Asparagine N-linked glycosylation (Homo sapiens)
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Description
N-linked glycosylation is the most important form of post-translational modification for proteins synthesized and folded in the Endoplasmic Reticulum (Stanley P et al, 2009). An early study in 1999 revealed that about 50% of the proteins in the Swiss-Prot database at the time were N-glycosylated (Apweiler R et al, 1999). It is now established that the majority of the proteins in the secretory pathway require glycosylation in order to achieve proper folding.
The addition of an N-glycan to a protein can have several roles (Shental-Bechor D and Levy Y, 2009). First, glycans enhance the solubility and stability of the proteins in the ER, the golgi and on the outside of the cell membrane, where the composition of the medium is strongly hydrophilic and where proteins, that are mostly hydrophobic, have difficulty folding properly. Second, N-glycans are used as signal molecules during the folding and transport process of the protein: they have the role of labels to determine when a protein must interact with a chaperon, be transported to the golgi, or targeted for degradation in case of major folding defects. Third, and most importantly, N-glycans on completely folded proteins are involved in a wide range of processes: they help determine the specificity of membrane receptors in innate immunity or in cell-to-cell interactions, they can change the properties of hormones and secreted proteins, or of the proteins in the vesicular system inside the cell.
All N-linked glycans are derived from a common 14-sugar oligosaccharide synthesized in the ER, which is attached co-translationally to a protein while this is being translated inside the reticulum. The process of the synthesis of this glycan, known as Synthesis of the N-glycan precursor or LLO, constitutes one of the most conserved pathways in eukaryotes, and has been also observed in some eubacteria. The attachment usually happens on an asparagine residue within the consensus sequence asparagine-X-threonine by an complex called oligosaccharyl transferase (OST).
After being attached to an unfolded protein, the glycan is used as a label molecule in the folding process (also known as Calnexin/Calreticulin cycle) (Lederkremer GZ, 2009). The majority of the glycoproteins in the ER require at least one glycosylated residue in order to achieve proper folding, even if it has been shown that a smaller portion of the proteins in the ER can be folded without this modification.
Once the glycoprotein has achieved proper folding, it is transported via the Cis-golgi through all the Golgi compartments, where the glycan is further modified according to the properties of the glycoprotein. This process involves relatively few enzymes but due to its combinatorial nature, can lead to several millions of different possible modifications. The exact topography of this network of reactions has not been established yet, representing one of the major challenges after the sequencing of the human genome (Hossler P et al, 2006).
Since N-glycosylation is involved in an great number of different processes, from cell-cell interaction to folding control, mutations in one of the genes involved in glycan assembly and/or modification can lead to severe development problems (often affecting the central nervous system). All the diseases in genes involved in glycosylation are collectively known as Congenital Disorders of Glycosylation (CDG) (Sparks SE et al, 2003), and classified as CDG type I for the genes in the LLO synthesis pathway, and CDG type II for the others. Original Pathway at Reactome: http://www.reactome.org/PathwayBrowser/#DB=gk_current&FOCUS_SPECIES_ID=48887&FOCUS_PATHWAY_ID=446203
The addition of an N-glycan to a protein can have several roles (Shental-Bechor D and Levy Y, 2009). First, glycans enhance the solubility and stability of the proteins in the ER, the golgi and on the outside of the cell membrane, where the composition of the medium is strongly hydrophilic and where proteins, that are mostly hydrophobic, have difficulty folding properly. Second, N-glycans are used as signal molecules during the folding and transport process of the protein: they have the role of labels to determine when a protein must interact with a chaperon, be transported to the golgi, or targeted for degradation in case of major folding defects. Third, and most importantly, N-glycans on completely folded proteins are involved in a wide range of processes: they help determine the specificity of membrane receptors in innate immunity or in cell-to-cell interactions, they can change the properties of hormones and secreted proteins, or of the proteins in the vesicular system inside the cell.
All N-linked glycans are derived from a common 14-sugar oligosaccharide synthesized in the ER, which is attached co-translationally to a protein while this is being translated inside the reticulum. The process of the synthesis of this glycan, known as Synthesis of the N-glycan precursor or LLO, constitutes one of the most conserved pathways in eukaryotes, and has been also observed in some eubacteria. The attachment usually happens on an asparagine residue within the consensus sequence asparagine-X-threonine by an complex called oligosaccharyl transferase (OST).
After being attached to an unfolded protein, the glycan is used as a label molecule in the folding process (also known as Calnexin/Calreticulin cycle) (Lederkremer GZ, 2009). The majority of the glycoproteins in the ER require at least one glycosylated residue in order to achieve proper folding, even if it has been shown that a smaller portion of the proteins in the ER can be folded without this modification.
Once the glycoprotein has achieved proper folding, it is transported via the Cis-golgi through all the Golgi compartments, where the glycan is further modified according to the properties of the glycoprotein. This process involves relatively few enzymes but due to its combinatorial nature, can lead to several millions of different possible modifications. The exact topography of this network of reactions has not been established yet, representing one of the major challenges after the sequencing of the human genome (Hossler P et al, 2006).
Since N-glycosylation is involved in an great number of different processes, from cell-cell interaction to folding control, mutations in one of the genes involved in glycan assembly and/or modification can lead to severe development problems (often affecting the central nervous system). All the diseases in genes involved in glycosylation are collectively known as Congenital Disorders of Glycosylation (CDG) (Sparks SE et al, 2003), and classified as CDG type I for the genes in the LLO synthesis pathway, and CDG type II for the others. Original Pathway at Reactome: http://www.reactome.org/PathwayBrowser/#DB=gk_current&FOCUS_SPECIES_ID=48887&FOCUS_PATHWAY_ID=446203
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- Christianson JC, Shaler TA, Tyler RE, Kopito RR.; ''OS-9 and GRP94 deliver mutant alpha1-antitrypsin to the Hrd1-SEL1L ubiquitin ligase complex for ERAD.''; PubMed Europe PMC Scholia
