共查询到20条相似文献，搜索用时 15 毫秒
1.
T cell activation by lipopeptide antigens 总被引：2，自引：0，他引：2
Moody DB Young DC Cheng TY Rosat JP Roura-Mir C O'Connor PB Zajonc DM Walz A Miller MJ Levery SB Wilson IA Costello CE Brenner MB 《Science (New York, N.Y.)》2004,303(5657):527-531
Unlike major histocompatibility proteins, which bind peptides, CD1 proteins display lipid antigens to T cells. Here, we report that CD1a presents a family of previously unknown lipopeptides from Mycobacterium tuberculosis, named didehydroxymycobactins because of their structural relation to mycobactin siderophores. T cell activation was mediated by the alphabeta T cell receptors and was specific for structure of the acyl and peptidic components of these antigens. These studies identify a means of intracellular pathogen detection and identify lipopeptides as a biochemical class of antigens for T cells, which, like conventional peptides, have a potential for marked structural diversity. 相似文献
2.
Phase transitions and heterogeneity in lipid bilayers 总被引：3，自引：0，他引：3
The optical reflectivity of several well-characterized lipid bilayer systems has been correlated with calorimetric studies of the membrane components. There is a large increase in mean membrane thickness when a bilayer is cooled below the transition temperature of the membrane lipid. Similar studies on membranes generated from a mixture of two lipids possessing different degrees of unsaturation suggest that between the characteristic transition temperatures of the two lipids, the bilayer contains clusters of gel and liquid crystalline lipid which coexist within the plane of the membrane. 相似文献
3.
A Angel 《Science (New York, N.Y.)》1969,163(864):288-290
Isolated brown adipose cell devoid of a basement membrane, readily synthesized a variety of lipids from radioctive acetate, a reactionaugmented by glucose and insulin. A large proportion of the newly formed fatty acids passed into the incubation medium. In intact brown adipose slices and isolated white adipose cells, most of the synthesized lipid was retained as glyceride esters. The date suggest that the rapid turnover of endogenously synthesized lipid in brown adipose cells is almost totally obscured in studies with intact tissue slices because of interstitial barriers to the egress of fatty acid. 相似文献
4.
CD8+ T cell cross-priming via transfer of proteasome substrates 总被引：1，自引：0，他引：1
Norbury CC Basta S Donohue KB Tscharke DC Princiotta MF Berglund P Gibbs J Bennink JR Yewdell JW 《Science (New York, N.Y.)》2004,304(5675):1318-1321
"Cross-priming" describes the activation of na?ve CD8+ T cells by professional antigen-presenting cells that have acquired viral or tumor antigens from "donor" cells. Antigen transfer is believed to be mediated by donor cell-derived molecular chaperones bearing short peptide ligands generated by proteasome degradation of protein antigens. We show here that cross-priming is based on the transfer of proteasome substrates rather than peptides. These findings are potentially important for the rational design of vaccines that elicit CD8+ T cell responses. 相似文献
5.
茶多酚和L-EGCG的抗烟致脂质过氧化作用 总被引：2，自引：0，他引：2
从茶叶中提取的天然多酚类化合物茶多酚和L-表没食子儿茶素没食子酸酯(L-EGCG)对由香烟气相物质诱发的大鼠肺细胞的脂质过氧化有很强的抑制作用,且复合体茶多酚及其主要单体L-EGCG抑制效果接近,同时两者对超氧阴离子自由基和羟自由基都有十分明显的清除作用,表明茶多酚与L-EGCG的抗脂质过氧化机理之一是有效地清除了脂质过氧化的启动子氧自由基. 相似文献
6.
