Distinct Pde4d Splice Variants Regulate Beta-Adrenergic Signaling In Neonatal Mouse Cardiac Myocytes

We have shown that inhibition of the cAMP-specific type 4 cyclic nucleotide phosphodiesterases (PDE4s) modifies beta-adrenergic signaling in mouse neonatal cardiac myocytes. In the present study, we further elucidated the role of individual PDE4 variants in the control of b1- and b2-adrenergic receptor (b1-AR and b2-AR) signaling. Stimulation of b2-AR resulted in a selective PKA-mediated activation of the PDE4D splice variant PDE4D5. Conversely, the variant PDE4D8 was predominantly activated by PKA upon b1-AR stimulation. Cyclic AMP-hydrolyzing (PDE) activity was co-immunoprecipiated with bARs from extracts of myocytes overexpressing b1-AR or b2-AR. This activity is due to PDE4D, because it was sensitive to PDE4-selective inhibitors and PDE activity was still recovered when cells deficient in PDE4A or PDE4B but not PDE4D were used. Moreover, the physical association of PDE4D variants and b-ARs was reproduced by co-IPs of recombinant PDE4D splice variants with b1- and b2-AR. Importantly, treatment with b-adrenergic agonists such as Isoproterenol diminished the PDE4D/b-AR co-IP indicating that this complex is dynamically regulated by b-AR signaling. Taken together, our results indicate that distinct PDE4D splice variants form macromolecular signaling complexes with and control the cAMP signals from b1- and b2-ARs. This research was supported by NIH grants HD20788 to M.C. and HL71078-01 to B.K.