title: Low density lipoprotein binds to proprotein convertase subtilisin/kexin type-9 (PCSK9) in human plasma and inhibits PCSK9-mediated low density lipoprotein receptor degradation.
abstract: Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a secreted protein that binds to the epidermal growth factor-like-A domain of the low density lipoprotein receptor (LDLR) and mediates LDLR degradation in liver. Gain-of-function mutations in PCSK9 are associated with autosomal dominant hypercholesterolemia in humans. Size-exclusion chromatography of human plasma has shown PCSK9 to be partly associated with undefined high molecular weight complexes within the LDL size range. We used density gradient centrifugation to isolate LDL in plasma pooled from 5 normolipidemic subjects and report that >40% of total PCSK9 was associated with LDL. Binding of fluorophore-labeled recombinant PCSK9 to isolated LDL in vitro was saturable with a K(D) ∼ 325 nM. This interaction was competed >95% by excess unlabeled PCSK9, and competition binding curves were consistent with a one-site binding model. An N-terminal region of the PCSK9 prodomain (amino acids 31-52) was required for binding to LDL in vitro. LDL dose-dependently inhibited binding and degradation of cell surface LDLRs by exogenous PCSK9 in HuH7 cells. LDL also inhibited PCSK9 binding to mutant LDLRs defective at binding LDL. These data suggest that association of PCSK9 with LDL particles in plasma lowers the ability of PCSK9 to bind to cell surface LDLRs, thereby blunting PCSK9-mediated LDLR degradation.
authors: Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada.
authors: Tanja
authors: T
authors: Kosenko
authors: Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada.
authors: Mia
authors: M
authors: Golder
authors: Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada.
authors: Geoffrey
authors: G
authors: Leblond
authors: Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada.
authors: Willy
authors: W
authors: Weng
authors: Department of Pathology and Laboratory Medicine, University of Ottawa Heart Institute, Ottawa, Ontario K1Y 4W7, Canada. Electronic address: tlagace@ottawaheart.ca.
authors: Thomas A
authors: TA
authors: Lagace
mesh_terms: D001667:Binding, Competitive; D045744:Cell Line, Tumor; D057809:HEK293 Cells; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood; D008077:Lipoproteins, LDL / Q000097:blood* / Q000737:chemistry; D008079:Lipoproteins, VLDL / Q000097:blood; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000097:blood* / Q000737:chemistry; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D059748:Proteolysis; D011973:Receptors, LDL / Q000737:chemistry / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000097:blood* / Q000737:chemistry
chemical_list: C573412:LDLR protein, human; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D011973:Receptors, LDL; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases
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