Flow antagonizes TNF-alpha signaling in endothelial cells by inhibiting caspase-dependent PKC zeta processing.
Unidirectional laminar flow is atheroprotective, in part by inhibiting cytokine-mediated endothelial cell (EC) inflammation and apoptosis. Previously, we showed that flow inhibited TNF-alpha signaling by preventing activation of JNK. Recently, PKCzeta was identified as the PKC isoform most strongly regulated by flow pattern, with increased PKCzeta activity in regions of disturbed flow versus unidirectional flow. Interestingly, PKCzeta is cleaved by caspases after TNF-alpha stimulation to generate a 50-kDa truncated form (CATzeta, catalytic domain of PKCzeta) with a higher kinase activity than the full-length protein. We hypothesized that flow would inhibit TNF-alpha-mediated PKCzeta cleavage and thereby CATzeta formation. We found that PKCzeta activity was required for TNF-alpha-mediated JNK and caspase-3 activation in ECs. PKCzeta was rapidly cleaved to generate CATzeta in cultured bovine and human aortic ECs and in intact rabbit vessels stimulated with TNF-alpha. This truncated form of PKCzeta enhanced JNK and caspase-3 activation. Interestingly, PKCzeta cleavage was prevented by inhibitors of PKCzeta, JNK, and caspase activities, suggesting that these enzymes, via regulating CATzeta formation, modulate caspase-3 activity in ECs. Finally, we found that flow reduced caspase-dependent processing of PKCzeta and caspase-3 activation. These results define a novel role for PKCzeta as a shared signaling mediator for flow and TNF-alpha, and important for flow-mediated inhibition of proinflammatory and apoptotic events in ECs.
Garin
Gwenaele
G
University of Rochester, Cardiovascular Research Institute, Box 679, 601 Elmwood Avenue, Rochester, NY 14642, USA.
Abe
Jun-ichi
J
Mohan
Amy
A
Lu
Weimin
W
Yan
Chen
C
Newby
Andrew C
AC
Rhaman
Arshad
A
Berk
Bradford C
BC
D000818:Animals; D001783:Blood Flow Velocity; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D008297:Male; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011817:Rabbits; D012212:Rheology / Q000379:methods; D015398:Signal Transduction / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000099221:Protein Kinase C zeta
D061945:Caspase Inhibitors; D020169:Caspases; D011493:Protein Kinase C; D014409:Tumor Necrosis Factor-alpha; D000099221:Protein Kinase C zeta