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Journal articleTenland E, Pochert A, Krishnan N, et al., 2019,
Effective delivery of the anti-mycobacterial peptide NZX in mesoporous silica nanoparticles
, PLoS ONE, Vol: 14, ISSN: 1932-6203BackgroundIntracellular delivery of antimicrobial agents by nanoparticles, such as mesoporous silica particles (MSPs), offers an interesting strategy to treat intracellular infections. In tuberculosis (TB), Mycobacterium tuberculosis avoids components of the immune system by residing primarily inside alveolar macrophages, which are the desired target for TB therapy.Methods and findingsWe have previously identified a peptide, called NZX, capable of inhibiting both clinical and multi-drug resistant strains of M. tuberculosis at therapeutic concentrations. In this study we analysed the potential of MSPs containing NZX for the treatment of tuberculosis. The MSPs released functional NZX gradually into simulated lung fluid and the peptide filled MSPs were easily taken up by primary macrophages. In an intracellular infection model, the peptide containing particles showed increased mycobacterial killing compared to free peptide. The therapeutic potential of peptide containing MSPs was investigated in a murine infection model, showing that MSPs preserved the effect to eliminate M. tuberculosis in vivo.ConclusionsIn this study we found that loading the antimicrobial peptide NZX into MSPs increased the inhibition of intracellular mycobacteria in primary macrophages and preserved the ability to eliminate M. tuberculosis in vivo in a murine model. Our studies provide evidence for the feasibility of using MSPs for treatment of tuberculosis.
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Journal articleLevanova N, Mattheis C, Carson D, et al., 2019,
The Legionella effector LtpM is a new type of phosphoinositide-activated glucosyltransferase
, JOURNAL OF BIOLOGICAL CHEMISTRY, Vol: 294, Pages: 2862-2879 -
Journal articleGomez-Valero L, Rusniok C, Carson D, et al., 2019,
More than 18,000 effectors in the Legionella genus genome provide multiple, independent combinations for replication in human cells
, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 116, Pages: 2265-2273, ISSN: 0027-8424 -
Journal articlePee CJE, Pader V, Ledger EVK, et al., 2019,
A FASII inhibitor prevents staphylococcal evasion of daptomycin by inhibiting phospholipid decoy production
, Antimicrobial Agents and Chemotherapy, Vol: 63, Pages: 1-18, ISSN: 0066-4804Daptomycin is a treatment of last resort for serious infections caused by drug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus. We have shown recently that S. aureus can evade daptomycin by releasing phospholipid decoys that sequester and inactivate the antibiotic, leading to treatment failure. Since phospholipid release occurs via an active process, we hypothesised that it could be inhibited, thereby increasing daptomycin efficacy. To identify opportunities for therapeutic interventions that block phospholipid release, we first determined how the host environment influenced the release of phospholipids and inactivation of daptomycin by S. aureus The addition of certain host-associated fatty acids to the growth medium enhanced phospholipid release. However, in serum, the sequestration of fatty acids by albumin restricted their availability to S. aureus sufficiently to prevent their use in the generation of released phospholipids. This finding implied that in host tissues S. aureus may be completely dependent upon endogenous phospholipid biosynthesis to generate lipids for release, providing a target for therapeutic intervention. To test this, we exposed S. aureus to AFN-1252, an inhibitor of the staphylococcal FASII fatty acid biosynthetic pathway, together with daptomycin. AFN-1252 efficiently blocked daptomycin-induced phospholipid decoy production, even in the case of isolates resistant to AFN-1252, which prevented the inactivation of daptomycin and resulted in sustained bacterial killing. In turn, daptomycin prevented the fatty acid-dependent emergence of AFN-1252-resistant isolates in vitro In summary, AFN-1252 significantly enhances daptomycin activity against S. aureusin vitro by blocking the production of phospholipid decoys, whilst daptomycin blocks the emergence of resistance to AFN-1252.
