26 research outputs found
The Phosphoarginine Phosphatase PtpB from Staphylococcus aureus Is Involved in Bacterial Stress Adaptation during Infection
Staphylococcus aureus continues to be a public health threat, especially in hospital settings.
Studies aimed at deciphering the molecular and cellular mechanisms that underlie pathogenesis,
host adaptation, and virulence are required to develop effective treatment strategies. Numerous
host-pathogen interactions were found to be dependent on phosphatases-mediated regulation. This
study focused on the analysis of the role of the low-molecular weight phosphatase PtpB, in particular,
during infection. Deletion of ptpB in S. aureus strain SA564 significantly reduced the capacity of the
mutant to withstand intracellular killing by THP-1 macrophages. When injected into normoglycemic
C57BL/6 mice, the SA564 âptpB mutant displayed markedly reduced bacterial loads in liver and
kidney tissues in a murine S. aureus abscess model when compared to the wild type. We also observed
that PtpB phosphatase-activity was sensitive to oxidative stress. Our quantitative transcript analyses
revealed that PtpB affects the transcription of various genes involved in oxidative stress adaptation
and infectivity. Thus, this study disclosed first insights into the physiological role of PtpB during
host interaction allowing us to link phosphatase-dependent regulation to oxidative bacterial stress
adaptation during infection
The Transcription Factor SpoVG Is of Major Importance for Biofilm Formation of Staphylococcus epidermidis under In Vitro Conditions, but Dispensable for In Vivo Biofilm Formation
Staphylococcus epidermidis is a common cause of device related infections on which pathogens
form biofilms (i.e., multilayered cell populations embedded in an extracellular matrix). Here, we
report that the transcription factor SpoVG is essential for the capacity of S. epidermidis to form such
biofilms on artificial surfaces under in vitro conditions. Inactivation of spoVG in the polysaccharide
intercellular adhesin (PIA) producing S. epidermidis strain 1457 yielded a mutant that, unlike its
parental strain, failed to produce a clear biofilm in a microtiter plate-based static biofilm assay. A
decreased biofilm formation capacity was also observed when 1457 âspoVG cells were co-cultured
with polyurethane-based peripheral venous catheter fragments under dynamic conditions, while
the cis-complemented 1457 âspoVG::spoVG derivative formed biofilms comparable to the levels seen
with the wild-type. Transcriptional studies demonstrated that the deletion of spoVG significantly
altered the expression of the intercellular adhesion (ica) locus by upregulating the transcription of
the ica operon repressor icaR and down-regulating the transcription of icaADBC. Electrophoretic
mobility shift assays (EMSA) revealed an interaction between SpoVG and the icaA-icaR intergenic
region, suggesting SpoVG to promote biofilm formation of S. epidermidis by modulating ica expression.
However, when mice were challenged with the 1457 âspoVG mutant in a foreign body infection
model, only marginal differences in biomasses produced on the infected catheter fragments between
the mutant and the parental strain were observed. These findings suggest that SpoVG is critical for the
PIA-dependent biofilm formation of S. epidermis under in vitro conditions, but is largely dispensable
for biofilm formation of this skin commensal under in vivo conditions
Characterization of the Secreted Acid Phosphatase SapS Reveals a Novel Virulence Factor of Staphylococcus aureus That Contributes to Survival and Virulence in Mice
Staphylococcus aureus possesses a large arsenal of immune-modulating factors, enabling it
to bypass the immune systemâs response. Here, we demonstrate that the acid phosphatase SapS is
secreted during macrophage infection and promotes its intracellular survival in this type of immune
cell. In animal models, the SA564 sapS mutant demonstrated a significantly lower bacterial burden
in liver and renal tissues of mice at four days post infection in comparison to the wild type, along
with lower pathogenicity in a zebrafish infection model. The SA564 sapS mutant elicits a lower
inflammatory response in mice than the wild-type strain, while S. aureus cells harbouring a functional
sapS induce a chemokine response that favours the recruitment of neutrophils to the infection site.
