title: Overexpression of full-length cholesteryl ester transfer protein in SW872 cells reduces lipid accumulation.
abstract: Cells produce two cholesteryl ester transfer protein (CETP) isoforms, full-length and a shorter variant produced by alternative splicing. Blocking synthesis of both isoforms disrupts lipid metabolism and storage. To further define the role of CETP in cellular lipid metabolism, we stably overexpressed full-length CETP in SW872 cells. These CETP(+) cells had several-fold higher intracellular CETP and accumulated 50% less TG due to a 26% decrease in TG synthesis and 2.5-fold higher TG turnover rate. Reduced TG synthesis was due to decreased fatty acid uptake and impaired conversion of diglyceride to TG even though diacylglycerol acyltransferase activity was normal. Sterol-regulatory element binding protein 1 mRNA levels were normal, and although PPARγ expression was reduced, the expression of several of its target genes including adipocyte triglyceride lipase, FASN, and APOE was normal. CETP(+) cells contained smaller lipid droplets, consistent with their higher levels of perilipin protein family (PLIN) 3 compared with PLIN1 and PLIN2. Intracellular CETP was mostly associated with the endoplasmic reticulum, although CETP near lipid droplets poorly colocalized with this membrane. A small pool of CETP resided in the cytoplasm, and a subfraction coisolated with lipid droplets. These data show that overexpression of full-length CETP disrupts lipid homeostasis resulting in the formation of smaller, more metabolically active lipid droplets.
authors.affiliation: Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195.
authors.forename: Lahoucine
authors.initials: L
authors.lastname: Izem
authors.affiliation: Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195.
authors.forename: Diane J
authors.initials: DJ
authors.lastname: Greene
authors.affiliation: Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Bialkowska
authors.affiliation: Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195. Electronic address: mortonr@ccf.org.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Morton
mesh_terms: D001057:Apolipoproteins E / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D053480:Cholesterol Ester Transfer Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D054890:Fatty Acid Synthase, Type I / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D047495:PPAR gamma / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics / Q000378:metabolism; D014280:Triglycerides / Q000235:genetics / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; C506642:CETP protein, human; D053480:Cholesterol Ester Transfer Proteins; D047495:PPAR gamma; D012333:RNA, Messenger; C497387:SREBF1 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D014280:Triglycerides; C518729:FASN protein, human; D054890:Fatty Acid Synthase, Type I
keywords: cellular localization; gene expression; lipid droplets; lipid metabolism; lipid turnover