1
|
Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. J Biol Chem 2024:107584. [PMID: 39025454 DOI: 10.1016/j.jbc.2024.107584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
Collapse
Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-Taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
| |
Collapse
|
2
|
Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.03.587922. [PMID: 38617304 PMCID: PMC11014557 DOI: 10.1101/2024.04.03.587922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
Collapse
Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I. Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N. Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| |
Collapse
|
3
|
Ramírez AS, Locher KP. Structural and mechanistic studies of the N-glycosylation machinery: from lipid-linked oligosaccharide biosynthesis to glycan transfer. Glycobiology 2023; 33:861-872. [PMID: 37399117 PMCID: PMC10859629 DOI: 10.1093/glycob/cwad053] [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: 05/29/2023] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/05/2023] Open
Abstract
N-linked protein glycosylation is a post-translational modification that exists in all domains of life. It involves two consecutive steps: (i) biosynthesis of a lipid-linked oligosaccharide (LLO), and (ii) glycan transfer from the LLO to asparagine residues in secretory proteins, which is catalyzed by the integral membrane enzyme oligosaccharyltransferase (OST). In the last decade, structural and functional studies of the N-glycosylation machinery have increased our mechanistic understanding of the pathway. The structures of bacterial and eukaryotic glycosyltransferases involved in LLO elongation provided an insight into the mechanism of LLO biosynthesis, whereas structures of OST enzymes revealed the molecular basis of sequon recognition and catalysis. In this review, we will discuss approaches used and insight obtained from these studies with a special emphasis on the design and preparation of substrate analogs.
Collapse
Affiliation(s)
- Ana S Ramírez
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich 8093, Switzerland
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich 8093, Switzerland
| |
Collapse
|
4
|
Wang Y, Kinoshita T. The role of lipid scramblases in regulating lipid distributions at cellular membranes. Biochem Soc Trans 2023; 51:1857-1869. [PMID: 37767549 DOI: 10.1042/bst20221455] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 09/12/2023] [Accepted: 09/19/2023] [Indexed: 09/29/2023]
Abstract
Glycerophospholipids, sphingolipids and cholesterol assemble into lipid bilayers that form the scaffold of cellular membranes, in which proteins are embedded. Membrane composition and membrane protein profiles differ between plasma and intracellular membranes and between the two leaflets of a membrane. Lipid distributions between two leaflets are mediated by lipid translocases, including flippases and scramblases. Flippases use ATP to catalyze the inward movement of specific lipids between leaflets. In contrast, bidirectional flip-flop movements of lipids across the membrane are mediated by scramblases in an ATP-independent manner. Scramblases have been implicated in disrupting the lipid asymmetry of the plasma membrane, protein glycosylation, autophagosome biogenesis, lipoprotein secretion, lipid droplet formation and communications between organelles. Although scramblases in plasma membranes were identified over 10 years ago, most progress about scramblases localized in intracellular membranes has been made in the last few years. Herein, we review the role of scramblases in regulating lipid distributions in cellular membranes, focusing primarily on intracellular membrane-localized scramblases.
Collapse
Affiliation(s)
- Yicheng Wang
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing 100190, China
| | - Taroh Kinoshita
- Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan
- WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
- Center for Infectious Disease Education and Research, Osaka University, Suita, Osaka 565-0871, Japan
| |
Collapse
|
5
|
Young KL, Fisher V, Deng X, Brody JA, Graff M, Lim E, Lin BM, Xu H, Amin N, An P, Aslibekyan S, Fohner AE, Hidalgo B, Lenzini P, Kraaij R, Medina-Gomez C, Prokić I, Rivadeneira F, Sitlani C, Tao R, van Rooij J, Zhang D, Broome JG, Buth EJ, Heavner BD, Jain D, Smith AV, Barnes K, Boorgula MP, Chavan S, Darbar D, De Andrade M, Guo X, Haessler J, Irvin MR, Kalyani RR, Kardia SLR, Kooperberg C, Kim W, Mathias RA, McDonald ML, Mitchell BD, Peyser PA, Regan EA, Redline S, Reiner AP, Rich SS, Rotter JI, Smith JA, Weiss S, Wiggins KL, Yanek LR, Arnett D, Heard-Costa NL, Leal S, Lin D, McKnight B, Province M, van Duijn CM, North KE, Cupples LA, Liu CT. Whole-exome sequence analysis of anthropometric traits illustrates challenges in identifying effects of rare genetic variants. HGG ADVANCES 2023; 4:100163. [PMID: 36568030 PMCID: PMC9772568 DOI: 10.1016/j.xhgg.2022.100163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 11/22/2022] [Indexed: 11/26/2022] Open
Abstract
Anthropometric traits, measuring body size and shape, are highly heritable and significant clinical risk factors for cardiometabolic disorders. These traits have been extensively studied in genome-wide association studies (GWASs), with hundreds of genome-wide significant loci identified. We performed a whole-exome sequence analysis of the genetics of height, body mass index (BMI) and waist/hip ratio (WHR). We meta-analyzed single-variant and gene-based associations of whole-exome sequence variation with height, BMI, and WHR in up to 22,004 individuals, and we assessed replication of our findings in up to 16,418 individuals from 10 independent cohorts from Trans-Omics for Precision Medicine (TOPMed). We identified four trait associations with single-nucleotide variants (SNVs; two for height and two for BMI) and replicated the LECT2 gene association with height. Our expression quantitative trait locus (eQTL) analysis within previously reported GWAS loci implicated CEP63 and RFT1 as potential functional genes for known height loci. We further assessed enrichment of SNVs, which were monogenic or syndromic variants within loci associated with our three traits. This led to the significant enrichment results for height, whereas we observed no Bonferroni-corrected significance for all SNVs. With a sample size of ∼20,000 whole-exome sequences in our discovery dataset, our findings demonstrate the importance of genomic sequencing in genetic association studies, yet they also illustrate the challenges in identifying effects of rare genetic variants.
Collapse
Affiliation(s)
- Kristin L Young
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
| | - Virginia Fisher
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| | - Xuan Deng
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| | - Jennifer A Brody
- Cardiovascular Health Research Unit, Department of Medicine, University of Washington, Seattle, WA 98101, USA
| | - Misa Graff
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
| | - Elise Lim
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| | - Bridget M Lin
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
| | - Hanfei Xu
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| | - Najaf Amin
- Department of Epidemiology, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Ping An
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stella Aslibekyan
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Alison E Fohner
- Department of Epidemiology, University of Washington, Seattle, WA 98101, USA.,Institute for Public Health Genetics, University of Washington, Seattle, WA 98101, USA
| | - Bertha Hidalgo
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Petra Lenzini
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Robert Kraaij
- Department of Internal Medicine, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Carolina Medina-Gomez
- Department of Internal Medicine, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Ivana Prokić
- Department of Epidemiology, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Fernando Rivadeneira
- Department of Internal Medicine, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Colleen Sitlani
- Cardiovascular Health Research Unit, Department of Medicine, University of Washington, Seattle, WA 98101, USA
| | - Ran Tao
- Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN 37232, USA.,Vanderbilt Genetics Institute, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeroen van Rooij
- Department of Internal Medicine, Erasmus MC, University Medical Center, Rotterdam 3015CN, the Netherlands
| | - Di Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jai G Broome
- Department of Biostatistics, University of Washington, Seattle, WA 98105, USA.,Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA 98105, USA
| | - Erin J Buth
- Department of Biostatistics, University of Washington, Seattle, WA 98105, USA
| | - Benjamin D Heavner
- Department of Biostatistics, University of Washington, Seattle, WA 98105, USA
| | - Deepti Jain
- Department of Biostatistics, University of Washington, Seattle, WA 98105, USA
| | - Albert V Smith
- Department of Biostatistics, University of Michigan, Ann Arbor, MI, USA
| | - Kathleen Barnes
- Division of Biomedical Informatics and Personalized Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.,Tempus Labs, Chicago, IL 60654, USA
| | - Meher Preethi Boorgula
- Division of Biomedical Informatics and Personalized Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Sameer Chavan
- Division of Biomedical Informatics and Personalized Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Dawood Darbar
- Division of Cardiology, Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA
| | - Mariza De Andrade
- Health Quantitative Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Xiuqing Guo
- The Institute for Translational Genomics and Population Sciences, Department of Pediatrics, The Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Jeffrey Haessler
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Marguerite R Irvin
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Rita R Kalyani
- Division of Endocrinology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Sharon L R Kardia
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Charles Kooperberg
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Wonji Kim
- Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Rasika A Mathias
- Division of Allergy and Clinical Immunology, Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Merry-Lynn McDonald
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - Patricia A Peyser
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | | | - Susan Redline
- Department of Medicine, Brigham & Women's Hospital, Boston, MA, USA
| | - Alexander P Reiner
- Department of Epidemiology, University of Washington, Seattle, WA 98101, USA.,Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Stephen S Rich
- Center for Public Health Genomics, University of Virginia, Charlottesville, VA, USA
| | - 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, USA
| | - Jennifer A Smith
- Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA
| | - Scott Weiss
- Channing Division of Network Medicine, Brigham and Women's Hospital, Boston, MA, USA
| | - Kerri L Wiggins
- Department of Medicine, University of Washington, Seattle, WA, USA
| | - Lisa R Yanek
- Division of General Internal Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Donna Arnett
- College of Public Health, University of Kentucky, Lexington, KY, USA
| | | | - Suzanne Leal
- Department of Neurology, Columbia University, New York City, NY, USA
| | - Danyu Lin
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
| | - Barbara McKnight
- Department of Biostatistics, University of Washington, Seattle, WA 98105, USA
| | - Michael Province
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | | | - Kari E North
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27516, USA
| | - L Adrienne Cupples
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| | - Ching-Ti Liu
- Department of Biostatistics, School of Public Health, Boston University, Boston, MA 02118, USA
| |
Collapse
|
6
|
Papi A, Zamani M, Shariati G, Sedaghat A, Seifi T, Negahdari S, Sedighzadeh SS, Zeighami J, Saberi A, Hamid M, Galehdari H. Whole exome sequencing reveals several novel variants in congenital disorders of glycosylation and glycogen storage diseases in seven patients from Iran. Mol Genet Genomic Med 2022; 11:e2099. [PMID: 36579437 PMCID: PMC9938746 DOI: 10.1002/mgg3.2099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 03/28/2022] [Accepted: 11/03/2022] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Congenital disorder of glycosylation (CDG) and Glycogen storage diseases (GSDs) are inborn metabolic disorders caused by defects in some metabolic pathways. These disorders are a heterogeneous group of diseases caused by impaired O- as well as N-glycosylation pathways. CDG patients show a broad spectrum of clinical presentations; many GSD types (PGM1-CDG) have muscle involvement and hypoglycemia. METHODS We applied WES for all seven patients presenting GSD and CDG symptoms. Then we analyzed the data using various tools to predict pathogenic variants in genes related to the patients' diseases. RESULTS In the present study, we identified pathogenic variants in Iranian patients suffering from GSD and CDG, which can be helpful for patient management, and family counseling. We detected seven pathogenic variants using whole exome sequencing (WES) in known AGL (c.1998A>G, c.3635T>C, c.3682C>T), PGM1 (c.779G>A), DPM1 (c.742T>C), RFT1 (c.127A>G), and GAA (c.1314C>A) genes. CONCLUSION The suspected clinical diagnosis of CDG and GSD patients was confirmed by identifying missense and or nonsense mutations in PGM1, DPM1, RFT1, GAA, and AGL genes by WES of all 7 cases. This study helps us understand the scenario of the disorder causes and consider the variants for quick disease diagnosis.
