Progress 12/01/03 to 12/31/07
Outputs
OUTPUTS: The primary goal of this project is to investigate mechanisms that regulate HIV transcription, in particular those that repress HIV transcription and contribute to proviral latency. We have shown that the receptor tyrosine kinase RON, which is expressed on tissue resident macrophages, represses HIV transcription by establishing a strong transcriptional pause suggesting that this is a critical regulatory step in provirus expression. HIV transcription could be induced by selectively targeting factors that negatively regulate transcription elongation or promote transcription termination. Based on the data HIV transcription is controlled by four distinct but coupled processes; transcription initiation, transcription elongation, transcription termination and chromatin structure. Related studies have indicated that Tat, a protein encoded by HIV, inhibits RON function by targeting this receptor for proteosome-dependent degradation. By diminishing RON expression, HIV establishes a
microenvironment that supports virus replication. Additional studies have characterized how non-receptor tyrosine kinases influence HIV transcription, packaging and replication. We have observed that the Src-kinase, Lck, and the Tec kinase, Itk, influence the packaging and release of the HIV virion. Current studies are examining the mechanisms by which these kinases influence assembly of HIV particles.
PARTICIPANTS: Avery August & Andrew Henderson (Veterinary & Biomedical Sciences)
TARGET AUDIENCES: State of Pennsylvania Citizens and health decision makers, national and international Health decision makers.
PROJECT MODIFICATIONS: Avery August was designated as PI upon the departure of Andrew Henderson.
Impacts
HIV latency presents a major barrier to eradicating virus from patients following current treatment protocols. In this study we are using biochemical and molecular approaches to understand how cellular signals influences HIV latency. Furthermore, studying how signal transduction alters HIV transcription will provide novel cellular targets that might be employed to control HIV replication. Finally, we hypothesize that HIV will serve as a paradigm for the expression of other genes regulated in macrophages and T cells, therefore providing general insights into mechanisms of tissue specific gene expression. This work could lead to novel ways to interfere with viral infections, including HIV and other lentiviruses.
Publications
- Peng, H.-H., S. Liang, A. J. Henderson, and C. Dong. 2007. Regulation of Interleukin-8 Expression in Melanoma-Stimulated Neutrophil Inflammatory Response. Exp. Cell Res. 331:551-559.
- Zhang, Z., A. Klatt, D. S. Gilmour, and A. J. Henderson. 2007. Negative Elongation Factor, NELF, Represses HIV Transcription by Pausing RNA Polymerase II Complex. J. Biol. Chem. 282:16981-16988.
- Kalantari, P., H. Vunta, U. D. Palempalli, C. C. Reddy, A. J. Henderson, and K. S. Prabhu. 2007. Nutritional control of HIV-AIDS - a case for selenium. Am. J. Infectious Diseases. 3:195-201.
- Zhang, Z., A. Klatt. A. J. Henderson, and D.S . Gilmour. 2007. Transcription termination factor Pcf11 limits the processivity of Pol II on an HIV provirus to repress gene expression. Genes Dev. 21:1609-1614.
- Kalantari, P. 2007. Positive and Negative Regulation of HIV in Macrophages: The Role of RON Receptor Tyrosine Kinase. Ph.D. Thesis. The Pennsylvania State University, University Park, PA. 156 pp.
- Klatt A. 2007. Cellular Signals Suppress HIV-1 Transcription by with Structural Reorganization and Activation of RNA Polymerase II Complex. Ph.D. Thesis. The Pennsylvania State University, University Park. PA. 265 pp.
