Desialylation of transferrin by liver endothelium is selective for its triantennary chain.
Liver endothelium can remove and transport the glycoprotein transferrin (TF). During this process the molecules are desialylated; however, in contrast with other such glycoproteins, for example caeruloplasmin, only half of transported TF is desialylated. To explore which component of TF is desialylated, we double-labelled fully sialylated TF with [3H]sialic acid residues and a 125I-protein moiety. This was then 'chased' through purified liver endothelium in pulse-chase experiments. Endothelium-conditioned TF was fractionated on an RCA120 affinity column into sialylated and desialylated components. Each component was then re-fractionated on a concanavalin A affinity column, which separates the glycoprotein according to the branching pattern of its glycan chain. The desialylated fraction was eluted only as a triantennary component, whereas the non-desialylated fraction consisted only of bi- and tetra-antennary chains. The significance of this selective desialylation of triantennary chain of TF in the subsequent metabolism of its iron content and its possible role in the pathogenesis of alcohol-induced hepatic siderosis are discussed.
Irie
S
S
Veterans Administration Medical Center, Jackson, MS.
Tavassoli
M
M
D000818:Animals; D001692:Biological Transport; D002846:Chromatography, Affinity; D003208:Concanavalin A; D004727:Endothelium / Q000378:metabolism; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism*; D019158:N-Acetylneuraminic Acid; D051381:Rats; D012794:Sialic Acids / Q000378:metabolism*; D014168:Transferrin / Q000302:isolation & purification / Q000378:metabolism*; D014316:Tritium
D007457:Iodine Radioisotopes; D012794:Sialic Acids; D014168:Transferrin; D014316:Tritium; D003208:Concanavalin A; D019158:N-Acetylneuraminic Acid