Caveolin-3 regulates compartmentation of cardiomyocyte beta2-adrenergic receptor-mediated cAMP signaling

The purpose of this study was to investigate whether caveolin-3 (Cav3) regulates localization of beta(2)-adrenergic receptor (beta(2)AR) and its cAMP signaling in healthy or failing cardiomyocytes. We co-expressed wildtype Cav3 or its dominant-negative mutant (Cav3DN) together with the Forster resonance energy transfer (FRET)-based cAMP sensor Epac2-camps in adult rat ventricular myocytes (ARVMs). FRET and scanning ion conductance microscopy were used to locally stimulate beta(2)-AR and to measure cytosolic cAMP. Cav3 overexpression increased the number of caveolae and decreased the magnitude of beta(2)-AR-cAMP signal. Conversely, Cav3DN expression resulted in an increased beta(2)-AR-cAMP response without altering the whole-cell L-type calcium current. Following local stimulation of Cav3DN-expressing ARVMs, beta(2)-AR response could only be generated in T-tubules. However, the normally compartmentalized beta(2)-AR-cAMP signal became diffuse, similar to the situation observed in heart failure. Finally, overexpression of Cav3 in failing myocytes led to partial beta(2)-AR redistribution back into the T-tubules. In conclusion, Cav3 plays a crucial role for the localization of beta(2)-AR and compartmentation of beta(2)-AR-cAMP signaling to the T-tubules of healthy ARVMs, and overexpression of Cav3 in failing myocytes can partially restore the disrupted localization of these receptors. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.