Abstract Body (Do not enter title and authors here): Background:
The low-density lipoprotein receptor (LDLR) in the liver plays a crucial role in clearing low-density lipoprotein cholesterol (LDL-C) from the bloodstream. Under atherogenic conditions, Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9), secreted by the liver, binds to LDLR on hepatocytes, preventing its recycling and enhancing its lysosomal degradation. Epsins, a family of ubiquitin-binding endocytic adaptors, are key regulators of atherogenesis. We aimed to determine whether and how liver epsins contribute to PCSK9-mediated LDLR endocytosis and degradation, thereby impairing LDL-C clearance and accelerating atherosclerosis.
Methods:
We utilized single-cell RNA sequencing (scRNA-seq), along with molecular, cellular, and biochemical analyses, to investigate the role of liver epsins in PCSK9-mediated LDLR degradation. Liver-specific epsin knockout (Liver-DKO) atherosclerotic models were generated in ApoE^-/- and PCSK9-AAV8-induced atheroprone mice fed on a Western diet. Additionally, we explored the therapeutic potential of nanoparticle-encapsulated siRNAs targeting epsins 1 and 2 in ApoE^-/- mice with established atherosclerosis.
Results:
Western diet (WD)-induced atherosclerosis was significantly attenuated in ApoE^-/- /Liver-DKO mice compared with ApoE^-/- controls, as well as in PCSK9-AAV8-induced Liver-DKO mice compared with PCSK9-AAV8-induced wild-type (WT) mice accompanied by reductions in blood cholesterol and triglyceride levels. Mechanistically, hepatocyte-derived scRNA-seq data analysis revealed increased pathways of LDL particle clearance in WD-fed ApoE^-/- /Liver-DKO mice compared with WD-fed ApoE^-/- controls, correlating with decreased plasma LDL-C levels. The absence of liver epsins led to an upregulation of LDLR protein expression in hepatocytes. We further demonstrated that epsins bind LDLR via the ubiquitin-interacting motif (UIM), enabling PCSK9-mediated LDLR degradation. Depleting epsins abolished this degradation, thereby preventing atheroma progression. Lastly, targeting liver epsins with nanoparticle-encapsulated epsins siRNAs effectively ameliorates dyslipidemia and inhibits atherosclerosis progression.
Conclusions:
Liver epsins drive atherogenesis by promoting PCSK9-mediated LDLR degradation, elevating circulating LDL-C levels and heightening lesional inflammation. Targeting epsins in the liver represents a promising therapeutic strategy to mitigate atherosclerosis by preserving LDLR and enhancing LDL-C clearance in the liver.