Gruhler A, Früh K
R.W. Johnson Pharmaceutical Research Institute, 3210 Merryfield Row, San Diego, CA 92121, USA.
Traffic. 2000 Apr;1(4):306-11. doi: 10.1034/j.1600-0854.2000.010403.x.
MHC class I molecules assemble with peptides in the endoplasmic reticulum (ER). To ensure that only peptide-loaded MHC molecules leave the ER, empty molecules are retained by ER-resident chaperones, most notably the MHC-specific tapasin. ER exit of class I MHC is also controlled by viruses, but for the opposite purpose of preventing peptide presentation to T cells. Interestingly, some viral proteins are able to retain MHC class I molecules in the ER despite being transported. By contrast, other viral proteins exit the ER only upon binding to class I MHC, thereby rerouting newly synthesized class I molecules to intracellular sites of proteolysis. Thus, immune escape can be achieved by reversing, inhibiting or redirecting the chaperone-assisted MHC class I folding, assembly and intracellular transport.
MHC I类分子在内质网（ER）中与肽段组装。为确保只有加载了肽段的MHC分子离开内质网，空载分子会被内质网驻留伴侣蛋白保留，其中最主要的是MHC特异性的塔帕辛（tapasin）。I类MHC分子从内质网的输出也受病毒控制，但目的相反，是为了阻止肽段呈递给T细胞。有趣的是，一些病毒蛋白尽管已被转运，但仍能够将MHC I类分子保留在内质网中。相比之下，其他病毒蛋白只有在与I类MHC结合后才会离开内质网，从而将新合成的I类分子重新导向细胞内的蛋白水解位点。因此，通过逆转、抑制或重定向伴侣蛋白辅助的MHC I类分子折叠、组装和细胞内转运，可以实现免疫逃逸。
