PACS2 is required for ox-LDL-induced endothelial cell apoptosis by regulating mitochondria-associated ER membrane formation and mitochondrial Ca2+ elevation

Oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell (EC) Apoptosis is the initial step of atherogenesis and associated with Ca²⁺ overload. Mitochondria-associated endoplasmic reticulum (ER) membrane (MAM), regulated by tethering proteins such as phosphofurin acidic cluster sorting protein 2 (PACS2), is essential for mitochondrial Ca²⁺ overload by mediating ER-mitochondria Ca²⁺ transfer. In our study, we aimed to investigate the role of PACS2 in ox-LDL-induced Apoptosis in human umbilical vein endothelial cells (HUVECs) and the underlying mechanisms. Ox-LDL dose- and time-dependently increased cell Apoptosis concomitant with mitochondrial Ca²⁺ elevation, mitochondrial membrane potential (MMP) loss, Reactive Oxygen Species (ROS) production, and cytochrome c release. Silencing PACS2 significantly inhibited ox-LDL-induced cell Apoptosis at 24 h in addition to the effects of ox-LDL on mitochondrial Ca²⁺, MMP, and ROS at 2 h. Besides, ox-LDL promoted PACS2 localization at mitochondria as well as ER-mitochondria contacts at 2 h. Not only that, ox-LDL upregulated PACS2 expression at 24 h. Furthermore, silencing PACS2 inhibited ox-LDL-induced mitochondrial localization of PACS2 and MAM formation at 24 h. Altogether, our findings suggest that PACS2 plays an important role in ox-LDL-induced EC Apoptosis by regulating MAM formation and mitochondrial Ca²⁺ elevation, implicating that PACS2 may be a promising therapeutic target for atherosclerosis.