Mutation of Threonine 422 to Glutamic Acid Mimics the Phosphorylation State and Alters the Action of Deltamethrin on Cav2.2

Effects of deltamethrin on voltage-sensitive calcium channels (VSCC) from rat brain (Cav2.2) expressed in Xenopus oocytes were assessed electrophysiologically. Deltamethrin reduced peak current of wild-type Cav2.2 in a stereospecific and concentration-dependent manner with an EC50 of 1 × 10−9 M. Phosphorylation of threonine 422 enhances voltage-sensitive calcium current, increases the probability that Cav2.2 will open under depolarizing conditions and antagonizes the inhibition of the channel by the betagamma subunit of heterotrimeric G-protein (Gβγ). Site-directed mutagenesis of threonine 422 to glutamic acid (T422E) results in a channel that acts as if it were permanently phosphorylated. Deltamethrin (10−7 M) significantly enhanced peak current via the T422E channel (1.5-fold) compared to the nontreated control and the increase was significantly greater than for either the wild-type (T422) or T422A (permanently unphosphorylated mutant) channels. The effect of deltamethrin on T422E Cav2.2 was stereospecific and concentration-dependent with an EC50 of 9.8 × 10−11 M. Thus, Cav2.2 is modified by deltamethrin but the resulting perturbation is dependent upon the phosphorylation state of threonine 422