title: Gene set enrichment analysis reveals several globally affected pathways due to SKI-1/S1P inhibition in HepG2 cells.
abstract: Sterol regulatory element-binding proteins (SREBPs) are transcription factors governing transcription of genes related to cholesterol and fatty acid metabolism. To become active, SREBPs must undergo a proteolytic cleavage to allow an active NH(2)-terminal segment to translocate into the nucleus. SKI-1/S1P is the first protease in the proteolytic activation cascade of SREBPs. SREBP inhibition may be useful, for example, in the treatment of liver steatosis caused by homocysteine-induced lipid synthesis. Accordingly, we overexpressed inhibitory prodomains (proSKI) of SKI-1/S1P in HepG2 cells to block SREBP activation to evaluate the potential of SKI-1/S1P in controlling cellular cholesterol synthesis. SKI-1/S1P inhibition resulted in reduced cholesterol synthesis and mRNA levels of the rate-limiting enzymes, HMG-CoA reductase and squalene epoxidase, in the cholesterol synthetic pathway. The inhibitory effect was maintained in the presence of homocysteine-induced endoplasmic reticulum stress. A gene set enrichment analysis was performed to elucidate other metabolic effects caused by SKI-1/S1P inhibition. SKI-1/S1P inhibition was observed to affect a number of other metabolic pathways, including glycolysis and citric acid cycle. These results demonstrate that inhibition of SREBPs decreases cholesterol synthesis in HepG2 cells both in the absence and presence of homocysteine. SKI-1/S1P inhibition may cause widespread changes in other key metabolic pathways.
authors.affiliation: Department of Neurology, Free University of Brussels, Brussels, Belgium.
authors.forename: Aloys
authors.initials: A
authors.lastname: De Windt
authors.forename: Myriam
authors.initials: M
authors.lastname: Rai
authors.forename: Lise
authors.initials: L
authors.lastname: Bernier
authors.forename: Karin
authors.initials: K
authors.lastname: Thelen
authors.forename: Juhani
authors.initials: J
authors.lastname: Soini
authors.forename: Chantal
authors.initials: C
authors.lastname: Lefebvre
authors.forename: Satyan
authors.initials: S
authors.lastname: Chintawar
authors.forename: Jacques
authors.initials: J
authors.lastname: Lavigne
authors.forename: Lilli
authors.initials: L
authors.lastname: Saarinen
authors.forename: Leena
authors.initials: L
authors.lastname: Kytömäki
authors.forename: Jon Scott
authors.initials: JS
authors.lastname: Munzer
authors.forename: Dieter
authors.initials: D
authors.lastname: Lütjohann
authors.forename: Massimo
authors.initials: M
authors.lastname: Pandolfo
authors.forename: Jean
authors.initials: J
authors.lastname: Davignon
authors.forename: Nabil G
authors.initials: NG
authors.lastname: Seidah
authors.forename: Reijo
authors.initials: R
authors.lastname: Laaksonen
mesh_terms: D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D006019:Glycolysis; D006710:Homocysteine / Q000378:metabolism*; D006801:Humans; D053858:Metabolic Networks and Pathways; D020411:Oligonucleotide Array Sequence Analysis; D043484:Proprotein Convertases / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D012697:Serine Endopeptidases; D051779:Sterol Regulatory Element Binding Proteins / Q000037:antagonists & inhibitors*
chemical_list: D012333:RNA, Messenger; D051779:Sterol Regulatory Element Binding Proteins; D006710:Homocysteine; D002784:Cholesterol; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; C115575:membrane-bound transcription factor peptidase, site 1