Effects of N-terminal mutations of threonine residues on PKC
sensitivity of the Cav1.2 channel. (A) Peak
Ba2+ currents recorded every 30 s. PMA was applied
during the time indicated by the horizontal black bar.
(Inset) Ba2+ currents elicited by a
depolarizing step from −80 mV to +10 mV. Current traces such as those
in the Inset were taken at time points a and b before
and during exposure to PMA. (B) Mean changes in peak
current amplitude in response to application of 100 nM PMA for
wild-type Cav1.2 (WT) and several N-terminal mutants. The
mean changes in current amplitude in response to PMA were as follows:
Cav1.2 wild-type, −61.5 ± 7.1%,
n = 6; N-terminal deletion [N-del (2–46)],
−2.9 ± 1.8%, n = 3; TTAA, −1.5 ± 1.5%,
n = 5; T27A, +3.2 ± 4.7%, n = 5;
T31A, +0.2 ± 3.5%, n = 3.