- Züchner S, Dallman J, Wen R, Beecham G, Naj A, Farooq A, Kohli MA, Whitehead PL, Hulme W, Konidari I, Edwards YJ, Cai G, Peter I, Seo D, Buxbaum JD, Haines JL, Blanton S, Young J, Alfonso E, Vance JM, Lam BL, Peričak-Vance MA.; ''Whole-exome sequencing links a variant in DHDDS to retinitis pigmentosa.''; PubMed Europe PMC Scholia
- Lederkremer GZ.; ''Glycoprotein folding, quality control and ER-associated degradation.''; PubMed Europe PMC Scholia
- Thiel C, Schwarz M, Peng J, Grzmil M, Hasilik M, Braulke T, Kohlschütter A, von Figura K, Lehle L, Körner C.; ''A new type of congenital disorders of glycosylation (CDG-Ii) provides new insights into the early steps of dolichol-linked oligosaccharide biosynthesis.''; PubMed Europe PMC Scholia
- Wada Y, Sakamoto M.; ''Isolation of the human phosphomannomutase gene (PMM1) and assignment to chromosome 22q13.''; PubMed Europe PMC Scholia
- Montiel MD, Krzewinski-Recchi MA, Delannoy P, Harduin-Lepers A.; ''Molecular cloning, gene organization and expression of the human UDP-GalNAc:Neu5Acalpha2-3Galbeta-R beta1,4-N-acetylgalactosaminyltransferase responsible for the biosynthesis of the blood group Sda/Cad antigen: evidence for an unusual extended cytoplasmic domain.''; PubMed Europe PMC Scholia
- Burda P, Aebi M.; ''The ALG10 locus of Saccharomyces cerevisiae encodes the alpha-1,2 glucosyltransferase of the endoplasmic reticulum: the terminal glucose of the lipid-linked oligosaccharide is required for efficient N-linked glycosylation.''; PubMed Europe PMC Scholia
- Kranz C, Denecke J, Lehle L, Sohlbach K, Jeske S, Meinhardt F, Rossi R, Gudowius S, Marquardt T.; ''Congenital disorder of glycosylation type Ik (CDG-Ik): a defect of mannosyltransferase I.''; PubMed Europe PMC Scholia
- Intra J, Perotti ME, Pavesi G, Horner D.; ''Comparative and phylogenetic analysis of alpha-L-fucosidase genes.''; PubMed Europe PMC Scholia
- Song BL, Sever N, DeBose-Boyd RA.; ''Gp78, a membrane-anchored ubiquitin ligase, associates with Insig-1 and couples sterol-regulated ubiquitination to degradation of HMG CoA reductase.''; PubMed Europe PMC Scholia
- Wickramasinghe S, Medrano JF.; ''Primer on genes encoding enzymes in sialic acid metabolism in mammals.''; PubMed Europe PMC Scholia
- Aronson NN, Kuranda MJ.; ''Lysosomal degradation of Asn-linked glycoproteins.''; PubMed Europe PMC Scholia
- Kudo T, Nakagawa H, Takahashi M, Hamaguchi J, Kamiyama N, Yokoo H, Nakanishi K, Nakagawa T, Kamiyama T, Deguchi K, Nishimura S, Todo S.; ''N-glycan alterations are associated with drug resistance in human hepatocellular carcinoma.''; PubMed Europe PMC Scholia
- Nauseef WM, McCormick SJ, Clark RA.; ''Calreticulin functions as a molecular chaperone in the biosynthesis of myeloperoxidase.''; PubMed Europe PMC Scholia
- Furukawa T, Youssef EM, Yatsuoka T, Yokoyama T, Makino N, Inoue H, Fukushige S, Hoshi M, Hayashi Y, Sunamura M, Horii A.; ''Cloning and characterization of the human UDP-N-acetylglucosamine: alpha-1,3-D-mannoside beta-1,4-N-acetylglucosaminyltransferase IV-homologue (hGnT-IV-H) gene.''; PubMed Europe PMC Scholia
- Vleugels W, Schollen E, Foulquier F, Matthijs G.; ''Screening for OST deficiencies in unsolved CDG-I patients.''; PubMed Europe PMC Scholia
- Lubas WA, Spiro RG.; ''Evaluation of the role of rat liver Golgi endo-alpha-D-mannosidase in processing N-linked oligosaccharides.''; PubMed Europe PMC Scholia
- Kasapkara CS, Tümer L, Ezgü FS, Hasanoğlu A, Race V, Matthijs G, Jaeken J.; ''SRD5A3-CDG: a patient with a novel mutation.''; PubMed Europe PMC Scholia
- McKnight GL, Mudri SL, Mathewes SL, Traxinger RR, Marshall S, Sheppard PO, O'Hara PJ.; ''Molecular cloning, cDNA sequence, and bacterial expression of human glutamine:fructose-6-phosphate amidotransferase.''; PubMed Europe PMC Scholia
- Karaveg K, Siriwardena A, Tempel W, Liu ZJ, Glushka J, Wang BC, Moremen KW.; ''Mechanism of class 1 (glycosylhydrolase family 47) {alpha}-mannosidases involved in N-glycan processing and endoplasmic reticulum quality control.''; PubMed Europe PMC Scholia
- Tremblay LO, Herscovics A.; ''Characterization of a cDNA encoding a novel human Golgi alpha 1, 2-mannosidase (IC) involved in N-glycan biosynthesis.''; PubMed Europe PMC Scholia
- Angata K, Suzuki M, McAuliffe J, Ding Y, Hindsgaul O, Fukuda M.; ''Differential biosynthesis of polysialic acid on neural cell adhesion molecule (NCAM) and oligosaccharide acceptors by three distinct alpha 2,8-sialyltransferases, ST8Sia IV (PST), ST8Sia II (STX), and ST8Sia III.''; PubMed Europe PMC Scholia
- Schollen E, Dorland L, de Koning TJ, Van Diggelen OP, Huijmans JG, Marquardt T, Babovic-Vuksanovic D, Patterson M, Imtiaz F, Winchester B, Adamowicz M, Pronicka E, Freeze H, Matthijs G.; ''Genomic organization of the human phosphomannose isomerase (MPI) gene and mutation analysis in patients with congenital disorders of glycosylation type Ib (CDG-Ib).''; PubMed Europe PMC Scholia
- Sun L, Eklund EA, Chung WK, Wang C, Cohen J, Freeze HH.; ''Congenital disorder of glycosylation id presenting with hyperinsulinemic hypoglycemia and islet cell hyperplasia.''; PubMed Europe PMC Scholia
- Suzuki T, Yano K, Sugimoto S, Kitajima K, Lennarz WJ, Inoue S, Inoue Y, Emori Y.; ''Endo-beta-N-acetylglucosaminidase, an enzyme involved in processing of free oligosaccharides in the cytosol.''; PubMed Europe PMC Scholia
- Timson DJ, Reece RJ.; ''Identification and characterisation of human aldose 1-epimerase.''; PubMed Europe PMC Scholia
- Senderek J, Müller JS, Dusl M, Strom TM, Guergueltcheva V, Diepolder I, Laval SH, Maxwell S, Cossins J, Krause S, Muelas N, Vilchez JJ, Colomer J, Mallebrera CJ, Nascimento A, Nafissi S, Kariminejad A, Nilipour Y, Bozorgmehr B, Najmabadi H, Rodolico C, Sieb JP, Steinlein OK, Schlotter B, Schoser B, Kirschner J, Herrmann R, Voit T, Oldfors A, Lindbergh C, Urtizberea A, von der Hagen M, Hübner A, Palace J, Bushby K, Straub V, Beeson D, Abicht A, Lochmüller H.; ''Hexosamine biosynthetic pathway mutations cause neuromuscular transmission defect.''; PubMed Europe PMC Scholia
- Suzuki T, Huang C, Fujihira H.; ''The cytoplasmic peptide:N-glycanase (NGLY1) - Structure, expression and cellular functions.''; PubMed Europe PMC Scholia
- Gao XD, Tachikawa H, Sato T, Jigami Y, Dean N.; ''Alg14 recruits Alg13 to the cytoplasmic face of the endoplasmic reticulum to form a novel bipartite UDP-N-acetylglucosamine transferase required for the second step of N-linked glycosylation.''; PubMed Europe PMC Scholia
- Sasaki N, Manya H, Okubo R, Kobayashi K, Ishida H, Toda T, Endo T, Nishihara S.; ''beta4GalT-II is a key regulator of glycosylation of the proteins involved in neuronal development.''; PubMed Europe PMC Scholia
- Takahashi S, Hori K, Takahashi K, Ogasawara H, Tomatsu M, Saito K.; ''Effects of nucleotides on N-acetyl-d-glucosamine 2-epimerases (renin-binding proteins): comparative biochemical studies.''; PubMed Europe PMC Scholia
- Yamaguchi Y, Ikeda Y, Takahashi T, Ihara H, Tanaka T, Sasho C, Uozumi N, Yanagidani S, Inoue S, Fujii J, Taniguchi N.; ''Genomic structure and promoter analysis of the human alpha1, 6-fucosyltransferase gene (FUT8).''; PubMed Europe PMC Scholia
- Wolf MJ, Rush JS, Waechter CJ.; ''Golgi-enriched membrane fractions from rat brain and liver contain long-chain polyisoprenyl pyrophosphate phosphatase activity.''; PubMed Europe PMC Scholia
- Clarke LA.; ''The mucopolysaccharidoses: a success of molecular medicine.''; PubMed Europe PMC Scholia
- Petrescu AJ, Milac AL, Petrescu SM, Dwek RA, Wormald MR.; ''Statistical analysis of the protein environment of N-glycosylation sites: implications for occupancy, structure, and folding.''; PubMed Europe PMC Scholia
- Harduin-Lepers A, Vallejo-Ruiz V, Krzewinski-Recchi MA, Samyn-Petit B, Julien S, Delannoy P.; ''The human sialyltransferase family.''; PubMed Europe PMC Scholia
- Cameron HS, Szczepaniak D, Weston BW.; ''Expression of human chromosome 19p alpha(1,3)-fucosyltransferase genes in normal tissues. Alternative splicing, polyadenylation, and isoforms.''; PubMed Europe PMC Scholia
- Matthijs G, Schollen E, Pardon E, Veiga-Da-Cunha M, Jaeken J, Cassiman JJ, Van Schaftingen E.; ''Mutations in PMM2, a phosphomannomutase gene on chromosome 16p13, in carbohydrate-deficient glycoprotein type I syndrome (Jaeken syndrome).''; PubMed Europe PMC Scholia
- Bergfeld AK, Pearce OM, Diaz SL, Pham T, Varki A.; ''Metabolism of vertebrate amino sugars with N-glycolyl groups: elucidating the intracellular fate of the non-human sialic acid N-glycolylneuraminic acid.''; PubMed Europe PMC Scholia
- Harada Y, Masahara-Negishi Y, Suzuki T.; ''Cytosolic-free oligosaccharides are predominantly generated by the degradation of dolichol-linked oligosaccharides in mammalian cells.''; PubMed Europe PMC Scholia
- Winchester B.; ''Lysosomal metabolism of glycoproteins.''; PubMed Europe PMC Scholia
- O'Reilly MK, Zhang G, Imperiali B.; ''In vitro evidence for the dual function of Alg2 and Alg11: essential mannosyltransferases in N-linked glycoprotein biosynthesis.''; PubMed Europe PMC Scholia
- Pang H, Koda Y, Soejima M, Kimura H.; ''Identification of human phosphoglucomutase 3 (PGM3) as N-acetylglucosamine-phosphate mutase (AGM1).''; PubMed Europe PMC Scholia
- Alanen HI, Williamson RA, Howard MJ, Hatahet FS, Salo KE, Kauppila A, Kellokumpu S, Ruddock LW.; ''ERp27, a new non-catalytic endoplasmic reticulum-located human protein disulfide isomerase family member, interacts with ERp57.''; PubMed Europe PMC Scholia
- Kumar R, Yang J, Larsen RD, Stanley P.; ''Cloning and expression of N-acetylglucosaminyltransferase I, the medial Golgi transferase that initiates complex N-linked carbohydrate formation.''; PubMed Europe PMC Scholia
- Akama TO, Nakagawa H, Wong NK, Sutton-Smith M, Dell A, Morris HR, Nakayama J, Nishimura S, Pai A, Moremen KW, Marth JD, Fukuda MN.; ''Essential and mutually compensatory roles of {alpha}-mannosidase II and {alpha}-mannosidase IIx in N-glycan processing in vivo in mice.''; PubMed Europe PMC Scholia
- Brynedal B, Wojcik J, Esposito F, Debailleul V, Yaouanq J, Martinelli-Boneschi F, Edan G, Comi G, Hillert J, Abderrahim H.; ''MGAT5 alters the severity of multiple sclerosis.''; PubMed Europe PMC Scholia
- Kelleher DJ, Gilmore R.; ''An evolving view of the eukaryotic oligosaccharyltransferase.''; PubMed Europe PMC Scholia
- Hinderlich S, Berger M, Schwarzkopf M, Effertz K, Reutter W.; ''Molecular cloning and characterization of murine and human N-acetylglucosamine kinase.''; PubMed Europe PMC Scholia
- Oriol R, Martinez-Duncker I, Chantret I, Mollicone R, Codogno P.; ''Common origin and evolution of glycosyltransferases using Dol-P-monosaccharides as donor substrate.''; PubMed Europe PMC Scholia
- Chantret I, Dupré T, Delenda C, Bucher S, Dancourt J, Barnier A, Charollais A, Heron D, Bader-Meunier B, Danos O, Seta N, Durand G, Oriol R, Codogno P, Moore SE.; ''Congenital disorders of glycosylation type Ig is defined by a deficiency in dolichyl-P-mannose:Man7GlcNAc2-PP-dolichyl mannosyltransferase.''; PubMed Europe PMC Scholia
- Hansske B, Thiel C, Lübke T, Hasilik M, Höning S, Peters V, Heidemann PH, Hoffmann GF, Berger EG, von Figura K, Körner C.; ''Deficiency of UDP-galactose:N-acetylglucosamine beta-1,4-galactosyltransferase I causes the congenital disorder of glycosylation type IId.''; PubMed Europe PMC Scholia
- Granovsky M, Fata J, Pawling J, Muller WJ, Khokha R, Dennis JW.; ''Suppression of tumor growth and metastasis in Mgat5-deficient mice.''; PubMed Europe PMC Scholia
- Imbach T, Burda P, Kuhnert P, Wevers RA, Aebi M, Berger EG, Hennet T.; ''A mutation in the human ortholog of the Saccharomyces cerevisiae ALG6 gene causes carbohydrate-deficient glycoprotein syndrome type-Ic.''; PubMed Europe PMC Scholia
- Kämpf M, Absmanner B, Schwarz M, Lehle L.; ''Biochemical characterization and membrane topology of Alg2 from Saccharomyces cerevisiae as a bifunctional alpha1,3- and 1,6-mannosyltransferase involved in lipid-linked oligosaccharide biosynthesis.''; PubMed Europe PMC Scholia
- Mi Y, Fiete D, Baenziger JU.; ''Ablation of GalNAc-4-sulfotransferase-1 enhances reproduction by altering the carbohydrate structures of luteinizing hormone in mice.''; PubMed Europe PMC Scholia
- Tian H, Miyoshi E, Kawaguchi N, Shaker M, Ito Y, Taniguchi N, Tsujimoto M, Matsuura N.; ''The implication of N-acetylglucosaminyltransferase V expression in gastric cancer.''; PubMed Europe PMC Scholia
- Serafini-Cessi F, Conte R.; ''Precipitin reaction between Sda-active human Tamm-Horsfall glycoprotein and anti-Sda-serum.''; PubMed Europe PMC Scholia
- 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.''; PubMed Europe PMC Scholia
- Maeda Y, Tanaka S, Hino J, Kangawa K, Kinoshita T.; ''Human dolichol-phosphate-mannose synthase consists of three subunits, DPM1, DPM2 and DPM3.''; PubMed Europe PMC Scholia
- Hiraoka N, Misra A, Belot F, Hindsgaul O, Fukuda M.; ''Molecular cloning and expression of two distinct human N-acetylgalactosamine 4-O-sulfotransferases that transfer sulfate to GalNAc beta 1-->4GlcNAc beta 1-->R in both N- and O-glycans.''; PubMed Europe PMC Scholia
- Tonetti M, Sturla L, Bisso A, Benatti U, De Flora A.; ''Synthesis of GDP-L-fucose by the human FX protein.''; PubMed Europe PMC Scholia
- Gonzalez DS, Karaveg K, Vandersall-Nairn AS, Lal A, Moremen KW.; ''Identification, expression, and characterization of a cDNA encoding human endoplasmic reticulum mannosidase I, the enzyme that catalyzes the first mannose trimming step in mammalian Asn-linked oligosaccharide biosynthesis.''; PubMed Europe PMC Scholia
- Arnold SM, Kaufman RJ.; ''The noncatalytic portion of human UDP-glucose: glycoprotein glucosyltransferase I confers UDP-glucose binding and transferase function to the catalytic domain.''; PubMed Europe PMC Scholia
- Saxena A, Yik JH, Weigel PH.; ''H2, the minor subunit of the human asialoglycoprotein receptor, trafficks intracellularly and forms homo-oligomers, but does not bind asialo-orosomucoid.''; PubMed Europe PMC Scholia
- Clarke JL, Watkins WM.; ''Expression of human alpha-l-fucosyltransferase gene homologs in monkey kidney COS cells and modification of potential fucosyltransferase acceptor substrates by an endogenous glycosidase.''; PubMed Europe PMC Scholia
