Pike Linda J
Washington University School of Medicine, Department of Biochemistry and Molecular Biophysics, 660 So. Euclid, Box 8231, St. Louis, MO 63110, USA.
J Lipid Res. 2003 Apr;44(4):655-67. doi: 10.1194/jlr.R200021-JLR200. Epub 2003 Feb 1.
Lipid rafts are subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids. They exist as distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents. Rafts appear to be small in size, but may constitute a relatively large fraction of the plasma membrane. While rafts have a distinctive protein and lipid composition, all rafts do not appear to be identical in terms of either the proteins or the lipids that they contain. A variety of proteins, especially those involved in cell signaling, have been shown to partition into lipid rafts. As a result, lipid rafts are thought to be involved in the regulation of signal transduction. Experimental evidence suggests that there are probably several different mechanisms through which rafts control cell signaling. For example, rafts may contain incomplete signaling pathways that are activated when a receptor or other required molecule is recruited into the raft. Rafts may also be important in limiting signaling, either by physical sequestration of signaling components to block nonspecific interactions, or by suppressing the intrinsic activity of signaling proteins present within rafts. This review provides an overview of the physical characteristics of lipid rafts and summarizes studies that have helped to elucidate the role of lipid rafts in signaling via receptor tyrosine kinases and G protein-coupled receptors.
脂筏是质膜的亚结构域，含有高浓度的胆固醇和糖鞘脂。它们以膜的独特液晶有序区域形式存在，对非离子去污剂的提取具有抗性。脂筏似乎尺寸较小，但可能占质膜的相对较大比例。虽然脂筏具有独特的蛋白质和脂质组成，但就其所包含的蛋白质或脂质而言，并非所有脂筏看起来都是相同的。多种蛋白质，尤其是那些参与细胞信号传导的蛋白质，已被证明可分配到脂筏中。因此，脂筏被认为参与信号转导的调节。实验证据表明，脂筏可能通过几种不同的机制控制细胞信号传导。例如, 脂筏可能包含不完整的信号通路，当受体或其他所需分子被招募到脂筏中时被激活。脂筏在限制信号传导方面也可能很重要，要么通过物理隔离信号成分以阻止非特异性相互作用，要么通过抑制脂筏中存在的信号蛋白的内在活性。本综述概述了脂筏的物理特性，并总结了有助于阐明脂筏在通过受体酪氨酸激酶和G蛋白偶联受体进行信号传导中作用的研究。
