Human lectin-like oxidized low-density lipoprotein receptor-1 functions as a dimer in living cells.
Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a unique scavenger receptor that plays important roles in atherogenesis and has been thought to function as a monomer. Using coimmunoprecipitation studies, we demonstrate that human LOX-1 (hLOX-1) forms constitutive homo-interactions in vivo. Western blot analysis of cell lysates under nonreducing or reducing conditions revealed one clear immunoreactive species corresponding to the size of a putative receptor dimer or a monomer, respectively, consistent with the presence of disulfide-linked hLOX-1 complexes. Site-directed mutagenesis studies indicated that cysteine 140 has a key role in the formation of these disulfide-linked hLOX-1 dimers. Eliminating this intermolecular disulfide bond markedly impairs the recognition of Escherichia coli by hLOX-1. Furthermore, these dimers can act as a "structural unit" to form noncovalently associated oligomers, as demonstrated by a membrane-impermeant crosslinker, which resulted in immunoreactive species corresponding to the sizes of putative tetramers and hexamers. These results provide the first evidence for the existence of hLOX-1 dimers/oligomers.
Xie
Qiuhong
Q
National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan.
Matsunaga
Shigeru
S
Niimi
Setsuko
S
Ogawa
Setsuko
S
Tokuyasu
Ken
K
Sakakibara
Yoshikiyo
Y
Machida
Sachiko
S
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000235:genetics; D019281:Dimerization; D005455:Fluorescent Antibody Technique; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000235:genetics; D011233:Precipitin Tests; D011973:Receptors, LDL / Q000235:genetics* / Q000378:metabolism*
D018076:DNA, Complementary; D011973:Receptors, LDL