Biology subjects

LaRock, D. L.

Publications and source records attributed to LaRock, D. L..

4 recordsLinked to original sources

bioRxiv2026

A protease-sensing circuit links neutrophil inflammation to virulence regulation in Streptococcus pyogenes

Streptococcus pyogenes (Group A Streptococcus) causes infections with a disproportionately hyperinflammatory response from the host, such as scarlet fever, necrotizing fasciitis, and toxic shock syndrome. Inflammation is specifically driven by S. pyogenes virulence factors, including the protease SpeB, but how inflammation impacts SpeB expression in return during disease is unknown. In this study, we identify a novel interaction between NETosis, a form of inflammatory cell death for neutrophils, and the induction of speB. Specifically, while the cathelicidin peptide LL-37 can repress speB through the two-component regulatory system CovRS, neutrophil proteases released during NETosis relieve repression of speB by degrading another repressor of speB, the bacterial protein Vfr. Furthermore, at high cell densities, SpeB autoregulates its expression through similar degradation of Vfr. Abrogating the formation of NETs or depleting neutrophils resulted in speB repression in vivo, showing the mutual host and pathogen counterattacks collectively lead to the pathological exacerbations characteristic of disease.

microbiology↗

bioRxiv2025

Therapeutic Inhibition of Metalloproteases by Tetracyclines during Infection by Multi-Drug Resistant Pseudomonas

IntroductionBoth host and microbial proteases contribute to the destruction of tissue during Pseudomonas aeruginosa pulmonary infections. We previously reported that beneficial therapeutic effects of metalloprotease inhibitors in Pseudomonas aeruginosa pulmonary infections are not only from targeting the host matrix metalloproteases, the intended target, but also from cross-inhibition of the secreted bacterial metalloprotease LasB. MethodsWe used computation modeling and biochemical assays to investigate whether doxycycline and other structurally-related antibiotics of the tetracycline family inhibit the Pseudomonas protease, LasB. Modeling infection in vitro with human neutrophils and in vivo with a murine model of pulmonary infection, we investigate the effect of on tetracyclines inhibit LasB activity, bacterial survival, and inflammation. ResultsTetracycline, doxycycline, minocycline, and sanocycline all inhibit proteolysis by Pseudomonas LasB. At sub-antimicrobial concentrations, this sensitizes the bacterium killing by neutrophils. During pulmonary infection, tetracyclines significantly reduce pathological inflammation in the lung. ConclusionsOur study shows that tetracycline-family antibiotics, known inhibitors of mammalian matrix metalloproteinases, also inhibit LasB and have beneficial anti-inflammatory activity during infections by extensively drug-resistant P. aeruginosa. By controlling pathological host inflammation, inhibiting bacterial virulence factors, and directly killing bacteria, tetracyclines can have tripartite therapeutic benefits.

microbiology↗

bioRxiv2021

Pro-IL-18 secreted by keratinocytes detects the group A streptococcal protease SpeB

Group A Streptococcus (GAS, Streptococcus pyogenes) is a professional human pathogen that commonly infects the skin. Keratinocytes are one of the first cells to contact GAS, and by inducing inflammation, they can initiate the earliest immune responses to pathogen invasion. Here, we characterized the proinflammatory cytokine repertoire produced by primary human keratinocytes and surrogate cell lines commonly used in vitro. Infection induces several cytokines and chemokines, but keratinocytes constitutively secrete IL-18 in a form that is inert (pro-IL-18) and lacks proinflammatory activity. Canonically, IL-18 activation and secretion are coupled through a single proteolytic event that is regulated intracellularly by the inflammasome protease caspase-1 in myeloid cells. The pool of extracellular pro-IL-18 generated by keratinocytes is poised to sense extracellular proteases and is directly processed into a mature active form by SpeB, a secreted GAS protease that is a critical virulent factor during skin infection. This mechanism contributes to the proinflammatory response against GAS, resulting in T cell activation and the secretion of IFN-{gamma} that restrict GAS growth. Other major bacterial pathogens and microbiota of this skin did not have significant IL-18-maturing ability. Taken together, these results suggest keratinocyte-secreted IL-18 is a sentinel that sounds an early alarm that is highly sensitive to GAS, yet tolerant to non-invasive members of the microbiota.

microbiology↗

bioRxiv2020

Group A Streptococcus Infection of the Nasopharynx Requires Proinflammatory Signaling Through the Interleukin-1 Receptor

Group A Streptococcus (GAS) is the etiologic agent of numerous high morbidity and high mortality diseases which commonly have a highly proinflammatory pathology. One factor contributing to this inflammation is the GAS protease SpeB, which directly activates the proinflammatory cytokine interleukin-1{beta} (IL-1{beta}), independent of the canonical inflammasome pathway. IL-1{beta} drives neutrophil activation and recruitment that limits bacterial growth and invasion during invasive skin and soft tissue infections like necrotizing fasciitis. GAS also causes pharyngitis (strep throat), and the upper respiratory tract is its primary nidus for growth and transmission. Since the fitness selection for the species is likely primarily for this site, we examined the process of IL-1{beta} activation in the murine nasopharynx. SpeB still activated IL-1{beta}, which was required for neutrophil migration, but this inflammation instead increased GAS replication. Inhibiting IL-1{beta} or depleting neutrophils, which both promote invasive infection, prevented GAS infection of the nasopharynx. Prior antibiotic exposure increased GAS growth in the murine nasopharynx, and antibiotics were sufficient to reverse the attenuation previously observed when IL-1{beta}, neutrophils, or SpeB were not present to drive inflammation. Therefore, the same fundamental mechanism has opposing effects on virulence at different body sites. Invasive disease may be limited in part due to specific adaptations for inducing host inflammation that are beneficial for pharyngitis. IMPORTANCEOur previous reports showed that Group A Streptococcus (GAS) protease SpeB directly activates the host proinflammatory cytokine IL-1{beta} and this restricts invasive skin infection. The upper respiratory tract is the primary site of GAS colonization and infection, but the host-pathogen interactions at this site are still largely unknown. We provide the first evidence that IL-1{beta}-mediated inflammation promotes upper respiratory tract infection. This provides experimental evidence that the notable inflammation of strep throat, which presents with significant swelling, pain, and neutrophil influx, is not an ineffectual immune response, but rather is a GAS-directed remodeling of this niche for its pathogenic benefit.

microbiology↗