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Trezise S, Kong IY, Hawkins ED, Herold MJ, Willis SN, Nutt SL. An arrayed CRISPR screen of primary B cells reveals the essential elements of the antibody secretion pathway. Front Immunol 2023; 14:1089243. [PMID: 36860866 PMCID: PMC9969136 DOI: 10.3389/fimmu.2023.1089243] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 01/25/2023] [Indexed: 02/15/2023] Open
Abstract
Background Humoral immunity depends on the differentiation of B cells into antibody secreting cells (ASCs). Excess or inappropriate ASC differentiation can lead to antibody-mediated autoimmune diseases, while impaired differentiation results in immunodeficiency. Methods We have used CRISPR/Cas9 technology in primary B cells to screen for regulators of terminal differentiation and antibody production. Results We identified several new positive (Sec61a1, Hspa5) and negative (Arhgef18, Pold1, Pax5, Ets1) regulators that impacted on the differentiation process. Other genes limited the proliferative capacity of activated B cells (Sumo2, Vcp, Selk). The largest number of genes identified in this screen (35) were required for antibody secretion. These included genes involved in endoplasmic reticulum-associated degradation and the unfolded protein response, as well as post-translational protein modifications. Discussion The genes identified in this study represent weak links in the antibody-secretion pathway that are potential drug targets for antibody-mediated diseases, as well as candidates for genes whose mutation results in primary immune deficiency.
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Affiliation(s)
- Stephanie Trezise
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia.,Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, United States
| | - Isabella Y Kong
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia.,Department of Pediatrics, Division of Pediatric Hematology/Oncology, Weill Cornell Medicine, New York, NY, United States
| | - Edwin D Hawkins
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
| | - Marco J Herold
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
| | - Simon N Willis
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
| | - Stephen L Nutt
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC, Australia.,Department of Medical Biology, The University of Melbourne, Parkville, VIC, Australia
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2
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Takeda Y, Kikuma T. UDP-glucose:Glycoprotein Glucosyltransferase–Selenof Complex: A Potential Glycoprotein-folding Machine. TRENDS GLYCOSCI GLYC 2022. [DOI: 10.4052/tigg.2118.1j] [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)
- Yoichi Takeda
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University
| | - Takashi Kikuma
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University
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3
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Takeda Y, Kikuma T. UDP-glucose:Glycoprotein Glucosyltransferase–Selenof Complex: A Potential Glycoprotein-folding Machine. TRENDS GLYCOSCI GLYC 2022. [DOI: 10.4052/tigg.2118.1e] [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)
- Yoichi Takeda
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University
| | - Takashi Kikuma
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University
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4
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Rosa-Fernandes L, Oba-Shinjo SM, Macedo-da-Silva J, Marie SKN, Palmisano G. Aberrant Protein Glycosylation in Brain Cancers, with Emphasis on Glioblastoma. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1382:39-70. [DOI: 10.1007/978-3-031-05460-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
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5
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Abstract
N-glycosylation is a highly conserved glycan modification, and more than 7000 proteins are N-glycosylated in humans. N-glycosylation has many biological functions such as protein folding, trafficking, and signal transduction. Thus, glycan modification to proteins is profoundly involved in numerous physiological and pathological processes. The N-glycan precursor is biosynthesized in the endoplasmic reticulum (ER) from dolichol phosphate by sequential enzymatic reactions to generate the dolichol-linked oligosaccharide composed of 14 sugar residues, Glc3Man9GlcNAc2. The oligosaccharide is then en bloc transferred to the consensus sequence N-X-S/T (X represents any amino acid except proline) of nascent proteins. Subsequently, the N-glycosylated nascent proteins enter the folding step, in which N-glycans contribute largely to attaining the correct protein fold by recruiting the lectin-like chaperones, calnexin, and calreticulin. Despite the N-glycan-dependent folding process, some glycoproteins do not fold correctly, and these misfolded glycoproteins are destined to degradation by proteasomes in the cytosol. Properly folded proteins are transported to the Golgi, and N-glycans undergo maturation by the sequential reactions of glycosidases and glycosyltransferases, generating complex-type N-glycans. N-Acetylglucosaminyltransferases (GnT-III, GnT-IV, and GnT-V) produce branched N-glycan structures, affording a higher complexity to N-glycans. In this chapter, we provide an overview of the biosynthetic pathway of N-glycans in the ER and Golgi.
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6
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Kanaki N, Matsuda A, Dejima K, Murata D, Nomura KH, Ohkura T, Gengyo-Ando K, Yoshina S, Mitani S, Nomura K. UDP-N-acetylglucosamine-dolichyl-phosphate N-acetylglucosaminephosphotransferase is indispensable for oogenesis, oocyte-to-embryo transition, and larval development of the nematode Caenorhabditis elegans. Glycobiology 2019; 29:163-178. [PMID: 30445613 DOI: 10.1093/glycob/cwy104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 11/09/2018] [Indexed: 12/13/2022] Open
Abstract
N-linked glycosylation of proteins is the most common post-translational modification of proteins. The enzyme UDP-N-acetylglucosamine-dolichyl-phosphate N-acetylglucosaminephosphotransferase (DPAGT1) catalyses the first step of N-glycosylation, and DPAGT1 knockout is embryonic lethal in mice. In this study, we identified the sole orthologue (algn-7) of the human DPAGT1 in the nematode C. elegans. The gene activity was disrupted by RNAi and deletion mutagenesis, which resulted in larval lethality, defects in oogenesis and oocyte-to-embryo transition. Endomitotic oocytes, abnormal fusion of pronuclei, abnormal AB cell rotation, disruption of permeation barriers of eggs, and abnormal expression of chitin and chitin synthase in oocytes and eggs were the typical phenotypes observed. The results indicate that N-glycosylation is indispensable for these processes. We further screened an N-glycosylated protein database of C. elegans, and identified 456 germline-expressed genes coding N-glycosylated proteins. By examining RNAi phenotypes, we identified five germline-expressed genes showing similar phenotypes to the algn-7 (RNAi) animals. They were ribo-1, stt-3, ptc-1, ptc-2, and vha-19. We identified known congenital disorders of glycosylation (CDG) genes (ribo-1 and stt-3) and a recently found CDG gene (vha-19). The results show that phenotype analyses using the nematode could be a powerful tool to detect new CDG candidate genes and their associated gene networks.
