A Suggested Role of a Host-Parasite Lipid Complex in Mycobacterial Infection

Kondo, Eiko; Kanai, Koomi

doi:10.7883/yoken1952.29.199

Cited by 21 publications

(8 citation statements)

References 15 publications

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“…Furthermore, M. tuberculosis strains with de- fects in this pathway have been shown to have increased cell envelope permeability (10) and are more susceptible to IFN-␥-mediated and IFN-␥-independent immunity (46,56). Importantly, PDIM deficiency appears to be particularly important to M. tuberculosis growth in the host environment, as isolates with deficiencies in this pathway have pronounced growth defects in the spleens and lungs of infected mice (11,19,47) and are more susceptible to the nitric oxide-dependent killing of macrophages (61). More recently, PDIM has been shown to play a role in M. tuberculosis interaction with the host macrophage cell envelope, inducing changes that favor receptor-mediated phagocytosis of the bacterium (2).…”

Section: Discussionmentioning

confidence: 99%

Upregulation of the Phthiocerol Dimycocerosate Biosynthetic Pathway by Rifampin-Resistant,rpoBMutant Mycobacterium tuberculosis

Bisson

Mehaffy²,

Broeckling

et al. 2012

J Bacteriol

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h Multidrug-resistant tuberculosis has emerged as a major threat to tuberculosis control. Phylogenetically related rifampin-resistant actinomycetes with mutations mapping to clinically dominant Mycobacterium tuberculosis mutations in the rpoB gene show upregulation of gene networks encoding secondary metabolites. We compared the expressed proteomes and metabolomes of two fully drug-susceptible clinical strains of M. tuberculosis (wild type) to those of their respective rifampin-resistant, rpoB mutant progeny strains with confirmed rifampin monoresistance following antitubercular therapy. Each of these strains was also used to infect gamma interferon-and lipopolysaccharide-activated murine J774A.1 macrophages to analyze transcriptional responses in a physiologically relevant model. Both rpoB mutants showed significant upregulation of the polyketide synthase genes ppsA-ppsE and drrA, which constitute an operon encoding multifunctional enzymes involved in the biosynthesis of phthiocerol dimycocerosate and other lipids in M. tuberculosis, but also of various secondary metabolites in related organisms, including antibiotics, such as erythromycin and rifamycins. ppsA (Rv2931), ppsB (Rv2932), and ppsC (Rv2933) were also found to be upregulated more than 10-fold in the Beijing rpoB mutant strain relative to its wild-type parent strain during infection of activated murine macrophages. In addition, metabolomics identified precursors of phthiocerol dimycocerosate, but not the intact molecule itself, in greater abundance in both rpoB mutant isolates. These data suggest that rpoB mutation in M. tuberculosis may trigger compensatory transcriptional changes in secondary metabolism genes analogous to those observed in related actinobacteria. These findings may assist in developing novel methods to diagnose and treat drug-resistant M. tuberculosis infections.A pproximately 9 million people develop active tuberculosis (TB) each year, resulting in nearly 2 million deaths annually (75). Recent progress controlling drug-susceptible TB has been made in many regions (50); however, drug resistance in Mycobacterium tuberculosis, including strains resistant to both first-line drugs, isoniazid and rifampin (multidrug-resistant [MDR] TB), has emerged as a threat to TB control worldwide (26, 65). Although international surveillance systems are inadequate, data from over 80 countries indicate that approximately 1 in 10 new cases of active TB have primary drug resistance (77), and MDR TB has been reported in essentially every country in which drug resistance has been studied (76). Treatment of MDR TB requires the use of costly and toxic second-line drugs for nearly 2 years and is associated with high rates of morbidity and mortality (65), which makes the spread of drug-resistant TB a major public health concern.Drug resistance in M. tuberculosis is due primarily to singlenucleotide polymorphisms in genes encoding key mycobacterial enzymes (6). The rpoB gene encodes the ␤-subunit of bacterial RNA polymerase, which is the target of rifampin (12...

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Section: Discussionmentioning

confidence: 99%

Upregulation of the Phthiocerol Dimycocerosate Biosynthetic Pathway by Rifampin-Resistant,rpoBMutant Mycobacterium tuberculosis

Bisson

Mehaffy²,

Broeckling

et al. 2012

J Bacteriol

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“…Indeed, A DIM-less Mtb strain was initially shown to display lower levels of replication and to elicit fewer lung surface tubercles than a DIM-producing strain [7]. An avirulent strain of Mtb coated with a mixture of DIM and cholesteryl oleate persisted longer than the uncoated strain in the spleen and lung of infected mice [8]. Consistent with these initial observations, two independent signature-tagged transposon mutagenesis studies have led to the isolation of Mtb mutants with a severe growth defect in mice [9],[10].…”

