Nodular sclerosing Hodgkin's disease and large cell lymphoma. Immunophenotypic characterization of a composite case

Composite lymphomas have rarely been reported in Hodgkin's disease (HD), except in the lymphocyte predominance sub-type, and immunohistochemical investigations have been performed in only few cases. We describe the histological and immunophenotypical findings in a case of composite nodular sclerosing HD and high-grade, large cell non-Hodgkin's lymphoma (NHL). In our case HD and NHL cells displayed striking morphological and immunophenotypical divergence, suggesting a lack of correlation between the two neoplasms.

Effects of S-carboxymethyl-L-cysteine on pulmonary sialyl transferase activity in vitro, in healthy and in sulphur-dioxide-induced bronchitic rats

S-carboxymethyl-L-cysteine (carbocysteine) improves the visco-elastic properties of bronchial mucus in vivo, possibly as a result of an increase in the relative proportions of sialomucins in bronchial mucus. Carbocysteine was therefore studied in vitro and ex vivo in both normal and bronchitic rats on pulmonary sialyl transferase, responsible for the addition of sialic acid to mucus glycoproteins. Bronchitis was induced in male Sprague-Dawley rats by repeated exposure to sulphur dioxide for two weeks. During this time they received either 500 mg kg-1 day-1 carbocysteine or its vehicle by the oral route. Rats not being exposed to SO2 received the same treatment. The animals were then killed, and subcellular fractions prepared by differential centrifugation of lung homogenates. Sialyl transferase was assayed using CMP-14C sialic acid as substrate and desialysed fetuin as exogenous acceptor. Enzyme activity was located in both the (Golgi-containing) 10,000 g and 100,000 g pellets with minor activity in the cytosolic supernatants. When tested in vitro between 10(-6) and 10(-3) M, carbocysteine had no effect on sialyl transferase activity in microsomes taken from healthy or bronchitis rats. Repeated administration of carbocysteine was without effect on the sialyl transferase activity in 10,000 g pellets taken from healthy rats. However, in bronchitic rats there was a small but statistically significant (P less than 0.05) increase in enzymic activity in the treated group compared to the animals receiving the vehicle. There was no difference in the activity of the microsomal enzyme compared to vehicle-treated controls in either healthy or bronchitic rats. We conclude that it is possible that an increase in sialyl transferase activity in a Golgi-containing fraction of bronchitic lungs could explain the relative increase in sialomucins in bronchitic subjects.

Assay of sialyltransferase activity by reversed-phase ion-pair high-performance liquid chromatography

Sialyltransferases (CMP-N-acetylneuraminic acid:glycoprotein sialyltransferases, EC 2.4.99.1) are involved in the transfer of a sialic acid moiety from CMP-N-acetylneuraminic acid (CMP-NeuAc) to an oligosaccharide side-chain of an acceptor, asialoglycoprotein (AGP), according to the following reaction: CMP-NeuAc + AGP----NeuAc-O-AGP + CMP. This enzyme occurs in elevated levels in the sera of patients with a wide variety of neoplastic diseases and its assay might be useful in monitoring treatment. Radioactive CMP-NeuAc has been used in assays and the radioactive sialylated product separated and counted by liquid scintillation spectrometry. This study shows that a simple, rapid, non-radiochemically based high-performance liquid chromatographic method developed for the analysis of CMP-sialic acid synthetase can be used for the quantitation of sialyltransferase activity by monitoring simultaneously the utilization of CMP-NeuAc and the release of CMP. We describe the application of this method to assay of commercially available sialyltransferase activity and to activities from synovial, ascites and gastric fluids.

