is required for beige fat tissue to generate heat upon cold exposure. Such a function of glycogen is linked to development of high-fat diet-induced obesity, thus extending our understanding about the physiological functions of glycogen.
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Affiliation(s)
- Shixuan Zhuo
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Meijuan Bai
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Zinan Wang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Lingling Chen
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Zixuan Li
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Xinyu Zhu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Jinzhu Chen
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Xiaoyi Ye
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Cheng Guo
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
| | - Yan Chen
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety, Shanghai Institute of Nutrition and HealthUniversity of Chinese Academy of Sciences, Chinese Academy of SciencesShanghaiPeople's Republic of China
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Żołnierkiewicz O, Rogacka D. Hyperglycemia - A culprit of podocyte pathology in the context of glycogen metabolism. Arch Biochem Biophys 2024; 753:109927. [PMID: 38350532 DOI: 10.1016/j.abb.2024.109927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 01/31/2024] [Accepted: 02/10/2024] [Indexed: 02/15/2024]
Abstract
Prolonged disruption in the balance of glucose can result in metabolic disorders. The kidneys play a significant role in regulating blood glucose levels. However, when exposed to chronic hyperglycemia, the kidneys' ability to handle glucose metabolism may be impaired, leading to an accumulation of glycogen. Earlier studies have shown that there can be a significant increase in glucose storage in the form of glycogen in the kidneys in diabetes. Podocytes play a crucial role in maintaining the integrity of filtration barrier. In diabetes, exposure to elevated glucose levels can lead to significant metabolic and structural changes in podocytes, contributing to kidney damage and the development of diabetic kidney disease. The accumulation of glycogen in podocytes is not a well-established phenomenon. However, a recent study has demonstrated the presence of glycogen granules in podocytes. This review delves into the intricate connections between hyperglycemia and glycogen metabolism within the context of the kidney, with special emphasis on podocytes. The aberrant storage of glycogen has the potential to detrimentally impact podocyte functionality and perturb their structural integrity. This review provides a comprehensive analysis of the alterations in cellular signaling pathways that may potentially lead to glycogen overproduction in podocytes.
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Affiliation(s)
- Olga Żołnierkiewicz
- Mossakowski Medical Research Institute, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland
| | - Dorota Rogacka
- Mossakowski Medical Research Institute, Polish Academy of Sciences, Laboratory of Molecular and Cellular Nephrology, Wita Stwosza 63, 80-308, Gdansk, Poland; University of Gdansk, Faculty of Chemistry, Department of Molecular Biotechnology, Wita Stwosza 63, 80-308, Gdansk, Poland.
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4
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Skeletal-Muscle-Specific Overexpression of Chrono Leads to Disruption of Glucose Metabolism and Exercise Capacity. LIFE (BASEL, SWITZERLAND) 2022; 12:life12081233. [PMID: 36013411 PMCID: PMC9410257 DOI: 10.3390/life12081233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/07/2022] [Accepted: 08/09/2022] [Indexed: 11/17/2022]
Abstract
Disruption of circadian rhythms is related to disorders of glucose metabolism, and the molecular clock also exists in skeletal muscle. The ChIP-derived repressor of network oscillator (Chrono) and brain and muscle ARNT-like 1 (Bmal1) are core circadian components. Chrono is considered to be the repressor of Bmal1, and the Chrono–Bmal1 pathway is important in regulating the circadian rhythm; it has been speculated that this pathway could be a new mechanism for regulating glucose metabolism. The purpose of this study was to investigate the effects of Chrono on glucose metabolism in skeletal muscle and exercise capacity by using mice with skeletal-muscle-specific overexpression of Chrono (Chrono TG) and wild-type (WT) mice as the animal models. The results of this cross-sectional study indicated that the Chrono TG mice had an impaired glucose tolerance, lower exercise capacity, and higher levels of nonfasted blood glucose and glycogen content in skeletal muscle compared to WT mice. In addition, the Chrono TG mice also showed a significant increase in the amount of Chrono bound to Bmal1 according to a co-IP analysis; a remarkable decrease in mRNA expression of Tbc1d1, Glut4, Hk2, Pfkm, Pdp1, Gbe1, and Phka1, as well as in activity of Hk and protein expression of Ldhb; but higher mRNA expression of Pdk4 and protein expression of Ldha compared with those of WT mice. These data suggested the skeletal-muscle-specific overexpression of Chrono led to a greater amount of Chrono bound to Bmal1, which then could affect the glucose transporter, glucose oxidation, and glycogen utilization in skeletal muscle, as well as exercise capacity.
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Nitschke S, Sullivan MA, Mitra S, Marchioni C, Lee JP Y, Smith BH, Ahonen S, Wu J, Chown E, Wang P, Petković S, Zhao X, DiGiovanni LF, Perri AM, Israelian L, Grossman TR, Kordasiewicz H, Vilaplana F, Iwai K, Nitschke F, Minassian BA. Glycogen synthase downregulation rescues the amylopectinosis of murine RBCK1 deficiency. Brain 2022; 145:2361-2377. [PMID: 35084461 PMCID: PMC9612801 DOI: 10.1093/brain/awac017] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/17/2021] [Accepted: 01/09/2022] [Indexed: 12/06/2023] Open
Abstract
Longer glucan chains tend to precipitate. Glycogen, by far the largest mammalian glucan and the largest molecule in the cytosol with up to 55 000 glucoses, does not, due to a highly regularly branched spherical structure that allows it to be perfused with cytosol. Aberrant construction of glycogen leads it to precipitate, accumulate into polyglucosan bodies that resemble plant starch amylopectin and cause disease. This pathology, amylopectinosis, is caused by mutations in a series of single genes whose functions are under active study toward understanding the mechanisms of proper glycogen construction. Concurrently, we are characterizing the physicochemical particularities of glycogen and polyglucosans associated with each gene. These genes include GBE1, EPM2A and EPM2B, which respectively encode the glycogen branching enzyme, the glycogen phosphatase laforin and the laforin-interacting E3 ubiquitin ligase malin, for which an unequivocal function is not yet known. Mutations in GBE1 cause a motor neuron disease (adult polyglucosan body disease), and mutations in EPM2A or EPM2B a fatal progressive myoclonus epilepsy (Lafora disease). RBCK1 deficiency causes an amylopectinosis with fatal skeletal and cardiac myopathy (polyglucosan body myopathy 1, OMIM# 615895). RBCK1 is a component of the linear ubiquitin chain assembly complex, with unique functions including generating linear ubiquitin chains and ubiquitinating hydroxyl (versus canonical amine) residues, including of glycogen. In a mouse model we now show (i) that the amylopectinosis of RBCK1 deficiency, like in adult polyglucosan body disease and Lafora disease, affects the brain; (ii) that RBCK1 deficiency glycogen, like in adult polyglucosan body disease and Lafora disease, has overlong branches; (iii) that unlike adult polyglucosan body disease but like Lafora disease, RBCK1 deficiency glycogen is hyperphosphorylated; and finally (iv) that unlike laforin-deficient Lafora disease but like malin-deficient Lafora disease, RBCK1 deficiency's glycogen hyperphosphorylation is limited to precipitated polyglucosans. In summary, the fundamental glycogen pathology of RBCK1 deficiency recapitulates that of malin-deficient Lafora disease. Additionally, we uncover sex and genetic background effects in RBCK1 deficiency on organ- and brain-region specific amylopectinoses, and in the brain on consequent neuroinflammation and behavioural deficits. Finally, we exploit the portion of the basic glycogen pathology that is common to adult polyglucosan body disease, both forms of Lafora disease and RBCK1 deficiency, namely overlong branches, to show that a unified approach based on downregulating glycogen synthase, the enzyme that elongates glycogen branches, can rescue all four diseases.
