Fas-induced caspase denitrosylation

Only a few intracellular S-nitrosylated proteins have been identified, and it is unknown if protein S-nitrosylation/denitrosylation is a component of signal transduction cascades. Caspase-3 zymogens were found to be S-nitrosylated on their catalytic-site cysteine in unstimulated human cell lines and denitrosylated upon activation of the Fas apoptotic pathway. Decreased caspase-3 S-nitrosylation was associated with an increase in intracellular caspase activity. Fas therefore activates caspase-3 not only by inducing the cleavage of the caspase zymogen to its active subunits, but also by stimulating the denitrosylation of its active-site thiol. Protein S-nitrosylation/denitrosylation can thus serve as a regulatory process in signal transduction pathways.     

Regulation of phagocytosis and [Ca2+]i flux by distinct regions of an Fc receptor.

The binding of multivalent immunoglobulin G complexes to Fc receptors (Fc gamma Rs) on macrophages activates multiple immune functions. A murine macrophage cell line, but not a fibroblast cell line, that was transfected with human Fc gamma RIIA mediated phagocytosis and an intracellular Ca2+ concentration ([Ca2+]i) flux upon cross-linking of human Fc gamma RIIA. Transfected macrophages that expressed a truncated receptor lacking 17 carboxy-terminal amino acids phagocytosed small antibody complexes. However, only wild-type transfectants phagocytosed labeled erythrocytes and fluxed [Ca2+]i. Thus, the cytoplasmic domain of human Fc gamma RIIA contains distinct functional regions.     

Signal transduction. FasL binds preassembled Fas

The binding of a ligand to its receptor has always been viewed as the trigger for signal transduction to ensue. However, as Golstein explains in his Perspective, new findings (Chan et al. and Siegel et al.) suggest that the Fas receptor preassembles into trimers without the help of its ligand, and that this preassembly conditions ligand binding, and thus subsequent signal transduction of a death signal.     

A 32-kD GTP-binding protein associated with the CD4-p56lck and CD8-p56lck T cell receptor complexes

The guanosine triphosphate (GTP)-binding proteins include signal-transducing heterotrimeric G proteins (for example, Gs, Gi), smaller GTP-binding proteins that function in protein sorting, and the oncogenic protein p21ras. The T cell receptor complexes CD4-p56lck and CD8-p56lck were found to include a 32- to 33-kilodalton phosphoprotein (p32) that was recognized by an antiserum to a consensus GTP-binding region in G proteins. Immunoprecipitated CD4 and CD8 complexes bound GTP and hydrolyzed it to guanosine diphosphate (GDP). The p32 protein was covalently linked to [alpha-32P]GTP by ultraviolet photoaffinity labeling. These results demonstrate an interaction between T cell receptor complexes and an intracellular GTP-binding protein.     

Structure of an extracellular gp130 cytokine receptor signaling complex

The activation of gp130, a shared signal-transducing receptor for a family of cytokines, is initiated by recognition of ligand followed by oligomerization into a higher order signaling complex. Kaposi's sarcoma-associated herpesvirus encodes a functional homolog of human interleukin-6 (IL-6) that activates human gp130. In the 2.4 angstrom crystal structure of the extracellular signaling assembly between viral IL-6 and human gp130, two complexes are cross-linked into a tetramer through direct interactions between the immunoglobulin domain of gp130 and site III of viral IL-6, which is necessary for receptor activation. Unlike human IL-6 (which uses many hydrophilic residues), the viral cytokine largely uses hydrophobic amino acids to contact gp130, which enhances the complementarity of the viral IL-6-gp130 binding interfaces. The cross-reactivity of gp130 is apparently due to a chemical plasticity evident in the amphipathic gp130 cytokine-binding sites.     

