Deletion of the C-terminal phosphorylation sites in the cardiac ?-subunit does not affect the basic ?-adrenergic response of the heart and the Ca(v)1.2 channel.

Phosphorylation of the cardiac ? subunit (Ca(v)?(2)) of the Ca(v)1.2 L-type Ca(2+) channel complex has been proposed as a mechanism for regulation of L-type Ca(2+) channels by various protein kinases including PKA, CaMKII, Akt/PKB, and PKG. To test this hypothesis directly in vivo, we generated a knock-in mouse line with targeted mutation of the Ca(v)?(2) gene by insertion of a stop codon after proline 501 in exon 14 (mouse sequence Cacnb2; ?Stop mouse). This mutation prevented translation of the Ca(v)?(2) C terminus that contains the relevant phosphorylation sites for the above protein kinases. Homozygous cardiac ?Stop mice were born at Mendelian ratio, had a normal life expectancy, and normal basal L-type I(Ca). The regulation of the L-type current by stimulation of the ?-adrenergic receptor was unaffected in vivo and in cardiomyocytes (CMs). ?Stop mice were cross-bred with mice expressing the Ca(v)1.2 gene containing the mutation S1928A (SA?Stop) or S1512A and S1570A (SF?Stop) in the C terminus of the ?(1C) subunit. The ?-adrenergic regulation of the cardiac I(Ca) was unaltered in these mouse lines. In contrast, truncation of the Ca(v)1.2 at Asp(1904) abolished ?-adrenergic up-regulation of I(Ca) in murine embryonic CMs. We conclude that phosphorylation of the C-terminal sites in Ca(v)?(2), Ser(1928), Ser(1512), and Ser(1570) of the Ca(v)1.2 protein is functionally not involved in the adrenergic regulation of the murine cardiac Ca(v)1.2 channel.     «

Phosphorylation of the cardiac ? subunit (Ca(v)?(2)) of the Ca(v)1.2 L-type Ca(2+) channel complex has been proposed as a mechanism for regulation of L-type Ca(2+) channels by various protein kinases including PKA, CaMKII, Akt/PKB, and PKG. To test this hypothesis directly in vivo, we generated a knock-in mouse line with targeted mutation of the Ca(v)?(2) gene by insertion of a stop codon after proline 501 in exon 14 (mouse sequence Cacnb2; ?Stop mouse). This mutation prevented translation of t...     »