Selective inhibitors of the glycosylphosphatidylinositol biosynthetic pathway of Trypanosoma brucei

Smith, Terry; Sharma, Deepak; Crossman, Arthur; Brimacombe, J. S.; Ferguson, Michael A. J.

doi:10.1093/emboj/18.21.5922

Cited by 61 publications

(51 citation statements)

References 62 publications

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“…Alternatively, the acyltransferase may only have access to this pool of GPIs if intermediates from different pathways are present in different membranes or have different membrane topologies. Given the distinct properties and probable function of inositol acylation in trypanosomes compared with animal cells, it has been proposed that the inositol acyltransferase may be a target for new anti-trypanosome therapeutics (Smith et al, 1999). However, the fact that this modification is restricted to nonessential protein-anchor precursors in Leishmania suggests that therapeutics such as these would not be useful against these parasites.…”

Section: Discussionmentioning

confidence: 99%

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Hilley

Zawadzki

McConville

et al. 2000

MBoC

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The major surface proteins of the parasitic protozoon Leishmania mexicana are anchored to the plasma membrane by glycosylphosphatidylinositol (GPI) anchors. We have cloned the L. mexicana GPI8 gene that encodes the catalytic component of the GPI:protein transamidase complex that adds GPI anchors to nascent cell surface proteins in the endoplasmic reticulum. Mutants lacking GPI8 (⌬GPI8) do not express detectable levels of GPI-anchored proteins and accumulate two putative protein-anchor precursors. However, the synthesis and cellular levels of other nonprotein-linked GPIs, including lipophosphoglycan and a major class of free GPIs, are not affected in the ⌬GPI8 mutant. Significantly, the ⌬GPI8 mutant displays normal growth in liquid culture, is capable of differentiating into replicating amastigotes within macrophages in vitro, and is infective to mice. These data suggest that GPI-anchored surface proteins are not essential to L. mexicana for its entry into and survival within mammalian host cells in vitro or in vivo and provide further support for the notion that free GPIs are essential for parasite growth. INTRODUCTIONLeishmania are protozoan parasites that cause a spectrum of diseases in humans. These parasites alternate between a flagellated promastigote stage that proliferates within the midgut of the sandfly vector and a nonmotile amastigote stage that invades mammalian macrophages, where they occupy the phagolysosome compartment. The cell surface of the promastigote stage is coated by a protective glycocalyx that comprises a number of glycosylphosphatidylinositol (GPI)-anchored glycoproteins, a complex GPI-anchored lipophosphoglycan (LPG), and a family of free GPIs (termed glycoinositolphospholipids [GIPLs]) Beverley and Turco, 1998; Figure 1). Components in this glycoclayx are thought to be essential for parasite survival and infectivity in the diverse host Beverley and Turco, 1998). The GPIanchored glycoproteins include an abundant metalloproteinase, termed gp63 or leishmanolysin, and the promastigote surface antigen (PSA2)/gp46 family of glycoproteins Murray et al., 1989;Frommel et al., 1990;Lohman et al., 1990). Gp63 has been shown to be proteolytically active against a wide variety of different peptide substrates and has been reported to act as a ligand for macrophage receptors, either directly or after opsonization with complement, to protect the parasites from complementmediated lysis and also to contribute to the pathology of lesion development (see Alexander and Russell, 1992;Joshi et al., 1998). However, the fact that these proteins are encoded by multicopy polymorphic genes (Button et al., 1989;Lohman et al., 1990;Symons et al., 1994) has hindered elucidation of their function by genetic analysis (Joshi et al., 1998). Moreover, surface expression of gp63 and PSA2 is dramatically down-regulated in the amastigote stage of some Leishmania species and variable within particular parasite populations of others (Bahr et al., 1993;Handman et al., 1995) such that the precise function of these parasite pro...

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Section: Discussionmentioning

confidence: 99%

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Hilley

Zawadzki

McConville

et al. 2000

MBoC

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“…Several potential inhibitors that exploit differences in the substrate specificity of the trypanosome and mammalian enzymes have been developed (317,325,327,329). Inhibitors of the fatty acid remodeling reactions also have potent trypanocidal activity (81).…”

