Autophagy Is Involved in Nutritional Stress Response and Differentiation in Trypanosoma cruzi

Abstract

Autophagy is the major mechanism used by eukaryotic cells to degrade and recycle proteins and organelles. Bioinformatics analysis of the genome of the protozoan parasite Trypanosoma cruzi revealed the presence of all components of the Atg8 conjugation system, whereas Atg12, Atg5, and Atg10 as the major components of the Atg12 pathway could not be identified. The two TcATG4 (autophagin) homologs present in the genome were found to correctly process the two ATG8 homologs after the conserved Gly residue. Functional studies revealed that both ATG4 homologues but only one T. cruzi ATG8 homolog (TcATG8.1) complemented yeast deletion strains. During starvation of the parasite, TcAtg8.1, but not TcAtg8.2, was found by immunofluorescence to be located in autophagosome-like vesicles. This confirms its function as an Atg8/LC3 homolog and its potential to be used as an autophagosomal marker. Most importantly, autophagy is involved in differentiation between developmental stages of T. cruzi, a process that is essential for parasite maintenance and survival. These findings suggest that the autophagy pathway could represent a target for a novel chemotherapeutic strategy against Chagas disease.

Inhibition of Target of Rapamycin Signaling and Stress Activate Autophagy in Chlamydomonas reinhardtii

“…4). In agreement with findings in plants and T. cruzi, where ATG4 proteases are constitutively expressed regardless of nutrient conditions (Yoshimoto et al, 2004;Alvarez et al, 2008), ATG4 activity was detected in Chlamydomonas cells under optimal and nutrientlimiting growth conditions ( Fig. 4; data not shown).…”

“…2), demonstrating the functionality of this protein in yeast ATG8-mediated processes. Yeast complementation assays have also been performed with Arabidopsis and Trypanosoma cruzi ATG8 homologs, and in contrast to CrATG8, these proteins were able to functionally replace yeast ATG8 under starvation conditions only (Ketelaar et al, 2004;Alvarez et al, 2008). Mutation of the conserved Gly residue to Ala in CrATG8 fully abolished pAPI processing, suggesting that despite the presence of the large C-terminal extension, CrATG8 could be processed and lipidated in yeast cells ( Fig.…”

“…In unicellular organisms such as yeast or protozoa, ATG8 was localized to tiny dots as well as larger spots distributed throughout the cytoplasm in rich medium (Kirisako et al, 1999;Kim et al, 2001;Alvarez et al, 2008). Nutrient depletion resulted in both organisms in an increase in the number of large spots, reflecting the activation of autophagy and the formation of mature autophagosomes.…”

Antagonic activities of Trypanosoma cruzi metacaspases affect the balance between cell proliferation, death and differentiation

“…We have previously shown the involvement of autophagy in this differentiation step. 36 Differentiation is a very complex process, which involves a number of changes in transcriptional and translational profiles, metabolism, surface of the parasite, which changes to protect the metacyclics from the immune response of the host, etc. Regulation of MCA3 levels might be a signal for the arrest of the epimastigotes, an early event in differentiation.…”

Ultrastructural and physiological changes induced by different stress conditions on the human parasite Trypanosoma cruzi

“…In T. cruzi, the presence of all components of the ubiquitin-like protein Atg8 conjugation system has been reported (Alvarez et al 2008).…”