scholarly journals Mycobacterium tuberculosis modifies cell wall carbohydrates during biofilm growth with a concomitant reduction in complement activation

2021 ◽  
Author(s):  
Thomas Keating ◽  
Samuel Lethbridge ◽  
Stephen R. Thomas ◽  
Luke J. Alderwick ◽  
Stephen C. Taylor ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Complement Activation ◽  
Lectin Pathway ◽  
Classical Pathway ◽  
Cellular Mechanisms ◽  
Biofilm Growth ◽  
Concomitant Reduction ◽  
Mycobacterial Cell Wall ◽  
New Vaccines

SummaryThere is an urgent need for drugs, new vaccines, and diagnostics for TB. It is recognised that research needed for the development of new vaccines for TB needs to be underpinned by understanding both the molecular and cellular mechanisms of host-pathogen interactions and how the immune response can be modulated to achieve protection with the use of a new vaccine for TB. Complement interacts with and orchestrates many aspects of the innate and adaptive immune responses and activation by Mycobacterium tuberculosis can be triggered by all three pathways. However, little is known about the contribution of each of these pathways during TB disease, particularly with respect to mycobacterial phenotype. There is strong evidence for extracellular communities of M. tuberculosis during TB disease (biofilms) that are found in the acellular rim of granulomas. These biofilms have been observed in cavities in lung resections from TB patients and are likely to be present in post-primary TB episodes in necrotic lesions. Our study aimed to understand more about the interactions between M. tuberculosis biofilms and complement activation, to determine which mycobacterial cell wall components are altered during biofilm growth, and how their alteration contributes to modulation of the complement response. We show that the lectin pathway has a reduced role compared to the classical pathway in initiating complement activation in biofilm bacteria. Analyses of the M. tuberculosis biofilm cell wall carbohydrate fractions revealed that there was reduced α-glucan compared to planktonically-grown bacteria. Reduced C3b/iC3b deposition directly onto biofilm carbohydrates was observed which was consistent with both the observed reduction of C3b/iC3b deposition on biofilm bacilli and a reduction in the contribution of the lectin pathway in initiating complement activation on whole bacteria from biofilms, compared to planktonically-grown bacteria.

scholarly journals Mycobacterium tuberculosis modifies cell wall carbohydrates during biofilm growth with a concomitant reduction in complement activation

2021 ◽  
pp. 100065
Author(s):  
Thomas Keating ◽  
Samuel Lethbridge ◽  
Jon C. Allnutt ◽  
Charlotte L. Hendon-Dunn ◽  
Stephen R. Thomas ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Complement Activation ◽  
Biofilm Growth ◽  
Concomitant Reduction ◽  
Cell Wall Carbohydrates

scholarly journals The Lectin Pathway of Complement Activation in Patients with Systemic Lupus Erythematosus

2018 ◽  
Vol 45 (8) ◽  
pp. 1136-1144 ◽  
Author(s):  
Anne Troldborg ◽  
Steffen Thiel ◽  
Marten Trendelenburg ◽  
Justa Friebus-Kardash ◽  
Josephine Nehring ◽  
...  
Keyword(s):  
Systemic Lupus Erythematosus ◽  
Pattern Recognition ◽  
Disease Activity ◽  
Lupus Erythematosus ◽  
Complement Activation ◽  
Lectin Pathway ◽  
Classical Pathway ◽  
Systemic Lupus ◽  
Over Time ◽  
Repeated Samples

