多聚磷酸相关蛋白结构及生物学功能

多聚磷酸（polyphosphate,polyP）是由几个到数百个磷酸基通过高能磷酸酐键连接而成的链状多聚体,存在于所有细胞生物中.多聚磷酸相关蛋白包括多聚磷酸相关酶和多聚磷酸结合蛋白.多聚磷酸相关酶如多聚磷酸激酶（polyphosphate kinase,PPK）催化polyPn生成polyPn+1的可逆反应;外切聚磷酸酶（exopolyphosphatase,PPX）、内切聚磷酸酶（endopolyphosphatase,PPN）能将polyP水解成磷酸残基;多聚磷酸依赖的激酶将polyP的磷转移到生物小分子上,如葡萄糖和烟酰胺腺嘌呤二核苷酸（nicotinamide adenine dinucleotide,NAD）,使其分别磷酸化为6 磷酸葡萄糖和烟酰胺腺嘌呤二核苷酸磷酸（nicotinamide adenine dinucleotide phosphate,NADP）.多聚磷酸结合蛋白可与多聚磷酸结合,发挥各种生物学功能.本文将简要介绍多聚磷酸相关蛋白的结构与主要生物学功能,以阐述多聚磷酸参与的细胞内生化过程.     

NADPH氧化酶在电磁辐射生物效应中的作用

电磁辐射是一种复合电磁波,而人体生命活动包含一系列的生物电活动,这些生物电对环境的电磁波敏感,因此,电磁辐射可对人体造成危害.关于电磁辐射诱导的生物效应研究虽多,然而其具体机制尚不清楚.近年来,发现烟酰胺腺嘌呤二核苷酸磷酸氧化酶(NADPH氧化酶),又称呼吸爆发氧化酶(respiratory burst oxidase homologue,Rboh)在电磁辐射产生的生物学效应中扮演重要角色,电磁辐射可直接或间接活化NADPH氧化酶复合体,然后NADPH氧化酶可以将细胞内NADPH的电子转移而形成活性氧,或者通过一系列炎症因子和相关基质金属蛋白酶等参与炎症、防御以及组织修复等生命过程.本文对NADPH氧化酶在电磁生物学效应中的作用进行了综述.     

Nampt基因表达调控机制

烟酰胺磷酸核糖转移酶(NAMPT)是烟酰胺腺嘌呤二核苷酸(NAD)生物合成途径的关键限速酶, 也被称为内脏脂肪素(Visfatin)或前B细胞克隆增强因子(PBEF)。它通过调节机体或细胞的NAD水平以及通过其他非酶机制等途径影响代谢、炎症反应、细胞的增殖、分化和凋亡, 特别是衰老等诸多过程。文章简要综述了近年来Nampt基因的表达调控及其转录的反馈调节机制研究进展。     

环化二磷酸腺苷核糖及其钙动员的功能

环化二磷酸腺苷核糖（cyclic ADP-ribose,cADPR）是烟酰胺腺嘌呤二核苷酸(NAD⁺)的代谢产物,是新近发现的一种细胞内第二信使．在许多哺乳类和无脊椎动物细胞中,cADPR能引起胞内钙库释放钙离子,其可能机制是：cADPR受体结合cADPR,通过Ryanodine受体或类Ryanodine受体介导的钙通道使cADPR敏感的钙库释放钙离子,此外,一条由一氧化氮（NO）、环化鸟苷酸（cGMP）和cADPR组成的细胞内信号转导途径可能存在于许多细胞中．     

NADPH氧化酶与HIF-α在肿瘤中的相互调控

烟酰胺腺嘌呤二核苷酸磷酸(NADPH)氧化酶是胞内活性氧簇(ROS)的主要来源,ROS在多种肿瘤的发生发展中起重要作用,但其具体的致病机制并非十分明确。缺氧诱导因子(HIF)通过调控其下游的多个靶基因如促红细胞生成素(EPO)、血管内皮生长因子(VEGF)、葡萄糖转运子(GLUT)进而促进肿瘤血管生成、细胞能量代谢和肿瘤转移等。在肿瘤内NADPH氧化酶介导的ROS通过多种信号途径上调HIF-α的表达;与此同时,HIF-α也能通过ROS调控NADPH氧化酶的表达,从而进一步促进肿瘤的发生发展。     

烟酰胺经调控p38MAPK信号通路对高血压脑出血大鼠的脑保护作用机制分析

摘要 目的：探讨烟酰胺经调控p38MAPK信号通路对高血压脑出血大鼠的脑保护作用机制。方法：选择48只SD大鼠,随机选择12只作为假手术组,其余36只进行高血压脑出血造模,对比4组大鼠的血肿体积、左扭转比率、神经功能变化、出血脑组织p-p38MAPK、p38MAPK蛋白表达、烟酰胺腺嘌呤二核苷酸、凋亡诱导因子含量及脑组织含水量。结果：与模型组相比,尼莫地平组、烟酰胺组的血肿体积明显缩小;与烟酰胺组相比,尼莫地平组的血肿体积明显缩小（P<0.05）;与干预前相比,干预后烟酰胺组、尼莫地平组的血肿体积明显缩小,模型组的血肿体积明显增多（P<0.05）。与模型组相比,假手术组、尼莫地平组、烟酰胺组的向左扭转比率、p-p38MAPK/p38MAPK、烟酰胺腺嘌呤二核苷酸明显较高,脑组织含水量、凋亡诱导因子含量明显较低;与烟酰胺组相比,尼莫地平组、假手术组的左扭转比率、p-p38MAPK/p38MAPK、烟酰胺腺嘌呤二核苷酸明显较高,脑组织含水量、凋亡诱导因子含量明显较低;与尼莫地平组相比,假手术组的左扭转比率、p-p38MAPK/p38MAPK、烟酰胺腺嘌呤二核苷酸明显较高,脑组织含水量、凋亡诱导因子含量明显较低（P<0.05）。结论：在高血压脑出血大鼠中,p38MAPK介导的细胞凋亡途径会加剧高血压脑出血的脑损伤,烟酰胺会经过抑制p38MAPK信号通路减轻高血压脑出血后的脑损伤。     

活性氧在气孔运动中的作用

水分代谢是植物基础代谢的重要组成部分,气孔开关精细地调节着植物水分散失和光合作用。气孔运动受到多种因子的调控,保卫细胞内大量的第二信使分子是响应外界刺激、调节保卫细胞代谢方式、改变保卫细胞水势进而引起气孔开关的重要功能组分。细胞内的活性氧就是其中重要的成员之一。保卫细胞中的活性氧包括过氧化氢、超氧阴离子自由基和羟自由基等,这些活性氧可以通过光合作用、呼吸作用产生或通过专门的酶催化合成,在触发下游生理反应、完成信号转导后由专门的酶将其清除。在植物激素(脱落酸、水杨酸)、一氧化氮、质外体钙调素、细胞外ATP等因子调节气孔运动的过程中,活性氧都发挥了介导作用。该文对于近年来活性氧在气孔运动过程中发挥的作用方面的研究进展进行了综述。     

气道上皮细胞P2Y嘌呤受体:从离子转运到免疫功能(英文)

水盐的转运调控对呼吸道、生殖系统以及消化道等多个器官系统的整体功能都至关重要。气道上皮的液体分泌就是通过离子转运产生的渗透压所驱动的,而这种腔面方向渗透梯度的决定因素则是氯离子(Cl-)的外向转运。在各类上皮细胞中,多种经典的信号转导级联都与离子运输的调节相关,其中包括两个为人熟知的胞内信号系统:细胞内钙离子浓度([Ca2+]i)的升高,以及环核苷酸,如环腺苷酸(cAMP)合成率的升高。Cl-的分泌主要是通过开放上皮细胞顶膜面Ca2+激活或cAMP激活的Cl-通道。另外基底面Ca2+激活或cAMP激活钾离子(K+)通道的开放同样对离子跨上皮转运的调节起重要作用,会使细胞超极化从而保持顶面Cl-通道开放,并持续释放Cl-。P2Y受体表达于几乎所有极性上皮的顶膜或基底膜面,并调控分泌液体与电解质的运输。人气道上皮细胞中有多种核苷酸受体的表达。细胞外核苷酸,如UTP和ATP,都是能发动钙离子浓度升高的促分泌素。它们从气道上皮细胞释放到胞外,又以自分泌的形式作用于上皮细胞并刺激跨膜离子转运。与此同时,最新研究结果证明在支气管上皮细胞与其它免疫细胞中,P2Y受体还具有分泌炎症因子的功能。     

