SELENOPROTEINS, NF-KB, AND HIV DISEASE IN IV DRUG USERS

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At a 1998 NIDA-sponsored workshop, the need for further research on the role of nutritional and metabolic factors in HIV/drug abuse was established. The evidence reviewed included data showing that malnutrition and low levels of the trace mineral selenium (Se) and other antioxidants are commonly evident in IV drug users (IDUs), who also show increased oxidative stress and lipid peroxidation as a consequence of IV drug use. Because a progressive decline in serum Se is well documented in HIV/AIDS, and correlations between Se status and HIV disease progression are firmly established, IDUs as a group are at increased risk for accelerated HIV-related morbidity and mortality. Significantly, some viruses, including a pox virus and HIV-1 (our preliminary data), encode homologues of glutathione peroxidase (GPx), the prototypical mammalian selenoprotein, in which selenocysteine is encoded by the UGA codon. This is particularly relevant for HIV- 1, because recent studies have shown that two cellular selenoproteins, GPx and thioredoxin reductase (TDR), are potent regulators of transcription factor NF-kappaB, which in turn regulates HIV-1 gene expression. Our preliminary theoretical and experimental data show that a novel HIV-1 gene, env-fs, is encoded in an overlapping reading frame of the env gene, and that the protein it codes for is a highly truncated Se-dependent GPx module, enzymatically active in in vitro assays. We have also identified several other active -1 frameshift sites and potential UGA suppression sites in HIV-1, in the protease and nef coding regions; the latter site has clear sequence similarities to the redox centers of TDR. This study will assess the hypothesis that these viral selenoproteins are involved in the connection between Se status and HIV-1 disease progression. Using in vitro methods, the specific aims are A1: to show that the relevant HIV-1 gene regions encode functional selenoproteins that have demonstrable biological activity, and that these novel proteins or isoforms (e.g. the extended nef TDR homolog) are actually expressed in infected cells; A2: to study the effects and interactions of the predicted viral selenoproteins (GPx, extended nef, pro-fs) on HIV-1 gene expression and activation by oxidative stress; A3: to show that viral selenoprotein synthesis contributes to the decline in cellular selenoprotein levels that has been previously demonstrated in HIV-1 infected cells, and that Se supplementation of infected cells can partially reverse this effect. The long- term goal is to establish a molecular basis for the use of Se supplements as a chemoprotectant in HIV+ drug users.