title: The tight junction-associated protein occludin is required for a postbinding step in hepatitis C virus entry and infection.
abstract: The precise mechanisms regulating hepatitis C virus (HCV) entry into hepatic cells remain unknown. However, several cell surface proteins have been identified as entry factors for this virus. Of these molecules, claudin-1, a tight junction (TJ) component, is considered a coreceptor required for HCV entry. Recently, we have demonstrated that HCV envelope glycoproteins (HCVgp) promote structural and functional TJ alterations. Additionally, we have shown that the intracellular interaction between viral E2 glycoprotein and occludin, another TJ-associated protein, could be the cause of the mislocalization of TJ proteins. Herein we demonstrated, by using cell culture-derived HCV particles (HCVcc), that interference of occludin expression markedly reduced HCV infection. Furthermore, our results with HCV pseudotyped particles indicated that occludin, but not other TJ-associated proteins, such as junctional adhesion molecule A or zonula occludens protein 1, was required for HCV entry. Using HCVcc, we demonstrated that occludin did not play an essential role in the initial attachment of HCV to target cells. Surface protein labeling experiments showed that both expression levels and cell surface localization of HCV (co)receptors CD81, scavenger receptor class B type I, and claudin-1 were not affected upon occludin knockdown. In addition, immunofluorescence confocal analysis showed that occludin interference did not affect subcellular distribution of the HCV (co)receptors analyzed. However, HCVgp fusion-associated events were altered after occludin silencing. In summary, we propose that occludin plays an essential role in HCV infection and probably affects late entry events. This observation may provide new insights into HCV infection and related pathogenesis.
authors.affiliation: Hospital Universitario de la Princesa, Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Benedicto
authors.forename: Francisca
authors.initials: F
authors.lastname: Molina-Jiménez
authors.forename: Birke
authors.initials: B
authors.lastname: Bartosch
authors.forename: François-Loïc
authors.initials: FL
authors.lastname: Cosset
authors.forename: Dimitri
authors.initials: D
authors.lastname: Lavillette
authors.forename: Jesús
authors.initials: J
authors.lastname: Prieto
authors.forename: Ricardo
authors.initials: R
authors.lastname: Moreno-Otero
authors.forename: Agustín
authors.initials: A
authors.lastname: Valenzuela-Fernández
authors.forename: Rafael
authors.initials: R
authors.lastname: Aldabe
authors.forename: Manuel
authors.initials: M
authors.lastname: López-Cabrera
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Majano
mesh_terms: D002460:Cell Line; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006526:Hepatitis C / Q000378:metabolism* / Q000821:virology; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D062793:Occludin; D011485:Protein Binding; D019108:Tight Junctions / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D053585:Virus Attachment; D053586:Virus Internalization
chemical_list: D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin