title: The ubiquitin/proteasome system mediates entry and endosomal trafficking of Kaposi's sarcoma-associated herpesvirus in endothelial cells.
abstract: Ubiquitination, a post-translational modification, mediates diverse cellular functions including endocytic transport of molecules. Kaposi's sarcoma-associated herpesvirus (KSHV), an enveloped herpesvirus, enters endothelial cells primarily through clathrin-mediated endocytosis. Whether ubiquitination and proteasome activity regulates KSHV entry and endocytosis remains unknown. We showed that inhibition of proteasome activity reduced KSHV entry into endothelial cells and intracellular trafficking to nuclei, thus preventing KSHV infection of the cells. Three-dimensional (3-D) analyses revealed accumulation of KSHV particles in a cytoplasmic compartment identified as EEA1+ endosomal vesicles upon proteasome inhibition. KSHV particles are colocalized with ubiquitin-binding proteins epsin and eps15. Furthermore, ubiquitination mediates internalization of both KSHV and one of its receptors integrin β1. KSHV particles are colocalized with activated forms of the E3 ligase c-Cbl. Knock-down of c-Cbl or inhibition of its phosphorylation reduced viral entry and intracellular trafficking, resulting in decreased KSHV infectivity. These results demonstrate that ubiquitination mediates internalization of both KSHV and one of its cognate receptors integrin β1, and identify c-Cbl as a potential E3 ligase that facilitates this process.
authors.affiliation: Tumor Virology Program, Greehey Children's Cancer Research Institute, and Department of Pediatrics, University of Texas Health Science Center San Antonio, San Antonio, Texas, United States of America.
authors.forename: Whitney
authors.initials: W
authors.lastname: Greene
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Meilan
authors.initials: M
authors.lastname: He
authors.forename: Colleen
authors.initials: C
authors.lastname: Witt
authors.forename: Fengchun
authors.initials: F
authors.lastname: Ye
authors.forename: Shou-Jiang
authors.initials: SJ
authors.lastname: Gao
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D002460:Cell Line; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D019288:Herpesvirus 8, Human / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism / Q000821:virology*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination; D053586:Virus Internalization
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C486204:EPN2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D019012:Integrin beta1; C108382:RABGEF1 protein, human; D034741:RNA, Small Interfering; C114154:epsin; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C067419:CBL protein, human