还生口服液抗癌作用机制的研究

报道了还生口服液对荷瘤小鼠（Ｓ１８０、ＥＡＣ、Ｌ６１５）癌细胞膜、红细胞膜Ｎａ＋，Ｋ＋－ＡＴＰａｓｅ活性的影响和对荷瘤小鼠红细胞膜免疫功能的影响。结果表明，还生口服液可显著抑制癌细胞膜、荷瘤小鼠红细胞膜Ｎａ＋，Ｋ＋－ＡＴＰａｓｅ的活性，同时可显著提高荷瘤小鼠红细胞膜的免疫功能，可使红细胞免疫复合物花环率（ＲＦＩＲ）降低，而使红细胞Ｃ３ｂ受体花环率（ＲＢＣ—Ｃ３ｂＲＲ）、红细胞Ｃ３ｂ受体花环促进率（ＲＦＥＲ）显著提高。本文结果揭示，还生口服液抗癌作用机制有部分是通过抑制癌细胞膜，荷瘤机体红细胞膜Ｎａ＋，Ｋ＋－ＡＴＰａｓｅ的活性，提高荷瘤机体红细胞免疫功能完成的。     

黄芪多糖对P_（388）小鼠红细胞免疫促进作用的机制研究

研究了黄芪多糖（ＡＰＳ）对淋巴白血病Ｐ＿（３８８）小鼠红细胞膜功能的影响。研究结果表明，ＡＰＳ（１０～４０ｍｇ／ｋｇ）可显著增加Ｐ３８８小鼠红细胞免疫功能，显著升高红细胞Ｃ３ｂ受体花环率（ＲＢＣ—Ｃ３ｂＲＲ）、红细胞Ｃ３ｂ受体花环促进率（ＲＦＥＲ），同时可降低红细胞免疫复合物花环率（ＲＢ—ＩＣＲＲ）、红细胞Ｃ３ｂ。受体花环抑制率（ＲＦＩＲ）。研究结果还表明，ＡＰＳ增强淋巴白血病Ｐ３８８。小鼠红细胞免疫功能的机制与ＡＰＳ降低Ｐ３８８小鼠红细胞膜过氧化脂质（工ＰＯ）含量、抑制红细胞膜蛋白与收缩蛋白交联高聚物（ＨＭＰ）的形成、增加红细胞膜封闭度、唾液酸含量、增强红细胞膜超氧化物歧化酶（ＳＯＤ）、过氧化氢酶（ＣＡＴ）、钠，钾—三磷酸腺苷酶（Ｎａ＋，Ｋ＋－ＡＴＰａｓｅ）活性有关。     

Red cell sodium fluxes catalysed by the sodium pump in the absence of K+ and ADP

In the absence of extracellular Na+ or K+, the sodium pump catalyses an ouabain-sensitive "uncoupled" Na+ efflux1-4. With red cell ghosts Glynn and Karlish5 showed that this Na+ efflux is accompanied by ATP hydrolysis and that extracellular sodium ions, at low concentrations, inhibit this efflux as well as the associated ATP hydrolysis. At higher concentrations, extracellular sodium ions restore the hydrolysis of ATP3,6 but it is not known whether there is an associated increase in Na+ efflux and, perhaps, an influx. To answer this question we have used inside-out red cell membrane vesicles which are specially suitable for controlling the composition of the medium at the two membrane surfaces while measuring 22Na+ fluxes in both directions. We report here that the sodium pump can operate in a mode in which influx and efflux of sodium are associated with ATP hydrolysis. This mode is different from the Na-Na exchange described by Garrahan and Glynn7, and Glynn and Hoffman8, which requires ADP as well as ATP9 and is probably associated with ADP-ATP exchage rather than ATP hydrolysis10,11.     

