Lectin-like oxidized low-density lipoprotein receptor (LOX-1) functions as an oligomer and oligomerization is dependent on receptor density.
Lectin-like oxidized low-density lipoprotein (LDL) receptor (LOX-1) exists as a homodimer formed by an intermolecular disulfide bond. Although the dimer is the minimum structural unit of LOX-1 on cell membranes, LOX-1 can form larger noncovalent oligomeric complexes. But, the functional unit of LOX-1 is not known. We quantitatively analyzed the correlation between cyan fluorescent protein-tagged LOX-1 expression and the fluorescence-labeled ligand (DiD-AcLDL) binding ability on each cell. The results clearly indicate that there is a threshold level of expression that enables LOX-1 to bind ligand. Above this threshold level, the ability of LOX-1 to bind ligand was proportional to its level of expression. Using the membrane impermeable crosslinker BS(3), we detected oligomers (primarily hexamers) only on the cell lines that stably expressed LOX-1 above the threshold level. In contrast, little oligomer or ligand binding was detected in cell lines expressing LOX-1 below the threshold level. Moreover, oligomerization was independent of ligand binding. These results indicate that the functional unit of LOX-1 is an oligomer and that oligomerization of LOX-1 is dependent on the receptor density on the plasma membrane.
Matsunaga
Shigeru
S
National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
Xie
Qiuhong
Q
Kumano
Miyuki
M
Niimi
Setsuko
S
Sekizawa
Kyoko
K
Sakakibara
Yoshikiyo
Y
Komba
Shiro
S
Machida
Sachiko
S
D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D008024:Ligands; D011485:Protein Binding; D051127:Scavenger Receptors, Class E / Q000378:metabolism* / Q000502:physiology*; D014162:Transfection
D008024:Ligands; C495137:OLR1 protein, human; D051127:Scavenger Receptors, Class E