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This Article Full Text Full Text (PDF) All Versions of this Article: 296/4/G805    most recent 90424.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Leblond, F. Articles by Levy, E. Search for Related Content PubMed PubMed Citation Articles by Leblond, F. Articles by Levy, E.

MUCOSAL BIOLOGY

Regulation of the proprotein convertase subtilisin/kexin type 9 in intestinal epithelial cells

Departments of ¹Nutrition and ²Biochemical Neuroendocrinology, Clinical Research Institute of Montréal; ³Department of Biochemistry, Research Center, CHU Sainte Justine, Université de Montréal, Montréal, Québec, Canada

Submitted 10 July 2008 ; accepted in final form 26 January 2009

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 µM) 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 µM) 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-β-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.

enterocyte; PCSK9; cholesterol; bile acids; farnesoid X receptor; SREBP-2