A multifunctional element in the mouse Igκ locus that specifies repertoire and Ig loci subnuclear location

Nonbiased V gene usage for V(D)J joining is essential for providing an optimal immune system, but no cis-acting sequence with this function has been uncovered. We previously identified a recombination silencer and heterochromatin targeting element in the Vκ-Jκ intervening sequence of germline Igκ transgenes, which we termed Sis. We now have generated Sis knockout mice in the endogenous locus. Intriguingly, Sis(-/-) mice exhibit a skewed Igκ repertoire with markedly decreased distal and enhanced proximal Vκ gene usage for primary rearrangement, which is associated with reduced occupancy of Ikaros and CCCTC-binding factor in the Vκ-Jκ intervening sequence in pre-B cells, proteins believed to be responsible for dampening the recombination of nearby Vκ genes and altering higher-order chromatin looping. Furthermore, monoallelic heterochromatin localization is significantly reduced in Sis(-/-) mice for Igκ in cis and IgH loci in trans in pre-B cells. Because Sis(-/-) mice still allelically excluded Igκ and IgH loci and still exhibited IgL isotype exclusion, we concluded that stable localization at pericentromeric heterochromatin is neither necessary nor sufficient for the establishment or maintenance of allelic exclusion. Hence, Sis is a novel multifunctional element that specifies repertoire and heterochromatin localization to Ig genes.     

Production of N-acetylgalactosaminyl-transferase 2 (GalNAc-T2) fused with secretory signal Igκ in insect cells

The human UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyl-transferase 2 (GalNAc-T2) is one of the key enzymes that initiate synthesis of hinge-region O-linked glycans of human immunoglobulin A1 (IgA1). We designed secreted soluble form of human GalNAc-T2 as a fusion protein containing mouse immunoglobulin light chain kappa secretory signal and expressed it using baculovirus and mammalian expression vectors. The recombinant protein was secreted by insect cells Sf9 and human HEK 293T cells in the culture medium. The protein was purified from the media using affinity Ni-NTA chromatography followed by stabilization of purified protein in 50mM Tris-HCl buffer at pH 7.4. Although the purity of recombinant GalNAc-T2 was comparable in both expression systems, the yield was higher in Sf9 insect expression system (2.5mg of GalNAc-T2 protein per 1L culture medium). The purified soluble recombinant GalNAc-T2 had an estimated molecular mass of 65.8kDa and its amino-acid sequence was confirmed by mass-spectrometric analysis. The enzymatic activity of Sf9-produced recombinant GalNAc-T2 was determined by the quantification of enzyme-mediated attachment of GalNAc to synthetic IgA1 hinge-region peptide as the acceptor and UDP-GalNAc as the donor. In conclusion, murine immunoglobulin kappa secretory signal was used for production of secreted enzymatically active GalNAc-T2 in insect baculovirus expression system.     

Evolution of a Vκ gene family

To examine the evolution of multigene families we have selected as an example an immunoglobulin light chain variable region subgroup (V24) which has been extensively characterized in inbred mice (Mus musculus domesticus). Homologous genes have been isolated and sequenced from Mus pahari, a genetically and geographically isolated species believed to be the oldest living representative of the genus. Southern blot analysis using probes corresponding to individual genes in this subgroup reveals changes in the overall size of the family occurring at the level of individual genes but not at the level of the entire family. Nucleotide sequence analysis indicates an absence of regulatory sequences such as the CAT and TATA boxes 5 to the coding region, but a decanucleotide sequence involved in light chain expression is highly conserved. Within coding regions highly complex patterns of variation are seen which appear to reflect quite different selective pressures on various subregions of the coding sequence. Complementarity determining regions (CDR) are conserved to different extents, with the first CDR region in all family members being among the most conserved segments of the molecule. Conservation is similarly variable among framework segments, indicating complex and variable evolutionary pressures not only at the level of individual genes or their products but also at subregions within homologous molecules.     

