CREB regulation of BK channel gene expression underlies rapid drug tolerance

Pharmacodynamic tolerance is believed to involve homeostatic mechanisms initiated to restore normal neural function. Drosophila exposed to a sedating dose of an organic solvent, such as benzyl alcohol or ethanol, acquire tolerance to subsequent sedation by that solvent. The slo gene encodes BK-type Ca(2+)-activated K(+) channels and has been linked to alcohol- and organic solvent-induced behavioral tolerance in mice, Caenorhabditis elegans (C. elegans) and Drosophila. The cyclic AMP response element-binding (CREB) proteins are transcription factors that have been mechanistically linked to some behavioral changes associated with drug addiction. Here, we show that benzyl alcohol sedation alters expression of both dCREB-A and dCREB2-b genes to increase production of positively acting CREB isoforms and to reduce expression of negatively acting CREB variants. Using a CREB-responsive reporter gene, we show that benzyl alcohol sedation increases CREB-mediated transcription. Chromatin immunoprecipitation assays show that the binding of dCREB2, with a phosphorylated kinase-inducible domain, increases immediately after benzyl alcohol sedation within the slo promoter region. Most importantly, we show that a loss-of-function allele of dCREB2 eliminates drug-induced upregulation of slo expression and the production of benzyl alcohol tolerance. This unambiguously links dCREB2 transcription factors to these two benzyl alcohol-induced phenotypes. These findings suggest that CREB positively regulates the expression of slo-encoded BK-type Ca(2+)-activated K(+) channels and that this gives rise to behavioral tolerance to benzyl alcohol sedation.