The large GTPase dynamin is required for hepatitis B virus protein secretion from hepatocytes.
OBJECTIVE
The hepatocellular transport pathways and cellular proteins utilized during the packaging and secretion of hepatitis B virus are poorly understood. In this study, we tested if the large GTPase dynamin, a protein involved in vesicle formation and secretion at the trans-Golgi network in hepatocytes, is also used by hepatitis B virus (HBV) in secreting viral proteins.


METHODS
Using HepG2.2.15 cells expressing the full-length HBV genome, we tested the effects of wild-type and mutant dynamin on the localization and secretion of two hepatitis B antigens, hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg). Distribution of these two antigens was analyzed morphologically in cells transiently transfected with wild-type or mutant dynamin constructs, whereas secretion of the antigens was measured by testing for antigen levels in the media of transfected cells.


RESULTS
Mutant dynamin was found to induce a striking redistribution of HBsAg and HBeAg to a perinuclear compartment, as well as a decrease in the levels of HBsAg and HBeAg present in cell culture media indicating a reduction in viral protein secretion. At the electron microscopy level, cells expressing the mutant dynamin showed a marked accumulation of viral particles in dilated cisternae of an uncharacterized cellular compartment.


CONCLUSIONS
Intact dynamin function is required for secretion of HBV proteins from hepatocytes through an uncharacterized cellular compartment.
Abdulkarim
Ahmad S
AS
Center for Basic Research in Digestive Diseases and Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA.
Cao
Hong
H
Huang
Bing
B
McNiven
Mark A
MA
D001692:Biological Transport; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D034285:Dynamin II / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D006514:Hepatitis B Surface Antigens / Q000378:metabolism*; D006513:Hepatitis B e Antigens / Q000378:metabolism*; D006515:Hepatitis B virus; D022781:Hepatocytes / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009154:Mutation; D014018:Tissue Distribution; D014162:Transfection; D014764:Viral Proteins / Q000378:metabolism*; D014771:Virion / Q000648:ultrastructure
D003470:Culture Media; D006514:Hepatitis B Surface Antigens; D006513:Hepatitis B e Antigens; D014764:Viral Proteins; D034285:Dynamin II