Yeast life-span extension by calorie restriction is independent of NAD fluctuation

Calorie restriction (CR) slows aging in numerous species. In the yeast Saccharomyces cerevisiae, this effect requires Sir2, a conserved NAD+-dependent deacetylase. We report that CR reduces nuclear NAD+ levels in vivo. Moreover, the activity of Sir2 and its human homologue SIRT1 are not affected by physiological alterations in the NAD+:NADH ratio. These data implicate alternate mechanisms of Sir2 regulation by CR.     

Comment on "HST2 mediates SIR2-independent life-span extension by calorie restriction"

Calorie restriction (CR) increases life span in yeast independently of Sir2. Lamming et al. (Reports, 16 September 2005, p. 1861) recently proposed that Sir2-independent life-span extension by CR is mediated by the Sir2 paralogs Hst1 and Hst2. Contradictory to this, we find that CR greatly increases life span in cells lacking Sir2, Hst1, and Hst2, which suggests that CR is not mediated by Sir2, Hst2, or Hst1.     

SIRT6 promotes DNA repair under stress by activating PARP1

Sirtuin 6 (SIRT6) is a mammalian homolog of the yeast Sir2 deacetylase. Mice deficient for SIRT6 exhibit genome instability. Here, we show that in mammalian cells subjected to oxidative stress SIRT6 is recruited to the sites of DNA double-strand breaks (DSBs) and stimulates DSB repair, through both nonhomologous end joining and homologous recombination. Our results indicate that SIRT6 physically associates with poly[adenosine diphosphate (ADP)-ribose] polymerase 1 (PARP1) and mono-ADP-ribosylates PARP1 on lysine residue 521, thereby stimulating PARP1 poly-ADP-ribosylase activity and enhancing DSB repair under oxidative stress.     

归芪多糖延缓细胞衰老的分子作用机制

以SIRT1和线粒体为切入点,采用分子生物学技术以及多种线粒体分析技术,深入探讨SIRT1和线粒体在衰老细胞中的作用,揭示归芪多糖延缓细胞衰老的分子作用机制。结果表明,AAP显著降低细胞的衰老程度并提高细胞活力,而Ex527阻断AAP的作用。同时,发现AAP增强细胞内SIRT1和CyclinD1的表达,降低p53的表达水平,在Ex527组中未观察到类似的逆转作用。线粒体分析结果显示,AAP可显著降低细胞内的活性氧水平,降低线粒体膜电位,减轻线粒体肿胀程度和增加线粒体内ATP含量,而Ex527的预处理消除这些作用。基于上述结果,推测AAP可能通过信号通路p53/p16和CyclinD/CDK4来改善线粒体功能,从而达到延缓衰老的作用,且这些作用与SIRT1密切相关。     

HST2 mediates SIR2-independent life-span extension by calorie restriction

Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet.     

流感病毒在诱导A549细胞凋亡过程中对SIRT1和P53蛋白的影响

采用流式细胞术观察了流感病毒诱导A549细胞凋亡的情况,同时应用Western blot方法研究了SIRT1和p53等蛋白的表达情况。结果表明:1000 TCID50/mL剂量流感病毒感染A549细胞后,细胞表现出典型的凋亡特征,且凋亡比例随感染时间延长而逐渐增加。在流感病毒诱导细胞凋亡过程中,SIRT1蛋白的表达下降,p-p53的表达上升。线粒体中Bax的表达上调,Bcl-2的表达下降。可见SIRT1蛋白参与了流感病毒诱导的A549细胞凋亡,SIRT1蛋白表达下调可能促进了Bax释放进入线粒体和p53蛋白功能的进一步发挥。     

Sirtuin 2 inhibitors rescue alpha-synuclein-mediated toxicity in models of Parkinson's disease

The sirtuins are members of the histone deacetylase family of proteins that participate in a variety of cellular functions and play a role in aging. We identified a potent inhibitor of sirtuin 2 (SIRT2) and found that inhibition of SIRT2 rescued alpha-synuclein toxicity and modified inclusion morphology in a cellular model of Parkinson's disease. Genetic inhibition of SIRT2 via small interfering RNA similarly rescued alpha-synuclein toxicity. Furthermore, the inhibitors protected against dopaminergic cell death both in vitro and in a Drosophila model of Parkinson's disease. The results suggest a link between neurodegeneration and aging.     

