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Skurat AV, Segvich DM, Contreras CJ, Hu YC, Hurley TD, DePaoli-Roach AA, Roach PJ. Impaired malin expression and interaction with partner proteins in Lafora disease. J Biol Chem 2024; 300:107271. [PMID: 38588813 PMCID: PMC11063907 DOI: 10.1016/j.jbc.2024.107271] [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: 02/17/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 04/10/2024] Open
Abstract
Lafora disease (LD) is an autosomal recessive myoclonus epilepsy with onset in the teenage years leading to death within a decade of onset. LD is characterized by the overaccumulation of hyperphosphorylated, poorly branched, insoluble, glycogen-like polymers called Lafora bodies. The disease is caused by mutations in either EPM2A, encoding laforin, a dual specificity phosphatase that dephosphorylates glycogen, or EMP2B, encoding malin, an E3-ubiquitin ligase. While glycogen is a widely accepted laforin substrate, substrates for malin have been difficult to identify partly due to the lack of malin antibodies able to detect malin in vivo. Here we describe a mouse model in which the malin gene is modified at the C-terminus to contain the c-myc tag sequence, making an expression of malin-myc readily detectable. Mass spectrometry analyses of immunoprecipitates using c-myc tag antibodies demonstrate that malin interacts with laforin and several glycogen-metabolizing enzymes. To investigate the role of laforin in these interactions we analyzed two additional mouse models: malin-myc/laforin knockout and malin-myc/LaforinCS, where laforin was either absent or the catalytic Cys was genomically mutated to Ser, respectively. The interaction of malin with partner proteins requires laforin but is not dependent on its catalytic activity or the presence of glycogen. Overall, the results demonstrate that laforin and malin form a complex in vivo, which stabilizes malin and enhances interaction with partner proteins to facilitate normal glycogen metabolism. They also provide insights into the development of LD and the rescue of the disease by the catalytically inactive phosphatase.
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Affiliation(s)
- Alexander V Skurat
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Dyann M Segvich
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Christopher J Contreras
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA
| | - Yueh-Chiang Hu
- Division of Developmental Biology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Thomas D Hurley
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
| | - Anna A DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
| | - Peter J Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana, USA; Lafora Epilepsy Cure Initiative, University of Kentucky College of Medicine, Lexington, Kentucky, USA
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Masson SWC, Madsen S, Cooke KC, Potter M, Vegas AD, Carroll L, Thillainadesan S, Cutler HB, Walder KR, Cooney GJ, Morahan G, Stöckli J, James DE. Leveraging genetic diversity to identify small molecules that reverse mouse skeletal muscle insulin resistance. eLife 2023; 12:RP86961. [PMID: 37494090 PMCID: PMC10371229 DOI: 10.7554/elife.86961] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023] Open
Abstract
Systems genetics has begun to tackle the complexity of insulin resistance by capitalising on computational advances to study high-diversity populations. 'Diversity Outbred in Australia (DOz)' is a population of genetically unique mice with profound metabolic heterogeneity. We leveraged this variance to explore skeletal muscle's contribution to whole-body insulin action through metabolic phenotyping and skeletal muscle proteomics of 215 DOz mice. Linear modelling identified 553 proteins that associated with whole-body insulin sensitivity (Matsuda Index) including regulators of endocytosis and muscle proteostasis. To enrich for causality, we refined this network by focusing on negatively associated, genetically regulated proteins, resulting in a 76-protein fingerprint of insulin resistance. We sought to perturb this network and restore insulin action with small molecules by integrating the Broad Institute Connectivity Map platform and in vitro assays of insulin action using the Prestwick chemical library. These complementary approaches identified the antibiotic thiostrepton as an insulin resistance reversal agent. Subsequent validation in ex vivo insulin-resistant mouse muscle and palmitate-induced insulin-resistant myotubes demonstrated potent insulin action restoration, potentially via upregulation of glycolysis. This work demonstrates the value of a drug-centric framework to validate systems-level analysis by identifying potential therapeutics for insulin resistance.
