Trond P Leren1. 1. Unit for Cardiac and Cardiovascular Genetics, Department of Medical Genetics, Oslo University Hospital, Oslo, Norway. Electronic address: trond.leren@rikshospitalet.no.
Abstract
OBJECTIVE: This article reviews the mechanism by which the low density lipoprotein receptor (LDLR) that has bound proprotein convertase subtilisin/kexin type 9 (PCSK9), is rerouted to intracellular degradation instead of being recycled. METHODS: A search of relevant published literature has been conducted. RESULTS: PCSK9 binds to the LDLR at the cell surface. It is the catalytic domain of PCSK9 that binds to the epidermal growth factor repeat A of the LDLR. The LDLR:PCSK9 complex is internalized through clathrin-mediated endocytosis. Due to an additional electrostatic interaction at acidic pH between the C-terminal domain of PCSK9 and the ligand-binding domain of the LDLR, PCSK9 remains bound to the LDLR in the sorting endosome. As a consequence, the LDLR fails to adopt a closed conformation and is degraded instead of being recycled. The mechanism for the failure of the LDLR to recycle appears to involve ectodomain cleavage of the extended LDLR by a cysteine cathepsin in the sorting endosome. The cleaved LDLR ectodomain will be confined to the vesicular part of the sorting endosome for degradation in the endosomal/lysosomal tract. CONCLUSION: Ectodomain cleavage of an LDLR with bound PCSK9 in the sorting endosome disrupts the normal recycling of the LDLR.
OBJECTIVE: This article reviews the mechanism by which the low density lipoprotein receptor (LDLR) that has bound proprotein convertase subtilisin/kexin type 9 (PCSK9), is rerouted to intracellular degradation instead of being recycled. METHODS: A search of relevant published literature has been conducted. RESULTS:PCSK9 binds to the LDLR at the cell surface. It is the catalytic domain of PCSK9 that binds to the epidermal growth factor repeat A of the LDLR. The LDLR:PCSK9 complex is internalized through clathrin-mediated endocytosis. Due to an additional electrostatic interaction at acidic pH between the C-terminal domain of PCSK9 and the ligand-binding domain of the LDLR, PCSK9 remains bound to the LDLR in the sorting endosome. As a consequence, the LDLR fails to adopt a closed conformation and is degraded instead of being recycled. The mechanism for the failure of the LDLR to recycle appears to involve ectodomain cleavage of the extended LDLR by a cysteine cathepsin in the sorting endosome. The cleaved LDLR ectodomain will be confined to the vesicular part of the sorting endosome for degradation in the endosomal/lysosomal tract. CONCLUSION: Ectodomain cleavage of an LDLR with bound PCSK9 in the sorting endosome disrupts the normal recycling of the LDLR.
Authors: Constantine E Kosmas; Andreas Sourlas; Kyriaki V Bouza; Eddy DeJesus; Delia Silverio; Peter D Montan; Eliscer Guzman Journal: Ann Transl Med Date: 2018-04
Authors: José Tuñón; Lina Badimón; Marie-Luce Bochaton-Piallat; Bertrand Cariou; Mat J Daemen; Jesus Egido; Paul C Evans; Imo E Hoefer; Daniel F J Ketelhuth; Esther Lutgens; Christian M Matter; Claudia Monaco; Sabine Steffens; Erik Stroes; Cécile Vindis; Christian Weber; Magnus Bäck Journal: Cardiovasc Res Date: 2019-01-01 Impact factor: 10.787