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.
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Institute for Molecular Bioscience, Centre for Microscopy and Microanalysis and Department of Physiology and Pharmacology, University of Queensland, Queensland 4072, Australia.
Luetterforst
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Lindsay
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Heino
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Ikonen
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Parton
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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