Human Cytomegalovirus Immediate Early Glycoprotein US3 Retains MHC Class I Molecules by Transient Association

• Published in: Traffic (Copenhagen, Denmark) Denmark), 2000-04, Vol.1 (4), p.318-325
• Main Authors: Gruhler, Albrecht, Peterson, Per A., Früh, Klaus
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antigen Presentation; Antimalarials - pharmacology; Brefeldin A - pharmacology; CD4 Antigens - metabolism; CD8 Antigens - metabolism; Cell Adhesion Molecules, Neuronal - metabolism; Cell Line; Cell Separation; Chloroquine - pharmacology; coatomer; Cytoplasm - metabolism; Cytosol - metabolism; endoplasmic reticulum; Endoplasmic Reticulum - metabolism; Epitopes; Flow Cytometry; Glycoproteins; Golgi; Golgi Apparatus - metabolism; GPI-Linked Proteins; HeLa Cells; herpesvirus; Hexosaminidases - metabolism; Histocompatibility Antigens Class I - metabolism; histocompatibility complex; Humans; Immediate-Early Proteins - metabolism; immune escape; intracellular protein transport; lysosome; Lysosomes - metabolism; Macrolides; Membrane Proteins; Microscopy, Confocal; Precipitin Tests; protein degradation; Protein Transport; Puromycin - pharmacology; retention; retrieval; Time Factors; Transfection
• ISSN: 1398-9219; 1600-0854
• DOI: 10.1034/j.1600-0854.2000.010405.x

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.