O-GlcNAcylation of Cofilin Promotes Breast Cancer Cell Invasion

O-GlcNAcylation is a post-translational modification that regulates a broad range of nuclear and cytoplasmic proteins and is emerging as a key regulator of various biological processes. Previous studies have shown that increased levels of global O-GlcNAcylation and O-GlcNAc transferase (OGT) are linked to the incidence of metastasis in breast cancer patients, but the molecular basis behind this is not fully known. In this study, we have determined that the actin-binding protein cofilin is O-GlcNAcylated by OGT and mainly, if not completely, mediates OGT modulation of cell mobility. O-GlcNAcylation at Ser-108 of cofilin is required for its proper localization in invadopodia at the leading edge of breast cancer cells during three-dimensional cell invasion. Loss of O-GlcNAcylation of cofilin leads to destabilization of invadopodia and impairs cell invasion, although the actin-severing activity or lamellipodial localization is not affected. Our study provides insights into the mechanism of post-translational modification in fine-tuning the regulation of cofilin activity and suggests its important implications in cancer metastasis.     

猪链球菌2型分选酶srtBCD 基因敲除株的构建及其生物学特性分析

【目的】阐明分选酶srtBCD基因在猪链球菌2型致病过程中的作用。【方法】利用同源重组原理构建中间为壮观霉素、两侧为srtBCD基因上下游片段的重组质粒,将构建好的质粒电转化入猪链球菌感受态,筛选srtBCD缺失的突变株,并通过组合PCR和逆转录PCR对其进行验证。生物学功能实验研究srtBCD突变株和野毒株05Z33在生长速率、粘附、毒力等方面的差异。【结果】组合PCR和逆转录PCR结果均证实srtBCD突变株构建成功,体外实验结果显示srtBCD缺失后细菌的生长速率减慢,与Hep-2上皮细胞的粘附率明显降低,小鼠毒力实验数据表明突变株毒力无明显变化。【结论】猪链球菌2型srtBCD基因与细菌的粘附能力有关,为进一步研究猪链球菌2型的致病机理奠定基础。     

Actin assembly by lithium ions.

The ability of Li+ to promote the assembly of actin has been compared with the more common cations used in actin assembly assays, K+, Mg2+, and Ca2+. The principal assay of actin assembly utilized was fluorescence photobleaching recovery (FPR), from which it is possible to determine the fraction of actin protomers incorporated into filaments and the average diffusion coefficients of the filaments. In addition, critical concentrations of actin over a range of concentrations of all of these cations have been determined using an assay that involves sonication and dilution of assembled actin filaments containing trace amounts of pyrene-labeled actin. The results demonstrate that Li+ is a more potent promoter of actin assembly than is K+. The more rapid assembly of actin in the presence of Li+ is attributable to an increased rate of filament elongation. Filaments assembled in equivalent concentrations of Li+ or K+ have the same diffusion coefficients, and thus presumably the same average lengths. The critical concentration of actin is about three times less in the presence of Li+ than in the presence of an equal concentration of K+. Cytochalasin D accelerates the rate of Li+-promoted actin assembly and reduces slightly the total fraction of actin assembly. However, cytochalasin D causes less shortening of filaments in the presence of Li+ than in the presence of K+ or Mg2+. By the criteria of assembly kinetics and critical concentration, Li+ is much less potent as a promoter of actin assembly than either Mg2+ or Ca2+. These results are discussed in terms of the role of electrostatic forces in the actin assembly mechanism and in terms of possible relationships to therapeutic and toxicity mechanisms for Li+.     