- Ide Y, Miyoshi E, Nakagawa T, Gu J, Tanemura M, Nishida T, Ito T, Yamamoto H, Kozutsumi Y, Taniguchi N.; ''Aberrant expression of N-acetylglucosaminyltransferase-IVa and IVb (GnT-IVa and b) in pancreatic cancer.''; PubMed Europe PMC Scholia
- Cipollo JF, Trimble RB, Chi JH, Yan Q, Dean N.; ''The yeast ALG11 gene specifies addition of the terminal alpha 1,2-Man to the Man5GlcNAc2-PP-dolichol N-glycosylation intermediate formed on the cytosolic side of the endoplasmic reticulum.''; PubMed Europe PMC Scholia
- Apweiler R, Hermjakob H, Sharon N.; ''On the frequency of protein glycosylation, as deduced from analysis of the SWISS-PROT database.''; PubMed Europe PMC Scholia
- Kinoshita T, Inoue N.; ''Dissecting and manipulating the pathway for glycosylphos-phatidylinositol-anchor biosynthesis.''; PubMed Europe PMC Scholia
- Lo Presti L, Cabuy E, Chiricolo M, Dall'Olio F.; ''Molecular cloning of the human beta1,4 N-acetylgalactosaminyltransferase responsible for the biosynthesis of the Sd(a) histo-blood group antigen: the sequence predicts a very long cytoplasmic domain.''; PubMed Europe PMC Scholia
- Alcock F, Swanton E.; ''Mammalian OS-9 is upregulated in response to endoplasmic reticulum stress and facilitates ubiquitination of misfolded glycoproteins.''; PubMed Europe PMC Scholia
- Schaub BE, Berger B, Berger EG, Rohrer J.; ''Transition of galactosyltransferase 1 from trans-Golgi cisterna to the trans-Golgi network is signal mediated.''; PubMed Europe PMC Scholia
- Schmid M, Prajczer S, Gruber LN, Bertocchi C, Gandini R, Pfaller W, Jennings P, Joannidis M.; ''Uromodulin facilitates neutrophil migration across renal epithelial monolayers.''; PubMed Europe PMC Scholia
- Misago M, Liao YF, Kudo S, Eto S, Mattei MG, Moremen KW, Fukuda MN.; ''Molecular cloning and expression of cDNAs encoding human alpha-mannosidase II and a previously unrecognized alpha-mannosidase IIx isozyme.''; PubMed Europe PMC Scholia
- Ciccarelli FD, von Mering C, Suyama M, Harrington ED, Izaurralde E, Bork P.; ''Complex genomic rearrangements lead to novel primate gene function.''; PubMed Europe PMC Scholia
- Zhou H, Sun L, Li J, Xu C, Yu F, Liu Y, Ji C, He J.; ''The crystal structure of human GDP-L-fucose synthase.''; PubMed Europe PMC Scholia
- Pinho SS, Reis CA, Paredes J, Magalhães AM, Ferreira AC, Figueiredo J, Xiaogang W, Carneiro F, Gärtner F, Seruca R.; ''The role of N-acetylglucosaminyltransferase III and V in the post-transcriptional modifications of E-cadherin.''; PubMed Europe PMC Scholia
- Willems PJ, Seo HC, Coucke P, Tonlorenzi R, O'Brien JS.; ''Spectrum of mutations in fucosidosis.''; PubMed Europe PMC Scholia
History
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External references
DataNodes
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Annotated Interactions
View all... |
Source | Target | Type | Database reference | Comment |
---|---|---|---|---|
2xGNPNAT1 | REACT_22233 (Reactome) | |||
2xUAP1-2 | REACT_22397 (Reactome) | |||
ALG10 homologue | REACT_22406 (Reactome) | |||
ALG11 | REACT_22156 (Reactome) | |||
ALG12 | REACT_22117 (Reactome) | |||
ALG13 ALG14 complex | REACT_22332 (Reactome) | |||
ALG1 | REACT_22214 (Reactome) | |||
ALG2 | REACT_22347 (Reactome) | |||
ALG2 | REACT_22383 (Reactome) | |||
ALG3 | REACT_22415 (Reactome) | |||
ALG5 | REACT_22143 (Reactome) | |||
ALG6 | REACT_22194 (Reactome) | |||
ALG8 | REACT_22158 (Reactome) | |||
ALG9 | REACT_22123 (Reactome) | |||
ALG9 | REACT_22307 (Reactome) | |||
Ac-CoA | REACT_22233 (Reactome) | |||
AcGlcN1P | REACT_22397 (Reactome) | |||
AcGlcN6P | Arrow | REACT_22233 (Reactome) | ||
Arrow | REACT_22117 (Reactome) | |||
Arrow | REACT_22123 (Reactome) | |||
Arrow | REACT_22156 (Reactome) | |||
Arrow | REACT_22158 (Reactome) | |||
Arrow | REACT_22194 (Reactome) | |||
Arrow | REACT_22307 (Reactome) | |||
Arrow | REACT_22347 (Reactome) | |||
Arrow | REACT_22383 (Reactome) | |||
Arrow | REACT_22406 (Reactome) | |||
Arrow | REACT_22415 (Reactome) | |||
Arrow | REACT_25047 (Reactome) | |||
Arrow | REACT_25136 (Reactome) | |||
Arrow | REACT_25205 (Reactome) | |||
Arrow | REACT_25217 (Reactome) | |||
Arrow | REACT_25236 (Reactome) | |||
Arrow | REACT_25341 (Reactome) | |||
B4GALT1-6 homodimers | REACT_25178 (Reactome) | |||
CALR CANX | Arrow | REACT_23791 (Reactome) | ||
CALR,CANX | REACT_23778 (Reactome) | |||
CDP | Arrow | REACT_22276 (Reactome) | ||
CTP | REACT_22276 (Reactome) | |||
CoA-SH | Arrow | REACT_22233 (Reactome) | ||
DOLDP | REACT_22114 (Reactome) | |||
DOLK | REACT_22276 (Reactome) | |||
DOLP | Arrow | REACT_22114 (Reactome) | ||
DOLP | Arrow | REACT_22117 (Reactome) | ||
DOLP | Arrow | REACT_22123 (Reactome) | ||
DOLP | Arrow | REACT_22158 (Reactome) | ||
DOLP | Arrow | REACT_22194 (Reactome) | ||
DOLP | Arrow | REACT_22208 (Reactome) | ||
DOLP | Arrow | REACT_22276 (Reactome) | ||
DOLP | Arrow | REACT_22307 (Reactome) | ||
DOLP | Arrow | REACT_22406 (Reactome) | ||
DOLP | Arrow | REACT_22415 (Reactome) | ||
DOLP | Arrow | REACT_25264 (Reactome) | ||
DOLPM | REACT_22117 (Reactome) | |||
DOLPM | REACT_22123 (Reactome) | |||
DOLPM | REACT_22307 (Reactome) | |||
DOLPM | REACT_22415 (Reactome) | |||
DOLPP1 | REACT_22114 (Reactome) | |||
DOLP | REACT_2036 (Reactome) | |||
DOLP | REACT_22143 (Reactome) | |||
DOLP | REACT_22147 (Reactome) | |||
DPAGT1 | REACT_22147 (Reactome) | |||
DPM1,2,3 | REACT_2036 (Reactome) | |||
DbGP | REACT_22158 (Reactome) | |||
DbGP | REACT_22194 (Reactome) | |||
DbGP | REACT_22406 (Reactome) | |||
DbGP | REACT_25264 (Reactome) | |||
Dolichol | REACT_22276 (Reactome) | |||
EDEM | REACT_25207 (Reactome) | |||
FUT8 | REACT_25399 (Reactome) | |||
Fru | REACT_22115 (Reactome) | |||
GDP-Fuc | REACT_25399 (Reactome) | |||
GDP-Man | Arrow | REACT_22254 (Reactome) | ||
GDP-Man | REACT_2036 (Reactome) | |||
GDP-Man | REACT_22156 (Reactome) | |||
GDP-Man | REACT_22214 (Reactome) | |||
GDP-Man | REACT_22347 (Reactome) | |||
GDP-Man | REACT_22383 (Reactome) | |||
GDP | Arrow | REACT_12554 (Reactome) | ||
GDP | Arrow | REACT_22156 (Reactome) | ||
GDP | Arrow | REACT_22214 (Reactome) | ||
GDP | Arrow | REACT_22347 (Reactome) | ||
GDP | Arrow | REACT_22383 (Reactome) | ||
GDP | Arrow | REACT_25399 (Reactome) | ||
GFPT1/2 | REACT_22115 (Reactome) | |||
GMPPA/B | REACT_22254 (Reactome) | |||
GTP | REACT_12554 (Reactome) | |||
GTP | REACT_22254 (Reactome) | |||
Glc | Arrow | REACT_23791 (Reactome) | ||
Glc | Arrow | REACT_23850 (Reactome) | ||
Glc | Arrow | REACT_23855 (Reactome) | ||
Glc | Arrow | REACT_25136 (Reactome) | ||
GlcN6P | Arrow | REACT_22115 (Reactome) | ||
GlcN6P | REACT_22233 (Reactome) | |||
GlcNAcDOLDP | Arrow | REACT_22147 (Reactome) | ||
GlcNAcDOLDP | REACT_22332 (Reactome) | |||
Glycoprotein with fucosyl alpha-1,6-GlcNAc | Arrow | REACT_25399 (Reactome) | ||
H2O | REACT_22114 (Reactome) | |||
L-Gln | REACT_22115 (Reactome) | |||
L-Glu | Arrow | REACT_22115 (Reactome) | ||
LMAN1 MCFD2 | REACT_25176 (Reactome) | |||
MAN1A1/A2/C1 | REACT_25205 (Reactome) | |||
MAN1A1/A2/C1 | REACT_25217 (Reactome) | |||
