Many pathogens have evolved sophisticated strategies to evade autophagy, a crucial cellular defense mechanism that typically targets and degrades invading microorganisms. By subverting or inhibiting autophagy, these pathogens can create a more favorable environment for their replication and survival within the host. For instance, some bacteria secrete factors that block autophagosome formation, while others might escape from autophagosomes before degradation. These evasion tactics are critical for the pathogens' ability to establish and maintain infections. Understanding the mechanisms by which pathogens avoid autophagy is crucial for developing new therapeutic strategies, as enhancing autophagy could bolster the host's immune response and aid in the elimination of pathogenic bacteria. Francisella tularensis can manipulate host cell pathways to prevent its detection and destruction by autophagy, thereby enhancing its virulence. Given the potential for F. tularensis to be used as a bioterrorism agent due to its high infectivity and ability to cause severe disease, research into how this pathogen evades autophagy is of critical importance. By unraveling these mechanisms, new therapeutic approaches could be developed to enhance autophagic responses and strengthen host defense against this and other similarly evasive pathogens.

• Keywords
• Francisella, autophagy, bacterial pathogenesis, host-pathogen interaction, virulence,
• MeSH
• Autophagy * MeSH
• Virulence Factors metabolism   MeSH
• Francisella tularensis * pathogenicity   immunology   physiology   MeSH
• Immune Evasion * MeSH
• Host-Pathogen Interactions * MeSH
• Humans MeSH
• Tularemia microbiology   immunology   MeSH
• Virulence MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Virulence Factors MeSH

HU protein is a member of nucleoid-associated proteins (NAPs) and is an important regulator of bacterial virulence, pathogenesis and survival. NAPs are mainly DNA structuring proteins that influence several molecular processes by binding the DNA. HU´s indispensable role in DNA-related processes in bacteria was described. HU protein is a necessary bacterial transcription factor and is considered to be a virulence determinant as well. Less is known about its direct role in host-pathogen interactions. The latest studies suggest that HU protein may be secreted outside bacteria and be a part of the extracellular matrix. Moreover, HU protein can be internalized in a host cell after bacterial infection. Its role in the host cell is not well described and further studies are extremely needed. Existing results suggest the involvement of HU protein in host cell immune response modulation in bacterial favor, which can help pathogens resist host defense mechanisms. A better understanding of the HU protein's role in the host cell will help to effective treatment development.

• Keywords
• HU protein, bacterial secretion, histone-like protein, host-pathogen interaction, nucleoid-associated protein, virulence,
• MeSH
• Bacterial Proteins * genetics   MeSH
• DNA, Bacterial metabolism   MeSH
• DNA-Binding Proteins * metabolism   MeSH
• DNA chemistry   MeSH
• Virulence Factors MeSH
• Host-Pathogen Interactions MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Bacterial Proteins * MeSH
• DNA, Bacterial MeSH
• DNA-Binding Proteins * MeSH
• DNA MeSH
• Virulence Factors MeSH

Regulation of gene transcription is the initial step in the complex process that controls gene expression within bacteria. Transcriptional control involves the joint effort of RNA polymerases and numerous other regulatory factors. Whether global or local, positive or negative, regulators play an essential role in the bacterial cell. For instance, some regulators specifically modify the transcription of virulence genes, thereby being indispensable to pathogenic bacteria. Here, we provide a comprehensive overview of important transcription factors and DNA-binding proteins described for the virulent bacterium Francisella tularensis, the causative agent of tularemia. This is an unexplored research area, and the poorly described networks of transcription factors merit additional experimental studies to help elucidate the molecular mechanisms of pathogenesis in this bacterium, and how they contribute to disease.

