Biogenesis of Autophagosome in Trichomonas vaginalis during Macroautophagy Induced by Rapamycin-treatment and Iron or Glucose Starvation Conditions

Selection of a suitable reference gene for gene-expression studies in Trichomonas gallinae under various biotic and abiotic stress conditions

Trichomonas gallinae, a globally distributed protozoan parasite, significantly affects the pigeon-breeding industry. T. gallinae infection mainly causes yellow ulcerative nodules on the upper respiratory tract and crop mucosa of pigeons, impeding normal breathing and feeding and ultimately causing death. Real-time quantitative PCR (qPCR) is a crucial technique for gene-expression analysis in molecular biology. Reference-gene selection for normalization is critical for ensuring this technique's accuracy. However, no systematic screening or validation of T. gallinae reference genes has been reported. This study quantified the transcript levels of ten candidate reference genes in T. gallinae isolates with different genotypes and culture conditions using qPCR. Using the geNorm, NormFinder, and BestKeeper algorithms, we assessed these reference genes' stabilities and ranked them using RankAggreg analysis. The most stable reference gene was tubulin beta chain (TUBB), while the widely used reference genes TUBG and GAPDH demonstrated poor stability. Additionally, we evaluated these candidate reference genes' stabilities using the T. gallinae TgaAtg8 gene. On using TUBB as a reference gene, TgaAtg8's expression profiles in T. gallinae isolates with different genotypes remained relatively consistent under various culture conditions. Conversely, using ACTB as a reference gene distorted the data. These findings provide valuable reference-gene-selection guidance for functional gene research and gene-expression analysis in T. gallinae.

Trichomonas vaginalis Legumain-2, TvLEGU-2, Is an Immunogenic Cysteine Peptidase Expressed during Trichomonal Infection

Trichomonas vaginalis is the causative agent of trichomoniasis, the most prevalent nonviral, neglected sexually transmitted disease worldwide. T. vaginalis has one of the largest degradomes among unicellular parasites. Cysteine peptidases (CPs) are the most abundant peptidases, constituting 50% of the degradome. Some CPs are virulence factors recognized by antibodies in trichomoniasis patient sera, and a few are found in vaginal secretions that show fluctuations in glucose concentrations during infection. The CPs of clan CD in T. vaginalis include 10 genes encoding legumain-like peptidases of the C13 family. TvLEGU-2 is one of them and has been identified in multiple proteomes, including the immunoproteome obtained with Tv (+) patient sera. Thus, our goals were to assess the effect of glucose on TvLEGU-2 expression, localization, and in vitro secretion and determine whether TvLEGU-2 is expressed during trichomonal infection. We performed qRT-PCR assays using parasites grown under different glucose conditions. We also generated a specific anti-TvLEGU-2 antibody against a synthetic peptide of the most divergent region of this CP and used it in Western blot (WB) and immunolocalization assays. Additionally, we cloned and expressed the tvlegu-2 gene (TVAG_385340), purified the recombinant TvLEGU-2 protein, and used it as an antigen for immunogenicity assays to test human sera from patients with vaginitis. Our results show that glucose does not affect tvlegu-2 expression but does affect localization in different parasite organelles, such as the plasma membrane, Golgi complex, hydrogenosomes, lysosomes, and secretion vesicles. TvLEGU-2 is secreted in vitro, is present in vaginal secretions, and is immunogenic in sera from Tv (+) patients, suggesting its relevance during trichomonal 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.

The autophagy pathway beyond model organisms: an evolutionary perspective

In this issue, we answer a frequently asked question regarding the evolution of the macroautophagy/autophagy pathway.

