脂肪细胞型脂肪酸结合蛋白的研究进展

脂肪细胞型脂肪酸结合蛋白（adipocyte fatty acid binding protein,AFABP/aP2）作为脂肪酸结合蛋白（FABPS）超家族成员之一,广泛存在于各种正常的组织细胞中,参与脂肪酸贮存,运输与降解等过程。近年来,对脂肪细胞型脂肪酸结合蛋白的研究已成为热点,本文就其主要特征及其与各类疾病的关系作一简要综述。     

脂肪细胞型脂肪酸结合蛋白的研究进展

脂肪细胞型脂肪酸结合蛋白(adipocyte fatty acid binding protein,AFABP/aP2)作为脂肪酸结合蛋白(FABPS)超家族成员之一,广泛存在于各种正常的组织细胞中,参与脂肪酸贮存,运输与降解等过程。近年来,对脂肪细胞型脂肪酸结合蛋白的研究已成为热点,本文就其主要特征及其与各类疾病的关系作一简要综述。     

人心型脂肪酸结合蛋白(H-FABP)的原核表达、纯化和冻干品的制备

目的：获得重组人心型脂肪酸结合蛋白,分析其活性及制备冻干品。方法：从GenBank中检索人源H-FABP CDs 序列,合成基因后构建原核表达载体pET-28a（+）-H-FABP。将表达载体转入E.coli BL21（DE3）,摸索pET-28a（+）-H-FABP最佳诱导条件,表达并纯化重组蛋白。使用检测试剂检测纯化后的重组H-FABP活性,研究最佳冻干方案并考察冻干品的稳定性。结果：经过优化诱导条件,重组H-FABP在BL21（DE3）中以可溶性蛋白形式表达。诱导条件为OD₆₀₀≈0.6,IPTG终浓度0.4mmol/L,30℃诱导4h。通过Ni²⁺亲和层析纯化可得到纯度大于95%的重组H-FABP蛋白。重组H-FABP冻干品可以在37℃稳定保存12d,25℃、4℃稳定保存至少4个月。结论：本项研究中的重组H-FABP表达体系成熟、蛋白活性高,冻干品稳定性好,为后续研究提供了稳定高效的生物原材料。     

In VitroRearing ofTrichogramma minutumRiley (Hymenoptera: Trichogrammatidae) for Ten Generations, with Quality Assessment Comparisons ofin Vitroandin VivoReared Adults

Trichogramma minutumRiley were reared for 10 generations on an artificial diet containing a yeast extract, FreeAmine III, nonfat dry milk, chicken egg yolk, chicken embryo extract, andManduca sexta(L.) egg liquid. Quality control parameters, including adult longevity, sex ratio, pupation rate, percentage of pupae to emerge as adults, adult female body length, number ofHelicoverpa zea(Boddie) eggs parasitized by a female, and percentage of deformed females were assessed and compared to insects rearedin vivoon irradiatedH. zeaeggs. The development time was longer forin vitroreared insects, but there were more deformed females in thein vitroculture. The sex ratio, however, was generally not significantly different between thein vitroandin vivocultures. Thein vitroreared females generally were larger, lived longer, and parasitized moreH. zeaeggs. Emergence of adults was in excess of 75% in all but the firstin vitrogeneration and was generally not significantly different from adult emergence in thein vivoculture. These findings will be of value in the development of a practical system forin vitromass rearing ofTrichogrammafor use in biological control.     

Syntheses and reactions of methyl (Z)-9,10-epoxy-13-oxo-(E)-11-octadecenoate and methyl (E)-9,10-epoxy-13-oxo-(E)-11-octadecenoate

The syntheses and reactions of two epoxyketoacids (methyl (Z)-9,10-epoxy-13-oxo-(E)-11-octadecenoate (IV) and methyl (E)-9,10-epoxy-13-oxo-(E)-11-octadecenoate (V)) are described. The synthetic method is based on the stereoselective oxidation of linoleic acid by soybean lipoxygenase to produce the corresponding 13-hydroperoxide. Reduction of the hydroperoxide with sodium borohydride followed by oxidation, esterification and epoxidation yielded the compounds IV and V with a global yield of 14% and 3%, respectively, referred to the diasteromerically pure isolated compounds. Confirmation of the structures was carried out by reduction of the ketone group with sodium borohydride and by the opening of the oxirane ring with methanolic boron trifluoride. The reduction of compounds IV and V with hydrogen mainly yielded the tetrahydrofuranoid fatty acid, methyl 10,13-epoxyoctadecanoate. This reaction may be considered a new procedure to obtain tetrahydrofuranoid fatty acids.     

