Carbohydrates as antigenic determinants of glycoproteins

Polyacrylamide gel electrophoresis of reducing saccharides labeled with the fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid: application to the enzymological structural analysis of oligosaccharides

Mono- and oligosaccharides, each containing a reducing end group, were labeled with the charged fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid and the resulting derivatives were separated with high resolution by polyacrylamide gel electrophoresis using a method developed recently (P. Jackson, Biochem. J. 1990, 270, 705-713) but with an alternative electrophoretic buffer system. The fluorescent derivatives of glucose and all its straight chain, alpha 1-4 linked, oligomers from maltose to maltoheptaose were well resolved. Various isomers such as maltose and lactose could be separated, as were maltose and cellobiose and some epimers, for instance glucose and galactose. The method was applied to the analysis of the partial sequential degradation of a complex oligosaccharide with neuraminidase and beta-galactosidase. Gels showing fluorescent saccharide band patterns were recorded in picomolar quantities either photographically or using an imaging system based on a cooled charge-coupled device.

Ontogenic expression of histo-blood group antigens in the intestines of suckling pigs: lectin histochemical and immunohistochemical analysis

The expression of intestinal histo-blood group AO and related antigens was investigated in piglets during an 8 week suckling period. Lectin histochemical and immunohistochemical analyses were undertaken on sections of resin-embedded intestinal tissue and semi-quantitative scoring systems were adopted for categories of lectins and monoclonal antibodies reactive with carbohydrate moieties present in core, backbone and terminal oligosaccharide sequences of histo-blood group antigens. Distinct age-related changes were observed in the terminal glycosylation of both secretory and membrane glycoconjugates. Histo-blood group A antigen was identified in intestinal mucin 5 weeks after birth and the precursor H antigen was found in goblet cells at week 1. H antigen was undetectable on intestinal membranes during the first 3 weeks of suckling but a conspicuous and sustained level of this form of fucosylation was apparent during the latter half of the suckling period. More complex membrane glycosylation involving further fucosylation and/or the expression of A antigen, was evident in the latter part of the suckling period. These temporal changes in membrane and secretory glycosylation may be physiologically important during intestinal adaptation and development in young pigs.

Glycosylation in intestinal epithelium

This chapter reviews the glycosylation reactions in the intestinal epithelium. The intestinal epithelium represents a good model system in which the glycosylation process can be studied. The intestinal epithelium is composed of two basic epithelial cell types: the absorptive enterocyte and the mucus-producing goblet cell. Gastrointestinal epithelial renewal ensues through the processes of cell proliferation, migration, and differentiation. This renewal occurs in discrete proliferative zones along the gastrointestinal tract. In the small intestine, this proliferative zone is restricted to the base of the crypts, whereas in the large intestine it is less restrictive, occurring in the basal two thirds of the crypt. A longitudinal section along the crypt-to-surface axis, cells in various degrees of differentiation is observed, providing a unique in vivo system in which to investigate differentiation-related glycosylation events. The glycoconjugate repertoire displayed by a given cell reflects its endogenous expression of glycosyltransferases. The role played by terminal oligosaccharide structures in cell–cell recognition phenomena and the expression of glycosyltransferases occupy a key position in the post-translational processing of glycoconjugates and thus influence cellular function.

Carcinoembryonic antigen gene family: molecular biology and clinical perspectives

The carcinoembryonic antigen (CEA) gene family belongs to the immunoglobulin super-gene family and can be divided into two main subgroups based on sequence comparisons. In humans it is clustered on the long arm of chromosome 19 and consists of approximately 20 genes. The CEA subgroup genes code for CEA and its classical crossreacting antigens, which are mainly membrane-bound, whereas the other subgroup genes encode the pregnancy-specific glycoproteins (PSG), which are secreted. Splice variants of individual genes and differential post-translational modifications of the resulting proteins, e.g., by glycosylation, indicate a high complexity in the number of putative CEA-related molecules. So far, only a limited number of CEA-related antigens in humans have been unequivocally assigned to a specific gene. Rodent CEA-related genes reveal a high sequence divergence and, in part, a completely different domain organization than the human CEA gene family, making it difficult to determine individual gene counterparts. However, rodent CEA-related genes can be assigned to human subgroups based on similarity of expression patterns, which is characteristic for the subgroups. Various functions have been determined for members of the CEA subgroup in vitro, including cell adhesion, bacterial binding, an accessory role for collagen binding or ecto-ATPases activity. Based on all that is known so far on its biology, the clinical outlook for the CEA family has been reassessed.

