Review

Authors: Nancy Guillén

The amoeba parasite is the causative agent of human amebiasis, an enteropathic disease affecting millions of people worldwide. This ancient protozoan is an elementary example of how parasites evolve with humans, e.g. taking advantage of multiple mechanisms to evade immune responses, interacting with microbiota for nutritional and protective needs, utilizing host resources for growth, division, and encystation. These skills of perpetuate the species and incidence of infection. However, in 10% of infected cases, the parasite turns into a pathogen; the host-parasite equilibrium is then disorganized, and the simple lifecycle based on two cell forms, trophozoites and cysts, becomes unbalanced. Trophozoites acquire a virulent phenotype which, when non-controlled, leads to intestinal invasion with the onset of amoebiasis symptoms. Virulent must cross mucus, epithelium, connective tissue and possibly blood. This highly mobile parasite faces various stresses and a powerful host immune response, with oxidative stress being a challenge for its survival. New emerging research avenues and omics technologies target gene regulation to determine human or parasitic factors activated upon infection, their role in virulence activation, and in pathogenesis; this research bears in mind that is a resident of the complex intestinal ecosystem. The goal is to eradicate amoebiasis from the planet, but the parasitic life of is ancient and complex and will likely continue to evolve with humans. Advances in these topics are summarized here.

Topics: Humans; Entamoeba histolytica; Virulence; Ecosystem; Amebiasis; Intestines

PubMed: 36519347
DOI: 10.1080/21505594.2022.2158656

Review

Authors: Mrigya Babuta, Sudha Bhattacharya, Alok Bhattacharya...

Calcium signaling plays a key role in many essential processes in almost all eukaryotic systems. It is believed that it may also be an important signaling system of the protist parasite Entamoeba histolytica. Motility, adhesion, cytolysis, and phagocytosis/trogocytosis are important steps in invasion and pathogenesis of E. histolytica, and Ca2+ signaling is thought to be associated with these processes leading to tissue invasion. There are a large number of Ca2+-binding proteins (CaBPs) in E. histolytica, and a number of these proteins appear to be associated with different steps in pathogenesis. The genome encodes 27 EF-hand-containing CaBPs in addition to a number of other Ca2+-binding domain/motif-containing proteins, which suggest intricate calcium signaling network in this parasite. Unlike other eukaryotes, a typical calmodulin-like protein has not been seen in E. histolytica. Though none of the CaBPs display sequence similarity with a typical calmodulin, extensive structural similarity has been seen in spite of lack of significant functional overlap with that of typical calmodulins. One of the unique features observed in E. histolytica is the identification of CaBPs (EhCaBP1, EhCaBP3) that have the ability to directly bind actin and modulate actin dynamics. Direct interaction of CaBPs with actin has not been seen in any other system. Pseudopod formation and phagocytosis are some of the processes that require actin dynamics, and some of the amoebic CaBPs (EhC2Pk, EhCaBP1, EhCaBP3, EhCaBP5) participate in this process. None of these E. histolytica CaBPs have any homolog in organisms other than different species of Entamoeba, suggesting a novel Ca2+ signaling pathway that has evolved in this genus.

Topics: Actins; Calcium; Calcium-Binding Proteins; Calmodulin; Entamoeba histolytica; Entamoebiasis; Phagocytosis; Protozoan Proteins

PubMed: 32379809
DOI: 10.1371/journal.ppat.1008214

Review

Authors: Silvia Castellanos-Castro, Jeni Bolaños, Esther Orozco...

Lipids are essential players in parasites pathogenesis. In particular, the highly phagocytic trophozoites of , the causative agent of amoebiasis, exhibit a dynamic membrane fusion and fission, in which lipids strongly participate; particularly during the overstated motility of the parasite to reach and attack the epithelia and ingest target cells. Synthesis and metabolism of lipids in this protozoan present remarkable difference with those performed by other eukaryotes. Here, we reviewed the current knowledge on lipids in . Trophozoites synthesize phosphatidylcholine and phosphatidylethanolamine by the Kennedy pathway; and sphingolipids, phosphatidylserine, and phosphatidylinositol, by processes similar to those used by other eukaryotes. However, trophozoites lack enzymes for cholesterol and fatty acids synthesis, which are scavenged from the host or culture medium by specific mechanisms. Cholesterol, a fundamental molecule for the expression of virulence, is transported from the medium into the trophozoites by EhNPC1 and EhNPC2 proteins. Inside cells, lipids are distributed by different pathways, including by the participation of the endosomal sorting complex required for transport (ESCRT), involved in vesicle fusion and fission. Cholesterol interacts with the phospholipid lysobisphosphatidic acid (LBPA) and EhADH, an ALIX family protein, also involved in phagocytosis. In this review, we summarize the known information on phospholipids synthesis and cholesterol transport as well as their metabolic pathways in ; highlighting the mechanisms used by trophozoites to dispose lipids involved in the virulence processes.

