Search Results (9)

Background: Lung ischemia reperfusion injury (LIRI) is a severe complication after lung transplantation (LT). Ferroptosis contributes to the pathogenesis of LIRI. Maresin1 (MaR1) is an endogenous pro-resolving lipid mediator that exerts protective effects against multiorgan diseases. However, the role and mechanism of MaR1 in the ferroptosis of LIRI after LT need to be further investigated. Methods: A mouse LT model and a pulmonary vascular endothelial cell line after hypoxia reoxygenation (H/R) culture were established in our study. Histological morphology and inflammatory cytokine levels predicted the severity of LIRI. Cell viability and cell injury were determined by CCK-8 and LDH assays. Ferroptosis biomarkers, including Fe²⁺, MDA, 4-HNE, and GSH, were assessed by relevant assay kits. Transferrin receptor (TFRC) and Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4) protein levels were examined by western blotting. In vitro, lipid peroxide levels were detected by DCFH-DA staining and flow cytometry analysis. The ultrastructure of mitochondria was imaged using transmission electron microscopy. Furthermore, the potential mechanism by which MaR1 regulates ferroptosis was explored and verified with signaling pathway inhibitors using Western blotting. Results: MaR1 protected mice from LIRI after LTx, which was reversed by the ferroptosis agonist Sorafenib in vivo. MaR1 administration decreased Fe²⁺, MDA, 4-HNE, TFRC, and ACSL4 contents, increased GSH levels, and ameliorated mitochondrial ultrastructural injury after LTx. In vitro, Sorafenib resulted in lower cell viability and worsened cell injury and enhanced the hallmarks of ferroptosis after H/R culture, which was rescued by MaR1 treatment. Mechanistically, the protein kinase A and YAP inhibitors partly blocked the effects of MaR1 on ferroptosis inhibition and LIRI protection. Conclusions: This study revealed that MaR1 alleviates LIRI and represses ischemia reperfusion-induced ferroptosis via the PKA-Hippo-YAP signaling pathway, which may offer a promising theoretical basis for the clinical application of organ protection after LTx. Full article

Chromobacterium spp. use a density-dependent cell-to-cell communication mechanism (quorum sensing, QS) to control various traits, including the pigment violacein biosynthesis. Recently, one of the type strains of this genus, previously deposited in the American Type Culture Collection under accession number C. violaceum 31532, was reclassified as C. subtsugae, making the QS data obtained for the first species irrelevant to the second. The goal of this study is to conduct transcriptomic and genomic analyses of the C. subtsugae ATCC 31532 (formerly C. violaceum ATCC 31532) strain to identify density-dependent regulated genes and the mechanisms of their QS control. Whole transcriptome dataset analysis comparing QS-negative mid-log phase and QS-positive early stationary phase samples revealed 35 down-regulated and 261 up-regulated genes, including 44 genes that increased transcription activity the most (log2 (fold change) > 4.0). In addition to the violacein biosynthesis, QS-controlled traits in C. subtsugae ATCC 31532 included the following: (i) cdeAB-oprM efflux pump; (ii) RND efflux transporter; (iii) chuPRSTUV iron acquisition system; (iv) polyamine transport system; (v) carbohydrate (semialdehydes) metabolic pathways; (vi) SAM/SPASM maturase system XYE (predicted); (vii) prophage proteins; and (viii) fucose-binding lectin II. Subsequent screening of the promoter regions of the up-regulated genes and operons in most cases showed the presence of CsuR AHL-receptor/transcriptional regulator binding sites with 56.25–68.75% similarity to the ideal 16-base-pair palindrome 5′-CTGTCCGATAGGACAG-3′ sequence, supporting the concept of QS control in C. subtsugae ATCC 31532 by the csuI-csuR gene pair. Notably, several transcriptional regulators (MarR, TetR/AcrR, HU family DNA-binding protein, helix-turn-helix domain-containing protein) were found to be under QS control. Based on these data, a hierarchical QS regulatory network in C. subtsugae ATCC 31532 was hypothesized that provides direct control of the target genes via a canonical autoinduction mechanism and further dissemination of the effect via the activity of QS-controlled transcriptional regulators. Full article