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Affiliation(s)
- Nanako Kanaki
- Department of Systems Life Sciences, Kyushu University Graduate School, Fukuoka, Japan
| | - Ayako Matsuda
- Department of Systems Life Sciences, Kyushu University Graduate School, Fukuoka, Japan
| | - Katsufumi Dejima
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.,Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Daisuke Murata
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Kazuko H Nomura
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Takashi Ohkura
- Department of Reproductive Biology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya, Tokyo, Japan
| | - Keiko Gengyo-Ando
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Sawako Yoshina
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Shohei Mitani
- Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo, Japan
| | - Kazuya Nomura
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan
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7
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Feng F, Yehia L, Ni Y, Chang YS, Jhiang SM, Eng C. A Nonpump Function of Sodium Iodide Symporter in Thyroid Cancer via Cross-talk with PTEN Signaling. Cancer Res 2018; 78:6121-6133. [PMID: 30217930 DOI: 10.1158/0008-5472.can-18-1954] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 08/15/2018] [Accepted: 09/11/2018] [Indexed: 01/21/2023]
Abstract
The sodium iodide symporter (NIS) is a classical iodide pump typically localized within the cell plasma membrane in thyroid cells, where NIS expression is believed to ensure success of mainstay radioiodide therapy in thyroid cancers. Although radioiodide uptake is generally reduced in thyroid cancer tissue, intracellular nonmembranous NIS has been reported to increase, suggesting that NIS serves a pump-independent function. Thyroid cancer is one of the major component cancers of Cowden syndrome, a subset of which is caused by germline mutations in PTEN In this study, we explored the noncanonical tumorigenic role of NIS in thyroid cancer cells in relation to PTEN signaling. PTEN knockdown in thyroid cancer cell lines stabilized intracellular NIS protein by promoting an interaction with NIS-LARG (leukemia-associated RhoA guanine exchange factor). Increased protein levels of cytoplasmic NIS enhanced RhoA activation and resulted in a promigration tumorigenic phenotype. Inhibition of NIS glycosylation through activation of the PI3K/AKT/mTOR signaling pathway contributed to mislocalization of NIS in the cytoplasm, facilitating its nonpump tumorigenic function through an interaction with LARG, which predominantly localized in the cytoplasm. Moreover, PTEN or PI3K/AKT/mTOR signaling could affect DPAGT1, a glycosylating enzyme involved in the initial step of N-linked glycosylation, to inhibit glycosylation of NIS. In summary, our results elucidate a pump-independent, protumorigenic role for NIS in thyroid cancer via its cross-talk with PTEN signaling.Significance: A novel pump-independent protumorigenic role of nonmembranous NIS challenges the presumption that radioiodine treatment of thyroid cancer is ineffective when transmembrane NIS is not expressed. Cancer Res; 78(21); 6121-33. ©2018 AACR.
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Affiliation(s)
- Fang Feng
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Nuclear Medicine, Xinhua Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, China
| | - Lamis Yehia
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio
| | - Ying Ni
- Center for Clinical Genomics, Cleveland Clinic, Cleveland, Ohio
| | - Yi Seok Chang
- Department of Physiology and Cell Biology, and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio
| | - Sissy Meihua Jhiang
- Department of Physiology and Cell Biology, and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio
| | - Charis Eng
- Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio. .,Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, Ohio.,Germline High Risk Cancer Focus Group, CASE Comprehensive Cancer Center, Case Western Reserve University, Cleveland, Ohio
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8
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Analysis of a dual domain phosphoglycosyl transferase reveals a ping-pong mechanism with a covalent enzyme intermediate. Proc Natl Acad Sci U S A 2017. [PMID: 28630348 DOI: 10.1073/pnas.1703397114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Phosphoglycosyl transferases (PGTs) are integral membrane proteins with diverse architectures that catalyze the formation of polyprenol diphosphate-linked glycans via phosphosugar transfer from a nucleotide diphosphate-sugar to a polyprenol phosphate. There are two PGT superfamilies that differ significantly in overall structure and topology. The polytopic PGT superfamily, represented by MraY and WecA, has been the subject of many studies because of its roles in peptidoglycan and O-antigen biosynthesis. In contrast, less is known about a second, extensive superfamily of PGTs that reveals a core structure with dual domain architecture featuring a C-terminal soluble globular domain and a predicted N-terminal membrane-associated domain. Representative members of this superfamily are the Campylobacter PglCs, which initiate N-linked glycoprotein biosynthesis and are implicated in virulence and pathogenicity. Despite the prevalence of dual domain PGTs, their mechanism of action is unknown. Here, we present the mechanistic analysis of PglC, a prototypic dual domain PGT from Campylobacter concisus Using a luminescence-based assay, together with substrate labeling and kinetics-based approaches, complementary experiments were carried out that support a ping-pong mechanism involving a covalent phosphosugar intermediate for PglC. Significantly, mass spectrometry-based approaches identified Asp93, which is part of a highly conserved AspGlu dyad found in all dual domain PGTs, as the active-site nucleophile of the enzyme involved in the formation of the covalent adduct. The existence of a covalent phosphosugar intermediate provides strong support for a ping-pong mechanism of PglC, differing fundamentally from the ternary complex mechanisms of representative polytopic PGTs.
