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Uehara K, Lee WD, Stefkovich M, Biswas D, Santoleri D, Garcia Whitlock A, Quinn W, Coopersmith T, Creasy KT, Rader DJ, Sakamoto K, Rabinowitz JD, Titchenell PM. mTORC1 controls murine postprandial hepatic glycogen synthesis via Ppp1r3b. J Clin Invest 2024; 134:e173782. [PMID: 38290087 PMCID: PMC10977990 DOI: 10.1172/jci173782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 01/26/2024] [Indexed: 02/01/2024] Open
Abstract
In response to a meal, insulin drives hepatic glycogen synthesis to help regulate systemic glucose homeostasis. The mechanistic target of rapamycin complex 1 (mTORC1) is a well-established insulin target and contributes to the postprandial control of liver lipid metabolism, autophagy, and protein synthesis. However, its role in hepatic glucose metabolism is less understood. Here, we used metabolomics, isotope tracing, and mouse genetics to define a role for liver mTORC1 signaling in the control of postprandial glycolytic intermediates and glycogen deposition. We show that mTORC1 is required for glycogen synthase activity and glycogenesis. Mechanistically, hepatic mTORC1 activity promotes the feeding-dependent induction of Ppp1r3b, a gene encoding a phosphatase important for glycogen synthase activity whose polymorphisms are linked to human diabetes. Reexpression of Ppp1r3b in livers lacking mTORC1 signaling enhances glycogen synthase activity and restores postprandial glycogen content. mTORC1-dependent transcriptional control of Ppp1r3b is facilitated by FOXO1, a well characterized transcriptional regulator involved in the hepatic response to nutrient intake. Collectively, we identify a role for mTORC1 signaling in the transcriptional regulation of Ppp1r3b and the subsequent induction of postprandial hepatic glycogen synthesis.
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Affiliation(s)
- Kahealani Uehara
- Institute for Diabetes, Obesity, and Metabolism
- Biochemistry and Molecular Biophysics Graduate Group, and
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Won Dong Lee
- Lewis Sigler Institute for Integrative Genomics
- Department of Chemistry, and
- Ludwig Institute for Cancer Research, Princeton Branch, Princeton, New Jersey, USA
| | | | - Dipsikha Biswas
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Dominic Santoleri
- Institute for Diabetes, Obesity, and Metabolism
- Biochemistry and Molecular Biophysics Graduate Group, and
| | | | | | | | - Kate Townsend Creasy
- Institute for Diabetes, Obesity, and Metabolism
- Department of Medicine, Division of Translational Medicine and Human Genetics, and
- Department of Biobehavioral Health Sciences, School of Nursing, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Daniel J. Rader
- Institute for Diabetes, Obesity, and Metabolism
- Department of Medicine, Division of Translational Medicine and Human Genetics, and
| | - Kei Sakamoto
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Joshua D. Rabinowitz
- Lewis Sigler Institute for Integrative Genomics
- Department of Chemistry, and
- Ludwig Institute for Cancer Research, Princeton Branch, Princeton, New Jersey, USA
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
| | - Paul M. Titchenell
- Institute for Diabetes, Obesity, and Metabolism
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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2
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Gao G, Gao N, Li S, Kuang W, Zhu L, Jiang W, Yu W, Guo J, Li Z, Yang C, Zhao Y. Genome-Wide Association Study of Meat Quality Traits in a Three-Way Crossbred Commercial Pig Population. Front Genet 2021; 12:614087. [PMID: 33815461 PMCID: PMC8010252 DOI: 10.3389/fgene.2021.614087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 02/12/2021] [Indexed: 01/12/2023] Open
Abstract
Meat quality is an important trait for pig-breeding programs aiming to meet consumers' demands. Geneticists must improve meat quality based on their understanding of the underlying genetic mechanisms. Previous studies showed that most meat-quality indicators were low-to-moderate heritability traits; therefore, improving meat quality using conventional techniques remains a challenge. Here, we performed a genome-wide association study of meat-quality traits using the GeneSeek Porcine SNP50K BeadChip in 582 crossbred Duroc × (Landrace × Yorkshire) commercial pigs (249 males and 333 females). Meat conductivity, marbling score, moisture, meat color, pH, and intramuscular fat (IMF) content were investigated. The genome-wide association study was performed using both fixed and random model Circulating Probability Unification (FarmCPU) and a mixed linear model (MLM) with the rMVP software. The genomic heritability of the studied traits ranged from 0.13 ± 0.07 to 0.55 ± 0.08 for conductivity and meat color, respectively. Thirty-two single-nucleotide polymorphisms (SNPs) were identified for meat quality in the crossbred pigs using both FarmCPU and MLM. Among the detected SNPs, five, nine, seven, four, six, and five were significantly associated with conductivity, IMF, marbling score, meat color, moisture, and pH, respectively. Several candidate genes for meat quality were identified in the detected genomic regions. These findings will contribute to the ongoing improvement of meat quality, meeting consumer demands and improving the economic outlook for the swine industry.
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Affiliation(s)
- Guangxiong Gao
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Ning Gao
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
- Guangxi Yangxiang Co., Ltd., Guigang, China
| | - Sicheng Li
- Guangxi Yangxiang Co., Ltd., Guigang, China
| | - Weijian Kuang
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Lin Zhu
- Guangxi Yangxiang Co., Ltd., Guigang, China
| | - Wei Jiang
- Guangxi Yangxiang Co., Ltd., Guigang, China
| | - Weiwei Yu
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Jinbiao Guo
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Zhili Li
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Chengzhong Yang
- School of Life Sciences and Engineering, Foshan University, Foshan, China
| | - Yunxiang Zhao
- School of Life Sciences and Engineering, Foshan University, Foshan, China
- Guangxi Yangxiang Co., Ltd., Guigang, China
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Casamayor A, Ariño J. Controlling Ser/Thr protein phosphatase PP1 activity and function through interaction with regulatory subunits. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2020; 122:231-288. [PMID: 32951813 DOI: 10.1016/bs.apcsb.2020.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protein phosphatase 1 is a major Ser/Thr protein phosphatase activity in eukaryotic cells. It is composed of a catalytic polypeptide (PP1C), with little substrate specificity, that interacts with a large variety of proteins of diverse structure (regulatory subunits). The diversity of holoenzymes that can be formed explain the multiplicity of cellular functions under the control of this phosphatase. In quite a few cases, regulatory subunits have an inhibitory role, downregulating the activity of the phosphatase. In this chapter we shall introduce PP1C and review the most relevant families of PP1C regulatory subunits, with particular emphasis in describing the structural basis for their interaction.
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Affiliation(s)
- Antonio Casamayor
- Institut de Biotecnologia i Biomedicina & Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola, del Vallès, Spain
| | - Joaquín Ariño
- Institut de Biotecnologia i Biomedicina & Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola, del Vallès, Spain
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Manning AK, Goustin AS, Kleinbrink EL, Thepsuwan P, Cai J, Ju D, Leong A, Udler MS, Brown JB, Goodarzi MO, Rotter JI, Sladek R, Meigs JB, Lipovich L. A Long Non-coding RNA, LOC157273, Is an Effector Transcript at the Chromosome 8p23.1- PPP1R3B Metabolic Traits and Type 2 Diabetes Risk Locus. Front Genet 2020; 11:615. [PMID: 32754192 PMCID: PMC7367044 DOI: 10.3389/fgene.2020.00615] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/20/2020] [Indexed: 01/08/2023] Open
Abstract
AIMS Causal transcripts at genomic loci associated with type 2 diabetes (T2D) are mostly unknown. The chr8p23.1 variant rs4841132, associated with an insulin-resistant diabetes risk phenotype, lies in the second exon of a long non-coding RNA (lncRNA) gene, LOC157273, located 175 kilobases from PPP1R3B, which encodes a key protein regulating insulin-mediated hepatic glycogen storage in humans. We hypothesized that LOC157273 regulates expression of PPP1R3B in human hepatocytes. METHODS We tested our hypothesis using Stellaris fluorescent in situ hybridization to assess subcellular localization of LOC157273; small interfering RNA (siRNA) knockdown of LOC157273, followed by RT-PCR to quantify LOC157273 and PPP1R3B expression; RNA-seq to quantify the whole-transcriptome gene expression response to LOC157273 knockdown; and an insulin-stimulated assay to measure hepatocyte glycogen deposition before and after knockdown. RESULTS We found that siRNA knockdown decreased LOC157273 transcript levels by approximately 80%, increased PPP1R3B mRNA levels by 1.7-fold, and increased glycogen deposition by >50% in primary human hepatocytes. An A/G heterozygous carrier (vs. three G/G carriers) had reduced LOC157273 abundance due to reduced transcription of the A allele and increased PPP1R3B expression and glycogen deposition. CONCLUSION We show that the lncRNA LOC157273 is a negative regulator of PPP1R3B expression and glycogen deposition in human hepatocytes and a causal transcript at an insulin-resistant T2D risk locus.