PD-L1 Ig在缓解肾移植急性排斥反应中的免疫调节作用

目的:探讨PD-L1 Ig(Programmed death ligand-1 immunoglobulin,程序性死亡配体-1免疫球蛋白)在缓解肾移植急性排斥反应中的免疫调节作用。方法:选择健康成年雄性Lewis大鼠24只作为供体,另取24只健康雄性Wistar大鼠作为受体。所选大鼠3个月龄,体重300 g±30 g,创建肾移植大鼠模型,并将其随机分为三组,空白对照组,对照组,和PD-L1 Ig组。空白对照组:灌注液,肾动脉灌注3分钟。PD-L1 Ig组:含1 m L的PD-L1 Ig的灌注液,肾动脉灌注3分钟。对照组不进行额外灌注操作。术后观察三组大鼠食欲、精神状态及生存情况。7天后取血标本观察肌酐、尿素氮、γ-干扰素(Interferon-γ, IFN-γ),白细胞介素-2(Interleukin-2, IL-2),白细胞介素-10 (Interleukin-10, IL-10)水平,同时三组各处死3只大鼠行肾脏病理学检查。结果:1.病理:对照组及空白对照组大鼠较模型大鼠有改善,仍有较多的炎细胞浸润,间质水肿,红细胞管型,肾小管上皮细胞脱落。而PD-L1 Ig组大鼠较模型大鼠、对照组及空白对照组有显著改善。2.生存状态和肾功能:PD-L1 Ig组大鼠生存时间最长50天,平均存活时间和体重均显著高于对照组和空白对照组,差异均有统计学意义(P0.05);血肌酐、尿素氮水平显著低于对照组和空白对照组,差异均有统计学意义(P0.05)。3.细胞因子变化:PD-L1 Ig组IFN-γ、IL-2水平显著低于空白对照组、对照组,差异均有统计学意义(P0.05);PD-L1 Ig组IL-10水平显著高于空白对照组、对照组,差异均有统计学意义(P0.05)。结论:PD-L1 Ig可降低IL-2和IFN-γ,提升IL-10,调节移植肾急性排斥反应的细胞因子平衡,改善肾功能,延长移植肾存活时间。     

IgG1 cytoplasmic tail is essential for cell surface expression in Igβ down-regulated cells

It has been shown that cytoplasmic tail of the IgG1 B cell receptors (BCRs) are essential for the induction of T-dependent immune responses. Also it has been revealed that unique tyrosine residue in the cytoplasmic tail of IgG2a has the potential of being phosphorylated at tyrosine and that this phosphorylation modulates BCR signaling. However, it still remains unclear whether such phosphorylation of IgG cytoplasmic tail is involved in the regulation of BCR surface expression. In order to approach the issue, we established and analyzed the cell lines which express wild-type or mutated forms of IgG1 BCR. As the result, we found that IgG1 BCR expressed normally on the surface of A20 B cell line independent of the cytoplasmic tail. In contrast, IgG1 BCR whose cytoplasmic tyrosine was replaced with glutamic acid which mimics phosphorylated tyrosine, was expressed most efficiently on the surface of non-B lineage cells and Igβ-down-regulated B cell lines. These results suggest that tyrosine residue in IgG cytoplasmic tail is playing a essential role for the efficient expression of IgG BCR on the cell surface when BCR associated signaling molecules, including Igβ, are down-regulated.     

噬菌体展示 protein A 及 protein L Ig 结合单结构域随机组合文库及 Ig 亲和筛选

Protein A 和 protein L 是细菌产生的两种结构和功能均不同的免疫球蛋白 (immunoglobulin , Ig) 结合分子,在细菌的致病中起重要作用 . 用含 SacⅠ位点的特定引物 PCR 分别扩增制备 protein A 的 A 、 B 、 C 、 D 抗体结合结构域和 protein L 的 B3 抗体结合结构域,各结构域 DNA 片段经 SacⅠ酶切后,再随机连接形成各种不同长度的分子组合文库,将该文库呈现在噬菌体表面构建了噬菌体展示 Ig 结合分子单结构域随机组合文库,所建组合文库容量为 2.3×10⁶个菌落形成单位,滴度为 4.1×10¹¹TU/ml , 包含各种单结构域片段,并以随机方式连接 . 用人 Ig 对该文库进行 4 轮亲和筛选,随机挑选 36 个代表性的阳性克隆进行序列测定分析表明,亲和筛选获得了多种非天然形式存在的新的 Ig 结合分子结构,其中 32 个克隆具有由 protein L 的单结构域和 protein A 的单结构域间隔重复排列而成的特征性 (MDPL-MDPA)n 结构 . 对噬菌体展示 Ig 结合分子单结构域随机组合文库的体外分子进化研究的尝试,为 Ig 结合分子的结构和功能研究提供了一新的途径,也为 Ig 结合分子的定向改造打下基础 .     