• Keywords
• Francisella, gene regulation, pathogenesis, transcription factor, virulence,
• Publication type
• Journal Article MeSH
• Review MeSH

Francisella tularensis is a Gram-negative, facultative intracellular bacterium, causing a severe disease called tularemia. It secretes unusually shaped nanotubular outer membrane vesicles (OMV) loaded with a number of virulence factors and immunoreactive proteins. In the present study, the vesicles were purified from a clinical isolate of subsp. holarctica strain FSC200. We here provide a comprehensive proteomic characterization of OMV using a novel approach in which a comparison of OMV and membrane fraction is performed in order to find proteins selectively enriched in OMV vs. membrane. Only these proteins were further considered to be really involved in the OMV function and/or their exceptional structure. OMV were also isolated from bacteria cultured under various cultivation conditions simulating the diverse environments of F. tularensis life cycle. These included conditions mimicking the milieu inside the mammalian host during inflammation: oxidative stress, low pH, and high temperature (42°C); and in contrast, low temperature (25°C). We observed several-fold increase in vesiculation rate and significant protein cargo changes for high temperature and low pH. Further proteomic characterization of stress-derived OMV gave us an insight how the bacterium responds to the hostile environment of a mammalian host through the release of differentially loaded OMV. Among the proteins preferentially and selectively packed into OMV during stressful cultivations, the previously described virulence factors connected to the unique intracellular trafficking of Francisella were detected. Considerable changes were also observed in a number of proteins involved in the biosynthesis and metabolism of the bacterial envelope components like O-antigen, lipid A, phospholipids, and fatty acids. Data are available via ProteomeXchange with identifier PXD013074.

• Keywords
• FSC200, Francisella tularensis, host–pathogen interaction, outer membrane vesicles, stress response, virulence factor,
• Publication type
• Journal Article MeSH

The nucleoid-associated HU proteins are small abundant DNA-binding proteins in bacterial cell which play an important role in the initiation of DNA replication, cell division, SOS response, control of gene expression and recombination. HU proteins bind to double stranded DNA non-specifically, but they exhibit high affinity to abnormal DNA structures as four-way junctions, gaps or nicks, which are generated during DNA damage. In many pathogens HU proteins regulate expression of genes involved in metabolism and virulence. Here, we show that the Francisella tularensis subsp. holarctica gene locus FTS_0886 codes for functional HU protein which is essential for full Francisella virulence and its resistance to oxidative stress. Further, our results demonstrate that the recombinant FtHU protein binds to double stranded DNA and protects it against free hydroxyl radicals generated via Fenton's reaction. Eventually, using an iTRAQ approach we identified proteins levels of which are affected by the deletion of hupB, among them for example Francisella pathogenicity island (FPI) proteins. The pleiotropic role of HU protein classifies it as a potential target for the development of therapeutics against tularemia.

• Keywords
• DNA binding protein, FPI, Francisella, HU protein, nucleoid-associated protein, virulence,
• MeSH
• Bacterial Proteins metabolism   MeSH
• Gene Deletion MeSH
• DNA-Binding Proteins metabolism   MeSH
• DNA metabolism   MeSH
• Virulence Factors metabolism   MeSH
• Francisella tularensis growth & development   physiology   MeSH
• Stress, Physiological MeSH
• Oxidative Stress MeSH
• Gene Expression Profiling MeSH
• Protein Binding MeSH
• Virulence MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Bacterial Proteins MeSH
• DNA-Binding Proteins MeSH
• DNA MeSH
• Virulence Factors MeSH
• histone-like protein HU, bacteria MeSH Browser

