Identification of an ApoA-I ligand domain that interacts with high-affinity binding sites on HepG2 cells.
We have previously described the presence of two (high- and low-affinity) HDL binding sites on the hepatoma cell line (HepG2) (R. Barbaras, X. Collet, H. Chap, and B. Perret (1994) Biochemistry 33, 2335-2340]. Moreover, apoA-I, the major HDL apolipoprotein, interacts with these two binding sites, while lipid-free apoA-I binds only to the high-affinity sites. Using tryptic HDL fragments and HepG2 cell monolayers as an "affinity matrix," we identified an apoA-I peptide of 16 amino acids, spanning between residues 62 and 77, as a ligand domain. The corresponding synthetic peptide displays high-affinity (K(d) approximately 10(-7) M) and low-capacity (B(max) 8 pmol/mg of cell protein) binding components. Competition experiments with this peptide, using (125)I-labeled free apoA-I as a ligand, show that this binding corresponds to the high-affinity binding sites already described. In conclusion, we identified the apoA-I 62-77 region as a specific high-affinity ligand domain of HDL on HepG2 cells.
Georgeaud
V
V
Institut Féderatif de Recherche d'Immunologie Moleculaire et Cellulaire, Hôpital Purpan, Toulouse, France.
Garcia
A
A
Cachot
D
D
Rolland
C
C
Tercé
F
F
Chap
H
H
Collet
X
X
Perret
B
B
Barbaras
R
R
D000595:Amino Acid Sequence; D000818:Animals; D016632:Apolipoprotein A-I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008075:Lipoproteins, HDL / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D014407:Tumor Cells, Cultured
D016632:Apolipoprotein A-I; D008024:Ligands; D008075:Lipoproteins, HDL; D010446:Peptide Fragments