scholarly journals The Lipid Virulence Factors of Mycobacterium tuberculosis Exert Multilayered Control over Autophagy-Related Pathways in Infected Human Macrophages

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 666 ◽  
Author(s):  
Aïcha Bah ◽  
Merlin Sanicas ◽  
Jérôme Nigou ◽  
Christophe Guilhot ◽  
Catherine Astarie-Dequeker ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Virulence Factors ◽  
Defense Mechanism ◽  
Immune Defense ◽  
Knock Out ◽  
Human Macrophages ◽  
Type Vii Secretion ◽  
Type Vii Secretion System ◽  
Phagosomal Membrane ◽  
Phthiocerol Dimycocerosates

Autophagy is an important innate immune defense mechanism that controls Mycobacterium tuberculosis (Mtb) growth inside macrophages. Autophagy machinery targets Mtb-containing phagosomes via xenophagy after damage to the phagosomal membrane due to the Type VII secretion system Esx-1 or via LC3-associated phagocytosis without phagosomal damage. Conversely, Mtb restricts autophagy-related pathways via the production of various bacterial protein factors. Although bacterial lipids are known to play strategic functions in Mtb pathogenesis, their role in autophagy manipulation remains largely unexplored. Here, we report that the lipid virulence factors sulfoglycolipids (SLs) and phthiocerol dimycocerosates (DIMs) control autophagy-related pathways through distinct mechanisms in human macrophages. Using knock-out and knock-in mutants of Mtb and Mycobacterium bovis BCG (Bacille Calmette Guerin) and purified lipids, we found that (i) Mtb mutants with DIM and SL deficiencies promoted functional autophagy via an MyD88-dependent and phagosomal damage-independent pathway in human macrophages; (ii) SLs limited this pathway by acting as TLR2 antagonists; (iii) DIMs prevented phagosomal damage-independent autophagy while promoting Esx-1-dependent xenophagy; (iv) and DIMs, but not SLs, limited the acidification of LC3-positive Mtb compartments. In total, our study reveals an unexpected and intricate role for Mtb lipid virulence factors in controlling autophagy-related pathways in human macrophages, thus providing further insight into the autophagy manipulation tactics deployed by intracellular bacterial pathogens.

scholarly journals Crystallographic observation of the movement of the membrane-distal domain of the T7SS core component EccB1 fromMycobacterium tuberculosis

2016 ◽  
Vol 72 (2) ◽  
pp. 139-144
Author(s):  
Xiao-Qian Xie ◽  
Xiao-Li Zhang ◽  
Chao Qi ◽  
De-Feng Li ◽  
Joy Fleming ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Atpase Activity ◽  
Virulence Factors ◽  
Conformational Changes ◽  
Secretion System ◽  
Secretion Systems ◽  
Core Component ◽  
Substrate Transport ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

The protein EccB1, a core component of the type VII secretion system (T7SS) ofMycobacterium tuberculosis, has been identified as an ATPase and is essential for the secretion of virulence factors by the ESX-1 system. In a previous study, EccB1 structures were determined in two different conformations. Here, two new conformations are identified and described. These four conformations present snapshots of the swinging movement of the membrane-distal domain A2. The movement of this domain involves conformational changes in two flexible loops (loop A, residues 243–264, and loop B, residues 324–341) which are rich in proline and glycine residues and connect domain A2 to domains C1 and B2. It is proposed that the movement of this domain is related to the ATPase activity of EccB1 and its homologues, as well as to the substrate transport of ESX secretion systems.

scholarly journals The Mycobacterium tuberculosis Phagosome in Human Macrophages Is Isolated from the Host Cell Cytoplasm

2002 ◽  
Vol 70 (10) ◽  
pp. 5800-5807 ◽  
Author(s):  
Daniel L. Clemens ◽  
Bai-Yu Lee ◽  
Marcus A. Horwitz
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Host Cell ◽  
Fluorescent Protein ◽  
Medium Size ◽  
Immunogold Electron Microscopy ◽  
Human Macrophages ◽  
Fab Fragments ◽  
Green Fluorescent ◽  
Major Surface ◽  
Phagosomal Membrane

