Reid P A, Watts C
Department of Biochemistry, University of Dundee, UK.
Nature. 1990 Aug 16;346(6285):655-7. doi: 10.1038/346655a0.
Class II major histocompatibility complex (MHC) glycoproteins associate with peptides derived from material endocytosed by antigen-presenting cells and processed along the endocytotic pathway. No consensus exists as to what extent class II molecules themselves are endocytosed and it is not known whether endocytosed MHC class II molecules can be recycled again to the cell surface--an itinerary which might allow a single cell-surface MHC molecule to associate with different peptides during its lifetime. We now show by using new cleavable labelling reagents that class II and class I MHC on B lymphoblastoid cells are continually endocytosed and recycled to the cell surface. The intracellular pool size is normally kept small by efficient recycling, but in the presence of primaquine the rate of recycling is slowed, thereby increasing the size of this pool substantially. On removal of the amine, the intracellular population recycles rapidly to restore the original distribution. These results reveal a cycle that might explain the rapid binding and turnover of some peptide/class II MHC complexes and the exchange of pre-existing for new peptides observed in living cells.
II类主要组织相容性复合体（MHC）糖蛋白与抗原呈递细胞内吞的物质衍生的肽结合，并沿内吞途径进行加工。关于II类分子本身被内吞的程度尚无共识，也不清楚内吞的MHC II类分子是否能再次循环到细胞表面——这种行程可能使单个细胞表面的MHC分子在其生命周期内与不同的肽结合。我们现在通过使用新的可裂解标记试剂表明，B淋巴母细胞上的II类和I类MHC会持续被内吞并循环到细胞表面。通过高效循环，细胞内池的大小通常保持较小，但在伯氨喹存在的情况下，循环速率减慢，从而使该池的大小显著增加。去除胺后，细胞内群体迅速循环以恢复原始分布。这些结果揭示了一个循环，这可能解释了一些肽/MHC II类复合物的快速结合和周转以及在活细胞中观察到的预先存在的肽与新肽的交换。