衣原体致病机制的研究进展

衣原体通过GAG和GAG受体粘附在宿主细胞表面。衣原体具有Ⅲ型分泌系统,通过该系统病原菌穿过宿主细胞壁可将胞浆蛋白分泌入宿主周质内,从而为病原菌进入宿主细胞提供条件。     

应用红细胞光敏模型评价抗光敏中药添加剂

 研究了紫外线或光敏药物单独存在的条件下以及不同照射时间和不同药物浓度条件对模型的影响。建立了长波紫外线诱导光敏药物致使红细胞溶血模型,通过检测红细胞损伤后上清液中的血红蛋白含量,计算溶血率,从而反映细胞损伤程度。结果表明,紫外线低剂量或氯丙嗪单一条件存在时,并不能引起红细胞溶血;当氯丙嗪含量为0.33mg/mL,紫外线照射30min可致红细胞50%溶血,照射60min可使细胞100%溶血。应用此模型对10种中药及植物成分进行检测,筛选出银杏叶提取液、茶多酚和葡萄籽提取液3种具有抗光敏功能的活性成分。其中,银杏叶中主要成分黄酮类物质通过广泛的紫外吸收能力从源头阻止紫外线对细胞膜的损伤,茶多酚、葡萄籽中的多酚类物质通过清除自由基等光产物对细胞膜起到保护作用。     

Lectin-like polypeptides of P. falciparum bind to red cell sialoglycoproteins

Attempts to control human malaria by immunological means could be compromised by antigenic variability within and between different strains of malarial parasites1. A useful alternative approach might be to block parasite antigens which are important in the mechanisms of invasion of red cells. As the major human parasite Plasmodium falciparum is highly specific for human red cells, isolation of the proteins involved in the recognition of red cells by this parasite might be of particular value. Recent studies suggest that the major red cell sialoglycoproteins (SGPs), glycophorins A, B and possibly C, may carry the sites recognized by the parasite2-4. Furthermore, because certain carbohydrates present on SGPs such as N-acetylglucosamine are able to block invasion by the parasite5, they may be involved in the initial interaction between parasite and red cell. We have now identified parasite proteins which bind to SGP or N-acetylglucosamine on Sepharose 4B columns. Three proteins, of molecular weights (MWs) 140,000 (140K), 70K and 35K, seem to be specifically bound by N-acetylglucosamine.     

预处理对于不同酵母细胞膜渗透性以及酶促磷酸化合成ATP的影响

酵母用于酶促磷酸化合成ATP主要受酵母细胞膜渗透性限制。显然,不同的预处理对不同菌株酵母细胞膜的渗透性有不同的影响。冷水浸洗的啤酒酵母和日晒干燥的面包酵母,其细胞膜的渗透性稍有提高,酶促磷酸化反应可在细胞内进行。因而可提供固定化细胞的条件,用于工业生产ATP。烘干的面包酵母和冰冻的白酒酵母,其细胞膜的渗透性大幅度增加,致使酶促磷酸化反应既不能在细胞内,也不能在细胞外进行,实验还证明,葡萄糖对白酒酵母细胞中的已糖激酶释放有促进作用,因而可用以提取酶液,或进一步制成固定化酶,工业生产ATP。     

几种血液病人红细胞膜蛋白组分的比较研究

为研究几种血液病人和正常人的红细胞膜蛋白的差异,采用ＳＤＳ－ＰＡＧＥ对红细胞影泡电泳。结果发现：一生溶贫病人膜蛋白的电泳图谱与正常人基本相似、膜蛋白组分含量属正常;贫血病人的膜蛋白中带４．１与带３的比值较正常的低,且带４．２下出现新带,与骨髓病主粗关的病人膜蛋白各组分变化较大。     

External Na dependence of ouabain-sensitive ATP:ADP exchange initiated by photolysis of intracellular caged-ATP in human red cell ghosts

Coupled active transport of Na+ and K+ across cellular plasma membranes is mediated by (Na+ + K+)-stimulated Mg2+-dependent ATPase. Active cation transport by this Na pump involves a cyclic Na-dependent phosphorylation of the enzyme by intracellular ATP and hydrolytic dephosphorylation of the phosphoenzyme, stimulated by K+ (ref. 1). In human red blood cells, skeletal muscle and squid axons, replacement of extracellular K by Na results in a ouabain-sensitive efflux of Na coupled to an influx of extracellular Na. There is apparently no net Na movement nor net hydrolysis of ATP. The rate of Na:Na exchange is stimulated by increased levels of ADP and exchange transport is not observed in cells totally depleted of intracellular ATP. These characteristics suggest that the biochemical mechanism underlying the Na exchange mode of the Na pump involves phosphorylation of the enzyme by ATP (which requires intracellular Na) followed by its dephosphorylation by ADP. Such a reaction has been observed in partially purified (Na+ + K+) ATPase from a variety of sources and its dependence on Na concentration has been described (although not previously for the red cell enzyme). In the present work, intracellular ATP:ADP exchange reaction was initiated by photoreleased ATP following brief irradiation at 350 nm of ghosts containing caged-ATP. The ouabain-sensitive component of the ensuing ATP:ADP exchange reaction shows a biphasic response to extracellular Na. External Na in the range 0--10 mM has an inhibitory effect whilst increasing concentrations beyond this range stimulate the rate of exchange in a roughly linear fashion up to 100 mM Na. These results represent the first direct demonstration of the sidedness of the effects of Na on this partial sequence in the overall enzyme cycle and bear a qualitative resemblance to the Na effects on the Na-ATPase which occur in the absence of intracellular ADP in human red blood cells.     

