Structural basis for phage-mediated activation and repression of bacterial DSR2 anti-phage defense system.

Silent information regulator 2 (Sir2) proteins typically catalyze NAD+-dependent protein deacetylation. The recently identified bacterial Sir2 domain-containing protein, defense-associated sirtuin 2 (DSR2), recognizes the phage tail tube and depletes NAD+ to abort phage propagation, which is counteracted by the phage-encoded DSR anti-defense 1 (DSAD1), but their molecular mechanisms remain unclear. Here, we determine cryo-EM structures of inactive DSR2 in its apo form, DSR2-DSAD1 and DSR2-DSAD1-NAD+, as well as active DSR2-tube and DSR2-tube-NAD+ complexes. DSR2 forms a tetramer with its C-terminal sensor domains (CTDs) in two distinct conformations: CTDclosed or CTDopen. Monomeric, rather than oligomeric, tail tube proteins preferentially bind to CTDclosed and activate Sir2 for NAD+ hydrolysis. DSAD1 binding to CTDopen allosterically inhibits tube binding and tube-mediated DSR2 activation. Our findings provide mechanistic insight into DSR2 assembly, tube-mediated DSR2 activation, and DSAD1-mediated inhibition and NAD+ substrate catalysis in bacterial DSR2 anti-phage defense systems.

Simulated weightlessness led to the transformation of glycolipid metabolism in the livers of mice / La antigravedad simulada provocó la transformación del metabolismo de los glicolípidos en el hígado de ratones / Antigravidade simulada levou à transformação do metabolismo de glicolipídios no fígado de camundongos

ABSTRACT Objectives: The effects of weightlessness on the liver were studied using a tail suspension (TS) male mouse model. Methods: The effects of 0-, 2- and 4-week TS (CON, TS2 and TS4 groups) on glycogen and lipid content, as well as on the molecular processes of the synthesis and degradation pathways, were examined. Results: (1) The number of glycogenosomes under ultrastructure and the glycogen content were considerably larger in the TS4 group than in the other two groups. (2) In the TS4 group, glycogen synthase activity remained constant while glycogen phosphorylase activity dropped, indicating that glycogen breakdown was reduced. (3) The livers of the TS2 group had the highest lipid and triglyceride content, indicating lipid buildup in the liver at this time. (4) In the TS2 group, the activities of the fatty acid synthesis-related factors acetyl-CoA carboxylase and fatty acid synthase increased, while hepatic lipase decreased, indicating that lipid synthesis increased, while decomposition decreased. (5) In the TS2 group, the protein expression of glucose transporters 1 and 2 increased. Conclusions: From TS2 weeks to TS4 weeks, the main energy consumption mode in the livers of mice transitioned from glucose metabolism to lipid metabolism as glucose use decreased. Level of evidence II; Comparative prospective study.

RESUMEN Objetivos: Se estudiaron los efectos de la antigravedad en el hígado utilizando un modelo de ratón macho en prueba de suspensión de la cola (TS, tail suspension). Métodos: Se examinaron los efectos de la TS a las 0, 2 y 4 semanas (grupos CON, TS2 y TS4) sobre el contenido de glucógeno y lípidos, así como sobre los procesos moleculares de las vías de síntesis y degradación. Resultados: (1) El número de glucogenosomas ultraestructurales y el contenido de glucógeno fueron expresivamente más altos en el grupo TS4 que en los otros dos grupos. (2) En el grupo TS4, la actividad de la glucógeno sintasa se mantuvo constante, mientras que la actividad de la glucógeno fosforilasa disminuyó, lo que indica que la degradación del glucógeno se redujo. (3) Los hígados del grupo TS2 presentaron el mayor contenido de lípidos y triglicéridos, lo que indica la acumulación de lípidos en el hígado en ese momento. (4) En el grupo TS2, la actividad de los factores relacionados con la síntesis de ácidos grasos acetil-CoA carboxilasa y ácido graso sintasa aumentó, mientras que la lipasa hepática disminuyó, indicando que la síntesis de lípidos aumentó mientras que la descomposición disminuyó. (5) En el grupo TS2, la expresión proteica de los transportadores de glucosa 1 y 2 aumentó. Conclusiones: Desde la semana TS2 hasta la semana TS4, el principal modo de consumo de energía en el hígado de los ratones pasó del metabolismo de la glucosa al metabolismo de los lípidos a medida que disminuía el uso de la glucosa. Nivel de Evidencia II, Estudio retrospectivo comparativo.

