Surface plasmon resonance study on functional significance of clustered organization of lectin-like oxidized LDL receptor (LOX-1)

Lectin-like oxidized low-density lipoprotein (OxLDL) receptor 1 (LOX-1) is the major OxLDL receptor of vascular endothelial cells and is involved in an early step of atherogenesis. LOX-1 exists as a disulfide-linked homodimer on the cell surface, which contains a pair of the ligand-binding domains (CTLD; C-type lectin-like domain). Recent research using living cells has suggested that the clustered state of LOX-1 dimer on the cell is functionally required. These results questioned how LOX-1 exists on the cell to achieve OxLDL binding. In this study, we revealed the functional significance of the clustered organization of the ligand-binding domain of LOX-1 with surface plasmon resonance. Biotinylated CTLD was immobilized on a streptavidin sensor chip to make CTLD clusters on the surface. In this state, the CTLD had high affinity for OxLDL with a dissociation constant (KD) in the nanomolar range. This value is comparable to the KD measured for LOX-1 on the cell. In contrast, a single homodimeric LOX-1 extracellular domain had lower affinity for OxLDL in the supra-micromolar range of KD. Monomeric CTLD showed marginal binding to OxLDL. In combination with the analyses on the loss-of-binding mutant W150A, we concluded that the clustered organization of the properly formed homodimeric CTLD is essential for the strong binding of LOX-1 to OxLDL.

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► Clustered CTLD showed affinity to OxLDL as found for LOX-1 on plasma membrane.
► LOX-1 binds to OxLDL in a multivalent manner.
► Properly formed CTLD dimer structure is required in the LOX-1 binding to OxLDL.