The lncRNA Gas5 is an activity-responsive scaffold that mediates cAMP-dependent synaptic plasticity.

Changes in the transcriptome are critical in shaping the structural plasticity of neurons, which underpins learning and long-term memory storage. Here, we explored the effect of two opposing, plasticity-associated pathways-cAMP second-messenger signaling and metabotropic glutamate receptor (mGluR1 and mGluR5) signaling-on the transcriptome in hippocampal neurons and how these pathways operate in distinct and coordinated manners to induce structural changes. Integration of transcriptome data and molecular pathway analysis identified central "hub" genes that were rapidly induced by cAMP and/or mGluR1/5 in hippocampal neurons. These included the long noncoding RNA (lncRNA) Gas5, whose expression was induced specifically by cAMP and which was targeted to dendrites by the kinesin motor protein KIF1A. In the dendrites, Gas5 interacted with various proteins and coding and noncoding RNAs associated with synaptic function and plasticity, and these interactions were altered by cAMP signaling. Gas5 interacted with the microRNA miR-26a-5p and sequestered it from several of its mRNA targets associated with neuronal function and whose translation was induced by cAMP. Gas5 was critical for excitatory synaptic transmission induced by cAMP but not those induced by mGluR1/5. Furthermore, Gas5 deficiency impaired dendritic branching and synapse morphology, and Gas5 abundance was decreased in the hippocampus of a mouse model of Alzheimer's disease. Together, these findings provide insight into the transcriptional networks involved in synaptic plasticity and a lncRNA interactome that mediates dendritically localized regulation of excitatory synaptic transmission and neuronal architecture.