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Affiliation(s)
- Silvia Nitschke
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mitchell A Sullivan
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
- Glycation and Diabetes Complications, Mater Research Institute–The University of Queensland, Translational Research Institute, Brisbane, QLD, 4102, Australia
| | - Sharmistha Mitra
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Charlotte R Marchioni
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jennifer P Y Lee
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Brandon H Smith
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Saija Ahonen
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Jun Wu
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Erin E Chown
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Peixiang Wang
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Sara Petković
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Xiaochu Zhao
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Laura F DiGiovanni
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Ami M Perri
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Lori Israelian
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
| | - Tamar R Grossman
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Carlsbad, California, USA
| | - Holly Kordasiewicz
- Department of Antisense Drug Discovery, Ionis Pharmaceuticals, Carlsbad, California, USA
| | - Francisco Vilaplana
- Division of Glycoscience, Department of Chemistry, KTH Royal Institute of Technology, AlbaNova University Centre, Stockholm 10691, Sweden
| | - Kazuhiro Iwai
- Department of Molecular and Cellular Physiology, Kyoto University School of Medicine, Kyoto 606-8501, Japan
| | - Felix Nitschke
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Berge A Minassian
- Program in Genetics and Genome Biology, The Hospital for Sick Children Research Institute, Toronto, ON M5G 0A4, Canada
- Division of Neurology, Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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6
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McCorvie TJ, Loria PM, Tu M, Han S, Shrestha L, Froese DS, Ferreira IM, Berg AP, Yue WW. Molecular basis for the regulation of human glycogen synthase by phosphorylation and glucose-6-phosphate. Nat Struct Mol Biol 2022; 29:628-638. [PMID: 35835870 PMCID: PMC9287172 DOI: 10.1038/s41594-022-00799-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 05/02/2022] [Indexed: 11/17/2022]
Abstract
Glycogen synthase (GYS1) is the central enzyme in muscle glycogen biosynthesis. GYS1 activity is inhibited by phosphorylation of its amino (N) and carboxyl (C) termini, which is relieved by allosteric activation of glucose-6-phosphate (Glc6P). We present cryo-EM structures at 3.0-4.0 Å resolution of phosphorylated human GYS1, in complex with a minimal interacting region of glycogenin, in the inhibited, activated and catalytically competent states. Phosphorylations of specific terminal residues are sensed by different arginine clusters, locking the GYS1 tetramer in an inhibited state via intersubunit interactions. The Glc6P activator promotes conformational change by disrupting these interactions and increases the flexibility of GYS1, such that it is poised to adopt a catalytically competent state when the sugar donor UDP-glucose (UDP-glc) binds. We also identify an inhibited-like conformation that has not transitioned into the activated state, in which the locking interaction of phosphorylation with the arginine cluster impedes subsequent conformational changes due to Glc6P binding. Our results address longstanding questions regarding the mechanism of human GYS1 regulation.
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Affiliation(s)
- Thomas J McCorvie
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK
| | - Paula M Loria
- Discovery Sciences, Worldwide Research and Development, Pfizer Inc., Groton, CT, USA
| | - Meihua Tu
- Medicine Design, Worldwide Research and Development, Pfizer Inc., Cambridge, MA, USA
| | - Seungil Han
- Discovery Sciences, Worldwide Research and Development, Pfizer Inc., Groton, CT, USA
| | - Leela Shrestha
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - D Sean Froese
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, University of Zürich, Zürich, Switzerland
| | - Igor M Ferreira
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Allison P Berg
- Rare Disease Research Unit, Worldwide Research and Development, Pfizer Inc., Cambridge, MA, USA.
| | - Wyatt W Yue
- Centre for Medicines Discovery, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, UK.
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7
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Santamans AM, Montalvo-Romeral V, Mora A, Lopez JA, González-Romero F, Jimenez-Blasco D, Rodríguez E, Pintor-Chocano A, Casanueva-Benítez C, Acín-Pérez R, Leiva-Vega L, Duran J, Guinovart JJ, Jiménez-Borreguero J, Enríquez JA, Villlalba-Orero M, Bolaños JP, Aspichueta P, Vázquez J, González-Terán B, Sabio G. p38γ and p38δ regulate postnatal cardiac metabolism through glycogen synthase 1. PLoS Biol 2021; 19:e3001447. [PMID: 34758018 PMCID: PMC8612745 DOI: 10.1371/journal.pbio.3001447] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 11/24/2021] [Accepted: 10/18/2021] [Indexed: 12/21/2022] Open
Abstract
During the first weeks of postnatal heart development, cardiomyocytes undergo a major adaptive metabolic shift from glycolytic energy production to fatty acid oxidation. This metabolic change is contemporaneous to the up-regulation and activation of the p38γ and p38δ stress-activated protein kinases in the heart. We demonstrate that p38γ/δ contribute to the early postnatal cardiac metabolic switch through inhibitory phosphorylation of glycogen synthase 1 (GYS1) and glycogen metabolism inactivation. Premature induction of p38γ/δ activation in cardiomyocytes of newborn mice results in an early GYS1 phosphorylation and inhibition of cardiac glycogen production, triggering an early metabolic shift that induces a deficit in cardiomyocyte fuel supply, leading to whole-body metabolic deregulation and maladaptive cardiac pathogenesis. Notably, the adverse effects of forced premature cardiac p38γ/δ activation in neonate mice are prevented by maternal diet supplementation of fatty acids during pregnancy and lactation. These results suggest that diet interventions have a potential for treating human cardiac genetic diseases that affect heart metabolism.
