The ESX-3 Secretion System Is Necessary for Iron and Zinc Homeostasis in Mycobacterium tuberculosis

Serafini, Agnese; Pisu, Davide; Palù, Giorgio; Rodríguez, G. Marcela; Manganelli, Riccardo

doi:10.1371/journal.pone.0078351

Cited by 105 publications

(113 citation statements)

References 69 publications

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“…It is possible that the conditional mutant accumulates both PimA and PIMs that allow the cells to undergo a few rounds of replication even after the pimA mRNA is depleted to a level lower than that found in wildtype cells. Similar findings have already been reported for other conditional mutants, which needed several rounds of subculturing before a phenotype was evident (52,53) or which were still able to undergo some cycles of cell replication after the depleted essential protein became undetectable by Western blotting (54).…”

Section: Figsupporting

confidence: 88%

The Phosphatidyl- myo -Inositol Mannosyltransferase PimA Is Essential for Mycobacterium tuberculosis Growth In Vitro and In Vivo

et al. 2014

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The cell envelope of Mycobacterium tuberculosis contains glycans and lipids of peculiar structure that play prominent roles in the biology and pathogenesis of tuberculosis. Consequently, the chemical structure and biosynthesis of the cell wall have been intensively investigated in order to identify novel drug targets. Here, we validate that the function of phosphatidyl-myo-inositol mannosyltransferase PimA is vital for M. tuberculosis in vitro and in vivo. PimA initiates the biosynthesis of phosphatidyl-myoinositol mannosides by transferring a mannosyl residue from GDP-Man to phosphatidyl-myo-inositol on the cytoplasmic side of the plasma membrane. To prove the essential nature of pimA in M. tuberculosis, we constructed a pimA conditional mutant by using the TetR-Pip off system and showed that downregulation of PimA expression causes bactericidality in batch cultures. Consistent with the biochemical reaction catalyzed by PimA, this phenotype was associated with markedly reduced levels of phosphatidyl-myo-inositol dimannosides, essential structural components of the mycobacterial cell envelope. In addition, the requirement of PimA for viability was clearly demonstrated during macrophage infection and in two different mouse models of infection, where a dramatic decrease in viable counts was observed upon silencing of the gene. Notably, depletion of PimA resulted in complete clearance of the mouse lungs during both the acute and chronic phases of infection. Altogether, the experimental data highlight the importance of the phosphatidyl-myo-inositol mannoside biosynthetic pathway for M. tuberculosis and confirm that PimA is a novel target for future drug discovery programs.T he lack of proper treatment for serious infectious diseases due to the emergence of multidrug resistance (MDR) underlines the need for the discovery of novel antibiotics (1). This is particularly true for tuberculosis (TB), for which 3.7% of new cases and 20% of previously treated cases are estimated to have MDR-TB. In several countries in Eastern Europe and central Asia, these numbers rise to 9 to 32% and more than 50%, respectively, making the situation particularly worrisome. In addition, in the case of TB, which claimed 1.3 million lives in 2012, the treatment of the leastcomplicated, drug-sensitive cases is lengthy and uncomfortable, and new drugs are urgently needed to shorten the regimen and make it more acceptable to the patients (2).The cell envelope of Mycobacterium tuberculosis represents a highly attractive target for the discovery of novel TB drugs. Supporting this notion, several key medicines used in the current TB therapy are inhibitors of essential enzymes participating in cell envelope biosynthesis. The first-line drug ethambutol has been shown to target at least three unique integral membrane-associated arabinofuranosyltransferases (EmbA, EmbB, and EmbC) involved in the biosynthesis of arabinogalactan (AG) and lipoarabinomannan (LAM) (3, 4). The inhibition of InhA by isoniazid (INH) in M. tuberculosis leads to the specific depl...

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Section: Figsupporting

confidence: 88%

The Phosphatidyl- myo -Inositol Mannosyltransferase PimA Is Essential for Mycobacterium tuberculosis Growth In Vitro and In Vivo

et al. 2014

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“…Additionally, zinc's regulatory effect on bacterial secretion has been demonstrated. Specifically, zinc stress activates the secretion of the EsxA toxin, a substrate of the type VII ESX-1 secretion system in Mycobacterium tuberculosis which arrests phagosome maturation, lyses cell membranes, and induces cell death (73,74). Conversely, zinc negatively regulates the type III secretion system in enteropathogenic E. coli, the ZirTS antivirulence secretion pathway in Salmonella, as well as the type VI secretion system in Burkholderia mallei and Burk-…”