NF-κ B和HIF-1在宫颈上皮内瘤变和鳞癌中表达的意义

目的：初步探索NF-κB和HIF-1在宫颈上皮内瘤变和宫颈鳞癌中的表达及临床病理学意义。方法：以宫颈上皮内瘤变和宫颈鳞癌病例为研究对象,应用免疫组织化学方法检测NF-κB和HIF-1的表达情况并分析其表达在宫颈癌变中的意义。结果：NF-κB在正常宫颈上皮、CINⅠ、CINⅡ、CINⅢ、鳞癌的阳性表达率分别为16%,36%,44%,68%,72%。总体比较存在显著性差异x2=21.636,p〈0.01。组间两两比较显示正常上皮与CINⅢ和鳞癌有显著性差异。HIF-1α在正常宫颈上皮、CINⅠ、CINⅡ、CINⅢ、鳞癌的阳性表达率分别为12%,20%,40%,68%,76%。总体比较存在显著性差异x2=32.733,p〈0.01。组间两两比较显示正常上皮与CINⅢ（x2=16.333 p〈0.001）和鳞癌（x2=20.779 p〈0.001）有显著性差异。结论：NF-κB和HIF-1与宫颈鳞癌的发生有关,可能作为早期诊断的标志物。     

EB病毒LMP1在鼻咽癌细胞中通过NFκB促进Igκ表达

利用已建立的受四环素调控ＬＭＰ１表达的鼻咽癌细胞系,用受ＣＭＶ启动子调控的ＮＦκＢ报道基因质粒ｐＮＦκＢ－ｌｕｃ的荧光素酶表达分析ＮＦκＢ的活性,并以核蛋白的Ｗｅｓｔｅｒｎ印迹方法观察ＬＭＰ１表达前后核内ＮＦκＢ组分ｐ６５量的改变,用全蛋白Ｗｅｓｔｅｒｎ印迹分析Ｉｇκ蛋白质的表达等方法,探讨在鼻咽癌中,ＥＢ病毒ＬＭＰ１蛋白是否通过核转录因子ＮＦκＢ促进免疫球蛋白κ轻链（Ｉｇκ）基因的表达。结果显示     

GEC1-κ Opioid Receptor Binding Involves Hydrophobic Interactions: GEC1 HAS CHAPERONE-LIKE EFFECT*S?

