title: Involvement of host cellular multivesicular body functions in hepatitis B virus budding.
abstract: Hepatitis B virus (HBV) is a major human pathogen that chronically infects approximately 350 million people, causing liver disease and liver cancer. HBV virions bud into an endoplasmic reticulum (ER)-associated intracellular compartment, but the mechanisms of HBV assembly, budding, and release remain poorly understood. Budding of retroviruses and some other enveloped RNA viruses from plasma membranes requires host functions involved in protein sorting into late endosomal multivesicular bodies (MVBs). To determine whether budding of DNA-containing HBV virions at intracellular membranes also involves MVB functions, we used immunofluorescence to show that, in human hepatoma cells, HBV envelope protein colocalizes with MVB proteins AIP1/ALIX and VPS4B. We also found that a dominant negative (DN) AIP1 mutant inhibited production and/or release of enveloped virions without significant effects on intracellular nucleocapsid formation, whereas DN VPS4B inhibited both nucleocapsid production and budding. By contrast, DN AIP1 and VPS4 had no effect on the efficiency of release of enveloped, nucleocapsid-lacking HBV subviral particles, which are produced in vast excess over virions, and dramatically increased the release of unenveloped, naked nucleocapsids by an apparently nonlytic route. Thus, host MVB functions are required for efficient budding and release of enveloped HBV virions and may be a valuable target for HBV control. Moreover, HBV enveloped virions, enveloped subviral particles, and unenveloped nucleocapsids are all released by distinct pathways with separate host factor requirements.
authors.affiliation: Institute for Molecular Virology, McArdle Laboratory for Cancer Research, University of Wisconsin, 1525 Linden Drive, Madison, WI 53706, USA.
authors.forename: Tokiko
authors.initials: T
authors.lastname: Watanabe
authors.forename: Ericka M
authors.initials: EM
authors.lastname: Sorensen
authors.forename: Akira
authors.initials: A
authors.lastname: Naito
authors.forename: Meghan
authors.initials: M
authors.lastname: Schott
authors.forename: Seungtaek
authors.initials: S
authors.lastname: Kim
authors.forename: Paul
authors.initials: P
authors.lastname: Ahlquist
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism*; D019085:Fluorescent Antibody Technique, Direct; D051528:Guanylate Kinases; D006515:Hepatitis B virus / Q000502:physiology*; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D018613:Microscopy, Confocal; D009154:Mutation; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D014759:Viral Envelope Proteins / Q000378:metabolism; D014771:Virion / Q000235:genetics / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; C117020:PDCD6IP protein, human; D011506:Proteins; D033921:Vesicular Transport Proteins; D014759:Viral Envelope Proteins; D051528:Guanylate Kinases; C485777:MAGI2 protein, human; D000251:Adenosine Triphosphatases; D000074183:ATPases Associated with Diverse Cellular Activities; C490304:VPS4B protein, human