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Affiliation(s)
- Stewart W C Masson
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Søren Madsen
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Kristen C Cooke
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Meg Potter
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Alexis Diaz Vegas
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Luke Carroll
- Australian Proteome Analysis Facility, Macquarie University, Macquarie Park, Australia
| | - Senthil Thillainadesan
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Harry B Cutler
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Ken R Walder
- School of Medicine, Deakin University, Geelong, Australia
| | - Gregory J Cooney
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - Grant Morahan
- Centre for Diabetes Research, Harry Perkins Institute of Medical Research, Murdoch, Australia
| | - Jacqueline Stöckli
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
| | - David E James
- Charles Perkins Centre, School of Life and Environmental Sciences, University of Sydney, Camperdown, Australia
- School of Medical Sciences University of Sydney, Sydney, Australia
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Pathomorphogenesis of Glycogen-Ground Glass Hepatocytic Inclusions (Polyglucosan Bodies) in Children after Liver Transplantation. Int J Mol Sci 2022; 23:ijms23179996. [PMID: 36077394 PMCID: PMC9456521 DOI: 10.3390/ijms23179996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 07/27/2022] [Accepted: 08/03/2022] [Indexed: 11/17/2022] Open
Abstract
Seventeen out of 764 liver biopsies from transplanted (Tx) livers in children showed glycogen-ground glass (GGG) hepatocytic inclusions. The inclusions were not present in pre-Tx or in the explanted or donor’s liver. Under the electron microscope (EM), the stored material within the cytosol appeared as non-membrane-bound aggregates of electron-lucent globoid or fibrillar granules, previously described as abnormally structured glycogen and identified as Polyglucosan bodies (PB). The appearance of GGG in our children was analogous to that of PB-GGG occurring in a number of congenital diseases due to gene mutations such as Lafora’s d., Andersen’s d., Adult Polyglucosan Body Disease and glycogenin deficiency. The same type of GGG was previously reported in the liver of patients undergoing transplants, immunosuppressive or antiblastic treatment. To explore the potential mechanism of GGG formation, we examined whether the drugs after whose treatment this phenomenon was observed could have a role. By carrying out molecular docking, we found that such drugs somehow present a high binding affinity for the active region of glycogenin, implicating that they can inactivate the protein, thus preventing its interaction with glycogen synthase (GS), as well as the maturation of the nascent glycogen towards gamma, beta or alfa glycogen granules. We could also demonstrate that PG inclusions consist of a complex of PAS positive material (glycogen) and glycogen-associated proteins, i.e., glicogenin-1 and -2 and ubiquitin. These features appear to be analogous to congenital GGG, suggesting that, in both cases, they result from the simultaneous dysregulation of glycogen synthesis and degradation. Drug-induced GGG appear to be toxic to the cell, despite their reversibility.
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Fastman NM, Liu Y, Ramanan V, Merritt H, Ambing E, DePaoli-Roach AA, Roach PJ, Hurley TD, Mellem KT, Ullman JC, Green E, Morgans D, Tzitzilonis C. The structural mechanism of human glycogen synthesis by the GYS1-GYG1 complex. Cell Rep 2022; 40:111041. [PMID: 35793618 DOI: 10.1016/j.celrep.2022.111041] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 04/15/2022] [Accepted: 06/11/2022] [Indexed: 11/03/2022] Open
Abstract
Glycogen is the primary energy reserve in mammals, and dysregulation of glycogen metabolism can result in glycogen storage diseases (GSDs). In muscle, glycogen synthesis is initiated by the enzymes glycogenin-1 (GYG1), which seeds the molecule by autoglucosylation, and glycogen synthase-1 (GYS1), which extends the glycogen chain. Although both enzymes are required for proper glycogen production, the nature of their interaction has been enigmatic. Here, we present the human GYS1:GYG1 complex in multiple conformations representing different functional states. We observe an asymmetric conformation of GYS1 that exposes an interface for close GYG1 association, and propose this state facilitates handoff of the GYG1-associated glycogen chain to a GYS1 subunit for elongation. Full activation of GYS1 widens the GYG1-binding groove, enabling GYG1 release concomitant with glycogen chain growth. This structural mechanism connecting chain nucleation and extension explains the apparent stepwise nature of glycogen synthesis and suggests distinct states to target for GSD-modifying therapeutics.
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Affiliation(s)
- Nathan M Fastman
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Yuxi Liu
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Vyas Ramanan
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Hanne Merritt
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Eileen Ambing
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Anna A DePaoli-Roach
- Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46220, USA
| | - Peter J Roach
- Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46220, USA
| | - Thomas D Hurley
- Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46220, USA
| | - Kevin T Mellem
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Julie C Ullman
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Eric Green
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - David Morgans
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA
| | - Christos Tzitzilonis
- Maze Therapeutics, 171 Oyster Point Blvd, Suite 300, South San Francisco, CA 94080, USA.
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Mechanism of glycogen synthase inactivation and interaction with glycogenin. Nat Commun 2022; 13:3372. [PMID: 35690592 PMCID: PMC9188544 DOI: 10.1038/s41467-022-31109-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 06/02/2022] [Indexed: 11/08/2022] Open
Abstract
Glycogen is the major glucose reserve in eukaryotes, and defects in glycogen metabolism and structure lead to disease. Glycogenesis involves interaction of glycogenin (GN) with glycogen synthase (GS), where GS is activated by glucose-6-phosphate (G6P) and inactivated by phosphorylation. We describe the 2.6 Å resolution cryo-EM structure of phosphorylated human GS revealing an autoinhibited GS tetramer flanked by two GN dimers. Phosphorylated N- and C-termini from two GS protomers converge near the G6P-binding pocket and buttress against GS regulatory helices. This keeps GS in an inactive conformation mediated by phospho-Ser641 interactions with a composite “arginine cradle”. Structure-guided mutagenesis perturbing interactions with phosphorylated tails led to increased basal/unstimulated GS activity. We propose that multivalent phosphorylation supports GS autoinhibition through interactions from a dynamic “spike” region, allowing a tuneable rheostat for regulating GS activity. This work therefore provides insights into glycogen synthesis regulation and facilitates studies of glycogen-related diseases. Glycogen is a major energy reserve in eukaryotes and is synthesised in part by glycogenin (GN) and glycogen synthase (GS). Here, authors describe the structural basis of GS regulation, specifically the mechanism of inactivation by phosphorylation.