Comparison of sialyl- and alpha-1,3-galactosyltransferase activity in NIH3T3 cells transformed with ras oncogene: increased beta-galactoside alpha-2,6-sialyltransferase

Previous studies have indicated that transfection of NIH3T3 cells with the ras oncogene induced modifications of the terminal glycosylation of N-linked glycans which appeared in the early stage after transfection. These changes affected especially the terminal part of N-linked glycans which is substituted with alpha-1,3-Gal residues in NIH3T3 and with Neu5Ac residues in the ras-transformed counterpart. We have transformed NIH3T3 cells with the human c-Ha-ras oncogene, evaluated tumorigenicity and metastatic capacity in vivo and compared alpha-1,3-galactosyltransferase, alpha-2,3- and alpha-2,6-sialyltransferases activities. By using different specific acceptors, we detected the enhancement of sialic acid transfer in transformed cells while the activity of alpha-1,3-galactosyltransferase remained unchanged. We showed that the higher sialyltransferase activity was due to the increase of beta-galactoside alpha-2,6-sialyltransferase in ras-transfectant although alpha-2,3-sialyltransferase was weakly expressed in these cells. On the basis of binding of different lectins, we correlated these observations with changes of protein glycosylation. We concluded that altered glycosylation of ras-transformed NIH3T3 is the result of a competitive effect of the enzymes acting for terminal glycosylation of N-linked glycans and the reflection of the higher expression of alpha-2,6-sialyltransferase.

[Sialyltransferase activity in the spermatic membrane and its relation to human fertility and sterility]

Sialyltransferase activity was determined on normospermic men sperm cells (greater than 80 x 10(6) sperm/ml and 75% motility) and oligospermic infertile sperm cells (less than 20 x 10(6) sperm/ml and less than 20% motility) and asthenospermic (greater than 40 x 10(6) sperm/ml and less than 10% motility). Sialytransferase activity is quantified by means of the transference of radioactivity of CMP-3H-sialic acid toward the exogenous acceptor (asialofetuin). The enzyme substrate complexes formed in presence of phosphotungstic acid result precipitated insoluble, which was retained on glass fiber filter. The sialyltransferase activity decrease in oligospermic sperm cells 62 +/- 3% and in the asthenospermic decreased 57 +/- 4% with respect normospermic sperm cells. The decrement on sialyltransferase activity in the infertile sperm, permits to assume that this enzyme probably participates as a direct cause of its pathology with detrimental structural and functional integrity of the plasma membrane.

Radioimmune assay of sialyltransferase and N-acetylgalactosaminyltransferase activities using specific antibodies on a 96-well filtration plate of a multiscreen assay system

A new assay method for glycosphingolipid glycosyl-transferase activities was developed using a 96-well filtration plate of a MultiScreen assay system. An acceptor glycosphingolipid and a donor radioactive nucleotide sugar were incubated with an enzyme source in a well of the filtration plate. After incubation, both identification and quantification of the reaction product were carried out simultaneously using a specific antibody for the product which was trapped on a filtration membrane of the plate as a complex with Staphylococcus aureus protein A (IgGSorb). This assay method was used for determining the activity of cytidine 5'-monophosphate-N-acetylneuraminic acid:Lcn4Cer alpha 2----6sialyltransferase and uridine 5'-diphosphate-N-acetyl galactosamine:GM3 N-acetylgalactosaminyltransferase. In addition to the simple and rapid identification and quantification of the product, this method proved to be as reliable and sensitive as the previously published assay procedures. Furthermore, this assay method can be used with a high concentration of detergent which should not be used in the other procedures described previously using enzyme-linked immunosorbent assay methods on a 96-well multiplate even if the enzyme reaction might require a certain percentage of the detergent concentration.

Expression of the CDw75 (beta-galactoside alpha 2,6-sialyltransferase) antigen on normal blood cells and in B-cell chronic lymphocytic leukaemia

