A caveolin dominant negative mutant associates with lipid bodies and induces intracellular cholesterol imbalance.
Recent studies have indicated a role for caveolin in regulating cholesterol-dependent signaling events. In the present study we have analyzed the role of caveolins in intracellular cholesterol cycling using a dominant negative caveolin mutant. The mutant caveolin protein, cav-3(DGV), specifically associates with the membrane surrounding large lipid droplets. These structures contain neutral lipids, and are accessed by caveolin 1-3 upon overexpression. Fluorescence, electron, and video microscopy observations are consistent with formation of the membrane-enclosed lipid rich structures by maturation of subdomains of the ER. The caveolin mutant causes the intracellular accumulation of free cholesterol (FC) in late endosomes, a decrease in surface cholesterol and a decrease in cholesterol efflux and synthesis. The amphiphile U18666A acts synergistically with cav(DGV) to increase intracellular accumulation of FC. Incubation of cells with oleic acid induces a significant accumulation of full-length caveolins in the enlarged lipid droplets. We conclude that caveolin can associate with the membrane surrounding lipid droplets and is a key component involved in intracellular cholesterol balance and lipid transport in fibroblasts.
Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis and Department of Physiology and Pharmacology, University of Queensland, Queensland 4072, Australia.
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Luetterforst
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Lindsay
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Heino
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Ikonen
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Parton
D000595:Amino Acid Sequence; D000736:Androstenes / Q000494:pharmacology; D000818:Animals; D000906:Antibodies; D001692:Biological Transport / Q000187:drug effects; D015415:Biomarkers / Q000032:analysis; D020126:Brefeldin A / Q000494:pharmacology; D051242:Caveolin 1; D022461:Caveolins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism; D005347:Fibroblasts; D005455:Fluorescent Antibody Technique; D005799:Genes, Dominant / Q000235:genetics; D006706:Homeostasis; D050356:Lipid Metabolism; D008854:Microscopy, Electron; D018715:Microscopy, Video; D009154:Mutation / Q000235:genetics*; D019301:Oleic Acid / Q000494:pharmacology; D015398:Signal Transduction
D000736:Androstenes; D000906:Antibodies; D015415:Biomarkers; D051242:Caveolin 1; D022461:Caveolins; D020126:Brefeldin A; D019301:Oleic Acid; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D002784:Cholesterol