Collapse
Affiliation(s)
- Atefe Papi
- Department of Genetics, Faculty of ScienceShahid Chamran University of AhvazAhvazIran
| | - Mina Zamani
- Department of Genetics, Faculty of ScienceShahid Chamran University of AhvazAhvazIran,Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran
| | - Gholamreza Shariati
- Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran,Department of Medical GeneticsJundishapur University of medical SciencesAhvazIran
| | - Alireza Sedaghat
- Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran,Health Research Institute, Diabetes Research CenterJundishapur University of Medical SciencesAhvazIran
| | - Tahere Seifi
- Department of Genetics, Faculty of ScienceShahid Chamran University of AhvazAhvazIran,Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran
| | - Samira Negahdari
- Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran,Legal Medicine Research CenterLegal Medicine OrganizationTehranIran
| | - Sahar Sadat Sedighzadeh
- Department of Genetics, Faculty of ScienceShahid Chamran University of AhvazAhvazIran,Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran
| | - Jawaher Zeighami
- Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran
| | - Alihossein Saberi
- Narges Medical Genetics and Prenatal Diagnosis LaboratoryAhvazIran,Department of Medical GeneticsJundishapur University of medical SciencesAhvazIran
| | - Mohammad Hamid
- Department of Molecular Medicine, Biotechnology Research CenterPasteur Institute of IranTehranIran
| | - Hamid Galehdari
- Department of Genetics, Faculty of ScienceShahid Chamran University of AhvazAhvazIran
| |
Collapse
|
7
|
Oyagawa CRM, Grimsey NL. Cannabinoid receptor CB 1 and CB 2 interacting proteins: Techniques, progress and perspectives. Methods Cell Biol 2021; 166:83-132. [PMID: 34752341 DOI: 10.1016/bs.mcb.2021.06.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cannabinoid receptors 1 and 2 (CB1 and CB2) are implicated in a range of physiological processes and have gained attention as promising therapeutic targets for a number of diseases. Protein-protein interactions play an integral role in modulating G protein-coupled receptor (GPCR) expression, subcellular distribution and signaling, and the identification and characterization of these will not only improve our understanding of GPCR function and biology, but may provide a novel avenue for therapeutic intervention. A variety of techniques are currently being used to investigate GPCR protein-protein interactions, including Förster/fluorescence and bioluminescence resonance energy transfer (FRET and BRET), proximity ligation assay (PLA), and bimolecular fluorescence complementation (BiFC). However, the reliable application of these methodologies is dependent on the use of appropriate controls and the consideration of the physiological context. Though not as extensively characterized as some other GPCRs, the investigation of CB1 and CB2 interacting proteins is a growing area of interest, and a range of interacting partners have been identified to date. This review summarizes the current state of the literature regarding the cannabinoid receptor interactome, provides commentary on the methodologies and techniques utilized, and discusses future perspectives.
Collapse
Affiliation(s)
- Caitlin R M Oyagawa
- Department of Pharmacology and Clinical Pharmacology, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand
| | - Natasha L Grimsey
- Department of Pharmacology and Clinical Pharmacology, School of Medical Sciences, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, New Zealand.
| |
Collapse
|
8
|
Davies JP, Almasy KM, McDonald EF, Plate L. Comparative Multiplexed Interactomics of SARS-CoV-2 and Homologous Coronavirus Nonstructural Proteins Identifies Unique and Shared Host-Cell Dependencies. ACS Infect Dis 2020; 6:3174-3189. [PMID: 33263384 PMCID: PMC7724760 DOI: 10.1021/acsinfecdis.0c00500] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Indexed: 12/15/2022]
Abstract
Human coronaviruses (hCoVs) have become a threat to global health and society, as evident from the SARS outbreak in 2002 caused by SARS-CoV-1 and the most recent COVID-19 pandemic caused by SARS-CoV-2. Despite a high sequence similarity between SARS-CoV-1 and -2, each strain has a distinctive virulence. A better understanding of the basic molecular mechanisms mediating changes in virulence is needed. Here, we profile the virus-host protein-protein interactions of two hCoV nonstructural proteins (nsps) that are critical for virus replication. We use tandem mass tag-multiplexed quantitative proteomics to sensitively compare and contrast the interactomes of nsp2 and nsp4 from three betacoronavirus strains: SARS-CoV-1, SARS-CoV-2, and hCoV-OC43-an endemic strain associated with the common cold. This approach enables the identification of both unique and shared host cell protein binding partners and the ability to further compare the enrichment of common interactions across homologues from related strains. We identify common nsp2 interactors involved in endoplasmic reticulum (ER) Ca2+ signaling and mitochondria biogenesis. We also identify nsp4 interactors unique to each strain, such as E3 ubiquitin ligase complexes for SARS-CoV-1 and ER homeostasis factors for SARS-CoV-2. Common nsp4 interactors include N-linked glycosylation machinery, unfolded protein response associated proteins, and antiviral innate immune signaling factors. Both nsp2 and nsp4 interactors are strongly enriched in proteins localized at mitochondria-associated ER membranes suggesting a new functional role for modulating host processes, such as calcium homeostasis, at these organelle contact sites. Our results shed light on the role these hCoV proteins play in the infection cycle, as well as host factors that may mediate the divergent pathogenesis of OC43 from SARS strains. Our mass spectrometry workflow enables rapid and robust comparisons of multiple bait proteins, which can be applied to additional viral proteins. Furthermore, the identified common interactions may present new targets for exploration by host-directed antiviral therapeutics.
Collapse
Affiliation(s)
- Jonathan P. Davies
- Department of Biological Sciences, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| | - Katherine M. Almasy
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| | - Eli F. McDonald
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
| | - Lars Plate
- Department of Biological Sciences, Immunology and Inflammation, Nashville, TN, USA
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| |
Collapse
|
9
|
Davies JP, Almasy KM, McDonald EF, Plate L. Comparative multiplexed interactomics of SARS-CoV-2 and homologous coronavirus non-structural proteins identifies unique and shared host-cell dependencies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2020:2020.07.13.201517. [PMID: 32699849 PMCID: PMC7373130 DOI: 10.1101/2020.07.13.201517] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Human coronaviruses (hCoV) have become a threat to global health and society, as evident from the SARS outbreak in 2002 caused by SARS-CoV-1 and the most recent COVID-19 pandemic caused by SARS-CoV-2. Despite high sequence similarity between SARS-CoV-1 and -2, each strain has distinctive virulence. A better understanding of the basic molecular mechanisms mediating changes in virulence is needed. Here, we profile the virus-host protein-protein interactions of two hCoV non-structural proteins (nsps) that are critical for virus replication. We use tandem mass tag-multiplexed quantitative proteomics to sensitively compare and contrast the interactomes of nsp2 and nsp4 from three betacoronavirus strains: SARS-CoV-1, SARS-CoV-2, and hCoV-OC43 - an endemic strain associated with the common cold. This approach enables the identification of both unique and shared host cell protein binding partners and the ability to further compare the enrichment of common interactions across homologs from related strains. We identify common nsp2 interactors involved in endoplasmic reticulum (ER) Ca 2+ signaling and mitochondria biogenesis. We also identifiy nsp4 interactors unique to each strain, such as E3 ubiquitin ligase complexes for SARS-CoV-1 and ER homeostasis factors for SARS-CoV-2. Common nsp4 interactors include N -linked glycosylation machinery, unfolded protein response (UPR) associated proteins, and anti-viral innate immune signaling factors. Both nsp2 and nsp4 interactors are strongly enriched in proteins localized at mitochondrial-associated ER membranes suggesting a new functional role for modulating host processes, such as calcium homeostasis, at these organelle contact sites. Our results shed light on the role these hCoV proteins play in the infection cycle, as well as host factors that may mediate the divergent pathogenesis of OC43 from SARS strains. Our mass spectrometry workflow enables rapid and robust comparisons of multiple bait proteins, which can be applied to additional viral proteins. Furthermore, the identified common interactions may present new targets for exploration by host-directed anti-viral therapeutics.
