The ways of a killer: how does Entamoeba histolytica elicit host cell death?

2011 ◽  
Vol 51 ◽  
pp. 193-210 ◽  
Author(s):  
Katherine S. Ralston ◽  
William A. Petri
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Entamoeba Histolytica ◽  
Calcium Influx ◽  
Protozoan Parasite ◽  
Basic Mechanism ◽  
Effector Proteins ◽  
Host Cells ◽  
Host Cell Death ◽  
Cytotoxic Effector

Entamoeba histolytica is the causative agent of amoebiasis in humans and is responsible for an estimated 100 000 deaths annually, making it the second leading cause of death due to a protozoan parasite after Plasmodium. Pathogenesis appears to result from the potent cytotoxic activity of the parasite, which kills host cells within minutes. The mechanism is unknown, but progress has been made in determining that cytotoxicity requires parasite Gal (galactose)/GalNAc (N-acetylgalactosamine) lectin-mediated adherence, target cell calcium influx, dephosphorylation and activation of caspase 3. Putative cytotoxic effector proteins such as amoebapores, proteases and various parasite membrane proteins have also been identified. Nonetheless the bona fide cytotoxic effector molecules remain unknown and it is unclear how the lethal hit is delivered. To better understand the basic mechanism of pathogenesis and to enable the development of new therapeutics, more work will be needed in order to determine how the parasite elicits host cell death.

scholarly journals Pathogen induced subversion of NAD+ metabolism mediating host cell death: a target for development of chemotherapeutics

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ayushi Chaurasiya ◽  
Swati Garg ◽  
Ashish Khanna ◽  
Chintam Narayana ◽  
Ved Prakash Dwivedi ◽  
...  
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Nicotinamide Adenine Dinucleotide ◽  
Malaria Parasite ◽  
Host Cells ◽  
Nicotinamide Adenine ◽  
Targeted Therapeutics ◽  
Nad Metabolism ◽  
Host Cell Death ◽  
Nanomolar Range

AbstractHijacking of host metabolic status by a pathogen for its regulated dissemination from the host is prerequisite for the propagation of infection. M. tuberculosis secretes an NAD+-glycohydrolase, TNT, to induce host necroptosis by hydrolyzing Nicotinamide adenine dinucleotide (NAD+). Herein, we expressed TNT in macrophages and erythrocytes; the host cells for M. tuberculosis and the malaria parasite respectively, and found that it reduced the NAD+ levels and thereby induced necroptosis and eryptosis resulting in premature dissemination of pathogen. Targeting TNT in M. tuberculosis or induced eryptosis in malaria parasite interferes with pathogen dissemination and reduction in the propagation of infection. Building upon our discovery that inhibition of pathogen-mediated host NAD+ modulation is a way forward for regulation of infection, we synthesized and screened some novel compounds that showed inhibition of NAD+-glycohydrolase activity and pathogen infection in the nanomolar range. Overall this study highlights the fundamental importance of pathogen-mediated modulation of host NAD+ homeostasis for its infection propagation and novel inhibitors as leads for host-targeted therapeutics.

scholarly journals Core N-Glycan Structures Are Critical for the Pathogenicity of Cryptococcus neoformans by Modulating Host Cell Death

mBio ◽  
2020 ◽  
Vol 11 (3) ◽  
Author(s):  
Eun Jung Thak ◽  
Su-Bin Lee ◽  
Shengjie Xu-Vanpala ◽  
Dong-Jik Lee ◽  
Seung-Yeon Chung ◽  
...  
Keyword(s):  
Cell Death ◽  
Fungal Infection ◽  
Host Cell ◽  
Host Cells ◽  
Glycan Structure ◽  
Macrophage Cell ◽  
Content Type ◽  
Host Cell Death ◽  
Intact Core