槲皮素对节律钟基因的调控研究*

目的:探讨槲皮素对节律钟基因表达的影响。方法:通过50%的马血清刺激诱导人骨肉瘤U2OS细胞同步化,利用槲皮素处理同步化后的U2OS细胞。进一步利用荧光定量PCR检测节律钟关键基因的变化。利用western blot检测槲皮素对组蛋白乙酰化的影响,并且通过试剂盒测定槲皮素对细胞内氧化型烟酰胺腺嘌呤二核苷酸(NAD+)的影响。通过尼克酰胺和槲皮素同时处理U2OS细胞,利用荧光定量PCR检测节律钟关键基因的变化。结果:U2OS细胞经过槲皮素处理后节律钟关键基因芳烃受体核转位蛋白3(brain and muscle Arnt-like protein-1,BMAL1),节律周期蛋白2(Period 2, PER2),孤儿核受体alpha(REV-ERBα)和蓝光受体蛋白1(Cryptochrome 1,CRY1)在转录水平的表达水平有明显的升高。槲皮素处理可以显著降低U2OS细胞的组蛋白乙酰化的水平,并且显著升高U2OS细胞内的氧化型烟酰胺腺嘌呤二核苷酸的水平。进一步研究发现,尼克酰胺(Nicotinamide,NAM)处理完全抑制了槲皮素对节律基因的影响。结论:槲皮素显著地激活了节律钟关键基因的mRNA表达水平,槲皮素对于节律基因的调控依赖于Sirtuins的活性,其机制可能是由于槲皮素增加了细胞内的氧化型烟酰胺腺嘌呤二核苷酸的水平所导致。     

Nampt在卵巢癌中的研究进展

尼克酰胺磷酸核糖转移酶(Nampt)是新近发现的一种主要由内脏脂肪细胞分泌的脂肪因子,结构复杂,存在基因多态性,具有多种生理功能:通过与胰岛素受体相互作用,在不同的情况下Nampt可表现出类胰岛素样作用;在细胞质中,能够催化烟酰胺腺嘌呤二核苷酸(NAD)的生物合成;作为分泌型的细胞因子,Nampt还可以诱导多种炎性因子的表达。最近发现,Nampt在卵巢癌中高表达,其与卵巢癌的发生发展可能有密切联系,它的发现为研究卵巢癌的发病机制增加了新内容,可能为卵巢癌的治疗提供一个新的靶点。     

Central functions of bicarbonate in S-type anion channel activation and OST1 protein kinase in CO2 signal transduction in guard cell

Plants respond to elevated CO(2) via carbonic anhydrases that mediate stomatal closing, but little is known about the early signalling mechanisms following the initial CO(2) response. It remains unclear whether CO(2), HCO(3)(-) or a combination activates downstream signalling. Here, we demonstrate that bicarbonate functions as a small-molecule activator of SLAC1 anion channels in guard cells. Elevated intracellular [HCO(3)(-)](i) with low [CO(2)] and [H(+)] activated S-type anion currents, whereas low [HCO(3)(-)](i) at high [CO(2)] and [H(+)] did not. Bicarbonate enhanced the intracellular Ca(2+) sensitivity of S-type anion channel activation in wild-type and ht1-2 kinase mutant guard cells. ht1-2 mutant guard cells exhibited enhanced bicarbonate sensitivity of S-type anion channel activation. The OST1 protein kinase has been reported not to affect CO(2) signalling. Unexpectedly, OST1 loss-of-function alleles showed strongly impaired CO(2)-induced stomatal closing and HCO(3)(-) activation of anion channels. Moreover, PYR/RCAR abscisic acid (ABA) receptor mutants slowed but did not abolish CO(2)/HCO(3)(-) signalling, redefining the convergence point of CO(2) and ABA signalling. A new working model of the sequence of CO(2) signalling events in gas exchange regulation is presented.     

