Showing papers by "Bassel E. Sawaya published in 2009"

Monocyte chemoattractant protein-1 (MCP-1): an overview.

Abstract: Chemokines constitute a family of chemoattractant cytokines and are subdivided into four families on the basis of the number and spacing of the conserved cysteine residues in the N-terminus of the protein. Chemokines play a major role in selectively recruiting monocytes, neutrophils, and lymphocytes, as well as in inducing chemotaxis through the activation of G-protein-coupled receptors. Monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulate migration and infiltration of monocytes/macrophages. Both CCL2 and its receptor CCR2 have been demonstrated to be induced and involved in various diseases. Migration of monocytes from the blood stream across the vascular endothelium is required for routine immunological surveillance of tissues, as well as in response to inflammation. This review will discuss these biological processes and the structure and function of CCL2.

p21(WAF1) gene promoter is epigenetically silenced by CTIP2 and SUV39H1.

Abstract: Mainly regulated at the transcriptional level, the cellular cyclin-dependent kinase inhibitor, CDKN1A/p21WAF1 (p21), is a major cell cycle regulator of the response to DNA damage, senescence and tumor suppression. Here, we report that COUP-TF-interacting protein 2 (CTIP2), recruited to the p21 gene promoter, silenced p21 gene transcription through interactions with histone deacetylases and methyltransferases. Importantly, treatment with the specific SUV39H1 inhibitor, chaetocin, repressed histone H3 lysine 9 trimethylation at the p21 gene promoter, stimulated p21 gene expression and induced cell cycle arrest. In addition, CTIP2 and SUV39H1 were recruited to the silenced p21 gene promoter to cooperatively inhibit p21 gene transcription. Induction of p21WAF1 gene upon human immunodeficiency virus 1 (HIV-1) infection benefits viral expression in macrophages. Here, we report that CTIP2 further abolishes Vpr-mediated stimulation of p21, thereby indirectly contributing to HIV-1 latency. Altogether, our results suggest that CTIP2 is a constitutive p21 gene suppressor that cooperates with SUV39H1 and histone methylation to silence the p21 gene transcription.

TNF Alpha Production in Morphine-Treated Human Neural Cells Is NF-κB-Dependent

Abstract: The cytokine tumor necrosis factor alpha (TNFα) is a key factor in several inflammatory diseases and its levels increase in response to a variety of internal or external stimuli. The regulation of the TNFα promoter is mediated by several transcription factors including the nuclear factor kappa B protein (NF-κB). This study examines the role of NF-κB in the regulation of TNFα production by morphine in microglia. Using reverse transcriptase polymerase chain reaction, we demonstrated the presence of morphine receptors in these cells. We next demonstrated the ability of morphine to promote TNFα production and secretion by these cells using a cytokine array assay. Transient transfection experiments led to the identification of the region located between nucleotides −751 and −615 within the TNFα promoter as being responsive to morphine treatment. The DNA sequence of this region contains a motif indicative of a potential NF-κB binding site. The use of a small interfering RNA directed against p65, a subunit of NF-κB, demonstrated that TNFα induction by morphine is NF-κB-dependent. All of the effects of morphine were reversed by the morphine inhibitor, naloxone. These data provide important insights into the effects of morphine on microglia.

Evidence for Activation of the TGF-β1 Promoter by C/EBPβ and Its Modulation by Smads

Abstract: The transforming growth factor-β1 (TGF-β1) is a cytokine involved in many biological events inlcuding immunosuppression, angiogenesis, cell growth, and apoptosis Expression of TGF-β1 at the transcriptional level is controlled by a series of ubiquitous and specialized factors whose activities can be modulated by a variety of signaling events Here we demonstrate that activity of the TGF-β1 promoter is increased by C/EBPβ, a DNA-binding transcription factor whose activity can be influenced by several immunomodulators, in astrocytes and microglial cells Interestingly, expression of Smad3 and Smad4, the downstream regulators of the TGF-β1-signaling pathway, impairs the activity of C/EBPβ on the TGF-β1 promoter Further, we demonstrate that MH2, a common domain among Smads that has protein-binding activities, interacts with C/EBPβ and decreases its association with a region of the TGF-β1 promoter that is responsive to C/EBPβ activation Interestingly, the p65 subunit of nuclear factor-κB (NF-κB), which also interacts with C/EBPβ, cooperates with MH2 and decreased DNA-binding and transcriptional activities of C/EBPβ on the TGF-β1 promoter These observations indicate that an autoregulatory mechanism, involving the MH2 domain of Smads, modulates activation of the TGF-β1 promoter by C/EBPβ Further, our results show that the interplay between NF-κB and C/EBPβ has an impact on the ability of C/EBPβ to stimulate TGF-β1 transcription, hence, suggesting that the cross-communication of signaling pathways that modulate NF-κB and C/EBPβ may dictate the level of TGF-β1 promoter activity

HIV-1 Vpr: a closer look at the multifunctional protein from the structural perspective.

Abstract: The human immunodeficiency virus-1 (HIV-1) Vpr protein plays multiple roles in HIV-1 replication In early infection, Vpr provides help in the nuclear localization of pre-integration complex Subsequently, Vpr induces cell cycle arrest of infected cells at G2/M phase Cell cycle arrest facilitates higher rate of viral gene transcription Vpr is also capable of activating transcription of viral and heterologous genes Vpr induces apoptosis in infected cells leading to loss of immune cells and onset of clinical AIDS Interestingly, Vpr is also considered as a passenger protein in the virus particles as it is incorporated into the virus particles through interaction with Gag The structure of full length Vpr has been resolved recently through NMR In this review, we have analysed the functions of Vpr using the available data from structural perspective Packing of the three helices of Vpr around a core formed by hydrophobic side chains and integrity of helical domains are critical for Vpr functions The distinct functions of Vpr have been attributed to structural integrity of different domains The unique distribution of acidic and basic residues in Vpr is an interesting feature Two hydrophobic pockets on the structure of Vpr are proposed to be important targets for modulating Vpr functions The inter-relationship between different functions of Vpr is discussed in the context of structure Based on bioinformatics analysis, we propose new targets for modulating Vpr functions, which need to be validated experimentally