cAMP at Perinuclear mAKAPα Signalosomes Is Regulated by Local Ca<sup>2+</sup> Signaling in Primary Hippocampal Neurons
Tomasz Boczek, Qian Yu, Ying Zhu, Kimberly L. Dodge‐Kafka, Jeffrey L. Goldberg, Michael S. Kapiloff
Abstract
The second messenger cyclic adenosine monophosphate (cAMP) is important for the regulation of neuronal structure and function, including neurite extension. A perinuclear cAMP compartment organized by the scaffold protein muscle A-kinase anchoring protein a (mAKAPa/AKAP6a) is sufficient and necessary for axon growth by rat hippocampal neurons in vitro. Here, we report that cAMP at mAKAPa signalosomes is regulated by local Ca 21 signaling that mediates activity-dependent cAMP elevation within that compartment. Simultaneous Forster resonance energy transfer (FRET) imaging using the protein kinase A (PKA) activity reporter AKAR4 and intensiometric imaging using the RCaMP1h fluorescent Ca 21 sensor revealed that membrane depolarization by KCl selectively induced activation of perinuclear PKA activity. Activity-dependent perinuclear PKA activity was dependent on expression of the mAKAPa scaffold, while both perinuclear Ca 21 elevation and PKA activation were dependent on voltage-dependent L-type Ca 21 channel activity. Importantly, chelation of Ca 21 by a nuclear envelope-localized parvalbumin fusion protein inhibited both activity-induced perinuclear PKA activity and axon elongation. Together, this study provides evidence for a model in which a neuronal perinuclear cAMP compartment is locally regulated by activity-dependent Ca 21 influx, providing local control for the enhancement of neurite extension.