The cytoskeletal protein vinculin contains transformation-sensitive, covalently bound lipid 总被引：10，自引：0，他引：10
Vinculin, which is associated with the cytoskeleton of many cells, has been suggested as a possible linker between microfilament bundles and the plasma membrane. Here it will be shown that fatty acid is covalently attached to vinculin in vivo. Furthermore, in chicken embryo fibroblasts infected with a temperature-sensitive mutant of Rous sarcoma virus, tsNY68, the acylation of vinculin at the permissive temperature was less than one-third that at the nonpermissive temperature. Thus, the covalent binding of lipid to vinculin is a transformation-sensitive event. The covalent modification of vinculin by lipids could be directly or indirectly involved in its reversible association with membranes. This modification may also provide a mechanism to alter the organization of vinculin within cells and thereby play a regulatory role in anchoring or stabilizing microfilament bundles at plasma membranes. 相似文献
7.
Dobrosotskaya IY Seegmiller AC Brown MS Goldstein JL Rawson RB 《Science (New York, N.Y.)》2002,296(5569):879-883
Animal cells exert exquisite control over the physical and chemical properties of their membranes, but the mechanisms are obscure. We show that phosphatidylethanolamine, the major phospholipid in Drosophila, controls the release of sterol regulatory element-binding protein (SREBP) from Drosophila cell membranes, exerting feedback control on the synthesis of fatty acids and phospholipids. The finding that SREBP processing is controlled by different lipids in mammals and flies (sterols and phosphatidylethanolamine, respectively) suggests that an essential function of SREBP is to monitor cell membrane composition and to adjust lipid synthesis accordingly. 相似文献
8.
A virus-encoded "superantigen" in a retrovirus-induced immunodeficiency syndrome of mice. 总被引：27，自引：0，他引：27
The development of an immunodeficiency syndrome of mice caused by a replication-defective murine leukemia virus (MuLV) is paradoxically associated with a rapid activation and proliferation of CD4+ T cells that are dependent on the presence of B cells. The responses of normal spleen cells to B cell lines that express the defective virus indicated that these lines express a cell surface determinant that shares "superantigenic" properties with some microbial antigens and Mls-like self antigens. This antigen elicited a potent proliferative response that was dependent on the presence of CD4+ T cells and was associated with selective expansion of cells bearing V beta 5. This response was markedly inhibited by a monoclonal antibody specific for the MuLV gag-encoded p30 antigen. 相似文献
9.
Extraction of lipids from the shed epidermis of the terrestrial snake Elaphe obsoleta obsoleta increases cutaneous water loss in vitro as much as 15-fold. Partial denaturation of epidermal keratin without lipid extraction increases cutaneous water loss only twofold. Histological observations and thin-layer and gas-liquid chromatography of the lipid extracts indicate a complex mixture of polar and neutral lipids predominantly in the mesos layer of the cornified epidermis. Comparative measurements of cutaneous water loss in other species of snakes and a lizard show that permeabilities differ naturally but are essentially identical after lipid extraction. These findings establish the importance of lipids in the permeability barrier of reptilian skin and suggest that keratin or scale morphology are of nominal importance in limiting water exchange. 相似文献
10.
Assistance of microbial glycolipid antigen processing by CD1e 总被引：1，自引：0，他引：1
de la Salle H Mariotti S Angenieux C Gilleron M Garcia-Alles LF Malm D Berg T Paoletti S Maître B Mourey L Salamero J Cazenave JP Hanau D Mori L Puzo G De Libero G 《Science (New York, N.Y.)》2005,310(5752):1321-1324
Complexes between CD1 molecules and self or microbial glycolipids represent important immunogenic ligands for specific subsets of T cells. However, the function of one of the CD1 family members, CD1e, has yet to be determined. Here, we show that the mycobacterial antigens hexamannosylated phosphatidyl-myo-inositols (PIM6) stimulate CD1b-restricted T cells only after partial digestion of the oligomannose moiety by lysosomal alpha-mannosidase and that soluble CD1e is required for this processing. Furthermore, recombinant CD1e was able to bind glycolipids and assist in the digestion of PIM6. We propose that, through this form of glycolipid editing, CD1e helps expand the repertoire of glycolipidic T cell antigens to optimize antimicrobial immune responses. 相似文献
11.
