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91.
Dual role of the CD44 molecule in T cell adhesion and activation 总被引:46,自引:0,他引:46
Y Shimizu G A Van Seventer R Siraganian L Wahl S Shaw 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(8):2457-2463
Studies of T cell adhesion and activation reveal two new functions of the CD44 molecule, a molecule now recognized to be identical to three molecules of functional interest: Pgp-1, Hermes, and extracellular matrix receptor type III (ECMRIII). By screening for mAb which inhibit T cell adhesion to E, we have identified a functionally unique CD44-specific mAb, NIH44-1, which partially inhibits T cell rosetting by binding to CD44 on the E. NIH44-1, which immunoprecipitates a protein of 85 to 110 kDa with broad tissue distribution, was determined to be specific for CD44 based on comparison of its tissue distribution with multiple CD44-specific reference mAb and sequential immunoprecipitation with such mAb. Anticipating a role for many adhesion molecules in signal transduction, we studied the effect of CD44 mAb on T cell activation and observed that CD44 mAb dramatically augments T cell proliferation induced by CD3- and CD2-receptor-mediated activation. The augmentation of the response to immobilized CD3 mAb by exhaustively monocyte-depleted T cells indicates that augmentation can be mediated by binding to the T cell. Thus, our studies demonstrate specific new roles for CD44 in T cell adhesion and activation. Furthermore, we suggest that: 1) CD44 has a role in adhesion of cells of multiple lineages; and 2) CD44 may participate in adhesion not (only) by functioning as an adhesion receptor but rather by serving as an anchorage site for other adhesion molecules. 相似文献
92.
Circular DNA is excised by immunoglobulin class switch recombination 总被引:28,自引:0,他引:28
We have purified extrachromosomal circular DNAs from adult mouse spleen cells, and cloned into a phage vector the BamHl fragments hybridizing with C mu and S gamma 1 probes. We obtained 52 S mu+S gamma 1+ clones by screening 1.4 million phage clones derived from spleen cells stimulated with bacterial lipopolysaccharide and interleukin 4. We have identified the breakpoints of six clones that contain S gamma 1 and S mu sequences fused in the 5' to 3' orientation. All these switch recombination sites were assigned to the central repetitive sequences of the S mu and S gamma 1 regions. Since the common S mu-S gamma 1 sequences at the recombination sites are at most 2 bases long, typical homologous recombination cannot account for their joining. These findings provide direct evidence that mu-gamma 1 class switching can occur by the looping out and excision of chromosomal DNA, with formation of a circle. 相似文献
93.
T Fujii K Kondo F Shimizu H Sone J Tanaka T Inoue 《Applied and environmental microbiology》1990,56(4):997-1003
An integration plasmid, pIARL28, containing the ribosomal DNA gene as a homologous recombination sequence was constructed for introduction of the alpha-acetolactate decarboxylase gene into brewer's yeast. The transformation efficiency of pIARL28 was 20- to 50-fold higher than those of the other YIp vectors, as yeast cells had approximately 140 copies of the ribosomal DNA gene. All transformants showed very high alpha-acetolactate decarboxylase activity due to the multiple integrated copies of the plasmid. The transformants were grown in nonselective conditions, and segregants which had maintained the alpha-acetolactate decarboxylase expression cassette but no other vector sequences were isolated. Southern analysis showed that these marker-excised segregants contained more than 20 copies of the alpha-acetolactate decarboxylase gene and were stably maintained under nonselective conditions. Fermentation tests confirmed that the diacetyl concentration was considerably reduced in wort fermented by these marker-excised segregants. The degree of reduction was related to the copy number of the alpha-acetolactate decarboxylase gene. 相似文献
94.
A G Krainev T Shimizu K Hiroya M Hatano 《Archives of biochemistry and biophysics》1992,298(1):198-203
Some eukaryotic cytochromes P450 (P450s) have a series of ionic amino acids, corresponding to Lys250, Arg251, and Lys253 residues in the P450 1A2 sequence. To understand the roles of those ionic amino acids in the catalytic function of P450, three single mutants, Lys250Leu, Arg251Leu, and Lys253Leu of P450 1A2 were obtained from yeast (Saccharomyces cerevisiae) expression system. Turnover numbers of the Arg251Leu mutant in dealkylation reactions of methoxy- and ethoxyresorufin catalyzed by the P450 reconstituted system were remarkably increased by sixfold compared to those of the wild type. The Lys250Leu and Lys253Leu mutants also showed turnover numbers higher than those of the wild type by three- to fourfold. Those catalytic activities were inhibited competitively by pyridine derivatives, nitrogenous axial ligands to the P450 heme. From those findings together with other spectral data, it was suggested that the ionic site of Lys250, Arg251, and Lys253 may be somehow located near the substrate recognition site and/or near the axial-ligand access channel of this enzyme. 相似文献
95.
Molecular cloning and characterization of the platelet-activating factor receptor gene expressed in the human heart. 总被引:4,自引:0,他引:4
T Sugimoto H Tsuchimochi C G McGregor H Mutoh T Shimizu Y Kurachi 《Biochemical and biophysical research communications》1992,189(2):617-624
PAF decreases cardiac contractility and blood pressure. To characterize the cardiac PAF receptor, we screened a human ventricular cDNA library in a low stringency condition, using a PCR product derived from guinea pig lung PAF receptor as a probe. Four clones were obtained and named HV1-4. In Xenopus oocytes injected with cRNA derived from HV3 or 4 but not from HV1 or 2, PAF elicited a Ca(2+)-activated Cl- current. HV3 and HV4 were duplicate clones, encoding a 342 amino-acid polypeptide which was identical to that of the human leukocyte PAF receptor. However, a portion of the 5' untranslated region of HV3 (or 4) was different from that of the leukocyte receptor cDNA. Northern blotting of human ventricles and atria using the HV3 insert showed a single band of approximately 4 kb. These results suggest a tissue-specific translational mechanism responsible for regulation of the expression of the PAF receptor mRNA in these tissues. 相似文献
96.