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Affiliation(s)
- Alisa K. Manning
- Clinical and Translational Epidemiology Unit, Mongan Institute, Massachusetts General Hospital, Boston, MA, United States
- Department of Medicine, Harvard Medical School, Boston, MA, United States
- Programs in Metabolism and Medical & Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, United States
| | - Anton Scott Goustin
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
| | - Erica L. Kleinbrink
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
| | - Pattaraporn Thepsuwan
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
| | - Juan Cai
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
| | - Donghong Ju
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
- Karmanos Cancer Institute at Wayne State University, Detroit, MI, United States
| | - Aaron Leong
- Programs in Metabolism and Medical & Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, United States
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, United States
- Division of General Internal Medicine, Massachusetts General Hospital, Boston, MA, United States
| | - Miriam S. Udler
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, United States
- Diabetes Unit, Massachusetts General Hospital, Boston, MA, United States
| | - James Bentley Brown
- Department of Statistics, University of California, Berkeley, Berkeley, CA, United States
- Centre for Computational Biology, University of Birmingham, Birmingham, United Kingdom
- Computational Biosciences Group, Biosciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA, United States
| | - Mark O. Goodarzi
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, United States
| | - Jerome I. Rotter
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, United States
| | - Robert Sladek
- Department of Human Genetics, McGill University, Montréal, QC, Canada
- Department of Medicine, McGill University, Montréal, QC, Canada
- McGill University and Genome Québec Innovation Centre, Montréal, QC, Canada
| | - James B. Meigs
- Department of Medicine, Harvard Medical School, Boston, MA, United States
- Programs in Metabolism and Medical & Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA, United States
- Division of General Internal Medicine, Massachusetts General Hospital, Boston, MA, United States
| | - Leonard Lipovich
- Center for Molecular Medicine & Genetics, Wayne State University, Detroit, MI, United States
- Department of Neurology, School of Medicine, Wayne State University, Detroit, MI, United States
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5
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Seidelin AS, Nordestgaard BG, Tybjærg-Hansen A, Stender S. Genetic Variation at PPP1R3B Increases Hepatic CT Attenuation and Interacts With Prandial Status on Plasma Glucose. J Clin Endocrinol Metab 2020; 105:5812597. [PMID: 32219298 DOI: 10.1210/clinem/dgaa151] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 03/23/2020] [Indexed: 01/08/2023]
Abstract
CONTEXT A common genetic variant near PPP1R3B (rs4841132G > A) has been associated with increased hepatic computed tomography (CT) attenuation and with plasma levels of glucose and liver enzymes. OBJECTIVE To elucidate the association of rs4841132 with hepatic CT attenuation, and to test if synergistic effects modify the association of the variant with plasma glucose and liver enzymes. DESIGN Population-based cohort study. SETTING AND PARTICIPANTS The Copenhagen City Heart Study and the Copenhagen General Population Study combined, totaling 107 192 individuals from the Danish general population. Hepatic CT scans were available in 6445 individuals. MAIN OUTCOME MEASURES Hepatic CT attenuation and plasma levels of glucose and liver enzymes. RESULTS The rs4841132 A-allele (rs4841132-A) was associated with higher hepatic CT attenuation (P = 5 × 10-6). The probability of carrying rs4841132-A increased with higher hepatic CT attenuation in the range above 65 Hounsfield units, but remained constant at the range below (P = 4 × 10-8 for nonlinearity). Rs4841132-A was associated with up to 0.17 mmol/L higher plasma glucose in fasting individuals, but with up to 0.17 mmol/L lower glucose in postprandial individuals (P = 6 × 10-5 for interaction between rs4841132 and time since last meal on plasma glucose). Finally, rs4841132-A was associated with up to 2 U/L higher plasma alanine transaminase (P = 3 × 10-6). This association was not modified by adiposity, alcohol intake, or steatogenic genetic risk. CONCLUSIONS Rs4841132-A associates with higher hepatic CT attenuation in a distinctly nonlinear manner, and its association with plasma glucose depends on prandial status. The overall association pattern supports that rs4841132-A promotes hepatic glycogen synthesis postprandially.
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Affiliation(s)
- Anne-Sofie Seidelin
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospitals and Faculty of Health, Copenhagen, Denmark
| | - Børge Grønne Nordestgaard
- Department of Clinical Biochemistry, Copenhagen University Hospitals and Faculty of Health, Copenhagen, Denmark
- The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospitals and Faculty of Health, Herlev, Denmark
- The Copenhagen City Heart Study, Bispebjerg and Frederiksberg Hospital, Copenhagen University Hospitals and Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne Tybjærg-Hansen
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospitals and Faculty of Health, Copenhagen, Denmark
- The Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospitals and Faculty of Health, Herlev, Denmark
- The Copenhagen City Heart Study, Bispebjerg and Frederiksberg Hospital, Copenhagen University Hospitals and Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Stefan Stender
- Department of Clinical Biochemistry, Rigshospitalet, Copenhagen University Hospitals and Faculty of Health, Copenhagen, Denmark
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Abstract
PURPOSE OF REVIEW Increased glucose production associated with hepatic insulin resistance contributes to the development of hyperglycemia in T2D. The molecular mechanisms accounting for increased glucose production remain controversial. Our aims were to review recent literature concerning molecular mechanisms regulating glucose production and to discuss these mechanisms in the context of physiological experiments and observations in humans and large animal models. RECENT FINDINGS Genetic intervention studies in rodents demonstrate that insulin can control hepatic glucose production through both direct effects on the liver, and through indirect effects to inhibit adipose tissue lipolysis and limit gluconeogenic substrate delivery. However, recent experiments in canine models indicate that the direct effects of insulin on the liver are dominant over the indirect effects to regulate glucose production. Recent molecular studies have also identified insulin-independent mechanisms by which hepatocytes sense intrahepatic carbohydrate levels to regulate carbohydrate disposal. Dysregulation of hepatic carbohydrate sensing systems may participate in increased glucose production in the development of diabetes.
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Affiliation(s)
- Ashot Sargsyan
- Duke Molecular Physiology Institute, Duke University, Durham, NC, USA
| | - Mark A Herman
- Duke Molecular Physiology Institute, Duke University, Durham, NC, USA.
- Division of Diabetes, Endocrinology, and Metabolism, Duke University, Durham, NC, USA.
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7
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Brautigan DL, Shenolikar S. Protein Serine/Threonine Phosphatases: Keys to Unlocking Regulators and Substrates. Annu Rev Biochem 2019; 87:921-964. [PMID: 29925267 DOI: 10.1146/annurev-biochem-062917-012332] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein serine/threonine phosphatases (PPPs) are ancient enzymes, with distinct types conserved across eukaryotic evolution. PPPs are segregated into types primarily on the basis of the unique interactions of PPP catalytic subunits with regulatory proteins. The resulting holoenzymes dock substrates distal to the active site to enhance specificity. This review focuses on the subunit and substrate interactions for PPP that depend on short linear motifs. Insights about these motifs from structures of holoenzymes open new opportunities for computational biology approaches to elucidate PPP networks. There is an expanding knowledge base of posttranslational modifications of PPP catalytic and regulatory subunits, as well as of their substrates, including phosphorylation, acetylation, and ubiquitination. Cross talk between these posttranslational modifications creates PPP-based signaling. Knowledge of PPP complexes, signaling clusters, as well as how PPPs communicate with each other in response to cellular signals should unlock the doors to PPP networks and signaling "clouds" that orchestrate and coordinate different aspects of cell physiology.
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Affiliation(s)
- David L Brautigan
- Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA;
| | - Shirish Shenolikar
- Signature Research Programs in Cardiovascular and Metabolic Disorders and Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore 169857
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8
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The Structure and the Regulation of Glycogen Phosphorylases in Brain. ADVANCES IN NEUROBIOLOGY 2019; 23:125-145. [DOI: 10.1007/978-3-030-27480-1_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Yu J, Deng T, Xiang S. Structural basis for protein phosphatase 1 recruitment by glycogen‐targeting subunits. FEBS J 2018; 285:4646-4659. [DOI: 10.1111/febs.14699] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 10/15/2018] [Accepted: 11/09/2018] [Indexed: 10/27/2022]
Affiliation(s)
- Jun Yu
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety Shanghai Institute of Nutrition and Health Shanghai Institutes for Biological Sciences University of Chinese Academy of Sciences Chinese Academy of Sciences Shanghai China
| | - Tingting Deng
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety Shanghai Institute of Nutrition and Health Shanghai Institutes for Biological Sciences University of Chinese Academy of Sciences Chinese Academy of Sciences Shanghai China
| | - Song Xiang
- CAS Key Laboratory of Nutrition, Metabolism and Food Safety Shanghai Institute of Nutrition and Health Shanghai Institutes for Biological Sciences University of Chinese Academy of Sciences Chinese Academy of Sciences Shanghai China
- Key laboratory of Immune Microenvironment and Disease (Ministry of Education) Tianjin Medical University China
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10
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Kumar GS, Choy MS, Koveal DM, Lorinsky MK, Lyons SP, Kettenbach AN, Page R, Peti W. Identification of the substrate recruitment mechanism of the muscle glycogen protein phosphatase 1 holoenzyme. SCIENCE ADVANCES 2018; 4:eaau6044. [PMID: 30443599 PMCID: PMC6235537 DOI: 10.1126/sciadv.aau6044] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 10/15/2018] [Indexed: 05/04/2023]
Abstract
Glycogen is the primary storage form of glucose. Glycogen synthesis and breakdown are tightly controlled by glycogen synthase (GYS) and phosphorylase, respectively. The enzyme responsible for dephosphorylating GYS and phosphorylase, which results in their activation (GYS) or inactivation (phosphorylase) to robustly stimulate glycogen synthesis, is protein phosphatase 1 (PP1). However, our understanding of how PP1 recruits these substrates is limited. Here, we show how PP1, together with its muscle glycogen-targeting (GM) regulatory subunit, recruits and selectively dephosphorylates its substrates. Our molecular data reveal that the GM carbohydrate binding module (GM CBM21), which is amino-terminal to the GM PP1 binding domain, has a dual function in directing PP1 substrate specificity: It either directly recruits substrates (i.e., GYS) or recruits them indirectly by localization (via glycogen for phosphorylase). Our data provide the molecular basis for PP1 regulation by GM and reveal how PP1-mediated dephosphorylation is driven by scaffolding-based substrate recruitment.
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Affiliation(s)
- Ganesan Senthil Kumar
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Meng S. Choy
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Dorothy M. Koveal
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI 02912, USA
| | - Michael K. Lorinsky
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI 02912, USA
| | - Scott P. Lyons
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Arminja N. Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Lebanon, NH 03756, USA
| | - Rebecca Page
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Wolfgang Peti
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Corresponding author.
