51
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Abstract
The flagellum and flagellar pocket are distinctive organelles present among all of the trypanosomatid protozoa. Currently, recognized functions for these organelles include generation of motility for the flagellum and dedicated secretory and endocytic activities for the flagellar pocket. The flagellar and flagellar pocket membranes have long been recognized as morphologically separate domains that are component parts of the plasma membrane that surrounds the entire cell. The structural and functional specialization of these two membranes has now been underscored by the identification of multiple proteins that are targeted selectively to each of these domains, and non-membrane proteins have also been identified that are targeted to the internal lumina of these organelles. Investigations on the functions of these organelle-specific proteins should continue to shed light on the unique biological activities of the flagellum and flagellar pocket. In addition, work has begun on identifying signals or modifications of these proteins that direct their targeting to the correct subcellular location. Future endeavors should further refine our knowledge of targeting signals and begin to dissect the molecular machinery involved in transporting and retaining each polypeptide at its designated cellular address.
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Affiliation(s)
- S M Landfear
- Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, 97201, Portland, OR, USA.
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52
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Abstract
Glycoconjugates are abundant and ubiquitious on the surface of many protozoan parasites. Their tremendous diversity has implicated their critical importance in the life cycle of these organisms. This review highlights our current knowledge of the major glycoconjugates, with particular emphasis on their structures, of representative protozoan parasites, including Leishmania, Trypanosoma, Giardia, Plasmodia, and others.
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Affiliation(s)
- A Guha-Niyogi
- Department of Molecular and Cellular Biochemistry, University of Kentucky Medical Center, Lexington KY 40536, USA
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53
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Hicks SJ, Theodoropoulos G, Carrington SD, Corfield AP. The role of mucins in host-parasite interactions. Part I-protozoan parasites. PARASITOLOGY TODAY (PERSONAL ED.) 2000; 16:476-81. [PMID: 11063858 DOI: 10.1016/s0169-4758(00)01773-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Parasite-derived mucin-like molecules might be involved in parasite attachment to and invasion of host cells. In addition, parasites might secrete mucin-degrading enzymes, enabling the penetration of protective mucus gels that overlie the mucosal surfaces of their potential hosts. Furthermore, they might generate binding ligands on the membrane-bound mucins of host cells by using specific glycosidases. It is possible that host mucins and mucin-like molecules prevent the establishment of parasites or facilitate parasite expulsion. They might also serve as a source of metabolic energy and adhesion ligands for those parasites adapted to exploit them. Sally Hicks and colleagues here review the biochemical properties of mucins and mucin-like molecules in relation to interactions (established and putative) between protozoan parasites and their hosts.
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Affiliation(s)
- S J Hicks
- Centre for Biomedical Sciences, School of Applied Sciences, University of Wales Institute Cardiff, Cardiff, UK.
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54
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Abstract
Proteophosphoglycans are an expanding family of highly glycosylated Leishmania proteins with many unusual and some unique structural features. The novel protein-glycan linkage in proteophosphoglycans - phosphoglycosylation of Ser by lipophosphoglycan-like structures - emerges as a major form of protein glycosylation in Leishmania. Here, Thomas Ilg reviews the chemical structure, the ultrastructure, the genes and the potential functions of different members of this novel family of parasite glycoproteins.
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Affiliation(s)
- T Ilg
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Corrensstrasse 38, 72076 Tübingen, Germany.
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55
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Späth GF, Epstein L, Leader B, Singer SM, Avila HA, Turco SJ, Beverley SM. Lipophosphoglycan is a virulence factor distinct from related glycoconjugates in the protozoan parasite Leishmania major. Proc Natl Acad Sci U S A 2000; 97:9258-63. [PMID: 10908670 PMCID: PMC16855 DOI: 10.1073/pnas.160257897] [Citation(s) in RCA: 233] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protozoan parasites of the genus Leishmania undergo a complex life cycle involving transmission by biting sand flies and replication within mammalian macrophage phagolysosomes. A major component of the Leishmania surface coat is the glycosylphosphatidylinositol (GPI)-anchored polysaccharide called lipophosphoglycan (LPG). LPG has been proposed to play many roles in the infectious cycle, including protection against complement and oxidants, serving as the major ligand for macrophage adhesion, and as a key factor mitigating host responses by deactivation of macrophage signaling pathways. However, all structural domains of LPG are shared by other major surface or secretory products, providing a biochemical redundancy that compromises the ability of in vitro tests to establish whether LPG itself is a virulence factor. To study truly lpg(-) parasites, we generated Leishmania major lacking the gene LPG1 [encoding a putative galactofuranosyl (Gal(f)) transferase] by targeted gene disruption. The lpg1(-) parasites lacked LPG but contained normal levels of related glycoconjugates and GPI-anchored proteins. Infections of susceptible mice and macrophages in vitro showed that these lpg(-) Leishmania were highly attenuated. Significantly and in contrast to previous LPG mutants, reintroduction of LPG1 into the lpg(-) parasites restored virulence. Thus, genetic approaches allow dissection of the roles of this complex family of interrelated parasite virulence factors, and definitively establish the role of LPG itself as a parasite virulence factor. Because the lpg1(-) mutant continue to synthesize bulk GPI-anchored Gal(f)-containing glycolipids other than LPG, a second pathway distinct from the Golgi-associated LPG synthetic compartment must exist.
