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)

Leukocyte rolling precedes firm adhesion and emigration in inflammatory cell recruitment. Both P-selectin, an endothelial lectin that binds to sialylated O-glycans containing sialyl-Lewisx (sLex) on the granulocyte surface, and leukocyte L-selectin have been shown to mediate leukocyte rolling in vivo. Here, we investigate rolling of isolated human neutrophils (PMN), HL-60 promyelocytes, and an L-selectin-transfected cell line (300.19-L) during trauma-induced inflammation in rat mesenteric venules. HL-60 cells, which express no L-selectin but abundant sLex, rolled effectively immediately after abdominal surgery. HL-60 cell rolling was almost completely abolished by pretreatment with sialidase or monoclonal antibody (MoAb) AM-3 recognizing sLex, and was reduced by about 80% by O-sialoglycoprotein-endopeptidase (OSGP). By contrast, 300.19-L cells rolled poorly immediately after surgery but rolled well between 40 and 120 minutes after surgery. Their rolling was completely inhibited by the blocking L-selectin MoAb LAM1-3, but not by a binding control MoAb. PMN express both L-selectin and clustered, sialylated glycoproteins including P-selectin glycoprotein ligand-1 (PSGL-1). PMN showed effective rolling at all times, which was abolished by sialidase or MoAb AM-3 pretreatment during the first 30 minutes after surgery, but not later, when PMN rolling was largely L-selectin-dependent. We conclude that in trauma-induced inflammation, a two-step mechanism accounts for most of myeloid cell rolling, which initially requires O-glycans and subsequently depends on L-selectin function.
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PMID:Sialylated O-glycans and L-selectin sequentially mediate myeloid cell rolling in vivo. 754 70

There are few examples of phosphorous carbohydrates described in higher animals. Here we have used recombinant molecules where the extracellular part of membrane receptors have been fused with the Fc part of human IgG (Rg-chimeras) to look at the prevalence of phosphorous carbohydrates. Also chimeras of a few hormones were used in this study. Thirteen Rg constructs were transfected into Cos cells and labelled with [32P]orthophosphate in phosphor deficient media. These Rg molecules were subsequently purified on protein A-Sepharose and submitted to SDS-PAGE and radiography. CD22Rg, CD62L-Rg and CD44Rg were all labelled very strongly with 32P. From CD22Rg and CD62L-Rg the label could be easily removed by N-glycosidase F, but the 32P label on CD44Rg was resistant to N-glycosidase treatment. However, after treatment with O-glycosidase combined with sialidase, CD44Rg retained only a fraction of the 32P. Weakly phosphorylated Rg molecules were CD62E-Rg and CD7Rg. However, CD7Rg did not seem to loose the label, only shift position after N-glycosidase treatment and CD62E-Rg did neither shift position nor loose any 32P label after the N-glycosidase treatment. Negative chimeras were CD40Rg, CD33Rg, Lamp-1Rg, CD34Rg, ICAM-1Rg, TNF alpha Rg, CD19Rg and CD5Rg. The phosphate label of CD22Rg was completely removed after ALP treatment and in CD44Rg most of the label was removed. ALP is not supposed to cleave phosphodiesterbonds leading to the conclusion that the phosphor is likely present in the form of phosphomonoesters. This result is interesting as alkaline phosphatase (ALP) is common on the outer cellsurface of many cell types and might interact with phosphorous carbohydrates on membrane proteins. The membrane from of CD22 was also transfected into Cos cells and labelled with 32P in phosphate free media. Subsequently the cells were lysed and CD22 affinity purified and analysed by SDS-PAGE and radiography. Under these conditions CD22 was shown to be 32P labelled, but only 20% of the label was removed by N-glycosidase F treatment. These results do not show that CD22, CD44 and CD62L are phosphorylated on carbohydrates under more physiological circumstances, but they do show that phosphorous carbohydrates might be more common in higher animals than what was been reported.
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PMID:Phosphorous carbohydrates on chimeric CD22, CD44 and CD62L. 887 16

Following activation of granulocytes, L-selectin (CD62L) is generally shed from the cellular surface, whereas Mac-1 (CD11b/CD18) expression is well known to increase. However, a number of studies in bovines and humans show that the expression of L-selectin may increase as well. This urged us to examine the possible existence of both L-selectin and Mac-1 reservoirs in bovine neutrophil and eosinophil populations through the use of flow cytometry in combination with an optimized method for cell membrane permeabilization. Augmented L-selectin and Mac-1 expression was detected in both granulocyte populations upon saponin treatment. Confocal microscopic studies indicated that both molecules exhibit a different pattern of subcellular localization. Incubation with sialidase revealed the existence of hidden L-selectin epitopes at the cell surface, while no additional Mac-1 epitopes were exposed. Platelet-activating factor stimulation decreased surface and total expression of L-selectin to the same extent in both populations, but solely affected Mac-1 surface expression on eosinophils. Moreover, cytoskeletal actin filaments and microtubules were found to be involved in the regulation of Mac-1 surface expression on bovine neutrophils and eosinophils. In marked contrast, expression of L-selectin was minimally affected by cytoskeleton perturbing agents. The present study indicates that L-selectin and Mac-1 adhesion molecules reside in distinctly located reservoirs in bovine granulocytes and can be selectively mobilized upon in vitro stimulation.
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PMID:Analysis of selective mobilization of L-selectin and Mac-1 reservoirs in bovine neutrophils and eosinophils. 1258 84