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Stender S, Smagris E, Lauridsen BK, Kofoed KF, Nordestgaard BG, Tybjærg-Hansen A, Pennacchio LA, Dickel DE, Cohen JC, Hobbs HH. Relationship between genetic variation at PPP1R3B and levels of liver glycogen and triglyceride. Hepatology 2018; 67:2182-2195. [PMID: 29266543 PMCID: PMC5991995 DOI: 10.1002/hep.29751] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/31/2017] [Accepted: 12/18/2017] [Indexed: 12/15/2022]
Abstract
UNLABELLED Genetic variation at rs4240624 on chromosome 8 is associated with an attenuated signal on hepatic computerized tomography, which has been attributed to changes in hepatic fat. The closest coding gene to rs4240624, PPP1R3B, encodes a protein that promotes hepatic glycogen synthesis. Here, we performed studies to determine whether the x-ray attenuation associated with rs4240624 is due to differences in hepatic glycogen or hepatic triglyceride content (HTGC). A sequence variant in complete linkage disequilibrium with rs4240624, rs4841132, was genotyped in the Dallas Heart Study (DHS), the Dallas Liver Study, and the Copenhagen Cohort (n = 112,428) of whom 1,539 had nonviral liver disease. The minor A-allele of rs4841132 was associated with increased hepatic x-ray attenuation (n = 1,572; P = 4 × 10-5 ), but not with HTGC (n = 2,674; P = 0.58). Rs4841132-A was associated with modest, but significant, elevations in serum alanine aminotransferase (ALT) in the Copenhagen Cohort (P = 3 × 10-4 ) and the DHS (P = 0.004), and with odds ratios for liver disease of 1.13 (95% CI, 0.97-1.31) and 1.23 (1.01-1.51), respectively. Mice lacking protein phosphatase 1 regulatory subunit 3B (PPP1R3B) were deficient in hepatic glycogen, whereas HTGC was unchanged. Hepatic overexpression of PPP1R3B caused accumulation of hepatic glycogen and elevated plasma levels of ALT, but did not change HTGC. CONCLUSION These observations are consistent with the notion that the minor allele of rs4841132 promotes a mild form of hepatic glycogenosis that is associated with hepatic injury. (Hepatology 2018;67:2182-2195).
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Affiliation(s)
- Stefan Stender
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390,Department of McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Eriks Smagris
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Bo K. Lauridsen
- Department of Clinical Biochemistry, Copenhagen University Hospital, Copenhagen University Hospital, Copenhagen, DK
| | - Klaus F. Kofoed
- Department of Cardiology and Radiology, Rigshospitalet, Copenhagen University Hospital, Copenhagen University Hospital, Copenhagen, DK
| | - Børge G. Nordestgaard
- Department of Clinical Biochemistry and Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Copenhagen University Hospital, Copenhagen, DK,The Copenhagen City Heart Study, Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, DK
| | - Anne Tybjærg-Hansen
- Department of Clinical Biochemistry, Copenhagen University Hospital, Copenhagen University Hospital, Copenhagen, DK,Department of Clinical Biochemistry and Copenhagen General Population Study, Herlev and Gentofte Hospital, Copenhagen University Hospital, Copenhagen University Hospital, Copenhagen, DK,The Copenhagen City Heart Study, Frederiksberg Hospital, Copenhagen University Hospital, Copenhagen, DK
| | | | | | - Jonathan C. Cohen
- Department of McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Helen H. Hobbs
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390,Department of McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, 75390
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12
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Li WJ, Yin RX, Huang JH, Bin Y, Chen WX, Cao XL. Association between the PPP1R3B polymorphisms and serum lipid traits, the risk of coronary artery disease and ischemic stroke in a southern Chinese Han population. Nutr Metab (Lond) 2018; 15:27. [PMID: 29681992 PMCID: PMC5898016 DOI: 10.1186/s12986-018-0266-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Accepted: 04/09/2018] [Indexed: 12/11/2022] Open
Abstract
Background Little is known about the association of the protein phosphatase 1 regulatory subunit 3B gene (PPP1R3B) single nucleotide polymorphisms (SNPs) and serum lipid levels, the risk of coronary artery disease (CAD) and ischemic stroke (IS) in the Chinese populations. This study detected such association in a Southern Chinese Han population. Methods Genotypes of 4 novel PPP1R3B SNPs (rs12785, rs330910, rs330915 and rs9949) in 1704 Han Chinese (CAD, 556; IS, 531 and control, 617) were determined by the Snapshot technology. Results The rs12785A and rs9949A allele frequency was higher in both CAD/IS patients than in controls. The rs330910T and rs330915T allele frequency was also higher in CAD patients than in controls. The rs330910T allele carriers in controls had lower serum low-density lipoprotein cholesterol (LDL-C) levels than the rs330910T allele non-carriers (P < 0.0014). The rs12785A, rs9949A and rs330910T allele carriers were associated with an increased risk of CAD (P = 0.008–0.004). There was strong linkage disequilibrium among the 4 SNPs in the controls and CAD/IS patients. The T-A-A-G haplotype was associated with a decreased risk of CAD and IS, whereas the A-A-T-A haplotype was associated with an increased risk for IS. Haplotype-environment interactions on the risk of CAD and IS were also observed. Conclusions Several PPP1R3B polymorphisms were associated with serum LDL-C levels, the risk of CAD and IS in the Southern Chinese Han population. But these findings still need to be confirmed in the other populations with larger sample sizes. Electronic supplementary material The online version of this article (10.1186/s12986-018-0266-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Wei-Jun Li
- 1Department of Cardiology, Institute of Cardiovascular Diseases, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
| | - Rui-Xing Yin
- 1Department of Cardiology, Institute of Cardiovascular Diseases, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
| | - Jian-Hua Huang
- 1Department of Cardiology, Institute of Cardiovascular Diseases, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
| | - Yuan Bin
- 1Department of Cardiology, Institute of Cardiovascular Diseases, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
| | - Wu-Xian Chen
- 1Department of Cardiology, Institute of Cardiovascular Diseases, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
| | - Xiao-Li Cao
- 2Department of Neurology, the First Affiliated Hospital, Guangxi Medical University, Nanning, 530021 Guangxi People's Republic of China
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13
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Mehta MB, Shewale SV, Sequeira RN, Millar JS, Hand NJ, Rader DJ. Hepatic protein phosphatase 1 regulatory subunit 3B (Ppp1r3b) promotes hepatic glycogen synthesis and thereby regulates fasting energy homeostasis. J Biol Chem 2017; 292:10444-10454. [PMID: 28473467 DOI: 10.1074/jbc.m116.766329] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 05/01/2017] [Indexed: 01/23/2023] Open
Abstract
Maintenance of whole-body glucose homeostasis is critical to glycemic function. Genetic variants mapping to chromosome 8p23.1 in genome-wide association studies have been linked to glycemic traits in humans. The gene of known function closest to the mapped region, PPP1R3B (protein phosphatase 1 regulatory subunit 3B), encodes a protein (GL) that regulates glycogen metabolism in the liver. We therefore sought to test the hypothesis that hepatic PPP1R3B is associated with glycemic traits. We generated mice with either liver-specific deletion (Ppp1r3bΔhep ) or liver-specific overexpression of Ppp1r3b The Ppp1r3b deletion significantly reduced glycogen synthase protein abundance, and the remaining protein was predominantly phosphorylated and inactive. As a consequence, glucose incorporation into hepatic glycogen was significantly impaired, total hepatic glycogen content was substantially decreased, and mice lacking hepatic Ppp1r3b had lower fasting plasma glucose than controls. The concomitant loss of liver glycogen impaired whole-body glucose homeostasis and increased hepatic expression of glycolytic enzymes in Ppp1r3bΔhep mice relative to controls in the postprandial state. Eight hours of fasting significantly increased the expression of two critical gluconeogenic enzymes, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase, above the levels in control livers. Conversely, the liver-specific overexpression of Ppp1r3b enhanced hepatic glycogen storage above that of controls and, as a result, delayed the onset of fasting-induced hypoglycemia. Moreover, mice overexpressing hepatic Ppp1r3b upon long-term fasting (12-36 h) were protected from blood ketone-body accumulation, unlike control and Ppp1r3bΔhep mice. These findings indicate a major role for Ppp1r3b in regulating hepatic glycogen stores and whole-body glucose/energy homeostasis.
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Affiliation(s)
- Minal B Mehta
- From the Division of Translational Medicine and Human Genetics.,the Department of Genetics, and
| | - Swapnil V Shewale
- From the Division of Translational Medicine and Human Genetics.,the Department of Genetics, and
| | | | - John S Millar
- From the Division of Translational Medicine and Human Genetics
| | | | - Daniel J Rader
- From the Division of Translational Medicine and Human Genetics, .,the Department of Genetics, and.,the Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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Ren D, Fisher LA, Zhao J, Wang L, Williams BC, Goldberg ML, Peng A. Cell cycle-dependent regulation of Greatwall kinase by protein phosphatase 1 and regulatory subunit 3B. J Biol Chem 2017; 292:10026-10034. [PMID: 28446604 DOI: 10.1074/jbc.m117.778233] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/25/2017] [Indexed: 11/06/2022] Open
Abstract
Greatwall (Gwl) kinase plays an essential role in the regulation of mitotic entry and progression. Mitotic activation of Gwl requires both cyclin-dependent kinase 1 (CDK1)-dependent phosphorylation and its autophosphorylation at an evolutionarily conserved serine residue near the carboxyl terminus (Ser-883 in Xenopus). In this study we show that Gwl associates with protein phosphatase 1 (PP1), particularly PP1γ, which mediates the dephosphorylation of Gwl Ser-883. Consistent with the mitotic activation of Gwl, its association with PP1 is disrupted in mitotic cells and egg extracts. During mitotic exit, PP1-dependent dephosphorylation of Gwl Ser-883 occurs prior to dephosphorylation of other mitotic substrates; replacing endogenous Gwl with a phosphomimetic S883E mutant blocks mitotic exit. Moreover, we identified PP1 regulatory subunit 3B (PPP1R3B) as a targeting subunit that can direct PP1 activity toward Gwl. PPP1R3B bridges PP1 and Gwl association and promotes Gwl Ser-883 dephosphorylation. Consistent with the cell cycle-dependent association of Gwl and PP1, Gwl and PPP1R3B dissociate in M phase. Interestingly, up-regulation of PPP1R3B facilitates mitotic exit and blocks mitotic entry. Thus, our study suggests PPP1R3B as a new cell cycle regulator that functions by governing Gwl dephosphorylation.