A new force-field program for the calculation of glycopeptides and its application to a heptacosapeptide-decasaccharide of immunoglobulin G1. Importance of 1-6-glycosidic linkages in carbohydrate.peptide interactions

Energetically favored conformations of glycopeptide 1 were calculated using the newly developed force-field program, GEGOP (geometry of glycopeptides). The three-dimensional structure of glycopeptide 1, which is part of the Fc fragment of IgG1, has been calculated. 1 contains 27 amino acid residues from Pro291 to Lys317 and a biantennary decasaccharide N-linked to Asn297. The conformations of the peptide and the carbohydrate parts are shown to be mutually dependent. Single glycosyl residues of 1 exhibit interaction energies of up to -31.8 kJ/mol with the peptide portion. Generally, only a few of the glycosyl residues of the oligosaccharide moiety express significant interaction energies with the peptide part. No easy prediction is possible of glycosyl residues which exhibit favorable interaction energies. However, in all of the calculated structures, the glycosyl residues of the 1-6-linked branches show strong attractive forces for the peptide part. 1-6-glycosidically linked branches can adopt a larger number of conformations than other linkages due to their high flexibility which allows more favorable interactions with proteins. We developed the GEGOP program in order to be able to study the preferred conformations of large glycopeptides. The program is based on the GESA (geometry of saccharides) program and utilizes the HSEA (hard sphere exo anomeric) force field for the carbohydrate part and the ECEPP/2 (empirical conformation energy program for peptides) force field [Némethy, G., Pottle, M. S. & Scheraga, H. A. (1983) J. Phys. Chem. 87, 1883-1887] for the peptide part. The GEGOP program allows the simultaneous relaxation of all rotational degrees of freedom of these glycoconjugates during the energy optimization process. Thus, mutual interactions between glycosyl and amino acid residues can be studied in detail.

Analysis of sequence diversity in hypervariable regions of the external glycoprotein of human immunodeficiency virus type 1

Nucleotide sequences in three hypervariable regions of the human immunodeficiency virus type 1 (HIV-1) env gene were obtained by sequencing provirus present in peripheral blood mononuclear cells of HIV-infected individuals. Single molecules of target sequences were isolated by limiting dilution and amplified in two stages by the polymerase chain reaction, using nested primers. The product was directly sequenced to avoid errors introduced by Taq polymerase during the amplification process. There was extensive variation between sequences from the same individual as well as between sequences from different individuals. Interpatient variability was markedly less in individuals infected from a common source. A high proportion of amino acid substitutions in the hypervariable regions altered the number and positions of potential N-linked glycosylation sites. Sequences in two hypervariable regions frequently contained short (3- to 15-bp) duplications or deletions, and by amplifying peripheral blood mononuclear cell DNA containing 10(2) or 10(3) proviral molecules and analyzing the product by high-resolution electrophoresis, the total number and abundance of distinct length variants within an individual could be estimated, providing a more comprehensive analysis of the variants present than would be obtained by sequencing alone. Sequences from many individuals showed frequent amino acid substitutions at certain key positions for neutralizing-antibody and cytotoxic T-cell recognition in the immunodominant loop. The rates of synonymous and nonsynonymous nucleotide substitution in the region of this and flanking regions indicate that strong positive selection for amino acid change is operating in the generation of antigenic diversity.

Difference in the ability of blood group-specific lectins and monoclonal antibodies to recognize the ABH antigens in human tissues

Twelve different kinds of blood group-specific lectins have been used along with monoclonal anti-A, -B and -H antibodies for detecting the corresponding antigens in selected human tissues. Although most of the lectins recognized the antigens in the tissue sections examined, they displayed marked differences in their recognition patterns in certain tissues. Helix asparsa agglutinin (HAA), Helix pomatia agglutinin (HPA) and monoclonal anti-A antibody recognized A antigens in the mucous cells of salivary glands from blood group A or AB nonsecretor as well as secretor individuals, whereas Dolichos biflorus agglutinin (DBA), Griffonia simplicifolia agglutinin-I (GSA-I), Sophora japonica agglutinin (SJA) and Vicia villosa agglutinin (VVA) did not bind to them from nonsecretors. A antigens in endothelial cells, lateral membrane of pancreatic acinar cells and small mucouslike cells of submandibular glands from some individuals were likewise recognized by HAA and HPA but not by other blood group A-specific lections. In contrast, both HAA and HPA did not recognize the A antigens in mucous cells of Brunner's glands while other A-specific lectins and monoclonal anti-A antibody reacted specifically with the antigens. Such a difference was not observed with lectins specific for blood group B. However, the B antigens in Brunner's glands were recognized by these lectins but not with monoclonal anti-B antibody. The difference in labelling ability was also noted among the blood group H-specific lectins and monoclonal anti-H antibody in endothelial cells of blood vessels. Ulex europaeus agglutinin-I reacted with these cells irrespective of ABO and the secretor status of the individuals, while Anguilla anguilla agglutinin and monoclonal anti-H antibody reacted only with those cells from blood group O individuals. No reaction was observed with Lotus tetragonolobus agglutinin in these tissue sites. These results suggest a great diversity of blood group antigens in different human tissues.

Environmental effects on protein glycosylation

Cultured mammalian cells are being used to produce proteins for therapeutic and diagnostic use because of their ability to perform complex post-translational modifications, including glycosylation. The oligosaccharide moieties can play an important role in defining several biological properties of glycoproteins, including clearance rate, immunogenicity, and biological specific activity. There is a growing interest in defining the factors that influence glycosylation, including the cell culture environment. In this review we organize the published data from in vitro cell culture and tissue culture studies that demonstrate direct effects of the culture environment on N-linked glycosylation.