ABSTRACT Cryptococcus neoformans is a human-pathogenic fungal pathogen that causes life-threatening meningoencephalitis in immunocompromised individuals. To investigate the roles of N-glycan core structure in cryptococcal pathogenicity, we constructed mutant strains of C. neoformans with defects in the assembly of lipid-linked N-glycans in the luminal side of the endoplasmic reticulum (ER). Deletion of ALG3 (alg3Δ), which encodes dolichyl-phosphate-mannose (Dol-P-Man)-dependent α-1,3-mannosyltransferase, resulted in the production of truncated neutral N-glycans carrying five mannose residues as a major species. Despite moderate or nondetectable defects in virulence-associated phenotypes in vitro, the alg3Δ mutant was avirulent in a mouse model of systemic cryptococcosis. Notably, the mutant did not show defects in early stages of host cell interaction during infection, including attachment to lung epithelial cells, opsonic/nonopsonic phagocytosis, and manipulation of phagosome acidification. However, the ability to drive macrophage cell death was greatly decreased in this mutant, without loss of cell wall remodeling capacity. Furthermore, deletion of ALG9 and ALG12, encoding Dol-P-Man-dependent α-1,2-mannosyltransferases and α-1,6-mannosyltransferases, generating truncated core N-glycans with six and seven mannose residues, respectively, also displayed remarkably reduced macrophage cell death and in vivo virulence. However, secretion levels of interleukin-1β (IL-1β) were not reduced in the bone marrow-derived dendritic cells obtained from Asc- and Gsdmd-deficient mice infected with the alg3Δ mutant strain, excluding the possibility that pyroptosis is a main host cell death pathway dependent on intact core N-glycans. Our results demonstrated N-glycan structures as a critical feature in modulating death of host cells, which is exploited by as a strategy for host cell escape for dissemination of C. neoformans. IMPORTANCE We previously reported that the outer mannose chains of N-glycans are dispensable for the virulence of C. neoformans, which is in stark contrast to findings for the other human-pathogenic yeast, Candida albicans. Here, we present evidence that an intact core N-glycan structure is required for C. neoformans pathogenicity by systematically analyzing alg3Δ, alg9Δ, and alg12Δ strains that have defects in lipid-linked N-glycan assembly and in in vivo virulence. The alg null mutants producing truncated core N-glycans were defective in inducing host cell death after phagocytosis, which is triggered as a mechanism of pulmonary escape and dissemination of C. neoformans, thus becoming inactive in causing fatal infection. The results clearly demonstrated the critical features of the N-glycan structure in mediating the interaction with host cells during fungal infection. The delineation of the roles of protein glycosylation in fungal pathogenesis not only provides insight into the glycan-based fungal infection mechanism but also will aid in the development of novel antifungal agents.

scholarly journals A Sequential Model of Host Cell Killing and Phagocytosis byEntamoeba histolytica

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Adam Sateriale ◽  
Christopher D. Huston
Keyword(s):  
Host Cell ◽  
Entamoeba Histolytica ◽  
Protozoan Parasite ◽  
Cell Killing ◽  
Host Cells ◽  
Strongly Correlated ◽  
Sequential Model ◽  
Recent Advances

The protozoan parasiteEntamoeba histolyticais responsible for invasive intestinal and extraintestinal amebiasis. The virulence ofEntamoeba histolyticais strongly correlated with the parasite's capacity to effectively kill and phagocytose host cells. The process by which host cells are killed and phagocytosed follows a sequential model of adherence, cell killing, initiation of phagocytosis, and engulfment. This paper presents recent advances in the cytolytic and phagocytic processes ofEntamoeba histolyticain context of the sequential model.

scholarly journals Listeria monocytogenes: The Impact of Cell Death on Infection and Immunity

Pathogens ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 8 ◽  
Author(s):  
Courtney McDougal ◽  
John-Demian Sauer
Keyword(s):  
Cell Death ◽  
Listeria Monocytogenes ◽  
Host Cell ◽  
Acute Infection ◽  
Host Cells ◽  
Cell Mediated Immunity ◽  
Cell Death Pathways ◽  
Host Cell Death ◽  
The Impact

Listeria monocytogenes has evolved exquisite mechanisms for invading host cells and spreading from cell-to-cell to ensure maintenance of its intracellular lifecycle. As such, it is not surprising that loss of the intracellular replication niche through induction of host cell death has significant implications on the development of disease and the subsequent immune response. Although L. monocytogenes can activate multiple pathways of host cell death, including necrosis, apoptosis, and pyroptosis, like most intracellular pathogens L. monocytogenes has evolved a series of adaptations that minimize host cell death to promote its virulence. Understanding how L. monocytogenes modulates cell death during infection could lead to novel therapeutic approaches. In addition, as L. monocytogenes is currently being developed as a tumor immunotherapy platform, understanding how cell death pathways influence the priming and quality of cell-mediated immunity is critical. This review will focus on the mechanisms by which L. monocytogenes modulates cell death, as well as the implications of cell death on acute infection and the generation of adaptive immunity.