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Affiliation(s)
- Dapeng Ren
- From the Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583 and
| | - Laura A Fisher
- From the Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583 and
| | - Jing Zhao
- From the Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583 and
| | - Ling Wang
- From the Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583 and
| | - Byron C Williams
- the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Michael L Goldberg
- the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853
| | - Aimin Peng
- From the Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Lincoln, Nebraska 68583 and
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15
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Chen P, Piaggi P, Traurig M, Bogardus C, Knowler WC, Baier LJ, Hanson RL. Differential methylation of genes in individuals exposed to maternal diabetes in utero. Diabetologia 2017; 60:645-655. [PMID: 28127622 PMCID: PMC7194355 DOI: 10.1007/s00125-016-4203-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 12/09/2016] [Indexed: 12/22/2022]
Abstract
AIMS/HYPOTHESIS Individuals exposed to maternal diabetes in utero are more likely to develop metabolic and cardiovascular diseases later in life. This may be partially attributable to epigenetic regulation of gene expression. We performed an epigenome-wide association study to examine whether differential DNA methylation, a major source of epigenetic regulation, can be observed in offspring of mothers with type 2 diabetes during the pregnancy (OMD) compared with offspring of mothers with no diabetes during the pregnancy (OMND). METHODS DNA methylation was measured in peripheral blood using the Illumina HumanMethylation450K BeadChip. A total of 423,311 CpG sites were analysed in 388 Pima Indian individuals, mean age at examination was 13.0 years, 187 of whom were OMD and 201 were OMND. Differences in methylation between OMD and OMND were assessed. RESULTS Forty-eight differentially methylated CpG sites (with an empirical false discovery rate ≤0.05), mapping to 29 genes and ten intergenic regions, were identified. The gene with the strongest evidence was LHX3, in which six CpG sites were hypermethylated in OMD compared with OMND (p ≤ 1.1 × 10-5). Similarly, a CpG near PRDM16 was hypermethylated in OMD (1.1% higher, p = 5.6 × 10-7), where hypermethylation also predicted future diabetes risk (HR 2.12 per SD methylation increase, p = 9.7 × 10-5). Hypermethylation near AK3 and hypomethylation at PCDHGA4 and STC1 were associated with exposure to diabetes in utero (AK3: 2.5% higher, p = 7.8 × 10-6; PCDHGA4: 2.8% lower, p = 3.0 × 10-5; STC1: 2.9% lower, p = 1.6 × 10-5) and decreased insulin secretory function among offspring with normal glucose tolerance (AK3: 0.088 SD lower per SD of methylation increase, p = 0.02; PCDHGA4: 0.08 lower SD per SD of methylation decrease, p = 0.03; STC1: 0.072 SD lower per SD of methylation decrease, p = 0.05). Seventeen CpG sites were also associated with BMI (p ≤ 0.05). Pathway analysis of the genes with at least one differentially methylated CpG (p < 0.005) showed enrichment for three relevant biological pathways. CONCLUSIONS/INTERPRETATION Intrauterine exposure to diabetes can affect methylation at multiple genomic sites. Methylation status at some of these sites can impair insulin secretion, increase body weight and increase risk of type 2 diabetes.
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Affiliation(s)
- Peng Chen
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - Paolo Piaggi
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - Michael Traurig
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - Clifton Bogardus
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - William C Knowler
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - Leslie J Baier
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA
| | - Robert L Hanson
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 1550 E. Indian School Rd, Phoenix, AZ, 85014, USA.
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Ruchti E, Roach P, DePaoli-Roach A, Magistretti P, Allaman I. Protein targeting to glycogen is a master regulator of glycogen synthesis in astrocytes. IBRO Rep 2016; 1:46-53. [PMID: 30135927 PMCID: PMC6084890 DOI: 10.1016/j.ibror.2016.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 10/03/2016] [Accepted: 10/03/2016] [Indexed: 01/21/2023] Open
Abstract
The storage and use of glycogen, the main energy reserve in the brain, is a metabolic feature of astrocytes. Glycogen synthesis is regulated by Protein Targeting to Glycogen (PTG), a member of specific glycogen-binding subunits of protein phosphatase-1 (PPP1). It positively regulates glycogen synthesis through de-phosphorylation of both glycogen synthase (activation) and glycogen phosphorylase (inactivation). In cultured astrocytes, PTG mRNA levels were previously shown to be enhanced by the neurotransmitter noradrenaline. To achieve further insight into the role of PTG in the regulation of astrocytic glycogen, its levels of expression were manipulated in primary cultures of mouse cortical astrocytes using adenovirus-mediated overexpression of tagged-PTG or siRNA to downregulate its expression. Infection of astrocytes with adenovirus led to a strong increase in PTG expression and was associated with massive glycogen accumulation (>100 fold), demonstrating that increased PTG expression is sufficient to induce glycogen synthesis and accumulation. In contrast, siRNA-mediated downregulation of PTG resulted in a 2-fold decrease in glycogen levels. Interestingly, PTG downregulation strongly impaired long-term astrocytic glycogen synthesis induced by insulin or noradrenaline. Finally, these effects of PTG downregulation on glycogen metabolism could also be observed in cultured astrocytes isolated from PTG-KO mice. Collectively, these observations point to a major role of PTG in the regulation of glycogen synthesis in astrocytes and indicate that conditions leading to changes in PTG expression will directly impact glycogen levels in this cell type.
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Affiliation(s)
- E. Ruchti
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
| | - P.J. Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - A.A. DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - P.J. Magistretti
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Centre de Neurosciences Psychiatriques, CHUV, Département de Psychiatrie, Site de Cery, CH-1008 Prilly/Lausanne, Switzerland
- King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - I. Allaman
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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17
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Tin A, Balakrishnan P, Beaty TH, Boerwinkle E, Hoogeveen RC, Young JH, Kao WHL. GCKR and PPP1R3B identified as genome-wide significant loci for plasma lactate: the Atherosclerosis Risk in Communities (ARIC) study. Diabet Med 2016; 33:968-75. [PMID: 26433129 PMCID: PMC4819009 DOI: 10.1111/dme.12971] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/28/2015] [Indexed: 12/22/2022]
Abstract
AIM To investigate the genetic influence of circulating lactate level, a marker of oxidative capacity associated with diabetes. METHODS We conducted a genome-wide association study of log-transformed plasma lactate levels in 6901 European-American participants in the Atherosclerosis Risk in Communities study. For regions that achieved genome-wide significance in European-American participants, we conducted candidate region analysis in African-American subjects and tested for interaction between metformin use and the index single nucleotide polymorphisms for plasma lactate in European-American subjects. RESULTS The genome-wide association study in European-American subjects identified two genome-wide significant loci, GCKR (rs1260326, T allele β=0.08; P=1.8×10(-47) ) and PPP1R3B/LOC157273 (rs9987289, A allele β=0.06; P=1.6×10(-9) ). The index single nucleotide polymorphisms in these two loci explain 3.3% of the variance in log-transformed plasma lactate levels among the European-American subjects. In the African-American subjects, based on a region-significant threshold, the index single nucleotide polymorphism at GCKR was associated with plasma lactate but that at PPP1R3B/LOC157273 was not. Metformin use appeared to strengthen the association between the index single nucleotide polymorphism at PPP1R3B/LOC157273 and plasma lactate in European-American subjects (P for interaction=0.01). CONCLUSIONS We identified GCKR and PPP1R3B/LOC157273 as two genome-wide significant loci of plasma lactate. Both loci are associated with other diabetes-related phenotypes. These findings increase our understanding of the genetic control of lactate metabolism.
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Affiliation(s)
- A Tin
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - P Balakrishnan
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - T H Beaty
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - E Boerwinkle
- Human Genetics Center, University of Texas School of Public Health, Houston, TX, USA
| | - R C Hoogeveen
- Department of Medicine, Baylor College of Medicine, Houston, TX, USA
- Center for Cardiovascular Disease Prevention, Methodist DeBakey Heart and Vascular Center, Houston, TX, USA
| | - J H Young
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Department of Medicine, The Johns Hopkins University, School of Medicine, Baltimore, MD, USA
- Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, MD, USA
| | - W H L Kao
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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18
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Zois CE, Harris AL. Glycogen metabolism has a key role in the cancer microenvironment and provides new targets for cancer therapy. J Mol Med (Berl) 2016; 94:137-54. [PMID: 26882899 PMCID: PMC4762924 DOI: 10.1007/s00109-015-1377-9] [Citation(s) in RCA: 159] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/21/2015] [Accepted: 12/28/2015] [Indexed: 12/13/2022]
Abstract
Metabolic reprogramming is a hallmark of cancer cells and contributes to their adaption within the tumour microenvironment and resistance to anticancer therapies. Recently, glycogen metabolism has become a recognised feature of cancer cells since it is upregulated in many tumour types, suggesting that it is an important aspect of cancer cell pathophysiology. Here, we provide an overview of glycogen metabolism and its regulation, with a focus on its role in metabolic reprogramming of cancer cells under stress conditions such as hypoxia, glucose deprivation and anticancer treatment. The various methods to detect glycogen in tumours in vivo as well as pharmacological modulators of glycogen metabolism are also reviewed. Finally, we discuss the therapeutic value of targeting glycogen metabolism as a strategy for combinational approaches in cancer treatment.
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Affiliation(s)
- Christos E Zois
- Molecular Oncology Laboratories, Department of Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford University, Oxford, OX3 9DS, UK.
| | - Adrian L Harris
- Molecular Oncology Laboratories, Department of Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford University, Oxford, OX3 9DS, UK.
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19
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Kahali B, Halligan B, Speliotes EK. Insights from Genome-Wide Association Analyses of Nonalcoholic Fatty Liver Disease. Semin Liver Dis 2015; 35:375-91. [PMID: 26676813 PMCID: PMC4941959 DOI: 10.1055/s-0035-1567870] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is caused by hepatic steatosis, which can progress to nonalcoholic steatohepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma in the absence of excessive alcohol consumption. Nonalcoholic fatty liver disease will become the number one cause of liver disease worldwide by 2020. Nonalcoholic fatty liver disease is correlated albeit imperfectly with obesity and other metabolic diseases such as diabetes, hyperlipidemia, and cardiovascular disease, but exactly how having one of these diseases contributes to the development of other metabolic diseases is only now being elucidated. Development of NAFLD and related metabolic diseases is genetically influenced in the population, and recent genome-wide association studies (GWASs) have discovered genetic variants that associate with these diseases. These GWAS-associated variants cannot only help us to identify individuals at high risk of developing NAFLD, but also to better understand its pathophysiology so that we can develop more effective treatments for this disease and related metabolic diseases in the future.