The Fas signaling pathway: more than a paradigm

Apoptosis and related forms of cell death have central importance in development, homeostasis, tumor surveillance, and the function of the immune system. Apoptosis is initiated by two principal pathways. The intrinsic pathway emerges from mitochondria, whereas the extrinsic pathway is activated by the ligation of death receptors. This Viewpoint introduces the basic mechanisms of the extrinsic pathway, using the example of the prototypical death receptor Fas and its role in apoptosis, but it also points out the increasingly understood importance of this receptor as a non-apoptotic signal transducer.     

Inhibition of PDGF beta receptor signal transduction by coexpression of a truncated receptor.

A mutated form of the platelet-derived growth factor (PDGF) beta receptor lacking most of its cytoplasmic domain was tested for its ability to block wild-type PDGF receptor function. PDGF induced the formation of complexes consisting of wild-type and truncated receptors. Such complexes were defective in autophosphorylation. When truncated receptors were expressed in excess compared to wild-type receptors, stimulation by PDGF of receptor autophosphorylation, association of phosphatidylinositol-3 kinase with the receptor, and calcium mobilization were blocked. Thus, a truncated receptor can inactivate wild-type receptor function by forming ligand-dependent receptor complexes (probably heterodimers) that are incapable of mediating the early steps of signal transduction.     

The structure of interleukin-2 complexed with its alpha receptor

Interleukin-2 (IL-2) is an immunoregulatory cytokine that binds sequentially to the alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gammac) receptor subunits. Here we present the 2.8 angstrom crystal structure of a complex between human IL-2 and IL-2Ralpha, which interact in a docking mode distinct from that of other cytokine receptor complexes. IL-2Ralpha is composed of strand-swapped "sushi-like" domains, unlike the classical cytokine receptor fold. As a result of this domain swap, IL-2Ralpha uses a composite surface to dock into a groove on IL-2 that also serves as a binding site for antagonist drugs. With this complex, we now have representative structures for each class of hematopoietic cytokine receptor-docking modules.     

急性乙型病毒性肝炎肝组织中Fas抗原和Fas配体的表达

探讨Ｆａｓ－ＦａｓＬ系统在急性病毒性肝炎发病中的作用。方法采用免疫组织化学技术对３８例急性乙型肝炎患者组织中Ｆａｓ和ＦａｓＬ表达进行检测，并与１０例正常肝组织作对照。结论：由ＣＴＬ－ＦａｓＬ系统介导的肝细胞凋亡在急性乙型肝炎的发病中可能起了较重要的作用。     

The human polyomavirus, JCV, uses serotonin receptors to infect cells

The human polyomavirus, JCV, causes the fatal demyelinating disease progressive multifocal leukoencephalopathy in immunocompromised patients. We found that the serotonergic receptor 5HT2AR could act as the cellular receptor for JCV on human glial cells. The 5HT2A receptor antagonists inhibited JCV infection, and monoclonal antibodies directed at 5HT2A receptors blocked infection of glial cells by JCV, but not by SV40. Transfection of 5HT2A receptor-negative HeLa cells with a 5HT2A receptor rescued virus infection, and this infection was blocked by antibody to the 5HT2A receptor. A tagged 5HT2A receptor colocalized with labeled JCV in an endosomal compartment following internalization. Serotonin receptor antagonists may thus be useful in the treatment of progressive multifocal leukoencephalopathy.     

