Developmental regulation of epithelial polarization by pre-mRNA splicing

摘要 肠上皮细胞的顶膜在生理和体内平衡中起着关键作用。许多 肠上皮细胞的特殊功能，如营养吸收，依赖于忠实地分选蛋白质 在生物合成递送过程中到达顶端膜。然而，驱动顶膜的细胞机制 蛋白质分类以及它在发育过程中如何成熟的定义很差。也不知道是什么控制了 在富含溶酶体的肠细胞（LRE）中顶端内吞作用的开始。发现根尖膜的机制 在体内极化，我们进行了正向遗传学筛选的因素所需的分类模型顶端 货物（O-聚糖-GFP，Og-GFP）在斑马鱼肠道。我们分离出不同类型的突变体， Og-GFP分选。我们的初步数据已经揭示了一种pH依赖的膜蛋白分选机制 在亚顶端内体中，降解途径或顶端膜。我们还发现了一个角色 对于调节前mRNA内含子剪接在激活顶端膜转运途径中的作用， 肠上皮细胞中的蛋白质递送和发育肠的LRE中的顶端内吞作用。我们的研究将 揭示基因和细胞机制的成熟至关重要的完全极化和生理活性 脊椎动物肠道的上皮细胞。

Abstract The apical membrane of epithelial cells in the intestine play critical roles in physiology and homeostasis. Many specialized functions of intestinal epithelial cells, such as nutrient absorption, depend on faithfully sorting proteins to the apical membrane during biosynthetic delivery. However, the cellular mechanisms driving apical membrane protein sorting and how it matures during development are poorly defined. Also unknown is what controls the onset of apical endocytosis in Lysosome Rich Enterocytes (LREs). To discover mechanisms of apical membrane polarization in vivo, we performed a forward genetics screen for factors required for sorting of a model apical cargo (O-glycan-GFP, Og-GFP) in the zebrafish intestine. We isolated distinct classes of mutants affecting apical Og-GFP sorting. Our preliminary data has uncovered a pH-dependent mechanism for sorting membrane proteins in subapical endosomes either to the degradative pathway or to the apical membrane. We also discovered a role for regulated pre-mRNA intron splicing in activating apical membrane transport pathways crucial for polarized protein delivery in enterocytes and for apical endocytosis in LREs of the developing intestine. Our studies will uncover genetic and cellular mechanisms crucial for the maturation of a fully polarized and physiologically active epithelium in the vertebrate gut.