Glycophorin A interferes in the agglutination of human erythrocytes by concanavalin A. Explanation of the requirement for enzymic predigestion.
Human erythrocytes become agglutinable with concanavalin A (Con A) after treatment with various proteinases or neuraminidase. The extent of agglutinability achieved with different enzymes is, however, different: Pronase, papain, trypsin, neuraminidase and chymotrypsin enhance the agglutinability in decreasing order, the last being barely effective. The actions of the enzymes on band 3, the Con A receptor, do not correlate with their abilities to increase the agglutinability: Pronase, papain and chymotrypsin cleave the protein, but not trypsin or neuraminidase. No significant differences are found in the number of Con A-binding sites or the affinities for the lectin between the normal and trypsin- or Pronase-treated cells. Thus the receptor does not seem to play a role in determining the Con A-agglutinability of erythrocytes. On the other hand, the cleavage of glycophorins, especially glycophorin A, and the release of sialic acid (in the peptide-bound form) are well-correlated with the enhancement in agglutination after the action of proteinases. The release of sialic acid by graded neuraminidase digestion and the increase in Con A-agglutinability show a correlation coefficient of 0.88. The major inhibitory role of glycophorin A in the process is indicated by the agglutination of En(a) heterozygous erythrocytes; the cells, known to bear about 50% glycophorin A molecules in their membrane, are agglutinated approximately half as well without proteolysis as are the trypsin-treated cells. Possible mechanisms by which glycophorin A could affect Con A-mediated agglutination are discussed.
Gokhale
S M
SM
Mehta
N G
NG
D003208:Concanavalin A / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000187:drug effects*; D006021:Glycophorins / Q000494:pharmacology*; D006384:Hemagglutination / Q000187:drug effects*; D006801:Humans; D019158:N-Acetylneuraminic Acid; D010447:Peptide Hydrolases / Q000494:pharmacology; D012794:Sialic Acids / Q000097:blood; D012795:Sialoglycoproteins / Q000494:pharmacology*
D006021:Glycophorins; D012794:Sialic Acids; D012795:Sialoglycoproteins; D003208:Concanavalin A; D010447:Peptide Hydrolases; D019158:N-Acetylneuraminic Acid