The DsbA homolog of Francisella tularensis was previously demonstrated to be required for intracellular replication and animal death. Disruption of the dsbA gene leads to a pleiotropic phenotype that could indirectly affect a number of different cellular pathways. To reveal the broad effects of DsbA, we compared fractions enriched in membrane proteins of the wild-type FSC200 strain with the dsbA deletion strain using a SILAC-based quantitative proteomic analysis. This analysis enabled identification of 63 proteins with significantly altered amounts in the dsbA mutant strain compared to the wild-type strain. These proteins comprise a quite heterogeneous group including hypothetical proteins, proteins associated with membrane structures, and potential secreted proteins. Many of them are known to be associated with F. tularensis virulence. Several proteins were selected for further studies focused on their potential role in tularemia's pathogenesis. Of them, only the gene encoding glyceraldehyde-3-phosphate dehydrogenase, an enzyme of glycolytic pathway, was found to be important for full virulence manifestations both in vivo and in vitro. We next created a viable mutant strain with deleted gapA gene and analyzed its phenotype. The gapA mutant is characterized by reduced virulence in mice, defective replication inside macrophages, and its ability to induce a protective immune response against systemic challenge with parental wild-type strain. We also demonstrate the multiple localization sites of this protein: In addition to within the cytosol, it was found on the cell surface, outside the cells, and in the culture medium. Recombinant GapA was successfully obtained, and it was shown that it binds host extracellular serum proteins like plasminogen, fibrinogen, and fibronectin.

• Keywords
• DsbA, Francisella tularensis, SILAC, glyceraldehyde-3-phosphate dehydrogenase, moonlighting,
• MeSH
• Gene Deletion * MeSH
• Virulence Factors analysis   MeSH
• Francisella tularensis enzymology   immunology   pathogenicity   MeSH
• Glyceraldehyde-3-Phosphate Dehydrogenases deficiency   metabolism   MeSH
• Blood Proteins metabolism   MeSH
• Microbial Viability MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Protein Disulfide-Isomerases deficiency   MeSH
• Proteome analysis   MeSH
• Salmonella Infections, Animal microbiology   pathology   MeSH
• Protein Binding MeSH
• Virulence MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Virulence Factors MeSH
• Glyceraldehyde-3-Phosphate Dehydrogenases MeSH
• Blood Proteins MeSH
• Protein Disulfide-Isomerases MeSH
• Proteome MeSH

Francisella tularensis subspecies tularensis is a highly virulent intracellular bacterial pathogen, causing the disease tularemia. However, a safe and effective vaccine for routine application against F. tularensis has not yet been developed. We have recently constructed the deletion mutants for the DsbA homolog protein (ΔdsbA/FSC200) and a hypothetical protein IglH (ΔiglH/FSC200) in the type B F. tularensis subsp. holarctica FSC200 strain, which exerted different protection capacity against parental virulent strain. In this study, we further investigated the immunological correlates for these different levels of protection provided by ΔdsbA/FSC200 and ΔiglH/FSC200 mutants. Our results show that ΔdsbA/FSC200 mutant, but not ΔiglH/FSC200 mutant, induces an early innate inflammatory response leading to strong Th1-like antibody response. Furthermore, vaccination with ΔdsbA/FSC200 mutant, but not with ΔiglH/FSC200, elicited protection against the subsequent challenge with type A SCHU S4 strain in mice. An immunoproteomic approach was used to map a spectrum of antigens targeted by Th1-like specific antibodies, and more than 80 bacterial antigens, including novel ones, were identified. Comparison of tularemic antigens recognized by the ΔdsbA/FSC200 post-vaccination and the SCHU S4 post-challenge sera then revealed the existence of 22 novel SCHU S4 specific antibody clones.

• Keywords
• antibody response, cytokines, immunoproteomics, protection, tularemia,
• MeSH
• Vaccines, Attenuated administration & dosage   genetics   immunology   MeSH
• Bacterial Vaccines administration & dosage   genetics   immunology   MeSH
• Cytokines metabolism   MeSH
• Virulence Factors deficiency   MeSH
• Francisella tularensis classification   enzymology   immunology   MeSH
• Disease Models, Animal MeSH
• Mice, Inbred BALB C MeSH
• Protein Disulfide-Isomerases deficiency   MeSH
• Th1 Cells immunology   MeSH
• Tularemia immunology   prevention & control   MeSH
• Antibody Formation * MeSH
• Cross Protection * MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Vaccines, Attenuated MeSH
• Bacterial Vaccines MeSH
• Cytokines MeSH
• Virulence Factors MeSH
• Protein Disulfide-Isomerases MeSH