Project #3. Positive feedback interaction between HIV-1 and HIF-1 a signaling pathway. HIV-1 infection of brain usually results in chronic inflammation, secretion of toxins, and induction of oxidative stress. Oxidative stress factors such as hydrogen peroxide, superoxide, and most notably, hypoxia inducible factor 1 alpha (HIF-1 a) can accelerate disease development and progression by activating HIV-1 replication and dysregulating cell function. HIF-1 a is a transcriptional activator that functions as a chief regulator of cellular and systemic oxygen homeostasis. Histological evaluation of AIDS brains with encephalitis revealed activation of HIF-1 a in several cells including microglia, macrophages, and astrocytes, all of which are targets for infection with HIV-1 and support its replication to various degrees. Accordingly, results from cell culture studies showed elevated levels of HIF-1 a upon infection of primary microglial cells with HIV-1. Further examination of HIF-1a expression in the presence of HIV-1 proteins suggested a major role for Vpr in induction of HIF-1 a at the transcription and post-transcription levels. While the molecular events involved in the elevation of HIF-1 a by Vpr remain to be investigated, our preliminary observations pointed to the activation of HIF-1 a transcription via cooperation of Vpr with the Sp1 and NF-icB transcription factors, and enhancement of the stability of HIF-1 oc protein by a series of reactors involving TNFoc, reactive oxygen species (ROS) and MAPK. Interestingly, the increase in the level of HIF-1 a has an impact on HIV-1 gene expression and several other host cell functions. For example, by cross-communicating with the p65 subunit of NF-icB, HIF-1 a can stimulate LTR transcription. Further, by influencing expression of several cell cycle controllers, including p21, HIF-1a can dysregulate cell cycle progression, affecting DMA repair and induce cellular abnormalities including mitochondria, presumably cytochrome c release. Thus, it is evident that the interplay between HIF-1 a and the HIV-1 regulatory proteins, Vpr and its cooperativity with several key cellular proteins, plays a seminal role in host homeostasis and viral gene expression and replication in CNS. The experimental design in this project will include a series of molecular, virological and histological approaches to unravel the mechanism of HIF-1 a involvement in HIV-1 induced CNS diseases. The outcome of these studies will shed light on undefined pathways by which HIV-1 exploits the cellular machinery to its own advantage. a
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