RESUMO Objetivos: Os efeitos da antigravidade no fígado foram estudados usando um modelo de camundongo macho com a suspensão pela cauda (TS, tail suspension). Métodos: Foram examinados os efeitos da TS em 0, 2 e 4 semanas (grupos CON, TS2 e TS4) sobre o conteúdo de glicogênio e lipídios, bem como nos processos moleculares das vias de síntese e degradação. Resultados: (1) O número de glicogenossomos ultraestruturais e o teor de glicogênio foram expressivamente maiores no grupo TS4 do que nos outros dois grupos. (2) No grupo TS4, a atividade de glicogênio sintase permaneceu constante, enquanto a atividade de glicogênio fosforilase caiu, indicando que a degradação do glicogênio foi reduzida. (3) Os fígados do grupo TS2 tiveram o maior teor lipídico e de triglicérides, indicando acúmulo de lipídios no fígado no momento. (4) No grupo TS2, a atividade dos fatores relacionados com a síntese de ácidos graxos acetil-CoA carboxilase e ácido graxo sintase aumentaram, enquanto a lipase hepática diminuiu, indicando que a síntese de lipídios aumentou, enquanto a decomposição diminuiu. (5) No grupo TS2, a expressão proteica dos transportadores de glicose 1 e 2 aumentou. Conclusões: De TS2 semanas para TS4 semanas, o principal modo de consumo de energia no fígado de camundongos passou do metabolismo da glicose para o metabolismo lipídico, à medida que o uso de glicose diminuiu. Nível de evidência II, Estudo retrospectivo comparativo.

Global gene expression analysis in liver of db/db mice treated with catalpol.

Catalpol, a major bioactive component from Rehmannia glutinosa, which has been used to treat diabetes. The present study was designed to elucidate the anti-diabetic effect and mechanism of action for catalpol in db/db mice. The db/db mice were randomly divided into six groups (10/group) according to their blood glucose levels: db/db control, metformin (positive control), and four dose levels of catalpol treatment (25, 50, 100, and 200 mg·kg-1), and 10 db/m mice were used as the normal control. All the groups were administered orally for 8 weeks. The levels of fasting blood glucose (FBG), random blood glucose (RBG), glucose tolerance, insulin tolerance, and glycated serum protein (GSP) and the globe gene expression in liver tissues were analyzed. Our results showed that catalpol treatment obviously reduced water intake and food intake in a dose-dependent manner. Catalpol treatment also remarkably reduce fasting blood glucose (FBG) and random blood glucose (RBG) in a dose-dependent manner. The RBG-lowering effect of catalpol was better than that of metformin. Furthermore, catalpol significantly improved glucose tolerance and insulin tolerance via increasing insulin sensitivity. Catalpol treatment significantly decreased GSP level. The comparisons of gene expression in liver tissues among normal control mice, db/db mice and catalpol treated mice (200 and 100 mg·kg-1) indicated that there were significant increases in the expressions of 287 genes, whichwere mainly involved in lipid metabolism, response to stress, energy metabolism, and cellular processes, and significant decreases in the expressions of 520 genes, which were mainly involved in cell growth, death, immune system, and response to stress. Four genes expressed differentially were linked to glucose metabolism or insulin signaling pathways, including Irs1 (insulin receptor substrate 1), Idh2 (isocitrate dehydrogenase 2 (NADP+), mitochondrial), G6pd2 (glucose-6-phosphate dehydrogenase 2), and SOCS3 (suppressor of cytokine signaling 3). In conclusion, catalpol ecerted significant hypoglycemic effect and remarkable therapeutic effect in db/db mice via modulating various gene expressions.

Spatial Distribution of Fine Particulate Matter in Underground Passageways.

The unfavorable locations of underground infrastructures and poor ventilation facilities can result in the deterioration of enclosed air quality. Some researchers have studied air quality and ventilation measures in different types of underground buildings. However, few studies have investigated the pollution in pedestrian passageways connecting underground structures. Hence, in this paper, we attempted to investigate the spatial distribution of fine particulate matter (PM2.5) in underground passageways. First, measurements were designed and conducted in a pedestrian passageway beneath the Shanghai South Railway Station, Shanghai, China. Second, numerical simulations were performed based on computational fluid dynamic (CFD) technology. Finally, the numerical simulations were extended to examine impacts of the ventilation measures on PM2.5 concentration with different inlet positions and air velocity in underground passageways. The simulation results showed good agreement with the experimental data, and the numerical model was validated to be an effective method to investigate the spatial distribution of PM2.5 in underground passageways. Results suggest that building additional entrances is an advisable method for improving air quality in the underground passageways of the Shanghai South Railway Station, while jet fans are not recommended. Findings of this study offer suggestions for mitigating PM2.5 pollution in underground passageways.