Cyclase-associated protein 1 is a binding partner of proprotein convertase subtilisin/kexin type-9 and is required for the degradation of low-density lipoprotein receptors by proprotein convertase subtilisin/kexin type-9

• Published in: European heart journal 2020-01, Vol.41 (2), p.239-252
• Main Authors: Jang, Hyun-Duk, Lee, Sang Eun, Yang, Jimin, Lee, Hyun-Chae, Shin, Dasom, Lee, Hwan, Lee, Jaewon, Jin, Sooryeonhwa, Kim, Soungchan, Lee, Seung Ji, You, Jihye, Park, Hyun-Woo, Nam, Ky-Youb, Lee, Sang-Hak, Park, Sahng Wook, Kim, Jin-Soo, Kim, Sang-Yeob, Kwon, Yoo-Wook, Kwak, Soo Heon, Yang, Han-Mo, Kim, Hyo-Soo
• Format: Article
• Language: English
• Subjects: Animals; Atherosclerosis - genetics; Atherosclerosis - metabolism; Basic Science; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cholesterol, LDL - blood; Disease Models, Animal; DNA - genetics; DNA Mutational Analysis; Humans; Mice; Mice, Knockout; Mutation; Proprotein Convertase 9 - genetics; Proprotein Convertase 9 - metabolism; Receptors, LDL - blood
• ISSN: 0195-668X; 1522-9645
• DOI: 10.1093/eurheartj/ehz566

Abstract Aims Proprotein convertase subtilisin/kexin type-9 (PCSK9), a molecular determinant of low-density lipoprotein (LDL) receptor (LDLR) fate, has emerged as a promising therapeutic target for atherosclerotic cardiovascular diseases. However, the precise mechanism by which PCSK9 regulates the internalization and lysosomal degradation of LDLR is unknown. Recently, we identified adenylyl cyclase-associated protein 1 (CAP1) as a receptor for human resistin whose globular C-terminus is structurally similar to the C-terminal cysteine-rich domain (CRD) of PCSK9. Herein, we investigated the role of CAP1 in PCSK9-mediated lysosomal degradation of LDLR and plasma LDL cholesterol (LDL-C) levels. Methods and results The direct binding between PCSK9 and CAP1 was confirmed by immunoprecipitation assay, far-western blot, biomolecular fluorescence complementation, and surface plasmon resonance assay. Fine mapping revealed that the CRD of PCSK9 binds with the Src homology 3 binding domain (SH3BD) of CAP1. Two loss-of-function polymorphisms found in human PCSK9 (S668R and G670E in CRD) were attributed to a defective interaction with CAP1. siRNA against CAP1 reduced the PCSK9-mediated degradation of LDLR in vitro. We generated CAP1 knock-out mice and found that the viable heterozygous CAP1 knock-out mice had higher protein levels of LDLR and lower LDL-C levels in the liver and plasma, respectively, than the control mice. Mechanistic analysis revealed that PCSK9-induced endocytosis and lysosomal degradation of LDLR were mediated by caveolin but not by clathrin, and they were dependent on binding between CAP1 and caveolin-1. Conclusion We identified CAP1 as a new binding partner of PCSK9 and a key mediator of caveolae-dependent endocytosis and lysosomal degradation of LDLR.