The transcriptional regulators of the MarR family play an important role in diverse bacterial physiologic functions, whereas their effect and intrinsic regulatory mechanism on the aquatic pathogenic bacterium Aeromonas hydrophila are, clearly, still unknown. In this study, we firstly constructed a deletion strain of AHA_2124 (ΔAHA_2124) of a MarR family transcriptional regulator in Aeromonas hydrophila ATCC 7966 (wild type), and found that the deletion of AHA_2124 caused significantly enhanced hemolytic activity, extracellular protease activity, and motility when compared with the wild type. The differentially abundant proteins (DAPs) were compared by using data-independent acquisition (DIA), based on a quantitative proteomics technology, between the ΔAHA_2124 strain and wild type, and there were 178 DAPs including 80 proteins up-regulated and 98 proteins down-regulated. The bioinformatics analysis showed that the deletion of gene AHA_2124 led to some changes in the abundance of proteins related to multiple biological processes, such as translation, peptide transport, and oxidation and reduction. These results provided a theoretical basis for better exploring the regulatory mechanism of the MarR family transcriptional regulators of Aeromonas hydrophila on bacterial physiological functions. Full article

The Sm protein superfamily includes Sm, like-Sm (Lsm), and Hfq proteins. Sm and Lsm proteins are found in the Eukarya and Archaea domains, respectively, while Hfq proteins exist in the Bacteria domain. Even though Sm and Hfq proteins have been extensively studied, archaeal Lsm proteins still require further exploration. In this work, different bioinformatics tools are used to understand the diversity and distribution of 168 Lsm proteins in 109 archaeal species to increase the global understanding of these proteins. All 109 archaeal species analyzed encode one to three Lsm proteins in their genome. Lsm proteins can be classified into two groups based on molecular weight. Regarding the gene environment of lsm genes, many of these genes are located adjacent to transcriptional regulators of the Lrp/AsnC and MarR families, RNA-binding proteins, and ribosomal protein L37e. Notably, only proteins from species of the class Halobacteria conserved the internal and external residues of the RNA-binding site identified in Pyrococcus abyssi, despite belonging to different taxonomic orders. In most species, the Lsm genes show associations with 11 genes: rpl7ae, rpl37e, fusA, flpA, purF, rrp4, rrp41, hel308, rpoD, rpoH, and rpoN. We propose that most archaeal Lsm proteins are related to the RNA metabolism, and the larger Lsm proteins could perform different functions and/or act through other mechanisms of action. Full article

Sulfane sulfur, including organic persulfide and polysulfide, is a normal cellular component, and its level varies during growth. It is emerging as a signaling molecule in bacteria, regulating the gene regulator MarR in Escherichia coli, MexR in Pseudomonas aeruginosa, and MgrA of Staphylococcus aureus. They are MarR-family regulators and are often repressors for multiple antibiotic resistance genes. Here, we report that another MarR-type regulator OhrR that represses the expression of itself and a thiol peroxidase gene ohr in P. aeruginosa PAO1 also responded to sulfane sulfur. PaOhrR formed disulfide bonds between three Cys residues within a dimer after polysulfide treatment. The modification reduced its affinity to its cognate DNA binding site. An Escherichia coli reporter system, in which mKate was under the repression of OhrR, showed that PaOhrR derepressed its controlled gene when polysulfide was added, whereas the mutant PaOhrR with two Cys residues changed to Ser residues did not respond to polysulfide. The expression of the PaOhrR-repressed mKate was significantly increased when the cells enter the late log phase when cellular sulfane sulfur reached a maximum, but the mKate expression under the control of the PaOhrR-C9SC19S double mutant was not increased. Furthermore, the expression levels of ohrR and ohr in P. aeruginosa PAO1 were significantly increased when cellular sulfane sulfur was high. Thus, PaOhrR senses both exogenous and intrinsic sulfane sulfur to derepress its controlled genes. The finding also suggests that sulfane sulfur may be a common inducer of the MarR-type regulators, which may confer the bacteria to resist certain stresses without being exposed to the stresses. Full article

Pseudomonas aeruginosa is a facultative human pathogen, causing acute and chronic infections that are especially dangerous for immunocompromised patients. The eradication of P. aeruginosa is difficult due to its intrinsic antibiotic resistance mechanisms, high adaptability, and genetic plasticity. The bacterium possesses multilevel regulatory systems engaging a huge repertoire of transcriptional regulators (TRs). Among these, the MarR family encompasses a number of proteins, mainly acting as repressors, which are involved in response to various environmental signals. In this work, we aimed to decipher the role of PA3458, a putative MarR-type TR from P. aeruginosa. Transcriptional profiling of P. aeruginosa PAO1161 overexpressing PA3458 showed changes in the mRNA level of 133 genes; among them, 100 were down-regulated, suggesting the repressor function of PA3458. Concomitantly, ChIP-seq analysis identified more than 300 PA3458 binding sites in P. aeruginosa. The PA3458 regulon encompasses genes involved in stress response, including the PA3459–PA3461 operon, which is divergent to PA3458. This operon encodes an asparagine synthase, a GNAT-family acetyltransferase, and a glutamyl aminopeptidase engaged in the production of N-acetylglutaminylglutamine amide (NAGGN), which is a potent bacterial osmoprotectant. We showed that PA3458-mediated control of PA3459–PA3461 expression is required for the adaptation of P. aeruginosa growth in high osmolarity. Overall, our data indicate that PA3458 plays a role in osmoadaptation control in P. aeruginosa. Full article

