脂肪酸诱导脂肪细胞促酰化蛋白抵抗及机制研究

目的:观察不同浓度单不饱和脂肪酸(油酸)和饱和脂肪酸(棕榈酸)对3T3-L1(前)脂肪细胞葡萄糖转运的影响,探讨高游离脂肪酸(FFA)负荷在促酰化蛋白(ASP)抵抗形成中的意义,及FFA诱导的3T3-L1(前)脂肪细胞ASP抵抗的机制。方法:体外培养3T3-L1细胞,诱导细胞分化,用不同浓度FFA作用于3T3-L1(前)脂肪细胞,孵育过夜后收获细胞,采用2-脱氧-[3H]-D-葡萄糖掺入法,观察3T3-L1成熟脂肪细胞和前脂肪细胞基础状态和ASP刺激状态的葡萄糖摄取率;采用Western blotting法检测基础状态和ASP刺激的鸟苷酸结合蛋白alpha-q/11(Gαq/11),鸟苷酸结合蛋白beta(Gβ),磷酸化蛋白激酶Calpha(p-PKCα)和磷酸化蛋白激酶Czeta(p-PKCζ)蛋白表达。结果:ASP刺激后,3T3-L1成熟脂肪细胞和前脂肪细胞葡萄糖摄取率分别是基础状态的1.98倍(P0.01)和2.87倍(P0.01)。低浓度FFA不影响ASP刺激的葡萄糖转运;而1.0mmol/L时油酸组和棕榈酸组ASP刺激的成熟脂肪细胞葡萄糖摄取率分别减少47%(P0.05)和34%(P0.05),前脂肪细胞葡萄糖摄取率分别减少43%(P0.05)和62%(P0.01)。1.0mmol/L油酸和棕榈酸抑制成熟脂肪细胞基础状态和ASP刺激的Gβ、Gαq/11、p-PKCα和p-PKCζ蛋白表达,油酸组ASP刺激的蛋白表达分别减少了47%Gβ(P0.01),44%Gαq/11(P0.05)、39%p-PKCα(P0.05)和20%p-PKCζ(P0.05);棕榈酸组也可观察到类似现象(P0.05或P0.01)。在前脂肪细胞,油酸仅抑制ASP刺激的p-PKCα和p-PKCζ(均P0.05)蛋白表达;而棕榈酸下调上述4种信号蛋白的表达(P0.05或P0.01)。结论:油酸或棕榈酸抑制3T3-L1成熟脂肪细胞和前脂肪细胞ASP刺激的葡萄糖转运,证明FFA诱导脂肪细胞产生胰岛素抵抗状态下同时存在ASP抵抗。FFA诱导的ASP抵抗的发生机制与其干扰ASP-C5L2信号转导途径有关。ASP抵抗参与了"脂毒性"-胰岛素抵抗/肥胖症的病理生理过程。     

Pim-3在大鼠脂肪组织中的表达及其与脂肪胰岛素抵抗的关系

目的: 检测Pim-3在脂肪中的表达,并探讨其在脂肪的胰岛素抵抗发生过程中的作用。方法: RT-PCR法检测脂肪组织中Pim-3 mRNA的表达,免疫荧光化学法检测Pim-3蛋白表达及亚细胞定位;检测胰岛素抵抗大鼠的附睾及肾周脂肪组织中Pim-3 mRNA表达变化;体外诱导大鼠骨髓间充质干细胞分化为脂肪细胞,油红O染色判断分化程度,并观察分化前后Pim-3表达变化。RT-PCR法检测高胰岛素(100 nmol/L)对骨髓间充质干细胞来源的脂肪细胞中Pim-3表达变化的影响。结果: (1) 脂肪组织中具有较高水平的Pim-3 mRNA表达,免疫荧光结果显示其蛋白主要分布于胞浆;(2)胰岛素抵抗大鼠附睾及肾周脂肪组织中Pim-3 mRNA表达显著低于对照组 (P<0.05) ;(3)大鼠骨髓间充质干细胞成功分化为脂肪细胞,分化后Pim-3 mRNA表达水平明显增高;(4)高胰岛素处理后,脂肪细胞中Pim-3 mRNA表达显著降低。结论: Pim-3表达于脂肪组织中,并可能参与骨髓间充质干细胞来源的脂肪细胞分化过程及脂肪组织胰岛素抵抗的发病过程。     

