Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For many years, molecular interactions with vascular endothelium have been studied in vitro on cultured endothelial cells. Yet, it is clear that the different environmental conditions in vivo vs. in vitro may cause phenotypic drift and altered expression of cell surface molecules. In this study, we identify several endothelial surface proteins of similar apparent molecular mass by radioiodination of cultured microvascular cells and by intravascular radioiodination of rat heart endothelium in situ. The radioiodinated surface polypeptides detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (followed by autoradiography) were subjected to lectin affinity chromatography in order to provide an additional screen for identifying common surface glycoproteins and a means for partial characterization of their glycans. With a battery of 18 lectins, seven major (gp140, gp120, gp100, gp85, gp75, gp60, gp47) and 6 minor (gp330, gp300, gp180, gp160, gp150, gp42) glycoproteins were identified on the cultured cells each with a different lectin binding profile. The lectin binding profiles of many endothelial glycoproteins in situ were similar to those of their counterparts in culture. A common set of seven major glycoproteins with the same apparent molecular masses was found in situ as well as in vitro. These common glycoproteins were characterized further using both sialidase digestion and sequential lectin affinity chromatography of cell lysates. Most of the glycoproteins appear to have both complex-type N-linked and O-linked glycans except for gp60 with only O-linked glycans, gp47 with only complex N-linked sugars, and gp42 with only simple N-linked sugars. A subset of sialoglycoproteins (gp140, gp120, gp100, gp60, gp47) was identified. One of them, gp120, is podocalyxin based on immunoprecipitation with specific antiserum and another one, gp60, is a recently identified albumin binding protein on the surface of cultured microvascular endothelial cells. This study shows that gp60 is indeed present on the surface of endothelium in situ and that it is a sialoglycoprotein with typical O-linked glycans. It is apparent that the continuous type of microvascular endothelium can indeed express in culture and in situ a common set of major glycoproteins.
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PMID:Lectin analysis of common glycoproteins detected on the surface of continuous microvascular endothelium in situ and in culture: identification of sialoglycoproteins. 208 27

A new sialic acid-specific lectin from the colonic parasite of squirrel monkeys Tritrichomonas mobilensis (TML) was tested on human and mouse tissues for histochemical staining properties. There were no substantial differences in reactivity between frozen and formalin fixed paraffin sections. TML staining was blocked by preincubation with sialic acid or by sialidase digestion. TML/anti-TML antibody histochemistry was identical with the TML-gold technique. The staining pattern was not blood group dependent. TML stained strongly the luminal membranes of normal vascular endothelium as well as endothelial neoplasms. Lymphatic vessels and capillaries of kidney glomeruli and lung alveolar septi were negative or only slightly positive. In parenchymatous organs luminal membrane positivity was dominant, preferably of cells lining ducts. Weak fine-granular cytoplasmic and basolateral membrane staining was also observed. Umbrella cells in transitional epithelium and basal layers of squamous epithelia showed strong reactivity with cell membranes. Mucin in respiratory epithelium was positive whereas gastrointestinal mucins failed to stain uniformly. Erythrocytes and most white blood cell types showed distinct membrane positivity. Acetylation or alkaline O-deacetylation of tissue sections did not substantially change TML reactivity. Oxidation, however, completely blocked TML staining except for respiratory epithelium and colonic mucin.
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PMID:Histochemical localization of sialylated glycoconjugates with Tritrichomonas mobilensis lectin (TLM). 883 52

