A Trypanosome Structure Involved in Transmitting Cytoplasmic Information During Cell Division

Moreira-Leite, Flávia; Sherwin, Trevor; Kohl, Linda; Gull, Keith

doi:10.1126/science.1063775

Cited by 144 publications

(161 citation statements)

References 21 publications

(12 reference statements)

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“…It has been postulated that these ␤-Gal-containing structures may be involved in retaining the TfR, and other recycling components, in the T. brucei flagellar pocket and the endosomal͞lysosomal membrane system (18). In addition to the aforementioned glycoproteins, five other transmembrane glycoproteins, ISG65, ISG75 (19), the ecto-phosphatase AcP115 (20), the Golgi-and lysosome-associated glycoprotein tGLP-1 (21), and the Fla-1 glycoprotein (22), the latter associated with flagellar adhesion to the cell body (23), are known to be glycosylated, but the nature of their carbohydrate chains is unknown. There are also other membrane proteins, such as Tb-29 (24), the cysteine-rich acidic membrane protein CRAM (25), the alanine-rich protein BARP (26), and the products of expression-site-associated genes (ESAGs) 1, 2, 3, 4, 10, and 11 (26,27), that are predicted to contain carbohydrate in the form of GPI anchors and͞or N-linked oligosaccharides.…”

Section: Discussionmentioning

confidence: 99%

Galactose metabolism is essential for the African sleeping sickness parasite Trypanosoma brucei

Roper

Güther

Milne

et al. 2002

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

100

116

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The tsetse fly-transmitted protozoan parasite Trypanosoma brucei is the causative agent of human African sleeping sickness and the cattle disease Nagana. The bloodstream form of the parasite uses a dense cell-surface coat of variant surface glycoprotein to escape the innate and adaptive immune responses of the mammalian host and a highly glycosylated transferrin receptor to take up host transferrin, an essential growth factor. These glycoproteins, as well as other flagellar pocket, endosomal, and lysosomal glycoproteins, are known to contain galactose. The parasite is unable to take up galactose, suggesting that it may depend on the action of UDPglucose 4 -epimerase for the conversion of UDP-Glc to UDP-Gal and subsequent incorporation of galactose into glycoconjugates via UDP-Gal-dependent galactosyltransferases. In this paper, we describe the cloning of T. brucei galE, encoding T. brucei UDP-Glc-4 -epimerase, and functional characterization by complementation of a galE-deficient Escherichia coli mutant and enzymatic assay of recombinant protein. A tetracycline-inducible conditional galE null mutant of T. brucei was created using a transgenic parasite expressing the TETR tetracycline repressor protein gene. Withdrawal of tetracycline led to a cessation of cell division and substantial cell death, demonstrating that galactose metabolism in T. brucei proceeds via UDP-Glc-4 -epimerase and is essential for parasite growth. After several days without tetracycline, cultures spontaneously recovered. These cells were shown to have undergone a genetic rearrangement that deleted the TETR gene. The results show that enzymes and transporters involved in galactose metabolism may be considered as potential therapeutic targets against African trypanosomiasis.UDP-Gal ͉ galE ͉ epimerase T he tsetse fly-transmitted protozoan parasite Trypanosoma brucei causes human African sleeping sickness and the related cattle disease Nagana. There are 300,000-500,000 cases of the human disease per year in sub-Saharan Africa (1). The bloodstream form of the parasite divides by binary fission in the blood, lymph, and interstitial fluids of the mammalian host, and causes cachexia and anaemia in cattle and neurological disturbances in man. These conditions are fatal if not treated, and existing chemotherapies are toxic and difficult to administer. The need for new, less-toxic therapeutics is widely acknowledged (1).The bloodstream form of T. brucei is rich in galactosecontaining glycoproteins, most notably the variant surface glycoprotein (VSG) that, at 5 ϫ 10 6 homodimers per cell, forms a dense cell-surface coat. The VSG coat is a macromolecular diffusion barrier that protects the parasite from the innate immune system and also enables the parasite to undergo antigenic variation. Thus, although an individual parasite only expresses one VSG gene at a time, the parasite population can stay ahead of the host's specific immune response to expressed VSGs when a few parasites switch expression to one of several hundred genes encoding immunologically ...

