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Selective and specific internalization of clostridial C3 ADP-ribosyltransferases into macrophages and monocytesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In conclusion, we identified macrophages/monocytes as target cells for clostridial C3 transferases and shed light on their selective uptake mechanism, which might contribute to understand the role of C3 transferases in pathogenesis. (Source: Cellular Microbiology)
Source: Cellular Microbiology - October 29, 2009 Category: Microbiology Authors: Jörg Fahrer, Jasmin Kuban, Karin Heine, Gabriel Rupps, Eva Kaiser, Edward Felder, Roland Benz, Holger Barth Source Type: journals

Variable expression of surface-exposed polymorphic membrane proteins in in vitro-grown Chlamydia trachomatisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The hypothesized variable expression of polymorphic membrane proteins (PmpA[ndash]PmpI) in Chlamydia trachomatis-infected patients was tested by examination of the expression of each Pmp subtype in in vitro-grown C. trachomatis. A panel of monospecific polyclonal and monoclonal antibodies was used to demonstrate surface exposure of Pmps of each subtype by differential immunofluorescence (IF) with and without prior detergent permeabilization of paraformaldehyde-fixed inclusions and for selected Pmps by immunogold labelling. Although specific transcript was detected for each pmp gene late in development, IF experiments with ...
Source: Cellular Microbiology - October 28, 2009 Category: Microbiology Authors: Chun Tan, Ru-ching Hsia, Huizhong Shou, Jose A. Carrasco, Roger G. Rank, Patrik M. Bavoil Source Type: journals

Autophagy supports Candida glabrata survival during phagocytosisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The opportunistic human fungal pathogen Candida glabrata is confronted with phagocytic cells of the host defence system. Survival of internalized cells is thought to contribute to successful dissemination. We investigated the reaction of engulfed C. glabrata cells using fluorescent protein fusions of the transcription factors CgYap1 and CgMig1 and catalase CgCta1. The expression level and peroxisomal localization of catalase was used to monitor the metabolic and stress status of internalized C. glabrata cells. These reporters revealed that the phagocytosed C. glabrata cells were exposed to transient oxidative stress and st...
Source: Cellular Microbiology - October 27, 2009 Category: Microbiology Authors: Andreas Roetzer, Nina Gratz, Pavel Kovarik, Christoph Schüller Source Type: journals

Zaire Ebola virus entry into human dendritic cells is insensitive to cathepsin L inhibitionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Cathepsins B and L contribute to Ebola virus (EBOV) entry into Vero cells and mouse embryonic fibroblasts. However, the role of cathepsins in EBOV-infection of human dendritic cells (DCs), important targets of infection in vivo, remains undefined. Here, EBOV-like particles containing a [beta]-lactamase[ndash]VP40 fusion reporter and Ebola virus were used to demonstrate the cathepsin dependence of EBOV entry into human monocyte-derived DCs. However, while DC infection is blocked by cathepsin B inhibitor, it is insensitive to cathepsin L inhibitor. Furthermore, DCs pre-treated for 48 h with TNF[alpha] were generally less sus...
Source: Cellular Microbiology - October 15, 2009 Category: Microbiology Authors: Osvaldo Martinez, Joshua Johnson, Balaji Manicassamy, Lijun Rong, Gene G. Olinger, Lisa E. Hensley, Christopher F. Basler Source Type: journals

Antigenic and phenotypic variations in fungiEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Mechanisms to vary the phenotypic characteristics of fungi are diverse and can be important for their life cycle. This review summarizes phenotypic variability in fungi and divides this phenomenon into three topics: (i) morphological transitions, which are environmentally induced and involve the entire fungal population, (ii) reversible phenotypic switching between different colony morphologies, which is restricted to a small fraction of the population, and (iii) antigenic variation of surface antigens, which can be immuno-dominant epitopes happens in individual fungal cells. (Source: Cellular Microbiology)
Source: Cellular Microbiology - October 6, 2009 Category: Microbiology Authors: Neena Jain, Bettina C. Fries Source Type: journals

ATP-dependent activation of an inflammasome in primary gingival epithelial cells infected by Porphyromonas gingivalisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Production of IL-1[beta] typically requires two-separate signals. The first signal, from a pathogen-associated molecular pattern, promotes intracellular production of immature cytokine. The second signal, derived from a danger signal such as extracellular ATP, results in assembly of an inflammasome, activation of caspase-1 and secretion of mature cytokine. The inflammasome component, Nalp3, plays a non-redundant role in caspase-1 activation in response to ATP binding to P2X7 in macrophages. Gingival epithelial cells (GECs) are an important component of the innate-immune response to periodontal bacteria. We had shown that G...
Source: Cellular Microbiology - October 6, 2009 Category: Microbiology Authors: Özlem Yilmaz, Ali Abdul Sater, Luyu Yao, Theofilos Koutouzis, Matthew Pettengill, David M. Ojcius Source Type: journals

Signalling through TLR2/MyD88 induces differentiation of murine bone marrow stem and progenitor cells to functional phagocytes in response to Candida albicansEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In conclusion, C. albicans may be sensed by TLRs on haematopoietic stem and progenitor cells to promote the host capability for rapidly replenishing myeloid cells that constitute the first line of defence against C. albicans. (Source: Cellular Microbiology)
Source: Cellular Microbiology - October 5, 2009 Category: Microbiology Authors: Alberto Yáñez, Ana Flores, Celia Murciano, José-Enrique O'Connor, Daniel Gozalbo, M. Luisa Gil Source Type: journals

