Effects of endogenous beta-amyloid overproduction on tau phosphorylation in cell culture

Alzheimer's disease is characterized by beta-amyloid (Abeta) overproduction and tau hyperphosphorylation. Recent studies have shown that synthetic Abeta promotes tau phosphorylation in vitro. However, whether endogenously overproduced Abeta promotes tau phosphorylation and the underlying mechanisms remain unknown. Here, we used mouse neuroblastoma N2a stably expressing wild-type amyloid precursor protein (APPwt) or the Swedish mutant APP (APPswe) to determine the alterations of phosphorylated tau and the related protein kinases. We found that phosphorylation of tau at paired helical filament (PHF)-1, pSer396 and pThr231 epitopes was significantly increased in cells transfected with APPwt and APPswe, which produced higher levels of Abeta than cells transfected with vector or amyloid precursor-like protein 1. The activity of glycogen synthase kinase-3 (GSK-3) was up-regulated with a concomitant reduction in the inhibitory phosphorylation of GSK-3 at its N-terminal Ser9 residue. In contrast, the activity of cyclin-dependent kinase-5 (CDK-5) and protein kinase C (PKC) was down-regulated. Inhibition of GSK-3 by LiCl, but not inhibition of CDK-5 by roscovitine, arrested Abeta secretion and tau phosphorylation. Inhibition of PKC by GF-109203X activated GSK-3, whereas activation of PKC by phorbol-12,13-dibutyrate inhibited GSK-3. These results suggest that endogenously overproduced Abeta induces increased tau phosphorylation through activation of GSK-3, and that inactivation of PKC is at least one of the mechanisms involved in GSK-3 activation.     

Hsp90α/β associates with the GSK3β/axin1/phospho-β-catenin complex in the human MCF-7 epithelial breast cancer model

Hsp90α/β, the signal transduction chaperone, maintains intracellular communication in normal, stem, and cancer cells. The well characterised association of Hsp90α/β with its client kinases form the framework of multiple signalling networks. GSK3β, a known Hsp90α/β client, mediates β-catenin phosphorylation as part of a cytoplasmic destruction complex which targets phospho-β-catenin to the 26S proteasome. The canonical Wnt/β-catenin pathway promotes stem cell self-renewal as well as oncogenesis. The degree of Hsp90α/β involvement in Wnt/β-catenin signalling needs clarification. Here, we describe the association of Hsp90α/β with GSK3β, β-catenin, phospho-β-catenin and the molecular scaffold, axin1, in the human MCF-7 epithelial breast cancer cell model using selective inhibition of Hsp90α/β, confocal laser scanning microscopy and immunoprecipitation. Our findings suggest that Hsp90α/β modulates the phosphorylation of β-catenin by interaction in common complex with GSK3β/axin1/β-catenin.     

A metabolic model for acetate uptake under anaerobic conditions by glycogen accumulating organisms: Stoichiometry, kinetics, and the effect of pH

A metabolic model for the stoichiometry of acetate uptake under anaerobic conditions by an enriched culture of glycogen accumulating organisms (GAOs) was developed and tested by experimental studies. Glycogen served as the source of both reducing power and energy to drive the process of acetate uptake. The amount of glycogen consumed and poly-beta-hydroxyvalerate (PHV) accumulated in the cells increased with increasing pH, indicating that the energy requirements for acetate uptake increased with pH. The composition of the accumulated poly-beta-hydroxyalkanoates (PHAs) was adequately predicted using the assumption that acetyl-CoA and propionyl-CoA condense randomly to produce PHA. In addition, the rate of acetate uptake was strongly affected by the pH. The rate decreased with increasing pH and this dependence could be described with a saturation type of expression. A comparison of the rate of acetate uptake at low pH with the rates observed in enriched cultures of phosphorus accumulating organisms (PAOs) indicated that GAOs are able to compete effectively with PAOs in nutrient removal systems under certain conditions.     

低温驯化后水椰八角铁甲生理活性物质含量的变化

【目的】分析低温驯化后水椰八角铁甲Octodonta nipae体内各种生理活性物质含量的变化,为揭示水椰八角铁甲耐寒机制提供理论基础。【方法】以25℃处理为对照,将水椰八角铁甲各虫态于12.5, 15, 17.5和20℃驯化处理10 d后,比较其体内的游离水、蛋白质、氨基酸、粗脂肪、甘油和可溶性糖原等生理活性物质含量的变化。【结果】低温驯化显著影响铁甲体内上述物质的含量水平。低温驯化能提高该铁甲体内甘油和游离氨基酸的含量,降低游离水、蛋白质、粗脂肪、可溶性糖原的含量。与对照相比,12.5℃驯化对该铁甲各虫态体内游离水含量存在显著影响(P<0.01);经12.5, 15, 17.5和20.0℃驯化后,该铁甲各虫态体内蛋白质、粗脂肪含量与对照相比均存在显著差异(P<0.01);经125,150和175℃驯化后,该铁甲各虫态体内游离氨基酸含量与对照存在显著差异(P<0.01);经12.5,15.0,17.5和20℃驯化后,该铁甲各虫态（2龄幼虫除外）体内甘油含量与对照相比存在显著差异(P<0.01);12.5, 15.0, 17.5和20℃驯化对除2龄幼虫、蛹和成虫外的铁甲其他各虫态体内可溶性糖原含量存在显著影响。经15.0℃驯化处理后铁甲各虫态体内平均甘油含量最高,比对照25℃的平均甘油含量高出约9.4倍,而经12.5℃驯化处理的虫体内的平均甘油含量仅增加3.5倍。【结论】低温驯化对水椰八角铁甲体内相关生理活性物质含量的影响效能是有限的;水椰八角铁甲可以根据不良的环境条件调节最佳的生理状况,以适应未来的环境和达到最强的适应性。     

