Ethanol regulates calcium channel subunits by protein kinase C δ-dependent and -independent mechanisms

Chronic exposure to ethanol increases the number of functional L-type voltage-gated calcium channels in neural cells. In PC12 cells, this adaptive response is mediated by protein kinase C delta (PKC delta), but the mechanisms by which this occurs are not known. Since expression of several different calcium channel subunits can increase the abundance of functional L-type channels, we sought to identify which subunits are regulated by ethanol. Incubation of PC12 cells with 120-150 mM ethanol for 6 days increased levels of alpha(1C), alpha(2), and beta(1b) subunit immunoreactivity in cell membranes and selectively increased the abundance of mRNA encoding the alpha(1C-1) splice variant of alpha(1C). In cells expressing a fragment of PKC delta (delta V1) that selectively inhibits PKC delta, there was no increase in membrane-associated alpha(1C), alpha(2), and beta(1b) immunoreactivity following chronic ethanol exposure. However, ethanol still increased levels of alpha(1C-1) mRNA in these cells. These results indicate that ethanol increases the abundance of L-type channels by at least two mechanisms; one involves increases in mRNA encoding a splice variant of alpha(1C) and the other is post-transcriptional, rate-limiting, and requires PKC delta.