title: Adenosine A3 receptor-mediated regulation of p38 and extracellular-regulated kinase ERK1/2 via phosphatidylinositol-3'-kinase.
abstract: The adenosine A(3) receptor generally couples to the G(i) class of heterotrimeric G proteins, thereby decreasing cAMP levels and also mediating signaling via release of betagamma subunits. Here we describe the central role of phosphatidylinositol-3'-kinase (PI3K) for adenosine A(3) receptor-induced intracellular signaling to the stress-activated protein kinase p38 and the extracellular signal-regulated protein kinases ERK1/2. We used Chinese hamster ovary cells expressing the human adenosine A(3) receptor, phospho-specific antibodies and different pharmacological tools to dissect the signaling pathways involving PI3K. The adenosine receptor agonist 5'N-ethylcarboxamidoadenosine induced a time- and dose-dependent increase in p38 and ERK1/2 phosphorylation, two signaling pathways that appeared also to be activated in the immortalized microglia cell line N13, which expressed endogenous adenosine A(3) receptors. The 5'N-ethylcarboxamidoadenosine-induced effects on p38 and ERK1/2 in CHO cells were blocked by pertussis toxin pretreatment and were sensitive to pharmacological inhibition of PI3K. In addition, inhibition of Rac/Cdc42, small GTPases of the Rho family, by clostridium toxin B, diminished p38 phosphorylation but did not affect ERK1/2. Furthermore, we identified the serine 727 site of signal transducer and activator of transcription STAT3 as a probable downstream target of ERK1/2, and thereby provide evidence that adenosine A(3) receptor mediated ERK1/2 activation has functional consequences.
authors.affiliation: Department of Physiology and Pharmacology, Section of Molecular Pharmacology, Karolinska Institutet, S-171 77, Stockholm, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Hammarberg
authors.forename: Bertil B
authors.initials: BB
authors.lastname: Fredholm
authors.forename: Gunnar
authors.initials: G
authors.lastname: Schulte
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D043684:Receptor, Adenosine A3 / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D012694:Serine / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004268:DNA-Binding Proteins; D043684:Receptor, Adenosine A3; D050796:STAT3 Transcription Factor; D015534:Trans-Activators; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020764:cdc42 GTP-Binding Protein