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Biology subjects

Auclair, K.

Publications and source records attributed to Auclair, K..

16 recordsLinked to original sources

A Compact Regulatory Logic Governs Fibroblast Cell State Plasticity in Fibrosis

Fibroblast activation drives organ failure across human diseases, yet its regulatory basis remains largely undefined. Here, we repressed 280 conserved disease-activated enhancers using CRISPR droplet sequencing (CROP-seq) in ~550,000 fibroblasts, constructing a regulome of 15 gene programs governing the profibrotic state. Systematic TF perturbation converged on MEOX1 as a central regulator, and fibroblast-specific Meox1 deletion in mice improved cardiac function, reduced fibrosis, and rewired profibrotic fibroblasts toward quiescence in heart failure. Effector gene perturbation in human cardiac fibroblasts revealed distinct regulators of contractility, migration, and inflammatory signaling, and these programs were conserved across profibrotic states in human lung, liver, and skin. Simultaneous repression of just six enhancers using a multiplexed dCas12a-KRAB system collapsed the profibrotic network, suppressed migration and contraction, and rewired fibroblast paracrine signaling to attenuate macrophage inflammation. These findings define the regulatory logic of fibroblast plasticity and establish a new framework for reprogramming profibrotic cell states in disease.

genomics↗

Exploring the antibiotic-producing capabilities of Canadian High Arctic bacteria

Microbial communities in harsh environments such as the Canadian high Arctic, remain a relatively unexplored source of antimicrobial natural products. In this study, we developed a pipeline for screening and evaluating bacterial isolates cultured from 23 Canadian high Arctic soil, sediment, and active-layer permafrost samples to discover antibacterial compounds. The pipeline incorporated an undergraduate studentsourcing program and produced created a collection of over 350 bacterial isolates with preliminary antibacterial activity. Following dereplication, whole genome sequencing and secondary screening by co-culture assays, five isolates were prioritized to test crude extracts for antibacterial activity. Among bioactive crude extracts from these isolates, the Pseudomonas isolate with the most potent activity against S. aureus was analyzed. Using liquid chromatography bioactivity guided fractionation, we identified a potential bioactive compound known as koreenceine A, a compound previously only isolated from a Pseudomonas from temperate soil and involved in gene expression of other their microbial community. Here we expanded the known antibiotic activity of koreenceine A and confirmed that a {triangleup}kecBCD genetic knockout of the putative biosynthetic gene cluster significantly abrogated the antibacterial activity.

microbiology↗

Pantetheinamides that inhibit the growth of intracellular Salmonella Typhimurium

The metabolic adaptability of intracellular pathogens, such as the Gram-negative Salmonella enterica serovar Typhimurium (STm), enables their survival in nutrient-restricted host environments, while also presenting an opportunity for selective antimicrobial targeting. Herein, we report the synthesis and screening of a small pantetheinamide library aimed at inhibiting the proliferation of STm within macrophages. Two lead compounds exhibited selective activity against intracellular STm and reduced bacterial burden in a murine colitis model. Mechanistic studies suggest their primary mode of action to be the inhibition of coenzyme A (CoA) biosynthesis via the PanD-PanZ regulatory complex, which is absent in host cells. Importantly, resistance pressure to our compound was shown to be significantly stronger in nutrient-limited media compared to nutrient-rich media, supporting the targeting of nutrient stress as a strategy to delay resistance. This work highlights the value of inhibiting pathogen-specific metabolic vulnerabilities in combination with host defence mechanisms to develop novel antimicrobials.

microbiology↗

Metabolic and genomic adaptations of Salmonella Typhimurium grown on itaconate

Salmonella enterica ser. Typhimurium (STm) is an enteric pathogen that causes almost 100 million cases of salmonellosis a year. A hallmark of STm is their ability to survive and replicate in the macrophages that phagocytose them. Inside the Salmonella-containing vesicles (SCV) STm is exposed to nutrient limitation and antimicrobial molecules, including itaconate, a dicarboxylate produced at millimolar concentrations by activated macrophages. STm has an itaconate degradation pathway that allows it to detoxify itaconate and convert it into pyruvate and acetyl-CoA. In the SCV, STm undergoes extensive metabolic reprogramming in response to the nutrient limitation and high stress environment, and strict catabolite control is employed at various stages of infection, depending on carbon source availability. The extent to which itaconate is used as a carbon source by STm is not currently well understood. Here, we explore the ability of STm to grow in media containing itaconate as the sole carbon source, identify the genes of the itaconate response operon necessary for itaconate degradation, and confirm their importance during infection of macrophages. Growth on itaconate was substantially slower than in carbon-rich or acetate media, with multiple subcultures allowing for increased growth rates. Genomic analysis suggests that mutations in the RpoS-stress response and increased expression of the DctA transporter improve growth on itaconate. Using metabolomics, it was revealed that growth on itaconate resulted in substantially reduced levels of gluconeogenesis compared to growth on acetate and increased glutathione disulfide levels, indicating a high level of oxidative stress. Overall, our results point towards the STm itaconate degradation pathway having a more important role in detoxifying itaconate, rather than using it as a carbon source inside the macrophage. Additionally, this study establishes media conditions that would enable the high throughput discovery of potential inhibitors of itaconate degradation.