scholarly journals Knockdown of Five Genes Encoding Uncharacterized Proteins Inhibits Entamoeba histolytica Phagocytosis of Dead Host Cells

2016 ◽  
Vol 84 (4) ◽  
pp. 1045-1053 ◽  
Author(s):  
Adam Sateriale ◽  
Peter Miller ◽  
Christopher D. Huston
Keyword(s):  
Host Cell ◽  
Entamoeba Histolytica ◽  
Protozoan Parasite ◽  
Host Cells ◽  
Data Set ◽  
Feed Forward ◽  
Content Type ◽  
Genes Encoding ◽  
Relative Specificity ◽  
Cell Engulfment

Entamoeba histolyticais the protozoan parasite that causes invasive amebiasis, which is endemic to many developing countries and characterized by dysentery and liver abscesses. The virulence ofE. histolyticacorrelates with the degree of host cell engulfment, or phagocytosis, andE. histolyticaphagocytosis alters amebic gene expression in a feed-forward manner that results in an increased phagocytic ability. Here, we used a streamlined RNA interference screen to silence the expression of 15 genes whose expression was upregulated in phagocyticE. histolyticatrophozoites to determine whether these genes actually function in the phagocytic process. When five of these genes were silenced, amebic strains with significant decreases in the ability to phagocytose apoptotic host cells were produced. Phagocytosis of live host cells, however, was largely unchanged, and the defects were surprisingly specific for phagocytosis. Two of the five encoded proteins, which we namedE. histolyticaILWEQ (EhILWEQ) andE. histolyticaBAR (EhBAR), were chosen for localization via SNAP tag labeling and localized to the site of partially formed phagosomes. Therefore, both EhILWEQ and EhBAR appear to contribute toE. histolyticavirulence through their function in phagocytosis, and the large proportion (5/15 [33%]) of gene-silenced strains with a reduced ability to phagocytose host cells validates the previously published microarray data set demonstrating feed-forward control ofE. histolyticaphagocytosis. Finally, although only limited conclusions can be drawn from studies using the virulence-deficient G3Entamoebastrain, the relative specificity of the defects induced for phagocytosis of apoptotic cells but not healthy cells suggests that cell killing may play a rate-limiting role in the process ofEntamoeba histolyticahost cell engulfment.

scholarly journals Intracellular Staphylococcus aureus employs the cysteine protease staphopain A to induce host cell death in epithelial cells

2020 ◽  
Author(s):  
Kathrin Stelzner ◽  
Tobias Hertlein ◽  
Aneta Sroka ◽  
Adriana Moldovan ◽  
Kerstin Paprotka ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Death ◽  
Epithelial Cells ◽  
Host Cell ◽  
Cysteine Protease ◽  
Host Cells ◽  
Upper Respiratory Tract ◽  
Intracellular Replication ◽  
Tissue Destruction ◽  
Host Cell Death

