Procyclin gene expression and loss of the variant surface glycoprotein during differentiation of Trypanosoma brucei.

Roditi, Isabel; Schwarz, Heinz; Pearson, Terry W.; Beecroft, Robert P.; Liu, M K; Richardson, Jennifer; Bühring, Hans Jörg; Pleiss, Jürgen; Bülow, Roland; Williams, Richard O.

doi:10.1083/jcb.108.2.737

Cited by 275 publications

(193 citation statements)

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“…The effect was even more dramatic in cells expressing dsRNA constitutively, which showed a reduction to 11% of the total sialic acid content found in control cells. Considering that T. brucei procyclic cells have ϳ3 ϫ 10 6 procyclin molecules on their surface, the observed levels of sialic acid in these parasites correspond to Ͻ1 sialic acid molecule/ procyclin (28). This result is consistent with the earlier observation that sialic acid is not required for the survival of procyclic trypanosomes during growth in vitro (3,29).…”

Section: Identification Of Genes Coding Forsupporting

confidence: 81%

Procyclic Trypanosoma brucei Expresses Separate Sialidase and trans-Sialidase Enzymes on Its Surface Membrane

Montagna

Donelson

Frasch

2006

Journal of Biological Chemistry

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The procyclic stage of Trypanosoma brucei in the insect vector expresses a surface-bound trans-sialidase (TbTS) that transfers sialic acid from glycoconjugates in the environment to glycosylphosphatidylinositol-anchored proteins on its surface membrane. RNA interference against TbTS abolished transsialidase activity in procyclic cells but did not diminish sialidase activity, suggesting the presence of a separate sialidase enzyme for hydrolyzing sialic acid. A search of the T. brucei genome sequence revealed seven other putative genes encoding proteins with varying similarity to TbTS. RNA interference directed against one of these proteins, TbSA C, greatly decreased the sialidase activity but had no effect on trans-sialidase activity. The deduced amino acid sequence of TbSA C shares only 40% identity with TbTS but conserves most of the relevant residues required for catalysis. However, the sialidase has a tryptophan substitution for a tyrosine at position 170 that is crucial in binding the terminal galactose that accepts the transferred sialic acid. When this same tryptophan substitution in the sialidase was placed into the recombinant trans-sialidase, the mutant enzyme lost almost all of its trans-sialidase activity and increased its sialidase activity, further confirming that the gene and protein identified correspond to the parasite sialidase. Thus, in contrast to all other trypanosomes analyzed to date that express either a trans-sialidase or a sialidase but not both, T. brucei expresses these two enzymatic activities in two separate proteins. These results suggest that African trypanosomes could regulate the amount of critical sialic acid residues on their surface by modulating differential expression of each of these enzymes.African trypanosomes are protozoan parasites responsible for sleeping sickness in humans and a similar disease in domestic animals called nagana. Their life cycle alternates between the bloodstream of a mammalian host and the tsetse fly vector (Glossina sp.). The surface of the bloodstream form of the parasite is completely covered with 10 7 copies of a single variant surface glycoprotein (VSG) 3 bearing a glycosylphosphatidylinositol (GPI) anchor. These bloodstream trypanosomes elude the immune response of the mammalian host by periodically switching from one VSG to another immunologically distinct VSG. The bloodstream form of the parasite differentiates into the procyclic form when ingested by the insect vector. This differentiation involves a remodeling of the surface in which the VSG coat is rapidly shed and replaced with a new set of invariant GPI-anchored glycoproteins known as procyclins (1). Procyclins have an unusual GPI anchor that, unlike the GPI anchor of VSGs, is decorated with branched poly-N-acetyllactosamine repeats capped by sialic acid residues (2). Trypanosomes are unable to synthesize sialic acid, but the procyclic form of the African trypanosome Trypanosoma brucei expresses a specific enzyme, trans-sialidase (TbTS), that transfers sialic acid from sialylated glyco...

