title: Human cytomegalovirus immediate early glycoprotein US3 retains MHC class I molecules by transient association.
abstract: Human cytomegalovirus (HCMV) interferes with major histocompatibility complex (MHC) class I antigen presentation by a sequential multistep process to escape T cell surveillance. During the immediate early phase of infection, the glycoprotein US3 prevents intracellular transport of MHC class I molecules. Interestingly, US3 displays a significantly shorter half-life than US3-retained MHC class I molecules. Here we show that US3 associates only transiently with MHC class I molecules, exits the ER, and is inefficiently retrieved from the Golgi. US3 was degraded in a post-Golgi compartment, most likely lysosomes, because: i) Brefeldin A treatment prolonged the half-life of US3; and ii) US3 co-localized with the lysosomal marker protein LAMP in chloroquine-treated cells. In contrast, MHC class I molecules remained stable in the ER. Upon inhibition of protein synthesis MHC class I molecules were released suggesting that a continuous supply of newly synthesized US3 molecules is required for inhibition of transport. Thus, US3 does not seem to retain MHC class I molecules by a retrieval mechanism. Instead, our observations are consistent with US3 preventing MHC class I trafficking by blocking forward transport.
authors.affiliation: R.W. Johnson Pharmaceutical Research Institute, 3210 Merryfield Row, San Diego, CA 92121, USA.
authors.forename: A
authors.initials: A
authors.lastname: Gruhler
authors.forename: P A
authors.initials: PA
authors.lastname: Peterson
authors.forename: K
authors.initials: K
authors.lastname: Früh
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017951:Antigen Presentation; D000962:Antimalarials / Q000494:pharmacology; D020126:Brefeldin A / Q000494:pharmacology; D015704:CD4 Antigens / Q000378:metabolism; D016827:CD8 Antigens / Q000378:metabolism; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002460:Cell Line; D002469:Cell Separation; D002738:Chloroquine / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000939:Epitopes; D005434:Flow Cytometry; D058851:GPI-Linked Proteins; D006023:Glycoproteins; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006596:Hexosaminidases / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D018942:Macrolides; D008565:Membrane Proteins; D018613:Microscopy, Confocal; D011233:Precipitin Tests; D021381:Protein Transport; D011691:Puromycin / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
chemical_list: D000900:Anti-Bacterial Agents; D000962:Antimalarials; D015704:CD4 Antigens; D016827:CD8 Antigens; D015816:Cell Adhesion Molecules, Neuronal; D000939:Epitopes; D058851:GPI-Linked Proteins; D006023:Glycoproteins; D015395:Histocompatibility Antigens Class I; D017874:Immediate-Early Proteins; D018942:Macrolides; D008565:Membrane Proteins; C095111:US3 protein, cytomegalovirus; C095362:limbic system-associated membrane protein; D020126:Brefeldin A; D011691:Puromycin; D002738:Chloroquine; D006596:Hexosaminidases