Regulation of p42/p44 mitogen-activated protein kinase by the human adenosine A(3) receptor in transfected CHO cells

In this study we have investigated whether the human adenosine A(3) recepto r activates p42/p44 mitogen-activated protein kinase (MAPK) in transfected Chinese hamster ovary (CHO) cells (designated CHO-A,). The high affinity ad enosine A, receptor agonist IB-MECA (1-deoxy-1-[6-[[(3-iodophenyl)methyl]am i 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) ce lls. Adenosine A, receptor-mediated increases in p42/p44 MAPK were sensitiv e to pertussis toxin and the MAPK kinase 1 inhibitor PD 98059 (2 ' -amino-3 ' -methoxyflavone). The broad range protein tyrosine kinase inhibitor geni stein and the phosphatidylinositol 3-kinase inhibitors wortmannin and LY 29 4002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one) also blocked adenos ine A3 receptor stimulation of p42/p44 MAPK. In contrast, inhibition of pro tein kinase C had no significant effect on adenosine A, receptor-induced p4 2/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 l uciferase reporter gene containing the c-fos promoter. Furthermore, IB-MECA -induced increases in luciferase gene expression were sensitive to pertussi s toxin, PD 98059, genistein, wortmannin and LY 294002. In conclusion, we h ave shown that the human adenosine A(3) receptor stimulates p42/p44 MAPK an d c-fos-mediated luciferase gene expression in transfected CHO cells. (C) 2 001 Elsevier Science B.V. All rights reserved.