We demonstrated previously that the protein GEC1 (glandular epithelial cell 1) bound to the human κ opioid receptor (hKOPR) and promoted cell surface expression of the receptor by facilitating its trafficking along the secretory pathway. Here we showed that three hKOPR residues (Phe³⁴⁵, Pro³⁴⁶, and Met³⁵⁰) and seven GEC1 residues (Tyr⁴⁹, Val⁵¹, Leu⁵⁵, Thr⁵⁶, Val⁵⁷, Phe⁶⁰, and Ile⁶⁴) are indispensable for the interaction. Modeling studies revealed that the interaction was mediated via direct contacts between the kinked hydrophobic fragment in hKOPR C-tail and the curved hydrophobic surface in GEC1 around the S2 β-strand. Intramolecular Leu⁴⁴-Tyr¹⁰⁹ interaction in GEC1 was important, likely by maintaining its structural integrity. Microtubule binding mediated by the GEC1 N-terminal domain was essential for the GEC1 effect. Expression of GEC1 also increased cell surface levels of the GluR1 subunit and the prostaglandin EP3.f receptor, which have FPXXM and FPXM sequences, respectively. With its widespread distribution in the nervous system and its predominantly hydrophobic interactions, GEC1 may have chaperone-like effects for many cell surface proteins along the biosynthesis pathway.κ opioid receptor (KOPR)² is one of the three major types of opioid receptors mediating effects of opioid drugs and endogenous opioid peptides. Stimulation of KOPR generates many effects in vivo, for example antinociception (especially for visceral chemical pain, antipruritis, and water diuresis (1). The KOPR agonist nalfurafine (TRK-820) is used clinically in Sweden for the treatment of uremic pruritus in kidney dialysis patients (2). Because KOPR agonists produce profound sedative effects, it has been proposed that KOPR agonists may be useful in treating mania, antagonists as anti-depressants, and partial agonists for the management of mania depression (3). KOPR antagonists may also be useful for curbing cocaine craving and as anti-anxiety drugs (4, 5).KOPR, a member of the rhodopsin subfamily of the seven-transmembrane receptor superfamily, is coupled preferentially to pertussis toxin-sensitive G proteins, namely G_i/o proteins (6). KOPR has been found to interact with several non-G protein-binding partners, such as Na⁺,H⁺-exchanger regulatory factor-1/ezrin-radixin-moesin-binding phosphoprotein-50 and the δ opioid receptor. These interactions have influence on signal transduction and trafficking of the receptor (7–9). By yeast two-hybrid (Y2H) assay using the hKOPR C-tail to screen a human brain cDNA library, we identified GEC1, also named GABA_A receptor-associated protein like 1 (GABARAPL1), to be a binding partner of hKOPR (10).GEC1 cDNA was first cloned as an early estrogen-regulated mRNA from guinea pig endometrial glandular epithelial cells by Pellerin et al. (11). Subsequently, it was cloned from other species, including human and house mouse (12). Interestingly, the amino acid sequences of GEC1 are completely conserved among all these species except orangutan, in which Arg⁹⁹ substitutes for His⁹⁹. Northern blot and immunoblotting analyses revealed that it has widespread tissue distribution (12–14). In particular, GEC1 was found to be abundant in the central nervous system and expressed throughout the rat brain (14, 15). This wide tissue distribution and the high sequence identity across species strongly suggest that GEC1 has important biological functions in mammalian cells.Based on sequence similarity, GEC1 is classified as a member of microtubule-associated proteins (MAPs), which also include GABA_A receptor-associated protein (GABARAP), Golgi-associated ATPase enhancer of 16 kDa (GATE16), GABARAP-like 3 (GABARAPL3), light chain 3 (LC3) of MAP 1A/1B, and the yeast autophagy protein 8 (Atg8) (12, 13). Among these homologues, GEC1 share the highest identity with GABARAPL3 (93%), followed by GABARAP (86%), GATE16 (61%), Atg8 (55%), and LC3 (∼30%).A growing body of evidence shows that this protein family is closely related to two distinct biological functions. Studies mainly on GABARAP, GATE16, and GEC1 indicate that they promote intracellular protein trafficking by enhancing vesicle fusion (10, 16–21). In addition, they facilitate degradation of proteins and intracellular organelles via autophagy-related pathways, which is bolstered largely by research on Atg8 and LC3 (22, 23).We previously reported that GEC1 interacted with the hKOPR C-tail and enhanced cell surface levels of hKOPR stably expressed in CHO cells. GEC1 expression enhances hKOPR expression through facilitating its anterograde trafficking along the protein biosynthesis pathway without affecting degradation of the receptor (10). This represented the first biological function reported for GEC1. Mansuy et al. (24) demonstrated that GEC1 interacted with tubulin and promoted microtubule bundling in vitro, and that green fluorescence protein-tagged GEC1 was localized in the perinuclear vesicles with a scattered pattern. Our electron microscopic studies in the rat brain showed that GEC1 was associated with ER, Golgi apparatus, endosome-like vesicles, and plasma membranes and scattered in cytoplasm in neurons (14). In addition, N-ethylmaleimide-sensitive factor, a protein critical for intracellular membrane-trafficking events, binds directly to GEC1 (10).In this study, we employed Y2H techniques to determine the amino acid residues in both GEC1 and hKOPR C-tail involved in the interaction. Further studies were then carried out in mammalian cells to examine if elimination of the interaction affected the effect of GEC1 on hKOPR expression. In addition, we generated a molecular model of GEC1 based on the x-ray crystal structure of GABARAP and found that the residues involved in hKOPR binding formed hydrophobic patches on the exterior surface of GEC1. Moreover, we found that the cytosolic tail of AMPA receptor subunit GluR1 has the same FPXXM motif as that found in the hKOPR C-tail to be involved in GEC1 binding and that GEC1 expression up-regulated GluR1.     

