Pore-forming toxins in infection and immunity

2021 ◽  
Author(s):  
Pratima Verma ◽  
Shraddha Gandhi ◽  
Kusum Lata ◽  
Kausik Chattopadhyay
Keyword(s):  
Pathogenic Bacteria ◽  
Plasma Membranes ◽  
Membrane Lipid ◽  
Host Cells ◽  
Target Cells ◽  
Permeability Barrier ◽  
Membrane Pore ◽  
Cellular Processes ◽  
Membrane Lipid Bilayer ◽  
Pore Forming Proteins

The integrity of the plasma membranes is extremely crucial for the survival and proper functioning of the cells. Organisms from all kingdoms of life employ specialized pore-forming proteins and toxins (PFPs and PFTs) that perforate cell membranes, and cause detrimental effects. PFPs/PFTs exert their damaging actions by forming oligomeric pores in the membrane lipid bilayer. PFPs/PFTs play important roles in diverse biological processes. Many pathogenic bacteria secrete PFTs for executing their virulence mechanisms. The immune system of the higher vertebrates employs PFPs to kill pathogen-infected cells and transformed cancer cells. The most obvious consequence of membrane pore-formation by the PFPs/PFTs is the killing of the target cells due to the disruption of the permeability barrier function of the plasma membranes. PFPs/PFTs can also activate diverse cellular processes that include activation of the stress-response pathways, induction of programmed cell death, and inflammation. Upon attack by the PFTs, host cells may also activate pathways to repair the injured membranes, restore cellular homeostasis, and trigger inflammatory immune responses. In this article, we present an overview of the diverse cellular responses that are triggered by the PFPs/PFTs, and their implications in the process of pathogen infection and immunity.

scholarly journals Molecular Signaling and Cellular Pathways for Virus Entry

ISRN Virology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Pei-I Chi ◽  
Hung-Jen Liu
Keyword(s):  
Signaling Pathways ◽  
Viral Entry ◽  
Virus Entry ◽  
Host Cells ◽  
Target Cells ◽  
Molecular Signaling ◽  
Cellular Processes ◽  
Cellular Pathways ◽  
Host Life ◽  
Endocytic Vesicles

The cell signaling plays a pivotal role in regulating cellular processes and is often manipulated by viruses as they rely on the functions offered by cells for their propagation. The first stage of their host life is to pass the genetic materials into the cell. Although some viruses can directly penetrate into cytosol, in fact, most virus entry into their host cells is through endocytosis. This machinery initiates with cell type specific cellular signaling pathways, and the signaling compounds can be proteins, lipids, and carbohydrates. The activation can be triggered in a very short time after virus binds on target cells, such as receptors. The signaling pathways involved in regulation of viral entry are wide diversity that often cross-talk between different endocytosis results. Furthermore, some viruses have the ability to use the multiple internalization pathways which leads to the regulation being even more complex. In this paper, we discuss some recent advances in our understanding of cellular pathways for virus entry, molecular signaling during virus entry, formation of endocytic vesicles, and the traffic.

scholarly journals Exosomes: Insights from Retinoblastoma and Other Eye Cancers

2020 ◽  
Vol 21 (19) ◽  
pp. 7055 ◽  
Author(s):  
Kashmiri Lande ◽  
Jitesh Gupta ◽  
Ravi Ranjan ◽  
Manjari Kiran ◽  
Luis Fernando Torres Solis ◽  
...  
Keyword(s):  
Membrane Lipid ◽  
Invasive Procedures ◽  
Cell Debris ◽  
Cellular Processes ◽  
Membrane Lipid Bilayer ◽  
Diagnostic Approaches ◽  
Tumor Exosomes ◽  
Cancer In Children ◽  
Different Parts

Exosomes, considered as cell debris or garbage bags, have been later characterized as nanometer-sized extracellular double-membrane lipid bilayer bio-vesicles secreted by the fusion of vesicular bodies with the plasma membrane. The constituents and the rate of exosomes formation differ in different pathophysiological conditions. Exosomes are also observed and studied in different parts of the eye, like the retina, cornea, aqueous, and vitreous humor. Tear fluid consists of exosomes that are shown to regulate various cellular processes. The role of exosomes in eye cancers, especially retinoblastoma (RB), is not well explored, although few studies point towards their presence. Retinoblastoma is an intraocular tumor that constitutes 3% of cases of cancer in children. Diagnosis of RB may require invasive procedures, which might lead to the spread of the disease to other parts. Due to this reason, better ways of diagnosis are being explored. Studies on the exosomes in RB tumors and serum might help designing better diagnostic approaches for RB. In this article, we reviewed studies on exosomes in the eye, with a special emphasis on RB. We also reviewed miRNAs expressed in RB tumor, serum, and cell lines and analyzed the targets of these miRNAs from the proteins identified in the RB tumor exosomes. hsa-miR-494 and hsa-miR-9, upregulated and downregulated, respectively in RB, have the maximum number of targets. Although oppositely regulated, they share the same targets in the proteins identified in RB tumor exosomes. Overall this review provides the up-to-date progress in the area of eye exosome research, with an emphasis on RB.

scholarly journals Engineered Reporter Phages for Rapid Bioluminescence-Based Detection and Differentiation of Viable Listeria Cells

2020 ◽  
Vol 86 (11) ◽  
Author(s):  
Susanne Meile ◽  
Anne Sarbach ◽  
Jiemin Du ◽  
Markus Schuppler ◽  
Carmen Saez ◽  
...  
Keyword(s):  
Food Production ◽  
Pathogenic Bacteria ◽  
False Negative ◽  
Host Cells ◽  
Target Cells ◽  
Broad Host Range ◽  
Specific Detection ◽  
Production Chain ◽  
Content Type ◽  
Culture Dependent

ABSTRACT The pathogen Listeria monocytogenes causes listeriosis, a severe foodborne disease associated with high mortality. Rapid and sensitive methods are required for specific detection of this pathogen during food production. Bioluminescence-based reporter bacteriophages are genetically engineered viruses that infect their host cells with high specificity and transduce a heterologous luciferase gene whose activity can be detected with high sensitivity to indicate the presence of viable target cells. Here, we use synthetic biology for de novo genome assembly and activation as well as CRISPR-Cas-assisted phage engineering to construct a set of reporter phages for the detection and differentiation of viable Listeria cells. Based on a single phage backbone, we compare the performance of four reporter phages that encode different crustacean, cnidarian, and bacterial luciferases. From this panel of reporter proteins, nanoluciferase (NLuc) was identified as a superior enzyme and was subsequently introduced into the genomes of a broad host range phage (A511) and two serovar 1/2- and serovar 4b/6a-specific Listeria phages (A006 and A500, respectively). The broad-range NLuc-based phage A511::nlucCPS detects one CFU of L. monocytogenes in 25 g of artificially contaminated milk, cold cuts, and lettuce within less than 24 h. In addition, this reporter phage successfully detected Listeria spp. in potentially contaminated natural food samples without producing false-positive or false-negative results. Finally, A006::nluc and A500::nluc enable serovar-specific Listeria diagnostics. In conclusion, these NLuc-based reporter phages enable rapid, ultrasensitive detection and differentiation of viable Listeria cells using a simple protocol that is 72 h faster than culture-dependent approaches. IMPORTANCE Culture-dependent methods are the gold standard for sensitive and specific detection of pathogenic bacteria within the food production chain. In contrast to molecular approaches, these methods detect viable cells, which is a key advantage for foods generated from heat-inactivated source material. However, culture-based diagnostics are typically much slower than molecular or proteomic strategies. Reporter phage assays combine the best of both worlds and allow for near online assessment of microbial safety because phage replication is extremely fast, highly target specific, and restricted to metabolically active host cells. In addition, reporter phage assays are inexpensive and do not require highly trained personnel, facilitating their on-site implementation. The reporter phages presented in this study not only allow for rapid detection but also enable an early estimation of the potential virulence of Listeria isolates from food production and processing sites.

scholarly journals CesL Regulates Type III Secretion Substrate Specificity of the Enteropathogenic E. coli Injectisome

2021 ◽  
Vol 9 (5) ◽  
pp. 1047
Author(s):  
Miguel Díaz-Guerrero ◽  
Meztlli O. Gaytán ◽  
Eduardo Soto ◽  
Norma Espinosa ◽  
Elizabeth García-Gómez ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
Effector Proteins ◽  
Host Cells ◽  
Target Cells ◽  
Remarkable Feature ◽  
Type Iii ◽  
Pairwise Interactions ◽  
Effector Secretion

The type III secretion system (T3SS) is a complex molecular device used by several pathogenic bacteria to translocate effector proteins directly into eukaryotic host cells. One remarkable feature of the T3SS is its ability to secrete different categories of proteins in a hierarchical manner, to ensure proper assembly and timely delivery of effectors into target cells. In enteropathogenic Escherichia coli, the substrate specificity switch from translocator to effector secretion is regulated by a gatekeeper complex composed of SepL, SepD, and CesL proteins. Here, we report a characterization of the CesL protein using biochemical and genetic approaches. We investigated discrepancies in the phenotype among different cesL deletion mutants and showed that CesL is indeed essential for translocator secretion and to prevent premature effector secretion. We also demonstrated that CesL engages in pairwise interactions with both SepL and SepD. Furthermore, while association of SepL to the membrane does not depended on CesL, the absence of any of the proteins forming the heterotrimeric complex compromised the intracellular stability of each component. In addition, we found that CesL interacts with the cytoplasmic domains of the export gate components EscU and EscV. We propose a mechanism for substrate secretion regulation governed by the SepL/SepD/CesL complex.

scholarly journals Delivery of Toxins and Effectors by Bacterial Membrane Vesicles

Toxins ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 845
Author(s):  
Adrian Macion ◽  
Agnieszka Wyszyńska ◽  
Renata Godlewska
Keyword(s):  
Virulence Factors ◽  
Pathogenic Bacteria ◽  
Membrane Vesicles ◽  
Cell Types ◽  
Oral Bacteria ◽  
Host Cells ◽  
Target Cells ◽  
Tissue Destruction ◽  
Secretion Systems ◽  
The Central Nervous System

Pathogenic bacteria interact with cells of their host via many factors. The surface components, i.e., adhesins, lipoproteins, LPS and glycoconjugates, are particularly important in the initial stages of colonization. They enable adhesion and multiplication, as well as the formation of biofilms. In contrast, virulence factors such as invasins and toxins act quickly to damage host cells, causing tissue destruction and, consequently, organ dysfunction. These proteins must be exported from the bacterium and delivered to the host cell in order to function effectively. Bacteria have developed a number of one- and two-step secretion systems to transport their proteins to target cells. Recently, several authors have postulated the existence of another transport system (sometimes called “secretion system type zero”), which utilizes extracellular structures, namely membrane vesicles (MVs). This review examines the role of MVs as transporters of virulence factors and the interaction of toxin-containing vesicles and other protein effectors with different human cell types. We focus on the unique ability of vesicles to cross the blood–brain barrier and deliver protein effectors from intestinal or oral bacteria to the central nervous system.

scholarly journals The Lipid-Modifying Multiple Peptide Resistance Factor Is an Oligomer Consisting of Distinct Interacting Synthase and Flippase Subunits

mBio ◽  
2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Christoph M. Ernst ◽  
Sebastian Kuhn ◽  
Christoph J. Slavetinsky ◽  
Bernhard Krismer ◽  
Simon Heilbronner ◽  
...  
Keyword(s):  
Amino Acids ◽  
Antimicrobial Agents ◽  
Membrane Surface ◽  
Integral Membrane Protein ◽  
Membrane Lipid ◽  
Host Cells ◽  
Content Type ◽  
Anionic Phospholipids ◽  
Outer Leaflet ◽  
Membrane Lipid Bilayer

