Substitutions at the Glu62 residue of human interleukin-2 differentially affect its binding to the α chain and the βγ complex of the interleukin-2 receptor

Human interleukin-2 (IL-2) α helix B is more conserved than the whole molecule, but has been less studied than other α helices of IL-2. Using site-directed mutagenesis, several IL-2 mutants in this helix were obtained. We found that the IL-2 mutant containing Leu at position 62 (Leu⁶²-IL-2) loses its ability to bind IL-2 receptor subunit α (IL-2Rα), but retains binding affinity to IL-2R subunit βγ as well as some bioactivity; nevertheless, another substitution at the same residue, Arg⁶² IL-2, loses its binding ability to both IL-2Rα and IL-2Rβγ, and can no longer stimulate IL-2-dependent cell growth, showing that Glu⁶² not only takes part in IL-2Rα binding, but can also affect IL-2 binding to IL-2Rβγ. In this regard, Glu⁶² may be a key site in the IL-2/IL-2Rα interaction, and can facilitate IL-2R ternary-complex formation, leading to IL-2Rα-mediated, IL-2-stimulated signal transduction.     

Protein kinase C in IL- 2 signal transduction

Interleukin-2 (IL-2), secreted principally by activated helper T-cells, plays a pivotal role in the generation and regulation of the immune response. The various biologic functions of IL-2 have been the focus of intensive study over the years and have been well worked out. By contrast, an understanding of the intracellular signals coupled to the IL-2 receptor and responsible for mediating IL-2 effects in T-cells is far less developed, and the role that protein kinase C (PKC) may play in the various cellular responses to IL-2 receptor activation is unclear. In this article we will discuss IL-2, its receptors, and IL-2 signal transduction in relation to the physiological roles PKC activation may play in IL-2-mediated activation of T-cells and other hematopoietic cells.     

EB病毒LMP1在鼻咽癌细胞系中通过NF-κB、AP-1促进IL-8分泌

目的：探讨EB病毒LMP1分子致瘤机制，在已证实鼻咽癌细胞系中LMP1有效激活NF－κB 或AP－1的基础上，对LMP1是否通过NF－κB 或AP－1促进IL－8分泌进行探讨。方法：以稳定表达LMP1及其3种突变体，空白载体的鼻咽癌细胞系[HNE2-LMP1,NHE2-MLP1(1-185),HNE2-LMP1(1-231),HNE2-LMP1Δ187-351和HNF3－pSG5]及antisense-LMP1处理的HNF2－LMP1鼻咽癌的细胞系为材料，将IL－8报道质粒瞬时导入这些细胞系中，通过测定luciferase值以反映LMP1是否促进IL－8转录；将mut AP-1/IL-8-luc或IκB α（S32A／S36A）表达质粒导入HNE2－LMP1细胞系中，比较其IL－8报道活性，以确定LMP1是否通过AP－1或NF－κB 诱导IL－8转录；利用ELISA方法测定HNE2－LMP1，HNE2－pSG5,anti-sese-LMP1处理的HNE2－LMP1鼻咽癌细胞系中的IL－8浓度，进一步从蛋白水平上确定LMP1是否促进IL－8分泌。结果：与HNE2－pSG5相比，在HNE2－LMP1，HNE2－LMP1Δ187－351和HNE2－LMP1（1－231）细胞系中IL－8报道活性分别升高了原来水平的11．5，8．6和3．4倍，而HNE2－LMP1（1－185）对IL－8报道活性不影响。在HNE2－LMP1细胞系中IL－8蛋白水平提高了17．4倍，而antisense-LMP1则使HNE2－LMP1细胞的IL－8报道活性及蛋白水平分别下降到原来水平的18．3％和9．2％，导入mutAP-1/IL-8-luc或IκBα（S32A／S36A）的HNE2－LMP1细胞中IL－8报道活性分别下降到原有水平39％和26％，结论：鼻咽癌细胞系中LMP1可能通过NF－κAP－1促进IL－8表达。     

