Brianna Dalesandro

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Antimicrobial activity, membrane interaction and stability of the D-amino acid substituted analogs of antimicrobial peptide W3R6.

J Photochem Photobiol B. 2019 Oct 13;200:111645

Authors: Li Y, Liu T, Liu Y, Tan Z, Ju Y, Yang Y, Dong W

Abstract
Antimicrobial peptide W3R6 was derived from chensinin-1b and showed potential as a novel antibiotics. However, W3R6 was susceptible to protease cleavage, which limited its therapeutic application. To improve the proteolytic resistance of W3R6, D-amino acids were incorporated into its sequence by specific amino acid substitution or whole sequence substitution according to the specificity of the cleavage site. In this study, partially substituted analog D-Arg-W3R6 and completely substituted D-enantiomer D-W3R6 were synthesized. The resistance of D-Arg-W3R6 and D-W3R6 to cleavage by the tested protease increased, particularly of D-W3R6. The antimicrobial activity of D-Arg-W3R6 was almost the same as that of the parent peptide W3R6, but the antimicrobial activity of D-W3R6 was slightly decreased. The hemolytic activity of both D-Arg-W3R6 and D-W3R6 was negligible. The CD spectrum of D-W3R6 exhibited symmetry with that of W3R6 in a membrane-mimetic environment. The membrane interaction between the D-amino acid substituted analogs and a real/mimic bacterial cell membrane was examined. The outer membrane depolarization, inner membrane permeability and dye leakage in three types of liposomes treated with D-Arg-W3R6 and D-W3R6 were not obviously different from W3R6, which could be due to the similar physical and chemical properties. In addition, these three peptides showed the binding ability with LPS micelles detected by ITC, and their ability to disrupt the LPS micelles was examined by DLS experiment and even neutralize the surface negative charge of E. coli cells. These results suggest that D-Arg-W3R6 is a promising antibiotic molecule.

PMID: 31671371 [PubMed - as supplied by publisher]

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Antigenic epitopes on the outer membrane protein A of Escherichia coli identified with single-chain variable fragment (scFv) antibodies.

Appl Microbiol Biotechnol. 2019 Jul;103(13):5285-5299

Authors: Mwale PF, Lee CH, Leu SJ, Lee YC, Wu HH, Lin LT, Lin TE, Huang YJ, Yang YY

Abstract
Bacterial meningitis is a severe disease that is fatal to one-third of patients. The major cause of meningitis in neonates is Escherichia coli (E. coli) K1. This bacterium synthesizes an outer membrane protein A (OmpA) that is responsible for the adhesion to (and invasion of) endothelial cells. Thus, the OmpA protein represents a potential target for developing diagnostic and therapeutic agents for meningitis. In this study, we expressed recombinant OmpA proteins with various molecular weights in E. coli. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was performed to check the molecular size of OmpA's full length (FL) and truncated proteins. OmpA-FL protein was purified for immunizing chickens to produce immunoglobulin yolk (IgY) antibodies. We applied phage display technology to construct antibody libraries (OmpA-FL scFv-S 1.1 × 107 and OmpA-FL scFv-L 5.01 × 106) to select specific anti-OmpA-FL scFv antibodies; these were characterized by their binding ability to recombinant or endogenous OmpA using ELISA, immunofluorescent staining, and confirmed with immunoblotting. We found 12 monoclonal antibodies that react to OmpA fragments; seven scFvs recognize fragments spanning amino acid (aa) residues 1-346, aa 1-287, aa 1-167, and aa 60-192, while five scFvs recognize fragments spanning aa 1-346 and aa 1-287 only. Two fragments (aa 246-346 and aa 287-346) were not recognized with any of the 12 scFvs. Together, the data suggest three antigenic epitopes (60 aa-160 aa, 161 aa-167 aa, 193 aa-245 aa) recognized by monoclonal antibodies. These scFv antibodies show strong reactivity against OmpA proteins. We believe that antibodies show promising diagnostic agents for E. coli K1 meningitis.

PMID: 31028439 [PubMed - indexed for MEDLINE]

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Identification of actinomycin D as a specific inhibitor of the alternative pathway of peptidoglycan biosynthesis.

J Antibiot (Tokyo). 2019 Oct 25;:

Authors: Ogasawara Y, Shimizu Y, Sato Y, Yoneda T, Inokuma Y, Dairi T

Abstract
Peptidoglycan is an indispensable component of bacterial cell walls. We recently discovered an alternative peptidoglycan biosynthetic pathway, which involves two enzymes, MurD2 and MurL, catalyzing the ligation of L-Glu to UDP-MurNAc-L-Ala and epimerization of the terminal L-Glu of the MurD2 product, respectively. Because the pathway operates in Xanthomonas oryze, a pathogen causing bacterial blight of rice, we searched for specific inhibitors from metabolites produced by actinomycetes to obtain a lead compound to function as an agrochemical. Actinomycin D was isolated from Streptomyces parvulus NBRC 13193 as a specific inhibitor of the pathway. In vitro analysis indicated that actinomycin D inhibited the MurD2 reaction.

PMID: 31654037 [PubMed - as supplied by publisher]

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Lysine-based Small Molecule Sensitizes Rifampicin and Tetracycline against Multidrug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa.

ACS Infect Dis. 2019 Oct 24;:

Authors: Konai MM, Haldar J

Abstract
The priority pathogen list published by the World Health Organization (WHO) has categorized carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa as the top two critical pathogens, and hence the development of novel antibacterial strategies to tackle such bacteria is highly necessary. Towards this aim, herein we report the efficacy of the combination of a lysine-based membrane-active small molecule, D-LANA-14 (D-lysine conjugated aliphatic norspermidine analogue bearing tetradecanoyl chain) and the obsolete/inactive antibiotics (such as, tetracycline and rifampicin) to combat these superbugs. The combination of D-LANA-14 and the antibiotics, tetracycline or rifampicin not only showed synergistic activity against growing planktonic cells of meropenem-resistant A. baumannii and P. aeruginosa clinical isolates, but was also capable of disrupting their established biofilms. More importantly, this synergistic effect was retained under in-vivo scenario, wherein the combination showed excellent efficacy in mice model of burn-wound infection with drastic reduction of bacterial burden. A combined treatment of D-LANA-14 (40 mg/kg) and rifampicin (40 mg/kg) showed 4.9 log and 4.0 log reduction in A. baumannii and P. aeruginosa viability, respectively. On the contrary, individual treatment of D-LANA-14 decreased bacterial burden by 2.3 log (A. baumannii) and 1.3 log (P. aeruginosa) and rifampicin reduced about 3.0 log (A. baumannii) and 1.6 log (P. aeruginosa). Owing to the membrane-active nature imparted by D-LANA-14, bacteria could not develop resistance against the combined treatment, whereas a high-level of resistance development was observed against the last resort Gram-negative antibiotic, colistin. Taken together, the results therefore indicate a great potential of this novel combination to be developed as therapeutic regimen to combat infections caused by critical Gram-negative pathogens.

PMID: 31646866 [PubMed - as supplied by publisher]

Scientists are developing a low cost, rapid diagnostic sensor test which aims to show the susceptibility of bacteria to antibiotics within 45 minutes.

Creating links: Building blocks equipped with an N‐hydroxysuccinimide and an ethynylphosphonamidate residue can be used as selective amine–thiol linkers with defined configuration. The high selectivity for cysteine can solve current issues of succinimidyl 4‐(N‐maleimidomethyl)cyclohexane‐1‐carboxylate associated with homo‐crosslinking side products under physiological conditions.

