Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.4.99.7 (sialyltransferase)
 1,534 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the glycoconjugates of the human bronchial glands at light and electron microscopic level by means of lectin histochemistry in combination with neuraminidase digestion and beta-elimination reaction. Both direct and indirect techniques using lectin-peroxidase, lectin-gold, and glycoprotein-gold complexes were applied. The binding pattern of the six lectins (ConA, HPA, DSA, WGA, LEA, and PNA) used in the present study suggests that mucous and serous cells of human bronchial glands contain both N- and O-glycosylated proteins in the secretory granules. Asparagine-linked oligosaccharides containing Gal(beta-1,4) GlcNAc and Man residues were abundant in serous cells. The demonstration of both the terminal Neu 5Ac (alpha-2,3, or 6) Gal (beta-1,4) GlcNAc sequence in the N-linked oligosaccharides of mucous cells and the terminal disaccharide Gal (beta-1,4) GlcNAc in the N-linked oligosaccharide chains of serous cells suggests the existence of complex type sugar chains N-glycosidically linked to the peptide region of the glycoproteins. The binding pattern of the DSA and the neuraminidase-DSA sequence provides evidence for the existence of sialyltransferase activity in the forming mucous granules of mucous bronchial cells.
 ...
PMID:Ultrastructural localization of glycoconjugates in human bronchial glands: the subcellular organization of N- and O-linked oligosaccharide chains. 155 69

The role of acidic glycosphingolipids in cell growth and differentiation was investigated using the multipotent leukemia cell line K562. When GM3 was added to cell culture media, the growth of K562 cells was remarkably inhibited and the cells were shown to have megakaryocytoid morphology. Ultrastructural study demonstrated that K562 cells treated with GM3 had platelet peroxidase-positive structures, which were considered to be the specific marker of megakaryocyte. Furthermore, AP-3 directed against an epitope present on membrane glycoprotein IIIa reacted with the GM3-treated cells. Free N-acetylneuraminic acid, GM1, GM2, GD1a, and a mixture of bovine brain gangliosides containing GD1a and GT1b did not affect growth of K562 cells or show morphological changes. According to chemical analyses, GM3 content increased in megakaryocytoid differentiation induced by tetradecanoylphorbol-13-acetate, whereas GM3 decreased in erythroid differentiation induced by hemin. Enzymatic analysis showed that the GM3 increase during megakaryocytoid differentiation was a result of the sialyltransferase activation. These results indicated that exogenous GM3 induced differentiation of K562 cells into a "GM3-rich" lineage, i.e., mainly megakaryocytoid lineage, and that GM3 accumulation in the GM3-rich lineage was the result of the activation of GM3 synthase. These findings strongly suggested that GM3 ganglioside, a minor membrane component, has a crucial role in not only the differentiation induction but also the determination of the differentiation direction in pluripotent K562 cells.
 ...
PMID:Ganglioside GM3 can induce megakaryocytoid differentiation of human leukemia cell line K562 cells. 200 80

The binding sites of the antibody to cytosolic sialidase on the rat and monkey photoreceptor cells were examined immunohistochemically using the avidin-biotinylated peroxidase method. In the rat photoreceptor cells, the antibody bound diffusely to the inner segment and the outer nuclear layers which are composed chiefly of rod cells. In the monkey photoreceptor cells, the antibody bound to the rod inner segments which were clearly distinct, morphologically, from the cone inner segments. The antibody also bound to the rod cell bodies in the outer nuclear layer. These binding patterns show that the antibody bound preferentially to rod photoreceptor cells. This observation is consistent with previous lectin histochemical findings that sialoglycans are preferentially present on the surfaces of rod photoreceptors, and in the rod-associated interphotoreceptor matrix. Sialidase in rod inner segments may function by balancing with sialyltransferase, also preferentially expressed in rod inner segments, to form sialyl residues on the termini of sugar chains in the rod-associated sialoglycoconjugates.
 ...
PMID:Immunohistochemical localization of cytosolic sialidase in photoreceptor cells. 887 86

Insulin regulates glucose transport in muscle and adipose tissue by triggering the translocation of a facilitative glucose transporter, GLUT4, from an intracellular compartment to the cell surface. It has previously been suggested that GLUT4 is segregated between endosomes, the trans-Golgi network (TGN), and a postendosomal storage compartment. The aim of the present study was to isolate the GLUT4 storage compartment in order to determine the relationship of this compartment to other organelles, its components, and its presence in different cell types. A crude intracellular membrane fraction was prepared from 3T3-L1 adipocytes and subjected to iodixanol equilibrium sedimentation analysis. Two distinct GLUT4-containing vesicle peaks were resolved by this procedure. The lighter of the two peaks (peak 2) was comprised of two overlapping peaks: peak 2b contained recycling endosomal markers such as the transferrin receptor (TfR), cellubrevin, and Rab4, and peak 2a was enriched in TGN markers (syntaxin 6, the cation-dependent mannose 6-phosphate receptor, sortilin, and sialyltransferase). Peak 1 contained a significant proportion of GLUT4 with a smaller but significant amount of cellubrevin and relatively little TfR. In agreement with these data, internalized transferrin (Tf) accumulated in peak 2 but not peak 1. There was a quantitatively greater loss of GLUT4 from peak 1 than from peak 2 in response to insulin stimulation. These data, combined with the observation that GLUT4 became more sensitive to ablation with Tf-horseradish peroxidase following insulin treatment, suggest that the vesicles enriched in peak 1 are highly insulin responsive. Iodixanol gradient analysis of membranes isolated from other cell types indicated that a substantial proportion of GLUT4 was targeted to peak 1 in skeletal muscle, whereas in CHO cells most of the GLUT4 was targeted to peak 2. These results indicate that in insulin-sensitive cells GLUT4 is targeted to a subpopulation of vesicles that appear, based on their protein composition, to be a derivative of the endosome. We suggest that the biogenesis of this compartment may mediate withdrawal of GLUT4 from the recycling system and provide the basis for the marked insulin responsiveness of GLUT4 that is unique to muscle and adipocytes.
 ...
PMID:Characterization of insulin-responsive GLUT4 storage vesicles isolated from 3T3-L1 adipocytes. 1059 43