Section: Biosynthesis Of Gpi Protein Anchorsmentioning

confidence: 99%

Secretory Pathway of Trypanosomatid Parasites

McConville

Mullin

Ilgoutz

et al. 2002

Microbiol Mol Biol Rev

222

191

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The Trypanosomatidae comprise a large group of parasitic protozoa, some of which cause important diseases in humans. These include Trypanosoma brucei (the causative agent of African sleeping sickness and nagana in cattle), Trypanosoma cruzi (the causative agent of Chagas' disease in Central and South America), and Leishmania spp. (the causative agent of visceral and [muco]cutaneous leishmaniasis throughout the tropics and subtropics). The cell surfaces of these parasites are covered in complex protein- or carbohydrate-rich coats that are required for parasite survival and infectivity in their respective insect vectors and mammalian hosts. These molecules are assembled in the secretory pathway. Recent advances in the genetic manipulation of these parasites as well as progress with the parasite genome projects has greatly advanced our understanding of processes that underlie secretory transport in trypanosomatids. This article provides an overview of the organization of the trypanosomatid secretory pathway and connections that exist with endocytic organelles and multiple lytic and storage vacuoles. A number of the molecular components that are required for vesicular transport have been identified, as have some of the sorting signals that direct proteins to the cell surface or organelles in the endosome-vacuole system. Finally, the subcellular organization of the major glycosylation pathways in these parasites is reviewed. Studies on these highly divergent eukaryotes provide important insights into the molecular processes underlying secretory transport that arose very early in eukaryotic evolution. They also reveal unusual or novel aspects of secretory transport and protein glycosylation that may be exploited in developing new antiparasite drugs

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“…A compound that inhibits GPI synthesis in mammalian cells and yeast but not in T. brucei has already been developed (42). It should, therefore, be possible to develop compounds that inhibit GPI synthesis in T. brucei but not in mammalian cells (43).…”

Section: Tbgpi10 Is Not Essential But Important For Growth Of Procyclmentioning

confidence: 99%

Critical roles of glycosylphosphatidylinositol for Trypanosoma brucei

Nagamune

Nozaki

Maeda

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

167

162

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Trypanosoma brucei, the protozoan parasite responsible for sleeping sickness, evades the immune response of mammalian hosts and digestion in the gut of the insect vector by means of its coat proteins tethered to the cell surface via glycosylphosphatidylinositol (GPI) anchors. To evaluate the importance of GPI for parasite survival, we cloned and disrupted a trypanosomal gene, TbGPI10, involved in biosynthesis of GPI. TbGPI10 encodes a protein of 558 amino acids having 25% and 23% sequence identity to human PIG-B and Saccharomyces cerevisiae Gpi10p, respectively. TbGPI10 restored biosynthesis of GPI in a mouse mutant cell line defective in mouse Pig-b gene. TbGPI10 also rescued the inviability of GPI10-disrupted S. cerevisiae, indicating that TbGPI10 is the orthologue of PIG-B͞GPI10 that is involved in the transfer of the third mannose to GPI. The bloodstream form of T. brucei could not lose TbGPI10; therefore, GPI synthesis is essential for growth of mammalian stage parasites. Procyclic form cells (insect stage parasites) lacking the surface coat proteins because of disruption of TbGPI10 are viable and grow slower than normal, provided that they are cultured in nonadherent flasks. In regular flasks, they adhered to the plastic surface and died. Infectivity to tsetse flies is partially impaired, particularly in the early stage. Therefore, parasitespecific inhibition of GPI biosynthesis should be an effective chemotherapy target against African trypanosomiasis.T rypanosoma brucei is a protozoan parasite invading humans and other mammals by transmission via tsetse flies. It causes sleeping sickness in humans and nagana disease in domestic animals living in the ''tsetse belt'' in central Africa. These are serious medical and agricultural problems for which safe and effective therapeutic and protective measures are highly desirable (1, 2).T. brucei has two distinct proliferative stages, a bloodstream stage living free in mammalian blood and an insect stage (or procyclic form) living in the midguts of tsetse flies. The cell surface of both stages of this unicellular parasite is covered by a large amount of glycosylphosphatidylinositol (GPI)-anchored proteins (3, 4): 10 7 variant surface glycoproteins per cell for the bloodstream form of the parasite and 3 ϫ 10 6 to 6 ϫ 10 6 procyclins (or procyclic acidic repetitive proteins) per cell of the procyclic form of the parasite (4-6), corresponding to 10% and 1-3%, respectively, of total proteins in these parasite stages (7,8). T. brucei evades the host's immune response by expressing structurally different forms of variant surface glycoproteins (4). Procyclins are thought to protect procyclic cells from digestion by the digestive enzymes in the fly (4, 6). In addition, T. brucei expresses a number of other GPI-anchored proteins, such as transferrin receptors in the bloodstream form (3, 4). Thus, the importance of GPI anchors for the survival and infection of T. brucei has been suggested, leading to the notion that the GPI biosynthesis pathway may be a good target for chemo...

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Selective inhibitors of the glycosylphosphatidylinositol biosynthetic pathway of Trypanosoma brucei

Cited by 61 publications

References 62 publications

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Secretory Pathway of Trypanosomatid Parasites

Critical roles of glycosylphosphatidylinositol for Trypanosoma brucei

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