Sleep disruption is tightly associated with Alzheimer's disease (AD), and recent studies suggest it can be causal. While somnopathic paths to AD remain poorly understood, the variety of such disorders associated with chronic sleep loss suggest that these mechanisms are general. This proposal aims to leverage a Drosophila model of presenilin (psn) hypofunction, the leading cause of familial Alzheimer's disease in humans, to investigate these mechanisms. Psn+/- flies have sleep-dependent memory and synaptic defects reminiscent of AD, and a whole- fly metabolomic screen we conducted identified a possible mechanism for these phenotypes: urea cycle hyper- activity, present in both psn+/- and sleep-deprived wild-type flies. I hypothesize that urea cycle disruption couples sleep loss to Alzheimer's disease, perhaps via regulation of autophagy.
Aim 1 will test whether urea cycle dysfunction links sleep disturbance to dementia-like psn+/- memory phenotypes, by examining how additional sleep manipulation modulate urea cycle throughput and testing the effects of urea cycle blockade and sleep deprivation on psn+/- memory defects.
Aim 2 will test whether sleep disturbance and urea cycle dysfunction are the causes of reduced autophagy in psn+/- flies, by testing the effects of urea cycle blockade, enforced sleep, and sleep deprivation on deposition of insoluble ubiquitinated protein aggregates and live- imaged autophagy flux.
Aim 2 will also test whether sleep deprivation is sufficient to disrupt autophagy in wild-type flies, and whether sleep deprivation in psn+/- flies can induce neuronal apoptosis as measured by TUNEL. Finally, Aim 3 will screen the brain metabolomes of psn+/- and sleep-deprived wild-type flies by mass spectroscopy for metabolic pathways our whole-fly screen may have missed, as well as determining whether urea cycle dysregulation by sleep disturbance occurs locally in the psn+/- brain. Through the innovative research strategy described in this proposal, Dr. Joseph Bedont will be trained in a new organism, to study fields in which he has room for growth, using several new techniques including mass spectroscopy. The proposed site, the University of Pennsylvania, provides all of the technical and intellectual resources necessary for success. The proposed sponsor, Dr. Amita Sehgal, is a world expert in Drosophila behavioral genetics and sleep, and a very successful mentor who will provide excellent scientific and career development support to the applicant. And the proposed training plan, especially activities planned with the sponsor and her long-standing collaborator Dr. Aalim Weljie, will provide all of the skills the applicant requires to fully leverage the training potential of the proposal. This proposal will give insight into whether urea cycle and autophagy dysregulation by sleep disturbance is an important contributor to somnopathic neurodegeneration in Alzheimer's disease, and identify possible additional paths to somnopathy for investigation in future studies.
Chronic sleep disruption may represent a common proximal cause of Alzheimer's disease and other neurodegenerative disorders, but the mechanism(s) by which sleep disturbance contribute to neurodegeneration are unclear. The overall aims of this proposal are to determine whether urea cycle disruption we show to occur after sleep deprivation and in presenilin hypofunctional flies contributes to Alzheimer's disease-like phenotypes in presenilin flies, and to identify additional candidate metabolic pathways that may link sleep to Alzheimer's disease. Long-term, this study represents an important step toward identifying potential points of therapeutic intervention early in the progression of Alzheimer's disease, when sleep defects tend to be pronounced, but proteinopathy and cell death are not yet severe.