Collapse
Affiliation(s)
- Jonathan P. Davies
- Department of Biological Sciences, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| | - Katherine M. Almasy
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| | - Eli F. McDonald
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
| | - Lars Plate
- Department of Biological Sciences, Immunology and Inflammation, Nashville, TN, USA
- Department of Chemistry, Vanderbilt University, Immunology and Inflammation, Nashville, TN, USA
- Vanderbilt Institute for Infection, Immunology and Inflammation, Nashville, TN, USA
| |
Collapse
|
10
|
The impact of short tandem repeat variation on gene expression. Nat Genet 2019; 51:1652-1659. [PMID: 31676866 PMCID: PMC6917484 DOI: 10.1038/s41588-019-0521-9] [Citation(s) in RCA: 114] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 09/25/2019] [Indexed: 12/20/2022]
Abstract
Short tandem repeats (STRs) have been implicated in a variety of complex traits in humans. However, genome-wide studies of the effects of STRs on gene expression thus far have had limited power to detect associations and provide insights into putative mechanisms. Here, we leverage whole-genome sequencing and expression data for 17 tissues from the Genotype-Tissue Expression Project to identify more than 28,000 STRs for which repeat number is associated with expression of nearby genes (eSTRs). We use fine-mapping to quantify the probability that each eSTR is causal and characterize the top 1,400 fine-mapped eSTRs. We identify hundreds of eSTRs linked with published genome-wide association study signals and implicate specific eSTRs in complex traits, including height, schizophrenia, inflammatory bowel disease and intelligence. Overall, our results support the hypothesis that eSTRs contribute to a range of human phenotypes, and our data should serve as a valuable resource for future studies of complex traits.
Collapse
|
11
|
Abstract
Congenital disorders of glycosylation (CDG) is a genetically heterogeneous and clinically polymorphic group of diseases caused by defects in various enzymes, the synthesis and processing of N-linked glycans or oligosaccharides into glycoproteins. Approximately half of all proteins expressed in cells are glycosylated to achieve their full functionality. Basically there are 2 variants of glycosylation: N-glycosylation and O-glycosylation. N-glycans are bound to the amide group of aspartine, whereas O-glycans are bonded to the hydroxyl group of serine or threonine. Synthesis of N-glycans occurs in 3 stages: the formation of nucleotide-linked sugars, assembly (in the cytosol and endoplasmic reticulum) and treatment (in the Golgi apparatus). Synthesis of O-glycans occurs mainly in the Golgi apparatus. The most frequently identified types of CDG are associated with a defect in the N-glycosylation pathway. CDGs are typically multisystem disorders with varying clinical manifestations such as hepatomegaly, cholestasis, liver failure, developmental delay, hypotonia, convulsions, facial dysmorphism and gastrointestinal disorders. Also histological findings showed liver fibrosis, malformation of the ducts, cirrhosis, and steatosis. CDGs typically present in the first months of life, and about 20% of patients do not survive to 5 years. The first line of CDG screening is based on the analysis of N-glycosylation of transf ferin. Exome sequencing or targeted gene panel is used for diagnosis. Several CDG subtypes are amenable to teraphy with mannose and galactose.
Collapse
|
12
|
Hacker B, Schultheiß C, Kurzik-Dumke U. Sequential cleavage of the proteins encoded by HNOT/ALG3, the human counterpart of the Drosophila NOT and yeast ALG3 gene, results in products acting in distinct cellular compartments. Hum Mol Genet 2018; 27:4231-4248. [PMID: 30192950 DOI: 10.1093/hmg/ddy315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/04/2018] [Indexed: 11/12/2022] Open
Abstract
This study provides first insights into the biosynthesis, structure, biochemistry and complex processing of the proteins encoded by hNOT/ALG3, the human counterpart of the Drosophila Neighbour of TID (NOT) and the yeast asparagine linked glycosylation 3 gene (ALG3), which encodes a mannosyltransferase. Unambiguous evidence that both the fly and human proteins act as mannosyltransferases has not been provided yet. Previously, we showed that hNOT/ALG3 encodes two alternatively spliced main transcripts, hNOT-1/ALG3-1 and hNOT-4/ALG3-4, and their 15 truncated derivatives that lack diverse sets of exons and/or carry point mutations that result in premature termination codons. Here we show that the truncated transcripts are not translated. The two main forms hNOT-1/ALG3-1 and -4, distinguishable by alternative exon 1, encode full-length precursors that undergo a complex posttranslational processing. To specifically detect the two full-length hNOT/ALG3 proteins and their distinct derivatives and to examine their expression profiles and cellular location we generated polyclonal antibodies against diverse parts of the putative full-length proteins. We provide experimental evidence for the N-glycosylation of the two precursors. This modification seems to be a prerequisite for their sequential cleavage resulting in derivatives destined to distinct cellular compartments and links them with the N-glycosylation machinery not as its functional component but as molecules functionally dependent on its action. We present the expression profiles and subcellular location of the two full-length proteins, their N-glycosylated forms and distinct cleavage products. Furthermore, using diverse bioinformatics tools, we characterize the properties and predict the 2D and 3D structure of the two proteins and, for comparative purposes, of their Drosophila counterpart.
Collapse
Affiliation(s)
- Benedikt Hacker
- Institute of Medical Microbiology and Hygiene, Laboratory for Comparative Tumour Biology, University Medical Centre, Johannes Gutenberg University, Obere Zahlbacher, Mainz, Germany
| | - Christoph Schultheiß
- Institute of Medical Microbiology and Hygiene, Laboratory for Comparative Tumour Biology, University Medical Centre, Johannes Gutenberg University, Obere Zahlbacher, Mainz, Germany
| | - Ursula Kurzik-Dumke
- Institute of Medical Microbiology and Hygiene, Laboratory for Comparative Tumour Biology, University Medical Centre, Johannes Gutenberg University, Obere Zahlbacher, Mainz, Germany
| |
Collapse
|
13
|
Abiramalatha T, Arunachal G, Muthusamy K, Thomas N. A family with floppy neonates with severe respiratory insufficiency: A lethal phenotype of RFT1-CDG due to a novel mutation. Eur J Med Genet 2018; 62:248-253. [PMID: 30071302 DOI: 10.1016/j.ejmg.2018.07.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 07/03/2018] [Accepted: 07/28/2018] [Indexed: 11/17/2022]
Abstract
Congenital disorders of glycosylation (CDG) are a rapidly expanding group of inborn errors of metabolism with around 100 types described so far. Because of the limited number of reported cases in each type except PMM2-CDG, the complete clinical picture of other types is not known. RFT1-CDG is a rare type, with ten cases reported in the literature. Our patient presented as a floppy neonate with severe respiratory insufficiency and ventilator dependence in the newborn period. He had fetal growth restriction, facial dysmorphism, high arched palate, bilateral cryptorchidism, hypoplastic pons and cerebellum and probable hearing impairment. He succumbed to the illness on day 24 of life. There was a similar history of two previous sibling deaths in the early neonatal period due to respiratory insufficiency and history of multiple neonatal and infant deaths in the extended family. Transferrin iso-electric focusing was normal. Clinical exome sequencing revealed a novel homozygous missense mutation (c.1018 G > A) in RFT1 gene [NM_052859; c.1018G > A; p.G340S; ENST00000296292] and the parents were heterozygous for the same (ClinVar SVC000778540). The pathogenic variants so far reported are all missense variants affecting the luminal loops; whereas the variant in our case is in the trans-membrane helical domain. A strong family history of neonatal deaths and similar presentations in the previous 2 siblings suggests the homogenous phenotype of this mutation. Severe respiratory insuffiency and ventilator dependence shows the lethality of the disease phenotype and incompatibility with survival beyond the neonatal period.
Collapse
Affiliation(s)
- Thangaraj Abiramalatha
- Department of Neonatology, Christian Medical College, Vellore, India; Department of Neonatology, Sri Ramachandra Medical College and Research Institute, Chennai, India
| | - Gautham Arunachal
- Department of Clinical Genetics, Christian Medical College, Vellore, India
| | - Karthik Muthusamy
- Department of Pediatric Neurology, Christian Medical College, Vellore, India
| | - Niranjan Thomas
- Department of Neonatology, Christian Medical College, Vellore, India.
| |
Collapse
|
14
|
Quelhas D, Jaeken J, Fortuna A, Azevedo L, Bandeira A, Matthijs G, Martins E. RFT1-CDG: Absence of Epilepsy and Deafness in Two Patients with Novel Pathogenic Variants. JIMD Rep 2018; 43:111-116. [PMID: 29923091 DOI: 10.1007/8904_2018_112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 04/29/2018] [Accepted: 05/03/2018] [Indexed: 12/14/2022] Open
Abstract
This report is on two novel patients with RFT1-CDG. Their phenotype is characterized by mild psychomotor disability, behavioral problems, ataxia, and mild dysmorphism. Neither of them shows signs of epilepsy, which was observed in all RFT1-CDG patients reported to date (n = 14). Also, deafness, which is often associated with this condition, was not observed in our patients. Molecular analysis of RFT1 showed biallelic missense variants including three novel ones: c.827G > A (p.G276D), c.73C > T (p.R25W), and c.208T > C (p.C70R).
