Mycobacterium tuberculosis PPiA interacts with host integrin receptor to exacerbate disease progression

In Silico Targeting and Immunological Profiling of PpiA in Mycobacterium tuberculosis: A Computational Approach

Tuberculosis (TB) remains a leading cause of mortality, with drug resistance highlighting the need for new vaccine targets. Peptidyl-prolyl isomerase A (PpiA), a conserved Mycobacterium tuberculosis (Mtb) protein, plays a role in bacterial stress adaptation and immune evasion, making it a potential target for immunotherapy. This study uses computational methods to assess PpiA's antigenicity, structural integrity, and immunogenic potential. The PpiA sequence was retrieved from NCBI and analyzed for antigenicity and allergenicity using VaxiJen, AllerTOP, and AllergenFP. Physicochemical properties were evaluated using ProtParam, and structural models were generated through PSIPRED and SWISS-MODEL. Structural validation was performed with MolProbity, QMEANDisCo, and ProSA-Web. B-cell epitopes were predicted using BepiPred 2.0 and IEDB, while T-cell epitopes were mapped via IEDB's MHC-I and MHC-II tools. Epitope conservation across Mtb strains was confirmed using ConSurf. Results indicate PpiA is highly antigenic, non-allergenic, and stable, with several immunogenic epitopes identified for both B- and T-cells. This study supports PpiA as a promising immunogenic target for TB vaccine development.

Ferroptosis-Related Genes as Molecular Markers in Bovine Mammary Epithelial Cells Challenged with Staphylococcus aureus

Staphylococcus aureus-induced mastitis is a significant cause of economic losses in the dairy industry, yet its molecular mechanisms remain poorly defined. Although ferroptosis, a regulated cell death process, is associated with inflammatory diseases, its role in bovine mastitis is unknown. In this study, 11 S. aureus strains were isolated from milk samples obtained from cows with clinical or subclinical mastitis. Transcriptome analysis of Mac-T cells challenged with isolated S. aureus identified differentially expressed genes (DEGs). Enrichment analysis revealed significant associations between DEG clusters and traits related to bovine mastitis. KEGG pathway enrichment revealed ferroptosis, Toll-like receptor, and TNF signaling as significantly enriched pathways. Weighted gene co-expression network analysis (WGCNA) further prioritized ferroptosis-related genes (HMOX1, SLC11A2, STEAP3, SAT1, and VDAC2) involved in iron metabolism. Notably, the expression levels of HMOX1 and SAT1 were significantly increased in S. aureus-challenged Mac-T cells, and this upregulation was consistent with trends observed in transcriptome data from mother-daughter pairs of cows with subclinical mastitis caused by S. aureus infection. Furthermore, Ferrostatin-1 treatment significantly reduced the expression of HMOX1 and SAT1 in S. aureus-challenged cells, confirming the involvement of ferroptosis in this process. This study reveals that ferroptosis plays a key role in S. aureus-induced mastitis and highlights its potential as a target for molecular breeding strategies aimed at improving bovine mastitis resistance.

Mycobacterium bovis Mb3523c protein regulates host ferroptosis via chaperone-mediated autophagy

The occurrence of necrosis during Mycobacterium bovis (M. bovis) infection is regarded as harmful to the host because it promotes the spread of M. bovis. Ferroptosis is a controlled type of cell death that occurs when there is an excessive buildup of both free iron and harmful lipid peroxides. Here, we demonstrate that the mammalian cell entry (Mce) 4 family protein Mb3523c triggers ferroptosis to promote M. bovis pathogenicity and dissemination. Mechanistically, Mb3523c, through its Y237 and G241 site, interacts with host HSP90 protein to stabilize the LAMP2A on the lysosome to promote the chaperone-mediated autophagy (CMA) pathway. Then, GPX4 is delivered to lysosomes for destruction via the CMA pathway, eventually inducing ferroptosis to promote M. bovis transmission. In summary, our findings offer novel insights into the molecular mechanisms of pathogen-induced ferroptosis, demonstrating that targeting the GPX4-dependent ferroptosis through blocking the M. bovis Mb3523c-host HSP90 interface represents a potential therapeutic strategy for tuberculosis (TB).Abbreviations: CFU: colony-forming units; CMA: chaperone-mediated autophagy; Co-IP: co-immunoprecipitation; Fer-1: ferrostatin-1; GPX4: glutathione peroxidase 4; HSP90: heat shock protein 90; LDH: lactate dehydrogenase; Mce: mammalian cell entry; MOI: multiplicity of infection; Nec-1: necrostatin-1; PI: propidium iodide; RCD: regulated cell death.