ABSTRACT Knowledge of whether Mycobacterium tuberculosis resides within a relatively impermeable membrane-bound vacuole or is free within the cytoplasm within its host cell is central to an understanding of the immunobiology of this intracellular parasite but is a matter of controversy. To explore this issue, we assessed the accessibility of medium-size protein molecules (Fab fragments of 50,000 Da) to M. tuberculosis within human macrophages. We infected the macrophages with wild-type or green fluorescent protein-expressing M. tuberculosis, microinjected Fab fragments directed against a major surface antigen of M. tuberculosis into the host cell, and assayed the accessibility of the bacteria to the Fab fragments by both immunofluorescence microscopy and immunogold electron microscopy. Whereas microinjected intact immunoglobulin G molecules against cytoplasmic early endosomal antigen 1 readily stained this antigen, microinjected Fab fragments against M. tuberculosis did not stain the bacterium within its phagosome. In contrast, microinjected Fab fragments against Listeria monocytogenes, an intracellular bacterium known to permeabilize its phagosomal membrane, strongly stained this bacterium. Our study shows that M. tuberculosis resides in an isolated phagosome that is relatively impermeable to cytoplasmic constituents.

scholarly journals The Whole-Genome Sequence of Plasmid-Bearing Staphylococcus argenteus Strain B3-25B from Retail Beef Liver Encodes the Type VII Secretion System and Several Virulence Factors

2019 ◽  
Vol 8 (45) ◽  
Author(s):  
Leena Neyaz ◽  
Anand B. Karki ◽  
Mohamed K. Fakhr
Keyword(s):  
Virulence Factors ◽  
Genome Sequence ◽  
Secretion System ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Circular Chromosome ◽  
Beef Liver ◽  
Content Type ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

The whole-genome sequence of Staphylococcus argenteus strain B3-25B, isolated from retail beef liver, comprises a circular chromosome (2,676,222 bp) and a single plasmid (21,570 bp). The chromosome harbors genes encoding the type VII secretion system and several virulence factors.

scholarly journals Structure and dynamics of the ESX-5 type VII secretion system of Mycobacterium tuberculosis

2020 ◽  
Author(s):  
Catalin M. Bunduc ◽  
Dirk Fahrenkamp ◽  
Jiri Wald ◽  
Roy Ummels ◽  
Wilbert Bitter ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protein Transport ◽  
Cell Envelope ◽  
Transmembrane Helix ◽  
Transport Systems ◽  
Secretion Systems ◽  
Type Vii Secretion ◽  
Membrane Complex ◽  
Type Vii Secretion System ◽  
Inner Membrane Complex

AbstractMycobacterium tuberculosis causes one of the most important infectious diseases in humans, leading to 1.5 million deaths every year. Specialized protein transport systems, called type VII secretion systems (T7SSs), are central for its virulence, but also crucial for nutrient and metabolite transport across the mycobacterial cell envelope. Here we present the first structure of an intact T7SS inner membrane complex of M. tuberculosis. We show how the 2.32 MDa, 165 transmembrane helices-containing ESX-5 assembly is restructured and stabilized as a trimer of dimers by the MycP5 protease. A trimer of MycP5 caps a central periplasmic dome-like chamber formed by three EccB5 dimers, with the proteolytic sites facing towards the cavity. This chamber suggests a central secretion and processing conduit. Complexes without MycP5 show disruption of the EccB5 periplasmic assembly and increased flexibility, highlighting the importance of this component for complex integrity. Beneath the EccB5-MycP5 chamber, dimers of the EccC5 ATPase assemble into three four-transmembrane helix bundles, which together seal the potential central secretion channel. Individual cytoplasmic EccC5 domains adopt two distinctive conformations, likely reflecting different secretion states. Our work suggests a novel mechanism of protein transport and provides a structural scaffold to aid drug development against the major human pathogen.

scholarly journals A Point Mutation in the Two-Component Regulator PhoP-PhoR Accounts for the Absence of Polyketide-Derived Acyltrehaloses but Not That of Phthiocerol Dimycocerosates in Mycobacterium tuberculosis H37Ra

2007 ◽  
Vol 190 (4) ◽  
pp. 1329-1334 ◽  
Author(s):  
Marie-Laure Chesne-Seck ◽  
Nathalie Barilone ◽  
Frédéric Boudou ◽  
Jesús Gonzalo Asensio ◽  
Pappachan E. Kolattukudy ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Point Mutation ◽  
Laboratory Strain ◽  
Base Substitution ◽  
Binding Region ◽  
Knock Out ◽  
Virulence Attenuation ◽  
Two Component ◽  
Mouse Model Of Infection ◽  
Phthiocerol Dimycocerosates