Formation of Postsynaptic-Like Membranes during Differentiation of Embryonic Stem Cellsin Vitro

To analyze the formation of neuromuscular junctions, mouse pluripotent embryonic stem (ES) cells were differentiated via embryoid bodies into skeletal muscle and neuronal cells. The developmentally controlled expression of skeletal muscle-specific genes coding for myf5, myogenin, myoD and myf6, α₁subunit of the L-type calcium channel, cell adhesion molecule M-cadherin, and neuron-specific genes encoding the 68-, 160-, and 200-kDa neurofilament proteins, synaptic vesicle protein synaptophysin, brain-specific proteoglycan neurocan, and microtubule-associated protein tau was demonstrated by RT-PCR analysis. In addition, genes specifically expressed at neuromuscular junctions, the γ- and ?-subunits of the nicotinic acetylcholine receptor (AChR) and the extracellular matrix protein S-laminin, were found. At the terminal differentiation stage characterized by the formation of multinucleated spontaneously contracting myotubes, the myogenic regulatory gene myf6 and the AChR ?-subunit gene, both specifically expressed in mature adult skeletal muscle, were found to be coexpressed. Only the terminally differentiated myotubes showed a clustering of nicotinic acetylcholine receptors (AChR) and a colocalization with agrin and synaptophysin. The formation of AChRs was also demonstrated on a functional level by using the patch clamp technique. Taken together, our results showed that during ES cell differentiationin vitroneuron- and muscle-specific genes are expressed in a developmentally controlled manner, resulting in the formation of postsynaptic-like membranes. Thus, the embryonic stem cell differentiation model will be helpful for studying cellular interactions at neuromuscular junctions by “loss of function” analysisin vitro.     

Polar Bear (Ursus maritimus) Adipose Tissue Fatty Acid Composition Compared to Fatty Acid Constituents of a Common Milk Replacer

This study compared the fatty acid composition of polar bear (Ursus maritimus) adipose tissue (n=2) to the fatty acid (FA) composition in published literature for maternal milk (n=3 samples) and a primary milk formula (liquid Esbilac, Pet Ag Inc., Hampshire, IL) commonly used in hand rearing, to look at possible dietary influences on ultimate body fat constituency. All tissue and commercial milk fatty acids were analyzed on a percent relative (% of fat) basis for consistency in reporting results and to make easier comparisons between samples with varying fat contents. Thirty‐eight individual fatty acid profiles were measured and the results tabulated into saturated, monounsaturated and polyunsaturated fats. The tissue adipose results for the two cubs had similar patterns throughout the assay. Saturated FA totals were 30% of the total fat, monounsaturated FA represented 50% of the total fat, and polyunsaturated FA was 15%. Similar fatty acid proportions were reported when comparing adipose to published data for maternal milk of polar bears. The most striking differences were between the commercial milk replacer (liquid Esbilac) and the tissue samples and maternal milk values. Esbilac FA summaries for saturated FAs were 24%, monounsaturated were 26%, and polyunsaturated comprised 50% of the total fat. Polyunsaturated fat in Esbilac is substantially higher than the tissue and milk scores. Although lipid sources from whole cream or half‐and‐half are used to increase the fat concentration of milk replacers for the hand‐reared polar bear cub, alternative ingredients such as fish oil may prove more suitable for this species, as their FA profiles better duplicate natural diets and resulting lipid stores in milk and adipose tissues of free‐ranging polar bears. Zoo Biol 0:1–11, 2006. © 2006 Wiley‐Liss, Inc.     

