A Rhodococcus qsdA-encoded enzyme defines a novel class of large-spectrum quorum-quenching lactonases

A gene involved in N-acyl homoserine lactone (N-AHSL) degradation was identified by screening a genomic library of Rhodococcus erythropolis strain W2. This gene, named qsdA (for quorum-sensing signal degradation), encodes an N-AHSL lactonase unrelated to the two previously characterized N-AHSL-degrading enzymes, i.e., the lactonase AiiA and the amidohydrolase AiiD. QsdA is related to phosphotriesterases and constitutes the reference of a novel class of N-AHSL degradation enzymes. It confers the ability to inactivate N-AHSLs with an acyl chain ranging from C(6) to C(14), with or without substitution at carbon 3. Screening of a collection of 15 Rhodococcus strains and strains closely related to this genus clearly highlighted the relationship between the ability to degrade N-AHSLs and the presence of the qsdA gene in Rhodococcus. Bacteria harboring the qsdA gene interfere very efficiently with quorum-sensing-regulated functions, demonstrating that qsdA is a valuable tool for developing quorum-quenching procedures.     

From Guard to Decoy: a new model for perception of plant pathogen effectors

The Guard Model for disease resistance postulates that plant resistance proteins act by monitoring (guarding) the target of their corresponding pathogen effector. We posit, however, that guarded effector targets are evolutionarily unstable in plant populations polymorphic for resistance (R) genes. Depending on the absence or presence of the R gene, guarded effector targets are subject to opposing selection forces (1) to evade manipulation by effectors (weaker interaction) and (2) to improve perception of effectors (stronger interaction). Duplication of the effector target gene or independent evolution of a target mimic could relax evolutionary constraints and result in a decoy that would be solely involved in effector perception. There is growing support for this Decoy Model from four diverse cases of effector perception involving Pto, Bs3, RCR3, and RIN4. We discuss the differences between the Guard and Decoy Models and their variants, hypothesize how decoys might have evolved, and suggest ways to challenge the Decoy Model.     

A Point Mutation in Translation Initiation Factor 2B Leads to a Continuous Hyper Stress State in Oligodendroglial-Derived Cells

Background

Mutations in eukaryotic translation initiation factor 2B (eIF2B) cause Childhood Ataxia with CNS Hypomyelination (CACH), also known as Vanishing White Matter disease (VWM). The disease is manifested by loss of brain myelin upon physiological stress. In a previous study, we showed that fibroblasts isolated from CACH/VWM patients are hypersensitive to pharmacologically-induced endoplasmic reticulum (ER) stress. Since brain cells from affected individuals are not available for research, we wished to assess the effect of eIF2B mutation on oligodendroglial-derived cells.

Methodology/Principal Findings

A rat oligodendroglial-derived cell line was used for a stable knock-down of eIF2B5 followed by stable expression of mutated eIF2B5(R195H) cDNA. In response to a pharmacological ER-stress agent, eIF2B5(R195H) expressing cells exhibited heightened ER-stress response demonstrated by hyper induction of ATF4, GADD34, Bip, PDIA1, PDIA3, PDIA4 and PDIA6 proteins. Moreover, even in the absence of a pharmacological stress agent, eIF2B5(R195H)-expressing cells exhibited high basal levels of ATF4, GADD34 and ER-associated Bip, PDIA1 and PDIA3.

Significance

The data provide evidence that oligodendroglial-derived cells expressing a mutated eIF2B constantly use their stress response mechanism as an adaptation mean in order to survive. The current study is the first to demonstrate the effects of eIF2B5 mutation on ER homeostasis in oligodendroglial-derived cells.     

Synthesis and protective effects of coumarin derivatives against oxidative stress induced by doxorubicin

The use of doxorubicin (DOX) in the treatment of solid tumors is limited by cardiotoxicity essentially due to oxidative stress generation. The aim of this study was to identify coumarin derivatives displaying a protective antioxidant activity without affecting DOX antitumoral efficiency. A set of eighteen coumarinic derivatives was synthesized. Their antioxidant power was evaluated in vitro with the FRAP (ferric reducing ability of plasma) method and in human breast adenocarcinoma MCF7 cells using H(2)DCFDA (2',7'-dichlorodihydrofluorescein diacetate) in a cytometric analysis. 4-Methyl-7,8-dihydroxycoumarin was found to exhibit an important antioxidant strength, a low cytotoxicity, and could decrease ROS (reactive oxygen species) production generated by DOX treatment without affecting DOX cytotoxicity in MCF7 cells.     

Déficit androgénique lié à l’âge. Que faut-il attendre de l’androgénothérapie?

