The effects of tunicamycin on the metabolism of acetylated low density lipoproteins.
The effect of tunicamycin (TM) on the metabolism of acetylated low-density lipoprotein (AcLDL) was examined to determine whether N-linked glycosylation is required for the proper function of the AcLDL pathway. Proteolytic degradation of [125I]-AcLDL was increased twofold in the presence of TM. This did not occur via an increase in total lysosomal enzyme activity or extracellular proteolysis; rather, the rate of uptake of [125I]-AcLDL was increased. The enhanced degradation of AcLDL did not lead to a commensurate increase in the rate of synthesis of cholesteryl oleate. Conversely, the rate of cholesterol esterification was reduced in the presence of TM. The uptake of [125I]-AcLDL was more sensitive to inhibition by chloroquine in TM-treated cells. However, the presence of TM did not affect the ability of chloroquine to inhibit constitutive recycling of AcLDL binding sites. These results suggest that N-linked glycosylation may be involved in the regulation of AcLDL metabolism in J774 cells.
Armstrong
D P
DP
Department of Biochemistry, Queens Medical Centre, Nottingham, England.
White
D A
DA
D000107:Acetylation; D000818:Animals; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D002788:Cholesterol Esters / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D006031:Glycosylation; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D014415:Tunicamycin / Q000494:pharmacology*
D002788:Cholesterol Esters; D008077:Lipoproteins, LDL; C032629:acetyl-LDL; D014415:Tunicamycin; C014409:cholesteryl oleate; D002738:Chloroquine; D010450:Endopeptidases