Effect of chloroquine on the degradation of L-fucose and the polypeptide moiety of plasma membrane glycoproteins.
To evaluate the role of lysosomes in the breakdown of the carbohydrate and the polypeptide moiety of plasma membrane glycoproteins, degradation of the plasma membrane glycoprotein gp120 was studied in the liver of rats treated with the lysosomotropic amine chloroquine. Half-lives of degradation of the terminal sugar L-fucose and of L-methionine of gp120 were measured in isolated plasma membranes after pulse-chase experiments in vivo. Chloroquine extended the plasma membrane half-life of the polypeptide moiety of gp120 from 51 h to 143 h. By contrast, L-fucose of gp120 in the plasma membrane was not affected by chloroquine, but decayed with the same short half-lives of 22 h and 23 h in both controls and chloroquine-treated rats. The data suggest that the protein portion of gp120 is degraded within the lysosomes. Conversely, the terminal sugar L-fucose is removed from the glycoprotein independent from proteolysis before segregation of the glycoprotein into the lysosomal compartment.
R
R
Tauber
K
K
Heinze
W
W
Reutter
D000818:Animals; D000937:Antigen-Antibody Reactions; D002462:Cell Membrane / Q000276:immunology; D002738:Chloroquine / Q000494:pharmacology*; D000939:Epitopes / Q000032:analysis; D005643:Fucose / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006207:Half-Life; D008099:Liver / Q000032:analysis; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D011233:Precipitin Tests; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000939:Epitopes; D006023:Glycoproteins; D008565:Membrane Proteins; D011506:Proteins; D005643:Fucose; D002738:Chloroquine