Collapse
Affiliation(s)
- D Quelhas
- Unidade de Bioquímica Genética, Centro de Genética Médica, Centro Hospitalar do Porto, Porto, Portugal. .,Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal.
| | - J Jaeken
- Center for Metabolic Diseases, KU Leuven, Leuven, Belgium
| | - A Fortuna
- Unidade de Bioquímica Genética, Centro de Genética Médica, Centro Hospitalar do Porto, Porto, Portugal.,Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal
| | - L Azevedo
- i3S-Instituto de Investigação e Inovação em Saúde, UP, Population Genetics and Evolution Group, Porto, Portugal.,IPATIMUP-Institute of Molecular Pathology and Immunology, UP, Porto, Portugal.,FCUP-Department of Biology, Faculty of Sciences, UP, Porto, Portugal
| | - A Bandeira
- Centro Referência Doenças Hereditárias do Metabolismo, Centro Hospitalar do Porto, Porto, Portugal
| | - G Matthijs
- Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - E Martins
- Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal.,Centro Referência Doenças Hereditárias do Metabolismo, Centro Hospitalar do Porto, Porto, Portugal
| |
Collapse
|
15
|
Gottier P, Gonzalez-Salgado A, Menon AK, Liu YC, Acosta-Serrano A, Bütikofer P. RFT1 Protein Affects Glycosylphosphatidylinositol (GPI) Anchor Glycosylation. J Biol Chem 2016; 292:1103-1111. [PMID: 27927990 DOI: 10.1074/jbc.m116.758367] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/17/2016] [Indexed: 12/16/2022] Open
Abstract
The membrane protein RFT1 is essential for normal protein N-glycosylation, but its precise function is not known. RFT1 was originally proposed to translocate the glycolipid Man5GlcNAc2-PP-dolichol (needed to synthesize N-glycan precursors) across the endoplasmic reticulum membrane, but subsequent studies showed that it does not play a direct role in transport. In contrast to the situation in yeast, RFT1 is not essential for growth of the parasitic protozoan Trypanosoma brucei, enabling the study of its function in a null background. We now report that lack of T. brucei RFT1 (TbRFT1) not only affects protein N-glycosylation but also glycosylphosphatidylinositol (GPI) anchor side-chain modification. Analysis by immunoblotting, metabolic labeling, and mass spectrometry demonstrated that the major GPI-anchored proteins of T. brucei procyclic forms have truncated GPI anchor side chains in TbRFT1 null parasites when compared with wild-type cells, a defect that is corrected by expressing a tagged copy of TbRFT1 in the null background. In vivo and in vitro labeling experiments using radiolabeled GPI precursors showed that GPI underglycosylation was not the result of decreased formation of the GPI precursor lipid or defective galactosylation of GPI intermediates in the endoplasmic reticulum, but rather due to modifications that are expected to occur in the Golgi apparatus. Unexpectedly, immunofluorescence microscopy localized TbRFT1 to both the endoplasmic reticulum and the Golgi, consistent with the proposal that TbRFT1 plays a direct or indirect role in GPI anchor glycosylation in the Golgi apparatus. Our results implicate RFT1 in a wider range of glycosylation processes than previously appreciated.
Collapse
Affiliation(s)
- Petra Gottier
- From the Institute of Biochemistry and Molecular Medicine and.,Graduate School of Cellular and Biochemical Sciences, University of Bern, 3012 Bern, Switzerland
| | | | - Anant K Menon
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065, and
| | | | - Alvaro Acosta-Serrano
- the Departments of Parasitology and.,Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Peter Bütikofer
- From the Institute of Biochemistry and Molecular Medicine and
| |
Collapse
|
16
|
Harada Y. Biosynthesis and Degradation of Dolichol-Linked Oligosaccharides. TRENDS GLYCOSCI GLYC 2016. [DOI: 10.4052/tigg.1512.1j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Yoichiro Harada
- Department of Systems Biology in Thromboregulation, Kagoshima University
| |
Collapse
|
17
|
Affiliation(s)
- Yoichiro Harada
- Department of Systems Biology in Thromboregulation, Kagoshima University
| |
Collapse
|
18
|
Congenital disorders of glycosylation: a concise chart of glycocalyx dysfunction. Trends Biochem Sci 2015; 40:377-84. [PMID: 25840516 DOI: 10.1016/j.tibs.2015.03.002] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 01/26/2015] [Accepted: 03/04/2015] [Indexed: 12/28/2022]
Abstract
Glycosylation is a ubiquitous modification of lipids and proteins. Despite the essential contribution of glycoconjugates to the viability of all living organisms, diseases of glycosylation in humans have only been identified over the past few decades. The recent development of next-generation DNA sequencing techniques has accelerated the pace of discovery of novel glycosylation defects. The description of multiple mutations across glycosylation pathways not only revealed tremendous diversity in functional impairments, but also pointed to phenotypic similarities, emphasizing the interconnected flow of substrates underlying glycan assembly. The current list of 100 known glycosylation disorders provides an overview of the significance of glycosylation in human development and physiology.
Collapse
|
19
|
Buczkowska A, Swiezewska E, Lefeber DJ. Genetic defects in dolichol metabolism. J Inherit Metab Dis 2015; 38:157-69. [PMID: 25270028 PMCID: PMC4281381 DOI: 10.1007/s10545-014-9760-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 07/25/2014] [Accepted: 08/01/2014] [Indexed: 11/27/2022]
Abstract
Congenital disorders of glycosylation (CDG) comprise a group of inborn errors of metabolism with abnormal glycosylation of proteins and lipids. Patients with defective protein N-glycosylation are identified in routine metabolic screening via analysis of serum transferrin glycosylation. Defects in the assembly of the dolichol linked Glc(3)Man(9)GlcNAc(2) glycan and its transfer to proteins lead to the (partial) absence of complete glycans on proteins. These defects are called CDG-I and are located in the endoplasmic reticulum (ER) or cytoplasm. Defects in the subsequent processing of protein bound glycans result in the presence of truncated glycans on proteins. These defects are called CDG-II and the enzymes involved are located mainly in the Golgi apparatus. In recent years, human defects have been identified in dolichol biosynthesis genes within the group of CDG-I patients. This has increased interest in dolichol metabolism, has resulted in specific recognizable clinical symptoms in CDG-I and has offered new mechanistic insights in dolichol biosynthesis. We here review its biosynthetic pathways, the clinical and biochemical phenotypes in dolichol-related CDG defects, up to the formation of dolichyl-P-mannose (Dol-P-Man), and discuss existing evidence of regulatory networks in dolichol metabolism to provide an outlook on therapeutic strategies.
Collapse
Affiliation(s)
- Anna Buczkowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Ewa Swiezewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
- Department of Lipid Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Dirk J. Lefeber
- Department of Neurology, Laboratory of Genetic, Endocrine and Metabolic Diseases, Radboud University Medical Center, Geert Grooteplein 10, 6525 GA Nijmegen, The Netherlands
| |
Collapse
|
20
|
Regal L, van Hasselt PM, Foulquier F, Cuppen I, Prinsen H, Jansen K, Keldermans L, De Meirleir L, Matthijs G, Jaeken J. ALG11-CDG: Three novel mutations and further characterization of the phenotype. Mol Genet Metab Rep 2014. [PMID: 28649519 PMCID: PMC5471160 DOI: 10.1016/j.ymgmr.2014.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
We report on two novel patients with ALG11-CDG. The phenotype was characterized by severe psychomotor disability, progressive microcephaly, sensorineural hearing loss, therapy-resistant epilepsy with burst suppression EEG, cerebral atrophy with, in one of them, neuronal heterotopia, and early lethality. Analysis of ALG11 revealed compound heterozygosity involving three novel mutations: the splice site mutation c.45-2A > T, the c.36dupG duplication, and the missense mutation c.479G > T (p.G160V) that was present in both.
Collapse
Affiliation(s)
- L Regal
- Center for Metabolic Diseases, University Hospital Gasthuisberg, Leuven, Belgium
| | - P M van Hasselt
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, Utrecht, The Netherlands
| | - F Foulquier
- Unité de Glycobiologie Structurale et Fonctionnelle, UMR/CNRS 8576, IFR147, Université de Sciences et Technologies de Lille, Villeneuve d'Ascq, France
| | - I Cuppen
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, Utrecht, The Netherlands
| | - Hcmt Prinsen
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, Utrecht, The Netherlands
| | - K Jansen
- Center for Metabolic Diseases, University Hospital Gasthuisberg, Leuven, Belgium
| | - L Keldermans
- Center for Human Genetics, Campus Gasthuisberg, Leuven, Belgium
| | - L De Meirleir
- Department of Pediatric Neurology and Metabolics, UZ Brussel, Brussels, Belgium
| | - G Matthijs
- Center for Human Genetics, Campus Gasthuisberg, Leuven, Belgium
| | - J Jaeken
- Center for Metabolic Diseases, University Hospital Gasthuisberg, Leuven, Belgium
| |
Collapse
|
21
|
Comparative Analysis of Protein Glycosylation Pathways in Humans and the Fungal Pathogen Candida albicans. Int J Microbiol 2014; 2014:267497. [PMID: 25104959 PMCID: PMC4106090 DOI: 10.1155/2014/267497] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/06/2014] [Indexed: 11/30/2022] Open
Abstract
Protein glycosylation pathways are present in all kingdoms of life and are metabolic pathways found in all the life kingdoms. Despite sharing commonalities in their synthesis, glycans attached to glycoproteins have species-specific structures generated by the presence of different sets of enzymes and acceptor substrates in each organism. In this review, we present a comparative analysis of the main glycosylation pathways shared by humans and the fungal pathogen Candida albicans: N-linked glycosylation, O-linked mannosylation and glycosylphosphatidylinositol-anchorage. The knowledge of similarities and divergences between these metabolic pathways could help find new pharmacological targets for C. albicans infection.
Collapse
|
22
|
Torrente M, Guetg A, Sass JO, Arps L, Ruckstuhl L, Camargo SMR, Verrey F. Amino acids regulate transgene expression in MDCK cells. PLoS One 2014; 9:e96823. [PMID: 24797296 PMCID: PMC4010483 DOI: 10.1371/journal.pone.0096823] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Accepted: 04/11/2014] [Indexed: 11/18/2022] Open
Abstract
Gene expression and cell growth rely on the intracellular concentration of amino acids, which in metazoans depends on extracellular amino acid availability and transmembrane transport. To investigate the impact of extracellular amino acid concentrations on the expression of a concentrative amino acid transporter, we overexpressed the main kidney proximal tubule luminal neutral amino acid transporter B0AT1-collectrin (SLC6A19-TMEM27) in MDCK cell epithelia. Exogenously expressed proteins co-localized at the luminal membrane and mediated neutral amino acid uptake. However, the transgenes were lost over few cell culture passages. In contrast, the expression of a control transgene remained stable. To test whether this loss was due to inappropriately high amino acid uptake, freshly transduced MDCK cell lines were cultivated either with physiological amounts of amino acids or with the high concentration found in standard cell culture media. Expression of exogenous transporters was unaffected by physiological amino acid concentration in the media. Interestingly, mycoplasma infection resulted in a significant increase in transgene expression and correlated with the rapid metabolism of L-arginine. However, L-arginine metabolites were shown to play no role in transgene expression. In contrast, activation of the GCN2 pathway revealed by an increase in eIF2α phosphorylation may trigger transgene derepression. Taken together, high extracellular amino acid concentration provided by cell culture media appears to inhibit the constitutive expression of concentrative amino acid transporters whereas L-arginine depletion by mycoplasma induces the expression of transgenes possibly via stimulation of the GCN2 pathway.
