Extracellular signal-regulated kinase 1/2-mediated transcriptional regulation of G-protein-coupled receptor kinase 3 expression in neuronal cells

Relatively small changes in G-protein-coupled receptor kinase (GRK) 3 expression (similar to 2-fold) profoundly affect alpha(2)-adrenergic receptor (AR) function and preferentially regulate neuronal alpha(2)A- and alpha B-2-AR signaling. In the present study, we provide evidence that epinephrine (EPI)-induced up-regulation of GRK3 protein expression in two neuronal cell lines, BE(2)-C cells (endogenously express alpha(2)A- and beta(2)-AR) and BN17 cells [endogenously express alpha B-2 (NG108) and transfected to express beta(2)-AR] is due in part to increased GRK3 gene expression. In both cell lines, the increase in GRK3 transcription occurred via an extracellular signal-regulated kinase (ERK) 1/2-dependent mechanism because the increase in GRK3 mRNA is eliminated in the presence of the mitogen-activated protein kinase/ERK kinase 1/2 inhibitor, U0126 [1,4-diamino-2,3-dicyano-1,4-bis (2-amino phenylthiobutadiene)]. EPI-induced GRK3 mRNA upregulation also is prevented in the presence of propranolol or phentolamine. Moreover, GRK3 mRNA did not increase in response to EPI treatment in NG108 cells (endogenously express alpha B-2-AR with no beta(2)-AR). Both these results suggest that simultaneous activation of alpha(2)- and beta(2)-AR by EPI is required for the ERK1/2-dependent increase in GRK3 mRNA. The EPI-induced increase in GRK3 mRNA was unaffected in the presence of the protein kinase C inhibitor, chelerythrine chloride. Finally, EPI treatment resulted in increased nuclear translocation and accumulation of the transcription factors, Sp-1 and Ap-2, in BE(2)-C cells. Taken together, our results demonstrate the involvement of the ERK1/2 pathway in selective up-regulation of GRK3 mRNA expression, possibly via activation of Sp-1 and Ap-2 transcription factors in neuronal cells.