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Thomsen C, Malfatti E, Jovanovic A, Roberts M, Kalev O, Lindberg C, Oldfors A. Proteomic characterisation of polyglucosan bodies in skeletal muscle in RBCK1 deficiency. Neuropathol Appl Neurobiol 2021; 48:e12761. [PMID: 34405429 DOI: 10.1111/nan.12761] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 07/24/2021] [Indexed: 12/21/2022]
Abstract
AIMS Several neurodegenerative and neuromuscular disorders are characterised by storage of polyglucosan, consisting of proteins and amylopectin-like polysaccharides, which are less branched than in normal glycogen. Such diseases include Lafora disease, branching enzyme deficiency, glycogenin-1 deficiency, polyglucosan body myopathy type 1 (PGBM1) due to RBCK1 deficiency and others. The protein composition of polyglucosan bodies is largely unknown. METHODS We combined quantitative mass spectrometry, immunohistochemical and western blot analyses to identify the principal protein components of polyglucosan bodies in PGBM1. Histologically stained tissue sections of skeletal muscle from four patients were used to isolate polyglucosan deposits and control regions by laser microdissection. Prior to mass spectrometry, samples were labelled with tandem mass tags that enable quantitative comparison and multiplexed analysis of dissected samples. To study the distribution and expression of the accumulated proteins, immunohistochemical and western blot analyses were performed. RESULTS Accumulated proteins were mainly components of glycogen metabolism and protein quality control pathways. The majority of fibres showed depletion of glycogen and redistribution of key enzymes of glycogen metabolism to the polyglucosan bodies. The polyglucosan bodies also showed accumulation of proteins involved in the ubiquitin-proteasome and autophagocytosis systems and protein chaperones. CONCLUSIONS The sequestration of key enzymes of glycogen metabolism to the polyglucosan bodies may explain the glycogen depletion in the fibres and muscle function impairment. The accumulation of components of the protein quality control systems and other proteins frequently found in protein aggregate disorders indicates that protein aggregation may be an essential part of the pathobiology of polyglucosan storage.
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Affiliation(s)
- Christer Thomsen
- Department of Laboratory Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Edoardo Malfatti
- APHP, North-East-Ile-de-France Neuromuscular Pathology Reference Center, Henri-Mondor University Hospital, Paris, France
| | - Ana Jovanovic
- The Mark Holland Metabolic Unit, Salford Royal NHS Foundation Trust, Salford, UK
| | - Mark Roberts
- Department of Neurology, Salford Royal NHS Foundation Trust, Salford, UK
| | - Ognian Kalev
- Neuromed Campus, Kepler University Hospital (Klinikum), Linz, Austria
| | | | - Anders Oldfors
- Department of Laboratory Medicine, University of Gothenburg, Gothenburg, Sweden
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Muñoz Sosa CJ, Issoglio FM, Carrizo ME. Crystal structure and mutational analysis of the human TRIM7 B30.2 domain provide insights into the molecular basis of its binding to glycogenin-1. J Biol Chem 2021; 296:100772. [PMID: 33989636 PMCID: PMC8203840 DOI: 10.1016/j.jbc.2021.100772] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/30/2021] [Accepted: 05/09/2021] [Indexed: 01/01/2023] Open
Abstract
Tripartite motif (TRIM)7 is an E3 ubiquitin ligase that was first identified through its interaction with glycogenin-1 (GN1), the autoglucosyltransferase that initiates glycogen biosynthesis. A growing body of evidence indicates that TRIM7 plays an important role in cancer development, viral pathogenesis, and atherosclerosis and, thus, represents a potential therapeutic target. TRIM family proteins share a multidomain architecture with a conserved N-terminal TRIM and a variable C-terminal domain. Human TRIM7 contains the canonical TRIM motif and a B30.2 domain at the C terminus. To contribute to the understanding of the mechanism of action of TRIM7, we solved the X-ray crystal structure of its B30.2 domain (TRIM7B30.2) in two crystal forms at resolutions of 1.6 Å and 1.8 Å. TRIM7B30.2 exhibits the typical B30.2 domain fold, consisting of two antiparallel β-sheets of seven and six strands, arranged as a distorted β-sandwich. Furthermore, two long loops partially cover the concave face of the β-sandwich defined by the β-sheet of six strands, thus forming a positively charged cavity. We used sequence conservation and mutational analyses to provide evidence of a putative binding interface for GN1. These studies showed that Leu423, Ser499, and Cys501 of TRIM7B30.2 and the C-terminal 33 amino acids of GN1 are critical for this binding interaction. Molecular dynamics simulations also revealed that hydrogen bond and hydrophobic interactions play a major role in the stability of a modeled TRIM7B30.2-GN1 C-terminal peptide complex. These data provide useful information that could be used to target this interaction for the development of potential therapeutic agents.