Cancer-associated carbohydrates identified by monoclonal antibodies

"New" carbohydrate structures on the surface of or secreted by cancer cells, identified as epitopes by monoclonal antibodies, are reviewed. These structures may represent the accumulation of precursor chains because of decreased activity of synthesizing enzymes, the production of new oligosaccharides due to increased or aberrant glycosylation of carbohydrate chains, a change in density of carbohydrates on the cell surface, or exposure of chains usually covered by other structures. Alterations in glycolipid synthesis include aberrant fucosylation and/or sialyation of the lacto series, sialylation or fucosylation of the globo series, and sialyation of the ganglio series. Many of these carbohydrate epitopes have become useful for the diagnosis, prognosis, and monitoring of patients with cancer. Some of the important markers include CA 15.3, CA 19.9, CA 50, CA 125, CA 242, MCA, SLEX, etc. Incomplete glycosylation of O-linked mucin oligosaccharide is recognized as the important "cancer antigen" B72.3, which is sialyated Tn. The oligosaccharide components of alpha-fetoprotein, carcinoembryonic antigen, and epidermal growth factor receptor are also reviewed. In many instances the glycosylation seen in cancer cells or their products reflects patterns seen during normal development. Thus, cancer-associated oligosaccharides are oncodevelopmental in nature. The biologic significance of carbohydrates on cell surfaces is not known, but several possibilities include a role in cell to cell recognition, intracellular processing of glycoproteins, cell activation, and ability of cancer cells to metastasize.

Oligosaccharide-related epitope specific for a brain-specific glycoprotein, 1D4 antigen

The characteristics of glycosylation of a brain-specific glycoprotein, 1D4 antigen, and the epitope recognized by its monoclonal antibody were studied. Removal of high-mannose and hybrid types of N-linked oligosaccharides by treatment with endoglycosidase H converted the molecular mass of the 1D4 antigen from 89 kDa to 78 kDa, but did not affect its reactivity with the 1D4 monoclonal antibody. Removal of all types of N-linked oligosaccharides by treatment with glycopeptidase F or removal of both N- and O-linked oligosaccharides by chemical treatment caused both reduction of the molecular mass of the antigen to 63 kDa and loss of its reactivity with the monoclonal antibody. These results suggest that the 1D4 monoclonal antibody recognizes a complex-type oligosaccharide-related epitope specific for the 1D4 antigen. Results also showed that N-linked glycosylation was not responsible for the charge heterogeneity of the 1D4 antigen. The oligosaccharide chain-related epitope was detected in rat brain but not in mouse, rabbit, or bovine brain, but the 1D4 antigen was recognized in rat and mouse brains with antiserum (polyclonal antibodies). These findings indicate that the oligosaccharide-related epitope is species specific. Furthermore, results with neuraminidase-treated 1D4 antigen indicated that sialic acids were not involved in the oligosaccharide-related epitope. These findings suggest that the 1D4 antigen may have the oligosaccharide structure specific for rat brain and itself.

The use of polyacrylamide-gel electrophoresis for the high-resolution separation of reducing saccharides labelled with the fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid. Detection of picomolar quantities by an imaging system based on a cooled charge-coupled device

Various monosaccharides, oligosaccharides and small polysaccharides were labelled covalently at their reducing end groups with the fluorophore 8-aminonaphthalene-1,3,6-trisulphonic acid (ANTS), and the resulting fluorescent derivatives were separated by high-resolution PAGE. The electrophoretic mobilities of the labelled saccharides are related largely to the compounds' Mr values, but they are also influenced by the individual chemical structures of the saccharides. Various positional isomers and some epimers, for instance galactose and glucose, were resolved. Oligosaccharide and small polysaccharide derivatives, prepared from an enzymic digest of starch, each differing in size by a single hexose residue and with a range of degrees of polymerization from 2 to 26, were all resolved in a single gel. The method was relatively rapid and simple to perform. It enabled multiple samples to be analysed in parallel with high sensitivity. The fluorescent-labelling procedure was virtually quantitative. As little as 1 pmol of ANTS-labelled saccharide was detected photographically when the gels were illuminated by u.v. light. When the gels were viewed using an imaging system based on a cooled charge-coupled device, as little as 0.2 pmol was detected. The method may be useful for the structural analysis of the carbohydrate moieties of glycoconjugates and other naturally occurring oligosaccharides.

Heterogeneity of the blood group ABH antigens and variation in the expression of these antigens of secretory granules in human cervical glands. An electron microscopic observation using lectins and monoclonal antibodies

Cytochemical localization of blood group ABH antigens was examined in secretory cells of human cervical glands by application of a post-embedding lectin-gold as well as immuno-gold labeling procedure using monoclonal antibodies. Blood group specific lectins such as Dolichos biflorus agglutinin (DBA), Helix pomatia agglutinin (HPA), Griffonia simplicifolia agglutinin I-B4 (GSAI-B4) and Ulex europaeus agglutinin-I (UEA-I) reacted with secretory granules but not with other cytoplasmic organellae such as nucleus and cell membrane. The reactivity of secretory granules with these lectins showed strict dependence on the blood group and secretor status of tissue donors. The binding patterns with these lectins were not homogeneous, but exhibited marked cellular and subcellular heterogeneity. Thus, for example, in blood group A individuals, some granules were stained strongly with DBA and others were weakly or not at all with the lectin. Such a heterogenous labeling with the lectin was observed even in the same cells. Similar results were obtained with UEA-I and GSAI-B4 staining in blood group O and B secretor individuals, respectively. Monoclonal antibodies likewise reacted specifically with the granules but they occasionally bound to some nucleus. The labeling pattern of the antibodies with the granules was essentially the same as those of lectins.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunochemical analysis of a monoclonal antibody recognizing a terminal glucuronic acid-containing epitope of insect acidic glycolipids

