Apolipoprotein J (apo J) is a secreted glycoprotein of which the exact function remains a matter for speculation. Apo J has been implicated in such diverse processes as sperm maturation, regulation of complement activation, programmed cell death, tissue remodelling and lipid transport. In this study a possible role for apo J in lipid transport was explored. Mouse peritoneal macrophages were incubated with acetylated low-density lipoprotein (AcLDL) to produce foam cells containing cholesterol and cholesteryl esters. Incubation of the foam cells with physiological concentrations of purified apo J led to a dose-dependent export of cholesterol. The appearance of cholesterol in the medium was associated predominantly with a decline in intracellular cholesteryl esters rather than intracellular free cholesterol. The kinetics of cholesterol release to apo J were similar to apo A-I, an established promoter of cholesterol efflux. Apo J was also shown to induce phospholipid efflux from cells, whereas the cholesterol exported to the medium was associated with the apo J. Studies using foam cells from apo E-null mice showed that the cholesterol exported to the medium was independent of apo E production by the cells. These results present the first evidence that apo J can promote cholesterol efflux from foam cells and indicates that it might have a function in cellular cholesterol homoeostasis in both normal and pathological situations.
Apolipoprotein J (clusterin) induces cholesterol export from macrophage-foam cells: a potential anti-atherogenic function?
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Ingrid C. GELISSEN, Tim HOCHGREBE, Mark R. WILSON, Simon B. EASTERBROOK-SMITH, Wendy JESSUP, Roger T. DEAN, Andrew J. BROWN; Apolipoprotein J (clusterin) induces cholesterol export from macrophage-foam cells: a potential anti-atherogenic function?. Biochem J 1 April 1998; 331 (1): 231–237. doi: https://doi.org/10.1042/bj3310231
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