Lipid sorting and formation of distinct plasma membrane domains during cell polarization in Drosophila

跨高尔基体网络(TGN)中的质膜成分(包括蛋白质和脂类)被分选到顶端和基侧的运输小泡中，并正确地输送到表面域是维持细胞极性的机制[1]。然而，他们未能解释细胞极性最初是如何建立的，以及蛋白质和脂类的分选机制在这一过程中可能起到什么作用。此外，目前尚不清楚是否在形成阻止侧向脂类扩散的膜屏障之前或之后建立了不同的膜室，以及这种屏障对于靶向机制可能具有什么作用。以前的研究表明，内吞途径在蛋白质和脂肪成分的极化靶向中发挥作用(2，3，4)。我们想要测试荧光脂类似物监测的内吞和生物合成途径上的膜运输是否对细胞极性的建立有显著影响。我们建议通过研究果蝇细胞内脂类转运和内吞途径的基因失活来测试细胞极性的建立和维持的影响。相反，一些被认为在细胞极性建立中起作用的基因也可能在蛋白质或脂肪分选中发挥作用。我们将通过使用具有细胞极性缺陷的果蝇突变体来研究这种可能性，以表征现有的靶向机制是否可能受到影响。最后，我们将使用果蝇基因组序列和基因预测程序来确定候选跨膜蛋白，这些蛋白可能在建立分隔顶端和基侧膜室的膜屏障方面发挥作用。这些候选基因的功能将使用现有的突变体或RNA干扰进行测试。

The sorting of plasma membrane components including proteins and lipids in the trans-Golgi network (TGN) into apical and basolateral transport vesicles and the correct delivery to surface domains are mechanisms by which cell polarity is maintained (1). However, they fail to explain how cell polarity is initially established and which role sorting mechanisms for proteins and lipids may play in this process. In addition, it is not understood whether distinct membrane compartments are established prior to or after formation of a membrane fence that blocks lateral lipid diffusion and what role such a fence may have for targeting mechanisms. Previous studies suggest a role of the endocytic pathway in polarized targeting of protein and lipid components (2,3,4). We want to test whether membrane trafficking along the endocytic and biosynthetic pathway monitored by fluorescent lipid analogs has pronounced effects on the establishment of cell polarity. We propose to test the effects on establishment and maintenance of cellular polarity by studying intracellular lipid transport and by gene inactivation of components of the endocytic pathway in Drosophila. Conversely, some genes for which a role in establishment of cell polarity has been ascribed may function in protein or lipid sorting as well. We will investigate this possibility by employing Drosophila mutants with defects in cellular polarity to characterize whether the existing targeting mechanisms may be affected. Finally, we will use the Drosophila genomic sequence and gene prediction programs to identify candidate transmembrane proteins with a possible role in establishing the membrane fence that separates apical from basolateral membrane compartments. The function of those candidate genes will be tested using existing mutants or RNA interference.