Glycerol suppresses glucose consumption in trypanosomes through metabolic contest.

Microorganisms must make the right choice for nutrient consumption to adapt to their changing environment. As a consequence, bacteria and yeasts have developed regulatory mechanisms involving nutrient sensing and signaling, known as "catabolite repression," allowing redirection of cell metabolism to maximize the consumption of an energy-efficient carbon source. Here, we report a new mechanism named "metabolic contest" for regulating the use of carbon sources without nutrient sensing and signaling.

Procyclic trypanosomes recycle glucose catabolites and TCA cycle intermediates to stimulate growth in the presence of physiological amounts of proline.

Trypanosoma brucei, a protist responsible for human African trypanosomiasis (sleeping sickness), is transmitted by the tsetse fly where the procyclic forms of the parasite develop in the proline-rich (1-2 mM) and glucose-depleted digestive tract. Proline is essential for the midgut colonization of the parasite in the insect vector, however other carbon sources could be available and used to feed its central metabolism. Here we show that procyclic trypanosomes can consume and metabolize metabolic intermediates, including those excreted from glucose catabolism (succinate, alanine and pyruvate), with the exception of acetate, which is the ultimate end-product excreted by the parasite.

Gluconeogenesis is essential for trypanosome development in the tsetse fly vector.

In the glucose-free environment that is the midgut of the tsetse fly vector, the procyclic form of Trypanosoma brucei primarily uses proline to feed its central carbon and energy metabolism. In these conditions, the parasite needs to produce glucose 6-phosphate (G6P) through gluconeogenesis from metabolism of non-glycolytic carbon source(s). We showed here that two phosphoenolpyruvate-producing enzymes, PEP carboxykinase (PEPCK) and pyruvate phosphate dikinase (PPDK) have a redundant function for the essential gluconeogenesis from proline.

Glycerol supports growth of the Trypanosoma brucei bloodstream forms in the absence of glucose: Analysis of metabolic adaptations on glycerol-rich conditions.

The bloodstream forms of Trypanosoma brucei (BSF), the parasite protist causing sleeping sickness, primarily proliferate in the blood of their mammalian hosts. The skin and adipose tissues were recently identified as additional major sites for parasite development. Glucose was the only carbon source known to be used by bloodstream trypanosomes to feed their central carbon metabolism, however, the metabolic behaviour of extravascular tissue-adapted parasites has not been addressed yet.

De novo biosynthesis of sterols and fatty acids in the Trypanosoma brucei procyclic form: Carbon source preferences and metabolic flux redistributions.

De novo biosynthesis of lipids is essential for Trypanosoma brucei, a protist responsible for the sleeping sickness. Here, we demonstrate that the ketogenic carbon sources, threonine, acetate and glucose, are precursors for both fatty acid and sterol synthesis, while leucine only contributes to sterol production in the tsetse fly midgut stage of the parasite. Degradation of these carbon sources into lipids was investigated using a combination of reverse genetics and analysis of radio-labelled precursors incorporation into lipids.

Expression, purification, and crystallization of type 1 isocitrate dehydrogenase from Trypanosoma brucei brucei.

Isocitrate dehydrogenases (IDHs) are metabolic enzymes that catalyze the oxidative decarboxylation of isocitrate to α-ketoglutarate. Depending on the electron acceptor and subcellular localization, these enzymes are classified as NADP-dependent IDH1 in the cytosol or peroxisomes, NADP-dependent IDH2 and NAD-dependent IDH3 in mitochondria. Trypanosoma brucei is a protozoan parasite that causes African sleeping sickness in humans and Nagana disease in animals.

Glycosomes: A comprehensive view of their metabolic roles in T. brucei.

Peroxisomes are single-membrane cellular organelles, present in most eukaryotic cells and organisms from human to yeast, fulfilling essential metabolic functions in lipid metabolism, free radical detoxification, differentiation, development, morphogenesis, etc. Interestingly, the protozoan parasite species Trypanosoma contains peroxisome-like organelles named glycosomes, which lack hallmark peroxisomal pathways and enzymes, such as catalase. Glycosomes are the only peroxisome-like organelles containing most enzymatic steps of the glycolytic pathway as well as enzymes of pyrimidine biosynthesis, purine salvage and biosynthesis of nucleotide sugars.

Combining reverse genetics and nuclear magnetic resonance-based metabolomics unravels trypanosome-specific metabolic pathways.

Numerous eukaryotes have developed specific metabolic traits that are not present in extensively studied model organisms. For instance, the procyclic insect form of Trypanosoma brucei, a parasite responsible for sleeping sickness in its mammalian-specific bloodstream form, metabolizes glucose into excreted succinate and acetate through pathways with unique features. Succinate is primarily produced from glucose-derived phosphoenolpyruvate in peroxisome-like organelles, also known as glycosomes, by a soluble NADH-dependent fumarate reductase only described in trypanosomes so far.

Triacylglycerol Storage in Lipid Droplets in Procyclic Trypanosoma brucei.

Carbon storage is likely to enable adaptation of trypanosomes to nutritional challenges or bottlenecks during their stage development and migration in the tsetse. Lipid droplets are candidates for this function. This report shows that feeding of T.

Cytosolic NADPH homeostasis in glucose-starved procyclic Trypanosoma brucei relies on malic enzyme and the pentose phosphate pathway fed by gluconeogenic flux.

All living organisms depend on NADPH production to feed essential biosyntheses and for oxidative stress defense. Protozoan parasites such as the sleeping sickness pathogen Trypanosoma brucei adapt to different host environments, carbon sources, and oxidative stresses during their infectious life cycle. The procyclic stage develops in the midgut of the tsetse insect vector, where they rely on proline as carbon source, although they prefer glucose when grown in rich media.

Acetate produced in the mitochondrion is the essential precursor for lipid biosynthesis in procyclic trypanosomes.

Acetyl-CoA produced in mitochondria from carbohydrate or amino acid catabolism needs to reach the cytosol to initiate de novo synthesis of fatty acids. All eukaryotes analyzed so far use a citrate/malate shuttle to transfer acetyl group equivalents from the mitochondrial matrix to the cytosol. Here we investigate how this acetyl group transfer occurs in the procyclic life cycle stage of Trypanosoma brucei, a protozoan parasite responsible of human sleeping sickness and economically important livestock diseases.