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9
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AglH, a thermophilic UDP-N-acetylglucosamine-1-phosphate:dolichyl phosphate GlcNAc-1-phosphotransferase initiating protein N-glycosylation pathway in Sulfolobus acidocaldarius, is capable of complementing the eukaryal Alg7. Extremophiles 2016; 21:121-134. [PMID: 27822701 PMCID: PMC5222938 DOI: 10.1007/s00792-016-0890-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 10/24/2016] [Indexed: 10/31/2022]
Abstract
AglH, a predicted UDP-GlcNAc-1-phosphate:dolichyl phosphate GlcNAc-1-phosphotransferase, is initiating the protein N-glycosylation pathway in the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius. AglH successfully replaced the endogenous GlcNAc-1-phosphotransferase activity of Alg7 in a conditional lethal Saccharomyces cerevisiae strain, in which the first step of the eukaryal protein N-glycosylation process was repressed. This study is one of the few examples of cross-domain complementation demonstrating a conserved polyprenyl phosphate transferase reaction within the eukaryal and archaeal domain like it was demonstrated for Methanococcus voltae (Shams-Eldin et al. 2008). The topology prediction and the alignment of the AglH membrane protein with GlcNAc-1-phosphotransferases from the three domains of life show significant conservation of amino acids within the different proposed cytoplasmic loops. Alanine mutations of selected conserved amino acids in the putative cytoplasmic loops II (D100), IV (F220) and V (F264) demonstrated the importance of these amino acids for cross-domain AlgH activity in in vitro complementation assays in S. cerevisiae. Furthermore, antibiotic treatment interfering directly with the activity of dolichyl phosphate GlcNAc-1-phosphotransferases confirmed the essentiality of N-glycosylation for cell survival.
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10
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Vacaru AM, Di Narzo AF, Howarth DL, Tsedensodnom O, Imrie D, Cinaroglu A, Amin S, Hao K, Sadler KC. Molecularly defined unfolded protein response subclasses have distinct correlations with fatty liver disease in zebrafish. Dis Model Mech 2015; 7:823-35. [PMID: 24973751 PMCID: PMC4073272 DOI: 10.1242/dmm.014472] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The unfolded protein response (UPR) is a complex network of sensors and target genes that ensure efficient folding of secretory proteins in the endoplasmic reticulum (ER). UPR activation is mediated by three main sensors, which regulate the expression of hundreds of targets. UPR activation can result in outcomes ranging from enhanced cellular function to cell dysfunction and cell death. How this pathway causes such different outcomes is unknown. Fatty liver disease (steatosis) is associated with markers of UPR activation and robust UPR induction can cause steatosis; however, in other cases, UPR activation can protect against this disease. By assessing the magnitude of activation of UPR sensors and target genes in the liver of zebrafish larvae exposed to three commonly used ER stressors (tunicamycin, thapsigargin and Brefeldin A), we have identified distinct combinations of UPR sensors and targets (i.e. subclasses) activated by each stressor. We found that only the UPR subclass characterized by maximal induction of UPR target genes, which we term a stressed-UPR, induced steatosis. Principal component analysis demonstrated a significant positive association between UPR target gene induction and steatosis. The same principal component analysis showed significant correlation with steatosis in samples from patients with fatty liver disease. We demonstrate that an adaptive UPR induced by a short exposure to thapsigargin prior to challenging with tunicamycin reduced both the induction of a stressed UPR and steatosis incidence. We conclude that a stressed UPR causes steatosis and an adaptive UPR prevents it, demonstrating that this pathway plays dichotomous roles in fatty liver disease.
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Affiliation(s)
- Ana M Vacaru
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Antonio Fabio Di Narzo
- Department of Genetics and Genomic Sciences and Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Deanna L Howarth
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Orkhontuya Tsedensodnom
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Dru Imrie
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Ayca Cinaroglu
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Salma Amin
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA
| | - Ke Hao
- Department of Genetics and Genomic Sciences and Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Kirsten C Sadler
- Department of Medicine/Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA. Department of Developmental and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Box 1020, 1 Gustave L. Levy Place, New York, NY 10029, USA. Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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11
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Wang X, Ju L, Fan J, Zhu Y, Liu X, Zhu K, Wu M, Li L. Histone H3K4 methyltransferase Mll1 regulates protein glycosylation and tunicamycin-induced apoptosis through transcriptional regulation. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:2592-602. [PMID: 24983772 DOI: 10.1016/j.bbamcr.2014.06.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 06/20/2014] [Accepted: 06/23/2014] [Indexed: 01/03/2023]
Abstract
Disrupting protein glycosylation induces ER (endoplasmic reticulum) stress, resulting in the activation of UPR (unfolded protein response) pathways. A key function of the UPR is to restore ER homeostasis, but prolonged or unsolved ER stress can lead to apoptosis. MLL1 (Mixed Lineage Leukemia 1, also named ALL-1 or HRX), a histone H3K4 methyltransferase in mammals, plays important roles in leukemogenesis, transcriptional regulation, cell cycle and development. Here, we find that Mll1 deficiency enhances UPR and apoptosis induced by the glycosylation inhibitor TM (tunicamycin). The abnormal regulation of the UPR appears to be caused by a defect in protein glycosylation. Furthermore, Mll1 directly binds to the promoters of H6pd, Galnt12 and Ugp2, which regulates H3K4 trimethylation and the subsequent expression of these genes. The knockdown of H6pd, Galnt12 or Ugp2 enhances TM-induced apoptosis in Mll1(+/+)MEF cells, whereas the ectopic expression of these proteins inhibits TM-induced apoptosis in Mll1(-/-) MEF cells. Together, our data suggest that the maturation of glycoproteins in the ER is subject to regulation at the epigenetic level by a histone methyltransferase whose abnormality can lead to cancer and developmental defects.
