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

包括蛋白质和脂质在内的质膜成分在反式高尔基网络（TGN）中分选到顶端和基底侧运输囊泡，并正确递送到表面结构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，以及蛋白质和脂质的分选机制在这一过程中可能发挥的作用。此外，目前尚不清楚不同的膜室是在膜栅栏形成之前还是之后建立的，膜栅栏阻断了脂质横向扩散，以及这种栅栏在靶向机制中可能起什么作用。先前的研究表明，内吞途径在蛋白质和脂质成分的极化靶向中发挥作用（2,3,4）。我们想测试沿着荧光脂质类似物监测的内吞和生物合成途径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质转运和内吞途径组分的基因失活来测试对细胞极性的建立和维持的影响。相反，一些在细胞极性建立中起作用的基因也可能在蛋白质或脂质分选中起作用。我们将通过使用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会受到影响。最后，我们将使用果蝇基因组序列和基因预测程序来鉴定候选跨膜蛋白，这些跨膜蛋白可能在建立分离根尖和基底外侧膜室的膜栅栏中起作用。这些候选基因的功能将通过现有的突变体或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.