A Novel In Vitro Multiple-Stress Dormancy Model for Mycobacterium tuberculosis Generates a Lipid-Loaded, Drug-Tolerant, Dormant Pathogen

Background: Mycobacterium tuberculosis (Mtb) becomes dormant and phenotypically drug resistant when it encounters multiple stresses within the host. Inability of currently available drugs to kill latent Mtb is a major impediment to curing and possibly eradicating tuberculosis (TB). Most in vitro dormancy models, using single stress factors, fail to generate a truly dormant Mtb population. An in vitro model that generates truly dormant Mtb cells is needed to elucidate the metabolic requirements that allow Mtb to successfully go through dormancy, identify new drug targets, and to screen drug candidates to discover novel drugs that can kill dormant pathogen. Methodology/Principal Findings: We developed a novel in vitro multiple-stress dormancy model for Mtb by applying combined stresses of low oxygen (5%), high CO2 (10%), low nutrient (10 % Dubos medium) and acidic pH (5.0), conditions Mtb is thought to encounter in the host. Under this condition, Mtb stopped replicating, lost acid-fastness, accumulated triacylglycerol (TG) and wax ester (WE), and concomitantly acquired phenotypic antibiotic-resistance. Putative neutral lipid biosynthetic genes were up-regulated. These genes may serve as potential targets for new antilatency drugs. The triacylglycerol synthase1 (tgs1) deletion mutant, with impaired ability to accumulate TG, exhibited a lesser degree of antibiotic tolerance and complementation restored antibiotic tolerance. Transcriptome analysis with microarray revealed the achievement of dormant state showing repression of energy generation, transcription and translation machineries an

Functional characterization of the Candida albicans homologue of secretion-associated and Ras-related (SarI) protein

NRC publication: Ye

Experimental evidence for anti-metastatic actions of apigenin: a mini review

Cancer metastasis is responsible for the majority of cancer-related deaths. Accordingly, to reduce metastasis remains a vital challenge in clinical practice, and phytochemicals have taken an attention as anti-metastatic agents. Apigenin, a plant flavone, showed anti-cancer effects against in various animal models, moreover its potentials inhibiting tumor metastasis have been reported. Herein, we analyzed the overall features at what apigenin inhibited metastasis and its action modes. We searched for articles in MEDLINE (Pubmed), EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) through March 2023. Total 6 animal studies presented anti-metastatic effects of apigenin using 5 difference experimental models, while the mechanisms involved modulations of epithelial-mesenchymal transition (EMT), matrix metalloproteinases (MMPs), angiogenesis, and various metastasis-related signaling pathways. This review provides an overall potential of apigenin as a candidate reducing the risk of cancer metastasis

AccD6, a Member of the Fas II Locus, Is a Functional Carboxyltransferase Subunit of the Acyl-Coenzyme A Carboxylase in Mycobacterium tuberculosis

The Mycobacterium tuberculosis acyl-coenzyme A (CoA) carboxylases provide the building blocks for de novo fatty acid biosynthesis by fatty acid synthase I (FAS I) and for the elongation of FAS I end products by the FAS II complex to produce meromycolic acids. The M. tuberculosis genome contains three biotin carboxylase subunits (AccA1 to -3) and six carboxyltransferase subunits (AccD1 to -6), with accD6 located in a genetic locus that contains members of the FAS II complex. We found by quantitative real-time PCR analysis that the transcripts of accA3, accD4, accD5, and accD6 are expressed at high levels during the exponential growth phases of M. tuberculosis in vitro. Microarray analysis of M. tuberculosis transcripts indicated that the transcripts for accA3, accD4, accD5, accD6, and accE were repressed during later growth stages. AccD4 and AccD5 have been previously studied, but there are no reports on the function of AccD6. We expressed AccA3 (α(3)) and AccD6 (β(6)) in E. coli and purified them by affinity chromatography. We report here that reconstitution of the α(3)-β(6) complex yielded an active acyl-CoA carboxylase. Kinetic characterization of this carboxylase showed that it preferentially carboxylated acetyl-CoA (1.1 nmol/mg/min) over propionyl-CoA (0.36 nmol/mg/min). The activity of the α(3)-β(6) complex was inhibited by the ɛ subunit. The α(3)-β(6) carboxylase was inhibited significantly by dimethyl itaconate, C75, haloxyfop, cerulenin, and 1,2-cyclohexanedione. Our results suggest that the β(6) subunit could play an important role in mycolic acid biosynthesis by providing malonyl-CoA to the FAS II complex

The serine/threonine protein phosphatase SIT4 modulates yeast-to-hypha morphogenesis and virulence in Candida albicans

Manque le text pdfNRC publication: Ye

Polyimide nonwoven fabric-reinforced, flexible phosphosilicate glass composite membranes for high-temperature/low-humidity proton exchange membrane fuel cells

We demonstrate polyimide (PI) nonwoven fabric-reinforced, flexible proton-conductive phosphosilicate glass composite membranes for potential application in high-temperature/low-humidity proton exchange membrane fuel cells (PEMFCs). The new reinforced composite membrane is fabricated via the impregnation of a 3-glycidyloxypropyl trimethoxysilane (GPTMS)/orthophosphoric acid (H 3PO 4) mixture into a PI nonwoven substrate followed by in situ sol-gel synthesis and hydrothermal treatment. This unique structural integrity enables the reinforced composite membrane to provide unprecedented improvement in the mechanical properties (notably flexibility and thickness) over typical bulk phosphosilicate glasses that are highly fragile and thick. Meanwhile, the highly porous structure of the PI reinforcing framework allows for the facile formation of a three-dimensionally interconnected phosphosilicate glass matrix in the reinforced composite membrane, which in turn offers favorable pathways for proton transport. Another advantageous feature of the reinforced composite membrane is higher proton conductivity under dehumidified conditions, as compared to a hydration-dependent polymer electrolyte membrane such as sulfonated poly(arylene ether sulfone) (SPAES). This superior proton conductivity of the reinforced composite membrane is further discussed with in-depth consideration of its architectural novelty and proton transport phenomena governed by the Grotthuss mechanism.close7

