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Intracellular Lifestyle (intracellular + lifestyle)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Listeriolysin O: a key protein of Listeria monocytogenes with multiple functions

FEMS MICROBIOLOGY REVIEWS, Issue 4 2006
Samer Kayal
Abstract Cholesterol-dependent cytolysins (CDCs) are produced by a large number of pathogenic Gram-positive bacteria. Most of these single-chain proteins are secreted in the extracellular medium. Among the species producing CDCs, only two species belonging to the genus Listeria (Listeria monocytogenes and Listeria ivanovii) are able to multiply intracellularly and release their toxins in the phagosomal compartment of the infected host cell. This review provides an updated overview on the importance of listeriolysin O (LLO) in the pathogenicity of L. monocytogenes, focusing mainly on two aspects: (1) the structure,function relationship of LLO and (2) its role in intra- and extracellular signalling. We first examine the specific sequence determinants, or protein domains, that make this cytolysin so well adapted to the intracellular lifestyle of L. monocytogenes. The roles that LLO has in cellular signalling events in the context of relations to pathogenesis are also discussed. [source]

Pathogen trafficking pathways and host phosphoinositide metabolism

MOLECULAR MICROBIOLOGY, Issue 6 2009
Stefan S. Weber
Summary Phosphoinositide (PI) glycerolipids are key regulators of eukaryotic signal transduction, cytoskeleton architecture and membrane dynamics. The host cell PI metabolism is targeted by intracellular bacterial pathogens, which evolved intricate strategies to modulate uptake processes and vesicle trafficking pathways. Upon entering eukaryotic host cells, pathogenic bacteria replicate in distinct vacuoles or in the host cytoplasm. Vacuolar pathogens manipulate PI levels to mimic or modify membranes of subcellular compartments and thereby establish their replicative niche. Legionella pneumophila, Brucella abortus, Mycobacterium tuberculosis and Salmonella enterica translocate effector proteins into the host cell, some of which anchor to the vacuolar membrane via PIs or enzymatically turnover PIs. Cytoplasmic pathogens target PI metabolism at the plasma membrane, thus modulating their uptake and antiapoptotic signalling pathways. Employing this strategy, Shigella flexneri directly injects a PI-modifying effector protein, while Listeria monocytogenes exploits PI metabolism indirectly by binding to transmembrane receptors. Thus, regardless of the intracellular lifestyle of the pathogen, PI metabolism is critically involved in the interactions with host cells. [source]

Quantitative proteomics of intracellular Porphyromonas gingivalis

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 23 2007
Qiangwei Xia
Abstract Whole-cell quantitative proteomic analyses were conducted to investigate the change from an extracellular to intracellular lifestyle for Porphyromonas gingivalis, a Gram-negative intracellular pathogen associated with periodontal disease. Global protein abundance data for P. gingivalis strain ATCC 33277 internalized for 18,h within human gingival epithelial cells and controls exposed to gingival cell culture medium were obtained at sufficient coverage to provide strong evidence that these changes are profound. A total of 385 proteins were overexpressed in internalized P. gingivalis relative to controls; 240 proteins were shown to be underexpressed. This represented in total about 28% of the protein encoding ORFs annotated for this organism, and slightly less than half of the proteins that were observed experimentally. Production of several proteases, including the classical virulence factors RgpA, RgpB, and Kgp, was decreased. A separate validation study was carried out in which a 16-fold dilution of the P. gingivalis proteome was compared to the undiluted sample in order to assess the quantitative false negative rate (all ratios truly alternative). Truly null (no change) abundance ratios from technical replicates were used to assess the rate of quantitative false positives over the entire proteome. A global comparison between the direction of abundance change observed and previously published bioinformatic gene pair predictions for P. gingivalis will assist with future studies of P. gingivalis gene regulation and operon prediction. [source]

Lounging in a lysosome: the intracellular lifestyle of Coxiella burnetii

CELLULAR MICROBIOLOGY, Issue 4 2007
Daniel E. Voth
Summary Most intracellular parasites employ sophisticated mechanisms to direct biogenesis of a vacuolar replicative niche that circumvents default maturation through the endolysosomal cascade. However, this is not the case of the Q fever bacterium, Coxiella burnetii. This hardy, obligate intracellular pathogen has evolved to not only survive, but to thrive, in the harshest of intracellular compartments: the phagolysosome. Following internalization, the nascent Coxiella phagosome ultimately develops into a large and spacious parasitophorous vacuole (PV) that acquires lysosomal characteristics such as acidic pH, acid hydrolases and cationic peptides, defences designed to rid the host of intruders. However, transit of Coxiella to this environment is initially stalled, a process that is apparently modulated by interactions with the autophagic pathway. Coxiella actively participates in biogenesis of its PV by synthesizing proteins that mediate phagosome stalling, autophagic interactions, and development and maintenance of the mature vacuole. Among the potential mechanisms mediating these processes is deployment of a type IV secretion system to deliver effector proteins to the host cytosol. Here we summarize our current understanding of the cellular events that occur during parasitism of host cells by Coxiella. [source]