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Affiliation(s)
- Xiang Wang
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Lingao Ju
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Jiadong Fan
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Yuan Zhu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiaolan Liu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Kun Zhu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Min Wu
- College of Life Sciences, Wuhan University, Wuhan, China.
| | - Lianyun Li
- College of Life Sciences, Wuhan University, Wuhan, China.
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12
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Zhao DJ, Zhang ZY, Harrison J, Kang L. Genome-wide analysis of transcriptional changes in the thoracic muscle of the migratory locust, Locusta migratoria, exposed to hypobaric hypoxia. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:1424-1431. [PMID: 22985864 DOI: 10.1016/j.jinsphys.2012.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Revised: 08/10/2012] [Accepted: 08/16/2012] [Indexed: 06/01/2023]
Abstract
Hypobaric hypoxia has both beneficial and detrimental effects on living organisms in high altitude regions. The impact of hypobaric hypoxia has been investigated in numerous vertebrates. However, it is still not well characterized how invertebrates respond to hypobaric hypoxia. In this study, we examined the transcriptional profiles of locust thoracic muscles using microarrays to disclose their strategies to cope with hypobaric hypoxia. We found that hypoxia-inducible factor (HIF) and its target genes did not respond significantly to hypobaric hypoxia. As with severe, normobaric hypoxia, mitochondrial activities were systemically suppressed, mainly involving in energy production and mitochondrial biogenesis. The surveillance processes, involving in clearance of dysfunctional proteins in endoplasmic reticulum, were activated, e.g. endoplasmic reticulum-associated degradation, protein glycosylation, and protein folding. In contrast to severe, normobaric hypoxia, glycolysis was suppressed and the pentose phosphate pathway strengthened. Our data suggested that hypobaric hypoxia induced an oxidative stress rather than an energy crisis in locust thoracic muscles. Our research provides a different perspective of biological responses to hypoxia, complementing the well-studied biological responses to extreme, normobaric hypoxia.
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Affiliation(s)
- De Jian Zhao
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China
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13
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Würde AE, Reunert J, Rust S, Hertzberg C, Haverkämper S, Nürnberg G, Nürnberg P, Lehle L, Rossi R, Marquardt T. Congenital disorder of glycosylation type Ij (CDG-Ij, DPAGT1-CDG): extending the clinical and molecular spectrum of a rare disease. Mol Genet Metab 2012; 105:634-41. [PMID: 22304930 DOI: 10.1016/j.ymgme.2012.01.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2012] [Accepted: 01/02/2012] [Indexed: 12/31/2022]
Abstract
Congenital disorders of glycosylation (CDG) are caused by enzymatic defects of the formation or processing of lipid-linked oligosaccharides and glycoproteins. Since the majority of proteins is glycosylated, a defect in a singular CDG enzyme leads to a multisytemic disease with secondary malfunction of thousands of proteins. CDG-Ij (DPAGT1-CDG) is caused by a defect of the human DPAGT1 (UDP-GlcNAc: Dolichol Phosphate N-Acetylglucosamine-1-Phosphotransferase), catalyzing the first step of N-linked glycosylation. So far the clinical phenotype of only one CDG-Ij patient has been described. The patient showed severe muscular hypotonia, intractable seizures, developmental delay, mental retardation, microcephaly and exotropia. Molecular studies of this patient revealed the heterozygous mutation c.660A>G (Y170C; paternal) in combination with an uncharacterized splicing defect (maternal). Two further mutations, c.890A>T (I297F) and c.162-8G>A as a splicing defect were detected when analyzing DPAGT1 in two affected siblings of a second family. We report two new patients with the novel homozygous mutation, c.341C>G (A114 G), causing a severe clinical phenotype, characterized by hyperexcitability, intractable seizures, bilateral cataracts, progressive microcephaly and muscular hypotonia. Both our patients died within their first year of life. With the discovery of this novel mutation and a detailed clinical description we extend the clinical features of CDG-Ij in order to improve early detection of this disease.
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Affiliation(s)
- A E Würde
- Universitätsklinikum Münster, Klinik und Poliklinik für Kinder- und Jugendmedizin-Allgemeine Pädiatrie, Münster, Germany.
