TY - JOUR T1 - Temporally and Spatially Localized PKA Activity within Learning and Memory Circuitry Regulated by Network Feedback JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0450-21.2022 SP - ENEURO.0450-21.2022 AU - James C. Sears AU - Kendal Broadie Y1 - 2022/03/17 UR - http://www.eneuro.org/content/early/2022/03/17/ENEURO.0450-21.2022.abstract N2 - Dynamic functional connectivity within brain circuits requires coordination of intercellular signaling and intracellular signal transduction. Critical roles for cAMP-dependent Protein Kinase A (PKA) signaling are well established in the Drosophila Mushroom Body (MB) learning and memory circuitry, but local PKA activity within this well-mapped neuronal network is uncharacterized. Here, we use an in vivo PKA activity sensor (PKA-SPARK) to test spatiotemporal regulatory requirements in the MB axon lobes. We find immature animals have little detectable PKA activity, whereas post-critical period adults show high field-selective activation primarily in just 3/16 defined output regions. In addition to the age-dependent PKA activity in distinct α’/β’ lobe nodes, females show sex-dependent elevation compared to males in these same restricted regions. Loss of neural cell body Fragile X Mental Retardation Protein (FMRP) and Rugose (human Neurobeachin) suppresses localized PKA activity, whereas over-expression of MB lobe PKA-synergist Meng-Po (human SBK1) promotes PKA activity. Elevated Meng-Po subverts the PKA age-dependence, with elevated activity in immature animals, and spatial-restriction, with striking γ lobe activity. Testing circuit signaling requirements with temperature-sensitive shibire (human Dynamin) blockade, we find broadly expanded PKA activity within the MB lobes. Using transgenic tetanus toxin to block MB synaptic output, we find greatly heightened PKA activity in virtually all MB lobe fields, although the age-dependence is maintained. We conclude spatiotemporally restricted PKA activity signaling within this well-mapped learning/memory circuit is age-dependent and sex-dependent, driven by FMRP-Rugose pathway activation, temporally promoted by Meng-Po kinase function, and restricted by output neurotransmission providing network feedback.Significance StatementLearning and memory requires the coordination of cell-cell circuit interactions with the appropriate downstream signal transduction. Plasticity regulation via cAMP-dependent PKA activation is among the best-characterized signaling pathways, but until recently it was very challenging to localize PKA signaling within brain circuits. We employ a new PKA biosensor to visualize local signaling in the Drosophila Mushroom Body; a network model consolidating ∼2000 Kenyon Cells into ∼16 output fields per brain hemisphere. We discover heightened PKA activity in just a few circuit regions, with age-dependent and sex-dependent requirements. Learning/memory mutants linked to intellectual and autism spectrum disorders reduce PKA activity. In contrast, PKA-synergist Meng-Po increases PKA activity. Neurotransmission blockade elevates and expands PKA activity, showing network feedback restricts localized signaling. ER -