拟南芥微丝加帽蛋白β亚基参与壳梭孢素诱导的气孔开放过程

气孔是植物响应外源信号,与环境进行水分和气体交换的门户。由外源信号引起的保卫细胞微丝骨架动态变化在气孔运动中发挥重要作用,但是具体的精确调节机制仍不清楚。微丝结合蛋白家族(ABPs) 是微丝动态组装最直接的调控者,它们的作用不容忽视。本文运用反向遗传学,以微丝结合蛋白—加帽蛋白 (CP) β-亚基 (CPB) 突变体cpb-3为实验材料,探究其在壳梭孢素 (FC)诱导气孔开放中的作用。结果发现:离体叶片干燥3 h,cpb-3突变体的叶片失水率为63.45%,明显高于野生型的48.99%。气孔开度测量及激光共聚焦显微镜观察发现,cpb-3突变体的气孔开放程度以及微丝动态重排对FC分子更敏感。气孔开度相比野生型增大了20% (P<0.05),含辐射状微丝排布的保卫细胞数量比例增幅达到58.3%,比对照组高出18.5%。此外,非损伤微测技术记录保卫细胞Ca²⁺、K⁺等跨膜运输动态,FC处理下,cpb-3突变体保卫细胞中Ca²⁺外流速度升至212.86 pmol cm^-2s^-1,野生型仅为68.76 pmol cm^-2s^-1,明显快于野生型。且K⁺内流也有相同表现。综上表明,微丝加帽蛋白CP的β亚基CPB可能通过调节保卫细胞微丝骨架动态重排以及离子流动,在FC诱导的气孔运动中发挥重要的作用。     

A shift of Phloem unloading from symplasmic to apoplasmic pathway is involved in developmental onset of ripening in grape berry

It remains unclear whether the phloem unloading pathway alters to adapt to developmental transition in fleshy fruits that accumulate high level of soluble sugars. Using a combination of electron microscopy, transport of the phloem-mobile symplasmic tracer carboxyfluorescein, movement of the companion cell-expressed and the green fluorescent protein-tagged viral movement protein, and assays of the sucrose cleavage enzymes, the pathway of phloem unloading was studied in the berries of a hybrid grape (Vitis vinifera x Vitis labrusca). Structural investigations showed that the sieve element-companion cell complex is apparently symplasmically connected through plasmodesmata with surrounding parenchyma cells throughout fruit development, though a small portion of plasmodesmata are apparently blocked in the ripening stage. Both carboxyfluorescein and the green fluorescent protein-tagged viral movement protein were released from the functional phloem strands during the early and middle stages of fruit development, whereas the two symplasmic tracers were confined to the phloem strands during the late stage. This reveals a shift of phloem unloading from symplasmic to apoplasmic pathway during fruit development. The turning point of the phloem unloading pathways was further shown to be at or just before onset of ripening, an important developmental checkpoint of grape berry. In addition, the levels of both the expression and activities of cell wall acid invertase increased around the onset of ripening and reached a high level in the late stage, providing further evidence for an operation of the apoplasmic unloading pathway after onset of ripening. These data demonstrate clearly the occurrence of an adaptive shift of phloem unloading pathway to developmental transition from growing phase to ripening in grape berry.     

Fermentation of a milk-soymilk and Lycium chinense Miller mixture using a new isolate of Lactobacillus paracasei subsp. paracasei NTU101 and Bifidobacterium longum

A milk–soymilk mixture was fermented using Lactobacillus paracasei subsp. paracasei NTU101 and Bifidobacterium longum BCRC11847 at different inoculum ratios (1:1, 1:2, 1:5, 2:1, and 5:1). When the inoculum ratio was 1:2, the cell numbers of both strains were balanced after 12 h of cultivation. The pH and titratable acidity were very similar at the various inoculum ratios of cultivation. The milk–soymilk mixture was supplemented with 5, 10, 15, and 20% Lycium chinense Miller juice and fermented with Lactobacillus paracasei subsp. paracasei NTU101 and B. longum BCRC11847. Sensory evaluation results showed that supplementation with 5% Lycium chinense Miller juice improved the acceptability of the fermented milk–soymilk. The fermented beverage was stored at 4°C for 14 days; variations in pH and titratable acidity were slight. The cell numbers of L. paracasei subsp. paracasei NTU101 and B. longum BCRC11847 in the fermented beverage were maintained at 1.2×10⁹ CFU/ml and 6.3×10⁸ CFU/ml, respectively, after 14 days of storage.     