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Affiliation(s)
- Bratati Kahali
- Division of Gastroenterology, Department of Internal Medicine, Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan
| | - Brian Halligan
- Division of Gastroenterology, Department of Internal Medicine, Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan
| | - Elizabeth K. Speliotes
- Division of Gastroenterology, Department of Internal Medicine, Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan
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20
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Cheng XY, He S, Liang XF, Song Y, Yuan XC, Li L, Wen ZY, Cai WJ, Tao YX. Molecular cloning, expression and single nucleotide polymorphisms of protein phosphatase 1 (PP1) in mandarin fish ( Siniperca chuatsi ). Comp Biochem Physiol B Biochem Mol Biol 2015; 189:69-79. [DOI: 10.1016/j.cbpb.2015.08.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 07/28/2015] [Accepted: 08/04/2015] [Indexed: 01/27/2023]
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21
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Role of glycogen phosphorylase in liver glycogen metabolism. Mol Aspects Med 2015; 46:34-45. [PMID: 26519772 DOI: 10.1016/j.mam.2015.09.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 09/11/2015] [Indexed: 02/05/2023]
Abstract
Liver glycogen is synthesized after a meal in response to an increase in blood glucose concentration in the portal vein and endocrine and neuroendocrine signals, and is degraded to glucose between meals to maintain blood glucose homeostasis. Glycogen degradation and synthesis during the diurnal cycle are mediated by changes in the activities of phosphorylase and glycogen synthase. Phosphorylase is regulated by phosphorylation of serine-14. Only the phosphorylated form of liver phosphorylase (GPa) is catalytically active. Interconversion between GPa and GPb (unphosphorylated) is dependent on the activities of phosphorylase kinase and of phosphorylase phosphatase. The latter comprises protein phosphatase-1 in conjunction with a glycogen-targeting protein (G-subunit) of the PPP1R3 family. At least two of six G-subunits (GL and PTG) expressed in liver are involved in GPa dephosphorylation. GPa to GPb interconversion is dependent on the conformational state of phosphorylase which can be relaxed (R) or tense (T) depending on the concentrations of allosteric effectors such as glucose, glucose 6-phosphate and adenine nucleotides and on the acetylation state of lysine residues. The G-subunit, GL, encoded by PPP1R3B gene is expressed at high levels in liver and can function as a phosphorylase phosphatase and a synthase phosphatase and has an allosteric binding site for GPa at the C-terminus which inhibits synthase phosphatase activity. GPa to GPb conversion is a major upstream event in the regulation of glycogen synthesis by glucose, its downstream metabolites and extracellular signals such as insulin and neurotransmitters.
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22
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Zois CE, Favaro E, Harris AL. Glycogen metabolism in cancer. Biochem Pharmacol 2014; 92:3-11. [PMID: 25219323 DOI: 10.1016/j.bcp.2014.09.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 08/29/2014] [Accepted: 09/04/2014] [Indexed: 12/30/2022]
Abstract
Since its identification more than 150 years ago, there has been an extensive characterisation of glycogen metabolism and its regulatory pathways in the two main glycogen storage organs of the body, i.e. liver and muscle. In recent years, glycogen metabolism has also been demonstrated to be upregulated in many tumour types, suggesting it is an important aspect of cancer cell pathophysiology. Here, we provide an overview of glycogen metabolism and its regulation, with a focus on its role in metabolic reprogramming of cancer cells. The various methods to detect glycogen in tumours in vivo are also reviewed. Finally, we discuss the targeting of glycogen metabolism as a strategy for cancer treatment.
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Affiliation(s)
- Christos E Zois
- Molecular Oncology Laboratories, Oxford University, Department of Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
| | - Elena Favaro
- Cell Death and Metabolism, Danish Cancer Society Research Center, Strandboulevarden 49, 2100 Copenhagen, Denmark.
| | - Adrian L Harris
- Molecular Oncology Laboratories, Oxford University, Department of Oncology, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
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23
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Korrodi-Gregório L, Esteves SLC, Fardilha M. Protein phosphatase 1 catalytic isoforms: specificity toward interacting proteins. Transl Res 2014; 164:366-91. [PMID: 25090308 DOI: 10.1016/j.trsl.2014.07.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/26/2014] [Accepted: 07/01/2014] [Indexed: 01/21/2023]
Abstract
The coordinated and reciprocal action of serine-threonine protein kinases and protein phosphatases produces transitory phosphorylation, a fundamental regulatory mechanism for many biological processes. Phosphoprotein phosphatase 1 (PPP1), a major serine-threonine phosphatase, in particular, is ubiquitously distributed and regulates a broad range of cellular functions, including glycogen metabolism, cell cycle progression, and muscle relaxation. PPP1 has evolved effective catalytic machinery but in vitro lacks substrate specificity. In vivo, its specificity is achieved not only by the existence of different PPP1 catalytic isoforms, but also by binding of the catalytic moiety to a large number of regulatory or targeting subunits. Here, we will address exhaustively the existence of diverse PPP1 catalytic isoforms and the relevance of their specific partners and consequent functions.
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Affiliation(s)
- Luís Korrodi-Gregório
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Sara L C Esteves
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal
| | - Margarida Fardilha
- Laboratório de Transdução de Sinais, Departamento de Biologia, Secção Autónoma de Ciências de Saúde, Centro de Biologia Celular, Universidade de Aveiro, Aveiro, Portugal.
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Zhang Y, Gan W, Tian C, Li H, Lin X, Chen Y. Association of PPP1R3B polymorphisms with blood lipid and C-reactive protein levels in a Chinese population (PPP1R3B C ). J Diabetes 2013; 5:275-81. [PMID: 23343124 DOI: 10.1111/1753-0407.12028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/09/2013] [Accepted: 01/21/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Genetic variants of PPP1R3B, a gene encoding a critical protein involved in hepatic glycogen metabolism, were recently reported to be associated with plasma levels of lipids and C-reactive protein (CRP) among populations of mostly European descent. The aim of the present study was to investigate whether the PPP1R3B variants are associated with plasma levels of lipids and inflammation factors in Chinese Han. METHODS Five single nucleotide polymorphisms (SNPs) of the PPP1R3B gene were genotyped and their associations with plasma lipids and CRP were determined in 1636 Chinese Han from Shanghai. RESULTS Three SNPs, namely rs2126259, rs9987289, and rs19334, were significantly associated with plasma levels of low-density lipoprotein-cholesterol, and rs2126259 and rs9987289 were further significantly associated with total cholesterol. The remaining two SNPs (rs189798 and rs330919) were significantly associated with plasma CRP levels, but not with plasma lipid levels. CONCLUSION Genetic polymorphisms of the PPP1R3B gene may contribute to variations in plasma lipids and CRP levels among Chinese Han individuals.
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Affiliation(s)
- Yongxian Zhang
- Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Shanghai, China
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25
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Lu YC, Yao X, Li YF, El-Gamil M, Dudley ME, Yang JC, Almeida JR, Douek DC, Samuels Y, Rosenberg SA, Robbins PF. Mutated PPP1R3B is recognized by T cells used to treat a melanoma patient who experienced a durable complete tumor regression. THE JOURNAL OF IMMUNOLOGY 2013; 190:6034-42. [PMID: 23690473 DOI: 10.4049/jimmunol.1202830] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Adoptive cell therapy with tumor-infiltrating lymphocytes (TILs) represents an effective treatment for patients with metastatic melanoma. However, most of the Ag targets recognized by effective melanoma-reactive TILs remain elusive. In this study, patient 2369 experienced a complete response, including regressions of bulky liver tumor masses, ongoing beyond 7 y following adoptive TIL transfer. The screening of a cDNA library generated from the autologous melanoma cell line resulted in the isolation of a mutated protein phosphatase 1, regulatory (inhibitor) subunit 3B (PPP1R3B) gene product. The mutated PPP1R3B peptide represents the immunodominant epitope recognized by tumor-reactive T cells in TIL 2369. Five years following adoptive transfer, peripheral blood T lymphocytes obtained from patient 2369 recognized the mutated PPP1R3B epitope. These results demonstrate that adoptive T cell therapy targeting a tumor-specific Ag can mediate long-term survival for a patient with metastatic melanoma. This study also provides an impetus to develop personalized immunotherapy targeting tumor-specific, mutated Ags.
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Affiliation(s)
- Yong-Chen Lu
- Surgery Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Abstract
This review traces the historical origins and conceptual developments leading to the current state of knowledge of the three superfamilies of protein Ser/Thr phosphatases. 'PR enzyme' was identified as an enzyme that inactivates glycogen phosphorylase, although it took 10 years before this ugly duckling was recognized for its true identity as a protein Ser/Thr phosphatase. Ethanol denaturation for purification in the 1970s yielded a phosphatase that exhibited broad specificity, which was resolved into type-1 and type-2 phosphatases in the 1980s. More recent developments show that regulation and specificity are achieved through assembly of multisubunit holoenzymes, transient phosphorylation and the action of inhibitor proteins. Still not widely appreciated, there are hundreds of discrete protein Ser/Thr phosphatases available to counteract protein kinases, offering potential therapeutic targets. Signalling networks and modelling schemes need to incorporate the full gamut of protein Ser/Thr phosphatases and their interconnections.
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Affiliation(s)
- David L Brautigan
- Department of Microbiology, Immunology and Cancer Biology, Center for Cell Signaling, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
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27
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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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Cinar MU, Kayan A, Uddin MJ, Jonas E, Tesfaye D, Phatsara C, Ponsuksili S, Wimmers K, Tholen E, Looft C, Jüngst H, Schellander K. Association and expression quantitative trait loci (eQTL) analysis of porcine AMBP, GC and PPP1R3B genes with meat quality traits. Mol Biol Rep 2011; 39:4809-21. [PMID: 21947951 DOI: 10.1007/s11033-011-1274-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 09/15/2011] [Indexed: 11/26/2022]
Abstract
The aim of this research was to screen polymorphism and to perform association study of porcine AMBP (alpha-1-microglobulin/bikunin precursor), GC (group-specific component protein) and PPP1R3B (protein phosphatase 1, regulatory (inhibitor) subunit 3B) genes with meat quality traits as well as to unravel the transcriptional regulation of these genes by expression QTL (eQTL) study. For this purpose, Duroc × Pietrain F2 resource population (DuPi; n = 313) and a commercial breed Pietrain (Pi; n = 110) were used for association and only DuPi for expression and eQTL study. A SNP was identified in the genes AMBP (g.22229C>T), GC (g.398C>T) and PPP1R3B (c.479A>G), respectively. In DuPi SNP of AMBP was associated (P < 0.05) with meat colour, pH(1L), pH(24L), pH(24H) and conductivity(24L); SNP of GC showed tendency to association (P < 0.10) with pH24H, conductivity(1L) and thawing loss, and SNP of PPP1R3B was associated (P < 0.05) with meat colour, pH(1L), pH(24L), pH(24H) and shear force. In Pi SNPs of AMBP and GC was associated with pH(24H) and PPP1R3B SNP was associated with pH(24L). The mRNA levels in Longissimus dorsi muscle tissue of these three genes were evaluated by using qRT-PCR to identify association between gene expression and meat quality traits as well as to analyse eQTL. The mRNA expression of PPP1R3B associated with pH(24L) (P < 0.05). Expression of these three genes was higher in animals with low pH of muscle. Linkage analysis using QTL Express revealed ten trans-regulated eQTL on seven porcine autosomes. Suggestive eQTL [P < 0.05, CW (chromosome-wide)] were found for PPP1R3B on SSC3 and 13. These results revealed that genetic variation and gene expression of these genes are associated with the meat quality traits. These three genes could influence meat quality and could be potential positional, physiological and functional candidate gene for meat quality traits in pigs. However, the analysis of eQTL also suggested that we need to consider additional genes encoding for transcription factors (TF), via fine-mapping underlying the eQTL peaks, in order to understand interaction among these genes.