Using monoclonal antibodies (mAb) characterized at the last International Workshop on Human Leucocyte Antigens, we examined the expression of CDw75 antigens (beta-galactoside alpha 2,6-sialyltransferase) on normal peripheral blood cells and on cells from patients with B-cell chronic lymphocytic leukaemia (CLL). The mAb used (HH2, EBU.65, EBU.141 and OKB4) detect different epitopes of CDw75. Normal peripheral blood B cells expressed high levels of CDw75 detectable with HH2, EBU.65 and EBU.141 but did not react with OKB4. Cells from patients with B-cell CLL closely resembled normal B cells. All CDw75 epitopes, including OKB4, were strongly expressed on some Namalwa variant Burkitt lymphoma cell lines. The OKB4 epitope was also present on red cells from all normal donors. The other CDw75 mAb were unreactive with red cells from some normal donors. The CDw75 epitope detected with EBU.65 was present on most CD4+ T cells and on a minority of CD8+ cells. HH2 and EBU.141 stained only small numbers of T lymphocytes. OKB4 did not react with T cells. EBU.65+, CD4+ T cells had low levels of expression of CD45R0, CD29, CD54 and CD58, and had high levels of CD45RA antigen. Phytohaemagglutinin (PHA) activation of cells led to the loss of EBU.65 binding. These results suggest that the CDw75 epitope recognized by the EBU.65 mAb is a marker of native T lymphocytes. On B CLL cells the epitopes detected with HH2, EBU.65 and EBU.141 were destroyed by treatment with neuraminidase. Treatment of B-CLL cells and red cells with neuraminidase increased the binding of OKB4, suggesting that this epitope is masked by sialic acid. The results suggest that CDw75 is a sialylated cell-surface antigen expressed in a number of tissue-specific isoforms.

Enzymic control of the expression of the X determinant (CD15) in human myeloid cells during maturation: the regulatory role of 6-sialytransferase

To establish the basis for the reduced expression of the X determinant on leukemic blasts and the changes in antigenic expression that occur during myeloid maturation, the presence on myeloid cells of X and related structures was examined in conjunction with studies on the activities of the glycosyltransferases involved in their biosynthesis. Expression of X and sialyl-X was weak on blasts in comparison with neutrophils despite the presence of the requisite precursor structures. Much higher levels of 3-fucosyltransferase activity were found in blasts than in neutrophils when nonsialylated substrates were used, but, whereas the enzyme in neutrophils reacted equally well with 3'-sialylated and nonsialylated acceptors, the enzyme in blasts showed a marked preference for nonsialylated substrates. 6'-Sialyltransferase activity was strong in blasts but was not detectable in neutrophils, whereas a much lower level of 3'-sialyltransferase activity was present in both blasts and neutrophils. Dimethyl sulfoxide-induced maturation of HL60 cells was associated with (1) a decrease in both 6'-sialyltransferase and 3-fucosyltransferase activities, (2) a change in the substrate specificity of 3-fucosyltransferase towards that found in mature cells, and (3) increased cell surface expression of sialyl-X. These results suggest that the reduced expression of X in myeloblasts is related to the presence of the strong 6'-sialyltransferase, which uses the precursor substrate at the expense of the 3-fucosyltransferase and prevents the synthesis of X and sialyl-X. The developmental regulation of the levels of 3'- and 6'-sialyltransferases, and the level and specificity of the 3-fucosyltransferases, therefore controls the expression of X and its degree of sialylation.

Expression of aberrant O-glycans attached to leukosialin in differentiation-deficient HL-60 cells

Promyelocytic leukemia HL-60 cells can be induced to differentiate into granulocytic cells by various agents including retinoic acid (RA), dimethyl sulfoxide, and 6-thioguanine (6-TG). Although the induced cells are no longer capable of proliferation, a few cells continue to divide in the presence of inducers, and these cells are resistant to terminal differentiation by these inducers (R. E. Gallagher, D. A. Giangiulio, C-S. Chang, C. J. Glover, and R. L. Felsted, Blood, 68: 1402-1406, 1986). The present study examined the structures of O-glycans attached to leukosialin, a major sialoglycoprotein in HL-60 cells, and the activities of glycosyltransferases involved in O-glycan synthesis. Leukosialin from RA-resistant and 6-TG-resistant HL-60 sublines migrated much more slowly than those from wild-type HL-60 cells when applied to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The dimethyl sulfoxide-resistant HL-60 subline, on the other hand, expressed leukosialin with a molecular weight similar to wild-type HL-60 cells. RA-resistant and 6-TG-resistant HL-60 cells were found to express a significant amount of tetrasaccharides that contain no sialic acid residue, while wild-type HL-60 cells expressed mainly disialosyl hexasaccharides and contained no detectable amount of asialo-oligosaccharides. Furthermore, wild-type HL-60 cells treated with the inducers for 4 days were found to express the same saccharides present in untreated wild-type HL-60 cells, indicating that the altered O-glycans present in RA and 6-TG sublines were not caused by a direct effect of these agents but rather are intrinsically unique to these sublines. To better understand the mechanisms underlying the differences in O-glycans, the activities of four sialyltransferases were measured: Gal beta 1----3GalNAc alpha 2----3sialyltransferase, Gal beta 1----4(3) GlcNAc alpha 2----3sialyltransferase, Gal beta 1----4GlcNAc alpha 2----6sialyltransferase, and GalNAc alpha 2----6sialyltransferase. Among them, Gal beta 1----3GalNAc alpha 2----3sialyltransferase and Gal beta 1----4(3)GlcNAc alpha 2----3sialyltransferase were much lower in the RA- or 6-TG-resistant HL-60 subline than in wild-type HL-60 cells. These findings indicate that the differences in O-glycans are due to the differences in alpha 2----3sialyltransferase activities. These results strongly suggest that O-glycans associated with leukosialin may play some role in HL-60 cell differentiation.

