PDE4D and PDE4B function in distinct subcellular compartments in mouse embryonic fibroblasts.

Signaling through cAMP regulates most cellular functions. The spatiotemporal control of cAMP is, therefore, crucial for differential regulation of specific cellular targets. Here we investigated the consequences of PDE4B or PDE4D gene ablation on cAMP signaling at a subcellular level using mouse embryonic fibroblasts. PDE4B ablation had no effect on the global or bulk cytosol accumulation of cAMP but increased both basal and hormone-dependent cAMP in a near-membrane pool. Conversely, PDE4D ablation enhanced agonist-induced cAMP accumulation in the bulk cytosol as well as at the plasma membrane. Both PDE4B and PDE4D ablation significantly modified the time course and the level of isoproterenol-induced phosphorylation of vasodilator-stimulated phosphoprotein, a membrane cytoskeletal component. A second membrane response through Toll-like receptor signaling, however, was only affected by PDE4B ablation. PDE4D but not PDE4B ablation significantly prolonged cAMP-response element-binding protein-mediated transcription. These findings demonstrate that PDE4D and PDE4B have specialized functions in mouse embryonic fibroblasts with PDE4B controlling cAMP in a discrete subdomain near the plasma membrane.