title: Entry of bunyaviruses into mammalian cells.
abstract: The Bunyaviridae constitute a large family of enveloped animal viruses, many members of which cause serious diseases. However, early bunyavirus-host cell interactions and entry mechanisms remain largely uncharacterized. Investigating Uukuniemi virus, a bunyavirus of the genus Phlebovirus, we found that virus attachment to the cell surface was specific but inefficient, with 25% of bound viruses being endocytosed within 10 min, mainly via noncoated vesicles. The viruses entered Rab5a+ early endosomes and, subsequently, Rab7a+ and LAMP-1+ late endosomes. Acid-activated penetration, occurring 20-40 min after internalization, required maturation of early to late endosomes. The pH threshold for viral membrane fusion was 5.4, and entry was sensitive to temperatures below 25 degrees C. Together, our results indicate that Uukuniemi virus penetrates host cells by acid-activated membrane fusion from late endosomal compartments. This study also highlights the importance of the degradative branch of the endocytic pathway in facilitating entry of late-penetrating viruses.
authors.affiliation: ETH Zurich, Institute of Biochemistry, Schafmattstrasse 18, CH-8093 Zurich, Switzerland.
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Lozach
authors.forename: Roberta
authors.initials: R
authors.lastname: Mancini
authors.forename: David
authors.initials: D
authors.lastname: Bitto
authors.forename: Roger
authors.initials: R
authors.lastname: Meier
authors.forename: Lisa
authors.initials: L
authors.lastname: Oestereich
authors.forename: Anna K
authors.initials: AK
authors.lastname: Overby
authors.forename: Ralf F
authors.initials: RF
authors.lastname: Pettersson
authors.forename: Ari
authors.initials: A
authors.lastname: Helenius
mesh_terms: D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D011992:Endosomes / Q000737:chemistry / Q000821:virology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D052118:Lysosomal-Associated Membrane Protein 1 / Q000032:analysis; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D018066:Uukuniemi virus / Q000502:physiology*; D053586:Virus Internalization; D020691:rab GTP-Binding Proteins / Q000032:analysis; D020696:rab5 GTP-Binding Proteins / Q000032:analysis; D000090802:rab7 GTP-Binding Proteins
chemical_list: D052118:Lysosomal-Associated Membrane Protein 1; D000090802:rab7 GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins