Molecular basis of b-adrenergic regulation of cardiac calcium current

Increased cardiac contractility during fight-or-flight response is caused by b-adrenergic augmentation of CaV1.2 channels. It is assumed that this iconic regulation involves phosphorylation of CaV1.2 a1/b-subunits. In transgenic murine hearts expressing fully PKA phosphorylation-deficient mutant a1C/b, this regulation persists, however, suggesting involvement of extra-channel factors. We here show that PKA up-regulates cardiac CaV1.2 channels by phosphorylating the small G-protein Rad, relieving constitutive inhibition of CaV1.2. Peroxidase-catalyzed labeling in mice hearts expressing ascorbate peroxidase conjugated-a1C or b2b with multiplexed quantitative proteomics allowed tracking of thousands of proteins in proximity of CaV1.2.