Hepatitis C virus core protein modulates TRAIL-mediated apoptosis by enhancing Bid cleavage and activation of mitochondria apoptosis signaling pathway

Hepatitis C virus (HCV) is a major human pathogen causing chronic liver disease, which leads to cirrhosis of liver and hepatocellular carcinoma. The HCV core protein, a viral nucleocapsid, has been shown to affect various intracellular events, including cell proliferation and apoptosis. However, the precise mechanisms of the effects are not fully understood. In this study, we show that HCV core protein sensitizes human hepatocellular carcinoma cell line, Huh7, conferred sensitivity to TRAIL-, but not Fas ligand-mediated apoptosis. Huh7 cells are resistant to TRAIL, despite the induction of caspase-8 after TRAIL engagement. However, HCV core protein induces TRAIL apoptosis signaling via sequential induction of caspase-8, Bid cleavage, activation of mitochondrial pathway, and effector caspase-3. HCV core protein also induces activation of caspase-9 after TRAIL engagement, and the induction of TRAIL sensitivity by HCV core protein could be reversed by caspase-9 inhibitor. Therefore, the HCV core protein-induced TRAIL-mediated apoptosis is dependent upon activation of caspase-8 downstream pathway to convey the death signal to mitochondria, leading to activation of mitochondrial signaling pathway and breaking the apoptosis resistance. These results combined indicate that the HCV core protein enhances TRAIL-, but not Fas ligand-mediated apoptotic cell death in Huh7 cells via a mechanism dependent on the activation of mitochondria apoptosis signaling pathway. These results suggest that HCV core protein may have a role in immune-mediated liver cell injury by modulation of TRAIL-induced apoptosis.     

Strong electrostatic loop-helix interactions in bundle motif protein structures.

Based on CHARMM potential (Brooks et al., 1983) an energetic analysis has been carried out for four typical 4-alpha-helix bundle proteins, i.e., methemerythrin, cytochrome b-562, cytochrome c', and bovine somatotropin. The bovine somatotropin possesses long loops, but all the other three proteins have short loops. It was found that in all these four 4-alpha-helix bundle motif structures the interaction between loops and helices was much stronger than the interaction among the four helices themselves. Particularly for the electrostatic interaction energy, the loop-helix interaction is overwhelmingly stronger than the interhelix interaction although the latter involves the favorable helix dipole interaction due to the antiparallel arrangement of neighboring alpha-helices. The present study indicates that such a conclusion holds true regardless of what loops, long or short, are in the 4-alpha-helix bundle protein, and also regardless of which empirical potential, ECEPP or CHARMM, is used for calculations although in CHARMM the electrostatic energy is much more heavily emphasized than in ECEPP. Therefore, no appropriate conclusion can be drawn in arguing whether the dipole interaction among the four alpha-helices play a stabilizing role or destabilizing role for a 4-alpha-helix bundle protein without taking into consideration the effect of interaction between helices and loops. The calculated results reported here provide, from a different point of view, insights that might be useful for revealing the essence of the driving forces during the folding of proteins.     

Human neutrophil-derived elastase induces airway smooth muscle cell proliferation

Neutrophils and their derived elastase are abundant in chronic inflammatory responses of asthma. This study aimed to investigate the mitogenic effect of elastase on airway smooth muscle (ASM) cells and the implicated signal transduction pathway. Near confluent cultured human ASM cells were treated with human neutrophil elastase (HNE, 0.01 to 0.5 microg/ml) or vehicle for 24 hours with or without extracellular signal-regulated kinase (ERK) inhibitor (PD98059, 30 microM), p38 kinase inhibitor (SB203580, 10 microM) or elastase inhibitor II (100 microg/ml). The ASM cell numbers were counted by a hemocytometer and DNA synthesis was assessed by flowcytometry. Western blots analysis for the expression of ERK, p38 and cyclin D1 was determined. HNE dose-dependently increased ASM cell numbers and the percentage of cells entering S-phase of cell cycle. This response was abolished by neutrophil elastase inhibitors and attenuated by PD98059, but not SB203580. HNE increased ERK phosphorylation and cyclin D1 expression. Pretreatment with PD98059 significantly inhibited elastase-induced cyclin D1 activity. The increased ASM cellular gap and cell shape change by proteolytic activity of HNE may be contributory to ERK activation and therefore cell proliferation. Our results demonstrate that HNE is mitogenic for ASM cells by increasing cyclin D1 activity through ERK signaling pathway.     

Integration of clinical and gene expression endpoints to explore furan-mediated hepatotoxicity

Molecular techniques, such as cDNA microarrays, are being used to aid in the elucidation of the mechanisms of toxicity of a variety of compounds. In this study, we evaluate the molecular effects of furan in the rat liver. Sprague-Dawley rats were exposed to 4 or 40 mg/kg furan for up to 14 days. Furan induced an initial degenerative and necrotic phenotype that was followed by inflammation and fibrosis, consistent with previous observations for this compound. RNA was harvested from each lobe of the liver at several time points to observe whether lobe-specific gene expression effects occurred. Similar gene expression changes were observed in all lobes, however the magnitude of gene expression change was more pronounced in the right lobe. Finally, to help determine the correlation between gene expression changes and liver pathology, we applied traditional microarray visualization tools to the assessment of clinical chemistry and pathology parameters.     