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Affiliation(s)
- Christian J Muñoz Sosa
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC) - CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Federico M Issoglio
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB NOVA), Oeiras, Portugal; Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) - CONICET and Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - María E Carrizo
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC) - CONICET and Departamento de Química Biológica Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Visuttijai K, Hedberg-Oldfors C, Thomsen C, Glamuzina E, Kornblum C, Tasca G, Hernandez-Lain A, Sandstedt J, Dellgren G, Roach P, Oldfors A. Glycogenin is Dispensable for Glycogen Synthesis in Human Muscle, and Glycogenin Deficiency Causes Polyglucosan Storage. J Clin Endocrinol Metab 2020; 105:5599738. [PMID: 31628455 PMCID: PMC7046021 DOI: 10.1210/clinem/dgz075] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 10/02/2019] [Indexed: 02/06/2023]
Abstract
CONTEXT Glycogenin is considered to be an essential primer for glycogen biosynthesis. Nevertheless, patients with glycogenin-1 deficiency due to biallelic GYG1 (NM_004130.3) mutations can store glycogen in muscle. Glycogenin-2 has been suggested as an alternative primer for glycogen synthesis in patients with glycogenin-1 deficiency. OBJECTIVE The objective of this article is to investigate the importance of glycogenin-1 and glycogenin-2 for glycogen synthesis in skeletal and cardiac muscle. DESIGN, SETTING, AND PATIENTS Glycogenin-1 and glycogenin-2 expression was analyzed by Western blot, mass spectrometry, and immunohistochemistry in liver, heart, and skeletal muscle from controls and in skeletal and cardiac muscle from patients with glycogenin-1 deficiency. RESULTS Glycogenin-1 and glycogenin-2 both were found to be expressed in the liver, but only glycogenin-1 was identified in heart and skeletal muscle from controls. In patients with truncating GYG1 mutations, neither glycogenin-1 nor glycogenin-2 was expressed in skeletal muscle. However, nonfunctional glycogenin-1 but not glycogenin-2 was identified in cardiac muscle from patients with cardiomyopathy due to GYG1 missense mutations. By immunohistochemistry, the mutated glycogenin-1 colocalized with the storage of glycogen and polyglucosan in cardiomyocytes. CONCLUSIONS Glycogen can be synthesized in the absence of glycogenin, and glycogenin-1 deficiency is not compensated for by upregulation of functional glycogenin-2. Absence of glycogenin-1 leads to the focal accumulation of glycogen and polyglucosan in skeletal muscle fibers. Expression of mutated glycogenin-1 in the heart is deleterious, and it leads to storage of abnormal glycogen and cardiomyopathy.
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Affiliation(s)
- Kittichate Visuttijai
- Department of Pathology and Genetics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Carola Hedberg-Oldfors
- Department of Pathology and Genetics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Christer Thomsen
- Department of Pathology and Genetics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emma Glamuzina
- National Metabolic Service, Starship Children’s Hospital, Auckland, New Zealand
| | | | - Giorgio Tasca
- Unità Operativa Complessa di Neurologia, Dipartimento di Scienze dell’Invecchiamento, Neurologiche, Ortopediche e della Testa-Collo, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
| | | | - Joakim Sandstedt
- Department of Clinical Chemistry, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Göran Dellgren
- Department of Cardiothoracic Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Peter Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Anders Oldfors
- Department of Pathology and Genetics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Correspondence and Reprint Requests: Anders Oldfors, Department of Pathology and Genetics, Institute of Biomedicine, University of Gothenburg, Sahlgrenska University Hospital, 41345, Gothenburg, Sweden. E-mail:
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9
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From the seminal discovery of proteoglycogen and glycogenin to emerging knowledge and research on glycogen biology. Biochem J 2019; 476:3109-3124. [DOI: 10.1042/bcj20190441] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 09/10/2019] [Accepted: 10/14/2019] [Indexed: 11/17/2022]
Abstract
AbstractAlthough the discovery of glycogen in the liver, attributed to Claude Bernard, happened more than 160 years ago, the mechanism involved in the initiation of glucose polymerization remained unknown. The discovery of glycogenin at the core of glycogen's structure and the initiation of its glucopolymerization is among one of the most exciting and relatively recent findings in Biochemistry. This review focuses on the initial steps leading to the seminal discoveries of proteoglycogen and glycogenin at the beginning of the 1980s, which paved the way for subsequent foundational breakthroughs that propelled forward this new research field. We also explore the current, as well as potential, impact this research field is having on human health and disease from the perspective of glycogen storage diseases. Important new questions arising from recent studies, their links to basic mechanisms involved in the de novo glycogen biogenesis, and the pervading presence of glycogenin across the evolutionary scale, fueled by high throughput -omics technologies, are also addressed.