甘露聚糖结合凝集素(MBL)对3T3-L1前脂肪细胞成脂分化的调节作用及机制

目的研究甘露聚糖结合凝集素(mannan-binding lectin,MBL)对3T3-L1前脂肪细胞成脂分化的调节及其机制。方法体外诱导3T3-L1前脂肪细胞成脂分化,同时给予不同浓度的MBL(0、1、10、20μg/ml)干预。CCK-8法检测细胞增殖能力变化,油红O染色和细胞内甘油三酯含量测定法分析脂质积累情况。Western blot及qRT-PCR检测脂肪细胞成脂分化相关因子PPARγ及C/EBPα的蛋白质及mRNA表达水平。Western blot分析脂肪合成调控信号分子Akt的表达及磷酸化。结果实验组各浓度MBL(0、1、10、20μg/ml)对3T3-L1前脂肪细胞增殖都无影响。3T3-L1前脂肪细胞诱导分化3 d,甘油三酯检测发现MBL处理组细胞内甘油三酯水平下降,并呈剂量依赖关系;油红O染色结果进一步显示,MBL处理组的脂滴数量显著减少,吸光度值也显著降低,同样呈现浓度依赖关系。Western blot及qRT-PCR检测结果证实,MBL处理组PPARγ和C/EBPα的蛋白质及mRNA表达水平均显著下降,呈剂量依赖性。在MBL干预下,Akt的磷酸化水平也明显下调。结论MBL通过Akt信号通路调控3T3-L1前脂肪细胞的成脂分化。     

促酰化蛋白诱导的前脂肪细胞分化过程中转录因子表达的时序性研究

目的：观察促酰化蛋白（ASP）诱导3T3-L1前脂肪细胞的分化过程，转录因子PPARγ、C/EBPδ、C/EBPα mRNA表达的强度及时序性。 方法： 以3T3-L1前脂肪细胞为实验对象，用ASP代替经典激素鸡尾酒诱导刺激中的胰岛素，即促酰化蛋白、1-甲基-3-异丁基黄嘌呤和地塞米松（ASP+IBMX+DEX）诱导3T3-L1前脂肪细胞分化，分别在诱导分化1 d、2 d、4 d、6 d、8 d收获细胞，采用RT-PCR法检测ASP诱导3T3-L1前脂肪细胞分化过程中转录因子PPARγ、C/EBPδ、C/EBPα mRNA表达的情况。 结果： PPARγ mRNA在诱导分化1 d时有低水平表达，在诱导分化过程中表达逐步升高，在终末分化阶段仍保持高水平表达。C/EBPδ mRNA在诱导分化1 d时有中等水平表达，在诱导分化2 d时表达水平最高，诱导分化4 d时表达明显减少，在诱导分化6 d和8 d，检测不到C/EBPδ mRNA的表达。C/EBPα mRNA在诱导分化1 d仅有低水平表达，在诱导分化过程中表达逐步升高，在终末分化阶段仍保持高水平表达。IBMX+DEX诱导前脂肪细胞分化过程中，PPARγ、C/EBPδ和C/EBPα mRNA分化早期也有一定升高，但明显低于ASP诱导的转录因子的表达。 结论： ASP对转录因子C/EBPδ、C/EBPα和PPARγ表达的时序性影响，可能是ASP诱导前脂肪细胞分化的重要分子机制之一。     

蛋白激酶C对3T3-L1脂肪细胞抵抗素表达的影响

目的：观察蛋白激酶C转导途径对3T3-L1脂肪细胞抵抗素表达的影响。方法：3T3-L1脂肪细胞诱导分化为成熟的脂肪细胞后，分别于培养瓶中加入浓度为50 nmol/L的12-肉豆蔻酰-13-乙酸佛波酯（PMA）和浓度为5 μmol/L马来酰亚胺甲磺酸盐(Ro-31-8220)，培养24 h，用RT-PCR的方法检测3T3-L1脂肪细胞抵抗素mRNA的表达，用Western blotting检测3T3-L1脂肪细胞抵抗素表达结果：PMA组可以明显提高3T3-L1脂肪细胞抵抗素基因及蛋白的表达，明显高于对照组，两者的差异显著（P<0.01）；Ro-31-8220组其表达低于对照组，两者的差异显著（P<0.01）。结论：蛋白激酶C转导途径可以调控3T3-L1脂肪细胞抵抗素的表达。     