ABSTRACT  Phospholipids are synthesized at the inner leaflet of the bacterial cytoplasmic membrane but have to be translocated to the outer leaflet to maintain membrane lipid bilayer composition and structure. Even though phospholipid flippases have been proposed to exist in bacteria, only one such protein, MprF, has been described. MprF is a large integral membrane protein found in several prokaryotic phyla, whose C terminus modifies phosphatidylglycerol (PG), the most common bacterial phospholipid, with lysine or alanine to modulate the membrane surface charge and, as a consequence, confer resistance to cationic antimicrobial agents such as daptomycin. In addition, MprF is a flippase for the resulting lipids, Lys-PG or Ala-PG. Here we demonstrate that the flippase activity resides in the N-terminal 6 to 8 transmembrane segments of the Staphylococcus aureus MprF and that several conserved, charged amino acids and a proline residue are crucial for flippase function. MprF protects S. aureus against the membrane-active antibiotic daptomycin only when both domains are present, but the two parts do not need to be covalently linked and can function in trans. The Lys-PG synthase and flippase domains were each found to homo-oligomerize and also to interact with each other, which illustrates how the two functional domains may act together. Moreover, full-length MprF proteins formed oligomers, indicating that MprF functions as a dimer or larger oligomer. Together our data reveal how bacterial phospholipid flippases may function in the context of lipid biosynthetic processes. IMPORTANCE  Bacterial cytoplasmic membranes are crucial for maintaining and protecting cellular integrity. For instance, they have to cope with membrane-damaging agents such as cationic antimicrobial peptides (CAMPs) produced by competing bacteria (bacteriocins), secreted by eukaryotic host cells (defensins), or used as antimicrobial therapy (daptomycin). The MprF protein is found in many Gram-positive, Gram-negative, and even archaeal commensals or pathogens and confers resistance to CAMPs by modifying anionic phospholipids with amino acids, thereby compromising the membrane interaction of CAMPs. Here we describe how MprF does not only modify phospholipids but uses an additional, distinct domain for translocating the resulting lysinylated phospholipids to the outer leaflet of the membrane. We reveal critical details for the structure and function of MprF, the first dedicated prokaryotic phospholipid flippase, which may pave the way for targeting MprF with new antimicrobials that would not kill bacteria but sensitize them to antibiotics and innate host defense molecules.

scholarly journals EspF Interacts with Nucleation-Promoting Factors To Recruit Junctional Proteins into Pedestals for Pedestal Maturation and Disruption of Paracellular Permeability

2008 ◽  
Vol 76 (9) ◽  
pp. 3854-3868 ◽  
Author(s):  
Janneth Peralta-Ramírez ◽  
J. Manuel Hernandez ◽  
Rebeca Manning-Cela ◽  
José Luna-Muñoz ◽  
Carlos Garcia-Tovar ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Actin Polymerization ◽  
Pdz Domain ◽  
Paracellular Permeability ◽  
Effector Proteins ◽  
Host Cells ◽  
Target Cells ◽  
Multifunctional Protein ◽  
Junctional Proteins ◽  
Syndrome Protein

ABSTRACT Many pathogenic bacteria subvert normal host cell processes by delivering effector proteins which mimic eukaryotic functions directly into target cells. EspF is a multifunctional protein injected into host cells by attaching and effacing pathogens, but its mechanism of action is not understood completely. In silico analyses of EspF revealed two key motifs: proline-rich domains and PDZ domain binding motifs. Such functional domains may allow EspF to act as an actin nucleation-promoting factor by mimicking host proteins. In agreement with these predictions, we found that EspF from rabbit enteropathogenic Escherichia coli (E22) participates in the regulation of actin polymerization by binding to a complex of proteins at the tight junctions (TJ). EspF bound to actin and profilin throughout the course of infection. However, after 2 h of infection, EspF also bound to the neural Wiskott-Aldrich syndrome protein and to the Arp2/3, zonula occludens-1 (ZO-1), and ZO-2 proteins. Moreover, EspF caused occludin, claudin, ZO-1, and ZO-2 redistribution and loss of transepithelial electrical resistance, suggesting that actin sequestration by EspF may cause local actin depolymerization leading to EspF-induced TJ disruption. Furthermore, EspF caused recruitment of these TJ proteins into the pedestals. An E22 strain lacking EspF did not cause TJ disruption and pedestals were smaller than those induced by the wild-type strain. Additionally, the pedestals were located mainly in the TJ. The overexpression of EspF caused bigger pedestals located along the length of the cells. Thus, actin sequestration by EspF allows the recruitment of junctional proteins into the pedestals, leading to the maturation of actin pedestals and the disruption of paracellular permeability.

scholarly journals Burkholderia cenocepacia transcriptome during the early contacts with giant plasma membrane vesicles derived from live bronchial epithelial cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andreia I. Pimenta ◽  
Nuno Bernardes ◽  
Marta M. Alves ◽  
Dalila Mil-Homens ◽  
Arsenio M. Fialho
Keyword(s):  
Membrane Vesicles ◽  
Bronchial Epithelial Cell ◽  
Host Cells ◽  
Burkholderia Cenocepacia ◽  
Transport Systems ◽  
Epithelial Cell Line ◽  
Plasma Membrane Vesicles ◽  
Bronchial Epithelial ◽  
Cellular Processes ◽  
Associated Functions

