TY  - JOUR
A1  - Blättner, Sebastian
A1  - Das, Sudip
A1  - Paprotka, Kerstin
A1  - Eilers, Ursula
A1  - Krischke, Markus
A1  - Kretschmer, Dorothee
A1  - Remmele, Christian W.
A1  - Dittrich, Marcus
A1  - Müller, Tobias
A1  - Schuelein-Voelk, Christina
A1  - Hertlein, Tobias
A1  - Mueller, Martin J.
A1  - Huettel, Bruno
A1  - Reinhardt, Richard
A1  - Ohlsen, Knut
A1  - Rudel, Thomas
A1  - Fraunholz, Martin J.
T1  - Staphylococcus aureus Exploits a Non-ribosomal Cyclic Dipeptide to Modulate Survival within Epithelial Cells and Phagocytes
JF  - PLoS Pathogens
N2  - Community-acquired (CA) Staphylococcus aureus cause various diseases even in healthy individuals. Enhanced virulence of CA-strains is partly attributed to increased production of toxins such as phenol-soluble modulins (PSM). The pathogen is internalized efficiently by mammalian host cells and intracellular S. aureus has recently been shown to contribute to disease. Upon internalization, cytotoxic S. aureus strains can disrupt phagosomal membranes and kill host cells in a PSM-dependent manner. However, PSM are not sufficient for these processes. Here we screened for factors required for intracellular S. aureus virulence. We infected escape reporter host cells with strains from an established transposon mutant library and detected phagosomal escape rates using automated microscopy. We thereby, among other factors, identified a non-ribosomal peptide synthetase (NRPS) to be required for efficient phagosomal escape and intracellular survival of S. aureus as well as induction of host cell death. By genetic complementation as well as supplementation with the synthetic NRPS product, the cyclic dipeptide phevalin, wild-type phenotypes were restored. We further demonstrate that the NRPS is contributing to virulence in a mouse pneumonia model. Together, our data illustrate a hitherto unrecognized function of the S. aureus NRPS and its dipeptide product during S. aureus infection.
KW  - cell death
KW  - cytotoxicity
KW  - Staphylococcus aureus
KW  - host cells
KW  - neutrophils
KW  - macrophages
KW  - transposable elements
KW  - epithelial cells
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180380
VL  - 12
IS  - 9
ER  - 
TY  - JOUR
A1  - Stelzner, Kathrin
A1  - Winkler, Ann-Cathrin
A1  - Liang, Chunguang
A1  - Boyny, Aziza
A1  - Ade, Carsten P.
A1  - Dandekar, Thomas
A1  - Fraunholz, Martin J.
A1  - Rudel, Thomas
T1  - Intracellular Staphylococcus aureus Perturbs the Host Cell Ca\(^{2+}\) Homeostasis To Promote Cell Death
JF  - mBio
N2  - The opportunistic human pathogen Staphylococcus aureus causes serious infectious diseases that range from superficial skin and soft tissue infections to necrotizing pneumonia and sepsis. While classically regarded as an extracellular pathogen, S. aureus is able to invade and survive within human cells. Host cell exit is associated with cell death, tissue destruction, and the spread of infection. The exact molecular mechanism employed by S. aureus to escape the host cell is still unclear. In this study, we performed a genome-wide small hairpin RNA (shRNA) screen and identified the calcium signaling pathway as being involved in intracellular infection. S. aureus induced a massive cytosolic Ca\(^{2+}\) increase in epithelial host cells after invasion and intracellular replication of the pathogen. This was paralleled by a decrease in endoplasmic reticulum Ca\(^{2+}\) concentration. Additionally, calcium ions from the extracellular space contributed to the cytosolic Ca2+ increase. As a consequence, we observed that the cytoplasmic Ca\(^{2+}\) rise led to an increase in mitochondrial Ca\(^{2+}\) concentration, the activation of calpains and caspases, and eventually to cell lysis of S. aureus-infected cells. Our study therefore suggests that intracellular S. aureus disturbs the host cell Ca\(^{2+}\) homeostasis and induces cytoplasmic Ca\(^{2+}\) overload, which results in both apoptotic and necrotic cell death in parallel or succession.

IMPORTANCE Despite being regarded as an extracellular bacterium, the pathogen Staphylococcus aureus can invade and survive within human cells. The intracellular niche is considered a hideout from the host immune system and antibiotic treatment and allows bacterial proliferation. Subsequently, the intracellular bacterium induces host cell death, which may facilitate the spread of infection and tissue destruction. So far, host cell factors exploited by intracellular S. aureus to promote cell death are only poorly characterized. We performed a genome-wide screen and found the calcium signaling pathway to play a role in S. aureus invasion and cytotoxicity. The intracellular bacterium induces a cytoplasmic and mitochondrial Ca\(^{2+}\) overload, which results in host cell death. Thus, this study first showed how an intracellular bacterium perturbs the host cell Ca\(^{2+}\) homeostasis."
KW  - Staphylococcus aureus
KW  - calcium signaling pathway
KW  - cell death
KW  - facultatively intracellular pathogens
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-231448
VL  - 11
ER  -