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Affiliation(s)
| | | | - Alfonso Mora
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Juan Antonio Lopez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Francisco González-Romero
- Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, Leioa, Spain
| | - Daniel Jimenez-Blasco
- Institute of Functional Biology and Genomics (IBFG), Universidad de Salamanca, CSIC, Salamanca, Spain
- Institute of Biomedical Research of Salamanca (IBSAL), Hospital Universitario de Salamanca, CSIC, Universidad de Salamanca, Salamanca, Spain
- Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Madrid, Spain
| | - Elena Rodríguez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | | | | | - Rebeca Acín-Pérez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Luis Leiva-Vega
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
| | - Jordi Duran
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | - Joan J. Guinovart
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
| | | | - José Antonio Enríquez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Madrid, Spain
| | - María Villlalba-Orero
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | - Juan P. Bolaños
- Institute of Functional Biology and Genomics (IBFG), Universidad de Salamanca, CSIC, Salamanca, Spain
- Institute of Biomedical Research of Salamanca (IBSAL), Hospital Universitario de Salamanca, CSIC, Universidad de Salamanca, Salamanca, Spain
- Centro de Investigación Biomédica en Red de Fragilidad y Envejecimiento Saludable (CIBERFES), Madrid, Spain
| | - Patricia Aspichueta
- Department of Physiology, Faculty of Medicine and Nursing, University of the Basque Country UPV/EHU, Leioa, Spain
- BioCruces Bizkaia Health Research Institute, Cruces University Hospital, Barakaldo, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Madrid, Spain
| | - Jesús Vázquez
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
- CIBER de Enfermedades Cardiovasculares (CIBERCV), Madrid, Spain
| | | | - Guadalupe Sabio
- Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
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8
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López-Soldado I, Guinovart JJ, Duran J. Increased liver glycogen levels enhance exercise capacity in mice. J Biol Chem 2021; 297:100976. [PMID: 34284060 PMCID: PMC8350413 DOI: 10.1016/j.jbc.2021.100976] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 07/15/2021] [Accepted: 07/16/2021] [Indexed: 12/22/2022] Open
Abstract
Muscle glycogen depletion has been proposed as one of the main causes of fatigue during exercise. However, few studies have addressed the contribution of liver glycogen to exercise performance. Using a low-intensity running protocol, here, we analyzed exercise capacity in mice overexpressing protein targeting to glycogen (PTG) specifically in the liver (PTGOE mice), which show a high concentration of glycogen in this organ. PTGOE mice showed improved exercise capacity, as determined by the distance covered and time ran in an extenuating endurance exercise, compared with control mice. Moreover, fasting decreased exercise capacity in control mice but not in PTGOE mice. After exercise, liver glycogen stores were totally depleted in control mice, but PTGOE mice maintained significant glycogen levels even in fasting conditions. In addition, PTGOE mice displayed an increased hepatic energy state after exercise compared with control mice. Exercise caused a reduction in the blood glucose concentration in control mice that was less pronounced in PTGOE mice. No changes were found in the levels of blood lactate, plasma free fatty acids, or β-hydroxybutyrate. Plasma glucagon was elevated after exercise in control mice, but not in PTGOE mice. Exercise-induced changes in skeletal muscle were similar in both genotypes. These results identify hepatic glycogen as a key regulator of endurance capacity in mice, an effect that may be exerted through the maintenance of blood glucose levels.
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Affiliation(s)
- Iliana López-Soldado
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.
| | - Joan J Guinovart
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain; Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Barcelona, Spain
| | - Jordi Duran
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain
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9
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Chown EE, Wang P, Zhao X, Crowder JJ, Strober JW, Sullivan MA, Xue Y, Bennett CS, Perri AM, Evers BM, Roach PJ, Depaoli‐Roach AA, Akman HO, Pederson BA, Minassian BA. GYS1 or PPP1R3C deficiency rescues murine adult polyglucosan body disease. Ann Clin Transl Neurol 2020; 7:2186-2198. [PMID: 33034425 PMCID: PMC7664254 DOI: 10.1002/acn3.51211] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVE Adult polyglucosan body disease (APBD) is an adult-onset neurological variant of glycogen storage disease type IV. APBD is caused by recessive mutations in the glycogen branching enzyme gene, and the consequent accumulation of poorly branched glycogen aggregates called polyglucosan bodies in the nervous system. There are presently no treatments for APBD. Here, we test whether downregulation of glycogen synthesis is therapeutic in a mouse model of the disease. METHODS We characterized the effects of knocking out two pro-glycogenic proteins in an APBD mouse model. APBD mice were crossed with mice deficient in glycogen synthase (GYS1), or mice deficient in protein phosphatase 1 regulatory subunit 3C (PPP1R3C), a protein involved in the activation of GYS1. Phenotypic and histological parameters were analyzed and glycogen was quantified. RESULTS APBD mice deficient in GYS1 or PPP1R3C demonstrated improvements in life span, morphology, and behavioral assays of neuromuscular function. Histological analysis revealed a reduction in polyglucosan body accumulation and of astro- and micro-gliosis in the brains of GYS1- and PPP1R3C-deficient APBD mice. Brain glycogen quantification confirmed the reduction in abnormal glycogen accumulation. Analysis of skeletal muscle, heart, and liver found that GYS1 deficiency reduced polyglucosan body accumulation in all three tissues and PPP1R3C knockout reduced skeletal muscle polyglucosan bodies. INTERPRETATION GYS1 and PPP1R3C are effective therapeutic targets in the APBD mouse model. These findings represent a critical step toward the development of a treatment for APBD and potentially other glycogen storage disease type IV patients.
