Neutrophil Mac-1 and MEL-14 adhesion proteins inversely regulated by chemotactic factors

The neutrophil Mac-1 and gp100MEL-14 adhesion proteins are involved in neutrophil extravasation during inflammation. Both the expression and activity of Mac-1 are greatly increased after neutrophil activation. In contrast, neutrophils shed gp100MEL-14 from the cell surface within 4 minutes after activation with chemotactic factors or phorbol esters, releasing a 96-kilodalton fragment of the antigen into the supernatant. Immunohistology showed that gp100MEL-14 was downregulated on neutrophils that had extravasated into inflamed tissue. The gp100MEL-14 adhesion protein may participate in the binding of unactivated neutrophils to the endothelium; rapid shedding of gp100MEL-14 may prevent extravasation into and damage of normal tissues by activated neutrophils.     

Molecular cloning of the chicken progesterone receptor

To define the functional domains of the progesterone receptor required for gene regulation, complementary DNA (cDNA) clones encoding the chicken progesterone receptor have been isolated from a chicken oviduct lambda gt11 cDNA expression library. Positive clones expressed antigenic determinants that cross-reacted with six monospecific antibodies derived from two independent sources. A 36-amino acid peptide sequence obtained by microsequencing of purified progesterone receptor was encoded by nucleotide sequences in the longest cDNA clone. Analysis of the amino acid sequence of the progesterone receptor deduced from the cDNA clones revealed a cysteine-rich region that was homologous to a region found in the estrogen and glucocorticoid receptors and to the avian erythroblastosis virus gag-erb-A fusion protein. Northern blot analysis with chicken progesterone receptor cDNA's indicated the existence of at least three messenger RNA species. These messages were found only in oviduct and could be induced by estrogens.     

Cell surface molecule associated with lymphocyte homing is a ubiquitinated branched-chain glycoprotein

Partial amino acid sequence analysis of a purified lymphocyte homing receptor demonstrates the presence of two amino termini, one of which corresponds precisely to the amino terminus of ubiquitin. This observation extends the province of this conserved polypeptide to the cell surface and leads to a proposed model of the receptor complex as a core polypeptide modified by glycosylation and ubiquitination. Independent antibodies to ubiquitin serve to identify additional cell surface species, an indication that ubiquitination of cell surface proteins may be more general. It is proposed that functional binding of lymphocytes to lymph node high endothelial venules might involve the ubiquitinated region of the receptor; if true, cell surface ubiquitin could play a more general role in cell-cell interaction and adhesion.     

A distinct endothelial cell recognition system that controls lymphocyte traffic into inflamed synovium

Lymphocytes are essential mediators of normal tissue inflammatory reactions and of pathologic tissue damage in, for example, rheumatoid arthritis and other autoimmune diseases. In a study of the mechanisms controlling lymphocyte entry into sites of inflammation from the blood, the function and specificity of lymphocyte-endothelial interactions were examined in inflamed joint tissue (synovium) from patients with rheumatoid arthritis. Synovial high endothelial venules (HEV) supported the binding of normal peripheral blood lymphocytes in vitro. The characteristics of this binding, which were similar to those of lymphocyte-HEV interactions controlling lymphocyte migration into organized lymphoid tissues, included a requirement for calcium ions, a dependence on metabolic activity, and a preferential adherence of circulating lymphocytes as opposed to immature thymocytes. However, the binding of lymphocytes to synovial HEV was not inhibited by a monoclonal antibody to lymphocyte receptors for lymph node HEV, and synovial HEV failed to bind either lymph node HEV-specific or mucosal HEV-specific B lymphoblastoid cells. The results suggest that a lymphocyte-endothelial cell recognition system that is distinct from such systems in organized lymphoid tissues directs the extravasation of normal lymphocytes as well as pathologically important effector cells into inflamed synovium.     

Islet allograft survival after a single course of treatment of recipient with antibody to L3T4

Allografts of pancreatic islets of Langerhans were induced to survive for an indefinite period in diabetic mice if, at the time of engraftment, the mice received a single course of treatment with a monoclonal antibody directed against the L3T4 determinant, a nonpolymorphic cell surface glycoprotein present on the cell surface of the murine T helper-inducer lymphocyte subset. This treatment allowed the survival of islets of Langerhans transplanted across a major histocompatibility barrier without additional immunosuppression. The results demonstrate that the lymphocyte subset defined by the expression of the L3T4 molecules is central to the induction of allograft rejection and provides a model for tolerance induction for organ allograft transplantation.     

