An AMP-activated protein kinase complex with two distinctive alpha subunits is involved in nutritional stress responses in Trypanosoma cruzi

Inhibition of AMPK activation in Echinococcus granulosus sensu stricto limits the parasite's glucose metabolism and survival

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by larvae of the Echinococcus granulosus sensu lato (s.l.) cluster. There is an urgent need to develop new drug targets and drug molecules to treat CE. Adenosine monophosphate (AMP)-activated protein kinase (AMPK), a serine/threonine protein kinase consisting of α, β, and γ subunits, plays a key role in the regulation of energy metabolism. However, the role of AMPK in regulating glucose metabolism in E. granulosus s.l. and its effects on parasite viability is unknown. In this study, we found that targeted knockdown of EgAMPKα or a small-molecule AMPK inhibitor inhibited the viability of E. granulosus sensu stricto (s.s.) and disrupted the ultrastructure. The results of in vivo experiments showed that the AMPK inhibitor had a significant therapeutic effect on E. granulosus s.s.-infected mice and resulted in the loss of cellular structures of the germinal layer. In addition, the inhibition of the EgAMPK/EgGLUT1 pathway limited glucose uptake and glucose metabolism functions in E. granulosus s.s.. Overall, our results suggest that EgAMPK can be a potential drug target for CE and that inhibition of EgAMPK activation is an effective strategy for the treatment of disease.

RNA-seq reveals that overexpression of TcUBP1 switches the gene expression pattern towards that of the infective form of Trypanosoma cruzi

Trypanosomes regulate gene expression mainly by using post-transcriptional mechanisms. Key factors responsible for carrying out this regulation are RNA-binding proteins (RBPs), affecting subcellular localization, translation, and/or transcript stability. Trypanosoma cruzi U-rich RBP 1 (TcUBP1) is a small protein that modulates the expression of several surface glycoproteins of the trypomastigote infective stage of the parasite. Its mRNA targets are known but the impact of its overexpression at the transcriptome level in the insect-dwelling epimastigote cells has not yet been investigated. Thus, in the present study, by using a tetracycline-inducible system, we generated a population of TcUBP1-overexpressing parasites and analyzed its effect by RNA-seq methodology. This allowed us to identify 793 up- and 371 down-regulated genes with respect to the wild-type control sample. Among the up-regulated genes, it was possible to identify members coding for the TcS superfamily, MASP, MUCI/II, and protein kinases, whereas among the down-regulated transcripts, we found mainly genes coding for ribosomal, mitochondrial, and synthetic pathway proteins. RNA-seq comparison with two previously published datasets revealed that the expression profile of this TcUBP1-overexpressing replicative epimastigote form resembles the transition to the infective metacyclic trypomastigote stage. We identified novel cis-regulatory elements in the 3'-untranslated region of the affected transcripts and confirmed that UBP1m -a signature TcUBP1 binding element previously characterized in our lab- is enriched in the list of stabilized genes. We can conclude that the overall effect of TcUBP1 overexpression on the epimastigote transcriptome is mainly the stabilization of mRNAs coding for proteins that are important for parasite infection.

Autophagy in protists and their hosts: When, how and why?

Pathogenic protists are a group of organisms responsible for causing a variety of human diseases including malaria, sleeping sickness, Chagas disease, leishmaniasis, and toxoplasmosis, among others. These diseases, which affect more than one billion people globally, mainly the poorest populations, are characterized by severe chronic stages and the lack of effective antiparasitic treatment. Parasitic protists display complex life-cycles and go through different cellular transformations in order to adapt to the different hosts they live in. Autophagy, a highly conserved cellular degradation process, has emerged as a key mechanism required for these differentiation processes, as well as other functions that are crucial to parasite fitness. In contrast to yeasts and mammals, protist autophagy is characterized by a modest number of conserved autophagy-related proteins (ATGs) that, even though, can drive the autophagosome formation and degradation. In addition, during their intracellular cycle, the interaction of these pathogens with the host autophagy system plays a crucial role resulting in a beneficial or harmful effect that is important for the outcome of the infection. In this review, we summarize the current state of knowledge on autophagy and other related mechanisms in pathogenic protists and their hosts. We sought to emphasize when, how, and why this process takes place, and the effects it may have on the parasitic cycle. A better understanding of the significance of autophagy for the protist life-cycle will potentially be helpful to design novel anti-parasitic strategies.

Rapid metabolic reprogramming mediated by the AMP-activated protein kinase during the lytic cycle of Toxoplasma gondii

The ubiquitous pathogen Toxoplasma gondii has a complex lifestyle with different metabolic activities at different stages that are intimately linked to the parasitic environments. Here we identified the eukaryotic regulator of cellular homeostasis AMP-activated protein kinase (AMPK) in Toxoplasma and discovered its role in metabolic programming during parasite's lytic cycle. The catalytic subunit AMPKα is quickly phosphorylated after the release of intracellular parasites to extracellular environments, driving energy-producing catabolism to power parasite motility and invasion into host cells. Once inside host cells, AMPKα phosphorylation is reduced to basal level to promote a balance between energy production and biomass synthesis, allowing robust parasite replication. AMPKγ depletion abolishes AMPKα phosphorylation and suppresses parasite growth, which can be partially rescued by overexpressing wildtype AMPKα but not the phosphorylation mutants. Thus, through the cyclic reprogramming by AMPK, the parasites' metabolic needs at each stage are satisfied and the lytic cycle progresses robustly.