Rapid intracellular pathway gives rise to cell surface expression of the MHC class II-associated invariant chain (CD74).
Rapid intracellular pathway gives rise to cell surface expression of the MHC class II-associated invariant chain (CD74).
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快速细胞内途径导致 MHC II 类相关不变链 (CD74) 的细胞表面表达。
作者：
N. Koch;G. Moldenhauer;W. Hofmann;P. Möller
在之前的研究中，已经表明II类和相关的不变多肽被分选到内吞途径，其中转运被延迟。不变链（Ii）降解后高尔基室，大概是一个内体囊泡，只有II类分子出现在细胞表面。通过使用抗人Ii的胞质外结构域的单克隆抗体，我们证明，通过电子显微镜和细胞荧光测定法，Ii在淋巴瘤细胞和人B淋巴细胞上的表面表达。我们研究了Ii的表面表达后，抑制布雷菲德菌素A的细胞内运输从内质网到高尔基体堆栈。这种处理迅速耗尽Ii的细胞表面。在随后不存在布雷菲德菌素A的情况下，Ii迅速出现在细胞表面。在5小时内，表面Ii（sIi）的先前水平被重建。氯喹消除消耗sIi的布雷菲德菌素A，显然是通过抑制sIi的内化。因为在其到达细胞表面的途径中，Ii不被蛋白水解消化，所以Ii和相关的II类分子可能在该途径中不被分离。免疫化学研究表明，在B淋巴瘤细胞系的细胞表面上，Ii和II类多肽的比例是相关的。
In previous investigations, it had been shown that class II and associated invariant polypeptides are sorted to an endocytic route where transport is delayed. Invariant chain (Ii) is degraded in a post-Golgi compartment, presumably an endosomal vesicle, and only class II molecules emerge on the cell surface. By using a mAb against the extracytoplasmic domain of human Ii, we demonstrate, by electron microscopy and by cytofluorometry, surface expression of Ii on lymphoma cells and on human B lymphocytes. We examined surface expression of Ii upon inhibition by brefeldin A of intracellular transport from the endoplasmic reticulum to the Golgi stack. This treatment rapidly depletes the cell surface of Ii. In the subsequent absence of brefeldin A, Ii appears rapidly at the cell surface. Within 5 h, the previous level of surface Ii (sIi) is reconstituted. Chloroquine abrogates depletion of sIi by brefeldin A, apparently by inhibition of internalization of sIi. Because on its route to the cell surface Ii is not proteolytically digested, it was possible that Ii and associated class II molecules are not separated on this pathway. Immunochemical studies reveal that on the cell surface of a B lymphoma cell line a proportion of Ii and class II polypeptides are associated.