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Affiliation(s)
- Mehmet Ulas Cinar
- Institute of Animal Science, Animal Breeding and Husbandry Group, University of Bonn, Endenicher Allee 15, 53115, Bonn, Germany
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Kelsall IR, Voss M, Munro S, Cuthbertson DJR, Cohen PTW. R3F, a novel membrane-associated glycogen targeting subunit of protein phosphatase 1 regulates glycogen synthase in astrocytoma cells in response to glucose and extracellular signals. J Neurochem 2011; 118:596-610. [DOI: 10.1111/j.1471-4159.2011.07345.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Le AV, Tavalin SJ, Dodge-Kafka KL. Identification of AKAP79 as a protein phosphatase 1 catalytic binding protein. Biochemistry 2011; 50:5279-91. [PMID: 21561082 PMCID: PMC3115558 DOI: 10.1021/bi200089z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The ubiquitously expressed and highly promiscuous protein phosphatase 1 (PP1) regulates many cellular processes. Targeting PP1 to specific locations within the cell allows for the regulation of PP1 by conferring substrate specificity. In the present study, we identified AKAP79 as a novel PP1 regulatory subunit. Immunoprecipitaiton of the AKAP from rat brain extract found that the PP1 catalytic subunit copurified with the anchoring protein. This is a direct interaction, demonstrated by pulldown experiments using purified proteins. Interestingly, the addition of AKAP79 to purified PP1 catalytic subunit decreased phosphatase activity with an IC(50) of 811 ± 0.56 nM of the anchoring protein. Analysis of AKAP79 identified a PP1 binding site that conformed to a consensus PP1 binding motif (FxxR/KxR/K) in the first 44 amino acids of the anchoring protein. This was confirmed when a peptide mimicking this region of AKAP79 was able to bind PP1 by both pulldown assay and surface plasmon resonance. However, PP1 was still able to bind to AKAP79 upon deletion of this region, suggesting additional sites of contact between the anchoring protein and the phosphatase. Importantly, this consensus PP1 binding motif was found not to be responsible for PP1 inhibition, but rather enhanced phosphatase activity, as deletion of this domain resulted in an increased inhibition of PP1 activity. Instead, a second interaction domain localized to residues 150-250 of AKAP79 was required for the inhibition of PP1. However, the inhibitory actions of AKAP79 on PP1 are substrate dependent, as the anchoring protein did not inhibit PP1 dephosphorylation of phospho-PSD-95, a substrate found in AKAP79 complexes in the brain. These combined observations suggest that AKAP79 acts as a PP1 regulatory subunit that can direct PP1 activity toward specific targets in the AKAP79 complex.
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Affiliation(s)
- Andrew. V. Le
- Pat and Jim Calhoun Center for Cardiology, University of Connecticut Health Center, Farmington, CT 06030
| | - Steven. J. Tavalin
- Department of Pharmacology, University of Tennessee Health Science Center, Memphis, Tennessee 38163
| | - Kimberly L. Dodge-Kafka
- Pat and Jim Calhoun Center for Cardiology, University of Connecticut Health Center, Farmington, CT 06030, 860-679-2452, Fax: 860-679-1426,
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Luo X, Zhang Y, Ruan X, Jiang X, Zhu L, Wang X, Ding Q, Liu W, Pan Y, Wang Z, Chen Y. Fasting-induced protein phosphatase 1 regulatory subunit contributes to postprandial blood glucose homeostasis via regulation of hepatic glycogenesis. Diabetes 2011; 60:1435-45. [PMID: 21471512 PMCID: PMC3292316 DOI: 10.2337/db10-1663] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE Most animals experience fasting-feeding cycles throughout their lives. It is well known that the liver plays a central role in regulating glycogen metabolism. However, how hepatic glycogenesis is coordinated with the fasting-feeding cycle to control postprandial glucose homeostasis remains largely unknown. This study determines the molecular mechanism underlying the coupling of hepatic glycogenesis with the fasting-feeding cycle. RESEARCH DESIGN AND METHODS Through a series of molecular, cellular, and animal studies, we investigated how PPP1R3G, a glycogen-targeting regulatory subunit of protein phosphatase 1 (PP1), is implicated in regulating hepatic glycogenesis and glucose homeostasis in a manner tightly orchestrated with the fasting-feeding cycle. RESULTS PPP1R3G in the liver is upregulated during fasting and downregulated after feeding. PPP1R3G associates with glycogen pellet, interacts with the catalytic subunit of PP1, and regulates glycogen synthase (GS) activity. Fasting glucose level is reduced when PPP1R3G is overexpressed in the liver. Hepatic knockdown of PPP1R3G reduces postprandial elevation of GS activity, decreases postprandial accumulation of liver glycogen, and decelerates postprandial clearance of blood glucose. Other glycogen-targeting regulatory subunits of PP1, such as PPP1R3B, PPP1R3C, and PPP1R3D, are downregulated by fasting and increased by feeding in the liver. CONCLUSIONS We propose that the opposite expression pattern of PPP1R3G versus other PP1 regulatory subunits comprise an intricate regulatory machinery to control hepatic glycogenesis during the fasting-feeding cycle. Because of its unique expression pattern, PPP1R3G plays a major role to control postprandial glucose homeostasis during the fasting-feeding transition via its regulation on liver glycogenesis.
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Garcia-Haro L, Garcia-Gimeno MA, Neumann D, Beullens M, Bollen M, Sanz P. The PP1‐R6 protein phosphatase holoenzyme is involved in the glucose‐induced dephosphorylation and inactivation of AMP‐activated protein kinase, a key regulator of insulin secretion, in MIN6 β cells. FASEB J 2010. [DOI: 10.1096/fj.10.166306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Luisa Garcia-Haro
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas and Centro de Investigación en Red de Enfermecedes Raras Valencia Spain
| | - Maria Adelaida Garcia-Gimeno
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas and Centro de Investigación en Red de Enfermecedes Raras Valencia Spain
| | | | - Monique Beullens
- Laboratory of Biosignaling and TherapeuticsDepartment of Molecular Cell BiologyUniversity of Leuven Leuven Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling and TherapeuticsDepartment of Molecular Cell BiologyUniversity of Leuven Leuven Belgium
| | - Pascual Sanz
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas and Centro de Investigación en Red de Enfermecedes Raras Valencia Spain
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Jurczak MJ, Zapater JL, Greenberg CC, Brady MJ. Generation of a dominant-negative glycogen targeting subunit for protein phosphatase-1. Obesity (Silver Spring) 2010; 18:1881-7. [PMID: 20203631 DOI: 10.1038/oby.2010.32] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Modulation of the expression of the protein phosphatase-1 (PP1) glycogen-targeting subunit PTG exerts profound effects on cellular glycogen metabolism in vitro and in vivo. PTG contains three distinct binding domains for glycogen, PP1, and a common site for glycogen synthase and phosphorylase. The impact of disrupting the PP1-binding domain on PTG function was examined in 3T3-L1 adipocytes. A full-length PTG mutant was generated as an adenoviral construct in which the valine and phenylalanine residues in the conserved PP1-binding domain were mutated to alanine (PTG-VF). Infection of fully differentiated 3T3-L1 adipocytes with the PTG-VF adenovirus reduced glycogen stores by over 50%. In vitro, PTG-VF competitively interfered with wild-type PTG action, suggesting that the mutant construct acted as a dominant-negative molecule. The reduction in cellular glycogen storage was due to a significantly increased rate of glycogen turnover. Interestingly, acute basal and insulin-stimulated glucose uptake and glycogen synthesis rates were enhanced in PTG-VF expressing cells vs. control 3T3-L1 adipocytes, likely as a compensatory response to the loss of glycogen stores. These results indicate that the mutation of the PP1-binding domain on PTG resulted in the generation of a dominant-negative molecule that impeded endogenous PTG action and reduced cellular glycogen levels, through enhancement of glycogenolysis rather than impairment of glycogen synthesis.
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Affiliation(s)
- Michael J Jurczak
- Department of Medicine, Section of Endocrinology, Diabetes, and Metabolism and the Committee on Molecular Metabolism and Nutrition, The University of Chicago, Chicago, Illinois, USA
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35
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Garcia-Haro L, Garcia-Gimeno MA, Neumann D, Beullens M, Bollen M, Sanz P. The PP1-R6 protein phosphatase holoenzyme is involved in the glucose-induced dephosphorylation and inactivation of AMP-activated protein kinase, a key regulator of insulin secretion, in MIN6 beta cells. FASEB J 2010; 24:5080-91. [PMID: 20724523 DOI: 10.1096/fj.10-166306] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Mammalian AMP-activated protein kinase (AMPK) is a serine/threonine protein kinase that acts as a sensor of cellular energy status. It is activated by phosphorylation of the catalytic subunit on Thr172. The main objective of this study was the identification of a phosphatase involved in the regulation of AMPK activity. Mouse MIN6 β cells were used to study the glucose-induced regulation of the phosphorylation of AMPK. Small interfering RNA (siRNA) technology was used to deplete putative phosphatase candidate genes that could affect AMPK regulation. The effect of the siRNAs used in the study was compared with the effect observed using a negative control siRNA. A protein phosphatase complex composed of the catalytic subunit of protein phosphatase-1 (PP1) and the regulatory subunit R6 participates in the glucose-induced dephosphorylation of AMPK. R6 interacts physically with the β-subunit of the AMPK complex and recruits PP1 to dephosphorylate the catalytic α-subunit on Thr172. siRNA depletion of R6 decreases glucose-induced insulin secretion due to the presence of a constitutively active AMPK complex. The characterization of the PP1-R6 complex identifies this holoenzyme as a possible target for therapeutic intervention with the aim of regulating the activity of AMPK in pancreatic β cells.
