Different activation of NF-κB by stimulation of dopamine D2L and D2S receptors through calcineurin activation

Abstract

Dopamine D2 receptor (D2R) has known to activate Ca2+/ calmodulin-dependent protein phosphatase, calcineurin by increasing in the intracellular Ca2+. We previously showed that D2LR (long isoform) and D2SR (short isoform) enhanced SRE and NF-κB, and conversely suppressed CRE transcriptional activities in NG108-15 cells stably expressed with these receptors (NGD2LR and NGD2SR). In this study, to investigate whether activation of calcineurin is involved in the transcriptional regulations through D2R, we evaluated effect of cyclosporin A, a selective calcineurin inhibitor, on them in NGD2LR and NGD2SR cells using luciferase reporter gene assay. We first confirmed that D2LR activates calcineurin in NG108-15 cells by measurement of dephosphorylation of dopamine- and cyclic AMP-regulated phosphoprotein Mr 32 000 (DARPP-32) at threonin 34 by immunoblot analysis with its phospho-specific antibody. Cyclosporin A treatment showed no change in suppression of forskolin-induced CRE activation or activation of SRE but significantly attenuated NF-κB activation by D2LR stimulation in NGD2LR cells. Interestingly, D2SR-induced NF-κB activation, which was weaker than that by D2LR stimulation, was not affected by cyclosporin A treatment in NGD2SR cells. Furthermore, D2SR stimulation did not cause dephosphorylation of DARPP-32 at threonin 34. Taken together, D2SR and D2LR may employ different signaling pathway on intracellular Ca2+ mobilization, thereby showing different NF-κB activation in the calcineurin-dependent manner.