Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mediation of cellular interactions by protein (lectin)-carbohydrate recognition presupposes the expression of respective surface determinants. Due to the importance of cellular contacts between bone marrow stromal cells, recently shown to express cell surface lectins, and tumor or normal progenitor cells for biosignaling and marrow egress, quantitation of cell surface sugar receptor expression by a panel of chemically glycosylated enzymes (tetrameric E. coli beta-galactosidase) for human leukemia/lymphoma cells was initiated. Cells of the new B lymphoblastoid line Croco II that are partially positive for the CD15-specific epitope expressed receptors for various sugar specificities on their surface, fulfilling an indispensable prerequisite for establishment of glycobiological interactions. Binding studies with increasing neoglycoenzyme concentrations up to saturation in four cases disclosed values for apparent affinity constants in the range of 25-200 nM with 0.25-3 x 10(5) bound probes per cell. The presence of receptors for constituents of carbohydrate chains of cellular glycoconjugates was also ascertained biochemically, namely for beta-galactosides, alpha-mannosides, alpha-fucosides and N-acetylgalactosaminides. Expression of this property was modulated by changes in the culture conditions, as revealed by binding studies with cells, derived from growth in medium containing different serum concentrations. These findings indicate that cell surface sugar receptors of tumor cells warrant further attention with respect to recognitive interactions.
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PMID:Establishment, characterization and determination of cell surface sugar receptor (lectin) expression by neoglycoenzymes of a human myeloid marker-expressing B lymphoblastoid cell line. 171 80

We assayed in the yeast S. cerevisiae the transcriptional transactivation activity of the c-myb products encoded by a normal thymus cDNA and of an aminoterminally truncated version of it (minus 58 amino acids) corresponding to the cDNAs isolated from lymphoma and leukemia cells from different origins. Both proto-oncogene products were expressed under the control of the galactose inducible GAL10 promoter. The reporter system used to monitor the transactivation potential of the myb products consisted of a CYCl-lacZ gene fusion in which the UASCYC signals were replaced by one or multiple copies of the myb recognition element (mRE). As shown by Northern blot analyses and by primer extension experiments both c-myb products increase the level of beta-galactosidase transcription. Interestingly, the c-myb product corresponding to lymphoma cDNAs stimulates transcription four to five times more efficiently than does the normal thymic c-myb product.
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PMID:Two c-myb proteins differing by their aminotermini exhibit different transcriptional transactivation activities (yeast/reporter-effector system). 199 38

Recognition of the carbohydrate part of cellular glycoconjugates by cell-surface sugar receptors may contribute to interactions, essential to the establishment of metastases. Comparison of the properties of strongly metastatic variants to their related, less metastatic counterparts offers a generally accepted approach to the discovery of metastasis-associated characteristics. The chemically induced murine lymphoma line Eb and its spontaneously arising variant ESb with increased potential for lung and liver colonization, the virally induced lymphosarcoma cell line RAW117-P and its in vivo selected variant H10 with increased potential for liver colonization, and the B16-F1 melanoma line and its in vivo selected variant F10 with increased potential for lung colonization, were chosen. A panel of 12 types of chemically glycosylated E. coli beta-galactosidase, exposing the pivotal carbohydrate residues for specific carbohydrate-dependent cell binding, was employed to study the expression of respective cell-surface sugar receptors on these cell lines. Specific binding occurred in a non-uniform manner for the individual probes. Systematic measurements at a non-saturating ligand concentration revealed quantitative differences between the 2 cell lines of each system. However, there were no consistent changes associated with the metastatic phenotype. A similar result was obtained employing Scatchard analyses for quantitative evaluation of binding characteristics in several cases. Surface receptor expression was responsive to chemical induction of differentiation in the lymphosarcoma model. Analyses of sugar-inhibitable cell adhesion to neoglycoprotein-coated plastic wells for the lymphoma and lymphosarcoma cells revealed that the presence of cell-surface sugar receptors, even at similar densities to those defined by neoglycoenzyme binding, will not necessarily translate into an identical adhesive response. Several carbohydrates, especially N-acetyl-D-galactosamine, can differentially affect this interaction at a non-toxic concentration in both model systems.
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PMID:Analysis of cell-surface sugar receptor expression by neoglycoenzyme binding and adhesion to plastic-immobilized neoglycoproteins for related weakly and strongly metastatic cell lines of murine tumor model systems. 216 45

