Tonic Inhibitory Role for cAMP in α1a-Adrenergic Receptor Coupling to Extracellular Signal-Regulated Kinases 1/2
- Xiuxiang Jiao1,2,
- Pedro J. Gonzalez-Cabrera1,
- Lei Xiao2,
- Michael E. Bradley1,
- Peter W. Abel1 and
- William B. Jeffries1,2
- 1Department of Pharmacology (X.J., M.E.B., P.W.A., W.B.J.) and2Nephrology Research Laboratory (X.J., W.B.J.), Creighton University School of Medicine, Omaha, Nebraska
- Dr. William B. Jeffries, Department of Pharmacology, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178. E-mail: wbjeff{at}creighton.edu
Abstract
α1a-Adrenergic receptors (ARs) couple to phosphoinositide hydrolysis, adenylyl cyclase, and mitogen-activated protein kinase (MAPK) pathways. However, the interaction among these signaling pathways in activating extracellular signal-regulated kinase 1/2 (ERK1/2) is not well understood. We investigated the coupling of α1a-ARs to ERK1/2 in Chinese hamster ovary (CHO)-K1 cells stably transfected with mouse α1a-ARs, as well as the interaction between ERK1/2 and norepinephrine-induced cAMP accumulation. α1a-AR activation by norepinephrine increased the cytosolic Ca2+ concentration and phosphorylated ERK1/2 in a time- and concentration-dependent manner. ERK1/2 phosphorylation was blocked by the MAPK kinase 1/2 inhibitor 2′-amino-3′-methoxyflavone (PD 98059) and the α1-AR antagonist prazosin. A transient elevation in intracellular Ca2+ was required for the phosphorylation of ERK1/2; however, activation of protein kinase C did not seem to be required for ERK1/2 phosphorylation. Norepinephrine also stimulated cAMP accumulation in transfected CHO-K1 cells in a concentration-dependent manner via α1a-ARs, which was blocked by the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid. Norepinephrine-induced ERK1/2 phosphorylation was inhibited by the adenylyl cyclase activator forskolin and was enhanced by the adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purine-6-amine (SQ 22536) and the protein kinase A inhibitor 4-cyano-3-methylisoquinoline. In conclusion, in transfected CHO-K1 cells, α1a-AR activation activates both phospholipase C and adenylyl cyclase-mediated signaling pathways. α1a-AR-mediated ERK1/2 phosphorylation was dependent on a rise in intracellular Ca2+, and this pathway was reciprocally regulated by the concomitant activation of adenylyl cyclase, which inhibits ERK1/2 phosphorylation. Thus, α1a-AR stimulation of cAMP production may play an important role in regulating ERK1/2 phosphorylation in cell lines and native tissues.
Footnotes
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↵1 Current address: Department of Cardiovascular Biology, Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195.
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↵2 Current address: Myocardial Biology Unit, Cardiovascular Division, Department of Medicine, Boston University School of Medicine, Boston, MA 02118.
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This work was supported by Grant 9607830S from the American Heart Association (to W.B.J.) and Grant HD 33430 from National Institutes of Health (to M.E.B.).
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DOI: 10.1124/jpet.102.037747
- Abbreviations:
- AR
- adrenergic receptor
- PLC
- phospholipase C
- MAPK
- mitogen-activated protein kinase
- IP3
- inositol 1,4,5-trisphosphate
- DAG
- diacylglycerol
- PKC
- protein kinase C
- ERK
- extracellular signal-regulated kinase
- MEK
- mitogen-activated protein kinase kinase
- PKA
- protein kinase A
- CHO
- Chinese hamster ovary
- PMA
- phorbol 12-myristate 13-acetate
- BAPTA
- 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid
- CMQ
- 4-cyano-3-methylisoquinoline
- AM
- acetoxymethyl ester
- PD 98059
- 2′-amino-3′-methoxyflavone
- BMY-7378
- 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione
- SQ 22536
- 9-(tetrahydro-2-furanyl)-9H-purine-6-amine
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- Received April 18, 2002.
- Accepted June 17, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