Changes in the ganglioside composition of human neuroblastoma cells under different growth conditions

The ganglioside composition of human neuroblastoma cells (LA-N-1 and LA-N-5) was studied in samples obtained from (1) original cells in tissue cultures, (2) tumors grown in nude mice inoculated with original cells and (3) cells in tissue cultures re-established from the mouse tumors. The amounts of "a" pathway gangliosides (GM2, GM1 and GD1a) and those of the "b" pathway (GD3, GD2, GD1b and GT1b) differed according to the culture conditions. The "b" pathway gangliosides were markedly increased in the tumors grown in nude mice. In contrast, the "a" pathway gangliosides were abundant in cultures of both original and re-established cells. We also measured the enzymatic activities of UDP-N-acetylgalactosamine: GM3, N-acetylgalactosaminyl transferase (EC 2.4.1.92) and of CMP-N-acetylneuraminic acid: GM3 sialyl transferase (EC 2.4.99.8) in neuroblastoma cells cultured under these conditions. These enzymes are thought to be the key enzymes involved in the synthesis of the "a" and "b" pathway gangliosides. Though there was no significant difference in the activity of N-acetylgalactosaminyl transferase between original cells and tumors in nude mice, re-established cells showed a definitely higher activity (3.5 times higher than in the original cells). On the other hand, tumors grown in nude mice had a markedly higher activity of sialyl transferase than that of original cells or re-established cells. These findings suggest that the culture conditions and/or the type of cell growth play some role in the synthesis and expression of gangliosides in neuroblastoma cells.

Glycolipids and glycosyltransferases in permanent cell lines established from human medulloblastomas

Medulloblastoma biopsies are heterogenous and might contain normal brain tissue, which limits the usefulness of such tumor material for biochemical analyses. We have, therefore, examined the gangliosides and their metabolism using the medulloblastoma cell lines. Daoy and D341 Med, cultured both in vitro and as xenografts in nude mice. The ganglioside patterns in the Daoy showed a switch from a high GM2, 70% (mol% of total ganglioside sialic acid) and low lactoseries gangliosides (2%) content in monolayer cultures, to a high proportion of lactoseries gangliosides (50%) and virtually no GM2 (1%) in xenografts, but an increased proportion of other a-series gangliosides. The D341 Med showed a similar change regarding the lacto-series gangliosides from 1% in suspension culture to 10% in xenografts. The activity of five glycosyltransferases, GM3, GD3, GM2, GM1 and LA2 synthases, did not parallel the ganglioside patterns and could not account for the noted variations therein. In the Daoy cell line the LA2 synthase as well as the GM2 synthase activity was relatively high in both culture systems, despite the marked difference in the expression of GM2 and the lactoseries gangliosides. These results suggest that environmental factors play a crucial role for the in vivo activity of the glycosyltransferases.

Sialyltransferase activity in AF10 myeloma cell line

A STA was observed in a human-derived myeloma cell line, AF10, that produces IgE paraprotein. The STA in the culture medium of the AF10 myeloma cell line was associated in the 24 to 48 hr period of incubation with IgE biosynthesis, and increased thereafter up to 72 hr, while IgE remained stable. These data support our previous observations that human myeloma cells are associated with a relatively high production of sialyltransferase, which is released to the medium, presumably by a mechanism of shedding.