Abstract

Herein, the application of N‐hydroxysuccinimide‐modified phosphonamidate building blocks for the incorporation of cysteine‐selective ethynylphosphonamidates into lysine residues of proteins, followed by thiol addition with small molecules and proteins, is reported. It is demonstrated that the building blocks significantly lower undesired homo‐crosslinking side products that can occur with commonly applied succinimidyl 4‐(N‐maleimidomethyl)cyclohexane‐1‐carboxylate (SMCC) under physiological pH. The previously demonstrated stability of the phosphonamidate moiety additionally solves the problem of premature maleimide hydrolysis, which can hamper the efficiency of subsequent thiol addition. Furthermore, a method to separate the phosphonamidate enantiomers to be able to synthesize protein conjugates in a defined configuration has been developed. Finally, the building blocks are applied to the construction of functional antibody–drug conjugates, analogously to FDA‐approved, SMCC‐linked Kadcyla, and to the synthesis of a functional antibody–protein conjugate.

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Complement and Bacterial Infections: From Molecular Mechanisms to Therapeutic Applications.

J Innate Immun. 2018;10(5-6):455-464

Authors: Heesterbeek DAC, Angelier ML, Harrison RA, Rooijakkers SHM

Abstract
Complement is a complex protein network of plasma, and an integral part of the innate immune system. Complement activation results in the rapid clearance of bacteria by immune cells, and direct bacterial killing via large pore-forming complexes. Here we review important recent discoveries in the complement field, focusing on interactions relevant for the defense against bacteria. Understanding the molecular interplay between complement and bacteria is of great importance for future therapies for infectious and inflammatory diseases. Antibodies that support complement-dependent bacterial killing are of interest for the development of alternative therapies to treat infections with antibiotic-resistant bacteria. Furthermore, a variety of novel therapeutic complement inhibitors have been developed to prevent unwanted complement activation in autoimmune inflammatory diseases. A better understanding of how such inhibitors may increase the risk of bacterial infections is essential if such therapies are to be successful.

PMID: 30149378 [PubMed - indexed for MEDLINE]

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Anti-Methicillin-Resistant Staphylococcus aureus Nanoantibiotics.

Front Pharmacol. 2019;10:1121

Authors: Labruère R, Sona AJ, Turos E

Abstract
Nanoparticle-based antibiotic constructs have become a popular area of investigation in the biomedical sciences. Much of this work has pertained to human diseases, largely in the cancer therapy arena. However, considerable research has also been devoted to the nanochemistry for controlling infectious diseases. Among these are ones due to bacterial infections, which can cause serious illnesses leading to death. The onset of multi-drug-resistant (MDR) infections such as those caused by the human pathogen Staphylococcus aureus has created a dearth of problems such as surgical complications, persistent infections, and lack of available treatments. In this article, we set out to review the primary literature on the design and development of new nanoparticle materials for the potential treatment of S. aureus infections, and areas that could be further expanded upon to make nanoparticle antibiotics a mainstay in clinical settings.

PMID: 31636560 [PubMed]

Nature Communications, Published online: 24 October 2019; doi:10.1038/s41467-019-12848-5

The activation of drugs within cellular systems may provide targeted therapies for cancer. Here, the authors make a drug delivery system that is activated within the cell and exploits XIAP expression to cleave a linker region, resulting in the self-assembly of the system and drug release within cancer cells.

Nature, Published online: 23 October 2019; doi:10.1038/s41586-019-1671-8

In a mouse tumour model, immunotherapy-induced rejection of tumour cells requires presentation of both MHC class I and MHC class II antigens, which activate CD4+ and CD8+ T cells, respectively.

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Protein A superantigen: structure, engineering and molecular basis of antibody recognition.

Protein Eng Des Sel. 2019 Oct 22;:

Authors: Mazigi O, Schofield P, Langley DB, Christ D

Abstract
Staphylococcus aureus interacts with the human immune system through the production of secreted factors. Key among these is protein A, a B-cell superantigen capable of interacting with both antibody Fc and VH regions. Here, we review structural and molecular features of this important example of naturally occurring bacterial superantigens, as well as engineered variants and their application in biotechnology.

