       Document 0590
 DOCN  M9550590
 TI    Human immunodeficiency virus type 1 Nef protein inhibits activation
       pathways in peripheral blood mononuclear cells and T-cell lines.
 DT    9505
 AU    Greenway A; Azad A; McPhee D; AIDS Cellular Biology Unit, National
       Centre in HIV Virology; Research, Macfarlane Burnet Centre for Medical
       Research,; Fairfield, Victoria, Australia.
 SO    J Virol. 1995 Mar;69(3):1842-50. Unique Identifier : AIDSLINE
       MED/95156617
 AB    Human immunodeficiency virus type 1 (HIV-1) Nef protein causes the loss
       of cell surface CD4 and interleukin-2 (IL-2) receptor (Tac) from
       peripheral blood mononuclear cells (PBMC) and CD4+ T-cell lines. As both
       CD4 and the IL-2 receptor play crucial roles in antigen-driven helper
       T-cell signalling and T-cell proliferation, respectively, the role of
       Nef in the viral life cycle may be to perturb signalling pathways
       emanating from these receptors. However, the intracellular targets for
       Nef that result in receptor down-regulation are unknown. Using a
       recombinant glutathione S-transferase-full-length 27 kDa Nef (Nef27)
       fusion protein, produced in Escherichia coli by translation from the
       first start codon of HIV-1 nef clone pNL4-3, as an affinity reagent to
       probe cytoplasmic extracts of MT-2 cells and PBMC, we have shown
       interaction with at least seven host cell protein species ranging from
       24 to 75 kDa. Immunoblotting identified four of these proteins as
       p56lck, CD4, p53, and p44mapk/erk1, all of which are intimately involved
       in intracellular signalling. To assess the relevance of these
       interactions and further define the biochemical activity of Nef in
       signal transduction pathways, highly purified Nef27 protein was
       introduced directly into PBMC by electroporation. Nef27-treated PBMC
       showed reduced proliferative responsiveness to exogenous recombinant
       IL-2. Normally, stimulation of T-cells by IL-2 or phorbol 12-myristate
       13-acetate provokes both augmentation of p56lck activity and
       corresponding posttranslational modification of p56lck. These changes
       were also inhibited by treatment of PBMC with Nef, suggesting that Nef
       interferes with activation of p56lck and as a consequence of signalling
       via the IL-2 receptor. Further evidence for Nef interfering with cell
       proliferation was the decreased production of the proto-oncogene c-myb,
       which is required for cell cycle progression, in Nef-treated MT-2 cells.
       In contrast to the binding characteristics and biological effects of
       Nef27, the alternate 25-kDa isoform of Nef (Nef25) produced by
       translation from the second start codon of HIV nef pNL4-3 (57 nucleotide
       residues downstream) was shown to interact with only three cellular
       proteins of approximately 26, 28, and 56 kDa from PBMC and MT-2 cells,
       one of which was identified as p56lck. Also, proliferation and
       posttranslational modification of p56lck in response to IL-2 stimulation
       were not profoundly affected by treatment of PBMC with Nef25 compared
       with Nef27.(ABSTRACT TRUNCATED AT 400 WORDS)
 DE    Amino Acid Sequence  Antigens, CD4/METABOLISM  Calmodulin-Dependent
       Protein Kinases/METABOLISM  Gene Products, nef/*METABOLISM/PHARMACOLOGY
       Human  HIV-1/*PATHOGENICITY  In Vitro  Interleukin-2/PHARMACOLOGY
       Leukocytes, Mononuclear/*IMMUNOLOGY  Lymphocyte Transformation/*DRUG
       EFFECTS  Molecular Sequence Data  Protein p53/METABOLISM  Protein
       Binding  Protein-Tyrosine Kinase/METABOLISM  Proto-Oncogene
       Proteins/METABOLISM  Proto-Oncogene Proteins c-jun/METABOLISM  Support,
       Non-U.S. Gov't  T-Lymphocytes/*IMMUNOLOGY  Tetradecanoylphorbol
       Acetate/PHARMACOLOGY  JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).