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10
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Cenacchi G, Papa V, Costa R, Pegoraro V, Marozzo R, Fanin M, Angelini C. Update on polyglucosan storage diseases. Virchows Arch 2019; 475:671-686. [DOI: 10.1007/s00428-019-02633-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 07/18/2019] [Accepted: 07/22/2019] [Indexed: 11/27/2022]
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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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Brewer MK, Gentry MS. Brain Glycogen Structure and Its Associated Proteins: Past, Present and Future. ADVANCES IN NEUROBIOLOGY 2019; 23:17-81. [PMID: 31667805 PMCID: PMC7239500 DOI: 10.1007/978-3-030-27480-1_2] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This chapter reviews the history of glycogen-related research and discusses in detail the structure, regulation, chemical properties and subcellular distribution of glycogen and its associated proteins, with particular focus on these aspects in brain tissue.
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Affiliation(s)
- M Kathryn Brewer
- Department of Molecular and Cellular Biochemistry, Epilepsy and Brain Metabolism Center, Lafora Epilepsy Cure Initiative, and Center for Structural Biology, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Matthew S Gentry
- Department of Molecular and Cellular Biochemistry, Epilepsy and Brain Metabolism Center, Lafora Epilepsy Cure Initiative, and Center for Structural Biology, University of Kentucky College of Medicine, Lexington, KY, USA.
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13
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Abstract
Glycogen, the primary storage form of glucose, is a rapid and accessible form of energy that can be supplied to tissues on demand. Each glycogen granule, or "glycosome," is considered an independent metabolic unit composed of a highly branched polysaccharide and various proteins involved in its metabolism. In this Minireview, we review the literature to follow the dynamic life of a glycogen granule in a multicompartmentalized system, i.e. the cell, and how and where glycogen granules appear and the factors governing its degradation. A better understanding of the importance of cellular compartmentalization as a regulator of glycogen metabolism is needed to unravel its role in brain energetics.
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Affiliation(s)
- Clara Prats
- Center for Healthy Aging, Copenhagen 2200, Denmark; Core Facility for Integrated Microscopy, Department of Biomedical Sciences, University of Copenhagen, Copenhagen 2200, Denmark.
| | - Terry E Graham
- Department of Human Health and Nutritional Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jane Shearer
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Calgary, Alberta T2N 1N4, Canada; Faculty of Kinesiology, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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14
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Li B, Meng J, Li L, Liu S, Wang T, Zhang G. Identification and Functional Characterization of the Glycogen Synthesis Related Gene Glycogenin in Pacific Oysters (Crassostrea gigas). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:7764-7773. [PMID: 28780871 DOI: 10.1021/acs.jafc.7b02720] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
High glycogen levels in the Pacific oyster (Crassostrea gigas) contribute to its flavor, quality, and hardiness. Glycogenin (CgGN) is the priming glucosyltransferase that initiates glycogen biosynthesis. We characterized the full sequence and function of C. gigas CgGN. Three CgGN isoforms (CgGN-α, β, and γ) containing alternative exon regions were isolated. CgGN expression varied seasonally in the adductor muscle and gonadal area and was the highest in the adductor muscle. Autoglycosylation of CgGN can interact with glycogen synthase (CgGS) to complete glycogen synthesis. Subcellular localization analysis showed that CgGN isoforms and CgGS were located in the cytoplasm. Additionally, a site-directed mutagenesis experiment revealed that the Tyr200Phe and Tyr202Phe mutations could affect CgGN autoglycosylation. This is the first study of glycogenin function in marine bivalves. These findings will improve our understanding of glycogen synthesis and accumulation mechanisms in mollusks. The data are potentially useful for breeding high-glycogen oysters.
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Affiliation(s)
- Busu Li
- University of Chinese Academy of Sciences , Beijing 100049, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, China
| | - Jie Meng
- Laboratory for Marine Fisheries and Aquaculture, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, Shandong, China
| | - Li Li
- Laboratory for Marine Fisheries and Aquaculture, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, Shandong, China
| | - Sheng Liu
- University of Chinese Academy of Sciences , Beijing 100049, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, China
| | - Ting Wang
- University of Chinese Academy of Sciences , Beijing 100049, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, China
| | - Guofan Zhang
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology , Qingdao 266000, China
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Testoni G, Duran J, García-Rocha M, Vilaplana F, Serrano AL, Sebastián D, López-Soldado I, Sullivan MA, Slebe F, Vilaseca M, Muñoz-Cánoves P, Guinovart JJ. Lack of Glycogenin Causes Glycogen Accumulation and Muscle Function Impairment. Cell Metab 2017; 26:256-266.e4. [PMID: 28683291 DOI: 10.1016/j.cmet.2017.06.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 05/08/2017] [Accepted: 06/13/2017] [Indexed: 11/27/2022]
Abstract
Glycogenin is considered essential for glycogen synthesis, as it acts as a primer for the initiation of the polysaccharide chain. Against expectations, glycogenin-deficient mice (Gyg KO) accumulate high amounts of glycogen in striated muscle. Furthermore, this glycogen contains no covalently bound protein, thereby demonstrating that a protein primer is not strictly necessary for the synthesis of the polysaccharide in vivo. Strikingly, in spite of the higher glycogen content, Gyg KO mice showed lower resting energy expenditure and less resistance than control animals when subjected to endurance exercise. These observations can be attributed to a switch of oxidative myofibers toward glycolytic metabolism. Mice overexpressing glycogen synthase in the muscle showed similar alterations, thus indicating that this switch is caused by the excess of glycogen. These results may explain the muscular defects of GSD XV patients, who lack glycogenin-1 and show high glycogen accumulation in muscle.
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Affiliation(s)
- Giorgia Testoni
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Jordi Duran
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid 28029, Spain
| | - Mar García-Rocha
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Francisco Vilaplana
- Division of Glycoscience, School of Biotechnology, KTH Royal Institute of Technology, AlbaNova University Centre, Stockholm 10691, Sweden
| | - Antonio L Serrano
- Cell Biology Group, Department of Experimental and Health Sciences, Pompeu Fabra University (UPF), CIBER on Neurodegenerative diseases (CIBERNED), Barcelona 08003, Spain
| | - David Sebastián
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid 28029, Spain; Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Barcelona 08028, Spain
| | - Iliana López-Soldado
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid 28029, Spain
| | - Mitchell A Sullivan
- Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Felipe Slebe
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Marta Vilaseca
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Pura Muñoz-Cánoves
- Cell Biology Group, Department of Experimental and Health Sciences, Pompeu Fabra University (UPF), CIBER on Neurodegenerative diseases (CIBERNED), Barcelona 08003, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain; Spanish National Center on Cardiovascular Research (CNIC), Madrid 28029, Spain
| | - Joan J Guinovart
- Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid 28029, Spain; Department of Biochemistry and Molecular Biomedicine, University of Barcelona, Barcelona 08028, Spain.
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17
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Zeqiraj E, Sicheri F. Getting a handle on glycogen synthase - Its interaction with glycogenin. Mol Aspects Med 2015; 46:63-9. [PMID: 26278983 DOI: 10.1016/j.mam.2015.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 08/04/2015] [Indexed: 02/08/2023]
Abstract
Glycogen is a polymer of glucose that serves as a major energy reserve in eukaryotes. It is synthesized through the cooperative action of glycogen synthase (GS), glycogenin (GN) and glycogen branching enzyme. GN initiates the first enzymatic step in the glycogen synthesis process by self glucosylation of a short 8-12 glucose residue primer. After interacting with GN, GS then extends this sugar primer to form glycogen particles of different sizes. We discuss recent developments in the structural biology characterization of GS and GN enzymes, which have contributed to a better understanding of how the two proteins interact and how they collaborate to synthesize glycogen particles.
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Affiliation(s)
- Elton Zeqiraj
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Room 1090, Toronto, ON M5G 1X5, Canada; Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Frank Sicheri
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Room 1090, Toronto, ON M5G 1X5, Canada; Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
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Hunter RW, Zeqiraj E, Morrice N, Sicheri F, Sakamoto K. Expression and purification of functional human glycogen synthase-1:glycogenin-1 complex in insect cells. Protein Expr Purif 2014; 108:23-29. [PMID: 25527037 PMCID: PMC4370744 DOI: 10.1016/j.pep.2014.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 12/07/2014] [Accepted: 12/10/2014] [Indexed: 12/31/2022]
Abstract
GYS1:GN1 complex expressed using bicistronic pFastBac-Dual vector in insect cells. A large quantity of highly-pure stoichiometric GYS1:GN1 complex obtained. Purified GYS1 is functional and heavily phosphorylated at several Ser/Thr residues. GYS1:GN1 complex will be useful to reveal its structural and biochemical properties.
We report the successful expression and purification of functional human muscle glycogen synthase (GYS1) in complex with human glycogenin-1 (GN1). Stoichiometric GYS1:GN1 complex was produced by co-expression of GYS1 and GN1 using a bicistronic pFastBac™-Dual expression vector, followed by affinity purification and subsequent size-exclusion chromatography. Mass spectrometry analysis identified that GYS1 is phosphorylated at several well-characterised and uncharacterised Ser/Thr residues. Biochemical analysis, including activity ratio (in the absence relative to that in the presence of glucose-6-phosphate) measurement, covalently attached phosphate estimation as well as phosphatase treatment, revealed that recombinant GYS1 is substantially more heavily phosphorylated than would be observed in intact human or rodent muscle tissues. A large quantity of highly-pure stoichiometric GYS1:GN1 complex will be useful to study its structural and biochemical properties in the future, which would reveal mechanistic insights into its functional role in glycogen biosynthesis.