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14
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Noffz C, Keppler-Ross S, Dean N. Hetero-oligomeric interactions between early glycosyltransferases of the dolichol cycle. Glycobiology 2009; 19:472-8. [PMID: 19129246 PMCID: PMC2667158 DOI: 10.1093/glycob/cwp001] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Revised: 01/02/2009] [Accepted: 01/03/2009] [Indexed: 11/14/2022] Open
Abstract
N-Linked glycosylation begins with the formation of a dolichol-linked oligosaccharide in the endoplasmic reticulum (ER). The first two steps of this pathway lead to the formation of GlcNAc(2)-PP-dolichol, whose synthesis is sequentially catalyzed by the Alg7p GlcNAc phosphotransferase and by the dimeric Alg13p/Alg14p UDP-GlcNAc transferase on the cytosolic face of the endoplasmic reticulum. Here, we show that the Alg7p, Alg13p, and Alg14p glycosyltransferases form a functional multienzyme complex. Coimmunoprecipitation and gel filtration assays demonstrate that the Alg7p/Alg13p/Alg14p complex is a hexamer with a native molecular weight of approximately 200 kDa and an Alg7p:Alg13:Alg14p stoichiometry of 1:1:1. These results highlight and extend the striking parallels that exist between these eukaryotic UDP-GlcNAc transferases and their bacterial MraY and MurG homologs that catalyze the first two steps of the lipid-linked peptidoglycan precursor. In addition to their preferred substrate and lipid acceptors, these enzymes are similar in their structure, chemistry, temporal, and spatial organization. These similarities point to an evolutionary link between the early steps of N-linked glycosylation and those of peptidoglycan synthesis.
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Affiliation(s)
- Christine Noffz
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | - Sabine Keppler-Ross
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | - Neta Dean
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
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15
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Identification of the archaeal alg7 gene homolog (encoding N-acetylglucosamine-1-phosphate transferase) of the N-linked glycosylation system by cross-domain complementation in Saccharomyces cerevisiae. J Bacteriol 2008; 190:2217-20. [PMID: 18178736 DOI: 10.1128/jb.01778-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Mv1751 gene product is thought to catalyze the first step in the N-glycosylation pathway in Methanococcus voltae. Here, we show that a conditional lethal mutation in the alg7 gene (N-acetylglucosamine-1-phosphate transferase) in Saccharomyces cerevisiae was successfully complemented with Mv1751, highlighting a rare case of cross-domain complementation.
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16
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Chaban B, Voisin S, Kelly J, Logan SM, Jarrell KF. Identification of genes involved in the biosynthesis and attachment of Methanococcus voltae N-linked glycans: insight into N-linked glycosylation pathways in Archaea. Mol Microbiol 2006; 61:259-68. [PMID: 16824110 DOI: 10.1111/j.1365-2958.2006.05226.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
N-linked glycosylation is recognized as an important post-translational modification across all three domains of life. However, the understanding of the genetic pathways for the assembly and attachment of N-linked glycans in eukaryotic and bacterial systems far outweighs the knowledge of comparable processes in Archaea. The recent characterization of a novel trisaccharide [beta-ManpNAcA6Thr-(1-4)-beta-GlcpNAc3NAcA-(1-3)-beta-GlcpNAc]N-linked to asparagine residues in Methanococcus voltae flagellin and S-layer proteins affords new opportunities to investigate N-linked glycosylation pathways in Archaea. In this contribution, the insertional inactivation of several candidate genes within the M. voltae genome and their resulting effects on flagellin and S-layer glycosylation are reported. Two of the candidate genes were shown to have effects on flagellin and S-layer protein molecular mass and N-linked glycan structure. Further examination revealed inactivation of either of these two genes also had effects on flagella assembly. These genes, designated agl (archaeal glycosylation) genes, include a glycosyl transferase (aglA) involved in the attachment of the terminal sugar to the glycan and an STT3 oligosaccharyl transferase homologue (aglB) involved in the transfer of the complete glycan to the flagellin and S-layer proteins. These findings document the first experimental evidence for genes involved in any glycosylation process within the domain Archaea.
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Affiliation(s)
- Bonnie Chaban
- Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, K7L 3N6, Canada
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17
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Tiede S, Storch S, Lübke T, Henrissat B, Bargal R, Raas-Rothschild A, Braulke T. Mucolipidosis II is caused by mutations in GNPTA encoding the alpha/beta GlcNAc-1-phosphotransferase. Nat Med 2005; 11:1109-12. [PMID: 16200072 DOI: 10.1038/nm1305] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Accepted: 08/31/2005] [Indexed: 11/09/2022]
Abstract
Mucolipidosis II (ML II) is a fatal lysosomal storage disorder resulting from defects in the multimeric GlcNAc-1-phosphotransferase responsible for the initial step in the generation of the mannose 6-phosphate (M6P) recognition marker. M6P residues on oligosaccharides of newly synthesized lysosomal enzymes are essential for efficient receptor-mediated transport to lysosomes. We used the recombinant GlcNAc-1-phosphotransferase gamma subunit as an affinity matrix to purify an unknown protein identified as the product of GNPTA (encoding GNPTA, previously known as MGC4170). The cDNA encodes a protein of 1,256 amino acids with two putative transmembrane domains and a complex preserved modular structure comprising at least six domains. The N-terminal domain of GNPTA, interrupted by a long insertion, shows similarities to bacterial capsule biosynthesis proteins. We identified seven mutations in GNPTA that lead to premature translational termination in six individuals with ML II. Retroviral transduction of fibroblasts from an individual with ML II resulted in the expression and localization of GNPTA in the Golgi apparatus, accompanied by the correction of hypersecretion of lysosomal enzymes. Our results provide evidence that GNPTA encodes a subunit of GlcNAc-1-phosphotransferase defective in individuals with ML II.
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Affiliation(s)
- Stephan Tiede
- Department of Biochemistry, Children's Hospital, University of Hamburg, Martinistr. 52, 20246 Hamburg, Germany
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18
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Wu X, Rush JS, Karaoglu D, Krasnewich D, Lubinsky MS, Waechter CJ, Gilmore R, Freeze HH. Deficiency of UDP-GlcNAc:Dolichol Phosphate N-Acetylglucosamine-1 Phosphate Transferase (DPAGT1) causes a novel congenital disorder of Glycosylation Type Ij. Hum Mutat 2003; 22:144-50. [PMID: 12872255 DOI: 10.1002/humu.10239] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Defects in the assembly of dolichol-linked oligosaccharide or its transfer to proteins result in severe, multi-system human diseases called Type I congenital disorders of glycosylation. We have identified a novel CDG type, CDG-Ij, resulting from deficiency in UDP-GlcNAc: dolichol phosphate N-acetyl-glucosamine-1 phosphate transferase (GPT) activity encoded by DPAGT1. The patient presents with severe hypotonia, medically intractable seizures, mental retardation, microcephaly, and exotropia. Metabolic labeling of cultured dermal fibroblasts from the patient with [2-(3)H]-mannose revealed lowered incorporation of radiolabel into full-length dolichol-linked oligosaccharides and glycoproteins. In vitro enzymatic analysis of microsomal fractions from the cultured cells indicated that oligosaccharyltransferase activity is normal, but the GPT activity is reduced to approximately 10% of normal levels while parents have heterozygous levels. The patient's paternal DPAGT1 allele contains a point mutation (660A>G) that replaces a highly conserved tyrosine with a cysteine (Y170C). The paternal allele cDNA produces a full-length protein with almost no activity when over-expressed in CHO cells. The maternal allele makes only about 12% normal mature mRNA, while the remainder shows a complex exon skipping pattern that shifts the reading frame encoding a truncated non-functional GPT protein. Thus, we conclude that the DPAGT1 gene defects are responsible for the CDG symptoms in this patient. Hum Mutat 22:144-150, 2003.
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Affiliation(s)
- Xiaohua Wu
- The Burnham Institute, La Jolla, California, USA
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19
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Sorensen TK, Dyer PS, Fierro F, Laube U, Peberdy JF. Characterisation of the gptA gene, encoding UDP N-acetylglucosamine: dolichol phosphate N-acetylglucosaminylphosphoryl transferase, from the filamentous fungus, Aspergillus niger. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1619:89-97. [PMID: 12495819 DOI: 10.1016/s0304-4165(02)00445-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The production of asparagine (N)-linked oligosaccharides is of vital importance in the formation of glycosylated proteins in eukaryotes and is mediated by the dolichol pathway. As part of studies to allow manipulation of this pathway, the gene coding for the production of the enzyme UDP N-acetylglucosamine: dolichol phosphate N-acetylglucosaminylphosphoryl transferase (GPT), catalysing the first step in the assembly of dolichol-linked oligosaccharides, was cloned from the filamentous fungus Aspergillus niger. Degenerate-PCR was used to amplify a 470-bp fragment of the gene, which was labelled as a probe to obtain a full-length clone from a genomic library of A. niger. This contained a 1557-bp open reading frame encoding a highly hydrophobic protein of 468 amino acids with a predicted molecular weight of 51.4 kDa. The gene contained two intron sequences and putative dolichol recognition sites (PDRSs) were present in the deduced amino acid sequence. Comparison with other eukaryotic GPTs revealed the A. niger GPT to share 45-47% identity with yeasts (Saccharomyces cerevisiae and Schizosaccharomyces pombe) and 41-42% identity with mammals (mouse, hamster, human). Nested-PCR of a cDNA library was used to confirm the position of an intron. A complete cDNA clone of A. niger gpt was obtained by employing a recombinant PCR approach. This was used to rescue a conditional lethal mutant of S. cerevisiae carrying a dysfunctional gpt gene by heterologous expression, confirming that the gpt genes from A. niger and S. cerevisiae are functionally equivalent.
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Affiliation(s)
- Tine Kring Sorensen
- School of Life and Environmental Sciences, University of Nottingham, University Park, Nottingham, UK
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20
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Zaia J, McClellan JE, Costello CE. Tandem mass spectrometric determination of the 4S/6S sulfation sequence in chondroitin sulfate oligosaccharides. Anal Chem 2001; 73:6030-9. [PMID: 11791576 DOI: 10.1021/ac015577t] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chondroitin sulfate (CS) is a glycosaminoglycan consisting of repeating uronic acid, N-acetylgalactosamine sulfate disaccharide units [-UroA(beta1,3)-GalNAcS(beta1,4)]n. Chondroitin sulfate type A (CSA) contains glucuronic acid, and 90% of the GalNAc residues are sulfated at the 4-position with 10% at the 6-position. Chondroitin sulfate type C (CSC) contains glucuronic acid, and 90% of the GalNAc residues are sulfated at the 6-position with 10% sulfated at the 4-position. These molecules are fragile due to their high degree of sulfation and are challenging to analyze as a result. This work presents the first evidence that tandem mass spectrometry can be used for the determination of a CS oligosaccharide sequence with respect to the positions of GalNAc sulfation. Using this technique, it is possible to analyze individual components from mixtures, saving much purification effort. Oligosaccharides produced from CSA and CSC are used in this work to demonstrate that CID MS/MS can be used to distinguish positional sulfation isomers. For charge states where charge equals the number of sulfates, abundant odd-numbered Bn and Yn ions are observed. The percent total ion abundances of these ions indicate the position of sulfation.
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Affiliation(s)
- J Zaia
- Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118, USA.
