Abstract
We compared DNA replication, protein biosynthesis, and mitogen-activated protein kinase (MAPK) activity in Rat 1 fibroblasts stably expressing either the α1B-adrenergic receptor (AR) or α1D-AR subtypes. Activation of both the α1B-AR and α1D-AR inhibited DNA synthesis (as assessed by [3H]thymidine incorporation). In contrast, both receptors stimulated protein biosynthesis (as measured by [35S]methionine incorporation) and activated extracellular signal-regulated kinase (ERK)1/2. Importantly, these responses were agonist-dependent for the α1B-AR, but were agonist-independent for the α1D-AR. Agonist activation of the α1B-AR resulted in increased p38 kinase activity, but not c-Jun NH2-terminal kinase (JNK) activity, whereas the α1D-AR activated JNK but not p38 kinase. Unlike ERK1/2, JNK activity was increased by agonist treatment in the α1D-AR cells. An ERK1/2-pathway inhibitor PD98059 had no effect on phenylephrine-mediated inhibition of DNA synthesis in either cell line but blocked protein biosynthesis mediated by both receptors. The p38 kinase inhibitor SB203580 blocked α1B-AR effects on [3H]thymidine and [35S]methionine incorporation in α1B-AR-expressing cells, but had no effect on α1D-AR-mediated growth responses, consistent with the inability of the α1D-AR to activate p38 kinase. Therefore, α1B- and α1D-ARs mediated similar growth responses but differ with respect to the MAPK family member involved and the requirement for agonist.
Footnotes
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↵1 Current Address: Bernard J. Dunn School of Pharmacy, Shenandoah University, 1460 University Dr., Winchester, VA 22601. E-mail: bwaldrop{at}su.edu
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This study was supported by an American Heart Association Scientist Development grant and the University of Kentucky Medical Center Research Fund (to G.R.P.), American Foundation for Pharmaceutical Education predoctoral fellowship (to B.A.W.), National Institutes of Health HL-38120 (to M.T.P.), and American Heart Association Grant-in-Aid (to M.T.P. and G.R.P.).
Abbreviations
- AR
- adrenergic receptor
- MAPK
- mitogen-activated protein kinase
- ERK
- extracellular signal-regulated kinase
- JNK
- c-Jun NH2-terminal kinase
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- PE
- phenylephrine
- PBS
- phosphate-buffered saline
- GST
- glutathioneS-transferase
- MBP
- myelin basic protein
- IOD
- integrated optical density
- DMSO
- dimethyl sulfoxide
- PAGE
- polyacrylamide gel electrophoresis
- CHO
- Chinese hamster ovary
- SB
- SB203580
- Received May 8, 2001.
- Accepted June 20, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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