The goal of this proposal is to characterize neuronal mitochondria function during HIV-associated neurocognitive disorders (HAND) and the mechanisms by which HIV proteins disrupt homeostatic neuronal mitochondria fission/fusion processes. Despite 30 years of research and the advent of highly active antiretroviral therapy (HAART), HAND persist. Moreover, HAART increases life expectancy and an increasingly large pool of HIV patients are managing viral infection confounded by processes of aging. Accordingly, there is great need for therapies capable ameliorating the devastating effects of HIV infiltrating the central nervous system (CNS). HIV enter the CNS in monocytes and subsequently reproduce, infect CNS cells and initiate a battery of inflammatory cascades that ultimately result in synaptic degradation, neurodegeneration and HAND. Progress has been made, but effective treatment for HAND remains elusive. Recent studies show that HIV proteins may interfere with normal function of mitochondrial fission/fusion proteins DRP1 and Mfn2, which may affect fission/fusion and mitophagy. Our preliminary data show DRP1 is increased and Mfn1 and Mfn 2 are decreased in postmortem brain tissue of HIV infected patients, suggesting a pro-fission environment. We found that recombinant HIV negative regulatory factor (Nef) and glycoprotein (gp)120 similarly increase neuronal DRP1 and decrease neuronal Mfn1 and Mfn2. These and other studies suggest mitochondria fission/fusion may be impaired in the CNS during HIV infection;a potential contributor to HAND. Therefore, we hypothesize that HIV proteins, Nef and/or gp120 bind DRP1, Mfn1 and/or Mfn2 and disrupt homeostatic mitochondria fission/fusion processes in neurons. To explore this possibility we propose the following aims:
Aim 1 : To characterize DRP1, Mfn1 and Mfn2 expression patterns and their interactions with HIV proteins in postmortem brain tissues from HIV infected donors.
Aim 2 : To investigate the role of HIV proteins in the cellular mechanisms of mitochondrial fission/fusion dysfunction and resulting neurotoxicity. To complete Aim 1 tissue from the California NeuroAIDS consortium will be analyzed for DRP1, Mfn1 and Mfn2 expression and their interactions with HIV proteins by co-immunoprecipitation, immunoblot, real-time polymerase chain reaction (RT2PCR), enzyme-linked immunosorbent assay (ELISA) and quantitative immunohistochemistry.
Aim 2 will be completed using lentiviral (LV) vectors expressing Nef, gp120, dominant negative (DN) DRP1, Mfn1 and Mfn2 in neuronal and microglial cell lines. DRP1, Mfn1 and Mfn 2 expression levels and function will be assessed via coimmunoprecipitation, immunoblot, RT2PCR, and quantitative immunocytochemistry. Completion of these studies will shed light on mitochondrial function during HIV infection. Scheme A [is that] HIV-infected microglia secrete progeny virus, cytokines and toxic viral proteins that lead to neurodegeneration and HAND. [Scheme] B [is that] proper functioning mitochondria fission/fusion processes are necessary for maintaining and constructing new neural pathways. Interference may lead to neurodegeneration via toxic viral proteins: 1. Binding neuron receptor and affecting DRP1 expression and/or 2. Binding fission/fusion machinery directly (DRP1, Mfn1, Mfn2) and altering function or half-life. These studies will provide valuable insight into neuronal mitochondria dynamics during HAND and other CNS disease, and possibly provide novel therapeutic targets.
Worldwide, over 30 million people are infected with HIV, and aged (>50 y/o) patients represent the fastest growing group of HIV-infected persons in the United States. As high as 50% of HIV patients are affected by HIV-associated neurocognitive disorders, and these effects are exacerbated with age. Our studies will provide details about how brain mitochondria fission and fusion mechanisms, essential for building new neural pathways, function during HIV pathogenesis of the brain.