NARC-1/PCSK9 and its natural mutants: zymogen cleavage and effects on the low density lipoprotein (LDL) receptor and LDL cholesterol.
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.
Benjannet
Suzanne
S
Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec H2W 1R7, Canada.
Rhainds
David
D
Essalmani
Rachid
R
Mayne
Janice
J
Wickham
Louise
L
Jin
Weijun
W
Asselin
Marie-Claude
MC
Hamelin
Josée
J
Varret
Mathilde
M
Allard
Delphine
D
Trillard
Mélanie
M
Abifadel
Marianne
M
Tebon
Angie
A
Attie
Alan D
AD
Rader
Daniel J
DJ
Boileau
Catherine
C
Brissette
Louise
L
Chrétien
Michel
M
Prat
Annik
A
Seidah
Nabil G
NG
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
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