title: NARC-1/PCSK9 and its natural mutants: zymogen cleavage and effects on the low density lipoprotein (LDL) receptor and LDL cholesterol.
abstract: The discovery of autosomal dominant hypercholesterolemic patients with mutations in the PCSK9 gene, encoding the proprotein convertase NARC-1, resulting in the missense mutations suggested a role in low density lipoprotein (LDL) metabolism. We show that the endoplasmic reticulum-localized proNARC-1 to NARC-1 zymogen conversion is Ca2+-independent and that within the zymogen autocatalytic processing site SSVFAQ [downward arrow]SIP Val at P4 and Pro at P3' are critical. The S127R and D374Y mutations result in approximately 50-60% and > or =98% decrease in zymogen processing, respectively. In contrast, the double [D374Y + N157K], F216L, and R218S natural mutants resulted in normal zymogen processing. The cell surface LDL receptor (LDLR) levels are reduced by 35% in lymphoblasts of S127R patients. The LDLR levels are also reduced in stable HepG2 cells overexpressing NARC-1 or its natural mutant S127R, and this reduction is abrogated in the presence of 5 mm ammonium chloride, suggesting that overexpression of NARC-1 increases the turnover rate of the LDLR. Adenoviral expression of wild type human NARC-1 in mice resulted in a maximal approximately 9-fold increase in circulating LDL cholesterol, while in LDLR-/- mice a delayed approximately 2-fold increase in LDL cholesterol was observed. In conclusion, NARC-1 seems to affect both the level of LDLR and that of circulating apoB-containing lipoproteins in an LDLR-dependent and -independent fashion.
authors.affiliation: Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Benjannet
authors.forename: David
authors.initials: D
authors.lastname: Rhainds
authors.forename: Rachid
authors.initials: R
authors.lastname: Essalmani
authors.forename: Janice
authors.initials: J
authors.lastname: Mayne
authors.forename: Louise
authors.initials: L
authors.lastname: Wickham
authors.forename: Weijun
authors.initials: W
authors.lastname: Jin
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Asselin
authors.forename: Josée
authors.initials: J
authors.lastname: Hamelin
authors.forename: Mathilde
authors.initials: M
authors.lastname: Varret
authors.forename: Delphine
authors.initials: D
authors.lastname: Allard
authors.forename: Mélanie
authors.initials: M
authors.lastname: Trillard
authors.forename: Marianne
authors.initials: M
authors.lastname: Abifadel
authors.forename: Angie
authors.initials: A
authors.lastname: Tebon
authors.forename: Alan D
authors.initials: AD
authors.lastname: Attie
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rader
authors.forename: Catherine
authors.initials: C
authors.lastname: Boileau
authors.forename: Louise
authors.initials: L
authors.lastname: Brissette
authors.forename: Michel
authors.initials: M
authors.lastname: Chrétien
authors.forename: Annik
authors.initials: A
authors.lastname: Prat
authors.forename: Nabil G
authors.initials: NG
authors.lastname: Seidah
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001055:Apolipoproteins B / Q000737:chemistry; D001665:Binding Sites; D015153:Blotting, Western; D002118:Calcium / Q000737:chemistry; D002384:Catalysis; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D002784:Cholesterol / Q000378:metabolism; D008078:Cholesterol, LDL / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004792:Enzyme Precursors / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D017353:Gene Deletion; D020868:Gene Silencing; D006579:Heterozygote; D006801:Humans; D006937:Hypercholesterolemia / Q000235:genetics; D008214:Lymphocytes / Q000378:metabolism; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D020125:Mutation, Missense; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011973:Receptors, LDL / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000235:genetics* / Q000502:physiology*; D013997:Time Factors; D014162:Transfection
chemical_list: D001055:Apolipoproteins B; D008078:Cholesterol, LDL; D018076:DNA, Complementary; D004792:Enzyme Precursors; D012333:RNA, Messenger; D011973:Receptors, LDL; D000643:Ammonium Chloride; D002784:Cholesterol; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D002118:Calcium