Increased nuclear NAD biosynthesis and SIRT1 activation prevent axonal degeneration

Axonal degeneration is an active program of self-destruction that is observed in many physiological and pathological settings. In Wallerian degeneration slow (wlds) mice, Wallerian degeneration in response to axonal injury is delayed because of a mutation that results in overexpression of a chimeric protein (Wlds) composed of the ubiquitin assembly protein Ufd2a and the nicotinamide adenine dinucleotide (NAD) biosynthetic enzyme Nmnat1. We demonstrate that increased Nmnat activity is responsible for the axon-sparing activity of the Wlds protein. Furthermore, we demonstrate that SIRT1, a mammalian ortholog of Sir2, is the downstream effector of increased Nmnat activity that leads to axonal protection. These findings suggest that novel therapeutic strategies directed at increasing the supply of NAD and/or Sir2 activation may be effective for treatment of diseases characterized by axonopathy and neurodegeneration.     

姜黄素通过SIRT1/FOXO1通路缓解玉米赤霉烯酮诱导的猪肾上皮细胞氧化损伤

【目的】探究姜黄素(Cur)对玉米赤霉烯酮(ZEA)诱导猪肾上皮细胞(PK-15)氧化损伤的保护作用，并基于SIRT1/FOXO1信号通路阐明其作用机制，为姜黄素的兽医临床应用提供依据。【方法】试验分为5组：对照组、ZEA组(36.55μg·mL^-1 ZEA)、Cur 6.25组(36.55μg·mL^-1 ZEA+6.25μmol·L^-1 Cur)、Cur 12.5组(36.55μg·mL^-1 ZEA+12.5μmol·L^-1 Cur)、Cur 25组(36.55μg·mL^-1 ZEA+25μmol·L^-1 Cur)；通过MTT法测定ZEA的半数抑制浓度和Cur对PK-15细胞的最大安全浓度；使用倒置显微镜观察PK-15细胞的形态变化；采用试剂盒检测细胞内活性氧(ROS)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)以及丙二醛(MDA)的水平；qRT-PCR检测细胞SIRT1、FOXO1、CAT、Mn-SOD的mRNA水平；West...     

Sir2-dependent activation of acetyl-CoA synthetase by deacetylation of active lysine

Acetyl-coenzyme A (CoA) synthetase (Acs) is an enzyme central to metabolism in prokaryotes and eukaryotes. Acs synthesizes acetyl CoA from acetate, adenosine triphosphate, and CoA through an acetyl-adenosine monophosphate (AMP) intermediate. Immunoblotting and mass spectrometry analysis showed that Salmonella enterica Acs enzyme activity is posttranslationally regulated by acetylation of lysine-609. Acetylation blocks synthesis of the adenylate intermediate but does not affect the thioester-forming activity of the enzyme. Activation of the acetylated enzyme requires the nicotinamide adenine dinucleotide-dependent protein deacetylase activity of the CobB Sir2 protein from S. enterica. We propose that acetylation modulates the activity of all the AMP-forming family of enzymes, including nonribosomal peptide synthetases, luciferase, and aryl- and acyl-CoA synthetases. These findings extend our knowledge of the roles of Sir2 proteins in gene silencing, chromosome stability, and cell aging and imply that lysine acetylation is a common regulatory mechanism in eukaryotes and prokaryotes.     

Requirement of NAD and SIR2 for life-span extension by calorie restriction in Saccharomyces cerevisiae

Calorie restriction extends life-span in a wide variety of organisms. Although it has been suggested that calorie restriction may work by reducing the levels of reactive oxygen species produced during respiration, the mechanism by which this regimen slows aging is uncertain. Here, we mimicked calorie restriction in yeast by physiological or genetic means and showed a substantial extension in life-span. This extension was not observed in strains mutant for SIR2 (which encodes the silencing protein Sir2p) or NPT1 (a gene in a pathway in the synthesis of NAD, the oxidized form of nicotinamide adenine dinucleotide). These findings suggest that the increased longevity induced by calorie restriction requires the activation of Sir2p by NAD.     