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Journal articleBallinger E, Mosior J, Hartman T, et al., 2019,
Opposing reactions in coenzyme A metabolism sensitize Mycobacterium tuberculosis to enzyme inhibition
, Science, Vol: 363, ISSN: 0036-8075INTRODUCTIONMycobacterium tuberculosis (Mtb) is the leading global cause of lethal infection in humans and accounts for the largest number of drug-resistant infections by a single bacterial pathogen. Resistance is particularly high against the most widely prescribed tuberculosis (TB) drug, isoniazid. Isoniazid blocks synthesis of mycolates, ultralong-chain fatty acids that provide structure to the waxy coat that surrounds Mtb cells and are incorporated into some of its virulence lipids. There is currently no known method to block the synthesis of both mycolates and nonmycolate-containing virulence lipids of Mtb at a single point of control. One such control point is phosphopantetheinyl transferase (PptT). PptT transfers 4′-phosphopantetheine (Ppt) from coenzyme A (CoA) to acyl carrier proteins (ACPs) that synthesize the lipids critical to Mtb structural integrity and virulence.RATIONALETB drug discovery often begins with whole-cell, high-throughput screens that yield compounds that kill Mtb by unknown means. Selection of Mtb mutants resistant to these compounds can indicate candidate targets of the active compound, but experimental validation is required to confirm the functionally relevant target, which is often an enzyme. A suitable target must be essential in vivo, such that its inhibition precludes development of TB in animal models, but also “vulnerable,” meaning that a pharmacologically attainable level of inhibition should be lethal to Mtb within a patient. The inhibitor should act only on Mtb, and resistance should be rare.RESULTSScreening a chemical library revealed an amidino-urea compound called “8918” that kills Mtb, including drug-resistant clinical isolates. 8918 inhibits Mtb in mice and spares other bacteria, yeast, and mammalian cells.Rare Mtb mutants resistant to 8918 bore a point mutation in the PptT gene rv2794c, altering an amino acid residue overlying the Ppt-binding pocket of PptT. When Mtb carried the mutant allel
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Journal articleAhmad L, Mashbat B, Leung C, et al., 2019,
Human TANK-binding kinase 1 is required for early autophagy induction upon herpes simplex virus 1 infection
, Journal of Allergy and Clinical Immunology, Vol: 143, Pages: 765-769.e7, ISSN: 0091-6749 -
Journal articleMullish BH, Ghani R, McDonald J, et al., 2019,
Faecal microbiota transplant for eradication of multidrug-resistant Enterobacteriaceae: a lesson in applying best practice? Re: 'A five-day course of oral antibiotics followed by faecal transplantation to eradicate carriage of multidrug-resistant Enterobacteriaceae: A Randomized Clinical Trial'
, Clinical Microbiology and Infection, Vol: 25, Pages: 912-913, ISSN: 1198-743X -
Journal articleTosi T, Hoshiga F, Millership C, et al., 2019,
Inhibition of the Staphylococcus aureus c-di-AMP cyclase DacA by direct interaction with the phosphoglucosamine mutase GlmM
, PLoS Pathogens, Vol: 15, Pages: 1-28, ISSN: 1553-7366c-di-AMP is an important second messenger molecule that plays a pivotal role in regulating fundamental cellular processes, including osmotic and cell wall homeostasis in many Gram-positive organisms. In the opportunistic human pathogen Staphylococcus aureus, c-di-AMP is produced by the membrane-anchored DacA enzyme. Inactivation of this enzyme leads to a growth arrest under standard laboratory growth conditions and a re-sensitization of methicillin-resistant S. aureus (MRSA) strains to ß-lactam antibiotics. The gene coding for DacA is part of the conserved three-gene dacA/ybbR/glmM operon that also encodes the proposed DacA regulator YbbR and the essential phosphoglucosamine mutase GlmM, which is required for the production of glucosamine-1-phosphate, an early intermediate of peptidoglycan synthesis. These three proteins are thought to form a complex in vivo and, in this manner, help to fine-tune the cellular c-di-AMP levels. To further characterize this important regulatory complex, we conducted a comprehensive structural and functional analysis of the S. aureus DacA and GlmM enzymes by determining the structures of the S. aureus GlmM enzyme and the catalytic domain of DacA. Both proteins were found to be dimers in solution as well as in the crystal structures. Further site-directed mutagenesis, structural and enzymatic studies showed that multiple DacA dimers need to interact for enzymatic activity. We also show that DacA and GlmM form a stable complex in vitro and that S. aureus GlmM, but not Escherichia coli or Pseudomonas aeruginosa GlmM, acts as a strong inhibitor of DacA function without the requirement of any additional cellular factor. Based on Small Angle X-ray Scattering (SAXS) data, a model of the complex revealed that GlmM likely inhibits DacA by masking the active site of the cyclase and preventing higher oligomer formation. Together these results provide an important mechanistic insight into how c-di-AMP production can be regulated in the cell.