Section: Introductionmentioning

confidence: 99%

Phthiocerol Dimycocerosates of M. tuberculosis Participate in Macrophage Invasion by Inducing Changes in the Organization of Plasma Membrane Lipids

et al. 2009

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Phthiocerol dimycocerosates (DIM) are major virulence factors of Mycobacterium tuberculosis (Mtb), in particular during the early step of infection when bacilli encounter their host macrophages. However, their cellular and molecular mechanisms of action remain unknown. Using Mtb mutants deleted for genes involved in DIM biosynthesis, we demonstrated that DIM participate both in the receptor-dependent phagocytosis of Mtb and the prevention of phagosomal acidification. The effects of DIM required a state of the membrane fluidity as demonstrated by experiments conducted with cholesterol-depleting drugs that abolished the differences in phagocytosis efficiency and phagosome acidification observed between wild-type and mutant strains. The insertion of a new cholesterol-pyrene probe in living cells demonstrated that the polarity of the membrane hydrophobic core changed upon contact with Mtb whereas the lateral diffusion of cholesterol was unaffected. This effect was dependent on DIM and was consistent with the effect observed following DIM insertion in model membrane. Therefore, we propose that DIM control the invasion of macrophages by Mtb by targeting lipid organisation in the host membrane, thereby modifying its biophysical properties. The DIM-induced changes in lipid ordering favour the efficiency of receptor-mediated phagocytosis of Mtb and contribute to the control of phagosomal pH driving bacilli in a protective niche.

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“…As early as 1974, it was recognized that a spontaneously arising PDIMdeficient variant of the laboratory strain H37Rv was attenuated in a guinea pig model of infection (11). Shortly thereafter, it was shown that the in vivo survival of an avirulent Mycobacterium tuberculosis strain was enhanced by coating the bacteria with cholesterol oleate and purified PDIM (16). A genetic link between PDIM production and virulence was not established until a quarter century later, when a large chromosomal locus was identified as playing an essential role in the biosynthesis and export of PDIM (3,4,6).…”

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confidence: 99%

Spontaneous Phthiocerol Dimycocerosate-Deficient Variants of Mycobacterium tuberculosis Are Susceptible to Gamma Interferon-Mediated Immunity

et al. 2011

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Onset of the adaptive immune response in mice infected with Mycobacterium tuberculosis is accompanied by slowing of bacterial replication and establishment of a chronic infection. Stabilization of bacterial numbers during the chronic phase of infection is dependent on the activity of the gamma interferon (IFN-␥)-inducible nitric oxide synthase (NOS2). Previously, we described a differential signature-tagged mutagenesis screen designed to identify M. tuberculosis "counterimmune" mechanisms and reported the isolation of three mutants in the H37Rv strain background containing transposon insertions in the rv0072, rv0405, and rv2958c genes. These mutants were impaired for replication and virulence in NOS2 ؊/؊ mice but were growth-proficient and virulent in IFN-␥ ؊/؊ mice, suggesting that the disrupted genes were required for bacterial resistance to an IFN-␥-dependent immune mechanism other than NOS2. Here, we report that the attenuation of these strains is attributable to an underlying transposon-independent deficiency in biosynthesis of phthiocerol dimycocerosate (PDIM), a cell wall lipid that is required for full virulence in mice. We performed whole-genome resequencing of a PDIM-deficient clone and identified a spontaneous point mutation in the putative polyketide synthase PpsD that results in a G44C amino acid substitution. We demonstrate by complementation with the wild-type ppsD gene and reversion of the ppsD gene to the wild-type sequence that the ppsD(G44C) point mutation is responsible for PDIM deficiency, virulence attenuation in NOS2 ؊/؊ and wild-type C57BL/6 mice, and a growth advantage in vitro in liquid culture. We conclude that PDIM biosynthesis is required for M. tuberculosis resistance to an IFN-␥-mediated immune response that is independent of NOS2.Pathogenic mycobacteria possess a unique array of complex cell wall-associated lipids. The most abundant of these lipids, the phthiocerol dimycocerosates (PDIMs) (Fig. 1), are among the best characterized (23). PDIMs contain long-chain diols esterified by methyl-branched fatty acid chains. As early as 1974, it was recognized that a spontaneously arising PDIMdeficient variant of the laboratory strain H37Rv was attenuated in a guinea pig model of infection (11). Shortly thereafter, it was shown that the in vivo survival of an avirulent Mycobacterium tuberculosis strain was enhanced by coating the bacteria with cholesterol oleate and purified PDIM (16). A genetic link between PDIM production and virulence was not established until a quarter century later, when a large chromosomal locus was identified as playing an essential role in the biosynthesis and export of PDIM (3,4,6). Transposon insertions within the fadD26, fadD28, mmpL7, and drrC genes, and in the putative transcriptional promoter region upstream of the fadD26 gene, were identified in strains deficient in surface-localized PDIM. The fadD26 and fadD28 mutants apparently fail to synthesize PDIM, whereas the mmpL7 and drrC mutants produce PDIM but accumulate it intracellularly, thus implicating these ...

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A Suggested Role of a Host-Parasite Lipid Complex in Mycobacterial Infection

Cited by 21 publications

References 15 publications

Upregulation of the Phthiocerol Dimycocerosate Biosynthetic Pathway by Rifampin-Resistant,rpoBMutant Mycobacterium tuberculosis

Upregulation of the Phthiocerol Dimycocerosate Biosynthetic Pathway by Rifampin-Resistant,rpoBMutant Mycobacterium tuberculosis

Phthiocerol Dimycocerosates of M. tuberculosis Participate in Macrophage Invasion by Inducing Changes in the Organization of Plasma Membrane Lipids

Spontaneous Phthiocerol Dimycocerosate-Deficient Variants of Mycobacterium tuberculosis Are Susceptible to Gamma Interferon-Mediated Immunity

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