title: Sterol regulatory element-binding protein-2 negatively regulates low density lipoprotein receptor-related protein transcription.
abstract: Low density lipoprotein receptor-related protein (LRP1) binds aggregated LDL (agLDL) leading to a high intracellular cholesteryl ester (CE) accumulation. AgLDL up-regulates LRP1 expression concomitantly with an LDL receptor (LDLR) and sterol regulatory element binding protein (SREBP-2) down-regulation. The objectives were to investigate whether SREBP-2 regulates LRP1 transcription and determine the molecular mechanisms involved in the process. Down-regulation of active SREBP-2 by nLDL and agLDL led to LDLR down-regulation and LRP1 up-regulation. Enforced expression of an active form of SREBP-2 (SREBP-2-NT, amino acid residues 1-468) decreased LRP1 expression and LRP1 promoter (WT-LRP1) luciferase activity in a dose-dependent manner. LDL did not exert any significant effect on LRP1 promoter activity when a putative sterol regulatory element (SRE) (5-GTGGGGTGA-3'; +225 to +233) was mutated (SRE-MT-LRP1). SREBP-2 overexpression exerted stronger down-regulatory effects on WT-LRP1 than on SRE-MT-LRP1 promoter activity both in control, nLDL- and agLDL-exposed HeLa cells. Gel mobility shift assays showed that recombinant SREBP-2-NT protein (1-468) binds to a double-stranded LRP1 DNA fragment (215 to 245) containing a wild-type (wt) SRE sequence but not to a mutated SRE (mt) sequence (5-GAATTCGA-3'). Our results demonstrate that LDL stimulates LRP1 transcription and decreases SREBP-2 active form which negatively regulates LRP1 transcription. SRE sequence (+225 to +233) plays a pivotal role for the down-regulatory effect of SREBP-2 on LRP1 promoter activity.
authors.affiliation: Cardiovascular Research Center, CSIC-ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, 08025, Spain.
authors.forename: V
authors.initials: V
authors.lastname: Llorente-Cortés
authors.forename: P
authors.initials: P
authors.lastname: Costales
authors.forename: J
authors.initials: J
authors.lastname: Bernués
authors.forename: S
authors.initials: S
authors.lastname: Camino-Lopez
authors.forename: L
authors.initials: L
authors.lastname: Badimon
mesh_terms: D020121:5' Untranslated Regions; D001483:Base Sequence; D001665:Binding Sites; D002788:Cholesterol Esters / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000235:genetics* / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D051782:Sterol Regulatory Element Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D020121:5' Untranslated Regions; D002788:Cholesterol Esters; D026502:LDL-Receptor Related Proteins; D008077:Lipoproteins, LDL; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2