Molecular cloning of complementary DNA encoding the avian receptor for vitamin D

Vitamin D3 receptors are intracellular proteins that mediate the nuclear action of the active metabolite 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. Two receptor-specific monoclonal antibodies were used to recover the complementary DNA (cDNA) of this regulatory protein from a chicken intestinal lambda gt11 cDNA expression library. The amino acid sequences that were deduced from this cDNA revealed a highly conserved cysteine-rich region that displayed homology with a domain characteristic of other steroid receptors and with the gag-erbA oncogene product of avian erythroblastosis virus. RNA selected via hybridization with this DNA sequence directed the cell-free synthesis of immunoprecipitable vitamin D3 receptor. Northern blot analysis of polyadenylated RNA with these cDNA probes revealed two vitamin D receptor messenger RNAs (mRNAs) of 2.6 and 3.2 kilobases in receptor-containing chicken tissues and a major cross-hybridizing receptor mRNA species of 4.2 kilobases in mouse 3T6 fibroblasts. The 4.2-kilobase species was substantially increased by prior exposure of 3T6 cells to 1,25(OH)2D3. This cDNA represents perhaps the rarest mRNA cloned to date in eukaryotes, as well as the first receptor sequence described for an authentic vitamin.     

A chemoattractant receptor controls development in Dictyostelium discoideum

During the early stages of its developmental program, Dictyostelium discoideum expresses cell surface cyclic adenosine monophosphate (cyclic AMP) receptors. It has been suggested that these receptors coordinate the aggregation of individual cells into a multicellular organism and regulate the expression of a large number of developmentally regulated genes. The complementary DNA (cDNA) for the cyclic AMP receptor has now been cloned from lambda gt-11 libraries by screening with specific antiserum. The 2-kilobase messenger RNA (mRNA) that encodes the receptor is undetectable in growing cells, rises to a maximum at 3 to 4 hours of development, and then declines. In vitro transcribed complementary RNA, when hybridized to cellular mRNA, specifically arrests in vitro translation of the receptor polypeptide. When the cDNA is expressed in Dictyostelium cells, the undifferentiated cells specifically bind cyclic AMP. Cell lines transformed with a vector that expresses complementary mRNA (antisense) do not express the cyclic AMP receptor protein. These cells fail to enter the aggregation stage of development during starvation, whereas control and wild-type cells aggregate and complete the developmental program within 24 hours. The phenotype of the antisense transformants suggests that the cyclic AMP receptor is essential for development. The deduced amino acid sequence of the receptor reveals a high percentage of hydrophobic residues grouped in seven domains, similar to the rhodopsins and other receptors believed to interact with G proteins. It shares amino acid sequence identity and is immunologically cross-reactive with bovine rhodopsin. A model is proposed in which the cyclic AMP receptor crosses the bilayer seven times with a serine-rich cytoplasmic carboxyl terminus, the proposed site of ligand-induced receptor phosphorylation.     

G1/S transition in normal human T-lymphocytes requires the nuclear protein encoded by c-myb

Exposure of peripheral blood mononuclear cells (PBMC) to an 18-base c-myb antisense oligomer before mitogen or antigen stimulation resulted in almost complete inhibition of c-myb messenger RNA and protein synthesis and blockade of T lymphocyte proliferation. Expression of early and late activation markers, interleukin-2 receptor and transferrin receptor, respectively, by PBMC was unaffected by antisense oligomer exposure as was the expression of c-myc messenger RNA. In contrast, histone H3 messenger RNA levels and DNA content were selectively decreased. These results suggest that c-myb protein deprivation does not perturb T lymphocyte activation or early molecular events that may prepare the cell for subsequent proliferation. Rather, it appears to specifically block cells in late G1 or early S phase of the cell cycle.     