Topics: Animals; Cholesterol; Entamoeba histolytica; Entamoebiasis; Fatty Acids; Humans; Lipid Metabolism; Lipids; Phagocytosis; Phospholipids; Protozoan Proteins; Trophozoites; Virulence; Virulence Factors

PubMed: 32211340
DOI: 10.3389/fcimb.2020.00075

Authors: Rene L Suleiman, Katherine S Ralston

Entamoeba histolytica is a parasitic protozoan and the causative agent of amoebiasis in humans. Amoebiasis has a high incidence of disease, resulting in ∼67,900 deaths per year, and it poses a tremendous burden of morbidity and mortality in children. Despite its importance, E. histolytica is an understudied parasite. These protocols describe the in vitro growth, maintenance, cryopreservation, genetic manipulation, and cloning of axenic E. histolytica trophozoites. There has been significant progress in genetic manipulation of this organism over the past decade, and these protocols outline the ways in which these advances can be implemented. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Culturing E. histolytica trophozoites Support Protocol 1: Preparation of TYI-S-33 medium Support Protocol 2: Lot testing of Biosate peptone and adult bovine serum for TYI-S-33 medium Basic Protocol 2: Cryopreservation of E. histolytica trophozoites Support Protocol 3: Preparation of cryoprotectant solutions Basic Protocol 3: Transfection of E. histolytica trophozoites with Attractene reagent Basic Protocol 4: Creating clonal lines using limiting dilution Basic Protocol 5: Knockdown of one to two genes with trigger-induced RNA interference Support Protocol 4: Evaluation of RNA interference knockdown with reverse transcriptase PCR Basic Protocol 6: E. histolytica growth curves.

Topics: Adult; Animals; Child; Culture Media; Entamoeba histolytica; Genetic Techniques; Humans; RNA Interference; Trophozoites

PubMed: 35085418
DOI: 10.1002/cpz1.327

Review

Authors: Attinder Chadha, Kris Chadee

Protozoan parasites have led to worldwide devastation because of their ability to cause infectious diseases. They have evolved as successful pathogens in part because of their remarkable and sophisticated ways to evade innate host defenses. This holds true for both intracellular and extracellular parasites that deploy multiple strategies to circumvent innate host defenses for their survival. The different strategies protozoan parasites use include hijacking the host cellular signaling pathways and transcription factors. In particular, the nuclear factor-κB (NF-κB) pathway seems to be an attractive target for different pathogens owing to their central role in regulating prompt innate immune responses in host defense. NF-κB is a ubiquitous transcription factor that plays an indispensable role not only in regulating immediate immune responses against invading pathogens but is also a critical regulator of cell proliferation and survival. The major immunomodulatory components include parasite surface and secreted proteins/enzymes and stimulation of host cells intracellular pathways and inflammatory caspases that directly or indirectly interfere with the NF-κB pathway to thwart immune responses that are directed for containment and/or elimination of the pathogen. To showcase how protozoan parasites exploits the NF-κB signaling pathway, this review highlights recent advances from and other protozoan parasites in contact with host cells that induce outside-in and inside-out signaling to modulate NF-κB in disease pathogenesis and survival in the host.

Topics: Animals; Entamoeba histolytica; Immunity, Innate; NF-kappa B; Parasites; Signal Transduction

PubMed: 34595137
DOI: 10.3389/fcimb.2021.748404

Review

Authors: I W Wilson, G D Weedall, N Hall...

Invasive amoebiasis caused by Entamoeba histolytica is a major global health problem. Virulence is a rare outcome of infection, occurring in fewer than 1 in 10 infections. Not all strains of the parasite are equally virulent, and understanding the mechanisms and causes of virulence is an important goal of Entamoeba research. The sequencing of the genome of E. histolytica and the related avirulent species Entamoeba dispar has allowed whole-genome-scale analyses of genetic divergence and differential gene expression to be undertaken. These studies have helped elucidate mechanisms of virulence and identified genes differentially expressed in virulent and avirulent parasites. Here, we review the current status of the E. histolytica and E. dispar genomes and the findings of a number of genome-scale studies comparing parasites of different virulence.

Topics: Animals; Entamoeba; Entamoeba histolytica; Entamoebiasis; Genome, Protozoan; Host-Parasite Interactions; Humans; Protozoan Proteins; Species Specificity; Virulence

PubMed: 21810102
DOI: 10.1111/j.1365-3024.2011.01325.x

Review

Authors: D A Bruckner

Entamoeba histolytica, the causative agent of amebiasis, was first described in 1875. Although a large number of people throughout the world are infected with this organism, only a small percentage will develop clinical symptoms. Morbidity and mortality due to E. histolytica vary from area to area and person to person. Recent findings have suggested that there are pathogenic and nonpathogenic strains of E. histolytica that can be differentiated by isoenzyme (zymodeme) analysis, monoclonal antibodies, and DNA probes. Whether pathogenicity is a genotypic trait or can be changed by environmental influences has not been resolved. Exchange of genetic material between strains of amebae can influence zymodeme patterns. Currently, detection of E. histolytica infections depends on examinations for ova and parasites and on serologic tests; however, the development of monoclonal antibodies and DNA probes specific for pathogenic zymodemes may be beneficial for clinical laboratory testing and therapeutic decisions when approved tests become available. A better understanding of the mechanisms of pathogenicity at the molecular level is evolving and should promote the development of vaccines and better target selection for therapeutic agents.