Obatoclax, a Pan-BCL-2 Inhibitor, Targets Cyclin D1 for Degradation to Induce Antiproliferation in Human Colorectal Carcinoma Cells

Colorectal cancer is the third most common cancer worldwide. Aberrant overexpression of antiapoptotic BCL-2 (B-cell lymphoma 2) family proteins is closely linked to tumorigenesis and poor prognosis in colorectal cancer. Obatoclax is an inhibitor targeting all antiapoptotic BCL-2 proteins. A previous study has described the antiproliferative action of obatoclax in one human colorectal cancer cell line without elucidating the underlying mechanisms. We herein reported that, in a panel of human colorectal cancer cell lines, obatoclax inhibits cell proliferation, suppresses clonogenicity, and induces G1-phase cell cycle arrest, along with cyclin D1 downregulation. Notably, ectopic cyclin D1 overexpression abrogated clonogenicity suppression but also G1-phase arrest elicited by obatoclax. Mechanistically, pre-treatment with the proteasome inhibitor MG-132 restored cyclin D1 levels in all obatoclax-treated cell lines. Cycloheximide chase analyses further revealed an evident reduction in the half-life of cyclin D1 protein by obatoclax, confirming that obatoclax downregulates cyclin D1 through induction of cyclin D1 proteasomal degradation. Lastly, threonine 286 phosphorylation of cyclin D1, which is essential for initiating cyclin D1 proteasomal degradation, was induced by obatoclax in one cell line but not others. Collectively, we reveal a novel anticancer mechanism of obatoclax by validating that obatoclax targets cyclin D1 for proteasomal degradation to downregulate cyclin D1 for inducing antiproliferation

Dual electrospray-assisted forced blending of thermodynamically immiscible polyelectrolyte mixtures

Polyelectrolytes have garnered significant attention as a key electrochemically-active component in a diversity of energy-related industry fields. Among enormous efforts to develop advanced polyelectrolytes, blending of different polyelectrolyte mixtures is suggested as a facile and efficient way. However, unavoidable thermodynamic immiscibility between the blend components has often caused serious challenges in the versatile fabrication of polyelectrolyte blends with desirable membrane properties. Here, as an unprecedented mixing strategy to address this issue, we demonstrate a new class of dual electrospray (DES)-assisted forced polymer blending. As a model system to explore the feasibility of this blending approach, Nafion and multiblock sulfonated hydrocarbon copolymer (denoted as sBlock) comprising sulfonated hydrophilic poly(arylene thioether sulfone) blocks and hydrophobic poly(arylene ether sulfone) blocks are chosen. The processing uniqueness and simplicity of the DES blending technique enable the successful fabrication of Nafion/sBlock blends (referred to as N/B blends) that are difficult to achieve with conventional blending methods due to their large miscibility difference. More notably, during the DES blending, nonsolvent-induced nanophase morphology reconstruction occurs in the N/B Blend, eventually giving rise to some difference in proton conductivity between experimental values and theoretically predicted ones. We envision that the DES-assisted forced blending strategy holds a great deal of promise as a versatile and scalable manufacturing technology to breakthrough the deadlock of thermodynamically immiscible polymer blends and also can be easily applicable to a wide variety of polymer blend systemsclose1

Obatoclax, a Pan-BCL-2 Inhibitor, Targets Cyclin D1 for Degradation to Induce Antiproliferation in Human Colorectal Carcinoma Cells

Colorectal cancer is the third most common cancer worldwide. Aberrant overexpression of antiapoptotic BCL-2 (B-cell lymphoma 2) family proteins is closely linked to tumorigenesis and poor prognosis in colorectal cancer. Obatoclax is an inhibitor targeting all antiapoptotic BCL-2 proteins. A previous study has described the antiproliferative action of obatoclax in one human colorectal cancer cell line without elucidating the underlying mechanisms. We herein reported that, in a panel of human colorectal cancer cell lines, obatoclax inhibits cell proliferation, suppresses clonogenicity, and induces G₁-phase cell cycle arrest, along with cyclin D1 downregulation. Notably, ectopic cyclin D1 overexpression abrogated clonogenicity suppression but also G₁-phase arrest elicited by obatoclax. Mechanistically, pre-treatment with the proteasome inhibitor MG-132 restored cyclin D1 levels in all obatoclax-treated cell lines. Cycloheximide chase analyses further revealed an evident reduction in the half-life of cyclin D1 protein by obatoclax, confirming that obatoclax downregulates cyclin D1 through induction of cyclin D1 proteasomal degradation. Lastly, threonine 286 phosphorylation of cyclin D1, which is essential for initiating cyclin D1 proteasomal degradation, was induced by obatoclax in one cell line but not others. Collectively, we reveal a novel anticancer mechanism of obatoclax by validating that obatoclax targets cyclin D1 for proteasomal degradation to downregulate cyclin D1 for inducing antiproliferation