Friday, May 9, 2025
5/9/2025
Modulation of Agr system by ClpC chaperone in S. aureus - PROJECT SUMMARY The long-term goal of our research is to understand virulence gene regulation in Staphylococcus aureus. S. aureus is an important human pathogen capable of causing a wide spectrum of infections in human and animals. The pathogenicity of this organism is dependent on various virulence factors produced during infection that are controlled by a large number of regulators. Elucidation of virulence regulation by this complex regulatory network is central to understanding pathogenesis of this pathogen. However, despite extensive efforts, our knowledge of virulence regulation is still very limited. We have previously identified ClpC as part of the regulatory network capable of regulating the transcription of a large number of genes, including virulence genes. ClpC is a protein chaperone involved in protein quality control, which does not have a DNA-binding motif. We therefore hypothesize that ClpC interacts with transcriptional regulators to affect gene transcription. Indeed, our recent results provided the initial evidence to support this hypothesis. One of the regulators we identified that could interact with ClpC is AgrA, a transcriptional regulator of the AgrAC two-component system, which is part of the Agr quorum sensing system in S. aureus. The Agr quorum sensing system also includes AgrB and AgrD that are involved in pheromone AIP (auto-inducing peptide) production needed for Agr autoactivation at high cell density. Agr has been shown to be a key regulator that affects the expression of many virulence genes. Our preliminary data showed that ClpC could activate the Agr system by directly interacting with AgrA as well as by positively affecting AIP production independent of AgrA autoactivation, suggesting that ClpC could affect Agr regulatory system at two different pathways. Accordingly, in this application, we propose two specific aims to study the potential mechanisms involved in this regulation. In the first aim, we will investigate how ClpC modulates AgrA regulatory activity. In the second aim, we will study how ClpC affects AIP production. ClpC has been shown to negatively affect regulators by partnering with ClpP protease. However, how ClpC can positively modulate a regulatory system is virtually unknown. Our studies proposed in this application will not only probe the potential novel mechanisms involved in gene regulation but will also advance our understanding virulence regulation in S. aureus.
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