(696.9) Endosomal b2-adrenergic receptor controls nuclear cAMP signal in learning and memory via sequestration of phosphodiesterase 4D

Poster Board Number: B80

Joseph Martinez (University of California), Ao Shen (Guangzhou Medical University), Bing Xu (University of California), Aleksandra Jovanovic (University of California), Yang Xiang (University of California)

Learning and memory-related behaviors depend on GPCR signaling to the nucleus to induce Immediate early gene (IEG) expression. However, the molecular mechanisms mediating this process remain unclear. We have previously identified a subpopulation of β2AR which is preferentially phosphorylated by GRK sites and internalized to the endosome upon stimulation. Here, we demonstrate that GRK phosphorylated endosomal β2 Adrenergic Receptor (β2AR) indirectly facilitates nuclear cAMP signaling through sequestration of a PDE4D/β-arrestin complex. Combining subcellular cAMP biosensors and transgenic mice, we found deleting GRK phosphorylation sites on β2AR (GRKD) blocked agonist-induced receptor endocytosis and nuclear cAMP signaling in hippocampal neurons. This resulted in impaired PKA-mediated IEGs expression in vitro, reduced learning induced IEG expression in vivo, and impaired long-term memory in a Morris water maze. Mechanistically, while β2AR stimulation promoted β-arrestin-dependent recruitment of PDE4D5, inhibition of β-arrestin-PDE4D5 association alone prevented β2AR-induced increases in nuclear cAMP signaling without affecting receptor endocytosis. Furthermore, direct PDE4 inhibition was sufficient to rescue the β2AR-induced nuclear cAMP signal in GRKD neurons and ameliorate the long-term memory deficits in GRKD mice. This work indicates that the sequestration of the β-arrestin/PDE4D complex by the GRK-phosphorylated β2AR critically controls the receptor-induced nuclear cAMP signals. This constitutes a novel mechanism by which GPCR activation promotes nuclear cAMP signaling through endocytosis dependent relocalization of PDE4D isoforms, IEG expression, and learning and memory-related behaviors.

This study was supported by NIH Grants GM129376 and T32GM099608. Mr. Martinez is the recipient of the NIH Blueprint D-SPAN award (F99NS120523).