Dysregulation of NGF‐signaling and Egr‐1 expression by Tat in neuronal cell culture

Darbinian-Sarkissian, Nune; Czernik, Marta; Peruzzi, Francesca; Gordon, Jennifer; Rappaport, Jay; Reiss, Krzysztof; Khalili, Kamel; Amini, Shohreh

doi:10.1002/jcp.20675

Cited by 12 publications

(12 citation statements)

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“…Supporting this finding, others have reported that the HIV-Tat protein reduces NGF-stimulated EGR1 expression in SK-N-MC cells, the neuroblastoma cell line used in our studies, acting via inhibition of the MAPK/Erk1/2 pathway (Darbinian-Sarkissian et al, 2006). Since EGR1 is reported as downregulated in models of several other neurodegenerative diseases (Blalock et al, 2003; Booth et al, 2004; Crocker et al, 2006), we asked whether EGR1 downregulation might be a consequence, at least in part, of macrophage/microglia activation present in many of these diseases, rather than the result of SIV infection per se .…”

Section: Discussionsupporting

confidence: 86%

“…Although EGR1 is activated via the MAPK1/2 pathway (Darbinian-Sarkissian et al, 2006) and would therefore be expected to be induced by chemokine stimulation, inhibition of this pathway could occur via “RAF1-AKT crosstalk”, in which RAF1 kinase activity (and downstream MAPK/ERK activation) is suppressed by PKB/AKT phosphorylation of Ser259 in a ligand-, concentration-, and time-course-dependent manner (Zimmermann and Moelling, 1999; Moelling et al, 2002) (Figure 6B). This inhibitory mechanism could be particularly effective after CCL8 stimulation, as it has been reported that binding of CCL8 to CCR2, in contrast to CCL2 binding, fails to induce nuclear translocation of activated ERK1 and downstream gene induction (O’Boyle et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

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An Integrated Systems Analysis Implicates EGR1 Downregulation in Simian Immunodeficiency Virus Encephalitis-Induced Neural Dysfunction

et al. 2009

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Human immunodeficiency virus (HIV)-associated dementia (HAD) is a syndrome occurring in HIV-infected patients with advanceddisease that likely develops as a result of macrophage and microglial activation as well as other immune events triggered by virus in the central nervous system. The most relevant experimental model of HAD, rhesus macaques exhibiting simian immunodeficiency virus (SIV) encephalitis (SIVE), closely reproduces the human disease and has been successfully used to advance our understanding of mechanisms underlying HAD. In this study we integrate gene expression data from uninfected and SIV-infected hippocampus with a human protein interaction network and discover modules of genes whose expression patterns distinguish these two states, to facilitate identification of neuronal genes that may contribute to SIVE/HIV cognitive deficits. Using this approach we identify several downregulated candidate genes and select one, EGR1, a key molecule in hippocampus-related learning and memory, for further study. We show that EGR1 is downregulated in SIV-infected hippocampus and that it can be downregulated in differentiated human neuroblastoma cells by treatment with CCL8, a product of activated microglia. Integration of expression data with protein interaction data to discover discriminatory modules of interacting proteins can be usefully used to prioritize differentially expressed genes for further study. Investigation of EGR1, selected in this manner, indicates that its downregulation in SIVE may occur as a consequence of the host response to infection, leading to deficits in cognition.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

An Integrated Systems Analysis Implicates EGR1 Downregulation in Simian Immunodeficiency Virus Encephalitis-Induced Neural Dysfunction

et al. 2009

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“…Nuclear proteins were extracted and 10 μg were incubated with 50,000 cpm of a [ 32 P]-labeled double-stranded oligodeoxyribonucleotide probe as previously described (Darbinian-Sarkissian et al , 2006; Romagnoli et al , 2008). Probes used in the gel shifts correspond to the BAG3 promoter AP2 site (-146 to −124; 5′-cgcgcccgcccgcggcgactcc-3′) and Ets site (-104 to −79; 5′-tcggaagggggaggcgggaggagg-3′).…”

Section: Methodsmentioning

confidence: 99%

“…ChiP assays used the ChIP assay kit (Upstate Biotechnology, Inc., Lake Placid, NY) as we have previously described (Darbinian-Sarkissian et al , 2006; Gentilella et al , 2008). Briefly, U-87 MG cells were transfected with and without T-Ag expression plasmid for 48h.…”