Screening of Regulatory mRNAs and miRNAs that Suppress Staphylococcus aureus Proliferation via Macrophage Ferroptosis

Ferroptosis is a unique form of regulated cell death that results from unrestricted lipid peroxidation, and it enhances the production of intracellular oxidative stress molecules. In this study, we investigated the effect of macrophage ferroptosis on the proliferation of Staphylococcus aureus (S. aureus) and sought potential host-directed therapy (HDT) targets for S. aureus. The study findings revealed that erastin concentrations (< 20 μM), which do not have an impact on macrophage proliferation, can effectively impede the proliferation of S. aureus within macrophages. High-throughput sequencing was used to identify DEGs and DEMIs in infected macrophages. Subsequently, the mRNA-miRNA regulatory network was successfully constructed, and two sets of molecules were selected. Experimental findings confirmed that mmu-miR-6935-5p exhibited complementary binding to specific sequences within the GM867 mRNA, and mmu-miR-7082-3p specifically bound to the GPR176 mRNA. Inducing ferroptosis in macrophages can effectively impede the proliferation of drug-resistant S. aureus. Notably, our study has identified GM867, GPR176, mmu-miR-6935-5p, and mmu-miR-7082-3p as key regulators involved in this process. These findings highlight the potential of targeting these four molecules for HDT, offering novel ways to combat drug-resistant S. aureus infection.

Beyond protein folding: The pleiotropic functions of PPIases in cellular processes and microbial virulence

Peptidyl prolyl cis/trans isomerases (PPIases), a ubiquitously distributed superfamily of enzymes, associated with signal transduction, trafficking, assembly, biofilm formation, stress tolerance, cell cycle regulation, gene expression and tissue regeneration, is a key regulator of metabolic disorders and microbial virulence. This review assumes an integrative approach, to provide a holistic overview of the structural and functional diversity of PPIases, examining their conformational dynamics, cellular distribution, and physiological significance. We explore their intricate involvement in cellular processes and virulence modulation in both eukaryotic and prokaryotic systems. Additionally, we evaluate the potential of these molecular chaperones as drug targets and vaccine candidates, emphasizing their relevance in therapeutic development. By synthesizing recent findings and providing a broader perspective on these proteins, this review aims to enhance our understanding of their multifaceted roles in biology and their potential applications in medicine.

Cleavage of cell junction proteins as a host invasion strategy in leptospirosis

Infection and invasion are the prerequisites for developing the disease symptoms in a host. While the probable mechanism of host invasion and pathogenesis is known in many pathogens, very little information is available on Leptospira invasion/pathogenesis. For causing systemic infection Leptospira must transmigrate across epithelial barriers, which is the most critical and challenging step. Extracellular and membrane-bound proteases play a crucial role in the invasion process. An extensive search for the proteins experimentally proven to be involved in the invasion process through cell junction cleavage in other pathogens has resulted in identifying 26 proteins. The similarity searches on the Leptospira genome for counterparts of these 26 pathogenesis-related proteins identified at least 12 probable coding sequences. The proteins were either extracellular or membrane-bound with a proteolytic domain to cleave the cell junction proteins. This review will emphasize our current understanding of the pathogenic aspects of host cell junction-pathogenic protein interactions involved in the invasion process. Further, potential candidate proteins with cell junction cleavage properties that may be exploited in the diagnostic/therapeutic aspects of leptospirosis will also be discussed. KEY POINTS: • The review focussed on the cell junction cleavage proteins in bacterial pathogenesis • Cell junction disruptors from Leptospira genome are identified using bioinformatics • The review provides insights into the therapeutic/diagnostic interventions possible.

