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.     

Structure of the quaternary complex of interleukin-2 with its alpha, beta, and gammac receptors

Interleukin-2 (IL-2) is an immunoregulatory cytokine that acts through a quaternary receptor signaling complex containing alpha (IL-2Ralpha), beta (IL-2Rbeta), and common gamma chain (gc) receptors. In the structure of the quaternary ectodomain complex as visualized at a resolution of 2.3 angstroms, the binding of IL-2Ralpha to IL-2 stabilizes a secondary binding site for presentation to IL-2Rbeta. gammac is then recruited to the composite surface formed by the IL-2/IL-2Rbeta complex. Consistent with its role as a shared receptor for IL-4, IL-7, IL-9, IL-15, and IL-21, gammac forms degenerate contacts with IL-2. The structure of gammac provides a rationale for loss-of-function mutations found in patients with X-linked severe combined immunodeficiency diseases (X-SCID). This complex structure provides a framework for other gammac-dependent cytokine-receptor interactions and for the engineering of improved IL-2 therapeutics.     

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.     

Beta 1-6 branching of Asn-linked oligosaccharides is directly associated with metastasis

Neoplastic transformation has been associated with a variety of structural changes in cell surface carbohydrates, most notably increased sialylation and beta 1-6-linked branching of complex-type asparagine (Asn)-linked oligosaccharides (that is, -GlcNAc beta 1-6Man alpha 1-6Man beta 1-). However, little is known about the relevant glycoproteins or how these transformation-related changes in oligosaccharide biosynthesis may affect the malignant phenotype. Here it is reported that a cell surface glycoprotein, gp 130, is a major target of increased beta 1-6-linked branching and that the expression of these oligosaccharide structures is directly related to the metastatic potential of the cells. Glycosylation mutants of a metastatic tumor cell line were selected that are deficient in both beta 1-6 GlcNAc transferase V activity and metastatic potential in situ. Moreover, induction of increased beta 1-6 branching in clones of a nonmetastatic murine mammary carcinoma correlated strongly with acquisition of metastatic potential. The results indicate that increased beta 1-6-linked branching of complex-type oligosaccharides on gp 130 may be an important feature of tumor progression related to increased metastatic potential.     

白细胞介素6及其受体在绵羊卵母细胞成熟过程中的表达

采用实时定量PCR技术检测了不同成熟培养时间绵羊卵母细胞和卵丘细胞白细胞介素6基因（interleukin-6 gene, IL-6）及其受体基因（interleukin-6 receptor gene, IL-6R）mRNA的相对表达量。结果显示,在体外成熟培养过程中,卵母细胞和卵丘细胞中持续表达IL-6及其受体IL-6R mRNA,培养4~8 h,其相对表达量呈现显著升高,随后则降低;在16~20 h时卵母细胞中IL-6 mRNA表达重新升高;相应的卵丘细胞在12~16h时IL-6R mRNA表达也升高。绵羊卵母细胞和卵丘细胞中IL-6和IL-6R mRNA的持续表达以及动力学变化提示了白细胞介素6在卵母细胞成熟过程中具有潜在调控作用。     

Structural mutations of the T cell receptor zeta chain and its role in T cell activation

T cell hybridomas that express zeta zeta, but not zeta eta, dimers in their T cell receptors (TCRs) produce interleukin-2 (IL-2) and undergo an inhibition of spontaneous growth when activated by antigen, antibodies to the receptor, or antibodies to Thy-1. Hybridomas without zeta and eta were reconstituted with mutated zeta chains. Cytoplasmic truncations of up to 40% of the zeta molecule reconstituted normal surface assembly of TCRs, but antigen-induced IL-2 secretion and growth inhibition were lost. In contrast, cross-linking antibodies to the TCR activated these cells. A point mutation conferred the same signaling phenotype as did the truncations and caused defective antigen-induced tyrosine kinase activation. Thus zeta allows the binding of antigen/major histocompatibility complex (MHC) to alpha beta to effect TCR signaling.     

白血病抑制因子（LIF）及其受体在月经 周期猕猴卵巢内的表达

应用免疫细胞化学方法对白血病抑制因子(leukemiainhibitoryfactor,LIF)、白血病抑制因子受体(leukemiainhibitoryfactorreceptor,LIFR)和gp130在月经周期猕猴卵巢内的表达进行了研究。结果表明:LIF、LIFR和gp130在猕猴卵巢内的表达量随月经周期的不同而变化,LIF及其受体在增殖期卵巢内的表达量高于分泌期的卵巢。LIF及其受体在原始卵泡、腔前卵泡和有腔卵泡的卵细胞内表达量均较高,在颗粒细胞、卵泡膜、卵巢生殖上皮和卵巢基质中有少量表达,而在闭锁卵泡、退化的黄体和卵巢髓质中未见表达。LIF及其受体在猕猴卵巢内的表达可能受卵巢分泌的类固醇激素所调控,LIF可能通过自分泌或旁分泌的方式在猕猴卵泡发育及排卵等过程中起重要作用。     

