Matrix-specific protein kinase A signaling regulates p21-activated kinase activation by flow in endothelial cells.
BACKGROUND
Atherosclerosis is initiated by blood flow patterns that activate inflammatory pathways in endothelial cells. Activation of inflammatory signaling by fluid shear stress is highly dependent on the composition of the subendothelial extracellular matrix. The basement membrane proteins laminin and collagen found in normal vessels suppress flow-induced p21 activated kinase (PAK) and nuclear factor (NF)-kappaB activation. By contrast, the provisional matrix proteins fibronectin and fibrinogen found in wounded or inflamed vessels support flow-induced PAK and NF-kappaB activation. PAK mediates both flow-induced permeability and matrix-specific activation of NF-kappaB.


OBJECTIVE
To elucidate the mechanisms regulating matrix-specific PAK activation.


RESULTS
We now show that matrix composition does not affect the upstream pathway by which flow activates PAK (integrin activation, Rac). Instead, basement membrane proteins enhance flow-induced protein kinase (PK)A activation, which suppresses PAK. Inhibiting PKA restored flow-induced PAK and NF-kappaB activation in cells on basement membrane proteins, whereas stimulating PKA inhibited flow-induced activation of inflammatory signaling in cells on fibronectin. PKA suppressed inflammatory signaling through PAK inhibition. Activating PKA by injection of the prostacyclin analog iloprost reduced PAK activation and inflammatory gene expression at sites of disturbed flow in vivo, whereas inhibiting PKA by PKA inhibitor (PKI) injection enhanced PAK activation and inflammatory gene expression. Inhibiting PAK prevented the enhancement of inflammatory gene expression by PKI.


CONCLUSIONS
Basement membrane proteins inhibit inflammatory signaling in endothelial cells via PKA-dependent inhibition of PAK.
Department Cell Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130, USA.
Steven Daniel
SD
Funk
Arif
A
Yurdagul
Jonette M
JM
Green
Krishna A
KA
Jhaveri
Martin Alexander
MA
Schwartz
A Wayne
AW
Orr
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage; D001485:Basement Membrane / Q000201:enzymology*; D002417:Cattle; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000008:administration & dosage; D006801:Humans; D016285:Iloprost / Q000008:administration & dosage; D007249:Inflammation / Q000188:drug therapy / Q000201:enzymology* / Q000503:physiopathology; D018836:Inflammation Mediators / Q000378:metabolism; D007274:Injections, Intraperitoneal; D016023:Integrins / Q000378:metabolism; D008297:Male; D040542:Mechanotransduction, Cellular / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D013314:Stress, Mechanical; D013997:Time Factors; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D054462:p21-Activated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism
D000893:Anti-Inflammatory Agents; D020536:Enzyme Activators; D018836:Inflammation Mediators; D016023:Integrins; D016328:NF-kappa B; D047428:Protein Kinase Inhibitors; D054462:p21-Activated Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D016285:Iloprost