AbstractStaphylococcus aureus is a major human pathogen, which can invade and survive in non-professional and professional phagocytes. Intracellularity is thought to contribute to pathogenicity and persistence of the bacterium. Upon internalization by epithelial cells, cytotoxic S. aureus strains can escape from the phagosome, replicate in the cytosol and induce host cell death. Here, we identified a staphylococcal cysteine protease to induce cell death by intracellular S. aureus after translocation into the host cell cytoplasm. We demonstrated that loss of staphopain A function leads to delayed onset of host cell death and prolonged intracellular replication of S. aureus in epithelial cells. Overexpression of staphopain A in a non-cytotoxic strain facilitated intracellular killing of the host cell even in the absence of detectable intracellular replication. Moreover, staphopain A contributed to efficient colonization of the lung in a mouse pneumonia model. Our study suggests that staphopain A is utilized by S. aureus to mediate escape from the host cell and thus contributes to tissue destruction and dissemination of infection.Author SummaryStaphylococcus aureus is a well-known antibiotic-resistant pathogen that emerges in hospital and community settings and can cause a variety of diseases ranging from skin abscesses to lung inflammation and blood poisoning. The bacterium asymptomatically colonizes the upper respiratory tract and skin of about one third of the human population and takes advantage of opportune conditions, like immunodeficiency or breached barriers, to cause infection. Although S. aureus is not regarded as a professional intracellular bacterium, it can be internalized by human cells and subsequently exit the host cells by induction of cell death, which is considered to cause tissue destruction and spread of infection. The bacterial virulence factors and underlying molecular mechanisms involved in the intracellular lifestyle of S. aureus remain largely unknown. We identified a bacterial cysteine protease to contribute to host cell death mediated by intracellular S. aureus. Staphopain A induced killing of the host cell after translocation of the pathogen into the cell cytosol, while bacterial proliferation was not required. Further, the protease enhanced survival of the pathogen during lung infection. These findings reveal a novel, intracellular role for the bacterial protease staphopain A.

scholarly journals Selective Host Cell Death by Staphylococcus aureus: A Strategy for Bacterial Persistence

2021 ◽  
Vol 11 ◽  
Author(s):  
Dominique Missiakas ◽  
Volker Winstel
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Death ◽  
Host Cell ◽  
Intervention Strategies ◽  
Host Cells ◽  
Intracellular Killing ◽  
Mammalian Development ◽  
Cell Responses ◽  
Cell Death Pathways ◽  
Host Cell Death

Host cell death programs are fundamental processes that shape cellular homeostasis, embryonic development, and tissue regeneration. Death signaling and downstream host cell responses are not only critical to guide mammalian development, they often act as terminal responses to invading pathogens. Here, we briefly review and contrast how invading pathogens and specifically Staphylococcus aureus manipulate apoptotic, necroptotic, and pyroptotic cell death modes to establish infection. Rather than invading host cells, S. aureus subverts these cells to produce diffusible molecules that cause death of neighboring hematopoietic cells and thus shapes an immune environment conducive to persistence. The exploitation of cell death pathways by S. aureus is yet another virulence strategy that must be juxtaposed to mechanisms of immune evasion, autophagy escape, and tolerance to intracellular killing, and brings us closer to the true portrait of this pathogen for the design of effective therapeutics and intervention strategies.

scholarly journals EnteropathogenicE. coli-induced barrier function alteration is not a consequence of host cell apoptosis

2008 ◽  
Vol 294 (5) ◽  
pp. G1165-G1170 ◽  
Author(s):  
V. K. Viswanathan ◽  
Andrew Weflen ◽  
Athanasia Koutsouris ◽  
Jennifer L. Roxas ◽  
Gail Hecht
Keyword(s):  
Cell Death ◽  
Tight Junction ◽  
Host Cell ◽  
Barrier Function ◽  
Type Iii Secretion ◽  
Host Cells ◽  
Epithelial Barrier ◽  
Type Iii ◽  
Barrier Disruption ◽  
Host Cell Death

Enteropathogenic Escherichia coli (EPEC) is a diarrheagenic pathogen that perturbs intestinal epithelial function. Many of the alterations in the host cells are mediated by effector molecules that are secreted directly into epithelial cells by the EPEC type III secretion system. The secreted effector molecule EspF plays a key role in redistributing tight junction proteins and altering epithelial barrier function. EspF has also been shown to localize to mitochondria and trigger membrane depolarization and eventual host cell death. The relationship, if any, between EspF-induced host cell death and epithelial barrier disruption is presently not known. Site-directed mutation of leucine 16 (L16E) of EspF impairs both mitochondrial localization and consequent host cell death. Although the mutation lies within a region critical for type III secretion, EspF(L16E) is secreted efficiently from EPEC. Despite its inability to promote cell death, EspF(L16E) was not impaired for tight junction alteration or barrier disruption. Consistent with this, the pan-caspase inhibitor Q-VD-OPH, despite reducing EPEC-induced host cell death, had no effect on infection-mediated barrier function alteration. Thus EPEC alters the epithelial barrier independent of its ability to induce host cell death.

