Ryzhov Sergey, Goldstein Anna E, Biaggioni Italo, Feoktistov Igor
Divisions of Cardiovascular Medicine, Vanderbilt University, Nashville, TN 37232-6300, USA.
Mol Pharmacol. 2006 Aug;70(2):727-35. doi: 10.1124/mol.106.022780. Epub 2006 May 17.
Human mast cells express functional A(2A) and A(2B) adenosine receptors. However, only stimulation of A(2B), not A(2A), leads to secretion of interleukin (IL)-4, an important step in adenosine receptor-mediated induction of IgE synthesis by B-cells. In this study, we investigate intracellular pathways that link stimulation of A(2B) receptors to IL-4 up-regulation in HMC-1 mast cells. Both A(2A) and A(2B) receptors couple to G(s) proteins and stimulate adenylate cyclase, but only A(2B) stimulates phospholipase Cbeta through coupling to G(q) proteins leading to activation of protein kinase C and calcium mobilization. Inhibition of phospholipase Cbeta completely blocked A(2B) receptor-dependent IL-4 secretion. The protein kinase C inhibitor 2-{8-[(dimethylamino)-methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-(1-methyl-1H-indol-3-yl)maleimide (Ro-32-0432) had no effect on A(2B) receptor-mediated IL-4 secretion but inhibited phorbol 12-myristate 13-acetate-stimulated IL-4 secretion. In contrast, chelation of intracellular Ca(2+) inhibited both A(2B) receptor- and ionomycin-dependent IL-4 secretion. This Ca(2+)-sensitive pathway probably includes calcineurin and nuclear factor of activated T cells, because A(2B) receptor-dependent IL-4 secretion was blocked with cyclosporin A or 11R-VIVIT peptide. G(s)-linked pathways also play a role in the A(2B) receptor-dependent stimulation of IL-4 secretion; inhibition of adenylate cyclase or protein kinase A attenuated A(2B) receptor-dependent IL-4 secretion. Although stimulation of adenylate cyclase with forskolin did not increase IL-4 secretion on its own, it potentiated the effect of Pasteurella multocida toxin by 2-fold and ionomycin by 3-fold. Both forskolin and stimulation of A(2B) receptors up-regulated NFATc1 protein levels. We conclude that A(2B) receptors up-regulate IL-4 through G(q) signaling that is potentiated via cross-talk with G(s)-coupled pathways.
人类肥大细胞表达功能性A(2A)和A(2B)腺苷受体。然而，只有A(2B)受体的刺激而非A(2A)受体的刺激会导致白细胞介素(IL)-4的分泌，这是腺苷受体介导的B细胞诱导IgE合成过程中的重要一步。在本研究中，我们探究了在HMC-1肥大细胞中将A(2B)受体刺激与IL-4上调联系起来的细胞内信号通路。A(2A)和A(2B)受体均与G(s)蛋白偶联并刺激腺苷酸环化酶，但只有A(2B)通过与G(q)蛋白偶联刺激磷脂酶Cβ，导致蛋白激酶C激活和钙动员。磷脂酶Cβ的抑制完全阻断了A(2B)受体依赖性IL-4分泌。蛋白激酶C抑制剂2-{8-[(二甲氨基)-甲基]-6,7,8,9-四氢吡啶并[1,2-a]吲哚-3-基}-3-(1-甲基-1H-吲哚-3-基)马来酰亚胺(Ro-32-0432)对A(2B)受体介导的IL-4分泌没有影响，但抑制了佛波醇12-肉豆蔻酸酯13-乙酸酯刺激的IL-4分泌。相反，细胞内Ca(2+)的螯合抑制了A(2B)受体依赖性和离子霉素依赖性IL-4分泌。这条Ca(2+)敏感通路可能包括钙调神经磷酸酶和活化T细胞核因子，因为A(2B)受体依赖性IL-4分泌被环孢素A或11R-VIVIT肽阻断。G(s)偶联的信号通路在A(2B)受体依赖性的IL-4分泌刺激中也起作用；腺苷酸环化酶或蛋白激酶A的抑制减弱了A(2B)受体依赖性IL-4分泌。尽管用福斯可林刺激腺苷酸环化酶本身不会增加IL-4分泌，但它使多杀巴斯德菌毒素的作用增强了2倍，使离子霉素的作用增强了3倍。福斯可林和A(2B)受体的刺激均上调了NFATc1蛋白水平。我们得出结论，A(2B)受体通过G(q)信号通路上调IL-4，该信号通路通过与G(s)偶联的信号通路的相互作用而增强。
