Developmental regulation of epithelial polarization by pre-mRNA splicing

摘要 肠上皮细胞的顶膜在生理和动态平衡中起着至关重要的作用。许多 肠道上皮细胞的特殊功能，如营养吸收，依赖于对蛋白质的准确分选 在生物合成输送过程中转移到顶膜。然而，驱动根尖膜的细胞机制 蛋白质的分类以及它在发育过程中是如何成熟的还没有明确的定义。同样未知的是什么控制着 富含溶酶体的肠细胞(LRE)的顶端内吞作用的开始。探讨根尖膜形成的机制 在活体内，我们对模型根尖分类所需的因素进行了正向遗传学筛查 斑马鱼肠道中的货物(O-葡聚糖-GFP，Og-GFP)。我们分离出影响心尖部的不同类别的突变体。 OG-GFP排序。我们的初步数据揭示了一种与pH有关的膜蛋白分选机制 在亚顶端的内体中，要么到降解途径，要么到顶膜。我们还发现了一个角色 调控的前mRNA内含子剪接激活对极化至关重要的顶膜运输途径 蛋白质在肠细胞中的传递和在发育中的肠道LRE中的顶端内吞作用。我们的研究将 揭示对完全极化和生理活性的成熟至关重要的遗传和细胞机制 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.