title: Cellular entry of ebola virus involves uptake by a macropinocytosis-like mechanism and subsequent trafficking through early and late endosomes.
abstract: Zaire ebolavirus (ZEBOV), a highly pathogenic zoonotic virus, poses serious public health, ecological and potential bioterrorism threats. Currently no specific therapy or vaccine is available. Virus entry is an attractive target for therapeutic intervention. However, current knowledge of the ZEBOV entry mechanism is limited. While it is known that ZEBOV enters cells through endocytosis, which of the cellular endocytic mechanisms used remains unclear. Previous studies have produced differing outcomes, indicating potential involvement of multiple routes but many of these studies were performed using noninfectious surrogate systems such as pseudotyped retroviral particles, which may not accurately recapitulate the entry characteristics of the morphologically distinct wild type virus. Here we used replication-competent infectious ZEBOV as well as morphologically similar virus-like particles in specific infection and entry assays to demonstrate that in HEK293T and Vero cells internalization of ZEBOV is independent of clathrin, caveolae, and dynamin. Instead the uptake mechanism has features of macropinocytosis. The binding of virus to cells appears to directly stimulate fluid phase uptake as well as localized actin polymerization. Inhibition of key regulators of macropinocytosis including Pak1 and CtBP/BARS as well as treatment with the drug EIPA, which affects macropinosome formation, resulted in significant reduction in ZEBOV entry and infection. It is also shown that following internalization, the virus enters the endolysosomal pathway and is trafficked through early and late endosomes, but the exact site of membrane fusion and nucleocapsid penetration in the cytoplasm remains unclear. This study identifies the route for ZEBOV entry and identifies the key cellular factors required for the uptake of this filamentous virus. The findings greatly expand our understanding of the ZEBOV entry mechanism that can be applied to development of new therapeutics as well as provide potential insight into the trafficking and entry mechanism of other filoviruses.
authors.affiliation: Department of Microbiology & Immunology, The University of Texas Medical Branch, Galveston, Texas, United States of America.
authors.forename: Mohammad F
authors.initials: MF
authors.lastname: Saeed
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Kolokoltsov
authors.forename: Thomas
authors.initials: T
authors.lastname: Albrecht
authors.forename: Robert A
authors.initials: RA
authors.lastname: Davey
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D021941:Caveolae / Q000378:metabolism / Q000821:virology; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D002966:Clathrin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029043:Ebolavirus / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism* / Q000821:virology*; D019142:Hemorrhagic Fever, Ebola / Q000378:metabolism / Q000517:prevention & control* / Q000821:virology; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008561:Membrane Fusion; D021962:Membrane Microdomains / Q000502:physiology; D010766:Phosphorylation; D010873:Pinocytosis / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014709:Vero Cells; D053586:Virus Internalization / Q000187:drug effects*; D014779:Virus Replication / Q000187:drug effects; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D002966:Clathrin; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D000584:Amiloride; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein; D054462:p21-Activated Kinases; C039614:ethylisopropylamiloride