真菌鞘糖脂的生物学功能及应用研究进展

丝状真菌作为一类重要的微生物，被广泛应用于发酵食品、工业酶和次生代谢物等工业生产中。真菌鞘糖脂主要由鞘氨醇、脂肪酸链和特殊的极性基团组成，根据极性基团的不同，分为中性鞘糖脂和酸性鞘糖脂两大类。鞘糖脂不仅参与真菌生长、细胞分化、增殖、细胞凋亡、逆境胁迫等重要生理活动，中性鞘糖脂还可作为功能性医药用品、化妆品和保健食品的重要活性组分。本文论述了真菌鞘糖脂的主要种类、结构、生物合成途径和及其参与丝状真菌生长、分化和响应逆境胁迫的生物学功能；探讨了真菌中性鞘糖脂作为抗菌肽的靶点和酸性鞘糖脂在开发抗真菌药物中的应用；同时还综述了中性鞘糖脂作为化妆品的保湿成分或保健食品的功能成分，在改善皮肤屏障功能和预防特应性皮炎中的重要作用的相关研究进展，尤其是来源于曲霉的中性鞘糖脂，可显著增强皮肤屏障功能，并可作为益生元预防肠道损伤；另外还探讨了曲霉尤其是米曲霉作为开发中性鞘糖脂生物资源的优势。     

鞘糖脂的新陈代谢与生理学功能（英文）

鞘糖脂由一个神经酰胺的脂骨架与一个或多个糖基连接形成,存在于细胞膜中,承担多种生理学功能。我们将对鞘糖脂的生物化学及生理学方面研究做一概述,随后简要介绍近年来鞘糖脂的临床研究进展。在讨论鞘糖脂生物化学方面的研究中,我们把重点放在介绍鞘脂类及鞘糖脂的结构和生合成途径。脂类生物合成和降解是通过一系列酶的参与紧密调控的,如果一种酶参与代谢失败会导致酶底物的大量堆积,会引起溶酶体贮积症,这种疾病是由具有分解代谢活性的水解酶缺失所造成的。随后,我们介绍鞘糖脂在细胞及动物体内的生理学方面的功能,以及鞘糖脂在临床方面的一些病症中所起的作用,即使许多细节还有待于进一步研究。     

妊娠期家兔子宫内膜的鞘糖脂表达

 妊娠期家兎子宫内膜的神经节苷脂(Gls)的含量明显低于动情期的,而中性鞘糖脂(NGSL)的含量则以妊娠中、晚期的最高,动情期最低。鞘糖脂组成变化最显著的是妊娠早期,由动情期到早孕GM_3从28.0％增加到52.7％,CMH.CDH由未测出分别增加到29.2％和21.9％,而糖链复杂的组分GD_3,GTlb和CPH的百分含量则明显减少,到妊娠中、晚期、短糖链组分逐渐减少,而复杂糖链组分渐增。中期妊娠内膜的(GIs)以GD_3为主要组分,占45％,明显高于其它各期。NGSL在妊娠中、晚期CPH增高达70％,与动情期水平相当。结果提示,妊娠期间子宫内膜的鞘糖脂含量与组成均发生明显变化,这些变化可能与子宫功能密切相关。特别是早孕对的变化,推测与子宫内膜和胚泡的识别,粘连特性的获得有关。     

糖苷合酶应用于糖蛋白和鞘糖脂的合成

糖苷合成酶是糖苷酶的亲核体氨基酸突变酶,催化寡糖的高效合成,可应用于寡糖的大规模生产。最近,糖苷合成酶被成功地应用于两类重要的生物分子——糖蛋白和鞘糖脂的高效合成,这必将对糖生物学和制药业的发展起到重要的推动作用。     

具不同淋巴道转移潜能小鼠肝癌瘤株细胞膜鞘糖脂比较研究

采用高效薄层层析（ＨＰＴＬＣ）对两株具有不同淋巴道转移潜能的小鼠腹水型肝癌瘤株细胞膜鞘糖脂组分进行了比较分析。低转移的ＣＬ－Ａ２瘤株神经节苷脂以ＧＭ３为主,高转移的ＣＬ－１６Ａ３瘤株则以ＧＭ２为主。两细胞株中性鞘糖脂各组分相对百分含量无较显著差异。脂结合唾液酸含量测定表明,ＣＬ－１６Ａ３瘤株脂结合唾液酸含量约为ＣＬ－Ａ２瘤株的三倍。提示,具有不同淋巴道转移潜能的瘤细胞,其质膜鞘糖脂的组成也不同。     

A rapid preparative method for isolation of neutral and acidic glycosphingolipids by radial thin-layer chromatography

An efficient method to separate neutral and acidic glycosphingolipids (GSLs) from their mixtures within a short period (45-60 min) and with low consumption of solvents (chloroform-methanol-water, 60/35/8 (v/v/v); 250-500 ml) has been developed. This method utilizes a centrifugal thin-layer chromatograph (Chromatotron) and the GSL mixtures (30-400 mg) are applied to glass plates coated with a 1-mm layer of silica gel 60 PF-254. The method (radial thin-layer chromatography) is rapid and simple and the recovery of glycosphingolipids is high (70-80%).     

Changes in glycosphingolipids during pollination in Oenothera missouriensis

The results of an analysis of the glycosphingolipids in the pollen and in the style of Oenothera missouriensis show that these membranous lipids ar     

Developmental changes in neutral glycosphingolipids of mouse placenta

The mammalian placenta is a unique organ for the study of developmental changes. Placentas of laboratory animals such as the mouse allow for the determination of the exact stage of pregnancy, which cannot be achieved with human placenta. In this study, neutral glycosphingolipids were isolated from mouse (inbred strain C57BL/6) placentas, from day 10 to day 18 of gestation, and were separated by high performance thin layer chromatography. Densitometric measurements after orcinol staining showed, at day 10 of gestation, the presence of mono-, tetra-, tri- and dihexosylceramide in decreasing quantities, as well as four unidentified spots. On day 12, the glycosphingolipid composition changed with the disappearance of the unidentified spots and the appearance of an orcinol positive spot migrating similarly to the Forssman antigen; no further changes occurred between days 12 and 18 of gestation. The identity of the Forssman-like glycosphingolipid with the Forssman antigen was established by binding of¹²⁵I labelledHelix pomatia agglutinin (-GalNAc specific) to glycosphingolipids separated on high performance thin layer chromatography plates, and by the reaction of the isolated glycosphingolipid with a monoclonal anti-Forssman antibody. The appearance of the Forssman antigen at day 12 of gestation coincided with the day of final maturation of the mouse placenta and subsequent cessation of growth, suggesting a possible role of the glycosphingolipid during embryonic development.Abbreviations asialo-GM₁ Gal 3GalNAc4Gal4Glc1Cer - BCIP 5-bromo-4-chloro-3-indolylphosphate - DHC lactosylceramide, Gal4Glc1Cer - Forssman antigen GalNAc3GalNAc3Gal4Gal4Glc1Cer - globoside GalNAc3Gal4Gal4Glc1Cer - GSL glycosphingolipids - HPA Helix pomatia agglutinin - HPTLC high performance thin layer chromatography - MHC galactosylceramide, Gal1Cer - MHC glucosylceramide, Glc1Cer - PBS phosphate-buffered saline - PNA peanut agglutinin - PVP poly(vinylpyrrolidone), mol. wt 40 000 - SBA soybean agglutinin - THC trihexosylceramide, Gal4Gal4Glc1Cer. To whom correspondence should be addressed.     

A new method for the isolation of the simple and highly complex glycosphingolipids from animal tissue

The most widely used methods for the extraction of glycosphingolipids from animal tissues are based on the use of chloroform/methanol mixtures. These methods, although suitable for a great majority of lipids, fail to remove highly complex glycosphingolipids. Reported here is a method for the isolation of the entire population of glycosphingolipids by means of a gradual degradation of tissue components and enrichment in carbohydrate conjugates resistant to alkali and proteases. Fresh gastric mucosa was homogenized and treated with alkali (β-elimination) and RNAase and DNAase to decrease the viscosity of the homogenate, followed by pronase digestion. Each treatment was completed by exhausitive dialysis against distilled water. The resultant tissue digest was partitioned with chloroform/methanol (2 : 1) to remove simple glycosphingolipids. The aqueous portion of the system was adjusted to 1.0% with Zwittergent?-314 and solubilized for 24 h by mixing. Thus, prepared sample subjected to Bio-Gel P60 column chromatography afforded five fractions. Of these, three were free of protein and contained carbohydrates, fatty acids and sphingosine. Further fractionation on Bio-Gel P10 and P6 columns followed by thin-layer chromatography afforded homogeneous components with all the characteristics of highly complex glycosphingolipids.     

Structural analysis of neutral glycosphingolipids from Ascaris suum adults (Nematoda: Ascaridida)

