Halin Josefin, Mattjus Peter
Department of Biosciences, Åbo Akademi University, Turku, Finland.
Biochim Biophys Acta. 2011 Dec;1808(12):2886-93. doi: 10.1016/j.bbamem.2011.08.030. Epub 2011 Sep 1.
The glycolipid transfer protein (GLTP) is capable of transporting glycolipids from a donor membrane, through the aqueous environment, to an acceptor membrane. The GLTP mediated glycolipid transfer from sphingomyelin membranes is very slow. In contrast, the transfer is fast from membranes composed of phosphatidylcholine. The lateral glycolipid membrane organization is known to be driven by their tendency to mix non-randomly with different membrane lipids. Consequently, the properties of the membrane lipids surrounding the glycolipids play an important role in the ability of GLTP to bind and transfer its substrates. Since GLTP transfer of glycolipids is almost nonexistent from sphingomyelin membranes, we have used this exceptionality to investigate if membrane intercalators can alter the membrane packing and induce glycolipid transfer. We found that the bile salts cholate, deoxycholate, taurocholate and taurodeoxycholate, cause glucosylceramide to become transferrable by GLTP. Other compounds, such as single chain lipids, ceramide and nonionic surfactants, that have membrane-perturbing effects, did not affect the transfer capability of GLTP. We speculate that the strong hydrogen bonding network formed in the interfacial region of glycosphingolipid-sphingomyelin membranes is disrupted by the membrane partition of the bile salts causing the glycosphingolipid to become transferrable.
糖脂转移蛋白（GLTP）能够将糖脂从供体膜穿过水环境运输到受体膜。GLTP介导的从鞘磷脂膜的糖脂转移非常缓慢。相比之下，从由磷脂酰胆碱组成的膜上的转移则很快。已知糖脂的侧向膜组织是由它们与不同膜脂非随机混合的倾向驱动的。因此，糖脂周围的膜脂性质在GLTP结合和转移其底物的能力中起着重要作用。由于GLTP几乎不能从鞘磷脂膜转移糖脂，我们利用这种特殊性来研究膜嵌入剂是否能改变膜的堆积并诱导糖脂转移。我们发现胆汁酸盐胆酸盐、脱氧胆酸盐、牛磺胆酸盐和牛磺脱氧胆酸盐能使神经酰胺葡萄糖苷可被GLTP转移。其他具有膜扰动作用的化合物，如单链脂质、神经酰胺和非离子表面活性剂，并不影响GLTP的转移能力。我们推测，胆汁酸盐在膜中的分配破坏了糖鞘脂 - 鞘磷脂膜界面区域形成的强氢键网络，导致糖鞘脂变得可转移。
