The important role for betaVLDLs binding at the fourth cysteine of first ligand-binding domain in the low-density lipoprotein receptor.
The low-density lipoprotein (LDL) receptor (LDLR) is a crucial role for binding and uptaking apolipoprotein (apo) B-containing lipoproteins, such as very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and LDL. The defect function of the LDLR causes familial hypercholesterolemia (FH), the phenotype of which is elevated plasma cholesterol and premature coronary heart disease (CHD). In the present study, we characterize the role of the cysteine residue of the ligand-binding domain of the LDLR. The mutant LDLR protein of cysteine for serine at codon 25 (25S-LDLR) was expressed in Chinese hamster ovary (CHO) cell line, ldl-A7. By Western blot analysis, the 25S-LDLR was detected with monoclonal antibody IgG-12D10, which reacts with the linker site of the LDLR but not with IgG-C7, which reacts with the NH2 terminus of the receptor. The 25S-LDLR bound LDL similarly to the wild-type LDLR, but the rate of uptake of LDL by the mutant receptor was only about half of that by the wild-type receptor. In contrast, the 25S-LDLR bound and internalized beta VLDL more avidly than LDL. These results suggest that the fourth cysteine residue of the first ligand-binding domain of the LDLR might be important for the internalization of atherogenic lipoproteins by vascular cells despite reduced LDL uptake, leading to atherosclerosis and premature cardiovascular disease.
Iwasaki
Tadao
T
Department of Advanced Medical Technology and Development, BML, Inc., Saitama, Japan.
Takahashi
Sadao
S
The Third Department of Internal Medicine, School of Medicine, Fukui University, Fukui, Japan.
Ishihara
Mitsuaki
M
Department of Advanced Medical Technology and Development, BML, Inc., Saitama, Japan.
Takahashi
Masafumi
M
Department of Organ Regeneration, Shinshu University Graduate School of Medicine, Matsumoto, Japan.
Ikeda
Uichi
U
Department of Organ Regeneration, Shinshu University Graduate School of Medicine, Matsumoto, Japan.
Shimada
Kazuyuki
K
Division of Cardiology, Department of Medicine, Jichi Medical School, Tochigi, Japan.
Fujino
Takahiro
T
Gene Research Center, Tohoku University, Sendai, Japan.
Yamamoto
Tokuo T
TT
Gene Research Center, Tohoku University, Sendai, Japan.
Hattori
Hiroaki
H
Department of Advanced Medical Technology and Development, BML, Inc., Saitama, Japan.
Emi
Mitsuru
M
Department of Molecular Biology, Institute of Gerontology, Nippon Medical University, 1-396 Kosugi-cho, Nakahara-ku, Kawasaki, 211-8533, Japan. memi@nms.ac.jp.
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D003545:Cysteine / Q000378:metabolism*; D017931:DNA Primers; D005434:Flow Cytometry; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000378:metabolism*; D008024:Ligands; D008079:Lipoproteins, VLDL / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D008024:Ligands; D008079:Lipoproteins, VLDL; D011973:Receptors, LDL; D003545:Cysteine