Pseudomonas aeruginosa thrives in multiple environments and is capable of causing life-threatening infections in immunocompromised patients. RsmA is a posttranscriptional regulator that controls virulence factor production and biofilm formation. In this study, we investigated the expression and activity of rsmA and the protein that it encodes, RsmA, in P. aeruginosa mucA mutant strains, which are common in chronic infections. We determined that AlgU regulates a previously unknown rsmA promoter in P. aeruginosa. Western blot analysis confirmed that AlgU controls rsmA expression in both a laboratory strain and a clinical isolate. RNase protection assays confirmed the presence of two rsmA transcripts and suggest that RpoS and AlgU regulate rsmA expression. Due to the increased amounts of RsmA in mucA mutant strains, a translational leader fusion of the RsmA target, tssA1, was constructed and tested in mucA, algU, retS, gacA, and rsmA mutant backgrounds to examine posttranscriptional activity. From these studies, we determined that RsmA is active in mucA22 mutants, suggesting a role for RsmA in mucA mutant strains. Taken together, we have demonstrated that AlgU controls rsmA transcription and is responsible for RsmA activity in mucA mutant strains. We propose that RsmA is active in P. aeruginosa mucA mutant strains and that RsmA also plays a role in chronic infections. IMPORTANCEP. aeruginosa causes severe infections in immunocompromised patients. The posttranscriptional regulator RsmA is known to control virulence and biofilm formation. We identify a new rsmA promoter and determine that AlgU is important in the control of rsmA expression. Mutant mucA strains that are considered mucoid were used to confirm increased rsmA expression from the AlgU promoter. We demonstrate, for the first time, that there is RsmA activity in mucoid P. aeruginosa strains. Our work suggests that RsmA may play a role during chronic infections as well as acute infections. Pseudomonas aeruginosa produces a myriad of virulence factors and can cause both acute and chronic infections (1, 2). To survive and persist, P. aeruginosa must coordinate gene expression in response to changing environmental conditions. Global regulatory networks respond to changing environmental conditions to allow the physiological changes necessary for survival to be made. The P. aeruginosa genome encodes many global regulatory systems, including posttranscriptional regulators, such as RsmA. RsmA is important in regulating several virulence factors involved in acute and chronic infections (3).Acute infections are characterized by motility and expression of the type III secretion system (4). RsmA positively regulates both motility and type III secretion system expression (4-6). A defining characteristic of chronic infections is biofilm formation, which includes the production of exopolysaccharides, such as alginate, and the type VI secretion system (T6SS) (7,8). RsmA is a negative regulator of the exopolysaccharide gene psl and the first hemolysin-coregulated se...
Cells respond to many stressors by senescing, acquiring stable growth arrest, morphologic and metabolic changes, and a proinflammatory senescence-associated secretory phenotype. The heterogeneity of senescent cells (SnCs) and senescence-associated secretory phenotype are vast, yet ill characterized. SnCs have diverse roles in health and disease and are therapeutically targetable, making characterization of SnCs and their detection a priority. The Cellular Senescence Network (SenNet), a National Institutes of Health Common Fund initiative, was established to address this need. The goal of SenNet is to map SnCs across the human lifespan to advance diagnostic and therapeutic approaches to improve human health. State-of-the-art methods will be applied to identify, define and map SnCs in 18 human tissues. A common coordinate framework will integrate data to create four-dimensional SnC atlases. Other key SenNet deliverables include innovative tools and technologies to detect SnCs, new SnC biomarkers and extensive public multi-omics datasets. This Perspective lays out the impetus, goals, approaches and products of SenNet.
Pseudomonas aeruginosa is an important pathogen of the immunocompromised, causing both acute and chronic infections. In cystic fibrosis (CF) patients, P. aeruginosa causes chronic disease. The impressive sensory network of P. aeruginosa allows the bacterium to sense and respond to a variety of stimuli found in diverse environments. Transcriptional regulators, including alternative sigma factors and response regulators, integrate signals changing gene expression, allowing P. aeruginosa to cause infection. The two-component transcriptional regulator AlgR is important in P. aeruginosa pathogenesis in both acute and chronic infections. In chronic infections, AlgR and the alternative sigma factor AlgU activate the genes responsible for alginate production. Previous work demonstrated that AlgU controls rsmA expression. RsmA is a posttranscriptional regulator that is antagonized by two small RNAs, RsmY and RsmZ. In this work, we demonstrate that AlgR directly activates rsmA expression from the same promoter as AlgU. In addition, phosphorylation was not necessary for AlgR activation of rsmA using algR and algZ mutant strains. AlgU and AlgR appear to affect the antagonizing small RNAs rsmY and rsmZ indirectly. RsmA was active in a mucA22 mutant strain using leader fusions of two RsmA targets, tssA1 and hcnA. AlgU and AlgR were necessary for posttranscriptional regulation of tssA1 and hcnA. Altogether, our work demonstrates that the alginate regulators AlgU and AlgR are important in the control of the RsmA posttranscriptional regulatory system. These findings suggest that RsmA plays an unknown role in mucoid strains due to AlgU and AlgR activities.IMPORTANCE P. aeruginosa infections are difficult to treat and frequently cause significant mortality in CF patients. Understanding the mechanisms of persistence is important. Our work has demonstrated that the alginate regulatory system also significantly impacts the posttranscriptional regulator system RsmA/Y/Z. We demonstrate that AlgR directly activates rsmA expression, and this impacts the RsmA regulon. This leads to the possibility that the RsmA/Y/Z system plays a role in helping P. aeruginosa persist during chronic infection. In addition, this furthers our understanding of the reach of the alginate regulators AlgU and AlgR.KEYWORDS P. aeruginosa, RsmA, AlgR, mucoid, Pseudomonas aeruginosa, cystic fibrosis, mucA, two-component regulatory systems T he opportunistic pathogen Pseudomonas aeruginosa possesses multiple virulence factors for causing disease. This allows P. aeruginosa to cause both acute and chronic infections. Acute infecting strains are characterized by the presence of type IV pili (T4P), flagella, and a type III secretion system (T3SS) (1-3). In contrast, chronic infecting strains diversify (4, 5) and frequently do not express T3SS, T4P, or flagella (6, 7). Chronic infecting strains often form biofilms composed of exopolysaccharides, such as alginate, and signal a decline in lung function in CF patients (8-11). Alginate
Idiopathic pulmonary fibrosis (IPF) is a fibrotic age-related chronic lung disease characterized by the accumulation of senescent cells. Whether impaired immune response is responsible for the accumulation of senescent cells in the IPF lung remains unknown. In this study, we characterized the NK phenotype in IPF lungs via flow cytometry using 5-dodecanoylaminofluorescein di-β-d-galactopyranoside, markers of tissue residence, and chemokine receptors. The effect of the lung microenvironment was evaluated using lung fibroblast (LF) conditioned media (CM), and the bleomycin-induced pulmonary fibrosis mouse model was used to assess the in vivo relationship between NK cells and the accumulation of senescent cells. We found that NK cells from the lower lobe of IPF patients exhibited immune-senescent and impaired CD57−NKG2A+ phenotype. We also observed that culture of NK cells from healthy donors in CM from IPF lower lobe lung fibroblasts induced a senescent-like phenotype and impaired cytotoxic capacity. There is an impaired NK recruitment by LF, and NKs presented decreased migration toward their CM. In addition, NK cell–depleted mice treated with bleomycin showed increased collagen deposition and accumulation of different populations of senescent cells compared with controls. The IPF lung microenvironment induces a dysfunctional NK phenotype limiting the clearance of lung senescent cells and the resolution of lung fibrosis. We propose that impaired NK activity could be one of the mechanisms responsible for perpetuating the accumulation of senescent cells in IPF lungs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.