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T Feizi

Publications and source records attributed to T Feizi.

At least 109 records · Page 6Linked to original sources
PubMed1989

Glycoprotein oligosaccharides as recognition structures.

A series of observations--the pronounced changes in the expression and distribution of oligosaccharide antigens during embryonic development, cell differentiation and oncogenesis, the prominence of these changing structures (oncodevelopmental antigens) on the receptor for epidermal growth factor, and the stimulation of receptor autophosphorylation following their perturbation with antibodies--has suggested that the oligosaccharides of growth factor receptors and complementary lectins may be intimately involved in molecular recognition events in growth and differentiation processes. For elucidating oligosaccharide recognition by diverse cellular and secreted proteins and microbial adhesins, a new technique has been developed which involves the overlay of immobilized oligosaccharide probes (neoglycolipids) derived from glycoproteins and other sources. New insights have been gained into carbohydrate recognition by several mammalian lectins, and a novel receptor system has been discovered in Escherichia coli isolated from patients with urinary tract infections. This new technique seems ideal for elucidating oligosaccharide recognition in diverse biological settings, and for 'quality control' of the sugar chains of recombinant glycoproteins engineered for the purpose of administration to man.

Animals↗
PubMed1989

Oligosaccharide-mediated interactions of the envelope glycoprotein gp120 of HIV-1 that are independent of CD4 recognition.

In this study carbohydrate-mediated interactions of the envelope glycoprotein, gp120, of HIV-1 were investigated. Oligosaccharide probes (neoglycolipids), prepared from the N-glycosidically-linked chains of the natural and recombinant forms of gp120, were used in conjunction with the intact glycoprotein to investigate reactivities with a soluble carbohydrate-binding protein (lectin) known as mannose-binding protein in human serum. Evidence is presented that the high-mannose-type oligosaccharides with seven, eight and nine mannose residues from both forms of gp120 are recognized by the serum lectin, and that these reactivities are unrelated to CD4 recognition. Reactivities of the two forms of envelope glycoprotein with macrophages derived from human blood monocytes and with the mannose-specific macrophage endocytosis receptor isolated from human placental membranes were also investigated. Evidence is presented that both forms of gp120 bind to the macrophage surface by multiple interactions in addition to CD4 binding, and that among these interactions is a carbohydrate-mediated binding to the endocytosis receptor. We propose that such carbohydrate-mediated interactions could form the basis of viral attachment to a variety of healthy and diseased tissues.

CD4 Antigens↗
PubMed1989

Sialo-oligosaccharide receptors for Mycoplasma pneumoniae and related oligosaccharides of poly-N-acetyllactosamine series are polarized at the cilia and apical-microvillar domains of the ciliated cells in human bronchial epithelium.

The occurrence and distribution of the sialo-oligosaccharide receptors (sialosyl-I and sialosyl-i) for Mycoplasma pneumoniae as well as other related oligosaccharide structures of poly-N-acetyllactosamine type, and their short-chain analogs based on galactose linked beta 1-4 or beta 1-3 to N-acetylglucosamine (Gal beta 1-4GlcNAc or Gal beta 1-3GlcNAc, respectively) were investigated in the human bronchial epithelium by histochemistry by using sequence-specific monoclonal antibodies and lectins. Among the mature epithelial cells, only ciliated cells were found to express the long-chain antigens, whereas mucus-secreting cells contained the short-chain antigens associated with mucus globules. The long-chain oligosaccharides were found to be highly polarized at the luminal aspects of the ciliated cells where the branched structures (I and sialosyl-I antigens) were detected both at the apical-microvillar border and on the cilia, but the linear structures (i, sialosyl-i, and VIM-2 antigens) were detected exclusively at the apical-microvillar border. These observations provide the first in situ visualization of the receptor structures for M. pneumoniae at the primary site of infection. The lack of sialo-oligosaccharide receptors in secretory cells and the mucus they produce provides a biochemical basis for evasion by this microorganism of the secreted mucus barrier.

Amino Sugars↗
PubMed1989

Oligosaccharides as recognition structures.

The diverse O-linked oligosaccharide structures of the glycoproteins in mucus have the potential for encoding a vast amount of biological information. A major challenge in modern cell biology is to devise ways of decoding the information in these and other oligosaccharide structures of N-linked chains and glycolipids. In this article, I highlight some studies of oligosaccharide antigenicity, and discuss the way the results are being interpreted with respect to oligosaccharide function. I conclude with a discussion of a new technology that is under development with the aim of investigating oligosaccharide recognition in diverse biological systems.

Antigens↗
PubMed1988

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.

Bacterial Adhesion↗
PubMed1988

Identification of a novel oligosaccharide backbone structure with a galactose residue monosubstituted at C-6 in human foetal gastrointestinal mucins.

