The role of wake-associated protein kinase A transients in intrinsic plasticity and learning through aging

项目总结:

Project Summary: Cognitive deficits including disruptions in hippocampal-dependent memory are a hallmark of aging. Predictably, aging-associated cognitive decline is exacerbated by sleep disruptions commonly seen in the aging and elderly population. However, there is a significant lack of understanding about the mechanism behind the interconnected processes of sleep, aging and learning. One significant challenge to unraveling these mechanisms has been the lack of tools to study intracellular and extracellular signals in real time with high temporal resolution. This has made it difficult to observe the modulation of these signals alongside such dynamic processes as sleep, learning and aging. To address these challenges, our lab developed a fluorescence-lifetime based optical sensor, FLIM-AKAR, which when used in combination with a custom-built fluorescence lifetime photometry (FLiP) rig has allowed us to observe the activity of cAMP-dependent protein kinase A (PKA), an important plasticity signal that has been implicated in the formation and consolidation of sleep-dependent learning and has been shown to enhance learning in aging mice. Paring 24-hour FLiP recordings in hippocampal CA1 with simultaneous electroencephalography (EEG) and electromyography (EMG) measurements revealed a synchronized, transient activation of PKA that is associated with transitions from sleep to wake. Due to its short duration, this signal has never been observed before in a behaving animal. Thus, this study aims to explore its function on both cellular and behavioral levels and elucidate how those functions may change in aging mice. Using photoactivatable adenylate cyclase (biPAC) and perforated patch clamp, I will determine whether transient PKA activation is sufficient to cause an increase in intrinsic excitability (IE), a known function of PKA and a known cellular correlate of learning. Further, by using biPAC and photoactivatable protein kinase inhibitor peptide (PA-PKI) to bidirectionally manipulate this transient PKA signal, I aim to determine whether increasing the frequency of these transients can rescue hippocampal- dependent learning deficits in aging mice or disrupt intact hippocampal-dependent learning in adult mice. Ultimately, our findings will provide a more nuanced understanding of how PKA functions at physiologic timescales and in the context of aging, sleep, and learning. This study will also stand as an example of how taking advantage of new optical tools can bolster our understanding of how the dynamics of cell signaling relate to complex behaviors.