Roles of c‐Src and PKC in production of persistent calcium sparklet activity

Abstract

The L‐type calcium channel (Cav1.2) is regulated by multiple kinases, including PKA and c‐Src, which phosphorylate the Cav1.2 C‐terminus at residues S1901 and Y2122 (Cav1.2c), respectively, to enhance Ca2+ entry. PKC also enhances Cav1.2 current under some conditions and promotes persistent Cav1.2 Ca2+ sparklet activity (quantal Ca2+ entry events); however, the PKC phosphorylation site is unclear. We addressed two questions using TIRF microscopy to measure Ca2+ sparklets in patch clamped HEK cells expressing Cav1.2c. 1) Does PKC produce persistent calcium sparklet activity through phosphorylation of S1901? 2) Is c‐Src involved in the production of persistent sparklet activity?Persistent sparklets (indicating a prolonged channel opening state) were defined as nPs > 0.2, where n= # of quantal levels and Ps= probability that a given sparklet site was active. Our results suggest that both PKC and c‐Src promote persistent calcium sparklet activity, possibly by phosphorylating residue Y2122 rather than S1901 on Cav1.2c.