MEMBRANE DYNAMICS IN POLARIZED EPITHELIAL CELLS

我们建议研究根尖膜分选的分子基础。 极化上皮细胞中的蛋白质。我们将通过比较 对比了两种不同的上皮细胞--MDCK (肾脏)和WIF-B(肝细胞)细胞--隔离和包二 顶端胞外酶。第一种是二肽基肽酶IV(DPPIV)， 属于单一跨膜(类型II)蛋白类； 第二个是5‘核苷酸酶(5’NT)，它是一种糖脂锚定的酶 蛋白。肝细胞使用间接的、从基底外侧到根尖的 跨细胞途径(S)传递这些蛋白，而mDCK细胞 直接从跨高尔基网络(TGN)交付。然而， 当MDCK细胞从长期药物治疗中恢复时 Brefeldin A，检索错误排序的DPPIV和5‘NT 并随后将它们送到根尖 表面(即，使用间接路线)。聚合型IgA受体 (PIGA-R)通常在两种细胞类型中使用跨细胞途径。做 这些蛋白质和细胞类型有共同的(间接)途径吗？多么 类似或不同的是间接机制与直接机制 根尖膜靶向？

We propose to study the molecular basis of sorting of apical membrane proteins in polarized epithelial cells. We will do this by comparing and contrasting how two different epithelial cells types--the MDCK (kidney) and the WIF-B (hepatocyte) cells-- sequester and package two apical ectoenzymes. The first is dipeptidyl peptidase IV (DPPIV), belonging to the class of single transmembrane (Type II) proteins; and the second is 5' nucleotidase (5'NT), a glycolipid-anchored protein. Hepatocytes use an indirect, basolateral-to-apical transcytotic pathway(s) to deliver these proteins, while MDCK cells deliver them directly from the trans-Golgi network (TGN). However, when MDCK cells recover from prolonged treatment with the drug Brefeldin A, the retrieve missorted DPPIV and 5'NT from the basolateral surface and subsequently deliver them to the apical surface (ie, use the indirect route). The polymeric IgA-receptor (pIgA-R) normally uses a transcytotic pathway in both cell types. Do these proteins and cell types share a common (indirect) pathway? How similar or different are the indirect versus direct mechanisms for apical membrane targeting?