A cloned, hybridoma cell-line was established that secreted the monoclonal antibody CAF-I following stimulation of the donor Balb/c mouse spleen cells by the total acidic fraction glycolipids of the third-instar larvae of Calliphora vicina (Insecta:Diptera). The monoclonal antibody isotype was IgG3 By qualitative (TLC-immunostaining) and semi-quantitative (enzyme-linked immunosorbent assay) methods, and comparison with the cross-reactivity of known monoclonal antibodies, the epitope was specifically located on the terminal, non-reducing end of the oligosaccharide chain of most of the insect acidic glycolipids. Following isolation of the two main acidic glycolipids of C. vicina larvae (A5c and Az5c), exoglycosidase treatment characterized the terminal disaccharide CAF-I epitope as glucuronic acid bound to subterminal galactose, both in the beta-anomeric configuration: G1cA beta-Ga1 beta-. The immunohistological distribution of this epitope in the dipteran, Drosophila melanogaster, showed its main expression to be in the imaginal discs and brain of the third-instar larva, and the retinula cells of the ommatidial elements of the compound eye retina of the adult female.

Observations and thoughts on oligosaccharide involvement in malignancy

This brief communication highlights some observations that have raised the possibility that the oligosaccharides of glycoproteins may have roles as ligands or recognition structures in cell growth regulation. The initial experience with a new technology designed for investigating roles of glycoprotein oligosaccharides as recognition structures is also discussed.

Action of endo-alpha-N-acetylgalactosaminidase from Alcaligenes sp. on amino acid-O-glycans: comparison with the enzyme from Diplococcus pneumoniae

Endo-alpha-N-acetylgalactosaminidase from Alcaligenes sp. released the disaccharide, Gal beta 1----3GalNAc, from both dansylated serine-GalNAc-Gal and threonine-GalNAc-Gal, and showed higher activity on the former than the latter. The Km values were 0.17 mM and 1.43 mM with DNS-Ser-GalNAc-Gal and DNS-Thr-GalNAc-Gal, respectively. The optimum pHs were found to be 4.5-7.5 and 4.5-6.0 on DNS-Ser-GalNAc-Gal and DNS-Thr-GalNAc-Gal, respectively. On the contrary, the enzyme from Diplococcus pneumoniae had low activity to release the disaccharide from the amino acid-O-glycans. The possibility that the same O-glycoside but linked to different aglycon amino acids may play a different biological role in glycoproteins is discussed.

Expression of IGF-I and IGF-II genes in the adult rat eye

We have investigated the transcription of IGF-I and IGF-II genes in the adult rat eye. Each eye was dissected into cornea, lens, sclera + choroid + pigment epithelium, and neural retina. Total cellular RNA was isolated from each of these tissues. Northern blot analysis using rat coding region cDNA probes revealed the presence of IGF-I and IGF-II specific transcripts in the retina and the sclera but not in the lens and cornea. Retina demonstrated the highest level of IGF-I and IGF-II expression. Our results suggest autocrine and paracrine effects of the IGFs and their possible involvement in normal eye physiology as well as in the pathogenesis of certain eye diseases.

Griffonia simplicifolia agglutinin-2-binding glycoprotein as a novel carbohydrate antigen of human colonic carcinoma

Griffonia simplicifolia agglutinin-2-binding glycoprotein (GBG) in human colonic carcinoma was examined immunochemically and histochemically, GBG was extracted from colonic carcinoma as a serum-type glycoprotein of 160 kilodaltons. GBG was not identical with carcinoembryonic antigen (CEA), since its molecular weight and localization in tissue sections were different from those of CEA. The non-reducing terminals of GBG probably carry N-acetylglucosamine, but not blood group determinants. Furthermore, GBG was released by phosphatidylinositol-specific phospholipase C from cell membrane. GBG was suggested to be anchored to the membrane via linkage to a glycosyl-phosphatidylinositol molecule. Among colonic carcinoma-associated antigens, serum-type glycoproteins having N-acetylglucosamine at non-reducing terminals have not previously been reported. GBG is a novel carbohydrate antigen of human colonic carcinoma.

