STIMULATION OF ACYL-COA-CHOLESTEROL ACYLTRANSFERASE ACTIVITY BY BREFELDIN-A IN MACROPHAGE J774 CELLS

Brefeldin A (BFA), an inhibitor of secretory pathway, enhances incorpo ration of radiolabeled cholesterol and oleate into cholesteryl esters in cultured cells [12]. We studied the mechanism for this effect of BF A in the macrophage J774. When incubated with 2.7 muM BFA in the absen ce of lipoproteins, J774 cells synthesized and accumulated 1.5- to 4-f old more cholesteryl esters than did cells which received no BFA. BFA caused neither an elevation of cholesterol synthesis, inhibition of it s secretion nor changes in cholesterol transport to plasma membrane, e sterification of plasma membrane cholesterol and cholesteryl ester hyd rolysis. Acyl-CoA:cholesterol acyltransferase (ACAT) activity in micro somes from BFA-treated cells was 1.5- to 1.8-fold higher than that fro m control cells. The effect of BFA was diminished by treatment with lo w temperature, which is known to abolish BFA effect on Golgi formation .