Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The phenomenon of tissue-specific homing of lymphocyte populations has been most clearly shown in larger domestic animals, such as the sheep and cow, yet the molecular interactions which control these processes in these animals have not been defined. Here we tested the cross-reactivity of four anti-human peripheral lymph node homing receptor (LECAM-1) (also known as LAM-1, LEC-CAM-1, Leu-8, TQ-1, or human equivalent of gp90 MEL-14) antibodies on bovine lymphocytes. These antibodies stained all bovine neutrophils and monocytes, and variable numbers of peripheral blood lymphocytes, as determined by flow cytometry. In young calves (less than 1 month old) virtually all circulating lymphocytes expressed LECAM-1, whereas the percentage of positive lymphocytes in older animals (greater than 1 year) varied from 17%-67%. Bovine LECAM-1 was rapidly lost from the cell surface of PMA-activated and chymotrypsin-treated cells. Anti-LECAM-1 monoclonal antibody blocked greater than 80% of bovine lymphocyte binding to peripheral lymph node high endothelial venules (HEV). Since the lectin domain of LECAM-1 is thought to mediate lymphocyte-HEV adhesion, we sought to establish further the similarity of the bovine, mouse, and human molecules by comparing nucleotide sequences in this region of the molecule. The polymerase chain reaction (PCR) was used to specifically clone the bovine lectin domain from single-strand cDNA. Subsequent sequencing showed an identity of greater than 80% at the nucleotide level with the human and mouse molecules. The predicted amino acid sequences were also highly conserved. Though striking similarities were seen between the bovine, mouse and human molecule, indicating evolutionary conservation of this family of proteins, notable differences were detected. The nucleotide sequence of the bovine lectin domain predicts one additional N-linked glycosylation site compared to mouse and human. Preliminary analysis suggested a more tissue-restricted expression of LECAM-1 in the compared to the human and mouse, which correlates with a better separation of lymphocyte homing phenotypes seen in these larger animals. Virtually all peripheral lymph node lymphocytes in 6-month-old calves expressed LECAM-1, whereas, ileal Peyer's patch lymphocytes were predominantly negative. Finally, by testing anti-human LECAM-1 antibodies in a different species we have established the co-expression of antigenic epitopes on leucocyte LECAM-1 and a molecule(s) expressed by endothelial cells.
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PMID:Characterization of the bovine peripheral lymph node homing receptor: a lectin cell adhesion molecule (LECAM). 137 68

P-selectin on platelets and endothelial cells and E-selectin on endothelial cells are leukocyte receptors that recognize lineage-specific carbohydrates on neutrophils and monocytes. The proposed ligands for these receptors contain the Le(x) core and sialic acid. Since other investigators have shown that both E-selectin and P-selectin bind to sialylated Le(x), we evaluated whether E-selectin and P-selectin recognize the same counter-receptor on leukocytes. The interaction of HL60 cells with Chinese hamster ovary (CHO) cells expressing P-selectin or E-selectin was studied. To determine whether a protein component is required in addition to sialyl Le(x) for either P-selectin or E-selectin recognition, HL60 cells or neutrophils were digested with proteases, including chymotrypsin, elastase, proteinase Glu-C, ficin, papain, or thermolysin. Cells treated with these proteases bound E-selectin but not P-selectin. Fucosidase or neuraminidase treatment of HL60 cells markedly decreased binding to both E-selectin- and P-selectin-expressing CHO cells. Growth of HL60 cells in tunicamycin inhibited the ability of these cells to support P-selectin-mediated binding and, to a lesser extent, E-selectin-mediated binding. Purified P-selectin inhibited CHO:P-selectin binding to HL60 cells, but incompletely inhibited CHO:E-selectin binding to HL60 cells. However, purified soluble E-selectin inhibited CHO:P-selectin and CHO:E-selectin binding to HL60 cells equivalently and completely. COS cells, unable to bind to E-selectin or P-selectin, bound E-selectin but not P-selectin upon transfection with alpha-1,3-fucosyltransferase or alpha-1,3/1,4-fucosyltransferase. Similarly, LEC 11 cells expressing sialyl Le(x) bound E-selectin- but not P-selectin-expressing CHO cells. Sambucus nigra lectin, specific for the sialyl-2,6 beta Gal/GalNAc linkage, inhibited P-selectin but not E-selectin binding to HL60 cells. Although sialic acid and Le(x) are components of the P-selectin ligand and the E-selectin ligand, these results indicate that the ligands are related, having overlapping specificities, but are structurally distinct. A protein component containing sialyl Le(x) in proximity to sialyl-2,6 beta Gal structures on the P-selectin ligand may contribute to its specificity for P-selectin.
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PMID:P-selectin and E-selectin. Distinct but overlapping leukocyte ligand specificities. 137 36