title: Hepatitis B virus x protein induces perinuclear mitochondrial clustering in microtubule- and Dynein-dependent manners.
abstract: The hepatitis B virus (HBV) X protein (HBx) is thought to play a key role in HBV replication and the development of liver cancer. It became apparent that HBx induces mitochondrial clustering at the nuclear periphery, but the molecular basis for mitochondrial clustering is not understood. Since mitochondria move along the cytoskeleton as a cargo of motor proteins, we hypothesized that mitochondrial clustering induced by HBx occurs by an altered intracellular motility. Here, we demonstrated that the treatment of HBx-expressing cells with a microtubule-disrupting drug (nocodazole) abrogated mitochondrial clustering, while the removal of nocodazole restored clustering within 30 to 60 min, indicating that mitochondrial transport is occurring in a microtubule-dependent manner. The addition of a cytochalasin D-disrupting actin filament, however, did not measurably affect mitochondrial clustering. Mitochondrial clustering was further studied by observations of HBV-related hepatoma cells and HBV-replicating cells. Importantly, the abrogation of the dynein activity in HBx-expressing cells by microinjection of a neutralizing anti-dynein intermediate-chain antibody, dynamitin overexpression, or the addition of a dynein ATPase inhibitor significantly suppressed the mitochondrial clustering. In addition, HBx induced the activation of the p38 mitogen-activated protein kinase (MAPK) and inhibition of the p38 kinase activity by SB203580-attenuated HBx-induced mitochondrial clustering. Taken together, HBx activation of the p38 MAPK contributed to the increase in the microtubule-dependent dynein activity. The data suggest that HBx plays a novel regulatory role in subcellular transport systems, perhaps facilitating the process of maturation and/or assembly of progeny particles during HBV replication. Furthermore, mitochondrion aggregation induced by HBx may represent a cellular process that underlies disease progression during chronic viral infection.
authors.affiliation: Department of Biochemistry, Ajou University School of Medicine, 5 Wonchon-dong, Yeongtong-gu, Suwon 443-721, Korea.
authors.forename: Sujeong
authors.initials: S
authors.lastname: Kim
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Seungmin
authors.initials: S
authors.lastname: Lee
authors.forename: Sung Woo
authors.initials: SW
authors.lastname: Kim
authors.forename: Seonghyang
authors.initials: S
authors.lastname: Sohn
authors.forename: Kyongmin
authors.initials: K
authors.lastname: Kim
authors.forename: Hyeseong
authors.initials: H
authors.lastname: Cho
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D004398:Dyneins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006509:Hepatitis B / Q000821:virology*; D006511:Hepatitis B Antigens / Q000502:physiology*; D006515:Hepatitis B virus / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008870:Microtubules / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015534:Trans-Activators / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D006511:Hepatitis B Antigens; D007093:Imidazoles; D011725:Pyridines; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D048051:p38 Mitogen-Activated Protein Kinases; D004398:Dyneins; C093642:SB 203580