Modulation of NF-κB activation in Theileria annulata-infected cloned cell lines is associated with detection of parasite-dependent IKK signalosomes and disruption of the actin cytoskeletonEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study two clonal cell lines were identified that show marked differences in the level of activated NF-[kappa]B. Further characterization of these lines demonstrated that elevated levels of activated NF-[kappa]B correlated with increased resistance to cell death and detection of parasite-associated IKK signalosomes, supporting results of our previous studies. Evidence was also provided for the existence of host- and parasite-dependent NF-[kappa]B activation pathways that are influenced by the architecture of the actin cytoskeleton. Despite this influence, it appears that the primary event required for formation of t...
Source: Cellular Microbiology - October 5, 2009 Category: Microbiology Authors: Jacqueline Schmuckli-Maurer, Jane Kinnaird, Sreerekha Pillai, Pascal Hermann, Sue McKellar, William Weir, Dirk Dobbelaere, Brian Shiels Source Type: journals

Passing GO (gene ontology) in plant pathogen biology: a report from the Xanthomonas Genomics ConferenceEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this report we give an overview of recent developments in this field that were presented during the meeting. These highlights included the unveiling of 11 new Xanthomonas genomic sequences, structural and functional insights into the peptide Ax21 elicitor, the first description of small non-coding RNAs in Xanthomonas and the role they play in the regulation of virulence, as well as a description of novel type III-secreted effectors which target different hosts. (Source: Cellular Microbiology)
Source: Cellular Microbiology - October 5, 2009 Category: Microbiology Authors: Robert P. Ryan, Ralf Koebnik, Boris Szurek, Tristan Boureau, Adriana Bernal, Adam Bogdanove, J. Maxwell Dow Source Type: journals

Anopheles gambiae innate immunityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The successful development of Plasmodium in Anopheles mosquitoes is governed by complex molecular and cellular interactions that we are just beginning to understand. Anopheles immune system has received particular attention as genetic evidence points clearly to its critical role in eliminating the majority of parasites invading the midgut epithelium. Several factors regulating Plasmodium development have been identified and tentatively assigned to the individual steps leading to mosquito immune reactions; non-self-recognition, signal modulation, signal transduction and effector mechanisms. Detailed knowledge of these steps...
Source: Cellular Microbiology - October 5, 2009 Category: Microbiology Authors: Hassan Yassine, Mike A. Osta Source Type: journals

Mycobacterium leprae induces insulin-like growth factor and promotes survival of Schwann cells upon serum withdrawalEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, it is shown that treatment of SCs with M. leprae significantly decreased cell death induced by serum deprivation. Not displayed by Mycobacterium smegmatis or Mycobacterium bovis BCG, the M. leprae survival effect was both dose dependent and specific. The conditioned medium (CM) of M. leprae-treated cultures was seen to mimic the protective effect of the bacteria, suggesting that soluble factors secreted by SCs in response to M. leprae were involved in cell survival. Indeed, by quantitative RT-PCR and dot blot/ELISA, it was demonstrated that M. leprae induced the expression and secretion of the SC survival fa...
Source: Cellular Microbiology - September 24, 2009 Category: Microbiology Authors: Luciana Silva Rodrigues, Elisa da Silva Maeda, Maria Elisabete Costa Moreira, Antonio Jorge Tempone, Lívia Silva Lobato, Victor Túlio Ribeiro-Resende, Lucineia Alves, Shaila Rossle, Ulisses Gazos Lopes, Maria Cristina Vidal Pessolani Source Type: journals

Molecular dissection of Salmonella-induced membrane ruffling versus invasionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Type III secretion system-mediated injection of a cocktail of bacterial proteins drives actin rearrangements, frequently adopting the shape of prominent protuberances of ruffling membrane, and culminating in host cell invasion of Gram-negative pathogens like Salmonella typhimurium. Different Salmonella effectors are able to bind actin and activate Rho-family GTPases, which have previously been implicated in mediating actin-dependent Salmonella entry by interacting with N-WASP or WAVE-complex, well-established activators of the actin nucleation machine Arp2/3-complex. Using genetic deletion and RNA interference studies, we ...
Source: Cellular Microbiology - September 23, 2009 Category: Microbiology Authors: Jan Hänisch, Julia Ehinger, Markus Ladwein, Manfred Rohde, Emmanuel Derivery, Tanja Bosse, Anika Steffen, Dirk Bumann, Benjamin Misselwitz, Wolf-Dietrich Hardt, Alexis Gautreau, Theresia E. B. Stradal, Klemens Rottner Source Type: journals

Salmonella – the ultimate insider. Salmonella virulence factors that modulate intracellular survivalEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Salmonella enterica serovar Typhimurium is a common facultative intracellular pathogen that causes food-borne gastroenteritis in millions of people worldwide. Intracellular survival and replication are important virulence determinants and the bacteria can be found in a variety of phagocytic and non-phagocytic cells in vivo. Invasion of host cells and intracellular survival are dependent on two type III secretion systems, T3SS1 and T3SS2, each of which translocates a distinct set of effector proteins. However, other virulence factors including ion transporters, superoxide dismutase, flagella and fimbriae are also involved i...
Source: Cellular Microbiology - September 22, 2009 Category: Microbiology Authors: J. Antonio Ibarra, Olivia Steele-Mortimer Source Type: journals

A highly sensitive FRET-based approach reveals secretion of the actin-binding protein toxofilin during Toxoplasma gondii infectionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We have utilized a highly sensitive approach based on fluorescence resonance energy transfer (FRET) and [beta]-lactamase (BLA), which we adapted for the detection of Toxoplasma gondii secreted proteins. This assay revealed that the actin-binding protein toxofilin appears to be secreted into host cells during invasion. To determine the function of toxofilin during infection, we engineered a type I (RH strain) parasite with a targeted deletion of the toxofilin gene and compared the phenotypes of control and toxofilin knockout ([Delta]txf) parasites in several in vitro assays, including invasion, growth, gliding motility, and...
Source: Cellular Microbiology - September 22, 2009 Category: Microbiology Authors: Melissa B. Lodoen, Christiane Gerke, John C. Boothroyd Source Type: journals

Differences in human macrophage receptor usage, lysosomal fusion kinetics and survival between logarithmic and metacyclic Leishmania infantum chagasi promastigotesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The obligate intracellular protozoan, Leishmania infantum chagasi (Lic) undergoes receptor-mediated phagocytosis by macrophages followed by a transient delay in phagolysosome maturation. We found differences in the pathway through which virulent Lic metacyclic promastigotes or avirulent logarithmic promastigotes are phagocytosed by human monocyte-derived macrophages (MDMs). Both logarithmic and metacyclic promastigotes entered MDMs through a compartment lined by the third complement receptor (CR3). In contrast, many logarithmic promastigotes entered through vacuoles lined by mannose receptors (MR) whereas most metacyclic p...
Source: Cellular Microbiology - September 16, 2009 Category: Microbiology Authors: Norikiyo Ueno, Carol L. Bratt, Nilda E. Rodriguez, Mary E. Wilson Source Type: journals

Antigenic variation in the African trypanosome: molecular mechanisms and phenotypic complexityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Antigenic variation is an immune evasion strategy that has evolved in viral, bacterial and protistan pathogens. In the African trypanosome this involves stochastic switches in the composition of a variant surface glycoprotein (VSG) coat, using a massive archive of silent VSG genes to change the identity of the single VSG expressed at a time. VSG switching is driven primarily by recombination reactions that move silent VSGs into specialized expression sites, though transcription-based switching can also occur. Here we discuss what is being revealed about the machinery that underlies these switching mechanisms, including wha...
Source: Cellular Microbiology - September 13, 2009 Category: Microbiology Authors: Liam J. Morrison, Lucio Marcello, Richard McCulloch Source Type: journals

Crohn's disease-associated adherent-invasive E. coli are selectively favoured by impaired autophagy to replicate intracellularlyEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Ileal lesions in Crohn's disease (CD) patients are colonized by pathogenic adherent-invasive Escherichia coli (AIEC) able to invade and to replicate within intestinal epithelial cells. Recent genome-wide association studies have highlighted the autophagy pathway as being associated with CD risk. In the present study we investigated whether defects in autophagy enhance replication of commensal and pathogenic Escherichia coli and CD-associated AIEC. We show that functional autophagy limits intracellular AIEC replication and that a subpopulation of the intracellular bacteria is located within LC3-positive autophagosomes. In I...
Source: Cellular Microbiology - September 10, 2009 Category: Microbiology Authors: Pierre Lapaquette, Anne-Lise Glasser, Alan Huett, Ramnik J. Xavier, Arlette Darfeuille-Michaud Source Type: journals

Secretory protein with RING finger domain (SPRING) specific to Trypanosoma cruzi is directed, as a ubiquitin ligase related protein, to the nucleus of host cellsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
While some intracellular bacterial and viral proteins secreted into host cell possess ubiquitin ligase (E3) activity for their profit, it has not been reported whether intracellular parasites secrete such molecules. We identified a gene that encodes a protein containing a secretory signal peptide and a RING finger domain in the intracellular protozoan parasite, Trypanosoma cruzi. This gene was specific to T. cruzi and was designated spring (secretory protein with RING finger domain). An in vitro ubiquitination assay showed that SPRING possessed E3 activity in a RING finger domain-dependent manner. SPRING could utilize huma...
Source: Cellular Microbiology - September 8, 2009 Category: Microbiology Authors: Muneaki Hashimoto, Eri Murata, Takashi Aoki Source Type: journals

Internalization-dependent recognition of Mycobacterium avium ssp. paratuberculosis by intestinal epithelial cellsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of Johne's disease, a highly prevalent chronic intestinal infection in domestic and wildlife ruminants. The microbial pathogenesis of MAP infection has attracted additional attention due to an association with the human enteric inflammatory Crohn's disease. MAP is acquired by the faecal[ndash]oral route prompting us to study the interaction with differentiated intestinal epithelial cells. MAP was rapidly internalized and accumulated in a late endosomal compartment. In contrast to other opportunistic mycobacteria or M. bovis, MAP induced significant epit...
Source: Cellular Microbiology - September 7, 2009 Category: Microbiology Authors: Johanna Pott, Tina Basler, Claudia U. Duerr, Manfred Rohde, Ralph Goethe, Mathias W. Hornef Source Type: journals

