Unchanged β-Adrenergic Stimulation of Cardiac L-type Calcium Channels in Cav1.2 Phosphorylation Site S1928A Mutant Mice

Phosphorylation of serine 1928 ( Ser(1928)) of the cardiac Ca(v)1.2 subunit of L-type Ca2+ channels has been proposed as the mechanism for regulation of L-type Ca2+ channels by protein kinase A (PKA). To test this directly in vivo, we generated a knock-in mouse with targeted mutation of Ser(1928) to alanine. This mutation did not affect basal L-type current characteristics or regulation of the L-type current by PKA and the beta-adrenergic receptor, whereas the mutation abolished phosphorylation of Cav1.2 by PKA. Therefore, our data show that PKA phosphorylation of Ser(1928) of Ca(v)1.2 is not functionally involved in beta-adrenergic stimulation of Ca(v)1.2-mediated Ca2+ influx into the cardiomyocyte.