A highly sensitive fluorometric assay for sialyltransferase activity using CMP-9-fluoresceinyl-NeuAc as donor

This paper presents a very sensitive fluorometric assay for sialyltransferase activity based on the transfer of 5-acetamido-9-deoxy-9-fluoresceinylthioure-idoneuraminic acid onto distinct glycoproteins, thus allowing determination of acceptor specificities. Acceptor protein-bound fluorescence was quantified after gel filtration which separated fluorescent sialoglycoprotein from the fluorescence-labeled CMP-glycoside donor. Kinetic constants obtained for five different purified sialyltransferases indicated that CMP-9-fluoresceinyl-NeuAc was a suitable donor substrate for each enzyme, affording low Km values and Vmax values comparable in magnitude (15-100%) to that obtained with the parent CMP-NeuAc. Sensitivity was enhanced 200- to 1000-fold compared to the radiometric sialyltransferase assay as it is used routinely. The method was applied to determination of the kinetic properties of purified rat liver alpha 2,6-sialyltransferase with four separate glycoprotein acceptors differing in glycan structure, employing very small amounts of donor, acceptor, and enzyme, and to the study of sialyltransferase activity of the human promyelocytic cell line HL-60 toward three different acceptors.

Direct assay of glycosphingolipid glycosyltransferase activities on thin-layer chromatogram

A modified method for the determination of glycosphingolipid glycosyltransferase activity using high-performance thin-layer chromatographic (HPTLC) plates has been developed. An acceptor glycosphingolipid was chromatographed on an HPTLC plate and was incubated with an enzyme mixture and an appropriate radioactive sugar nucleotide. After incubation, the plate was washed with phosphate buffer and 2% Tween 80. The radiolabeled reaction product was scrapped off the plate and the radioactivity determined using a liquid scintillation counter or, alternatively, the plate was exposed to an X-ray film to reveal the radioactive product. We have used this assay method to determine the activities of rat brain cytidine 5'-monophosphate-N-acetylneuraminic acid: LacCer-, GM3-, GM1-, or GD3-sialyltransferases. This method is sensitive, fast, and reliable and is capable of assaying simultaneously the activities of glycosyltransferases with multiple acceptor specificity. It should be useful in monitoring the enzyme activities present in various column fractions during chromatographic fractionation of glycosyltransferases with different substrate specificities.

Cell surface sialoprotein alterations in metastatic murine colon cancer cell lines selected in an animal model for colon cancer metastasis

Alterations in cell surface proteins and glycoproteins may play a key role in determining the metastatic behavior of tumor cells. The cell surface proteins of a series of related murine colon cancer cells selected in an animal model for colon cancer metastasis (R. S. Bresalier et al., Cancer Res., 47: 1398-1406, 1987) were therefore compared by a variety of biochemical methods. Lactoperoxidase-catalyzed iodination of cell surface proteins followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated quantitative and qualitative differences in the cell surface protein profiles of parental cell line 51B (low metastatic potential) and its metastatic derivatives 51B LiM 5 and 51B LiM 6. Labeling of sialic acid-containing proteins suggested that, in the case of at least four of these proteins (Mr 170,000, 120,000, 95,000, and 55,000), this represented an increase in radioactive labeling of sialoglycoproteins from the metastatic lines. Affinity chromatography of solubilized 125I-labeled cell membrane proteins revealed a 2- to 3-fold increase in wheat germ agglutinin and Sambucus nigra lectin binding associated with the metastatic lines, compared to the poorly metastatic parent. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of material eluted from these columns demonstrated enhancement of proteins from the metastatic cells corresponding in molecular weight to the previously identified major sialoglycoproteins. Neuraminidase-releasable membrane-associated sialic acid and sialyltransferase activities were 2- to 3-fold higher in the metastatic cell lines compared to the parental line. Liver colonization after intrasplenic injection of the various lines into syngeneic mice was dramatically reduced by prior removal of cell surface sialic acid. Immunohistochemical staining of primary and metastatic tumors formed after cecal injection of parental 51B suggested selective metastasis by wheat germ agglutinin-binding tumor cells. These results further support the concept that cell membrane sialylation is important in determining the metastatic potential of cancer cells.

