The -Derived Ketoacids, Indole Pyruvate and Hydroxyphenylpyruvate, Induce HO-1 Expression and Suppress Inflammatory Responses in Human Dendritic Cells.

The extracellular parasite and causative agent of African sleeping sickness () has evolved a number of strategies to avoid immune detection in the host. One recently described mechanism involves the conversion of host-derived amino acids to aromatic ketoacids, which are detected at relatively high concentrations in the bloodstream of infected individuals. These ketoacids have been shown to directly suppress inflammatory responses in murine immune cells, as well as acting as potent inducers of the stress response enzyme, heme oxygenase 1 (HO-1), which has proven anti-inflammatory properties.

The Trypanosome-Derived Metabolite Indole-3-Pyruvate Inhibits Prostaglandin Production in Macrophages by Targeting COX2.

The protozoan parasite is the causative agent of the neglected tropical disease human African trypanosomiasis, otherwise known as sleeping sickness. Trypanosomes have evolved many immune-evasion mechanisms to facilitate their own survival, as well as prolonging host survival to ensure completion of the parasitic life cycle. A key feature of the bloodstream form of is the secretion of aromatic keto acids, which are metabolized from tryptophan.

Genetic and immunological basis of human African trypanosomiasis.

Human African trypanosomiasis, or sleeping sickness, results from infection by two subspecies of the protozoan flagellate parasite Trypanosoma brucei, termed Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, prevalent in western and eastern Africa respectively. These subspecies escape the trypanolytic potential of human serum, which efficiently acts against the prototype species Trypanosoma brucei brucei, responsible for the Nagana disease in cattle. We review the various strategies and components used by trypanosomes to counteract the immune defences of their host, highlighting the adaptive genomic evolution that occurred in both parasite and host to take the lead in this battle.

The KIFC1 Kinesin Ensures the Fast Antibody Clearance Required for Parasite Infectivity.

Human innate immunity to involves the trypanosome C-terminal kinesin KIFC1, which transports internalized trypanolytic factor apolipoprotein L1 (APOL1) within the parasite. We show that KIFC1 preferentially associates with cholesterol-containing membranes and is indispensable for mammalian infectivity. Knockdown of KIFC1 did not affect trypanosome growth but rendered the parasites unable to infect mice unless antibody synthesis was compromised.

Queuine Micronutrient Deficiency Promotes Warburg Metabolism and Reversal of the Mitochondrial ATP Synthase in Hela Cells.

Queuine is a eukaryotic micronutrient, derived exclusively from eubacteria. It is incorporated into both cytosolic and mitochondrial transfer RNA to generate a queuosine nucleotide at position 34 of the anticodon loop. The transfer RNA of primary tumors has been shown to be hypomodified with respect to queuosine, with decreased levels correlating with disease progression and poor patient survival.

Secreted Aromatic Ketoacids Activate the Nrf2/HO-1 Pathway and Suppress Pro-inflammatory Responses in Primary Murine Glia and Macrophages.

African trypanosomes, such as (), are protozoan parasites of the mammalian vasculature and central nervous system that are best known for causing fatal human sleeping sickness. As exclusively extracellular parasites, trypanosomes are subject to constant challenge from host immune defenses but they have developed very effective strategies to evade and modulate these responses to maintain an infection while simultaneously prolonging host survival. Here we investigate host parasite interactions, especially within the CNS context, which are not well-understood.

Metabolic reprogramming during the life cycle.

Cellular metabolic activity is a highly complex, dynamic, regulated process that is influenced by numerous factors, including extracellular environmental signals, nutrient availability and the physiological and developmental status of the cell. The causative agent of sleeping sickness, , is an exclusively extracellular protozoan parasite that encounters very different extracellular environments during its life cycle within the mammalian host and tsetse fly insect vector. In order to meet these challenges, there are significant alterations in the major energetic and metabolic pathways of these highly adaptable parasites.

Trypanosoma brucei metabolite indolepyruvate decreases HIF-1α and glycolysis in macrophages as a mechanism of innate immune evasion.

The parasite Trypanasoma brucei causes African trypanosomiasis, known as sleeping sickness in humans and nagana in domestic animals. These diseases are a major burden in the 36 sub-Saharan African countries where the tsetse fly vector is endemic. Untreated trypanosomiasis is fatal and the current treatments are stage-dependent and can be problematic during the meningoencephalitic stage, where no new therapies have been developed in recent years and the current drugs have a low therapeutic index.

Coupling of lysosomal and mitochondrial membrane permeabilization in trypanolysis by APOL1.

Humans resist infection by the African parasite Trypanosoma brucei owing to the trypanolytic activity of the serum apolipoprotein L1 (APOL1). Following uptake by endocytosis in the parasite, APOL1 forms pores in endolysosomal membranes and triggers lysosome swelling. Here we show that APOL1 induces both lysosomal and mitochondrial membrane permeabilization (LMP and MMP).

Mechanism of Trypanosoma brucei gambiense resistance to human serum.

The African parasite Trypanosoma brucei gambiense accounts for 97% of human sleeping sickness cases. T. b.

Inhibition of late-stage autophagy synergistically enhances pyrrolo-1,5-benzoxazepine-6-induced apoptotic cell death in human colon cancer cells.

The pyrrolo-1,5-benzoxazepines (PBOXs) are a novel group of selective apoptotic agents displaying promising therapeutic potential in both ex vivo chemotherapy-refractory patient samples and in vivo murine carcinoma models. In this report, we present novel data concerning the induction of autophagy by the PBOXs in adenocarcinoma-derived colon cancer cells. Autophagy is a lysosome-dependent degradative pathway recently associated with chemotherapy.

