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.

Inhibition of Lassa Virus Glycoprotein Cleavage and Multicycle Replication by Site 1 Protease-Adapted α1-Antitrypsin Variants

“…The glycoproteins of the Old World arenaviruses LASV and LCMV were the first viral glycoproteins that were shown to be proteolytically processed by S1P [23,26], which normally plays important physiological regulatory roles in cholesterol metabolism, ER stress response, cartilage development and other cellular processes [21,27,28,29,30,31]. Using systematic mutational analysis of the LCMV GP cleavage site, the consensus motif R-(R/K/ H)-L-(A/L/S/T/F) was determined, which is conserved in the glycoprotein sequences of the Old World viruses LASV, Mopeia and Mobala, as well as the New World virus Pichinde, suggesting that all arenavirus glycoproteins are cleaved by S1P [26,32].…”

Cancer type-specific prioritization strategy for targetable dependencies developed from the DepMap profile of head and neck cancer

“…Lastly, MBTPS1 or site-1 protease catalyzes the proteolytic activation of transcription factor sterol regulatory element-binding proteins 56 and the cyclic AMP-dependent activating transcription factor 6 56 . It is involved in regulation of many metabolic pathways including glycolysis, citric acid cycle and fatty acid biosynthesis 37 .…”

VisANT: an integrative framework for networks in systems biology

“…If differential expression manifests itself at the level of pathways or functionally coherent sets of genes, it may be more powerful to perform statistical testing for differential expression on a prior defined gene sets. A representative method is the Gene Set Enrichment Analysis [49][50][51][52]. In addition, such analyses will help to determine which pathways/modules are turned on/off for a given expression profile.…”