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Rojas R, Segovia C, Trombert AN, Santander J, Manque P. The effect of tunicamycin on the glucose uptake, growth, and cellular adhesion in the protozoan parasite Crithidia fasciculata. Curr Microbiol 2014; 69:541-8. [PMID: 24894907 DOI: 10.1007/s00284-014-0620-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/08/2014] [Indexed: 01/17/2023]
Abstract
Crithidia fasciculata represents a very interesting model organism to study biochemical, cellular, and genetic processes unique to members of the family of the Trypanosomatidae. Thus, C. fasciculata parasitizes several species of insects and has been widely used to test new therapeutic strategies against parasitic infections. By using tunicamycin, a potent inhibitor of glycosylation in asparaginyl residues of glycoproteins (N-glycosylation), we demonstrate that N-glycosylation in C. fasciculata cells is involved in modulating glucose uptake, dramatically impacting growth, and cell adhesion. C. fasciculata treated with tunicamycin was severely affected in their ability to replicate and to adhere to polystyrene substrates and losing their ability to aggregate into small and large groups. Moreover, under tunicamycin treatment, the parasites were considerably shorter and rounder and displayed alterations in cytoplasmic vesicles formation. Furthermore, glucose uptake was significantly impaired in a tunicamycin dose-dependent manner; however, no cytotoxic effect was observed. Interestingly, this effect was reversible. Thus, when tunicamycin was removed from the culture media, the parasites recovered its growth rate, cell adhesion properties, and glucose uptake. Collectively, these results suggest that changes in the tunicamycin-dependent glycosylation levels can influence glucose uptake, cell growth, and adhesion in the protozoan parasite C. fasciculata.
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Affiliation(s)
- Robert Rojas
- Nucleus for Microbiology and Immunity, Center for Genomics and Bioinformatics, Faculty of Sciences, Universidad Mayor, Campus Huechuraba, Camino La Pirámide 5750, Huechuraba, Santiago, Chile,
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2
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Abstract
Proteins following the secretory pathway acquire their proper tertiary and in certain cases also quaternary structures in the endoplasmic reticulum (ER). Incompletely folded species are retained in the ER and eventually degraded. One of the molecular mechanisms by which cells achieve this conformational sorting is based on monoglucosylated N-glycans (Glc1Man5-9GlcNAc2) present on nascent glycoproteins in the ER. This chapter discusses two of the steps that regulate the abundance of such N-glycan structures, including glycoprotein deglucosylation (by glucosidase II) and reglucosylation (by the UDP-Glc:glycoprotein glucosyltransferase), as well as an overview of methods to evaluate the N-glycans prevalent during glycoprotein biogenesis in the ER.
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Affiliation(s)
- E Sergio Trombetta
- Department of Cell Biology, Yale University School of Medicine, P.O. Box 208002, New Haven, CT 06520-8002, USA.
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Trombetta ES, Helenius A. Conformational requirements for glycoprotein reglucosylation in the endoplasmic reticulum. J Cell Biol 2000; 148:1123-29. [PMID: 10725325 PMCID: PMC2174309 DOI: 10.1083/jcb.148.6.1123] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/1999] [Accepted: 02/08/2000] [Indexed: 11/26/2022] Open
Abstract
Newly synthesized glycoproteins interact during folding and quality control in the ER with calnexin and calreticulin, two lectins specific for monoglucosylated oligosaccharides. Binding and release are regulated by two enzymes, glucosidase II and UDP-Glc:glycoprotein:glycosyltransferase (GT), which cyclically remove and reattach the essential glucose residues on the N-linked oligosaccharides. GT acts as a folding sensor in the cycle, selectively reglucosylating incompletely folded glycoproteins and promoting binding of its substrates to the lectins. To investigate how nonnative protein conformations are recognized and directed to this unique chaperone system, we analyzed the interaction of GT with a series of model substrates with well defined conformations derived from RNaseB. We found that conformations with slight perturbations were not reglucosylated by GT. In contrast, a partially structured nonnative form was efficiently recognized by the enzyme. When this form was converted back to a nativelike state, concomitant loss of recognition by GT occurred, reproducing the reglucosylation conditions observed in vivo with isolated components. Moreover, fully unfolded conformers were poorly recognized. The results indicated that GT is able to distinguish between different nonnative conformations with a distinct preference for partially structured conformers. The findings suggest that discrete populations of nonnative conformations are selectively reglucosylated to participate in the calnexin/calreticulin chaperone pathway.