红鳍东方鲀去乙酰化酶SIRT3基因的克隆及原核表达

从红鳍东方鲀(Takifugu rubripes)肝脏组织中提取总RNA,通过RT–PCR扩增,获得SIRT3基因的编码阅读框(ORF),用原核表达载体p ET32a(+)构建p ET32a/SIRT3重组质粒,用异丙基–β–D–硫代半乳糖苷(IPTG)将重组质粒p ET32a/STRT3在大肠杆菌Rosetta(DE3)进行诱导表达,并用镍柱纯化融合表达蛋白。结果显示,红鳍东方鲀SIRT3基因(tr SIRT3)ORF区大小为1 263 bp大小,编码420个氨基酸。经IPTG诱导表达后,获得1个带组氨酸(His)标签的融合蛋白,目的蛋白主要存在于上清溶液中,为可溶性表达。用镍离子亲和层析柱对重组蛋白进行纯化,获得了相对分子质量约66 000的重组蛋白。     

猪胎儿成纤维细胞SOD1基因差异表达研究

 在研究模式生物衰老机制的过程中,发现衰老受某些特定基因的调控。为研究细胞内铜锌超氧化物歧化酶(Cu/ZnSOD,SOD1) 在不同代数的猪胎儿成纤维细胞的差异表达,本试验收集正常传代生长的5,10,15,20,25,30,35,40,45,50,55,60,65,70代的猪胎儿成纤维细胞,分别提取细胞总RNA;采用RT-PCR技术,检测不同代数猪胎儿成纤维细胞SOD1的表达。结果表明猪SOD1在第5代猪胎儿成纤维细胞中表达水平最高,随着细胞代数的增加,表达量逐渐下降,到第70代表达量为最低。结果将为进一步揭示细胞衰老的分子机制提供有价值的参考,同时为丰富猪的分子生物学提供新素材。     

猪I型补体受体与C3b活性片段相互结合的体外检测

【目的】检测猪红细胞类补体受体I型（Complement receptor 1-like,CR1-like）与C3b活性片段能否发生结合,以期为阐明猪红细胞发挥免疫粘附功能的分子机理提供科学数据。【方法】利用前期已构建的CR1-like_(3-6)、CR1-like_(8-11)功能域片段的重组质粒建立酵母双杂交检测体系,运用酵母共转化的方法将诱饵质粒（重组pGBKT7-CR1-like）与捕获质粒（重组pGADT7-C3b）共同转入Y2HGold酵母细胞中,分别利用一缺平板SD/-Leu、SD/-Trp和二缺平板SD/-Leu/-Trp（DDO）严格筛选共转化成功的酵母细胞,再根据报告因子是否表达来鉴别转化子在SD/-Leu/-Trp/X-α-Gal（DDO/X）、SD/-Leu/-Trp/X-α-Gal/Aba（DDO/X/A）二缺培养板上的生长情况,并结合菌落的颜色变化现象综合判定CR1-like活性片段与补体C3b在酵母细胞中是否发生相互结合;然后运用免疫沉淀技术分离酵母细胞中CR1-like与C3b结合复合物,并对该复合物的特异性进行Western blot鉴定。【结果】试验成功将pGBKT7-CR1-like与pGADT7-C3b基因共转入Y2HGold酵母细胞。共转化的酵母克隆在SD/-Leu、SD/-Trp、DDO平板上能够正常生长,在DDO/X、DDO/X/A平板上正常生长且菌落呈现蓝色,由此表明,试验中酵母双杂交系统建立成功,并通过试验获得了阳性酵母克隆。共同转化了pGBKT7-CR1-like和pGADT7-C3b质粒的酵母菌落PCR反向鉴定结果显示,在共转化的酵母菌中含有目的基因CR1-like_(3-6)和CR1-like_(8-11),共转化组的质粒酶切后出现C3b基因片段,与设计大小一致,说明重组质粒成功共转化入酵母细胞中。免疫沉淀试验中应用pGBKT7载体的标签抗体c-Myc沉淀酵母细胞中的融合蛋白,以c-Myc为一抗进行Western blot检测发现,单独转化了pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)的融合蛋白在50 kD处出现特异性条带;共转化pGBKT7-CR1-like_(3-6) + pGADT7-C3b和共转化pGBKT7-CR1-like_(8-11) + pGADT7-C3b的酵母融合蛋白在83 kD处出现特异性条带;以HA单克隆抗体为一抗进行Western blot检测时,在pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)融合蛋白中没有出现特异性条带,只有3、4泳道中共转化的酵母融合蛋白在83 kD处出现特异性条带,表明在Y2HGold酵母细胞中存在CR1-like与C3b识别结合的复合物。使用CR1-like单克隆抗体沉淀酵母细胞中的融合蛋白,以CR1-like单克隆抗体为一抗进行Western blot检测发现,单独转化了pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)的融合蛋白在50 kD处出现特异性条带;共转化pGBKT7-CR1-like_(3-6) + pGADT7-C3b和共转化pGBKT7-CR1-like_(8-11) + pGADT7-C3b的酵母融合蛋白在83 kD处出现特异性条带;以C3单克隆抗体为一抗进行Western blot检测发现,在pGBKT7-CR1-like_(3-6)和pGBKT7-CR1-like_(8-11)融合蛋白中没有出现特异性条带,泳道3、4所示只有共转化的酵母融合蛋白在83 kD处出现特异性条带,表明在Y2HGold酵母细胞中存在具有生物活性的CR1-like与C3b识别结合的复合物。通过多个单克隆抗体杂交结果,可看出诱饵质粒的表达产物CR1-like_(3-6)、CR1-like_(8-11)片段与捕获质粒的表达产物C3b片段可在酵母细胞内发生结合。【结论】猪红细胞CR1-like发挥免疫粘附功能的识别配体为C3b,为猪红细胞CR1-like功能域分子结构的进一步解析提供了重要数据依据。     