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Section: Discussionmentioning

confidence: 99%

Galactose metabolism is essential for the African sleeping sickness parasite Trypanosoma brucei

Roper

Güther

Milne

et al. 2002

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

100

116

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“…Furthermore, in a typical growing trypanosome cell, the new flagellum is attached along its length to the cell body via a cytoskeletal junction structure known as the flagellar attachment zone (Robinson et al, 1995), and also to the old flagellum at the anterior end via the flagella connector (Briggs et al, 2004;Moreira-Leite et al, 2001). Together, the structures of these complexes help guide cell morphogenesis and maintain the correct polarity of underlying cell structures as it prepares for cytokinesis (Briggs et al, 2004;Moreira-Leite et al, 2001;Ngo et al, 1998;Robinson et al, 1995) and help define the site of cleavage furrow initiation (Kohl et al, 2003). In some TbSPT2 RNAi +Tet cells, the growing daughter flagellum was not connected to the old flagellum either at the tip or across partial or full length of the cell body (Fig.…”

Section: Journal Of Cell Science 121 (4)mentioning

confidence: 99%

Sphingolipid synthesis is necessary for kinetoplast segregation and cytokinesis in Trypanosoma brucei

Fridberg

Olson

Nakayasu

et al. 2008

Journal of Cell Science

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Sphingolipids and their metabolites have been thought crucial for cell growth and cell cycle progression, membrane and protein trafficking, signal transduction, and formation of lipid rafts; however, recent studies in trypanosomes point to the dispensability of sphingolipids in some of these processes. In this study, we explore the requirements for de novo sphingolipid biosynthesis in the insect life cycle stage of the African trypanosome Trypanosoma brucei by inhibiting the enzyme serine palmitoyltransferase (SPT2) by using RNA interference or treatment with a potent SPT2 inhibitor myriocin. Mass spectrometry revealed that upon SPT2 inhibition, the parasites contained substantially reduced levels of inositolphosphorylceramide. Although phosphatidylcholine and cholesterol levels were increased to compensate for this loss, the cells were ultimately not viable. The most striking result of sphingolipid reduction in procyclic T. brucei was aberrant cytokinesis, characterized by incomplete cleavage-furrow formation, delayed kinetoplast segregation and emergence of cells with abnormal DNA content. Organelle replication continued despite sphingolipid depletion, indicating that sphingolipids act as second messengers regulating cellular proliferation and completion of cytokinesis. Distention of the mitochondrial membrane, formation of multilamellar structures within the mitochondrion and near the nucleus, accumulation of lipid bodies and, less commonly, disruption of the Golgi complex were observed after prolonged sphingolipid depletion. These findings suggest that some aspects of vesicular trafficking may be compromised. However, flagellar membrane targeting and the association of the flagellar membrane protein calflagin with detergent-resistant membranes were not affected, indicating that the vesicular trafficking defects were mild. Our studies indicate that sphingolipid biosynthesis is vital for cell cycle progression and cell survival, but not essential for the normal trafficking of flagellar membrane-associated proteins or lipid raft formation in procyclic T. brucei.

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“…The assembling trypanosome flagellum tip has a flagella connector (FC), which is a mobile membrane junction linking it to the side of the old flagellum, an association that is implicated in inheritance of cell pattern (9,14,15). The FC has a complex structure and can be divided into five distinct zones ( Fig.…”

mentioning

confidence: 99%

“…The FC then provides constant attachment of the extending new flagellum tip on the old flagellum while migrating along the old flagellum (14,15). This migration is independent of new axoneme elongation (12,16).…”

mentioning

confidence: 99%

Protein diversity in discrete structures at the distal tip of the trypanosome flagellum

Varga

Moreira-Leite

Portman

et al. 2017

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

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The distal end of the eukaryotic flagellum/cilium is important for axonemal growth and signaling and has distinct biomechanical properties. Specific flagellum tip structures exist, yet their composition, dynamics, and functions are largely unknown. We used biochemical approaches to identify seven constituents of the flagella connector at the tip of an assembling trypanosome flagellum and three constituents of the axonemal capping structure at the tips of both assembling and mature flagella. Both tip structures contain evolutionarily conserved as well as kinetoplastid-specific proteins, and component assembly into the structures occurs very early during flagellum extension. Localization and functional studies reveal that the flagella connector membrane junction is attached to the tips of extending microtubules of the assembling flagellum by a kinesin-15 family member. On the opposite side, a kinetoplastid-specific kinesin facilitates attachment of the junction to the microtubules in the mature flagellum. Functional studies also suggest roles of several other components and the definition of subdomains in the tip structures.

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A Trypanosome Structure Involved in Transmitting Cytoplasmic Information During Cell Division

Cited by 144 publications

References 21 publications

Galactose metabolism is essential for the African sleeping sickness parasite Trypanosoma brucei

Galactose metabolism is essential for the African sleeping sickness parasite Trypanosoma brucei

Sphingolipid synthesis is necessary for kinetoplast segregation and cytokinesis in Trypanosoma brucei

Protein diversity in discrete structures at the distal tip of the trypanosome flagellum

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