MAN1A1/A2/C1 | REACT_25341 (Reactome) | |||
MAN1B1 | REACT_24995 (Reactome) | |||
MAN1B1 | REACT_25093 (Reactome) | |||
MAN1B1 | REACT_25126 (Reactome) | |||
MAN1B1 | REACT_25313 (Reactome) | |||
MAN2 Zn2+ | REACT_25047 (Reactome) | |||
MANEA | REACT_25136 (Reactome) | |||
MDCDD | Arrow | REACT_22214 (Reactome) | ||
MDCDD | REACT_22347 (Reactome) | |||
MGAT1 | REACT_25236 (Reactome) | |||
MGAT2 | REACT_25253 (Reactome) | |||
MGAT3 | REACT_25005 (Reactome) | |||
MGAT4s | REACT_25009 (Reactome) | |||
MGAT5 | REACT_25314 (Reactome) | |||
MLEC | Arrow | REACT_23850 (Reactome) | ||
MLEC | REACT_23783 (Reactome) | |||
MOGS | REACT_23855 (Reactome) | |||
MPI | REACT_22388 (Reactome) | |||
Man1P | REACT_22254 (Reactome) | |||
Man | Arrow | REACT_24995 (Reactome) | ||
Man | Arrow | REACT_25047 (Reactome) | ||
Man | Arrow | REACT_25093 (Reactome) | ||
Man | Arrow | REACT_25126 (Reactome) | ||
Man | Arrow | REACT_25205 (Reactome) | ||
Man | Arrow | REACT_25217 (Reactome) | ||
Man | Arrow | REACT_25313 (Reactome) | ||
Man | Arrow | REACT_25341 (Reactome) | ||
N,N'-DCDOLDP | Arrow | REACT_22332 (Reactome) | ||
N,N'-DCDOLDP | REACT_22214 (Reactome) | |||
NGP | REACT_24990 (Reactome) | |||
NGP | REACT_25005 (Reactome) | |||
NGP | REACT_25009 (Reactome) | |||
NGP | REACT_25115 (Reactome) | |||
NGP | REACT_25121 (Reactome) | |||
NGP | REACT_25178 (Reactome) | |||
NGP | REACT_25314 (Reactome) | |||
NGP | REACT_25399 (Reactome) | |||
OANA- | REACT_24990 (Reactome) | |||
OANA- | REACT_25115 (Reactome) | |||
OANA- | REACT_25121 (Reactome) | |||
OST complex | REACT_22208 (Reactome) | |||
PDIA3 | Arrow | REACT_23791 (Reactome) | ||
PDIA3 | REACT_23831 (Reactome) | |||
PGM3 | REACT_22269 (Reactome) | |||
PMM1/2 | REACT_22437 (Reactome) | |||
PPi | Arrow | REACT_22254 (Reactome) | ||
PPi | Arrow | REACT_22397 (Reactome) | ||
PREB | REACT_12554 (Reactome) | |||
Pi | Arrow | REACT_12396 (Reactome) | ||
Pi | Arrow | REACT_12456 (Reactome) | ||
Pi | Arrow | REACT_22114 (Reactome) | ||
REACT_12393 (Reactome) | Sar1p-GTP recruits the cytoplasmic Sec23p-Sec24p complex. Though not represented in the subsequent steps, Sec23p-Sec24p would bind to members of the p24 protein family of possible cargo receptors, and together with Sar1p bind the appropiate v-SNARE, and Rab-GTP. | |||
REACT_12396 (Reactome) | Sar1p-GTP hydrolysis is increased 15-30-fold by Sec23p. Sar1p-GDP is released as a result of this hydrolysis and used in further vesicle sculpting cycles. Sar1p-GTP hydrolysis occurs at two critical points during the cycle, first (as represented here) as a proofreading step, insuring that the cargo is loaded. Later in the cycle Sar1p-GTP hydrolysis triggers the uncoating of the budded vesicle. | |||
REACT_12422 (Reactome) | Cytosolic Sec13p-Sec31p complexes bind to pre-bound Sec23p-Sec24p complexes. | |||
REACT_12456 (Reactome) | Vesicle uncoating is triggered by Sar1p-GTP hydrolysis leaving only the vesicle cargo and the v-SNARE to target the vesicle to the Golgi membrane. | |||
REACT_12554 (Reactome) | Sar1p-GDP is recruited to the ER membrane by the transmembrane GEF (Guanine nucleotide exchange factor) Sec12, where it is converted to Sar1p-GTP. | |||
REACT_12610 (Reactome) | Once loaded the vesicles become fully sculpted, pinch off from the ER and bud into the cytosol. | |||
REACT_2036 (Reactome) | Cytosolic GDP-mannose reacts with dolichyl phosphate in the endoplasmic reticulum membrane to form dolichyl phosphate D-mannose. The reaction is catalyzed by dolichyl-phosphate mannosyltransferase, a heterotrimeric protein embedded in the endoplasmic reticulum membrane. The first subunit of the heterotrimer appears to be the actual catalyst, and the other two subunits appear to stabilize it (Maeda et al. 2000). | |||
REACT_22114 (Reactome) | In the last step of the N-glycan precursor biosynthesis pathway, the mature N-glycan (Glc3Man9GlcNAc2) is removed from the dolichyl diphosphate molecule upon which it has been synthesized, and attached to a nascent protein. In this process, a dolichyl diphosphate molecule is released and once de-phosphorylated by dolichyl diphosphatase 1 (DOLPP1) to obtain dolichyl phosphate, it can be used as a substrate for the synthesis of another N-glycan oligosaccharide (Wedgwood JF and Strominger JL, 1980). | |||
REACT_22115 (Reactome) | Glucosamine-fructose 6-phosphate aminotransferase (GFAT) is the first and rate-limiting enzyme in the hexosamine synthesis pathway, and thus formation of hexosamines like N-acetylglucosamine (GlcNAc). This enzyme probably plays a role in limiting the availability of substrates for the N- and O- linked glycosylation of proteins. Two isoforms, GFAT 1 and 2, have been identified (McKnight GL et al, 1992; Oki T et al, 1999). GFAT is required normal functioning of neuromuscular synaptic transmission. Defects in the gene expressing this protein leads to altered muscle fiber morphology and impaired neuromuscular junction development (Senderek et al, 2011). | |||
REACT_22117 (Reactome) | ||||
REACT_22123 (Reactome) | ||||
REACT_22143 (Reactome) | Dolichyl-phosphate beta-glucosyltransferase (ALG5) associated with the endoplasmic reticulum (ER) membrane catalyzes the reaction of cytosolic UDP-glucose with dolichyl phosphate exposed on the cytosolic face of the ER membrane to form Dolichyl-P-glucose with its glucose moiety oriented toward the cytosol (Imbach T et al, 1999). | |||
REACT_22147 (Reactome) | In the first step of N-glycan precursor (LLO) synthesis, N-acetylglucosamine is added, via an alpha-1,3 linkage, to a molecule of dolichyl phosphate, producing N-acetyl-D-glucosaminyl-diphosphodolichol (Eckert V et al, 1998). This reaction is catalyzed by DPAGT1 (ALG7 in yeast), mutations in which are associated with CDG disorder type I-J (Wu X et al, 2003). The dolichyl phosphate acts as an anchor for the LLO, so the following sugar-addition reactions take place on a sugar anchored in the ER membrane. | |||
REACT_22156 (Reactome) | ||||
REACT_22158 (Reactome) | ||||
REACT_22194 (Reactome) | ||||
REACT_22208 (Reactome) | ||||
REACT_22214 (Reactome) | A mannose is added to the N-glycan precursor via a beta-1,4 linkage. The reaction is catalyzed by ALG1 (Takahashi T et al, 2000). Defects in ALG1 lead to congenital disorder of glycosylation type 1K (CDG1K) (Schwarz M et al, 2004; Kranz C et al, 2004; Grubenmann CE et al, 2004). | |||
REACT_22233 (Reactome) | Cytosolic GNPNAT1 catalyzes the reaction of glucosamine 6-phosphate and acetyl-CoA to form N-acetyl-glucosamine 6-phosphate (GlcNAc6P) and CoA-SH. Structural studies indicate that the active form of the enzyme is a dimer (Wang J et al, 2008). | |||
REACT_22245 (Reactome) | Dolichyl-phosphate-glucose is flipped toward the luminal side of the ER membrane (Imbach T et al, 1999). The exact mechanism and proteins involved in this step are not clear yet, but it is known that it must be carried out by a different flippase than the one that catalyzes the flipping of the N-glycan precursor (Sanyal S et al, 2008). | |||