Collapse
Affiliation(s)
- Marta Torrente
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Adriano Guetg
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Jörn Oliver Sass
- Division of Clinical Chemistry & Biochemistry, University Children's Hospital, Zurich, Zurich, Switzerland
| | - Lisa Arps
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Lisa Ruckstuhl
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Simone M. R. Camargo
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - François Verrey
- Institute of Physiology and Zurich Center of Integrative Human Physiology, University of Zurich, Zurich, Switzerland
- * E-mail:
| |
Collapse
|
23
|
Ondruskova N, Vesela K, Hansikova H, Magner M, Zeman J, Honzik T. RFT1-CDG in adult siblings with novel mutations. Mol Genet Metab 2012; 107:760-2. [PMID: 23111317 DOI: 10.1016/j.ymgme.2012.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2012] [Revised: 10/07/2012] [Accepted: 10/07/2012] [Indexed: 11/29/2022]
Abstract
RFT1-CDG is a rare N-glycosylation disorder. Only 6 children with RFT1-CDG have been described, all with failure to thrive, feeding problems, hypotonia, developmental delay, epilepsy, decreased vision, deafness and thrombotic complications. We report on two young adult siblings with RFT1-CDG, compound heterozygotes for the novel missense mutations c.1222A>G (p.M408V) and c.1325G>A (p.R442Q) in RFT1 gene. Similar to the previously described patients, these siblings have profound intellectual disability but no feeding problems or failure to thrive. Their epilepsy is well controlled and coagulopathy is mild without clinical consequences. In addition, visual acuity is normal in both patients and hearing impairment is present only in one. Our findings extend the phenotype associated with RFT1-CDG.
Collapse
Affiliation(s)
- Nina Ondruskova
- Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | | | | | | | | | | |
Collapse
|
24
|
Matthijs G, Rymen D, Millón MBB, Souche E, Race V. Approaches to homozygosity mapping and exome sequencing for the identification of novel types of CDG. Glycoconj J 2012; 30:67-76. [PMID: 22983704 DOI: 10.1007/s10719-012-9445-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2012] [Revised: 08/21/2012] [Accepted: 08/22/2012] [Indexed: 12/18/2022]
Abstract
In the past decade, the identification of most genes involved in Congenital Disorders of Glycosylation (CDG) (type I) was achieved by a combination of biochemical, cell biological and glycobiological investigations. This has been truly successful for CDG-I, because the candidate genes could be selected on the basis of the homology of the synthetic pathway of the dolichol linked oligosaccharide in human and yeast. On the contrary, only a few CDG-II defects were elucidated, be it that some of the discoveries represent wonderful breakthroughs, like e.g, the identification of the COG defects. In general, many rare genetic defects have been identified by positional cloning. However, only a few types of CDG have effectively been elucidated by linkage analysis and so-called reverse genetics. The reason is that the families were relatively small and could-except for CDG-PMM2-not be pooled for analysis. Hence, a large number of CDG cases has long remained unsolved because the search for the culprit gene was very laborious, due to the heterogeneous phenotype and the myriad of candidate defects. This has changed when homozygosity mapping came of age, because it could be applied to small (consanguineous) families. Many novel CDG genes have been discovered in this way. But the best has yet to come: what we are currently witnessing, is an explosion of novel CDG defects, thanks to exome sequencing: seven novel types were published over a period of only two years. It is expected that exome sequencing will soon become a diagnostic tool, that will continuously uncover new facets of this fascinating group of diseases.
Collapse
Affiliation(s)
- Gert Matthijs
- Center for Human Genetics, University of Leuven, Herestraat 49, 3000, Leuven, Belgium.
| | | | | | | | | |
Collapse
|
25
|
Diseases of glycosylation beyond classical congenital disorders of glycosylation. Biochim Biophys Acta Gen Subj 2012; 1820:1306-17. [DOI: 10.1016/j.bbagen.2012.02.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/31/2012] [Accepted: 02/02/2012] [Indexed: 12/30/2022]
|
26
|
Abstract
In a complex multicellular organism, different cell types engage in specialist functions, and as a result, the secretory output of cells and tissues varies widely. Whereas some quiescent cell types secrete minor amounts of proteins, tissues like the pancreas, producing insulin and other hormones, and mature B cells, producing antibodies, place a great demand on their endoplasmic reticulum (ER). Our understanding of how protein secretion in general is controlled in the ER is now quite sophisticated. However, there remain gaps in our knowledge, particularly when applying insight gained from model systems to the more complex situations found in vivo. This article describes recent advances in our understanding of the ER and its role in preparing proteins for secretion, with an emphasis on glycoprotein quality control and pathways of disulfide bond formation.
Collapse
Affiliation(s)
- Adam M Benham
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom.
| |
Collapse
|
27
|
Abstract
Glycosylation is an essential process by which sugars are attached to proteins and lipids. Complete lack of glycosylation is not compatible with life. Because of the widespread function of glycosylation, inherited disorders of glycosylation are multisystemic. Since the identification of the first defect on N-linked glycosylation in the 1980s, there are over 40 different congenital protein hypoglycosylation diseases. This review will include defects of N-linked glycosylation, O-linked glycosylation and disorders of combined N- and O-linked glycosylation.
Collapse
Affiliation(s)
- Susan E Sparks
- Department of Pediatrics, Levine Children's Hospital at Carolinas Medical Center, Charlotte, NC, USA; Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| |
Collapse
|
28
|
Abstract
PURPOSE OF REVIEW Congenital disorders of glycosylation (CDG) have grown enormously since the discovery of the first protein glycosylation defect in 1980, presenting with a broad clinical spectrum. Expansion in number and complexity of the CDG group has even necessitated a new nomenclature. By 2011, the CDG group includes lipid glycosylation disorders and other related processes and almost 50 distinct disorders. RECENT FINDINGS Current research has not only expanded the spectrum of CDG types, but has also given novel insight into those previously described. The discovery of genetic defects in the conserved oligomeric Golgi complex, affecting protein glycosylation and processing through the secretory pathway, raised the concept of 'secondary' glycosylation disorders. The number of lipid glycosylation disorders, linking lipid synthesis to CDG, that were previously regarded as rare, is also increasing rapidly. In other areas of research, the bridge between muscular dystrophies and metabolic disorders is being further reinforced with the discovery of additional defects in the DPM-CDG subgroup, a CDG characterized by significant muscle involvement. SUMMARY It is of great importance that clinicians stay up-to-date on the field of CDG and consider it in their differential diagnosis of unknown syndromal presentations. Nevertheless, many advances have yet to be made, including information on the natural course of CDG. The lack of treatment for nearly all CDG types is striking, and the field must continue to push for innovative therapies. Clinicians and researchers must work together to describe the natural course and, most importantly, collaborate to find new therapies.
Collapse
|
29
|
Van Hove JLK, Lohr NJ. Metabolic and monogenic causes of seizures in neonates and young infants. Mol Genet Metab 2011; 104:214-30. [PMID: 21839663 DOI: 10.1016/j.ymgme.2011.04.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2011] [Revised: 04/20/2011] [Accepted: 04/20/2011] [Indexed: 11/22/2022]
Abstract
Seizures in neonates or young infants present a frequent diagnostic challenge. After exclusion of acquired causes, disturbances of the internal homeostasis and brain malformations, the physician must evaluate for inborn errors of metabolism and for other non-malformative genetic disorders as the cause of seizures. The metabolic causes can be categorized into disorders of neurotransmitter metabolism, disorders of energy production, and synthetic or catabolic disorders associated with brain malformation, dysfunction and degeneration. Other genetic conditions involve channelopathies, and disorders resulting in abnormal growth, differentiation and formation of neuronal populations. These conditions are important given their potential for treatment and the risk for recurrence in the family. In this paper, we will succinctly review the metabolic and genetic non-malformative causes of seizures in neonates and infants less than 6 months of age. We will then provide differential diagnostic clues and a practical paradigm for their evaluation.
Collapse
Affiliation(s)
- Johan L K Van Hove
- Department of Pediatrics, University of Colorado, Clinical Genetics, Aurora, CO 80045, USA.
| | | |
Collapse
|
30
|
Jaeken J. Congenital disorders of glycosylation (CDG): it's (nearly) all in it! J Inherit Metab Dis 2011; 34:853-8. [PMID: 21384229 DOI: 10.1007/s10545-011-9299-3] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 02/08/2011] [Accepted: 02/10/2011] [Indexed: 12/28/2022]
Abstract
Congenital disorders of glycosylation (CDG) is a booming class of metabolic diseases. Its number has increased nearly fourfold (to 45) since 2003, the year of the Komrower lecture, entitled 'Congenital disorders of glycosylation CDG): It's all in it!'. This paper presents an overview of recently discovered CDG and CDG phenotypes, of a diagnostic approach, of (the lack of) treatment, of CDG genetics, of a novel CDG nomenclature and classification, and of some future directions in the CDG field.
