Iκκ mediates NF-κB activation in human immunodeficiency virus- infected cells

Department of Immunology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Journal of Virology (Impact Factor: 4.65). 06/1999; 73(5):3893-903.
Source: PubMed

ABSTRACT Human monocytes and macrophages are persistent reservoirs of human immunodeficiency virus (HIV) type-1. Persistent HIV infection of these cells results in increased levels of NF-kappaB in the nucleus secondary to increased IkappaBalpha, IkappaBbeta, and IkappaBepsilon degradation, a mechanism postulated to regulate viral persistence. To characterize the molecular mechanisms regulating HIV-mediated degradation of IkappaB, we have sought to identify the regulatory domains of IkappaBalpha targeted by HIV infection. Using monocytic cells stably expressing different transdominant molecules of IkappaBalpha, we determined that persistent HIV infection of these cells targets the NH2 but not the COOH terminus of IkappaBalpha. Further analysis demonstrated that phosphorylation at S32 and S36 is necessary for HIV-dependent IkappaBalpha degradation and NF-kappaB activation. Of the putative N-terminal IkappaBalpha kinases, we demonstrated that the Ikappakappa complex, but not p90(rsk), is activated by HIV infection and mediates HIV-dependent NF-kappaB activation. Analysis of viral replication in cells that constitutively express IkappaBalpha negative transdominant molecules demonstrated a lack of correlation between virus-induced NF-kappaB (p65/p50) nuclear translocation and degree of viral persistence in human monocytes.

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Available from: Sergey A Trushin, Aug 10, 2015
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    • "Nuclear and cytoplasmic extracts were prepared as described previously (Asin et al, 1999), with minor modications. Cells were washed with cold PBS twice, gently scraped from the dishes, transferred to microcentrifuge tubes, and centrifuged for 10 minutes at 3,000 £ g. "
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    ABSTRACT: Moloney murine leukemia virus (MoMuLV)-ts1-mediated neuronal degeneration in mice is likely due to loss of glial support and release of inflammatory cytokines and neurotoxins from surrounding ts1-infected glial cells including astrocytes. NF-κB is a transcription factor that participates in the transcriptional activation of a variety of immune and inflammatory genes. We investigated whether ts1 activates NF-κB in astrocytes and examined the mechanism(s) responsible for the activation of NF-κB by ts1 infection in vitro. Here we present evidence that ts1 infection of astrocytes in vitro activates NF-κB by enhanced proteolysis of the NF-κB inhibitors, IκBα and IκBβ. In in vitro studies using protease inhibitors, IκBα proteolysis in ts1-infected astrocytes was significantly blocked by a specific calpain inhibitor calpeptin but not by MG-132, a specific proteasome inhibitor, whereas rapid IκBβ proteolysis was blocked by MG-132. Furthermore, treatment with MG-132 increased levels of multi-ubiquitinated IκBβ protein in ts1-infected astrocytes. These results indicate that the calpain proteolysis is a major mechanism of IκBα proteolysis in ts1-infected astrocytes. Additionally, ts1 infection of astrocytes in vitro increased expression of inducible nitric oxide synthase (iNOS), a NF-κB-dependent gene product. Our results suggest that NF-κB activation in ts1-infected astrocytes is mediated by enhanced proteolysis of IκBα and IκBβ through two different proteolytic pathways, the calpain and ubiquitin-proteasome pathways, resulting in increased expression of iNOS, a NF-κB-dependent gene.
    Journal of NeuroVirology 01/2001; 7(5):466-475. DOI:10.1080/135502801753170327 · 3.32 Impact Factor
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    • "Using U937 monocytic cells and HIV-infected U937 cells as a model of chronic HIV infection, Kelly et al. reported an increased level of constitutive expression of the ␤-chemokines RANTES and MIP-1␣ (Kelly et al., 1998). Chronic infection of myelomonocytic U937 or PLB985 cells produces constitutive NF-␬B activity and recent data have shown that chronic and de novo HIV infection of monocytic cells results in selective activation of NF-␬B (p50/p65) via the activation of the IKK␤ subunit of the recently identified I␬B␣ kinase (IKK) complex (De- Luca et al., 1999; Asin et al., 1999). Since several chemokine genes are regulated in part by NF-␬B, it is likely that upregulation of constitutive and induced chemokine expression are due to an HIV-mediated increase in NF-␬B transactivation in chronically infected cells (reviewed in Roulston et al., 1995). "
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    ABSTRACT: The importance of chemokine expression on HIV infection has been emphasized by the discovery that infection of CD4+ T cells by M-tropic strains of HIV-1 is antagonized by the chemokines RANTES, MIP-1α, and MIP-1β, which are natural ligands of CCR5, a major coreceptor for macrophagetropic (M-tropic) isolates of HIV-1. Similarly, the CCR2b ligands MCP-1 and MCP-3 inhibit productive infection of PBMCs by both CCR5- and CXCR4-dependent strains of HIV-1, suggesting that expression of the MCP-1 chemokine may affect HIV infection via signaling through the CCR2 receptor and subsequent desensitization of the CCR5 and/or CXCR4 signaling pathway. Given the major role played by chemokine receptors in HIV-1 fusion/entry and the regulatory effects of chemokines on HIV-1 infection, we examined the pattern of chemokine gene expression in HIV-1-infected myeloid cells and in primary monocyte/macrophages. Chronic HIV-1 infection of U937 monocytic cells increased the expression of RANTES, MIP-1α, MIP-1β, and IL-8 chemokine genes, but strongly inhibited PMA/PHA- and TNFα-induced MCP-1 gene transcription. HIV-1-mediated inhibition of MCP-1 transcription and secretion was further confirmed in de novo HIV-1-infected U937 cells and correlated with a delay in HIV- and signal-induced NF-κB binding to the MCP-1 promoter. The inhibition of MCP-1 gene expression may provide a mechanism by which HIV-1 escapes the early influence of chemokine expression in monocytic cells.
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