Interaction of a putative BH3 domain of clusterin with anti-apoptotic Bcl-2 family proteins as revealed by NMR spectroscopy

Clusterin (CLU) is a multifunctional glycoprotein that is overexpressed in prostate and breast cancers. Although CLU is known to be involved in the regulation of apoptosis and cell survival, the precise molecular mechanism underlying the pro-apoptotic function of nuclear CLU (nCLU) remains unclear. In this study, we identified a conserved BH3 motif in C-terminal coiled coil (CC2) region of nCLU by sequence analysis and characterized the molecular interaction of the putative nCLU BH3 domain with anti-apoptotic Bcl-2 family proteins by nuclear magnetic resonance (NMR) spectroscopy. The chemical shift perturbation data demonstrated that the nCLU BH3 domain binds to pro-apoptotic BH3 peptide-binding grooves in both Bcl-X_L and Bcl-2. A structural model of the Bcl-X_L/nCLU BH3 peptide complex reveals that the binding mode is remarkably similar to those of other Bcl-X_L/BH3 peptide complexes. In addition, mutational analysis confirmed that Leu323 and Asp328 of nCLU BH3 domain, absolutely conserved in the BH3 motifs of BH3-only protein family, are critical for binding to Bcl-X_L. Taken altogether, our results suggest a molecular basis for the pro-apoptotic function of nCLU by elucidating the residue specific interactions of the BH3 motif in nCLU with anti-apoptotic Bcl-2 family proteins.     

Effects of grazing management system on plant community structure and functioning in a semiarid steppe: scaling from species to community

Under the aim of searching for a more sustainable grazing management system, a mixed management system (grazing and haymaking alternate annually) was proposed and tested against traditional management system (used consistently either for grazing or haymaking) in the semiarid grassland of Inner Mongolia with a field manipulation experiment. The responses of aboveground biomass to the two grazing management systems were examined across different levels of organization (i.e., species, plant functional group, and community) and in five consecutive years from 2005 to 2009. The effects of the two systems on seed production potential of four dominant species (Leymus chinensis, Stipa grandis, Agropyron cristatum, Cleistogenes squarrosa) were also investigated. Our results demonstrate that, in the traditional system, aboveground biomass production across all the levels of organization was reduced by grazing. In mixed system, however, no significantly negative relationship between the biomass response and stocking rate was detected at all organization levels. Precipitation fluctuation had strong influence on biomass responses, and compared to the traditional system the slope of the biomass-precipitation relationship tends to be higher in the mixed system. This effect might be attributed to the more positive response of L. chinensis and A. cristatum to increase in precipitation. In the traditional system, both the ratio and the density of reproductive tillers of the grazing subplots were significantly reduced compared to the haymaking or ungrazed control plots. In the mixed system, there was no significant difference between the haymaking subplots and the ungrazed control plots, regardless of the grazing pressures imposed on the haymaking subplots in the previous growing season. Our findings suggest that the mixed system mitigates the sheep grazing-induced species shift and it tends to be more responsive to increasing precipitation as compared to the traditional system. Therefore, replacement of the traditional grazing strategy with the mixed system could provide an important contribution to sustainable land-use of the Inner Mongolia grasslands.     

The spectrum of median craniofacial dysplasia

Given the multiple permutations in craniofacial malformations, classification of median craniofacial dysplasia or midline Tessier no. 0 to 14 clefts has been difficult and disjointed. In this review, the authors present a summary of normal embryology, prior terminology, and their proposed new classification system. Median craniofacial dysplasia has tissue agenesis and holoprosencephaly at one end (the hypoplasias), frontonasal hyperplasia and excessive tissue (the hyperplasias) at the other end, and abnormal splitting or clefting and normal tissue volume (dysraphia) occupying the middle portion of the spectrum. These three distinct subclassifications have different forms of anomalies within their groups.     