Different Drugs, Same End: Ultrastructural Hallmarks of Autophagy in Pathogenic Protozoa

Protozoan parasites interact with a wide variety of organisms ranging from bacteria to humans, representing one of the most common causes of parasitic diseases and an important public health problem affecting hundreds of millions of people worldwide. The current treatment for these parasitic diseases remains unsatisfactory and, in some cases, very limited. Treatment limitations together with the increased resistance of the pathogens represent a challenge for the improvement of the patient’s quality of life. The continuous search for alternative preclinical drugs is mandatory, but the mechanisms of action of several of these compounds have not been described. Electron microscopy is a powerful tool for the identification of drug targets in almost all cellular models. Interestingly, ultrastructural analysis showed that several classes of antiparasitic compounds induced similar autophagic phenotypes in trypanosomatids, trichomonadids, and apicomplexan parasites as well as in Giardia intestinalis and Entamoeba spp. with the presence of an increased number of autophagosomes as well as remarkable endoplasmic reticulum profiles surrounding different organelles. Autophagy is a physiological process of eukaryotes that maintains homeostasis by the self-digestion of nonfunctional organelles and/or macromolecules, limiting redundant and damaged cellular components. Here, we focus on protozoan autophagy to subvert drug effects, discussing its importance for successful chemotherapy.

The Autophagy Machinery in Human-Parasitic Protists; Diverse Functions for Universally Conserved Proteins

Autophagy is a eukaryotic cellular machinery that is able to degrade large intracellular components, including organelles, and plays a pivotal role in cellular homeostasis. Target materials are enclosed by a double membrane vesicle called autophagosome, whose formation is coordinated by autophagy-related proteins (ATGs). Studies of yeast and Metazoa have identified approximately 40 ATGs. Genome projects for unicellular eukaryotes revealed that some ATGs are conserved in all eukaryotic supergroups but others have arisen or were lost during evolution in some specific lineages. In spite of an apparent reduction in the ATG molecular machinery found in parasitic protists, it has become clear that ATGs play an important role in stage differentiation or organelle maintenance, sometimes with an original function that is unrelated to canonical degradative autophagy. In this review, we aim to briefly summarize the current state of knowledge in parasitic protists, in the light of the latest important findings from more canonical model organisms. Determining the roles of ATGs and the diversity of their functions in various lineages is an important challenge for understanding the evolutionary background of autophagy.

Ubiquitin-Like Modifiers: Emerging Regulators of Protozoan Parasites

Post-translational protein regulation allows for fine-tuning of cellular functions and involves a wide range of modifications, including ubiquitin and ubiquitin-like modifiers (Ubls). The dynamic balance of Ubl conjugation and removal shapes the fates of target substrates, in turn modulating various cellular processes. The mechanistic aspects of Ubl pathways and their biological roles have been largely established in yeast, plants, and mammalian cells. However, these modifiers may be utilised differently in highly specialised and divergent organisms, such as parasitic protozoa. In this review, we explore how these parasites employ Ubls, in particular SUMO, NEDD8, ATG8, ATG12, URM1, and UFM1, to regulate their unconventional cellular physiology. We discuss emerging data that provide evidence of Ubl-mediated regulation of unique parasite-specific processes, as well as the distinctive features of Ubl pathways in parasitic protozoa. We also highlight the potential to leverage these essential regulators and their cognate enzymatic machinery for development of therapeutics to protect against the diseases caused by protozoan parasites.

Rasal2 suppresses breast cancer cell proliferation modulated by secretory autophagy

Rasal2, a Ras-GTPase-activating protein (RasGAP), is a tumor suppressor in Luminal B breast cancer, frequently metastatic and recurrent. Exosomes (Exos) are small membrane vesicles secreted by various cell types, including tumor cells, recognized as vehicles for cell-to-cell communication. Our study aimed to investigate whether Rasal2 regulates breast cancer cell growth via affecting this process. In this paper, we described that Rasal2 knockout (KO) in MCF-7 cells enhanced exosomal release and increased autophagy-related proteins in exosomal fraction, while attenuated by exosome release inhibitor GW4869. Moreover, MCF-7 cells with chloroquine (CQ) treatment boosted Rasal2 KO-induced secretory autophagy. In addition, we presented that exosomes derived from KO MCF-7 cells (KO-exo) significantly promoted breast cancer cell proliferation compared to those from MCF-7 cells transfected with an empty crispr-cas9 plasmid serving as controls (sgNT-exo); however, exosomes purified from KO MCF-7 cells co-cultured with 3-methyladenine ((3-MA + KO)-exo)/CQ ((CQ + KO)-exo) dramatically inhibited/facilitated MCF-7 cell proliferation in contrast to KO-exo group, separately. In conclusion, our findings revealed a new mechanism of Rasal2 in the regulation of breast cancer cell proliferation via autophagy-exo-mediated pathway.