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Affiliation(s)
- G F Späth
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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56
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Mreyen M, Champion A, Srinivasan S, Karuso P, Williams KL, Packer NH. Multiple O-glycoforms on the spore coat protein SP96 in Dictyostelium discoideum. Fuc(alpha1-3)GlcNAc-alpha-1-P-Ser is the major modification. J Biol Chem 2000; 275:12164-74. [PMID: 10766852 DOI: 10.1074/jbc.275.16.12164] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A decreased level of fucosylation on certain spore coat proteins of Dictyostelium discoideum alters the permeability of the spore coat. Here the post-translational modifications of a major spore coat protein, SP96, are studied in a wild type strain (X22) and a fucosylation-defective mutant (HU2470). A novel phosphoglycan structure on SP96 of the wild type strain, consisting of Fuc(alpha1-3)GlcNAc-alpha-1-P-Ser(,) was identified by electrospray ionization mass spectrometry and NMR. It was shown using monosaccharide and gas chromatography mass spectrometry analysis that SP96 in the mutant HU2470 contained approximately 20% of wild type levels of fucose, as a result of a missing terminal fucose on the novel glycan structure. The results support previous predictions, based on inhibition studies on different fucose-deficient strains, about the nature of monoclonal antibody epitopes identified by monoclonal antibodies MUD62 and MUD166, which are known to identify O-linked glycans (Champion, A., Griffiths, K., Gooley, A. A., Gonzalez, B. Y., Gritzali, M., West, C. M., and Williams, K. L. (1995) Microbiology 141, 785-797). Quantitative studies on wild type SP96 indicated that there were approximately 60 sites with phosphodiester-linked N-acetylglucosamine-fucose disaccharide units and a further approximately 20 sites with fucose directly linked to the protein. Over 70% of the serine sites are modified, with less than 1% of these sites as phosphoserine. Threonine and tyrosine residues were not found to be modified.
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Affiliation(s)
- M Mreyen
- Macquarie University Centre for Analytical Biotechnology, Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
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57
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Moody-Haupt S, Patterson JH, Mirelman D, McConville MJ. The major surface antigens of Entamoeba histolytica trophozoites are GPI-anchored proteophosphoglycans. J Mol Biol 2000; 297:409-20. [PMID: 10715210 DOI: 10.1006/jmbi.2000.3577] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Trophozoites of the parasitic protozoa, Entamoeba histolytica, synthesize a cell surface lipoglycoconjugate, termed lipophosphoglycan, which is thought to be an important virulence factor and potential vaccine candidate against invasive amebiasis. Here, we show that the E. histolytica lipophosphoglycans are in fact glycosylphosphatidylinositol (GPI)-anchored proteophosphoglycans (PPGs). These PPGs contain a highly acidic polypeptide component which is rich in Asp, Glu and phosphoserine residues. This polypeptide component is extensively modified with linear glycan chains having the general structure, [Glcalpha1-6](n)Glcbeta1-6Gal (where n=2-23). These glycan chains can be released after mild-acid hydrolysis with trifluoroacetic or hydrofluoric acid and are probably attached to phosphoserine residues in the polypeptide backbone. The PPGs are further modified with a GPI anchor which differs from all other eukaryotic GPI anchors so far characterized in containing a glycan core with the structure, Gal(1)Man(2)GlcN-myo-inositol, and in being heterogeneously modified with chains of alpha-galactose. Trophozoites of the pathogenic HM-1:IMSS strain synthesize two distinct classes of PPG which have polydisperse molecular masses of 50-180 kDa (PPG-1) and 35-60 kDa (PPG-2) and are modified with glucan side-chains of different average lengths. In contrast, the non-pathogenic Rahman strain synthesizes one class of PPG which is only elaborated with short disaccharide side-chains (i.e. Glcbeta1-6Gal). However, the PPGs are abundant in all strains (8x10(7) copies per cell) and are likely to form a protective surface coat.
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Affiliation(s)
- S Moody-Haupt
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
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58
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Sacks DL, Modi G, Rowton E, Späth G, Epstein L, Turco SJ, Beverley SM. The role of phosphoglycans in Leishmania-sand fly interactions. Proc Natl Acad Sci U S A 2000; 97:406-11. [PMID: 10618431 PMCID: PMC26676 DOI: 10.1073/pnas.97.1.406] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Leishmania promastigotes synthesize an abundance of phosphoglycans, either attached to the cell surface through phosphatidylinositol anchors (lipophosphoglycan, LPG) or secreted as protein-containing glycoconjugates. These phosphoglycans are thought to promote the survival of the parasite within both its vertebrate and invertebrate hosts. The relative contributions of different phosphoglycan-containing molecules in Leishmania-sand fly interactions were tested by using mutants specifically deficient in either total phosphoglycans or LPG alone. Leishmania donovani promastigotes deficient in both LPG and protein-linked phosphoglycans because of loss of LPG2 (encoding the Golgi GDP-Man transporter) failed to survive the hydrolytic environment within the early blood-fed midgut. In contrast, L. donovani and Leishmania major mutants deficient solely in LPG expression because of loss of LPG1 (involved in biosynthesis of the core oligosaccharide LPG domain) had only a slight reduction in the survival and growth of promastigotes within the early blood-fed midgut. The ability of the LPG1-deficient promastigotes to persist in the midgut after blood meal excretion was completely lost, and this defect was correlated with their inability to bind to midgut epithelial cells in vitro. For both mutants, when phosphoglycan expression was restored to wild-type levels by reintroduction of LPG1 or LPG2 (as appropriate), then the wild-type phenotype was also restored. We conclude, first, that LPG is not essential for survival in the early blood-fed midgut but, along with other secreted phosphoglycan-containing glycoconjugates, can protect promastigotes from the digestive enzymes in the gut and, second, that LPG is required to mediate midgut attachment and to maintain infection in the fly during excretion of the digested blood meal.