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21
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Zaia J, Costello CE. Compositional analysis of glycosaminoglycans by electrospray mass spectrometry. Anal Chem 2001; 73:233-9. [PMID: 11199971 DOI: 10.1021/ac000777a] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The purpose of this work is to analyze glycosaminoglycans (GAGs) directly from complex mixtures without the need to purify individual components. Novel conditions for negative ion electrospray MS of chondroitin sulfate (CS) oligosaccharides are described in which sodium adduction and fragmentation are avoided. Differentiation between positional sulfation isomers is demonstrated for CS disaccharides, and a selected reaction monitoring scheme is used to quantify sulfation isomers in disaccharides liberated from decorin and biglycan. A size exclusion chromatography LC/MS method is shown to be effective for compositional analysis of longer CS oligosaccharides. The SEC step serves to simplify the composition of GAGs entering the mass spectrometer at any time, thus allowing the masses of the constituent molecules to be extracted. Mass spectrometric detection produces far more information than conventional UV or fluorescent detectors and allows the monosaccharide composition of individual components to be determined.
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Affiliation(s)
- J Zaia
- Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118, USA.
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22
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Shams-Eldin H, Azzouz N, Eckert V, Blaschke T, Kedees MH, Hübel A, Schwarz RT. The Schizosaccharomyces pombe GPI8 gene complements a Saccharomyces cerevisiae GPI8 anchoring mutant. Yeast 2001; 18:33-9. [PMID: 11124699 DOI: 10.1002/1097-0061(200101)18:1<33::aid-yea648>3.0.co;2-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The final step in glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins consists of a transamidation reaction, in which preassembled GPI donors are substituted for C-terminal signal sequences in nascent polypeptides. The Saccharomyces cerevisiae GPI8 gene (ScGPI8) encodes a protein which is involved in the GPI transamidation reaction. We have cloned and isolated the Schizosaccharomyces pombe GPI8 homologous gene (SpGPI8). The SpGPI8 gene encodes a protein of 411 amino acids with a calculated molecular weight of about 47 kDa. It shows 53.5% identity with the ScGPI8 and complements a S. cerevisiae GPI8 anchoring mutant.
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Affiliation(s)
- H Shams-Eldin
- Medizinisches Zentrum für Hygiene und Med. Mikrobiologie, Institut für Virologie, Robert-Koch-Strasse 17, 35037 Marburg, Germany.
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23
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Takahashi T, Honda R, Nishikawa Y. Cloning of the human cDNA which can complement the defect of the yeast mannosyltransferase I-deficient mutant alg 1. Glycobiology 2000; 10:321-7. [PMID: 10704531 DOI: 10.1093/glycob/10.3.321] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The assembly of the lipid-linked oligosaccharide, Glc(3)Man(9)GlcNAc(2)-P-P-Dol, occurs on the rough ER membrane in an ordered stepwise manner. The process is highly conserved among eukaryotes. In order to isolate the human mannosyltransferase I (MT-I) gene involved in the process, we used the Saccharomyces cerevisiae MT-I gene ( ALG1 ), which has already been cloned. On searching the EST database with the amino acid sequence of the ALG1 gene product, we detected seven related human EST clones. A human fetal brain cDNA library was screened by PCR using gene-specific primers based on the EST nucleotide sequences and a 430 bp cDNA fragment was amplified. The cDNA library was rescreened with this 430 bp cDNA, and two cDNA clones (HR1-3 and HR1-4) were isolated and sequenced. On a homology search of the EST database with the nucleotide sequence of HR1-3, we detected a novel human EST clone, AA675921 (GenBank accession number). Based on the nucleotide sequences of AA675921 and HR1-4, we designed gene-specific PCR primers, which allowed to amplify a 1.8 kb cDNA from human fetal brain cDNA. This cDNA was cloned and shown to contain an ORF encoding a protein of 464 amino acids. We designated this ORF as Hmat-1. The amino acid sequence deduced from the Hmat-1 gene showed several highly conserved regions shared with the yeast and nematode MT-I sequences. Furthermore, this 1.8 kb cDNA successfully complemented the S. cerevisiae alg1-1 mutation, indicating that the Hmat-1 gene encodes the human MT-I and that the function of this enzyme was conserved between yeast and human.
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Affiliation(s)
- T Takahashi
- Laboratory for Glycobiology and Glycotechnology, Department of Industrial Chemistry, School of Engineering, Tokai University, 1117 Kitakaname, Hiratsuka City, Kanagawa 259-1292, Japan
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24
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Mazhari-Tabrizi R, Blank M, Mumberg D, Funk M, Schwarz RT, Eckert V. Chromosomal promoter replacement in Saccharomyces cerevisiae: construction of conditional lethal strains for the cloning of glycosyltransferases from various organisms. Glycoconj J 1999; 16:673-9. [PMID: 11003550 DOI: 10.1023/a:1007132907235] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Heterologous complementation in yeast has been a successful tool for cloning and characterisation of genes from various organisms. Therefore we constructed conditionally lethal Saccharomyces cerevisiae strains by replacing the endogenous promoter from the genes of interest (glycosyltransferases) by the stringently regulated GAL1-promoter, by a technique called chromosomal promoter replacement. Such yeast strains were constructed for the genes Alg 1, Alg7, Sec59, Wbp1 involved in N-Glycosylation, the genes Gpi2, Gpi3/Spt14, Gaal, Pis1, involved in GPI-anchor biosynthesis and Dpm involved in both pathways. All strains show the expected conditionally lethal phenotype on glucose-containing medium when expression of the respective gene is turned off.
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Affiliation(s)
- R Mazhari-Tabrizi
- Institut für Medizinische Mikrobiologie und Hygiene, Philipps-Universität-Marburg, Germany.