水稻NBS-LRR类抗稻瘟病蛋白Pik-h的互作蛋白筛选

【目的】利用酵母双杂交系统,以组成抗稻瘟病基因Pik-h介导的抗病反应途径。【方法】以含抗稻瘟病基因Pik-h的近等基因系IRBL8为材料,取稻瘟病菌(Magnaporthe oryzae)GD0193接种12和24 h后的水稻叶片,等量混合后提取总RNA,按照2个紧密连锁且功能独立的Pikh-1和Pikh-2蛋白为诱饵,在水稻叶片中筛选与之互作的蛋白,以便深入研究抗病基因Pik-h的酵母双杂交试剂盒（Make Your Own “Mate&Plate” Library System）的要求构建水稻叶片靶标cDNA文库。利用快速重组克隆的方法构建pGBKT7-Pikh1和pGBKT7-Pikh2诱饵载体,并分别将它们转化至酵母菌株Y2H Gold,提取细胞总蛋白后利用Western blot检测Pikh1和Pikh2的表达情况,并对这2个诱饵载体自激活和毒性分析后进行酵母双杂交筛选。提取SD/-Ade/-Leu/-Trp/ -His/X-α-Gal筛选平板培养基上呈蓝色的酵母单克隆的质粒,将其分别与对应的诱饵载体共转化酵母菌株Y2H Gold,涂布于筛选平板培养基上进行互作的重复验证,将通过重复验证的质粒测序分析所得的序列比对水稻基因组数据库以确定目的基因,并对这些基因进行gene ontology（GO）注释分析以确定其分子功能、生物过程及细胞组成。【结果】靶标cDNA文库的库容量约为2.2×10⁶,插入片段长度均大于400 bp,表明水稻cDNA文库质量高。诱饵载体pGBKT7-Pikh1和pGBKT7-Pikh2均能在酵母细胞中正确表达出对应的Pikh1及Pikh2蛋白,无自激活活性而且对酵母无毒性作用,符合文库筛选的要求。利用含有诱饵载体的酵母菌株Y2H Gold与靶标文库菌株Y187结合（Mating）的方式筛选,获得13个与Pikh-1相互作用的蛋白、5个与Pikh-2相互作用的蛋白,其中有2个与Pikh-1及Pikh-2同时存在相互作用。这些蛋白包括4个在逆境响应或激素信号转导过程中起到重要作用的（辅）转录因子、3个信号蛋白、4个参与光合作用的叶绿体蛋白、1个含有U-BOX结构域的蛋白及4个未知功能蛋白。【结论】成功构建了适宜于研究抗病基因（R基因）介导反应途径的酵母双杂交cDNA文库,筛选出Pik-h的互作蛋白,为进一步研究Pik-h或其他抗稻瘟病基因介导的抗病机制打下了基础。     

Deletion in cysteine-rich region of LDL receptor impedes transport to cell surface in WHHL rabbit

The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal with familial hypercholesterolemia, produces a mutant receptor for plasma low-density lipoprotein (LDL) that is not transported to the cell surface at a normal rate. Cloning and sequencing of complementary DNA's from normal and WHHL rabbits, shows that this defect arises from an in-frame deletion of 12 nucleotides that eliminates four amino acids from the cysteine-rich ligand binding domain of the LDL receptor. A similar mutation, detected by S1 nuclease mapping of LDL receptor messenger RNA, occurred in a patient with familial hypercholesterolemia whose receptor also fails to be transported to the cell surface. These findings suggest that animal cells may have fail-safe mechanisms that prevent the surface expression of improperly folded proteins with unpaired or improperly bonded cysteine residues.     

干旱与NaHCO3胁迫下柽柳基因表达的比较

用cDNA微阵列技术比较了NaHCO3及干旱胁迫下柽柳基因的表达异同。柽柳分别采用0.4mol/L的NaHCO3和干旱处理约30h后取材,分离总RNA,选用Cy3和Cy5进行标记,并与载有柽柳基因的cDNA微阵列杂交,比较了柽柳干旱胁迫的基因表达谱和NaHCO3胁迫的基因表达谱。结果显示,2种胁迫下,有14条基因共同下调表达,31条基因共同上调表达,说明柽柳的抗旱耐盐性状相似性较高。有1个基因在干旱胁迫下为上调表达,在NaHCO3胁迫下为下调表达。同时,和Lea蛋白、脱水诱导蛋白RD22同源的基因在干旱胁迫下表达量升高明显,但NaHCO3胁迫表达量上升不明显;NaHCO3胁迫使与SMDC基因和水通道蛋白同源的基因表达量明显上升,而干旱胁迫其表达量无明显升高,提示了柽柳的抗旱、耐盐性状也存在明显的差异。     

Cloning and sequencing of porcine LH-hCG receptor cDNA: variants lacking transmembrane domain

Complementary DNA clones, encoding the LH-hCG (luteinizing hormone-human choriogonadotropic hormone) receptor were isolated by screening a lambda gt11 library with monoclonal antibodies. The primary structure of the protein was deduced from the DNA sequence analysis; the protein contains 696 amino acids with a putative signal peptide of 27 amino acids. Hydropathy analysis suggests the existence of seven transmembrane domains that show homology with the corresponding regions of other G protein-coupled receptors. Three other types of clones corresponding to shorter proteins were observed, in which the putative transmembrane domain was absent. These probably arose through alternative splicing. RNA blot analysis showed similar patterns in testis and ovary with a major RNA of 4700 nucleotides and several minor species. The messenger RNA was expressed in COS-7 cells, yielding a protein that bound hCG with the same affinity as the testicular receptor.     