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Affiliation(s)
- E S Trombetta
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002, USA.
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Labriola C, Cazzulo JJ, Parodi AJ. Trypanosoma cruzi calreticulin is a lectin that binds monoglucosylated oligosaccharides but not protein moieties of glycoproteins. Mol Biol Cell 1999; 10:1381-94. [PMID: 10233151 PMCID: PMC25283 DOI: 10.1091/mbc.10.5.1381] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Trypanosoma cruzi is a protozoan parasite that belongs to an early branch in evolution. Although it lacks several features of the pathway of protein N-glycosylation and oligosaccharide processing present in the endoplasmic reticulum of higher eukaryotes, it displays UDP-Glc:glycoprotein glucosyltransferase and glucosidase II activities. It is herewith reported that this protozoan also expresses a calreticulin-like molecule, the third component of the quality control of glycoprotein folding. No calnexin-encoding gene was detected. Recombinant T. cruzi calreticulin specifically recognized free monoglucosylated high-mannose-type oligosaccharides. Addition of anti-calreticulin serum to extracts obtained from cells pulse-chased with [35S]Met plus [35S]Cys immunoprecipitated two proteins that were identified as calreticulin and the lysosomal proteinase cruzipain (a major soluble glycoprotein). The latter but not the former protein disappeared from immunoprecipitates upon chasing cells. Contrary to what happens in mammalian cells, addition of the glucosidase II inhibitor 1-deoxynojirimycin promoted calreticulin-cruzipain interaction. This result is consistent with the known pathway of protein N-glycosylation and oligosaccharide processing occurring in T. cruzi. A treatment of the calreticulin-cruzipain complexes with endo-beta-N-acetylglucosaminidase H either before or after addition of anti-calreticulin serum completely disrupted calreticulin-cruzipain interaction. In addition, mature monoglucosylated but not unglucosylated cruzipain isolated from lysosomes was found to interact with recombinant calreticulin. It was concluded that the quality control of glycoprotein folding appeared early in evolution, and that T. cruzi calreticulin binds monoglucosylated oligosaccharides but not the protein moiety of cruzipain. Furthermore, evidence is presented indicating that glucosyltransferase glucosylated cruzipain at its last folding stages.
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Affiliation(s)
- C Labriola
- Instituto de Investigaciones Bioquímicas Fundación Campomar, 1405 Buenos Aires, Argentina
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Fanchiotti S, Fernández F, D'Alessio C, Parodi AJ. The UDP-Glc:Glycoprotein glucosyltransferase is essential for Schizosaccharomyces pombe viability under conditions of extreme endoplasmic reticulum stress. J Cell Biol 1998; 143:625-35. [PMID: 9813085 PMCID: PMC2148152 DOI: 10.1083/jcb.143.3.625] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/1998] [Revised: 08/26/1998] [Indexed: 11/25/2022] Open
Abstract
Interaction of monoglucosylated oligosaccharides with ER lectins (calnexin and/or calreticulin) facilitates glycoprotein folding but this interaction is not essential for cell viability under normal conditions. We obtained two distinct single Schizosaccharomyces pombe mutants deficient in either one of the two pathways leading to the formation of monoglucosylated oligosaccharides. The alg6 mutant does not glucosy- late lipid-linked oligosaccharides and transfers Man9GlcNAc2 to nascent polypeptide chains and the gpt1 mutant lacks UDP-Glc:glycoprotein glucosyltransferase (GT). Both single mutants grew normally at 28 degreesC. On the other hand, gpt1/alg6 double-mutant cells grew very slowly and with a rounded morphology at 28 degreesC and did not grow at 37 degreesC. The wild-type phenotype was restored by transfection of the double mutant with a GT-encoding expression vector or by addition of 1 M sorbitol to the medium, indicating that the double mutant is affected in cell wall formation. It is suggested that facilitation of glycoprotein folding mediated by the interaction of monoglucosylated oligosaccharides with calnexin is essential for cell viability under conditions of extreme ER stress such as underglycosylation of proteins caused by the alg6 mutation and high temperature. In contrast, gls2/alg6 double-mutant cells that transfer Man9GlcNAc2 and that are unable to remove the glucose units added by GT as they lack glucosidase II (GII), grew at 37 degreesC and had, when grown at 28 degreesC, a phenotype of growth and morphology almost identical to that of wild-type cells. These results indicate that facilitation of glycoprotein folding mediated by the interaction of calnexin and monoglucosylated oligosaccharides does not necessarily require cycles of reglucosylation-deglucosylation catalyzed by GT and GII.
