Infection with Trypanosoma lewisi or Trypanosoma musculi may promote the spread of Toxoplasma gondii.

Toxoplasma gondii can infect almost all warm-blooded vertebrates with pathogensis being largely influenced by the host immune status. As important epidemiological hosts, rodents are globally distributed and are also commonly found infected with haemoflagellates, such as those in the genus Trypanosoma. We here address whether and how co-infection with trypanosomes can influence T. gondii infection in laboratory models. Rats of five strains, co-infected with T. lewisi and mice of four strains, co-infected with T. musculi, were found to be more or less susceptible to T. gondii infection, respectively, with corresponding increased or decreased brain cyst burdens. Downregulation of iNOS expression and decreased NO production or reverse were observed in the peritoneal macrophages of rats or mice, infected with trypanosomes, respectively. Trypanosoma lewisi and T. musculi can modulate host immune responses, either by enhancement or suppression and influence the outcome of Toxoplasma infection.

A specific basal body linker protein provides the connection function for basal body inheritance in trypanosomes.

Centrioles and basal bodies (CBBs) are found in physically linked pairs, and in mammalian cells intercentriole connections (G1-G2 tether and S-M linker) regulate centriole duplication and function. In trypanosomes BBs are not associated with the spindle and function in flagellum/cilia nucleation with an additional role in mitochondrial genome (kinetoplast DNA [kDNA]) segregation. Here, we describe BBLP, a BB/pro-BB (pBB) linker protein in Trypanosoma brucei predicted to be a large coiled-coil protein conserved in the kinetoplastida. Colocalization with the centriole marker SAS6 showed that BBLP localizes between the BB/pBB pair, throughout the cell cycle, with a stronger signal in the old flagellum BB/pBB pair. Importantly, RNA interference (RNAi) depletion of BBLP leads to a conspicuous splitting of the BB/pBB pair associated only with the new flagellum. BBLP RNAi is lethal in the bloodstream form of the parasite and perturbs mitochondrial kDNA inheritance. Immunogold labeling confirmed that BBLP is localized to a cytoskeletal component of the BB/pBB linker, and tagged protein induction showed that BBLP is incorporated de novo in both new and old flagella BB pairs of dividing cells. We show that the two aspects of CBB disengagement-loss of orthogonal orientation and ability to separate and move apart-are consistent but separable events in evolutionarily diverse cells and we provide a unifying model explaining centriole/BB linkage differences between such cells.

Vacuolar ATPase depletion contributes to dysregulation of endocytosis in bloodstream forms of Trypanosoma brucei.

BACKGROUND: Vacuolar H+-ATPase (V-ATPase) is a highly conserved protein complex which hydrolyzes ATP and pumps protons to acidify vacuolar vesicles. Beyond its role in pH maintenance, the involvement of V-ATPase in endocytosis is well documented in mammals and plants but is less clear in Trypanosoma brucei. METHODS: In this study, the subcellular localization of V-ATPase subunit B (TbVAB) of T. brucei was assessed via in situ N-terminal YFP-tagging and immunofluorescence assays. Transgenic bloodstream forms (BSF) of T. brucei were generated which comprised either a V-ATPase subunit B (TbVAB) conditional knockout or a V-ATPase subunit A (TbVAA) knockdown. Acridine orange and BCECF-AM were employed to assess the roles of V-ATPase in the pH regulation of BSF T. brucei. The endocytic activities of three markers were also characterized by flow cytometry analyses. Furthermore, trypanosomes were counted from trypanolysis treatment groups (either containing 1% or 5% NHS) and endocytosed trypanosome lytic factor (TLF) was also analyzed by an immunoblotting assay. RESULTS: TbVAB was found to localize to acidocalcisomes, lysosomes and probably also to endosomes of BSF of T. brucei and was demonstrated to be essential for cell growth. TbVAB depletion neutralized acidic organelles at 24 hours post-tetracycline depletion (hpd), meanwhile the steady state intracellular pH increased from 7.016 ± 0.013 to 7.422 ± 0.058. Trypanosomes with TbVAB depletion at 24 hpd were found to take up more transferrin (2.068 ± 0.277 fold) but less tomato lectin (49.31 ± 22.57%) by endocytosis, while no significant change was detected in dextran uptake. Similar endocytic dysregulated phenotypes were also observed in TbVAA knockdown cells. In addition, TbVAB depleted trypanosomes showed a low uptake of TLF and exhibited less sensitive to lysis in both 1% and 5% NHS treatments. CONCLUSIONS: TbVAB is a key component of V-ATPase and was found to play a key function in endocytosis as well as exhibiting different effects in a receptor/cargo dependent manner in BSF of T. brucei. Besides vacuolar alkalinization, the dysregulation of endocytosis in TbVAB depleted T. brucei is considered to contribute to the reduced sensitivity to lysis by normal human serum.

An efficient cumate-inducible system for procyclic and bloodstream form Trypanosoma brucei.

In Trypanosoma brucei, the tetracycline-inducible system enables tightly-regulated, highly-efficient expression of recombinant proteins or double-stranded RNA in both procyclic and bloodstream form cells, providing useful molecular genetic tools to study gene functions. An alternative, vanillic acid-inducible system is recently described for procyclic T. brucei, providing ∼18-fold increase in GFP reporter expression upon induction (Sunter JD. Mol. Biochem. Parasitol. 2016, 207:45-48). Here we describe a cumate-inducible system that allows efficient, tunable gene expression showing >300-fold increase in GFP expression upon induction. The cumate-inducible system can be used alone or together with the tetracycline-inducible system, in both procyclic and bloodstream form T. brucei. Efficient cumate-inducible expression is also achieved in T. brucei-infected mice.

ATP-driven and AMPK-independent autophagy in an early branching eukaryotic parasite.

Autophagy is a catabolic cellular process required to maintain protein synthesis, energy production and other essential activities in starved cells. While the exact nutrient sensor(s) is yet to be identified, deprivation of amino acids, glucose, growth factor and other nutrients can serve as metabolic stimuli to initiate autophagy in higher eukaryotes. In the early-branching unicellular parasite Trypanosoma brucei, which can proliferate as procyclic form (PCF) in the tsetse fly or as bloodstream form (BSF) in animal hosts, autophagy is robustly triggered by amino acid deficiency but not by glucose depletion. Taking advantage of the clearly defined adenosine triphosphate (ATP) production pathways in T. brucei, we have shown that autophagic activity depends on the levels of cellular ATP production, using either glucose or proline as a carbon source. While autophagosome formation positively correlates with cellular ATP levels; perturbation of ATP production by removing carbon sources or genetic silencing of enzymes involved in ATP generation pathways, also inhibited autophagy. This obligate energy dependence and the lack of glucose starvation-induced autophagy in T. brucei may reflect an adaptation to its specialized, parasitic life style.