Abstract
α1-Adrenoceptor subtypes (α1A-, α1B-, α1D-) are known to couple to similar signaling pathways, although differences among the subtypes do exist. As a more sensitive assay, we used oligonucleotide microarrays to identify gene expression changes in Rat-1 fibroblasts stably expressing each individual subtype. We report the gene expressions that change by at least a factor of 2 or more. Gene expression profiles significantly changed equally among all three subtypes, despite the unequal efficacy of the inositol phosphate response. Gene expressions were clustered into cytokines/growth factors, transcription factors, enzymes, and extracellular matrix proteins. There were also a number of individual subtype-specific changes in gene expression, suggesting a link to independent pathways. In addition, all three α1-AR subtypes robustly stimulated the transcription of the prohypertrophic cytokine interleukin (IL)-6, but differentially altered members of the IL-6 signaling pathway (gp-130 and STAT3). This was confirmed by measurement of secreted IL-6, activated STAT3, and gp-130 levels. Activation of STAT3 Tyr705 phosphorylation by the α1-ARs was not through IL-6 activation but was synergistic with IL-6, suggesting direct effects. Interestingly, α1B-AR stimulation caused the dimerization-dependent phosphorylation of Tyr705 on STAT3 but did not activate the transcriptional-dependent phosphorylation of Ser727. The α1B-AR also constitutively down-regulated the protein levels of gp-130. These results suggest that the α1B-AR has differential effects on the phosphorylation status of the STAT3 pathway and may not be as prohypertrophic as the other two subtypes.
Footnotes
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↵1 Present address: GlaxoSmithKline Inc., 5 Moore Drive, PO Box 13398, Research Triangle Park, NC 27709.
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This work was funded by R01-HL61438 (to D.M.P.), a local American Heart Association fellowship to (to S.A.R. and P.J.G.-C.), an NRSA (to D.F.M.), and a T32-HL07914 training grant in Vascular Cell Biology (to B.R. and J.Y.).
- Abbreviations:
- AR
- adrenergic receptor
- GPCR
- G protein-coupled receptor
- IL
- interleukin
- IP
- inositol phosphate
- MAPK
- mitogen-activated protein kinase
- STAT
- signal transducer and activator of transcription
- 125I-BE-2254
- 2-[β-(4-hydroxy-3-[125I]iodophenyl)ethylaminomethyl]tetralone
- DMEM
- Dulbecco's modified essential medium
- PBS
- phosphate-buffered saline
- CCF
- Cleveland Clinic Foundation
- PM
- perfectly matched
- MM
- mismatched
- ELISA
- enzyme-linked immunosorbent assay
- JAK
- Janus tyrosine kinase
- LIF
- leukemia inhibitory factor
- VEGF
- vascular endothelial growth factor
- gp
- glycoprotein
- Received August 29, 2002.
- Accepted February 4, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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