Priming of signal transducer and activator of transcription proteins for cytokine-triggered polyubiquitylation and degradation by the A2a adenosine receptor

Safhi, M. M. A., Rutherford, C., Ledent, C., Sands, W. A. and Palmer, T. M. (2010) Priming of signal transducer and activator of transcription proteins for cytokine-triggered polyubiquitylation and degradation by the A2a adenosine receptor. Molecular Pharmacology, 77(6), pp. 968-978. (doi: 10.1124/mol.109.062455)

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Publisher's URL: http://dx.doi.org/10.1124/mol.109.062455

Abstract

Here we demonstrate that overexpression of the human A2a adenosine receptor (A2AAR) in vascular endothelial cells confers an ability of interferon-α and a soluble IL-6 receptor/IL-6 (sIL-6Rα/IL-6) trans-signaling complex to trigger the down-regulation of signal transducer and activator of transcription (STAT) proteins. It is noteworthy that STAT down-regulation could be reversed by coincubation with A2AAR-selective inverse agonist 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM241385) but not adenosine deaminase, suggesting that constitutive activation of the receptor was responsible for the effect. Moreover, STAT down-regulation was selectively abolished by proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132), whereas lysosome inhibitor chloroquine was without effect. Down-regulation required Janus kinase (JAK) activity and a Tyr705→Phe-mutated STAT3 was resistant to the phenomenon, suggesting that JAK-mediated phosphorylation of this residue is required. Consistent with this hypothesis, treatment of A2AAR-overexpressing cells with sIL-6Rα/IL-6 triggered the accumulation of polyubiquitylated wild-type but not Tyr705→Phe-mutated STAT3. Support for a functional role of this process was provided by the observation that A2AAR overexpression attenuated the JAK/STAT-dependent up-regulation of vascular endothelial growth factor receptor-2 by sIL-6Rα/IL-6. Consistent with a role for endogenous A2AARs in regulating STAT protein levels, prolonged exposure of endogenous A2AARs in endothelial cells with ZM241385 in vitro triggered the up-regulation of STAT3, whereas deletion of the A2AAR in vivo potentiated STAT1 expression and phosphorylation. Together, these experiments support a model whereby the A2AAR can prime JAK-phosphorylated STATs for polyubiquitylation and proteasomal degradation and represents a new mechanism by which an anti-inflammatory seven-transmembrane receptor can negatively regulate JAK/STAT signaling.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sands, Dr William and Palmer, Dr Timothy and Rutherford, Dr Claire
Authors: Safhi, M. M. A., Rutherford, C., Ledent, C., Sands, W. A., and Palmer, T. M.
Subjects:Q Science > Q Science (General)
College/School:College of Medical Veterinary and Life Sciences
College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Molecular Pharmacology
Publisher:American Society for Pharmacology and Experimental Therapeutics
ISSN:0026-895X
ISSN (Online):1521-0111
Published Online:25 February 2010
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
464231Priming phosphorylated STAT proteins for cytokine-triggered degradation in vascular endothelial cells: A new anti-inflammatory role for the A2A adenosine receptor.Timothy PalmerBritish Heart Foundation (BHF)PG/07/082/23623RI CARDIOVASCULAR & MEDICAL SCIENCES
342741Mechanisms underlying anti-inflammatory effects of adenosine receptor gene transferTimothy PalmerHeart Research UK (HEART-RES)2460/02/05RI CARDIOVASCULAR & MEDICAL SCIENCES
498581EPAC1 and ERK-dependent activation of C/EBP transcription factors: a new cyclic AMP-activated anti-inflammatory gene expression module in vascular endothelial cellsTimothy PalmerBritish Heart Foundation (BHF)PG/08/125/26415RI CARDIOVASCULAR & MEDICAL SCIENCES