Sterol-mediated regulation of hormone-sensitive lipase in 3T3-L1 adipocytes.
We previously reported that intracellular free cholesterol at physiological concentrations regulates the activity of neutral cholesterol esterase (N-CEase) in macrophages. The objective of the present study is to investigate whether the regulation of N-CEase by cholesterol is generally observed in other types of cells such as adipocytes with high activity of hormone-sensitive lipase (HSL), the same gene product as N-CEase. 3T3-L1 adipocytes were cultured with and without cholesterol (1-30 microg/mL) or 25-hydroxycholesterol (0.1-10 microg/mL), and changes in the N-CEase activity, expression of HSL mRNA, and protein were examined. Incubation (24 h) of cells with cholesterol did not change N-CEase activity, but incubation with 25-hydroxycholesterol decreased the activity in a concentration-dependent manner by 24 (24 h) and 54% (36 h). Quantitative reverse transcription-PCR indicated that 25-hydroxycholesterol (10 microg/mL) did not influence expression of HSL mRNA. However, Western blot analysis showed that this sterol reduced HSL protein by 72 (24 h) and by 93% (36 h), respectively. It was concluded that sterol-mediated regulation of HSL/N-CEase occurs not only in macrophages but also in adipocytes, and regulation appears to occur not at a transcriptional level but by a post-transcriptional process. Sterol-mediated proteolysis may be involved in the loss of HSL protein.
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects* / Q000201:enzymology*; D000818:Animals; D002784:Cholesterol / Q000378:metabolism / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006888:Hydroxycholesterols / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D002787:Sterol Esterase / Q000235:genetics / Q000378:metabolism*; D013261:Sterols / Q000494:pharmacology*
D006888:Hydroxycholesterols; D012333:RNA, Messenger; D013261:Sterols; C007997:25-hydroxycholesterol; D002784:Cholesterol; D002787:Sterol Esterase