Collapse
Affiliation(s)
- Jaak Jaeken
- Universitair Ziekenhuis Gasthuisberg, Herestraat 49, 3000, Leuven, Belgium.
| |
Collapse
|
31
|
Vleugels W, Duvet S, Peanne R, Mir AM, Cacan R, Michalski JC, Matthijs G, Foulquier F. Identification of phosphorylated oligosaccharides in cells of patients with a congenital disorders of glycosylation (CDG-I). Biochimie 2011; 93:823-33. [PMID: 21315133 DOI: 10.1016/j.biochi.2011.01.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 01/29/2011] [Indexed: 11/24/2022]
Abstract
Protein N-glycosylation is initiated by the dolichol cycle in which the oligosaccharide precursor Glc(3)Man(9)GlcNAc(2)-PP-dolichol is assembled in the endoplasmic reticulum (ER). One critical step in the dolichol cycle concerns the availability of Dol-P at the cytosolic face of the ER membrane. In RFT1 cells, the lipid-linked oligosaccharide (LLO) intermediate Man(5)GlcNAc(2)-PP-Dol accumulates at the cytosolic face of the ER membrane. Since Dol-P is a rate-limiting intermediate during protein N-glycosylation, continuous accumulation of Man(5)GlcNAc(2)-PP-Dol would block the dolichol cycle. Hence, we investigated the molecular mechanisms by which accumulating Man(5)GlcNAc(2)-PP-Dol could be catabolized in RFT1 cells. On the basis of metabolic labeling experiments and in comparison to human control cells, we identified phosphorylated oligosaccharides (POS), not found in human control cells and present evidence that they originate from the accumulating LLO intermediates. In addition, POS were also detected in other CDG patients' cells accumulating specific LLO intermediates at different cellular locations. Moreover, the enzymatic activity that hydrolyses oligosaccharide-PP-Dol into POS was identified in human microsomal membranes and required Mn(2+) for optimal activity. In CDG patients' cells, we thus identified and characterized POS that could result from the catabolism of accumulating LLO intermediates.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, B-3000 Leuven, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Haeuptle MA, Welti M, Troxler H, Hülsmeier AJ, Imbach T, Hennet T. Improvement of dolichol-linked oligosaccharide biosynthesis by the squalene synthase inhibitor zaragozic acid. J Biol Chem 2010; 286:6085-91. [PMID: 21183681 DOI: 10.1074/jbc.m110.165795] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The majority of congenital disorders of glycosylation (CDG) are caused by defects of dolichol (Dol)-linked oligosaccharide assembly, which lead to under-occupancy of N-glycosylation sites. Most mutations encountered in CDG are hypomorphic, thus leaving residual activity to the affected biosynthetic enzymes. We hypothesized that increased cellular levels of Dol-linked substrates might compensate for the low biosynthetic activity and thereby improve the output of protein N-glycosylation in CDG. To this end, we investigated the potential of the squalene synthase inhibitor zaragozic acid A to redirect the flow of the polyisoprene pathway toward Dol by lowering cholesterol biosynthesis. The addition of zaragozic acid A to CDG fibroblasts with a Dol-P-Man synthase defect led to the formation of longer Dol-P species and to increased Dol-P-Man levels. This treatment was shown to decrease the pathologic accumulation of incomplete Dol pyrophosphate-GlcNAc(2)Man(5) in Dol-P-Man synthase-deficient fibroblasts. Zaragozic acid A treatment also decreased the amount of truncated protein N-linked oligosaccharides in these CDG fibroblasts. The increased cellular levels of Dol-P-Man and possibly the decreased cholesterol levels in zaragozic acid A-treated cells also led to increased availability of the glycosylphosphatidylinositol anchor as shown by the elevated cell-surface expression of the CD59 protein. This study shows that manipulation of the cellular Dol pool, as achieved by zaragozic acid A addition, may represent a valuable approach to improve N-linked glycosylation in CDG cells.
Collapse
Affiliation(s)
- Micha A Haeuptle
- Institute of Physiology, University of Zürich, CH-8057 Zürich, Switzerland
| | | | | | | | | | | |
Collapse
|
33
|
Song H, Qian W, Wang H, Qiu B. Identification and functional characterization of the HpALG11 and the HpRFT1 genes involved in N-linked glycosylation in the methylotrophic yeast Hansenula polymorpha. Glycobiology 2010; 20:1665-74. [DOI: 10.1093/glycob/cwq121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
34
|
Janssen MJ, Waanders E, Woudenberg J, Lefeber DJ, Drenth JPH. Congenital disorders of glycosylation in hepatology: the example of polycystic liver disease. J Hepatol 2010; 52:432-40. [PMID: 20138683 DOI: 10.1016/j.jhep.2009.12.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autosomal dominant polycystic liver disease (PCLD) is a rare progressive disorder characterized by an increased liver volume due to many (>20) fluid-filled cysts of biliary origin. Disease causing mutations in PRKCSH or SEC63 are found in approximately 25% of the PCLD patients. Both gene products function in the endoplasmic reticulum, however, the molecular mechanism behind cyst formation remains to be elucidated. As part of the translocon complex, SEC63 plays a role in protein import into the ER and is implicated in the export of unfolded proteins to the cytoplasm during ER-associated degradation (ERAD). PRKCSH codes for the beta-subunit of glucosidase II (hepatocystin), which cleaves two glucose residues of Glc(3)Man(9)GlcNAc(2) N-glycans on proteins. Hepatocystin is thereby directly involved in the protein folding process by regulating protein binding to calnexin/calreticulin in the ER. A separate group of genetic diseases affecting protein N-glycosylation in the ER is formed by the congenital disorders of glycosylation (CDG). In distinct subtypes of this autosomal recessive multisystem disease specific liver symptoms have been reported that overlap with PCLD. Recent research revealed novel insights in PCLD disease pathology such as the absence of hepatocystin from cyst epithelia indicating a two-hit model for PCLD cystogenesis. This opens the way to speculate about a recessive mechanism for PCLD pathophysiology and shared molecular pathways between CDG and PCLD. In this review we will discuss the clinical-genetic features of PCLD and CDG as well as their biochemical pathways with the aim to identify novel directions of research into cystogenesis.
Collapse
Affiliation(s)
- Manoe J Janssen
- Department of Gastroenterology and Hepatology, Institute for Genetic & Metabolic Disease, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | | | | | | |
Collapse
|
35
|
Haeuptle MA, Hennet T. Congenital disorders of glycosylation: an update on defects affecting the biosynthesis of dolichol-linked oligosaccharides. Hum Mutat 2010; 30:1628-41. [PMID: 19862844 DOI: 10.1002/humu.21126] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Defects in the biosynthesis of the oligosaccharide precursor for N-glycosylation lead to decreased occupancy of glycosylation sites and thereby to diseases known as congenital disorders of glycosylation (CDG). In the last 20 years, approximately 1,000 CDG patients have been identified presenting with multiple organ dysfunctions. This review sets the state of the art by listing all mutations identified in the 15 genes (PMM2, MPI, DPAGT1, ALG1, ALG2, ALG3, ALG9, ALG12, ALG6, ALG8, DOLK, DPM1, DPM3, MPDU1, and RFT1) that yield a deficiency of dolichol-linked oligosaccharide biosynthesis. The present analysis shows that most mutations lead to substitutions of strongly conserved amino acid residues across eukaryotes. Furthermore, the comparison between the different forms of CDG affecting dolichol-linked oligosaccharide biosynthesis shows that the severity of the disease does not relate to the position of the mutated gene along this biosynthetic pathway.
Collapse
Affiliation(s)
- Micha A Haeuptle
- Institute of Physiology, University of Zürich, Zürich, Switzerland
| | | |
Collapse
|
36
|
Rind N, Schmeiser V, Thiel C, Absmanner B, Lübbehusen J, Hocks J, Apeshiotis N, Wilichowski E, Lehle L, Körner C. A severe human metabolic disease caused by deficiency of the endoplasmatic mannosyltransferase hALG11 leads to congenital disorder of glycosylation-Ip. Hum Mol Genet 2010; 19:1413-24. [PMID: 20080937 DOI: 10.1093/hmg/ddq016] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A new type of congenital disorders of glycosylation, designated CDG-Ip, is caused by the deficiency of GDP-Man:Man3GlcNAc2-PP-dolichol-alpha1,2-mannosyltransferase, encoded by the human ortholog of ALG11 from yeast. The patient presented with a multisystemic disorder characterized by muscular hypotonia, seizures, developmental retardation and death at the age of 2 years. The isoelectric focusing pattern of the patient's serum transferrin showed the partial loss of complete N-glycan side chains, which is a characteristic sign for CDG-I. Analysis of dolichol-linked oligosaccharides in patient-derived fibroblasts revealed an accumulation of Man3GlcNAc2-PP-dolichol and Man4GlcNAc2-PP-dolichol. Determination of mannosyltransferase activities of early steps of lipid-linked oligosaccharide biosynthesis in fibroblasts indicated that the patient was deficient in elongating Man3GlcNAc2-PP-dolichol. These findings gave rise to genetic analysis of the hALG11 cDNA, in which homozygosity for mutation c.T257C (p.L86S) was identified. Verification of the mutation as a primary cause for the genetic defect was proved by retroviral expression of human wild-type and mutated ALG11 cDNA in patient-derived fibroblasts as well as using a yeast alg11 deletion strain as a heterologous expression system for hALG11 variants. Immunofluorescence examinations combined with western blotting showed no differences of intracellular localization or expression of ALG11 between control and patient fibroblasts, respectively, indicating no mislocalization or degradation of the mutated transferase.