hIL-2分泌肽序列在HepG2细胞中对hEndostatin表达和分泌差异的影响

目的:了解分泌肽序列在HepG2细胞中对人内皮抑素基因(hEndostatin)的cDNA表达和分泌差异的影响。方法:构建不含hIL-2分泌肽序列的真核表达载体pBlast-hEndo质粒, 转染人的HepG2细胞株, 用RT-PCR的方法检测HepG2(pBlast-hIL2-hEndo), HepG2(pBlast-hEndo), HepG2(pBlast-Mcs)和HepG2中hEndostatin的mRNA表达水平, 及制备4种细胞的总蛋白和收集各自的培养上清, 进行Westernblot分析蛋白表达和分泌的差异。结果:发现HepG2(pBlast-hIL2-hEndo)中hEndostatin的mRNA的水平显著高于HepG2(pBlast-hEndo)。而仅在HepG2(pBlast-hIL-2-hEndo)的细胞总蛋白和上清, 及HepG2(pBlast-hEndo)的细胞总蛋白中检测到hEndostatin表达, 在其它各株细胞总蛋白及上清中, 未检测到hEndostatin。结论:hIL-2分泌肽序列能促进hEndostatin基因在HepG2细胞中表达及分泌。     

T cell stimulation in the absence of exogenous antigen: a T cell signal is induced by both MHC-dependent and -independent mechanisms

Mature T cells residing in peripheral lymphoid organs have frequent contact with antigen presenting cells (APC). Such contact may be required for T cell survival, but the degree to which signals in mature T cells are induced by TCR recognition of self peptide/MHC complexes is unclear. We have used induction of the early growth response gene 1 (Egr1) as an indicator of signal transduction in 3.L2 (I-Ek-restricted) T cells interacting with APC in the absence of exogenous antigen. The data show that Egr1 can be induced in 3.L2 T cells by TCR recognition of self peptides presented by I-Ek. However, a more transient induction of Egr1 can be induced in 3.L2 T cells interacting with dendritic cells derived from class II/beta2m double-deficient mice. Egr1 induction after T cell-APC contact was also observed in a freshly isolated polyclonal CD4 T cell population. The data suggest that self peptide/MHC recognition by the TCR induces a signal in T cells and that dendritic cells can also induce a more transient T cell signal by an MHC-independent mechanism.     

SOCS1与T细胞分化发育及功能调控的研究进展

细胞因子参与介导了机体天然免疫和获得性免疫应答反应，SOCS家族是近年来发现的通过JAK／STAT途径抑制细胞因子信号转导通路的负性调控蛋白。目前SOCS家族成员中以SOCS1的研究最为深入。SOCS1的缺失会导致T细胞胸腺选择受阻，以IFNγ为主的多种细胞因子的过量分泌，T细胞表面活化分子表达增加等等。因此，SOCS1的正常表达对于T细胞的分化发育和自身稳定发挥了重要作用。     

N-乙酰半胱氨酸对慢性间歇缺氧大鼠海马神经元凋亡及氧化应激的影响

目的：探讨N-乙酰半胱氨酸(NAC)对慢性间歇缺氧(CIH)模型大鼠海马组织氧化应激及海马神经元凋亡的影响。方法:30只雄性Wistar大鼠随机分为慢性缺氧组、NAC治疗组及正常对照组3组，每组10只。采用化学比色法测定海马组织丙二醛(MDA)、超氧化物歧化酶(SOD)水平，同时应用免疫组化方法检测海马CA1 区磷酸化JNK(p-JNK)表达水平，应用TUNEL法检测海马CA1区神经元凋亡率。结果:NAC治疗组 MDA水平低于CIH组（1.71±0.43 vs 1.37±0.26，P＜0.05）、SOD活性高于CIH组（44.94±14.01 vs 57.66±14.07，P＜0.05），p-JNK表达水平低于CIH组 （0.53±0.10 vs 0.39±0.16，P＜0.05），海马神经元凋亡率显著低于CIH组（0.32±0.18 vs 0.20±0.11，P＜0.05）。结论:NAC能抑制慢性间歇缺氧导致的氧化应激，从而影响JNK信号转导通路，减少海马神经元凋亡。     

