Structure of a filamentous phosphoglycoprotein polymer: the secreted acid phosphatase of Leishmania mexicana

Stierhof, York‐Dieter; Wiese, Martin; Ilg, Thomas; Overath, Peter; Häner, Markus; Aebi, Ueli

doi:10.1006/jmbi.1998.2012

Cited by 25 publications

(14 citation statements)

References 31 publications

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“…In particular, mPPG may be, due to its unusual structure, an ideal molecule as a complement acceptor and as a ligand for macrophage and sandfly midgut receptors. A conservative estimate of a contour length of 200 pm per amino acid in a phosphoglycosylated polypeptide domain (50,51) suggests that mPPG may extend more than 300 nm above the plasma membrane making it highly accessible for binding partners, whereas even the longest forms of LPG with 40 repeat units cannot extend further than 40 nm, more common estimates being 9 -17 nm (Refs. 53 and 54; compare Fig.…”

Section: Discussionmentioning

confidence: 99%

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

Ilg¹,

Montgomery²,

Stierhof³

et al. 1999

Journal of Biological Chemistry

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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.Leishmania are kinetoplastid protozoan parasites with a digenetic life cycle and are responsible for several important human diseases, ranging from mild skin ulcers to fatal visceral disease. Several forms of extracellular flagellated Leishmania promastigotes colonize the digestive tract of vector sandflies. After transmission to the mammalian host by the bite of the insect, the parasites transform to the obligatory intracellular, nonflagellated amastigotes, which reside in the phagolysosomes of macrophages (1). Both Leishmania life stages synthesize complex and unique glycoconjugates, which are either displayed on their surface (2) or secreted (3). These glycoconjugates, which are thought to have crucial functions for parasite survival, development, and virulence in the sandfly vector and the mammalian macrophage, include a family of phosphoglycan-modified molecules, which comprises lipid-linked, protein-linked, and unlinked forms (4 -6). Lipophosphoglycan (LPG) 1 is the best studied representative of this family: it consists of 1-alkyl-2-lyso-phosphatidylinositol that is linked via a diphosphoheptasaccharide core to a linear polymer of up to 40 phosphodiester-linked disaccharides that are modified by species-, strain-, and stage-specific side chains. The polymer chain terminates with variable neutral cap oligosaccharides (2).

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Section: Discussionmentioning

confidence: 99%

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

Ilg¹,

Montgomery²,

Stierhof³

et al. 1999

Journal of Biological Chemistry

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“…These glycoconjugates have been shown to play important roles in parasite virulence both in vector and the mammalian host (2)(3)(4)(5)(6). Among these PPGs are newly described mucin-like glycoproteins present on the surface and secreted by both promastigote and amastigote stages of Leishmania.…”

Section: Immunization With the Dna-encoding N-terminal Domain Of Protmentioning

confidence: 99%

Immunization with the DNA-Encoding N-Terminal Domain of Proteophosphoglycan of Leishmania donovani Generates Th1-Type Immunoprotective Response against Experimental Visceral Leishmaniasis

Samant

Gupta

Kumari

et al. 2009

The Journal of Immunology

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Leishmania produce several types of mucin-like glycoproteins called proteophosphoglycans (PPGs) which exist as secretory as well as surface-bound forms in both promastigotes and amastigotes. The structure and function of PPGs have been reported to be species and stage specific as in the case of Leishmania major and Leishmania mexicana; there has been no such information available for Leishmania donovani. We have recently demonstrated that PPG is differentially expressed in sodium stibogluconate-sensitive and -resistant clinical isolates of L. donovani. To further elucidate the structure and function of the ppg gene of L. donovani, a partial sequence of its N-terminal domain of 1.6 kb containing the majority of antigenic determinants, was successfully cloned and expressed in prokaryotic as well as mammalian cells. We further evaluated the DNA-encoding N-terminal domain of the ppg gene as a vaccine in golden hamsters (Mesocricetus auratus) against the L. donovani challenge. The prophylactic efficacy to the tune of ∼80% was observed in vaccinated hamsters and all of them could survive beyond 6 mo after challenge. The efficacy was supported by a surge in inducible NO synthase, IFN-γ, TNF-α, and IL-12 mRNA levels along with extreme down-regulation of TGF-β, IL-4, and IL-10. A rise in the level of Leishmania-specific IgG2 was also observed which was indicative of enhanced cellular immune response. The results suggest the N-terminal domain of L. donovani ppg as a potential DNA vaccine against visceral leishmaniasis.

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“…In all three cases, the extensive phosphoglycosylation leads to an extended filamentous structure of the repeats that can be readily visualized by electron microscopy [20,22,37]. This situation is reminiscent of the different mammalian mucins which also exhibit no similarity to each other with respect to the sequence or the number of amino acids in their repeats but form similar rod-like structures in the O-glycosylated regions (reviewed in [38]).…”

Section: Discussionmentioning

confidence: 99%

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

Göpfert

Goehring

Klein

et al. 1999

Biochemical Journal

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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-expressedppg2 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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Structure of a filamentous phosphoglycoprotein polymer: the secreted acid phosphatase of Leishmania mexicana

Cited by 25 publications

References 31 publications

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

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

Immunization with the DNA-Encoding N-Terminal Domain of Proteophosphoglycan of Leishmania donovani Generates Th1-Type Immunoprotective Response against Experimental Visceral Leishmaniasis

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

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