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Affiliation(s)
- S Fanchiotti
- Instituto de Investigaciones Bioquímicas Fundación Campomar, 1405 Buenos Aires, Argentina
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Parodi AJ. The quality control of glycoprotein folding in the endoplasmic reticulum, a trip from trypanosomes to mammals. Braz J Med Biol Res 1998; 31:601-14. [PMID: 9698764 DOI: 10.1590/s0100-879x1998000500002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The present review deals with the stages of synthesis and processing of asparagine-linked oligosaccharides occurring in the lumen of the endoplasmic reticulum and their relationship to the acquisition by glycoproteins of their proper tertiary structures. Special emphasis is placed on reactions taking place in trypanosomatid protozoa since their study has allowed the detection of the transient glucosylation of glycoproteins catalyzed by UDP-Glc:glycoprotein glucosyltransferase and glucosidase II. The former enzyme has the unique property of covalently tagging improperly folded conformations by catalyzing the formation of protein-linked Glc1Man7GlcNAc2, Glc1Man8GlcNac2 and Glc1Man9GlcNAc2 from the unglucosylated proteins. Glucosyl-transferase is a soluble protein of the endoplasmic reticulum that recognizes protein domains exposed in denatured but not in native conformations (probably hydrophobic amino acids) and the innermost N-acetylglucosamine unit that is hidden from macromolecular probes in most native glycoproteins. In vivo, the glucose units are removed by glucosidase II. The influence of oligosaccharides in glycoprotein folding is reviewed as well as the participation of endoplasmic reticulum chaperones (calnexin and calreticulin) that recognize monoglucosylated species in the same process. A model for the quality control of glycoprotein folding in the endoplasmic reticulum, i.e., the mechanism by which cells recognize the tertiary structure of glycoproteins and only allow transit to the Golgi apparatus of properly folded species, is discussed. The main elements of this control are calnexin and calreticulin as retaining components, the UDP-Glc:glycoprotein glucosyltransferase as a sensor of tertiary structures and glucosidase II as the releasing agent.
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Affiliation(s)
- A J Parodi
- Instituto de Investigaciones Bioquímicas, Fundación Campomar, Buenos Aires, Argentina.
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Chapter 2b Glycoproteins of parasites. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0167-7306(08)60281-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Kelley RJ, Brickman MJ, Balber AE. Processing and transport of a lysosomal membrane glycoprotein is developmentally regulated in African trypanosomes. Mol Biochem Parasitol 1995; 74:167-78. [PMID: 8719158 DOI: 10.1016/0166-6851(95)02493-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We have used pulse-chase immunoprecipitations methods to study early post-translational processing of CBI-gp, a lysosomal membrane glycoprotein expressed by African trypanosomes, Rap67, a polyclonal antibody to CBI-gp, immunoprecipitated a 100-kDa glycoprotein, gp100, from both bloodstream forms (BF) and procyclic forms (PF) of Trypanosoma brucei gambiense immediately after a 5-min pulse with radiomethionine. N-Glycanase digestion released a 67-kDa core protein, p67, from gp100 of both life cycle forms V8 protease digestion of p67 from BF and PF yielded 13 identical methionyl peptides, suggesting that gp100 from both life cycle forms have very similar or identical p67 core molecules. In BF, gp 100 carried both endoglycosidase H (EndoH)-resistant and EndoH-sensitive, N-linked oligosaccharides immediately after labeling. In PF, all the N-linked sugars on gp100 were EndoH sensitive. In BF, gp100 chased progressively into slower migrating 150-180-kDa components that obtained the CBI epitope, traveled to the cell surface where they could be biotinylated, and were proteolytically processed. The increase in mass of gp100 during chase in BF resulted from an elongation of N-linked oligosaccharides. Maturation of gp100 into 150-180-kDa CBI-gp was inhibited if BF were chased in the presence of glucosidase inhibitors castanospermine or deoxynojirimycin. In PF, gp100 did not increase in mass, could not be biotinylated on the cell surface, and was not proetolyzed during extended chases. Cryoimmunoelectron microscopy revealed that the antigens detected by rap67 are abundant in lysosomes and endosomes in both BF and PF. Thus, BF and PF express very similar or identical lysosomal membrane glycoproteins but process and transport them in very different ways.
