Institut National de la Santé et de la Recherché Médicale, Unité 1013, Paris 75015, France.
EMBO Rep. 2011 Dec 1;12(12):1257-64. doi: 10.1038/embor.2011.203.
Major histocompatibility complex (MHC) class I cross-presentation is thought to involve two pathways, one of which depends on both the TAP transporters and the proteasome and the other on neither. We found that preincubation of TAP-deficient dendritic cells at low temperature increases the density of MHC class I at the surface and fully restores cross-presentation of phagocytosed antigen, but not of soluble antigen internalized through receptors. Restoration of cross-presentation by TAP-deficient cells requires antigen degradation by the proteasome. Thus, TAP might mainly be required for recycling cell surface class I molecules during cross-presentation of phagocytosed antigens. Furthermore, phagosomes-but not endosomes-seem to have a TAP-independent mechanism to import peptides generated by cytosolic proteasome complexes.
主要组织相容性复合体（MHC）I 类交叉呈递被认为涉及两种途径，一种途径既依赖于 TAP 转运体又依赖于蛋白酶体，另一种途径则既不依赖于 TAP 转运体又不依赖于蛋白酶体。我们发现，在低温下预先孵育 TAP 缺陷型树突状细胞会增加 MHC I 类在表面的密度，并完全恢复吞噬抗原的交叉呈递，但不能恢复通过受体内化的可溶性抗原的交叉呈递。TAP 缺陷型细胞通过抗原降解蛋白酶体恢复交叉呈递。因此，TAP 可能主要用于在吞噬抗原的交叉呈递过程中循环利用细胞表面的 I 类分子。此外，吞噬体——而不是内体——似乎有一种不依赖 TAP 的机制来导入由细胞质蛋白酶体复合物产生的肽。
