Norkin L C
Department of Microbiology, University of Massachusetts, Amherst 01003-5720, USA.
Immunol Rev. 1999 Apr;168:13-22. doi: 10.1111/j.1600-065x.1999.tb01279.x.
MHC class I molecules are a necessary component of the cell surface receptor for simian virus 40 (SV40). After binding to class I molecules, SV40 enters cells via a unique endocytic pathway that involves caveolae, rather than clathrin-coated pits. This pathway is dependent on a transmembrane signal that SV40 transmits from the cell surface. Furthermore, it delivers SV40 to the endoplasmic reticulum, rather than to the endosomal/lysosomal compartment, which is the usual target for endocytic traffic. The glycosphingolipid and cholesterol-enriched plasma membrane domains that contain caveolae are also enriched for class I molecules, relative to whole plasma membrane. Nevertheless, although class I molecules bind SV40, they do not enter with SV40, nor do they enter spontaneously into uninfected SV40 host cells. Instead, they are shed from the cell surface by the activity of a metalloprotease. These results imply the existence of a putative secondary receptor for SV40 that might mediate SV40 entry. It is not yet clear whether class I molecules are active in transmitting the SV40 signal. Monoclonal antibodies against class I molecules also induce a signal in the SV40 host cells. However, the antibody-induced signal is mediated by mitogen-activated protein kinase (MAP kinase), whereas the SV40 signal is independent of MAP kinase.
MHC I类分子是猿猴病毒40（SV40）细胞表面受体的必要组成部分。与I类分子结合后，SV40通过一种独特的内吞途径进入细胞，该途径涉及小窝，而非网格蛋白包被小窝。此途径依赖于SV40从细胞表面传递的跨膜信号。此外，它将SV40递送至内质网，而非内体/溶酶体区室，内体/溶酶体区室是内吞运输的通常靶点。相对于整个质膜，含有小窝的富含糖鞘脂和胆固醇的质膜结构域中I类分子也更为富集。然而，尽管I类分子结合SV40，但它们并不与SV40一起进入细胞，也不会自发进入未感染的SV40宿主细胞。相反，它们通过金属蛋白酶的活性从细胞表面脱落。这些结果表明可能存在一种假定的SV40辅助受体，它可能介导SV40的进入。目前尚不清楚I类分子在传递SV40信号方面是否具有活性。针对I类分子的单克隆抗体也会在SV40宿主细胞中诱导信号。然而，抗体诱导的信号由丝裂原活化蛋白激酶（MAP激酶）介导，而SV40信号独立于MAP激酶。
