title: Decreased lipid synthesis in livers of mice with disrupted Site-1 protease gene.
abstract: Site-1 protease (S1P) cleaves membrane-bound sterol regulatory element-binding proteins (SREBPs), allowing their transcription-stimulating domains to translocate to the nucleus where they activate genes governing lipid synthesis. S1P is a potential target for lipid-lowering drugs, but the effect of S1P blockade in animals is unknown. Here, we disrupt the S1P gene in mice. Homozygous germ-line disruptions of S1P were embryonically lethal. To disrupt the gene inducibly in liver, we generated mice homozygous for a floxed S1P allele and heterozygous for a transgene encoding Cre recombinase under control of the IFN-inducible MX1 promoter. When IFN was produced, 70-90% of S1P alleles in liver were inactivated, and S1P mRNA and protein were reduced. Nuclear SREBPs declined, as did mRNAs for SREBP target genes. Cholesterol and fatty acid biosynthesis in hepatocytes declined by 75%. Low density lipoprotein (LDL) receptor mRNA declined by 50%, as did the clearance of (125)I-labeled LDL from plasma, but plasma cholesterol fell, suggesting that LDL production was reduced. These data raise the possibility that S1P inhibitors may be effective lipid-lowering agents, but they suggest that nearly complete inhibition will be required.
authors.affiliation: Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9046, USA.
authors.forename: J
authors.initials: J
authors.lastname: Yang
authors.forename: J L
authors.initials: JL
authors.lastname: Goldstein
authors.forename: R E
authors.initials: RE
authors.lastname: Hammer
authors.forename: Y A
authors.initials: YA
authors.lastname: Moon
authors.forename: M S
authors.initials: MS
authors.lastname: Brown
authors.forename: J D
authors.initials: JD
authors.lastname: Horton
mesh_terms: D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002784:Cholesterol / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis; D018390:Gene Targeting; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids / Q000096:biosynthesis*; D008077:Lipoproteins, LDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D043484:Proprotein Convertases; D012333:RNA, Messenger / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000502:physiology*; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D005227:Fatty Acids; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids; D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D012333:RNA, Messenger; C102196:SREBP cleavage-activating protein; C497388:Srebf1 protein, mouse; C497391:Srebf2 protein, mouse; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; D002784:Cholesterol; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; C115575:membrane-bound transcription factor peptidase, site 1