Protein degradation and age-related cognitive impairment

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Project abstract: The cognitive deficits that occur in normal aging as well an in age-related neurodegenerative disease are a major public health challenge. Recent work has highlighted the importance of protein homeostasis in the aging process in general, and in maintaining the functional integrity of neurons in particular. Deficits in protein degradation and targeted autophagy have been linked to several neurodegenerative disorders including Alzheimer's disease. The ubiquitin- proteasome system (UPS) is a major mechanism for protein regulation in all eukaryotic cells. Importantly, our research over the last several years has highlighted the key role of protein degradation driven by specific cellular activity in the induction and stability of synaptic plasticity related to memory in several key brain areas. The formation as well as the subsequent retrieval and use of simple associative memories involve increased polyubiquitination of key regulatory and structural proteins. Both learning and memory recall also trigger a CaMKII-dependent increase in the activity of the 20S proteasome. This proposal describes work that will evaluate our recent preliminary observation that alterations in UPS function may be a critical factor underlying memory impairments in aged rats. Under Aim 1 we will quantify proteasome activity and key activity related signals (e.g., phosphorylation of Rpt6) in young adult (3 mo), middle aged (15 mo) and aged (22 mo) animals. We will compare unstimulated values to those seen after retrieval of previously learned information and compare data from the hippocampus, amygdala, and prefrontal cortex. Aim 2 will test whether dietary pretreatment with methylene blue, which should upregulate metabolic and proteolytic capacity in neurons, will rescue age- related deficits in memory and UPS activity. Together, this set of experiments could provide the basis for several new lines of work related to the neurobiology of age-related cognitive impairment.