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Affiliation(s)
- Erin E. Chown
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
- Institute of Medical ScienceUniversity of TorontoTorontoOntarioCanada
| | - Peixiang Wang
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
| | - Xiaochu Zhao
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
| | - Justin J. Crowder
- Indiana University School of Medicine‐MuncieBall State UniversityMuncieIndianaUSA
| | - Jordan W. Strober
- Indiana University School of Medicine‐MuncieBall State UniversityMuncieIndianaUSA
| | - Mitchell A. Sullivan
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
- Glycation and DiabetesMater Research Institute‐University of QueenslandTranslational Research InstituteBrisbaneQueenslandAustralia
| | - Yunlin Xue
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
| | - Cody S. Bennett
- Indiana University School of Medicine‐MuncieBall State UniversityMuncieIndianaUSA
| | - Ami M. Perri
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
| | - Bret M. Evers
- Department of PathologyUniversity of Texas SouthwesternDallasTexasUSA
| | - Peter J. Roach
- Department of Biochemistry and Molecular BiologyIndiana University School of MedicineIndianapolisIndianaUSA
| | - Anna A. Depaoli‐Roach
- Department of Biochemistry and Molecular BiologyIndiana University School of MedicineIndianapolisIndianaUSA
| | - H. Orhan Akman
- Department of NeurologyH. Houston Merritt Neuromuscular Research CenterColumbia University Medical CenterNew YorkNew YorkUSA
| | | | - Berge A. Minassian
- Genetics and Genome Biology ProgramThe Hospital for Sick ChildrenPeter Gilgan Centre for Research and LearningTorontoOntarioCanada
- Division of NeurologyDepartment of PediatricsUniversity of Texas SouthwesternDallasTexasUSA
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Pederson BA. Structure and Regulation of Glycogen Synthase in the Brain. ADVANCES IN NEUROBIOLOGY 2019; 23:83-123. [PMID: 31667806 DOI: 10.1007/978-3-030-27480-1_3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Brain glycogen synthesis is a regulated, multi-step process that begins with glucose transport across the blood brain barrier and culminates with the actions of glycogen synthase and the glycogen branching enzyme to elongate glucose chains and introduce branch points in a growing glycogen molecule. This review focuses on the synthesis of glycogen in the brain, with an emphasis on glycogen synthase, but draws on salient studies in mammalian muscle and liver as well as baker's yeast, with the goal of providing a more comprehensive view of glycogen synthesis and highlighting potential areas for further study in the brain. In addition, deficiencies in the glycogen biosynthetic enzymes which lead to glycogen storage diseases in humans are discussed, highlighting effects on the brain and discussing findings in genetically modified animal models that recapitulate these diseases. Finally, implications of glycogen synthesis in neurodegenerative and other diseases that impact the brain are presented.
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11
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Over-expression of muscle glycogen synthase in human diabetic nephropathy. Histochem Cell Biol 2014; 143:313-24. [PMID: 25371328 DOI: 10.1007/s00418-014-1290-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2014] [Indexed: 01/15/2023]
Abstract
Diabetic nephropathy (DN) is a major complication of diabetic patients and the leading cause of end-stage renal disease. Glomerular dysfunction plays a critical role in DN, but deterioration of renal function also correlates with tubular alterations. Human DN is characterized by glycogen accumulation in tubules. Although this pathological feature has long been recognized, little information exists about the triggering mechanism. In this study, we detected over-expression of muscle glycogen synthase (MGS) in diabetic human kidney. This enhanced expression suggests the participation of MGS in renal metabolic changes associated with diabetes. HK2 human renal cell line exhibited an intrinsic ability to synthesize glycogen, which was enhanced after over-expression of protein targeting to glycogen. A correlation between increased glycogen amount and cell death was observed. Based on a previous transcriptome study on human diabetic kidney disease, significant differences in the expression of genes involved in glycogen metabolism were analyzed. We propose that glucose, but not insulin, is the main modulator of MGS activity in HK2 cells, suggesting that blood glucose control is the best approach to modulate renal glycogen-induced damage during long-term diabetes.
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12
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Takezawa Y, Kohsaka S, Nakajima K. Transient down-regulation and restoration of glycogen synthase levels in axotomized rat facial motoneurons. Brain Res 2014; 1586:34-45. [PMID: 25152465 DOI: 10.1016/j.brainres.2014.08.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 08/15/2014] [Accepted: 08/16/2014] [Indexed: 11/19/2022]
Abstract
In adult rats, transection of the facial nerve causes a functional down-regulation of motoneurons and glial activation/proliferation. It has not been clear how energy-supplying systems are regulated in an axotomized facial nucleus. Here we investigated the regulation of molecules involved in glycogen degradation/synthesis in axotomized facial nuclei in rats. Immunoblotting revealed that the amounts of glycogen phosphorylase in the contralateral and ipsilateral nuclei were unchanged for the first 14 days, whereas the amount of glycogen synthase in the axotomized facial nuclei was significantly decreased from days 7-14 post-insult. A quantitative analysis estimated that the glycogen synthase levels in the transected nucleus were reduced to approx. 50% at 14 days post-injury. An immunohistochemical study showed that the injured motoneurons had decreased expressions of glycogen synthase proteins. The glycogen synthase levels in the axotomized facial nucleus had returned to control levels by 5 weeks post-insult, as had the cholinergic markers. The immunohistochemical study also revealed the recovery of glycogen synthase levels at the later stage. The glycogen phosphorylase levels in the injured nucleus were not significantly changed during weeks 3-5 post-insult. Taken together, these results demonstrated that the injured facial motoneurons transiently reduced glycogen synthase levels at around 1-2 weeks post-insult, but restored the levels at 4-5 weeks post-insult.
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Affiliation(s)
- Yosuke Takezawa
- Department of Bioinformatics, Faculty of Engineering, Soka University, Tokyo 192-8577, Japan
| | - Shinichi Kohsaka
- Department of Neurochemistry, National Institute of Neuroscience, Tokyo 187-8502, Japan
| | - Kazuyuki Nakajima
- Department of Bioinformatics, Faculty of Engineering, Soka University, Tokyo 192-8577, Japan.
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13
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Wang L, Xiong Y, Zuo B, Lei M, Ren Z, Xu D. Molecular and functional characterization of glycogen synthase in the porcine satellite cells under insulin treatment. Mol Cell Biochem 2011; 360:169-80. [PMID: 21931959 DOI: 10.1007/s11010-011-1054-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 09/08/2011] [Indexed: 12/24/2022]
Abstract
Glycogen synthase (GS) catalyzes the key step of glycogen synthesis and plays an important role in glycogen metabolism in liver and muscle. In this study, we cloned the cDNA and promoter sequences of porcine glycogen synthesis genes (GYS1 and GYS2). Expression analysis revealed that porcine GYS1 was highly expressed in the skeletal muscle and heart. GYS2 was expressed specifically in liver and subcutaneous adipose tissue. The expression level of GYS1 was up-regulated from proliferation to differentiation in the porcine satellite cells, and insulin did not significantly affect the transcription of GYS1. Insulin stimulated 72-h-differentiated satellite cells as indicated by decrease in phosphorylation of GS, but did not affect GYS1 transcription and total GS protein level, suggesting that the effect of insulin is primarily mediated via posttranscriptional control rather than regulated at the transcriptional level. Four single-nucleotide polymorphisms (SNPs) were detected in the promoter and cDNA sequences of porcine GYS1. Association analyses revealed that the GYS1 Hin6I and MvaI polymorphisms both had significant associations (P < 0.05) with pH of M. longissimus dorsi (pHLD), M. biceps femoris (pHBF) and M. semipinalis capitis (pHSC) at 45 min postmortem. These results provide useful information for further investigation on the function of glycogen synthase in porcine skeletal muscle.