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Affiliation(s)
- D L Sacks
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA.
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59
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Klein C, Göpfert U, Goehring N, Stierhof YD, Ilg T. Proteophosphoglycans of Leishmania mexicana. Identification, purification, structural and ultrastructural characterization of the secreted promastigote proteophosphoglycan pPPG2, a stage-specific glycoisoform of amastigote aPPG. Biochem J 1999; 344 Pt 3:775-86. [PMID: 10585864 PMCID: PMC1220699 DOI: 10.1042/bj3440775] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Protozoan parasites of the genus Leishmania secrete a range of proteophosphoglycans that appear to be important for successful colonization of the sandfly and for virulence in the mammalian host. A hallmark of these molecules is extensive phosphoglycosylation by phosphoglycan chains via the unusual linkage Manalpha1-PO(4)-Ser. In this study we have identified and purified to apparent homogeneity a novel proteophosphoglycan (pPPG2) which is secreted by Leishmania mexicana promastigotes (sandfly stage). Amino acid analysis and immunoblots using polypeptide-specific antisera suggest that pPPG2 shares a common protein backbone with a proteophosphoglycan (aPPG) secreted by Leishmania mexicana amastigotes (mammalian stage). Both pPPG2 and aPPG show a similar degree of Ser phosphoglycosylation (50. 5 mol% vs. 44.6 mol%), but the structure of their phosphoglycan chains is developmentally regulated: in contrast to aPPG which displays unique, complex and highly branched glycan chains [Ilg, Craik, Currie, Multhaup, and Bacic (1998) J. Biol. Chem. 273, 13509-13523], pPPG2 contains short unbranched structures consisting of >60 mol% neutral glycans, most likely (Manalpha1-2)(0-5)Man and Galbeta1-4Man, as well as about 40 mol% monophosphorylated glycans of the proposed structures PO(4)-6Galbeta1-4Man and PO(4)-6(Glcbeta1-3)Galbeta1-4Man. The major differences between pPPG2 and aPPG with respect to their apparent molecular mass, their ultrastructure and their proteinase sensitivity are most likely a consequence of this stage-specific glycosylation of their common protein backbone.
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Affiliation(s)
- C Klein
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie Corrensstrasse 38, D-72076 Tübingen, Germany
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60
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Göpfert U, Goehring N, Klein C, Ilg T. Proteophosphoglycans of Leishmania mexicana. Molecular cloning and characterization of the Leishmania mexicana ppg2 gene encoding the proteophosphoglycans aPPG and pPPG2 that are secreted by amastigotes and promastigotes. Biochem J 1999; 344 Pt 3:787-95. [PMID: 10585865 PMCID: PMC1220700 DOI: 10.1042/bj3440787] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Intracellular amastigotes of the pathogenic protozoon Leishmania mexicana secrete an extensively phosphoglycosylated proteophosphoglycan (aPPG) into the phagolysosome of mammalian host macrophages, that appears to fulfil important functions for the parasites. Promastigotes (the sandfly vector forms) of the same species secrete a proteophosphoglycan with identical protein backbone but exhibiting stage-specific phosphoglycosylation patterns [Klein, Göpfert, Goehring, Stierhof and Ilg (1999) Biochem. J. 344, 775-786]. In this study we report the cloning of the novel repeat-containing proteophosphoglycan gene ppg2 by antibody screening of a Leishmania mexicana amastigote cDNA expression library. ppg2 is equally expressed in promastigotes and amastigotes at the mRNA level. Targeted gene replacement of both alleles of the single copy gene ppg2 results in the loss of pPPG2 expression in promastigotes. Antisera against Escherichia coli-expressed ppg2 recognize the deglycosylated forms of aPPG as well as pPPG2. These results confirm that ppg2 encodes the protein backbones of aPPG and pPPG2. An unusual finding is that ppg2 exhibits two stable allelic forms, ppg2a and ppg2b. Their main difference lies in the number of central 72 bp DNA repeats (7 versus 8). ppg2a and ppg2b encode polypeptide chains of 574 and 598 amino acids, respectively, that show no homology to known proteins. The novel 24 amino acid Ser-rich peptide repeats encoded by the 72 bp DNA repeats are targets for Ser phosphoglycosylation in Leishmania mexicana.
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Affiliation(s)
- U Göpfert
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Corrensstrasse 38, D-72076 Tübingen, Germany
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61
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Higson AP, Tsvetkov YE, Ferguson MA, Nikolaev AV. The synthesis of Leishmania major phosphoglycan fragments. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(99)01946-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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62
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Abstract
Leishmania are digenetic protozoa which inhabit two highly specific hosts, the sandfly, where they grow as motile flagellated promastigotes in the gut, and the mammalian macrophage, where they survive and grow intracellularly as non-flagellated amastigotes in the phagolysosome. Leishmaniasis is the outcome of an evolutionary 'arms race' between the host's immune system and the parasite's evasion mechanisms, which ensure survival and transmission in the population. The diverse spectrum of patterns and severity of disease reflect the varying contributions of parasite virulence factors and host responses, some of which act in a host protective manner while others exacerbate disease. This chapter describes the interaction of the Leishmania with their hosts, with emphasis on the molecules and mechanisms evolved by the parasites to avoid, subvert or exploit the environments in the sandfly and the macrophage, and to move from one to the other.
