Serotonin 1A receptor coupling to NF‐κB studied using inducible receptor expression in hippocampal neuron‐derived cells

Abstract

AbstractThe mechanism of serotonin 1A receptor (5‐HT1A‐R) mediated activation of NF‐κB has been studied in non‐neural cells, but this pathway has not been elucidated in neuronal cells. We have used inducible expression of the 5‐HT1A‐R in the hippocampal neuron‐derived HN2 cells to analyze the coupling of this receptor to NF‐κB. A construct harboring luciferase cDNA driven by a minimal promoter under the control of an NF‐κB‐specific enhancer element was transfected into these 5‐HT1A‐R‐expressing HN2 cells. Using luciferase expression in the transfected cells, we have studied 5‐HT1A‐R agonist evoked activation of NF‐κB. Inhibition of either mitogen activated protein kinase (MAPK) pathway with PD98059 or protein kinase C (PKC) with GFX caused elevation of the basal level of NF‐κB activity but did not affect 5‐HT1A‐R mediated activation of NF‐κB. Furthermore, neither the basal level of NF‐κB nor its activation by a 5‐HT1A‐R agonist was altered by dibutyrylcAMP. Thus, the MAPK pathway and PKC cause inhibition of the basal NF‐κB activity and the 5‐HT1A‐R‐linked NF‐κB activation does not require MAPK, PKC, and cAMP. Intriguingly, Western blot analysis showed that 5‐HT1A‐R mediates activation of both CaMKII and PI‐3K. This 5‐HT1A‐R‐evoked the stimulation of CaMKII was reversed in the presence of a PI‐3K inhibitor. Therefore, the likely mechanism of 5‐HT1A‐R mediated induction of NF‐κB in neuronal cells involves activation of PI‐3K upstream of CaMKII. This reveals a novel pathway that could be crucial in the functional activity of brain neurons.