GM1-containing lipid rafts are depleted within clathrin-coated pits
GM1-containing lipid rafts are depleted within clathrin-coated pits
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DOI：
10.1016/s0960-9822(03)00209-4
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发表时间：
2003-04-15
期刊：
影响因子：
9.2
通讯作者：
Nichols, BJ
中科院分区：
文献类型：
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作者：
Nichols, BJ
最近的研究表明，脂筏的标志物是最有可能被内化的质膜成分之一，不依赖于笼蛋白包裹的小孔，有证据表明脂筏可能在内吞运输中发挥作用[1-5]。然而，脂筏本身通常是纯粹用生化术语定义的，即对洗涤剂提取的抵抗力。活细胞膜中是否存在木筏仍然存在争议[6-8]，它们相对于内吞机制的分布还没有被研究过。这项研究使用荧光共振能量转移(FRET)来表明，在活细胞的质膜[PM]中，至少在也包括GPI连接蛋白的簇中发现了标记有霍乱毒素B亚单位(CTB)的糖鞘糖脂GM1[9，10]。这些簇是胆固醇依赖的，不包括转铁蛋白受体等非RAFT蛋白，因此具有预测的脂筏特性。这种类型的脂筏在很大程度上被排除在PM的网状蛋白阳性区域之外它们以与细胞表面其他部位相同的浓度分布在小窝阳性区域内。这些数据为一种模型提供了证据，在该模型中，脂筏均匀地分布在非极化细胞的大部分质膜上，但被阻止进入笼罩着网状蛋白的凹坑。
Recent studies show that markers for lipid rafts are among the plasma membrane components most likely to be internalized independently of clathrin-coated pits, and there is evidence to suggest that lipid rafts may play a functional role in endocytic trafficking [1-5]. However, lipid rafts themselves are commonly defined purely in biochemical terms, by resistance to detergent extraction. The existence of rafts in live-cell membranes remains controversial [6-8], and their distribution relative to endocytic machinery has not been investigated. This study employs fluorescence resonance energy transfer (FRET) to show that in the plasma membrane [PM) of living cells the glycosphingolipid GM1, labeled with cholera toxin B subunit (CTB) [9, 10], is found at least in part within clusters that also include GPI-linked proteins. These clusters are cholesterol-dependent and exclude non-raft proteins such as transferrin receptor and so possess predicted properties of lipid rafts. This type of lipid raft is largely excluded from clathrin-positive regions of the PM. They are found within Caveolin-positive regions at the same concentration as at the rest of the cell surface. The data provide evidence for a model in which lipid rafts are distributed uniformly across most of the PM of nonpolarized cells but are prevented from entering clathrin-coated pits.