P-selectin (CD62P) is a Ca2+-dependent endogenous lectin that can be expressed by vascular endothelium and platelets. The major ligand for P-selectin on leukocytes is P-selectin glycoprotein ligand-1 (PSGL-1). P-selectin can also bind to carcinoma cells, but the nature of the ligand(s) on these cells is unknown. Here we investigated the P-selectin binding to a breast and a small cell lung carcinoma cell line that are negative for PSGL-1. We report that CD24, a mucin-type glycosylphosphatidylinositol-linked cell surface molecule on human neutrophils, pre B lymphocytes, and many tumors can promote binding to P-selectin. Latex beads coated with purified CD24 from the two carcinoma cell lines but also neutrophils could bind specifically to P-selectin-IgG. The binding was dependent on divalent cations and was abolished by treatment with O-sialoglycoprotein endopeptidase but not endoglycosidase F or sialidase. The beads were stained with a monoclonal antibody (MoAb) to CD57 (HNK-1 carbohydrate epitope) but did not react with MoAbs against the sialylLe(x/a) epitope. The carcinoma cells and CD24-beads derived from these cells could bind to activated platelets or P-selectin transfected Chinese hamster ovary cells (P-CHO) in a P-selectin-dependent manner and this binding was blocked by soluble CD24. Transfection of human adenocarcinoma cells with CD24 enhanced the P-selectin-dependent binding to activated platelets. Treatment of the carcinoma cells or the CD24 transfectant with phosphatidylinositol-specific phospholipase C reduced CD24 expression and P-selectin-IgG binding concomitantly. These results establish a role of CD24 as a novel ligand for P-selectin on tumor cells. The CD24/P-selectin binding pathway could be important in the dissimination of tumor cells by facilitating the interaction with platelets or endothelial cells.
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PMID:CD24, a mucin-type glycoprotein, is a ligand for P-selectin on human tumor cells. 912 46

The adherence of sickle red blood cells (RBCs) to the vascular endothelium may contribute to painful vaso-occlusion in sickle cell disease. Sickle cell adherence involves several receptor-mediated processes and may be potentiated by the up-regulated expression of adhesion molecules on activated endothelial cells. Recent results showed that thrombin rapidly increases the adhesivity of endothelial cells for sickle erythrocytes. The current report presents the first evidence for the novel adhesion of normal and, to a greater extent, sickle RBCs to endothelial P-selectin. Studies of the possible interaction of erythrocytes with P-selectin revealed that either P-selectin blocking monoclonal antibodies or sialyl Lewis tetrasaccharide inhibits the enhanced adherence of normal and sickle cells to thrombin-treated endothelial cells. Both RBC types also adhere to immobilized recombinant P-selectin. Pretreating erythrocytes with sialidase reduces their adherence to activated endothelial cells and to immobilized recombinant P-selectin. Herein the first evidence is presented for the binding of normal or sickle erythrocytes to P-selectin. This novel finding suggests that P-selectin inhibition be considered as a potential approach to therapy for the treatment of painful vaso-occlusion in sickle cell disease.
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PMID:P-selectin mediates the adhesion of sickle erythrocytes to the endothelium. 1153 35

Selectin-mediated binding of tumor cells to platelets, leukocytes, and vascular endothelium may regulate their hematogenous spread in the microvasculature. We recently reported that CD44 variant isoforms (CD44v) on LS174T colon carcinoma cells possess selectin binding activity. Here we extended those findings by showing that T84 and Colo205 colon carcinoma cells bind selectins via sialidase-sensitive O-linked glycans presented on CD44v, independent of heparan and chondroitin sulfate. To assess the functional role of CD44v in selectin-mediated binding, we quantified the adhesion to selectins of T84 cell subpopulations sorted based on their CD44 expression levels and stable LS174T cell lines generated using CD44 short hairpin RNA. High versus low CD44-expressing T84 cells tethered more efficiently to P- and L-selectin, but not E-selectin, and rolled more slowly on P- and E-selectin. Knocking down CD44 expression on LS174T cells inhibited binding to P-selectin and increased rolling velocities over P- and L-selectin relative to control-transfected cells, without affecting tethering and rolling on E-selectin, however. Blot rolling analysis revealed the presence of alternative sialylated glycoproteins with molecular masses of approximately 170 and approximately 130 kDa, which can mediate selectin binding in CD44-knockdown cells. Heparin diminishes the avidity of colon carcinoma cells for P- and L-selectin, which may compromise integrin-mediated firm adhesion to host cells and mitigate metastasis. Our finding that CD44v is a functional P-selectin ligand on colon carcinoma provides a novel perspective on the enhanced metastatic potential associated with tumor CD44v overexpression and the role of selectins in metastasis.
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PMID:Selectin ligand expression regulates the initial vascular interactions of colon carcinoma cells: the roles of CD44v and alternative sialofucosylated selectin ligands. 1713 56