Induction of activator protein 1 (AP-1) in macrophages by human immunodeficiency virus type-1 NEF is a cell-type-specific response that requires both hck and MAPK signaling events.
Human immunodeficiency virus type 1 (HIV-1) Nef is important for viral infectivity and pathogenicity. HIV-1 infection is associated with inappropriate activation and defects in the function of monocytes/macrophages. We have studied the effects of HIV-1 Nef in the murine (RAW264.7) and human (THP-1) monocyte-macrophage cell lines. Investigation of the activator protein-1 (AP-1) transcription factor showed that Nef expression induced both its DNA binding and transcriptional activities. Increased AP-1 DNA binding activity in RAW264.7 cells was associated with raised levels of c-Fos expression and induction of mRNA for the AP-1 responsive tissue inhibitor of metalloproteinases-1 (TIMP-1) gene. Mutagenesis and kinase inhibition studies were employed to determine signaling pathways used by Nef to induce AP-1. Data from these studies indicated that induction of AP-1 by Nef is likely to be mediated through the MAPK (ERK1 and 2) signaling pathway and requires the proline-rich PxxP motif of Nef, suggesting the involvement of upstream protein kinases belonging to the Src family. Effects of Nef on AP-1 induction were cell lineage-specific, being stimulatory in macrophages, inhibitory in T cells and without effect in HeLa cells. These latter two observations led us to test the possibility that cell-specific interactions of Nef with Src family proteins may modulate AP-1 activity. To this end we demonstrated that a dominant-negative Hck mutant caused inhibition of Nef-mediated AP-1 DNA binding activity in RAW cells. In conclusion, induction of AP-1 by Nef is a specific feature of human and murine macrophage cell lines that requires signal transduction events involving Hck and MAPKs.
Biggs
T E
TE
Southampton General Hospital, Southampton, SO16 6YD, UK.
Cooke
S J
SJ
Barton
C H
CH
Harris
M P
MP
Saksela
K
K
Mann
D A
DA
D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015693:Gene Products, nef / Q000378:metabolism*; D016762:Genes, fos; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051572:Proto-Oncogene Proteins c-hck; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000096:biosynthesis* / Q000378:metabolism; D014162:Transfection; D054311:nef Gene Products, Human Immunodeficiency Virus
D017931:DNA Primers; D004268:DNA-Binding Proteins; D015693:Gene Products, nef; D011518:Proto-Oncogene Proteins; D018808:Transcription Factor AP-1; D054311:nef Gene Products, Human Immunodeficiency Virus; D011505:Protein-Tyrosine Kinases; C496631:HCK protein, human; D051572:Proto-Oncogene Proteins c-hck; D017871:Calcium-Calmodulin-Dependent Protein Kinases