Ser1901of α1Csubunit is required for the PKA-mediated enhancement of L-type Ca2+channel currents but not for the negative shift of activation

Abstract

Cardiac L‐type Ca²⁺ channel is facilitated by protein kinase A (PKA)‐mediated phosphorylation. Here, we investigated the role of Ser¹⁹⁰¹, a putative phosphorylation site in the carboxy‐terminal of rat brain type‐II α_1C subunit (rbCII), in the PKA‐mediated regulation. Forskolin (3 μM) enhanced Ca²⁺ channel currents (I _Ca) and shifted the activation curve to negative voltages, which were abolished by protein kinase inhibitor. Replacement of Ser¹⁹⁰¹ of rbCII by Ala abolished the enhancement of I _Ca by forskolin but not the shift of the activation curve. These results indicate that Ser¹⁹⁰¹ is required for the PKA‐mediated enhancement of I _Ca, and that the voltage‐dependence of the activation of I _Ca appears to be modulated via another PKA phosphorylation site.