Temporal correlation of the memory deficit with Alzheimer-like lesions induced by activation of glycogen synthase kinase-3

We have reported that activation of glycogen synthase kinase-3 (GSK-3) by ventricle injection of wortmannin (WT) and GF-109203X (GFX) induces Alzheimer-like memory deficit in rats [Liu et al., J. Neurochem. 87 (2003), 1333]. To further explore the factors responsible for the memory loss, we studied here the temporal alterations of GSK-3, tau phosphorylation, beta-amyloid (Abeta), and acetylcholine (ACh) after injection of WT/GFX, and analyzed their correlation with the memory loss. We observed that the severe memory deficit occurred at 24 and 48 h, and simultaneously, GSK-3 activation, tau hyperphosphorylation at Thr231, Ser396, and Ser404 and decline of ACh in hippocampus were detected, and these changes were mostly recovered at 72 and 96 h after the injection of WT/GFX. Remarkable increase of Abeta and intracellular accumulation of argentophilic substances were detected at 72 h. Pearson analysis showed that the memory deficit was correlated with GSK-3 activation, tau hyperphosphorylation, and decline of ACh but not with Abeta overproduction. Our data provide direct evidence demonstrating that activation of GSK-3 by WT/GFX may cause memory deficit through tau hyperphosphorylation and suppression of ACh in hippocampus.     

桃小食心虫越冬幼虫过冷却能力及体内生化物质动态

为研究桃小食心虫Carposina niponensis Walsingham自然种群过冷却能力的变化动态,从生理生化水平上探讨桃小食心虫幼虫耐寒机制,测定了桃小食心虫幼虫在越冬前后不同月份的过冷却点、体内含水量、脂肪、蛋白和糖原的含量。结果表明:桃小食心虫越冬幼虫的过冷却点(super-cooling point, SCP)和结冰点(freezing point, FP)随越冬期温度降低而逐渐降低, 并在冬季过后随温度升高而逐渐升高,其中在3月份时最低,分别为-14.89℃和-9.95℃,显著低于其它月份。幼虫体内含水量、总蛋白含量、糖原含量在越冬前后变化趋势与SCP变化相似并且各自又有不同的特点,但在2月份时都达最低,分别为44.83%、32.44μg/mg、1.95μg/mg。幼虫体内的总脂肪含量由越冬初期(2008-10)的29.04％逐渐降低至越冬后期(2009-06)的15.56％。结果说明桃小食心虫幼虫越冬过程中体内水分、总蛋白、糖原等生化物质含量的变化与其抗寒能力存在一定的联系,显示了其对冬季温度变化的生态适应。     

A novel homozygous 10 nucleotide deletion in BBS10 causes Bardet–Biedl syndrome in a Pakistani family

Bardet–Biedl Syndrome is a multisystem autosomal recessive disorder characterized by central obesity, polydactyly, hypogonadism, learning difficulties, rod-cone dystrophy and renal dysplasia. Bardet–Biedl Syndrome has a prevalence rate ranging from 1 in 100,000 to 1 in 160,000 births although there are communities where Bardet–Biedl Syndrome is found at a higher frequency due to consanguinity. We report here a Pakistani consanguineous family with two affected sons with typical clinical features of Bardet–Biedl Syndrome, in addition to abnormal liver functioning and bilateral basal ganglia calcification, the latter feature being typical of Fahr's disease. Homozygous regions obtained from SNP array depicted three known genes BBS10, BBS14 and BBS2. Bidirectional sequencing of all coding exons by traditional sequencing of all these three genes showed a homozygous deletion of 10 nucleotides (c.1958_1967del), in BBS10 in both affected brothers. The segregation analysis revealed that the parents, paternal grandfather, maternal grandmother and an unaffected sister were heterozygous for the deletion. Such a large deletion in BBS10 has not been reported previously in any population and is likely to be contributing to the phenotype of Bardet–Biedl Syndrome in this family.     

Reconstitution of the destruction complex defines roles of AXIN polymers and APC in β-catenin capture,phosphorylation, and ubiquitylation

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