The post-translational processing of beta-glucuronidase in BW5147 mouse lymphoma cells is slow relative to other newly synthesized lysosomal enzymes. To characterize this slow maturation the acid hydrolase was immunoprecipitated from cells pulse-labeled with [2-3H]mannose. Radiolabeled beta-glucuronidase migrated as the precursor form of the enzyme for up to 4 h of chase, whereas another acid hydrolase, beta-galactosidase, was processed completely to its mature form within this same time period. Both beta-glucuronidase and beta-galactosidase obtained high levels of mannose 6-phosphate (Man 6-P) within 60 min of their biosynthesis. The Man 6-P content of beta-galactosidase declined rapidly during a subsequent chase while that of beta-glucuronidase remained high during the first 4 h of chase and then slowly declined. 3H-Labeled phosphorylated high mannose-type oligosaccharides isolated from beta-glucuronidase after 1 h of chase were composed primarily of species with one or two phosphodiester groups, but oligosaccharides with one and two phosphomonoesters became the predominant phosphorylated species with longer chase times. The phosphorylated oligosaccharides attached to other newly synthesized acid hydrolases, on the other hand, contained primarily phosphodiester species at all chase times. When BW5147 cells were pulsed with [3H]mannose and chased in the presence of monensin to disrupt transport, the number of phosphorylated oligosaccharides recovered from beta-glucuronidase was comparable to the quantity recovered from the enzyme produced by non-drug-treated cells. The number of phosphorylated units recovered from all other newly synthesized acid hydrolases, however, was greater in the presence of the ionophore than in its absence. Nondenaturing gel electrophoresis studies indicated that beta-glucuronidase existed in two forms at steady state within BW5147 cells and, as such, was similar to liver beta-glucuronidase in which a large percentage of the enzyme was present as a complex bound to egasyn. These data suggest that newly synthesized beta-glucuronidase produced by BW5147 cells complexes with an egasyn-like protein within the endoplasmic reticulum. This interaction retards the enzyme's migration through the secretory apparatus but does not prevent its access to Golgi-associated processing enzymes.
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PMID:beta-Glucuronidase is transported slowly to lysosomes in BW5147 mouse lymphoma cells: evidence that the prelysosomal enzyme is not restricted to the endoplasmic reticulum. 222 12

A sensitive and reproducible enzyme-linked immunosorbent assay (ELISA) has been developed using T cell hybridomas as coating antigen, for detection of Fc receptors for IgA (Fc alpha R). T-T hybridomas were generated from fusions of Fc alpha R+ T cell clones from mouse Peyer's patches with the Fc alpha R- R1.1 T lymphoma cell line. The 2 T-T hybridomas (designated Th HA) used here express Fc alpha R as determined by a rosette method and by ELISA. Th HA cells were cultured under conditions for maximum Fc alpha R expression, were added to individual wells of 96-well EIA plates, and were fixed in situ with glutaraldehyde. Plates were incubated with purified mouse monoclonal IgA, IgM or IgG1 and were developed with beta-galactosidase-coupled goat IgG antibodies specific for mouse heavy chains. Using the ELISA, both Th HA cell lines were shown to express significant levels of Fc alpha R, lower but detectable Fc mu R, and no discernible Fc gamma 1R. Interestingly, the rosette assay only allowed detection of receptors for IgA. When splenic lymphocytes were used, good Fc mu R and less Fc alpha R expression occurred on these cells as determined by ELISA and rosetting; however, no Fc gamma 1R cells were detected by either method. Thus, the ELISA is sensitive and reproducible, and allows an objective measurement of FcR expressed on T cells.
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PMID:An enzyme-linked immunosorbent assay (ELISA) for detection of Fc alpha receptors on isotype-specific T cells. 293 84

The 3'-terminal regions of the human T-cell leukemia virus I (HTLV-I) and HTLV-II genomes encode a novel gene product. We showed that expression of this region fused to the beta-galactosidase gene in bacteria produces a protein recognized by adult T-cell leukemia-lymphoma patient sera. Rabbit antibodies raised against this protein specifically precipitated the 42-kilodalton x-lor gene protein from HTLV-I-infected cells.
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PMID:Expression of the x-lor gene of human T-cell leukemia virus I in Escherichia coli. 299 73

The myc gene has been implicated in the genesis of various neoplasms in birds, mice, and humans and was originally identified as the cellular homologue of the transforming gene (v-myc) of the avian myelocytomatosis virus MC29. For specific antisera to be obtained for the myc gene product, a bacterial expression vector was constructed in which the coding sequences for approximately 20 kd of MC29 p110gag-myc (amino acid residues 502 to 678) were placed between the coding sequences for the amino terminal 13 kd of Rous sarcoma virus pp60src and the coding sequences for 112 kd of beta-galactosidase. Expression of this tripartite gene was driven by a hybrid trp-lac promoter under lac repressor control. Induction of expression resulted in the production of a 145-kd hybrid protein containing src, myc, and beta-galactosidase sequences. The hybrid protein was purified and injected into rabbits to produce antisera. The resultant antisera immunoprecipitated p110gag-myc and p58myc -p60myc from MC29- and MH2-infected nonproducer quail fibroblasts, respectively. In addition, the antisera also immunoprecipitated a 58-kd protein from the bursal lymphoma cell line BK25, which was identified as chicken c (cellular)-myc gene product.
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PMID:Isolation of antibodies specific for avian viral and cellular myc proteins. 299 37

