Induction of activator protein 1 (AP-1) in macrophages by human immunodeficiency virus type-1 NEF is a cell-type-specific response that requires bothHck and MAPK signaling events

Human immunodeficiency virus type 1 (HIV-1) Nef is important for viral infe ctivity and pathogenicity. :HIV-1 infection is associated with inappropriat e 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 an d induction of mRNA for the AP-1 responsive tissue inhibitor of metalloprot einases-1 (TIMP-1) gene. Mutagenesis and kinase inhibition studies were emp loyed to deter-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 st udies indicated that induction of AP-1 by Nef is likely to be mediated thro ugh the MAPK (ERK1 and 2) signaling pathway and requires the proline-rich P xxP motif of Nef, suggesting the involvement of upstream protein kinases be longing to the Src family. Effects of Nef on AP-1 induction were cell linea ge-specific, being stimulatory in macrophages, inhibitory in T cells and wi thout effect in HeLa cells. These latter two observations led us to test th e possibility that cell-specific interactions of Nef with Src family protei ns 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 acti vity in RAW cells. In conclusion, induction of AP-1 by Nef is a specific fe ature of human and murine macrophage cell lines that requires signal transd uction events involving Hck and MAPKs. (C) 1999 Academic Press.