Type 4 phosphodiesterase plays different integrating roles in different cellular domains in pyramidal cortical neurons.
We investigated the role of phosphodiesterases (PDEs) in the integration of cAMP signals and protein kinase A (PKA) activity following beta-adrenergic stimulation, by carrying out real-time imaging of male mouse pyramidal cortical neurons expressing biosensors to monitor cAMP levels (Epac1-camps and Epac2-camps300) or PKA activity (AKAR2). In the soma, isoproterenol (ISO) increased the PKA signal to approximately half the maximal response obtained with forskolin, with a characteristic beta(1) pharmacology and an EC(50) of 4.5 nm. This response was related to free cAMP levels in the submicromolar range. The specific type 4 PDE (PDE4) inhibitor rolipram had a very small effect alone, but strongly potentiated the PKA response to ISO. Blockers of other PDEs had no effect. PDE4 thus acts as a brake in the propagation of the beta(1)-adrenergic signal from the membrane to the bulk somatic cytosol. The results for a submembrane domain were markedly different, whether recorded with a PKA-sensitive potassium current related to the slow AHP or by two-photon imaging of small distal dendrites. The responses to ISO were stronger than in the bulk cytosol. This is consistent with the cAMP/PKA signal being strong at the membrane, as shown by electrophysiology, and favored in cellular domains with a high surface area to volume ratio, in which this signal was detected by imaging. Rolipram alone also produced a strong cAMP/PKA signal, revealing tonic cAMP production. PDE4 thus appears as a crucial integrator with different physiological implications in different subcellular domains.
Castro
Liliana R V
LR
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7102, Paris, France.
Gervasi
Nicolas
N
Guiot
Elvire
E
Cavellini
Laetitia
L
Nikolaev
Viacheslav O
VO
Paupardin-Tritsch
Danièle
D
Vincent
Pierre
P
D000262:Adenylyl Cyclases / Q000378:metabolism; D058665:Adrenergic beta-1 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002491:Central Nervous System Agents / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism*; D003712:Dendrites / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010296:Parietal Lobe / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism; D020889:Rolipram / Q000494:pharmacology
D058665:Adrenergic beta-1 Receptor Agonists; D000318:Adrenergic beta-Agonists; D002491:Central Nervous System Agents; D058988:Phosphodiesterase 4 Inhibitors; D010726:Phosphodiesterase Inhibitors; D018342:Receptors, Adrenergic, beta-1; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D000262:Adenylyl Cyclases; D020889:Rolipram; D007545:Isoproterenol; D011188:Potassium