运输应激对猪脾脏IL-2、IL-6和IL-10 mRNAs表达的影响及其调控机制

【目的】探讨不同时间运输应激对猪脾脏中IL-2mRNA、IL-6mRNA、IL-10mRNA及其IL-2RmRNA、IL-6RmRNA表达的影响,并探讨P38MAPK-NF-κB信号途径对其表达的调控作用。【方法】将19头体重50kg左右的猪随机分为4组,分别进行0、1、2和4h公路运输,运输结束后立即扑杀取脾脏,液氮保存,用荧光定量PCR的方法对3种细胞因子及其IL-2RmRNA、IL-6RmRNA进行定量;另用ELISA方法检测试验猪脾脏组织匀浆液中P38MAPK含量的动态变化;激光扫描共聚焦显微镜观察NF-κB运输前后在脾脏细胞中的分布。【结果】经1、2和4h的运输应激后,脾脏中IL-10、IL-6及IL-6RmRNA的表达发生了显著的变化,P38MAPK变化不明显,NF-κB在脾脏中的表达是先上升,随后稍微下降,到4h时又升高并高于其它3个组;且NF-κB的入核率也呈现同样的变化趋势。【结论】运输应激可引起猪脾脏IL-6mRNA、IL-10mRNA和IL-6RmRNA表达的显著变化,且存在时效性;相关性分析表明,在所检测的3种细胞因子中,脾脏主要对运输过程中IL-6水平起重要的调节作用,结合细胞因子表达调控的信号机制表明,NF-κB可能对运输过程中猪脾脏相关细胞因子变化起重要的调控作用。     

Cloning and expression of the human interleukin-6 (BSF-2/IFN beta 2) receptor

Interleukin-6 (IL-6/BSF-2/IFN beta 2) is a multifunctional cytokine that regulates the growth and differentiation of various tissues, and is known particularly for its role in the immune response and acute phase reactions. A complementary DNA encoding the human IL-6 receptor (IL-6-R) has now been isolated. The IL-6-R consists of 468 amino acids, including a signal peptide of approximately 19 amino acids and a domain of approximately 90 amino acids that is similar to a domain in the immunoglobulin (Ig) superfamily. The cytoplasmic domain of approximately 82 amino acids lacks a tyrosine/kinase domain, unlike other growth factor receptors.     

Orc6 involved in DNA replication,chromosome segregation,and cytokinesis

Origin recognition complex (ORC) proteins serve as a landing pad for the assembly of a multiprotein prereplicative complex, which is required to initiate DNA replication. During mitosis, the smallest subunit of human ORC, Orc6, localizes to kinetochores and to a reticular-like structure around the cell periphery. As chromosomes segregate during anaphase, the reticular structures align along the plane of cell division and some Orc6 localizes to the midbody before cells separate. Silencing of Orc6 expression by small interfering RNA (siRNA) resulted in cells with multipolar spindles, aberrant mitosis, formation of multinucleated cells, and decreased DNA replication. Prolonged periods of Orc6 depletion caused a decrease in cell proliferation and increased cell death. These results implicate Orc6 as an essential gene that coordinates chromosome replication and segregation with cytokinesis.     

Essential cytoplasmic translocation of a cytokine receptor-assembled signaling complex

Cytokine signaling is thought to require assembly of multicomponent signaling complexes at cytoplasmic segments of membrane-embedded receptors, in which receptor-proximal protein kinases are activated. Indeed, CD40, a tumor necrosis factor receptor (TNFR) family member, forms a complex containing adaptor molecules TRAF2 and TRAF3, ubiquitin-conjugating enzyme Ubc13, cellular inhibitor of apoptosis proteins 1 and 2 (c-IAP1/2), IkappaB kinase regulatory subunit IKKgamma (also called NEMO), and mitogen-activated protein kinase (MAPK) kinase kinase MEKK1 upon ligation. TRAF2, Ubc13, and IKKgamma were required for complex assembly and activation of MEKK1 and MAPK cascades. However, these kinases were not activated unless the multicomponent signaling complex translocated from CD40 to the cytosol upon c-IAP1/2-induced degradation of TRAF3. This two-stage signaling mechanism may apply to other innate immune receptors, accounting for spatial and temporal separation of MAPK and IKK signaling.     

Characterization of gp41 as the transmembrane protein coded by the HTLV-III/LAV envelope gene

Radiolabeled amino acid sequencing was used to characterize gp41, an antigen of HTLV-III/LAV, the virus believed to be the etiological agent of the acquired immune deficiency syndrome. This antigen is the one most commonly detected in immunoblot assays by sera of patients with AIDS or AIDS-related complex (ARC) and other individuals infected with HTLV-III/LAV. A mouse monoclonal antibody that was reactive with gp41 precipitated a 160-kilodalton protein (gp160) in addition to gp41, but did not precipitate a 120-kilodalton protein (gp120) from extracts of metabolically labeled cells producing HTLV-III. Extracts of infected cells that had been labeled with tritiated leucine or isoleucine were immunoprecipitated with the monoclonal antibody. The immunoprecipitates were fractionated by polyacrylamide gel electrophoresis and the p41 was eluted from the gel bands and subjected to amino-terminal radiolabeled amino acid sequencing by the semiautomated Edman degradation. Leucine residues occurred in cycles 7, 9, 12, 26, 33, and 34 among 40 cycles and isoleucine occurred in cycle 4 among 24 cycles analyzed. Comparison of the data with the deduced amino acid sequence of the env gene product of HTLV-III precisely placed gp41 in the COOH-terminal region of the env gene product. Gp160 is thus the primary env gene product and it is processed into gp120 and gp41.     

