Human erythrocyte sialidase is linked to the plasma membrane by a glycosylphosphatidylinositol anchor and partly located on the outer surface (original) (raw)
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Effect of sialidase on the viability of erythrocytes in circulation
American Journal of Hematology, 1976
Sialic acid has been detected on the erythrocyte surface of a number of different species of animals. The objective of this investigation was to determine the physiological significance of these sialyl residues to the viability of erythrocytes in circulation. Methods have been described for the determination of total sialic acid on red blood cells and the conditions under which it may be released with sialidase. Chicken, dog, goat, and rabbit were chosen for these studies because of the differences in the amount (3 X 106-72 X l o 6 residues per erythrocyte), and type (N-acetyl-or N-glycolyl-neuraminic acids) of sialic acid found on the surface of their erythrocytes. Radioactive tagging with Na2 51 Cr04 was used to monitor the effect of sialidase on the viability of erythrocytes upon autologous transfusion. By the two criteria used to assess the viability of erythrocytes ~ the percentage of erythrocytes surviving 24 hr after the autologous transfusion, and the half-life of those red blood cells in circulation that survive the first 24 hrit is apparent that the presence of sialic acid on the cell surface is crucial for the survival of nonnucleated mammalian erythrocytes. The loss of viability of dog erythrocytes can be elicited by the removal of approximately 10% of the total sialic acid. In marked contrast to the behavior of mammalian erythrocytes, sialidase-treated chicken erythrocytes appear t o retain their viability in circulation.
Acidic and neutral sialidase in the erythrocyte membrane of type 2 diabetic patients
2010
patients Acidic and neutral sialidase in the erythrocyte membrane of type 2 diabetic http://bloodjournal.hematologylibrary.org/content/99/3/1064.full.html Updated information and services can be found at: (1174 articles) Red Cells Articles on similar topics can be found in the following Blood collections http://bloodjournal.hematologylibrary.org/site/misc/rights.xhtml#repub\_requests
Glycoconjugate Journal, 2006
Glycosphingolipids and glycoproteins play pivotal roles in the complex series of events governing cell adhesion and signal transduction. Aberrant glycosilation, typical of tumor cells, represents a key event in the induction of invasion and metastasis. Sialidases remove sialic acid residues from sialoconjugates and, in mammals, these enzymes have been proved to be involved in several cellular phenomena, including cell proliferation and differentiation, membrane function, and malignant transformation. Herein we show that only the lysosomal sialidase Neu1 and the plasma membrane-associated sialidase Neu3 are expressed in CFU-E erythroid precursors and K562 erythroleukemic cells. Tumour cells show much higher expression levels than CFU-E cells and, during differentiation, the content of the two enzymes progressively decreases. The sialoglycoconjugate pattern is different in the two cell types. In fact, the differentiating erythroid precursors show an increase of the typical erythrocyte sphingolipids, whereas K562 cells treated with butyrate show a marked increase of GD1a, GM2, PE, and ceramide. Finally, during differentiation the sialoglycoprotein content of erythroid cells shows a marked increase, and in K562 cells the process induces the synthesis of some sialoglycoprotein typical of the erythroid membrane. Overall, these results point out the great differences in sialoglycoconjugate and sialidase patterns exhibited by normal and tumour cells.
Biophysical Journal, 2005
Although cell membranes normally resist the hydrolytic action of secretory phospholipase A2 (sPLA2), they become susceptible during apoptosis or after cellular trauma. Experimentally, susceptibility to the enzyme can be induced by loading cells with calcium. In human erythrocytes, the ability of the calcium ionophore to cause susceptibility depends on temperature, occurring best above ∼35°C. Considerable evidence from experiments with artificial bilayers suggests that hydrolysis of membrane lipids requires two steps. First, the enzyme adsorbs to the membrane surface, and second, a phospholipid diffuses from the membrane into the active site of the adsorbed enzyme. Analysis of kinetic experiments suggested that this mechanism can explain the action of sPLA2 on erythrocyte membranes and that temperature and calcium loading promote the second step. This conclusion was further supported by binding experiments and assessment of membrane lipid packing. The adsorption of fluorescent-labeled sPLA2 was insensitive to either temperature or ionophore treatment. In contrast, the fluorescence of merocyanine 540, a probe sensitive to lipid packing, was affected by both. Lipid packing decreased modestly as temperature was raised from 20 to 60°C. Calcium loading enhanced packing at temperatures in the low end of this range, but greatly reduced packing at higher temperatures. This result was corroborated by measurements of the rate of extraction of a fluorescent phosphatidylcholine analog from erythrocyte membranes. Furthermore, drugs known to inhibit susceptibility in erythrocytes also prevented the increase in phospholipid extraction rate. These results argue that the two-step model applies to biological as well as artificial membranes and that a limiting step in the hydrolysis of erythrocyte membranes is the ability of phospholipids to migrate into the active site of adsorbed enzyme.
Uptake of sialic acid by human erythrocyte. Characterization of a transport system
Biochimie, 2003
C] N-acetylneuraminic acid, the cells incorporated this sugar, as demonstrated by the identification of labelled N-acetylmannosamine in the cytosol, as a result of the action of the sialic acid pyruvate-lyase we discovered previously (Biochimie 84 ). The mechanism is saturable and indicates the presence of a limited number of transporter molecules in the RBC membrane. This transport process may have relevance to the desialylation of membrane glycoconjugates which occurs during ageing of erythrocytes.
Membrane anchoring and surface distribution of glycohydrolases of human erythrocyte membranes
FEBS Letters, 2000
The membrane anchoring of the following glycohydrolases of human erythrocyte plasma membranes was investigated: α‐ and β‐D‐glucosidase, α‐ and β‐D‐galactosidase, β‐D‐glucuronidase, N‐acetyl‐β‐D‐glucosaminidase, α‐D‐mannosidase, and α‐L‐fucosidase. Optimized fluorimetric methods for the assay of these enzymes were set up. Treatment of the ghost preparation with 1.0 mol/l (optimal concentration) NaCl caused release ranging from 4.2% of α‐D‐glucosidase to 70% of β‐D‐galactosidase; treatment with 0.4% (optimal concentration) Triton X‐100 liberated 5.1% of β‐D‐galactosidase to 89% of α‐D‐glucosidase; treatment with 1.75% (optimal concentration) octylglucoside yielded solubilization from 6.3% of β‐D‐galactosidase to 85% of α‐D‐glucosidase. Treatment with phosphoinositide‐specific phospholipase C caused no liberation of any of the studied glycohydrolases. These results are consistent with the notion that the above glycohydrolases are differently anchored or associated with the erythrocyte ...