Activation of Signal Transducers and Activators of Transcription by α1A-Adrenergic Receptor Stimulation in PC12 Cells
Abstract
In PC12 cells stably expressing α1A-adrenergic receptors (ARs), norepinephrine (NE) activates several mitogen-activated protein kinase pathways and causes differentiation (Williams et al., 1998). Using retroviral luciferase reporters, we found that NE also activated both signal transducers and activators of transcription (Stat) and γ-interferon-activated sequence-mediated transcriptional responses, with maximal effects similar to those caused by interleukin-6 (IL-6). UTP and epidermal growth factor had no effect, whereas nerve growth factor caused a small Stat activation. Responses to NE were blocked by prazosin and depended on receptor density. Responses to NE were not blocked by inhibitors of mitogen-activated protein kinase kinase (PD98059), protein kinase C (GFX203290), Src (PP2), Jak2 (AG490), or the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid. The p38 mitogen-activated protein kinase inhibitors SB202190 and SB203580 blocked Stat activation by NE, the epidermal growth factor receptor inhibitor AG1478 caused a small inhibition, but the phosphoinositide 3 kinase inhibitor LY294002 potentiated both responses. Gel shifts confirmed formation of nuclear factors binding to both Stat and γ-interferon-activated sequence consensus sequences in response to NE and IL-6. Immunoprecipitation experiments showed that IL-6 increased tyrosine phosphorylation of Stat1 and Stat3 in PC12 cells, whereas NE caused a sustained increase in tyrosine phosphorylation of Stat1. These results suggest that α1A-AR stimulation causes Stat-mediated transcriptional responses in PC12 cells that are not downstream of known second messenger or tyrosine kinase pathways.
Footnotes
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Send reprint requests to: Kenneth P. Minneman, Ph.D., Department of Pharmacology, Emory University, Atlanta, GA. E-mail:kminneman{at}pharm.emory.edu
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↵1 T.J.M. is an Established Investigator of the American Heart Association.
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This study was supported by National Institutes of Health Grants NS 32706 (to K.P.M.) and HL52810 and HL 56107 (to T.J.M.).
- Abbreviations:
- AR
- adrenergic receptor
- GPCR
- G protein-coupled receptor
- NE
- norepinephrine
- MAPK
- mitogen-activated protein kinase
- NGF
- nerve growth factor
- Stats
- signal transducers and activators of transcription
- EGF
- epidermal growth factor
- IL-6
- interleukin 6
- IPTG
- isopropyl β-d-thiogalactoside
- GAS
- γ-interferon activated sequence
- DTT
- dithiothreitol
- PMSF
- phenylmethylsulfonyl fluoride
- PAGE
- polyacrylamide gel electrophoresis
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- Received August 12, 1999.
- Accepted December 31, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
