Role of p38 MAPK and MAPKAPK-2 in angiotensin II-induced Akt activation in vascular smooth muscle cells.
Angiotensin II activates a variety of signaling pathways in vascular smooth muscle cells (VSMCs), including the MAPKs and Akt, both of which are required for hypertrophy. However, little is known about the relationship between these kinases or about the upstream activators of Akt. In this study, we tested the hypothesis that the reactive oxygen species (ROS)-sensitive kinase p38 MAPK and its substrate MAPKAPK-2 mediate Akt activation in VSMCs. In unstimulated VSMCs, Akt and p38 MAPK are constitutively associated and remain so after angiotensin II stimulation. Inhibition of p38 MAPK activity with SB-203580 dose-dependently inhibits Akt phosphorylation on Ser(473), but not Thr(308). Angiotensin II-induced phosphorylation of MAPKAPK-2 is also attenuated by SB-203580, as well as by inhibitors of ROS. In addition, angiotensin II stimulates the association of MAPKAPK-2 with the Akt-p38 MAPK complex, and an in vitro kinase assay shows that MAPKAPK-2 immunoprecipitates of VSMC lysates phosphorylate recombinant Akt in an angiotensin II-inducible manner. Finally, intracellular delivery of a MAPKAPK-2 peptide inhibitor blocks Akt phosphorylation on Ser(473). These results suggest that the p38 MAPK-MAPKAPK-2 pathway mediates Akt activation by angiotensin II in these cells by recruiting active MAPKAPK-2 to a signaling complex that includes both Akt and p38 MAPK. Through this mechanism, p38 MAPK confers ROS sensitivity to Akt and facilitates downstream signaling. These results provide evidence for a novel signaling complex that may help to spatially organize hypertrophy-related, ROS-sensitive signaling in VSMCs.
Taniyama
Yoshihiro
Y
Division of Cardiology, Department of Medicine, Emory University, 319 WMB, 1639 Pierce Drive, Atlanta, GA 30322, USA.
Ushio-Fukai
Masuko
M
Hitomi
Hirofumi
H
Rocic
Petra
P
Kingsley
Michael J
MJ
Pfahnl
Chun
C
Weber
David S
DS
Alexander
R Wayne
RW
Griendling
Kathy K
KK
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D002478:Cells, Cultured; D047908:Intracellular Signaling Peptides and Proteins; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D000804:Angiotensin II; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species; D014662:Vasoconstrictor Agents; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2; C494920:Akt1 protein, rat