Abstract
The Class B type I scavenger receptor I (SR-BI) is a physiologically relevant high density lipoprotein (HDL) receptor that can mediate selective cholesteryl ester (CE) uptake by cells. Direct interaction of apolipoprotein E (apoE) with this receptor has never been demonstrated, and its implication in CE uptake is still controversial. By using a human adrenal cell line (NCI-H295R), we have addressed the role of apoE in binding to SR-BI and in selective CE uptake from lipoproteins to cells. This cell line does not secrete apoE and SR-BI is its major HDL-binding protein. We can now provide evidence that 1) free apoE is a ligand for SR-BI, 2) apoE associated to lipids or in lipoproteins does not modulate binding or CE-selective uptake by the SR-BI pathway, and 3) the direct interaction of free apoE to SR-BI leads to an increase in CE uptake from lipoproteins of both low and high densities. We propose that this direct interaction could modify SR-BI structure in cell membranes and potentiate CE uptake.
MeSH terms
-
Apolipoproteins E / metabolism*
-
Binding Sites
-
Binding, Competitive
-
CD36 Antigens / chemistry
-
CD36 Antigens / metabolism*
-
Cell Line
-
Cell Membrane / metabolism
-
Cholesterol Esters / pharmacokinetics*
-
Dose-Response Relationship, Drug
-
Electrophoresis, Polyacrylamide Gel
-
Enzyme-Linked Immunosorbent Assay
-
Glycosides / metabolism
-
Humans
-
Hydrolysis
-
Ligands
-
Lipid Metabolism
-
Lipoproteins / metabolism*
-
Lipoproteins, HDL / metabolism
-
Lipoproteins, LDL / metabolism
-
Membrane Proteins*
-
Protein Binding
-
Receptors, Immunologic*
-
Receptors, Lipoprotein*
-
Receptors, Scavenger
-
Recombinant Proteins / metabolism
-
Scavenger Receptors, Class B
-
Thrombin / metabolism
-
Tumor Cells, Cultured
Substances
-
Apolipoproteins E
-
CD36 Antigens
-
Cholesterol Esters
-
Glycosides
-
Ligands
-
Lipoproteins
-
Lipoproteins, HDL
-
Lipoproteins, LDL
-
Membrane Proteins
-
Receptors, Immunologic
-
Receptors, Lipoprotein
-
Receptors, Scavenger
-
Recombinant Proteins
-
SCARB1 protein, human
-
Scarb1 protein, mouse
-
Scavenger Receptors, Class B
-
very high density lipoproteins
-
xylosides
-
Thrombin