scholarly journals Heme-deficient metabolism and impaired cellular differentiation as an evolutionary trade-off for human infectivity in Trypanosoma brucei gambiense

2020 ◽  
Author(s):  
Eva Horáková ◽  
Laurence Lecordier ◽  
Paula Cunha ◽  
Roman Sobotka ◽  
Piya Changmai ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Trypanosoma Brucei ◽  
Cellular Differentiation ◽  
Genetically Engineered ◽  
Trade Off ◽  
Knock Out ◽  
African Trypanosomes ◽  
Trypanosoma Brucei Gambiense ◽  
Developmental Progression ◽  
Trypanosome Lytic Factor

Abstract Resistance to African trypanosomes in humans relies on targeting of a trypanosome lytic factor 1 (TLF1) to trypanosome haptoglobin-hemoglobin receptor (HpHbR). While TLF1 avoidance by the inactivation of the HpHbR contributes to Trypanosoma brucei gambiense human infectivity, the evolutionary trade-off of this adaptation is unknown. Both T. b. gambiense with inactive HpHbR, as well as a genetically engineered T.b.brucei HpHbR knock-out show only trace levels of intracellular heme and lack the downstream hemoprotein activities, thereby providing an extraordinary example of aerobic parasite proliferation in the absence of heme. We further show that HpHbR facilitates the developmental progression by inducing PAD-1 expression that is associated with the formation of cell cycle-arrested stumpy forms in T. b.brucei . Accordingly, T. b. gambiense was found to be poorly competent for slender-to-stumpy differentiation unless a functional HpHbR receptor derived from T. b. brucei was genetically restored.

scholarly journals Single cell transcriptomic analysis of bloodstream form Trypanosoma brucei reconstructs cell cycle progression and differentiation via quorum sensing

2020 ◽  
Author(s):  
Emma Marie Briggs ◽  
Richard McCulloch ◽  
Keith Roland Matthews ◽  
Thomas Dan Otto
Keyword(s):  
Cell Cycle ◽  
Single Cell ◽  
Trypanosoma Brucei ◽  
Expression Patterns ◽  
Life Cycles ◽  
Bloodstream Form ◽  
Cycle Phase ◽  
Mammalian Host ◽  
Marker Genes ◽  
African Trypanosomes

The life cycles of African trypanosomes are dependent on several differentiation steps, where parasites transition between replicative and non-replicative forms specialised for infectivity and survival in mammal and tsetse fly hosts. Here, we use single cell transcriptomics (scRNA-seq) to dissect the asynchronous differentiation of replicative slender to transmissible stumpy bloodstream form Trypanosoma brucei. Using oligopeptide-induced differentiation, we accurately modelled stumpy development in vitro and captured the transcriptomes of 9,344 slender and stumpy stage parasites, as well as parasites transitioning between these extremes. Using this framework, we detail the relative order of biological events during development, profile dynamic gene expression patterns and identify putative novel regulators. Using marker genes to deduce the cell cycle phase of each parasite, we additionally map the cell cycle of proliferating parasites and position stumpy cell cycle exit at early G1, with subsequent progression to a distinct G0 state. We also explored the role of one gene, ZC3H20, with transient elevated expression at the key slender to stumpy transition point. By scRNA-seq analysis of ZC3H20 null parasites exposed to oligopeptides and mapping the resulting transcriptome to our atlas of differentiation, we identified the point of action for this key regulator. Using a developmental transition relevant for both virulence in the mammalian host and disease transmission, our data provide a paradigm for the temporal mapping of differentiation events and regulators in the trypanosome life cycle.

scholarly journals Mechanism of Trypanosoma brucei gambiense (group 1) resistance to human trypanosome lytic factor

2010 ◽  
Vol 107 (37) ◽  
pp. 16137-16141 ◽  
Author(s):  
R. Kieft ◽  
P. Capewell ◽  
C. M. R. Turner ◽  
N. J. Veitch ◽  
A. MacLeod ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Trypanosoma Brucei Gambiense ◽  
Trypanosome Lytic Factor ◽  
Group 1

scholarly journals Expression site attenuation mechanistically links antigenic variation and development in Trypanosoma brucei

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Christopher Batram ◽  
Nicola G Jones ◽  
Christian J Janzen ◽  
Sebastian M Markert ◽  
Markus Engstler
Keyword(s):  
Trypanosoma Brucei ◽  
Histone Methylation ◽  
Antigenic Variation ◽  
Tsetse Fly ◽  
Developmental Competence ◽  
Surface Glycoprotein ◽  
G1 Phase ◽  
African Trypanosomes ◽  
Developmental Progression ◽  
Expression Site

We have discovered a new mechanism of monoallelic gene expression that links antigenic variation, cell cycle, and development in the model parasite Trypanosoma brucei. African trypanosomes possess hundreds of variant surface glycoprotein (VSG) genes, but only one is expressed from a telomeric expression site (ES) at any given time. We found that the expression of a second VSG alone is sufficient to silence the active VSG gene and directionally attenuate the ES by disruptor of telomeric silencing-1B (DOT1B)-mediated histone methylation. Three conserved expression-site-associated genes (ESAGs) appear to serve as signal for ES attenuation. Their depletion causes G1-phase dormancy and reversible initiation of the slender-to-stumpy differentiation pathway. ES-attenuated slender bloodstream trypanosomes gain full developmental competence for transformation to the tsetse fly stage. This surprising connection between antigenic variation and developmental progression provides an unexpected point of attack against the deadly sleeping sickness.

scholarly journals Dissecting the Metabolic Roles of Pteridine Reductase 1 in Trypanosoma brucei and Leishmania major

2011 ◽  
Vol 286 (12) ◽  
pp. 10429-10438 ◽  
Author(s):  
Han B. Ong ◽  
Natasha Sienkiewicz ◽  
Susan Wyllie ◽  
Alan H. Fairlamb
Keyword(s):  
Trypanosoma Brucei ◽  
Drug Target ◽  
Enzyme Assay ◽  
Leishmania Major ◽  
Dual Role ◽  
Kinetic Properties ◽  
Dihydropteridine Reductase ◽  
Knock Out ◽  
African Trypanosomes ◽  
Dependent Activity

Leishmania parasites are pteridine auxotrophs that use an NADPH-dependent pteridine reductase 1 (PTR1) and NADH-dependent quinonoid dihydropteridine reductase (QDPR) to salvage and maintain intracellular pools of tetrahydrobiopterin (H4B). However, the African trypanosome lacks a credible candidate QDPR in its genome despite maintaining apparent QDPR activity. Here we provide evidence that the NADH-dependent activity previously reported by others is an assay artifact. Using an HPLC-based enzyme assay, we demonstrate that there is an NADPH-dependent QDPR activity associated with both TbPTR1 and LmPTR1. The kinetic properties of recombinant PTR1s are reported at physiological pH and ionic strength and compared with LmQDPR. Specificity constants (kcat/Km) for LmPTR1 are similar with dihydrobiopterin (H2B) and quinonoid dihydrobiopterin (qH2B) as substrates and about 20-fold lower than LmQDPR with qH2B. In contrast, TbPTR1 shows a 10-fold higher kcat/Km for H2B over qH2B. Analysis of Trypanosoma brucei isolated from infected rats revealed that H4B (430 nm, 98% of total biopterin) was the predominant intracellular pterin, consistent with a dual role in the salvage and regeneration of H4B. Gene knock-out experiments confirmed this: PTR1-nulls could only be obtained from lines overexpressing LmQDPR with H4B as a medium supplement. These cells grew normally with H4B, which spontaneously oxidizes to qH2B, but were unable to survive in the absence of pterin or with either biopterin or H2B in the medium. These findings establish that PTR1 has an essential and dual role in pterin metabolism in African trypanosomes and underline its potential as a drug target.

Maintaining the protective variant surface glycoprotein coat of African trypanosomes

2005 ◽  
Vol 33 (5) ◽  
pp. 981-982 ◽  
Author(s):  
G. Rudenko
Keyword(s):  
Cell Cycle ◽  
Trypanosoma Brucei ◽  
Chronic Infection ◽  
Cell Cycle Progression ◽  
Surface Glycoprotein ◽  
Variant Surface Glycoprotein ◽  
Cycle Progression ◽  
African Trypanosomes ◽  
Immune Attack ◽  
Protective Variant

The African trypanosome Trypanosoma brucei has a precarious existence as an extracellular parasite of the mammalian bloodstream, where it is faced with continuous immune attack. Key to survival is a dense VSG (variant surface glycoprotein) coat, which is repeatedly switched during the course of a chronic infection. New data demonstrate a link between VSG synthesis and cell cycle progression, indicating that VSG is monitored during the trypanosome cell cycle.

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