Characterization of the redox control of HIV-Tat proteostasis by cellular NQO1

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1) Project Summary/Abstract Latent human immunodeficiency virus (HIV) persists in pools of dormant infected cells (called “viral reservoirs”) that are unaffected by combined antiretroviral therapies (cARTs). Anatomic compartments hard to reach with therapeutic drugs as the brain and gut are viral sanctuaries harboring reservoirs or maintaining low-grade infections. In virologically suppressed individuals, latent proviruses in those reservoirs become stochastically active upon the discontinuation of cART, reseeding the infection. HIV infects long-lived brain cells indirectly damaging neurons. The action of a persistent brain infection causes a set of syndromes called HIV associated neurocognitive disorders (HAND). cART decreased the incidence of severe HAND such as HIV-associated dementia; however milder forms of HAND still are prevalent, having a disproportionate incidence on racial/ethnic minorities and a considerable socioeconomic impact. Viral neurotoxins to be released by infected cells despite cART and the oxidative stress caused by the cART drugs themselves are both significant factors in HAND. All the above support the need for efficient suppression of the HIV infection. Disable integrated proviruses using gene editing, although promising, is still a risky proposition and has several major issues, such as the generation of escape mutations, which must be resolved before moving gene-editing to clinical use. Eradication/sterilization of the infected cells could have adverse outcomes in the CNS sensitive/drug- protected environment. The reservoirs inactivation by inducing deep-latency (“block and lock”) strategies are more suitable for the brain because they do not require activate, killing, and clearing the infected brain cells Nevertheless, all of these strategies require a level of control on the provirus activity explaining the considerable interest in understanding viral latency mechanisms. A feedback mechanism driven by the expression of the trans-activator of transcription (Tat) protein regulates productive provirus transcription. Tat cellular levels under or over a threshold result in provirus entry or exit from latency. A pharmacologically exploitable feedback mechanism, involving the viral regulatory protein Rev and a host cytoprotective enzyme NQO1, stabilizes the cellular level of Tat (proteostasis) required for the virus. NQO1 also stabilizes cellular levels of many proteins essential for the cell well-being maintenance and to cope with the viral infection. Our objective is to investigate this poorly characterized proteostasis mechanism to facilitate its targeting. We are proposing to investigate: (1) the physical complexes involved, their association thermodynamics, and structure, using biophysical methods with purified proteins; and (2) the effect of modify NQO1 activity on viral latency, on the damage to neurons produced by extracellular Tat or cART, and off-target effects on oxidative- and unfolde protein stress responses. Controlling proviral transcription by disrupting Tat proteostasis has the potential to be a significantly synergistic part of viral activity manipulation in the eradication or lifelong inactivation of viral reservoirs, as well as of neuroprotective therapies that decrease the detrimental effects of Tat in the CNS.