Quantitative trait locus analysis of circulating adhesion molecules in hyperlipidemic apolipoprotein E-deficient mice

Circulating soluble adhesion molecules have been suggested as useful markers to predict several clinical conditions such as atherosclerosis, type 2 diabetes, obesity, and hypertension. To determine genetic factors influencing plasma levels of soluble vascular cell adhesion molecule-1 (VCAM-1) and P-selectin, quantitative trait locus (QTL) analysis was performed on an intercross between C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains deficient in apolipoprotein E-deficient (apoE^−/−). Female F₂ mice were fed a western diet for 12 weeks. One significant QTL, named sVcam1 (71 cM, LOD 3.9), on chromosome 9 and three suggestive QTLs on chromosomes 5, 13 and 15 were identified to affect soluble VCAM-1 levels. Soluble P-selectin levels were controlled by one significant QTL, named sSelp1 (8.5 cM, LOD 3.4), on chromosome 16 and two suggestive QTLs on chromosomes 10 and 13. Both adhesion molecules showed significant or an apparent trend of correlations with body weight, total cholesterol, and LDL/VLDL cholesterol levels in the F₂ population. These results indicate that plasma VCAM-1 and P-selectin levels are complex traits regulated by multiple genes, and this regulation is conferred, at least partially, by acting on body weight and lipid metabolism in hyperlipidemic apoE^−/− mice. Zuobiao Yuan and Zhiguang Su contributed equally.     

Polyamines content and physiological and biochemical responses to ladder concentration of nickel stress in Hydrocharis dubia (Bl.) Backer leaves

Influence of ladder concentration of nickel (Ni) on the leaves of Hydrocharis dubia were studied after 3 days treatment. The accumulation of Ni, the content of polyamines, proline, malondialdehyde (MDA) and soluble protein, as well as the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the leaves were investigated. The result indicated that the toxicity of Ni manifested in respective aspect of physiological and biochemical characters. Significant increase of Ni concentration in the leaf tissue was observed, which was concentration dependent. Visible symptoms of Ni toxicity: chlorosis and necrosis occurred following the 3rd day. Meantime, treatment with Ni resulted in the increase in the generation rate of O₂^•− in the leaves. SOD and CAT activities decreased significantly in response to Ni treatment, it was possibly the reason of accumulation of O₂^•−. However, a several-fold decrease in POD activities was found. Our results indicated that because of prolonged increases in O₂^•− level, oxidative damage, measured as the level of lipid peroxidation, occured in the leaves of Ni treated fronds. The changes of the content of polyamines (PAs) were also investigated in the leaves of Hydrocharis dubia. Ni treatment significantly increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby significantly reducing the ratio of free (Spd + Spm)/Put in leaves, which has been considered as the signal under stress. Although the trend that PS-conjugated PAs and PIS-bound PAs changed the same as free PAs, they changed in more less extent.     

Noncanonical E2 variant-independent function of UBC13 in promoting checkpoint protein assembly

The E2 ubiquitin-conjugating enzyme UBC13 plays pivotal roles in diverse biological processes. Recent studies have elucidated that UBC13, in concert with the E3 ubiquitin ligase RNF8, propagates the DNA damage signal via a ubiquitylation-dependent signaling pathway. However, mechanistically how UBC13 mediates its role in promoting checkpoint protein assembly and its genetic requirement for E2 variants remain elusive. Here we provide evidence to support the idea that the E3 ubiquitin ligase complex RNF8-UBC13 functions independently of E2 variants and is sufficient in facilitating ubiquitin conjugations and accumulation of DNA damage mediator 53BP1 at DNA breaks. The RNF8 RING domain serves as the molecular platform to anchor UBC13 at the damaged chromatin, where localized ubiquitylation events allow sustained accumulation of checkpoint proteins. Intriguingly, we found that only a group of RING domains derived from E3 ubiquitin ligases, which have been shown to interact with UBC13, enabled UBC13-mediated FK2 and 53BP1 focus formation at DNA breaks. We propose that the RNF8 RING domain selects and loads a subset of UBC13 molecules, distinct from those that exist as heterodimers, onto sites of double-strand breaks, which facilitates the amplification of DNA damage signals.     

Comparative proteomic analysis provides new insights into the fiber elongating process in cotton

A comparative proteomic analysis was performed to explore the mechanism of cell elongation in developing cotton fibers. The temporal changes of global proteomes at five representative development stages (5-25 days post-anthesis [dpa]) were examined using 2-D electrophoresis. Among approximately 1800 stained protein spots reproducibly detected on each gel, 235 spots were differentially expressed with significant dynamics in elongating fibers. Of these, 120 spots showed a more than 2-fold change in at least one stage point, and 21 spots appeared to be specific to developmental stages. Furthermore, 106 differentially expressed proteins were identified from mass spectrometry to match 66 unique protein species. These proteins involve different cellular and metabolic processes with obvious functional tendencies toward energy/carbohydrate metabolism, protein turnover, cytoskeleton dynamics, cellular responses and redox homeostasis, indicating a good correlation between development-dependent proteins and fiber biochemical processes, as well as morphogenesis. Newly identified proteins such as phospholipase D alpha, vf14-3-3 protein, small ras-related protein, and GDP dissociation inhibitor will advance our knowledge of the complicated regulatory network. Identification of these proteins, combined with their changes in abundance, provides a global view of the development-dependent protein changes in cotton fibers, and offers a framework for further functional research of target proteins associated with fiber development.     

