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Simultaneous Activation of α 2 ‐ and β 2 ‐AR by EPI is Required For the ERK1/2‐Dependent Increase in GRK3 Transcription In Neuronal Cells
Author(s) -
Salim Samina,
Standifer Kelly M.,
Eikenburg Douglas C.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a426-d
Subject(s) - protein kinase c , messenger rna , chemistry , microbiology and biotechnology , mapk/erk pathway , transcription (linguistics) , propranolol , kinase , transcription factor , biology , gene , endocrinology , biochemistry , linguistics , philosophy
Relatively small changes in GRK3 expression (~2‐fold) profoundly affect alpha 2 (α 2 )‐adrenergic receptor (AR) function and preferentially regulate neuronal α 2A ‐ and α 2B ‐ 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 α 2A and β 2 ‐AR) and BN17 (endogenously express α 2B and transfected with human β 2 ‐AR) is due in part to increased GRK3 gene expression. Using semi‐quantitative reverse transcriptase polymerase chain reaction (RT‐PCR), we observed that the increase in GRK3 transcription occurred via 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 the β‐AR antagonist propranolol or the α‐AR antagonist phentolamine. Moreover, GRK3 mRNA did not increase in response to EPI treatment in NG108 cells (endogenously express α 2B ‐AR). Both these results suggest that simultaneous activation of α 2 ‐ and β 2 ‐AR by EPI is required for the ERK1/2‐dependent increase in GRK3 mRNA. EPI treatment resulted in increased nuclear translocation and accumulation of the transcription factors, Sp‐1 and Ap‐2 while propranolol treatment prevented nuclear translocation in BE(2)‐C cells. Finally, the EPI‐induced increase in GRK3 mRNA was unaffected by the PKC inhibitor, chelerythrine chloride, and EPI had no effect on GRK2 mRNA in any of the cell lines. Taken together, our study demonstrates the involvement of the ERK1/2 pathway in selective up‐regulation of GRK3 mRNA expression possibly via activation of Sp‐1 and Ap‐2 in neuronal cells. (Supported by the American Heart Association, Texas Affiliate, #0555032Y (DCE) and NIH DA01738 (KMS))