An assay method for ganglioside synthase using anion-exchange chromatography

A rapid procedure which is based on combined ion-exchange chromatography and solubility was established for determination of the activity of ganglioside synthases and cerebroside sulfotransferase. The procedure consists of selective elution of radiolabeled reaction products (acidic glycolipids) freed from labeled precursors and breakdown products on a DEAE-Sephadex column and of direct radioassay of the products in the eluate. Monosialogangliosides were eluted from the column with 40 mM ammonium acetate (AcONH4) in methanol, cerebroside sulfate with 90 mM AcONH4 in methanol, and disialogangliosides with 40 mM AcONH4 in isopropanol/n-hexane/water (55/20/19, v/v/v). The established procedure is simple, reproducible, and economical. Using rat Golgi membrane as enzyme source the recovery rate of the products was over 95%.

Increased CMP-NeuAc:Gal beta 1,4GlcNAc-R alpha 2,6 sialyltransferase activity in human colorectal cancer tissues

The sialyltransferase activities of 10 human colorectal specimens were compared with those of the corresponding adjacent normal mucosa. Using asialofetuin as an acceptor we found, in tumor tissues of 9 out of 10 patients, an increased sialyltransferase activity towards the N-linked chains as determined upon peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase (PNGase) treatment. On the contrary, the activity towards the O-linked chains was not significantly changed. When the specificity of the sialyltransferase acting on N-linked chains was investigated by using N-acetyl-lactosamine (Gal beta 1,4GlcNAc) as an acceptor, we found that the alpha 2,6 sialyltransferase activity expressed by both normal and tumor colorectal tissues was far higher than the alpha 2,3-activity and that alpha 2,6 was the only sialyltransferase activity increased in tumor tissues. Kinetic analysis revealed that normal and tumor alpha 2,6 sialyltransferases have the same apparent Km for the acceptor substrate (469 and 465 microns), but normal enzyme has a higher Km for CMP-NeuAc (303 microns) than the tumor enzyme (50 microns). The higher affinity of tumor enzyme for the nucleotide-sugar might partially explain its increased activity in tumor tissues. In addition, tumor tissues contain a lower amount of sialic acid despite the increase in alpha 2,6 sialyltransferase activity.

Sialyltransferase activity in plasma cells of multiple myeloma

A marked elevation of sialyltransferase activity (STA) was observed in a solid tumor of plasma cells, which had been removed from a patient with multiple myeloma (MM), as compared to normal lymphatic tissues. STA was also determined in mononuclear bone marrow cells of 10 patients with MM and found to be 12 times higher than that of bone marrow mononuclear cells from 5 patients with non-malignant disorders (with less than 1% plasma cells in the bone marrow aspirate). A significant correlation was found between STA and the number of plasma cells in the bone marrow aspirate.

Measurement of sialyl-transferase activity in isolated colonic mucosal cells of the rat

An assay for sialyl-transferase activity in isolated rat colonic mucosal cells has been developed. Total and specific activity with asialobovine sub-mandibular gland glycoprotein and endogenous substrates was approximately two-fold higher in the proximal, relative to the distal, colon. These activities were similar when asialo-alpha-acid glycoprotein was used as substrate. Endogenous activity was approximately 10-fold lower than with exogenous substrates in both proximal and distal colonic segments. Analysis of total and specific sialyl-transferase activity up to 7 weeks after jejunoileal bypass (JIB) and sham operation showed a marked increase at the first week, decreasing toward normal by week 7. Similar differences between proximal and distal colon, and with the type of substrate, were found with both groups of operated animals. Histochemical analysis showed small elevation after 1 week for sialo and sulphomucins after the JIB operation only.

Anabolic sialosylation of gangliosides in situ in rat brain cortical slices

Radiolabeling of the sialic acid residues of gangliosides was examined in thin slices of rat brain cerebral cortex incubated under physiologic conditions in the presence of either [14C]N-acetyl-mannosamine (ManNAc) or cytidine 5'-monophosphoryl-[14C]N-acetyl-neuraminic acid (CMP-NeuAc). CMP-NeuAc is the direct donor substrate in the transfer of sialic acid to gangliosides by sialosyl transferases (SATs), including ectosialosyl transferases at the cell surface. ManNAc must be internalized by the neural cells (neuronal or glial) where it serves as an obligate precursor for the biosynthesis of the NeuAc moiety of intracellular CMP-NeuAc, via multiple reactions in the cytosol and nucleus. When exogenous [14C]ManNAc was supplied, there appeared to be a 2-h lag period before label was incorporated measurably into ganglioside sialic acid. That was followed by rapid ganglioside labeling continuing up to 6 h. There was high incorporation into ganglioside GM1. Labeling by ManNAc was inhibited by monensin, a monovalent cationophore that blocks anabolic transport in medial and trans Golgi. Extracellular CMP-NeuAc was not internalized by the cells. CMP-[14C]NeuAc labeling of gangliosides had no lag period, reached a maximum within 2 h, and then began to level. The label distribution among gangliosides was high in GD3, but quite low in GM1. CMP-NeuAc labeling was not inhibited by 10(-7) M monensin. These findings support a model in which ManNAc labels gangliosides by an intracellular route involving monensin-sensitive, Golgi-associated SATs. In this intracellular system, the major labeled products are gangliosides of the gangliotetraosyl series (GM1, GD1a, etc.).(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for an O-glycan sialylation system in brain. Characterization of a beta-galactoside alpha 2,3-sialyltransferase from rat brain regulating the expression of an alpha-N-acetylgalactosaminide alpha 2,6-sialyltransferase activity

We present evidence for the existence in rat brain of several sialyltransferases able to sialylate sequentially asialofetuin. [14C]Sialylated glycans of asialofetuin were analyzed by gel filtration. Three types of [14C]sialylated glycans were synthesized: N-glycans and monosialylated and disialylated O-glycans. The varying effects of N-ethylmaleimide, lysophosphatidylcholine (lysoPtdCho) and trypsin, were helpful in the identification of these different sialyltransferases. One of them, selectively inhibited by N-ethylmaleimide, was identified as the Neu5Ac alpha 2----3Gal beta 1----3GalNAc-R:alpha 2----6 sialyltransferase previously described [Baubichon-Cortay, H., Serres-Guillaumond, M., Louisot, P. and Broquet, P. (1986) Carbohydr. Res. 149, 209-223]. This enzyme was responsible for the synthesis of disialylated O-glycans. LysoPtdCho and trypsin selectively inhibited the enzyme responsible for the synthesis of monosialylated O-glycan. N-ethylmaleimide, lysoPtdCho and trypsin did not inhibit Neu5Ac transfer onto N-glycans, giving evidence for three different molecular species. To identify the enzyme responsible for monosialylated O-glycan synthesis, we used another substrate: Gal beta 1----3GalNAc--protein obtained after galactosylation of desialylated ovine mucin by a GalNAc-R:beta 1----3 galactosyltransferase from porcine submaxillary gland. This acceptor was devoid of N-glycans and of NeuAc in alpha 2----3 linkages on the galactose residue. When using N-ethylmaleimide we obtained the synthesis of only one product, a monosialylated structure. After structural analysis by HPLC on SAX and SiNH2 columns, we identified this product as Neu5Ac alpha 2----3Gal beta 1----3GalNAc. The enzyme leading to synthesis of this monosialylated O-glycan was identified as a Gal beta 1----3GalNAc-R:alpha 2----3 sialyltransferase. When using lysoPtdCho and trypsin, sialylation was completely abolished, although the Neu5Ac alpha 2----3Gal beta 1----3GalNAc-R:alpha 2----6 sialyltransferase was not inhibited. We provided thus evidence for the interpendence between the two enzymes, the alpha 2----3 sialyltransferase regulates the alpha 2----6 sialyltransferase activity since it synthesizes the alpha 2----6 sialyltransferase substrate.

