Received for publication November 15, 2006.
Revised January 23, 2007.
Accepted for publication January 23, 2007.

ERK1/2 Mediated Transcriptional Regulation of GRK3 Expression In Neuronal Cells

Abstract

Relatively small changes in GRK3 expression (~2-fold) profoundly affect alpha2-adrenergic receptor (₂-AR) function and preferentially regulate neuronal _2A - and _2B-AR signaling. In the present study, we provide evidence that EPI-induced up-regulation of GRK3 protein expression in two neuronal cell lines, BE(2)-C (endogenously express _2A and ₂-AR) and BN17 (endogenously express _2B (NG108) and transfected to express ₂-AR) is due in part to increased GRK3 gene expression. In both cell lines, the increase in GRK3 transcription occurred via an ERK 1/2-dependent mechanism as the increase in GRK3 mRNA is eliminated in the presence of MEK1/2 inhibitor, U0126. EPI-induced GRK3 mRNA up-regulation 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 _2B-AR with no ₂-AR). Both these results suggest that simultaneous activation of ₂- and 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 PKC 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.

Key words: 2-adrenoceptors, 2-adrenoceptors, ERK1/2, GRK3, mRNA, transcription