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Affiliation(s)
- Linjie Wang
- Key Laboratory of Swine Genetics and Breeding, Ministry of Agriculture, College of Animal Science, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China
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Kruszynska YT, Ciaraldi TP, Henry RR. Regulation of Glucose Metabolism in Skeletal Muscle. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070218] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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15
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Lee YC, Chang CJ, Bali D, Chen YT, Yan YT. Glycogen-branching enzyme deficiency leads to abnormal cardiac development: novel insights into glycogen storage disease IV. Hum Mol Genet 2010; 20:455-65. [DOI: 10.1093/hmg/ddq492] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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16
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Molecular characterization of glycogen synthase 1 and its tissue expression profile with type II hexokinase and muscle-type phosphofructokinase in horses. Mol Biol Rep 2010; 38:461-9. [DOI: 10.1007/s11033-010-0129-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 03/23/2010] [Indexed: 01/07/2023]
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17
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Pederson BA, Schroeder JM, Parker GE, Smith MW, DePaoli-Roach AA, Roach PJ. Glucose metabolism in mice lacking muscle glycogen synthase. Diabetes 2005; 54:3466-73. [PMID: 16306363 DOI: 10.2337/diabetes.54.12.3466] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glycogen is an important component of whole-body glucose metabolism. MGSKO mice lack skeletal muscle glycogen due to disruption of the GYS1 gene, which encodes muscle glycogen synthase. MGSKO mice were 5-10% smaller than wild-type littermates with less body fat. They have more oxidative muscle fibers and, based on the activation state of AMP-activated protein kinase, more capacity to oxidize fatty acids. Blood glucose in fed and fasted MGSKO mice was comparable to wild-type littermates. Serum insulin was lower in fed but not in fasted MGSKO animals. In a glucose tolerance test, MGSKO mice disposed of glucose more effectively than wild-type animals and had a more sustained elevation of serum insulin. This result was not explained by increased conversion to serum lactate or by enhanced storage of glucose in the liver. However, glucose infusion rate in a euglycemic-hyperinsulinemic clamp was normal in MGSKO mice despite diminished muscle glucose uptake. During the clamp, MGSKO animals accumulated significantly higher levels of liver glycogen as compared with wild-type littermates. Although disruption of the GYS1 gene negatively affects muscle glucose uptake, overall glucose tolerance is actually improved, possibly because of a role for GYS1 in tissues other than muscle.
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Affiliation(s)
- Bartholomew A Pederson
- Department of Biochemistry and Molecular Biology and Center for Diabetes Research, Indiana University School of Medicine, Indianapolis, Indiana, USA
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18
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Pederson BA, Chen H, Schroeder JM, Shou W, DePaoli-Roach AA, Roach PJ. Abnormal cardiac development in the absence of heart glycogen. Mol Cell Biol 2004; 24:7179-87. [PMID: 15282316 PMCID: PMC479719 DOI: 10.1128/mcb.24.16.7179-7187.2004] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycogen serves as a repository of glucose in many mammalian tissues. Mice lacking this glucose reserve in muscle, heart, and several other tissues were generated by disruption of the GYS1 gene, which encodes an isoform of glycogen synthase. Crossing mice heterozygous for the GYS1 disruption resulted in a significant underrepresentation of GYS1-null mice in the offspring. Timed matings established that Mendelian inheritance was followed for up to 18.5 days postcoitum (dpc) and that approximately 90% of GYS1-null animals died soon after birth due to impaired cardiac function. Defects in cardiac development began between 11.5 and 14.5 dpc. At 18.5 dpc, the hearts were significantly smaller, with reduced ventricular chamber size and enlarged atria. Consistent with impaired cardiac function, edema, pooling of blood, and hemorrhagic liver were seen. Glycogen synthase and glycogen were undetectable in cardiac muscle and skeletal muscle from the surviving null mice, and the hearts showed normal morphology and function. Congenital heart disease is one of the most common birth defects in humans, at up to 1 in 50 live births. The results provide the first direct evidence that the ability to synthesize glycogen in cardiac muscle is critical for normal heart development and hence that its impairment could be a significant contributor to congenital heart defects.
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Affiliation(s)
- Bartholomew A Pederson
- Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, IN 46202-5122, USA
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Fredriksson J, Ridderstråle M, Groop L, Orho-Melander M. Characterization of the human skeletal muscle glycogen synthase gene (GYS1) promoter. Eur J Clin Invest 2004; 34:113-21. [PMID: 14764074 DOI: 10.1111/j.1365-2362.2004.01299.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Impaired activation of the human skeletal muscle glycogen synthase by insulin is typical for type 2 diabetic patients. Regulation of glycogen synthase occurs mainly by phosphorylation/dephoshorylation but little is known whether there also is transcriptional regulation. Therefore we studied transcriptional regulation of the human skeletal muscle glycogen synthase gene (GYS1) and evaluated the effects of insulin and forskolin on the promoter activity. METHODS Seven promoter fragments were expressed in C2C12 myoblasts and myotubes and in HEK293 cells, and the luciferase assay was used to determine transcriptional activity. RESULTS The highest luciferase activity, 350-fold of the promoterless vector, was obtained with nucleotides -692 to +59 in myotubes (P < 0.001), while the nucleotides -250 to +59 provided the highest, 45-fold, activity in the HEK293 cells (P < 0.001). Longer promoter constructs (nucleotides -971, -1707 and -2158 to +59, respectively) had low promoter activity in both cell types. Forskolin treatment for 24 h resulted in approximately 30% decreased promoter activity in myotubes (P < 0.05). Insulin treatment for 0.5-3 h did not increase GYS1 promoter activity; instead the activity was slightly but significantly decreased after 24 h in myotubes (P < 0.005). CONCLUSIONS From our results we conclude that basal GYS1 promoter activity is obtained from the first 250 nucleotides of the promoter, while the nucleotides -692 to -544 seem to be responsible for muscle-specific expression, and nucleotides -971 to -692 for negative regulation. In myotubes, the GYS1 promoter was sensitive to negative regulation by forskolin, whereas insulin did not increase GYS1 transcription.
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20
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Cid E, Gomis RR, Geremia RA, Guinovart JJ, Ferrer JC. Identification of two essential glutamic acid residues in glycogen synthase. J Biol Chem 2000; 275:33614-21. [PMID: 10924520 DOI: 10.1074/jbc.m005358200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The detailed catalytic mechanism by which glycosyltransferases catalyze the transfer of a glycosyl residue from a donor sugar to an acceptor is not known. Through the multiple alignment of all known eukaryotic glycogen synthases we have found an invariant 17-amino acid stretch enclosed within the most conserved region of the members of this family. This peptide includes an E-X(7)-E motif, which is highly conserved in four families of retaining glycosyltransferases. Site-directed mutagenesis was performed in human muscle glycogen synthase to analyze the roles of the two conserved Glu residues (Glu-510 and Glu-518) of the motif. Proteins were transiently expressed in COS-1 cells as fusions to green fluorescence protein. The E510A and E518A mutant proteins retained the ability to translocate from the nucleus to the cytosol in response to glucose and to bind to intracellular glycogen. Although the E518A variant had approximately 6% of the catalytic activity shown by the green fluorescence protein-human muscle glycogen synthase fusion protein, the E510A mutation inactivated the enzyme. These results led us to conclude that the E-X(7)-E motif is part of the active site of eukaryotic glycogen synthases and that both conserved Glu residues are involved in catalysis. We propose that Glu-510 may function as the nucleophile and Glu-518 as the general acid/base catalyst.