Rapid assay of beta-galactosidase and sialyltransferase by lectin affinity high performance liquid chromatography with fluorescence detection

Fluorescein isothiocyanate (FITC)-labelled asialotransferrin and pyridyl aminated oligosaccharides were prepared from asialotransferrin and human milk using affinity chromatography and high performance liquid chromatography (HPLC), respectively. These substances were incubated with galactosidase or sialyltransferase and then examined by lectin affinity HPLC. The elution patterns changed according to the period of incubation and amount of enzyme. This analytical method using lectin affinity HPLC with fluorescence labelled glycoprotein or oligosaccharides as the substrates has great value for detecting these enzyme under the same chromatographic conditions. In addition, differences were noted in the activity of beta-galactosidase toward oligosaccharides having the Gal beta(1----3)GlcNAc or Gal beta(1----4)GlcNAc structure at reducing termini.

Neutral and sialosyl glycosphingolipid composition and metabolism of human T-lymphoblastic cell line MOLT-3 cells: distinctive changes as markers specific for their differentiation

Changes in the composition and metabolism of glycosphingolipid (GSL), which is one of the cell surface constituents, during cell differentiation of human T-lymphoblastic leukemia cell line MOLT-3 cells were examined with special reference to their alterations in E rosette-forming capacity and expression of surface antigens specific for T-cell lineage. Three molecular species of neutral GSL and greater than or equal to 13 molecular species of acidic sialosyl-GSL (ganglioside) were detectable on high-performance thin-layer chromatography (HPTLC) in untreated MOLT-3 cells. The major components were ceramide monohexoside and gangliosides GM3 and GD1a. When the cells were induced by 12-O-tetradecanoyl phorbol 13-acetate (TPA) to differentiate into more mature T cells, the ganglioside composition changed distinctively, and the total ganglioside content increased considerably; mono-, di-, and tri-sialosyl gangliosides concomitantly showed significant increase, but no new molecular species of GSL specific for the differentiation were detected. The activity of one sialyltransferases, CMP-sialic acid:CDH sialyltransferase, which synthesizes ganglioside GM3 and the total sialic acid content of the cell surface, parallelled the extent of cell differentiation. Examination of another human T-lymphoblastic leukemia cell line, HPB-ALL, indicated that TPA could also induce the cells to differentiate along T-cell lineage and that changes in the ganglioside pattern during differentiation are similar to those of MOLT-3 cells. The results indicate that human T-lymphoid cell differentiation intimately involves elongation of neutral oligosaccharide-moieties and the addition of sialic acid residues to gangliosides, resulting in more mature T cells containing higher gangliosides. Both the sialyltransferase activity and the sialic acid content, as well as the ganglioside pattern, might be new biochemical markers specific for human T-lymphoblastic cell differentiation.

Comparative study of the levels of sialyltransferases responsible for the formation of sugar chains in glycoproteins and gangliosides in rat liver and hepatomas

Sialyltransferases responsible for the formation of sugar chains in glycoproteins were studied in rat hepatoma in comparison with rat liver. Hepatoma induced by feeding Wistar rats with 3'-methyl-4-dimethylaminoazobenzene (MeDAB) was more active than Wistar liver in sialylating asialo-orosomucoid, and this was due to an increased activity of Gal(beta 1----4)GlcNAc (alpha 2----6) sialyltransferase, the major sialyltransferase in these tissues. Gal(beta 1----3,4)GlcNAc (alpha 2----3) sialyltransferase and the sialyltransferase acting on asialo-bovine submaxillary mucin were, however, decreased in the hepatoma. A similar pattern of sialyltransferase alterations was observed in regenerating liver and other tumors such as AH-109A hepatoma and Sato lung cancer, both of which had been inoculated into Donryu rats. In contrast to these sialyltransferases, the activities of the sialyltransferases responsible for the formation of gangliosides were markedly different even between Wistar and Donryu livers. When compared with Wistar liver, MeDAB-induced hepatoma was higher in lactosylceramide- and lower in GM3-sialyltransferase activity, but these two activities were both lower in AH-109A compared with Donryu liver.