Biology subjects

DiMaggio, D. A.

Publications and source records attributed to DiMaggio, D. A..

3 recordsLinked to original sources

bioRxiv2025

Pyrimidine sufficiency is required for Sae two-component system signaling in Staphylococcus aureus

Nucleotide metabolism in pathogens is essential for their virulence, supporting growth, survival, and immune evasion during infection. Virulence in Staphylococcus aureus is driven by the production of virulence factors that facilitate nutrient acquisition and promote immune evasion and subversion. One key virulence regulatory system is the Sae two-component system (TCS), which upregulates the production of various virulence factors. The sensor histidine kinase SaeS, a member of the intramembrane family of histidine kinases (IM-HKs), lacks a signal-binding domain, leaving the mechanisms by which these HKs sense signals and regulate gene expression unclear. We report that de novo pyrimidine biosynthesis is essential for maintaining Sae activity. Disruption of genes involved in pyrimidine biosynthesis reduces Sae-dependent promoter activity under pyrimidine-limited conditions. Phos-tag electrophoresis confirmed that pyrimidine limitation impacts SaeS kinase activity. The effect of pyrimidine limitation on SaeS was abrogated in a strain producing only the catalytic domain, suggesting that pyrimidines regulate SaeS activity at the membrane. Additionally, defective pyrimidine biosynthesis caused membrane defects and increased incorporation of free fatty acids into the membrane. Further, providing an extracellular sink for free fatty acids restored Sae activity in these mutants. Our study highlights the interplay between nucleotide metabolism and membrane integrity in regulating virulence factor expression through signal transduction systems in pathogens. ImportanceVirulence is often correlated with nutrient depletion, but our understanding of this coordination is incomplete. In S. aureus, the Sae two-component system (Sae TCS) is a major regulator of virulence factor production and secretion, but as the sensor histidine kinase SaeS lacks an obvious domain to perceive its inducing signal, basic questions surrounding how the kinase is triggered persist. This study aims to investigate the mechanism by which pyrimidines act to promote the activity of the SaeS kinase in S. aureus and further expands on the importance of the roles of pyrimidines in regulating envelope biogenesis. Understanding this intersection between nucleotide metabolism and virulence regulation opens up the possibility for the development of targeted anti-virulence strategies against S. aureus infections.

microbiology↗

bioRxiv2024

CodY controls the SaeR/S two-component system by modulating branched-chain fatty acid synthesis in Staphylococcus aureus

Staphylococcus aureus is a Gram-positive, opportunistic human pathogen that is a leading cause of skin and soft tissue infections and invasive disease worldwide. Virulence in this bacterium is tightly controlled by a network of regulatory factors. One such factor is the global regulatory protein CodY. CodY links branched-chain amino acid sufficiency to the production of surface-associated and secreted factors that facilitate immune evasion and subversion. Our previous work revealed that CodY regulates virulence factor gene expression indirectly in part by controlling the activity of the SaeRS two-component system. While this is correlated with an increase in membrane anteiso-15:0 and -17:0 branched-chain fatty acids (BCFAs) derived from isoleucine, the true mechanism of control has remained elusive. Herein, we report that CodY-dependent regulation of SaeS sensor kinase activity requires BCFA synthesis. During periods of nutrient sufficiency, BCFA synthesis and Sae TCS activity is heavily suppressed by CodY-dependent repression of the ilv-leu operon and the isoleucine-specific permease gene brnQ2. In a codY null mutant, which simulates extreme nutrient limitation, de-repression of ilv-leu and brnQ2 directs the synthesis of enzymes in redundant de novo and import pathways to catalyze the production of BCFA precursors. Overexpression of brnQ2 independent of CodY is sufficient to increase membrane anteiso BCFAs, Sae-dependent promoter activity, and SaeR[~]P levels. Our results further clarify the molecular mechanism by which CodY controls virulence in S. aureus. IMPORTANCEExpression of bacterial virulence genes often correlates with the exhaustion of nutrients, but how the signaling of nutrient availability and the resulting physiological responses are coordinated is unclear. In S. aureus, CodY controls the activity of two major regulators of virulence - the Agr and Sae two-component systems - by unknown mechanisms. This work identifies a mechanism by which CodY controls the activity of the sensor kinase SaeS by modulating the flux of anteiso branched-chain amino acids to the membrane. Understanding the mechanism adds to our understanding of how bacterial physiology and metabolism are linked to virulence and underscores the homeostatic nature of virulence. Understanding the mechanism also opens potential avenues for targeted therapeutic strategies against S. aureus infections.

physiology↗

bioRxiv2024

Discovery of an anti-virulence compound that targets the Staphylococcus aureus SaeRS two-component system to inhibit toxic shock syndrome toxin 1 (TSST-1) production

Menstrual toxic shock syndrome (mTSS) is a rare but severe disorder associated with the use of menstrual products such as high-absorbency tampons and is caused by Staphylococcus aureus strains that produce the toxic shock syndrome toxin-1 (TSST-1) superantigen. Herein, we screened a library of 3920 small bioactive molecules for the ability to inhibit transcription of the TSST-1 gene without inhibiting growth of S. aureus. The dominant positive regulator of TSST-1 is the SaeRS two-component system (TCS), and we identified phenazopyridine hydrochloride (PP-HCl) that repressed production of TSST-1 by inhibiting the kinase function of SaeS. PP-HCl competed with ATP for binding of the kinase SaeS leading to decreased phosphorylation of SaeR and reduced expression of TSST-1 as well as several other secreted virulence factors known to be regulated by SaeRS. PP-HCl targets virulence of S. aureus, but it also decreases the impact of TSST-1 on human lymphocytes without affecting the healthy vaginal microbiota. Our findings demonstrate the promising potential of PP-HCl as a therapeutic strategy against mTSS.

microbiology↗