Anaerobic Metabolism in T4 Acanthamoeba Genotype

Oxidase enzyme genes are differentially expressed during Acanthamoeba castellanii encystment

Acanthamoeba castellanii, a ubiquitous protozoan, is responsible for significant diseases such as Acanthamoeba keratitis and granulomatous amoebic encephalitis. A crucial survival strategy of A. castellanii involves the formation of highly resistant cysts during adverse conditions. This study delves into the cellular processes underpinning encystment, focusing on gene expression changes related to reactive oxygen species (ROS) balance, with a particular emphasis on mitochondrial processes. Our findings reveal a dynamic response within the mitochondria during encystment, with the downregulation of key enzymes involved in oxidative phosphorylation (COX, AOX, and NADHalt) during the initial 48 h, followed by their overexpression at 72 h. This orchestrated response likely creates a pro-oxidative environment, facilitating encystment. Analysis of other ROS processing enzymes across the cell reveals differential expression patterns. Notably, antioxidant enzymes, such as catalases, glutaredoxins, glutathione S-transferases, peroxiredoxins, and thioredoxins, mirror the mitochondrial trend of downregulation followed by upregulation. Additionally, glycolysis and gluconeogenesis are downregulated during the early stages in order to potentially balance the metabolic requirement of the cyst. Our study underscores the importance of ROS regulation in Acanthamoeba encystment. Understanding these mechanisms offers insights into infection control and identifies potential therapeutic targets. This work contributes to unraveling the complex biology of A. castellanii and may aid in combatting Acanthamoeba-related infections. Further research into ROS and oxidase enzymes is warranted, given the organism's remarkable respiratory versatility.

A history of over 40 years of potentially pathogenic free-living amoeba studies in Brazil - a systematic review

Free-living amoeba (FLA) group includes the potentially pathogenic genera Acanthamoeba, Naegleria, Balamuthia, Sappinia, and Vermamoeba, causative agents of human infections (encephalitis, keratitis, and disseminated diseases). In Brazil, the first report on pathogenic FLA was published in the 70s and showed meningoencephalitis caused by Naegleria spp. FLA studies are emerging, but no literature review is available to investigate this trend in Brazil critically. Thus, the present work aims to integrate and discuss these data. Scopus, PubMed, and Web of Science were searched, retrieving studies from 1974 to 2020. The screening process resulted in 178 papers, which were clustered into core and auxiliary classes and sorted into five categories: wet-bench studies, dry-bench studies, clinical reports, environmental identifications, and literature reviews. The papers dating from the last ten years account for 75% (134/178) of the total publications, indicating the FLA topic has gained Brazilian interest. Moreover, 81% (144/178) address Acanthamoeba-related matter, revealing this genus as the most prevalent in all categories. Brazil’s Southeast, South, and Midwest geographic regions accounted for 96% (171/178) of the publications studied in the present work. To the best of our knowledge, this review is the pioneer in summarising the FLA research history in Brazil.

First Reports of Effects of Insulin, Human-like Insulin Receptors and Adapter Proteins in Acanthamoeba castellanii

The insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1-R) play key roles in growth, regulation of nutrient metabolism and carbohydrate homeostasis. Insulin-like molecules in prokaryotes and other early life have been reported. However, an account of metabolic effects of insulin, transcriptomic evidence of expression of glucose transporting channels (GLUT) and homology modelling of IR and IGF1-R like proteins in unicellular life-forms have yet to be established. Acanthamoeba spp. has existed for about 2 billion years and is one of the earliest mitochondriate unicellular eukaryotic cells on Earth. Despite Acanthamoeba spp. being grown in a medium called peptone-yeast-glucose (PYG) for over 50 years, the mechanism and regulation of glucose uptake by IR or IGF1-R molecules in this microbe has not yet been reported. Several methods were utilized to validate the effects of insulin on trophozoites of A. castellanii, including: growth assays with insulin, estimation of glucose and potassium (K+) entry into the cell, and histology showing anabolic effects on proteins. Bioinformatic computational tools and homology modeling demonstrated the involvement of IR like proteins, GLUT, and adapter proteins in mediating the IR cascade. Growth assays showed proliferative effects in a dose range of 2.98-5.97 µmol/mL of insulin. After insulin exposure, A. castellanii trophozoites displayed enhanced Periodic acid-Sciff (PAS) staining. Amino acid sequence similarities and homology modelling revealed ACA1_163470 in Acanthamoeba spp. to be a homolog of human-IR. Acanthamoeba protein ACA1_336150 shares similarities with IGF1-R. Additionally, some proteins like ACA1_060920 have attributes of GLUT like channels on homology modelling and show similarity with human GLUT. Knowledge of IR and insulin effects in Acanthamoeba spp. contributes to its biology and advances current understanding behind the evolution of IR and IGF1-R signalling cascade.