胰岛素和人参皂甙 Rg1对脂联素mRNA 表达的影响

目的:探讨不同浓度的胰岛素和人参皂甙Rg1对体外3T3-L1脂肪细胞脂联素(adiponectin) mRNA 表达的影响。方法:通过不同浓度胰岛素和Rg1与3T3-L1脂肪细胞共同培养，以β-actin为内对照，半定量逆转录PCR法测定脂联素 mRNA表达。结果:随着胰岛素浓度的升高，脂联素 mRNA 表达逐渐降低，在胰岛素浓度 ≥100 nmol/L 时具有显著差异（P<0.05）;40 mg/L Rg1能有效逆转高胰岛素对脂联素mRNA 表达的抑制作用（P<0.05）。结论:体外高胰岛素水平可使3T3-L1细胞脂联素表达下降，Rg1可逆转体外高胰岛素降低脂联素表达的作用。     

胰岛素、地塞米松、肿瘤坏死因子α能调节脂联素的表达和分泌

目的通过体外培养的3T3-L1脂肪细胞模型,研究胰岛素、地塞米松和肿瘤坏死因子α(TNFα)对脂肪细胞因子脂联素(Acrp30)的mRNA表达和蛋白分泌的影响。方法用150nmol/L胰岛素、100nmol/L地塞米松和10ng/ml TNFα刺激分化完全的3T3-L1细胞16h,提取细胞RNA,运用半定量RT-PCR技术检测Acrp30mRNA表达量的变化;另外,用同样浓度的胰岛素、地塞米松和TNFα刺激分化完全的3T3-L1细胞1、2、4、16h,用Western印迹技术检测Acrp30分泌的变化。结果胰岛素、地塞米松和TNFα均能下调Acrp30mRNA的表达;地塞米松和TNFα减少Acrp30的蛋白分泌;而胰岛素仅能瞬时刺激Acrp30的蛋白分泌,作用时间超过4h对Acrp30的分泌并无影响。结论血浆脂联素蛋白浓度在翻译后水平被调节,包括翻译和(或)分泌水平。     

miR-202通过抑制PGC1β表达促进3T3-L1前脂肪细胞分化

目的观察miR-202对3T3-L1前脂肪细胞分化的影响及可能的机制。方法通过慢病毒感染构建稳定表达AMO-miR-202和乱序对照miRNA细胞系,随后诱导分化。至分化的第9天,油红O染色观察细胞内脂滴的情况;RT-PCR检测过氧化物酶体激活增殖受体γ2(PPARγ2)和a P2的基因表达;Western blot检测PPARγ2、a P2和miR-202靶基因PPARγ辅助活化因子1β(PGC1β)蛋白表达。结果经293T细胞慢病毒包装AMO-miR-202、乱序对照miRNA,荧光显微镜下可见约80%~90%荧光细胞;将上述2组病毒液分别感染3T3-L1前脂肪细胞后,可见约70%~80%荧光细胞。AMO-miR-202组细胞内脂滴及PPARγ2和a P2的mRNA表达显著低于乱序对照组和对照组(P<0.05)。与乱序对照组和对照组相比,AMO-miR-202组PGC1β蛋白表达显著增加(P<0.05),PPARγ2和a P2蛋白表达显著降低(P<0.01),而乱序对照组和脂肪细胞组上述指标无明显差异。结论 miR-202可能通过抑制PGC1β、提高PPARγ2和a P2的表达促进3T3-L1前脂肪细胞分化。     

果糖通过激活Akt信号通路促进3T3-L1细胞的脂肪分化

目的:研究果糖(fructose)对3T3-L1前脂肪细胞分化过程的影响及其作用机制。方法:对体外培养的3T3-L1前脂肪细胞给予鸡尾酒法诱导脂肪分化,并使用1 g/L的果糖进行诱导干预。油红O染色法定量分析细胞内的脂质含量;RT-qPCR法检测脂肪分化过程中脂滴包被蛋白2(Plin2)、CCAAT/增强子结合蛋白(C/EBP)α和C/EBPβ的mRNA表达水平;Western blot检测脂肪分化标志蛋白过氧化物酶体增殖物激活受体γ(PPARγ)和脂肪细胞蛋白2(αP2)的蛋白表达水平。结果:与单纯用分化培养基(DM)的对照组相比,实验(DM+fructose)组的脂肪细胞体积及胞质内脂滴积累量显著增加,脂肪分化标志蛋白PPARγ和aP2的表达水平显著上调(P0.01),Plin2、C/EBPα和C/EBPβ的mRNA表达水平亦显著上调(P0.05)。此外,加入果糖之后Akt信号通路中的关键分子Akt的磷酸化水平显著增加(P0.01),加入Akt特异性阻断剂之后,PPARγ和aP2的表达水平显著下调。结论:果糖能够促进3T3-L1细胞的脂肪分化,可能是通过激活Akt信号通路实现的。     