Multiple mechanisms underlie rapid expansion of an invasive alien plant

? With growing concerns over serious ecological problems, a particular challenge is to reveal the complex mechanisms underlying rapid expansion of invasive species. Ageratina adenophora is of particular interest in addressing this question. ? We used geographic information systems and logistic regression to identify the geographic and environmental factors contributing to the presence of A. adenophora. Join-count spatial statistics with reproduction mode examination were employed to elucidate the spatiotemporal dispersal mechanisms. ? Multiple factors have significantly contributed to the rapid expansion of A. adenophora. Its biological traits, favoring dispersal by water and wind coupled with local spatiotemporally heterogeneous geography and ecology, promote invasion downstream and upstream along river valleys, while other factors associated with human activities facilitate its invasion over high mountains and across river valleys, providing new scope for progressive invasions. We further identified an unusual invasion event of A. adenophora subsequent to a great flood that amplified its dispersal ability from vegetative propagules and seeds. ? These findings suggest that dynamic interactions of multiple factors in heterogeneous ecogeographical environments - a 'combinatorial' invasion mechanism - would generate an unexpected invasion rate of an alien species or a seemingly stochastic invasion event.     

Analysis of white blood cell counts in mice after gamma- or proton-radiation exposure

In the coming decades human space exploration is expected to move beyond low-Earth orbit. This transition involves increasing mission time and therefore an increased risk of radiation exposure from solar particle event (SPE) radiation. Acute radiation effects after exposure to SPE radiation are of prime importance due to potential mission-threatening consequences. The major objective of this study was to characterize the dose-response relationship for proton and γ radiation delivered at doses up to 2 Gy at high (0.5 Gy/min) and low (0.5 Gy/h) dose rates using white blood cell (WBC) counts as a biological end point. The results demonstrate a dose-dependent decrease in WBC counts in mice exposed to high- and low-dose-rate proton and γ radiation, suggesting that astronauts exposed to SPE-like radiation may experience a significant decrease in circulating leukocytes.     

Dual effects of estrogen on vascular smooth muscle cells: receptor-mediated proliferative vs. metabolite-induced pro-senescent actions

Objective

To investigate the mechanism for the dual effects of estrogen on vascular smooth muscle cells (VSMCs).

Methods

Cultured rat VSMCs were exposed to gradient concentrations (10⁻⁹-10⁻⁵ M) of 17β-estradiol (E₂) with or without pre-administration of a broad-spectrum CYP450 inhibitor 1-aminobenzotriazole (ABT) (10 × 10⁻⁶ M) and an estrogen receptor (ER) antagonist ICI 182,780 (10⁻⁶ M), respectively. The growth, cell cycle progression, premature senescence, estrogen metabolites, reactive oxygen species (ROS) and DNA damage of the cells were analyzed with cell counting assay, flow cytometry, Western blot, liquid chromatography-mass spectrometry and comet assay, respectively.

Results

E₂ in its physiological levels from 10⁻⁹ M to 10⁻⁸ M had a concentration-dependent promoting effect on growth of VSMCs. However, when the concentration increased over 10⁻⁸ M, the growth-promoting effect gradually reversed to a growth-inhibiting action. When the activity of CYP450s was blocked by ABT, the growth-promoting effect of E₂ increased and did not reverse at high concentrations. Whereas when the ERs were blocked by ICI 182,780, E₂ showed a pure growth-inhibiting effect. The E₂ metabolites 2- and 4-hydroxyestradiols accumulated with the increase of E₂ over 10⁻⁸ M, which accompanied by increased ROS, DNA damage and cellular senescence. All of these changes were eliminated by block of CYP450s, indicating that the VSMC growth inhibition by E₂ is due to an increased production of ROS from accumulated E₂ metabolites which induces DNA damage, leading to VSMC premature senescence.

Conclusion

The complex effect of E₂ is due to two opposite actions: one ER-mediated and proliferative, and the other estrogen metabolite-induced and pro-senescent.     

Hydrolysis of cellulose in synergistic mixtures of β-glucosidase and endo/exocellulase Cel9A from <Emphasis Type="Italic">Thermobifida fusca</Emphasis>

The synergism between the endo/exocellulase, Cel9A, and β-glucosidase (βgl) of Thermobifida fusca was investigated. Wild type βgl or S319C, a βgl mutant with significantly improved cellobiase activity, were added to Cel9A. Both wild type and mutant βgl enhanced the Cel9A hydrolysis of carboxymethyl cellulose (CMC) and filter paper by 50–100% compared to Cel9A alone. No enhancement occurred with addition of E388A, an inactive form of βgl. HPLC analysis showed that, with Cel9A alone, the resulting hydrolysate of glucose and cellobiose contained about half glucose; after addition of equimolar amounts of either wild type βgl or mutant S319C to Cel9A, the hydrolysate contained more than 85% glucose. βgl thus acted synergistically with Cel9A by converting cello-oligomers to glucose; this reduced the soluble sugar accumulation during hydrolysis of cellulose.