Interaction of the IL-2 receptor with the src-family kinase p56lck: identification of novel intermolecular association

In the interleukin-2 (IL-2) system, intracellular signal transduction is triggered by the beta chain of the IL-2 receptor (IL-2R beta); however, the responsible signaling mechanism remains unidentified. Evidence for the formation of a stable complex of IL-2R beta and the lymphocyte-specific protein tyrosine kinase p56lck is presented. Specific association sites were identified in the tyrosine kinase catalytic domain of p56lck and in the cytoplasmic domain of IL-2R beta. As a result of interaction, IL-2R beta became phosphorylated in vitro by p56lck. Treatment of T lymphocytes with IL-2 promotes p56lck kinase activity. These data suggest the participation of p56lck as a critical signaling molecule downstream of IL-2R via a novel interaction.     

Expression of Interleukin–6 and Interleukin-6 Receptor in Ovine Oocytes During In vitroMaturation

To study the effects of interleukin-6 (IL-6) and its receptor (IL-6R) during in vitro maturation of ovine oocytes, the mRNA and protein expression levels of IL-6 and IL-6R, along with their localization, were examined during ovine oocytes maturation in vitro through real-time PCR, Western blotting, and immunohistochemistry. Specific patterns of expression of IL-6 and IL-6R were observed at both mRNA and protein levels at each stage of ovine oocytes maturation. IL-6 and IL-6R were distributed primarily on the surface of the cell membrane, with little expression in the cytoplasm or nucleus. IL-6 and IL-6R were expressed significantly at higher levels in the maturation around 4 h, and then decreased dramatically. However the level slightly elevated at 20-24 h. The role of IL-6 and IL-6R on oocytes maturation was studied through in vitro addition of recombinant human IL-6 in different concentrations. The addition of 10 ng mL⁻¹ IL-6 significantly increased the rates of oocytes maturation (P<0.05), but did not affect the rates of development of the subsequence IVF ovine embryos. In summary, IL-6 is likely to play an important role in the early ovine oocytes maturation. The expression patterns of the IL-6 and IL-6R on the ovine oocytes maturation open up the possibility of regulatory role of the cytokine in ovine oocytes maturation.     

Common and distinct elements in cellular signaling via EGF and FGF receptors

Signaling pathways that are activated by epidermal growth factor (EGF) or fibroblast growth factor (FGF) receptors have been identified and compared (detailed Connections Maps are available at Science's Signal Transduction Knowledge Environment). Both receptors stimulate a similar complement of intracellular signaling pathways. However, whereas activated EGF receptors (EGFRs) function as the main platform for recruitment of signaling proteins, signaling through the FGF receptors (FGFRs) is mediated primarily by assembly of a multidocking protein complex. Moreover, FGFR signaling is subject to additional intracellular and extracellular control mechanisms that do not affect EGFR signaling. The differential circuitry of the intracellular networks that are activated by EGFR and FGFR may affect signal specificity and physiological responses.     

An architectural framework that may lie at the core of the postsynaptic density

The postsynaptic density (PSD) is a complex assembly of proteins associated with the postsynaptic membrane that organizes neurotransmitter receptors, signaling pathways, and regulatory elements within a cytoskeletal matrix. Here we show that the sterile alpha motif domain of rat Shank3/ProSAP2, a master scaffolding protein located deep within the PSD, can form large sheets composed of helical fibers stacked side by side. Zn2+, which is found in high concentrations in the PSD, binds tightly to Shank3 and may regulate assembly. Sheets of the Shank protein could form a platform for the construction of the PSD complex.     

Structure of the S15,S6,S18-rRNA complex: assembly of the 30S ribosome central domain

The crystal structure of a 70-kilodalton ribonucleoprotein complex from the central domain of the Thermus thermophilus 30S ribosomal subunit was solved at 2.6 angstrom resolution. The complex consists of a 104-nucleotide RNA fragment composed of two three-helix junctions that lie at the end of a central helix, and the ribosomal proteins S15, S6, and S18. S15 binds the ribosomal RNA early in the assembly of the 30S ribosomal subunit, stabilizing a conformational reorganization of the two three-helix junctions that creates the RNA fold necessary for subsequent binding of S6 and S18. The structure of the complex demonstrates the central role of S15-induced reorganization of central domain RNA for the subsequent steps of ribosome assembly.