Differences in variation of human immunodeficiency virus type 1 sequences from Henan and Shanghai regions of China

Illegally paid blood donation was a risk factor for HIV acquisition exclusively in Henan and Hubei Provinces of China, and not in Shanghai. Nucleotide sequences in the gag and env genes of HIV-1 were compared between isolates from Henan and Shanghai regions of China to test whether an expected higher degree of a common source of infections from this unique blood donation transmission risk would be evident as decreased variation among Henan isolates in an exploratory cross-sectional analysis. Among 38 isolates studied, 23 of 23 (100%) from Henan and 8 of 15 (54%) from Shanghai were subtype B. In addition, fewer sequence differences were found in gp41 of subtype B isolates from Henan than from Shanghai isolates. Further studies with additional controls are therefore warranted to confirm the role of the degree of a common source of infections in differences in HIV variation across populations. Fundation items: The Vanderbilt-Meharry Center for AIDS Research (P30 AI 54999); R.T.D (R01 AI 29193); Start Fund of Ministry of Education of China (for Hong-zhou LU, 2004BA719A10).     

土壤原生动物对川滇高山栎恢复时间的响应及生长季动态

青藏高原东缘生态环境脆弱, 森林频繁遭到砍伐, 生物多样性受到严重威胁, 森林砍伐后的生态恢复成为研究热点。原生动物在生态恢复中作为指示生物起着重要作用。本文就未砍伐、砍伐后不同恢复时期(20年、10年和1年)生的川滇高山栎(Quercus aquifolioides)林的土壤理化性质和原生动物在生长季的变化进行比较研究, 以探讨生长季不同月份、不同恢复期的原生动物数量变化规律, 分析土壤理化性质与其相关性。结果表明: (1)恢复10年和1年的林地的鞭毛虫数量(193个/g干土, 164个/g干土)显著高于原始林地(22个/g干土), 肉足虫在恢复1年的林地中数量最多(600个/g干土), 纤毛虫数量则随次生演替进程逐渐增多。(2)在生长季不同月份原生动物的数量呈先增加后减少的趋势。鞭毛虫和肉足虫的峰值分别出现在7月和8月, 而纤毛虫的数量在7、8、9月明显高于6月。(3)原生动物数量与土壤理化性质密切相关。鞭毛虫数量与pH值呈显著正相关(P = 0.019), 纤毛虫数量与铵态氮(P = 0.002)和碳氮比呈显著正相关(P = 0.022), 肉足虫数量与硝态氮(P = 0.008)和碳氮比(P = 0.016)呈显著负相关。结果显示, 三种原生动物数量在生长季不同月份表现出较大的波动性, 其数量变化受土壤理化性质等多种因素调控。纤毛虫数量对川滇高山栎林砍伐恢复有正响应, 而鞭毛虫、肉足虫数量有负响应。     

Inhibition of Hedgehog Delays Liver Regeneration through Disrupting the Cell Cycle

Liver regeneration is a complicated biological process orchestrated by various liver resident cells. Hepatic cell proliferation and reconstruction of the hepatic architecture involve multiple signaling pathways. It has been reported that the Hh signal is involved in liver regeneration. However, the signal transduction pathways and cell types involved are ill studied. This study aimed to investigate hedgehog signal response cell types and the specific molecular mechanism involved in the process of liver regeneration. Partial hepatectomy (PH) of 70% was performed on ICR (Institute of Cancer Research) mice to study the process of liver regeneration. We found that the hedgehog signal was activated significantly after PH, including hedgehog ligands, receptors and intracellular signaling molecules. Ligand signals were mainly expressed in bile duct cells and non-parenchymal hepatic cells, while receptors were expressed in hepatocytes and some non-parenchymal cells. Inhibition of the hedgehog signal treated with vismodegib reduced the liver regeneration rate after partial hepatectomy, including inhibition of hepatic cell proliferation by decreasing Cyclin D expression and disturbing the cell cycle through the accumulation of Cyclin B. The current study reveals the important role of the hedgehog signal and its participation in the regulation of hepatic cell proliferation and the cell cycle during liver regeneration. It provides new insight into the recovery of the liver after liver resection.