The Role of cAMP/PKA Dysregulation in Aging and the Initial Stages of Alzheimer'sDisease

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Project Summary/Abstract Late-onset Alzheimer’s disease (LOAD) is a growing public health crisis that already costs our country billions of dollars each year. Currently there are no treatments to slow the progression of LOAD. Age is the largest risk factor for LOAD. There are two key pathological hallmarks of the disease, amyloid beta plaques and neurofibrillary tangles composed of hyperphosphorylated tau. This project focuses on studying the molecular mechanisms by which aging contributes to initial stages of LOAD pathology, particularly tau phosphorylation. To better understand these mechanisms, this project takes advantage of two animal models, aged rats and macaques. Macaques represent a close approximation of the human aging cortex in regards to circuitry and LOAD pathology; however, they are technically challenging. Rats on the other hand do not develop plaques or tangles but do demonstrate age-related cognitive decline and preliminary evidence suggests they present with early stages of tau phosphorylation. Furthermore, rodents provide a breadth of molecular tools to investigate the exact mechanisms by which age-related changes contribute to AD pathology. Previous work from the Nairn and Arnsten labs has demonstrated an increase in cAMP/PKA signaling with age in both of these models, which correlates with tau phosphorylation and cognitive decline. Thus, the proposed project examines the molecular drivers of aberrant cAMP/PKA signaling with age. Aim 1a investigates the role of age-related increases in neuroinflammatory signaling in driving excess cAMP production by removing the brakes, through dysregulation of phosphodiesterases. Aim 1b focuses on the ways in which increases in cAMP/PKA signaling generate a deleterious positive-feedback signaling cascade through phosphorylation of the ryanodine receptor. I plan to investigate how PKA phosphorylation of the ryanodine receptor can increase calcium release from ryanodine receptors and further drive cAMP production. Both of these sub-aims examine the effects of aberrant signaling on PKA phosphorylation of tau and their impact on cognitive decline. Aim 2 expands the scope of these studies through the development of a novel mass spectrometry approach to analyze phosphorylated tau. This novel approach is able to monitor phospho-sites throughout the protein as well as the enrichment of kinase motifs between conditions; thus, enabling a more complete understanding of tau modifications, and the signaling pathways underlying them. Combining this new approach with traditional biochemical assays of tau protein behavior with the use of phosphomimetics, Aim 2 will be able to investigate the important steps by which age-related changes in cAMP/PKA contribute to LOAD tau pathology. Through the aims of this project I will receive extensive training in mass spectrometry, biostatistics, and cortical neurobiology, all of which will prepare me for my desired career in translational neurobiology research. Overall, this project investigates novel molecular targets that represent new therapeutic targets for the treatment of LOAD.