Arabidopsis OST1 protein kinase mediates the regulation of stomatal aperture by abscisic acid and acts upstream of reactive oxygen species production

During drought, the plant hormone abscisic acid (ABA) triggers stomatal closure, thus reducing water loss. Using infrared thermography, we isolated two allelic Arabidopsis mutants (ost1-1 and ost1-2) impaired in the ability to limit their transpiration upon drought. These recessive ost1 mutations disrupted ABA induction of stomatal closure as well as ABA inhibition of light-induced stomatal opening. By contrast, the ost1 mutations did not affect stomatal regulation by light or CO(2), suggesting that OST1 is involved specifically in ABA signaling. The OST1 gene was isolated by positional cloning and was found to be expressed in stomatal guard cells and vascular tissue. In-gel assays indicated that OST1 is an ABA-activated protein kinase related to the Vicia faba ABA-activated protein kinase (AAPK). Reactive oxygen species (ROS) were shown recently to be an essential intermediate in guard cell ABA signaling. ABA-induced ROS production was disrupted in ost1 guard cells, whereas applied H(2)O(2) or calcium elicited the same degree of stomatal closure in ost1 as in the wild type. These results suggest that OST1 acts in the interval between ABA perception and ROS production. The relative positions of ost1 and the other ABA-insensitive mutations in the ABA signaling network (abi1-1, abi2-1, and gca2) are discussed.     

Open stomata 1 (OST1) kinase controls R–type anion channel QUAC1 in Arabidopsis guard cells

Under drought stress, the stress hormone ABA addresses the SnR kinase OST1 via its cytosolic receptor and the protein phosphatase ABI1. Upon activation, OST1 phosphorylates the guard cell S–type anion channel SLAC1. Arabidopsis ABI1 and OST1 loss‐of‐function mutants are characterized by an extreme wilting 'open stomata′ phenotype. Given the fact that guard cells express both SLAC‐ and R–/QUAC‐type anion channels, we questioned whether OST1, besides SLAC1, also controls the QUAC1 channel. In other words, are ABI1/OST1 defects preventing both of the guard cell anion channel types from operating properly in terms of stomatal closure? The activation of the R–/QUAC‐type anion channel by ABA signaling kinase OST1 and phosphatase ABI1 was analyzed in two experimental systems: Arabidopsis guard cells and the plant cell‐free background of Xenopus oocytes. Patch‐clamp studies on guard cells show that ABA activates R–/QUAC‐type currents of wild‐type plants, but to a much lesser extent in those of abi1–1 and ost1–2 mutants. In the oocyte system the co‐expression of QUAC1 and OST1 resulted in a pronounced activation of the R–type anion channel. These studies indicate that OST1 is addressing both S–/SLAC‐ and R–/QUAC‐type guard cell anion channels, and explain why the ost1–2 mutant is much more sensitive to drought than single slac1 or quac1 mutants.     