The oligosaccharides of influenza virus hemagglutinin expressed in insect cells by a baculovirus vector

The hemagglutinin of fowl plague virus has been expressed in Spodoptera frugiperda (SF) cell cultures using a baculovirus vector. To elucidate the structure of the carbohydrate side chains, radioactively labeled oligosaccharides were liberated by treatment with endoglucosaminidase H and glycopeptidase F. Sequential degradation with exoglycosidases and chromatographic analyses revealed the presence of oligomannosidic side chains, predominantly of the structures Man5-9GlcNAc2, and the truncated oligosaccharide cores Man3GlcNAc2 and Man3[Fuc]GlcNAc2. Polyacrylamide gel electrophoresis of endoglycosidase-treated hemagglutinin showed that most side chains of the HA1 subunit are truncated, whereas the HA2 subunit has one oligomannosidic and one truncated oligosaccharide. Comparison of these results with the glycosylation pattern of hemagglutinin obtained from vertebrate cells allowed a tentative allocation of the oligosaccharides to individual glycosylation sites. The results indicate that SF cells have the capacity to trim N-glycans to trimannosyl cores and to further process these by the addition of fucose. Thus, the complex oligosaccharides found on hemagglutinin from vertebrate hosts are replaced on hemagglutinin derived from insect cells by small truncated side chains.

Isolation and characterization of blood group N antigen precursor glycoproteins with Thomsen-Friedenreich (T) activity, N antigen precursor glycoproteins and T-active glycoproteins from cyst fluids of malignant ovarian clear cell carcinoma

1. Two perchloric acid-soluble glycoprotein fractions from cyst fluids of 2 patients with ovarian clear cell carcinoma in malignant were subjected to a systematic affinity chromatography using Vicia unijuga lectin-Cellulofine column and Arachis hypogaea lectin-Cellulofine column and separated into four glycoproteins, blood group N antigen precursor glycoprotein with Thomsen-Friedenreich (T) activity, N antigen precursor glycoprotein, T-active glycoprotein and serologically inactive glycoprotein, respectively. 2. These serologically active glycoproteins isolated in yields of 0.3-3.3% of PASFs, were proved to be mucin-type glycoproteins with Mw of 509,000-2,772,000 Da and contained 33.9-81.7% carbohydrates.

Isolation and partial characterization of two glycoproteins from human liver metastases of sigmoid colon carcinoma

1. Perchloric acid-soluble glycoprotein fraction (PASF) extracted from human liver metastases (LM) of sigmoid colon carcinoma was chromatographed on a DEAE-cellulose column. The main fraction (DEAE-nonadsorbed fraction) passed through the column was then subjected to Sephacryl S-200 superfine gel filtration and separated into 12 fractions. 2. Among 12 fractions, only both Fractions 3 and 4 were demonstrated to be chemically and immunologically homogeneous glycoproteins, respectively, by a combination of chemical composition analysis, SDS-PAGE and EITB assay using antisera against the DEAE-nonadsorbed fractions of PASFs from human LMs, normal liver (NL) and normal sigmoid colon (NSC). Each of Fractions 3 and 4 reacted with anti-LM serum to give one immuno complex on a nitrocellulose sheet in EITB assay, but did not react with anti-NL and -NSC sera. 3. Apparent molecular weights of 80,900 and 62,100, respectively, were found for Fractions 3 and 4. Both the fractions, respectively, had abnormal sugar compositions. Fraction 3 contained sialic acid, fucose, galactose, N-acetylglucosamine and N-acetylgalactosamine, but lacked glucose and mannose, and Fraction 4 contained sialic acid, fucose, galactose and N-acetylglucosamine, but lacked glucose, mannose and N-acetylgalactosamine, as sugar components.

Expression of endogenous receptors for neoglycoproteins in Dunning R3327 rat prostatic carcinoma

An important animal model for human prostatic adenocarcinoma is the Dunning R3327 rat carcinoma. In the present study this tumor was further characterized by analyzing the expression of endogenous sugar-binding proteins using glycohistochemistry and immunocytochemistry as well as affinity chromatography and gel electrophoresis. Our glycohistochemical and glycobiochemical results provide evidence for the presence of specific receptors for various carbohydrate moieties. Remarkably, basal cells of the Dunning tumor contain an endogenous lectin with specificity for beta-galactosides that is not found in basal cells of the normal rat prostate. This finding was corroborated using polyclonal antibodies against an immunologically related beta-galactoside-specific lectin from bovine heart. Basal cells of prostatic carcinoma may therefore behave different from normal basal cells. This difference could have a significant impact on the development of prostatic cancer.

Immunohistochemical localization of 14 kDa beta-galactoside-binding lectin in various organs of rat

Immunohistochemical localization of 14 kDa beta-galactoside-binding lectin in various organs of adult rat was achieved using a monospecific antibody raised against lectin purified from rat lung. The antibody-stained cells were formed into small aggregates, thin fascicles, or thick bundles in the walls of blood vessels, gastrointestinal tracts and urogenital organs. From the patterns of distribution, as well as their organization, these immunoreactive cells were regarded as smooth muscle cells. This was confirmed by a double immunofluorescence study using a mixture of anti 14 kDa lectin and anti alpha-smooth muscle-specific actin antibodies. Strong 14 kDa lectin immunoreactivity was seen in the pericellular matrix of smooth muscle cells in intact organs as well as in detergent-treated organs from which all cellular components were extracted. From these findings, it is suggested that the 14 kDa lectin may be externalized by smooth muscle cells into their pericellular matrix and participate in the crosslinking of the complementary glycoconjugate(s) localized at that site. The macromolecular xomplex of glycoconjugates thus formed around smooth muscle cells may play a role in anchoring smooth muscle cells to the pericellular connective tissue thereby permitting the force of muscle contraction to be efficiently transmitted to the surrounding connective tissue proper.