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Affiliation(s)
- Roger W Hunter
- Nestlé Institute of Health Sciences SA, EPFL Innovation Park, bâtiment G, 1015 Lausanne, Switzerland
| | - Elton Zeqiraj
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
| | - Nicholas Morrice
- Beatson Institute for Cancer Research, Bearsden, Glasgow G61 1BD, UK
| | - Frank Sicheri
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada; Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Kei Sakamoto
- Nestlé Institute of Health Sciences SA, EPFL Innovation Park, bâtiment G, 1015 Lausanne, Switzerland.
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Malfatti E, Nilsson J, Hedberg-Oldfors C, Hernandez-Lain A, Michel F, Dominguez-Gonzalez C, Viennet G, Akman HO, Kornblum C, Van den Bergh P, Romero NB, Engel AG, DiMauro S, Oldfors A. A new muscle glycogen storage disease associated with glycogenin-1 deficiency. Ann Neurol 2014; 76:891-8. [PMID: 25272951 PMCID: PMC4348070 DOI: 10.1002/ana.24284] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 09/30/2014] [Accepted: 09/30/2014] [Indexed: 12/27/2022]
Abstract
We describe a slowly progressive myopathy in 7 unrelated adult patients with storage of polyglucosan in muscle fibers. Genetic investigation revealed homozygous or compound heterozygous deleterious variants in the glycogenin-1 gene (GYG1). Most patients showed depletion of glycogenin-1 in skeletal muscle, whereas 1 showed presence of glycogenin-1 lacking the C-terminal that normally binds glycogen synthase. Our results indicate that either depletion of glycogenin-1 or impaired interaction with glycogen synthase underlies this new form of glycogen storage disease that differs from a previously reported patient with GYG1 mutations who showed profound glycogen depletion in skeletal muscle and accumulation of glycogenin-1.
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Affiliation(s)
- Edoardo Malfatti
- Department of Pathology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden; Myology Institute, Neuromuscular Morphology Unit, Pierre and Marie Curie University, Pitié-Salpêtrière University Hospital Group, Sorbonne Universities, Paris, France
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20
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Structural basis for the recruitment of glycogen synthase by glycogenin. Proc Natl Acad Sci U S A 2014; 111:E2831-40. [PMID: 24982189 DOI: 10.1073/pnas.1402926111] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Glycogen is a primary form of energy storage in eukaryotes that is essential for glucose homeostasis. The glycogen polymer is synthesized from glucose through the cooperative action of glycogen synthase (GS), glycogenin (GN), and glycogen branching enzyme and forms particles that range in size from 10 to 290 nm. GS is regulated by allosteric activation upon glucose-6-phosphate binding and inactivation by phosphorylation on its N- and C-terminal regulatory tails. GS alone is incapable of starting synthesis of a glycogen particle de novo, but instead it extends preexisting chains initiated by glycogenin. The molecular determinants by which GS recognizes self-glucosylated GN, the first step in glycogenesis, are unknown. We describe the crystal structure of Caenorhabditis elegans GS in complex with a minimal GS targeting sequence in GN and show that a 34-residue region of GN binds to a conserved surface on GS that is distinct from previously characterized allosteric and binding surfaces on the enzyme. The interaction identified in the GS-GN costructure is required for GS-GN interaction and for glycogen synthesis in a cell-free system and in intact cells. The interaction of full-length GS-GN proteins is enhanced by an avidity effect imparted by a dimeric state of GN and a tetrameric state of GS. Finally, the structure of the N- and C-terminal regulatory tails of GS provide a basis for understanding phosphoregulation of glycogen synthesis. These results uncover a central molecular mechanism that governs glycogen metabolism.
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Expression and purification of functional human glycogen synthase-1 (hGYS1) in insect cells. Protein Expr Purif 2013; 90:78-83. [PMID: 23711380 DOI: 10.1016/j.pep.2013.05.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 05/17/2013] [Accepted: 05/18/2013] [Indexed: 01/02/2023]
Abstract
We have successfully expressed and purified active human glycogen synthase-1 (hGYS1). Successful production of the recombinant hGYS1 protein was achieved by co-expression of hGYS1 and rabbit glycogenin (rGYG1) using the MultiBac baculovirus expression system (BEVS). Functional measurements of activity ratios of hGYS1 in the absence and presence of glucose-6-phosphate and treatment with phosphatase indicate that the expressed protein is heavily phosphorylated. We used mass spectrometry to further characterize the sites of phosphorylation, which include most of the known regulatory phosphorylation sites, as well as several sites unique to the insect cell over-expression. Obtaining large quantities of functional hGYS1 will be invaluable for future structural studies as well as detailed studies on the effects on specific sites of phosphorylation.
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Abstract
Glycogen is a branched polymer of glucose that acts as a store of energy in times of nutritional sufficiency for utilization in times of need. Its metabolism has been the subject of extensive investigation and much is known about its regulation by hormones such as insulin, glucagon and adrenaline (epinephrine). There has been debate over the relative importance of allosteric compared with covalent control of the key biosynthetic enzyme, glycogen synthase, as well as the relative importance of glucose entry into cells compared with glycogen synthase regulation in determining glycogen accumulation. Significant new developments in eukaryotic glycogen metabolism over the last decade or so include: (i) three-dimensional structures of the biosynthetic enzymes glycogenin and glycogen synthase, with associated implications for mechanism and control; (ii) analyses of several genetically engineered mice with altered glycogen metabolism that shed light on the mechanism of control; (iii) greater appreciation of the spatial aspects of glycogen metabolism, including more focus on the lysosomal degradation of glycogen; and (iv) glycogen phosphorylation and advances in the study of Lafora disease, which is emerging as a glycogen storage disease.
