| Summary: | 碩士 === 台北醫學院 === 醫學研究所 === 89 === Abstract
Several lipid droplet-associated proteins are involved in regulating the intracellular lipid metabolism. However, the molecular basis of the acute hormonal regulation and mechanism of lipolysis in cells remains unclear. In this study, intracellular lipid droplets were isolated from rat adrenocortical cells and adipocytes. The lipid droplet-associated proteins were analyzed by electrophoresis and Western blotting. We found that actin(43kD) was copurified with both lipid droplet preparations. According to the data of one and two dimensional electrophoresis and Western blot, lipid droplet-associated actin was confirmed as beta isoform. Immunofluorescence with anti-b-actin antibody showed that b-actin not only constructed the stress fibers, but also located on the surface of lipid droplet. In addition, FITC-phalloidin staining displayed lipid droplet-associated actin was globular type. To investigate the interaction between b-actin and intracellular lipid droplets, the redistribution of b-actin was examined by administration of dibutyryl cyclic AMP and cytochalasin D. After treatment of dibutyryl cyclic AMP to stimulate lipolysis and steroidogenesis, lipid droplets were decreased in size. Immunofluorescence with anti-b-actin antibody revealed that the number of stress fibers were decreased and b-actin was translocated from the surface of lipid droplets into cytoplasm in cultured adrenocortical cells. After treatment of cytochalasin D to depolymerize actin filaments, scattered b-actin granules were observed in cytosol and each methanol-resistant lipid droplet was surrounded by a bright rim. These data demonstrated that the lipid droplet-associated globular b-actin might protect lipid droplets from methanol extraction or lipolysis.
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