Streptomycetes are well-known producers of numerous bioactive secondary metabolites widely used in medicine, agriculture, and veterinary. Usually, their genomes encode 20–30 clusters for the biosynthesis of natural products. Generally, the onset and production of these compounds are tightly coordinated at multiple regulatory levels, including cluster-situated transcriptional factors. Rishirilides are biologically active type II polyketides produced by Streptomyces bottropensis. The complex regulation of rishirilides biosynthesis includes the interplay of four regulatory proteins encoded by the rsl-gene cluster: three SARP family regulators (RslR1-R3) and one MarR-type transcriptional factor (RslR4). In this work, employing gene deletion and overexpression experiments we revealed RslR1-R3 to be positive regulators of the biosynthetic pathway. Additionally, transcriptional analysis indicated that rslR2 is regulated by RslR1 and RslR3. Furthermore, RslR3 directly activates the transcription of rslR2, which stems from binding of RslR3 to the rslR2 promoter. Genetic and biochemical analyses demonstrated that RslR4 represses the transcription of the MFS transporter rslT4 and of its own gene. Moreover, DNA-binding affinity of RslR4 is strictly controlled by specific interaction with rishirilides and some of their biosynthetic precursors. Altogether, our findings revealed the intricate regulatory network of teamworking cluster-situated regulators governing the biosynthesis of rishirilides and strain self-immunity. Full article

Garlic plants (Allium sativum L.) produce antimicrobial compounds, such as diallyl thiosulfinate (allicin) and diallyl polysulfanes. Here, we investigated the transcriptome and protein S-thioallylomes under allicin and diallyl tetrasulfane (DAS4) exposure in the Gram-positive bacterium Bacillus subtilis. Allicin and DAS4 caused a similar thiol-specific oxidative stress response, protein and DNA damage as revealed by the induction of the OhrR, PerR, Spx, YodB, CatR, HypR, AdhR, HxlR, LexA, CymR, CtsR, and HrcA regulons in the transcriptome. At the proteome level, we identified, in total, 108 S-thioallylated proteins under allicin and/or DAS4 stress. The S-thioallylome includes enzymes involved in the biosynthesis of surfactin (SrfAA, SrfAB), amino acids (SerA, MetE, YxjG, YitJ, CysJ, GlnA, YwaA), nucleotides (PurB, PurC, PyrAB, GuaB), translation factors (EF-Tu, EF-Ts, EF-G), antioxidant enzymes (AhpC, MsrB), as well as redox-sensitive MarR/OhrR and DUF24-family regulators (OhrR, HypR, YodB, CatR). Growth phenotype analysis revealed that the low molecular weight thiol bacillithiol, as well as the OhrR, Spx, and HypR regulons, confer protection against allicin and DAS4 stress. Altogether, we show here that allicin and DAS4 cause a strong oxidative, disulfide and sulfur stress response in the transcriptome and widespread S-thioallylation of redox-sensitive proteins in B. subtilis. The results further reveal that allicin and polysulfanes have similar modes of actions and thiol-reactivities and modify a similar set of redox-sensitive proteins by S-thioallylation. Full article

The MarR (multiple antibiotic resistance regulator) family of prokaryotic transcriptional regulators includes proteins critical for control of virulence factor production, bacterial response to antibiotic and oxidative stresses and catabolism of environmental aromatic compounds. Recognition of the adaptive cellular responses mediated by MarR homologs, and the clinical isolation of antibioticresistant bacterial strains harboring MarR mutations, has garnered increasing medical and agricultural attention to this family. MarR proteins exist as homodimers in both free and DNA-bound states. Sequence specific DNA-binding to palindromic or pseudopalindromic sites is mediated by a conserved winged helix fold and, for numerous homologs, this association is attenuated by specific anionic lipophilic ligands. The mechanism of ligand-mediated allosteric control of DNA binding is unique amongst prokaryotic transcriptional regulators in that the DNA- and ligandbinding domains almost completely overlap in the residues involved. Until recently, our understanding of ligand-binding has been limited to a MarR-salicylate cocrystal structure, with little information on the allosteric mechanisms linking ligand-recognition and DNA-binding. However, recent biochemical and biophysical data on MarR homologs have begun to resolve the mechanisms by which these proteins mediate ligand-responsive transcriptional control. Full article