Restoration of mature etiolated cucumber hypocotyl cell wall susceptibility to expansin by pretreatment with fungal pectinases and EGTA in vitro

Mature plant cell walls lose their ability to expand and become unresponsive to expansin. This phenomenon is believed to be due to cross-linking of hemicellulose, pectin, or phenolic groups in the wall. By screening various hydrolytic enzymes, we found that pretreatment of nongrowing, heat-inactivated, basal cucumber (Cucumis sativus) hypocotyls with pectin lyase (Pel1) from Aspergillus japonicus could restore reconstituted exogenous expansin-induced extension in mature cell walls in vitro. Recombinant pectate lyase A (PelA) and polygalacturonase (PG) from Aspergillus spp. exhibited similar capacity to Pel1. Pel1, PelA, and PG also enhanced the reconstituted expansin-induced extension of the apical (elongating) segments of cucumber hypocotyls. However, the effective concentrations of PelA and PG for enhancing the reconstituted expansin-induced extension were greater in the apical segments than in the basal segments, whereas Pel1 behaved in the opposite manner. These data are consistent with distribution of more methyl-esterified pectin in cell walls of the apical segments and less esterified pectin in the basal segments. Associated with the degree of esterification of pectin, more calcium was found in cell walls of basal segments compared to apical segments. Pretreatment of the calcium chelator EGTA could also restore mature cell walls' susceptibility to expansin by removing calcium from mature cell walls. Because recombinant pectinases do not hydrolyze other wall polysaccharides, and endoglucanase, xylanase, and protease cannot restore the mature wall's extensibility, we can conclude that the pectin network, especially calcium-pectate bridges, may be the primary factor that determines cucumber hypocotyl mature cell walls' unresponsiveness to expansin.     

热休克蛋白60与细胞凋亡

热休克蛋白60(heat shock protein 60, HSP60)是主要存在于线粒体内的分子伴侣蛋白,对于维持线粒体蛋白的正常结构和功能不可或缺.线粒体中的HSP60可作用于凋亡相关因子而抑制线粒体凋亡通路的激活,并且能够减少线粒体产生氧自由基;胞浆中的少量HSP60亦可通过与凋亡相关因子的相互作用等途径抑制细胞凋亡.相反,在某些刺激因素作用下或者HSP60细胞定位异常时,HSP60可产生促凋亡效应.HSP60在细胞凋亡中的双重作用及其对于肿瘤等疾病诊治的意义已引起高度关注.     

Modification of BECN1 by ISG15 plays a crucial role in autophagy regulation by type I IFN/interferon

ISG15 (ISG15 ubiquitin-like modifier), a ubiquitin-like protein, is one of the major type I IFN (interferon) effector systems. ISG15 can be conjugated to target proteins (ISGylation) via the stepwise action of E1, E2, and E3 enzymes. Conjugated ISG15 can be removed (deISGylated) from target proteins by USP18 (ubiquitin-specific peptidase 18). Here we investigated the role of deISGylation by USP18 in regulating autophagy and EGFR degradation in cells treated with type I IFNs. We show that type I IFN induced expression of ISG15 leads to ISGylation of BECN1 at Lys117, as well as Lys263, Lys265, and Lys266 which competes with Lys63 ubiquitination of BECN1. We demonstrate that ISGylation of BECN1 at Lys117, as well as Lys263, Lys265, and Lys266 serve an important role in negative regulation of intracellular processes including autophagy and EGFR degradation that are critically dependent upon the activity of class III PtdIns 3-kinase. Our studies provide fundamental new mechanistic insights into the innate immunity response implemented by type I IFNs.     

<Emphasis Type="Italic">Enterococcus faecalis</Emphasis> promotes osteoclast differentiation within an osteoblast/osteoclast co-culture system

Objective

To investigate the effects of heat-killed Enterococcus faecalis ATCC 29212 and P25RC clinical strain (derived from an obturated root canal with apical periodontitis) on osteoclast differentiation within an osteoblast/osteoclast co-culture system.

Results

Heat-killed E. faecalis significantly increased the proportion of multinucleated osteoclastic cells (MNCs) within the co-culture system. The IL-6 level was significantly increased upon exposure to heat-killed E. faecalis. Gene expression levels of NFATc1 and cathepsin K were significantly up-regulated compared to the untreated control. EphrinB2 and EphB4 expressions at both the mRNA and protein levels were also significantly upregulated compared to the untreated control.

Conclusions

Heat-killed E. faecalis can induce osteoclast differentiation within the osteoblast/osteoclast co-culture system in vitro, possibly through ephrinB2-EphB4 bidirectional signaling.

     

多甲藻属扫描电镜样品制备方法的比较研究

用扫描电镜(SEM)观察藻类细胞的表面形态特征,是研究藻类的系统分类、形态和生态学的重要手段之一。