内蒙古白绒山羊VEGF164基因毛囊特异性表达载体的构建及胎儿成纤维细胞的稳定转染

 【目的】构建绒山羊血管内皮生长因子164（vascular endothelial growth factor 164,VEGF164）基因的毛囊特异表达载体并稳定转染胎儿成纤维细胞,筛选获得稳定表达红色荧光蛋白和毛囊特异表达VEGF164并可用于核移植的转基因细胞克隆。【方法】以pCDsRed2载体为基本骨架将VEGF164基因亚克隆到KAP6-1启动子下游,接续连接红色荧光蛋白表达元件,构建VEGF164基因毛囊特异表达载体pCDsRed2-KV（6.3 kb）。外源表达载体以lipofectamineTM2000介导转染胎儿成纤维细胞,G418筛选获得稳定转染的细胞克隆。PCR鉴定外源基因在细胞基因组中的整合。【结果】在构建的表达载体pCDsRed2-KV中,VEGF164基因被正确连接在毛囊特异性启动子KAP6-1下游,基因下游按顺序连接CMV启动子和红色荧光蛋白基因;外源KAP6-1启动子和VEGF164基因整合到细胞基因组中。【结论】成功构建稳定表达红色荧光蛋白和毛囊特异表达VEGF164的真核表达载体,稳定转染绒山羊胎儿成纤维细胞,为下一步通过克隆技术获得转VEGF164基因绒山羊提供了条件。     

Rapid progression to AIDS in HIV+ individuals with a structural variant of the chemokine receptor CX3CR1

Human immunodeficiency virus (HIV) enters cells in vitro via CD4 and a coreceptor. Which of 15 known coreceptors are important in vivo is poorly defined but may be inferred from disease-modifying mutations, as for CCR5. Here two single nucleotide polymorphisms are described in Caucasians in CX3CR1, an HIV coreceptor and leukocyte chemotactic/adhesion receptor for the chemokine fractalkine. HIV-infected patients homozygous for CX3CR1-I249 M280, a variant haplotype affecting two amino acids (isoleucine-249 and methionine-280), progressed to AIDS more rapidly than those with other haplotypes. Functional CX3CR1 analysis showed that fractalkine binding is reduced among patients homozygous for this particular haplotype. Thus, CX3CR1-I249 M280 is a recessive genetic risk factor in HIV/AIDS.     

去乙酰化酶SIRT1在猪不同组织中的表达规律性分析

[目的]分析去乙酰化酶SIRT1在猪不同组织中的表达规律性,为研究猪SIRT1基因功能奠定基础.[方法]采用RT-PCR和Western blotting方法检测猪脑、肝脏、胰脏、脂肪、卵巢、肾脏、心脏、脾脏等组织中SIRT1基因mRNA和蛋白的表达量.[结果]在猪脑、肝脏、胰脏、脂肪、卵巢、肾脏、心脏、脾脏等组织中均有SIRT1 mRNA和蛋白表达,且以卵巢组织中的表达量最高,心脏中的表达量最低.[结论]去乙酰化酶SIRT1在猪不同组织中的表达具有一定规律性,可能与猪的脂肪代谢和繁殖活动密切相关,直接或间接调节猪的能量代谢和生殖活动.