An oligosaccharide purified from a major penta- to hexa-saccharide fraction of human meconium glycoproteins has been shown by m.s. and n.m.r. analysis to have a novel backbone structure containing an internal galactose residue monosubstituted at C-6 by N-acetylglucosamine: (Formula: see text). This oligosaccharide may represent a biosynthetic product of a previously unrecognized N-acetylglucosaminyltransferase catalysing formation of a linear GlcNAc beta 1-6Gal sequence.

Carbohydrate Conformation↗
PubMed1988

Improved procedure for the construction of neoglycolipids having antigenic and lectin-binding activities, from reducing oligosaccharides.

Conditions have been established for the rapid and efficient conjugation of reducing oligosaccharides (di- to deca-saccharides) to dipalmitoyl phosphatidylethanolamine. The resulting neoglycolipids derived from several naturally occurring oligosaccharides and a series of N-linked high-mannose-type oligosaccharides released by hydrazinolysis from RNAase B showed specific and potent reactivities, as appropriate, with monoclonal antibodies to blood group Lewis(b), blood group A or a stage-specific embryonic (SSEA-1) antigen, or the lectin concanavalin A.

Amination↗
PubMed1988

Carbohydrate structures of the human-immunodeficiency-virus (HIV) recombinant envelope glycoprotein gp120 produced in Chinese-hamster ovary cells.

The present paper describes the structures of the N-linked oligosaccharides of the human-immunodeficiency-virus (HIV) envelope glycoprotein gp120 (cloned from the HTLV-III B isolate and expressed as a secreted fusion protein after transfection of Chinese-hamster ovary cells), which is known to bind with high affinity to human T4-lymphocytes. Oligosaccharides were released from peptide by hydrazinolysis, fractionated by paper electrophoresis, high-performance lectin-affinity chromatography and Bio-Gel P-4 column chromatography, and their structures determined by sequential exoglycosidase digestions in conjunction with methylation analysis. The glycoprotein was found to be unique in its diversity of oligosaccharide structures. These include high-mannose type and hybrid type, as well as four categories of complex-type chains: mono-, bi-, tri- and tetra-antennary, with or without N-acetyl-lactosamine repeats, and with or without a core-region fucose residue. Among the sialidase-treated oligosaccharides, no less than 29 structures were identified as follows: (formula; see text) where G is galactose, GN is N-acetylglucosamine, M is mannose, F is fucose, and '+/- ' means that residues are present in a proportion of chains. The actual number of oligosaccharide structures is much greater, since before desialylation there was evidence that, among the hybrid and complex-type chains, all but 6% contained sialic acid at the C-3 position of terminal galactose residues, and partially sialylated forms of the bi- and multi-antennary chains were present. Detailed evidence for the proposed oligosaccharide sequences will be published as a supplementary paper [T. Mizuochi, M. W. Spellman, M. Larkin, J. Solomon, L. J. Basa & T. Feizi (1988) Biomed. Chromatogr., in the press].

Animals↗
PubMed1988

A novel carbohydrate, differentiation antigen on fucogangliosides of human myeloid cells recognized by monoclonal antibody VIM-2.

A mouse monoclonal antibody, VIM-2, specific for human blood cells of myelomonocytic lineage, was found to bind to a series of minor gangliosides isolated from the cells of patients with chronic myelogenous leukemia (Uemura, K., Macher, B.A., DeGregorio, M., Scudder, P., Buehler, J., Knapp, W., and Feizi, T. (1985) Biochim. Biophys. Acta 846, 26-36). TLC immunostaining studies with the VIM-2 antibody of gangliosides from normal human neutrophils, acute myeloid leukemia, and chronic myelogenous leukemia cells showed that the total amount and the ratio of the VIM-2 gangliosides varies among these different myeloid cells and appears to be related to the level of cellular differentiation. Purification of these gangliosides from chronic myelogenous leukemia cells was aided by a sensitive enzyme-linked immunosorbent assay procedure used in conjunction with high performance liquid chromatography. Structures for two of the immunoreactive gangliosides (a ceramide decasaccharide, VIII3NeuAcV3-Fuc-nLc8Cer and a ceramide dodecasaccharide X3-NeuAcVII3Fuc-nLc10Cer) are proposed from negative ion fast atom bombardment mass spectrometry of the native gangliosides, methylation analysis, and the combined use of glycosidase treatment and TLC immunostaining with carbohydrate sequence specific antibodies. The VIM-2 antigen was thus characterized as involving the sialofucooligosaccharide sequence.

Antibodies, Monoclonal↗
PubMed1988

500-MHz 1H-n.m.r. and conformational studies of fucosyloligosaccharides recognised by monoclonal antibodies with specificities related to Le(a), Le(b), and SSEA-1.

