B. Venerando

C. Tringali

F. D\u2019Avila

L. Anastasia

N. Papini

English

F. D’Avila

AIR Universita degli studi di Milano

SODIUM CARBONATE TREATMENT CAUSES THE RELEASE OF ACIDIC SIALIDASE PRESENT ON HUMAN ERYTHROCYTE MEMBRANESD’Avila F., Tringali C., Papini N., Anastasia L., Venerando B. INTRODUCTION AND METHODSSialidases are enzymes widely distributed in nature that play a key role in the metabolism of sialoglycoconjugates. It is becoming evident that the partial desialylation of senescent erythrocyte membrane sialoglycoconjugates constitutes a primary or preliminary signal for erythrophagocytosis. The removal of sialic acid from the sialoglycoconjugates is assumed to be promoted by the sialidases present on the membranes. The presence of two sialidases in human erythrocytes has been previously reported. One acts optimally at acidic pH (4.2-4.7) and the other at neutral pH. In order to identify the exact nature of these two sialidases, we treated the erythrocyte membranes with 0,1 M sodium carbonate buffer pH 11,5. This treatment is one of the methods used to discriminate between peripheral and integral cell membrane proteins. We analyzed the solubilized and non-extractable proteins by western blot and by sialidase activity analysis.    RESULTS AND CONCLUSIONSThe sodium carbonate treatment led to the release of 50% acidic sialidase into the supernatant, whereas the neutral sialidase remained totally in the pellet. Our results suggest that the acidic enzyme is a peripheral protein. The released enzyme has been analyzed also using polyclonal anti-Neu1 antibodies. Our data reveal that Neu1 sialidase is present on the erythrocyte membranes and that the alkaline treatment causes the partial release of this sialidase from the membranes. Neu1 is usually located in a multienzymatic complex in the lysosomes of mammalian cells, but using antibodies against the other components of the complex, we observed that Neu1 is alone on the erythrocyte membrane.

Sodium carbonate treatment causes the release of acidic sialidase present on human erythrocyte membranes

https://air.unimi.it/bitstream/2434/49859/1/abstract%20Francesca%20D%27Avila.doc

Sodium carbonate treatment causes the release of acidic sialidase present on human erythrocyte membranes

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AIR Universita degli studi di Milano