title: Investigations on the evolutionary conservation of PCSK9 reveal a functionally important protrusion.
abstract: Proprotein convertase subtilisin/kexin type 9 (PCSK9) interferes with the recycling of low-density lipoprotein (LDL) receptor (LDLR). This leads to LDLR degradation and reduced cellular uptake of plasma LDL. Naturally occurring human PCSK9 loss-of-function mutations are associated with low levels of plasma LDL cholesterol and a reduced risk of coronary heart disease. PCSK9 gain-of-function mutations result in lower LDL clearance and increased risk of atherosclerosis. The exact mechanism by which PCSK9 disrupts the normal recycling of LDLR remains to be determined. In this study, we have assembled homologs of human PCSK9 from 20 vertebrates, a cephalochordate and mollusks in order to search for conserved regions of PCSK9 that may be important for the PCSK9-mediated degradation of LDLR. We found a large, conserved protrusion on the surface of the PCSK9 catalytic domain and have performed site-directed mutagenesis experiments for 13 residues on this protrusion. A cluster of residues that is important for the degradation of LDLR by PCSK9 was identified. Another cluster of residues, at the opposite end of the conserved protrusion, appears to be involved in the physical interaction with a putative inhibitor of PCSK9. This study identifies the residues, sequence segments and surface patches of PCSK9 that are under strong purifying selection and provides important information for future studies of PCSK9 mutants and for investigations on the function of this regulator of cholesterol homeostasis.
authors.affiliation: Medical Genetics Laboratory, Department of Medical Genetics, Rikshospitalet University Hospital, Oslo, Norway.
authors.forename: Jamie
authors.initials: J
authors.lastname: Cameron
authors.forename: Øystein L
authors.initials: ØL
authors.lastname: Holla
authors.forename: Knut Erik
authors.initials: KE
authors.lastname: Berge
authors.forename: Mari Ann
authors.initials: MA
authors.lastname: Kulseth
authors.forename: Trine
authors.initials: T
authors.lastname: Ranheim
authors.forename: Trond P
authors.initials: TP
authors.lastname: Leren
authors.forename: Jon K
authors.initials: JK
authors.lastname: Laerdahl
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D002417:Cattle; D002460:Cell Line; D043344:Chordata / Q000235:genetics; D019143:Evolution, Molecular; D045683:Furin / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008077:Lipoproteins, LDL; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D045683:Furin