ABSTRACT Similarities between Mycobacterium tuberculosis phoP-phoR mutants and the attenuated laboratory strain M. tuberculosis H37Ra in terms of morphological and cytochemical properties, lipid content, gene expression and virulence attenuation prompted us to analyze the functionality of this two-component regulator in the latter strain. Sequence analysis revealed a base substitution resulting in a one-amino-acid change in the likely DNA-binding region of PhoP in H37Ra relative to H37Rv. Using gel-shift assays, we show that this mutation abrogates the ability of the H37Ra PhoP protein to bind to a 40-bp segment of its own promoter. Consistent with this result, the phoP gene from H37Rv but not that from H37Ra was able to restore the synthesis of sulfolipids, diacyltrehaloses and polyacyltrehaloses in an isogenic phoP-phoR knock-out mutant of M. tuberculosis Moreover, complementation of H37Ra with phoP from H37Rv fully restored sulfolipid, diacyltrehalose and polyacyltrehalose synthesis, clearly indicating that the lack of production of these lipids in H37Ra is solely due to the point mutation in phoP. Using a pks2-3/4 knock-out mutant of M. tuberculosis H37Rv, evidence is further provided that the above-mentioned polyketide-derived acyltrehaloses do not significantly contribute to the virulence of the tubercle bacillus in a mouse model of infection. Reasons for the attenuation of H37Ra thus most likely stand in other virulence factors, many of which are expected to belong to the PhoP regulon and another of which, unrelated to PhoP, appears to be the lack of production of phthiocerol dimycocerosates in this strain.

scholarly journals CFP-10 from Mycobacterium tuberculosis Selectively Activates Human Neutrophils through a Pertussis Toxin-Sensitive Chemotactic Receptor

2014 ◽  
Vol 83 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Amanda Welin ◽  
Halla Björnsdottir ◽  
Malene Winther ◽  
Karin Christenson ◽  
Tudor Oprea ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Pertussis Toxin ◽  
Human Neutrophils ◽  
Content Type ◽  
Chaperone Function ◽  
Type Vii Secretion ◽  
Chaperone Protein ◽  
Type Vii Secretion System ◽  
G Protein Coupled

Upon infection withMycobacterium tuberculosis, neutrophils are massively recruited to the lungs, but the role of these cells in combating the infection is poorly understood. Through a type VII secretion system,M. tuberculosisreleases a heterodimeric protein complex, containing a 6-kDa early secreted antigenic target (ESAT-6) and a 10-kDa culture filtrate protein (CFP-10), that is essential for virulence. Whereas the ESAT-6 component possesses multiple virulence-related activities, no direct biological activity of CFP-10 has been shown, and CFP-10 has been described as a chaperone protein for ESAT-6. We here show that the ESAT-6:CFP-10 complex induces a transient release of Ca2+from intracellular stores in human neutrophils. Surprisingly, CFP-10 rather than ESAT-6 was responsible for triggering the Ca2+response, in a pertussis toxin-sensitive manner, suggesting the involvement of a G-protein-coupled receptor. In line with this, the response was accompanied by neutrophil chemotaxis and activation of the superoxide-producing NADPH-oxidase. Neutrophils were unique among leukocytes in responding to CFP-10, as monocytes and lymphocytes failed to produce a Ca2+signal upon stimulation with theM. tuberculosisprotein. Hence, CFP-10 may contribute specifically to neutrophil recruitment and activation duringM. tuberculosisinfection, representing a novel biological role for CFP-10 in the ESAT-6:CFP-10 complex, beyond the previously described chaperone function.

scholarly journals A heterodimer of EsxA and EsxB is involved in sporulation and is secreted by a type VII secretion system in Streptomyces coelicolor

Microbiology ◽  
2010 ◽  
Vol 156 (6) ◽  
pp. 1719-1729 ◽  
Author(s):  
Sandra Akpe San Roman ◽  
Paul D. Facey ◽  
Lorena Fernandez-Martinez ◽  
Caridad Rodriguez ◽  
Carlos Vallin ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Streptomyces Coelicolor ◽  
Regulatory Gene ◽  
Secretion System ◽  
Model Species ◽  
Type Vii Secretion ◽  
Expression Of Genes ◽  
Dna Contents ◽  
Aerial Hyphae ◽  
Type Vii Secretion System

An esx locus, related to the multiple esx loci of Mycobacterium tuberculosis, is conserved in all sequenced Streptomyces genomes, where it is associated with the developmental regulatory gene bldB. Here we demonstrate that the esxBA operon, comprising part of the locus, has a novel morphogenetic function in the model species Streptomyces coelicolor. This operon encodes two proteins belonging to the WXG-100 superfamily that can form a heterodimer and are secreted in the absence of signal sequences. A mutation in esxBA results in a delay in sporulation, with eventual development of aerial hyphae with chains of abnormally sized spore compartments possessing irregular DNA contents. During early sporulation, expression of the operon is elevated in a bldB mutant. Other genes in the locus, notably SCO5734 and SCO5721, encode components of a type VII secretion system. Disruption of either of these genes prevents secretion of EsxAB but has no effect on sporulation. To explain the morphogenetic function of EsxAB, we propose that the heterodimer sequesters a regulator of expression of genes involved in nucleoid organization during sporulation.

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