title: HIV-1 Nef promotes the localization of Gag to the cell membrane and facilitates viral cell-to-cell transfer.
abstract: BACKGROUND
  Newly synthesized HIV-1 particles assemble at the plasma membrane of infected cells, before being released as free virions or being transferred through direct cell-to-cell contacts to neighboring cells. Localization of HIV-1 Gag precursor at the cell membrane is necessary and sufficient to trigger viral assembly, whereas the GagPol precursor is additionally required to generate a fully matured virion. HIV-1 Nef is an accessory protein that optimizes viral replication through partly defined mechanisms. Whether Nef modulates Gag and/or GagPol localization and assembly at the membrane and facilitates viral cell-to-cell transfer has not been extensively characterized so far.
  
  
  RESULTS
  We report that Nef increases the total amount of Gag proteins present in infected cells, and promotes Gag localization at the cell membrane. Moreover, the processing of p55 into p24 is improved in the presence of Nef. We also examined the effect of Nef during HIV-1 cell-to-cell transfer. We show that without Nef, viral transfer through direct contacts between infected cells and target cells is impaired. With a nef-deleted virus, the number of HIV-1 positive target cells after a short 2h co-culture is reduced, and viral material transferred to uninfected cells is less matured. At later time points, this defect is associated with a reduction in the productive infection of new target cells.
  
  
  CONCLUSIONS
  Our results highlight a previously unappreciated role of Nef during the viral replication cycle. Nef promotes HIV-1 Gag membrane localization and processing, and facilitates viral cell-to-cell transfer.
authors.affiliation: Département de Virologie, Institut Pasteur, Unité Virus et Immunité, 28 rue du Docteur Roux, Paris F-75015, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Malbec
authors.forename: Marion
authors.initials: M
authors.lastname: Sourisseau
authors.forename: Florence
authors.initials: F
authors.lastname: Guivel-Benhassine
authors.forename: Françoise
authors.initials: F
authors.lastname: Porrot
authors.forename: Fabien
authors.initials: F
authors.lastname: Blanchet
authors.forename: Olivier
authors.initials: O
authors.lastname: Schwartz
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Casartelli
mesh_terms: D002460:Cell Line; D002462:Cell Membrane / Q000821:virology*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D019065:Virus Assembly; D053586:Virus Internalization; D057074:Virus Release; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D054301:gag Gene Products, Human Immunodeficiency Virus; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1
references.citation: J Exp Med. 2004 Jan 19;199(2):283-93
references.pmid: 14734528
references.citation: Microbes Infect. 2002 Feb;4(2):189-99
references.pmid: 11880052
references.citation: Microbiol Immunol. 2010 Dec;54(12):734-46
references.pmid: 21091985
references.citation: Retrovirology. 2009 Oct 13;6:89
references.pmid: 19825175
references.citation: Virology. 2004 Oct 10;328(1):36-44
references.pmid: 15380356
references.citation: J Virol. 1992 Nov;66(11):6547-54
references.pmid: 1404602
references.citation: EMBO J. 2007 Jan 24;26(2):516-26
references.pmid: 17215865
references.citation: Cell Host Microbe. 2008 Apr 17;3(4):245-52
references.pmid: 18342597
references.citation: J Cell Biol. 2003 Aug 4;162(3):443-55
references.pmid: 12885763
references.citation: J Virol. 2004 Sep;78(17):9560-3
references.pmid: 15308748
references.citation: Trends Microbiol. 2013 Mar;21(3):136-44
references.pmid: 23266279
references.citation: Cell Immunol. 2009;254(2):142-8
references.pmid: 18835599
references.citation: J Virol. 2007 Dec;81(24):13916-21
references.pmid: 17913807
references.citation: Proc Natl Acad Sci U S A. 2008 Jan 8;105(1):294-9
references.pmid: 18172216
references.citation: Annu Rev Cell Dev Biol. 2004;20:395-425
references.pmid: 15473846
references.citation: PLoS Pathog. 2010 Nov 18;6(11):e1001200
references.pmid: 21124996
references.citation: J Virol. 2009 Oct;83(20):10527-37
references.pmid: 19706714
references.citation: Proc Natl Acad Sci U S A. 1989 Dec;86(23):9544-8
references.pmid: 2687883
references.citation: J Virol. 2010 Jan;84(2):976-82
references.pmid: 19889767
references.citation: Science. 1995 Nov 10;270(5238):988-91
references.pmid: 7481804
references.citation: Cell. 2005 Mar 11;120(5):663-74
references.pmid: 15766529
references.citation: Cell. 2009 May 1;137(3):433-44
references.pmid: 19410541
references.citation: Nature. 1988 Jan 21;331(6153):280-3
references.pmid: 2447506
references.citation: Nat Rev Immunol. 2007 Apr;7(4):310-7
references.pmid: 17380160
references.citation: Immunol Rev. 2013 Jan;251(1):113-24
references.pmid: 23278744
references.citation: FEBS Lett. 2011 Nov 4;585(21):3367-71
references.pmid: 21970979
references.citation: J Virol. 2011 Jul;85(14):7169-76
references.pmid: 21543479
references.citation: Expert Opin Ther Targets. 2009 Aug;13(8):895-908
references.pmid: 19534569
references.citation: J Virol. 2013 Mar;87(6):3348-60
references.pmid: 23302874
references.citation: J Virol. 2004 Feb;78(3):1552-63
references.pmid: 14722309
references.citation: N Engl J Med. 1995 Jan 26;332(4):228-32
references.pmid: 7808489
references.citation: Science. 1988 Sep 16;241(4872):1481-5
references.pmid: 3262235
references.citation: J Virol. 1993 Jun;67(6):3274-80
references.pmid: 8497051
references.citation: J Virol. 1993 Dec;67(12):6956-64
references.pmid: 8230418
references.citation: J Virol. 2011 Aug;85(15):7672-82
references.pmid: 21593177
references.citation: PLoS Pathog. 2010 Jun 17;6(6):e1000955
references.pmid: 20585562
references.citation: Cell Host Microbe. 2007 Aug 16;2(2):85-95
references.pmid: 18005723
references.citation: Science. 2009 Mar 27;323(5922):1743-7
references.pmid: 19325119
references.citation: Proc Natl Acad Sci U S A. 1993 Jun 15;90(12):5549-53
references.pmid: 8516299
references.citation: Retrovirology. 2007 Oct 01;4:70
references.pmid: 17908312
references.citation: Physiology (Bethesda). 2011 Aug;26(4):236-51
references.pmid: 21841072
references.citation: Nat Immunol. 2006 Mar;7(3):302-10
references.pmid: 16429138
references.citation: Proc Natl Acad Sci U S A. 1989 Feb;86(4):1128-32
references.pmid: 2784001
references.citation: Mol Biol Int. 2012;2012:979765
references.pmid: 22830021
references.citation: J Virol. 2012 Apr;86(7):3924-33
references.pmid: 22258237
references.citation: AIDS. 1999;13 Suppl A:S137-62
references.pmid: 10885772
references.citation: J Virol. 2004 Oct;78(19):10803-13
references.pmid: 15367647
references.citation: Biochem Soc Trans. 2009 Feb;37(Pt 1):181-4
references.pmid: 19143627
references.citation: J Virol. 1997 Aug;71(8):5871-7
references.pmid: 9223476
references.citation: Cell Host Microbe. 2009 Aug 20;6(2):174-86
references.pmid: 19683683
references.citation: Nature. 2008 Jul 10;454(7201):236-40
references.pmid: 18500329
references.citation: Science. 1996 Mar 15;271(5255):1582-6
references.pmid: 8599114
references.citation: Curr Opin HIV AIDS. 2009 Mar;4(2):143-9
references.pmid: 19339954
references.citation: J Virol. 2008 Feb;82(3):1166-74
references.pmid: 18032517
references.citation: J Virol. 2010 Mar;84(5):2282-93
references.pmid: 20015995
references.citation: AIDS. 2003 Jun 13;17(9):1291-301
references.pmid: 12799550
references.citation: Mol Aspects Med. 2010 Oct;31(5):418-33
references.pmid: 20594957
references.citation: PLoS Pathog. 2009 Nov;5(11):e1000652
references.pmid: 19893629
references.citation: Cell. 1991 May 17;65(4):651-62
references.pmid: 2032289
references.citation: Virology. 1999 Dec 20;265(2):173-7
references.pmid: 10600589
references.citation: Eur J Cell Biol. 2011 Nov;90(11):913-21
references.pmid: 21044805
references.citation: PLoS Biol. 2006 Dec;4(12):e435
references.pmid: 17147474
references.citation: J Virol. 2007 Nov;81(22):12582-95
references.pmid: 17728240
references.citation: FEBS Lett. 2003 Jul 31;548(1-3):37-42
references.pmid: 12885404
references.citation: Cell Host Microbe. 2011 Dec 15;10(6):551-62
references.pmid: 22177560
references.citation: Nature. 2011 Aug 17;477(7362):95-8
references.pmid: 21849975
references.citation: J Virol. 2004 May;78(10):5311-23
references.pmid: 15137387
references.citation: Immunol Rev. 1999 Apr;168:51-63
references.pmid: 10399064
references.citation: Nat Cell Biol. 2008 Feb;10(2):211-9
references.pmid: 18193035
references.citation: J Virol. 2007 Feb;81(3):1534-6
references.pmid: 17108041
references.citation: J Virol. 2012 Oct;86(20):11242-53
references.pmid: 22875976
references.citation: J Virol. 1998 Mar;72(3):2208-12
references.pmid: 9499078
references.citation: J Virol. 1995 Jul;69(7):4053-9
references.pmid: 7539505
references.citation: Nature. 2012 Oct 11;490(7419):283-7
references.pmid: 22854780
references.citation: Proc Natl Acad Sci U S A. 2010 May 18;107(20):9364-9
references.pmid: 20439730
references.citation: J Virol. 2007 Jan;81(2):1000-12
references.pmid: 17079292
references.citation: J Virol. 2013 Apr;87(7):3729-40
references.pmid: 23325686
references.citation: Viruses. 2010 Aug;2(8):1666-80
references.pmid: 21994700
references.citation: PLoS Pathog. 2008 Mar 07;4(3):e1000015
references.pmid: 18369466
references.citation: J Virol. 1992 Nov;66(11):6304-13
references.pmid: 1383561
references.citation: Nucleic Acids Res. 2011 Aug;39(14):5879-92
references.pmid: 21459854
references.citation: J Virol. 1993 Apr;67(4):2266-75
references.pmid: 8445731
references.citation: J Virol. 2009 Jun;83(12):6234-46
references.pmid: 19369333