Membrane structure: some general principles 总被引：55，自引：0，他引：55
M S Bretscher 《Science (New York, N.Y.)》1973,181(100):622-629
The arrangement of lipids and some proteins in the erythrocyte membrane has been discussed. The conclusions from this are listed here as a set of general guidelines for the structure of membranes of higher organisms: some of these rules may be wrong. But at this stage it seems useful to sharpen our thoughts in this way and thereby focus attention on various specific points. 1) The basis of a membrane is a lipid bilayer with (i) choline phospholipids and glycolipids in the external half and (ii) amino (and possibly some choline) phospholipids in the cytoplasmic half. There is effectively no lipid exchange across the bilayer (unless enzymatically catalyzed) (68). 2) Some proteins extend across the bilayer. Where this is so, they will in general have carbohydrate on their surface remote from the cytoplasm. This carbohydrate may prevent the protein diffusing out of the membrane into the cytoplasm; it acts as a lock on the protein. 3) Just as lipids do not flip-flop, proteins do not rotate across the membrane. Lateral motion or rotation of lipids and proteins in the plane of the bilayer may be expected. 4) Most membrane protein is associated with the inner, cytoplasmic, urface of the membrane. Proteins are not usually associated exclusively with the outer half of the lipid bilayer. 5) Membrane proteins are a special class of cytoplasmic proteins, not of secreted proteins. 相似文献
12.
13.
Lipid phosphates can act as signaling molecules to influence cell division, apoptosis, and migration. wunen and wunen2 encode Drosophila lipid phosphate phosphohydrolases, integral membrane enzymes that dephosphorylate extracellular lipid phosphates. wun and wun2 act redundantly in somatic tissues to repel migrating germ cells, although the mechanism by which germ cells respond is unclear. Here, we report that wun2 also functions in germ cells, enabling them to perceive the wun/wun2-related signal from the soma. Upon Wun2 expression, cultured insect cells dephosphorylate and internalize exogenously supplied lipid phosphate. We propose that Drosophila germ cell migration and survival are controlled by competition for hydrolysis of a lipid phosphate between germ cells and soma. 相似文献
14.
del Pozo MA Alderson NB Kiosses WB Chiang HH Anderson RG Schwartz MA 《Science (New York, N.Y.)》2004,303(5659):839-842
Translocation of the small GTP-binding protein Rac1 to the cell plasma membrane is essential for activating downstream effectors and requires integrin-mediated adhesion of cells to extracellular matrix. We report that active Rac1 binds preferentially to low-density, cholesterol-rich membranes, and specificity is determined at least in part by membrane lipids. Cell detachment triggered internalization of plasma membrane cholesterol and lipid raft markers. Preventing internalization maintained Rac1 membrane targeting and effector activation in nonadherent cells. Regulation of lipid rafts by integrin signals may regulate the location of membrane domains such as lipid rafts and thereby control domain-specific signaling events in anchorage-dependent cells. 相似文献
15.
最早对脂滴的研究可以追溯到19 世纪,Richard Altmann 和E.B. Wilson 都描述了细胞
中的脂肪滴,并推测了它们的起源(Altmann, 1890;威尔逊,1896)。早期,脂滴的高衍射特性为其
鉴定提供了便利的光学条件。20 世纪初,由于它们被认为是大多数细胞的组成部分,这种细胞
器被称为脂质体。然而,在20 世纪60 年代末,人造脂质体被发明出来,并很快取代了这个名
字。从那时起,这种细胞器被有过许多名称,包括脂滴、脂体、脂体、脂滴和脂质体。在植物中,
它们通常被称为油体。随着这一领域的迅速发展,它似乎已经定名为“脂滴”。几十年来,除了
形态学研究,脂滴的其他方面几乎没有受到关注。1991 年,脂肪细胞中与脂滴相关的磷酸蛋白
perilipin 的发现,引起人们对这种细胞器的新关注。从那时起,关于脂滴的论文数量急剧增加,
关于脂滴的功能也逐渐被重视起来。 相似文献
16.
