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 alpha (mAKAPalpha/AKAP6alpha) is sufficient and necessary for axon growth by rat hippocampal neurons in vitro Here, we report that cAMP at mAKAPalpha signalosomes is regulated by local Ca2+ signaling that mediates activity-dependent cAMP elevation within that compartment. Simultaneous Forster resonance energy transfer (FRET) imaging using the PKA activity reporter AKAR4 and intensiometric imaging using the RCaMP1h fluorescent Ca2+ sensor revealed that membrane depolarization by KCl selectively induced activation of perinuclear PKA activity. Activity-dependent perinuclear PKA activity was dependent upon expression of the mAKAPalpha scaffold, while both perinuclear Ca2+ elevation and PKA activation were dependent upon voltage-dependent L-type Ca2+ channel activity. Importantly, chelation of Ca2+ 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 Ca2+ influx, providing local control for the enhancement of neurite extension.Significance statement cAMP-dependent signaling has been implicated as a positive regulator of neurite outgrowth and axon regeneration. However, the mechanisms regulating cAMP signaling relevant to these processes remain largely unknown. Live cell imaging techniques are used to study the regulation by local Ca2+ signals of an mAKAPalpha-associated cAMP compartment at the neuronal nuclear envelope, providing new mechanistic insight into CNS neuronal signaling transduction conferring axon outgrowth.

View details for DOI 10.1523/ENEURO.0298-20.2021

View details for PubMedID 33495246