The severe depletion of cholesteryl ester (CE) in adrenocortical cells of apoA-I-/- mice suggests that apolipoprotein (apo) A-I plays an important role in the high density lipoprotein (HDL) CE selective uptake process mediated by scavenger receptor BI (SR-BI) in vivo. A recent study showed that apoA-I-/- HDL binds to SR-BI with the same affinity as apoA-I+/+ HDL, but apoA-I-/- HDL has a decreased Vmax for CE transfer from the HDL particle to adrenal cells. The present study was designed to determine the basis for the reduced selective uptake of CE from apoA-I-/- HDL. Variations in apoA-I-/- HDL particle diameter, free cholesterol or phospholipid content, or the apoE or apoA-II content of apoA-I-/- HDL had little effect on HDL CE selective uptake into Y1-BS1 adrenal cells. Lecithin cholesterol acyltransferase treatment alone or addition of apoA-I to apoA-I-/- HDL alone also had little effect. However, addition of apoA-I to apoA-I-/- HDL in the presence of lecithin cholesterol acyltransferase reorganized the large heterogeneous apoA-I-/- HDL to a more discrete particle with enhanced CE selective uptake activity. These results show a unique role for apoA-I in HDL CE selective uptake that is distinct from its role as a ligand for HDL binding to SR-BI. These data suggest that the conformation of apoA-I at the HDL surface is important for the efficient transfer of CE to the cell.
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - Feb 14 2003|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology