Human Immunodeficiency Virus Type 1 Nef Protein Sensitizes CD4+ T Lymphoid Cells to Apoptosis via Functional Upregulation of the CD95/CD95 Ligand Pathway

• Published in: Blood 1999-02, Vol.93 (3), p.1000-1010
• Main Authors: Zauli, Giorgio, Gibellini, Davide, Secchiero, Paola, Dutartre, Hélène, Olive, Daniel, Capitani, Silvano, Collette, Yves
• Format: Article
• Language: English
• Subjects: Apoptosis; Biological and medical sciences; CD4-Positive T-Lymphocytes - metabolism; CD4-Positive T-Lymphocytes - pathology; CD4-Positive T-Lymphocytes - virology; Cell Line; Colforsin - pharmacology; Cyclic AMP-Dependent Protein Kinases - metabolism; Enzyme Activation - drug effects; Experimental viral diseases and models; Fas Ligand Protein; fas Receptor - biosynthesis; fas Receptor - genetics; Gene Products, nef - physiology; Genes, nef; HIV Infections - immunology; HIV Infections - pathology; HIV-1 - physiology; Humans; Immunology; Infectious diseases; Jurkat Cells; Life Sciences; Medical sciences; Membrane Glycoproteins - biosynthesis; Membrane Glycoproteins - genetics; Microbiology and Parasitology; nef Gene Products, Human Immunodeficiency Virus; Up-Regulation; Viral diseases; Virology
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V93.3.1000

Many viruses have evolved genes encoding proteins that regulate cell death by apoptosis. The human immunodeficiency virus type 1 (HIV-1) Nef protein alters T-cell development and signaling and is required for optimal viral replication and pathogenicity in vivo. To analyze the interference of Nef with cell survival, we used both regulated and constitutively expressed nef alleles in stably transfected T-cell lines. Nef-expressing cells were sensitized to cell death by apoptosis, which was specifically exacerbated by an anti-CD95 IgM monoclonal antibody (MoAb). Flow cytometric analysis showed that the surface expression of both CD95 and CD95 ligand (CD95L) was upregulated by endogenous Nef expression. Nef-mediated apoptosis was almost completely suppressed by the addition in culture of an anti-CD95 Fab′ IgG MoAb, which specifically blocks CD95/CD95L interactions. Lastly, mutation of a proline motif in the core region of the nef gene, which disrupts its ability to interact with cellular kinases and reduces HIV-1 replication in vitro, completely abrogated the Nef-mediated induction of apoptosis as well as its ability to upregulate surface CD95 and CD95L. These findings may provide molecular insight into the role of endogenous Nef in the T-cell depletion observed in vivo, particularly HIV-specific cytotoxic CD8+ T cells.