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25
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Marek KW, Vijay IK, Marth JD. A recessive deletion in the GlcNAc-1-phosphotransferase gene results in peri-implantation embryonic lethality. Glycobiology 1999; 9:1263-71. [PMID: 10536042 DOI: 10.1093/glycob/9.11.1263] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Formation of the dolichol oligosaccharide precursor is essential for the production of asparagine- (N-) linked oligosaccharides (N-glycans) in eukaryotic cells. The first step in precursor biosynthesis requires the enzyme UDP-GlcNAc: dolichol phosphate N-acetylglucosamine-1-phosphate transferase (GPT). Without GPT activity, subsequent steps necessary in constructing the oligosaccharide precursor cannot occur. Inhibition of this biosynthetic step using tunicamycin, a GlcNAc analog, produces a deficiency in N-glycosylation in cell lines and embryonic lethality during preimplantation development in vitro, suggesting that N-glycan formation is essential in early embryogenesis. In exploring structure-function relationships among N-glycans, and since tunicamycin has various reported biochemical activities; we have generated a germline deletion in the mouse GPT gene. GPT mutant embryos were analyzed and the phenotypes obtained were compared with previous studies using tunicamycin. We find that embryos homozygous for a deletion in the GPT gene complete preimplantation development and also implant in the uterine epithelium, but die shortly thereafter between days 4-5 postfertilization with cell degeneration apparent among both embryonic and extraembryonic cell types. Of cells derived from these early embryos, neither trophoblast nor embryonic endodermal lineages are able to survive in culture in vitro. These results indicate that GPT function is essential in early embryogenesis and suggest that N-glycosylation is needed for the viability of cells comprising the peri-implantation stage embryo.
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Affiliation(s)
- K W Marek
- Howard Hughes Medical Institute, Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA
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26
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Strahl-Bolsinger S, Scheinost A. Transmembrane topology of pmt1p, a member of an evolutionarily conserved family of protein O-mannosyltransferases. J Biol Chem 1999; 274:9068-75. [PMID: 10085156 DOI: 10.1074/jbc.274.13.9068] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The identification of the evolutionarily conserved family of dolichyl-phosphate-D-mannose:protein O-mannosyltransferases (Pmts) revealed that protein O-mannosylation plays an essential role in a number of physiologically important processes. Strikingly, all members of the Pmt protein family share almost identical hydropathy profiles; a central hydrophilic domain is flanked by amino- and carboxyl-terminal sequences containing several putative transmembrane helices. This pattern is of particular interest because it diverges from structural models of all glycosyltransferases characterized so far. Here, we examine the transmembrane topology of Pmt1p, an integral membrane protein of the endoplasmic reticulum, from Saccharomyces cerevisiae. Structural predictions were directly tested by site-directed mutagenesis of endogenous N-glycosylation sites, by fusing a topology-sensitive monitor protein domain to carboxyl-terminal truncated versions of the Pmt1 protein and, in addition, by N-glycosylation scanning. Based on our results we propose a seven-transmembrane helical model for the yeast Pmt1p mannosyltransferase. The Pmt1p amino terminus faces the cytoplasm, whereas the carboxyl terminus faces the lumen of the endoplasmic reticulum. A large hydrophilic segment that is oriented toward the lumen of the endoplasmic reticulum is flanked by five amino-terminal and two carboxyl-terminal membrane spanning domains. We could demonstrate that this central loop is essential for the function of Pmt1p.
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Affiliation(s)
- S Strahl-Bolsinger
- Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, 93040 Regensburg, Germany.
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27
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Kukuruzinska MA, Lennon K. Protein N-glycosylation: molecular genetics and functional significance. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 1998; 9:415-48. [PMID: 9825220 DOI: 10.1177/10454411980090040301] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Protein N-glycosylation is a metabolic process that has been highly conserved in evolution. In all eukaryotes, N-glycosylation is obligatory for viability. It functions by modifying appropriate asparagine residues of proteins with oligosaccharide structures, thus influencing their properties and bioactivities. N-glycoprotein biosynthesis involves a multitude of enzymes, glycosyltransferases, and glycosidases, encoded by distinct genes. The majority of these enzymes are transmembrane proteins that function in the endoplasmic reticulum and Golgi apparatus in an ordered and well-orchestrated manner. The complexity of N-glycosylation is augmented by the fact that different asparagine residues within the same polypeptide may be modified with different oligosaccharide structures, and various proteins are distinguished from one another by the characteristics of their carbohydrate moieties. Furthermore, biological consequences of derivatization of proteins with N-glycans range from subtle to significant. In the past, all these features of N-glycosylation have posed a formidable challenge to an elucidation of the physiological role for this modification. Recent advances in molecular genetics, combined with the availability of diverse in vivo experimental systems ranging from yeast to transgenic mice, have expedited the identification, isolation, and characterization of N-glycosylation genes. As a result, rather unexpected information regarding relationships between N-glycosylation and other cellular functions--including secretion, cytoskeletal organization, proliferation, and apoptosis--has emerged. Concurrently, increased understanding of molecular details of N-glycosylation has facilitated the alignment between N-glycosylation deficiencies and human diseases, and has highlighted the possibility of using N-glycan expression on cells as potential determinants of disease and its progression. Recent studies suggest correlations between N-glycosylation capacities of cells and drug sensitivities, as well as susceptibility to infection. Therefore, knowledge of the regulatory features of N-glycosylation may prove useful in the design of novel therapeutics. While facing the demanding task of defining properties, functions, and regulation of the numerous, as yet uncharacterized, N-glycosylation genes, glycobiologists of the 21st century offer exciting possibilities for new approaches to disease diagnosis, prevention, and cure.
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Affiliation(s)
- M A Kukuruzinska
- Department of Molecular and Cell Biology, School of Dental Medicine, Boston University Medical Center, Massachusetts 02118, USA
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