title: Targeting of hepatitis C virus core protein to mitochondria through a novel C-terminal localization motif.
abstract: The hepatitis C virus (HCV) core protein represents the first 191 amino acids of the viral precursor polyprotein and is cotranslationally inserted into the membrane of the endoplasmic reticulum (ER). Processing at position 179 by a recently identified intramembrane signal peptide peptidase leads to the generation and potential cytosolic release of a 179-amino-acid matured form of the core protein. Using confocal microscopy, we observed that a fraction of the mature core protein colocalized with mitochondrial markers in core-expressing HeLa cells and in Huh-7 cells containing the full-length HCV replicon. Subcellular fractionation confirmed this observation and showed that the core protein associates with purified mitochondrial fractions devoid of ER contaminants. The core protein also fractionated with mitochondrion-associated membranes, a site of physical contact between the ER and mitochondria. Using immunoelectron microscopy and in vitro mitochondrial import assays, we showed that the core protein is located on the mitochondrial outer membrane. A stretch of 10 amino acids within the hydrophobic C terminus of the processed core protein conferred mitochondrial localization when it was fused to green fluorescent protein. The location of the core protein in the outer mitochondrial membrane suggests that it could modulate apoptosis or lipid transfer, both of which are associated with this subcellular compartment, during HCV infection.
authors.affiliation: Department of Molecular Virology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Schwer
authors.forename: Shaotang
authors.initials: S
authors.lastname: Ren
authors.forename: Thomas
authors.initials: T
authors.lastname: Pietschmann
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kartenbeck
authors.forename: Katrin
authors.initials: K
authors.lastname: Kaehlcke
authors.forename: Ralf
authors.initials: R
authors.lastname: Bartenschlager
authors.forename: T S Benedict
authors.initials: TS
authors.lastname: Yen
authors.forename: Melanie
authors.initials: M
authors.lastname: Ott
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism; D016174:Hepacivirus / Q000737:chemistry*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D021381:Protein Transport; D014758:Viral Core Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014758:Viral Core Proteins