13935
2011
eng
930-936
6
204
article
1
2016-10-14
--
--
Extracellular Calcium Reduction Strongly Increases the Lytic Capacity of Pneumolysin From Streptococcus Pneumoniae in Brain Tissue
Background
Streptococcus pneumoniae causes serious diseases such as pneumonia and meningitis. Its major pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, which produces lytic pores at high concentrations. At low concentrations, it has other effects, including induction of apoptosis. Many cellular effects of pneumolysin appear to be calcium dependent.
Methods
Live imaging of primary mouse astroglia exposed to sublytic amounts of pneumolysin at various concentrations of extracellular calcium was used to measure changes in cellular permeability (as judged by lactate dehydrogenase release and propidium iodide chromatin staining). Individual pore properties were analyzed by conductance across artificial lipid bilayer. Tissue toxicity was studied in continuously oxygenated acute brain slices.
Results
The reduction of extracellular calcium increased the lytic capacity of the toxin due to increased membrane binding. Reduction of calcium did not influence the conductance properties of individual toxin pores. In acute cortical brain slices, the reduction of extracellular calcium from 2 to 1 mM conferred lytic activity to pathophysiologically relevant nonlytic concentrations of pneumolysin.
Conclusions
Reduction of extracellular calcium strongly enhanced the lytic capacity of pneumolysin due to increased membrane binding. Thus, extracellular calcium concentration should be considered as a factor of primary importance for the course of pneumococcal meningitis. "
The Journal of Infectious Diseases
10.1093/infdis/jir434
urn:nbn:de:bvb:20-opus-139356
The Journal of Infectious Diseases, Volume 204, Issue 6, 15 September 2011, Pages 930–936
false
true
Carolin Wippel
Christina Förtsch
Sabrina Hupp
Elke Maier
Roland Benz
Jiangtao Ma
Timothy J Mitchell
Asparouh I Iliev
eng
uncontrolled
bacteria
Medizin und Gesundheit
open_access
Rudolf-Virchow-Zentrum
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/13935/052_Wippel_JID.pdf
13229
2013
eng
636-646
3
425
article
1
2016-04-15
--
--
Direct Transmembrane Interaction between Actin and the Pore-Competent, Cholesterol-Dependent Cytolysin Pneumolysin
The eukaryotic actin cytoskeleton is an evolutionarily well-established pathogen target, as a large number of bacterial factors disturb its dynamics to alter the function of the host cells. These pathogenic factors modulate or mimic actin effector proteins or they modify actin directly, leading to an imbalance of the precisely regulated actin turnover. Here, we show that the pore-forming, cholesterol-dependent cytolysin pneumolysin (PLY), a major neurotoxin of Streptococcus pneumoniae, has the capacity to bind actin directly and to enhance actin polymerisation in vitro. In cells, the toxin co-localised with F-actin shortly after exposure, and this direct interaction was verified by Förster resonance energy transfer. PLY was capable of exerting its effect on actin through the lipid bilayer of giant unilamellar vesicles, but only when its pore competence was preserved. The dissociation constant of G-actin binding to PLY in a biochemical environment was 170–190 nM, which is indicative of a high-affinity interaction, comparable to the affinity of other intracellular actin-binding factors. Our results demonstrate the first example of a direct interaction of a pore-forming toxin with cytoskeletal components, suggesting that the cross talk between pore-forming cytolysins and cells is more complex than previously thought.
Journal of Molecular Biology
10.1016/j.jmb.2012.11.034
urn:nbn:de:bvb:20-opus-132297
Journal of Molecular Biology (2013) 425, 636–646. DOI:10.1016/j.jmb.2012.11.034
Sabrina Hupp
Christina Förtsch
Carolin Wippel
Jiangtao Ma
Timothy J. Mitchell
Asparouh I. Iliev
eng
uncontrolled
pore-forming toxin
eng
uncontrolled
cholesterol-dependent cytolysin
eng
uncontrolled
actin
eng
uncontrolled
membrane
eng
uncontrolled
pneumolysin
Pharmakologie, Therapeutik
open_access
Institut für Pharmakologie und Toxikologie
Rudolf-Virchow-Zentrum
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/13229/151_Hupp_Journal_of_Molecular_Biology.pdf
13046
2013
eng
e1003380
6
9
article
1
2016-03-23
--
--
Bacterial Cytolysin during Meningitis Disrupts the Regulation of Glutamate in the Brain, Leading to Synaptic Damage
Abstract
Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage.
Author Summary
Bacterial meningitis is one of the most devastating brain diseases. Among the bacteria that cause meningitis, Streptococcus pneumoniae is the most common. Meningitis predominantly affects children, especially in the Third World, and most of them do not survive. Those that do survive often suffer permanent brain damage and hearing problems. The exact morphological substrates of brain damage in Streptococcus pneumoniae meningitis remain largely unknown. In our experiments, we found that the brain cortex of patients with meningitis demonstrated a loss of synapses (the contact points among neurons, responsible for the processes of learning and memory), and we identified the major pneumococcal neurotoxin pneumolysin as a sufficient cause of this loss. The effect was not direct but was mediated by the brain neurotransmitter glutamate, which was released upon toxin binding by one of the non-neuronal cell types of the brain – the astrocytes. Pneumolysin initiated calcium influx in astrocytes and subsequent glutamate release. Glutamate damaged the synapses via NMDA-receptors – a mechanism similar to the damage occurring in brain ischemia. Thus, we show that synaptic loss is present in pneumococcal meningitis, and we identify the toxic bacterial protein pneumolysin as the major factor in this process. These findings alter our understanding of bacterial meningitis and establish new therapeutic strategies for this fatal disease.
PLoS Pathogens
10.1371/journal.ppat.1003380
urn:nbn:de:bvb:20-opus-130462
PLoS Pathogens 9(6): e1003380. doi:10.1371/journal.ppat.1003380
Carolin Wippel
Jana Maurer
Christina Fortsch
Sabrina Hupp
Alexandra Bohl
Jiangtao Ma
Timothy J. Mitchell
Stephanie Bunkowski
Wolfgang Brück
Roland Nau
Asparouh I. Iliev
eng
uncontrolled
synapses
eng
uncontrolled
brain damage
eng
uncontrolled
astrocytes
eng
uncontrolled
neuronal dendrites
eng
uncontrolled
meningitis
eng
uncontrolled
glutamate
eng
uncontrolled
bacterial meningitis
eng
uncontrolled
neocortex
Medizin und Gesundheit
open_access
Institut für Pharmakologie und Toxikologie
Rudolf-Virchow-Zentrum
Universität Würzburg
https://opus.bibliothek.uni-wuerzburg.de/files/13046/112_Wippel_Maurer_Förtsch.pdf