Y Ogoma H Kobayashi T Fujii Y Kondo A Hachimori T Shimizu M Hatano 《International journal of biological macromolecules》1990,12(3):185-188
19F-n.m.r. spectra were measured to investigate the effects of Ca2+ and Zn2+ on the interaction of trifluoperazine (TFP) with three S100 proteins. It was found that TFP binds to S100a and S100ao proteins irrespective of the presence of Ca2+ and Zn2+, while in the presence of Ca2+ the apparent affinity of TFP to the proteins was greater than that in its absence or in the presence of Zn2+. In contrast, the binding affinity of TRP to S100b protein in the presence and absence of metal ions was lower than to S100a and S100ao proteins. These results suggested that TFP binds to each S100 protein in two ways: one is Ca2(+)- or Zn2(+)-dependent specific manner and another is Ca2(+)- or Zn2(+)-independent non-specific manner. 相似文献
97.
Takashi Kamaishi Tetsuo Hashimoto Yoshihiro Nakamura Fuminori Nakamura Shigenori Murata Norihiro Okada Ken-ichi Okamoto Makoto Shimizu Masami Hasegawa 《Journal of molecular evolution》1996,42(2):257-263
Partial regions of the mRNA encoding a major part of translation elongation factor 1 (EF-1) from a mitochondrion-lacking protozoan,Glugea plecoglossi, that belongs to microsporidians, were amplified by polymerase chain reaction (PCR) and their primary structures were analyzed. The deduced amino acid sequence was highly divergent from typical EF-1's of eukaryotes, although it clearly showed a eukaryotic feature when aligned with homologs of the three primary kingdoms. Maximum likelihood (ML) analyses on the basis of six different stochastic models of amino acid substitutions and a maximum parsimony (MP) analysis consistently suggest that among eukaryotic species being analyzed,G. plecoglossi is likely to represent the earliest offshoot of eukaryotes. Microsporidians might be the extremely ancient eukaryotes which have diverged before an occurrence of mitochondrial symbiosis.
Sequence availability: The nucleotide sequence data reported here appear in the GSDB, DDBJ, EMBL, and NCBI databases with the accession number D32139 相似文献
98.
Aino virus (AIV; JaNAr 28 strain) 103 TCID50/0.2 ml was inoculated in the yolk sac of 8-day-old chick embryos. Recovery and titration of the virus from various organs including the central nervous system (CNS) and skeletal muscle were performed at 2, 4, 7, 10 and 13 days after inoculation (PI). AIV was systemically disseminated and proliferated even 2 days PI. The titers of the recovered virus from the CNS and from skeletal muscle was the highest at 4 days PI and declined with time, whereas hydranencephaly, arthrogryposis and cerebellar hypoplasia developed at 7 days PI and gradually progressed until 13 days PI. 相似文献
99.
We investigated the optimum conditions for the formation of nitrile hydratase (NHase), which acts on indole-3-acetonitrile,
in Agrobacterium tumefaciens. Good inducers for enzyme formation have been found to be roughly classified into three representative types of amides such
as pivalamide, crotonamide and ɛ-caprolactam. When the strain was cultivated in the optimum culture medium containing ɛ-caprolactam
as an inducer, in particular, the specific activity of NHase in the culture was 13 000 times higher than that without addition
of amides, nitriles or acids. In this case, NHase formed accounted for 12% of the total cellular soluble protein. The purified
NHase did not act on ɛ-caprolactam, and ɛ-caprolactam was not degraded during the cultivation by the strain, suggesting that
ɛ-caprolactam seems to keep driving the NHase induction mechanism.
Received: 3 March 1995/Received revision: 13 July 1995/Accepted: 7 September 1995 相似文献
100.
Genomic imprinting of the human serotonin-receptor (HTR2) gene involved in development of retinoblastoma. 总被引:5,自引:1,他引:4 下载免费PDF全文
M. V. Kato T. Shimizu M. Nagayoshi A. Kaneko M. S. Sasaki Y. Ikawa 《American journal of human genetics》1996,59(5):1084-1090
Epidemiological and genetic studies of retinoblastoma (RB) suggested that imprinted genes might be genetically linked to the RB gene. In this study, we found that the human serotonin-receptor, HTR2, gene, which had been mapped nearby the RB gene on chromosome 13, was expressed only in human fibroblasts with a maternal allele and not in cells without a maternal allele. The 5' genomic region of the human HTR2 gene was cloned by PCR-mediated method. Only the 5' region of the gene was methylated in cells with the maternal gene, and it was not methylated in cells without the maternal gene. A polymorphism of PvuII site of the gene was also found and useful for the segregation analysis in a family of a RB patient and for analysis of loss of heterozygosity on chromosome 13 in tumor and its parental origin. These results suggest that the human HTR2 gene might be affected by genomic imprinting and that exclusive expression of the maternal HTR2 gene may be associated with the delayed occurrence of RB, which had lost the maternal chromosome 13. 相似文献