Nitric oxide/cGMP signalling induces Escherichia coli K1 receptor expression and modulates the permeability in human brain endothelial cell monolayers during invasionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Escherichia coli K1 invasion of human brain microvascular endothelial cells (HBMEC) mediated by outer membrane protein A (OmpA) results in the leakage of HBMEC monolayers. Despite the influence of nitric oxide (NO) in endothelial cell tight junction integrity, its role in E. coli-induced HBMEC monolayer permeability is poorly defined. Here, we demonstrate that E. coli invasion of HBMEC stimulates NO production by increasing the inducible nitric oxide synthase (iNOS) expression. Exposure to NO-producing agents enhanced the invasion of OmpA+E. coli and thereby increased the permeability of HBMEC. OmpA+E. coli-induced NO prod...
Source: Cellular Microbiology - September 1, 2009 Category: Microbiology Authors: Rahul Mittal, Nemani V. Prasadarao Source Type: journals

The bacterial virulence factor NleA is required for the disruption of intestinal tight junctions by enteropathogenic Escherichia coliEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Enteropathogenic Escherichia coli (EPEC) is a diarrhoeal pathogen that adheres to epithelial cells of the small intestine and uses a type III secretion system to inject effector proteins into host cells. EPEC infection leads to disruption of host intestinal tight junctions that are important for maintaining intestinal barrier function. This disruption is dependent on the bacterial type III secretion system, as well as the translocated effectors EspF and Map. Here we show that a third type III translocated bacterial effector protein, NleA, is also involved in tight junction disruption during EPEC infection. Using the drug B...
Source: Cellular Microbiology - August 26, 2009 Category: Microbiology Authors: Ajitha Thanabalasuriar, Athanasia Koutsouris, Andrew Weflen, Mark Mimee, Gail Hecht, Samantha Gruenheid Source Type: journals

Serine-71 phosphorylation of Rac1/Cdc42 diminishes the pathogenic effect of Clostridium difficile toxin AEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Clostridium difficile toxin A and B (TcdA/TcdB) are glucosyltransferases that glucosylate GTPases of the Rho family. The epidermal growth factor (EGF) positively modulates C. difficile toxin-induced disturbance of the intestinal barrier function by an unknown mechanism. We found that EGF-treated CaCo-2 monolayers were less susceptible to TcdA-catalysed glucosylation of Rac1 but not of RhoA, which correlated with phosphorylation of Rac1 at Ser-71. Phospho-Rac1/phospho-Cdc42 (Ser-71) still bound to the PAK-CRIB domain indicating an active state. A more detailed characterization of phospho-Rac1 was performed using the phospho...
Source: Cellular Microbiology - August 25, 2009 Category: Microbiology Authors: Janett Schoentaube, Alexandra Olling, Helma Tatge, Ingo Just, Ralf Gerhard Source Type: journals

Antigenic variation in Giardia lambliaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Giardia lamblia undergoes antigenic variation, both in vitro and within the intestines of infected individuals. Variant-specific surface proteins (VSPs) cover the entire surface of the trophozoites and are the main antigens recognized by the host. Only 1 of about 200 VSP genes encoded by the Giardia genome is expressed on the surface of individual Giardia cells at any time; however, VSP antigen switching occurs spontaneously. In the recent year, significant advances in the knowledge of the antigen switching process have been achieved, which strongly suggests that antigenic variation in Giardia is regulated at the post-tran...
Source: Cellular Microbiology - August 25, 2009 Category: Microbiology Authors: Cesar G. Prucca, Hugo D. Lujan Source Type: journals

'Nothing is permanent but change'† – antigenic variation in persistent bacterial pathogensEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Pathogens persist in immunocompetent mammalian hosts using various strategies, including evasion of immune effectors by antigenic variation. Among highly antigenically variant bacteria, gene conversion is used to generate novel expressed variants from otherwise silent donor sequences. Recombination using oligonucleotide segments from multiple donors is a combinatorial mechanism that tremendously expands the variant repertoire, allowing thousands of variants to be generated from a relatively small donor pool. Three bacterial pathogens, each encoded by a small genome (< 1.2 Mb), illustrate this variant generating capacity an...
Source: Cellular Microbiology - August 24, 2009 Category: Microbiology Authors: Guy H. Palmer, Troy Bankhead, Sheila A. Lukehart Source Type: journals

New insights into Chlamydia intracellular survival mechanismsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Chlamydia sp. are responsible for a wide range of diseases of significant clinical and public health importance. In this review, we highlight how recent cellular and functional genomic approaches have significantly increased our knowledge of the pathogenic mechanisms used by these genetically intractable bacteria. As the extensive repertoire of chlamydial proteins that are translocated into the mammalian host is identified and characterized, a molecular understanding of how Chlamydiae co-opt host cellular functions and block innate immune pathways is beginning to emerge. (Source: Cellular Microbiology)
Source: Cellular Microbiology - August 17, 2009 Category: Microbiology Authors: Jordan L. Cocchiaro, Raphael H. Valdivia Source Type: journals

N-glycosylated proteins and distinct lipooligosaccharide glycoforms of Campylobacter jejuni target the human C-type lectin receptor MGLEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
An increasing number of bacterial pathogens produce an array of glycoproteins of unknown function. Here we report that Campylobacter jejuni proteins that are modified by the N-linked glycosylation machinery encoded by the pgl locus bind the human Macrophage Galactose-type lectin (MGL). MGL receptor binding was abrogated by EDTA and N-acetylgalactosamine (GalNAc) and was successfully transferred to Escherichia coli by introducing the C. jejuni pgl locus together with a glycan acceptor protein. In addition to glycoproteins, C. jejuni lipooligosaccharide with a terminal GalNAc residue was recognized by MGL. Recombinant E. col...
Source: Cellular Microbiology - August 12, 2009 Category: Microbiology Authors: Nina M. van Sorge, Nancy M. C. Bleumink, Sandra J. van Vliet, Eirikur Saeland, W. -Ludo van der Pol, Yvette van Kooyk, Jos P. M. van Putten Source Type: journals