scholarly journals Host Cell Death due to EnteropathogenicEscherichia coli Has Features of Apoptosis

1999 ◽  
Vol 67 (5) ◽  
pp. 2575-2584 ◽  
Author(s):  
John K. Crane ◽  
Swastika Majumdar ◽  
Donald F. Pickhardt
Keyword(s):  
Cell Death ◽  
Host Cell ◽  
Propidium Iodide ◽  
Tyrosine Kinases ◽  
Enteric Bacteria ◽  
Host Cells ◽  
Watery Diarrhea ◽  
Iodide Uptake ◽  
Host Cell Death

ABSTRACT Enteropathogenic Escherichia coli (EPEC) is a cause of prolonged watery diarrhea in children in developing countries. The ability of EPEC to kill host cells was investigated in vitro in assays using two human cultured cell lines, HeLa (cervical) and T84 (colonic). EPEC killed epithelial cells as assessed by permeability to the vital dyes trypan blue and propidium iodide. In addition, EPEC triggered changes in the host cell, suggesting apoptosis as the mode of death; such changes included early expression of phosphatidylserine on the host cell surface and internucleosomal cleavage of host cell DNA. Genistein, an inhibitor of tyrosine kinases, and wortmannin, an inhibitor of host phosphatidylinositol 3-kinase, markedly increased EPEC-induced cell death and enhanced the features of apoptosis. EPEC-induced cell death was contact dependent and required adherence of live bacteria to the host cell. A quantitative assay for EPEC-induced cell death was developed by using the propidium iodide uptake method adapted to a fluorescence plate reader. With EPEC, the rate and extent of host cell death were less that what has been reported forSalmonella, Shigella, and Yersinia, three other genera of enteric bacteria known to cause apoptosis. However, rapid apoptosis of the host cell may not favor the pathogenic strategy of EPEC, a mucosa-adhering, noninvasive pathogen.

scholarly journals The Secreted Effector Protein EspZ Is Essential for Virulence of Rabbit Enteropathogenic Escherichia coli

2015 ◽  
Vol 83 (3) ◽  
pp. 1139-1149 ◽  
Author(s):  
John Scott Wilbur ◽  
Wyatt Byrd ◽  
Shylaja Ramamurthy ◽  
Hannah E. Ledvina ◽  
Khaldoon Khirfan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Death ◽  
Epithelial Cell ◽  
Host Cell ◽  
Bacterial Colonization ◽  
Clinical Signs ◽  
Effector Proteins ◽  
Host Cells ◽  
Tunel Staining

Attaching and effacing (A/E) pathogens adhere intimately to intestinal enterocytes and efface brush border microvilli. A key virulence strategy of A/E pathogens is the type III secretion system (T3SS)-mediated delivery of effector proteins into host cells. The secreted protein EspZ is postulated to promote enterocyte survival by regulating the T3SS and/or by modulating epithelial signaling pathways. To explore the role of EspZ in A/E pathogen virulence, we generated an isogenicespZdeletion strain (ΔespZ) and correspondingcis-complemented derivatives of rabbit enteropathogenicEscherichia coliand compared their abilities to regulate the T3SS and influence host cell survivalin vitro. For virulence studies, rabbits infected with these strains were monitored for bacterial colonization, clinical signs, and intestinal tissue alterations. Consistent with data from previous reports,espZ-transfected epithelial cells were refractory to infection-dependent effector translocation. Also, the ΔespZstrain induced greater host cell death than did the parent and complemented strains. In rabbit infections, fecal ΔespZstrain levels were 10-fold lower than those of the parent strain at 1 day postinfection, while the complemented strain was recovered at intermediate levels. In contrast to the parent and complemented mutants, ΔespZmutant fecal carriage progressively decreased on subsequent days. ΔespZmutant-infected animals gained weight steadily over the infection period, failed to show characteristic disease symptoms, and displayed minimal infection-induced histological alterations. Terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) staining of intestinal sections revealed increased epithelial cell apoptosis on day 1 after infection with the ΔespZstrain compared to animals infected with the parent or complemented strains. Thus, EspZ-dependent host cell cytoprotection likely prevents epithelial cell death and sloughing and thereby promotes bacterial colonization.

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