RT Journal Article
SR Electronic
T1 Pharmacological Analysis of Calcium Responses Mediated by the Human A3 Adenosine Receptor in Monocyte-Derived Dendritic Cells and Recombinant Cells
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 342
OP 350
DO 10.1124/mol.63.2.342
VO 63
IS 2
A1 James Fossetta
A1 James Jackson
A1 Gregory Deno
A1 Xuedong Fan
A1 Xixuan Karen Du
A1 Loretta Bober
A1 Anne Soudé-Bermejo
A1 Odette de Bouteiller
A1 Christophe Caux
A1 Charles Lunn
A1 Daniel Lundell
A1 R. Kyle Palmer
YR 2003
UL http://molpharm.aspetjournals.org/content/63/2/342.abstract
AB Extensive characterization of adenosine receptors expressed by human monocyte-derived dendritic cells (MDDCs) was performed with quantitative polymerase chain reaction, radioligand binding, and calcium signaling. Transcript for the A3 adenosine receptor was elevated more than 100-fold in immature MDDCs compared with monocyte precursors. A3 receptor transcript was substantially diminished, and A2A receptor transcript increased, by lipopolysaccharide maturation of MDDCs. Saturation binding ofN6-(3-[125I]iodo-4-aminobenzyl)-adenosine-5′-N-methyluronamide ([125I]AB-MECA) to membranes from immature MDDCs yieldedBmax of 298 fmol/mg of protein andKD of 0.7 nM. Competition against [125I]AB-MECA binding confirmed the site to be the A3 receptor. Adenosine elicited pertussis toxin-sensitive calcium responses with EC50 values ranging as low as 2 nM. The order of potency for related agonists wasN6-(3-iodobenzyl)-adenosine-5′-N-methylcarboxamide (IB-MECA) ≥ I-AB-MECA > 2Cl-IB-MECA ≥ adenosine > 2-[p-(2-carboxyethyl)phenylethylamino]-5′-N-ethylcarboxyamidoadenosine (CGS21680). The order of efficacy was adenosine ≥ CGS21680 > IB-MECA ≥ I-AB-MECA > 2Cl-IB-MECA. Calcium responses to 2Cl-IB-MECA and CGS21680, and the lower range of adenosine concentrations, were completely blocked by 10 nMN-(2-methoxyphenyl)-N-[2-(3-pyridyl)quinazolin-4-yl]urea (VUF5574) but not by 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (SCH58261) or 8-cyclopentyl-1,3-dipropylxanthine. Pretreatment with 100 nM 2Cl-IB-MECA eliminated responses to CGS21680 but not to monocyte inhibitory protein-1α. For comparison, dose-response functions were obtained from double-recombinant human embryonic kidney 293 cells expressing the human A3 receptor and a chimeric Gαq-i3 protein, which was required to establish A3-mediated calcium signaling. The pharmacological profile of calcium signaling elicited by adenosine-related agonists in the double-recombinant cells was essentially identical to that obtained from immature MDDCs. Our results provide an extensive analysis of A3-mediated calcium signaling and unequivocally identify immature MDDCs as native expressers of the human A3 receptor. The American Society for Pharmacology and Experimental Therapeutics