title: Inhibition of T-cell receptor-induced actin remodeling and relocalization of Lck are evolutionarily conserved activities of lentiviral Nef proteins.
abstract: Nef, an important pathogenicity factor of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV), elevates virus replication in vivo. Among other activities, Nef affects T-cell receptor (TCR) signaling via several mechanisms. For HIV-1 Nef these include alteration of the organization and function of the immunological synapse (IS) such as relocalization of the Lck kinase, as well as early inhibition of TCR/CD3 complex (TCR-CD3)-mediated actin rearrangements and tyrosine phosphorylation. Although most SIV and HIV-2 Nef alleles (group 2) potently downregulate cell surface TCR-CD3, this activity was lost in the viral lineage that gave rise to HIV-1 and its SIV counterparts (group 1). To address the contribution of TCR-CD3 downregulation to Nef effects on TCR signal initiation, we compared the activities of 18 group 1 and group 2 Nef proteins, as well as SIV Nef mutants with defects in TCR-CD3 downmodulation. We found that alteration of Lck's subcellular localization is largely conserved and occurs independently of actin remodeling inhibition or TCR-CD3 downregulation. Surprisingly, Nef proteins of both groups also strongly reduced TCR-induced actin remodeling and tyrosine phosphorylation on TCR-stimulatory surfaces and TCR-CD3 downmodulation competence by group 2 Nef proteins only slightly elevated these effects. Furthermore, Nef proteins from HIV-1 and SIV reduced conjugation between infected primary human T lymphocytes and Raji B cells and potently prevented F-actin polarization at the IS independently of their ability to downmodulate TCR-CD3. These results establish alterations of early TCR signaling events at the IS, including F-actin remodeling and relocalization of Lck, as evolutionary conserved activities of highly divergent lentiviral Nef proteins.
authors.affiliation: Department of Virology, University of Heidelberg, INF 324, 69120 Heidelberg, Germany.
authors.forename: Jochen M
authors.initials: JM
authors.lastname: Rudolph
authors.forename: Nina
authors.initials: N
authors.lastname: Eickel
authors.forename: Claudia
authors.initials: C
authors.lastname: Haller
authors.forename: Michael
authors.initials: M
authors.lastname: Schindler
authors.forename: Oliver T
authors.initials: OT
authors.lastname: Fackler
mesh_terms: D000199:Actins / Q000502:physiology*; D017124:Conserved Sequence; D015536:Down-Regulation; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000502:physiology*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins / Q000502:physiology; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000502:physiology*
chemical_list: D000199:Actins; C429284:NEF protein, SIV; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011948:Receptors, Antigen, T-Cell; D054334:Viral Regulatory and Accessory Proteins; D054311:nef Gene Products, Human Immunodeficiency Virus; C514837:nef protein, Human immunodeficiency virus 1; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)