脂联素siRNA对3T3-L1细胞基础葡萄糖转运的影响

目的：构建携带小鼠脂联素（Acrp30）siRNA腺病毒载体，并检测其对小鼠脂肪细胞Acrp30表达以及对3T3-L1脂肪细胞基础葡萄糖转运的影响。方法:设计并化学合成小鼠脂肪细胞Acrp30 siRNA片段，将其亚克隆入AdEaxy XL 腺病毒载体系统，在293细胞内包装扩增为重组腺病毒。用此重组腺病毒感染3T3-L1脂肪细胞，用RT-PCR和ELISA检测其Acrp30 mRNA和蛋白表达。采用2-Deoxy-［3H］D-glucose掺入法测定脂肪细胞葡萄糖转运。结果:设计并构建了小鼠Acrp30 基因特异性siRNA腺病毒载体，该载体感染脂肪细胞后，能显著抑制Acrp30 mRNA和蛋白表达，影响3T3-L1脂肪细胞基础葡萄糖的转运，与对照组相比，差异显著(P<0.05)。结论:构建的Acrp30 基因特异性siRNA腺病毒载体能有效地抑制脂联素在3T3-L1脂肪细胞中的表达，从而影响3T3-L1脂肪细胞基础葡萄糖转运。     

蛋白质与蛋白质相互作用的研究进展

通过研究蛋白质与蛋白质的相互作用，人们能更好地注释蛋白质的功能，解码生命现象，特别是在新药物的设计上具有极大的实用价值，这是后基因组研究的重要任务之一。蛋白质结构的剖析、计算机分子模拟技术的发展和分子生物学技术更新为研究蛋白质间相互作用创造了各种有利条件。     

Global analysis of protein function using protein microarrays

Protein microarrays containing thousands of proteins arrayed at high density can be prepared and probed for a wide variety of activities, thereby allowing the large scale analysis of many proteins simultaneously. In addition to identifying the activities of many previously uncharacterized proteins, protein microarrays can reveal new activities of well-characterized proteins, thus providing new insights about the functions of these proteins. Below, we describe the construction and use of protein microarrays and their applications using yeast as a model system.     

TSHR蛋白表达质粒的构建和TSHR蛋白的表达

目的：为获得足量的ＴＳＨＲ蛋白及建立Ｇｒａｖｅｓ’病的动物模型。方法：将构建于ｐＣＲ＾ＴＭ３中的ＴＳＨＲ ｃＤＮＡ经限制性内切酶处理后,重新构建于表达型载体ＰｉｎＰｏｉｎｔ Ｘ质粒中,经酶切分析和ＰＣＲ检测,并在Ｅ．ｃｏｌｉ ＪＭ１０９中表达,Ｗｅｓｔｅｒｎ ｂｌｏｔｉｎｇ免疫印迹法检测其免疫活性．结果：证明ＴＳＨＲ ｃＤＡ基因正确地重组于ＰｉｎＰｏｉｎｔ Ｘ中,并在Ｅ．ｃｏｌｉ ＪＭ１０９中表达     

Application to immunoassays of the fusion protein between protein ZZ and enhanced green fluorescent protein

Enhanced green fluorescent protein (EGFP) from Aequorea victoria was fused to the C terminal region of protein ZZ, an artificial synthetic IgG Fc fragment binding protein derived from tandem repeats of the B domain of protein A. The ZZ-EGFP fusion protein was expressed in Escherichia coli with a His(6) tag and purified in high yield by one-step Ni(2+) chelating affinity chromatography. It was then used in the immunoblot analysis of GST and TNFalpha as well as in immunofluorescent assays of 293T cells transfected with IRF3, an interferon regulatory factor which localized in cytoplasm without virus infection. The fusion protein also performed effectively in FACS analysis of surface integrin beta3 subunit on 293 T cells. The chimeric protein bound various antibodies from different animal sources, directed against a variety of proteins. Thus, ZZ-EGFP showed broad promise in potential immunological applications.     