- Strasner A. 2007. The Relationship Between T Cell Signals and HIV: The Positive and the Negatives. Ph.D. Thesis. The Pennsylvania State University, University Park, PA. 243 pp.
|
Progress 01/01/06 to 12/31/06
Outputs
The primary object of this project is to investigate how HIV infection leads to inappropriate inflammation and the onset of secondary diseases including those of the central nervous system. Furthermore, we have focused on how cellular signals establish HIV latency. Recent studies include determining how the receptor tyrosine kinase RON, which is expressed on tissue resident macrophages influence HIV transcription. We have shown that RON suppresses HIV transcription in macrophages by establishing a strong transcriptional pause suggesting that this is a critical regulatory step in provirus expression. Supporting this hypothesis, if we disrupt the complex responsible for establishing the pause, HIV expression is enhanced. Based on our findings HIV transcription is then regulated by four distinct but coupled processes; Transcription initiation, transcription elongation, transcription termination and chromatin structure. Related studies have indicated that Tat, a protein
encoded by HIV, inhibits RON function by targeting this receptor for proteosome-dependent degradation. By diminishing RON expression, HIV establishes a microenvironment that supports virus replication. We are looking at the expression of RON in brain and lung tissues to see if AIDS patients express reduce levels of the receptor. Additional studies have characterized how signaling CD28 influences HIV transcription, packaging and replication. We have observed that a critical Src-kinase for T cell activation, Lck, influence the packaging and release of the HIV virion. Furthermore, we have generated reagents to look at quantitative requirements for efficient signal transduction.
Impacts
In this study we are using biochemical and molecular approaches to understand how cellular signals influences HIV transcription in the context of macrophages and T cells. Studying how signal transduction alters HIV transcription will provide novel cellular targets that might be employed to control HIV replication in various macrophage subsets. Furthermore, these studies will provide new insights into how latent cell populations are established and maintained in different tissues. HIV latency presents a major barrier to eradicating virus from patients following current treatment protocols. In addition, understanding whether HIV modulates RON activity will provide critical insights into mechanisms that initiate and sustain HIV-associated pathologies. Finally, we will hypothesize that HIV will serve as a paradigm for the expression of other genes regulated in macrophages and T cells, therefore providing general insights into mechanisms of tissue specific gene
expression.
Publications
- Wilson, R.L., Fuentes, S.M., Wang, P., Taddeo, E.C., Klatt, A., Henderson, A.J., and He. B. 2006. Function of small hydrophobic proteins of paramyxovirus.J Virol. 2006 80:1700-1709.
- Gekonge, B. 2006. Membrane Asymmetry in Apoptotic Cells, Signals Associated with Phagocytosis and their Impact on HIV Transcription. Ph.D. Thesis. The Pennsylvania State University, University Park, PA. 133 pp.
- Gekonge B.N., Schiralli G., Schlegel, R.A., and Henderson, A.J. 2006. Signal transduction induced by apoptotic cells inhibits HIV transcription in monocytes/macrophages. J Leukoc Biol. 80:953-60.
|
Progress 01/01/05 to 12/31/05
Outputs
The primary focus of this project is to understand mechanisms by which HIV infection leads to inappropriate inflammation and the onset of secondary diseases including those of the central nervous system. For these studies we have examined how a receptor tyrosine kinase, RON, which negatively regulates macrophage functions associated with inflammation, regulates HIV transcription as well as how the virus impacts RON expression. Recent studies have indicated that decrease expression of RON is correlated with central nervous system disease in both a mouse model and human patients. Furthermore, signals initiated from RON inhibit the binding of specific transcription factors and transcriptional elongation factors to the HIV long terminal repeat which functions as the promoter for the provirus. These most recent data suggest that RON influences the initiation and efficiency of HIV transcription. Related studies have indicated that HIV inhibits RON function by targeting this
receptor for proteosome-dependent degradation. By diminishing RON expression and function, HIV appears to establish a microenvironment that is conducive for robust virus expression. Additional studies have characterized how signaling events in T cells influence HIV transcription, packaging and replication.
Impacts
In this study we are using biochemical and molecular approaches to understand how RON influences HIV transcription in the context of macrophages. Studying how RON alters HIV transcription will provide novel cellular targets that might be employed to control HIV replication in various macrophage subsets. Furthermore, these studies will provide new insights into how latent cell populations are established and maintained in different tissues. In addition, understanding whether HIV modulates RON activity will provide critical insights into mechanisms that initiate and sustain HIV-associated pathologies. Finally, RON regulates a number of other cellular genes and we suspect that this project will provide a better appreciation of general mechanisms of macrophage-specific gene expression during inflammation and wound repair.