The translational landscape of mTOR signalling steers cancer initiation and metastasis

The mammalian target of rapamycin (mTOR) kinase is a master regulator of protein synthesis that couples nutrient sensing to cell growth and cancer. However, the downstream translationally regulated nodes of gene expression that may direct cancer development are poorly characterized. Using ribosome profiling, we uncover specialized translation of the prostate cancer genome by oncogenic mTOR signalling, revealing a remarkably specific repertoire of genes involved in cell proliferation, metabolism and invasion. We extend these findings by functionally characterizing a class of translationally controlled pro-invasion messenger RNAs that we show direct prostate cancer invasion and metastasis downstream of oncogenic mTOR signalling. Furthermore, we develop a clinically relevant ATP site inhibitor of mTOR, INK128, which reprograms this gene expression signature with therapeutic benefit for prostate cancer metastasis, for which there is presently no cure. Together, these findings extend our understanding of how the 'cancerous' translation machinery steers specific cancer cell behaviours, including metastasis, and may be therapeutically targeted.     

Noradrenaline contracts arteries by activating voltage-dependent calcium channels

Noradrenaline (NA) regulates arterial smooth muscle tone and hence blood vessel diameter and blood flow. NA apparently increases tone by causing a calcium influx through the cell membrane. Two calcium influx pathways have been proposed: voltage-activated calcium channels and NA-activated calcium-permeable channels that are voltage-insensitive. Although voltage-activated calcium channels have been identified in arterial smooth muscle, voltage-insensitive calcium channels activated by NA have not. We show here that NA contractions of rabbit mesenteric arteries increase with depolarization. The increase parallels the elevation of open-state probability (P0) of single, voltage-dependent calcium channels. The action of noradrenaline can be explained by NA-activating voltage-dependent calcium channels, rather than by opening a second type of channel. We show directly that NA increases the open-state probability of single calcium channels. Thus, in the presence of NA, calcium entry through voltage-dependent calcium channels can regulate smooth muscle tone at physiological membrane potentials. These results may have relevance to pathophysiological conditions such as hypertension.     

Ebola virus entry requires the cholesterol transporter Niemann-Pick C1

Infections by the Ebola and Marburg filoviruses cause a rapidly fatal haemorrhagic fever in humans for which no approved antivirals are available. Filovirus entry is mediated by the viral spike glycoprotein (GP), which attaches viral particles to the cell surface, delivers them to endosomes and catalyses fusion between viral and endosomal membranes. Additional host factors in the endosomal compartment are probably required for viral membrane fusion; however, despite considerable efforts, these critical host factors have defied molecular identification. Here we describe a genome-wide haploid genetic screen in human cells to identify host factors required for Ebola virus entry. Our screen uncovered 67 mutations disrupting all six members of the homotypic fusion and vacuole protein-sorting (HOPS) multisubunit tethering complex, which is involved in the fusion of endosomes to lysosomes, and 39 independent mutations that disrupt the endo/lysosomal cholesterol transporter protein Niemann-Pick C1 (NPC1). Cells defective for the HOPS complex or NPC1 function, including primary fibroblasts derived from human Niemann-Pick type C1 disease patients, are resistant to infection by Ebola virus and Marburg virus, but remain fully susceptible to a suite of unrelated viruses. We show that membrane fusion mediated by filovirus glycoproteins and viral escape from the vesicular compartment require the NPC1 protein, independent of its known function in cholesterol transport. Our findings uncover unique features of the entry pathway used by filoviruses and indicate potential antiviral strategies to combat these deadly agents.     