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Journal articlePolo LM, Xu Y, Hornyak P, et al., 2019,
Efficient single-strand break repair requires binding to both poly(ADP-Ribose) and DNA by the central BRCT domain of XRCC1
, Cell Reports, Vol: 26, Pages: 573-581.e5, ISSN: 2211-1247XRCC1 accelerates repair of DNA single-strand breaks by acting as a scaffold protein for the recruitment of Polβ, LigIIIα, and end-processing factors, such as PNKP and APTX. XRCC1 itself is recruited to DNA damage through interaction of its central BRCT domain with poly(ADP-ribose) chains generated by PARP1 or PARP2. XRCC1 is believed to interact directly with DNA at sites of damage, but the molecular basis for this interaction within XRCC1 remains unclear. We now show that the central BRCT domain simultaneously mediates interaction of XRCC1 with poly(ADP-ribose) and DNA, through separate and non-overlapping binding sites on opposite faces of the domain. Mutation of residues within the DNA binding site, which includes the site of a common disease-associated human polymorphism, affects DNA binding of this XRCC1 domain in vitro and impairs XRCC1 recruitment and retention at DNA damage and repair of single-strand breaks in vivo.
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Journal articleAndreasen M, Meisl G, Taylor JD, et al., 2019,
Physical determinants of amyloid assembly in biofilm formation
, mBio, Vol: 10, ISSN: 2150-7511A wide range of bacterial pathogens have been shown to form biofilms, which significantly increase their resistance to environmental stresses, such as antibiotics, and are thus of central importance in the context of bacterial diseases. One of the major structural components of these bacterial biofilms are amyloid fibrils, yet the mechanism of fibril assembly and its importance for biofilm formation are currently not fully understood. By studying fibril formation in vitro, in a model system of two common but unrelated biofilm-forming proteins, FapC from Pseudomonas fluorescens and CsgA from Escherichia coli, we found that the two proteins have a common aggregation mechanism. In both systems, fibril formation proceeds via nucleated growth of linear fibrils exhibiting similar measured rates of elongation, with negligible fibril self-replication. These similarities between two unrelated systems suggest that convergent evolution plays a key role in tuning the assembly kinetics of functional amyloid fibrils and indicates that only a narrow window of mechanisms and assembly rates allows for successful biofilm formation. Thus, the amyloid assembly reaction is likely to represent a means for controlling biofilm formation, both by the organism and by possible inhibitory drugs.IMPORTANCE Biofilms are generated by bacteria, embedded in the formed extracellular matrix. The biofilm's function is to improve the survival of a bacterial colony through, for example, increased resistance to antibiotics or other environmental stresses. Proteins secreted by the bacteria act as a major structural component of this extracellular matrix, as they self-assemble into highly stable amyloid fibrils, making the biofilm very difficult to degrade by physical and chemical means once formed. By studying the self-assembly mechanism of the fibrils from their monomeric precursors in two unrelated bacteria, our experimental and theoretical approaches shed light on the mechanism of functional amyloid as
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