Topics: Animals; Entamoeba histolytica; Entamoebiasis; Forecasting; Humans; Male

PubMed: 1423215
DOI: 10.1128/CMR.5.4.356

Review

Authors: Jesús Valdés-Flores, Itzel López-Rosas, César López-Camarillo...

In eukaryotic cells, the life cycle of mRNA molecules is modulated in response to environmental signals and cell-cell communication in order to support cellular homeostasis. Capping, splicing and polyadenylation in the nucleus lead to the formation of transcripts that are suitable for translation in cytoplasm, until mRNA decay occurs in P-bodies. Although pre-mRNA processing and degradation mechanisms have usually been studied separately, they occur simultaneously and in a coordinated manner through protein-protein interactions, maintaining the integrity of gene expression. In the past few years, the availability of the genome sequence of , the protozoan parasite responsible for human amoebiasis, coupled to the development of the so-called "omics" technologies provided new opportunities for the study of mRNA processing and turnover in this pathogen. Here, we review the current knowledge about the molecular basis for splicing, 3' end formation and mRNA degradation in amoeba, which suggest the conservation of events related to mRNA life throughout evolution. We also present the functional characterization of some key proteins and describe some interactions that indicate the relevance of cooperative regulatory events for gene expression in this human parasite.

Topics: Amebiasis; Animals; Entamoeba histolytica; Evolution, Molecular; Humans; Polyadenylation; Protozoan Proteins; RNA Precursors; RNA Splicing; RNA Stability; RNA, Messenger

PubMed: 29971219
DOI: 10.3389/fcimb.2018.00199

Authors: Hongze Zhang, Qingshan Li, Hang Zhou...

UNLABELLED

is an enteric protozoan parasite that causes human amebic colitis and extraintestinal abscesses. As a prerequisite for parasite colonization and invasion, adherence of is predominantly mediated by galactose (Gal)- and N-acetyl-d-galactosamine (GalNAc)-inhibitable lectins. The intermediate subunit (Igl) of Gal-/GalNAc-inhibitable lectin is a cysteine-rich protein containing multiple CXXC motifs and is considered a key factor affecting trophozoite's pathogenicity. However, details of the function of Igl during parasite adherence remain unclear. Here, using segmentally expressed Igl proteins and a CHO cell model transfected with Igl fragments, we identified a carbohydrate-recognition domain (CRD)-like region between amino acids 989 and 1,088. Through single- and double-point mutations in the Igl segments, two core CXXC motifs responsible for carbohydrate recognition in the CRD-like region, which are highly conserved among several lectins, were confirmed. In addition to adhesion, the roles of CRD-like region and its core CXXC motifs in various pathogenic effects were further explored. To our knowledge, this is the first report showing an adhesion-related region in Igl. The identification and characterization of this CRD-like region provides further insights into molecular mechanisms underlying pathogenicity and also aids in the determination of a potential drug target in this parasite.

IMPORTANCE

adhesion mainly depends on galactose (Gal)-/N-acetyl-d-galactosamine (GalNAc)-inhibitable lectins, subsequently triggering a series of amebic reactions. Among the three subunits of Gal-/GalNAc-inhibitable lectin, heavy subunit and intermediate subunit (Igl) have exhibited lectin activity, but that of Igl remains poorly understood. In this study, we confirmed a carbohydrate-recognition domain (CRD)-like limiting region in Igl and further identified its two core CXXC motifs responsible for carbohydrate recognition. Moreover, the role of Igl's CRD-like region and its CXXC motifs in hemolysis and pathogenic effects was explored. This is the first study to determine an adhesion-related region in Igl protein, providing a new reference direction for subsequent research studies. Since the potential homogeneity of galectin-2 in several mammals and Igl CRD-like region, it could be meaningful to relate the corresponding pathogeneses and phenotypes of these two proteins. Except for adhesion, studies on the involvement of Igl CRD-like region in different parasite-host interactions are also promising.

Topics: Entamoeba histolytica; Lectins; Animals; Humans; Cricetulus; CHO Cells; Protozoan Proteins; Acetylgalactosamine; Galactose; Entamoebiasis; Trophozoites; Amino Acid Motifs; Protein Domains; Cell Adhesion; Carbohydrates

PubMed: 39365081
DOI: 10.1128/spectrum.00538-24

Authors: Anjan Debnath, Mario Alberto Rodriguez, Serge Ankri...

Topics: Amebicides; Anisomycin; Asymptomatic Diseases; Drug Discovery; Dysentery, Amebic; Entamoeba histolytica; Flavonoids; Gene Expression Regulation; Humans; Life Cycle Stages; Metabolic Networks and Pathways; Metronidazole; Piperidines; Prodigiosin; Protozoan Proteins; Pyridines; Severity of Illness Index

PubMed: 31338336
DOI: 10.3389/fcimb.2019.00247