microbiology↗

Thiazole substitution of a labile amide bond - a new option towards stable pantothenamide-mimics

The emergence and spread of artemisinin-resistant, malaria-causing P. falciparum provide the impetus for the development of novel antimalarials. Pantothenamides are potent inhibitors of malaria parasite proliferation, however their clinical use is hindered by pantetheinase-mediated degradation in human serum. Here we report the synthesis and biological activity of a series of pantothenamide-mimics in which the labile amide bond is replaced by a thiazole ring with various orientations. Out of 23 novel compounds generated and tested in the presence of pantetheinase, several display sub-micromolar antiplasmodial activity in vitro. A selection of compounds was studied in more detail and CoA biosynthesis and/or utilisation pathways were confirmed to be the target. Toxicity to human cells was not observed. Kinetic studies identified the selected compounds as substrates of the HsPanK3 enzyme, but with much lower affinity compared to that of the natural substrate pantothenate. The most potent thiazole-bearing antiplasmodial compound was found to bind to PfPanK with a 120-fold higher affinity compared to HsPanK, highlighting excellent selectivity, not only against the key first enzyme in the CoA biosynthesis pathway, but also at the whole-cell level. In conclusion, thiazole substitution of the labile amide bond represents a promising avenue for the development of antimalarial pantothenamide-mimics.

pharmacology and toxicology↗

Chromatin Remodeling Drives Immune-Fibroblast Crosstalk in Heart Failure Pathogenesis

Chronic inflammation and tissue fibrosis are common stress responses that worsen organ function, yet the molecular mechanisms governing their crosstalk are poorly understood. In diseased organs, stress-induced changes in gene expression fuel maladaptive cell state transitions and pathological interaction between diverse cellular compartments. Although chronic fibroblast activation worsens dysfunction of lung, liver, kidney, and heart, and exacerbates many cancers, the stress-sensing mechanisms initiating the transcriptional activation of fibroblasts are not well understood. Here, we show that conditional deletion of the transcription co-activator Brd4 in Cx3cr1-positive myeloid cells ameliorates heart failure and is associated with a dramatic reduction in fibroblast activation. Analysis of single-cell chromatin accessibility and BRD4 occupancy in vivo in Cx3cr1-positive cells identified a large enhancer proximal to Interleukin-1 beta (Il1b), and a series of CRISPR deletions revealed the precise stress-dependent regulatory element that controlled expression of Il1b in disease. Secreted IL1B functioned non-cell autonomously to activate a p65/RELA-dependent enhancer near the transcription factor MEOX1, resulting in a profibrotic response in human cardiac fibroblasts. In vivo, antibody-mediated IL1B neutralization prevented stress-induced expression of MEOX1, inhibited fibroblast activation, and improved cardiac function in heart failure. The elucidation of BRD4-dependent crosstalk between a specific immune cell subset and fibroblasts through IL1B provides new therapeutic strategies for heart disease and other disorders of chronic inflammation and maladaptive tissue remodeling.

molecular biology↗

Efficient mechano-enzymatic hydrolysis of polylactic acid under moist-solid conditions.

Quantitative mechano-enzymatic depolymerisation of polylactic acid to lactic acid was achieved at 55{degrees}C using the Humicola insolens cutinase enzyme in moist-solid reaction mixtures. The resulting lactic acid was easily recovered, and the crude product was pure enough to be used in further synthesis of a value-added compound, a known benzimidazole-based drug precursor. The presented mechano-enzymatic depolymerisation strategy enables the closed-loop recycling of untreated polylactic acid under mild conditions, using a renewable, non-toxic catalyst and producing minimum solvent waste.

biochemistry↗

Solid-state enzymatic hydrolysis of mixed PET-cotton textiles

Waste polyester textiles trap copious amounts of useful polymers, which are not recycled due to separation challenges and partial structural degradation during use and thermo-mechanical recycling. Chemical recycling of polyethylene terephthalate (PET) through depolymerization can provide a feedstock of recycled monomers to make "as-new" polymers, and reduce the accumulation of plastic waste in landfills. Enzymes are highly specific, renewable, environmentally benign catalysts, with hydrolases available that are active on common PET textile fibers and on cotton. The enzymatic PET recycling methods in development, however, have thus far been limited to clean, high-quality PET feedstocks, and most such processes require an energy-intensive melt-amorphization step ahead of enzymatic depolymerization. Here we report that high-crystallinity PET in mixed PET/cotton textiles can be directly and selectively depolymerized to terephthalic acid (TPA) by using a commercial cutinase from Humicola insolens under moist-solid reaction conditions, affording up to 30 {+/-} 2% yield of TPA. The process is readily combined with cotton depolymerisation through simultaneous application of cellulase enzymes (CTec2(R)), providing up to 83 {+/-} 4% yield of glucose without any negative influence on the TPA yield. The herein presented selective and/or simultaneous enzymatic hydrolysis of PET/cotton textiles in solid reaction mixtures can expand the biocatalytic recycling processes of PET to less-valuable waste materials, and significantly increase its profitability through operating at very high solid-loading (40%), without the need for melt-amorphization.