REACT_22254 (Reactome) | Mannose 1-phosphate is converted to GDP-Mannose by mannose-1-phosphate guanyltransferase alpha and beta forms (GMPPA/B). This enzyme had originally been characterized from rat and bovine sources (Verachtert H et al, 1966) and more recently from pig (Ning B and Elbein AD, 2000). | |||
REACT_22262 (Reactome) | The precursor of the N-glycan sugar, now in the form of (GlcNAc)2 (Man)5 (PP-Dol), is flipped across the ER membrane, moving it from the cytosolic side into the ER lumen. The exact mechanism of this translocation is not well understood: the protein RFT1 is known to be involved (Helenius et al, 2002), along with an unknown flippase, which is distinct from the one that flips the Dol-P linked precursors (Dol-P-Mannose and Dol-P-glucose) (Sanyal et al, 2008). Defects in RFT1 are associated with Congenital Disorder of Glycosylation 1N (CDG1N) (Haeuptle MA et al, 2008). | |||
REACT_22269 (Reactome) | Cytosolic PGM3 catalyzes the isomerization of N-acetyl-D-glucosamine 6-phosphate (GlcNAc6P) to form N-acetyl-D-glucosamine 1-phosphate (GlcNAc1P) (Pang H et al, 2002). | |||
REACT_22276 (Reactome) | The phosphorylation of a dolichol residue of the ER membrane is a starting step in the N-glycan biosynthesis pathway (Fernandez F et al, 2002). Defects in DOLK are the cause of congenital disorder of glycosylation type 1M (CDG1M), also known as dolichol kinase deficiency (Kranz C et al, 2007). | |||
REACT_22307 (Reactome) | ||||
REACT_22332 (Reactome) | A second N-acetylglucosamine is added to the N-glycan precursor via a beta-1,4 linkage. This reaction is catalyzed by the ALG13:ALG14 complex, in which ALG13 functions as the catalyst and ALG14 functions as a membrane anchor which recruits ALG13 to the cytosolic face of ER (Gao XD et al, 2005). | |||
REACT_22347 (Reactome) | A second mannose is added to the N-glycan precursor via an alpha-1,3 linkage. The reaction is catalyzed by the mannosyltransferase ALG2. This is a bifunctional enzyme with both alpha 1,3- and alpha 1,6-mannosyltransferase activities. In humans, only the alpha 1,3 activity used in this reaction has been elucidated (Thiel C et al, 2003). Defects in ALG2 are the cause of CDG1I (Thiel C et al, 2003). | |||
REACT_22383 (Reactome) | ||||
REACT_22388 (Reactome) | Mannose-6-phosphate isomerase (MPI) converts Fructose 6-phosphate to Mannose 6-phosphate (Proudfoot AE et al, 1994). Defects in this gene are associated with congenital disorder of glycosylation type 1B (CDG1B). Oral administration of mannose is an efficient therapy against this defect (Schollen E et al, 2000). | |||
REACT_22397 (Reactome) | Cytosolic UAP1 catalyzes the reaction of N-acetyl-D-glucosamine 1-phosphate (GlcNAc1P) and UTP to UDP-N-acetyl-D-glucosamine and pyrophosphate. Structural studies indicate that the active form of the enzyme is a dimer (Peneff C et al, 2001). | |||
REACT_22406 (Reactome) | ||||
REACT_22415 (Reactome) | ||||
REACT_22437 (Reactome) | Phosphomannomutase 1 and 2 (PMM1 and PMM2) catalyze the isomerization of Mannose 6-phosphate to Mannose 1-phosphate (Wada Y and Sakamoto M et al, 1997; Matthijs G et al, February 1997). Mutations in the PMM2 gene are one of the causes of Jaeken syndrome. a disease of glycosylation, type CDGIa. (Matthijs G et al, May 1997). | |||
REACT_23773 (Reactome) | Proteins with folding defects get transported to the Endoplasmic Reticulum Quality Control Compartment (Molinari, 2007). | |||
REACT_23778 (Reactome) | Calnexin (membrane protein) and calreticulin (soluble in ER) are two lectins (proteins that can bind a glycan) which recognize the mono-glucosylated form of the N-glycan and mediate the folding of the glycoproteins to which they are attached to (Ou WJ et al, 1993; Nauseef Wm et al, 1995). Calmegin is another chaperone with the same role expressed only in testis (van Lith M et al, 2007). These lectins act as chaperons, providing a protected environment where the unfolded glycoprotein can fold without forming interactions with other proteins or components in the ER. The unfolded protein can loop between these two steps multiple time, therefore this process is called the 'calnexin/calreticulin cycle'. If the protein achieves correct folding, it is modified by Mannosidase I and then moved to the cis-Golgi where the glycan is further processed. | |||
REACT_23783 (Reactome) | A recently discovered protein called malectin is known to recognize the Glc(2)Man(9)GlcNAc(2) glycan (Schallus T et al, 2008). The exact role of this interaction is not clear but malectin is thought to regulate the availability of this substrate to glucosidase II, or to act as a chaperone to stabilize the unfolded protein. | |||
REACT_23791 (Reactome) | While the protein is bound to the chaperone complex, the glycan is still accessible to glucosidase II, which eventually removes the last remaining glucose residue. This also results in breaking the interaction between the chaperone and the glycoprotein, independently of whether the latter has achieved proper folding (Pelletier MF et al, 2000). This has been interpreted as a 'timing mechanism', in which a protein has only a limited period of time to achieve correct folding when bound to the chaperone, to avoid the scenario where proteins that take too long to fold would block the availability of CNX or CRT. Proteins with folding defects get transported to the Endoplasmic Reticulum Quality Control Compartment, while proteins with correct folding are transported to the cis-Golgi where the glycan is further modified. | |||
REACT_23831 (Reactome) | ERp57/ERp27 is a thiol-oxidoreductase that interacts with calnexin and mediates the formation of disulfide bonds in the unfolded glycoprotein (Alanen HI et al, 2006). | |||
REACT_23850 (Reactome) | A second glucose is removed from the N-linked glycan. The removal of an alpha1,3 glucose moiety is catalyzed by glucosidase II, a complex composed of an alpha subunit (GANAB) with catalytic activity and a beta subunit (GLU2B; PRKCSH), probably with regulatory and recruitment function (Pelletier MF et al, 2000). GANAB can exist in two different isoforms, but both are able to catalyze both of the reactions catalyzed by glucosidase II (Pelletier MF et al, 2000). Defects in PRKCSH are a cause of polycystic liver disease (PCLD). | |||
REACT_23855 (Reactome) | After the glycosylated precursor is attached to the protein, the outer alpha-1,2-linked glucose is removed by glucosidase I (MOGS, GCS1 in yeast). This is a mandatory step for the protein folding control and glycan extension, and defects in MOGS are associated with congenital disorder of glycosylation type IIb (CDGIIb) (De Praeter CM et al, 2000; Völker C et al, 2002). | |||
REACT_23986 (Reactome) | Correctly folded proteins, after being released from the Calnexin/Calreticulin cycle, are translocated to the Golgi (Hauri H et al, 2000; Hauri HP et al, 2002; Molinari, 2007). | |||