Self-nonself discrimination by T cells 总被引：28，自引：0，他引：28
The alpha beta T cell receptor (TCR) recognizes antigens that are presented by major histocompatibility complex (MHC)-encoded cell surface molecules by binding to both the antigen and the MHC molecules. Discrimination of self from nonself antigens and MHC molecules is achieved by negative and positive selection of T cells in the thymus: potentially harmful T cells with receptors that bind to self antigens plus self MHC molecules are deleted before they can mount immune responses. In contrast, the maturation of useful T cells with receptors that bind foreign antigens plus self MHC molecules requires the binding of their receptor to MHC molecules on thymic epithelium in the absence of foreign antigen. The binding of the TCR to either class I or class II MHC molecules directs differentiation of the selected cells into either CD4-8+ (killer) or CD4+8- (helper) T cells, respectively. 相似文献
17.
In invertebrate nervous systems, some long-lasting increases in synaptic efficacy result from changes in the presynaptic cell. In the vertebrate nervous system, the best understood long-lasting change in synaptic strength is long-term potentiation (LTP) in the CA1 region of the hippocampus. Here the process is initiated postsynaptically, but the site of the persistent change is unresolved. Single CA3 hippocampal pyramidal cells receive excitatory inputs from associational-commissural fibers and from the mossy fibers of dentate granule cells and both pathways exhibit LTP. Although the induction of associational-commissural LTP requires in the postsynaptic cell N-methyl-D-aspartate (NMDA) receptor activation, membrane depolarization, and a rise in calcium, mossy fiber LTP does not. Paired-pulse facilitation, which is an index of increased transmitter release, is unaltered during associational-commissural LTP but is reduced during mossy fiber LTP. Thus, both the induction and the persistent change may be presynaptic in mossy fiber LTP but not in associational-commissural LTP. 相似文献
18.
HIV-infected cells are killed by rCD4-ricin A chain 总被引：21，自引：0，他引：21
M A Till V Ghetie T Gregory E J Patzer J P Porter J W Uhr D J Capon E S Vitetta 《Science (New York, N.Y.)》1988,242(4882):1166-1168
The gp120 envelope glycoprotein of the human immunodeficiency virus (HIV), which is expressed on the surface of many HIV-infected cells, binds to the cell surface molecule CD4. Soluble derivatives of recombinant CD4 (rCD4) that bind gp120 with high affinity are attractive vehicles for targeting a cytotoxic reagent to HIV-infected cells. Soluble rCD4 was conjugated to the active subunit of the toxin ricin. This conjugate killed HIV-infected H9 cells but was 1/1000 as toxic to uninfected H9 cells (which do not express gp120) and was not toxic to Daudi cells (which express major histocompatibility class II antigens, the putative natural ligand for cell surface CD4). Specific killing of infected cells can be blocked by rgp120, rCD4, or a monoclonal antibody to the gp120 binding site on CD4. 相似文献
19.
Antigen bias in T cell cross-priming 总被引：1，自引：0，他引：1
Wolkers MC Brouwenstijn N Bakker AH Toebes M Schumacher TN 《Science (New York, N.Y.)》2004,304(5675):1314-1317
Activated CD8+ T cells detect virally infected cells and tumor cells by recognition of major histocompatibility complex class I-bound peptides derived from degraded, endogenously produced proteins. In contrast, CD8+ T cell activation often occurs through interaction with specialized antigen-presenting cells displaying peptides acquired from an exogenous cellular source, a process termed cross-priming. Here, we observed a marked inefficiency in exogenous presentation of epitopes derived from signal sequences in mouse models. These data indicate that certain virus- and tumor-associated antigens may not be detected by CD8+ T cells because of impaired cross-priming. Such differences in the ability to cross-present antigens should form important considerations in vaccine design. 相似文献
20.
观察急性髓系白血病患者原发性ｍｄｒ１基因产物Ｐ－１７０与ＣＤ３４抗原表达与预后的关系。方法。常规分离３１例急性髓系白血病细胞,然后分别进行细胞免疫化学检查,观察了细胞膜分化抗原变化和ｍｄｒ１基因产物Ｐ－１７０反应。结论：Ｐ－１７０和ＣＤ３４表达是急性髓系白血病患者对化疗抵抗的标志。 相似文献