title: The amphipathic helix of adenovirus capsid protein VI contributes to penton release and postentry sorting.
abstract: Nuclear delivery of the adenoviral genome requires that the capsid cross the limiting membrane of the endocytic compartment and traverse the cytosol to reach the nucleus. This endosomal escape is initiated upon internalization and involves a highly coordinated process of partial disassembly of the entering capsid to release the membrane lytic internal capsid protein VI. Using wild-type and protein VI-mutated human adenovirus serotype 5 (HAdV-C5), we show that capsid stability and membrane rupture are major determinants of entry-related sorting of incoming adenovirus virions. Furthermore, by using electron cryomicroscopy, as well as penton- and protein VI-specific antibodies, we show that the amphipathic helix of protein VI contributes to capsid stability by preventing premature disassembly and deployment of pentons and protein VI. Thus, the helix has a dual function in maintaining the metastable state of the capsid by preventing premature disassembly and mediating efficient membrane lysis to evade lysosomal targeting. Based on these findings and structural data from cryo-electron microscopy, we suggest a refined disassembly mechanism upon entry.
  
  
  OBJECTIVE
  In this study, we show the intricate connection of adenovirus particle stability and the entry-dependent release of the membrane-lytic capsid protein VI required for endosomal escape. We show that the amphipathic helix of the adenovirus internal protein VI is required to stabilize pentons in the particle while coinciding with penton release upon entry and that release of protein VI mediates membrane lysis, thereby preventing lysosomal sorting. We suggest that this dual functionality of protein VI ensures an optimal disassembly process by balancing the metastable state of the mature adenovirus particle.
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France.
authors.forename: Ruben
authors.initials: R
authors.lastname: Martinez
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
authors.forename: Pascale
authors.initials: P
authors.lastname: Schellenberger
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
authors.forename: Daven
authors.initials: D
authors.lastname: Vasishtan
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France.
authors.forename: Cindy
authors.initials: C
authors.lastname: Aknin
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France.
authors.forename: Sisley
authors.initials: S
authors.lastname: Austin
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Dacheux
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Rayne
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
authors.forename: Alistair
authors.initials: A
authors.lastname: Siebert
authors.affiliation: Max von Pettenkofer Institute, Ludwig-Maximilian University Munich, Munich, Germany.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Ruzsics
authors.affiliation: Oxford Particle Imaging Centre, Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
authors.forename: Kay
authors.initials: K
authors.lastname: Gruenewald
authors.affiliation: Microbiologie Fondamentale et Pathogénicité, MFP CNRS UMR 5234, Université Bordeaux, Bordeaux, France harald.wodrich@u-bordeaux2.fr.
authors.forename: Harald
authors.initials: H
authors.lastname: Wodrich
mesh_terms: D000260:Adenoviruses, Human / Q000235:genetics / Q000502:physiology*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D020285:Cryoelectron Microscopy; D006801:Humans; D053586:Virus Internalization; D057646:Virus Uncoating
chemical_list: D036022:Capsid Proteins; C043322:penton protein, adenovirus; C090876:polypeptide VI, adenovirus