title: The Proprotein Convertase Subtilisin/Kexin Type 9-resistant R410S Low Density Lipoprotein Receptor Mutation: A NOVEL MECHANISM CAUSING FAMILIAL HYPERCHOLESTEROLEMIA.
abstract: Familial hypercholesterolemia (FH) is characterized by severely elevated low density lipoprotein (LDL) cholesterol. Herein, we identified an FH patient presenting novel compound heterozygote mutations R410S and G592E of the LDL receptor (LDLR). The patient responded modestly to maximum rosuvastatin plus ezetimibe therapy, even in combination with a PCSK9 monoclonal antibody injection. Using cell biology and molecular dynamics simulations, we aimed to define the underlying mechanism(s) by which these LDLR mutations affect LDL metabolism and lead to hypercholesterolemia. Our data showed that the LDLR-G592E is a class 2b mutant, because it mostly failed to exit the endoplasmic reticulum and was degraded. Even though LDLR-R410S and LDLR-WT were similar in levels of cell surface and total receptor and bound equally well to LDL or extracellular PCSK9, the LDLR-R410S was resistant to exogenous PCSK9-mediated degradation in endosomes/lysosomes and showed reduced LDL internalization and degradation relative to LDLR-WT. Evidence is provided for a tighter association of LDL with LDLR-R410S at acidic pH, a reduced LDL delivery to late endosomes/lysosomes, and an increased release in the medium of the bound/internalized LDL, as compared with LDLR-WT. These data suggested that LDLR-R410S recycles loaded with its LDL-cargo. Our findings demonstrate that LDLR-R410S represents an LDLR loss-of-function through a novel class 8 FH-causing mechanism, thereby rationalizing the observed phenotype.
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Delia
authors.initials: D
authors.lastname: Susan-Resiga
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Girard
authors.affiliation: the Department of Medicine, McGill University, Montreal, Quebec H3G 2M1, Canada.
authors.forename: Robert Scott
authors.initials: RS
authors.lastname: Kiss
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Rachid
authors.initials: R
authors.lastname: Essalmani
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Josée
authors.initials: J
authors.lastname: Hamelin
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Asselin
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Zuhier
authors.initials: Z
authors.lastname: Awan
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Chutikarn
authors.initials: C
authors.lastname: Butkinaree
authors.affiliation: the Laboratory of Supramolecular Chemistry, Department of Chemistry, University of Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Fleury
authors.affiliation: the Laboratory of Supramolecular Chemistry, Department of Chemistry, University of Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada.
authors.forename: Armand
authors.initials: A
authors.lastname: Soldera
authors.affiliation: the Laboratory of Supramolecular Chemistry, Department of Chemistry, University of Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada.
authors.forename: Yves L
authors.initials: YL
authors.lastname: Dory
authors.affiliation: Nutrition, Metabolism, and Atherosclerosis Clinic, Institut de Recherches Cliniques de Montréal, affiliated with University of Montreal, Montreal, Quebec H2W 1R7, Canada.
authors.forename: Alexis
authors.initials: A
authors.lastname: Baass
authors.affiliation: From the Laboratory of Biochemical Neuroendocrinology, Montreal, Quebec H2W 1R7, Canada. Electronic address: seidahn@ircm.qc.ca.
authors.forename: Nabil G
authors.initials: NG
authors.lastname: Seidah
mesh_terms: D019943:Amino Acid Substitution; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D006938:Hyperlipoproteinemia Type II / Q000235:genetics / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D008297:Male; D020125:Mutation, Missense; D000071449:Proprotein Convertase 9 / Q000378:metabolism*; D011485:Protein Binding; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism
chemical_list: C573412:LDLR protein, human; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9
keywords: LDL receptor; cell biology; cholesterol metabolism; familial hypercholesterolemia; human natural mutations; loss-of-function; low density lipoprotein (LDL); lysosome; proprotein convertase subtilisin/kexin type 9 (PCSK9); subcellular localization