Section: Discussionmentioning

confidence: 99%

The Human Antimicrobial Protein Calgranulin C Participates in Control of Helicobacter pylori Growth and Regulation of Virulence

et al. 2015

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f During infectious processes, antimicrobial proteins are produced by both epithelial cells and innate immune cells. Some of these antimicrobial molecules function by targeting transition metals and sequestering these metals in a process referred to as "nutritional immunity." This chelation strategy ultimately starves invading pathogens, limiting their growth within the vertebrate host. Recent evidence suggests that these metal-binding antimicrobial molecules have the capacity to affect bacterial virulence, including toxin secretion systems. Our previous work showed that the S100A8/S100A9 heterodimer (calprotectin, or calgranulin A/B) binds zinc and represses the elaboration of the H. pylori cag type IV secretion system (T4SS). However, there are several other S100 proteins that are produced in response to infection. We hypothesized that the zinc-binding protein S100A12 (calgranulin C) is induced in response to H. pylori infection and also plays a role in controlling H. pylori growth and virulence. To test this, we analyzed gastric biopsy specimens from H. pylori-positive and -negative patients for S100A12 expression. These assays showed that S100A12 is induced in response to H. pylori infection and inhibits bacterial growth and viability in vitro by binding nutrient zinc. Furthermore, the data establish that the zinc-binding activity of the S100A12 protein represses the activity of the cag T4SS, as evidenced by the gastric cell "hummingbird" phenotype, interleukin 8 (IL-8) secretion, and CagA translocation assays. In addition, high-resolution field emission gun scanning electron microscopy (FEG-SEM) was used to demonstrate that S100A12 represses biogenesis of the cag T4SS. Together with our previous work, these data reveal that multiple S100 proteins can repress the elaboration of an oncogenic bacterial surface organelle. Helicobacter pylori is a Gram-negative member of the Epsilonproteobacteria commonly found in the human stomach (1). More than 50% of the world's population is chronically infected with H. pylori, despite a robust immune response to this bacterium (2, 3). The vast majority of infected persons exhibit no symptoms of disease; however, the presence of this pathogen can increase the risk of negative outcomes, including duodenal ulcer, dysplasia, mucosa-associated lymphoid tissue (MALT) lymphoma, and invasive gastric cancer (4). Negative outcomes of H. pylori infection are associated with multiple factors, including host genetics, environmental contributions such as diet and smoking, and bacterial virulence properties.One major virulence factor that contributes to H. pylori-associated disease outcomes is the cag pathogenicity island-encoded type IV secretion system (cag T4SS) (5). The cag T4SS is a macromolecular nanomachine responsible for translocating substrates, including peptidoglycan and the oncogenic effector molecule CagA, into host epithelial cells (6). The translocation activity of the cag T4SS leads to multiple consequences in host cell biology, including cytoskeletal rearrangements, indu...

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“…Early studies by Ratledge and Dover (8,46) and recent reports (45,(47)(48)(49)(50) have addressed the transport of iron across the mycobacterial envelope and export of the desferrisiderophore from the cytoplasm in M. smegmatis and M. tuberculosis. Unlike the wealth of information on the ferrisiderophore receptors in E. coli (11), identification and characterization of iron-regulated envelope proteins (IREPs) as iron transporters have been slow to come in mycobacteria, mainly due to the difficulties faced in the genetic manipulation of mycobacteria.…”

Section: Transport Of Iron Across the Mycobacterial Membranementioning

confidence: 99%

Iron Homeostasis in Mycobacterium tuberculosis: Mechanistic Insights into Siderophore-Mediated Iron Uptake

2016

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Mycobacterium tuberculosis requires iron for normal growth but faces a limitation of the metal ion due to its low solubility at biological pH and the withholding of iron by the mammalian host. The pathogen expresses the Fe 3؉ -specific siderophores mycobactin and carboxymycobactin to chelate the metal ion from insoluble iron and the host proteins transferrin, lactoferrin, and ferritin. Siderophore-mediated iron uptake is essential for the survival of M. tuberculosis, as knockout mutants, which were defective in siderophore synthesis or uptake, failed to survive in low-iron medium and inside macrophages. But as excess iron is toxic due to its catalytic role in the generation of free radicals, regulation of iron uptake is necessary to maintain optimal levels of intracellular iron. The focus of this review is to present a comprehensive overview of iron homeostasis in M. tuberculosis that is discussed in the context of mycobactin biosynthesis, transport of iron across the mycobacterial cell envelope, and storage of excess iron. The clinical significance of the serum iron status and the expression of the iron-regulated protein HupB in tuberculosis (TB) patients is presented here, highlighting the potential of HupB as a marker, notably in extrapulmonary TB cases.

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The ESX-3 Secretion System Is Necessary for Iron and Zinc Homeostasis in Mycobacterium tuberculosis

Cited by 105 publications

References 69 publications

The Phosphatidyl- myo -Inositol Mannosyltransferase PimA Is Essential for Mycobacterium tuberculosis Growth In Vitro and In Vivo

The Phosphatidyl- myo -Inositol Mannosyltransferase PimA Is Essential for Mycobacterium tuberculosis Growth In Vitro and In Vivo

The Human Antimicrobial Protein Calgranulin C Participates in Control of Helicobacter pylori Growth and Regulation of Virulence

Iron Homeostasis in Mycobacterium tuberculosis: Mechanistic Insights into Siderophore-Mediated Iron Uptake

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