A plant fucosyltransferase with human Lewis blood-group specificity

A fucosyltransferase from mung bean seedling was found to transfer L-fucose from GDP-fucose to the Type 1 disaccharide beta-D-Galp-(1----3)-beta-D-GlcpNAc-OR [R = (CH2)8COOMe]. The product, which was detected by an anti-Lea antibody in a novel ELISA assay, was isolated and shown to be the human Lea blood-group determinant beta-D-Galp-(1----3)-[alpha-L-Fucp-(1----4)]-beta-D-GlcpNAc-OR by 1H-n.m.r. spectroscopy. This enzyme activity is distinct from that of the human Lewis-fucosyl-transferase since alpha-L-Fucp-(1----2)-beta-D-Galp-(1----4)-beta-D-Glcp-OR is a very poor substrate, while the Type 2 disaccharide beta-D-Galp-(1----4)-beta-D-GlcpNAc-OR is not an acceptor. In common with the Lewis fucosyltransferase, the H-Type 1 trisaccharide alpha-L-Fucp-(1----2)-beta-D-Galp-(1----3)-beta-D-GlcpNAc-OR was an excellent substrate for the enzyme. This new enzyme activity was further characterized with respect to pH, nucleotide, Mn2+ dependence, and acceptor specificity against a panel of synthetic oligosaccharides.

Analysis of wheat germ agglutinin (WGA), Phaseolus vulgaris leucoagglutinin (PHA-L), and lens culinaris agglutinin (LCA) binding to isolated rat neocortical membrane glycoproteins and to brain tissue sections

Different lectin transport directions--either anterograde or retrograde in tracing neuronal pathways--have been attributed to different sugar specificities of the lectins. To test this hypothesis, transmembrane neocortical glycoproteins were isolated to analyze their lectin-binding properties. The lectins tested exhibited a broad binding pattern to these glycoproteins. Arguing against the above-mentioned hypothesis, sugar residues of transmembranal glycoproteins probably are not exclusively responsible for the different transport directions observed in lectin tracing.

An activation antigen on a subpopulation of B lymphocytes identified by the monoclonal antibody CMRF-17

The identification of membrane molecules expressed on subpopulations of B lymphocytes is of potential significance because these molecules may be candidates for regulating the activation, proliferation and differentiation of B cells. A new monoclonal antibody, CMRF-17, which reacts with a subpopulation of tonsil B lymphocytes has been produced. The antibody did not react with T lymphocytes in tonsil or peripheral blood nor most peripheral blood B lymphocytes but did label erythrocytes and some platelets. In tonsil, the germinal centre cells, cells in the interfollicular region and endothelial cells were positive, but mantle zone B cells were negative. Double labelling experiments showed that CMRF-17 reacted with activated tonsillar lymphocytes. The antigen recognized by CMRF-17 was heat stable, resistant to treatment with proteolytic enzymes and neuraminidase and was shown to be a carbohydrate determinant on one or more glycolipids. These characteristics of the antigen recognized by CMRF-17 and its pattern of reactivity distinguish this antibody from other monoclonal antibodies recognizing B-cell activation markers. It was notable that of the B-lymphoid malignancies tested to date, including those of probable follicular origin, few stained with CMRF-17.

Is the profile of binding of a panel of neoglycoproteins useful as a diagnostic marker in human lung cancer?

Histomorphological evaluation of the profile of carbohydrate-binding proteins with specificities to alpha- and beta-glucosides (maltose, cellobiose), alpha-L-fucosides (L-fucose), alpha-D-mannosides (D-mannose), a N-acetylated sugar, present in natural glycoconjugates (N-acetyl-D-glucosamine), two negatively charged sugars (glucuronic acid and sialic acid), rhamnose (6-deoxy-L-mannose) or to heparin has been assessed. 133 cases of formalin fixed, paraffin embedded human lung carcinoma specimens (45 cases of epidermoid carcinoma, 24 cases of small cell anaplastic carcinoma, 48 cases of adenocarcinoma, and 16 cases of large cell anaplastic carcinoma) as well as 14 cases with epithelial or biphasic mesothelioma and 7 cases of pleuritis carcinomatosa were incubated with biotinylated, suitably modified neoglycoproteins or heparin for detecting the corresponding endogenous sugar receptors (lectins). Histochemical reaction was demonstrated by use of the avidin-biotin-method. Significant differences were obtained between the different markers used for each cell type as well as between the different cell types. For separating small cell anaplastic carcinoma from non small cell anaplastic carcinoma the markers carrying the histochemically crucial maltose, fucose, and mannose residues are useful, showing a positive reaction to only 4-8% of the small cell anaplastic carcinoma cases compared to 60-80% of the non small cell carcinoma cases. For separation of mesothelioma from pleuritis carcinomatosa a carrier, modified by attachment of N-acetylglucosamine moieties is the most useful marker being negative in all cases of the analyzed mesothelioma cases and being positive in 62-80% of the adenocarcinoma cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental changes in galactosyltransferase activity in the rat small intestine

During postnatal development, UDP-Gal: GlcNAc(beta 1-4)-galactosyltransferase (4 beta-GT) and UDP-Gal:GalNAc(beta 1-3)-galactosyltransferase (3 beta-GT) activities were increased by 17- and 24-fold, respectively, in the rat small intestine. The injection of cortisone into suckling rats resulted in precocious induction of distal 4 beta- and 3 beta-GT activities by 2.7- and 1.8-fold, respectively. Injection of phorbol-12-myristate-13-acetate (PMA) resulted in precocious induction of distal 3 beta-GT by 2.7-fold. These results suggest that intestinal galactosyltransferase activities are under developmental regulation and can be modified by cortisone and PMA.

