Regulation of p42/p44 mitogen-activated protein kinase by the human adenosine A3 receptor in transfected CHO cells

In this study we have investigated whether the human adenosine A(3) receptor activates p42/p44 mitogen-activated protein kinase (MAPK) in transfected Chinese hamster ovary (CHO) cells (designated CHO-A,). The high affinity adenosine A, receptor agonist IB-MECA (1-deoxy-1-[6-[[(3-iodophenyl)methyl]ami stimulated time (peak activation occurring after 5 min) and concentration-dependent (pEC(50) = 9.0 +/- 0.2) increases in p42/p44 MAPK in CHO-A(3) cells. Adenosine A, receptor-mediated increases in p42/p44 MAPK were sensitive to pertussis toxin and the MAPK kinase 1 inhibitor PD 98059 (2 ' -amino-3 ' -methoxyflavone). The broad range protein tyrosine kinase inhibitor genistein and the phosphatidylinositol 3-kinase inhibitors wortmannin and LY 294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one) also blocked adenosine A3 receptor stimulation of p42/p44 MAPK. In contrast, inhibition of protein kinase C had no significant effect on adenosine A, receptor-induced p42/p44 MAPK activation. IB-MECA (pEC(50) = 10.1 +/- 0.2) also increased the expression of luciferase in CHO-A(3) cells transiently transfected with a luciferase reporter gene containing the c-fos promoter. Furthermore, IB-MECA-induced increases in luciferase gene expression were sensitive to pertussis toxin, PD 98059, genistein, wortmannin and LY 294002. In conclusion, we have shown that the human adenosine A(3) receptor stimulates p42/p44 MAPK and c-fos-mediated luciferase gene expression in transfected CHO cells. (C) 2001 Elsevier Science B.V. All rights reserved.