AbstractBurkholderia cenocepacia is known for its capacity of adherence and interaction with the host, causing severe opportunistic lung infections in cystic fibrosis patients. In this work we produced Giant Plasma Membrane Vesicles (GPMVs) from a bronchial epithelial cell line and validated their use as a cell-like alternative to investigate the steps involved in the adhesion process of B. cenocepacia. RNA-sequencing was performed and the analysis of the B. cenocepacia K56-2 transcriptome after the first contacts with the surface of host cells allowed the recognition of genes implicated in bacterial adaptation and virulence-associated functions. The sensing of host membranes led to a transcriptional shift that caused a cascade of metabolic and physiological adaptations to the host specific environment. Many of the differentially expressed genes encode proteins related with central metabolic pathways, transport systems, cellular processes, and virulence traits. The understanding of the changes in gene expression that occur in the early steps of infection can uncover new proteins implicated in B. cenocepacia-host cell adhesion, against which new blocking agents could be designed to control the progression of the infectious process.

scholarly journals Glycosylation is a key in SARS-CoV-2 infection

2021 ◽  
Author(s):  
Celso A. Reis ◽  
Rudolf Tauber ◽  
Véronique Blanchard
Keyword(s):  
Adaptive Immune Response ◽  
Protective Role ◽  
Host Cells ◽  
Target Cells ◽  
Receptor Binding Domain ◽  
Serological Testing ◽  
Virus Binding ◽  
Adaptive Immune ◽  
Cytokine Cascade ◽  
Different Levels

AbstractSARS-CoV-2 causes the respiratory syndrome COVID-19 and is responsible for the current pandemic. The S protein of SARS-CoV-2-mediating virus binding to target cells and subsequent viral uptake is extensively glycosylated. Here we focus on how glycosylation of both SARS-CoV-2 and target cells crucially impacts SARS-CoV-2 infection at different levels: (1) virus binding and entry to host cells, with glycosaminoglycans of host cells acting as a necessary co-factor for SARS-CoV-2 infection by interacting with the receptor-binding domain of the SARS-CoV-2 spike glycoprotein, (2) innate and adaptive immune response where glycosylation plays both a protective role and contributes to immune evasion by masking of viral polypeptide epitopes and may add to the cytokine cascade via non-fucosylated IgG, and (3) therapy and vaccination where a monoclonal antibody-neutralizing SARS-CoV-2 was shown to interact also with a distinct glycan epitope on the SARS-CoV-2 spike protein. These evidences highlight the importance of ensuring that glycans are considered when tackling this disease, particularly in the development of vaccines, therapeutic strategies and serological testing.

scholarly journals Trastuzumab Modulates the Protein Cargo of Extracellular Vesicles Released by ERBB2+ Breast Cancer Cells

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 199
Author(s):  
Silvia Marconi ◽  
Sara Santamaria ◽  
Martina Bartolucci ◽  
Sara Stigliani ◽  
Cinzia Aiello ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Extracellular Vesicles ◽  
Breast Cancer Cells ◽  
Culture Supernatant ◽  
High Resolution Mass Spectrometry ◽  
Recombinant Antibody ◽  
Target Cells ◽  
Cellular Processes ◽  
Erbb2 Signaling

Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab on ERBB2 cancer cells are well known, those on the extracellular vesicles (EVs) released from these cells are scarce. This study focused on ERBB2+ breast cancer cells and aimed to establish what type of EVs they release and whether Trastuzumab affects their morphology and molecular composition. To these aims, we performed immunoelectron microscopy, immunoblot, and high-resolution mass spectrometry analyses on EVs purified by differential centrifugation of culture supernatant. Here, we show that EVs released from ERBB2+ breast cancer cells are polymorphic in size and appearance and that ERBB2 is preferentially associated with large (120 nm) EVs. Moreover, we report that Trastuzumab (Tz) induces the expression of a specific glycosylated 50 kDa isoform of the CD63 tetraspanin and modulates the expression of 51 EVs proteins, including TOP1. Because these proteins are functionally associated with organelle organization, cytokinesis, and response to lipids, we suggest that Tz may influence these cellular processes in target cells at distant sites via modified EVs.

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