Mycobacterial peptidyl prolyl isomerase A activates STING-TBK1-IRF3 signaling to promote IFNβ release in macrophages

Peptidyl prolyl isomerases (PPIases) are well-conserved protein-folding enzymes that moonlight as regulators of bacterial virulence. Peptidyl prolyl isomerase A, PPiA (Rv0009) is a secretory protein of Mycobacterium tuberculosis that possesses sequence and structural similarity to eukaryotic cyclophilins. In this study, we validated the interaction of PPiA with stimulator of interferon genes (STING) using both, Escherichia coli-based and mammalian in vitro expression systems. In vitro pull-down assays confirmed that the cytosolic domain of STING interacts with PPiA, and moreover, we found that PPiA could induce dimerization of STING in macrophages. In silico docking analyses suggested that the PXXP (PDP) motif of PPiA is crucial for interaction with STING, and concordantly, mutations in the PDP domain (PPiA MUT-II) abrogated this interaction, as well as the ability of PPiA to facilitate STING dimerization. In agreement with these observations, fluorescence microscopy demonstrated that STING and wild-type PPiA, but not PPiA MUT-II, could colocalize when expressed in HEK293 cells. Highlighting the importance of the PDP domain further, PPiA, but not PPiA MUT-II could activate Tank binding kinase 1 (TBK1)-interferon regulatory factor 3 (IRF3) signaling to promote the release of interferon-beta (IFNβ). PPiA, but not PPiA MUT-II expressed in Mycobacterium smegmatis induced IFNβ release and facilitated bacterial survival in macrophages in a STING-dependent manner. The PPiA-induced release of IFNβ was c-GAS independent. We conclude that PPiA is a previously undescribed mycobacterial regulator of STING-dependent type I interferon production from macrophages.

Mycobacterium tuberculosis infection induces a novel type of cell death: Ferroptosis

Ferroptosis is a lipid peroxidation-driven and iron-dependent form of programmed cell death, which is involved in a variety of physical processes and multiple diseases. Numerous reports have demonstrated that ferroptosis is closely related to the pathophysiological processes of Mycobacterium tuberculosis (M. tuberculosis) infection and is characterized by the accumulation of excess lipid peroxides on the cell membrane. In this study, the various functions of ferroptosis, and the therapeutic strategies and diagnostic biomarkers of tuberculosis, were summarized. Notably, this review provides insights into the molecular mechanisms and functions of M. tuberculosis-induced ferroptosis, suggesting potential future therapeutic and diagnostic markers for tuberculosis.

Virulence Factors of Mycobacterium tuberculosis as Modulators of Cell Death Mechanisms

Mycobacterium tuberculosis (Mtb) modulates diverse cell death pathways to escape the host immune responses and favor its dissemination, a complex process of interest in pathogenesis-related studies. The main virulence factors of Mtb that alter cell death pathways are classified according to their origin as either non-protein (for instance, lipomannan) or protein (such as the PE family and ESX secretion system). The 38 kDa lipoprotein, ESAT-6 (early antigen-secreted protein 6 kDa), and another secreted protein, tuberculosis necrotizing toxin (TNT), induces necroptosis, thereby allowing mycobacteria to survive inside the cell. The inhibition of pyroptosis by blocking inflammasome activation by Zmp1 and PknF is another pathway that aids the intracellular replication of Mtb. Autophagy inhibition is another mechanism that allows Mtb to escape the immune response. The enhanced intracellular survival (Eis) protein, other proteins, such as ESX-1, SecA2, SapM, PE6, and certain microRNAs, also facilitate Mtb host immune escape process. In summary, Mtb affects the microenvironment of cell death to avoid an effective immune response and facilitate its spread. A thorough study of these pathways would help identify therapeutic targets to prevent the survival of mycobacteria in the host.

Sepsis - it is all about the platelets

Sepsis is accompanied by thrombocytopenia and the severity of the thrombocytopenia is associated with mortality. This thrombocytopenia is characteristic of disseminated intravascular coagulation (DIC), the sepsis-associated coagulopathy. Many of the pathogens, both bacterial and viral, that cause sepsis also directly activate platelets, which suggests that pathogen-induced platelet activation leads to systemic thrombosis and drives the multi-organ failure of DIC. In this paper we review the mechanisms of platelet activation by pathogens and the evidence for a role for anti-platelet agents in the management of sepsis.

A mycobacterial effector promotes ferroptosis-dependent pathogenicity and dissemination

Ferroptosis is a lipid peroxidation-driven and iron-dependent programmed cell death involved in multiple physical processes and various diseases. Emerging evidence suggests that several pathogens manipulate ferroptosis for their pathogenicity and dissemination, but the underlying molecular mechanisms remain elusive. Here, we identify that protein tyrosine phosphatase A (PtpA), an effector secreted by tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis (Mtb), triggers ferroptosis to promote Mtb pathogenicity and dissemination. Mechanistically, PtpA, through its Cys11 site, interacts with host RanGDP to enter host cell nucleus. Then, the nuclear PtpA enhances asymmetric dimethylation of histone H3 arginine 2 (H3R2me2a) via targeting protein arginine methyltransferase 6 (PRMT6), thus inhibiting glutathione peroxidase 4 (GPX4) expression, eventually inducing ferroptosis to promote Mtb pathogenicity and dissemination. Taken together, our findings provide insights into molecular mechanisms of pathogen-induced ferroptosis, indicating a potential TB treatment via blocking Mtb PtpA-host PRMT6 interface to target GPX4-dependent ferroptosis.

Mycobacterium tuberculosis-macrophage interaction: Molecular updates

Mycobacterium tuberculosis (Mtb), the causative agent of Tuberculosis (TB), remains a pathogen of great interest on a global scale. This airborne pathogen affects the lungs, where it interacts with macrophages. Acidic pH, oxidative and nitrosative stressors, and food restrictions make the macrophage's internal milieu unfriendly to foreign bodies. Mtb subverts the host immune system and causes infection due to its genetic arsenal and secreted effector proteins. In vivo and in vitro research have examined Mtb-host macrophage interaction. This interaction is a crucial stage in Mtb infection because lung macrophages are the first immune cells Mtb encounters in the host. This review summarizes Mtb effectors that interact with macrophages. It also examines how macrophages control and eliminate Mtb and how Mtb manipulates macrophage defense mechanisms for its own survival. Understanding these mechanisms is crucial for TB prevention, diagnosis, and treatment.

Characteristics of alveolar macrophages in bronchioalveolar lavage fluids from active tuberculosis patients identified by single-cell RNA sequencing

Tuberculosis (TB), is an infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), and presents with high morbidity and mortality. Alveolar macrophages play an important role in TB pathogenesis although there is heterogeneity and functional plasticity. This study aimed to show the characteristics of alveolar macrophages from bronchioalveolar lavage fluid (BALF) in active TB patients. Single-cell RNA sequencing (scRNA-seq) was performed on BALF cells from three patients with active TB and additional scRNA-seq data from three healthy adults were established as controls. Transcriptional profiles were analyzed and compared by differential geneexpression and functional enrichment analysis. We applied pseudo-temporal trajectory analysis to investigate correlations and heterogeneity within alveolar macrophage subclusters. Alveolar macrophages from active TB patients at the single-cell resolution are described. We found that TB patients have higher cellular percentages in five macrophage subclusters. Alveolar macrophage subclusters with increased percentages were involved in inflammatory signaling pathways as well as the basic macrophage functions. The TB-increased alveolar macrophage subclusters might be derived from M1-like polarization state, before switching to an M2-like polarization state with the development ofM. tuberculosis infection. Cell-cell communications of alveolar macrophages also increased and enhanced in active TB patients. Overall, our study demonstrated the characteristics of alveolar macrophages from BALF in active TB patients by using scRNA-seq.