The endocytosis of oxidized LDL via the activation of the angiotensin II type 1 receptor

概要

〔目的(Purpose))
Arrestin-dependent internalization of a G-protein-coupled receptor (GPCR) can intracellularly transport adjacent molecules. In this study, we analyzed direct downstream signaling pathways of ATI by oxLDL; and investigated if the oxLDL-LOX-1 complex utilizes ATI-parrestin internalization to undergo endocytosis.

〔方法ならびに成績(Methods/Results))
Methods: We used CHO-cells stably transfected with LOX-1 (CH0-L0X-1),ATI (CHO-AT1), LOX-1 and ATI (CHO-LOX-1- AT 1),and LOX-1 and mutated ATI that lacks ability to activate G protein or P-arrestin pathway (CHO-LOX-1-mAT 1).Activation of Gaq and Gai were quantified by measuring the accumulation of IP1 and the inhibition of forskolin-induced cAMP production, respectively. Endocytosis of the oxLDL-LOX-1 complex tlirough the ATI-p-arrestin pathway was detected by real-time imaging of the membrane dynamics of LOX-1, and visualization of endocytosis of oxLDL. Accumulation of oxLD was performed with artificial CHO-cells and human endothelial cells by genetic or pharmaceutic approach inhibited ATI -P-arrestin pathway.

Results: Using genetically modified CHO cells, we found that oxLDL induced Gai-dependent inhibition of cAMP production only in the presence of both LOX-1 and ATI with intact G protein binding. In contrast, oxLDL did not induce the accumulation of IP 1,a downstream of Gaq signaling. Real-time imaging of cellular membrane revealed that oxLDL induced endocytosis of LOX-1 that depends on the intact parrestin pathway of ATI. oxLDL accumulated in CHO cells expressing both LOX-1 and ATI more prominently than those expressing LOX-1 or ATI alone.
This enhanced accumulation depended on the parrestin-binding potency of ATI, and was abolished by dominant-negative parrestin. Accumulation of oxLDL was similarly attenuated by knockdown of ATI-P-arrestin or LOX-1 in human vascular endothelial cells.

〔稔括(Conclusion)]
Taken together, our findings indicate that oxLDL triggers selective G protein activation and parrestiri-dependent internalization of ATI whereby the oxLDL-LOX-1 complex imdergo endocytosis.