Protein phosphatase 2A effectively modulates basal L-type Ca2+ current by dephosphorylating Cav1.2 at serine 1866 in mouse cardiac myocytes

Calcium (Ca2+) influx through Cav1.2 L-type Ca2+ channels is an important event for cardiac excitation–contraction (E–C) coupling. The functional regulation of Cav1.2 is controlled by multiple kinases and phosphatases. It has been well documented that phosphorylation of Cav1.2 by PKA or other kinases is sufficient for the upregulation of channel activity. However, little is known about the role of protein phosphatases in counterbalancing the phosphorylation of Cav1.2, especially the degree to which protein phosphatase 2A (PP2A)-mediated dephosphorylation is involved in the regulation of Cav1.2 in the mouse heart. Here, we report a physical interaction between PP2A and the C-terminus of Cav1.2 in mouse heart extracts as revealed by coimmunoprecipitation. This interaction was further confirmed by the observation that PP2A and Cav1.2 are colocalized in isolated mouse cardiomyocytes. Specifically, PP2A was bound at serine 1866 in the C-terminus of Cav1.2, and PP2A-induced Cav1.2 dephosphorylation at serine 1866 was observed in mouse cardiomyocytes. Importantly, the density of L-type calcium current increased in line with the increase in the phosphorylation at serine 1866 of Cav1.2 in cardiac-specific PP2A Cα knockout mice. These phenomena were reproduced by treatment with okadaic acid, a PP2A inhibitor, in H9c2 cells. In summary, our data reveal the functional role of PP2A in cardiac Cav1.2 regulation.

► PP2A interacted with calcium channel Cav1.2 in mouse heart.
► PP2A and Cav1.2 protein colocalized in isolated mouse cardiomyocyte.
► PP2A dephosphorylated serine 1866 of Cav1.2.
► The increase of Cav1.2 phosphorylation potentiated ICa-L in PP2A/Cα KO mice hearts.
► OA treatment increased Cav1.2 phosphorylation and [Ca2+]i in myocyte H9c2.