Yao Yao, Hong Shangyu, Zhou Hu, Yuan Taichang, Zeng Rong, Liao Kan
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
Cell Res. 2009 Apr;19(4):497-506. doi: 10.1038/cr.2009.27.
Morphologically, caveolae and lipid rafts are two different membrane structures. They are often reported to share similar lipid and protein compositions, and are considered to be two subtypes of membrane lipid microdomains. By modifying sucrose density gradient flotation centrifugation, which is used to isolate lipid microdomains, we were able to separate caveolae and noncaveolar lipid microdomains into two distinct fractions. The caveolar membranes are membrane vesicles of 100-nm diameter, enriched with caveolin-1 and flotillin-1. The noncaveolar lipid microdomains are amorphous membranes and most likely the coalescence of heterogeneous lipid rafts. They are depleted of caveolin-1 and are more enriched with cholesterol and sphingolipids than the caveolae. Many membrane proteins, such as insulin-like growth factor-1 receptor (membrane receptor), aquaporin-1 (membrane transporter), Thy-1 and N-cadherin (glycosylphosphatidylinositol-anchored membrane protein and membrane glycoprotein), are specifically associated with noncaveolar lipid microdomains, but not with caveolae. These results indicate that the lipid and protein compositions of caveolae differ from those of noncaveolar lipid microdomains. The difference in their protein compositions implies that these two membrane microdomains may have different cellular functions.
从形态学上看，小窝和脂筏是两种不同的膜结构。它们常被报道具有相似的脂质和蛋白质组成，并被认为是膜脂质微区的两种亚型。通过改进用于分离脂质微区的蔗糖密度梯度浮选离心法，我们能够将小窝和非小窝脂质微区分成两个不同的组分。小窝膜是直径为100纳米的膜泡，富含小窝蛋白-1和浮舰蛋白-1。非小窝脂质微区是无定形膜，很可能是异质性脂筏的聚集体。它们不含小窝蛋白-1，且比小窝富含更多的胆固醇和鞘脂。许多膜蛋白，如胰岛素样生长因子-1受体（膜受体）、水通道蛋白-1（膜转运蛋白）、Thy-1和N-钙黏蛋白（糖基磷脂酰肌醇锚定膜蛋白和膜糖蛋白），与非小窝脂质微区特异性相关，而与小窝无关。这些结果表明，小窝的脂质和蛋白质组成与非小窝脂质微区不同。它们蛋白质组成的差异意味着这两种膜微区可能具有不同的细胞功能。
