Protein Kinase C Participates in Up‐Regulation of Dihydropyridine‐Sensitive Calcium Channels by Ethanol

Abstract

Exposure to ethanol for several days increases the expression of dihydropyridine-sensitive, voltage-dependent Ca²⁺ channels in brain and in the neural cell line PC12. Since protein phosphorylation is a major mechanism by which ion channels are regulated, we used protein kinase inhibitors to investigate whether ethanol-induced up-regulation of Ca²⁺ channels involves activation of a protein kinase. Sphingosine and polymixin B, which inhibit protein kinase C and calmodulin-dependent kinases, prevented the enhancement of ⁴⁵Ca²⁺ uptake induced by exposure of PC12 cells to ethanol for 4 days. In addition, sphingosine blocked the ability of ethanol to increase the number of [³H]dihydropyridine binding sites in PC12 cell membranes. Sphingosine's effect was prevented by simultaneous exposure to phorbol 12,13-dibutyrate, a potent activator of protein kinase C. Therefore, protein kinase C appears to be involved in the up-regulation of dihydropyridine-sensitive Ca²⁺ channels during prolonged exposure to ethanol.