biochemistry↗

Structural dynamics of cytochrome P450 3A4 in the presence of substrates and cytochrome P450 reductase

Cytochrome P450 3A4 (CYP3A4) is the most important drug-metabolizing enzyme in humans and has been associated with harmful drug interactions. The activity of CYP3A4 is known to be modulated by several compounds, as well as by the electron transfer partner, cytochrome P450 reductase (CPR). The underlying mechanism of these effects however is poorly understood. We have used hydrogen-deuterium exchange mass spectroscopy (HDX-MS) to investigate the impact of CPR and three different substrates (7-benzyloxy-4-trifluoromethyl-coumarin, testosterone and progesterone) on the conformational dynamics of CYP3A4. Here, we report that interaction of CYP3A4 with substrates or with the oxidized or reduced form of CPR leads to a global rigidification of the CYP3A4 structure. This was evident from a suppression of deuterium exchange in several regions of CYP3A4, including those known to be involved in protein-protein interactions (C-helix) as well as substrate binding and specificity (B-, E-helices and K/{beta}1-loop). Furthermore, the bimodal isotopic distributions observed for some CYP3A4-derived peptides were drastically impacted by CPR and/or substrates, suggesting the existence of stable CYP3A4 conformational populations that are perturbed by ligand/CPR binding. The results have implications for understanding the mechanisms of allostery, ligand binding, and catalysis in CYP enzymes.

biochemistry↗

Exploring heteroaromatic rings as a replacement for the labile amide of antiplasmodial pantothenamides

The Plasmodium parasites that cause malaria are adept at developing resistance to antimalarial drugs, necessitating the search for new antiplasmodials. Although several amide analogs of pantothenate (pantothenamides) show potent antiplasmodial activity, hydrolysis by pantetheinases (or vanins) present in blood rapidly inactivates them. We report herein the facile synthesis and biological activity of a small library of pantothenamide analogs in which the labile amide group is replaced with a variety of heteroaromatic rings. Several of the new analogs display antiplasmodial activity in the nanomolar range against P. falciparum and/or P. knowlesi in the presence of pantetheinase. A previously reported triazole and an isoxazole derivative presented here were further characterized and found to possess high selectivity indices, medium or high Caco-2 permeability, and medium or low microsomal clearance in vitro. Although we show here that the two compounds fail to suppress proliferation of P. berghei in vivo, pharmacokinetic and contact time data presented provide a benchmark for the compound profile required to achieve antiplasmodial activity in mice and should facilitate lead optimization.

pharmacology and toxicology↗

The antimicrobial activity of the macrophage metabolite itaconate is synergistic with acidity.

The production of itaconate by macrophages was only discovered in 2011. A rapidly increasing number of studies have since revealed essential biological roles for itaconate, ranging from antimicrobial to immunomodulator. Itaconate has been estimated to reach low-millimolar concentrations in activated macrophages, including those within infected lungs and brains, whereas itaconates MIC towards several bacterial strains were measured to be in the low-to-mid-millimolar range, casting some doubts on the antibacterial role of itaconate in vivo. Several of these investigations, in particular those measuring MIC values of itaconate or itaconic acid, have however tended to ignore the high acidity of this small diacid (pKas 3.85 and 5.45), thereby potentially biasing the MIC measurements. We report herein that: 1) at high concentration, itaconic acid can significantly reduce the pH of growth media; 2) the antibacterial activity of itaconate increases in a synergistic manner with acidity; 3) this synergistic effect is not simply due to increased permeability of monoanionic itaconate; 4) considering that the MIC of itaconate is many fold lower under acidic conditions for all strains tested, itaconate may serve an antimicrobial role, particularly in acidic vesicles such as the phagolysosome; and 5) differential growth behavior in the presence of disodium itaconate versus itaconic acid may serve to rapidly screen bacterial strains for their ability to metabolize itaconate. Our results further support the hypothesis that inhibitors of itaconate degradation in bacteria may provide a new strategy to treat infections.

microbiology↗

Small molecule resensitizes Salmonella to itaconate and decreases bacterial proliferation in macrophages

