Platelet-activating factor downregulates the expression of liver X receptor-α and its target genes in human neutrophils

Liver X receptors (LXRs) are ligand-activated members of the nuclear receptor superfamily that regulate the expression of genes involved in lipid metabolism and inflammation, although their role in inflammation and immunity is less well known. It has been reported that oxysterols/LXRs may act as anti-inflammatory molecules, although opposite actions have also been reported. In this study, we investigated the effect of platelet-activating factor (PAF), a proinflammatory molecule, on LXRα signalling in human neutrophils. We found that PAF exerted an inhibitory effect on mRNA expression of TO901317-induced LXRα, ATP-binding cassette transporter A1, ATP-binding cassette transporter G1, and sterol response element binding protein 1c. This negative action was mediated by the PAF receptor, and was dependent on the release of reactive oxygen species elicited by PAF, as it was enhanced by pro-oxidant treatment and reversed by antioxidants. Current data also support the idea that PAF induces phosphorylation of the LXRα molecule in an extracellular signal-regulated kinase 1/2-mediated fashion. These results suggest that a possible mechanism by which PAF exerts its proinflammatory effect is through the downregulation of LXRα and its related genes, which supports the notion that LXRα ligands exert a modulatory role in the neutrophil-mediated inflammatory response.

Nitrogen regulation of protein–protein interactions and transcript levels of GlnK PII regulator and AmtB ammonium transporter homologs in Archaea

Gene homologs of GlnK PII regulators and AmtB-type ammonium transporters are often paired on prokaryotic genomes, suggesting these proteins share an ancient functional relationship. Here, we demonstrate for the first time in Archaea that GlnK associates with AmtB in membrane fractions after ammonium shock, thus, providing a further insight into GlnK-AmtB as an ancient nitrogen sensor pair. For this work, Haloferax mediterranei was advanced for study through the generation of a pyrE2-based counterselection system that was used for targeted gene deletion and expression of Flag-tagged proteins from their native promoters. AmtB1-Flag was detected in membrane fractions of cells grown on nitrate and was found to coimmunoprecipitate with GlnK after ammonium shock. Thus, in analogy to bacteria, the archaeal GlnK PII may block the AmtB1 ammonium transporter under nitrogen-rich conditions. In addition to this regulated protein–protein interaction, the archaeal amtB-glnK gene pairs were found to be highly regulated by nitrogen availability with transcript levels high under conditions of nitrogen limitation and low during nitrogen excess. While transcript levels of glnK-amtB are similarly regulated by nitrogen availability in bacteria, transcriptional regulators of the bacterial glnK promoter including activation by the two-component signal transduction proteins NtrC (GlnG, NRI) and NtrB (GlnL, NRII) and sigma factor σN (σ54) are not conserved in archaea suggesting a novel mechanism of transcriptional control.

Elaboración de materiales curriculares para el desarrollo de la competencia lingüística árabe. Ejercicios gramaticales A1

El objetivo de esta red es la creación de un Cuaderno de ejercicios gramaticales de lengua árabe en el nivel A1 del Marco Común Europeo de Referencia para las Lenguas (MCERL). Se justifica por la escasez de este tipo de materiales ajustados al MCERL, y su necesidad para la progresión en el aprendizaje de la competencia lingüística en contextos docentes presenciales, pero, sobre todo, no presenciales. Las características principales que se le han dado al Cuaderno, además de su ajuste al currículo de lengua árabe y al nivel A1 del MCERL, son: graduación de los ejercicios según dificultad; adecuado como material de autoaprendizaje sin profesor; de fácil ampliación, y trasladable a una plataforma digital. El Cuaderno será utilizado durante el próximo curso con los alumnos de lengua árabe del primer año de los grados de Estudios Árabes e Islámicos y de Traducción e Interpretación, para ser posteriormente ampliado en papel y/o adaptado a una plataforma virtual de enseñanza / aprendizaje, especialmente, Moodle UA.