title: Reduction of circulating PCSK9 and LDL-C levels by liver-specific knockdown of HNF1α in normolipidemic mice.
abstract: The transcription factors hepatic nuclear factor (HNF)1α and HNF1β can bind to the HNF1 site on the proprotein convertase subtilisin/kexin type 9 (PCSK9) promoter to activate transcription in HepG2 cells. However, it is unknown whether one or both HNF1 factors are obligatory for transactivating hepatic PCSK9 gene expression in vivo. We developed shRNA adenoviral constructs (Ad-shHNF1α and Ad-shHNF1β) to examine the effects of knockdown of HNF1α or HNF1β on PCSK9 expression and its consequent impact on LDL receptor (LDLR) protein levels in cultured hepatic cells and liver tissue. We demonstrated that infection with Ad-shHNF1α, but not Ad-shHNF1β, markedly reduced PCSK9 mRNA expression in HepG2 cells with a concomitant increase in LDLR protein abundance. Injecting Ad-shHNF1α in mice fed a normal diet significantly (∼ 50%) reduced liver mRNA expression and serum concentration of PCSK9 with a concomitant increase (∼ 1.9-fold) in hepatic LDLR protein abundance. Furthermore, we observed a modest but significant reduction in circulating LDL cholesterol after knockdown of HNF1α in these normolipidemic mice. Consistent with the observation that knockdown of HNF1β did not affect PCSK9 mRNA or protein expression in cultured hepatic cells, Ad-shHNF1β infection in mice resulted in no change in the hepatic mRNA expression or serum content of PCSK9. Altogether, our study demonstrates that HNF1α, but not HNF1β, is the primary positive regulator of PCSK9 transcription in mouse liver.
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 Department of Medicine, Stanford University, Stanford, CA 94305.
authors: Vikram Ravindra
authors: VR
authors: Shende
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304.
authors: Minhao
authors: M
authors: Wu
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304 Department of Medicine, Stanford University, Stanford, CA 94305.
authors: Amar Bahadur
authors: AB
authors: Singh
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304.
authors: Bin
authors: B
authors: Dong
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304.
authors: Chin Fung Kelvin
authors: CF
authors: Kan
authors: Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304.
authors: Jingwen
authors: J
authors: Liu
mesh_terms: D000818:Animals; D008078:Cholesterol, LDL / Q000097:blood*; D004032:Diet; D015971:Gene Expression Regulation, Enzymologic; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D056945:Hep G2 Cells; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000172:deficiency* / Q000235:genetics*; D051539:Hepatocyte Nuclear Factor 1-beta / Q000172:deficiency / Q000235:genetics; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D009928:Organ Specificity; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000097:blood*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000097:blood*
chemical_list: D008078:Cholesterol, LDL; D051538:Hepatocyte Nuclear Factor 1-alpha; C496496:Hnf1b protein, mouse; D012333:RNA, Messenger; D051539:Hepatocyte Nuclear Factor 1-beta; C472126:Pcsk9 protein, mouse; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases
keywords: hepatic nuclear factor 1α; hepatic nuclear factor 1β; low density lipoprotein cholesterol; low density lipoprotein receptor; proprotein convertase subtilisin/kexin type 9
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