Biology subjects

Federle, M. J.

Publications and source records attributed to Federle, M. J..

2 recordsLinked to original sources

bioRxiv2020

Colonization of the murine oropharynx by Streptococcus pyogenes is governed by the Rgg2/3 quorum sensing system

Streptococcus pyogenes is a human-restricted pathogen most often found in the human nasopharynx. Multiple bacterial factors are known to contribute to persistent colonization of this niche, and many are important in mucosal immunity and vaccine development. In this work, mice were infected intranasally with transcriptional regulator mutants of the Rgg2/3 quorum sensing (QS) system--a peptide-based signaling system conserved in sequenced isolates of S. pyogenes. Deletion of the QS systems transcriptional activator ({Delta}rgg2) dramatically diminished the percentage of colonized mice while deletion of the transcriptional repressor ({Delta}rgg3) increased the percentage of colonized mice compared to wild type. Stimulation of the QS system using synthetic pheromones prior to inoculation did not significantly increase the percentage of animals colonized, indicating that QS-dependent colonization is responsive to the intrinsic conditions within the host upper respiratory tract. Bacterial RNA extracted directly from oropharyngeal swabs and evaluated by quantitative RT-PCR subsequently confirmed QS upregulation within one hour of inoculation. In the nasal-associated lymphoid tissue (NALT), a muted inflammatory response to the {Delta}rgg2 bacteria suggests that their rapid elimination failed to elicit the previously characterized response to intranasal inoculation of GAS. This work identifies a new transcriptional regulatory system governing the ability of S. pyogenes to colonize the nasopharynx and provides knowledge that could help lead to decolonization therapeutics. Author SummaryStreptococcus pyogenes is responsible for a wide spectrum of diseases ranging from common pharyngitis to infrequent invasive infections like necrotizing fasciitis. The ability of this microorganism to persist in the human oropharynx predisposes colonized individuals to a variety of superficial and invasive diseases which lead to significant morbidities and mortality. Identification of the regulatory systems that augment the bacterias ability to colonize the oropharynx provides potential targets against which molecular therapeutics can be designed. Here we show that the Rgg2/3 quorum sensing system, an interbacterial communication system, governs the ability of S. pyogenes to colonize the murine oropharynx. Disruption of the systems transcriptional activator reduced colonization dramatically, eliminated the transcription of two sets of genes known to be activated by the Rgg2/3 system, and tempered the innate immune response seen when S. pyogenes is intranasally infected into the mouse.

microbiology↗

bioRxiv2020

Structural basis of Rgg protein binding to their regulatory pheromones and target DNA promoters

Rgg family proteins, such as Rgg2 and Rgg3, have emerged as primary quorum-sensing regulated transcription factors in Streptococcus species, controlling virulence, antimicrobial resistance, and biofilm formation. Rgg2 and Rgg3 function is regulated by their interaction with oligopeptide quorum-sensing signals called short hydrophobic peptides (SHPs). The molecular basis of Rgg-SHP and Rgg-target DNA promoter specificity was unknown. To close this gap, we determined the cryo-EM structure of Streptococcus thermophilus Rgg3 bound to its quorum-sensing signal, SHP3, and the X-ray crystal structure of Rgg3 alone. Comparison of these structures to that of an Rgg in complex with cyclosporin A (CsA), an inhibitor of SHP-induced Rgg activity, reveals the molecular basis of CsA function. Furthermore, to determine how Rgg proteins recognize DNA promoters, we determined X-ray crystal structures of both S. dysgalactiae Rgg2 and S. thermophilus Rgg3 in complex with their target DNA promoters. The physiological importance of the observed Rgg-DNA interactions was dissected using in vivo genetic experiments and in vitro biochemical assays. Based on these structure-function studies, we present a revised unifying model of Rgg regulatory interplay. In contrast to existing models, where Rgg2 proteins are transcriptional activators and Rgg3 proteins are transcriptional repressors, we propose that both are capable of transcriptional activation. However, when Rgg proteins with different activation requirements compete for the same DNA promoters, those with more stringent activation requirements function as repressors by blocking promoter access of the SHP-bound conformationally active Rgg proteins. While a similar gene expression regulatory scenario has not been previously described, in all likelihood it is not unique to streptococci. Significance StatementSecreted peptide pheromones regulate critical biological processes in Gram-positive bacteria. In streptococci such as the human pathogen S. pyogenes, oligopeptide pheromones, like the short hydrophobic peptides (SHPs), regulate virulence, antimicrobial resistance, and biofilm formation. SHPs directly regulate the activity of transcription factors called Rgg2 and Rgg3. We present the cryo-EM structure of Rgg3 in complex with SHP3, as well as X-ray crystal structures of Rgg2 bound to target promoter DNA, Rgg3 bound to target promoter DNA, and Rgg3 alone. Based on the cryo-EM, X-ray crystallographic, biochemical, and genetic studies presented here, we provide not only detailed mechanistic insight into the molecular basis of Rgg3-SHP3, Rgg2-DNA, and Rgg3-DNA binding specificity, but also a new model of transcription factor regulatory interplay.

microbiology↗