Abscisic acid-regulated responses of aba2-1 under osmotic stress: the abscisic acid-inducible antioxidant defence system and reactive oxygen species production

We investigated the interaction among abscisic acid (ABA), reactive oxygen species (ROS) and antioxidant defence system in the transduction of osmotic stress signalling using Arabidopsis thaliana WT (Columbia ecotype, WT) and an ABA-deficient mutant (aba2-1). For this, 50 μm ABA and osmotic stress, induced with 40% (w/v) polyethylene glycol (PEG8000; -0.7 MPa), were applied to WT and aba2-1 for 6, 12 or 24 h. Time course analysis was undertaken for determination of total/isoenzyme activity of the antioxidant enzymes, superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), NADPH oxidase (NOX; EC 1.6.3.1) activity; scavenging activity of the hydroxyl radical (OH˙), hydrogen peroxide (H(2) O(2) ); endogenous ABA and malondialdehyde (MDA). The highest H(2) O(2) and MDA content was found in PEG-treated groups of both genotypes, but with more in aba2-1. ABA treatment under stress reduced the accumulation of H(2) O(2) and MDA, while it promoted activity of SOD, CAT and APX. APX activity was higher than CAT activity in ABA-treated WT and aba2-1, indicating a protective role of APX rather than CAT during osmotic stress-induced oxidative damage. Treatment with ABA also significantly induced increased NOX activity. Oxidative damage was lower in ABA-treated seedlings of both genotypes, which was associated with greater activity of SOD (Mn-SOD1 and 2 and Fe-SOD isoenzymes), CAT and APX in these seedlings after 24 h of stress. These results suggest that osmotic stress effects were overcome by ABA treatment because of increased SOD, CAT, APX and NOX.     

Phosphorylation of the Arabidopsis AtrbohF NADPH oxidase by OST1 protein kinase

The plant hormone abscisic acid (ABA) triggers production of reactive oxygen species (ROS) in guard cells via the AtrbohD and AtrbohF NADPH oxidases, leading to stomatal closure. The ABA-activated SnRK2 protein kinase open stomata 1 (OST1) (SRK2E/SnRK2.6) acts upstream of ROS in guard cell ABA signaling. Here, we report that OST1 phosphorylates Ser13 and Ser174 on AtrbohF. In addition, substitution of Ser174 to Ala results in a ∼40% reduction in the phosphorylation of AtrbohF by OST1. We also show that OST1 physically interacts with AtrbohF. These results provide biochemical evidence suggesting that OST1 regulates AtrbohF activity.

Structured summary

MINT-7260179, MINT-7260147, MINT-7260165: OST1 (uniprotkb:Q940H6) phosphorylates (MI:0217) ATRBOHF (uniprotkb:O48538) by protein kinase assay (MI:0424)MINT-7260208: OST1 (uniprotkb:Q940H6) and ATRBOHF (uniprotkb:O48538) physically interact (MI:0915) by bimolecular fluorescence complementation (MI:0809)     

激动素和丁二酸拌种对玉米衰老过程中抗氧化系统和植物激素的影响

以‘郑单958’（晚衰型品种）和‘豫单2002’（早衰型品种）为实验材料,采用盆栽方式,0．03μg·kg-1的外源激动素（KT）和300mg·kg-1丁二酸复合剂进行拌种处理,研究拌种后玉米根叶衰老指标的变化及其化学调控效应。结果表明：激动素和丁二酸混合拌种后根系与叶片中超氧阴离子（O2-）产生速率、丙二醛（MDA）及脱落酸（ABA）含量低于其对照,而超氧化物歧化酶（SOD）活性和生长素（IAA）含量却较高,据此认为膜脂过氧化得到缓解,根叶的生理功能期延长;且在整个生育期内各个叶位叶的MDA含量、SOD活性、ABA和IAA含量高于根系,但其O2-和IAA／ABA较低,表明根系的衰老早于叶片。综上可以推测,激动素和丁二酸拌种能有效防止根叶早衰,为提高玉米产量打下基础。     

棉花叶片衰老过程中激素和膜脂过氧化的关系

以陆地棉品种辽棉9号的去根幼苗为材料,对其进行暗诱导衰老培养.在培养液中分别加入6-BA、ABA、GSH、H2O2、CaCl2、A23187 和A23187 CaCl2,测定在不同培养条件下棉花去根幼苗叶片内源激素、SOD酶活性和MDA含量的变化.结果表明:棉花叶片衰老表现为细胞分裂素含量的下降和ABA含量的上升.6-BA、GSH和钙离子均延缓叶片的衰老,ABA和H2O2促进叶片的衰老.     