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Affiliation(s)
- Luisa Garcia-Haro
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Cientificas and Centro de Investigación en Red de Enfermecedes Raras, Valencia, Spain
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36
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Zhang L, Liu H. Novel therapeutics based on inhibiting the interaction of glycogen phosphorylase and GL-subunit of glycogen-associated protein phosphatase 1: WO2009127723. Expert Opin Ther Pat 2010; 20:969-73. [DOI: 10.1517/13543771003781923] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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37
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Disruption of the allosteric phosphorylase a regulation of the hepatic glycogen-targeted protein phosphatase 1 improves glucose tolerance in vivo. Cell Signal 2009; 21:1123-34. [DOI: 10.1016/j.cellsig.2009.03.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Accepted: 03/02/2009] [Indexed: 11/17/2022]
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38
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Karis ND, Loughlin WA, Jenkins ID, Healy PC. Glycogen phosphorylase inhibitory effects of 2-oxo-1,2-dihydropyridin-3-yl amide derivatives. Bioorg Med Chem 2009; 17:4724-33. [DOI: 10.1016/j.bmc.2009.04.049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 04/22/2009] [Accepted: 04/23/2009] [Indexed: 10/20/2022]
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39
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Schweiker SS, Loughlin WA, Brown CL, Pierens GK. Synthesis of new modified truncated peptides and inhibition of glycogen phosphorylase. J Pept Sci 2009; 15:442-50. [DOI: 10.1002/psc.1140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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40
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Danos AM, Osmanovic S, Brady MJ. Differential regulation of glycogenolysis by mutant protein phosphatase-1 glycogen-targeting subunits. J Biol Chem 2009; 284:19544-53. [PMID: 19487702 DOI: 10.1074/jbc.m109.015073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PTG and G(L) are hepatic protein phosphatase-1 (PP1) glycogen-targeting subunits, which direct PP1 activity against glycogen synthase (GS) and/or phosphorylase (GP). The C-terminal 16 amino residues of G(L) comprise a high affinity binding site for GP that regulates bound PP1 activity against GS. In this study, a truncated G(L) construct lacking the GP-binding site (G(L)tr) and a chimeric PTG molecule containing the C-terminal site (PTG-G(L)) were generated. As expected, GP binding to glutathione S-transferase (GST)-G(L)tr was reduced, whereas GP binding to GST-PTG-G(L) was increased 2- to 3-fold versus GST-PTG. In contrast, PP1 binding to all proteins was equivalent. Primary mouse hepatocytes were infected with adenoviral constructs for each subunit, and their effects on glycogen metabolism were investigated. G(L)tr expression was more effective at promoting GP inactivation, GS activation, and glycogen accumulation than G(L). Removal of the regulatory GP-binding site from G(L)tr completely blocked the inactivation of GS seen in G(L)-expressing cells following a drop in extracellular glucose. As a result, G(L)tr expression prevented glycogen mobilization under 5 mm glucose conditions. In contrast, equivalent overexpression of PTG or PTG-G(L) caused a similar increase in glycogen-targeted PP1 levels and GS dephosphorylation. Surprisingly, GP dephosphorylation was significantly reduced in PTG-G(L)-overexpressing cells. As a result, PTG-G(L) expression permitted glycogenolysis under 5 mm glucose conditions that was prevented in PTG-expressing cells. Thus, expression of constructs that contained the high affinity GP-binding site (G(L) and PTG-G(L)) displayed reduced glycogen accumulation and enhanced glycogenolysis compared with their respective controls, albeit via different mechanisms.
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Affiliation(s)
- Arpad M Danos
- Department of Medicine, Section of Endocrinology, Diabetes and Metabolism, University of Chicago, Chicago, Illinois 60637, USA
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41
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Vernia S, Solaz-Fuster MC, Gimeno-Alcañiz JV, Rubio T, García-Haro L, Foretz M, de Córdoba SR, Sanz P. AMP-activated protein kinase phosphorylates R5/PTG, the glycogen targeting subunit of the R5/PTG-protein phosphatase 1 holoenzyme, and accelerates its down-regulation by the laforin-malin complex. J Biol Chem 2009; 284:8247-55. [PMID: 19171932 DOI: 10.1074/jbc.m808492200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
R5/PTG is one of the glycogen targeting subunits of type 1 protein phosphatase, a master regulator of glycogen synthesis. R5/PTG recruits the phosphatase to the places where glycogen synthesis occurs, allowing the activation of glycogen synthase and the inactivation of glycogen phosphorylase, thus increasing glycogen synthesis and decreasing its degradation. In this report, we show that the activity of R5/PTG is regulated by AMP-activated protein kinase (AMPK). We demonstrate that AMPK interacts physically with R5/PTG and modifies its basal phosphorylation status. We have also mapped the major phosphorylation sites of R5/PTG by mass spectrometry analysis, observing that phosphorylation of Ser-8 and Ser-268 increased upon activation of AMPK. We have recently described that the activity of R5/PTG is down-regulated by the laforin-malin complex, composed of a dual specificity phosphatase (laforin) and an E3-ubiquitin ligase (malin). We now demonstrate that phosphorylation of R5/PTG at Ser-8 by AMPK accelerates its laforin/malin-dependent ubiquitination and subsequent proteasomal degradation, which results in a decrease of its glycogenic activity. Thus, our results define a novel role of AMPK in glycogen homeostasis.
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Affiliation(s)
- Santiago Vernia
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (CSIC) and CIBER de Enfermedades Raras (CIBERER), Jaime Roig 11, Valencia 46010, Spain
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Abstract
Conversion of glucose into glycogen is a major pathway that contributes to the removal of glucose from the portal vein by the liver in the postprandial state. It is regulated in part by the increase in blood-glucose concentration in the portal vein, which activates glucokinase, the first enzyme in the pathway, causing an increase in the concentration of glucose 6-P (glucose 6-phosphate), which modulates the phosphorylation state of downstream enzymes by acting synergistically with other allosteric effectors. Glucokinase is regulated by a hierarchy of transcriptional and post-transcriptional mechanisms that are only partially understood. In the fasted state, glucokinase is in part sequestered in the nucleus in an inactive state, complexed to a specific regulatory protein, GKRP (glucokinase regulatory protein). This reserve pool is rapidly mobilized to the cytoplasm in the postprandial state in response to an elevated concentration of glucose. The translocation of glucokinase between the nucleus and cytoplasm is modulated by various metabolic and hormonal conditions. The elevated glucose 6-P concentration, consequent to glucokinase activation, has a synergistic effect with glucose in promoting dephosphorylation (inactivation) of glycogen phosphorylase and inducing dephosphorylation (activation) of glycogen synthase. The latter involves both a direct ligand-induced conformational change and depletion of the phosphorylated form of glycogen phosphorylase, which is a potent allosteric inhibitor of glycogen synthase phosphatase activity associated with the glycogen-targeting protein, GL [hepatic glycogen-targeting subunit of PP-1 (protein phosphatase-1) encoded by PPP1R3B]. Defects in both the activation of glucokinase and in the dephosphorylation of glycogen phosphorylase are potential contributing factors to the dysregulation of hepatic glucose metabolism in Type 2 diabetes.
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Worby CA, Gentry MS, Dixon JE. Malin decreases glycogen accumulation by promoting the degradation of protein targeting to glycogen (PTG). J Biol Chem 2008; 283:4069-76. [PMID: 18070875 PMCID: PMC2251628 DOI: 10.1074/jbc.m708712200] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Lafora disease (LD) is an autosomal recessive neurodegenerative disease that results in progressive myoclonus epilepsy and death. LD is caused by mutations in either the E3 ubiquitin ligase malin or the dual specificity phosphatase laforin. A hallmark of LD is the accumulation of insoluble glycogen in the cytoplasm of cells from most tissues. Glycogen metabolism is regulated by phosphorylation of key metabolic enzymes. One regulator of this phosphorylation is protein targeting to glycogen (PTG/R5), a scaffold protein that binds both glycogen and many of the enzymes involved in glycogen synthesis, including protein phosphatase 1 (PP1), glycogen synthase, phosphorylase, and laforin. Overexpression of PTG markedly increases glycogen accumulation, and decreased PTG expression decreases glycogen stores. To investigate if malin and laforin play a role in glycogen metabolism, we overexpressed PTG, malin, and laforin in tissue culture cells. We found that expression of malin or laforin decreased PTG-stimulated glycogen accumulation by 25%, and co-expression of malin and laforin abolished PTG-stimulated glycogen accumulation. Consistent with this result, we found that malin ubiquitinates PTG in a laforin-dependent manner, both in vivo and in vitro, and targets PTG for proteasome-dependent degradation. These results suggest an additional mechanism, involving laforin and malin, in regulating glycogen metabolism.
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Affiliation(s)
- Carolyn A Worby
- Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0721, USA
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Pautsch A, Stadler N, Wissdorf O, Langkopf E, Moreth W, Streicher R. Molecular recognition of the protein phosphatase 1 glycogen targeting subunit by glycogen phosphorylase. J Biol Chem 2008; 283:8913-8. [PMID: 18198182 DOI: 10.1074/jbc.m706612200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Disrupting the interaction between glycogen phosphorylase and the glycogen targeting subunit (G(L)) of protein phosphatase 1 is emerging as a novel target for the treatment of type 2 diabetes. To elucidate the molecular basis of binding, we have determined the crystal structure of liver phosphorylase bound to a G(L)-derived peptide. The structure reveals the C terminus of G(L) binding in a hydrophobically collapsed conformation to the allosteric regulator-binding site at the phosphorylase dimer interface. G(L) mimics interactions that are otherwise employed by the activator AMP. Functional studies show that G(L) binds tighter than AMP and confirm that the C-terminal Tyr-Tyr motif is the major determinant for G(L) binding potency. Our study validates the G(L)-phosphorylase interface as a novel target for small molecule interaction.