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23
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D'Hulst C, Mérida A. The priming of storage glucan synthesis from bacteria to plants: current knowledge and new developments. THE NEW PHYTOLOGIST 2010; 188:13-21. [PMID: 20618917 DOI: 10.1111/j.1469-8137.2010.03361.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Starch is the main polymer in which carbon and energy are stored in land plants, algae and some cyanobacteria. It plays a crucial role in the physiology of these organisms and also represents an important polymer for humans, in terms of both diet and nonfood industry uses. Recent efforts have elucidated most of the steps involved in the synthesis of starch. However, the process that initiates the synthesis of the starch granule remains unclear. Here, we outline the similarities between the synthesis of starch and the synthesis of glycogen, the other widespread and abundant glucose-based polymer in living cells. We place special emphasis on the mechanisms of initiation of the glycogen granule and current knowledge concerning the initiation of the starch granule. We also discuss recent discoveries regarding the function of starch synthases in the priming of the starch granule and possible interactions with other elements of the starch synthesis machinery.
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Affiliation(s)
- Christophe D'Hulst
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR8576 CNRS/USTL, IFR 147, Université des Sciences et Technologies de Lille, 59655 Villeneuve d'Ascq Cedex, France
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24
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Savage DB, Zhai L, Ravikumar B, Choi CS, Snaar JE, McGuire AC, Wou SE, Medina-Gomez G, Kim S, Bock CB, Segvich DM, Vidal-Puig A, Wareham NJ, Shulman GI, Karpe F, Taylor R, Pederson BA, Roach PJ, O'Rahilly S, DePaoli-Roach AA. A prevalent variant in PPP1R3A impairs glycogen synthesis and reduces muscle glycogen content in humans and mice. PLoS Med 2008; 5:e27. [PMID: 18232732 PMCID: PMC2214798 DOI: 10.1371/journal.pmed.0050027] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 12/13/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Stored glycogen is an important source of energy for skeletal muscle. Human genetic disorders primarily affecting skeletal muscle glycogen turnover are well-recognised, but rare. We previously reported that a frameshift/premature stop mutation in PPP1R3A, the gene encoding RGL, a key regulator of muscle glycogen metabolism, was present in 1.36% of participants from a population of white individuals in the UK. However, the functional implications of the mutation were not known. The objective of this study was to characterise the molecular and physiological consequences of this genetic variant. METHODS AND FINDINGS In this study we found a similar prevalence of the variant in an independent UK white population of 744 participants (1.46%) and, using in vivo (13)C magnetic resonance spectroscopy studies, demonstrate that human carriers (n = 6) of the variant have low basal (65% lower, p = 0.002) and postprandial muscle glycogen levels. Mice engineered to express the equivalent mutation had similarly decreased muscle glycogen levels (40% lower in heterozygous knock-in mice, p < 0.05). In muscle tissue from these mice, failure of the truncated mutant to bind glycogen and colocalize with glycogen synthase (GS) decreased GS and increased glycogen phosphorylase activity states, which account for the decreased glycogen content. CONCLUSIONS Thus, PPP1R3A C1984DeltaAG (stop codon 668) is, to our knowledge, the first prevalent mutation described that directly impairs glycogen synthesis and decreases glycogen levels in human skeletal muscle. The fact that it is present in approximately 1 in 70 UK whites increases the potential biomedical relevance of these observations.
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Affiliation(s)
- David B Savage
- Department of Clinical Biochemistry and Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Lanmin Zhai
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Balasubramanian Ravikumar
- School of Clinical Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Cheol Soo Choi
- Department of Internal Medicine and Cellular and Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Johanna E Snaar
- Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom
| | - Amanda C McGuire
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Sung-Eun Wou
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Gemma Medina-Gomez
- Department of Clinical Biochemistry and Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Sheene Kim
- Department of Internal Medicine and Cellular and Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Cheryl B Bock
- Comprehensive Cancer Centre, Duke University Medical Centre, Durham, North Carolina, United States of America
| | - Dyann M Segvich
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Antonio Vidal-Puig
- Department of Clinical Biochemistry and Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Nicholas J Wareham
- Medical Research Council Epidemiology Unit, Elsie Widdowson Laboratory, Cambridge, United Kingdom
| | - Gerald I Shulman
- Department of Internal Medicine and Cellular and Molecular Physiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Fredrik Karpe
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, United Kingdom
| | - Roy Taylor
- School of Clinical Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
| | - Bartholomew A Pederson
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Peter J Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
| | - Stephen O'Rahilly
- Department of Clinical Biochemistry and Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Anna A DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, United States of America
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