Histopathologic evaluation of application of labeled neoglycoproteins in primary bronchus carcinoma

Neoglycoproteins are readily available conjugates of a histochemically inert carrier protein and histochemically crucial carbohydrate moieties which are covalently attached to the carrier protein by chemical synthesis. Biotinylation renders these conjugates detectable in formalin-fixed, paraffin-embedded tissue sections of human lung cancer by standard staining protocols, thereby localizing endogenous receptors for carbohydrate moieties. Examination of 30 cases of main types of human lung cancer revealed the presence of alpha-fucosyl-, alpha-mannosyl-, and alpha-glucosyl-specific receptors in adenocarcinomas or epidermoid carcinomas with high positivity rates. The extent of the expression of receptors for alpha- and beta-galactosides appeared to be comparatively lower. Within the standard protocol, using a concentration of the biotinylated probes of 10 micrograms/mL, this panel of probes consistently failed to detect endogenous sugar receptors in ten cases of small cell anaplastic carcinoma of the lung. Whereas none of the sections from the tumor cases bound the sulfated fucan fucoidan, the accompanying inflammatory cells, especially the granulocytes, expressed receptors for the sulfated fucan. Pronounced labeling for macrophages was observed for the alpha-galactoside-specific probe, whereas no binding to inflammatory cells and pneumocytes was detectable for the beta-galactoside-specific probe. The results indicate that expression of endogenous receptors for neoglycoproteins may be useful in discriminating between small cell and non-small cell lung carcinoma and carcinomatous cells from accompanying inflammatory cells.

Changes of glycoconjugates in human hepatocellular carcinoma

Receptors of 12 lectins in 25 cases of human hepatocellular carcinomas (HCC) were histochemically investigated by avidin-biotin-peroxidase complex (ABC) method. Liver tissues of five cirrhotic patients and five normal subjects were used as controls. SJA receptor was absent both in HCC and controls, while LCA and PSA receptors were present in all tissues studied here. Receptors of DBA, PHA, PNA, UEAI and SBA which did not bind to normal, cirrhotic and pericarcinomatous liver tissues had the positive rates of 4%, 44%, 16%, 4% and 12% in HCC, respectively. Four lectins which strongly bound to the non-cancer liver tissues had their receptors in 96% (ConA, WGA, RCAI) and 36% (BSAI) of HCC. The pretreatment of tissue sections with neuraminidase abolished most of WGA receptors and exposed some PNA binding sites. There were many differences in lectin distribution between HCC and noncancer liver tissues. The changes of glycoconjugates in HCC were discussed.

A hypothesis on the dual significance of ABH, Lewis and related antigens

ABH and related antigens appeared a long time ago in the evolution of vertebrates on tissues in contact with the external environment, which suggests that the polymorphism given by these antigens might play a role in the relationships of the species with pathogens. However, they are also oncodevelopmental markers and some recent experimental data suggest that they might play a role in cell-cell recognition at some stages of development. This type of function is difficult to reconcile with the polymorphic nature of these markers unless one considers that the glycosyltransferases necessary for the synthesis of the active structures are encoded by various members of multigene families. Some non-polymorphic members of the families would have their expression limited in time and space during development, leading to the same antigenic patterns in every individual, and these could reappear in some tumours, while the expression of other polymorphic members (A/B/O, H/h, Se/se, Le/le), leading to a variety of antigenic phenotypes, would be expressed at later stages and remain so during the whole life of the individual. The corresponding antigens could disappear from some cancer cells. It is argued that the ABH and related antigens would have primarily been involved in cell-cell recognition phenomena. The polymorphism would have evolved later from gene duplication under environmental pressure, the expression on erythrocytes which occurred very late in evolutionary time probably being of very little biological significance.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.

New type of adhesive specificity revealed by oligosaccharide probes in Escherichia coli from patients with urinary tract infection

A series of oligosaccharides derived from glycoproteins or from human milk were coupled to lipid and used as probes of the binding specificities of Escherichia coli isolated from patients with urinary tract infections. Selective binding to the glycoprotein oligosaccharide probes rich in mannose residues (high-mannose type) was demonstrated with fimbriated E coli that give mannose-inhibitable haemagglutination. This observation is in accordance with predictions from inhibition studies. Binding studies with the human milk oligosaccharide probes, which resemble structures found on host-cell membranes, revealed adhesive specificity unrelated to the presence of fimbriae. This new type of host oligosaccharide receptor is affected by the presence of the blood group genetic markers. It involves the disaccharide sequence linked to the membrane-associated lipid moiety of host-cell glycolipids, and may have a role in initiation of infection on damaged epithelial cell membranes.

