Activation of HIV-1 long terminal repeat transcription and virus replication via NF-kappa B-dependent and -independent pathways by potent phosphotyrosine phosphatase inhibitors, the peroxovanadium compounds

Replication of human immunodeficiency virus type 1 (HIV-1) is increased by different cytokines and T cell activators, also known to modulate tyrosine phosphorylation levels, A novel class of protein tyrosine phosphatase (PTP) inhibitors, peroxovanadium (pV) compounds, were tested for a putative effect on HIV-1 long terminal repeat (LTR) activity, We found that these PTP inhibitors markedly enhanced HIV-1 LTR activity in 1G5 cells, a stably transfected cell line that harbors an HIV-1 LTR-driven luciferase construct, A direct correlation between the extent of tyrosine phosphorylation and the level of HIV-1 LTR inducibility was seen after treatment with three different pV compounds, Transient transfection experiments were carried out in several T cell lines, and after addition of pV, a marked increase in HIV-1 LTR activity was measured, Monocytoid cells were tested using U937-derived cell lines and were also found to be sensitive to the pV-mediated potentiating effect on HIV-1 LTR activity, A significant reduction of the pV-mediated increase in HIV-1 LTR activity was seen in cells transiently transfected with an HIV-1 LTR-driven luciferase construct bearing a mutation in both NF-kappa B binding sites although detectable levels of induction remained, Electrophoretic mobility shift assays allowed the identification of the nuclear translocation of the NF-kappa B p50.p65 heterodimer complex induced by pV compounds, A dominant negative version of the repressor I kappa B alpha mutated on serines 32 and 36 impeded pV-induced NF-kappa B-dependent luciferase activity, Western blot analysis showed a clear diminution in the protein level of I kappa B alpha starting 30 min after pV treatment of Jurkat E6.1 cells which is indicative of its degradation, On the other hand, no increase in tyrosine phosphorylation was ob sewed on I kappa B alpha itself, Finally, we tested the PTP inhibitors on four cell lines latently infected with HIV-1 and showed a consistent pV-mediated increase in virion production, Thus, our studies suggest that pV-mediated activation of HIV-1 LTR activity is controlled by the nuclear translocation of the NF-kappa B transcription factor, which is mediated by I kappa B alpha serine phosphorylation and degradation, but also by a still undefined NF-kappa B-independent pathway.