PMID: 31641749 [PubMed - as supplied by publisher]

Nature Immunology, Published online: 22 October 2019; doi:10.1038/s41590-019-0536-5

CAR T cells for heart disease

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A sample-to-answer, portable platform for rapid detection of pathogens with a smartphone interface.

Lab Chip. 2019 Oct 17;:

Authors: Ma YD, Li KH, Chen YH, Lee YM, Chou ST, Lai YY, Huang PC, Ma HP, Lee GB

Abstract
Emerging and re-emerging infectious diseases pose global threats to human health. Although several conventional diagnostic methods have been widely adopted in the clinic, the long turn-around times of "gold standard" culture-based techniques, as well as the limited sensitivity of lateral-flow strip assays, thwart medical progress. In this study, a smartphone-controlled, automated, and portable system was developed for rapid molecular diagnosis of pathogens (including viruses and bacteria) via the use of a colorimetric loop-mediated isothermal amplification (LAMP) approach on a passive, self-driven microfluidic device. The system was capable of 1) purifying viral or bacterial samples with specific affinity reagents that had been pre-conjugated to magnetic beads, 2) lysing pathogens at low temperatures, 3) executing isothermal nucleic acid amplification, and 4) quantifying the results of colorimetric assays for detection of pathogens with an integrated color sensor. The entire, 40 min analytical process was automatically performed with a novel punching-press mechanism that could be controlled and monitored by a smartphone. As a proof of concept, the influenza A (H1N1) virus and methicillin-resistant Staphylococcus aureus bacteria were used to characterize and optimize the device, and the limits of detection were experimentally found to be 3.2 × 10-3 hemagglutinating units (HAU) per reaction and 30 colony-forming units (CFU) per reaction, respectively; both such values represent high enough sensitivity for clinical adoption. Moreover, the colorimetric assay could be both qualitative and quantitative for detection of pathogens. This is the first instance of an easy-to-use, automated, and portable system for accurate and sensitive molecular diagnosis of either viruses or bacteria, and it is envisioned that this smartphone-controlled apparatus may serve as a platform for clinical, point-of-care pathogen detection, particularly in resource-limited settings.

PMID: 31620745 [PubMed - as supplied by publisher]

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Characterization of the beta-lactam-resistant enzyme in Acanthamoeba castellanii.

Int J Antimicrob Agents. 2019 Oct 14;:

Authors: Chen CH, Huang CL, He MS, Huang FC, Lin WC

Abstract
Beta-lactams are well known as the best antibiotics for inhibiting the crosslink between the adjacent polysaccharide chains and peptides to cause bacterial cell lysis. There are no reports about the action and resistance mechanisms of beta-lactams in protozoa. Acanthamoeba castellanii is a free-living protozoan pathogen capable of causing blinding keratitis and fatal granulomatous encephalitis. When Acanthamoeba is exposed to harsh conditions, it differentiates into the cyst stage to avoid environmental stresses, such as drug treatment. In this study, we show that the mature encystation rate of Acanthamoeba castellanii is decreased by treatment with cefotaxime (CTX) and clavulanic acid (CLA); however, the drugs do not kill the amoeba. We hypothesize that β-lactam antibiotics may disturb double wall synthesis during the encystation process of Acanthamoeba. Interestingly, CTX is considered a powerful β-lactam; on the contrary, CLA is considered a weak β-lactam and an efficient β-lactamase inhibitor. We demonstrated that Acanthamoeba expresses β-lactamases to disturb the inhibition of the encystation process by β-lactams. To reveal the functions of Acanthamoeba β-lactamase, we produced a recombinant Acanthamoeba β-lactamase in Escherichia coli and showed resistance to β-lactams such as cefotaxime, cefuroxime, penicillin, and meropenem. Consequently, we suggest that Acanthamoeba produces enzymes similar to β-lactamase to avoid interference from the environment. In this study, we provide a new point of view on an important gene responsible for drug tolerance and advocate for the development of more efficient medicine against Acanthamoeba infection.

