Biology subjects

Pope, A. N.

Publications and source records attributed to Pope, A. N..

4 recordsLinked to original sources

bioRxiv2026

PhoPQ is an upstream regulator of quorum sensing in small colony variant subpopulations of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen that is hospital-endemic, forming biofilms on medical equipment and causing thousands of hospital-acquired infections each year. The success of P. aeruginosa as an opportunistic pathogen is linked to its phenotypic and genotypic adaptability. Relatedly, P. aeruginosa forms a small colony subpopulation in response to stresses like oxygen limitation and antibiotic exposure. Additionally, P. aeruginosa coordinates population-level decisions using a mechanism of cell-cell communication called quorum sensing. P. aeruginosa uses these signaling pathways to control virulence factor production and biofilm formation in the host. We show that certain quorum-sensing mutations promote phenotypic variation; specifically, deletion of lasR and autoinducer modulating mutations in rhlI enhanced small colony formation in a time course-dependent manner. Using transcriptome analyses of isogenic small and large colony variants, we show that small colony formation is driven in part by the PhoPQ two-component signal transduction system in quorum-sensing mutant backgrounds. Specifically, our data show that unphosphorylated PhoP represses rhlR gene expression, and that subsequent de-repression of quorum sensing contributes to the production of virulence factors and the small colony phenotype. In total, these findings provide insight on how mutations evolved by clinical strains might serve as a bet-hedging strategy to promote the formation of a small colony phenotype and alter quorum-sensing signaling within a subpopulation of a community.

microbiology↗

bioRxiv2025

RhlR quorum-sensing receptor ligand sensitivity regulates the differential expression of phenazine genes in Pseudomonas aeruginosa

Bacteria control individualistic and group behaviors using a form of cell-cell communication called quorum sensing. Quorum sensing relies on the production of chemical signals called autoinducers and the subsequent detection of those signals by a cognate receptor. Many Gram-negative bacteria use the LuxR-type family of transcription factor receptors that bind to acyl-homoserine lactone autoinducer signals to regulate their function as DNA-binding proteins. A subclass of this family of transcription factor receptors requires their cognate autoinducer to fold and dimerize to bind DNA to regulate gene expression and, thus, traits associated with quorum sensing, such as biofilm formation and virulence factor production. Here, we use a chemical-genetic approach to determine the structural basis for ligand selection by the quorum-sensing receptor RhlR from Pseudomonas aeruginosa. The native ligand for RhlR is N-butyryl-L-homoserine lactone, and this protein-ligand interaction is important for initiating gene expression in P. aeruginosa. We determine key residues that drive ligand specificity and selectivity of RhlR to define the role of ligand-driven RhlR-dependent gene regulation of quorum-sensing traits, namely the differential expression of the phenazine genes, which encode the enzymes responsible for the synthesis of the redox-sensitive virulence factor pyocyanin, among other phenazines. Furthermore, we provide a chemical-genetic framework for future studies aimed at disrupting the RhlR-ligand interaction to suppress virulence in P. aeruginosa, an important nosocomial pathogen with widespread antimicrobial resistance.

microbiology↗

bioRxiv2025

Brief Pulses of High-Level Fluid Shear Stress Enhance Metastatic Potential and Rapidly Alter the Metabolism of Cancer Cells.

Circulating tumor cells (CTCs) face challenges to their survival including mechanical and oxidative stresses that are different from cancer cells in solid primary and metastatic tumors. The impact of adaptations to the fluid microenvironment of the circulation on the outcome of the metastatic cascade are not well understood. Here we find that cancer cells (PC-3, MDA-MB-231, Myc-CaP) exposed to brief pulses of high-level FSS exhibit enhanced invasiveness and anchorage-independent proliferation in vitro and enhanced metastatic colonization/tumor formation in vivo. Cancer cells exposed to FSS rapidly alter their metabolism in a manner that promotes survival by providing energy for cytoskeletal remodeling and contractility as well as reducing equivalents to counter oxidative stress associated with cell detachment. Thus, exposure to FSS may provide CTCs an unexpected survival benefit that promotes metastatic colonization.

cancer biology↗

bioRxiv2024

Evolution of PqsE as a Pseudomonas aeruginosa-specific regulator of LuxR-type receptors: insights from Pseudomonas and Burkholderia

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that poses a significant public health threat, particularly in healthcare settings. A key determinant of P. aeruginosa virulence is the regulated synthesis and release of extracellular products, which is controlled by a cell density-dependent signaling system known as quorum sensing (QS). P. aeruginosa uses a complex QS network, including two systems that rely on diffusible N-acylhomoserine lactone (AHL) signal molecules. The LuxR-type receptor RhlR is unique in that it requires not only its cognate AHL but also the accessory protein PqsE to maximally bind to promoter DNA and to initiate transcription. Our group demonstrated that PqsE physically interacts with RhlR, enhancing its affinity for target promoters across the P. aeruginosa genome. Although LuxR-type receptors are widespread in Gram-negative bacteria and important for pathogenesis, PqsE orthologs are restricted to Pseudomonas and Burkholderia species. This study explored the conservation of PqsE and examined PqsE ortholog structure-function across different species. Our results show that PqsE in Pseudomonas retain their functional interactions with RhlR homologs, unlike PqsE orthologs in Burkholderia spp., which do not interact with their respective LuxR-type receptors. Additionally, we assessed the AHL preferences of different receptors and hypothesized that the PqsE-RhlR interaction evolved to stabilize the inherently unstable RhlR, preventing its degradation. Indeed, we observe higher levels of RhlR protein turnover in a strain lacking pqsE compared to WT, which can be rescued in a strain lacking the Lon protease. IMPORTANCEPseudomonas aeruginosa, a major pathogen for patients with cystic fibrosis and a primary constituent of healthcare-associated infections, relies on a complex quorum-sensing (QS) network to coordinate virulence factor production. Central to this system is the interaction between two proteins, PqsE and RhlR, which drive gene expression essential for pathogenesis. Our study investigates the conservation of the PqsE-RhlR interaction across related bacterial species, revealing that PqsE in Pseudomonas can enhance RhlR activity, while orthologs in Burkholderia lack this capacity. These findings offer new insights into the specificity and evolution of QS mechanisms, highlighting the PqsE-RhlR interaction as a potentially selective target for treating P. aeruginosa infections.

microbiology↗