Molecular and biochemical characterization of key enzymes in the cysteine and serine metabolic pathways of Acanthamoeba castellanii

Background

Acanthamoeba spp. can cause serious human infections, including Acanthamoeba keratitis, granulomatous amoebic encephalitis and cutaneous acanthamoebiasis. Cysteine biosynthesis and the L-serine metabolic pathway play important roles in the energy metabolism of Acanthamoeba spp. However, no study has confirmed the functions of cysteine synthase (AcCS) in the cysteine pathway and phosphoglycerate dehydrogenase (AcGDH) or phosphoserine aminotransferase (AcSPAT) in the non-phosphorylation serine metabolic pathway of Acanthamoeba.

Methods

The AcCS, AcGDH and AcSPAT genes were amplified by PCR, and their recombinant proteins were expressed in Escherichia coli. Polyclonal antibodies against the recombinant proteins were prepared in mice and used to determine the subcellular localisation of each native protein by confocal laser scanning microscopy. The enzymatic activity of each recombinant protein was also analysed. Furthermore, each gene expression level was analysed by quantitative PCR after treatment with different concentrations of cysteine or L-serine.

Results

The AcCS gene encodes a 382-amino acid protein with a predicted molecular mass of 43.1 kDa and an isoelectric point (pI) of 8.11. The AcGDH gene encodes a 350-amino acid protein with a predicted molecular mass of 39.1 kDa and a pI of 5.51. The AcSPAT gene encodes a 354-amino acid protein with a predicted molecular mass of 38.3 kDa and a pI of 6.26. Recombinant AcCS exhibited a high cysteine synthesis activity using O-acetylserine and Na₂S as substrates. Both GDH and SPAT catalysed degradation, rather than synthesis, of serine. Exogenous L-serine or cysteine inhibited the expression of all three enzymes in a time- and dose-dependent manner.

Conclusions

This study demonstrated that AcCS participates in cysteine biosynthesis and serine degradation via the non-phosphorylation serine metabolic pathway, providing a molecular basis for the discovery of novel anti-Acanthamoeba drugs.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3188-7) contains supplementary material, which is available to authorized users.

Development and optimization of new culture media for Acanthamoeba spp. (Protozoa: Amoebozoa)

The isolation and growth in axenic liquid media of Acanthamoeba strains is necessary in order to carry out primary in vitro drug screening. Amoebic isolates which are hard to grow in the current liquid media have been reported. Such circumstances hampers the ability of conducting drug sensitivity tests. Therefore, finding suitable universal growth media for Acanthamoeba species is required. The present study was aimed at the development of liquid medium suitable for growing a fastidious (F) genotype T3 Acanthamoeba isolate, and eventually for other genotypes of this genus as well. Trophozoite growth was indirectly monitored by respiration analysis with oxygen-sensitive microplates (OSM) and further confirmed by manual counting. Media were empirically designed and tested first in a non-fastidious (NF) T3 isolate and then tested with 14 different strains, including the fastidious one. Combinations of nutritive components such as meat/vegetable broth, LB medium, malt and skimmed milk led to the design of new media suitable for culturing all the isolates tested, in conditions similar to those obtained in standard culture media such as PYG or CERVA.