固始鸡免疫器官内细胞凋亡基因Fas和FasL的动态表达

 【目的】探讨固始鸡免疫器官内细胞凋亡基因Fas和FasL的动态表达。【方法】应用免疫组织化学技术和Leica 显微图像处理系统,对细胞凋亡基因Fas和FasL在固始鸡免疫器官内的动态表达进行研究。【结果】Fas在不同发育阶段固始鸡免疫器官内均有表达,但表达量均不相同,呈波浪样动态变化;Fas表达于固始鸡免疫器官内淋巴细胞细胞膜和细胞质,不表达于细胞核;Fas表达阳性细胞在固始鸡不同免疫器官内分布位置不同,呈散在或簇团状分布：法氏囊内阳性细胞主要分布于黏膜靠近上皮细胞的固有膜层内、淋巴小结与淋巴小结之间区域、淋巴小结边缘,淋巴小结内少量淋巴细胞也有Fas表达;胸腺内主要分布于胸腺小叶髓质,极少出现在皮质内;脾脏内主要分布于红髓和边缘区、淋巴小结周围和动脉周围淋巴鞘周围的区域,动脉周围淋巴鞘极少有Fas表达,淋巴小结无Fas表达。FasL在固始鸡免疫器官内的表达与Fas相似,但表达量与Fas相比较少。【结论】细胞凋亡基因Fas和FasL参与了固始鸡免疫器官内淋巴细胞发育分化过程中的凋亡调控,并对免疫器官的稳定发挥重要作用。     

尖锐湿疣角质形成细胞凋亡与Fas、Bcl-2及PCNA的表达

目的 :检测尖锐湿疣 (CA)角质形成细胞凋亡和Fas、Bcl 2及PCNA的表达 ,探讨它们在CA发病中的作用及关系。方法 :对 5 1例CA上皮和 18例正常上皮分别采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记技术检测细胞凋亡 ,采用免疫组化ABC法检测Fas、Bcl 2及PCNA的表达。结果 :CA上皮凋亡指数与正常上皮无明显差异 (P >0 .0 5 ) ,CA上皮Fas、Bcl 2及PCNA指数显著高于正常上皮 (P <0 .0 1) ,Fas表达与Bcl 2表达呈中度正相关 (r=0 .318,P <0 .0 5 )。结论 :CA上皮细胞凋亡与Fas、Bcl 2及PCNA的表达可能与CA的发病有关。     

基于分子动力学的miRNA 3'端与Argonaute蛋白PAZ功能域相互作用的研究

应用分子动力学方法研究了人类miRNA 3'末端3碱基与PAZ功能域的结合模式,并采用线性相互作用能方法计算miRNA 3'末端片段与PAZ之间的结合自由能.结果表明:miRNA 3'末端碱基组成决定了其和PAZ功能域的结合模式以及结合自由能,UGU与PAZ的结合最为稳定,结合自由能为-37.248kJ/mol,而CGA与PAZ的结合情况相对不太稳定,结合自由能为-5.418 kJ/mol; miRNA 3'端与PAZ的结合自由能与其在人类miRNA基因中的分布频率存在一定的相关性,UGU在人类基因中占6.768％,而CGA仅占0.414％.本研究结果可为进一步研究miRNA与Argonaute蛋白的相互作用以及对人类疾病防治和生物进化探索提供重要信息.     

A domain in TNF receptors that mediates ligand-independent receptor assembly and signaling

A conserved domain in the extracellular region of the 60- and 80-kilodalton tumor necrosis factor receptors (TNFRs) was identified that mediates specific ligand-independent assembly of receptor trimers. This pre-ligand-binding assembly domain (PLAD) is physically distinct from the domain that forms the major contacts with ligand, but is necessary and sufficient for the assembly of TNFR complexes that bind TNF-alpha and mediate signaling. Other members of the TNFR superfamily, including TRAIL receptor 1 and CD40, show similar homotypic association. Thus, TNFRs and related receptors appear to function as preformed complexes rather than as individual receptor subunits that oligomerize after ligand binding.     