Neural-specific ablation of the scaffold protein JSAP1 in mice causes neonatal death

We previously identified c-Jun NH₂-terminal kinase (JNK)/stress-activated protein kinase-associated protein 1 (JSAP1, also known as JNK-interacting protein 3) as a scaffolding factor for JNK intracellular signaling pathways. Targeted gene-disruption studies have shown that JSAP1-null mice are unable to breathe and die shortly after birth. Although neural defects might be responsible for their death, there has been no convincing evidence for this. Here we first generated genetically engineered mice carrying a loxP-flanked (floxed) jsap1 gene. To evaluate the validity of this deletion as a jsap1 conditional knockout (KO), we created mice in which the same exon was deleted in all cell lineages, and compared their phenotypes with those of the jsap1 conventional KO mice reported previously. The two KO lines showed indistinguishable phenotypes, i.e., neonatal death and morphological defects in the telencephalon, indicating that the conditional deletion was a true null mutation. We then introduced the floxed jsap1 deletion mutant specifically into the neural lineage, and found that the jsap1 conditional KO mice showed essentially the same phenotypes as the JSAP1-null mice. These results strongly suggest that the neonatal death of jsap1-deficient mice is caused by defects in the nervous system.     

基因芯片对大鼠肝移植急性排斥反应T淋巴细胞信号传导基因表达变化的研究

目的：从基因水平研究肝移植急性排斥反应中T淋巴细胞信号传导途径。方法：利用4096条大鼠cDNA克隆的基因芯片对从急性排斥组Wistar→SD(n=5)和对照组SD→SD(n=5)两组肝移植大鼠T细胞中抽提、纯化mRNA，扩增、逆转录成cDNA，荧光标记后与芯片杂交，扫描后筛选出差异表达的基因。结果：在4096个基因中共发现差异表达基因190条，其中ll条与细胞信号传导有关的基因差异表达明显：MHC(3条)、CD3抗原(1条)相关基因；蛋白酶类：蛋白激酶C结合蛋白、蛋白酪氨酸磷酸酯酶D型受体、磷脂酰肌醇二磷酸酶基因各l条；涉及核酸信号传导、激活、转录、翻译的基因3条。结论：T细胞在肝移植术后排斥反应中信号传导机制涉及多个基因，基因芯片技术的大规模筛选为进一步研究T细胞在排斥反应中的信号传导途径提供了客观依据和目标。     

Protein kinase mediators of integrin signal transduction

 Protein kinases are important mediators of signal transduction initiated by soluble growth factors and cytokines. Cellular interactions with the extracellular matrix are mediated largely by members of the integrin class of cell adhesion molecules, which also subsume signal transduction functions required for cell growth, differentiation, and survival. Here we review the involvement of protein kinases in mediating integrin intracellular signal transduction and the possible role for these molecules in regulating integrin adhesion. Although in most cases mechanistic details are incomplete, the emerging theme of protein kinases mediating cross-talk between growth factor receptor and integrin signalling systems provides a timely backdrop against which to present new developments in this area. The contribution of the actin cytoskeleton to integrin signal transduction is discussed, with respect to the concept of ’solid-state’ signalling providing a mechanism for imposing order on the protein-protein interactions which underlie signal discrimination. Moreover, we review evidence that dysregulated integrin signalling contributes to pathological processes including arthritis, thrombasthenia, leucocyte adhesion deficiencies, and tumour angiogenesis and invasion. Received: 14 May 1996 / Accepted: 2 July 1996