Cholesterol-dependent actin remodeling via RhoA and Rac1 activation by the<i>Streptococcus pneumoniae</i>toxin pneumolysin

Iliev, Alexandar; Djannatian, Jasmin Roya; Nau, Roland; Mitchell, Tim; Wouters, Fred S.

doi:10.1073/pnas.0608213104

Cited by 81 publications

(105 citation statements)

References 40 publications

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“…We found that PLY treatment activates RhoA and reduces Rac1 activity in HL-MVECs, thereby increasing the ratio of RhoA/Rac1 activity and favoring barrier-compromising processes and resulting in a dramatic loss of VE-cadherin expression (Figure 4). In contrast to our findings in HL-MVECs, sublytic concentrations of PLY were shown to preferentially activate RhoA and Rac1 in neuroblastoma cells (39,40). Although Rac1 enforces the endothelial junctions, it can also become part of a barrier-disturbing mechanism as an activator of ROS-generating NADPH oxidase (41).…”

Section: Discussioncontrasting

confidence: 55%

Protein Kinase C-α and Arginase I Mediate Pneumolysin-Induced Pulmonary Endothelial Hyperpermeability

Lucas

Yang

Gorshkov

et al. 2012

Am J Respir Cell Mol Biol

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Antibiotics-induced release of the pore-forming virulence factor pneumolysin (PLY) in patients with pneumococcal pneumonia results in its presence days after lungs are sterile and is a major factor responsible for the induction of permeability edema. Here we sought to identify major mechanisms mediating PLY-induced endothelial dysfunction. We evaluated PLY-induced endothelial hyperpermeability in human lung microvascular endothelial cells (HL-MVECs) and human lung pulmonary artery endothelial cells in vitro and in mice instilled intratracheally with PLY. PLY increases permeability in endothelial monolayers by reducing stable and dynamic microtubule content and modulating VE-cadherin expression. These events, dependent upon an increased calcium influx, are preceded by protein kinase C (PKC)-a activation, perturbation of the RhoA/Rac1 balance, and an increase in myosin light chain phosphorylation. At later time points, PLY treatment increases the expression and activity of arginase in HL-MVECs. Arginase inhibition abrogates and suppresses PLY-induced endothelial barrier dysfunction by restoring NO generation. Consequently, a specific PKC-a inhibitor and the TNF-derived tonoplast intrinsic protein peptide, which blunts PLY-induced PKC-a activation, are able to prevent activation of arginase in HL-MVECs and to reduce PLY-induced endothelial hyperpermeability in mice. Arginase I (AI) 1/2 /arginase II (AII) 2/2 C57BL/6 mice, displaying a significantly reduced arginase I expression in the lungs, are significantly less sensitive to PLY-induced capillary leak than their wild-type or AI 1/1 /AII 2/2 counterparts, indicating an important role for arginase I in PLYinduced endothelial hyperpermeability. These results identify PKC-a and arginase I as potential upstream and downstream therapeutic targets in PLY-induced pulmonary endothelial dysfunction.Keywords: PKC; arginase; pneumococcus; pneumolysin; TNF Although severe pneumonia remains the leading cause of mortality worldwide in children aged less than 5 years (1), community-acquired pneumonia represents a major cause of morbidity and mortality mainly in elderly patients (2). Despite the use of potent antibiotics and aggressive intensive care support, the fatality rate associated with Streptococcus pneumoniae, accounting for 45% of all cases of community-acquired pneumonia, is approximately 20% (1, 2). Pulmonary permeability edema, a major complication of severe pneumonia characterized by endothelial hyperpermeability, can occur days after initiation of antibiotics therapy when tissues are sterile and the pneumonia is clearing and correlates with the presence of the bacterial virulence factor pneumolysin (PLY) (3, 4). This cytoplasmic hemolytic protein is released during bacterial lysis, as occurs after treatment with b-lactam antibiotics (5). PLYinduced lung injury was suggested to result from direct pneumotoxic effects on the alveolar-capillary barrier rather than from resident or recruited phagocytic cells (6).Upon binding of PLY to cholesterol in cell membranes, oligo...