Objective.The pathogenesis of systemic lupus erythematosus (SLE) involves complement activation. Activation of complement through the classical pathway (CP) is well established. However, complement activation through pattern recognition not only happens through the CP, but also through the lectin pathway (LP). We investigated the hypothesis that the LP is activated in SLE and involved in the pathogenesis of the disease.Methods.Using immunoassays developed in-house, we measured concentrations of LP proteins in a cohort of 372 patients with SLE and 170 controls. We estimated complement activation measuring total C3, and investigated whether LP protein concentrations were associated with complement activation and disease activity. Protein changes and disease activity over time were assessed in a cohort of 52 patients with SLE followed with repeated samples over a 5-year period.Results.Concentrations of LP proteins in SLE were altered compared with controls. The differences observed in LP proteins associated with complement activation were reflected by a decrease in total C3. The pattern recognition molecules (M-ficolin, CL-L1, and CL-K1), the serine protease (MASP-3), and the associated protein (MAp19) displayed a negative correlation with disease activity. Changes in MASP-2 concentrations over time correlated significantly with increased disease activity. Association between active proteinuria and serum concentration was observed for MASP-3 and MAp19.Conclusion.In patients with SLE, we measured specific changes in LP proteins that are associated with complement activation and disease activity, indicating that the LP is activated in patients with SLE. These novel findings substantiate the involvement of the LP in SLE.

Structure of the Mycobacterium tuberculosis OmpATb protein: A model of an oligomeric channel in the mycobacterial cell wall

2010 ◽  
Vol 79 (2) ◽  
pp. 645-661 ◽  
Author(s):  
Yinshan Yang ◽  
Daniel Auguin ◽  
Stéphane Delbecq ◽  
Emilie Dumas ◽  
Gérard Molle ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Protein A ◽  
Mycobacterial Cell ◽  
Mycobacterial Cell Wall

scholarly journals Mycobacterium tuberculosis Lipomannan Induces Apoptosis and Interleukin-12 Production in Macrophages

2004 ◽  
Vol 72 (4) ◽  
pp. 2067-2074 ◽  
Author(s):  
D. N. Dao ◽  
L. Kremer ◽  
Y. Guérardel ◽  
A. Molano ◽  
W. R. Jacobs ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Function Analysis ◽  
Specific Interaction ◽  
Interleukin 12 ◽  
Mycobacterial Species ◽  
Immunostimulatory Activity ◽  
Mycobacterium Chelonae ◽  
Toll Like Receptor 2 ◽  
Mycobacterial Cell Wall

ABSTRACT The mycobacterial cell wall component lipoarabinomannan (LAM) has been described as a virulence factor of Mycobacterium tuberculosis, and modification of the terminal arabinan residues of this compound with mannose caps (producing mannosyl-capped LAM [ManLAM]) in M. tuberculosis or with phosphoinositol caps (producing phosphoinositol-capped LAM [PILAM]) in Mycobacterium smegmatis has been implicated in various functions associated with these lipoglycans. A structure-function analysis was performed by using LAMs and their biosynthetic precursor lipomannans (LMs) isolated from different mycobacterial species on the basis of their capacity to induce the production of interleukin-12 (IL-12) and/or apoptosis of macrophage cell lines. Independent of the mycobacterial species, ManLAMs did not induce IL-12 gene expression or apoptosis of macrophages, whereas PILAMs induced IL-12 secretion and apoptosis. Interestingly, uncapped LAM purified from Mycobacterium chelonae did not induce IL-12 secretion or apoptosis. Furthermore, LMs, independent of their mycobacterial origins, were potent inducers of IL-12 and apoptosis. The precursor of LM, phosphatidyl-myo-inositol dimannoside, had no activity, suggesting that the mannan core of LM was required for the activity of LM. The specific interaction of LM with Toll-like receptor 2 (TLR-2) but not with TLR-4 suggested that these responses were mediated via the TLR-2 signaling pathway. Our experiments revealed an important immunostimulatory activity of the biosynthetic LAM precursor LM. The ratio of LAM to LM in the cell wall of mycobacteria may be an important determinant of virulence, and enzymes that modify LM could provide targets for development of antituberculosis drugs and for derivation of attenuated strains of M. tuberculosis.

scholarly journals Multiple Mutations in Mycobacterium tuberculosis MmpL3 Increase Resistance to MmpL3 Inhibitors

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Matthew B. McNeil ◽  
Theresa O’Malley ◽  
Devon Dennison ◽  
Catherine D. Shelton ◽  
Bjorn Sunde ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Drug Targets ◽  
New Drugs ◽  
Content Type ◽  
Mechanism Of Resistance ◽  
Primary Mechanism ◽  
Resistant Mutants ◽  
Mycobacterial Cell Wall