N-乙酰半胱氨酸对大鼠肝脏缺血再灌注损伤NF-κ B和ICAM-1表达的影响

目的：探讨大鼠肝脏缺血再灌注损伤NF-κB和ICAM-1表达情况及NAC的保护作用机制。方法：45只雄性SD大鼠随机分成三组：假手术组（Sham组,n=5）;缺血再灌注损伤组（I/R组,n=20）缺血60min后分别再灌注1、3、6、12h;N-乙酰半胱氨酸组（NAC组,n=20）：先自阴茎背静脉给大鼠注射溶于生理盐水的NAC,20min后再按I/R组处理。在各规定的再灌注时间点,分别采用western-blot和免疫组化方法测定肝组织中NF-κB和ICAM-1的表达。结果：I/R组和NAC组再灌注1、3、6、12h后,NF-κB的表达均明显高于Sham组（p〈0.01）,于再灌注3h达到高峰;ICAM-1的表达均明显高于Sham组（p〈0.01）,于再灌注6h达到高峰。NAC组再灌注1、3、6h与I/R组相同时间点比较：NF-κB和ICAM-1的表达均低于I/R组（p〈0.05）。NAC组再灌注12h与I/R组相同时间点比较：NF-κB和ICAM-1的表达虽然在数值上有所减少,但统计学上无差异（p〉0.05）。结论：大鼠肝脏缺血再灌注后NF-κB和ICAM-1表达增加,NAC可抑制NF-κB激活,减少ICAM-1表达减轻大鼠肝脏缺血再灌注损伤。     

Coevolution of Antibody Stability and Vκ CDR-L3 Canonical Structure

Antibodies recognize antigens through six hypervariable loops, five of which have a limited set of conformations known as canonical structures. For κ light chains, the majority of CDR-L3 [the third hypervariable loop of the light chain variable domain (V_L)] adopts the type 1 canonical structure (CS1), with a cis-proline at position 95. Here, we present the design and structural studies of the monoclonal antibody mAb15 and related mutants that contained a series of progressively germline mutations only in the heavy chain variable domain (V_H) that ultimately led to an increase of more than 11 °C in the melting temperature (T_m) of the antigen-binding fragment (Fab). The all-trans CDR-L3 structure in the wild type is significantly different from any known CDR-L3 canonical structures. In the thermally stable mutants, the L94^L-S95^L peptide bond adopts an energetically unfavorable non-X-proline cis conformation, but the overall CDR-L3 loop converted to CS1. The stabilized V_H appears to function as a specific molecular chaperone that facilitated the trans-cis isomerization of S95^L. Thus, it is plausible that proline is the evolutionary choice to maintain overall structure and stability for V_L. These results provide new insights into the evolution of CS1 and suggest a potential molecular switch mechanism at position 95 that links CDR-L3 structural diversity and antibody stability and will have implications for antibody engineering.     

新型受体药物CTLA4－Ig的应用

新型受体药物ＣＴＬＡ４－Ｉｇ的应用方向东,刘宏,王小宁（第一军医大学分子免疫学研究所,广州５１０５１５）关键词受体药物,免疫抑制剂,基因重组利用生物体的一些天然或改造的受体作为治疗用药是目前国际上研究的热点之一,特别是在筛选有效的免疫抑制剂方面。细胞...     

Hypoxia-increased RAGE expression regulates chemotaxis and pro-inflammatory cytokines release through nuclear translocation of NF-κ B and HIF1α in THP-1 cells

The potential role of hypoxia in mediating the receptor for advanced glycation end products (RAGE) expression deserves to be confirmed. And the role of RAGE in hypoxia-induced chemotaxis and inflammation is still unclear. In present study, THP-1?cells were pretreated with siRNA to block HIF1α, NF-κ B, or RAGE, followed by exposed to hypoxia (combined with H₂O₂ or SNP), and then RAGE expression, nuclear translocation of HIF1α and NF-κ B, release of TNF-α and IL-1β, as well as expression of MCP-1 and CCR2 were measured. The results revealed that RAGE mRNA and protein in THP-1?cells were significantly increased after exposed into hypoxia atmosphere, especially into the solution containing SNP or H₂O₂. Moreover, SNP or H₂O₂ exposure could further amplify hypoxia-induced nuclear translocation of HIF-1α and NF-κ B. Knockdown HIF-1α or NF-κ B by siRNAs could reduce hypoxia- and oxidative stress-induced RAGE hyper-expression. And pretreatment THP-1?cells with RAGE siRNA or NF-κ B siRNA could reduce hypoxia- and oxidative stress-induced expression of MCP-1 and CCR2, and release of TNF-α and IL-1β. Thus, hypoxia not only increases RAGE expression in THP-1?cells by promoting nuclear translocation of NF-κ B and HIF1α, but also regulates chemotaxis and pro-inflammatory cytokines release, which may be partially mediated through upregulation of RAGE expression.