A novel protein kinase A-independent, beta-arrestin-1-dependent signaling pathway for p38 mitogen-activated protein kinase activation by beta2-adrenergic receptors.
A growing body of evidence has demonstrated that p38 mitogen-activated protein kinase (MAPK) has a crucial role in various physiological and pathological processes mediated by beta(2)-adrenergic receptors (beta(2)-ARs). However, the detailed mechanism of beta(2)-ARs-induced p38 MAPK activation has not yet been fully defined. The present study demonstrates a novel kinetic model of p38 MAPK activation induced by beta(2)-ARs in human embryonic kidney 293A cells. The beta(2)-AR agonist isoproterenol induced a time-dependent biphasic phosphorylation of p38 MAPK: the early phase peaked at 10 min, and was followed by a delayed phase that appeared at 90 min and was sustained for 6 h. Interestingly, inhibition of the cAMP/protein kinase A (PKA) pathway failed to affect the early phosphorylation but abolished the delayed activation. By contrast, silencing of beta-arrestin-1 expression by small interfering RNA inhibited the early phase activation of p38 MAPK. Furthermore, the NADPH oxidase complex is a downstream target of beta-arrestin-1, as evidenced by the fact that isoproterenol-induced Rac1 activation was also suppressed by beta-arrestin-1 knockdown. In addition, early phase activation of p38 MAPK was prevented by inactivation of Rac1 and NADPH oxidase by pharmacological inhibitors, overexpression of a dominant negative mutant of Rac1, and p47(phox) knockdown by RNA interference. Of note, we demonstrated that only early activation of p38 MAPK is involved in isoproterenol-induced F-actin rearrangement. Collectively, these data suggest that the classic cAMP/PKA pathway is responsible for the delayed activation, whereas a beta-arrestin-1/Rac1/NADPH oxidase-dependent signaling is a heretofore unrecognized mechanism for beta(2)-AR-mediated early activation of p38 MAPK.
Gong
Kaizheng
K
Institute of Vascular Medicine, Peking University Third Hospital and Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Beijing 100191, China.
Li
Zijian
Z
Xu
Ming
M
Du
Jianhai
J
Lv
Zhizhen
Z
Zhang
Youyi
Y
D019390:Arrestins / Q000378:metabolism*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D019255:NADPH Oxidases / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D015398:Signal Transduction; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
C000605253:ARRB1 protein, human; D019390:Arrestins; D034741:RNA, Small Interfering; D018343:Receptors, Adrenergic, beta-2; D000071559:beta-Arrestin 1; D000071557:beta-Arrestins; D000242:Cyclic AMP; D019255:NADPH Oxidases; D017868:Cyclic AMP-Dependent Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases