Perilipin A increases triacylglycerol storage by decreasing the rate of triacylglycerol hydrolysis
Perilipin A increases triacylglycerol storage by decreasing the rate of triacylglycerol hydrolysis
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DOI：
10.1074/jbc.m007322200
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发表时间：
2000-12-08
影响因子：
4.8
通讯作者：
Londos, C
中科院分区：
文献类型：
--
作者：
Brasaemle, DL;Rubin, B;Londos, C
脂周蛋白是脂肪细胞脂滴表面最丰富的蛋白质，也存在于类固醇生成细胞中。为了研究periilipin的功能，主要亚型periilipin A在通常缺乏periilipin的成纤维细胞3T3-L1前脂肪细胞中异位表达。在对照细胞中，用Bodipy 493/503对中性脂质进行荧光染色，发现脂滴数量较少，分布广泛，而在稳定表达perilipin a的细胞中，脂滴数量较多，紧密聚集在细胞质的一个或两个区域。免疫荧光显微镜显示异位的周脂素A定位于微小的簇状脂滴表面；使用蔗糖梯度对细胞进行亚细胞分离，证实perilipin A只定位于脂滴。表达perilipin A的细胞储存的三酰甘油比对照细胞多6-30倍，这是由于三酰甘油储存的脂肪分解减少了。在表达perilippin A的脂载细胞中，储存的三酰甘油的脂解速度比在脂载对照细胞中慢5倍。当三酰甘油合成被6mum三酰甘油c阻断时，这种三酰甘油的稳定不是由于perilipin A的表达抑制了三酰甘油脂肪酶的活性。我们得出结论，perilipin A通过形成屏障减少可溶性脂肪酶接近储存的脂质，从而抑制三酰甘油水解，从而增加了细胞中三酰甘油的含量。这些研究表明，perilipin A在调节脂肪细胞中甘油三酯的储存和脂肪分解中起主要作用。
The perilipins are the most abundant proteins at the surfaces of lipid droplets in adipocytes and are also found in steroidogenic cells. To investigate perilipin function, perilipin A, the predominant isoform, was ectopically expressed in fibroblastic 3T3-L1 pre-adipocytes that normally lack the perilipins. In control cells, fluorescent staining of neutral lipids with Bodipy 493/503 showed a few minute and widely dispersed lipid droplets, while in cells stably expressing perilipin A, the lipid droplets were more numerous and tightly clustered in one or two regions of the cytoplasm. Immunofluorescence microscopy revealed that the ectopic perilipin A localized to the surfaces of the tiny clustered lipid droplets; subcellular fractionation of the cells using sucrose gradients confirmed that the perilipin A localized exclusively to lipid droplets. Cells expressing perilipin A stored 6-30-fold more triacylglycerol than control cells due to reduced lipolysis of triacylglycerol stores. The lipolysis of stored triacylglycerol was 5 times slower in lipid-loaded cells expressing perilipin A than in lipid-loaded control cells, when triacylglycerol synthesis was blocked with 6 muM triacsin C. This stabilization of triacylglycerol was not due to the suppression of triacylglycerol lipase activity by the expression of perilipin A. We conclude that perilipin A increases the triacylglycerol content of cells by forming a barrier that reduces the access of soluble lipases to stored lipids, thus inhibiting triacylglycerol hydrolysis. These studies suggest that perilipin A plays a major role in the regulation of triacylglycerol storage and lipolysis in adipocytes.