The neutral glycosphingolipid fraction from adults of the pig parasitic nematode, Ascaris suum, was resolved into four components on thin-layer chromatography. The high-performance liquid chromatography-isolated components were structurally analysed by: methylation analysis; exoglycosidase cleavage; gas-liquid chromatography/mass spectrometry; liquid secondary-ion mass spectrometry; and, in particular, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their chemical structures were determined as: Glc(β1-1)ceramide, Man(β1-4)Glc(β1-1)ceramide, GlcNAc(β1-3)Man(β1-4)Glc(β1-1)ceramide and Gal(α1-3)GalNAc(β1-4)GlcNAc(β1-3)Man(β1-4)Glc(β1-1)ceramide; and were characterized as belonging to the arthro-series of protostomial glycosphingolipids. No glycosphingolipid component corresponding to ceramide tetrasaccharide was detected during these analyses. The ceramide composition of the parent glycosphingolipids was dominated by the 2-(R)-hydroxy C24:0 fatty acid, cerebronic acid, and C17 sphingoid-bases: 15-methylhexadecasphing-4-enine and 15-methylhexadecaphinganine in approximately equal proportions. The component ceramide monohexoside was characterized by an additional 15-methylhexadecaphytosphingosine. Abbreviations: CDH, ceramide dihexoside; Cer, ceramide; CMH, ceramide monohexoside; CPH, ceramide pentahexoside; CTH, ceramide trihexoside; CTetH, ceramide tetrahexoside; Hex, hexose; HexNAc, N-acetylhexosamine; HPTLC, high-performance thin-layer chromatography; LSIMS, liquid secondary-ion mass spectrometry; MALDI-TOF-MS, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; N-, Nz- and A-glyco(sphingo)lipids, neutral, neutralzwitterionic and acidic glyco(sphingo)lipids, respectively This revised version was published online in November 2006 with corrections to the Cover Date.     

Biosynthesis of eukaryotic cell surface glycosphingolipids using solubilized glycosyltransferases

Two fucsyltransferases (FucT-2 and FucT-3) have been solubilized from Golgi-rich membrane fraction of bovine spleen, using a cationic detergent. FucT-3 was distinguished from FucT-2 by comparing their kinetic parameters and heat stability. FucT-2 and FucT-3 lost activity (85 %) and (5 %), respectively, when heated at 55°C for 10 sec. Two galactosyltransferases (GalT-3 and GalT-4) and two sialyltransferases (SAT-2 and SAT-3) have also been solubilized from embryonic chicken brain membranes using nonionic detergents. Affinity chromatography and microisoelectric focusing were used to separate these enzymes into functionally pure fractions. Anomeric and positional linkages in some of the products (LM1 and LD1c) have also been established. The terminal NeuAc(α2-8) linkage in GD3 and LD1c was established by identification of the partially methylated penultimate [Ac-¹⁴C]sialic acid.     

One carbon metabolism and its implication in health and immune functions

One carbon (1C) metabolism is critical for cellular viability and physiological homeostasis. Starting from its crucial involvement in purine biosynthesis to posttranslational modification of proteins, 1C metabolism contributes significantly to the development and cellular differentiation through methionine and folate cycles that are pivotal for cellular function. Genetic polymorphisms of several genes of these pathways are implicated in disease pathogenesis and drug metabolism. Metabolic products of 1C metabolism have significant roles in epigenetic modifications through DNA and histone protein methylation. Homocysteine is a product that has clinical significance in the diagnosis and prognosis of several critical illnesses, including chronic immune diseases and cancers. Regulation of the function and differentiation of immune cells, including T-cells, B-cells, macrophages, and so forth, are directly influenced by 1C metabolism and thus have direct implications in several immune disease biology. Recent research on therapeutic approaches is targeting nuclear, cytoplasmic, and mitochondrial 1C metabolism to manage and treat metabolic (i.e., type 2 diabetes), neurodegenerative (i.e., Alzheimer's disease), or immune (i.e., rheumatoid arthritis) diseases. 1C metabolism is being explored for therapeutic intervention as a common determinant for a spectrum of immune and metabolic diseases. Identifying the association or correlation between essential metabolic products of this pathway and disease onset or prognosis would further facilitate the clinical monitoring of diseases.     

A simplified procedure for the preparation of tritiated GM1 ganglioside and other glycosphingolipids

The ganglioside II³NeuAc-GgOse₄Cer and other glycosphingolipids can be radiolabeled to high specific activity by the galactose oxidase-NaB³H₄ procedure, by purifying the oxidized compounds prior to reductive labeling. The oxidized products are separated from nonoxidized compounds and detergents (Triton X-100 and sodium taurocholate) present during the enzymatic oxidation. Since the oxidized derivatives are separated, the final specific activity depends solely upon the specific activity of the NaB³H₄ and the reduction conditions.     

Axin研究进展

Axin作为一种多功能的支架蛋白参与了多种生理病理过程,涉及到胚胎发育、肿瘤形成、细胞凋亡、糖原代谢等过程,至少在Wnt信号转导通路、应激反应蛋白激酶(SAPK)信号通路、转化生长因子β(TGFβ)信号通路和胰岛素信号转导通路中扮演着重要的角色。对Axin的研究将有助于对胚胎发育、肿瘤形成等重要的生物学问题进一步了解,同时对细胞信号调控网络有一个新的认识。现从Axin在相关疾病、代谢及主要细胞信号通路中的作用等方面对其研究进展做一综述。     

microRNAs及其功能的研究进展

microRNAs(miRNAs)是一类高度保守的、非编码的小分子RNA,通过与靶基因转录的mRNA互补配对在转录后水平调节靶基因的表达。miRNAs对多种生物学过程起必要调控作用。现对microRNAs的合成、作用机制及功能的最新研究进展作一综述。