A plasma membrane receptor kinase, GHR1, mediates abscisic acid- and hydrogen peroxide-regulated stomatal movement in Arabidopsis

The plant hormone abscisic acid (ABA) regulates stomatal movement under drought stress, and this regulation requires hydrogen peroxide (H2O2). We isolated GUARD CELL HYDROGEN PEROXIDE-RESISTANT1 (GHR1), which encodes a receptor-like kinase localized on the plasma membrane in Arabidopsis thaliana. ghr1 mutants were defective ABA and H2O2 induction of stomatal closure. Genetic analysis indicates that GHR1 is a critical early component in ABA signaling. The ghr1 mutation impaired ABA- and H2O2-regulated activation of S-type anion currents in guard cells. Furthermore, GHR1 physically interacted with, phosphorylated, and activated the S-type anion channel SLOW ANION CHANNEL-ASSOCIATED1 when coexpressed in Xenopus laevis oocytes, and this activation was inhibited by ABA-INSENSITIVE2 (ABI2) but not ABI1. Our study identifies a critical component in ABA and H2O2 signaling that is involved in stomatal movement and resolves a long-standing mystery about the differential functions of ABI1 and ABI2 in this process.     

Immunohistochemical detection of blue light-induced phosphorylation of the plasma membrane H+-ATPase in stomatal guard cells

Blue light (BL) receptor phototropins activate the plasma membrane H(+)-ATPase in guard cells through phosphorylation of a penultimate threonine and subsequent binding of the 14-3-3 protein to the phosphorylated C-terminus of H?-ATPase, mediating stomatal opening. To date, detection of the phosphorylation level of the guard cell H?-ATPase has been performed biochemically using guard cell protoplasts (GCPs). However, preparation of GCPs from Arabidopsis for this purpose requires >5,000 rosette leaves and takes >8 h. Here, we show that BL-induced phosphorylation of guard cell H?-ATPase is detected in the epidermis from a single Arabidopsis rosette leaf via an immunohistochemical method using a specific antibody against the phosphorylated penultimate threonine of H?-ATPase. BL-induced phosphorylation of the H?-ATPase was detected immunohistochemically in the wild type, but not in a phot1-5 phot2-1 double mutant. Moreover, we found that physiological concentrations of the phytohormone ABA completely inhibited BL-induced phosphorylation of guard cell H?-ATPase in the epidermis, and that inhibition by ABA in the epidermis is more sensitive than in GCPs. These results indicate that this immunohistochemical method is very useful for detecting the phosphorylation status of guard cell H?-ATPase. Thus, we applied this technique to ABA-insensitive mutants (abi1-1, abi2-1 and ost1-2) and found that ABA had no effect on BL-induced phosphorylation in these mutants. These results indicate that inhibition of BL-induced phosphorylation of guard cell H?-ATPase by ABA is regulated by ABI1, ABI2 and OST1, which are known to be early ABA signaling components for a wide range of ABA responses in plants.     

H_2O_2-NOX系统：一种植物体内重要的发育调控与胁迫响应机制

以H2O2为中心的活性氧（reactive oxygen species,ROS）的产生是动植物发育与响应外界生物与非生物胁迫的普遍特征,其在生理和分子2个水平上调控植物的发育和对外界胁迫的响应,并与一系列信号转导过程相关联。作为关键的ROS产生酶,质膜NADPH氧化酶（plasma membrane NADPH oxidase,PM-NOX）在植物应对各种生物和非生物胁迫中具有重要作用,被广泛认为是胁迫条件下植物细胞ROS产生并积累的主要来源。该文简要综述了近年来人们在植物细胞ROS产生、清除、生理功能以及PM-NOX酶的结构特征与功能等方面的研究进展,并认为H2O2-NOX系统是一种植物体内普遍存在的重要发育调控与胁迫响应机制。