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Affiliation(s)
- R J Kelley
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
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Fernández FS, Trombetta SE, Hellman U, Parodi AJ. Purification to homogeneity of UDP-glucose:glycoprotein glucosyltransferase from Schizosaccharomyces pombe and apparent absence of the enzyme fro Saccharomyces cerevisiae. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)43870-7] [Citation(s) in RCA: 86] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Helenius A. How N-linked oligosaccharides affect glycoprotein folding in the endoplasmic reticulum. Mol Biol Cell 1994; 5:253-65. [PMID: 8049518 PMCID: PMC301034 DOI: 10.1091/mbc.5.3.253] [Citation(s) in RCA: 475] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- A Helenius
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510
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Parodi AJ. Biosynthesis of protein-linked oligosaccharides in trypanosomatid flagellates. ACTA ACUST UNITED AC 1993; 9:373-7. [PMID: 15463672 DOI: 10.1016/0169-4758(93)90086-u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this article, Armando Parodi presents a summary of the knowledge of the structure and biosynthesis of mammalian Asn-linked (N-linked) oligosacchorides and compares this with what is known in trypanosomatids.
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Affiliation(s)
- A J Parodi
- Instituto de Investigociones Bioquímicas Fundación Campomar, Antonio Machado 151, 1405 Buenos Aires, Argentina
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12
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Purification to apparent homogeneity and partial characterization of rat liver UDP-glucose:glycoprotein glucosyltransferase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50413-6] [Citation(s) in RCA: 110] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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13
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Sousa MC, Ferrero-Garcia MA, Parodi AJ. Recognition of the oligosaccharide and protein moieties of glycoproteins by the UDP-Glc:glycoprotein glucosyltransferase. Biochemistry 1992; 31:97-105. [PMID: 1531024 DOI: 10.1021/bi00116a015] [Citation(s) in RCA: 248] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
It was found, in cell-free assays, that the Man8GlcNAc2 and Man7GlcNAc2 isomers having the mannose unit to which the glucose is added were glucosylated by the rat liver glucosyltransferase at 50 and 15%, respectively, of the rate of Man9GlcNAc2 glucosylation. This indicates that processing by endoplasmic reticulum mannosidases decreases the extent of glycoprotein glucosylation. All five different glycoproteins tested (bovine and porcine thyroglobulins, phytohemagglutinin, soybean agglutinin, and bovine pancreas ribonuclease B) were found to be poorly glucosylated or not glucosylated unless they were subjected to treatments that modified their native conformations. The effect of denaturation was not to expose the oligosaccharides but to make protein determinants, required for enzymatic activity, accessible to the glucosyltransferase because (a) cleavage of denatured glycoproteins by unspecific (Pronase) or specific (trypsin) proteases abolished their glucose acceptor capacities almost completely except when the tryptic peptides were held together by disulfide bonds and (b) high mannose oligosaccharides in native glycoproteins, although poorly glucosylated or not glucosylated, were accessible to macromolecular probes as concanavalin A-Sepharose, endo-beta-N-acetylglucosaminidase H, and jack bean alpha-mannosidase. In addition, denatured, endo-beta-N-acetylglucosaminidase H deglycosylated glycoproteins were found to be potent inhibitors of the glucosylation of denatured glycoproteins. It is suggested that in vivo only unfolded, partially folded, and malfolded glycoproteins are glucosylated and that glucosylation stops upon adoption of the correct conformation, a process that hides the protein determinants (possibly hydrophobic amino acids) from the glucosyltransferase.
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Affiliation(s)
- M C Sousa
- Instituto de Investigaciones Bioquimicas, Fundación Campomar, Buenos Aires, Argentina
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