The Research On Mechanisms Of Autophagy And Metabolismrelated Factors Involved In HIV-1 Tat Transactivation

The human immunodeficiency virus-1(HIV-1) is a retrovirus that causes the acquired immunodeficiency syndrome(AIDS). Trans-activator of transcription(Tat), which can transactivate HIV-1 long terminal repeats(LTRs) is encoded by tat gene. Due to the significant role in HIV-1 life cycle of Tat, Tat maybe become the novel target in anti-HIV research. Autophagy and metabolism status paly an important role in the processes of virus infection. In this subject, we mainly studied the effects of autophagy and metabolism-related factors on HIV-1 Tat transactivation and their molecular mechaisms. Tanshinone II A is the extract from traditional Chinese medical herbs Danshen, it has been shown to involve in many biological activities including anti-tumor, anti-oxidative, antiviral, anti-mutagenic, and so on. We explored the effects of Tanshinone II A on metabolism, and the consequent effects on HIV-1 Tat transactivation and its signaling pathway.In this study, we found that Tat could promote the phosphorylation of protein kinase B(Akt) and mammalian target of rapamycin(mTOR), activated Akt/mTOR signaling pathway, thus decreased the expression of autophagy-related proteins ATG 7, ATG 5 and Beclin 1. PI3K(phosphatidylinositol 3-kinase)/Akt/mTOR signaling pathway inhibitors rapamycin and 3-methyladenine could reverse the process. Besides, metabolism-related factors pyruvate kinase M2(PKM2) and AMP-activated protein kinase(AMPK) could change the level of autophagy through Akt/mTOR signaling pathway, the knockdown of PKM2 and the activation of AMPK by AICAR blocked Akt and mTOR phosphorylation, inhibited Akt/mTOR signaling pathway, consequently improved the expression of autophagy-related proteins ATG 7, ATG 5 and Beclin 1 in TZM-bl cells. Conversely, the knockdown of AMPK played a opposite role on Akt/mTOR signaling pathway and autophagy. Rapamycin, 3-methyladenine, knockdown of PKM2 and activation of AMPK inhibited HIV-1 Tat transactivation, while the knockdown of AMPK played the inverse effects. PI3K/Akt/mTOR signaling pathway, PKM2 and AMPK regulated HIV-1 Tat transactivation through the regulation of autophagy,Tanshinone II A, as an antioxidant, altered cellular redox status through promoting the expression of nuclear factor erythroid2-related factor2(Nrf2), it reversed Tat-induced production of reactive oxygen species(ROS) and decline of glutathione(GSH) level. Tanshinone II A improved silent mating type information regulation 2 homolog 1(SIRT1) activity inhibited by Tat without the alteration of SIRT1 protein expression. Also, Tanshinone II A reversed the inhibition of Nicotinamide Phosphoribosyltransferase(Nampt) expression and depletion of nicotinamide adenine dinucleotide(NAD+) induced by Tat through the activation of AMPK signaling pathway. Tanshinone II A inhibited HIV-1 Tat transactivation through redox-regulated AMPK-Nampt-SIRT1 pathway.In conclusion, autophagy was involved in HIV-1 Tat transactivation. Metabolism-related factors effected HIV-1 Tat transactivation through the regulation of autophagy and Nampt-SIRT1 pathway. The study on relationship of autophagy, metabolism-related factors and HIV-1 Tat transactivation makes us have a deeper understanding of interaction between host cells and viruses, thus provides a new inspiration for treatment and drug screening of HIV-1.