REACT_24990 (Reactome) | Addition of sialic acid to galactose-containing N-glycan. Sialic acid is usually found at terminal positions of the N-glycan. This imparts a negative charge at neutral pH this adds a negative charge which affects the chemico-physical and biological properties of the N-glycans (for a review, see Schauer R 2000); moreover, this modification can lead to the addition of extraordinarily long antennae such as polysialic acid (hundreds of sials) or poly lactosamine repeats (dozens of disaccharide repeats) (Harduin-Lepers A, 2001), while the number of modifications on the antennae of N-glycans is usually lower. There are over 20 sialyltransferases known in humans, 5 of which are known to act on N-glycans. ST6Gal I (ST6GAL1) is the only alpha-2,6-sialyltransferase known to transfer sialic acid to galactose on N-Glycans (Dall'Olio F, 2000). A second beta-Galactoside alpha-2,6-sialyltransferase has been characterized, but this enzyme acts mainly on oligosaccharides (Krzewinski-Recchi MA et al 2003). Sialic acids can also be added via an alpha-2,3-linkage to galactose on N-glycans by ST3GalIV(ST3GAL4) (Ellies et al 2002). ST8Sia II (ST8SIA2), ST8Sia III (ST8SIA3), and ST8Sia IV (ST8SIA6) have alpha-2,8-activity (Angata K et al 1997; Angata et al 2000; Angata K, Fuduka M 2003). | |||
REACT_24995 (Reactome) | The enzyme ER Man I can slowly trim up to four of the mannoses on the N-glycan on unfolded proteins accumulated in the ER. This step describes the removal of the mannose in the B position (Gonzalez et al, 1999: Hirao et al, 2006). | |||
REACT_25005 (Reactome) | The addition of a bisecting GlcNAc to a complex N-glycan by MGAT3 is one of the most important regulatory steps in N-glycosylation, directing the pathway toward the synthesis of complex and hybrid N-glycans. This addition changes the structure of the N-glycan and inhibits further modification by MGAT2, MGAT4, MGAT5A/B and FUT8. Defects in MGAT3 have been shown to be associated with predisposition to cancer and several developmental defects (Song et al 2010; Stanley 2002). | |||
REACT_25009 (Reactome) | N-acetylglucosaminyltransferase (GnT)-IV catalyzes the addition of GlcNAc beta,1,4 on the GlcNAc beta1,2 Man,alpha1,3 arm of both complex and hybrid N-glycans (Oguri S et al, 2006). Two human GnT-IV isozymes have been characterized (MGAT4A, MGAT4B) , plus a putative MGAT4C on chromosome 2 (Furukawa T et al, 1999). Aberrant expression of MGAT4A or MGAT4B is associated with pancreatic cancer (Ide Y et al, 2006; Kudo T et al , 2007) | |||
REACT_25047 (Reactome) | The removal of mannoses on the alpha,1,6 arm by MAN2A1 or MAN2A2 is required for efficient formation of complex-type N-glycans (Misago M et al, 1995; Crispin M et al, 2007). These two enzymes carry out the same function and the disruption of both inhibits the formation of complex N-glycans in vivo (Akama TO et al, 2006). | |||
REACT_25057 (Reactome) | Glycoproteins with lesser folding defects get transported back to the ER and the CNX/CRT complex (Lederkremer, 2009). | |||
REACT_25093 (Reactome) | The enzyme ER Man I can slowly trim up to four of the mannoses on the N-glycan on unfolded proteins accumulated in the ER. This step describes the removal of the mannose in the A position (Hirao et al, 2006; Frenkel et al, 2003). | |||
REACT_25115 (Reactome) | Addition of sialic acid to galactose-containing N-glycan. Sialic acid is usually found at terminal positions of the N-glycan. This imparts a negative charge at neutral pH this adds a negative charge which affects the chemico-physical and biological properties of the N-glycans (for a review, see Schauer R 2000); moreover, this modification can lead to the addition of extraordinarily long antennae such as polysialic acid (hundreds of sials) or poly lactosamine repeats (dozens of disaccharide repeats) (Harduin-Lepers A, 2001), while the number of modifications on the antennae of N-glycans is usually lower. There are over 20 sialyltransferases known in humans, 5 of which are known to act on N-glycans. ST6Gal I (ST6GAL1) is the only alpha-2,6-sialyltransferase known to transfer sialic acid to galactose on N-Glycans (Dall'Olio F, 2000). A second beta-Galactoside alpha-2,6-sialyltransferase has been characterized, but this enzyme acts mainly on oligosaccharides (Krzewinski-Recchi MA et al 2003). Sialic acids can also be added via an alpha-2,3-linkage to galactose on N-glycans by ST3GalIV(ST3GAL4) (Ellies et al 2002). ST8Sia II (ST8SIA2), ST8Sia III (ST8SIA3), and ST8Sia IV (ST8SIA6) have alpha-2,8-activity (Angata K et al 1997; Angata et al 2000; Angata K, Fuduka M 2003). | |||
REACT_25121 (Reactome) | Addition of sialic acid to galactose-containing N-glycan. Sialic acid is usually found at terminal positions of the N-glycan. This imparts a negative charge at neutral pH this adds a negative charge which affects the chemico-physical and biological properties of the N-glycans (for a review, see Schauer R 2000); moreover, this modification can lead to the addition of extraordinarily long antennae such as polysialic acid (hundreds of sials) or poly lactosamine repeats (dozens of disaccharide repeats) (Harduin-Lepers A, 2001), while the number of modifications on the antennae of N-glycans is usually lower. There are over 20 sialyltransferases known in humans, 5 of which are known to act on N-glycans. ST6Gal I (ST6GAL1) is the only alpha-2,6-sialyltransferase known to transfer sialic acid to galactose on N-Glycans (Dall'Olio F, 2000). A second beta-Galactoside alpha-2,6-sialyltransferase has been characterized, but this enzyme acts mainly on oligosaccharides (Krzewinski-Recchi MA et al 2003). Sialic acids can also be added via an alpha-2,3-linkage to galactose on N-glycans by ST3GalIV(ST3GAL4) (Ellies et al 2002). ST8Sia II (ST8SIA2), ST8Sia III (ST8SIA3), and ST8Sia IV (ST8SIA6) have alpha-2,8-activity (Angata K et al 1997; Angata et al 2000; Angata K, Fuduka M 2003). | |||
REACT_25126 (Reactome) | The enzyme ER Man I can slowly trim up to four of the mannoses on the N-glycan on unfolded proteins accumulated in the ER. This step describes the removal of the mannose in the C position (Hirao et al, 2006). | |||
REACT_25136 (Reactome) | Cells exposed to castanospermine or 1-deoxynojirimycin (inhibitors of the glucosidase enzymes GCS1 and GANAB), are still able to carry out glycosylation and produce complex glycans. This is due to the existence of an alternative route catalyzed by the enzyme endomannosidase (Moore and Spiro, 1990). Glycoproteins that pass through this route probably skip or have a reduced interaction with the Calnexin/Calreticulin cycle, and are transported to the cis-golgi through a route that has not been described yet (probably through the general ER to Golgi flow). Here, the Endomannosidase enzyme, which resides on the Golgi membrane (Hardt et al 2005; Hamilton et al 2005) is able to remove the tri-, di-, or mono-glucose substituted mannose on branch A, leading to a deglucosylated N-glycan structure (Lubas and Spiro, 1988). | |||
REACT_25176 (Reactome) | The LMAN1(also known as ERGIC-53)/MCFD2 complex recognizes Man8 and Man9 N-glycans released by the Calnexin/Calreticulin cycle and mediate their transport to the Golgi (Nyefeler B et al, 2003; Zhang B et al, 2003). Man8 glycan transfer is shown here. | |||
