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

The entry of blood-borne lymphocytes into most secondary lymphoid organs is initiated by a highly specific adhesive interaction with the specialized cuboidal endothelial cells of high endothelial venules (HEV). The adhesive receptors on lymphocytes that dictate interactions with HEV in different lymphoid organs are called homing receptors, signifying their critical role in controlling organ-selective lymphocyte migration. Considerable work has established that the mouse peripheral lymph node homing receptor (pnHR), defined by the mAb MEL-14, functions as a lectin-like adhesive protein. We have previously shown that sialidase treatment of peripheral lymph node (PN) HEV abrogates lymphocyte attachment to the HEV both in vivo and in vitro. We extend this evidence by demonstrating that Limax agglutinin (LA), a sialic acid-specific lectin, when reacted with HEV exposed in cryostat-cut tissue sections, blocks lymphocyte attachment to PN HEV and, unexpectedly, to the HEV of Peyer's patches (PP) as well. Using a recombinant form of the pnHR as a histochemical probe for its cognate adhesive site (HEV-ligand) on PN HEV, we demonstrate that both sialidase and Limax agglutinin functionally inactive this ligand. It is concluded that the requirement for sialic acid is at the level of the pnHR interaction with its HEV ligand. A distinct sialyloligosaccharide may encode the recognition determinant of a PP HEV ligand.
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PMID:Requirement for sialic acid on the endothelial ligand of a lymphocyte homing receptor. 227 86

During the course of their recirculation through the body, blood-borne lymphocytes specifically adhere to high endothelial venules (HEV) within secondary lymphoid organs such as peripheral lymph nodes (PN) and gut-associated Peyer's patches (PP). This adherence event, which initiates the extravasation of the lymphocyte, is highly specific in terms of the class of lymphocyte and the anatomic location of the HEV. We review evidence that the lymphocyte adhesive molecule ('homing receptor') involved in attachment to PN HEV is a carbohydrate-binding receptor (lectin-like) with specificity for mannose-6-phosphate (M6P)-like ligands. We describe the use of a novel cytochemical probe for the detection and characterization of cell surface carbohydrate-binding receptors. Using a M6P-based probe, we show that the carbohydrate-binding receptor on lymphocytes is closely-related or identical to the MEL-14 antigen, a putative homing receptor identified by a monoclonal antibody. Evidence is presented that the lymphocyte attachment sites on both PN and PP HEV are inactivated by mild periodate oxidation and hence are probably carbohydrate in nature. Yet, the sites are biochemically distinguishable in that one class (PN) requires sialidase-sensitive structures whereas the other (PP) does not. We raise the possibility that diversity in the carbohydrate-based recognition determinants on HEV may underlie the adhesive specificities in this system.
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PMID:Lymphocyte attachment to high endothelial venules during recirculation: a possible role for carbohydrates as recognition determinants. 302 59

Endogenous expression of human membrane type ganglioside sialidase (Neu3) was examined in various cell lines including NB-1, U87MG, SK-MEL-2, SK-N-MC, HepG2, Hep3B, Jurkat, HL-60, K562, ECV304, Hela and MCF-7. Expression was detected in the neuroblastoma cell lines NB-1 and SK-N-MC, and also in erythroleukemia K562 cells, but not in any other cells. We isolated a Neu3 cDNA from K562 cells and expressed a His-tagged derivative in a bacterial expression system. The purified recombinant product of approximately 48 kDa had sialidase activity toward 4-methyl-umbelliferyl-alpha-D-N-acetylneuraminic acid (4MU-NeuAc). The optimal pH of the purified Neu3 protein for GD3 ganglioside was 4.5. The enzyme also efficiently hydrolyzed GD3, GD1a, GD1b and GM3 whereas sialyllactose, 4MU-NeuAc, GM1 and GM2 were poor substrates, and it had no activity against sialylated glycoproteins such as fetuin, transferrin and orosomucoid. We conclude that the sialidase activity of Neu3 is specific for gangliosides.
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PMID:Molecular characterization of membrane type and ganglioside-specific sialidase (Neu3) expressed in E. coli. 1517 41