500-MHz 1H-n.m.r. spectroscopy has been used to examine several fucosylated oligosaccharides in studies to characterise carbohydrate antigenic determinants recognised by monoclonal antibodies. Reduction of the oligosaccharides to give additional variants for analysis showed that oligosaccharides having an alpha-L-fucosyl group linked to the reducing end residue have markedly different chemical shifts, and in some instances different antigenic activity, compared to their alditols. This information was incorporated into space filling molecular models of the oligosaccharides in order to predict the topography of atoms recognised by the antibody combining sites. These studies are an intermediate stage in the full characterisation of oligosaccharide conformation and molecular recognition by methods which accurately determine torsional angles and through-space internuclear distances.

Antibodies, Monoclonal↗
PubMed1988

Further studies of oligosaccharide recognition by the soluble 13 kDa lectin of bovine heart muscle. Ability to accommodate the blood-group-H and -B-related sequences.

Oligosaccharide recognition by the 13 kDa soluble lectin from bovine heart muscle has been investigated by inhibition of binding of the 125I-labelled lectin to trypsin-treated rabbit erythrocytes. The results indicate that the Type 1 (Gal beta 1-3GlcNAc) and the Type 2 (Gal beta 1-4GlcNAc) backbone structures are the basic recognition units, and that the blood-group-H structure, the blood-group-B structure, the 'B-like' structure [afucosyl-(blood group B)] and the alpha 2-3 sialylated analogues of the backbone structures can also be accommodated and hence are candidate receptor structures for the lectin. A comparison of available inhibition data on six other soluble beta-galactoside-binding lectins (three from human lung and three from rat lung) has shown some common features among these and the bovine lectin, e.g. in general a stronger reaction with N-acetyl-lactosamine than with lactose, and a lack of reaction with 3-fucosyl-lactose and 6-sialyl-lactose. However, there are distinctive features among the lectins, e.g. differences in relative reactions with the blood-group-A structure, and no two of the lectins appear to be identical in their fine specificities.

ABO Blood-Group System↗
PubMed1988

Structural characterization by chromatographic profiling of the oligosaccharides of human immunodeficiency virus (HIV) recombinant envelope glycoprotein gp120 produced in Chinese hamster ovary cells.

This report together with the paper by T. Mizuochi, M. W. Spellman, M. Larkin, J. Solomon, L. J. Basa and T. Feizi (1988) Biochem. J. 254, 599-603 describes the structural elucidation of the N-linked oligosaccharides of the HIV envelope glycoprotein, gp120 (cloned from the HTLV-III B isolate and expressed as a secreted fusion protein after transfection of Chinese hamster ovary cells), which is known to bind with high affinity to human T4 lymphocytes. Oligosaccharides were released from peptide by hydrazinolysis, fractionated by paper electrophoresis, high performance lectin affinity chromatography and Bio-Gel P-4 column chromatography, and their structures determined by sequential exoglycosidase digestions in conjunction with methylation analysis. The glycoprotein was found to be unique in its diversity of oligosaccharide structures. These include high-mannose type and hybrid type, as well as four categories of complex type chains: mono-, bi-, tri- and tetra-antennary, with or without N-acetyllactosamine repeats, and with or without a core region fucose residue. Among the sialidase-treated oligosaccharides no less than 29 structures were identified as follows: (formula; see text) where G = galactose; GN = N-acetylglucosamine; M = mannose; F = fucose; +/- = residues present in a proportion of chains. The actual number of oligosaccharide structures is much greater since before desialylation there was evidence that among the hybrid and complex type chains all but 6% contained sialic acid at the C-3 position of terminal galactose residues, and partially sialylated forms of the bi- and multiantennary chains were present.

Animals↗
PubMed1988

Oligosaccharides in molecular recognition.

The development, organization and growth of complex organisms as well as their interactions with the environment involve an intricate array of molecular recognition events. There is an increased awareness of the involvement of oligosaccharides in many of these processes. In this article, studies of oligosaccharide antigenicity, and the way these have been interpreted with respect to oligosaccharide function will be discussed. In addition, examples of oligosaccharides as receptor, first, as receptors and determinants of susceptibility to an exogenous infective agent and secondly, as recognition structures possibly involved in endogenous interactions, will be described. This will be followed by a discussion of the recent hypothesis in which oligosaccharides are envisaged as recognition structures and integral components of cell growth-regulating networks. Finally, an outline of new strategies for decoding the information content in glycoprotein oligosaccharides will be given.

Antigens↗
PubMed1988

Evidence for occurrence of passively adsorbed I antigen activity on a cultured strain of Mycoplasma pneumoniae.