PMID: 31622653 [PubMed - as supplied by publisher]

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Fluorescence Imaging of Bacterial Killing by Antimicrobial Peptide Dendrimer G3KL.

ACS Infect Dis. 2019 Oct 16;:

Authors: Gan BH, Siriwardena TN, Javor S, Darbre T, Reymond JL

Abstract
we recently discovered that peptide dendrimers such as G3KL ((KL)8(KKL)4(KKL)2KKL, K = branching L-lysine) exert strong activity against Gram-negative bacteria including Pseudomonas aeruginosa, Acinetobacter baumannii and Escherichia coli. Herein we report a detailed mechanistic study using fluorescence labeled analogs bearing fluorescein (G3KL-Fluo) or dansyl (G3KL-Dansyl), which show a similar bioactivity profile as G3KL. Imaging bacterial killing by super-resolution stimulated emission depletion (STED) microscopy, time-lapse imaging and transmission electron microscopy (TEM) reveals that the dendrimer localizes at the bacterial membrane, induces membrane depolarization and permeabilization, and destroys the outer leaflet and the inner membrane. G3KL accumulates in bacteria against which it is active, however it only weakly penetrates into eukaryotic cells without inducing significant toxicity. G3KL furthermore binds to lipopolysaccharide (LPS) and inhibits LPS induced release of TNF-α by macrophages similarly to polymyxin B. Taken together, these experiments show that G3KL behaves as a potent membrane disruptive antimicrobial peptide.

PMID: 31618574 [PubMed - as supplied by publisher]

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Listeria monocytogenes hijacks CD147 to ensure proper membrane protrusion formation and efficient bacterial dissemination.

Cell Mol Life Sci. 2019 Oct;76(20):4165-4178

Authors: Dhanda AS, Lulic KT, Yu C, Chiu RH, Bukrinsky M, Guttman JA

Abstract
Efficient cell-to-cell transfer of Listeria monocytogenes (L. monocytogenes) requires the proper formation of actin-rich membrane protrusions. To date, only the host proteins ezrin, the binding partner of ezrin, CD44, as well as cyclophilin A (CypA) have been identified as crucial components for L. monocytogenes membrane protrusion stabilization and, thus, efficient cell-to-cell movement of the microbes. Here, we examine the classical binding partner of CypA, CD147, and find that this membrane protein is also hijacked by the bacteria for their cellular dissemination. CD147 is enriched at the plasma membrane surrounding the membrane protrusions as well as the resulting invaginations generated in neighboring cells. In cells depleted of CD147, these actin-rich structures appear similar to those generated in CypA depleted cells as they are significantly shorter and more contorted as compared to their straighter counterparts formed in wild-type control cells. The presence of malformed membrane protrusions hampers the ability of L. monocytogenes to efficiently disseminate from CD147-depleted cells. Our findings uncover another important host protein needed for L. monocytogenes membrane protrusion formation and efficient microbial dissemination.

PMID: 31076805 [PubMed - indexed for MEDLINE]

Exclusively intramolecular: The conformationally induced activation of the amide bond, the idea behind the “CyClick” strategy, is exploited for the macrocyclization of peptides and precludes the formation of dimers or oligomers via intermolecular reactions. This method is tolerant to variety of peptide aldehydes and has been applied for the synthesis of 12‐ to 23‐membered rings.

Abstract

Here, we report a novel “CyClick” strategy for the macrocyclization of peptides that works in an exclusively intramolecular fashion thereby precluding the formation of dimers and oligomers via intermolecular reactions. The CyClick chemistry is highly chemoselective for the N‐terminus of the peptide with a C‐terminal aldehyde. In this protocol, the peptide conformation internally directs activation of the backbone amide bond and thereby facilitates formation of a stable 4‐imidazolidinone‐fused cyclic peptide with high diastereoselectivity (>99 %). This method is tolerant to a variety of peptide aldehydes and has been applied for the synthesis of 12‐ to 23‐membered rings with varying amino acid compositions in one pot under mild reaction conditions. The reaction generated peptide macrocycles featuring a 4‐imidazolidinone in their scaffolds, which acts as an endocyclic control element that promotes intramolecular hydrogen bonding and leads to macrocycles with conformationally rigid turn structures.

