Erythrocytes sialidase

Chiarini, A., Fiorilli, A., di Francesco, L., Venerando, B., and Tettamanti, G., 1993, Human erythrocyte sialidase is linked to the plasma membrane by a glycosylphosphatidylinositol anchor and partly located on the outer surface, Glycoconj. J. 10 64-71. 

Although most of the sialidases have been purified by classical methods of enzyme isolation, affinity chromatography is now coming more and more into use, as is indicated by the foregoing examples of purification of sialidases. The adsorbent first used for chromatography of sialidases was sialic acid bound to the surface of intact erythrocytes ... 

Desialylation of thrombocytes478 477 and erythrocytes also leads to their disappearance from circulation. Treatment of erythrocytes from different mammals, including man, with sialidase results in rapid clearance of these cells from the blood stream within a few hours, a phenomenon first observed by Perona and coworkers,478 and later investigated in various laboratories it was reviewed in Ref. 479. In man, the life-time of red blood-cells decreases from the normal 120 days to 2 h after sialidase treatment.4811... 

Complete desialylation of erythrocytes is not necessary for erythrocyte sequestration liberation of 15-20% of membrane sialic acids was found to be sufficient for a significant diminution of the life-time of erythrocytes.481,482 For an in vitro system with rat-peritoneal macrophages (see later), this threshold value was found to be only 10% when using soluble V. cholerae sialidase, but it was —30% when the erythrocytes were treated with the same enzyme immobilized on Sepharose.488... 

It is at present unclear whether the different clearing-mechanisms of rabbit erythrocytes observed after treatment with sialidase and a-D-galactosidase, respectively, are mediated by two different antibodies, one causing sequestration by macrophages after deposition of C3b complexes on the erythrocyte surface as the second step in the aforementioned mechanism, and the other leading to intravascular destruction of erythrocytes by activation of the whole complement cascade. 

The following experiments arc at variance with such a clearance mechanism. Incubation of rabbit erythrocytes with V. cholerae sialidase in the presence of inhibiting concentrations of Neu2en5Ac protects surface sialic acids and, correspondingly, survival of the cells in circulation.142 Treatment of erythrocytes by V. cholerae sialidase immobilized on Sepharose 4B, allowing complete separation of the enzyme from the cells after incubation, resulted in engulfment of these cells by macrophages at a rate similar to that observed with cells treated with the soluble enzyme. 1 1... 

A similar mechanism is apparently responsible for removing old erythrocytes from the mammalian bloodstream. Newly synthesized erythrocytes have several membrane glycoproteins with oligosaccharide chains that end in NeuSAc. When the sialic acid residues are removed by withdrawing a sample of blood, treating it with sialidase in vitro, and reintroducing it into the circulation, the treated erythrocytes disappear from the bloodstream within a few hours those with intact oligosaccharides (erythrocytes withdrawn and reintroduced without sialidase treatment) continue to circulate for days. 

In a recent paper (3l) it was demonstrated that the removal of sialic acid from human erythrocytes with Vibrio oholerae sialidase abolished hemagglutination by Sendai virus. Hemagglutination titers were restored selectively by the incorporation of NeuAc with 8-galactoside a2-+3sialyltransferase which has a strict... 

The peanut Arachis hypogaea) contains a lectin with anti-T (Gal(Pl-3)GalNAc) activity [174]. This antigen appears on human erythrocytes following treatment with sialidase and leads to the phenomenon known as polyagglutinability as monitored by the peanut lectin [175]. Peanut agglutinin, purified by numerous affinity purification schemes, is a tetrameric protein composed of four carbohydrate-free subunits, A/f = 27000Da[176]. The lectin is a metalloprotein rich in acidic and hydroxylic amino acids and devoid of cysteine [176]. 

The invasion of human erythrocytes by plasmoidal merozoites is a key event during malaria infection. Sialidase treatment of the erythrocytes renders the cells resistant to invasion by different isolates of P. falciparum, suggesting that the interaction between the parasite and the erythrocytes is mediated by a plasmodial lectin specific for sialic acid [145]. Different mezoroite surface components have been proposed as the putative lectins, among them the well-defined surface antigen Pf200 [146]. Binding of the isolated... 

Pilatte Y, Tisserand EM, Greffard A, Bignon J, Lambr6 CR (1990) Anticarbohydrate autoantibodies to sialidase-treated erythrocytes and thymocytes in serum from patients with pulmonary sarcoidosis. Am J Med, 88 486-492. 

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