Yuki Iwayanagi1, Tappei Takada, Hiroshi Suzuki. 1. Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, The University of Tokyo, Tokyo, Japan.
Abstract
PURPOSE: Niemann-Pick C1-like 1 (NPC1L1) has been identified as a target of ezetimibe and found to be responsible for intestinal cholesterol absorption. Although, it was recently demonstrated that sterol responsive element binding protein 2 (SREBP2) is responsible for the cholesterol-dependent down-regulation of NPC1L1, the molecular mechanism of NPC1L1 expression is not fully understood. In the present study, we examined the involvement of hepatocyte nuclear factor 4alpha (HNF4alpha), a key modulator of lipid metabolism, in the transcriptional regulation of human NPC1L1 gene. METHODS: Reporter gene assays and EMSAs were performed using human NPC1L1 promoter constructs and the effect of siHNF4alpha was examined. RESULTS: Transfection of SREBP2 induced the transcriptional activities of NPC1L1 and additional transfection of HNF4alpha results in a marked stimulation of the activities. Studies with deletion mutants indicated that important elements are located within 264 nt upstream in the human NPC1L1 promoter. In addition, studies with mutations in putative binding sites of HNF4alpha indicated the existence of binding sites in -209 to -197 and -52 to -40. Moreover, HNF4alpha knockdown resulted in the reduced expression and regulation by cholesterol. CONCLUSIONS: It is concluded that HNF4alpha plays a crucial role in the expression and regulation of human NPC1L1 gene.
PURPOSE:Niemann-Pick C1-like 1 (NPC1L1) has been identified as a target of ezetimibe and found to be responsible for intestinal cholesterol absorption. Although, it was recently demonstrated that sterol responsive element binding protein 2 (SREBP2) is responsible for the cholesterol-dependent down-regulation of NPC1L1, the molecular mechanism of NPC1L1 expression is not fully understood. In the present study, we examined the involvement of hepatocyte nuclear factor 4alpha (HNF4alpha), a key modulator of lipid metabolism, in the transcriptional regulation of humanNPC1L1 gene. METHODS: Reporter gene assays and EMSAs were performed using humanNPC1L1 promoter constructs and the effect of siHNF4alpha was examined. RESULTS: Transfection of SREBP2 induced the transcriptional activities of NPC1L1 and additional transfection of HNF4alpha results in a marked stimulation of the activities. Studies with deletion mutants indicated that important elements are located within 264 nt upstream in the humanNPC1L1 promoter. In addition, studies with mutations in putative binding sites of HNF4alpha indicated the existence of binding sites in -209 to -197 and -52 to -40. Moreover, HNF4alpha knockdown resulted in the reduced expression and regulation by cholesterol. CONCLUSIONS: It is concluded that HNF4alpha plays a crucial role in the expression and regulation of humanNPC1L1 gene.
Authors: Scott W Altmann; Harry R Davis; Li-Ji Zhu; Xiaorui Yao; Lizbeth M Hoos; Glen Tetzloff; Sai Prasad N Iyer; Maureen Maguire; Andrei Golovko; Ming Zeng; Luquan Wang; Nicholas Murgolo; Michael P Graziano Journal: Science Date: 2004-02-20 Impact factor: 47.728
Authors: Margarita Garcia-Calvo; JeanMarie Lisnock; Herbert G Bull; Brian E Hawes; Duane A Burnett; Matthew P Braun; James H Crona; Harry R Davis; Dennis C Dean; Patricia A Detmers; Michael P Graziano; Meredith Hughes; D Euan Macintyre; Anthony Ogawa; Kim A O'neill; Sai Prasad N Iyer; Diane E Shevell; Marsha M Smith; Yui S Tang; Amanda M Makarewicz; Feroze Ujjainwalla; Scott W Altmann; Kevin T Chapman; Nancy A Thornberry Journal: Proc Natl Acad Sci U S A Date: 2005-05-31 Impact factor: 11.205
Authors: Ryan E Temel; Weiqing Tang; Yinyan Ma; Lawrence L Rudel; Mark C Willingham; Yiannis A Ioannou; Joanna P Davies; Lisa-Mari Nilsson; Liqing Yu Journal: J Clin Invest Date: 2007-07 Impact factor: 14.808
Authors: James Rhee; Yusuke Inoue; J Cliff Yoon; Pere Puigserver; Melina Fan; Frank J Gonzalez; Bruce M Spiegelman Journal: Proc Natl Acad Sci U S A Date: 2003-03-21 Impact factor: 11.205
Authors: André J Tremblay; Benoît Lamarche; Valéry Lemelin; Lizbeth Hoos; Suzanne Benjannet; Nabil G Seidah; Harry R Davis; Patrick Couture Journal: J Lipid Res Date: 2010-12-01 Impact factor: 5.922