灵芝提取物对红细胞膜磷脂成分及电泳率的影响

采用家兔红细胞和血小板，以薄层色谱扫描法和显微（细胞）电泳法，探讨灵芝对家兔红细胞膜磷脂成分及电泳率的影响。结果显示：实验组红细胞膜磷脂成分中磷脂酰胆碱显著增多（P＜0．01），而鞘磷脂类，磷脂酰乙醇胺都程度不同的减少（P＜0．05），特别是磷脂酰丝氨酸含量，鞘磷脂类／磷脂酰胆碱及磷脂酰丝氨酸／磷脂酰胆碱比值显著减小（P＜0．01）。血小板及红细胞的电泳率显著高于对照组。表明灵芝对维持细胞膜的稳态有重要作用。     

Control of CFTR chloride conductance by ATP levels through non-hydrolytic binding.

Site-specific mutation and membrane reconstitution experiments provide compelling evidence that the product of the gene which is at fault in the disease cystic fibrosis, termed the cystic fibrosis transmembrane conductance regulator (CFTR), is a small-conductance chloride channel activated by phosphorylation. As transport of chloride ions is passive, the predicted presence of two nucleotide-binding domains in CFTR seems as puzzling as a report that ATP hydrolysis is essential to activate the channel. We now find that in the sweat duct, which expresses high levels of CFTR and has a very high Cl- conductance, intracellular concentrations of ATP must be about normal (5 mM) for activation of this conductance, apparently by a non-hydrolytic, perhaps allosteric, mechanism. This passive dependence on ATP should mean that even a modest depletion of cell energy levels will significantly lower the energy demands of electrolyte transport by decreasing chloride conductance. We believe this direct coupling between cellular ATP levels and chloride channel activity is an adaptive mechanism to protect the tissue from damage resulting from excessive energy depletion.     

Shigella flexneri induces apoptosis in infected macrophages.

The Gram-negative bacterial pathogen Shigella flexneri causes dysentery by invading the human colonic mucosa. Bacteria are phagocytosed by enterocytes, escape from the phagosome into the cytoplasm and spread to adjacent cells. After crossing the epithelium, Shigella reaches the lamina propria of intestinal villi, the first line of defence. This tissue is densely populated with phagocytes that are killed in great numbers, resulting in abscesses. The genes required for cell invasion and macrophage killing are located on a 220-kilobase plasmid. We report here on the mechanism of cytotoxicity used by S. flexneri to kill macrophages. Each of four different strains was tested for its capacity to induce cell death. An invasive strain induced programmed cell death (apoptosis), whereas its non-invasive, plasmidcured isogenic strain was not toxic; neither was a mutant in ipa B (ref. 10) (invasion protein antigen), a gene necessary for entry. A non-invasive strain expressing the haemolysin operon of Escherichia coli induced accidental cell death (necrosis), demonstrating that other bacterial cytotoxic mechanisms do not lead to apoptosis. This is the first evidence that an invasive bacterial pathogen can induce suicide in its host cells.     

Structural rearrangements in the membrane penetration protein of a non-enveloped virus

Non-enveloped virus particles (those that lack a lipid-bilayer membrane) must breach the membrane of a target host cell to gain access to its cytoplasm. So far, the molecular mechanism of this membrane penetration step has resisted structural analysis. The spike protein VP4 is a principal component in the entry apparatus of rotavirus, a non-enveloped virus that causes gastroenteritis and kills 440,000 children each year. Trypsin cleavage of VP4 primes the virus for entry by triggering a rearrangement that rigidifies the VP4 spikes. We have determined the crystal structure, at 3.2 A resolution, of the main part of VP4 that projects from the virion. The crystal structure reveals a coiled-coil stabilized trimer. Comparison of this structure with the two-fold clustered VP4 spikes in a approximately 12 A resolution image reconstruction from electron cryomicroscopy of trypsin-primed virions shows that VP4 also undergoes a second rearrangement, in which the oligomer reorganizes and each subunit folds back on itself, translocating a potential membrane-interaction peptide from one end of the spike to the other. This rearrangement resembles the conformational transitions of membrane fusion proteins of enveloped viruses.     