ABSTRACT The Mycobacterium tuberculosis protein MmpL3 performs an essential role in cell wall synthesis, since it effects the transport of trehalose monomycolates across the inner membrane. Numerous structurally diverse pharmacophores have been identified as inhibitors of MmpL3 largely based on the identification of resistant isolates with mutations in MmpL3. For some compounds, it is possible there are different primary or secondary targets. Here, we have investigated resistance to the spiral amine class of compounds. Isolation and sequencing of resistant mutants demonstrated that all had mutations in MmpL3. We hypothesized that if additional targets of this pharmacophore existed, then successive rounds to generate resistant isolates might reveal mutations in other loci. Since compounds were still active against resistant isolates, albeit with reduced potency, we isolated resistant mutants in this background at higher concentrations. After a second round of isolation with the spiral amine, we found additional mutations in MmpL3. To increase our chance of finding alternative targets, we ran a third round of isolation using a different molecule scaffold (AU1235, an adamantyl urea). Surprisingly, we obtained further mutations in MmpL3. Multiple mutations in MmpL3 increased the level and spectrum of resistance to different pharmacophores but did not incur a fitness cost in vitro. These results support the hypothesis that MmpL3 is the primary mechanism of resistance and likely target for these pharmacophores. IMPORTANCE Mycobacterium tuberculosis is a major global human pathogen, and new drugs and new drug targets are urgently required. Cell wall biosynthesis is a major target of current tuberculosis drugs and of new agents under development. Several new classes of molecules appear to have the same target, MmpL3, which is involved in the export and synthesis of the mycobacterial cell wall. However, there is still debate over whether MmpL3 is the primary or only target for these classes. We wanted to confirm the mechanism of resistance for one series. We identified mutations in MmpL3 which led to resistance to the spiral amine series. High-level resistance to these compounds and two other series was conferred by multiple mutations in the same protein (MmpL3). These mutations did not reduce growth rate in culture. These results support the hypothesis that MmpL3 is the primary mechanism of resistance and likely target for these pharmacophores.

scholarly journals Pleiotropic Effects of Cell Wall Amidase LytA on Streptococcus pneumoniae Sensitivity to the Host Immune Response

2014 ◽  
Vol 83 (2) ◽  
pp. 591-603 ◽  
Author(s):  
Elisa Ramos-Sevillano ◽  
Ana Urzainqui ◽  
Susana Campuzano ◽  
Miriam Moscoso ◽  
Fernando González-Camacho ◽  
...  
Keyword(s):  
Immune Response ◽  
Cell Wall ◽  
Streptococcus Pneumoniae ◽  
Complement Activation ◽  
Host Immune Response ◽  
Factor H ◽  
Pleiotropic Effects ◽  
Complement C3 ◽  
Classical Pathway ◽  
Content Type

The complement system is a key component of the host immune response for the recognition and clearance ofStreptococcus pneumoniae. In this study, we demonstrate that the amidase LytA, the main pneumococcal autolysin, inhibits complement-mediated immunity independently of effects on pneumolysin by a complex process of impaired complement activation, increased binding of complement regulators, and direct degradation of complement C3. The use of human sera depleted of either C1q or factor B confirmed that LytA prevented activation of both the classical and alternative pathways, whereas pneumolysin inhibited only the classical pathway. LytA prevented binding of C1q and the acute-phase protein C-reactive protein toS. pneumoniae, thereby reducing activation of the classical pathway on the bacterial surface. In addition, LytA increased recruitment of the complement downregulators C4BP and factor H to the pneumococcal cell wall and directly cleaved C3b and iC3b to generate degradation products. As a consequence, C3b deposition and phagocytosis increased in the absence of LytA and were markedly enhanced for thelytA plydouble mutant, confirming that a combination of LytA and Ply is essential for the establishment of pneumococcal pneumonia and sepsis in a murine model of infection. These data demonstrate that LytA has pleiotropic effects on complement activation, a finding which, in combination with the effects of pneumolysin on complement to assist with pneumococcal complement evasion, confirms a major role of both proteins for the full virulence of the microorganism during septicemia.

