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A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection
Published on: February 28, 2019
Infection-mimicking conditions alter expression patterns of the highly abundant extracellular protease Jep in a
Gina Wockenfuß1, Jöran Tebben1, Larissa M Busch1
1Department of Functional Genomics, Interfaculty Institute of Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany.
Abstract:
The opportunistic pathogen Staphylococcus aureus colonizes a broad spectrum of different hosts and intra-host niches. Recently, it has been demonstrated that mouse-adapted S. aureus strains are better suited to investigate S. aureus infections in the mouse model than human-adapted strains. One of the most studied mouse-adapted strains is JSNZ (CC88-MSSA). Under control conditions at 37 °C, JSNZ secretes very large amounts of the prophage-encoded serine protease Jep (JSNZ extracellular protease). Given S. aureus' ability to colonize a broad variety of host niches, we investigated Jep expression at transcript and protein levels under several physiological conditions, such as different temperatures (37 °C, 42 °C and 32 °C), and infection-relevant stress conditions (iron and oxygen limitation). Gene expression and protein abundance of Jep differed between the different conditions, with elevated levels at 42 °C and under iron limitation and reduced levels at 32 °C and under oxygen limitation. Mass spectrometry analysis proved that Jep is the major protein in the JSNZ supernatant making up to 75% at 37 °C and 42 °C, as well as under iron limitation. In silico predictions and Northern blot analyses revealed that jep is encoded as a monocistronic transcript of approximately 900 bp, showing prophage-independent regulation. Correlation analysis of protein abundances and additional in silico analysis suggest SaeR and PurR as potential regulators of jep. To extend these observations to a pathophysiological context, we additionally examined Jep abundance in a murine infection model and found it to be the most abundant secreted protein there as well.
Insights
Staphylococcus aureus JSNZ strain secretes large amounts of the JSNZ extracellular protease (Jep). Jep expression and abundance varied with temperature and nutrient availability, and it was the major secreted protein in a mouse infection model.
Area of Science:
- Microbiology
- Proteomics
- Bacterial Pathogenesis
Background:
- Staphylococcus aureus is an opportunistic pathogen colonizing diverse hosts and niches.
- Mouse-adapted strains like JSNZ are valuable for studying S. aureus infections.
- The JSNZ strain secretes significant amounts of the serine protease Jep under standard conditions.
Purpose of the Study:
- To investigate the expression and regulation of the JSNZ extracellular protease (Jep) under various physiological and stress conditions.
- To determine Jep's abundance in vitro and in a murine infection model.
- To identify potential regulators of Jep expression.
Main Methods:
- Quantitative analysis of Jep transcript and protein levels under different temperatures (32°C, 37°C, 42°C) and stress conditions (iron and oxygen limitation).
- Mass spectrometry to identify and quantify secreted proteins in JSNZ.
- Northern blot analysis and in silico predictions to analyze jep transcript structure and regulation.
- Correlation analysis and in silico methods to identify potential regulatory elements (SaeR, PurR).
- Analysis of Jep abundance in a murine infection model.
Main Results:
- Jep expression and protein abundance varied significantly with temperature and nutrient availability, showing higher levels at 42°C and under iron limitation, and reduced levels at 32°C and oxygen limitation.
- Jep was identified as the major secreted protein (up to 75%) in JSNZ supernatant under optimal conditions and iron limitation.
- The jep gene is transcribed as a monocistronic transcript, independently regulated from prophages.
- SaeR and PurR were suggested as potential regulators of jep.
- Jep was confirmed as the most abundant secreted protein in a murine infection model.
Conclusions:
- Jep expression in Staphylococcus aureus JSNZ is dynamically regulated by environmental factors relevant to host colonization and infection.
- Jep is a highly abundant secreted protein, suggesting a significant role in S. aureus pathogenesis.
- Further research into Jep's function and regulation by SaeR and PurR could reveal new therapeutic targets.
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