To study metastasis at the single-cell level we transduced highly metastatic ESb lymphoma cells with a retroviral expression vector containing the lacZ (bacterial beta-galactosidase) gene. This allowed single ESb-lacZ tumor cells to be detected in infiltrated target organs by means of X-Gal staining. Despite expression of the lacZ gene, the tumor cells were still tumorigenic, highly metastatic, unchanged in phenotype and therefore comparable to parental ESb cells. After spontaneous metastasis, whole-organ staining revealed metastatic foci at the surface of the liver. In histological liver sections, metastatic clusters and single dispersed tumor cells could be detected. In contrast to whole-organ staining, histological examination revealed scattered distribution of tumor cells throughout the organ, which was not evident with parental ESb cells. In addition, clusters with diffuse or dense (focal) appearance were found, in correlation with the whole-organ staining. Expression of the foreign lacZ gene allowed the metastatic spread of tumor cells to liver and spleen to be quantified approximately by FACS analysis. Furthermore, it was shown that the newly expressed beta-gal was expressed not only intercellularly but also at the cell surface. There it could be recognized by MAbs and cytotoxic T-cells (CTL). beta-gal did not affect CTL recognition of the ESb tumor-associated antigen. In conclusion, lacZ could be used as a genetic marker for a highly metastatic lymphoma, to define scattered metastatic spread in the liver at the single-cell level and to quantify the tumor load by FACS analysis.
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PMID:Scattered micrometastases visualized at the single-cell level: detection and re-isolation of lacZ-labeled metastasized lymphoma cells. 751 21

Rat natural killer cell Met-ase-1 (RNK-Met-1) is a 30,000 M(r) serine protease (granzyme) found in the cytolytic granules of CD3- large granular lymphocytes (LGL) with natural killer (NK) activity. To characterize the genomic sequences responsible for the CD3- LGL-restricted expression of this gene, we screened a rat genomic library with RNK-Met-1 cDNA, and obtained bacteriophage clones that contained the RNK-Met-1 gene. The RNK-Met-1 gene comprises 5 exons and spans approximately 5.2 kilobases (kb), exhibiting a similar structural organization to a class of CTL-serine proteases with protease catalytic residues encoded near the borders of exons 2, 3, and 5. The 5'-flanking region of the RNK-Met-1 gene contains a number of putative promoter and enhancer regulatory elements and shares several regions of homology with the 5'-flanking region of the mouse perforin gene. We have prepared nested deletions from approximately 3.3 kb of the 5'-flanking region of the RNK-Met-1 gene, and inserted these upstream of the chloramphenicol acetyltransferase (CAT) reporter gene. These 5'-flanking RNK-Met-1-CAT constructs were transiently transfected into rat LGL leukemia, T-lymphoma, and basophilic leukemia cell lines. The transcriptional activity of the RNK-Met-1 5'-flanking region was strong, restricted to the RNK-16 LGL leukemia and controlled by several positive cis-acting regions spread over at least 3.3 kb. The longest and most active 5'-flanking region (-3341 to -33) was also used to drive specific expression of beta-galactosidase in RNK-16. These data are consistent with the NK cell-specific expression of RNK-Met-1 and suggest the potential utility of this gene promoter in the development of transgene models of NK cell biology in vivo.
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PMID:Cloning and characterization of a novel NK cell-specific serine protease gene and its functional 5'-flanking sequences. 760 1

CD28 is a 44 kDa Ig superfamily cell surface molecule expressed on most mature T cells. Through its interaction with the recently identified B7/BB1 counter-receptor, it is believed to play an important role as a co-stimulator of T cells along with the TCR-CD3 complex. Activation of T cells with CD28 mAbs synergizes with TCR-CD3 and CD2 stimulation, resulting in long term T cell proliferation, differentiation of cytotoxic T cells and production of large amounts of cytokines. In order to further delineate the role of CD28 in signal transduction and T cell activation, human CD28 was transfected into CD3+ murine T cell hybridomas. High levels of cell surface CD28 expression was achieved by protoplast fusion. The transfected molecule retained all the native CD28 mAb epitopes found on human T cells. In these transfectants, CD28 mAbs, similarly to CD3 mAbs, were able to induce Ca2+ mobilization, IL-2 promoter induction (measured as beta-galactosidase activity in T cells hybridomas pre-transfected with the IL-2-lac Z reporter gene), IL-2 secretion, TNF alpha production and apoptosis (observed as growth arrest and genome fragmentation). The parental host cells, or cells transfected with vector alone, responded only to mAbs to CD3. IL-2 secretion in the transfectants was obtained using either an IgM mAb to CD28 or IgG mAbs presented on the surface of IgG-FcR+ B lymphoma cells. Optimal activation via CD28 was inhibited by suboptimal concentrations of soluble CD3 mAb, suggesting an interaction between the two pathways. The immunosuppressive drugs Cyclosporin A and FK506 completely blocked CD28 and CD3 mediated IL-2 production in these transfectants whereas rapamycin had only a partial inhibitory effect. Finally, since the transfected human CD28 molecule confers full functional responsiveness to the murine T cell hybridomas without the need for costimulators such as PMA, this model is ideal for studying the structure-function relationships of the CD28 molecule as well as the transmembrane and cytoplasmic associations implied in CD28 signaling.
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PMID:Functional expression of human CD28 in murine T cell hybridomas. 830 98


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