Pathogenicity of Mycobacterium tuberculosis is closely related to its ability to survive and replicate in the hostile environment of macrophages. For some pathogenic bacteria, secretion of ATP-utilizing enzymes into the extracellular environment aids in pathogen survival via P2Z receptormediated, ATP-induced death of infected macrophages. A component of these enzymes is nucleoside diphosphate kinase (Ndk). The ndk gene was cloned from M. tuberculosis H 37 Rv and expressed in Escherichia coli. Ndk was secreted into the culture medium by M. tuberculosis, as determined by enzymatic activity and Western blotting. Purified Ndk enhanced ATP-induced macrophage cell death, as assayed by the release of [ 14 C]adenine. A catalytic mutant of Ndk failed to enhance ATP-induced macrophage cell death, and periodate-oxidized ATP (oATP), an irreversible inhibitor of P2Z receptor, blocked ATP/Ndk-induced cell death. Purified Ndk was also found to be autophosphorylated with broad specificity for all nucleotides. Conversion of His117fiGln, which is part of the nucleotide-binding site, abolished autophosphorylation. Purified Ndk also showed GTPase activity. Collectively, these results indicate that secreted Ndk of M. tuberculosis acts as a cytotoxic factor for macrophages, which may help in dissemination of the bacilli and evasion of the immune system. Keywords: cytotoxic; Mycobacterium; nucleoside diphosphate kinase; tuberculosis; GTPase.Mycobacterium tuberculosis, the causative agent of tuberculosis, normally replicates in host macrophages. The pathogen has evolved several mechanisms to circumvent the hostile environment of macrophages. These include, (a) inhibition of phagosome-lysosome fusion [1], (b) inhibition of phagosome acidification [2], (c) recruitment and retention of tryptophan/aspartate-containing coat protein on phagosomes to prevent their delivery to lysosomes [3], and (d) expression of members of the host-induced PE-PGRS family of proteins [4]. Another process that occurs with many bacterial pathogens concerns surface-associated P2Z receptors of macrophages. These receptors are involved in the killing of infected macrophages via external ATP that is effluxed from macrophages after activation by the invading pathogen [5]. A component of this system is the bacterial ATP-utilizing enzymes, that are secreted by bacterial pathogens such as, Pseudomonas aeruginosa [6,7], Vibrio cholerae [8], Burkholderia cepacia [9], and from Trichinella spiralis, an intracellular, parasitic nematode [10]. Culture supernatant from P. aeruginosa, V. cholerae, and B. cepacia, harboring Ndk and other ATP-utilizing enzymes, is cytotoxic for macrophages and mast cells when ATP is present at millimolar concentrations [7][8][9]. Ndk is also secreted by the nonpathogenic bacterium M. bovis BCG [11], but addition of culture supernatant of M. bovis BCG prevents ATP-mediated cell death [11]. The culture supernatant of M. bovis BCG also contains an ATPase that can modulate ATP concentrations. As studies on Ndk have been performed using culture supern...

The current literature about Plk1 inhibitors and knockout studies favor Plk1 inhibition as a potential antitumor therapy.

Protein kinases have a diverse array of functions in bacterial physiology, with a distinct role in the regulation of development, stress responses, and pathogenicity. pknF, one of the 11 kinases of Mycobacterium tuberculosis, encodes an autophosphorylating, transmembrane serine/threonine protein kinase, which is absent in the fast-growing, nonpathogenic Mycobacterium smegmatis. Herein, we investigate the physiological role of PknF using an antisense strategy with M. tuberculosis and expressing PknF and its kinase mutant (K41M) in M. smegmatis. Expression of PknF in M. smegmatis led to reduction in the growth rate and shortening and swelling of cells with constrictions. Interestingly, an antisense strain of M. tuberculosis expressing a low level of PknF displayed fast growth and a deformed cell morphology compared to the wild-type strain. Electron microscopy showed that most of the cells of the antisense strain were of a smaller size with an aberrant septum. Furthermore, nutrient transport analysis of these strains was conducted using 3 H-labeled and 14 C-labeled substrates. A significant increase in the uptake of D-glucose but not of glycerol, leucine, or oleic acid was observed in the antisense strain compared to the wild-type strain. The results suggest that PknF plays a direct/indirect role in the regulation of glucose transport, cell growth, and septum formation in M. tuberculosis.

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HGF with its anti-fibrotic effect provides a promising new therapeutic approach by protecting lung from fibrotic remodeling and also promoting normal regeneration of lung. The development of HGF mimetics may provide a potential attractive therapy for treatment of this devastating and complex disease.