Retinoic acid is a negative regulator of the neuropeptide Y/ peptide YY Y1 receptor gene in SK-N-MC cells

To identify effectors of neuropeptide Y Y1 receptor gene expression predicted by putative regulatory elements in its 5' flanking region, we examined the effects of several transcriptionally active agents on Y1 receptor mRNA levels and ¹²⁵I-peptide YY binding capacity in SK-N-MC cells. Phorbol ester caused a rapid, transient 2.6-fold increase in Y1R mRNA levels. However, all trans-retinoic acid caused a rapid, sustained decrease in Y1 receptor mRNA levels (to 25% of control). Cycloheximide pretreatment did not attenuate the maximal inhibitory effect of retinoic acid, but it prolonged the time to achieve maximal efficacy. The retinoic acid effect was secondary to both a significant decrease in Y1 receptor mRNA stability and a decreased Y1 receptor gene transcription rate. Y1 receptor binding capacity was also significantly decreased after retinoic acid treatment (368 ± 25 vs. 496 ± 28 fmol/mg of protein for control). These data support a role for retinoic acid as an important agent regulating Y1 receptor gene expression and mediating Y1 receptor down-regulation.