Role of protein N-glycosylation in pathogenesis of human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1), the retrovirus responsible for acquired immunodeficiency syndrome (AIDS), contains two heavily glycosylated envelope proteins, gp120 and gp41, which mediate attachment of virions to glycosylated cell surface receptor molecules (CD4 antigens) and appear to be responsible for syncytium formation and associated cytopathic effects of this virus. A comprehensive study of the effects of N-linked glycoprotein processing inhibitors on HIV-1 replication, infectivity, cytopathicity, target-cell infectibility, syncytium formation, and gp120 electrophoretic mobility was conducted to assess the importance of protein glycosylation in the pathogenesis of HIV-1 in vitro. The electrophoretic mobility of gp120 was decreased when gp120 was synthesized in the presence of castanospermine or 1-deoxynojirimycin (inhibitors of glucosidase I), increased when gp120 was synthesized in the presence of 1-deoxymannojirimycin (mannosidase I) or swainsonine (mannosidase II), and unaffected when gp120 was synthesized in the presence of bromoconduritol (glucosidase II). Inhibition by tunicamycin (lipid-linked oligosaccharide precursor synthesis), castanospermine, 1-deoxynojirimycin, and 1-deoxymannojirimycin attenuated HIV-1 infectivity and blocked HIV-1-induced syncytium formation and cytopathicity, whereas bromoconduritol and swainsonine failed to have such effects. None of the inhibitors interfered with virus replication in acutely infected cells or affected the ability of target cells to form syncytia with untreated HIV-1-infected cells. These results demonstrate that protein N-glycosylation is critical to the pathogenesis of HIV-1 at the levels of viral infectivity and cytopathicity but not at the level of virus replication or of host-cell infectibility.

Monoclonal antibodies identify common and differentiation-specific antigens on the plasma membrane of guard cells of Vicia faba L

Monoclonal antibodies were raised against the plasma membrane of Vicia faba L. guard cells by immunizing either with total membranes from purified guard-cell protoplasts or with sealed, predominantly right-side-out plasma-membrane vesicles prepared from abaxial epidermes of V. faba by aqueous two-phase partitioning. Hybridoma screening was performed by enzyme-linked immunosorbent assay using polystyrene-adsorbed plasma-membrane vesicles as solid phase and by indirect immunofluorescence analysis using unfixed, immobilized protoplasts in a microvolume Terasaki assay. A range of monoclonal antibodies was characterized and is reported here. One monoclonal antibody, G26-6-B2, is guard-cell-specific and does not react with mesophyll-cell protoplasts of the same species. It binds to a periodate-resistant but trypsin-labile epitope, probably a differentiation-specific plasma-membrane protein.

Biodistribution of neoglycoproteins in mice bearing solid Ehrlich tumor

Synthetic neoglycoproteins were employed for the specific detection of their corresponding cellular sugar receptors, such as endogenous lectins, by specific protein-carbohydrate interaction. A panel of 16 radioiodinated probes with defined carbohydrate content, attached to the carrier protein bovine serum albumin, disclosed marked differences in the expression of corresponding sugar receptors on Ehrlich ascites tumor cells in vitro as an exemplary tumor model. To quantify tumor uptake in the more complex in vivo situation and to assess binding to individual organs attributable to the various types of carbohydrates we determined the biodistribution of the radiolabelled neoglycoproteins 48 h after injection into tumor-bearing mice. The individual pattern of retention of radioactivity demonstrated distinct properties of the different organs that need to be accounted for in drug-targeting and tumor-imaging studies, based on protein-carbohydrate interactions. Combined tumor-to-blood and tumor-to-muscle ratios of neoglycoprotein accumulation were well above 1 after covalent attachment of xylose or glucuronic acid, respectively, to the carrier protein. These data constitute the basis for further refinements of the carbohydrate part of suitable neoglycoproteins to allow a potentially rational application of neoglycoproteins as drug-targeting vehicles and tumor-imaging radiopharmaceuticals.

Analysis of the multiple forms of Gaucher spleen sphingolipid activator protein 2

Gaucher spleen sphingolipid activator protein 2 was fractionated into concanavalin A binding- and non-binding fractions. These fractions each contained several bands on non-denaturing polyacrylamide gel electrophoresis (PAGE). The two fractions were further fractionated by electroblotting the proteins from preparative gels onto nitrocellulose, staining with Ponceau S to locate the bands of protein and then eluting the protein components from the nitrocellulose. A total of ten fractions, each containing only one or two major components, was collected. All of these subfractions activated beta-glucocerebrosidase and sphingomyelinase and most subfractions also activated beta-galactocerebrosidase. The structural relationship of the bands was investigated using endoglycosidase digestions. The results indicated that the two bands with the fastest mobility on non-denaturing PAGE did not contain any carbohydrate. The remaining bands showed only limited or partial digestion with endoglycosidase H and endoglycosidase D, but were readily hydrolysed with endoglycosidase F. The products of these digestions included bands with similar mobilities to the non-carbohydrate containing bands.