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Affiliation(s)
- E Handman
- Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria, Australia
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63
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Ilg T, Montgomery J, Stierhof YD, Handman E. Molecular cloning and characterization of a novel repeat-containing Leishmania major gene, ppg1, that encodes a membrane-associated form of proteophosphoglycan with a putative glycosylphosphatidylinositol anchor. J Biol Chem 1999; 274:31410-20. [PMID: 10531342 DOI: 10.1074/jbc.274.44.31410] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Leishmania parasites secrete a variety of proteins that are modified by phosphoglycan chains structurally similar to those of the cell surface glycolipid lipophosphoglycan. These proteins are collectively called proteophosphoglycans. We report here the cloning and sequencing of a novel Leishmania major proteophosphoglycan gene, ppg1. It encodes a large polypeptide of approximately 2300 amino acids. The N-terminal domain of approximately 70 kDa exhibits 11 imperfect amino acid repeats that show some homology to promastigote surface glycoproteins of the psa2/gp46 complex. The large central domain apparently consists exclusively of approximately 100 repetitive peptides of the sequence APSASSSSA(P/S)SSSSS(+/-S). Gene fusion experiments demonstrate that these peptide repeats are the targets of phosphoglycosylation in Leishmania and that they form extended filamentous structures reminiscent of mammalian mucins. The C-terminal domain contains a functional glycosylphosphatidylinositol anchor addition signal sequence, which confers cell surface localization to a normally secreted Leishmania acid phosphatase, when fused to its C terminus. Antibody binding studies show that the ppg1 gene product is phosphoglycosylated by phosphoglycan repeats and cap oligosaccharides. In contrast to previously characterized proteophosphoglycans, the ppg1 gene product is predominantly membrane-associated and it is expressed on the promastigote cell surface. Therefore this membrane-bound proteophosphoglycan may be important for direct host-parasite interactions.
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Affiliation(s)
- T Ilg
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Corrensstrasse 38, D-72076 Tübingen, Germany.
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64
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Abstract
Leishmaniasis is a major health problem to humans and is caused by one of the world's major pathogens, the Leishmania parasite. These protozoa have the remarkable ability to avoid destruction in hostile environments they encounter throughout their life cycle. That Leishmania parasites have adapted to not only survive, but to proliferate largely is due to the protection conferred by unique glycoconjugates that are either on the parasites' cell surface or secreted. Most of these specialized molecules are members of a family of phosphoglycans while others are a family of glycosylinositol phospholipids. Together they have been implicated in a surprisingly large number of functions for the parasites throughout their life cycle and, therefore, are key players in their pathogenesis. This review summarizes the biological roles of these glycoconjugates and how they are believed to contribute to Leishmania survival in destructive surroundings.
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Affiliation(s)
- A Descoteaux
- Institut Armand-Frappier, Université du Québec, Laval, Canada
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65
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Stierhof YD, Bates PA, Jacobson RL, Rogers ME, Schlein Y, Handman E, Ilg T. Filamentous proteophosphoglycan secreted by Leishmania promastigotes forms gel-like three-dimensional networks that obstruct the digestive tract of infected sandfly vectors. Eur J Cell Biol 1999; 78:675-89. [PMID: 10569240 DOI: 10.1016/s0171-9335(99)80036-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Development of Leishmania parasites in the digestive tract of their sandfly vectors involves several morphological transformations from the intracellular mammalian amastigote via a succession of free and gut wall-attached promastigote stages to the infective metacyclic promastigotes. At the foregut midgut transition of Leishmania-infected sandflies a gel-like plug of unknown origin and composition is formed, which contains high numbers of parasites, that occludes the gut lumen and which may be responsible for the often observed inability of infected sandflies to draw blood. This "blocked fly" phenotype has been linked to efficient transmission of infectious metacyclic promastigotes from the vector to the mammalian host. We show by immunofluorescence and immunoelectron microscopy on two Leishmania/sandfly vector combinations (Leishmania mexicana/Lutzomyia longipalpis and L. major/Phlebotomus papatasi) that the gel-like mass is formed mainly by a parasite-derived mucin-like filamentous proteophosphoglycan (fPPG) whereas the Leishmania polymeric secreted acid phosphatase (SAP) is not a major component of this plug. fPPG forms a dense three-dimensional network of filaments which engulf the promastigote cell bodies in a gel-like mass. We propose that the continuous secretion of fPPG by promastigotes in the sandfly gut, that causes plug formation, is an important factor for the efficient transmission to the mammalian host.
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Affiliation(s)
- Y D Stierhof
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen/Germany
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66
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Wiese M, Görcke I, Overath P. Expression and species-specific glycosylation of Leishmania mexicana secreted acid phosphatase in Leishmania major. Mol Biochem Parasitol 1999; 102:325-9. [PMID: 10498187 DOI: 10.1016/s0166-6851(99)00095-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- M Wiese
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany.
