Lectin-like oxidized low-density lipoprotein receptor (LOX-1) functions as an oligomer and oligomerization is dependent on receptor density |
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Authors: | Matsunaga Shigeru Xie Qiuhong Kumano Miyuki Niimi Setsuko Sekizawa Kyoko Sakakibara Yoshikiyo Komba Shiro Machida Sachiko |
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Institution: | National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan. |
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Abstract: | 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. |
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Keywords: | Lectin-like oxidized LDL receptor (LOX-1) Oxidized LDL Oligomer Receptor oligomerization Ligand binding |
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