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signaling alters the shear stress-mediated increases in endothelial nitric oxide synthase transcription: role of STAT31Vascular Biology Center, Medical College of Georgia, Augusta, Georgia; and 2Department of Pediatrics, Northwestern University, Chicago, Illinois
Submitted 27 October 2008 ; accepted in final form 29 December 2008
We have previously shown that the regulation of endothelial nitric oxide synthase (eNOS) in endothelial cells isolated from fetal lamb under static conditions is positively regulated by PKC
. In this study, we explore the role of PKC
in regulating shear-induced upregulation of eNOS. We found that shear caused a decrease in PKC
activation. Modulation of PKC
before shear with a dominant negative mutant of PKC
(DN PKC
) or bryostatin (a known PKC
activator) demonstrated that PKC
inhibition potentiates the shear-mediated increases in eNOS expression and activity, while PKC
activation inhibited these events. To gain insight into the mechanism by which PKC
inhibits shear-induced eNOS expression, we examined activation of STAT3, a known target for PKC
phosphorylation. We found that shear decreased the phosphorylation of STAT3. Further the transfection of cells with DN PKC
reduced, while PKC
activation enhanced, STAT3 phosphorylation in the presence of shear. Transfection of cells with a dominant negative mutant of STAT3 enhanced eNOS promoter activity and nitric oxide production in response to shear. Finally, we found that mutating the STAT3 binding site sequence within the eNOS promoter increased promoter activity in response to shear and that this was no longer inhibited by bryostatin. In conclusion, shear decreases PKC
activity and, subsequently, reduces STAT3 binding to the eNOS promoter. This signaling pathway plays a previously unidentified role in the regulation of eNOS expression by shear stress.
cell signaling; phosphorylation; endothelial cell; biomechanical forces
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