Collapse
Affiliation(s)
- Nina Rind
- Center for Child and Adolescent Medicine, Center for Metabolic Diseases Heidelberg, Department I, Im Neuenheimer Feld 153, D-69120 Heidelberg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Vleugels W, Haeuptle MA, Ng BG, Michalski JC, Battini R, Dionisi-Vici C, Ludman MD, Jaeken J, Foulquier F, Freeze HH, Matthijs G, Hennet T. RFT1 deficiency in three novel CDG patients. Hum Mutat 2009; 30:1428-34. [PMID: 19701946 DOI: 10.1002/humu.21085] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The medical significance of N-glycosylation is underlined by a group of inherited human disorders called Congenital Disorders of Glycosylation (CDG). One key step in the biosynthesis of the Glc(3)Man(9)GlcNAc(2)-PP-dolichol precursor, essential for N-glycosylation, is the translocation of Man(5)GlcNAc(2)-PP-dolichol across the endoplasmic reticulum membrane. This step is facilitated by the RFT1 protein. Recently, the first RFT1-deficient CDG (RFT1-CDG) patient was identified and presented a severe N-glycosylation disorder. In the present study, we describe three novel CDG patients with an RFT1 deficiency. The first patient was homozygous for the earlier reported RFT1 missense mutation (c.199C>T; p.R67C), whereas the two other patients were homozygous for the missense mutation c.454A>G (p.K152E) and c.892G>A (p.E298 K), respectively. The pathogenic character of the novel mutations was illustrated by the accumulation of Man(5)GlcNAc(2)-PP-dolichol and by reduced recombinant DNase 1 secretion. Both the glycosylation pattern and recombinant DNase 1 secretion could be normalized by expression of normal RFT1 cDNA in the patients' fibroblasts. The clinical phenotype of these patients comprised typical CDG symptoms in addition to sensorineural deafness, rarely reported in CDG patients. The identification of additional RFT1-deficient patients allowed to delineate the main clinical picture of RFT1-CDG and confirmed the crucial role of RFT1 in Man(5)GlcNAc(2)-PP-dolichol translocation.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, Leuven, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Jaeken J, Vleugels W, Régal L, Corchia C, Goemans N, Haeuptle MA, Foulquier F, Hennet T, Matthijs G, Dionisi-Vici C. RFT1-CDG: deafness as a novel feature of congenital disorders of glycosylation. J Inherit Metab Dis 2009; 32 Suppl 1:S335-8. [PMID: 19856127 DOI: 10.1007/s10545-009-1297-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/24/2009] [Accepted: 09/25/2009] [Indexed: 10/20/2022]
Abstract
Congenital disorders of glycosylation (CDG) are genetic diseases due to defects in the synthesis of glycans and in the attachment of glycans to lipids and proteins. Actually, some 42 CDG are known including defects in protein N-glycosylation, in protein O-glycosylation, in lipid glycosylation, and in multiple and other glycosylation pathways. Most CDG are multisystem diseases and a large number of signs and symptoms have already been reported in CDG. An exception to this is deafness. This symptom has not been observed as a consistent feature in CDG. In 2008, a novel defect was identified in protein N-glycosylation, namely in RFT1. This is a defect in the assembly of N-glycans. RFT1 is involved in the transfer of Man(5)GlcNAc(2)-PP-Dol from the cytoplasmic to the luminal side of the endoplasmic reticulum. According to the novel nomenclature (non-italicized gene symbol followed by -CDG) this defect is named RFT1-CDG. Recently, three other patients with RFT1-CDG have been reported and here we report two novel patients. Remarkably, all six patients with RFT1-CDG show sensorineural deafness as part of a severe neurological syndrome. We conclude that RFT1-CDG is the first 'deafness-CDG'. CDG should be included in the work-up of congenital, particularly syndromic, hearing loss.
Collapse
Affiliation(s)
- J Jaeken
- Center for Metabolic Disease, University of Leuven, Leuven, Belgium.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Vesela K, Honzik T, Hansikova H, Haeuptle MA, Semberova J, Stranak Z, Hennet T, Zeman J. A new case of ALG8 deficiency (CDG Ih). J Inherit Metab Dis 2009; 32 Suppl 1. [PMID: 19688606 DOI: 10.1007/s10545-009-1203-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 06/15/2009] [Accepted: 06/18/2009] [Indexed: 12/16/2022]
Abstract
UNLABELLED Congenital disorders of glycosylation (CDG) represent an expanding group of inherited diseases. One of them, ALG8 deficiency (CDG Ih), leads to protein N-glycosylation defects caused by malfunction of glucosyltransferase 2 (Dol-P-Glc:Glc1-Man(9)-GlcNAc(2)-P-P-Dol glucosyltransferase) resulting in inefficient addition of the second glucose residue onto lipid-linked oligosaccharides. So far, only five patients have been described with ALG8 deficiency. We present a new patient with neonatal onset. The girl was born at the 29th week of gestation complicated by oligohydramnios. Although the early postnatal adaptation was uneventful (Apgar score 8 and 9 at 5 and 10 min), generalized oedema, multifocal myoclonic seizures, and bleeding due to combined coagulopathy were present from the first day. Diarrhoea progressing to protein-losing enteropathy with ascites and pericardial effusion developed in the third week of life. Pharmacoresistant seizures and cortical, cerebellar and optic nerve atrophy indicated neurological involvement. No symptoms of liver disease except coagulopathy were observed; however, steatofibrosis with cholestasis was found at autopsy. The girl died at the age of 2 months owing to the progressive general oedema, bleeding and cardio-respiratory insufficiency. Molecular analysis revealed two heterozygous mutations in the ALG8 gene: c.139A>C (p.T47P) and the novel mutation c.1090C>T (p.R364X). CONCLUSION The prognosis of patients with ALG8 deficiency is unfavourable. The majority of affected children have early onset of the disease with heterogeneous symptoms including multiple organ dysfunction, coagulopathy and protein-losing enteropathy. Neurological impairment is not a general clinical symptom, but it has to be taken into consideration when thinking about ALG8 deficiency.
Collapse
Affiliation(s)
- K Vesela
- Department of Pediatrics, First Faculty of Medicine, Charles University, Ke Karlovu 2, 128 08, Prague 2, Czech Republic.
| | | | | | | | | | | | | | | |
Collapse
|
40
|
Footitt EJ, Karimova A, Burch M, Yayeh T, Dupré T, Vuillaumier-Barrot S, Chantret I, Moore SEH, Seta N, Grunewald S. Cardiomyopathy in the congenital disorders of glycosylation (CDG): a case of late presentation and literature review. J Inherit Metab Dis 2009; 32 Suppl 1:S313-9. [PMID: 19757145 DOI: 10.1007/s10545-009-1262-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 07/28/2009] [Accepted: 07/30/2009] [Indexed: 11/25/2022]
Abstract
The congenital disorders of glycosylation (CDG) are a recently described group of inherited multisystem disorders characterized by defects predominantly of N- and O-glycosylation of proteins. Cardiomyopathy in CDG has previously been described in several subtypes; it is usually associated with high morbidity and mortality and the majority of cases present in the first 2 years of life. This is the first case with presentation in late childhood and the article reviews current literature. An 11-year-old female with a background of learning difficulties presented in cardiac failure secondary to severe dilated cardiomyopathy. Prior to the diagnosis of CDG, her condition deteriorated; she required mechanical support (Excor Berlin Heart) and was listed for cardiac transplant. Investigations included screening for glycosylation disorders, and isoelectric focusing of transferrin revealed an abnormal type 1 pattern. Analysis of phosphomannomutase and phosphomannose isomerase showed normal enzyme activity, excluding PMM2 (CDG Ia) and MPI (CDG Ib). Lipid-linked oligosaccharide and mutational studies have not yet defined the defect. Despite aggressive therapy there were persistent difficulties achieving adequate anticoagulation and she developed multiple life-threatening thrombotic complications. She was removed from the transplant list and died from overwhelming sepsis 5 weeks following admission. This case emphasizes the need to screen all children with an undiagnosed cardiomyopathy for CDG, regardless of age, and where possible to exclude CDG before the use of cardiac bridging devices. It highlights the many practical and ethical challenges that may be encountered where clinical knowledge and experience are still evolving.
Collapse
Affiliation(s)
- E J Footitt
- Metabolic Medicine Unit, Great Ormond Street Hospital for Children with UCL Institute of Child Health, London, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Clayton PT, Grunewald S. Comprehensive description of the phenotype of the first case of congenital disorder of glycosylation due to RFT1 deficiency (CDG In). J Inherit Metab Dis 2009; 32 Suppl 1:S137-9. [PMID: 19267216 DOI: 10.1007/s10545-009-1108-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 12/30/2008] [Accepted: 01/13/2009] [Indexed: 10/21/2022]
Abstract
Very recently, Haeuptle and colleagues described a new glycosylation defect due to RFT1 deficiency (CDG In). Accumulation of intracellular DolPP-GlcNAc(2)Man(5) with absence of cytosolic GlcNAc(2)Man(5) resembled the profile of a yeast mutant deficient in RFT1, a protein that is thought to have a role as a flippase. This is the first detailed description of the clinical phenotype of this patient. It was a severe disorder affecting intrauterine development and movement, and leading to intrauterine growth retardation. The child was born with several musculoskeletal abnormalities including arthrogryposis. Postnatally, severe reflux and irregular bowl movements contributed to failure to thrive. The patient showed very little development and no vision and suffered from drug-resistant epilepsy. Abnormal coagulation resulted in thrombosis and the patient died at the age of 4 years from a pulmonary embolus.
