Cross-talk between caveolae and glycosylphosphatidylinositol-rich domains
Cross-talk between caveolae and glycosylphosphatidylinositol-rich domains
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DOI：
10.1074/jbc.m102039200
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发表时间：
2001-08-17
影响因子：
4.8
通讯作者：
van der Goot, FG
中科院分区：
文献类型：
--
作者：
Abrami, L;Fivaz, M;van der Goot, FG
大多数哺乳动物细胞的质膜中至少有两种类型的脂质微区：非内陷的脂筏和小凹。糖基磷脂酰肌醇 (GPI) 锚定蛋白构成一类在稳定状态下富集于筏中但不富集于小窝中的蛋白质。我们分析了取消 GPI 生物合成对筏、小窝和胆固醇水平的影响。 GPI 缺陷细胞是通过筛选对成孔毒素气溶素的抗性而获得的，气溶素使用此类蛋白质作为受体。尽管不存在 GPI 锚定蛋白，突变细胞仍然含有脂筏，这表明 GPI 锚定蛋白不是这些结构域的关键结构元件。有趣的是，小凹特异性膜蛋白 Caveolin-1 和 2 在 GPI 缺陷细胞中表达上调，而 flotillin-I 和 GM1 则以正常水平表达。此外，表面凹坑的数量也有所增加。这种效应是特异的，因为通过基因再补充恢复 GPI 生物合成，将小窝蛋白表达和表面小窝数量恢复到野生型水平。通过观察野生型细胞中caveolin-1的过度表达导致GPI锚定蛋白的表达减少，证实了GPI锚定蛋白和caveolin-1的表达之间的负相关性。在缺乏小窝的细胞中，GPI锚定蛋白的缺失导致胆固醇水平升高，这表明GPI锚定蛋白可能在胆固醇稳态中发挥作用，而在某些细胞（例如中国仓鼠卵巢细胞）中，这种作用可以通过小窝蛋白的上调来补偿。
Most mammalian cells have in their plasma membrane at least two types of lipid microdomains, non-invaginated lipid rafts and caveolae. Glycosylphosphatidylinositol (GPI)-anchored proteins constitute a class of proteins that are enriched in rafts but not caveolae at steady state. We have analyzed the effects of abolishing GPI biosynthesis on rafts, caveolae, and cholesterol levels. GPI-deficient cells were obtained by screening for resistance to the pore-forming toxin aerolysin, which uses this class of proteins as receptors. Despite the absence of GPI-anchored proteins, mutant cells still contained lipid rafts, indicating that GPI-anchored proteins are not crucial structural elements of these domains. Interestingly, the caveolae-specific membrane proteins, caveolin-1 and 2, were up-regulated in GPI-deficient cells, in contrast to flotillin-I and GM1, which were expressed at normal levels. Additionally, the number of surface caveolae was increased. This effect was specific since recovery of GPI biosynthesis by gene recomplementation restored caveolin expression and the number of surface caveolae to wild type levels. The inverse correlation between the expression of GPI-anchored proteins and caveolin-1 was confirmed by the observation that overexpression of caveolin-1 in wild type cells led to a decrease in the expression of GPI-anchored proteins. In cells lacking caveolae, the absence of GPI-anchored proteins caused an increase in cholesterol levels, suggesting a possible role of GPI-anchored proteins in cholesterol homeostasis, which in some cells, such as Chinese hamster ovary cells, can be compensated by caveolin up-regulation.