Antibodies can be developed to directly inhibit almost any protein, but their inability to enter the cytosol limits inhibitory antibodies to membrane-associated or extracellular targets. Developing a cytosolic antibody delivery system would offer unique opportunities to directly inhibit and study intracellular protein function. Here we demonstrate that IgG antibodies that...

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In situ identification of Gram-negative bacteria in human lungs using a topical fluorescent peptide targeting lipid A.

Sci Transl Med. 2018 10 24;10(464):

Authors: Akram AR, Chankeshwara SV, Scholefield E, Aslam T, McDonald N, Megia-Fernandez A, Marshall A, Mills B, Avlonitis N, Craven TH, Smyth AM, Collie DS, Gray C, Hirani N, Hill AT, Govan JR, Walsh T, Haslett C, Bradley M, Dhaliwal K

Abstract
Respiratory infections in mechanically ventilated patients caused by Gram-negative bacteria are a major cause of morbidity. Rapid and unequivocal determination of the presence, localization, and abundance of bacteria is critical for positive resolution of the infections and could be used for patient stratification and for monitoring treatment efficacy. Here, we developed an in situ approach to visualize Gram-negative bacterial species and cellular infiltrates in distal human lungs in real time. We used optical endomicroscopy to visualize a water-soluble optical imaging probe based on the antimicrobial peptide polymyxin conjugated to an environmentally sensitive fluorophore. The probe was chemically stable and nontoxic and, after in-human intrapulmonary microdosing, enabled the specific detection of Gram-negative bacteria in distal human airways and alveoli within minutes. The results suggest that pulmonary molecular imaging using a topically administered fluorescent probe targeting bacterial lipid A is safe and practical, enabling rapid in situ identification of Gram-negative bacteria in humans.

PMID: 30355797 [PubMed - indexed for MEDLINE]

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Phage resistance at the cost of virulence: Listeria monocytogenes serovar 4b requires galactosylated teichoic acids for InlB-mediated invasion.

PLoS Pathog. 2019 Oct;15(10):e1008032

Authors: Sumrall ET, Shen Y, Keller AP, Rismondo J, Pavlou M, Eugster MR, Boulos S, Disson O, Thouvenot P, Kilcher S, Wollscheid B, Cabanes D, Lecuit M, Gründling A, Loessner MJ

Abstract
The intracellular pathogen Listeria monocytogenes is distinguished by its ability to invade and replicate within mammalian cells. Remarkably, of the 15 serovars within the genus, strains belonging to serovar 4b cause the majority of listeriosis clinical cases and outbreaks. The Listeria O-antigens are defined by subtle structural differences amongst the peptidoglycan-associated wall-teichoic acids (WTAs), and their specific glycosylation patterns. Here, we outline the genetic determinants required for WTA decoration in serovar 4b L. monocytogenes, and demonstrate the exact nature of the 4b-specific antigen. We show that challenge by bacteriophages selects for surviving clones that feature mutations in genes involved in teichoic acid glycosylation, leading to a loss of galactose from both wall teichoic acid and lipoteichoic acid molecules, and a switch from serovar 4b to 4d. Surprisingly, loss of this galactose decoration not only prevents phage adsorption, but leads to a complete loss of surface-associated Internalin B (InlB),the inability to form actin tails, and a virulence attenuation in vivo. We show that InlB specifically recognizes and attaches to galactosylated teichoic acid polymers, and is secreted upon loss of this modification, leading to a drastically reduced cellular invasiveness. Consequently, these phage-insensitive bacteria are unable to interact with cMet and gC1q-R host cell receptors, which normally trigger cellular uptake upon interaction with InlB. Collectively, we provide detailed mechanistic insight into the dual role of a surface antigen crucial for both phage adsorption and cellular invasiveness, demonstrating a trade-off between phage resistance and virulence in this opportunistic pathogen.

PMID: 31589660 [PubMed - in process]

In or out? Cyclic oligochalcogenides (COCs), inhibit, rather than mediate, uptake into bacteria. This conclusion, resulting from the synthesis and evaluation of a series of COC–antibiotic conjugates, supports that COCs penetrate mammalian cells along nontrivial uptake pathways involving dynamic covalent exchange chemistry, mobility along disulfide tracks, and adaptive micellar pores.

Abstract

Cellular uptake mediated by cyclic oligochalcogenides (COCs) is emerging as a conceptually innovative method to penetrate mammalian cells. Their mode of action is based on dynamic covalent oligochalcogenide exchange with cellular thiols. To test thiol‐mediated uptake in bacteria, five antibiotics have been equipped with up to three different COCs: One diselenolane and two dithiolanes. We found that the COCs do not activate antibiotics in Gram‐negative bacteria. In Gram‐positive bacteria, the COCs inactivate antibiotics that act in the cytoplasm and reduce the activity of antibiotics that act on the cell surface. These results indicate that thiol‐mediated uptake operates in neither of the membranes of bacteria. COCs are likely to exchange with thiols on the inner, maybe also on the outer membrane, but do not move on. Concerning mammalian cells, the absence of a COC‐mediated uptake into bacteria observed in this study disfavors trivial mechanisms, such as passive diffusion, and supports the existence of more sophisticated, so far poorly understood uptake pathways.

ABSTRACT

Diet influences health in multiple ways. One important effect of diet is on the gut microbiota. The effects of diet are often related to an individual’s specific microbiota composition. The close links between health, diet, and gut microbiota are illustrated in a new mouse model of sepsis where the combination of a high-fat/low-fiber Western diet, antibiotics, and surgery promotes the development of lethal sepsis. Diet can also influence infection via the gut microbiota beyond sepsis. Future studies with this model may inform the use of microbiota analysis and personalized diets to protect surgery patients from infection and sepsis.

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Phylogenetic and biochemical analyses of mycobacterial L,D-transpeptidases reveal a distinct enzyme class that is preferentially acylated by meropenem.

ACS Infect Dis. 2019 Oct 09;:

Authors: Zandi T, Marshburn RL, Stateler PK, Brammer Basta L

Abstract
The genomes of diverse mycobacterial species encode multiple proteins with the canonical L,D-transpeptidase (Ldt) sequence motif. The reason for this apparent redundancy is not well understood, but evidence suggests paralogous Ldts may serve niche roles in maintaining and/or remodeling mycobacterial peptidoglycan. We examined 323 mycobacterial Ldts and determined these enzymes cluster into six clades. We identified a variably represented yet distinct Ldt class (class 6) containing Mycobacterium smegmatis (Msm) LdtF and built a homology model of Msm LdtF toward elucidating class 6 structural and functional differences. We report class 6 Ldts have structurally divergent catalytic domains containing a 10-residue insertion near the active site, and additionally determined that meropenem preferentially acylates LdtF. Our data demonstrate an evolutionary basis for mycobacterial Ldt multiplicity that lends support to the idea that paralogous Ldts serve non-redundant roles in vivo and suggests class 6 Ldts can be selectively targeted by specific carbapenem antibiotics.

PMID: 31597040 [PubMed - as supplied by publisher]

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Liposidomycin, the first reported nucleoside antibiotic inhibitor of peptidoglycan biosynthesis translocase I: The discovery of liposidomycin and related compounds with a perspective on their application to new antibiotics.

