Low S H, Wong S H, Tang B L, Subramaniam V N, Hong W J
Laboratory of Molecular and Cell Biology of Membranes, National University of Singapore.
J Biol Chem. 1991 Jul 15;266(20):13391-6.
Dipeptidyl peptidase IV (DPPIV) is a type II membrane glycoprotein that is predominantly localized to the apical plasma membrane in various epithelial cells. In order to understand in more detail the biogenesis and sorting of DPPIV, the cDNA for rat DPPIV was inserted into a mammalian plasmid expression vector so that DPPIV expression was driven by a control region composed of the SV40 early promoter region fused to the enhancer of the Rous sarcoma virus. Madin-Darby canine kidney cells transfected with this construct were found to express the DPPIV protein. In these transfected cells, the majority of DPPIV was present on the apial cell surface. This observation suggests that the information for apical surface localization is inherent in the DPPIV molecule itself and that this sorting information is decipherable in the epithelial cells of a different species. DPPIV is transported efficiently from the endoplasmic reticulum to the Golgi apparatus as assessed by pulse-chase experiments. Furthermore, evidence is presented which suggests that the majority of DPPIV is sorted intracellularly to the apical cell surface. The same protein has, however, been reported to be sorted by an indirect pathway through transcytosis from the basolateral to the apical cell surface in hepatocytes (Bartles, J.R., Feracci, H., M., Stinger, B., and Hubbard, A.L. (1987) J. Cell Biol. 105, 1241-1251). This study suggests that the same protein can take two different pathways in different cell types for its correct apical cell surface localization.
二肽基肽酶IV（DPPIV）是一种II型膜糖蛋白，主要定位于各种上皮细胞的顶端质膜。为了更详细地了解DPPIV的生物合成和分选过程，将大鼠DPPIV的cDNA插入到哺乳动物质粒表达载体中，使DPPIV的表达由一个由SV40早期启动子区域与劳氏肉瘤病毒增强子融合而成的控制区域驱动。用该构建体转染的Madin-Darby犬肾细胞被发现表达DPPIV蛋白。在这些转染细胞中，大多数DPPIV存在于细胞顶端表面。这一观察结果表明，顶端表面定位信息存在于DPPIV分子本身，并且这种分选信息在不同物种的上皮细胞中是可解读的。通过脉冲追踪实验评估，DPPIV能有效地从内质网转运到高尔基体。此外，有证据表明，大多数DPPIV在细胞内被分选到顶端细胞表面。然而，据报道，在肝细胞中，相同的蛋白质通过一种间接途径，即通过转胞吞作用从基底外侧细胞表面分选到顶端细胞表面（Bartles, J.R., Feracci, H., M., Stinger, B., and Hubbard, A.L. (1987) J. Cell Biol. 105, 1241 - 1251）。这项研究表明，相同的蛋白质在不同细胞类型中可以通过两种不同的途径实现其正确的顶端细胞表面定位。