Cell invasion of Yersinia pseudotuberculosis by invasin and YadA requires protein kinase C, phospholipase C-γ1 and Akt kinaseEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The outer membrane proteins YadA and invasin of Yersinia pseudotuberculosis promote invasion into mammalian cells through [beta]1-integrins and trigger the production of interleukin (IL)-8. FAK, c-Src and the PI3 kinase were previously found to be important for both YadA- and invasin-promoted uptake. Here, we demonstrate that two different downstream effectors of PI3 kinase, Akt and phospholipase C[gamma]1 are required for efficient cell invasion. Inhibition of Akt or phospholipase C-[gamma] (PLC-[gamma])1 by pharmaceutical agents as well as reduced expression of the isoforms Akt1 and Akt2, and of PLC-[gamma]1 by RNA inter...
Source: Cellular Microbiology - August 12, 2009 Category: Microbiology Authors: Frank Uliczka, Tina Kornprobst, Julia Eitel, Daniela Schneider, Petra Dersch Source Type: journals

Imaging the assembly, structure and activity of type III secretion systemsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The type III secretion system (T3SS) is a sophisticated molecular machinery of Gram-negative bacteria used to 'inject' (translocate) bacterial proteins (effectors) into eukaryotic cells. For this, the T3SS has to assemble into a multiprotein complex, which is constituted of distinct parts; a basal body spanning the two bacterial membranes connected with a cytoplasmic bulb, an attached needle structure resembling a molecular syringe, and a distal needle tip structure that re-organizes into a 'translocon', which is a protein complex that inserts into the host cellular membrane. Upon engaging with eukaryotic cells, the T3SSs ...
Source: Cellular Microbiology - August 11, 2009 Category: Microbiology Authors: Jost Enninga, Ilan Rosenshine Source Type: journals

Morphogenesis of hepatitis B virus and its subviral envelope particlesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
After cell hijacking and intracellular amplification, non-lytic enveloped viruses are usually released from the infected cell by budding across internal membranes or through the plasma membrane. The enveloped human hepatitis B virus (HBV) is an example of virus using an intracellular compartment to form new virions. Four decades after its discovery, HBV is still the primary cause of death by cancer due to a viral infection worldwide. Despite numerous studies on HBV genome replication little is known about its morphogenesis process. In addition to viral neogenesis, the HBV envelope proteins have the capability without any o...
Source: Cellular Microbiology - August 5, 2009 Category: Microbiology Authors: Romuald Patient, Christophe Hourioux, Philippe Roingeard Source Type: journals

Unique physiology of host–parasite interactions in microsporidia infectionsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Microsporidia are intracellular parasites of all major animal lineages and have a described diversity of over 1200 species and an actual diversity that is estimated to be much higher. They are important pathogens of mammals, and are now one of the most common infections among immunocompromised humans. Although related to fungi, microsporidia are atypical in genomic biology, cell structure and infection mechanism. Host cell infection involves the rapid expulsion of a polar tube from a dormant spore to pierce the host cell membrane and allow the direct transfer of the spore contents into the host cell cytoplasm. This intimat...
Source: Cellular Microbiology - August 4, 2009 Category: Microbiology Authors: Bryony A. P. Williams Source Type: journals

Cell type-specific effects of Yersinia pseudotuberculosis virulence effectorsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
One important feature of Yersinia pseudotuberculosis that enables resistance against the host immune defence is delivery of the antiphagocytic effectors YopH and YopE into phagocytic cells. The tyrosine phosphatase YopH influences integrin signalling, and YopE impairs cytoskeletal dynamics by inactivating Rho GTPases. Here, we report the impact of these effectors on internalization by dendritic cells (DCs), which internalize antigens to orchestrate host immune responses. We found that this pathogen resists internalization by DCs via YopE. YopH that is important for blocking phagocytosis by macrophages and neutrophils and w...
Source: Cellular Microbiology - August 3, 2009 Category: Microbiology Authors: Anna Fahlgren, Linda Westermark, Karen Akopyan, Maria Fällman Source Type: journals

Ubiquitination of the bacterial inositol phosphatase, SopB, regulates its biological activity at the plasma membraneEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The Salmonella type III effector, SopB, is an inositol polyphosphate phosphatase that modulates host cell phospholipids at the plasma membrane and the nascent Salmonella-containing vacuole (SCV). Translocated SopB persists for many hours after infection and is ubiquitinated but the significance of this covalent modification has not been investigated. Here we identify by mass spectrometry six lysine residues of SopB that are mono-ubiquitinated. Substitution of these six lysine residues with arginine, SopB-K6R, almost completely eliminated SopB ubiquitination. We found that ubiquitination does not affect SopB stability or me...
Source: Cellular Microbiology - August 3, 2009 Category: Microbiology Authors: Leigh A. Knodler, Seth Winfree, Dan Drecktrah, Robin Ireland, Olivia Steele-Mortimer Source Type: journals

The impact of vector-mediated neutrophil recruitment on cutaneous leishmaniasisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The dynamic process of pathogen transmission by the bite of an insect vector combines several biological processes that have undergone extensive co-evolution. Whereas the host response to an insect bite is only occasionally confronted with the parasitic pathogens that competent vectors might transmit, the transmitted parasites will always be confronted with the acute, wound-healing response that is initiated by the bite itself. Invariably, this response involves neutrophils. In the case of Leishmania, infection is initiated in the skin following the bite of an infected sand fly, suggesting that Leishmania must possess some...
Source: Cellular Microbiology - August 2, 2009 Category: Microbiology Authors: Nathan C. Peters, David L. Sacks Source Type: journals

Reticulocyte binding protein homologues are key adhesins during erythrocyte invasion by Plasmodium falciparumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The Apicomplexan parasite responsible for the most virulent form of malaria, Plasmodium falciparum, invades human erythrocytes through multiple ligand[ndash]receptor interactions. The P. falciparum reticulocyte-binding protein homologue (PfRh or PfRBL) family have been implicated in the invasion process but their exact role is unknown. PfRh1 and PfRh4, members of this protein family, bind to red blood cells and function in merozoite invasion during which they undergo a series of proteolytic cleavage events before and during entry into the host cell. The ectodomain of PfRh1 and PfRh4 are processed to produce fragments consi...
Source: Cellular Microbiology - July 30, 2009 Category: Microbiology Authors: Tony Triglia, Wai-Hong Tham, Anthony Hodder, Alan F. Cowman Source Type: journals

The Bordetella type III secretion system effector BteA contains a conserved N-terminal motif that guides bacterial virulence factors to lipid raftsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The Bordetella type III secretion system (T3SS) effector protein BteA is necessary and sufficient for rapid cytotoxicity in a wide range of mammalian cells. We show that BteA is highly conserved and functionally interchangeable between Bordetella bronchiseptica, Bordetella pertussis and Bordetella parapertussis. The identification of BteA sequences required for cytotoxicity allowed the construction of non-cytotoxic mutants for localization studies. BteA derivatives were targeted to lipid rafts and showed clear colocalization with cortical actin, ezrin and the lipid raft marker GM1. We hypothesized that BteA associates with...
Source: Cellular Microbiology - July 23, 2009 Category: Microbiology Authors: Christopher T. French, Ekaterina M. Panina, Sylvia H. Yeh, Natasha Griffith, Diego G. Arambula, Jeff F. Miller Source Type: journals

Galactofuranose attenuates cellular adhesion of Aspergillus fumigatusEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Galactofuranose (Galf) is a major molecule found in cell wall polysaccharides, secreted glycoproteins, membrane lipophosphoglycans and sphingolipids of Aspergillus fumigatus. The initial step in the Galf synthetic pathway is the re-arrangement of UDP-galactopyranose to UDP-Galf through the action of UDP-galactopyranose mutase. A mutant lacking the AfUGM1 gene encoding the UDP-galactopyranose mutase has been constructed. In the mutant, though there is a moderate reduction in the mycelial growth associated with an increased branching, it remains as pathogenic and as resistant to cell wall inhibitors and phagocytes as the wil...
Source: Cellular Microbiology - July 21, 2009 Category: Microbiology Authors: Claude Lamarre, Rémi Beau, Viviane Balloy, Thierry Fontaine, Joanne Wong Sak Hoi, Stéphanie Guadagnini, Nadia Berkova, Michel Chignard, Anne Beauvais, Jean-Paul Latgé Source Type: journals

Plant immunity: a lesson from pathogenic bacterial effector proteinsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Phytopathogenic bacteria inject an array of effector proteins into host cells to alter host physiology and assist the infection process. Some of these effectors can also trigger disease resistance as a result of recognition in the plant cell by cytoplasmic immune receptors. In addition to effector-triggered immunity, plants immunity can be triggered upon the detection of Pathogen/Microbe-Associated Molecular Patterns by surface-localized immune receptors. Recent progress indicates that many bacterial effector proteins use a variety of biochemical properties to directly attack key components of PAMP-triggered immunity and e...
Source: Cellular Microbiology - July 19, 2009 Category: Microbiology Authors: Haitao Cui, Tingting Xiang, Jian-Min Zhou Source Type: journals

Lipopolysaccharide-induced innate immune responses in primary hepatocytes downregulates woodchuck hepatitis virus replication via interferon-independent pathwaysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Our previous studies have shown that Toll-like receptor (TLR) ligands, Poly I:C and lipopolysaccharide (LPS), are able to activate non-parenchymal liver cells and trigger the production of interferon (IFN) to inhibit hepatitis B virus replication in vivo and in vitro. However, little is known about TLR-mediated cellular responses in primary hepatocytes. By the model of woodchuck hepatitis virus (WHV) infected primary woodchuck hepatocytes (PWHs), Poly I:C and LPS stimulation resulted in upregulation of cellular antiviral genes and relevant TLRs mRNA expression respectively. LPS stimulation led to a pronounced reduction of ...
Source: Cellular Microbiology - July 19, 2009 Category: Microbiology Authors: Xiaoyong Zhang, Zhongji Meng, Song Qiu, Yang Xu, Dongliang Yang, Jörg F. Schlaak, Michael Roggendorf, Mengji Lu Source Type: journals

Temporal resolution of two-tracked NF-κB activation by Legionella pneumophilaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The intracellular pathogen Legionella pneumophila activates the transcription factor NF-[kappa]B in macrophages and human epithelial cells, contributing to cytokine production and anti-apoptosis. The former is important for the innate immune response to infection, the latter for intracellular replication by securing host cell survival. Here, we demonstrate biphasic activation of NF-[kappa]B by L. pneumophila in human epithelial cells, using a p65-GFP expressing variant of A549 cells. Early in infection, a strong but transient nuclear translocation of p65 was observed. Only flagellin-deficient ([Delta]fliA and [Delta]flaA) ...
Source: Cellular Microbiology - July 16, 2009 Category: Microbiology Authors: Sina Bartfeld, Cecilia Engels, Bianca Bauer, Philipp Aurass, Antje Flieger, Holger Brüggemann, Thomas F. Meyer Source Type: journals

Sialylated ligands on pathogenic Trypanosoma cruzi interact with Siglec-E (sialic acid-binding Ig-like lectin-E)Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Trypanosoma cruzi causes a suppression of the immune system leading to persistence in host cells. The trans-sialidase expressed by T. cruzi is a major virulence factor and transfers sialic acid from host glycoconjugates to mucin-like molecules on the parasite. Here we demonstrate that these sialylated structures play a role in the immunosuppression. We used two T. cruzi strains, whose TS activity correlated with their pathogenicity. The Tulahuen strain, characterized by a high TS activity efficiently infected mice, whereas the Tehuantepec strain showing a reduced TS activity could not establish a patent parasitemia. In vit...
Source: Cellular Microbiology - July 13, 2009 Category: Microbiology Authors: Hanna Erdmann, Christiane Steeg, Friedrich Koch-Nolte, Bernhard Fleischer, Thomas Jacobs Source Type: journals

New roles for perforins and proteases in apicomplexan egressEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Egress is a pivotal step in the life cycle of intracellular pathogens initiating the transition from an expiring host cell to a fresh target cell. While much attention has been focused on understanding cell invasion by intracellular pathogens, recent work is providing a new appreciation of mechanisms and therapeutic potential of microbial egress. This review highlights recent insight into cell egress by apicomplexan parasites and emerging contributions of membranolytic and proteolytic secretory products, along with host proteases. New findings suggest that Toxoplasma gondii secretes a pore-forming protein, TgPLP1, during e...
Source: Cellular Microbiology - July 12, 2009 Category: Microbiology Authors: Marijo S. Roiko, Vern B. Carruthers Source Type: journals

How microbes utilize host ubiquitinationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Activity, abundance and localization of eukaryotic proteins can be regulated through covalent attachment of ubiquitin and ubiquitin-like moieties. Ubiquitination is important in various aspects of immunity. Pathogens utilize host ubiquitination for the suppression of immune signalling and reprogramming host processes to promote microbial life. They deliver so-called effector molecules into host cells, which functionally or structurally resemble components of the host ubiquitination machinery utilizing this enzymatic process or they secrete molecules to inhibit ubiquitin-mediated degradation. Since prokaryotic pathogens lac...
Source: Cellular Microbiology - July 4, 2009 Category: Microbiology Authors: Thomas Spallek, Silke Robatzek, Vera Göhre Source Type: journals

The perplexing functions and surprising origins of Legionella pneumophila type IV secretion effectorsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Only a limited number of bacterial pathogens evade destruction by phagocytic cells such as macrophages. Legionella pneumophila is a Gram-negative [gamma]-proteobacterial species that can infect and replicate in alveolar macrophages, causing Legionnaires' disease, a severe pneumonia. L. pneumophila uses a complex secretion system to inject host cells with effector proteins capable of disrupting or altering the host cell processes. The L. pneumophila effectors target multiple processes but are essentially aimed at modifying the properties of the L. pneumophila phagosome by altering vesicular trafficking, gradually creating a...
Source: Cellular Microbiology - June 25, 2009 Category: Microbiology Authors: Irina S. Franco, Howard A. Shuman, Xavier Charpentier Source Type: journals

Control of mucosal polymicrobial populations by innate immunityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The gastrointestinal tract carries out the complex process of localizing the polymicrobial populations of the indigenous microbiota to the lumenal side of the GI mucosa while absorbing nutrients from the lumen and preventing damage to the mucosa. This process is accomplished through a combination of physical, innate and adaptive host defences and a 'strategic alliance' with members of the microbiota. To cope with the constant exposure to a diverse microbial community, the GI tract, through the actions of a number of specialized cells in the epithelium and lamina propria, has layers of humoral, physical and cellular defence...
Source: Cellular Microbiology - June 24, 2009 Category: Microbiology Authors: Katie L. Mason, Gary B. Huffnagle Source Type: journals

Human Toll-like receptor 4 responses to P. gingivalis are regulated by lipid A 1- and 4'-phosphatase activitiesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Signal transduction following binding of lipopolysaccharide (LPS) to Toll-like receptor 4 (TLR4) is an essential aspect of host innate immune responses to infection by Gram-negative pathogens. Here, we describe a novel molecular mechanism used by a prevalent human bacterial pathogen to evade and subvert the human innate immune system. We show that the oral pathogen, Porphyromonas gingivalis, uses endogenous lipid A 1- and 4'-phosphatase activities to modify its LPS, creating immunologically silent, non-phosphorylated lipid A. This unique lipid A provides a highly effective mechanism employed by this bacterium to evade TLR4...
Source: Cellular Microbiology - June 21, 2009 Category: Microbiology Authors: Stephen R. Coats, Jace W. Jones, Christopher T. Do, Pamela H. Braham, Brian W. Bainbridge, Thao T. To, David R. Goodlett, Robert K. Ernst, Richard P. Darveau Source Type: journals

