Phosphatidylinositol 3-kinase gamma mediates shear stress-dependent activation of JNK in endothelial cells.
Shear stress differentially activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) by mechanisms involving Galphai2 and Gbeta/gamma proteins, respectively, in bovine aortic endothelial cells (BAEC). The early events in this signaling mechanism by which G proteins regulate ERK and JNK in response to shear stress have not been defined. Here we show that BAEC endogenously express a G protein-dependent form of phosphatidylinositol 3-kinase, PI3Kgamma, and its activity is stimulated by shear stress. PI3Kgamma activity was measured in vitro using BAEC that were transiently transfected with an epitope-tagged PI3Kgamma (vsv-PI3Kgamma). Exposure of BAEC to shear stress rapidly and transiently stimulated the activity of vsv-PI3Kgamma (maximum by 15 s, with a return to basal after 1-min exposure to 5 dyn/cm2 shear stress). Activity of vsv-PI3Kgamma was stimulated by shear stress intensities as low as 0.5 dyn/cm2. Treatment of BAEC with an inhibitor of PI3K, wortmannin, inhibited shear-dependent activation of JNK but had no effect on that of ERK. Furthermore, expression of a kinase-inactive mutant (PI3KgammaK799R) in BAEC inhibited the shear-dependent activation of JNK but not ERK. Taken together, these results suggest that PI3Kgamma selectively regulates the shear-sensitive JNK pathway. This differential and novel signaling pathway may be responsible for coordinating various mechanosensitive events in endothelial cells.
Go
Y M
YM
Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Park
H
H
Maland
M C
MC
Darley-Usmar
V M
VM
Stoyanov
B
B
Wetzker
R
R
Jo
H
H
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000473:pathology / Q000502:physiology*; D004789:Enzyme Activation; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013314:Stress, Mechanical
D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases