Prostratin antagonizes HIV latency by activating NF-kappaB.
A subset of quiescent memory CD4 T cells harboring integrated but transcriptionally silent proviruses poses a currently insurmountable barrier to the eradication of the human immunodeficiency virus (HIV) in infected patients. Induction of HIV gene expression in these latently infected cells by immune activating agents has been proposed as one approach to confer sensitivity to antiretroviral therapy. Interest has recently focused on the non-tumor-promoting phorbol ester, prostratin, as a potential agent to activate latent HIV proviruses. Using multiple Jurkat T cell lines containing integrated but transcriptionally latent HIV proviruses (J-Lat cells), we now demonstrate that prostratin effectively activates HIV gene expression in these latently infected cells. We further show that prostratin acts by stimulating IKK-dependent phosphorylation and degradation of IkappaBalpha, leading to the rapid nuclear translocation of NF-kappaB and activation of the HIV-1 long terminal repeat in a kappaB enhancer-dependent manner. In contrast, NFAT and AP-1 are not induced by prostratin. Using chromatin immunoprecipitation assays to identify host transcription factors recruited to the latent HIV-1 promoter in living cells, we find that prostratin induces RelA binding. Analysis of potential upstream signal transducers demonstrates that prostratin stimulates membrane translocation of classical, novel, and atypical protein kinase C (PKC) isoforms. Studies with isoform-specific PKC inhibitors suggest that the novel PKCs play a particularly prominent role in the prostratin response. These findings provide new insights into the molecular pathway through which prostratin antagonizes HIV latency highlighting a central role for the action of NF-kappaB.
Gladstone Institute of Virology and Immunology, University of California, San Francisco, San Francisco, California 94141, USA.
Samuel A
SA
Williams
Lin-Feng
LF
Chen
Hakju
H
Kwon
David
D
Fenard
Dwayne
D
Bisgrove
Eric
E
Verdin
Warner C
WC
Greene
D021581:Active Transport, Cell Nucleus; D015496:CD4-Positive T-Lymphocytes / Q000821:virology; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D006678:HIV / Q000502:physiology*; D016325:HIV Long Terminal Repeat; D006801:Humans; D051550:I-kappa B Kinase; D019169:Jurkat Cells; D016328:NF-kappa B / Q000187:drug effects / Q000378:metabolism*; D010703:Phorbol Esters / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017735:Virus Latency / Q000187:drug effects*
D016328:NF-kappa B; D010703:Phorbol Esters; C070999:prostratin; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D011493:Protein Kinase C