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67
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Piani A, Ilg T, Elefanty AG, Curtis J, Handman E. Leishmania major proteophosphoglycan is expressed by amastigotes and has an immunomodulatory effect on macrophage function. Microbes Infect 1999; 1:589-99. [PMID: 10611735 DOI: 10.1016/s1286-4579(99)80058-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteophosphoglycan (PPG) is a newly described mucin-like glycoprotein found on the surface of Leishmania major promastigotes and secreted in the culture supernatant. We show here that antigenically similar PPGs are present in several Leishmania species. PPG could also be detected on the surface of amastigotes and in small, parasite-free vesicles in infected macrophages. Because of the similarity of its carbohydrate chains to lipophosphoglycan, a parasite receptor for host macrophages, PPG was tested for binding to macrophages. PPG bound to macrophages and was internalized in a time-dependent manner. PPG inhibited the production of tumor necrosis factor-alpha and synergized with interferon-gamma to stimulate the production of nitric oxide by macrophages. PPG may contribute to the binding of Leishmania to host cells and may play a role in modulating the biology of the infected macrophage at the early stage of infection.
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MESH Headings
- Animals
- Antigens, Protozoan/chemistry
- Antigens, Protozoan/immunology
- Antigens, Protozoan/metabolism
- Antigens, Protozoan/pharmacology
- Cells, Cultured
- Drug Synergism
- Endocytosis
- Fluorescent Antibody Technique
- Glycosphingolipids/chemistry
- Interferon-gamma/pharmacology
- Kinetics
- Leishmania donovani/chemistry
- Leishmania donovani/immunology
- Leishmania major/chemistry
- Leishmania major/growth & development
- Leishmania major/immunology
- Leishmania major/metabolism
- Leishmania mexicana/chemistry
- Leishmania mexicana/immunology
- Lipopolysaccharides/antagonists & inhibitors
- Lipopolysaccharides/pharmacology
- Lysosomes/metabolism
- Macrophages, Peritoneal/drug effects
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/parasitology
- Membrane Proteins/chemistry
- Membrane Proteins/immunology
- Membrane Proteins/metabolism
- Membrane Proteins/pharmacology
- Mice
- Mice, Inbred C3H
- Nitric Oxide/biosynthesis
- Nitric Oxide/metabolism
- Proteoglycans/chemistry
- Proteoglycans/immunology
- Proteoglycans/metabolism
- Proteoglycans/pharmacology
- Protozoan Proteins
- Tumor Necrosis Factor-alpha/biosynthesis
- Tumor Necrosis Factor-alpha/immunology
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Affiliation(s)
- A Piani
- The Walter and Eliza Hall Institute of Medical Research, Victoria 3050, Australia
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68
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Moss JM, Reid GE, Mullin KA, Zawadzki JL, Simpson RJ, McConville MJ. Characterization of a novel GDP-mannose:Serine-protein mannose-1-phosphotransferase from Leishmania mexicana. J Biol Chem 1999; 274:6678-88. [PMID: 10037765 DOI: 10.1074/jbc.274.10.6678] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protozoan parasites of the genus Leishmania secrete a number of glycoproteins and mucin-like proteoglycans that appear to be important parasite virulence factors. We have previously proposed that the polypeptide backbones of these molecules are extensively modified with a complex array of phosphoglycan chains that are linked to Ser/Thr-rich domains via a common Manalpha1-PO4-Ser linkage (Ilg, T., Overath, P., Ferguson, M. A. J., Rutherford, T., Campbell, D. G., and McConville, M. J. (1994) J. Biol. Chem. 269, 24073-24081). In this study, we show that Leishmania mexicana promastigotes contain a peptide-specific mannose-1-phosphotransferase (pep-MPT) activity that adds Manalpha1-P to serine residues in a range of defined peptides. The presence and location of the Manalpha1-PO4-Ser linkage in these peptides were determined by electrospray ionization mass spectrometry and chemical and enzymatic treatments. The pep-MPT activity was solubilized in non-ionic detergents, was dependent on Mn2+, utilized GDP-Man as the mannose donor, and was expressed in all developmental stages of the parasite. The pep-MPT activity was maximal against peptides containing Ser/Thr-rich domains of the endogenous acceptors and, based on competition assays with oligosaccharide acceptors, was distinct from other leishmanial MPTs involved in the initiation and elongation of lipid-linked phosphoglycan chains. In subcellular fractionation experiments, pep-MPT was resolved from the endoplasmic reticulum marker BiP, but had an overlapping distribution with the cis-Golgi marker Rab1. Although Man-PO4 residues in the mature secreted glycoproteins are extensively modified with mannose oligosaccharides and phosphoglycan chains, similar modifications were not added to peptide-linked Man-PO4 residues in the in vitro assays. Similarly, Man-PO4 residues on endogenous polypeptide acceptors were also poorly extended, although the elongating enzymes were still active, suggesting that the pep-MPT activity and elongating enzymes may be present in separate subcellular compartments.
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Affiliation(s)
- J M Moss
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3052, Australia
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69
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van Casteren W. Characterisation and modification of the exopolysaccharide produced by Lactococcus lactis subsp. cremoris B40. Carbohydr Polym 1998. [DOI: 10.1016/s0144-8617(98)00044-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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70
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Stierhof YD, Wiese M, Ilg T, Overath P, Häner M, Aebi U. Structure of a filamentous phosphoglycoprotein polymer: the secreted acid phosphatase of Leishmania mexicana. J Mol Biol 1998; 282:137-48. [PMID: 9733646 DOI: 10.1006/jmbi.1998.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The insect stage of the protozoan parasite Leishmania mexicana secretes a filamentous acid phosphatase (secreted acid phosphatase, SAP), a polymeric phosphoglycoprotein. The wild-type (wt) SAP filament is a copolymer composed of two related gene products SAP1 and SAP2, which are identical in the enzymatically active NH2-terminal domain and the COOH-terminal domain, but differ in the length of a highly glycosylated Ser/Thr-rich repeat region (32 amino acids and 383 amino acids, respectively) which is located between these domains. When expressed separately, full length SAP1, SAP2, or the NH2-terminal domain alone, are able to assemble into filaments. The Ser/Thr-rich region is the exclusive target for a novel type of O-glycosylation via phosphoserines. By using glycerol spraying/low-angle rotary metal shadowing and labelling with monoclonal antibodies it is demonstrated that the repetitive region adopts an extended conformation forming side arms which project radially from the filament core and terminate with the COOH-terminal domain. The length of the side arms of SAP1 and SAP2 (20 nm and 90 nm, respectively) corresponds to the predicted length of the Ser/Thr-rich repeat region of SAP1 and SAP2. Mass determination by scanning electron microscopy (STEM) shows that one morphologically defined globular particle of the filament core is a polypeptide dimer. We propose a model for the filament core, in which the globular NH2-terminal SAP domains form one strand composed of polypeptide dimers or two tightly associated strands of monomers which may twist into a double helix, similar to actin filaments. The highly O-glycosylated side arms project from the filament core conferring an overall bottle-brush-like appearance. The L. mexicana SAP is compared to SAPs secreted by the closely related species L. amazonensis and L. donovani.
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Affiliation(s)
- Y D Stierhof
- Abteilung Membranbiochemie, Max-Planck-Institut für Biologie, Corrensstrasse 38, Tübingen, D-72076, Germany.
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71
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Descoteaux A, Mengeling BJ, Beverley SM, Turco SJ. Leishmania donovani has distinct mannosylphosphoryltransferases for the initiation and elongation phases of lipophosphoglycan repeating unit biosynthesis. Mol Biochem Parasitol 1998; 94:27-40. [PMID: 9719508 DOI: 10.1016/s0166-6851(98)00047-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Lipophosphoglycan (LPG) is the predominant surface glycoconjugate of Leishmania promastigotes and plays several roles in the infectious cycle of this protozoan parasite. The salient feature of LPG is the presence of 15-30 copies of a disaccharide-phosphate repeating unit Gal(beta1,4)Man(alpha1-PO4), which is also found on many other secreted molecules (secretory acid phosphatase, phosphoglycan, proteophosphoglycan). This structural diversity suggests that a multiplicity of enzymes mediating repeating unit addition may exist, especially for the mannosylphosphoryltransferases (MPTs), which initiate repeating unit synthesis. This work has taken a combined biochemical-genetic approach to resolve this issue. An lpg- mutant of Leishmania donovani, JEDI, was obtained by antibody selection against cells expressing a repeating unit epitope of LPG. Metabolic and surface labeling experiments revealed that JEDI cells accumulated a truncated form of LPG bearing only a single repeating unit: [Gal(beta 1,4)Man(alpha1-PO4)][Gal(alpha1,6)Gal(alpha1,3)Gal(f)(beta1,3)[Glc(alpha 1-PO4)]Man(alpha1,3)Man(alpha1,4)GlcN(alpha1,6)]-PI. Enzymatic assays of microsomal preparations showed that JEDI lacked MPT activity when tested with a repeating unit acceptor but retained wild-type levels of the MPT activity with an LPG glycan core acceptor. These data indicate that at least two distinct MPT activities are required for LPG repeating unit synthesis: one involved in the 'initiation' of repeating unit synthesis on the LPG core (iMPT), and a second (lacking in JEDI) participating in the 'elongation' phase of repeating unit addition (eMPT), leading to the mature full-length LPG.
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Affiliation(s)
- A Descoteaux
- Department of Biochemistry, University of Kentucky Medical Center, Lexington 40536, USA
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72
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Webb JR, Campos-Neto A, Ovendale PJ, Martin TI, Stromberg EJ, Badaro R, Reed SG. Human and murine immune responses to a novel Leishmania major recombinant protein encoded by members of a multicopy gene family. Infect Immun 1998; 66:3279-89. [PMID: 9632596 PMCID: PMC108343 DOI: 10.1128/iai.66.7.3279-3289.1998] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/1998] [Accepted: 04/20/1998] [Indexed: 02/07/2023] Open
Abstract
Vaccination of BALB/c mice with Leishmania major promastigote culture filtrate proteins plus Corynebacterium parvum confers resistance to infection with L. major. To define immunogenic components of this protein mixture, we used sera from vaccinated mice to screen an L. major amastigote cDNA expression library. One of the immunoreactive clones thus obtained encoded a novel protein of L. major with a molecular mass of 22.1 kDa. The predicted amino acid sequence of this clone exhibited significant homology to eukaryotic thiol-specific-antioxidant (TSA) proteins. Therefore, we have designated this protein L. major TSA protein. Southern blot hybridization analyses indicate that there are multiple copies of the TSA gene in all species of Leishmania analyzed. Northern blot analyses demonstrated that the TSA gene is constitutively expressed in L. major promastigotes and amastigotes. Recombinant TSA protein containing an amino-terminal six-histidine tag was expressed in Escherichia coli with the pET17b system and was purified to homogeneity by affinity chromatography. Immunization of BALB/c mice with recombinant TSA protein resulted in the development of strong cellular immune responses and conferred protective immune responses against infection with L. major when the protein was combined with interleukin 12. In addition, recombinant TSA protein elicited in vitro proliferative responses from peripheral blood mononuclear cells of human leishmaniasis patients and significant TSA protein-specific antibody titers were detected in sera of both cutaneous-leishmaniasis and visceral-leishmaniasis patients. Together, these data suggest that the TSA protein may be useful as a component of a subunit vaccine against leishmaniasis.
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Affiliation(s)
- J R Webb
- Infectious Disease Research Institute, University of Washington, Seattle, Washington, USA
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73
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Ilg T, Craik D, Currie G, Multhaup G, Bacic A. Stage-specific proteophosphoglycan from Leishmania mexicana amastigotes. Structural characterization of novel mono-, di-, and triphosphorylated phosphodiester-linked oligosaccharides. J Biol Chem 1998; 273:13509-23. [PMID: 9593686 DOI: 10.1074/jbc.273.22.13509] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intracellular amastigotes of the protozoan parasite Leishmania mexicana secrete a macromolecular proteophosphoglycan (aPPG) into the phagolysosome of their host cell, the mammalian macrophage. The structures of aPPG glycans were analyzed by a combination of high pH anion exchange high pressure liquid chromatography, gas chromatography-mass spectrometry, enzymatic digestions, electrospray-mass spectrometry as well as 1H and 31P NMR spectroscopy. Some glycans are identical to oligosaccharides known from Leishmania mexicana promastigote lipophosphoglycan and secreted acid phosphatase. However, the majority of the aPPG glycans represent amastigote stage-specific and novel structures. These include neutral glycans ([Glcbeta1-3]1-2Galbeta1-4Man, Galbeta1-3Galbeta1-4Man, Galbeta1-3Glcbeta1-3Galbeta1-4Man), several monophosphorylated glycans containing the conserved phosphodisaccharide backbone (R-3-[PO4-6-Gal]beta1-4Man) but carrying stage-specific modifications (R = Galbeta1-, [Glcbeta1-3]1-2Glcbeta1-), and monophosphorylated aPPG tri- and tetrasaccharides that are uniquely phosphorylated on the terminal hexose (PO4-6-Glcbeta1-3Galbeta1-4Man, PO4-6-Glcbeta1-3Glcbeta1-3Galbeta1-4Man, PO4-6-Galbeta1-3Glcbeta1-3Galbeta1-4Man). In addition aPPG contains highly unusual di- and triphosphorylated glycans whose major species are PO4-6-Glcbeta1-3Glcbeta1-3[PO4-6-Gal]beta1-4Man, PO4-6-Galbeta1-3Glcbeta1-3[PO4-6-Gal]beta1-4Man, PO4-6-Galbeta1-3Glcbeta1-3Glcbeta1-3[PO4-6-Gal]beta1-+ ++4Man, PO4-6-Glcbeta1-3[PO4-6-Glc]beta1-3[PO4-6-Gal]beta1-4Man, PO4-6-Galbeta1-3[PO4-6-Glc]beta1-3Glcbeta1-3[PO4-6-Gal]beta1 -4Man, and PO4-6-Glcbeta1-3[PO4-6-Glc]beta1-3Glcbeta1-3[PO4-6-Gal]beta1 -4Man. These glycans are linked together by the conserved phosphodiester R-Manalpha1-PO4-6-Gal-R or the novel phosphodiester R-Manalpha1-PO4-6-Glc-R and are connected to Ser(P) of the protein backbone most likely via the linkage R-Manalpha1-PO4-Ser. The variety of stage-specific glycan structures in Leishmania mexicana aPPG suggests the presence of developmentally regulated amastigote glycosyltransferases which may be potential anti-parasite drug targets.
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Affiliation(s)
- T Ilg
- Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Victoria 3052, Australia.
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74
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Bogdan C, Röllinghoff M. The immune response to Leishmania: mechanisms of parasite control and evasion. Int J Parasitol 1998; 28:121-34. [PMID: 9504340 DOI: 10.1016/s0020-7519(97)00169-0] [Citation(s) in RCA: 192] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
After transmission of Leishmania parasites by sandflies, disease manifestation of the infection requires mechanisms which allow the parasites to replicate in the mammalian host and to resist, at least initially, its innate and acquired antileishmanial defence. Likewise, lifelong persistence of Leishmania parasites, as it occurs even in cases of clinical healing of the infection, points to the existence of strategies which enable the parasite to partially circumvent the protective adaptive immune response of the host. In this review we will discuss the mechanisms which can be invoked to contribute to the initial, as well as long-term, survival of Leishmania parasites in the host organism. These include the passive protection of the parasite against antileishmanial products and the retreat into "safe target cells", the active suppression of the synthesis of reactive oxygen or nitrogen intermediates, the modulation of the host cytokine response, the inhibition of antigen-presentation and T cell-stimulation, and the induction and expansion of counterprotective T helper cells. It is probable that none of these mechanisms alone is sufficient to guarantee the survival of Leishmania, but together they might provide the safe environment which protects the parasite from elimination.
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Affiliation(s)
- C Bogdan
- Institute of Clinical Microbiology and Immunology, University of Erlangen, Germany.
