[Characterization of HDL receptor and its ligand in cultured smooth muscle cells isolated from rabbit aorta].
The characteristics of HDL3 binding sites on cultured smooth muscle cells originally isolated from rabbit aorta were studied with 125I-labelled rabbit HDL3. The results indicated that specific and high-affinity HDL3 binding sites were present on the surface of smooth muscle cells (Bmax = 0.321 micrograms/mg cell protein; KD = 5.6 x 10(-8) mol/L). The presence of a high concentration of non-labelled apo A1 blocked the 125I-HDL3 binding rate by 50%. 125I-HDL3 pretreated (blocked) with rat antirabbit apo A1 IgG lost up to 70% of its original binding activity. Additionally, rabbit apo A1 was isolated, purified and its amino acid composition analyzed. The binding rate of 125I-HDL3 to smooth muscle cells was not affected by the presence of various concentrations of cholesterol. It was also relatively unaffected by trypsin or pronase treatment and independent of Ca2+ concentration. The optimal temperature and pH were 4 degrees C and 2 respectively. All of these characteristics differ from those of the LDL receptors. These results suggest that apo A1 is a major ligand of HDL3 receptors.
Xu
Q
Q
Institute of Basic Medical Sciences, Beijing.
D000818:Animals; D001011:Aorta / Q000378:metabolism; D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000494:pharmacology; D001665:Binding Sites; D002352:Carrier Proteins; D002478:Cells, Cultured; D008024:Ligands; D008075:Lipoproteins, HDL / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D016601:RNA-Binding Proteins; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018110:Receptors, Lipoprotein
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D002352:Carrier Proteins; D008024:Ligands; D008075:Lipoproteins, HDL; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface; D018110:Receptors, Lipoprotein; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein