title: Discrete microdomains with high concentration of cAMP in stimulated rat neonatal cardiac myocytes.
abstract: The second messenger cyclic adenosine monophosphate (cAMP) is the most important modulator of sympathetic control over cardiac contractility. In cardiac myocytes and many other cell types, however, cAMP transduces the signal generated upon stimulation of various receptors and activates different cellular functions, raising the issue of how specificity can be achieved. In the general field of signal transduction, the view is emerging that specificity is guaranteed by tight localization of signaling events. Here, we show that in neonatal rat cardiac myocytes, beta-adrenergic stimulation generates multiple microdomains with increased concentration of cAMP in correspondence with the region of the transverse tubule/junctional sarcoplasmic reticulum membrane. The restricted pools of cAMP show a range of action as small as approximately 1 micrometer, and free diffusion of the second messenger is limited by the activity of phosphodiesterases. Furthermore, we demonstrate that such gradients of cAMP specifically activate a subset of protein kinase A molecules anchored in proximity to the T tubule.
authors.affiliation: Department of Biomedical Sciences and Venetian Institute for Molecular Medicine, University of Padua, Via Orus 2, 35129 Padua, Italy. manuela.zaccolo@unipd.it
authors.forename: Manuela
authors.initials: M
authors.lastname: Zaccolo
authors.forename: Tullio
authors.initials: T
authors.lastname: Pozzan
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D054758:A Kinase Anchor Proteins; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005453:Fluorescence; D049452:Green Fluorescent Proteins; D007425:Intracellular Membranes / Q000378:metabolism; D007700:Kinetics; D008164:Luminescent Proteins; D015778:Minor Histocompatibility Antigens; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D009638:Norepinephrine / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000494:pharmacology; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D015290:Second Messenger Systems; D014162:Transfection
chemical_list: D054758:A Kinase Anchor Proteins; C085467:AKAP13 protein, human; D048868:Adaptor Proteins, Signal Transducing; D008164:Luminescent Proteins; D015778:Minor Histocompatibility Antigens; D010726:Phosphodiesterase Inhibitors; D011518:Proto-Oncogene Proteins; D011943:Receptors, Adrenergic, beta; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015056:1-Methyl-3-isobutylxanthine; D009638:Norepinephrine