Collapse
Affiliation(s)
- P T Clayton
- Metabolic Medicine Unit, Great Ormond Street Hospital with UCL Institute of Child Health, Great Ormond Street, London, WC1N 3JH, UK
| | | |
Collapse
|
42
|
Paesold-Burda P, Maag C, Troxler H, Foulquier F, Kleinert P, Schnabel S, Baumgartner M, Hennet T. Deficiency in COG5 causes a moderate form of congenital disorders of glycosylation. Hum Mol Genet 2009; 18:4350-6. [DOI: 10.1093/hmg/ddp389] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
43
|
Lefeber DJ, Schönberger J, Morava E, Guillard M, Huyben KM, Verrijp K, Grafakou O, Evangeliou A, Preijers FW, Manta P, Yildiz J, Grünewald S, Spilioti M, van den Elzen C, Klein D, Hess D, Ashida H, Hofsteenge J, Maeda Y, van den Heuvel L, Lammens M, Lehle L, Wevers RA. Deficiency of Dol-P-Man synthase subunit DPM3 bridges the congenital disorders of glycosylation with the dystroglycanopathies. Am J Hum Genet 2009; 85:76-86. [PMID: 19576565 DOI: 10.1016/j.ajhg.2009.06.006] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 06/04/2009] [Accepted: 06/12/2009] [Indexed: 11/28/2022] Open
Abstract
Alpha-dystroglycanopathies such as Walker Warburg syndrome represent an important subgroup of the muscular dystrophies that have been related to defective O-mannosylation of alpha-dystroglycan. In many patients, the underlying genetic etiology remains unsolved. Isolated muscular dystrophy has not been described in the congenital disorders of glycosylation (CDG) caused by N-linked protein glycosylation defects. Here, we present a genetic N-glycosylation disorder with muscular dystrophy in the group of CDG type I. Extensive biochemical investigations revealed a strongly reduced dolichol-phosphate-mannose (Dol-P-Man) synthase activity. Sequencing of the three DPM subunits and complementation of DPM3-deficient CHO2.38 cells showed a pathogenic p.L85S missense mutation in the strongly conserved coiled-coil domain of DPM3 that tethers catalytic DPM1 to the ER membrane. Cotransfection experiments in CHO cells showed a reduced binding capacity of DPM3(L85S) for DPM1. Investigation of the four Dol-P-Man-dependent glycosylation pathways in the ER revealed strongly reduced O-mannosylation of alpha-dystroglycan in a muscle biopsy, thereby explaining the clinical phenotype of muscular dystrophy. This mild Dol-P-Man biosynthesis defect due to DPM3 mutations is a cause for alpha-dystroglycanopathy, thereby bridging the congenital disorders of glycosylation with the dystroglycanopathies.
Collapse
Affiliation(s)
- Dirk J Lefeber
- Laboratory of Pediatrics & Neurology, Institute for Genetic and Metabolic Disease, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Rush JS, Gao N, Lehrman MA, Matveev S, Waechter CJ. Suppression of Rft1 expression does not impair the transbilayer movement of Man5GlcNAc2-P-P-dolichol in sealed microsomes from yeast. J Biol Chem 2009; 284:19835-42. [PMID: 19494107 DOI: 10.1074/jbc.m109.000893] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To further evaluate the role of Rft1 in the transbilayer movement of Man(5)GlcNAc(2)-P-P-dolichol (M5-DLO), a series of experiments was conducted with intact cells and sealed microsomal vesicles. First, an unexpectedly large accumulation (37-fold) of M5-DLO was observed in Rft1-depleted cells (YG1137) relative to Glc(3)Man(9)GlcNAc(2)-P-P-Dol in wild type (SS328) cells when glycolipid levels were compared by fluorophore-assisted carbohydrate electrophoresis analysis. When sealed microsomes from wild type cells and cells depleted of Rft1 were incubated with GDP-[(3)H]mannose or UDP-[(3)H]GlcNAc in the presence of unlabeled GDP-Man, no difference was observed in the rate of synthesis of [(3)H]Man(9)GlcNAc(2)-P-P-dolichol or Man(9)[(3)H]GlcNAc(2)-P-P-dolichol, respectively. In addition, no difference was seen in the level of M5-DLO flippase activity in sealed wild type and Rft1-depleted microsomal vesicles when the activity was assessed by the transport of GlcNAc(2)-P-P-Dol(15), a water-soluble analogue. The entry of the analogue into the lumenal compartment was confirmed by demonstrating that [(3)H]chitobiosyl units were transferred to endogenous peptide acceptors via the yeast oligosaccharyltransferase when sealed vesicles were incubated with [(3)H]GlcNAc(2)-P-P-Dol(15) in the presence of an exogenously supplied acceptor peptide. In addition, several enzymes involved in Dol-P and lipid intermediate biosynthesis were found to be up-regulated in Rft1-depleted cells. All of these results indicate that although Rft1 may play a critical role in vivo, depletion of this protein does not impair the transbilayer movement of M5-DLO in sealed microsomal fractions prepared from disrupted cells.
Collapse
Affiliation(s)
- Jeffrey S Rush
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA
| | | | | | | | | |
Collapse
|
45
|
Core glycosylation of collagen is initiated by two beta(1-O)galactosyltransferases. Mol Cell Biol 2008; 29:943-52. [PMID: 19075007 DOI: 10.1128/mcb.02085-07] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Collagen is a trimer of three left-handed alpha chains representing repeats of the motif Gly-X-Y, where (hydroxy)proline and (hydroxy)lysine residues are often found at positions X and Y. Selected hydroxylysines are further modified by the addition of galactose and glucose-galactose units. Collagen glycosylation takes place in the endoplasmic reticulum before triple-helix formation and is mediated by beta(1-O)galactosyl- and alpha(1-2)glucosyltransferase enzymes. We have identified two collagen galactosyltransferases using affinity chromatography and tandem mass spectrometry protein sequencing. The two collagen beta(1-O)galactosyltransferases corresponded to the GLT25D1 and GLT25D2 proteins. Recombinant GLT25D1 and GLT25D2 enzymes showed a strong galactosyltransferase activity toward various types of collagen and toward the serum mannose-binding lectin MBL, which contains a collagen domain. Amino acid analysis of the products of GLT25D1 and GLT25D2 reactions confirmed the transfer of galactose to hydroxylysine residues. The GLT25D1 gene is constitutively expressed in human tissues, whereas the GLT25D2 gene is expressed only at low levels in the nervous system. The GLT25D1 and GLT25D2 enzymes are similar to CEECAM1, to which we could not attribute any collagen galactosyltransferase activity. The GLT25D1 and GLT25D2 genes now allow addressing of the biological significance of collagen glycosylation and the importance of this posttranslational modification in the etiology of connective tissue disorders.
Collapse
|
46
|
Glycosylation diseases: quo vadis? Biochim Biophys Acta Mol Basis Dis 2008; 1792:925-30. [PMID: 19061954 DOI: 10.1016/j.bbadis.2008.11.002] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Revised: 11/03/2008] [Accepted: 11/06/2008] [Indexed: 12/29/2022]
Abstract
About 250 to 500 glycogenes (genes that are directly involved in glycan assembly) are in the human genome representing about 1-2% of the total genome. Over 40 human congenital diseases associated with glycogene mutations have been described to date. It is almost certain that the causative glycogene mutations for many more congenital diseases remain to be discovered. Some glycogenes are involved in the synthesis of only a specific protein and/or a specific class of glycan whereas others play a role in the biosynthesis of more than one glycan class. Mutations in the latter type of glycogene result in complex clinical phenotypes that present difficult diagnostic problems to the clinician. In order to understand in biochemical terms the clinical signs and symptoms of a patient with a glycogene mutation, one must understand how the glycogene works. That requires, first of all, determination of the target protein or proteins of the glycogene followed by an understanding of the role, if any, of the glycogene-dependent glycan in the functions of the protein. Many glycogenes act on thousands of glycoproteins. There are unfortunately no general methods to identify all the potentially large number of glycogene target proteins and which of these proteins are responsible for the mutant phenotypes. Whereas biochemical methods have been highly successful in the discovery of glycogenes responsible for many congenital diseases, it has more recently been necessary to use other methods such as homozygosity mapping. Accurate diagnosis of many recently discovered diseases has become difficult and new diagnostic procedures must be developed. Last but not least is the lack of effective treatment for most of these children and of animal models that can be used to test new therapies.
Collapse
|
47
|
Sanyal S, Frank CG, Menon AK. Distinct flippases translocate glycerophospholipids and oligosaccharide diphosphate dolichols across the endoplasmic reticulum. Biochemistry 2008; 47:7937-46. [PMID: 18597486 PMCID: PMC2646664 DOI: 10.1021/bi800723n] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
![]()
Transbilayer movement, or flip-flop, of lipids across the endoplasmic reticulum (ER) is required for membrane biogenesis, protein glycosylation, and GPI anchoring. Specific ER membrane proteins, flippases, are proposed to facilitate lipid flip-flop, but no ER flippase has been biochemically identified. The glycolipid Glc3Man9GlcNAc2-PP-dolichol is the oligosaccharide donor for protein N-glycosylation reactions in the ER lumen. Synthesis of Glc3Man9GlcNAc2-PP-dolichol is initiated on the cytoplasmic side of the ER and completed on the lumenal side, requiring flipping of the intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) across the ER. Here we report the reconstitution of M5-DLO flipping in proteoliposomes generated from Triton X-100-extracted Saccharomyces cerevisiae microsomal proteins. Flipping was assayed by using the lectin Concanavalin A to capture M5-DLOs that had been translocated from the inner to the outer leaflet of the vesicles. M5-DLO flipping in the reconstituted system was ATP-independent and trypsin-sensitive and required a membrane protein(s) that sedimented at ∼4 S. Man7GlcNAc2-PP-dolichol, a higher-order lipid intermediate, was flipped >10-fold more slowly than M5-DLO at 25 °C. Chromatography on Cibacron Blue dye resin enriched M5-DLO flippase activity ∼5-fold and resolved it from both the ER glycerophospholipid flippase activity and the genetically identified flippase candidate Rft1 [Helenius, J., et al. (2002) Nature 415, 447−450]. The latter result indicates that Rft1 is not the M5-DLO flippase. Our data (i) demonstrate that the ER has at least two distinct flippase proteins, each specifically capable of translocating a class of phospholipid, and (ii) provide, for the first time, a biochemical means of identifying the M5-DLO flippase.
Collapse
Affiliation(s)
- Sumana Sanyal
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065, USA
| | | | | |
Collapse
|