scholarly journals Synthesis and Biological Aspects of Mycolic Acids: An Important Target AgainstMycobacterium tuberculosis

2008 ◽  
Vol 8 ◽  
pp. 720-751 ◽  
Author(s):  
Marcus Vinícius Nora de Souza ◽  
Marcelle de Lima Ferreira ◽  
Alessandra Campbell Pinheiro ◽  
Maurício Frota Saraiva ◽  
Mauro Vieira de Almeida ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Cell Walls ◽  
Important Class ◽  
Cellular Targets ◽  
Mycolic Acids ◽  
Important Target ◽  
Novel Drugs ◽  
Biological Aspects ◽  
Mycobacterial Cell Wall

Mycolic acids are an important class of compounds, basically found in the cell walls of a group of bacteria known as mycolata taxon, exemplified by the most famous bacteria of this group, theMycobacterium tuberculosis(M. tb.), the agent responsible for the disease known as tuberculosis (TB). Mycolic acids are important for the survival of M. tb. For example, they are able to help fight against hydrophobic drugs and dehydration, and also allow this bacterium to be more effective in the host's immune system by growing inside macrophages. Due to the importance of the mycolic acids for maintenance of the integrity of the mycobacterial cell wall, these compounds become attractive cellular targets for the development of novel drugs against TB. In this context, the aim of this article is to highlight the importance of mycolic acids in drug discovery.

Identification of inhibitors targeting Mycobacterium tuberculosis cell wall biosynthesis via dynamic combinatorial chemistry

2017 ◽  
Vol 53 (77) ◽  
pp. 10632-10635 ◽  
Author(s):  
Jian Fu ◽  
Huixiao Fu ◽  
Marc Dieu ◽  
Iman Halloum ◽  
Laurent Kremer ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Combinatorial Chemistry ◽  
Cell Wall Biosynthesis ◽  
Combinatorial Approach ◽  
Dynamic Combinatorial Chemistry ◽  
Mycobacterial Cell ◽  
Essential Enzyme ◽  
Mycobacterial Cell Wall

In this study, we report a dynamic combinatorial approach along with highly efficient in situ screening to identify inhibitors of UDP-galactopyranose mutase (UGM), an essential enzyme involved in mycobacterial cell wall biosynthesis.

scholarly journals Functional Complementation of the Essential Gene fabG1 of Mycobacterium tuberculosis by Mycobacterium smegmatis fabG but Not Escherichia coli fabG

2007 ◽  
Vol 189 (10) ◽  
pp. 3721-3728 ◽  
Author(s):  
Tanya Parish ◽  
Gretta Roberts ◽  
Francoise Laval ◽  
Merrill Schaeffer ◽  
Mamadou Daffé ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Mycobacterium Smegmatis ◽  
Essential Gene ◽  
Permeability Barrier ◽  
Type I ◽  
Type Ii ◽  
Mycolic Acids ◽  
Mycobacterial Cell Wall

ABSTRACT Mycolic acids are a key component of the mycobacterial cell wall, providing structure and forming a major permeability barrier. In Mycobacterium tuberculosis mycolic acids are synthesized by type I and type II fatty acid synthases. One of the enzymes of the type II system is encoded by fabG1. We demonstrate here that this gene can be deleted from the M. tuberculosis chromosome only when another functional copy is provided elsewhere, showing that under normal culture conditions fabG1 is essential. FabG1 activity can be replaced by the corresponding enzyme from the closely related species Mycobacterium smegmatis but not by the enzyme from Escherichia coli. M. tuberculosis carrying FabG from M. smegmatis showed no phenotypic changes, and both the mycolic acids and cell wall permeability were unchanged. Thus, M. tuberculosis and M. smegmatis enzymes are interchangeable and do not control the lengths and types of mycolic acids synthesized.

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