Cyclic AMP imaging in adult cardiac myocytes reveals far-reaching beta1-adrenergic but locally confined beta2-adrenergic receptor-mediated signaling

Circ Res. 2006 Nov 10;99(10):1084-91. doi: 10.1161/01.RES.0000250046.69918.d5. Epub 2006 Oct 12.


Beta(1)- and beta(2)-adrenergic receptors (betaARs) are known to differentially regulate cardiomyocyte contraction and growth. We tested the hypothesis that these differences are attributable to spatial compartmentation of the second messenger cAMP. Using a fluorescent resonance energy transfer (FRET)-based approach, we directly monitored the spatial and temporal distribution of cAMP in adult cardiomyocytes. We developed a new cAMP-FRET sensor (termed HCN2-camps) based on a single cAMP binding domain of the hyperpolarization activated cyclic nucleotide-gated potassium channel 2 (HCN2). Its cytosolic distribution, high dynamic range, and sensitivity make HCN2-camps particularly well suited to monitor subcellular localization of cardiomyocyte cAMP. We generated HCN2-camps transgenic mice and performed single-cell FRET imaging on freshly isolated cardiomyocytes. Whole-cell superfusion with isoproterenol showed a moderate elevation of cAMP. Application of various phosphodiesterase (PDE) inhibitors revealed stringent control of cAMP through PDE4>PDE2>PDE3. The beta(1)AR-mediated cAMP signals were entirely dependent on PDE4 activity, whereas beta(2)AR-mediated cAMP was under control of multiple PDE isoforms. beta(1)AR subtype-specific stimulation yielded approximately 2-fold greater cAMP responses compared with selective beta(2)-subtype stimulation, even on treatment with the nonselective PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) (DeltaFRET, 17.3+/-1.3% [beta(1)AR] versus 8.8+/-0.4% [beta(2)AR]). Treatment with pertussis toxin to inactivate G(i) did not affect cAMP production. Localized beta(1)AR stimulation generated a cAMP gradient propagating throughout the cell, whereas local beta(2)AR stimulation did not elicit marked cAMP diffusion. Our data reveal that in adult cardiac myocytes, beta(1)ARs induce far-reaching cAMP signals, whereas beta(2)AR-induced cAMP remains locally confined.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Agonists / pharmacology
  • Animals
  • Biosensing Techniques / methods
  • Cyclic AMP / genetics
  • Cyclic AMP / metabolism*
  • Fluorescence Resonance Energy Transfer / methods
  • Humans
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Ion Channels / biosynthesis
  • Ion Channels / genetics
  • Ion Channels / metabolism
  • Isoenzymes / metabolism
  • Mice
  • Mice, Transgenic
  • Models, Molecular
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / metabolism*
  • Phosphoric Diester Hydrolases / metabolism
  • Potassium Channels
  • Protein Structure, Tertiary
  • Receptors, Adrenergic, beta-1 / metabolism*
  • Receptors, Adrenergic, beta-2 / metabolism*
  • Signal Transduction


  • Adrenergic beta-Agonists
  • HCN2 protein, human
  • Hcn2 protein, mouse
  • Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
  • Ion Channels
  • Isoenzymes
  • Potassium Channels
  • Receptors, Adrenergic, beta-1
  • Receptors, Adrenergic, beta-2
  • Cyclic AMP
  • Phosphoric Diester Hydrolases