Publications
- Tsutsui, S., Noorbakhsh, F., Sullivan, A., Henderson, A.J., Warren, K., Waltz, S. and Power, C. 2005. RON receptor tyrosine kinase-regulated innate immunity is protective in an animal model of multiple sclerosis. Ann. Neurol. 57:883-895.
- Ragin, M., Hu, J., Henderson, A.J. and August, A. 2005. A role for the Tec family kinase ITK in regulating SEB induced Interleukin-2 production in vivo via the JNK pathway. BMC Immunology 6:19
- Yang, P. 2005. Requirement for, and, Appropriation of, Activating Signals by HIV-1 in Infected CD4+ T Cells. Ph.D. Thesis. The Pennsylvania State University, University Park, PA. 133 pp.
- Peng, H.-H., Hodgson, L., Henderson, A.J. and Dong, C. 2005. Involvement of phospholipase C signaling in melanoma cell-induced endothelial cell junction disassembly. Front. Bioscience 10:1597-1606.
- Yang, P. and Henderson, A.J. 2005. Nef targets Cbl for hyper-phosphorylation in HIV-1 infected T cells. Virology 336:219-228.
|
Progress 01/01/04 to 12/31/04
Outputs
Inappropriate activation of macrophages and microglia cells contributes to several inflammatory diseases in the central nervous system including ischemia, Multiple Sclerosis and HIV-associated dementia. We have been focusing on how HIV infection leads to the aberrant induction of inflammatory mediators which directly contribute to central nervous system diseases. The mechanisms that initiate and maintain inflammation after HIV-1 infection in the brain have not been well studied. Furthermore, it is not understood why in HIV-associated central nervous system diseases, macrophages and microglia are biased toward inflammation rather than production of mediators that control inflammation. We have focused on the receptor tyrosine kinase RON, a critical negative regulator of macrophage function and inflammation, to determine whether this receptor regulates HIV-1 expression. Overexpressing RON in monocytes/macrophages demonstrates that RON inhibits HIV proviral transcription
in part by decreasing the binding activity of NF-kappaB to the HIV-1 long terminal repeat. The signal transduction events emanating from RON are currently being explored. Because macrophages and microglia cells are a critical reservoir for HIV-1 in the CNS, we examined brain tissues for RON expression and detected RON in astrocytes, cortical neurons, and monocytoid cells. RON was detected in all control patients who were HIV seronegative (n = 7)), whereas six of nine brain samples obtained from AIDS patients exhibited reduced RON protein. These data suggest that RON initiates signaling pathways that negatively regulate HIV-1 transcription in monocytes/macrophages and that HIV-1 suppresses RON function by decreasing protein levels in the brain to assure efficient replication. Furthermore, HIV-1 infection would compromise the ability of RON to protect against inflammation and consequent CNS damage. HIV-dependent mechanisms that overcome these signals are currently being examined. Recent
results suggest that the HIV-encoded transcriptional activator, Tat, can bypass the suppressive affect of RON signaling. Mechanisms by which Tat overcomes the negative signals of RON are currently under investigation.
Impacts
Using a combination of cellular and biochemical approaches signals that potentially inhibit HIV expression will be characterized. Some of these signals protect the brain against damage but HIV infection can disrupt these signals, trigger inappropriate inflammation and severe central nervous system disease. Studying how signals alter alter HIV expression will provide novel targets that might be used to control HIV infection. In addition, understanding whether HIV directly targets these negative signals to assure its own replication will provide insights into mechanisms that initiate and sustain HIV-associated CNS pathologies as well as provide rational targets for prevention and treatment of these diseases.
Publications
- Lee, E. S., Kalantari, P., Tsutsui, S., Klatt, A., Holden, J., Correll, P. H., Power, C. and Henderson, A. J. 2004. The receptor tyrosine kinase RON, a negative regulator of inflammation, inhibits HIV transcription and is decreased in brains of AIDS patients. J. Immunol. 173:6864-6872.
|
|