Sorting of lens aquaporins and connexins into raft and nonraft bilayers: role of protein homo-oligomerization.
Sorting of lens aquaporins and connexins into raft and nonraft bilayers: role of protein homo-oligomerization.
复制标题
将晶状体水通道蛋白和连接蛋白分类成筏和非筏双层：蛋白质同源寡聚化的作用。
DOI：
10.1016/j.bpj.2009.08.026
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发表时间：
2009
影响因子：
3.4
通讯作者：
McIntosh,ThomasJ
中科院分区：
文献类型：
--
作者：
Tong,Jihong;Briggs,MargaretM;Mlaver,David;Vidal,Adriana;McIntosh,ThomasJ
眼睛透镜中的两类通道形成蛋白，即水通道水通道蛋白-0（AQP-0）和连接蛋白Cx46和Cx 50，优先位于透镜质膜的不同区域（1，2）。由于这些膜含有高浓度的胆固醇和鞘磷脂，以及磷脂如具有不饱和烃链的磷脂酰胆碱，因此在这些膜中形成微区（筏）。在这里，我们测试的假设，分选成脂质微域可以发挥作用的AQP-0和连接蛋白的膜平面的处置。对于粗膜组分和由磷脂酰胆碱/鞘磷脂/胆固醇脂质双层中的透镜蛋白组成的脂蛋白体，去污剂提取实验表明，连接蛋白主要位于去污剂可溶性膜（DSM）组分中，而AQP-0在去污剂抗性膜和DSM组分中均被发现。分析纯化的AQP-0在含有筏的双层中的重构表明，AQP-0的微区位置依赖于蛋白/脂质比。AQP-0几乎仅位于DSM中，AQP-0/脂质比例为1：1200，而大约50%的蛋白质以1：100的比例被隔离到抗洗涤剂膜中，冷冻断裂实验表明AQP-0寡聚化（3）。与这些去污剂提取结果一致，共聚焦显微镜图像显示AQP-0被隔离到1：100蛋白质/脂质膜中的筏微结构域中。综上所述，这些结果表明，AQP-0和连接蛋白可以被隔离在膜中的蛋白质-脂质相互作用，如修改AQP-0同源寡聚化。
Two classes of channel-forming proteins in the eye lens, the water channel aquaporin-0 (AQP-0) and the connexins Cx46 and Cx50, are preferentially located in different regions of lens plasma membranes (1,2). Because these membranes contain high concentrations of cholesterol and sphingomyelin, as well as phospholipids such as phosphatidylcholine with unsaturated hydrocarbon chains, microdomains (rafts) form in these membranes. Here we test the hypothesis that sorting into lipid microdomains can play a role in the disposition of AQP-0 and the connexins in the plane of the membrane. For both crude membrane fractions and proteoliposomes composed of lens proteins in phosphatidylcholine/sphingomyelin/cholesterol lipid bilayers, detergent extraction experiments showed that the connexins were located primarily in detergent soluble membrane (DSM) fractions, whereas AQP-0 was found in both detergent resistant membrane and DSM fractions. Analysis of purified AQP-0 reconstituted in raft-containing bilayers showed that the microdomain location of AQP-0 depended on protein/lipid ratio. AQP-0 was located almost exclusively in DSMs at a 1:1200 AQP-0/lipid ratio, whereas ∼50% of the protein was sequestered into detergent resistant membranes at a 1:100 ratio, where freeze-fracture experiments show that AQP-0 oligomerizes (3). Consistent with these detergent extraction results, confocal microscopy images showed that AQP-0 was sequestered into raft microdomains in the 1:100 protein/lipid membranes. Taken together these results indicate that AQP-0 and connexins can be segregated in the membrane by protein-lipid interactions as modified by AQP-0 homo-oligomerization.