Metabolite profiles of polyhydroxyalkanoate-producing Ralstonia eutropha H16

This study describes metabolite profiles of Ralstonia eutropha H16 focusing on biosynthesis of polyhydroxyalkanoates (PHAs), bacterial polyesters attracted as biodegradable bio-based plastics. As CoA-thioesters are important intermediates in PHA biosynthesis, four kinds of acyl-CoAs with medium chain length were prepared and used to establish analytical conditions for capillary electrophoresis-electron spray ionization-tandem mass spectrometry (CE–ESI-MS/MS). Metabolites were extracted from R. eutropha cells in growth, PHA production, and stationary phases on fructose and PHA production phase on octanoate, and subjected to stable isotope dilution-based comparative quantification by multiple reaction monitoring using CE–ESI-MS/MS and ¹³C-labeled metabolites prepared by extraction from R. eutropha mutant grown on U-¹³C₆-glucose. This procedure allowed to quantify relative changes of 94 ionic metabolites including CoA-thioesters. Hexose-phosphates except for glucose 1-phosphate were decreased in the PHA production phase than in the growth phase, suggesting reduced flux of sugar degradation after the cell growth. Several intermediates in TCA cycle and gluconeogenesis were increased in the PHA production phase on octanoate. Interestingly, ribulose 1,5-bisphosphate were detected in all the samples examined, raising possibilities of CO₂ fixation by Calvin–Benson–Bassham cycle in this bacterium even under heterotrophic growth conditions. Turnover of acyl moieties through β-oxidation was suggested to be active on fructose, as CoA-thioesters of C₆ and C₈ were detected in the fructose-grown cells. In addition, major metabolic pools in R. eutropha cells were estimated from the signal intensities. The results of the present study provided new insights into global metabolisms in PHA-producing R. eutropha.     

Ultrathin 2D TiS2 Nanosheets for High Capacity and Long‐Life Sodium Ion Batteries

Sodium ion batteries are now attracting great attention, mainly because of the abundance of sodium resources and their cheap raw materials. 2D materials possess a unique structure for sodium storage. Among them, transition metal chalcogenides exhibit significant potential for rechargeable battery devices due to their tunable composition, remarkable structural stability, fast ion transport, and robust kinetics. Herein, ultrathin TiS₂ nanosheets are synthesized by a shear‐mixing method and exhibit outstanding cycling performance (386 mAh g^?1 after 200 cycles at 0.2 A g^?1). To clarify the variations of galvanostatic curves and superior cycling performance, the mechanism and morphology changes are systematically investigated. This facile synthesis method is expected to shed light on the preparation of ultrathin 2D materials, whose unique morphologies could easily enable their application in rechargeable batteries.     

The cellular and molecular regulation of 1,25(OH)2D3 production

The synthesis of 1,25(OH)₂D₃ is a critical control point in the regulation of calcium metabolism, and possibly in the growth and differentiation of a number of cell types. This paper reviews our current understanding of the regulation of this process at the cellular and molecular levels, with the emphasis on the mechanisms of feedback control 1,25(OH)₂D₃ itself, control of parathyroid hormone, the roles of cyclic AMP dependent protein kinase and protein kinase C, and the interaction between the various intracellular regulators of 1,25(OH)₂D₃ production.     

Multiple causation of phylogeographical pattern as revealed by nested clade analysis of the bamboo viper (Trimeresurus stejnegeri) within Taiwan

In order to assess the utility of nested clade analysis, both standard phylogenetic algorithms and nested clade analysis were performed on a geographically widespread survey of mitochondrial DNA haplotypes of the bamboo viper, Trimeresurus stejnegeri, within Taiwan. Gross tree topologies were congruent for all analyses and indicated the presence of two geographically overlapping clades within Taiwan. The smaller lineage was restricted to the north and east coasts, whereas the larger lineage occupied all but the northern range of the species within Taiwan including the Pacific offshore populations of Green and Orchid Islands. The phylogeographical pattern supports the existence of at least one colonization event from the continent since the initial isolation of Taiwan from the mainland in the Pliocene. However, determining the exact number of colonization events was not possible due to the simultaneous vicariant forces of hypothesized continental landbridge connections and the occurrence of dramatic in situ orogenesis throughout the Pleistocene. Nested clade analysis provided multiple temporal and spatial population historical inferences that are not possible with standard analyses and therefore should become widely applied to future phylogeographical studies.     

Metabolic engineering of Escherichia coli for 1-butanol production

Compared to ethanol, butanol offers many advantages as a substitute for gasoline because of higher energy content and higher hydrophobicity. Typically, 1-butanol is produced by Clostridium in a mixed-product fermentation. To facilitate strain improvement for specificity and productivity, we engineered a synthetic pathway in Escherichia coli and demonstrated the production of 1-butanol from this non-native user-friendly host. Alternative genes and competing pathway deletions were evaluated for 1-butanol production. Results show promise for using E. coli for 1-butanol production.