Asparagine endopeptidase cleaves apolipoprotein A1 and accelerates pathogenesis of atherosclerosis
Mengmeng Wang, Bowei Li, Shuke Nie, Xin Meng, Guangxing Wang, Menghan Yang, Wenxin Dang, Kangning He, Tucheng Sun, Ping Xu, Xifei Yang, Keqiang Ye
Mengmeng Wang, Bowei Li, Shuke Nie, Xin Meng, Guangxing Wang, Menghan Yang, Wenxin Dang, Kangning He, Tucheng Sun, Ping Xu, Xifei Yang, Keqiang Ye
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Research Article Cardiology Vascular biology

Asparagine endopeptidase cleaves apolipoprotein A1 and accelerates pathogenesis of atherosclerosis

Abstract

Atherosclerosis is a slowly progressing inflammatory disease characterized with cholesterol disorder and intimal plaques. Asparagine endopeptidase (AEP) is an endolysosomal protease that is activated under acidic conditions and is elevated substantially in both plasma and plaques of patients with atherosclerosis. However, how AEP accelerates atherosclerosis development remains incompletely understood, especially from the view of cholesterol metabolism. This project aims to reveal the crucial substrate of AEP during atherosclerosis plaque formation and to lay the foundation for developing novel therapeutic agents for Atherosclerosis. Here, we show that AEP is augmented in the atherosclerosis plaques obtained from patients and proteolytically cuts apolipoprotein A1 (APOA1) and impairs cholesterol efflux and high-density lipoprotein (HDL) formation, facilitating atherosclerosis pathologies. AEP is activated in the liver and aorta of apolipoprotein E–null (APOE-null) mice, and deletion of AEP from APOE–/– mice attenuates atherosclerosis. APOA1, an essential lipoprotein in HDL for cholesterol efflux, is cleaved by AEP at N208 residue in the liver and atherosclerotic macrophages of APOE–/– mice. Blockade of APOA1 cleavage by AEP via N208A mutation or its specific inhibitor, #11a, substantially diminishes atherosclerosis in both APOE–/– and LDLR–/– mice. Hence, our findings support that AEP disrupts cholesterol metabolism and accelerates the development of atherosclerosis.

Authors

Mengmeng Wang, Bowei Li, Shuke Nie, Xin Meng, Guangxing Wang, Menghan Yang, Wenxin Dang, Kangning He, Tucheng Sun, Ping Xu, Xifei Yang, Keqiang Ye

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Figure 1

Increased AEP activation in the liver and aorta of APOE–/– mice.

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Increased AEP activation in the liver and aorta of APOE–/– mice. (A–L) A...
(A–L) APOE–/– mice were fed with a HFD for 0–12 weeks. (A) Representative macroscopic images and quantification of aortic arch and aortic root stained with H&E and ORO (n = 9 per group). Scale bars: 1 mm (top); 25 μm (bottom 2 rows). (B) Representative macrographs and quantification of aorta stained with ORO (n = 6 per group). Scale bar: 1 mm. (C) AEP enzymatic activities of aorta (n = 3 per group). (D and E) Western blot images and quantification of C/EBP-β and AEP levels in aorta (n = 3 per group). (F and G) IF staining and quantification of CD68 (green) and AEP (red) in aorta. Nuclei were counter-stained with DAPI (blue). Scale bar: 20 μm. (H and I) Western blot images and quantification of C/EBP-β and AEP levels in liver (n = 3 per group). (J) AEP enzymatic activities of liver (n = 6 per group). (K and L) IF staining and quantification of AEP (white) in liver. Nuclei were counter stained with DAPI (blue). Scale bar: 20 μm. All data are presented as the mean ± SEM from 3 to 6 independent experiments. 1-way ANOVA with Tukey’s post hoc test (A–C, E, G, I, K, and L); 1-way ANOVA with Kruskal–Wallis test (C/EBP-β in I and L). *P < 0.05; **P < 0.01; ***P < 0.001.