MptpB Inhibitor Improves the Action of Antibiotics against Mycobacterium tuberculosis and Nontuberculous Mycobacterium avium Infections

Functional Characterization of MIP_07528 of Mycobacterium indicus pranii for Tyrosine Phosphatase Activity Displays Sensitivity to Oxidative Inactivation and Plays a Role in Immunomodulation

Mycobacterium indicus pranii (MIP), an atypical mycobacterium originally developed as an anti-leprosy vaccine, has emerged as a potent immunomodulator with diverse therapeutic applications. Despite its clinical significance, molecular mechanisms underlying MIP's immunomodulatory properties remain largely unexplored. Bacterial phosphatases are recognized as crucial virulence factors that enable pathogens to evade host defenses by modulating host immune signaling pathways, including phosphoinositide metabolism. MIP_07528 was identified as a putative protein tyrosine phosphatase B (PtpB) ortholog through in silico analysis, with significant sequence conservation observed within catalytic domains of pathogenic mycobacterial PtpB proteins. Phosphatase activity was detected in both cell lysate and culture filtrate fractions, revealing differential expression patterns between MIP and M. tuberculosis. Upregulation of MIP_07528 was demonstrated under oxidative stress, suggesting involvement in stress adaptation. The recombinant protein exhibited distinctive kinetic properties, characterized by higher substrate affinity yet increased susceptibility to oxidative inactivation compared to its M. tuberculosis counterpart. In macrophages, MIP_07528 suppressed pro-inflammatory cytokines while enhancing anti-inflammatory IL-10 production. These findings establish MIP_07528 as a functional phosphatase that may contribute to MIP's immunomodulatory properties. This work advances understanding of phosphatase function in non-pathogenic mycobacteria while providing insights into virulence factor evolution and establishing a foundation for novel antimicrobial strategies.

Deciphering tuberculosis: lysosome-centric insights into pathogenesis and therapies

Tuberculosis is a widely spread disease caused by Mycobacterium tuberculosis (Mtb). The pathogenicity of the pathogen is closely associated with the immune defense mechanisms of the host cells. As key cellular degradation and metabolic centers, lysosomes critically regulate tuberculosis infection. When Mtb invades the host, it is taken up by macrophages and enters phagosomes. Subsequently, the phagosomes fuse with lysosomes and form phagolysosomes, which eliminate the pathogenic bacteria through the acidic environment and hydrolytic enzymes within lysosomes. However, Mtb can interfere with the normal functions of lysosomes through various strategies. It can secrete specific factors (such as ESAT-6, ppk-1, and AcpM) to inhibit the acidification of lysosomes, enzyme activity, and the fusion of phagosomes and lysosomes, thereby enabling Mtb proliferation within host cells. An in-depth exploration of the mechanism of the interaction between Mtb and lysosomes will both uncover bacterial immune evasion strategies and identify novel anti-tuberculosis therapeutic targets.

Combating Tuberculosis via Restoring the Host Immune Capacity by Targeting M. tb Kinases and Phosphatases

Mycobacterium tuberculosis (M. tb) is a remarkably versatile pathogen that possesses a unique ability to counteract the host's defence mechanisms to control the infection. Several mycobacterial protein kinases and phosphatases were found to play a key role in impeding phagosome maturation in macrophages and accordingly blocking the phagosome-lysosome fusion, therefore allowing the bacteria to survive. During phagocytosis, both M. tb and the host's phagocytic cells develop mechanisms to fight each other, resulting in pathogen elimination or survival. In this respect, M. tb uses a phosphorylation-based signal transduction mechanism, whereby it senses extracellular signals from the host and initiates the appropriate adaptation responses. Indeed, the ability of M. tb to exist in different states in the host (persistent quiescent state or actively replicating mode) is mainly mediated through protein phosphorylation/dephosphorylation signalling. The M. tb regulatory and defensive responses coordinate different aspects of the bacilli's physiology, for instance, cell wall components, metabolic activity, virulence, and growth. Herein, we will discuss the implication of M. tb kinases and phosphatases in hijacking the host immune system, perpetuating the infection. In addition, the role of PknG, MPtpA, MPtpB, and SapM inhibitors in resetting the host immune system will be highlighted.