Antimicrobial resistance is a global health crisis offering little reprieve. The situation urgently calls for new drug targets and therapies for infections. We have previously suggested a different approach to treat infections, termed bacterio-modulation, in which a compound modulates the bacterial response to the host immune defense. Herein we show that monocytes infected with Salmonella enterica spp. Typhimurium can be cured using non-antimicrobial compounds that resensitize the bacterium to itaconate, a macrophage-derived antimicrobial metabolite. We propose that this represents a novel strategy to treat infections.

microbiology↗

Clean Enzymatic depolymerization of highly crystalline polyethylene terephthalate in moist-solid reaction mixtures

Less than 9% of the plastic produced is recycled after use, contributing to the global plastic pollution problem. While polyethylene terephthalate (PET) is one of the most common plastics, its thermomechanical recycling generates a material of lesser quality. Enzymes are highly selective, renewable catalysts active at mild temperatures; however, the current consensus is that they lack activity towards the more crystalline forms of PET. We report here that when used in moist-solid reaction mixtures instead of the typical dilute aqueous solutions, enzymes can directly depolymerize high crystallinity PET in 13-fold higher space-time yield and a 15-fold higher enzyme efficiency than prior reports. Further, this process shows a 26-fold selectivity for terephthalic acid over other hydrolysis products, which allows the direct synthesis of UiO-66 metal-organic framework.Competing Interest StatementThe authors have declared no competing interest.View Full Text

biochemistry↗

Combining small-molecule bioconjugation and hydrogen-deuterium exchange mass spectrometry (HDX-MS) to expose allostery: the case of human cytochrome P450 3A4

We report herein a novel approach to study allostery which combines the use of carefully selected bioconjugates and hydrogen-deuterium exchange mass spectrometry (HDX-MS). The utility of our method is demonstrated using human cytochrome P450 3A4 (CYP3A4). CYP3A4 is arguably the most important drug-metabolizing enzyme, and as such, is involved in numerous drug interactions. Diverse allosteric ligand effects have been reported for this enzyme, yet the structural mechanism of these phenomena remain poorly understood. We have described different CYP3A4-effector bioconjugates, some of which mimic the allosteric effect of positive effectors on CYP3A4, while others show activity enhancement even though the label does not occupy the allosteric pocket (agonistic), or do not show activation while still blocking the allosteric site (antagonistic). These bioonjugates were studied here by HDX-MS, which enabled us to better define the position of the allosteric site, and to identify important regions involved in CYP3A4 activation.

biochemistry↗

Rapid mechanoenzymatic saccharification of lignocellulosic biomass without bulk water or chemical pre-treatment

Lignocellulosic material is an abundant renewable resource with the potential to replace petroleum as a feedstock for the production of fuels and chemicals. The large scale deployment of biomass saccharification is, however, hampered by the necessity to use aggressive reagents and conditions, formation of side-products, and the difficulty to reach elevated monosaccharide concentrations in the crude product. Herein we report the high efficacy of Reactive Aging (or Raging, a technique where enzymatic reaction mixtures, without any bulk aqueous or organic solvent, are treated to multiple cycles of milling and aging) for gram-scale saccharification of raw lignocellulosic biomass samples from different agricultural sources (corn stover, wheat straw, and sugarcane bagasse). The solvent-free enzymatic conversion of lignocellulosic biomass was found to proceed in excellent yields (ca. 90%) at protein loadings as low as 2% w/w, without the need for any prior chemical pre-treatment or high temperatures, to produce highly concentrated (molar) monosaccharides. This crude product of mechanoenzymatic depolymerization is non-toxic to bacteria and can be used as a carbon source for bacterial growth.

biochemistry↗

Mutations in the pantothenate kinase of the malaria parasite P. falciparum confer resistance or hypersensitivity to diverse pantothenate analogues

The malaria-causing blood stage of Plasmodium falciparum requires extracellular pantothenate for proliferation. The parasite converts pantothenate into coenzyme A (CoA) via five enzymes, the first being a pantothenate kinase (PfPanK). Multiple antiplasmodial pantothenate analogues, including pantothenol and CJ-15,801, kill the parasite by targeting CoA biosynthesis/utilisation. Their mechanism of action, however, remains unknown. Here, we show that parasites pressured with pantothenol or CJ-15,801 become resistant to these analogues. Whole-genome sequencing revealed mutations in one of two putative PanK genes (Pfpank1) in each resistant line. These mutations significantly alter PfPanK activity, with two conferring a fitness cost, consistent with Pfpank1 coding for a functional PanK that is essential for normal growth. The mutants exhibit a different sensitivity profile to recently-described, potent, antiplasmodial pantothenate analogues, with one line being hypersensitive. We provide evidence consistent with different pantothenate analogue classes having different mechanisms of action: some inhibit CoA biosynthesis while others inhibit CoA-utilising enzymes.

pharmacology and toxicology↗