Clearance Pathways in the CNS in Aging and HIV

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DESCRIPTION (provided by applicant): Currently over 30 million people live with HIV worldwide. In the US, the aging population represents one of the fastest growing groups with HIV. The Center for Disease Control estimates that by the year 2015, half of all Americans living with HIV will be over the age of 50. The mechanisms of neurodegeneration in aged individuals are not completely understood, however HIV activates apoptotic pathways, dysregulates calcium homeostasis and promotes oxidative stress. Moreover, recent studies have shown that HIV proteins might interfere with clearance pathways such as autophagy, a pathway necessary for protein quality control and elimination of defective older intracellular organelles. Deficits i autophagy have been described in Alzheimer's Disease (AD), Parkinson's Disease (PD) and other aging-related disorders, similarly, neurodegeneration has been linked to defects in autophagy in patients with HIV. We have recently shown that abnormal functioning of the autophagy pathway is associated with progressive accumulation of Amyloid-beta (A¿), ¿-synuclein (¿-syn) and Tau in the CNS of aged HIV human cases and in transgenic (tg) mice expressing HIV-gp120 protein (GFAP-gp120 tg). In this context our hypothesis is that HIV proteins such as Nef might interfere with autophagy by interacting with components of the autophagocytic pathway such as Beclin1. In aged patients with chronic HIV infection, this might result in reduced clearance of neurotoxic proteins and neurodegeneration. The main objectives of this proposal will be to a) better understand the mechanisms through which HIV proteins interfere with autophagy leading to protein accumulation and neurotoxicity, and b) to determine whether activation of the autophagy pathway is neuroprotective in preclinical models of HIV neurotoxicity and aging. For this purpose we propose the following Aims: Aim 1: To analyze interactions between HIV proteins and components of the autophagy pathway in brains of aged patients with chronic HIV infection. Aim 2: To investigate the role of HIV proteins in the cellular mechanisms of autophagy dysfunction and neurotoxicity. Aim 3. To determine whether autophagy activation in vivo ameliorates neurodegenerative and behavioral deficits in aged transgenic rodent models of HIV neurotoxicity. This project has the potential to further elucidate the role of autophagy as key downstream mediator of HIV-protein neurotoxicity during aging, which could lead to the development of new therapies and models of HIV-associated neurodegeneration and neuroprotection. Since alterations in autophagy are also present in AD and PD, this project may have broader applications for therapeutic advancements in other age-related neurodegenerative disorders. PUBLIC HEALTH RELEVANCE: In the US, the aging population represents one of the fastest growing groups with HIV however the mechanisms underlying neurodegeneration in aged HIV individuals remain unclear. Recent studies have shown that HIV proteins might interfere with autophagy, a pathway necessary for protein quality control. For this project we propose to better understand the mechanisms through which HIV proteins interfere with autophagy leading to protein accumulation and neurotoxicity, and to determine whether activation of the autophagy pathway is neuroprotective in preclinical models of HIV neurotoxicity and aging.