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

Previous studies from our laboratory have demonstrated that stimulatio n of 5-hydroxytryptamine(2A) receptors in rat cerebellar granule cells produces an increase in the levels of 5-hydroxytryptamine(2A) recepto r messenger RNA and binding sites, and that this up-regulation require s de novo RNA and protein synthesis. Here we showed that up-regulation of 5-hydroxytryptamine(2A) receptor binding sites induced by stimulat ion with the 5-hydroxytryptamine(2A/2C) receptor agonist, (+/-)-(2,5-d imethoxy-4-iodophenyl)-2-aminopropane (DOI), is associated with an inc rease in the 5-hydroxytryptamine(2A) receptor transcription rate. To e xamine the possible role of transcriptional activation in DOI-induced 5-hydroxytryptamine(2A) receptor up-regulation, we studied the effects of DOI on transcription Factor binding to activator protein-1 and cyc lic AMP-responsive element (CRE) DNA consensus sequences. We found tha t DOI induces a time-dependent increase in activator protein-1 and CRE transcription factor binding activity, which is blocked by 5-hydroxyt ryptamine(2A) receptor antagonists. Similar to 5-hydroxytryptamine(2A) receptor up-regulation. DOI-induced activator protein-1 binding is su ppressed by inhibitors of calmodulin and Ca2+/calmodulin-dependent kin ases. The increased activator protein-1 binding is effectively compete d by excessive activator protein-1 and CRE sequences as well as endoge nous activator protein-1-like sequences present in the rat 5-hydroxytr yptamine(2A) receptor gene. Supershift assays revealed that cAMP-respo nsive element-binding protein (CREB) and Jun D are common components o f both activator protein-1 and CRE binding complexes. DOI also increas ed the level of phospho-CREB in a time-dependent manner. The binding o f phospho-CREB transcription Factor to the activator protein-1 site su ggests that CREB may modulate the transcription of genes that contain activator protein-1 but lack CRE site in their promoters, through inte raction with the activator protein-1 site. The rat 5-hydroxytryptamine (2A) receptor up-regulation may involve such a mechanism. (C) 1998 IBR O. Published by Elsevier Science Ltd.