- Modulation of cardiac Ca(V)1.2 channels by dihydropyridine and phosphatase inhibitor requires Ser-1142 in the domain III pore loop. Erxleben, C., Gomez-Alegria, C., Darden, T., Mori, Y., Birnbaumer, L., Armstrong, D.L. Proc. Natl. Acad. Sci. U.S.A. (2003)