Developmental changes and metabolic reprogramming during establishment of infection and progression of Trypanosoma brucei brucei through its insect host

Abstract

Trypanosoma brucei ssp , unicellular parasites causing human and animal trypanosomiasis, are transmitted between mammals by tsetse flies. Periodic changes in variant surface glycoproteins (VSG), which form the parasite coat in the mammal, allow them to evade the host immune response. Different isolates of T. brucei show heterogeneity in their repertoires of VSG genes and have single nucleotide polymorphisms and indels that can impact on genome editing. T. brucei brucei EATRO1125 (AnTaR1 serodeme) is an isolate that is used increasingly often because it is pleomorphic in mammals and fly transmissible, two characteristics that have been lost by the most commonly used laboratory stocks. We present a genome assembly of EATRO1125, including contigs for the intermediate and mini-chromosomes that serve as repositories of VSG genes. In addition, de novo transcriptome assemblies were performed using Illumina sequences from tsetse-derived trypanosomes. Reads of 150 bases enabled closely related members of multigene families to be discriminated. This revealed that the transcriptome of midgut-derived parasites is dynamic, starting with the expression of high affinity hexose transporters and glycolytic enzymes and then switching to proline uptake and catabolism. These changes resemble the transition from early to late procyclic forms in culture. Further metabolic reprogramming, including upregulation of tricarboxylic acid cycle enzymes, occurs in the proventriculus. Many transcripts upregulated in the salivary glands encode surface proteins, among them 7 metacyclic VSGs, multiple BARPs and GCS1/HAP2, a marker for gametes. A novel family of transmembrane proteins, containing polythreonine stretches that are predicted to be O-glycosylation sites, was also identified. Finally, RNA-Seq data were used to create an optimised annotation file with 5’ and 3’ untranslated regions accurately mapped for 9302 genes. We anticipate that this will be of use in identifying transcripts obtained by single cell sequencing technologies.

A multi-adenylate cyclase regulator at the flagellar tip controls African trypanosome transmission

“…Upon heterodimerization, this may result in activation or dominant-negative inhibition, dependent on AC isoform composition of the tip domain and changing environmental stimuli to fine-tune cAMP levels. In agreement to the model, AC isoform diversity and non-redundancy at the flagellar tip 7 and differential expression of transcripts encoding AC isoforms in trypanosomes colonizing midgut, cardia or salivary glands 34,35 have been reported. CARP3 depletion might result in local compositional imbalance of AC isoforms possibly due to isoform-specific quantitative differences in CARP3-mediated complex stability.…”

“…Trypanosomes shuttle between the bloodstream and tissues of a mammalian host and the alimentary tract and salivary glands of a tsetse fly undergoing a series of developmental transitions that result in defined adapted stages 33 . Cyclic AMP signaling was suggested to play a role in stage development due to differential expression of transcripts encoding AC isoforms in trypanosomes colonizing midgut, proventriculus or salivary glands, respectively 34,35 . During their complex journey through the insect vector, trypanosomes are in intimate contact with host tissue surfaces and have to cope with several bottlenecks 36 .…”

The mitochondrial genome segregation system ofT. brucei: Single p197 molecules connect the basal body with the outer membrane

“…The following lines of evidence suggest that p197 is much larger than 197 kDa. Recent sequencing of the genome of the T. b. brucei EATRO1125 strain revealed that p197 has at least 26 repeats of 175 aa (43), indicating that the molecular weight of p197 might be as large as 660 kDa. That would make it to one of the largest trypanosomal proteins known.…”

Cryo-electron tomography sheds light on the elastic nature of theTrypanosoma bruceitripartite attachment complex

“…Its N-terminus localizes at the OMM, while the C-terminus localizes to the proximal end of the BB/ pBB (Aeschlimann et al, 2022). In addition, p197 contains a central section of 26-28 nearly identical repeats of 175-182 amino acids (Aeschlimann et al, 2022;Naguleswaran et al, 2021).…”