title: Regulation of the proprotein convertase subtilisin/kexin type 9 in intestinal epithelial cells.
abstract: Proprotein convertase subtilisin/kexin type 9 (PCSK9) posttranslationally promotes the degradation of the low-density lipoprotein receptor (LDLr) in hepatocytes and increases plasma LDL cholesterol. It is not clear, however, whether PCSK9 plays a role in the small intestine. Here, we characterized the patterns of variations of PCSK9 and LDLr in fully differentiated Caco-2/15 cells as a function of various potential effectors. Cholesterol (100 microM) solubilized in albumin or micelles significantly downregulated PCSK9 gene (30%, P<0.05) and protein expression (50%, P<0.05), surprisingly in concert with a decrease in LDLr protein levels (45%, P<0.05). Cells treated with 25-hydroxycholesterol (50 microM) also displayed significant reduction in PCSK9 gene (37%, P<0.01) and protein (75% P<0.001) expression, whereas LDLr showed a decrease at the gene (30%, P<0.05) and protein (57%, P<0.01) levels, respectively. The amounts of PCSK9 mRNA and protein in Caco-2/15 cells were associated to the regulation of 3-hydroxy-3-methylglutaryl-CoA reductase and sterol regulatory element binding protein-2 (SREBP-2) that can transcriptionally activate PCSK9 via sterol-regulatory elements located in its proximal promoter region. On the other hand, depletion of cholesterol content by hydroxypropyl-beta-cyclodextrin upregulated PCSK9 transcripts (20%, P<0.05) and protein mass (540%, P<0.001), in parallel with SREBP-2 protein levels. The addition of bile acids (BA) taurocholate and deoxycholate to the apical culture medium lowered PCSK9 gene expression (25%, P<0.01) and raised PCSK9 protein expression (30%, P<0.01), respectively, probably via the modulation of farnesoid X receptor. Furthermore, unconjugated and conjugated BA exhibited different effects on PCSK9 and LDLr. Altogether, these data indicate that intestinal PCSK9 is highly modulated by sterols and emphasize the distinct effects of BA species.
authors.affiliation: Department of Nutrition, Clinical Research Institute of Montréal, Montreal, Quebec, Canada, H3T 1C5.
authors.forename: François
authors.initials: F
authors.lastname: Leblond
authors.forename: Nabil G
authors.initials: NG
authors.lastname: Seidah
authors.forename: Louis-Philippe
authors.initials: LP
authors.lastname: Précourt
authors.forename: Edgard
authors.initials: E
authors.lastname: Delvin
authors.forename: Michel
authors.initials: M
authors.lastname: Dominguez
authors.forename: Emile
authors.initials: E
authors.lastname: Levy
mesh_terms: D001647:Bile Acids and Salts; D018938:Caco-2 Cells; D002784:Cholesterol / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006888:Hydroxycholesterols / Q000494:pharmacology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology* / Q000187:drug effects; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics / Q000378:metabolism
chemical_list: D001647:Bile Acids and Salts; D006888:Hydroxycholesterols; D012333:RNA, Messenger; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2; C007997:25-hydroxycholesterol; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases