Chen Mingyi, Sawamura Tatsuya
Department of Vascular Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan.
J Mol Cell Cardiol. 2005 Sep;39(3):553-61. doi: 10.1016/j.yjmcc.2005.05.001.
Lectin-like oxidized LDL receptor-1 (LOX-1) is an oxidized low-density lipoprotein (OxLDL) receptor found in endothelial cells and a member of the natural killer (NK) receptor gene complex. Here, we demonstrate that the ability of LOX-1 binding to OxLDL distinguishes it from other NK receptors. Domain swapping of the lectin-like domain between LOX-1 and the NK cell receptors CD94, NKG2D, and LY-49A demonstrated the crucial role of this domain for recognition of OxLDL by LOX-1, but not for the correct cell-surface sorting of LOX-1. Using LOX-1 GFP fusion constructs, we find that the combination of cytoplasmic and transmembrane domains of LOX-1 is sufficient to target the chimeric protein to the cell-surface. Using N-terminal deletions we determined that the correct cell-surface localization is dependent on a positively charged motif present in the cytosolic juxtamembrane region of LOX-1. Furthermore, the extracellular localization of the LOX-1 C-terminus is disrupted when we mutated the cytoplasmic basic amino acids, Lys-22, Lys-23 and Lys-25 to Glu. Collectively, these results indicate that the N-terminal cytoplasmic domain of LOX-1 determines the correct expression of the lectin domain on the cell-surface.
凝集素样氧化型低密度脂蛋白受体-1（LOX-1）是一种在内皮细胞中发现的氧化型低密度脂蛋白（OxLDL）受体，也是自然杀伤（NK）受体基因复合体的成员。在此，我们证明了LOX-1与OxLDL结合的能力使其有别于其他NK受体。在LOX-1与NK细胞受体CD94、NKG2D和LY-49A之间进行凝集素样结构域的结构域交换，证明了该结构域对LOX-1识别OxLDL起着关键作用，但对LOX-1在细胞表面的正确分选并非如此。使用LOX-1绿色荧光蛋白融合构建体，我们发现LOX-1的胞质结构域和跨膜结构域的组合足以将嵌合蛋白靶向到细胞表面。通过N端缺失，我们确定正确的细胞表面定位取决于LOX-1胞质近膜区域中存在的带正电荷基序。此外，当我们将胞质碱性氨基酸Lys-22、Lys-23和Lys-25突变为Glu时，LOX-1 C端的细胞外定位被破坏。总的来说，这些结果表明LOX-1的N端胞质结构域决定了凝集素结构域在细胞表面的正确表达。