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Section: Discussioncontrasting

confidence: 55%

Protein Kinase C-α and Arginase I Mediate Pneumolysin-Induced Pulmonary Endothelial Hyperpermeability

Lucas

Yang

Gorshkov

et al. 2012

Am J Respir Cell Mol Biol

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“…Thus, a question that has yet to be answered is how S. pneumoniae PLY regulates NFAT activation. One possibility is that PLY induces Ca 2ϩ influx into the cells through its pore-forming action (37,38). PLY has been known as a direct inducer of Ca 2ϩ influx into the cells.…”

Section: Discussionmentioning

confidence: 99%

Tumor Suppressor Cylindromatosis Acts as a Negative Regulator for Streptococcus pneumoniae-induced NFAT Signaling

Koga

Lim

Jono

et al. 2008

Journal of Biological Chemistry

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Gram-positive bacterium Streptococcus pneumoniae is an important human pathogen that colonizes the upper respiratory tract and is also the major cause of morbidity and mortality worldwide. S. pneumoniae causes invasive diseases such as pneumonia, meningitis, and otitis media. Despite the importance of pneumococcal diseases, little is known about the molecular mechanisms by which S. pneumoniae-induced inflammation is regulated, especially the negative regulatory mechanisms. Here we show that S. pneumoniae activates nuclear factor of activated T cells (NFAT) signaling pathway and the subsequent up-regulation of inflammatory mediators via a key pneumococcal virulence factor, pneumolysin. We also demonstrate that S. pneumoniae activates NFAT transcription factor independently of Toll-like receptors 2 and 4. Moreover, S. pneumoniae induces NFAT activation via both Ca 2؉ -calcineurin and transforming growth factor-␤-activated kinase 1 (TAK1)-mitogen-activated protein kinase kinase (MKK) 3/6-p38␣/␤-dependent signaling pathways. Interestingly, we found for the first time that tumor suppressor cylindromatosis (CYLD) acts as a negative regulator for S. pneumoniae-induced NFAT signaling pathway via a deubiquitination-dependent mechanism. Finally, we showed that CYLD interacts with and deubiquitinates TAK1 to negatively regulate the activation of the downstream MKK3/6-p38␣/␤ pathway. Our studies thus bring new insights into the molecular pathogenesis of S. pneumoniae infections through the NFAT-dependent mechanism and further identify CYLD as a negative regulator for NFAT signaling, thereby opening up new therapeutic targets for these diseases.

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“…Cholesterol inactivation experiments were performed in a manner similar to that described by Iliev et al (34). Supernatant from autolyzed bacteria (3.5 ϫ 10 9 bacteria/ml before autolysis) was mixed with cholesterol (Sigma) at concentrations of up to 500 ng/ml at 37°C for 20 min.…”

Section: Inhibition Of Ply Activity By Cholesterolmentioning

confidence: 99%

Pneumolysin Released duringStreptococcus pneumoniaeAutolysis Is a Potent Activator of Intracellular Oxygen Radical Production in Neutrophils

et al. 2008

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Streptococcus pneumoniae is a major cause of otitis media, pneumonia, meningitis, and septicemia in humans. The host defense against this pathogen largely depends on bacterial killing by neutrophils. A peculiar property of pneumococci is their tendency to undergo autolysis, i.e., autoinduced disruption of the bacterial cell wall mediated by activation of the enzyme LytA, under stationary growth conditions. LytA is a virulence factor, but the molecular background for this has not been fully clarified. Here we examine how bacterial compounds released upon autolysis affect the production of reactive oxygen species (ROS) in neutrophils. We found that the S. pneumoniae strains A17 and D39 induced activation of the NADPH oxidase and the production of ROS in human neutrophils and that this activation was blocked when LytA was inactivated. The ROS-inducing bacterial substance released from autolyzed bacteria was identified as the cytoplasmic toxin pneumolysin. Further screening of clinical pneumococcal strains of various sero-and genotypes revealed that selected strains expressing toxins with reduced pneumolysin-dependent hemolytic activity had decreased abilities to induce ROS in neutrophils. Furthermore, a mutated form of purified pneumolysin lacking hemolytic and complement binding functions (PdT) did not induce any oxygen radical production. The ROS produced in response to pneumolysin formed mainly intracellularly, which may explain why this production was not detected previously. ROS released intracellularly may function as signaling molecules, modifying the function of neutrophils in bacterial defense.

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Cholesterol-dependent actin remodeling via RhoA and Rac1 activation by theStreptococcus pneumoniaetoxin pneumolysin

Cited by 81 publications

References 40 publications

Protein Kinase C-α and Arginase I Mediate Pneumolysin-Induced Pulmonary Endothelial Hyperpermeability

Protein Kinase C-α and Arginase I Mediate Pneumolysin-Induced Pulmonary Endothelial Hyperpermeability

Tumor Suppressor Cylindromatosis Acts as a Negative Regulator for Streptococcus pneumoniae-induced NFAT Signaling

Pneumolysin Released duringStreptococcus pneumoniaeAutolysis Is a Potent Activator of Intracellular Oxygen Radical Production in Neutrophils

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