Biology subjects

Glover, R. C.

Publications and source records attributed to Glover, R. C..

3 recordsLinked to original sources

bioRxiv2022

A genome-wide screen in macrophages identifies PTEN as required for myeloid restriction of Listeria monocytogenes infection

Listeria monocytogenes (Lm) is an intracellular foodborne pathogen which causes the severe disease listeriosis in immunocompromised individuals. Macrophages play a dual role during Lm infection by both promoting dissemination of Lm from the gastrointestinal tract and limiting bacterial growth upon immune activation. Despite the relevance of macrophages to Lm infection, the mechanisms underlying phagocytosis of Lm by macrophages are not well understood. To identify host factors important for Lm infection of macrophages, we performed an unbiased CRISPR/Cas9 screen which revealed pathways that are specific to phagocytosis of Lm and those that are required for internalization of bacteria generally. Specifically, we discovered the tumor suppressor PTEN promotes macrophage phagocytosis of Lm and L. ivanovii, but not other Gram-positive bacteria. Additionally, we found that PTEN enhances phagocytosis of Lm via its lipid phosphatase activity by promoting adherence to macrophages. Using conditional knockout mice lacking Pten in myeloid cells, we show that PTEN-dependent phagocytosis is important for host protection during oral Lm infection. Overall, this study provides a comprehensive identification of macrophage factors involved in regulating Lm uptake and characterizes the function of one factor, PTEN, during Lm infection in vitro and in vivo. Importantly, these results demonstrate a role for opsonin-independent phagocytosis in Lm pathogenesis and suggest that macrophages play a primarily protective role during foodborne listeriosis. Author SummaryListeria monocytogenes (Lm) is a bacterial pathogen that causes the foodborne illness listeriosis primarily in immunocompromised, elderly, and pregnant individuals. Listeriosis is one of the deadliest bacterial infections known, with a mortality rate of ~30% even when treated with antibiotics. The high mortality rate of listeriosis is due to inefficient restriction of Lm by the immune system, and subsequent spread of bacteria beyond the gastrointestinal tract to internal organs such as the liver and brain. Macrophages are important for immune clearance of Lm but are also hypothesized to promote dissemination of intracellular Lm; thus, studies of Lm-macrophage interactions are critical for understanding the balance between bacterial growth and restriction by these phagocytes. We performed a forward genetic screen in macrophages and discovered that the tumor suppressor PTEN promotes phagocytosis of Lm by enhancing adherence to macrophages. These results demonstrate a novel function of macrophage PTEN, which canonically acts as a repressor of phagocytosis. In addition, we found that PTEN protects mice from severe disease and lowers bacterial burdens following oral inoculation of Lm. Our results demonstrate for the first time that macrophage phagocytosis is an important immune defense against invasive Lm during the foodborne route of infection.

microbiology↗

bioRxiv2021

The global redox-responsive transcriptional regulator Rex represses fermentative metabolism and is required for Listeria monocytogenes pathogenesis

The Gram-positive bacterium Listeria monocytogenes is the causative agent of the foodborne disease listeriosis, one of the deadliest bacterial infections known. In order to cause disease, L. monocytogenes must properly coordinate its metabolic and virulence programs in response to rapidly changing environments within the host. However, the mechanisms by which L. monocytogenes senses and adapts to the many stressors encountered as it transits through the gastrointestinal (GI) tract and disseminates to peripheral organs are not well understood. In this study, we investigated the role of the redox-responsive transcriptional regulator Rex in L. monocytogenes growth and pathogenesis. Rex is a conserved canonical transcriptional repressor that monitors the intracellular redox state of the cell by sensing the ratio of reduced and oxidized nicotinamide adenine dinucleotides (NADH and NAD+, respectively). Here, we demonstrated that L. monocytogenes Rex represses fermentative metabolism and is therefore required for optimal growth in the presence of oxygen. We also show that Rex represses the production of virulence factors required for survival and invasion of the GI tract, as a strain lacking rex was more resistant to acidified bile and invaded host cells better than wt. Consistent with these results, Rex was dispensable for colonizing the GI tract and disseminating to peripheral organs in an oral listeriosis model of infection. However, Rex-dependent regulation was required for colonizing the spleen and liver, and L. monocytogenes lacking the Rex repressor were nearly sterilized from the gallbladder. Taken together, these results demonstrated that Rex functions as a repressor of fermentative metabolism and suggests a role for Rex-dependent regulation in L. monocytogenes pathogenesis. Importantly, the gallbladder is the bacterial reservoir during listeriosis, and our data suggest redox sensing and Rex-dependent regulation are necessary for bacterial survival and replication in this organ. AUTHOR SUMMARYListeriosis is a foodborne illness caused by Listeria monocytogenes and is one of the deadliest bacterial infections known, with a mortality rate of up to 30%. Following ingestion of contaminated food, L. monocytogenes disseminates from the gastrointestinal (GI) tract to peripheral organs, including the spleen, liver, and gallbladder. In this work, we investigated the role of the global redox-responsive regulator Rex in L. monocytogenes growth and pathogenesis. We demonstrated that Rex derepression coordinates expression of genes necessary in the GI tract during infection, including fermentative metabolism, bile resistance, and invasion of host cells. Accordingly, Rex was dispensable for colonizing the GI tract of mice during an oral listeriosis infection. Interestingly, Rex-dependent regulation was required for bacterial replication in the spleen, liver, and gallbladder. Taken together, our results demonstrate that Rex-mediated redox sensing and transcriptional regulation are important for L. monocytogenes metabolic adaptation and virulence.

microbiology↗

bioRxiv2020

4-hydroxy-2-nonenal antimicrobial toxicity is neutralized by an intracellular pathogen.

Pathogens encounter numerous antimicrobial responses, including the reactive oxygen species (ROS) burst. ROS-mediated oxidation of host membrane poly-unsaturated fatty acids (PUFAs) generates the toxic alpha-beta carbonyl 4-hydroxy-2-nonenal (4-HNE). Though studied extensively in the context of sterile inflammation, 4-HNEs role during infection remains limited. Here we found that 4-HNE is generated during bacterial infection and that the intracellular pathogen Listeria monocytogenes induces a specific set of genes in response to 4-HNE exposure. A component of the L. monocytogenes 4-HNE response is the expression of the genes rha1 and rha2 which code for two NADPH-dependent oxidoreductases that collectively counter 4-HNE toxicity. Heterologous expression of rha1/2 in Bacillus subtilis significantly increased bacterial resistance to 4-HNE both in vitro and following phagocytosis by murine macrophages. Our work demonstrates that 4-HNE is a previously unappreciated component of ROS-mediated toxicity and that L. monocytogenes has evolved specific countermeasures to survive within its presence.

microbiology↗