宫颈癌患者血清可溶性Apo-1／Fas水平变化及其临床意义

目的 观察宫颈癌患者血清可溶性Apo-1／Fas（sApo-1／Fas）水平变化及其临床意义。方法应用酶联免疫吸附试验法（ELISA）对30例正常人及60例宫颈癌患者的血清sApo-1／Fas水平进行检测,并比较20例宫颈癌患者根治术前后血清sApo-1／Fas水平。结果Ⅰ、Ⅱ、Ⅲ、Ⅳ期宫颈癌患者的血清sApo-1／Fas水平均明显高于正常对照组（P〈0．01）;Ⅳ期宫颈癌患者的血清sApo-1／Fas水平明显高于其他各期,Ⅲ期明显高于Ⅱ期,Ⅱ期又明显高于Ⅰ期,差异均有统计学意义（P〈0．01）;宫颈癌患者根治术后的血清sApo-1／Fas水平明显低于术前（P〈0．01）。结论动态检测血清sApo-1／Fas水平可能对判断宫颈癌病情和预后有一定程度的参考意义。     

GBP5 promotes NLRP3 inflammasome assembly and immunity in mammals

Inflammasomes are sensory complexes that alert the immune system to the presence of infection or tissue damage. These complexes assemble NLR (nucleotide binding and oligomerization, leucine-rich repeat) or ALR (absent in melanoma 2-like receptor) proteins to activate caspase-1 cleavage and interleukin (IL)-1β/IL-18 secretion. Here, we identified a non-NLR/ALR human protein that stimulates inflammasome assembly: guanylate binding protein 5 (GBP5). GBP5 promoted selective NLRP3 inflammasome responses to pathogenic bacteria and soluble but not crystalline inflammasome priming agents. Generation of Gbp5(-/-) mice revealed pronounced caspase-1 and IL-1β/IL-18 cleavage defects in vitro and impaired host defense and Nlrp3-dependent inflammatory responses in vivo. Thus, GBP5 serves as a unique rheostat for NLRP3 inflammasome activation and extends our understanding of the inflammasome complex beyond its core machinery.     

地塞米松对特发性血小板减少性紫癜外周血淋巴细胞凋亡及Fas/FasL的影响

目的 :观察地塞米松对特发性血小板减少性紫癜 (ITP)外周血淋巴细胞凋亡及 Fas、Fas L表达的影响及其临床意义。方法 :用流式细胞仪检测 30例 ITP患儿治疗前后外周血淋巴细胞凋亡率及 Fas、Fas L蛋白表达。结果 :治疗前淋巴细胞凋亡率及 Fas、Fas L蛋白表达与对照组相比差异无统计学意义 (P>0 .0 5)。治疗后血小板增加时淋巴细胞凋亡率增加 ,Fas、Fas L蛋白表达上调 ,与治疗前相比差异有显著性意义 (P<0 .0 1 )。结论 :地塞米松可显著促进 ITP患儿外周血淋巴细胞的凋亡 ,上调淋巴细胞 Fas、Fas L的表达 ,有助于清除激活的淋巴细胞。     

The Fc and not CD4 receptor mediates antibody enhancement of HIV infection in human cells

Antibodies that enhance human immunodeficiency virus (HIV) infectivity have been found in the blood of infected individuals and in infected or immunized animals. These findings raise serious concern for the development of a safe vaccine against acquired immunodeficiency syndrome. To address the in vivo relevance and mechanism of this phenomenon, antibody-dependent enhancement of HIV infectivity in peripheral blood macrophages, lymphocytes, and human fibroblastoid cells was studied. Neither Leu3a, a monoclonal antibody directed against the CD4 receptor, nor soluble recombinant CD4 even at high concentrations prevented this enhancement. The addition of monoclonal antibody to the Fc receptor III (anti-FcRIII), but not of antibodies that react with FcRI or FcRII, inhibited HIV type 1 and HIV type 2 enhancement in peripheral blood macrophages. Although enhancement of HIV infection in CD4+ lymphocytes could not be blocked by anti-FcRIII, it was inhibited by the addition of human immunoglobulin G aggregates. The results indicate that the FcRIII receptor on human macrophages and possibly another Fc receptor on human CD4+ lymphocytes mediate antibody-dependent enhancement of HIV infectivity and that this phenomenon proceeds through a mechanism independent of the CD4 protein.