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Affiliation(s)
- E Cid
- Departament de Bioquimica i Biologia Molecular, Universitat de Barcelona, Barcelona E-08028, Spain
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21
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Chibalin AV, Yu M, Ryder JW, Song XM, Galuska D, Krook A, Wallberg-Henriksson H, Zierath JR. Exercise-induced changes in expression and activity of proteins involved in insulin signal transduction in skeletal muscle: differential effects on insulin-receptor substrates 1 and 2. Proc Natl Acad Sci U S A 2000; 97:38-43. [PMID: 10618367 PMCID: PMC26612 DOI: 10.1073/pnas.97.1.38] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Level of physical activity is linked to improved glucose homeostasis. We determined whether exercise alters the expression and/or activity of proteins involved in insulin-signal transduction in skeletal muscle. Wistar rats swam 6 h per day for 1 or 5 days. Epitrochlearis muscles were excised 16 h after the last exercise bout, and were incubated with or without insulin (120 nM). Insulin-stimulated glucose transport increased 30% and 50% after 1 and 5 days of exercise, respectively. Glycogen content increased 2- and 4-fold after 1 and 5 days of exercise, with no change in glycogen synthase expression. Protein expression of the glucose transporter GLUT4 and the insulin receptor increased 2-fold after 1 day, with no further change after 5 days of exercise. Insulin-stimulated receptor tyrosine phosphorylation increased 2-fold after 5 days of exercise. Insulin-stimulated tyrosine phosphorylation of insulin-receptor substrate (IRS) 1 and associated phosphatidylinositol (PI) 3-kinase activity increased 2.5- and 3. 5-fold after 1 and 5 days of exercise, despite reduced (50%) IRS-1 protein content after 5 days of exercise. After 1 day of exercise, IRS-2 protein expression increased 2.6-fold and basal and insulin-stimulated IRS-2 associated PI 3-kinase activity increased 2. 8-fold and 9-fold, respectively. In contrast to IRS-1, IRS-2 expression and associated PI 3-kinase activity normalized to sedentary levels after 5 days of exercise. Insulin-stimulated Akt phosphorylation increased 5-fold after 5 days of exercise. In conclusion, increased insulin-stimulated glucose transport after exercise is not limited to increased GLUT4 expression. Exercise leads to increased expression and function of several proteins involved in insulin-signal transduction. Furthermore, the differential response of IRS-1 and IRS-2 to exercise suggests that these molecules have specialized, rather than redundant, roles in insulin signaling in skeletal muscle.
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Affiliation(s)
- A V Chibalin
- Department of Surgical Sciences, Karolinska Hospital, S-171 76, Karolinska Institutet, S-171 77, Stockholm, Sweden
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22
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Pellegri G, Rossier C, Magistretti PJ, Martin JL. Cloning, localization and induction of mouse brain glycogen synthase. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1996; 38:191-9. [PMID: 8793107 DOI: 10.1016/0169-328x(95)00305-c] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The cDNA for mouse brain glycogen synthase has been isolated by screening a mouse cerebral cortical astrocyte lambda ZAP II cDNA library. The mouse brain glycogen synthase cDNA is 3.5 kilobases in length and encodes a protein of 737 amino acids. The coding sequence of mouse brain glycogen synthase cDNA shares approximately 87% nucleotide identity and approximately 96% amino acid identity with the muscle isozyme, while the degree of identity is lower with the liver isozyme. The regional distribution of glycogen synthase mRNA determined by in situ hybridization in the mouse brain reveals a wide distribution throughout the central nervous system with highest densities observed in the cerebellum, hippocampus and olfactory bulb. At the cellular level the expression of brain glycogen synthase mRNA is localized both in astrocytes and neurons with, however, the higher levels observed in astrocytes. Vasoactive intestinal peptide and noradrenaline, two neurotransmitters previously shown to induce a glycogen resynthesis in cultured astrocytes, upregulate the expression of glycogen synthase mRNA in this cell type but not in neurons.
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Affiliation(s)
- G Pellegri
- Laboratoire de Recherche Neurologique, Institut de Physiologie et Service de Neurologie du CHUV, Faculté de Médecine Université de Lausanne, Switzerland
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Skurat AV, Roach PJ. Phosphorylation of sites 3a and 3b (Ser640 and Ser644) in the control of rabbit muscle glycogen synthase. J Biol Chem 1995; 270:12491-7. [PMID: 7759494 DOI: 10.1074/jbc.270.21.12491] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Glycogen synthase kinase-3 inactivates rabbit muscle glycogen synthase by sequential phosphorylation of four COOH-terminal residues Ser652 (site 4), Ser648 (site 3c), Ser644 (site 3b), and Ser640 (site 3a). Effective recognition of glycogen synthase by glycogen synthase kinase-3 occurs only after the phosphorylation of Ser656 (site 5) catalyzed by casein kinase II. The present study addresses specifically the role of sites 3a and 3b in the regulation of glycogen synthase expressed in COS cells. Simultaneous Ser-->Ala substitutions at sites 3 a, b and c, 4, and 5 in the same protein molecule eliminated 32P labeling in the proteolytic fragment Arg634-Lys682, which contains these sites. This mutant enzyme (which also had a Ser-->Ala substitution at site 2 in the NH2 terminus) had a -/+ glucose-6-P activity ratio of approximately 0.8, similar to that of totally dephosphorylated enzyme. Reinstating serine residues at either site 3a or site 3b restored labeling in the Arg634-Lys682 peptide and caused a decrease in the activity ratio to 0.4-0.6. When both sites 3a and 3b were reintroduced, there was complete inactivation of the enzyme. Thus, sites 3a and 3b are sufficient for the inactivation of glycogen synthase and act synergistically to control activity. This investigation demonstrates the existence of an alternate mechanism for the phosphorylation of sites 3a and 3b that does not depend on prior phosphorylation of site 5.