酵母双杂交筛选与小麦黄花叶病毒P2互作的寄主因子

小麦黄花叶病毒(wheat yellow mosaic virus,WYMV)隶属马铃薯Y病毒科(Potyviridae),大麦黄花叶病毒属(Bymovirus).该病毒基因组是由两条正义单链RNA1和RNA2构成,共编码10个蛋白,其编码的P2在病毒的复制过程中发挥重要功能.文章构建了小麦cDNA酵母文库,通过共转试...     

利用酵母双杂交系统筛选介体异沙叶蝉中与小麦矮缩病毒外壳蛋白互作的蛋白质

【目的】利用分离泛素酵母双杂交膜系统（split-ubiquitin yeast membrane system）,以小麦矮缩病毒（Wheat dwarf virus,WDV）的外壳蛋白（CP）基因为诱饵对异沙叶蝉（Psammotettix alienus L.）cDNA文库进行筛选,研究异沙叶蝉传播WDV的分子机制。【方法】以笔者实验室饲养的异沙叶蝉为材料,提取其总RNA后取100 ng进行纯化,利用SMART法反转录合成ds cDNA,经过Sfi I酶切纯化,连接到pPR3-N文库载体上,构建得到以pPR3-N为载体的异沙叶蝉分离泛素酵母双杂交膜系统cDNA文库。同时,构建带有Sfi I酶切位点的诱饵载体pDHB1-WDV CP,经功能检测后用诱饵载体初步筛选pPR3-N空文库,寻找适合筛库的条件和确定His基因产物抑制剂3-氨基-1,2,4-三唑（3-AT）的使用浓度。然后用诱饵载体筛选异沙叶蝉cDNA文库,对筛选结果进行分析,再通过共转验证和β-半乳糖苷酶检测进一步验证是否发生互作。利用Uniprot和KEGG在线网站,对筛到的蛋白进行gene ontology（GO）注释和Pathway分析。【结果】初级文库库容量超过2.0×10⁶ cfu,文库实际扩增数量大于1.3×10⁶ cfu,文库重组率大于97%,扩增文库插入片段平均长度大于1 000 bp,表明异沙叶蝉cDNA文库的质量较高。酶切验证显示诱饵载体pDHB1-WDV-CP中CP的插入完整而准确。功能检测表明融合蛋白能够正确表达。在3-AT浓度为5 mmol?L^-1的筛选条件下,诱饵载体筛选异沙叶蝉cDNA文库得到280个克隆,经测序和Blast比对分析最终得到12个可能与WDV的CP发生互作的异沙叶蝉蛋白质。将这12个蛋白质再次进行共转验证和β-半乳糖苷酶检测,最终得到9个蛋白质与WDV CP互作。GO注释显示,9个蛋白参与的生物过程包括蛋白去磷酸化、碳水化合物代谢过程、先天性免疫应答、模式识别受体的信号通路、运输、同向运输和乙醇氧化等;分子功能包括金属离子结合活性、蛋白磷酸酶活性、信号模式识别受体的活性、水解酶活性、磷酸离子载体活性和叶酸运输活性等。参考KEGG数据库,这些蛋白参与的代谢途径有泛素介导的蛋白水解途径、内吞作用、花生四烯酸代谢途径、cAMP信号通路和模式识别受体的信号通路等。【结论】异沙叶蝉分离泛素酵母双杂交膜系统cDNA文库的成功构建与筛选,为研究异沙叶蝉与小麦矮缩病毒的互作机制研究奠定了基础。     

Involvement of sialic acid on endothelial cells in organ-specific lymphocyte recirculation

Mouse lymphocytes incubated on cryostat-cut sections of lymphoid organs (lymph nodes and Peyer's patches) specifically adhere to the endothelium of high endothelial venules (HEV), the specialized blood vessels to which recirculating lymphocytes attach as they migrate from the blood into the parenchyma of the lymphoid organs. Treatment of sections with sialidase eliminated the binding of lymphocytes to peripheral lymph node HEV, had no effect on binding to Peyer's patch HEV, and had an intermediate effect on mesenteric lymph node HEV. These results suggest that sialic acid on endothelial cells may be an organ-specific recognition determinant for lymphocyte attachment.