5-hydroxytryptamine 2A receptor stimulation induces activator protein-1 and cyclic AMP-responsive element binding with cyclic AMP-responsive element-binding protein and jun D as common components in cerebellar neurons

Abstract

Previous studies from our laboratory have demonstrated that stimulation of 5-hydroxytryptamine 2A receptors in rat cerebellar granule cells produces an increase in the levels of 5-hydroxytryptamine 2A receptor messenger RNA and binding sites, and that this up-regulation requires de novo RNA and protein synthesis. Here we showed that up-regulation of 5-hydroxytryptamine 2A receptor binding sites induced by stimulation with the 5-hydroxytryptamine 2A/2C receptor agonist, (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, is associated with an increase in the 5-hydroxytryptamine 2A receptor transcription rate. To examine the possible role of transcriptional activation in (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-induced 5-hydroxytryptamine 2A receptor up-regulation, we studied the effects of (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane on transcription factor binding to activator protein-1 and cyclic AMP-responsive element DNA consensus sequences. We found that (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane induces a time-dependent increase in activator protein-1 and cyclic AMP-responsive element transcription factor binding activity, which is blocked by 5-hydroxytryptamine 2A receptor antagonists. Similar to 5-hydroxytryptamine 2A receptor up-regulation, (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane-induced activator protein-1 binding is suppressed by inhibitors of calmodulin and Ca 2+/calmodulin-dependent kinases. The increased activator protein-1 binding is effectively competed by excessive activator protein-1 and cyclic AMP-responsive element sequences as well as endogenous activator protein-1 like sequences present in rat 5-hydroxytryptamine 2A receptor gene. Supershift assays revealed that cAMP-responsive element-binding protein and Jun D are common components of both activator protein-1 and cyclic AMP-responsive element binding complexes. (±)-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane also increased the level of phospho-cyclic AMP-responsive element-binding protein protein in a time-dependent manner. The binding of phospho-cyclic AMP-responsive element-binding protein transcription factor to the activator protein-1 site suggests that cyclic AMP-responsive element-binding protein may modulate the transcription of genes that contain activator protein-1 but lack cyclic AMP-responsive element site in their promoters, through interaction with the activator protein-1 site. The rat 5-hydroxytryptamine 2A receptor up-regulation may involve such a mechanism.