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Affiliation(s)
- A V Skurat
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis 46202-5122, USA
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Lin T, Lawrence J. Activation of ribosomal protein S6 kinases does not increase glycogen synthesis or glucose transport in rat adipocytes. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)31957-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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Michaels JE, Cardell RR. Localization of glycogen synthase activity in liver of fasted normal and adrenalectomized rats after injection of dexamethasone. Anat Rec (Hoboken) 1993; 236:486-92. [PMID: 8363053 DOI: 10.1002/ar.1092360309] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hepatic glycogen synthase activity was localized in normal and adrenalectomized (ADX) rats after fasting overnight and in fasted ADX rats after injection of dexamethasone (DEX) 2-8 h prior to sacrifice to stimulate glycogen synthesis. Cryostat sections were incubated in medium containing substrate to demonstrate glycogen synthase activity as indicated by glycogen synthesized during incubation. Sections from fasted normal rats showed limited dispersed glycogen synthase activity in both periportal and centrilobular regions. In contrast, activity for glycogen synthase in hepatocytes from fasted ADX rats appeared as large aggregates in random hepatocytes throughout the lobule. Two hours after injection of DEX the reaction product appeared as aggregates in some hepatocytes, but other cells revealed dispersed enzyme activity. Glycogen synthase activity was evident in more hepatocytes after 4 h treatment with DEX and after 8 h virtually all hepatocytes contained abundant reaction product. The results suggest that synthase activity becomes concentrated in limited regions of selected hepatocytes in fasted ADX rats. DEX stimulation of glycogen synthesis for 4-8 h results in increased enzyme activity.
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Affiliation(s)
- J E Michaels
- Department of Anatomy and Cell Biology, University of Cincinnati College of Medicine, Ohio 45267-0521
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Vestergaard H, Lund S, Larsen FS, Bjerrum OJ, Pedersen O. Glycogen synthase and phosphofructokinase protein and mRNA levels in skeletal muscle from insulin-resistant patients with non-insulin-dependent diabetes mellitus. J Clin Invest 1993; 91:2342-50. [PMID: 8514849 PMCID: PMC443291 DOI: 10.1172/jci116466] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In patients with non-insulin-dependent diabetes mellitus (NIDDM) and matched control subjects we examined the interrelationships between in vivo nonoxidative glucose metabolism and glucose oxidation and the muscle activities, as well as the immunoreactive protein and mRNA levels of the rate-limiting enzymes in glycogen synthesis and glycolysis, glycogen synthase (GS) and phosphofructokinase (PFK), respectively. Analysis of biopsies of quadriceps muscle from 19 NIDDM patients and 19 control subjects showed in the basal state a 30% decrease (P < 0.005) in total GS activity and a 38% decrease (P < 0.001) in GS mRNA/microgram DNA in NIDDM patients, whereas the GS protein level was normal. The enzymatic activity and protein and mRNA levels of PFK were all normal in diabetic patients. In subgroups of NIDDM patients and control subjects an insulin-glucose clamp in combination with indirect calorimetry was performed. The rate of insulin-stimulated nonoxidative glucose metabolism was decreased by 47% (P < 0.005) in NIDDM patients, whereas the glucose oxidation rate was normal. The PFK activity, protein level, and mRNA/microgram DNA remained unchanged. The relative activation of GS by glucose-6-phosphate was 33% lower (P < 0.02), whereas GS mRNA/micrograms DNA was 37% lower (P < 0.05) in the diabetic patients after 4 h of hyperinsulinemia. Total GS immunoreactive mass remained normal. In conclusion, qualitative but not quantitative posttranslational abnormalities of the GS protein in muscle determine the reduced insulin-stimulated nonoxidative glucose metabolism in NIDDM.
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Carabaza A, Arino J, Fox JW, Villar-Palasi C, Guinovart JJ. Purification, characterization and partial amino acid sequence of glycogen synthase from Saccharomyces cerevisiae. Biochem J 1990; 268:401-7. [PMID: 2114092 PMCID: PMC1131446 DOI: 10.1042/bj2680401] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Glycogen synthase from Saccharomyces cerevisiae was purified to homogeneity. The enzyme showed a subunit molecular mass of 80 kDa. The holoenzyme appears to be a tetramer. Antibodies developed against purified yeast glycogen synthase inactivated the enzyme in yeast extracts and allowed the detection of the protein in Western blots. Amino acid analysis showed that the enzyme is very rich in glutamate and/or glutamine residues. The N-terminal sequence (11 amino acid residues) was determined. In addition, selected tryptic-digest peptides were purified by reverse-phase h.p.l.c. and submitted to gas-phase sequencing. Up to eight sequences (79 amino acid residues) could be aligned with the human muscle enzyme sequence. Levels of identity range between 37 and 100%, indicating that, although human and yeast glycogen synthases probably share some conserved regions, significant differences in their primary structure should be expected.
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Affiliation(s)
- A Carabaza
- Departament de Bioquímica i Biologia Molecular, Facultat de Veterinària, Universitat Autònoma de Barcelona, Spain
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Bai G, Zhang ZJ, Werner R, Nuttall FQ, Tan AW, Lee EY. The primary structure of rat liver glycogen synthase deduced by cDNA cloning. Absence of phosphorylation sites 1a and 1b. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39007-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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29
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Rasmussen LH, Juhl H, Esmann V, Petersen HU. Glycogen synthase from human and bovine polymorphonuclear leukocyte. Immunochemical characterization and comparison to glycogen synthase from rat and rabbit muscle and liver cells. FEBS Lett 1988; 230:116-20. [PMID: 2450780 DOI: 10.1016/0014-5793(88)80653-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glycogen synthase from human and bovine polymorphonuclear leukocytes was purified to homogeneity. Rabbit antisera were raised against the two glycogen synthases and used for immunochemical analysis. Western blotting analysis showed that the subunit of glycogen synthase in crude homogenates of human and bovine leukocytes in both cases has an Mr of 85,000. The existence of a cross-reactivity between the two enzymes and the corresponding antisera demonstrates immunological similarities between bovine and human leukocyte glycogen synthase. In addition, both antisera recognize glycogen synthase in crude cellular extracts from rabbit and rat liver and from skeletal muscle. Leukocyte glycogen synthase, therefore, cannot be classified as either muscle (M-type) or liver (L-type) glycogen synthase and our results do not support the proposed immunochemical distinction between M- and L-type glycogen synthase.
