Inhibition of Cardiac L-Type Calcium Channels by Protein Kinase C Phosphorylation of Two Sites in the N-Terminal Domain

• Published in: Proceedings of the National Academy of Sciences - PNAS 2000-10, Vol.97 (22), p.12334-12338
• Main Authors: McHugh, Damian, Sharp, Elizabeth M., Scheuer, Todd, Catterall, William A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Biological Sciences; Calcium; Calcium Channels, L-Type - chemistry; Calcium Channels, L-Type - genetics; Calcium Channels, L-Type - metabolism; Cell Line; Cell lines; Cells; Drug regulation; Enzyme Activation; Heart; Humans; Kidney cells; Molecular Sequence Data; Mutagenesis; Mutation; Myocardium - metabolism; Oocytes; Phosphorylation; Physiological regulation; Protein isoforms; Protein Kinase C - metabolism; Proteins; Sequence Homology, Amino Acid; Threonine - metabolism; Transformed cell line
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.210384297

We have investigated the mechanism underlying the modulation of the cardiac L-type Ca2+current by protein kinase C(PKC). Using the patch-clamp technique, we found that PKC activation by 4-α -phorbol 12-myristate 13-acetate (PMA) or rac-1-oleyl-2-acetylglycerol (OAG) caused a substantial reduction in Ba2+current through Cav1.2 channels composed of α11.2, β1b, and α2δ1subunits expressed in tsA-201 cells. In contrast, Ba2+current through a cloned brain isoform of the Cav1.2 channel (rbC-II) was unaffected by PKC activation. Two potential sites of PKC phosphorylation are present at positions 27 and 31 in the cardiac form of Cav1.2, but not in the brain form. Deletion of N-terminal residues 2-46 prevented PKC inhibition. Conversion of the threonines at positions 27 and 31 to alanine also abolished the PKC sensitivity of Cav1.2. Mutant Cav1.2 channels in which the threonines were converted singly to alanines were also insensitive to PKC modulation, suggesting that phosphorylation of both residues is required for PKC-dependent modulation. Consistent with this, mutating each of the threonines individually to aspartate in separate mutants restored the PKC sensitivity of Cav1.2, indicating that a change in net charge by phosphorylation of both sites is responsible for inhibition. Our results define the molecular basis for inhibition of cardiac Cav1.2 channels by the PKC pathway.