J Antibiot (Tokyo). 2019 Oct 04;:

Authors: Kimura KI

Abstract
Liposidomycin is a uridyl liponucleoside antibiotic isolated from Streptomyces griseosporeus RK-1061. It was discovered by Isono in 1985, who had previously isolated and developed a related peptidyl nucleoside antibiotic, polyoxin, a specific inhibitor of chitin synthases, as a pesticide. He subsequently isolated liposidomycin, a specific inhibitor of bacterial peptidoglycan biosynthesis from actinomycetes, using a similar approach to the discovery of polyoxin. Liposidomycin has no cytotoxicity against BALB/3T3 cells but has antimicrobial activity against Mycobacterium spp. through inhibition of MraY (MurX) [phospho-N-acetylmuramoyl-pentapeptide transferase (translocase I, EC 2.7.8.13)]. Since the discovery of liposidomycin, several liposidomycin-type antibiotics, including caprazamycin, A-90289, and muraminomycin, have been reported, and their total synthesis and/or biosynthetic cluster genes have been studied. Most advanced, a semisynthetic compound derived from caprazamycin, CPZEN-45, is being developed as an antituberculosis agent. Translocase I is an interesting and tractable molecular target for new antituberculosis and antibiotic drug discovery against multidrug-resistant bacteria. This review is dedicated to Dr Isono on the occasion of his 88th birthday to recognize his role in the study of nucleoside antibiotics.

PMID: 31582803 [PubMed - as supplied by publisher]

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A tri-ionic anchor mechanism drives Ube2N-specific recruitment and K63-chain ubiquitination in TRIM ligases.

Nat Commun. 2019 Oct 03;10(1):4502

Authors: Kiss L, Zeng J, Dickson CF, Mallery DL, Yang JC, McLaughlin SH, Boland A, Neuhaus D, James LC

Abstract
The cytosolic antibody receptor TRIM21 possesses unique ubiquitination activity that drives broad-spectrum anti-pathogen targeting and underpins the protein depletion technology Trim-Away. This activity is dependent on formation of self-anchored, K63-linked ubiquitin chains by the heterodimeric E2 enzyme Ube2N/Ube2V2. Here we reveal how TRIM21 facilitates ubiquitin transfer and differentiates this E2 from other closely related enzymes. A tri-ionic motif provides optimally distributed anchor points that allow TRIM21 to wrap an Ube2N~Ub complex around its RING domain, locking the closed conformation and promoting ubiquitin discharge. Mutation of these anchor points inhibits ubiquitination with Ube2N/Ube2V2, viral neutralization and immune signalling. We show that the same mechanism is employed by the anti-HIV restriction factor TRIM5 and identify spatially conserved ionic anchor points in other Ube2N-recruiting RING E3s. The tri-ionic motif is exclusively required for Ube2N but not Ube2D1 activity and provides a generic E2-specific catalysis mechanism for RING E3s.

PMID: 31582740 [PubMed - in process]

Scientists in Australia have developed a world-first compound that can keep cells alive and functioning in a perfectly healthy state when they otherwise would have died.

A DNA nanopump is produced with azobenzene‐functionalized DNA strands for efficient and controllable drug release through the photoisomerization of azobenzene fueled by the simultaneous UV and visible‐light emissions of upconversion nanoparticles (UCNPs) under NIR irradiation. This triggers the release of an anticancer drug and enhances anticancer therapy.

Abstract

Stimulus‐responsive drug release possesses considerable significance in cancer therapy. This work reports an upconversion‐luminescence‐fueled DNA–azobenzene nanopump for rapid and efficient drug release. The nanopump is constructed by assembling the azobenzene‐functionalized DNA strands on upconversion nanoparticles (UCNPs). Doxorubicin (DOX) is loaded in the nanopump by intercalation in the DNA helix. Under NIR light, the UCNPs emit both UV and visible photons to fuel the continuous photoisomerization of azo, which acts as an impeller pump to trigger cyclic DNA hybridization and dehybridization for controllable DOX release. In a relatively short period, this system demonstrates 86.7 % DOX release. By assembling HIV‐1 TAT peptide and hyaluronic acid on the system, targeting of the cancer‐cell nucleus is achieved for perinuclear aggregation of DOX and enhanced anticancer therapy. This highly effective drug delivery nanopump could contribute to chemotherapy development.