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Affiliation(s)
- L H Rasmussen
- Department of Medicine and Infectious Diseases, Marselisborg Hospital, Aarhus, Denmark
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30
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Abstract
Antisera against glycogen synthase from canine brain were prepared and used for investigation of the localization of the enzyme in the brain. Antisera cross-reacted only with the 88-kilodalton protein that is the subunit of brain glycogen synthase. Immunoreactivity of glycogen synthase was universally distributed in all regions of the brain, although hippocampus, cerebral cortex, caudatoputamen, and cerebellar cortex had relatively high immunoreactivity. Light microscopic examination revealed that the immunoreactivity was found in all cell types, such as neurons in several regions, astrocytes, ependymal cells surrounding the ventricle, oligodendrocytes, and epithelial cells of the choroid plexus in the ventricle. Immunoreactive intensity was more prominent in neurons than glial cells. Immunostaining may be a useful tool for investigation of the state of glycogen metabolism under normal and pathological conditions.
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Affiliation(s)
- N Inoue
- Department of Neurosurgery, Kumamoto University Medical School, Japan
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31
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Wolleben CD, McPherson RK, Rulfs J, Johnson GL, Miller TB. Phosphorylation of rat heart glycogen synthase: studies in cardiomyocytes and in vitro phosphorylations with cAMP-dependent kinase and protein phosphatase-1. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 928:98-106. [PMID: 3030451 DOI: 10.1016/0167-4889(87)90090-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The phosphorylation of glycogen synthase has been studied in freshly isolated adult rat cardiomyocytes. Six peaks of 32P-labeled tryptic peptides are recovered via C-18 high performance liquid chromatography (HPLC) when synthase is immunoprecipitated from 32P-labeled cardiomyocytes and digested with trypsin. When epinephrine treated cells are used as a source of enzyme, the same HPLC profile is obtained with a dramatic enhancement of 32P recovered in two of the HPLC peaks. In vitro phosphorylation of rat heart synthase by cAMP-dependent protein kinase stimulates the conversion of synthase from the I to the D form and results in the recovery of the same tryptic peptides from the C-18 as is the case for synthase derived from cardiomyocytes. Treatment of cAMP-dependent kinase phosphorylated synthase with protein phosphatase-1 leads to a reactivation of the enzyme and a dephosphorylation of the same tryptic peptides that are selectively phosphorylated in epinephrine treated cardiomyocytes. These results are discussed in relation to hormonal control of glycogen metabolism in cardiac tissue.
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Inoue N, Iwasa T, Fukunaga K, Matsukado Y, Miyamoto E. Phosphorylation and inactivation of brain glycogen synthase by a multifunctional calmodulin-dependent protein kinase. J Neurochem 1987; 48:981-8. [PMID: 3100725 DOI: 10.1111/j.1471-4159.1987.tb05613.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glycogen synthase was partially purified from canine brain to about 70% purity. The purified enzyme showed differences from the properties of the skeletal muscle enzyme with respect to molecular weights of the holoenzyme and subunit and phosphopeptide mapping. The multifunctional calmodulin-dependent protein kinase from the brain phosphorylated brain glycogen synthase with concomitant inactivation of the enzyme. Although about 1.3 mol of phosphate/mol subunit was maximally incorporated into glycogen synthase, 0.4 mol of phosphate/mol subunit was sufficient for the maximal inactivation of the enzyme. The results indicate that brain glycogen synthase is regulated in a calmodulin-dependent manner similarly to the skeletal muscle enzyme, but that the brain enzyme is different from the skeletal muscle enzyme.
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33
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Liver isozyme of rabbit glycogen synthase. Amino acid sequences surrounding phosphorylation sites recognized by cyclic AMP-dependent protein kinase. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)75975-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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34
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Wang Y, Camici M, Lee FT, Ahmad Z, DePaoli-Roach AA, Roach PJ. Multiple phosphorylation sites of rat liver glycogen synthase. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 888:225-36. [PMID: 3091084 DOI: 10.1016/0167-4889(86)90025-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Rat liver glycogen synthase was purified to homogeneity by an improved procedure that yielded enzyme almost exclusively as a polypeptide of Mr 85,000. The phosphorylation of this enzyme by eight protein kinases was analyzed by cleavage of the enzyme subunit followed by mapping of the phosphopeptides using polyacrylamide gel electrophoresis in the presence of SDS, reverse-phase high-performance liquid chromatography and thin-layer electrophoresis. Cyclic AMP-dependent protein kinase, phosphorylase kinase, protein kinase C and the calmodulin-dependent protein kinase all phosphorylated the same small peptide (approx. 20 amino acids) located in a 14 kDa CNBr-fragment (CB-1). Calmodulin-dependent protein kinase and protein kinase C also modified second sites in CB-1. A larger CNBr-fragment (CB-2) of approx. 28 kDa was the dominant site of action for casein kinases I and II, FA/GSK-3 and the heparin-activated protein kinase. The sites modified were all localized in a 14 kDa species generated by trypsin digestion. Further proteolysis with V8 proteinase indicated that FA/GSK-3 and the heparin-activated enzyme recognized the same smaller peptide within CB-2, which may also be phosphorylated by casein kinase 1. Casein kinase 1 also modified a distinct peptide, as did casein kinase II. The results lead us to suggest homology to the muscle enzyme with regard to CB-1 phosphorylation and the region recognized by FA/GSK-3, which in rabbit muscle is characterized by a high density of proline and serine residues. A striking difference with the muscle isozyme is the apparent lack of phosphorylations corresponding to the muscle sites 1a and 1b. These results provide further evidence for the presence of liver- and muscle-specific glycogen synthase isozymes in the rat. That the isozymes differ subtly as to phosphorylation sites may provide a clue to the functional differences between the isozymes.
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35
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Osawa S, Chiu RH, McDonough A, Miller TB, Johnson GL. Isolation of partial cDNAs for rat liver and muscle glycogen phosphorylase isozymes. FEBS Lett 1986; 202:282-8. [PMID: 2424788 DOI: 10.1016/0014-5793(86)80702-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
cDNA clones for the rat liver and muscle glycogen phosphorylase isozymes have been isolated using isozyme-selective antibodies and libraries prepared in the expression vector, lambda gt11. A 1.2 kb cDNA coding for the carboxy-terminal domain of rat liver phosphorylase was found to have 82% homology with the amino acid sequence of rabbit muscle phosphorylase. Limited sequencing of rat muscle phosphorylase cDNA indicated a 95% homology with the rabbit muscle enzyme. The rat liver clone has eight additional amino acid residues at the COOH-terminus compared to the rat muscle clone. Furthermore, 17 of 26 (65%) residues between amino acids 815-840 differ between liver and muscle isozymes. The similarity in enzymatic properties and conservation of structure except at the COOH-terminus suggest that the liver and muscle phosphorylase isozymes do not exist in order to have significant differences in the regulation of glycogen breakdown in the two tissues. Rather, the phosphorylase isozymes probably evolved for tissue-specific transcriptional regulation of the genes in liver and muscle.
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36
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12 Liver Glycogen Synthase. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/s1874-6047(08)60437-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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