title: Inhibition of the acidification of endosomes and lysosomes by the antibiotic concanamycin B in macrophage J774.
abstract: The antibiotic concanamycin B was found to inhibit oxidized-low-density-lipoprotein(LDL)-induced accumulation of lipid droplets in the macrophage J774 at a concentration of 5-10 nM. Concanamycin B inhibited cholesteryl-ester synthesis from [14C]oleate by 50% at 14 nM without affecting the synthesis of triacylglycerol and polar lipids. Degradation of internalized oxidized 125I-LDL was inhibited by about 80% in cells treated with 25 nM concanamycin B, while cell-surface binding of oxidized 125I-LDL at 4 degrees C, uptake of surface-bound oxidized 125I-LDL and microsomal acyl-CoA:cholesterol acyltransferase activity were not significantly affected by the antibiotic at 25 nM. When J774 cells were treated with 25 nM concanamycin B at 37 degrees C for 60 min, there was a reduction of about 50% in the activity of cell-surface receptors. This reduction appeared to be due to partial trapping of the receptors within the cells. Concanamycin B significantly inhibited ATP-dependent acidification of endosomes and lysosomes of the J774 cells at a concentration of 4 nM. Since acidic condition of these organelles is required for receptor recycling and hydrolysis of lipoproteins, the results demonstrate that concanamycin-B inhibition of oxidized-LDL-induced accumulation of lipid droplets and cholesteryl esters in macrophages J774 is associated with reduced ATP-dependent acidification of these organelles.
authors.affiliation: Department of Applied Biological Science, Tokyo Noko University, Japan.
authors.forename: J T
authors.initials: JT
authors.lastname: Woo
authors.forename: C
authors.initials: C
authors.lastname: Shinohara
authors.forename: K
authors.initials: K
authors.lastname: Sakai
authors.forename: K
authors.initials: K
authors.lastname: Hasumi
authors.forename: A
authors.initials: A
authors.lastname: Endo
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002460:Cell Line; D002788:Cholesterol Esters / Q000378:metabolism; D004705:Endocytosis; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D018942:Macrolides; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051379:Mice; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D015388:Organelles / Q000187:drug effects / Q000378:metabolism*; D011973:Receptors, LDL / Q000187:drug effects / Q000378:metabolism; D002785:Sterol O-Acyltransferase / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002788:Cholesterol Esters; D008077:Lipoproteins, LDL; D018942:Macrolides; D009829:Oleic Acids; D011973:Receptors, LDL; D019301:Oleic Acid; C036979:concanamycin B; D000255:Adenosine Triphosphate; D002785:Sterol O-Acyltransferase