Stimulation of Cell Surface F ₁ -ATPase Activity by Apolipoprotein A-I Inhibits Endothelial Cell Apoptosis and Promotes Proliferation

Abstract

Objectives— Several findings argue for a protective effect of high-density lipoproteins (HDLs) against endothelial dysfunction. The molecular mechanisms underlying this protective effect are not fully understood, although recent works suggest that the actions of HDL on the endothelium are initiated by multiple interactions between HDLs (lipid or protein moiety) and cell surface receptors. We previously showed that the mitochondrial related F 1 -ATPase is a cell surface receptor for HDLs and their main atheroprotective apolipoprotein (apoA-I). Herein we test the hypothesis that the cell surface F 1 -ATPase may contribute to the ability of apoA-I and HDLs to maintain endothelial cell survival. Methods and Results— Cell imaging and binding assays confirmed the presence of the F 1 -ATPase at the surface of human umbilical vein endothelial cells (HUVECs) and its ability to bind apoA-I. Cell surface F 1 -ATPase activity (ATP hydrolysis into ADP) was stimulated by apoA-I and was inhibited by its specific inhibitor IF 1 -H49K. Furthermore the antiapoptotic and proliferative effects of apoA-I on HUVECs were totally blocked by the F 1 -ATPase ligands IF 1 -H49K, angiostatin and anti-βF 1 -ATPase antibody, independently of the scavenger receptor SR-BI and ABCA1. Conclusion— This study suggests an important contribution of cell surface F 1 -ATPase to apoA-I-mediated endothelial cell survival, which may contribute to the atheroprotective functions of apoA-I.

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HDL and Atherothrombotic Vascular Disease

“…Moreover, levels of the apoptosis-inducing protein truncated Bid are reduced in endothelial cells cultured in the presence of HDLs, whereas endothelial expression of the antiapoptotic protein Bcl-xL is enhanced (Riwanto et al 2013). The capacity of HDLs to attenuate apoptosis in endothelial cells requires induction of phosphatidylinositol 3-kinase (PI3K)/Akt/endothelial nitric oxide synthase (eNOS) signaling (Nofer et al 2001b;Riwanto et al 2013) and was attributed to apoA-I (Radojkovic et al 2009) as well as HDL-associated lysophospholipids (Kimura et al 2001;Nofer et al 2001b). More recently, a lower clusterin (or apoJ) and increased apoC-III content in the HDLs of patients with stable coronary artery disease or acute coronary syndrome was found to be associated with reduced antiapoptotic activities in human endothelial cells (Riwanto et al 2013).…”