Identification and characterization of a stage specific membrane protein involved in flagellar attachment in Trypanosoma brucei.

Flagellar attachment is a visibly striking morphological feature of African trypanosomes but little is known about the requirements for attachment at a molecular level. This study characterizes a previously undescribed membrane protein, FLA3, which plays an essential role in flagellar attachment in Trypanosoma brucei. FLA3 is heavily N-glycosylated, locates to the flagellar attachment zone and appears to be a bloodstream stage specific protein.

The vascular targeting agent Combretastatin-A4 directly induces autophagy in adenocarcinoma-derived colon cancer cells.

Recent clinical data demonstrated that the vascular targeting agent Combretastatin-A4 phosphate (CA-4P) prolonged survival of patients with advanced anaplastic thyroid cancer without any adverse side effects. However, as a single agent CA-4 failed to reduce tumour growth in the murine CT-26 adenocarcinoma colon cancer model. Furthermore, the molecular mechanism of the innate resistance of HT-29 human adenocarcinoma cells to CA-4 is largely unknown.

Identification and characterization of an unusual class I myosin involved in vesicle traffic in Trypanosoma brucei.

Myosins are a multimember family of motor proteins with diverse functions in eukaryotic cells. African trypanosomes possess only two candidate myosins and thus represent a useful system for functional analysis of these motors. One of these candidates is an unusual class I myosin (TbMyo1) that is expressed at similar levels but organized differently during the life cycle of Trypanosoma brucei.

Alanine aminotransferase of Trypanosoma brucei--a key role in proline metabolism in procyclic life forms.

African trypanosomes possess high levels of alanine aminotransferase (EC 2.6.1.

Loss of actin does not affect export of newly synthesized proteins to the surface of Trypanosoma brucei.

Vesicle traffic to and from the surface is highly polarized in African trypanosomes. Actin is required for polarized endocytic traffic in bloodstream forms of African trypanosomes but its role in other pathways has remained equivocal. A combination of metabolic pulse chase labelling and surface biotinylation during the chase period along with the use of conditional RNA interference was employed to demonstrate that substantial loss of actin had no effect on the export of newly synthesized proteins to the surface of bloodstream and procyclic forms of Trypanosoma brucei.

The trypanolytic factor of human serum.

African trypanosomes (the prototype of which is Trypanosoma brucei brucei) are protozoan parasites that infect a wide range of mammals. Human blood, unlike the blood of other mammals, has efficient trypanolytic activity, and this needs to be counteracted by these parasites. Resistance to this activity has arisen in two subspecies of Trypanosoma brucei - Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense - allowing these parasites to infect humans, and this results in sleeping sickness in East Africa and West Africa, respectively.

Apolipoprotein L-I promotes trypanosome lysis by forming pores in lysosomal membranes.

Apolipoprotein L-I is the trypanolytic factor of human serum. Here we show that this protein contains a membrane pore-forming domain functionally similar to that of bacterial colicins, flanked by a membrane-addressing domain. In lipid bilayer membranes, apolipoprotein L-I formed anion channels.

Characterization of two protein disulfide isomerases from the endocytic pathway of bloodstream forms of Trypanosoma brucei.

Proteins from the endocytic pathway in bloodstream forms of Trypanosome brucei are modified by the addition of linear poly-N-acetyllactosamine side chains, which permits their isolation by tomato lectin affinity chromatography. Antibodies against this tomato lectin binding fraction were employed to screen a cDNA expression library from bloodstream forms of T. brucei.

A differential role for actin during the life cycle of Trypanosoma brucei.

Actin is expressed at similar levels but in different locations in bloodstream and procyclic forms of Trypanosoma brucei. In bloodstream forms actin colocalizes with the highly polarized endocytic pathway, whereas in procyclic forms it is distributed throughout the cell. RNA interference demonstrated that in bloodstream forms, actin is an essential protein.

A chromosomal SIR2 homologue with both histone NAD-dependent ADP-ribosyltransferase and deacetylase activities is involved in DNA repair in Trypanosoma brucei.

SIR2-like proteins have been implicated in a wide range of cellular events including chromosome silencing, chromosome segregation, DNA recombination and the determination of life span. We report here the molecular and functional characterization of a SIR2-related protein from the protozoan parasite Trypanosoma brucei, which we termed TbSIR2RP1. This protein is a chromosome-associated NAD-dependent enzyme which, in contrast to other known proteins of this family, catalyses both ADP-ribosylation and deacetylation of histones, particulary H2A and H2B.

Apolipoprotein L-I is the trypanosome lytic factor of human serum.

Human sleeping sickness in east Africa is caused by the parasite Trypanosoma brucei rhodesiense. The basis of this pathology is the resistance of these parasites to lysis by normal human serum (NHS). Resistance to NHS is conferred by a gene that encodes a truncated form of the variant surface glycoprotein termed serum resistance associated protein (SRA).

A protein kinase specifically associated with proliferative forms of Trypanosoma brucei is functionally related to a yeast kinase involved in the co-ordination of cell shape and division.

The life cycle of African trypanosomes is characterized by the alternation of proliferative and quiescent stages but the molecular details of this process remain unknown. Here, we describe a new cytoplasmic protein kinase from Trypanosoma brucei, termed TBPK50, that belongs to a family of protein kinases involved in the regulation of the cell cycle, cell shape and proliferation. TBPK50 is expressed only in proliferative forms but is totally absent in quiescent cells despite the fact that the gene is constitutively transcribed at the same level throughout the life cycle.