Regulation of human D 1 dopamine receptor function and gene expression in SK-N-MC neuroblastoma cells

Abstract

SK-N-MC human neuroblastoma cells express functional D 1, but not D 5, dopaminergic receptors. Stimulating cells with dopamine or the D 1-selective agonist, SKF R-38393, rapidly (t 1/2=1 h) resulted in >95% attenuation of dopamine-mediated accumulation of cyclic AMP, without any change in D 1 dopamine receptor levels. Prolonged (>4 h) exposure of cells to dopamine attenuated D 1 receptor levels to 45–50% of control (t 1/2=8 h) and was accompanied by a loss of high-affinity binding sites. At the molecular level, the expression of D 1 receptor messenger RNA was bimodal: an initial increase (by ∼60%) of receptor messenger RNA within 2 h of treatment of cells with dopamine was followed by a decline to 50% below control messenger RNA levels. Low concentrations (1–10 nM) of dopamine also potentiated D 1 messenger RNA levels (up to 48%), resulting in a twofold increase in receptor levels. Transfection studies with the cloned human D 1 promoter construct, pGL-D1P, indicated that the up-regulation of D 1 messenger RNA was due to activation of promoter by dopamine. The dopamine-mediated up-regulation of both D 1 receptor messenger RNA and promoter was prevented by the D 1-selective antagonist, SCH 23390. The results suggest that dopamine regulates D 1 receptor gene and protein expression in a bimodal manner, partly through activation of the receptor promoter. Moreover, the effects of dopamine are independent of the second messenger, cyclic AMP.