极低密度脂蛋白受体亚型与脂蛋白的结合效应及其摄取能力的差异

Difference of Lipoprotein Binding and Internalization between Two Isoforms of Very Low Density Lipoprotein Receptor

目的探讨人极低密度脂蛋白受体(VLDLR)不同亚型与配体的结合效应及其摄取能力的差异,明确其在脂蛋白代谢和泡沫细胞形成中的作用。方法应用基因重组技术获得分别稳定表达全长VLDLR(Ⅰ型)和O-link糖链区缺失的VLDLR(Ⅱ型)的ldl-A7细胞株。核素标记VLDLR的天然配体VLDL、-βVLDL以观察配体结合能力;以VLDL温育细胞,检测细胞内脂质含量,油红O染色法观察胞内脂质堆积及泡沫细胞形成情况。结果实验发现,稳定表达Ⅰ型VLDLR的ldl-A7细胞表面结合125I-VLDL和125I--βVLDL的量与胞内甘油三酯和总胆固醇的含量均明显高于表达Ⅱ型VLDLR的ldl-A7细胞,泡沫细胞形成显著。结论Ⅰ型VLDLR与VLDL、-βVLDL的结合和摄取能力明显高于Ⅱ型VLDLR,泡沫细胞形成过程中Ⅰ型VLDLR发挥着重要作用。

Objective To explore the difference of ligand binding and internalization between two isoforms of very low density lipoprotein receptor （VLDLR）, and clarify the roles of the isoforms of VLDLR in lipoprotein metabolism and foam cells formation. Methods The ldl-A7 cell lines which expressed the VLDLR were recombined with the O, linked sugar region （type Ⅰ VLDLR） and that without the O-linked sugar region （type Ⅱ VLDLR） stably by gene recombination technique. The natural ligands （VLDL and β-VLDL） of VLDLR were tagged with radioactive isotope ^125I so as to observe the ligand binding capability. After incubated with VLDL for different time, the contents of triglyeeride and total cholesterol in cells were measured, and the formation of foam cells and accumulation of lipid in cells were observed by oil red O staining. Results In the study on lipoprotein binding, it was found that surface binding of ^125I-VLDL or ^125 I-β-VLDL of ldl A7 cells transformed with type Ⅰ VLDLR recombinant （ldl-A7 VR-I） was more higher than that of ldl-A7 cells transformed with type Ⅱ VLDLR recombinant （ldl- A7 -VR- Ⅱ ）. The lipid measuring results showed that the contents of triglyceride and total cholesterol in ldl-A7-VR- Ⅰ were much higher than those in ldl A7-VR- Ⅱ , and ldl AT-VR- Ⅰ could transform into foam cells notably. Conclusion Type Ⅰ VLDLR plays a more important role in lipoprotein metabolism and foam cells formation than type Ⅱ VLDLR.