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Affiliation(s)
- Alexander Pautsch
- Department of Lead Discovery, Boehringer Ingelheim GmbH & Co. KG, Birkendorferstrasse 65, Biberach, Germany.
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45
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Jurczak MJ, Danos AM, Rehrmann VR, Brady MJ. The role of protein translocation in the regulation of glycogen metabolism. J Cell Biochem 2008; 104:435-43. [DOI: 10.1002/jcb.21634] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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46
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Kelsall IR, Munro S, Hallyburton I, Treadway JL, Cohen PTW. The hepatic PP1 glycogen-targeting subunit interaction with phosphorylaseacan be blocked by C-terminal tyrosine deletion or an indole drug. FEBS Lett 2007; 581:4749-53. [PMID: 17870073 DOI: 10.1016/j.febslet.2007.08.073] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2007] [Revised: 08/28/2007] [Accepted: 08/29/2007] [Indexed: 11/16/2022]
Abstract
The inhibition of hepatic glycogen-associated protein phosphatase-1 (PP1-G(L)) by glycogen phosphorylase a prevents the dephosphorylation and activation of glycogen synthase, suppressing glycogen synthesis when glycogenolysis is activated. Here, we show that a peptide ((280)LGPYY(284)) comprising the last five amino acids of G(L) retains high-affinity interaction with phosphorylase a and that the two tyrosines play crucial roles. Tyr284 deletion abolishes binding of phosphorylase a to G(L) and replacement by phenylalanine is insufficient to restore high-affinity binding. We show that a phosphorylase inhibitor blocks the interaction of phosphorylase a with the G(L) C-terminus, suggesting that the latter interaction could be targeted to develop an anti-diabetic drug.
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Affiliation(s)
- Ian R Kelsall
- Medical Research Council, Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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Montori-Grau M, Guitart M, Lerin C, Andreu A, Newgard C, García-Martínez C, Gómez-Foix A. Expression and glycogenic effect of glycogen-targeting protein phosphatase 1 regulatory subunit GL in cultured human muscle. Biochem J 2007; 405:107-13. [PMID: 17555403 PMCID: PMC1925244 DOI: 10.1042/bj20061572] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glycogen-targeting PP1 (protein phosphatase 1) subunit G(L) (coded for by the PPP1R3B gene) is expressed in human, but not rodent, skeletal muscle. Its effects on muscle glycogen metabolism are unknown. We show that G(L) mRNA levels in primary cultured human myotubes are similar to those in freshly excised muscle, unlike subunits G(M) (gene PPP1R3A) or PTG (protein targeting to glycogen; gene PPP1R3C), which decrease strikingly. In cultured myotubes, expression of the genes coding for G(L), G(M) and PTG is not regulated by glucose or insulin. Overexpression of G(L) activates myotube GS (glycogen synthase), glycogenesis in glucose-replete and -depleted cells and glycogen accumulation. Compared with overexpressed G(M), G(L) has a more potent activating effect on glycogenesis, while marked enhancement of their combined action is only observed in glucose-replete cells. G(L) does not affect GP (glycogen phosphorylase) activity, while co-overexpression with muscle GP impairs G(L) activation of GS in glucose-replete cells. G(L) enhances long-term glycogenesis additively to glucose depletion and insulin, although G(L) does not change the phosphorylation of GSK3 (GS kinase 3) on Ser9 or its upstream regulator kinase Akt/protein kinase B on Ser473, nor its response to insulin. In conclusion, in cultured human myotubes, the G(L) gene is expressed as in muscle tissue and is unresponsive to glucose or insulin, as are G(M) and PTG genes. G(L) activates GS regardless of glucose, does not regulate GP and stimulates glycogenesis in combination with insulin and glucose depletion.
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Affiliation(s)
- Marta Montori-Grau
- *Departament de Bioquímica i Biologia Molecular, Facultat de Biología, Universitat de Barcelona, 08028-Barcelona, Spain
| | - Maria Guitart
- *Departament de Bioquímica i Biologia Molecular, Facultat de Biología, Universitat de Barcelona, 08028-Barcelona, Spain
| | - Carles Lerin
- *Departament de Bioquímica i Biologia Molecular, Facultat de Biología, Universitat de Barcelona, 08028-Barcelona, Spain
| | - Antonio L. Andreu
- †Centre d’Investigació en Bioquímica i Biologia Molecular (A.L.A.), University Hospital Vall d'Hebron, 08035-Barcelona, Spain
| | - Christopher B. Newgard
- ‡Sarah W. Stedman Nutrition and Metabolism Center and Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27704, U.S.A
| | - Cèlia García-Martínez
- *Departament de Bioquímica i Biologia Molecular, Facultat de Biología, Universitat de Barcelona, 08028-Barcelona, Spain
| | - Anna M. Gómez-Foix
- *Departament de Bioquímica i Biologia Molecular, Facultat de Biología, Universitat de Barcelona, 08028-Barcelona, Spain
- To whom correspondence should be addressed (email )
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Jurczak MJ, Danos AM, Rehrmann VR, Allison MB, Greenberg CC, Brady MJ. Transgenic overexpression of protein targeting to glycogen markedly increases adipocytic glycogen storage in mice. Am J Physiol Endocrinol Metab 2007; 292:E952-63. [PMID: 17132821 DOI: 10.1152/ajpendo.00559.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adipocytes express the rate-limiting enzymes required for glycogen metabolism and increase glycogen synthesis in response to insulin. However, the physiological function of adipocytic glycogen in vivo is unclear, due in part to the low absolute levels and the apparent biophysical constraints of adipocyte morphology on glycogen accumulation. To further study the regulation of glycogen metabolism in adipose tissue, transgenic mice were generated that overexpressed the protein phosphatase-1 (PP1) glycogen-targeting subunit (PTG) driven by the adipocyte fatty acid binding protein (aP2) promoter. Exogenous PTG was detected in gonadal, perirenal, and brown fat depots, but it was not detected in any other tissue examined. PTG overexpression resulted in a modest redistribution of PP1 to glycogen particles, corresponding to a threefold increase in the glycogen synthase activity ratio. Glycogen synthase protein levels were also increased twofold, resulting in a combined greater than sixfold enhancement of basal glycogen synthase specific activity. Adipocytic glycogen levels were increased 200- to 400-fold in transgenic animals, and this increase was maintained to 1 yr of age. In contrast, lipid metabolism in transgenic adipose tissue was not significantly altered, as assessed by lipogenic rates, weight gain on normal or high-fat diets, or circulating free fatty acid levels after a fast. However, circulating and adipocytic leptin levels were doubled in transgenic animals, whereas adiponectin expression was unchanged. Cumulatively, these data indicate that murine adipocytes are capable of storing far higher levels of glycogen than previously reported. Furthermore, these results were obtained by overexpression of an endogenous adipocytic protein, suggesting that mechanisms may exist in vivo to maintain adipocytic glycogen storage at a physiological set point.
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Affiliation(s)
- Michael J Jurczak
- Department of Medicine, University of Chicago, MC1027, 5841 S. Maryland Ave., Chicago, IL 60637, USA
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Dunn JS, Mlynarski WM, Pezzolesi MG, Borowiec M, Powers C, Krolewski AS, Doria A. Examination of PPP1R3B as a candidate gene for the type 2 diabetes and MODY loci on chromosome 8p23. Ann Hum Genet 2006; 70:587-93. [PMID: 16907705 DOI: 10.1111/j.1469-1809.2005.00248.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The product of the PPP1R3B gene (G(L)) is the regulatory subunit of PP1 - a serine/threonine phosphatase involved in the modulation of glycogen synthesis in the liver and skeletal muscle. The PPP1R3B gene is located on chromosome 8p23 in a region that has been linked with type 2 diabetes and maturity-onset diabetes of the young (MODY). We examined whether sequence variants at the PPP1R3B locus are responsible for the linkage with diabetes observed at this location. RT-PCR analysis revealed the existence of two alternative promoters. These and the two exons of this gene were sequenced in the probands of 13 Joslin families showing the strongest evidence of linkage at 8p23. A total of 20 variants were observed: two in the 5' flanking region, one in the intron (9 bp 5' of exon 2), and 17 in the 3' UTR. The intronic variant generated a new acceptor splice site, resulting in an alternative splice variant with a longer 5' UTR. However, neither this nor other variants segregated with diabetes in the 13 'linked' families. Furthermore, allele frequencies were similar in 90 family probands from the Joslin Study and 347 unrelated controls. Thus, genetic variability in the PPP1R3B gene does not appear to contribute to diabetes in our mostly Caucasian families. However, a role cannot be excluded in other populations such as the Japanese, among whom linkage to diabetes is also observed at 8p23 and a non-synonymous mutation has been detected in the PPP1R3B gene.
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Affiliation(s)
- J S Dunn
- Section on Genetics and Epidemiology, Joslin Diabetes Center, Boston, Massachusetts 02215, USA
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50
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Niimi T, Kurotani R, Kimura S, Kitagawa Y. Identification and expression of alternative splice variants of the mouse Ppp1r3b gene in lung epithelial cells. Biochem Biophys Res Commun 2006; 349:588-96. [PMID: 16949035 DOI: 10.1016/j.bbrc.2006.08.091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2006] [Accepted: 08/15/2006] [Indexed: 01/12/2023]
Abstract
Hepatic glycogen-targeting subunit GL of protein phosphatase-1 (PP1), which is encoded by the gene Ppp1r3b, is one of a family of proteins that target PP1 to glycogen and regulate its activity on enzymes of glycogen metabolism. GL is primarily expressed in the liver where it promotes hepatic glycogen synthesis in response to insulin. Here, we show that GL is highly expressed in embryonic mouse lungs. GL utilizes two alternative promoters and 5' non-coding exons, which produce at least three alternatively spliced transcripts that encode identical proteins. Expression of GL in the lung is detectable as early as embryonic day (E) 12.5 and increases by E16.5, however, it declines before birth. In situ hybridization of mouse embryonic lung revealed that GL is expressed in bronchial epithelial cells. Thus, the temporal and spatial expression of GL in the lung suggests that it has a potential role in glycogen metabolism during lung development.
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Affiliation(s)
- Tomoaki Niimi
- Department of Bioengineering Sciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
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