Oxygen uptake occurs faster than sodium pumping in bee retina after a light flash

When neurones are active there is an entry of Na+, which must subsequently be pumped out, and an increase in their oxygen consumption rate (Qo2). The Na+ pump derives its energy from ATP, splitting it into ADP and Pi, and it has reasonably been proposed that the changes in concentrations of ATP, ADP and Pi lead to a stimulation of the O2 consumption by the mitochondria and hence to a restoration of the stock of ATP. Here we present evidence suggesting that Qo2 must be controlled differently in the retinal photoreceptor cells of the honeybee drone. Stimulation of drone photoreceptors with a flash of light causes an entry of Na+ (ref. 4) and a transient increase in Qo2 that indicates respiration of the right order of magnitude to provide ATP to pump the Na+ out. We report intracellular recordings of changes in intracellular sodium (Nai+) and potassium (Ki+) in response to single light flashes and have compared the time course of extra oxygen consumption (delta Qo2) with these ion changes and other indices of Na+ pumping. We found that the time course of pumping seems to lag behind the time course of delta Qo2. It follows that the mitochondrial respiration must be stimulated by some signal which is generated earlier than the rise in ADP produced by the Na+ pump.     

Export by red blood cells of nitric oxide bioactivity

Previous studies support a model in which the physiological O2 gradient is transduced by haemoglobin into the coordinate release from red blood cells of O2 and nitric oxide (NO)-derived vasoactivity to optimize oxygen delivery in the arterial periphery. But whereas both O2 and NO diffuse into red blood cells, only O2 can diffuse out. Thus, for the dilation of blood vessels by red blood cells, there must be a mechanism to export NO-related vasoactivity, and current models of NO-mediated intercellular communication should be revised. Here we show that in human erythrocytes haemoglobin-derived S-nitrosothiol (SNO), generated from imported NO, is associated predominantly with the red blood cell membrane, and principally with cysteine residues in the haemoglobin-binding cytoplasmic domain of the anion exchanger AE1. Interaction with AE1 promotes the deoxygenated structure in SNO-haemoglobin, which subserves NO group transfer to the membrane. Furthermore, we show that vasodilatory activity is released from this membrane precinct by deoxygenation. Thus, the oxygen-regulated cellular mechanism that couples the synthesis and export of haemoglobin-derived NO bioactivity operates, at least in part, through formation of AE1-SNO at the membrane-cytosol interface.     

Intracellular ATP directly blocks K+ channels in pancreatic B-cells

It is known that glucose-induced depolarization of pancreatic B-cells is due to reduced membrane K+-permeability and is coupled to an increase in the rate of glycolysis, but there has been no direct evidence linking specific metabolic processes or products to the closing of membrane K+ channels. During patch-clamp studies of proton inhibition of Ca2+-activated K+ channels [GK(Ca)] in B-cells, we identified a second K+-selective channel which is rapidly and reversibly inhibited by ATP applied to the cytoplasmic surface of the membrane. This channel is spontaneously active in excised patches and frequently coexists with GK(Ca) channels yet is insensitive to membrane potential and to intracellular free Ca2+ and pH. Blocking of the channel is ATP-specific and appears not to require metabolism of the ATP. This ATP-sensitive K+ channel [GK(ATP)] may be a link between metabolism and membrane K+-permeability in pancreatic B-cells.     

LTRPC7 is a Mg.ATP-regulated divalent cation channel required for cell viability

The molecular mechanisms that regulate basal or background entry of divalent cations into mammalian cells are poorly understood. Here we describe the cloning and functional characterization of a Ca2+- and Mg2+-permeable divalent cation channel, LTRPC7 (nomenclature compatible with that proposed in ref. 1), a new member of the LTRPC family of putative ion channels. Targeted deletion of LTRPC7 in DT-40 B cells was lethal, indicating that LTRPC7 has a fundamental and nonredundant role in cellular physiology. Electrophysiological analysis of HEK-293 cells overexpressing recombinant LTRPC7 showed large currents regulated by millimolar levels of intracellular Mg.ATP and Mg.GTP with the permeation properties of a voltage-independent divalent cation influx pathway. Analysis of several cultured cell types demonstrated small magnesium-nucleotide-regulated metal ion currents (MagNuM) with regulation and permeation properties essentially identical to the large currents observed in cells expressing recombinant LTRPC7. Our data indicate that LTRPC7, by virtue of its sensitivity to physiological Mg.ATP levels, may be involved in a fundamental process that adjusts plasma membrane divalent cation fluxes according to the metabolic state of the cell.