title: Evidence for functional adenosine A3 receptors in microglia cells.
abstract: Adenosine exerts its effects through four subtypes of G-protein-coupled receptors (GPCRs): adenosine A1 and A3 receptors (A3R), which generally couple to Gi proteins and adenosine A2A and A2B receptors that activate Gs proteins. Though there is evidence for the expression of mRNA for the A3R in the central nervous system, evidence for functional receptors has depended on drugs with uncertain specificity. Here, we show that A3Rs mediating functional responses are present in microglia cells. By selectively stimulating the A3R in both primary mouse microglia cells and the N13 microglia cell line with the agonist Cl-IB-MECA, we have found a biphasic, partly Gi protein-dependent influence on the phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2). ERK1/2 activation was assessed by immunoblotting with phospho-specific antibodies. The involvement of the A3R in Cl-IB-MECA-induced ERK1/2 phosphorylation was confirmed by demonstrating that those effects are absent in primary mouse microglia cells isolated from mice lacking the gene for the A3R.
authors.affiliation: Karolinska Institutet, Department of Physiology and Pharmacology, Section of Molecular Pharmacology, Stockholm, Sweden.
authors.forename: Christian
authors.initials: C
authors.lastname: Hammarberg
authors.forename: Gunnar
authors.initials: G
authors.lastname: Schulte
authors.forename: Bertil B
authors.initials: BB
authors.lastname: Fredholm
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D058906:Purinergic P1 Receptor Agonists; D012333:RNA, Messenger / Q000378:metabolism; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D058906:Purinergic P1 Receptor Agonists; D012333:RNA, Messenger; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D020928:Mitogen-Activated Protein Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go