Biology subjects

Bhargavi, G.

Publications and source records attributed to Bhargavi, G..

4 recordsLinked to original sources

bioRxiv2025

Proteomic analysis of Mycobacterium tuberculosis lacking a putative short-chain dehydrogenase (Rv0148)

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that survives in host cells by resisting hostile antimicrobial defenses. However, the molecules and mechanisms that contribute to Mtbs intracellular survival are not fully understood. We have previously reported that Rv0148, a putative short-chain dehydrogenase/reductase, plays a significant role in Mtb stress response and virulence in in vitro and in vivo models. To further understand the role of Rv0148 in regulating global functions of Mtb, we performed comparative proteomic analysis between pathogenic wild-type (WT) and{Delta} rv0148 mutant strains. Our mass spectrometry-based proteomics approach identified a total of 738 and 469 proteins, respectively, in the WT and{Delta} rv0148 mutant, with distinct expression patterns. Gene Ontology analysis revealed significant enrichment of proteins involved in biological processes such as resistant to host immune response and protein homeostasis in{Delta} rv0148 mutant, while peptidoglycan biosynthesis and ribosomal metabolism pathways were downregulated. Further network analysis revealed dysregulation of proteins involved in bacterial stress response, cell wall components, ribosomal and secretory proteins, suggesting impaired translational machinery in{Delta} rv0148 mutant. Functional categorization of differentially regulated proteins in{Delta} rv0148 mutant showed broad reprogramming in intermediary metabolism, stress adaptation, and secretion. These findings indicate that Rv0148 functions as a global regulatory node, which influences remodeling of cell wall components and bacterial physiology, potentially balancing survival and stress adaptation mechanisms in Mtb. IMPORTANCEMycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a notorious pathogen that can resist the hostile host environment to survive intracellularly and to cause disease. However, the molecular determinants that contribute to Mtbs adaptation to resist the host-imposed stress conditions are not fully understood. Previous in vitro and in vivo studies have shown that Rv0148, a putative short-chain dehydrogenase/reductase, is involved in Mtb stress response and virulence. In this study, the genome wide proteomic profile of Mtb mutant lacking Rv0148 ({Delta}rv0148) was investigated. Compared to the wild type Mtb strain, striking changes in proteome profile of{Delta} rv0148 mutant was noted. Proteins involved in the ESX secretion system, stress response, ribosomal protein metabolism and cell wall components were significantly affected in the{Delta} rv0148 mutant. The impact of these changes in biological functions that link Rv0148s role in Mtbs adaptation to stress conditions is discussed.

microbiology↗

bioRxiv2025

Inflammasome activation differences underpin different Mycobacterium tuberculosis infection outcomes

The clinical outcome of Mycobacterium tuberculosis (Mtb) infection ranges from latent/non-progressive disease to active/progressive tuberculosis (TB), but the cellular events contributing to these variable outcomes remain unknown. Here, we report that progressive Mtb infection is associated with upregulation of guanylate-binding protein-1 (GBP1), hypoxia-inducible factor 1 (HIF-1) and elevated NLR family pyrin domain-containing (NLRP3) inflammasome activation pathways. Using rabbit lungs and in primary rabbit and human macrophages as well as human THP-1 cell line-derived macrophages for infection with laboratory (H37Rv) or clinical Mtb strains (HN878 or CDC1551) that differ in virulence, we show that NLRP3 inflammasome activation by HIF-1 and GBP1 leads to elevated mitochondrial stress, apoptosis and necrosis during progressive infection by HN878. These biological functions and pathways are dampened in rabbit lungs, primary rabbit and human macrophages during non-progressive infection by CDC1551. These findings are consistent with and confirmed by Mtb infection studies of macrophages knocked-down for HIF-1 or GBP1 expression. Our study indicates that differences in HIF-1- and GBP1-mediated NLRP3 inflammasome activation influence the outcome of Mtb infection to active or latent TB.

immunology↗

bioRxiv2023

Rv0687 a Putative Short-Chain Dehydrogenase is indispensable for pathogenesis of Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb), a successful human pathogen, resides in host sentinel cells and combats the stressful intracellular environment induced by reactive oxygen and nitrogen species during infection. Mtb employs several evasion mechanisms in the face of the host as a survival strategy, including detoxifying enzymes as short-chain dehydrogenases/ reductases (SDRs) to withstand host-generated insults. In this study, using specialized transduction we have generated a Rv0687 deletion mutant and its complemented strain and investigated the functional role of Rv0687, a member of SDRs family genes in Mtb pathogenesis. Wildtype (WT) and mutant Mtb strain lacking Rv0687 (Rv{Delta}0687) were tested for in-vitro stress response and in-vivo survival in macrophages and mice models of infection. The study demonstrates that Rv0687 is crucial for sustaining bacterial growth in nutrition-limited conditions. The deletion of Rv0687 elevated the sensitivity of Mtb to oxidative and nitrosative stress-inducing agents. Furthermore, the lack of Rv0687 compromised the survival of Mtb in primary bone marrow macrophages and led to an increase in the levels of the secreted proinflammatory cytokines TNF-, and MIP-1. Interestingly, the growth of WT and Rv{Delta}0687 was similar in the lungs of infected immunocompromised mice however, a significant reduction in Rv{Delta}0687 growth was observed in the spleen of immunocompromised Rag-/- mice at 4 weeks post-infection. Moreover Rag-/- mice infected with Rv{Delta}0687 survived longer compared to WT Mtb strain. Additionally, we observed significant reduction in bacterial burden in spleens and lungs of immunocompetent C57BL/6 mice infected with Rv{Delta}0687 compared to complemented and WT Mtb strains. Collectively, this study reveals that Rv0687 plays a role in Mtb pathogenesis.

microbiology↗

bioRxiv2023

Fatty acid metabolism in neutrophils promotes lung damage and bacterial replication during tuberculosis.

Mycobacterium tuberculosis (Mtb) infection triggers a significant influx of neutrophils to the lungs, which is linked to tuberculosis (TB) severity. The mechanism by which Mtb infection induces neutrophillic inflammation remains unclear. Using a clinically relevant and hypervirulent Mtb strain from the W-Beijing family, HN878, we found that genes related to both glycolysis and fatty acid metabolism are upregulated in the lung neutrophils of susceptible mice. Similar effects in gene expression were observed in rabbits, and humans with pulmonary TB compared to healthy controls. Inhibiting glycolysis with 2-deoxy D-glucose (2-DG) exacerbated disease pathology, while fatty acid oxidation (FAO) inhibitor Etomoxir (ETO) improved outcomes by reducing weight loss, immunopathology, and bacterial replication within neutrophils in genetically susceptible mice. Notably, ETO reduced neutrophil production in the bone marrow and their recruitment to the lungs. ETO specifically restrained the recruitment of Ly6Glow/dim immature neutrophil population, which is elevated during disease progression and harbors the bulk of bacilli. In a transwell setup, we demonstrated that ETO dose-dependently inhibited neutrophil chemotaxis towards infected macrophages. In summary, our research highlights the crucial role of fatty acid metabolism in regulating neutrophilic inflammation during TB and provides a rationale for targeting immunometabolism of neutrophils for potential TB treatment.

immunology↗