With the exception of disease or drug-induced changes in Leydig cell function, aging is accompanied by specific changes of androgen status in healthy men. The level of testosterone production decreases in contrast with the rise in plasma protein testosterone binding capacity. Free testosterone, considered to be the biologically active fraction, decreases, leading to tissue androgen deficiency. The resulting clinical picture mimics hypogonadism, including physical and psychological asthenia, decreased libido and sexual behaviour, increased fat mass and decreased lean mass, gynaecomastia, osteoporosis and pro-atherogenic metabolic changes. The cut-off value for plasma testosterone below which androgen deficiency can be considered to be responsible for clinical signs is a key point which determines the therapeutic approach. In the absence of clearly validated data in healthy aging males, this cut-off value has been consensually defined as the mean plasma testosterone levels of men between 30 and 50 years of age minus two standard deviations, corresponding to the zone of hypogonadism in adult males. The association of clinical signs compatible with hypogonadism and reduced total (or preferably bioavailable) plasma testosterone level justifies initiation of hormone replacement therapy after excluding any contraindications (especially prostatic). The aim of this treatment is to reverse the consequences of age-related hypogonadism. Some benefits of this treatment have been clearly demonstrated, such as a decrease of fat mass, and an increase of lean mass and muscle strength. Similarly, bone mineral density increases, particularly in men with the lowest pretreatment plasma testosterone levels. It must be stressed that these changes are observed in truly hypogonadal aging men, but not in aging men with normal plasma testosterone levels. Testosterone replacement therapy can promote the development of gynaecomastia, while dihydrotestosterone tends to reduce gynaecomastia. Finally, androgen replacement therapy appears to improve a hypogonadism-related decrease in libido or sexual behaviour, provided other associated non-endocrine factors have been previously treated. Androgen replacement therapy improves well-being, and physical and psychological asthenia in hypogonadal men. However, this treatment has not been demonstrated to be effective in healthy aging men. Although androgen replacement therapy does not have a negative impact on lipid parameters, its possible cardiovascular protective effects have not yet been demonstrated. In conclusion, androgen replacement therapy, respecting the contraindications, is beneficial in patients of all ages with clearly demonstrated hypogonadism, but has no efficacy on symptoms in other cases.     

Human T-lymphocyte cytotoxicity and proliferation directed by a single chimeric TCRzeta /CD28 receptor.

Artificial receptors provide a promising approach to target T lymphocytes to tumor antigens. However, the receptors described thus far produce either an activation or a co-stimulatory signal alone, thus limiting the spectrum of functions accomplished by the genetically modified cells. Here we show that human primary T lymphocytes expressing fusion receptors directed to prostate-specific membrane antigen (PSMA) and containing combined T-cell receptor-zeta (TCRzeta), and CD28 signaling elements, effectively lyse tumor cells expressing PSMA. When stimulated by cell-surface PSMA, retrovirally transduced lymphocytes undergo robust proliferation, expanding by more than 2 logs in three weeks, and produce large amounts of interleukin-2 (IL-2). Importantly, the amplified cell populations retain their antigen-specific cytolytic activity. These data demonstrate that fusion receptors containing both TCR and CD28 signaling moieties are potent molecules able to redirect and amplify human T-cell responses. These findings have important implications for adoptive immunotherapy of cancer, especially in the context of tumor cells that fail to express major histocompatibility complex antigens and co-stimulatory molecules.     

Salmonella enters a dormant state within human epithelial cells for persistent infection

Salmonella Typhimurium (S. Typhimurium) is an enteric bacterium capable of invading a wide range of hosts, including rodents and humans. It targets different host cell types showing different intracellular lifestyles. S. Typhimurium colonizes different intracellular niches and is able to either actively divide at various rates or remain dormant to persist. A comprehensive tool to determine these distinct S. Typhimurium lifestyles remains lacking. Here we developed a novel fluorescent reporter, Salmonella INtracellular Analyzer (SINA), compatible for fluorescence microscopy and flow cytometry in single-bacterium level quantification. This identified a S. Typhimurium subpopulation in infected epithelial cells that exhibits a unique phenotype in comparison to the previously documented vacuolar or cytosolic S. Typhimurium. This subpopulation entered a dormant state in a vesicular compartment distinct from the conventional Salmonella-containing vacuoles (SCV) as well as the previously reported niche of dormant S. Typhimurium in macrophages. The dormant S. Typhimurium inside enterocytes were viable and expressed Salmonella Pathogenicity Island 2 (SPI-2) virulence factors at later time points. We found that the formation of these dormant S. Typhimurium is not triggered by the loss of SPI-2 effector secretion but it is regulated by (p)ppGpp-mediated stringent response through RelA and SpoT. We predict that intraepithelial dormant S. Typhimurium represents an important pathogen niche and provides an alternative strategy for S. Typhimurium pathogenicity and its persistence.     

The chemical compound ‘Heatin’ stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1-subfamily of nitrilases

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth-based adaptations that enhance leaf-cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4-2–deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound ‘Heatin’, containing 1-iminomethyl-2-naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin-mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1-subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin-mediated hypocotyl elongation requires the NITRILASE1-subfamily members, NIT1 and NIT2. Heatin inhibits NIT1-subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1-subfamily substrate indole-3-acetonitrile in vivo. However, levels of the NIT1-subfamily product, bioactive auxin (indole-3-acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1-subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole-3-acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.