The aim of this study was to investigate whether I antigen occurs in association with Mycoplasma pneumoniae in a form that may be immunogenic during natural infection or experimental immunization. I antigen activity was detected by radioimmunoassay in suspensions of M. pneumoniae MY11965 and in the soluble phase of mycoplasma lysates prepared with Triton X-100. There was evidence for the occurrence of I antigen in at least two macromolecular forms. The first form partitioned in the lipid phase following chloroform-methanol extraction and chromatographed on thin-layer chromatograms as a ceramide decasaccharide. The second form was associated with the residue after lipid extraction and was solubilized by treatment with sodium dodecyl sulfate or pepsin; this component was tentatively designated a glycoprotein or polysaccharide and was not investigated further. In a lipid extract from mycoplasmas that had been surface labeled by the galactose oxidase-NaB3H4 method, two 3H-labeled glycolipids were detected as minor components which chromatographed on thin-layer chromatograms in the region of an authentic I-active ceramide decasaccharide. However, no significant radioactivity was incorporated into glycolipids after metabolic labeling with [3H]glucosamine. These observations suggested that the mycoplasmas contained surface-associated glycolipids with I antigen activity that were of exogenous origin. This was supported by the observations that horse, rabbit, and fetal calf sera contained I antigen activity and that the I antigen activity in M. pneumoniae cultures reflected the levels found in the sera included in the culture media. From rabbit serum, which expressed the highest antigen activity, an I-active glycolipid was isolated that chromatographed as a ceramide decasaccharide. I-active substances passively adsorbed onto M. pneumoniae are potentially immunogenic. However, we consider these unlikely to be the main stimulus for autoantibody production in natural infection, since the autoantibodies elicited are restricted to the I carbohydrate antigen and there is a lack of antibodies to other glycolipids that may be adsorbed from serous and cellular components of the host tissues. In our view, the more likely stimulus is the specific complex formed between the mycoplasma and the sialo-oligosaccharide receptors of the Ii antigen type, as suggested previously.

Animals↗
PubMed1988

Developmental patterning of carbohydrate antigens during early embryogenesis of the chick: expression of antigens of the poly-N-acetyllactosamine series.

This report describes a striking temporal and spatial patterning of specific carbohydrate sequences in the developing chick embryo. By using oligosaccharide sequence-specific monoclonal antibodies as immunohistochemical reagents in conjunction with neuraminidase, it was possible to visualize the occurrence, as well as the changes in distribution, of oligosaccharides of the poly-N-acetyllactosamine series. These were (a) long-chain unbranched sequences reactive with anti-i Den, (b) long-chain branched sequences reactive with anti-I Step and (c) short-chain branched sequences reactive with anti-I Ma and (d) their sialylated forms. The salient observations with serial sections of embryos from the unincubated to the 17th stage were as follows. (1) A pronounced anteroposterior patterning appeared during neuroectodermal development, such that the long-chain unbranched and long-chain branched sequences, which were abundant on the ectoderm of the earlier stages, were replaced by short-chain branched sialo-oligosaccharides in the developing brain and anterior neural tube. (2) A striking anteroposterior and mediolateral patterning developed in the subectodermal extracellular spaces. The long-chain linear and short-chain non-sialylated sequences demarcated regions favourable for migration of the lateral plate mesoderm. (3) A distinction was made between the dorsal and ventral routes of the trunk neural crest in that the extracellular matrix of the dorsal route only was associated with long-chain linear and short-chain sialylated branched sequences. (4) A circumscribed perinotochordal distribution of the short-chain sialylated branched sequences was observed in the region of the future centra of the vertebrae. (5) An abundance of long-chain linear and long-chain sialylated branched structures was detected in primordial germ cells which permitted their identification during migration. These observations suggest that oligosaccharides of the poly-N-acetyllactosamine series may have roles as short-range, region-specific information factors during morphogenetic events that take place in the developing embryo, and they open the way to the search for recognition proteins (e.g. endogenous lectins) specific for each of these oligosaccharide structures.

Animals↗
PubMed1987

Amino acid sequence of beta-galactoside-binding bovine heart lectin. Member of a novel class of vertebrate proteins.

A variety of animal tissues contain beta-galactoside-binding lectins with molecular masses in the range 13-17 kDa. There is evidence that these lectins may constitute a new protein family although their function in vivo is not yet clear. In this work the major part of the amino acid sequence of the 13 kDa lectin from bovine heart muscle has been determined. Comparison of this sequence with the cDNA-deduced sequence published for the chick embryo skin lectin showed 58% homology. Comparison of the bovine lectin sequence with partial sequences from two cDNA clones from a human hepatoma library and partial amino acid sequences of human lung lectin showed 70, 40 and 85% homology, respectively. The sequences of these vertebrate lectins are thus clearly related, supporting earlier results of immunological cross-reactivity within this group of proteins. Computer searching of protein sequence databases did not detect significant homologies between the bovine lectin sequence and other known proteins.

Amino Acid Sequence↗