Protein Kinase C ε Mediates Up-Regulation of N-Type Calcium Channels by Ethanol

Abstract

Brief exposure to ethanol inhibits L-type and N-type voltage-gated calcium channels in neural cells. Although chronic ethanol exposure up-regulates the density and function of L-type channels via a protein kinase C (PKC) δ-dependent mechanism, the effect of prolonged ethanol exposure on N-type channels is not known. Using PC12 cells, we found that exposure to 25 to 150 mM ethanol for 0 to 8 days produced a time- and concentration-dependent increase in the density of binding sites for the N-type channel antagonist ¹²⁵I-ω-conotoxin GVIA. This was associated with an increase in ω-conotoxin GVIA-sensitive, depolarization-evoked rises in [Ca²⁺]_i. Increases in¹²⁵I-ω-conotoxin GVIA binding also were observed in the frontal cortex and the hippocampus, but not in the thalamus of mice exposed to ethanol vapor for 3 days. In PC12 cells, increases in¹²⁵I-ω-conotoxin GVIA binding were blocked by the PKC inhibitor bisindolylmaleimide I and by expression of a selective peptide inhibitor of PKCε. Expression of a selective inhibitor of PKCδ did not alter ethanol-induced increases in¹²⁵I-ω-conotoxin GVIA binding. These findings indicate that PKCε mediates up-regulation of N-type channels by ethanol. Because N-type channels modulate calcium-dependent neurotransmitter release, these findings suggest a mechanism that may contribute to neuronal hyperexcitability observed during alcohol withdrawal.