Phosphorylation of the influenza A virus protein PB1-F2 by PKC is crucial for apoptosis promoting functions in monocytesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The 11th influenza A virus (IAV) protein PB1-F2 is encoded by an alternative reading frame of the PB1 polymerase gene and found in the nucleus, cytosol and at the mitochondria of infected cells, the latter is consistent with experimental evidence for its pro-apoptotic function. Here, the function of PB1-F2 as a phosphoprotein was characterized. PB1-F2 derived from isolate IAVPR8 and synthetic fragments thereof were phosphorylated in vitro by purified protein kinase C (PKC) and cellular extract. Constitutively active PKC[alpha] interacts with PB1-F2 in yeast two-hybrid assays. 32P radiolabelling of transfected 293T cells re...
Source: Cellular Microbiology - June 10, 2009 Category: Microbiology Authors: David Mitzner, Sabine Eva Dudek, Nicole Studtrucker, Darisuren Anhlan, Igor Mazur, Josef Wissing, Lothar Jänsch, Ludmilla Wixler, Karsten Bruns, Alok Sharma, Victor Wray, Peter Henklein, Stephan Ludwig, Ulrich Schubert Source Type: journals

Alternative infectious entry pathways for dengue virus serotypes into mammalian cellsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The entry of two dengue virus (DENV) serotypes into Vero cells was analysed using biochemical inhibitors, dominant negative mutants of cellular proteins involved in endocytic pathways, fluorescence microscopy and infectivity determinations. By treatment with dansylcadaverine and chlorpromazine and overexpression of a dominant negative form of the Eps15 protein, a clathrin-mediated endocytosis for productive DENV-1 internalization into Vero cells was demonstrated whereas the infectious entry of DENV-2 in the same cell system was independent of clathrin. Treatment with the inhibitors nystatin and methyl-[beta]-cyclodextrin, ...
Source: Cellular Microbiology - June 10, 2009 Category: Microbiology Authors: Eliana G. Acosta, Viviana Castilla, Elsa B. Damonte Source Type: journals

Porphyromonas gingivalis invades human trophoblasts and inhibits proliferation by inducing G1 arrest and apoptosisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Porphyromonas gingivalis is an oral pathogen that is also associated with serious systemic conditions such as preterm delivery. Here we investigated the interaction between P. gingivalis and a cell line of extravillous trophoblasts (HTR-8) derived from the human placenta. P. gingivalis internalized within HTR-8 cells and inhibited proliferation through induction of arrest in the G1 phase of the cell cycle. G1 arrest was associated with decreased expression of cyclin D and of CDKs 2, 4 and 6. In addition, levels of CDK inhibitors p15, p16, p18 and p21 were increased following P. gingivalis infection. The amount of Rb was di...
Source: Cellular Microbiology - June 10, 2009 Category: Microbiology Authors: Hiroaki Inaba, Masae Kuboniwa, Brian Bainbridge, Özlem Yilmaz, Joseph Katz, Kathleen T. Shiverick, Atsuo Amano, Richard J. Lamont Source Type: journals

Phosphatidylinositol-phosphates mediate cytoskeletal reorganization during phagocytosis via a unique modular protein consisting of RhoGEF/DH and FYVE domains in the parasitic protozoon Entamoeba histolyticaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
To understand the roles of phosphoinositides [PtdIns] in phagocytosis of parasitic eukaryotes, we examined the interaction of phosphatidylinositol-3-phosphate [PtdIns(3)P] and putative PtdIns-P-binding proteins during phagocytosis in the enteric protozoan parasite Entamoeba histolytica. It was previously shown that phagocytosis in E. histolytica is indispensable for virulence and is inhibited by PtdIns 3-kinase inhibitors. We demonstrated by time-lapse live imaging that during the initiation of phagocytosis, the PtdIns(3)P biomarker GFP[ndash]Hrs[ndash]FYVE, was translocated to the phagocytic cup, phagosome, and to tunnel-...
Source: Cellular Microbiology - June 2, 2009 Category: Microbiology Authors: Kumiko Nakada-Tsukui, Hiroyuki Okada, Biswa Nath Mitra, Tomoyoshi Nozaki Source Type: journals

Plasmodium berghei-infection induces volume-regulated anion channel-like activity in human hepatoma cellsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Parasite infection can lead to alterations in the permeability of host plasma membranes. Presented here is the first demonstration that this phenomenon occurs in Plasmodium-infected liver cells. Using the whole-cell patch-clamp technique, volume-regulated anion channel (VRAC) activity was characterized in Huh-7 cells (a human hepatoma cell line) before and after infection with Plasmodium berghei. Consistent with the presence of VRACs, hypotonic bath solution induced large ion currents in Huh-7 cells that rectified outwardly, reversed close to the equilibrium potential for Cl- and were inhibited by tamoxifen, clomiphene, me...
Source: Cellular Microbiology - June 2, 2009 Category: Microbiology Authors: Miguel Prudêncio, Elvira T. Derbyshire, Catarina A. Marques, Sanjeev Krishna, Maria M. Mota, Henry M. Staines Source Type: journals