Phosphorylation of hepatitis C virus core protein by protein kinase A and protein kinase C

Hepatitis C virus (HCV) core protein can form capsid-like particles and is believed to be the viral capsid protein. Besides its structural functions, this protein is also known to possess multiple regulatory functions. In this article, we have studied the possible phosphorylation of HCV core protein in two different human liver-derived cell lines Huh7 and HepG2. Our results indicated that the HCV core protein could be phosphorylated, albeit inefficiently, independent of its downstream E1 protein in these two cell lines. Two of the basal phosphorylation sites were identified to be serine-53 and serine-116. The phosphorylation of the core protein could be enhanced by the PKC activator phorbol 12-myristic 13-acetate (PMA), and the PKA activator forskolin, and these enhancements could be abolished by the respective inhibitors of PKC and PKA, indicating that the core protein is a substrate of these two kinases. While both serine-53 and serine-116 served as the PKC phosphorylation sites, serine-116 appeared to be the major PKA phosphorylation site. Further analyses using serine-to-alanine mutation to mimic dephosphorylation and serine-to-aspartic acid mutation to mimic phosphorylation revealed that the conversion of serine-116 to aspartic acid led to an enhanced nuclear localization of the core protein. This observation indicates that one function of phosphorylation may be to regulate the nuclear localization of the core protein.     

H protein, a minor protein of TMV virions, contains sequences of the viral coat protein

H protein, a minor protein found associated with virions of tobacco mosaic virus (TMV) at an average of about one copy per virion and previously believed to be host-coded (Asselin and Zaitlin, 1978, Virology 91, 173-181), has been shown to contain sequences of the viral capsid protein. Two-dimensional tryptic peptide maps of 125I-labeled H protein (Mr 26,500) and coat protein (Mr 17,500) from TMV strains U1 and Dahlemense show that the respective H proteins contain most if not all of the labeled peptides of the coat proteins in addition to 2-3 unique peptides. The H proteins also contain unique antigenic determinants, as antibodies can be isolated which react strongly with the H protein but not with the coat protein of Dahlemense TMV. Finally, amino acid composition analysis of the U1-TMV H protein has shown the presence of methionine and histidine, amino acids not present in the coat protein of that strain. H protein appears to contain the same NH2 terminus as coat protein, as there is an H protein tryptic peptide that both comigrates in a two-dimensional system and produces the same acid cleavage product as the NH2-terminal tryptic peptide of coat protein. H protein also seems to have the same COOH terminus as coat protein, as cyanogen bromide digestion of Dahlemense-TMV coat protein and H protein indicates that each has a methionine about 12 amino acids from one terminus (known to be the COOH terminus of the coat protein). Thus, H protein is not structurally equivalent to coat protein with an addition on either its NH2 or COOH terminus. However, H protein does not appear to be a noncovalent aggregate of coat protein and some other protein. Rather, the model we favor for H protein structure is that of a branched fusion product between coat protein and another polypeptide of host or viral origin.     

Migration of axonal protein: Absence of a protein concentration gradient and effect of inhibition of protein synthesis

Summary Two experiments have been performed to gain insight into the mechanisms of axoplasmic protein migration. In the first the concentration of protein along cat optic nerves was measured to determine if a concentration gradient was present which might drive protein in a proximo-distal direction. None was found. In the second experiment we endeavored to determine if axonal protein migration would continue despite cycloheximide-induced inhibition of protein synthesis in the cell body. It did continue to migrate and with no significant change in rate (0.8–1.0 mm/day). It is concluded that these experiments rule out diffusion down a proximo-distal concentration gradient as a mechanism for axonal protein migration.Supported by USPHS Grant NB-05038 and USPHS 5T56M 1604-10.     

Isolations of protein A and protein G from the bacterial surface

Ten tested cultures each of Staphylococcus aureus (S. aureus) and of Streptococcus belonging to serological group G bound human IgG to a high extent. Protein A could be solubilized from strain Cowan I of S. aureus by lysozyme, mutanolysine, hydroxylammoniumchloride, hot acid extraction or lysostaphin and subsequently purified by affinity chromatography on human IgG-sepharose. The purified protein A preparation had molecular weights between 29,000 and 63,000 D and inhibited binding of 125I-labeled human IgG to S. aureus Cowan I. Protein G could be solubilized from strain 26540 of the G-streptococci with lysozyme or hot acid extraction and purified by affinity chromatography on human IgG-sepharose. The purified protein G revealed a molecular weight of 67,000 D and inhibited binding of human IgG to the G-streptococci.