Age Impaired ER Homeostasis in Wake-Active Neurons: BiP/Nox2 Crosstalk

University Of Pennsylvania, Philadelphia PA

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Abstract

DESCRIPTION (provided by applicant): Normal aging results in a relentless deterioration of both sleep and wakefulness. Impairments in both behavioral states become more pronounced in many age-dependent neurodegenerative processes. Impaired wakefulness interferes with cognitive function and quality of life for millions of older Americans. The proposed studies are a collaborative effort between two labs to merge pathways of age-related neural injury that each lab has identified. Dr. Naidoo has recently demonstrated that prolonged wakefulness activates the unfolded protein response in the brain. Young mice maintain protein homeostasis, in part, by increasing BiP and attenuating protein translation. In contrast, aged animals mount an insufficient BiP response and manifest ER dyshomeostasis with increased GADD153/CHOP. Her lab will explore the role BiP plays in age-related declines in ER homeostatic response to prolonged wakefulness using murine models with altered BiP levels globally and in select wake neuronal groups (Aim 1). Dr. Veasey's laboratory has identified neuronal NADPH oxidase as a major contributor to protein damage in a model of oxidative injury. These NADPH oxidase-positive neurons (noradrenergic and dopaminergic) develop age-related impaired ER homeostasis earlier than in non-NADPH oxidase wake neurons. Her group has identified increased endoplasmic reticulum (ER) injury with GADD153/CHOP activation, ribosomal disaggregation and protein aggregation in the NADPH oxidase-positive wake neurons. Having select groups of wake-active neurons with differential age-related injury presents a valuable tool with which to identify mechanisms by which aging impairs wake function. We hypothesize that repeated NADPH oxidase activation in catecholaminergic neurons across the lifetime disrupts ER homeostasis in these neurons sufficiently to result in a progressive accumulation of irreversibly misfolded proteins (Aim 2). The studies are designed to determine why select populations of wake neurons are more susceptible to age-related injury and will link two pathogenic mechanisms implicated in the aging of protein homeostasis to explain differential susceptibility to aging decline in neuronal function. Wake impairments may lead to novel therapeutic approaches to enhance daytime functioning in healthy elderly and those with neurodegenerative processes. The proposed studies examine mechanisms by which aging impairs wakefulness. We hypothesize that an oxidase enzyme in wake neurons progressively disrupts the chaperoning system in the endoplasmic reticulum. Consequently protein homeostasis is compromised and toxic protein aggregates accumulate.