Functional analysis of LR11 in vascular smooth muscle cells

LR 11是LDL受体家族的一员，在增生内膜的血管平滑肌细胞（SMC）中高度表达，但在中膜中不表达。为了进一步阐明LR 11在动脉粥样硬化过程中的作用，我们研究了LR 11过表达SMC的迁移和侵袭活动。将LR 11 cDNA转染到大鼠SMC系A7 r5中。与模拟细胞（C-1）相比，在PDGF-BB存在下，转染的细胞（R-1和R-2）分别显示出3.5-4.0倍高的LR 11蛋白表达、1.7-1.8倍增加的迁移和2.0-2.2倍增加的侵袭活性。通过添加受体相关蛋白（RAP）、抗LR 11抗体或Apo E，这些增加基本消除。免疫学分析表明，LR 11过表达细胞中尿激酶型纤溶酶原激活物受体（uPAR）水平升高。抗uPA和抗uPAR抗体降低R-1和R-2细胞的迁移和侵袭活性至基线水平。RAP、抗ER 11抗体和载脂蛋白E使LR 11过表达细胞中的uPAR表达降低约50%。与对照组相比，R-1和R-2细胞中uPAR的细胞催化活性显著降低。从动脉粥样硬化兔髂动脉内膜分离培养的平滑肌细胞显示LR 11和uPAR表达水平增加，并增强迁移和侵袭相比，从中层平滑肌细胞。LR 11的过表达可能通过调节uPA/uPAR系统诱导内膜SMC的迁移和侵袭活性增强。

LR11, a member of the LDL receptor family, is highly expressed in vascular smooth muscle cells (SMCs) of the hyperplastic intima, but not media. To further clarify the involvement of LR11 in the process of atherosclerosis, we have characterized the migration and invasion activities, of LR11-overexpressing SMCs. LR11 cDNA was transfected into the rat SMC line, A7r5. Compared to mock cells (C-1), in the presence of PDGF-BB the transfected cells (R-1 and R-2) showed 3.5-4.0-fold higher expression of LR11 protein, 1.7-1.8-fold increased migration, and 2.0-2.2-fold elevated invasion activities, respectively. The increases were essentially abolished by the addition of receptor-associated protein (RAP), anti-LR11 antibodies, or Apo E. Immunological analyzes showed that urokinase-type plasminogen activator receptor (uPAR) levels were increased in LR11-overexpressing cells. Anti-uPA and anti-uPAR antibodies reduced the migration and invasion activities of R-1 and R-2 cells to baseline levels. RAP, anti-ER11 antibodies, and apo E decreased uPAR expression in the LR11-overexpressing cells by 〜50%. Cellular catabolism of uPAR was significantly decreased in R-1 and R-2 cells compared to control. Cultured SMCs isolated from intimae of atherosclerotic rabbit aortas showed increased expression levels of LR11 and uPAR, and enhanced migration and invasion compared to SMCs from medial layers. Overexpression of LR11 induces enhanced migration and invasion activities of intimal SMCs in vitro, likely via its regulation of the uPA/uPAR system.