MceG stabilizes the Mce1 and Mce4 transporters in Mycobacterium tuberculosis

Lipids are important nutrients for Mycobacterium tuberculosis (Mtb) to support bacterial survival in mammalian tissues and host cells. Fatty acids and cholesterol are imported across the Mtb cell wall via the dedicated Mce1 and Mce4 transporters, respectively. It is thought that the Mce1 and Mce4 transporters are comprised of subunits that confer substrate specificity and proteins that couple lipid transport to ATP hydrolysis, similar to other bacterial ABC transporters. However, unlike canonical bacterial ABC transporters, Mce1 and Mce4 appear to share a single ATPase, MceG. Previously, it was established that Mce1 and Mce4 are destabilized when key transporter subunits are rendered nonfunctional; therefore, we investigated here the role of MceG in Mce1 and Mce4 protein stability. We determined that key residues in the Walker B domain of MceG are required for the Mce1- and Mce4-mediated transport of fatty acids and cholesterol. Previously, it has been established that Mce1 and Mce4 are destabilized and/or degraded when key transporter subunits are rendered nonfunctional, thus we investigated a role for MceG in stabilizing Mce1 and Mce4. Using an unbiased quantitative proteomic approach, we demonstrate that Mce1 and Mce4 proteins are specifically degraded in mutants lacking MceG. Furthermore, bacteria expressing Walker B mutant variants of MceG failed to stabilize Mce1 and Mce4, and we show that deleting MceG impacts the fitness of Mtb in the lungs of mice. Thus, we conclude that MceG represents an enzymatic weakness that can be potentially leveraged to disable and destabilize both the Mce1 and Mce4 transporters in Mtb.

Oncostatin M expression induced by bacterial triggers drives airway inflammatory and mucus secretion in severe asthma

[Figure: see text].

[Efficiency of the differentiated use of physiobalneotherapy for borderline mental disorders in mothers of children with cerebral palsy]

BACKGROUND

Child disability, especially as a result of nervous system diseases, affects all aspects of family life, causing extreme emotional and physical exhaustion in parents. However, today there is not enough scientific evidence on the features of development of nonpsychotic mental disorders in parents raising children with cerebral palsy and on the possibilities of using modern physiotherapy methods to correct these conditions and comorbidities. Considering that sanatorium-resort rehabilitation in children with cerebral palsy is accompanied by their parents, it is urgent to optimize clinical and functional approaches to treating mothers with borderline mental disorders with the simultaneous rehabilitation of children in sanatorium-resort conditions.

AIM

To study the efficiency of sanatorium-resort treatment aimed at the psychological correction of mothers accompanying children with cerebral palsy to a sanatorium.

MATERIAL AND METHODS

The study enrolled 151 mothers who had borderline mental disorders and raised children with cerebral palsy. A study group included 103 women aged 33.2±0.6 years; a comparison group consisted of 48 mothers aged 31.8±0.5 years. The examination was conducted before sanatorium-resort treatment and after a therapy cycle. The mothers underwent clinical and psychodiagnostic examinations via the standardized Minnesota Multiphasic Personality Inventory (a short form) MMPI-mini (adapted by L.N. Sobchik, 2000); emotional and motivational sphere study the WAM (well-being, activity, mood) questionnaire, the Spielberger-Khanin Inventory, and the Depression Rating Scale (adapted by T.I. Balashova). The patients of both groups received combination treatment: the comparison group (n=48) had a general sanatorium-resort therapeutic complex and group psychotherapy; the study group (n=103) additionally took valerian-bromine baths based on sodium chloride water with a mineralization of 20 g/dm³), and a transcranial magnetic therapy cycle.

RESULTS

The general sanatorium-and-resort complex with psychotherapy predominantly affected the quality of night sleep (p<0.01) and reduced personality disorders according to the hypochondria scale (from 74.60±7.52 to 52.91±4.04 scores, p<0.01). The additional use of transcranial magnetic therapy and valerian-bromine baths based on sodium chloride water in the mothers had a psychocorrecting effect recorded according to basic (hysteria, psychopathy, psychasthenia) scales. Reduced depression was noted in 36.4% of the mothers (7% in the comparison group).

CONCLUSION

Transcranial magnetic therapy used in combination with valerian-bromine baths based on sodium chloride water and with psychotherapy in mothers with borderline mental disorders, by taking into account psychological dysregulation, contributed to increases in the body's clinical and functional reserves within 6-8 months and to the preservation of psychological adaptation in 54.7% of cases. Incorporation of a maternal psychocorrective complex into the sanatorium-resort treatment of a child with cerebral palsy is a promising method for improving the quality of treatment outcomes in a sanatorium.

The genetic requirements of fatty acid import by Mycobacterium tuberculosis within macrophages

Mycobacterium tuberculosis (Mtb) imports and metabolizes fatty acids to maintain infection within human macrophages. Although this is a well-established paradigm, the bacterial factors required for fatty acid import are poorly understood. Previously, we found that LucA and Mce1 are required for fatty acid import in Mtb (Nazarova et al., 2017). Here, we identified additional Mtb mutants that have a reduced ability to import a fluorescent fatty acid substrate during infection within macrophages. This screen identified the novel genes as rv2799 and rv0966c as be necessary for fatty acid import and confirmed the central role for Rv3723/LucA and putative components of the Mce1 fatty acid transporter (Rv0200/OmamB, Rv0172/Mce1D, and Rv0655/MceG) in this process.

Growth of Mycobacterium tuberculosis in vivo segregates with host macrophage metabolism and ontogeny

This study by Huang et al. demonstrates that lung macrophages of differing ontogeny respond divergently to Mycobacterium tuberculosis infection in vivo. Alveolar macrophages and interstitial macrophages adopt different metabolic states that promote or control M. tuberculosis growth, respectively.

To understand how infection by Mycobacterium tuberculosis (Mtb) is modulated by host cell phenotype, we characterized those host phagocytes that controlled or supported bacterial growth during early infection, focusing on the ontologically distinct alveolar macrophage (AM) and interstitial macrophage (IM) lineages. Using fluorescent Mtb reporter strains, we found that bacilli in AM exhibited lower stress and higher bacterial replication than those in IM. Interestingly, depletion of AM reduced bacterial burden, whereas depletion of IM increased bacterial burden. Transcriptomic analysis revealed that IMs were glycolytically active, whereas AMs were committed to fatty acid oxidation. Intoxication of infected mice with the glycolytic inhibitor, 2-deoxyglucose, decreased the number of IMs yet increased the bacterial burden in the lung. Furthermore, in in vitro macrophage infections, 2-deoxyglucose treatment increased bacterial growth, whereas the fatty acid oxidation inhibitor etomoxir constrained bacterial growth. We hypothesize that different macrophage lineages respond divergently to Mtb infection, with IMs exhibiting nutritional restriction and controlling bacterial growth and AMs representing a more nutritionally permissive environment.

Flow Cytometric Quantification of Fatty Acid Uptake by Mycobacterium tuberculosis in Macrophages

Mycobacterium tuberculosis (Mtb) has evolved to assimilate fatty acids from its host. However, until recently, there was no reliable way to quantify fatty acid uptake by the bacteria during host cell infection. Here we describe a new method to quantify fatty acid uptake by intracellular bacilli. We infect macrophages with Mtb constitutively expressing mCherry and then metabolically label them with Bodipy-palmitate. Following the labeling procedure, we isolate Mtb-containing phagosomes on a sucrose cushion and disrupt the phagosomes with detergent. After extensive washes, the isolated bacteria are analyzed by flow cytometry to determine the level of Bodipy-palmitate signal associated with the bacteria. Using a Mtb mutant strain defective in fatty acid uptake in liquid culture we determined that this mutant assimilated 10-fold less Bodipy-palmitate than the wild type strain during infection in macrophages. This quantitative method of fatty acid uptake can be used to further identify pathways involved in lipid uptake by intracellular Mtb and possibly other bacteria.

Rv3723/LucA coordinates fatty acid and cholesterol uptake in Mycobacterium tuberculosis

Pathogenic bacteria have evolved highly specialized systems to extract essential nutrients from their hosts. Mycobacterium tuberculosis (Mtb) scavenges lipids (cholesterol and fatty acids) to maintain infections in mammals but mechanisms and proteins responsible for the import of fatty acids in Mtb were previously unknown. Here, we identify and determine that the previously uncharacterized protein Rv3723/LucA, functions to integrate cholesterol and fatty acid uptake in Mtb. Rv3723/LucA interacts with subunits of the Mce1 and Mce4 complexes to coordinate the activities of these nutrient transporters by maintaining their stability. We also demonstrate that Mce1 functions as a fatty acid transporter in Mtb and determine that facilitating cholesterol and fatty acid import via Rv3723/LucA is required for full bacterial virulence in vivo. These data establish that fatty acid and cholesterol assimilation are inexorably linked in Mtb and reveals a key function for Rv3723/LucA in in coordinating thetransport of both these substrates.

Growing and Handling of Mycobacterium tuberculosis for Macrophage Infection Assays

Macrophage survival assays are a critical component of any Mycobacterium tuberculosis research program. Here we describe the methods that we use routinely for infection of macrophages of various origins. The protocols are efficient, relatively simple and are accepted widely. We provide users with methods for the infection of small numbers of macrophages-more suitable for microscopy; and for larger numbers of macrophages-for flow cytometry analysis or extraction for biochemical characterization.

Misregulation of the broad-range phospholipase C activity increases the susceptibility of Listeria monocytogenes to intracellular killing by neutrophils

Listeria monocytogenes is a facultative intracellular bacterial pathogen that tightly regulates the activities of various virulence factors during infection. A mutant strain (the plcBDpro mutant) that has lost the ability to control the activity of a phospholipase C (PC-PLC) is attenuated a hundred fold in mice. This attenuation is not due to a lack of bacterial fitness, but appears to result from a modified host response to infection. The transcriptomic pattern of immune-related genes indicated that PC-PLC did not enhance the innate immune response in infected macrophages. However, it partially protected the cells from bacteria-mediated mitochondrial fragmentation. In mice, the plcBDpro mutant transiently caused an increase in liver pathology, as judged by the size of neutrophil-filled micro-abscesses. Moreover, the plcBDpro mutant was more susceptible to intracellular killing by neutrophils than wild-type L. monocytogenes. Together, these data indicate that in vivo attenuation of the plcBDpro mutant results from its reduced ability to disrupt mitochondrial homeostasis and to resist intracellular killing by neutrophils.

Role of lipid components in formation and reactivation of Mycobacterium smegmatis "nonculturable" cells

We have found that transition of actively dividing Mycobacterium smegmatis cells into the dormant "nonculturable" state is accompanied by increase in the protein/lipid ratio and disappearance of one of the main lipid components of the mycobacterial cells, trehalose monomycolate. In this case, oleic acid is accumulated in the culture medium due to its secretion by the mycobacterial cells. Addition of lipids of different classes to "nonculturable" M. smegmatis cells induces their resuscitation. The lipid reactivating effect is evidently caused by the presence of fatty acids in their composition, because free fatty acids also exhibited reactivation effect. Oleic acid in concentration of 0.05-3 μg/ml exhibited maximal effect, and that allows us to draw a conclusion concerning its signal role in the transition of dormant cells into active state.