Our in vitro and quantitative transcript analysis show that SapS has an effect on S. aureus capacity to
adapt to oxidative stress during growth. SapS is also involved in S. aureus biofilm formation. Thus,
this study shows for the first time that SapS plays a significant role during infection, most likely
through inhibiting a variety of the hostâs defence mechanisms
Phosphorylation of the Cav3.2 T-type calcium channel directly regulates its gating properties
Phosphorylation of the Cav3.2 T-type calcium channel directly regulates its gating properties
Phosphorylation is a major mechanism regulating the activity of ion channels that remains poorly understood with respect to T-type calcium channels (Cav3). These channels are low voltage-activated calcium channels that play a key role in cellular excitability and various physiological functions. Their dysfunction has been linked to several neurological disorders, including absence epilepsy and neuropathic pain. Recent studies have revealed that T-type channels are modulated by a variety of serine/threonine protein kinase pathways, which indicates the need for a systematic analysis of T-type channel phosphorylation. Here, we immunopurified Cav3.2 channels from rat brain, and we used high-resolution MS to construct the first, to our knowledge, in vivo phosphorylation map of a voltage-gated calcium channel in a mammalian brain. We identified as many as 34 phosphorylation sites, and we show that the vast majority of these sites are also phosphorylated on the human Cav3.2 expressed in HEK293T cells. In patch-clamp studies, treatment of the channel with alkaline phosphatase as well as analysis of dephosphomimetic mutants revealed that phosphorylation regulates important functional properties of Cav3.2 channels, including voltage-dependent activation and inactivation and kinetics. We also identified that the phosphorylation of a locus situated in the loop I-II S442/S445/T446 is crucial for this regulation. Our data show that Cav3.2 channels are highly phosphorylated in the mammalian brain and establish phosphorylation as an important mechanism involved in the dynamic regulation of Cav3.2 channel gating properties
Phosphorylation-mediated regulation of the Staphylococcus aureus secreted tyrosine phosphatase PtpA
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The Phosphoarginine Phosphatase PtpB from Staphylococcus aureus Is Involved in Bacterial Stress Adaptation during Infection
Staphylococcus aureus continues to be a public health threat, especially in hospital settings. Studies aimed at deciphering the molecular and cellular mechanisms that underlie pathogenesis, host adaptation, and virulence are required to develop effective treatment strategies. Numerous host-pathogen interactions were found to be dependent on phosphatases-mediated regulation. This study focused on the analysis of the role of the low-molecular weight phosphatase PtpB, in particular, during infection. Deletion of ptpB in S. aureus strain SA564 significantly reduced the capacity of the mutant to withstand intracellular killing by THP-1 macrophages. When injected into normoglycemic C57BL/6 mice, the SA564 ÎptpB mutant displayed markedly reduced bacterial loads in liver and kidney tissues in a murine S. aureus abscess model when compared to the wild type. We also observed that PtpB phosphatase-activity was sensitive to oxidative stress. Our quantitative transcript analyses revealed that PtpB affects the transcription of various genes involved in oxidative stress adaptation and infectivity. Thus, this study disclosed first insights into the physiological role of PtpB during host interaction allowing us to link phosphatase-dependent regulation to oxidative bacterial stress adaptation during infection
The Coxiella burnetii secreted protein kinase CstK influences vacuole development and interacts with the GTPase-activating protein TBC1D5
Investigating Pathogenicity and Virulence of Staphylococcus pettenkoferi: An Emerging Pathogen
International audienceStaphylococcus pettenkoferi is a coagulase-negative Staphylococcus identified in 2002 that has been implicated in human diseases as an opportunistic pathogenic bacterium. Its multiresistant character is becoming a major health problem, yet the pathogenicity of S. pettenkoferi is poorly characterized. In this study, the pathogenicity of a S. pettenkoferi clinical isolate from diabetic foot osteomyelitis was compared with a Staphylococcus aureus strain in various in vitro and in vivo experiments. Growth kinetics were compared against S. aureus, and bacteria survival was assessed in the RAW 264.7 murine macrophage cell line, the THP-1 human leukemia monocytic cell line, and the HaCaT human keratinocyte cell line. Ex vivo analysis was performed in whole blood survival assays and in vivo assays via the infection model of zebrafish embryos. Moreover, whole-genome analysis was performed. Our results show that S. pettenkoferi was able to survive in human blood, human keratinocytes, murine macrophages, and human macrophages. S. pettenkoferi demonstrated its virulence by causing substantial embryo mortality in the zebrafish model. Genomic analysis revealed virulence factors such as biofilm-encoding genes (e.g., icaABCD; rsbUVW) and regulator-encoding genes (e.g., agr, mgrA, sarA, saeS) well characterized in S. aureus. This study thus advances the knowledge of this under-investigated pathogen and validates the zebrafish infection model for this bacterium
Characterisation of the purified human sodium/iodide symporter reveals that the protein is mainly present in a dimeric form and permits the detailed study of a native C-terminal fragment
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