Characterization of surface proteins and glycoproteins on red blood cells from mice infected with haemosporidia:Plasmodium bergheiinfections of BALB/c mice

Abstract

SUMMARYThe surface proteins and glycoproteins of red cells fromPlasmodium berghei-infected blood have been radio-isotope labelled and compared with those of normal mouse erythrocytes using the following protein labelling probes: lactoperoxidase-catalysed radio-iodination of tyrosyl residues, periodate oxidation and NaB3H4reduction of sialic acid and oxidation of galactosyl/N-acetylgalactosaminyl residues by galactose oxidase with subsequent NaB3H4reduction. DuringP.bergheiinfection, new tyrosyl-labelled proteins with apparent molecular weights (Mr) of 60000, 54000, 40000 and 27500 appeared on the surface of most, if not all, red cells in the blood. Purified multinucleate cells (mostly reticulocytes) differed only in that they also had a surface protein withMrof 83000. However, this molecule is thought to be specific to mouse reticulocytes rather than derived from parasites. In contrast to the relatively minor changes detected with radio-iodination, striking changes inglycoproteinradio-isotope labelling resulted from infection. All of the red cells in infected blood of greater than 20% parasitaemia lost their periodate-sensitive glycoprotein sialic acid. With some samples there was little change in glycoprotein labelling by the galactose oxidase method, provided neuraminidase was also added. Modification of the exocyclic hydroxyls of sialic acid is postulated to account for this. Other blood samples exhibited a dramatic loss of galactose oxidase-dependent labelling. It is suggested that these observations may relate to the excessive red cell destruction of uninfected as well as infected cells which has been inferred in many haemosporidial infections, including malaria.