Attachment of the flagellate Giardia lamblia: role of reducing agents, serum, temperature, and ionic composition.

Gillin, Frances D.; Reiner, David S.

doi:10.1128/mcb.2.4.369

Cited by 44 publications

(32 citation statements)

References 8 publications

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“…This parasite is unusual in its requirement for cysteine at millimolar concentrations for survival, growth, and attachment in vitro (41). Furthermore, we have demonstrated reduced -SH groups exposed on the outer surface of trophozoites by flow cytometry with a thiol-specific fluorescent hapten (42).…”

Section: Discussionmentioning

confidence: 92%

Isolation and expression of the gene for a major surface protein of Giardia lamblia.

Gillin

Hagblom

Harwood

et al. 1990

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

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126

107

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To study the interactions between the parasitic protozoan Giardia lamblia and its environment, we have cloned the gene that encodes the two major surface-labeled trophozoite protein species. Sequence analysis of this gene reveals a single open reading frame specifying a hydrophilic, cysteine-rich (11.8%) protein of 72.5-kDa molecular mass with an amino-terminal signal peptide and a postulated hydrophobic membrane-spanning anchor region near the carboxyl terminus. Most of the cysteine residues (58 of 84) are in the motif Cys-Xaa-Xaa-Cys, which is dispersed 29 times throughout the sequence. Antibodies against the recombinant protein react with the entire surface of live trophozoites, including flagella and adhesive disc. These antibodies inhibit trophozoite attachment, prevent growth, and immunoprecipitate the major =66-and 85-kDa proteins from surface-labeled live trophozoites. The recombinant Escherichia coli also expresses polypeptides of -66-and 85-kDa molecular mass, which are not fusion proteins. This suggests that the processing and/or conformational changes that lead to production of these two peptide species in E. coli reflect those that occur in Giardia. The abundance of cysteine residues suggests that the native proteins on the parasite surface may contain numerous disulfide bonds, which would promote resistance to intestinal fluid proteases and to the detergent activity of bile salts and would help to explain the survival of Giardia in the human small intestine.

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Section: Discussionmentioning

confidence: 92%

Isolation and expression of the gene for a major surface protein of Giardia lamblia.

Gillin

Hagblom

Harwood

et al. 1990

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

Self Cite

126

107

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show abstract

“…Cysteine also provides a partial protection from the toxicity of oxygen that is not seen with other reducing agents, including cystine, and therefore appears to be a specific effect of cysteine (109,110,113). Cysteine is not synthesized de novo and is not synthesized from cystine (202).…”

Section: Amino Acid Metabolismmentioning

confidence: 99%

“…8) surrounds the disk (82). The disk contains the contractile proteins actinin, ␣-actinin, myosin, and tropomyosin (103) ment depends on active metabolism and is inhibited by temperatures below 37°C, increased oxygen levels, or reduced cysteine concentrations (109,113). Ultrastructurally, the ventral disk includes a set of microtubules containing 13 protofilaments and linked to the ventral membrane.…”

Section: Cytoskeleton and Motilitymentioning

confidence: 99%

Biology ofGiardia lamblia

2001

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Giardia lamblia is a common cause of diarrhea in humans and other mammals throughout the world. It can be distinguished from other Giardia species by light or electron microscopy. The two major genotypes of G. lamblia that infect humans are so different genetically and biologically that they may warrant separate species or subspecies designations. Trophozoites have nuclei and a well-developed cytoskeleton but lack mitochondria, peroxisomes, and the components of oxidative phosphorylation. They have an endomembrane system with at least some characteristics of the Golgi complex and encoplasmic reticulum, which becomes more extensive in encysting organisms. The primitive nature of the organelles and metabolism, as well as small-subunit rRNA phylogeny, has led to the proposal that Giardia spp. are among the most primitive eukaryotes. G. lamblia probably has a ploidy of 4 and a genome size of approximately 10 to 12 Mb divided among five chromosomes. Most genes have short 5′ and 3′ untranslated regions and promoter regions that are near the initiation codon. Trophozoites exhibit antigenic variation of an extensive repertoire of cysteine-rich variant-specific surface proteins. Expression is allele specific, and changes in expression from one vsp gene to another have not been associated with sequence alterations or gene rearrangements. The Giardia genome project promises to greatly increase our understanding of this interesting and enigmatic organism

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“…The effect of various lectins on growth of G. lamblia trophozoites in vitro was determined by a modification of a previously described method (18). Briefly, cultures were initiated by addition of 2.5 x 104 trophozoites in 0.1 ml of medium to vials (15 x 45 mm) containing 3.9 ml of medium containing one of the following lectins: Con A, PHA, SBA, S-WGA, Aaptos papillata agglutinin, LBA 100 dg/mn'l (100 ag/ml-'), WGA (10, 50, 100 ttg/ml-') and WGA (100 /ig/ml1') plus GlcNAc (2 tg/ml-').…”

Section: Methodsmentioning

confidence: 99%

Growth inhibition of the intestinal parasite Giardia lamblia by a dietary lectin is associated with arrest of the cell cycle.

Ortega-Barrı́a

Ward²,

Keusch³

et al. 1994

J. Clin. Invest.

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Giardia lamblia, a cause of diarrheal disease throughout the world, is a protozoan parasite that thrives in the small intestine. It is shown here that wheat germ agglutinin (WGA), a naturally occurring lectin widely consumed in normal human diets, reversibly inhibits the growth of G. lamblia trophozoites in vitro, and reduces infection by G. muris in the adult mouse model of giardiasis. The inhibitory effect was dose related, not associated with cytotoxicity and reversed by N-acetyl-D-glucosamine in accordance with the known specificity of the lectin and in agreement with the presence of GlcNAc residues on the surface membrane of G. lamblia trophozoites. Cell cycle analysis revealed that parasites grown in the presence of WGA are arrested in the G21 M phase, providing an explanation for the lectin-induced inhibition of cell proliferation. Comparison of electrophoretic profiles by lectin blot analysis revealed both glycoprotein induction and suppression in growth-arrested organisms. Our findings raise the possibility that blocking trophozoite growth with naturally occurring dietary lectins may influence the course of giardiasis. In addition, the study of cell cycle arrest by WGA may provide a model to study the regulation of cell division in lower eukaryotes. (J. Clin. Invest. 1994Invest. . 94:2283Invest. -2288

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Attachment of the flagellate Giardia lamblia: role of reducing agents, serum, temperature, and ionic composition.

Cited by 44 publications

References 8 publications

Isolation and expression of the gene for a major surface protein of Giardia lamblia.

Isolation and expression of the gene for a major surface protein of Giardia lamblia.

Biology ofGiardia lamblia

Growth inhibition of the intestinal parasite Giardia lamblia by a dietary lectin is associated with arrest of the cell cycle.

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