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75
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Abstract
There are a number of different glycoproteins that have been identified relatively recently which contain oligosaccharides linked to serine or threonine in a peptide backbone via phosphodiesters. It is possible that these glycoproteins may form an alternative structural class of glycosylation. This modification has been referred to as phosphoglycosylation (Mehta et al., 1996; J. Biol. Chem., 271, 10897-10903), and has been reported in slime molds and several unicellular parasites. In this review, examples of phosphoglycosylation from different biological sources are discussed. Those which are well characterized have been found to be highly variable with respect to the glycan moiety, while sharing some common features. An experimental approach detailing how to determine whether a protein is phosphoglycosylated is also presented.
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Affiliation(s)
- P A Haynes
- Department of Molecular Biotechnology, Box 357730, University of Washington, Seattle, WA 98195-7730, USA
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76
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Peters C, Kawakami M, Kaul M, Ilg T, Overath P, Aebischer T. Secreted proteophosphoglycan of Leishmania mexicana amastigotes activates complement by triggering the mannan binding lectin pathway. Eur J Immunol 1997; 27:2666-72. [PMID: 9368624 DOI: 10.1002/eji.1830271028] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cutaneous lesions induced by infection of mice with the protozoan parasite, Leishmania mexicana, contain abundant amounts of a high molecular mass proteophosphoglycan (PPG), which is secreted by the amastigote stage residing in phagolysosomes of macrophages and can then be released into the tissue upon rupture of the infected cells. Amastigote PPG forms sausage-shaped but soluble particles and belongs to a novel class of serine-rich proteins that are extensively O-glycosylated by phosphooligosaccharides capped by mannooligosaccharides. The purified molecule is shown here to efficiently activate complement (C) and deplete hemolytic activity of normal serum and may prevent the opsonization of L. mexicana amastigotes. Complement activation is Ca2+ dependent but does not depend on antibodies or the complement component C1. PPG binds to serum mannan binding protein (MBP), thus activating the MBP-associated serine protease, P100. Subsequently, the C cascade is triggered through C4 leading to covalent modification probably of carbohydrate hydroxyls of PPG by C3 fragments. Thus, PPG is able to activate C via the mannan binding lectin pathway which is unusual for secreted, soluble products of microbial origin. The proteophosphoglycan-induced complement activation is postulated to contribute to the lesion development and pathology caused by the parasite.
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Affiliation(s)
- C Peters
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany
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77
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Ferguson MA. The surface glycoconjugates of trypanosomatid parasites. Philos Trans R Soc Lond B Biol Sci 1997; 352:1295-302. [PMID: 9355120 PMCID: PMC1692025 DOI: 10.1098/rstb.1997.0113] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Insect-transmitted protozoan parasites of the order Kinetoplastida, suborder Trypanosomatina, include Trypanosoma brucei (aetiological agent of African sleeping sickness), Trypanosoma cruzi (aetiological agent of Chagas' disease in South and Central America) and Leishmania spp. (aetiological agents of a variety of diseases throughout the tropics and sub-tropics). The structures of the most abundant cell-surface molecules of these organisms is reviewed and correlated with the different modes of parasitism of the three groups of parasites. The major surface molecules are all glycosylphosphatidylinositol (GPI)-anchored glycoproteins, such as the variant surface glycoproteins of T. brucei and the surface mucins of T. cruzi, or complex glycophospholipids, such as the lipophosphoglycans and glycoinositolphospholipids of the leishmanias. Significantly, all of the aforementioned structures share a motif of Man alpha 1-4GlcN alpha 1-6-myo-inositol-1-HPO4-lipid and can therefore be considered to be members of a GPI superfamily.
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Affiliation(s)
- M A Ferguson
- Department of Biochemistry, University of Dundee, UK
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78
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Peters C, Stierhof YD, Ilg T. Proteophosphoglycan secreted by Leishmania mexicana amastigotes causes vacuole formation in macrophages. Infect Immun 1997; 65:783-6. [PMID: 9009342 PMCID: PMC176125 DOI: 10.1128/iai.65.2.783-786.1997] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The amastigote form of Leishmania mexicana parasites colonizes macrophage phagolysosomes and induces the enlargement of these compartments to form huge parasitophorous vacuoles. We report here that a purified secreted amastigote product, proteophosphoglycan, is a macromolecule which causes vacuolization of peritoneal macrophages in vitro. Secretion of this glycoconjugate by intracellular parasites may contribute to the expansion of phagolysosomal compartments in infected cells.
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Affiliation(s)
- C Peters
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, Tübingen, Germany
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79
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Overath P, Stierhof YD, Wiese M. Endocytosis and secretion in trypanosomatid parasites — Tumultuous traffic in a pocket. Trends Cell Biol 1997; 7:27-33. [PMID: 17708895 DOI: 10.1016/s0962-8924(97)10046-0] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Trypanosomatids are flagellated protozoan parasites of invertebrates, vertebrates and plants. Some species, found in the subtropics and tropics, cause chronic diseases in humans and domestic animals. The surface of the trypanosomatid provides a shield against environmental challenges, ligands for interaction with host cells, as well as receptors and transporters for the uptake of nutrients. Communication between the parasite and its environment is confined to the flagellar pocket, an invagination of the plasma membrane around the base of the flagellum. In this review, the authors discuss endocytosis, secretion and membrane trafficking in Trypanosoma and Leishmania.
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