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Section: Identification Of Genes Coding Forsupporting

confidence: 81%

Procyclic Trypanosoma brucei Expresses Separate Sialidase and trans-Sialidase Enzymes on Its Surface Membrane

Montagna

Donelson

Frasch

2006

Journal of Biological Chemistry

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“…Figure 1 shows the abundance of each mRNA (COX I, II, III, and VI) at intervals during the first 10 h of differentiation. The transcript abundance of COX I, II, and VI increased significantly during the first 2-4 h of differentiation, approximately matching the induction kinetics of the mRNA for the EP procyclin surface antigen (Roditi et al, 1989). For COX III, the RNA abundance did not increase during differentiation and was somewhat variable between experiments.…”

Section: Kinetoplast Dna (Kdna)-encoded Cox Complex Mrnas Are Not Govmentioning

confidence: 81%

Mitochondrial Development during Life Cycle Differentiation of African Trypanosomes: Evidence for a Kinetoplast-dependent Differentiation Control Point

Timms

Deursen

Hendriks

et al. 2002

MBoC

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Life cycle differentiation of African trypanosomes entails developmental regulation of mitochondrial activity. This requires regulation of the nuclear genome and the kinetoplast, the trypanosome's unusual mitochondrial genome. To investigate the potential cross talk between the nuclear and mitochondrial genome during the events of differentiation, we have 1) disrupted expression of a nuclear-encoded component of the cytochrome oxidase (COX) complex; and 2) generated dyskinetoplastid cells, which lack a mitochondrial genome. Using RNA interference (RNAi) and by disrupting the nuclear COX VI gene, we demonstrate independent regulation of COX component mRNAs encoded in the nucleus and kinetoplast. However, two independent approaches (acriflavine treatment and RNA interference ablation of mitochondrial topoisomerase II) failed to establish clonal lines of dyskinetoplastid bloodstream forms. Nevertheless, dyskinetoplastid forms generated in vivo could undergo two life cycle differentiation events: transition from bloodstream slender to stumpy forms and the initiation of transformation to procyclic forms. However, they subsequently arrested at a specific point in this developmental program before cell cycle reentry. These results provide strong evidence for a requirement for kinetoplast DNA in the bloodstream and for a kinetoplast-dependent control point during differentiation to procyclic forms.

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“…Both the N-glycoslyated EP-PARP species and the GPEET-PARP species have been isolated and structurally characterized. Both forms are believed to adopt highly extended rod-like structures (Roditi et al 1989;Treumann et al 1997) and both contain GPI anchors with an unusual lipid structure and large polydisperse carbohydrate side chains made of branched polylactosamine repeats, i.e. Galb1-4GlcNAc repeat units (¢gure 1b) (Field et al 1991;Ferguson et al 1993;Treumann et al 1997).…”

Section: T H E Su R Fac E O F Trypa Nosoma Bruceimentioning

confidence: 99%

The surface glycoconjugates of trypanosomatid parasites

Ferguson

1997

Phil. Trans. R. Soc. Lond. B

127

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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 di¡erent 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. Signi¢cantly, all of the aforementioned structures share a motif of Man1-4GlcN1-6-myo-inositol-1-HPO 4 -lipid and can therefore be considered to be members of a GPI superfamily.

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Procyclin gene expression and loss of the variant surface glycoprotein during differentiation of Trypanosoma brucei.

Cited by 275 publications

References 45 publications

Procyclic Trypanosoma brucei Expresses Separate Sialidase and trans-Sialidase Enzymes on Its Surface Membrane

Procyclic Trypanosoma brucei Expresses Separate Sialidase and trans-Sialidase Enzymes on Its Surface Membrane

Mitochondrial Development during Life Cycle Differentiation of African Trypanosomes: Evidence for a Kinetoplast-dependent Differentiation Control Point

The surface glycoconjugates of trypanosomatid parasites

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