Low-temperature effect on the sterol-dependent processing of SREBPs and transcription of related genes in HepG2 cells

Ishaiahu Shechter, Peihua Dai, Mark A. Roseman, Sita D. Gupta, Bert B. Boyer, Guimin Guan

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Lowering the growth temperature of HepG2 cells from 37°C to 20°C results in a 73% reduction in human squalene synthase (HSS) protein, a 76% reduction in HSS mRNA, and a 96% reduction in promoter activity of a secreted alkaline phosphatase-HSS reporter gene. A similar decrease in either mRNA or protein levels is observed for 3-hydroxy-3-methylglutaryl CoA reductase, farnesyl diphosphate synthase, the LDL receptor, and fatty acid synthase. All these proteins and mRNAs show either a decrease or a complete loss of sterol-dependent regulation in cells grown at 20°C. In contrast, sterol regulatory element binding proteins (SREBPs)-1 and -2 exhibit a 2- to 3-fold increase in mRNA levels at 20°C. The membrane-bound form of the SREBPs is dramatically increased, but the proteolytic processing to the nuclear (N-SREBP) form is inhibited under these conditions. Overexpression of the N-SREBP or SREBP cleavage-activating protein (SCAP), but not site-1 or site-2 proteases, restores the activation of the HSS promoter at 20°C, most likely by liberating the SCAP-SREBP complex so that it can move to the Golgi for processing. These results indicate that the cholesterol synthesizing machinery is down-regulated at low temperatures, and points to the transport of the SCAP-SREBP complex to the Golgi as the specific down-regulated step.

Original languageEnglish (US)
Pages (from-to)1581-1590
Number of pages10
JournalJournal of lipid research
Volume44
Issue number8
DOIs
StatePublished - Aug 1 2003

Keywords

  • Cholesterol metabolism
  • Sterol regulatory element binding protein
  • Transcriptional regulation

ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology
  • Cell Biology

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