REACT_25178 (Reactome) | Addition of a galactose residue on N-acetylglucosamine. The family of beta 4-galactosyltransferases is composed by at least six known members with different K(m) and acceptor specifities (Guo S et al, 2001) and probably originated by duplication (Lo NW et al, 1998). B4GALT1 is associated with Congenital Disorder of Glycosylation of type IId (Hansske B et al, 2002), and is expressed as two splicing isoforms of which only one is localizated in the Golgi system (Lopez LC et al, 1991; Schaub BE et al, 2006). B4GALT2 is key in the regulation of proteins involved in neuronal development (Sasaki N et al, 2005). | |||
REACT_25205 (Reactome) | In the cis-Golgi, Man7, Man8 or Man9 N-glycans are progressively trimmed to Man5 N-glycans. The reaction can be catalyzed by one of three known mannosidases, expressed in different tissues and with slightly different affinity. These enzymes trim the mannoses in a different order (Tremblay and Herscovics, 2000), but produce the same output with 5 mannoses. A small confusion on the nomenclature of these genes coding for these enzymes is present in the literature: the standard HGNC symbols are MAN1A1, MAN1A2, MAN1C1, but MAN1A2 is also referred to as MAN1B in certain publications, while MAN1B1 is the enzyme acting in the ERQC compartment on unfolded glycoproteins. Moreover, the names do not correspond to a preference of these enzymes for which of the three mannose branches these trim first. | |||
REACT_25207 (Reactome) | Proteins with major folding defects are extracted from futile folding cycles in the calnexin chaperone system and the ER Quality Control Compartment, and are translocated back to the citosol for degradation. The N-glycan is used as a signal to distinguish proteins to be degraded, upon recognition by EDEM1, EDEM2 and EDEM3, three ER-stress-induced members of the glycosyl hydrolase 47 family (see Olivari S, Molinari M 2007 for a review) and OS9 (Mikami K, 2010; Hosokawa N, 2009). | |||
REACT_25217 (Reactome) | In the cis-Golgi, Man7, Man8 or Man9 N-glycans are progressively trimmed to Man5 N-glycans. The reaction can be catalyzed by one of three known mannosidases, expressed in different tissues and with slightly different affinity. These enzymes trim the mannoses in a different order (Tremblay and Herscovics, 2000), but produce the same output with 5 mannoses. A small confusion on the nomenclature of these genes coding for these enzymes is present in the literature: the standard HGNC symbols are MAN1A1, MAN1A2, MAN1C1, but MAN1A2 is also referred to as MAN1B in certain publications, while MAN1B1 is the enzyme acting in the ERQC compartment on unfolded glycoproteins. Moreover, the names do not correspond to a preference of these enzymes for which of the three mannose branches these trim first. | |||
REACT_25236 (Reactome) | ||||
REACT_25253 (Reactome) | ||||
REACT_25264 (Reactome) | ||||
REACT_25313 (Reactome) | Removal of the second mannose on the alpha 1,3 branch (Frenzel Z et al, 2003). | |||
REACT_25314 (Reactome) | N-acetylglucosaminyltransferase (GnT)-V catalyzes the addition of GlcNAc beta 1,4 on the GlcNAc beta1,2 Man,alpha1,6 arm of complex type N-Glycans (Park C et al, 1999; Granowski M et al, 2000; Wang L et al, 2007). The activity of MGAT5 competes with MGAT3 (Pinho SS et al, 2009) and is associated with gastric cancer (Tian H et al, 2008) and multiple sclerosis (Brynedal B et al, 2010). | |||
REACT_25341 (Reactome) | In the cis-Golgi, Man7, Man8 or Man9 N-glycans are progressively trimmed to Man5 N-glycans. The reaction can be catalyzed by one of three known mannosidases, expressed in different tissues and with slightly different affinity. These enzymes trim the mannoses in a different order (Tremblay and Herscovics, 2000), but produce the same output with 5 mannoses. A small confusion on the nomenclature of these genes coding for these enzymes is present in the literature: the standard HGNC symbols are MAN1A1, MAN1A2, MAN1C1, but MAN1A2 is also referred to as MAN1B in certain publications, while MAN1B1 is the enzyme acting in the ERQC compartment on unfolded glycoproteins. Moreover, the names do not correspond to a preference of these enzymes for which of the three mannose branches these trim first. | |||
REACT_25399 (Reactome) | Addition of a fucose moiety as an alpha 1-6 linkage to the first GlcNAc residue of the N-glycan (Clarke JL, Watkins WM 1999; Yamaguchi Y et al, 1999; Yamaguchi Y et al 2000). | |||
REACT_652 (Reactome) | Dolichyl phosphate D-mannose is flipped in the endoplasmic reticulum membrane so that its mannose moiety is oriented inwards, towards the endoplasmic reticulum lumen, where it is accessible to transferases catalyzing the synthesis of glycolipids and glycoproteins (Kinoshita and Inoue 2000). | |||
RFT1 | REACT_22262 (Reactome) | |||
SAR1B | Arrow | REACT_12456 (Reactome) | ||
SEC13 | Arrow | REACT_12456 (Reactome) | ||
SEC13 | REACT_12422 (Reactome) | |||
SEC23A | Arrow | REACT_12456 (Reactome) | ||
SEC31A | Arrow | REACT_12456 (Reactome) | ||
SEC31A | REACT_12422 (Reactome) | |||
ST3GAL4 | REACT_25121 (Reactome) | |||
ST6GAL1 | REACT_24990 (Reactome) | |||
ST8SIAs | REACT_25115 (Reactome) | |||
Sar1b GDP Complex | Arrow | REACT_12396 (Reactome) | ||
Sar1b GDP Complex | REACT_12554 (Reactome) | |||
Sar1b
GTP Sec23p Sec24p | REACT_12396 (Reactome) | |||
Sar1b
GTP Sec23p Sec24p | REACT_12422 (Reactome) | |||
Sar1b GTP Complex | Arrow | REACT_12554 (Reactome) | ||
Sar1b GTP Complex | REACT_12393 (Reactome) | |||
Sar1b
Sec23p Sec24p Sec13p Sec31p Complex | REACT_12456 (Reactome) | |||
Sec23p Sec24p Complex | Arrow | REACT_12396 (Reactome) | ||
Sec23p Sec24p Complex | REACT_12393 (Reactome) | |||
Sec24 | Arrow | REACT_12456 (Reactome) | ||
UDP-AcGlcN | Arrow | REACT_22397 (Reactome) | ||
UDP-AcGlcN | REACT_22147 (Reactome) | |||
UDP-AcGlcN | REACT_22332 (Reactome) | |||
UDP-Gal | REACT_25178 (Reactome) | |||
UDP-GlcNAc | REACT_25005 (Reactome) | |||
UDP-GlcNAc | REACT_25009 (Reactome) | |||
UDP-GlcNAc | REACT_25236 (Reactome) | |||
UDP-GlcNAc | REACT_25253 (Reactome) | |||
UDP-GlcNAc | REACT_25314 (Reactome) | |||
UDP-Glc | REACT_22143 (Reactome) | |||
UDP | Arrow | REACT_22332 (Reactome) | ||
UDP | Arrow | REACT_25236 (Reactome) | ||
UGGT1/2 | REACT_25264 (Reactome) | |||
UMP | Arrow | REACT_22147 (Reactome) | ||
UTP | REACT_22397 (Reactome) | |||
glucosidase II | REACT_23791 (Reactome) | |||
glucosidase II | REACT_23850 (Reactome) | |||
unfolded protein | Arrow | REACT_22208 (Reactome) | ||
unfolded protein | Arrow | REACT_23850 (Reactome) | ||
unfolded protein | Arrow | REACT_23855 (Reactome) | ||
unfolded protein | Arrow | REACT_24995 (Reactome) | ||
unfolded protein | Arrow | REACT_25093 (Reactome) | ||
unfolded protein | Arrow | REACT_25126 (Reactome) | ||
unfolded protein | Arrow | REACT_25207 (Reactome) | ||
unfolded protein | Arrow | REACT_25264 (Reactome) | ||
unfolded protein | Arrow | REACT_25313 (Reactome) | ||
unfolded protein | REACT_23778 (Reactome) | |||
unfolded protein | REACT_23783 (Reactome) | |||
unfolded protein | REACT_23831 (Reactome) | |||
unfolded protein | REACT_25207 (Reactome) | |||
unfolded protein glycan | Arrow | REACT_23791 (Reactome) | ||
unfolded protein | REACT_22208 (Reactome) |