犬卵母细胞的体内成熟环境与体外成熟培养

犬(Canis familiaris)是生物医学研究的最重要模型动物之一.但由于生殖生理的特殊性,其卵母细胞的体外培养成熟率低,辅助生殖研究进展缓慢,严重制约了该动物在生物科学研究中的运用.在犬科动物体内,排卵前卵母细胞处于高浓度孕酮的卵泡环境中,在生发泡期排到输卵管内,并在此恢复和完成减数分裂.因此,犬卵母细胞体外成熟所需的条件不同于其他哺乳动物,目前主要采用以添加相关因子的M199作为培养液,但体外培养发育至MⅡ期的比率仅为15%～20%.所以,必须在了解犬卵母细胞体内成熟机制的基础上,建立一套类似于体内生理环境的体外成熟培养体系.本文在阐述犬卵母细胞体内成熟生理过程的基础上,对其体外成熟培养方法和影响因素的研究现状进行分析,为相关研究提供参考.     

Occurrence of 13(S)-Hydroxyoctadecadienoic Acid in Biological Samples

The oxygenated metabolite of linoleic acid, 13(S)-hydroxyoctadecadienoic acid has recently been shown to play a role in cellular regulation. To detect this molecule in biological systems, we recently developed a specific polyclonal antibody. Using this antibody, we report the presence of 13(S)-hydroxyoctadecadienoic acid in human urine, cell culture media, and untreated goat serum for the first time by a specific, sensitive, and rapid enzyme immunoassay. Furthermore, the enzyme linked immunosorbent assay data are verified by gas chromatography/mass spectrometry analysis of the same samples.     

Extracellular fatty acid binding protein (Ex-FABP) modulation by inflammatory agents: "physiological" acute phase response in endochondral bone formation

Ex-FABP, extracellular fatty acid binding protein, is a 21 kDa lipocalin expressed in hypertrophic cartilage, muscle and heart during chick embryo development and in granulocytes. Ex-FABP synthesis was increased in chondrocyte and myoblast cultures by inflammatory agents (LPS; IL6) and repressed by antiinflammatory agents. Expression of Ex-FABP and specific gelatinases is paralleled in hypertrophic cartilage; LPS specifically induced high molecular weight gelatinase ( > 200 kDa). LPS-treated hypertrophic chondrocytes showed increased chemotactic activity for endothelial cells paralleled by increased expression of transferrin. A high amount of Ex-FABP was expressed in adult pathological cartilage both in dyschondroplastic and osteoarthritic chickens. Controls were negative. Ex-FABP could represent a stress protein physiologically expressed in tissues where active remodelling is taking place during development and in tissues characterized by an acute phase response due to pathological conditions. We also suggest that during endochondral bone formation other responses characteristic of a local inflammatory status, such as gelatinase production and angiogenic factor secretion, are "physiologically" activated.     

脂肪酸合成酶在肿瘤中表达的调节机制

脂肪酸合成酶（fatty acid synthase,FASN）是肿瘤脂质生成的一种关键酶,在催化脂肪酸合成的最后一步中发挥重要作用。FASN在许多肿瘤细胞中过表达而在相应的正常细胞中却不表达。有证据表明FASN是一个代谢性癌基因,在癌细胞中高表达,在肿瘤生长和存活中有重要的作用。FASN在肿瘤中的表达调节是一个很复杂的过程,包括转录水平、翻译后控制和微环境状态的影响。正确认识FASN在肿瘤中的表达调节机制和研究新的FASN抑制剂,为成功治疗肿瘤提供一种新的思路。     

猪I-FABP基因的分子克隆与组织特异性表达分析

小肠型脂肪酸结合蛋白对长链脂肪酸具有高度的亲和力,参与脂肪酸的吸收和细胞内转运。利用cDNA末端快速扩增（RACE）技术并结合同源克隆策略,克隆到了编码猪小肠型脂肪酸结合蛋白基因（I-FABP）的全长cDNA序列（GenBank接受号：AY960624）,并对系统发育关系等进行了生物信息学分析。猪I-FABP基因的cDNA序列全长614 bp,其中包括399bp的开放式读码框（ORF）,43bp的5’末端非编码区（5’URT）和172bp的3’末端非编码区（3’URT）,编码132个氨基酸残基蛋白,在氨基酸水半上与其他物种的I-FABP具有高度的同源性。以邻接法（Neigbor-Joining,NJ）所构建的系统发育关系表明,猪I-FABP与其他物种的,I-FABP属于同一类群,且与人的遗传距离最近。Northern杂交和半定量RT—PCR分析发现,猪I-FABP在猪体组织中出现约620bp大小的转录本,且在猪体组织中广泛存在,但在小肠组织中表达量最为丰富。     

乙肝病毒X与Tab1蛋白相互作用的体内外验证

目的:借助实验室前期质谱分析技术和数据分析研究基础,采用免疫共沉淀(Co-IP)和蛋白质沉降实验(GST pull-down)验证HBV X蛋白与Tab1蛋白的相互作用,为进一步研究HBx在HBV慢性感染致癌机制中的作用提供一定的实验依据。方法:成功构建pGEX-2TK-GST-HBx质粒,对GST-HBx融合蛋白进行诱导表达,与GST-beads结合孵育,构建pcDNA3.1/myc-His(-)BTab1,转染293T细胞使其表达,然后GST pull-down体外试验验证二者的相互作用;构建pcDNA3.1/myc-His(-)B-Tab1和pcDNA3.1-3×flag-HBx真核表达质粒,共转染293T和HepG2细胞使其表达,通过Co-IP实验验证抗Myc抗体可以将HBx从细胞裂解液中沉淀下来,证实了它们在两种细胞系中存在相互作用。结果:显示了HBx和Tab1在体内外条件下能够发生相互作用,为进一步明确HBV X蛋白功能及作用机制奠定基础。     

猪L-FABP基因的克隆、表达特征及遗传多态性研究

FABPs属于脂结合蛋白超家族成员,是一类分子量较小而对脂肪酸有高亲和力的蛋白质,广泛存在于脊椎动物和非脊椎动物的细胞质中.FABPs担当细胞内脂肪酸的运输任务,它们与脂肪酸结合将其运输到脂肪酸氧化的位置、脂肪酸脂化成甘油三醋或磷脂的位置,或者进入细胞核内发挥其可能的调控功能.因此FABPs对脂类代谢具有重要的调控作用.本研究把L-FABP基因作为影响猪肌内脂肪含量的候选基因.为此,利用cDNA末端快速扩增(RACE)和PCR技术,克隆到猪肝脏型脂肪酸结合蛋白基因(L-FABP)的全长cDNA序列(GenBank登录号AY960623)和部分基因组序列(GenBank登录号DQ182323).猪L-FABP基因的cDNA序列全长518 bp,该序列包括起始密码子TGA和38 bp的5'末端非编码区(5'URT),终止密码子TAG和99 bp的3'末端非编码区(3'URT),在3'URT结构区域中包含polyA加尾信号序列AATAAA.猪L-FABP基因与其他FABPs基因一样,也由4个外显子(67 bp、173 bp、93 bp和51 bp)和3个内含子组成,内含子1和3的大小是1 679bp和565 bp,没有获得内含子2的序列,外显子和内含子剪接处符合GT/AG规律.应用Clustal W/X程序对猪L-FABP与其他物种的L-FABP进行多重序列比对,发现猪L-FABP与人、大鼠、鸡的L-FABP的相似性分别为89.8%、81.9%和72.4%.亲水性分析表明,猪L-FABP也是一个潜在的跨膜蛋白,在氨基酸残基57-65之间有一个明显的跨膜α螺旋.应用半定量RT-PCR分析发现,猪L-FABP在猪体组织中广泛存在,但在肝脏和小肠组织中表达量最为丰富.分析还发现,所克隆得到的编码区核苷酸序列与已知猪L-FABP基因的编码区核苷酸序列存在一定的变异,分别是外显子2中T→C(116位)、C→T(231位)、C→A(236位)和A→C(258位),演绎成氨基酸在Leu74Met存在差异.为进一步证实这些突变位点在猪群中真实存在,利用PCR-SSCP检测方法对4个猪种(藏猪、大河猪、雅南猪和约克夏)的157头个体的外显子2全序列进行SNP位点多态性片段的基因型分型,结果发现一个C→T的单核苷酸多态,等位基因频率在中国地方猪种(藏猪、大河猪、雅南猪)与国外约克夏猪种间存在极显著的差异(P＜0.01).连锁分析发现,基因型CC的肌内脂肪含量(4.86±0.22%)显著的高于基因型CT(4.16±0.23%)和TT(4.05±0.27%)的肌内脂肪含量(P＜0.05).因此,推测L-FABP基因可能是影响猪肌内脂肪含量的主效基因或与主效基因紧密连锁的标记基因,并且能够在分子标记辅助选择中用于对猪肌内脂肪含量的遗传改良.     

Probing the Interaction of Brain Fatty Acid Binding Protein (B-FABP) with Model Membranes

Brain fatty acid-binding protein (B-FABP) interacts with biological membranes and delivers polyunsaturated fatty acids (FAs) via a collisional mechanism. The binding of FAs in the protein and the interaction with membranes involve a motif called “portal region”, formed by two small α-helices, A1 and A2, connected by a loop. We used a combination of site-directed mutagenesis and electron spin resonance to probe the changes in the protein and in the membrane model induced by their interaction. Spin labeled B-FABP mutants and lipidic spin probes incorporated into a membrane model confirmed that B-FABP interacts with micelles through the portal region and led to structural changes in the protein as well in the micelles. These changes were greater in the presence of LPG when compared to the LPC models. ESR spectra of B-FABP labeled mutants showed the presence of two groups of residues that responded to the presence of micelles in opposite ways. In the presence of lysophospholipids, group I of residues, whose side chains point outwards from the contact region between the helices, had their mobility decreased in an environment of lower polarity when compared to the same residues in solution. The second group, composed by residues with side chains situated at the interface between the α-helices, experienced an increase in mobility in the presence of the model membranes. These modifications in the ESR spectra of B-FABP mutants are compatible with a less ordered structure of the portal region inner residues (group II) that is likely to facilitate the delivery of FAs to target membranes. On the other hand, residues in group I and micelle components have their mobilities decreased probably as a result of the formation of a collisional complex. Our results bring new insights for the understanding of the gating and delivery mechanisms of FABPs.     

茄科雷尔氏菌脂酰CoA脱饱和酶和环丙烷脂肪酸合成酶的鉴定

茄科雷尔氏菌(Ralstonia solanacearum)是一种危害严重的土传植物致病菌,其宿主范围广泛,在世界各地严重影响重要经济作物的生产.研究茄科雷尔氏菌的生理特性,探索其致病机理,有利于研发防治青枯病的技术与方法.脂肪酸是细菌细胞重要的组成物质,但是茄科雷尔氏菌脂肪酸合成的机制尚不清晰.本文以茄科雷尔氏菌GMI1000为材料,鉴定了该菌的脂酰Co A脱饱和酶和环丙烷脂肪酸合成酶,并分析了这两种酶在不饱和脂肪酸和环丙烷脂肪酸合成中的作用.结果显示,茄科雷尔氏菌RSc2450编码脂酰Co A脱饱和酶,参与其不饱和脂肪酸合成,但是该菌还存在其他不饱和脂肪酸合成途径.同时发现在茄科雷尔氏菌编码两个可能的环丙烷脂肪酸合成酶蛋白质中,仅有Cfa1(RSc0776)参与了该菌环丙烷脂肪酸的合成,并在低p H和高渗透压的耐受中起作用.该研究结果为深入研究茄科雷尔氏菌脂肪酸合成代谢特点及致病机理奠定了基础.     

番茄SlTpx原核表达蛋白的体外功能分析*

H₂O₂是一种重要的信号分子,参与植物体内多种生理代谢活动,但过量的H₂O₂破坏生物大分子,从而使细胞受到毒害。硫氧还蛋白过氧化物酶(thioredoxin peroxidase,Tpx)通过清除H₂O₂在保护植物免受氧化损伤方面起着重要作用。为进一步研究番茄Tpx基因(SlTpx)的功能,构建了番茄SlTpx原核表达载体,并诱导和纯化了SlTpx蛋白,发现该蛋白质大小约为21 kDa。为检测SlTpx的抗氧化功能,通过体外的混合功能氧化酶(MFO)实验、过氧化氢清除实验和SlTpx蛋白体外抗重金属和H₂O₂实验,证明SlTpx可以保护DNA不受有害活性氧切割,并且提高大肠杆菌抵抗重金属和H₂O₂胁迫的能力。为揭示SlTpx在植物中的功能和作用机制奠定基础。