Section: Methodsmentioning

confidence: 99%

Evidence for modulation of BAG3 by polyomavirus JC early protein

Basile

Darbinian

Kaminski

et al. 2009

Journal of General Virology

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Polyomavirus JC (JCV) infects oligodendrocytes and astrocytes in the brain and is the cause of the demyelinating disease progressive multifocal leukoencephalopathy (PML). In cell culture, JCV infection is characterized by severe damage to cellular DNA, which begins early in infection, and a viral cytopathic effect, which is observed late in infection. Nevertheless, these JCV-infected cells show a low level of apoptosis, at both the early and late stages of infection. This suggests that there is conflicting interplay between viral anti-apoptotic pathways that seek to optimize virus production, e.g. through T antigen (T-Ag)-p53 interaction, and cellular pro-apoptotic pathways that seek to eliminate virally infected cells. The apoptosis regulatory protein BAG3 is a member of the human Bcl-2-associated athanogene (BAG) family of proteins, which function as molecular co-chaperones through their interaction with Hsc70/Hsp70 and function in the regulation of the cellular stress response, proliferation and apoptosis. This study showed that BAG3 protein is downregulated upon JCV infection and that this effect is mediated by JCV T-Ag via repression of the BAG3 promoter. The site of action of T-Ag was mapped to an AP2 site in the BAG3 promoter, and gel shift and chromatin immunoprecipitation assays showed that T-Ag inhibited AP2 binding to this site, resulting in downregulation of BAG3 promoter expression. Using BAG3 and T-Ag expression and BAG3 siRNA, it was found that BAG3 and T-Ag had antagonistic effects on the induction of apoptosis, being anti-apoptotic and pro-apoptotic, respectively. The significance of these interactions to the JCV life cycle is discussed. INTRODUCTIONThe human polyomavirus JC (JCV) opportunistically infects the oligodendrocytes and astrocytes of the brain during development of the demyelinating disease progressive multifocal leukoencephalopathy (PML). The pathology of PML is thought to involve the destruction of oligodendrocytes, the myelin-producing cells of the brain, by lytic infection with JCV. In contrast, astrocytes do not undergo lytic infection but rather adopt a 'bizarre' morphology, yet are still productively infected as judged by the production of viral capsid protein observed by immunohistochemistry and virions observed by electron microscopy (Del Valle et al., 2008; Mázló et al., 2001). PML occurs primarily in individuals with highly suppressed immune function, especially those with human immunodeficiency virus (HIV)/AIDS (Hou & Major, 2000;Khalili et al., 2006). The JCV genome is a circular, supercoiled DNA, which is small in size (5130 bp) and has two coding regions (early and late) and a non-coding regulatory region (Frisque et al., 1984;Cole, 1996). Infection with JCV is common in childhood after which the virus becomes latent. In circumstances of severe immunosuppression, e.g. HIV/AIDS, JCV can reactivate in the central nervus system (CNS) leading to the destruction of oligodendrocytes, which produce myelin, and to PML (Hou & Major, 2000;Khalili et al., 2006).We have developed a...

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“…SK-N-MC cell lines expressing CFP-Tat and CFP (cyan fluorescent protein) were developed by stably transfecting SK-N-MC cells with CFP-Tat or pECFP-C1 (Clontech, Mountain View, CA) and clonal expression as described previously (Darbinian-Sarkissian et al, 2006). …”

Section: Methodsmentioning

confidence: 99%

HIV‐1 Tat inhibits NGF‐Induced Egr‐1 transcriptional activity and consequent p35 expression in neural cells

Darbinian

Darbinyan

Czernik

et al. 2008

Journal Cellular Physiology

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Infection with HIV-1 causes degeneration of neurons leading to motor and cognitive dysfunction in AIDS patients. One of the key viral regulatory proteins, Tat, which is released by infected cells, can be taken up by various uninfected cells including neurons and by dysregulating several biological events induces cell injury and death. In earlier studies, we demonstrated that treatment of neuronal cells with Tat affects the nerve growth factor (NGF) signaling pathway involving MAPK/ERK. Here we demonstrate that a decrease in the level of Egr-1, one of the targets for MAPK, by Tat has a negative impact on the level of p35 expression in NGF-treated neural cells. Further, we demonstrate a reduced level of Egr-1 association with the p35 promoter sequence in NGF-treated cells expressing Tat. As p35, by associating with Cdk5, phosphorylates several neuronal proteins including neurofilaments and plays a role in neuronal differentiation and survival, we examined kinase activity of p35 complexes obtained from cells expressing Tat. Results from H1 kinase assays showed reduced activity of the p35 complex from Tat-expressing cells in comparison to that from control cells. Accordingly, the level of phosphorylated neurofilaments was diminished in Tat-expressing cells. Similarly, treatment of PC12 cells with Tat protein or supernatant from HIV-1 infected cells decreased kinase activity of p35 in these cells. These observations ascribe a role for Tat in altering p35 expression and its activity that affects phosphorylation of proteins involved in neuronal cell survival.HIV-1 proteins may induce neuronal apoptosis in AIDS patients with neurological disorders by dysregulating the regulatory events responsible for cell growth, survival, and programmed cell death (Adle-Biassette et al., 1995;New et al., 1997;Macho et al., 1999;Kaul et al., 2001Kaul et al., , 2005Xu et al., 2004;Kaul and Lipton, 2006;King et al., 2006). Upon entry into the CNS, HIV-1 productively infects brain macrophages and microglia leading to production of large amounts of viral proteins including Tat, which, in turn, can induce neuronal damage. Tat is a viral transcriptional activator that plays a critical role in the replication of HIV-1 and has the ability to interact with several important cellular regulatory proteins and alter their function (Dingwall et al., 1989;Jeang et al., 1993;Cujec et al., 1997;Greenberg et al., 1997;Hottiger and Nabel, 1998;Wei et al., 1998;Sawaya et al., 2000;Liu et al., 2002). It is thought that Tat possesses neurotoxic activity through its unusual ability to be released by infected cells and be taken up in a biologically active form by the neighboring uninfected cells including neurons (Frankel and Pabo, 1988;Ensoli et al., 1993;Philippon et al., 1994;Li et al., 1995;Ma and Nath, 1997 understood, earlier studies revealed that activation of glycogen synthase kinase 3β (GSK3β) by Tat via PI3 kinase and Akt may contribute to neurotoxicity of this protein (Maggirwar et al., 1999; Sui et al., 2006a,b). It has also been found tha...

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Dysregulation of NGF‐signaling and Egr‐1 expression by Tat in neuronal cell culture

Cited by 12 publications

References 71 publications

An Integrated Systems Analysis Implicates EGR1 Downregulation in Simian Immunodeficiency Virus Encephalitis-Induced Neural Dysfunction

An Integrated Systems Analysis Implicates EGR1 Downregulation in Simian Immunodeficiency Virus Encephalitis-Induced Neural Dysfunction

Evidence for modulation of BAG3 by polyomavirus JC early protein

HIV‐1 Tat inhibits NGF‐Induced Egr‐1 transcriptional activity and consequent p35 expression in neural cells

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