Effect of AdPAK1(K298A) on JNK and VE cadherin. (A) Kinase-inactive PAK1, AdPAK1(K298A), reduces TNF-induced JNK activity and junctional protein phosphorylation. TNF-induced JNK activation was examined in cells infected with either Ad-lacZ (control) or Ad-PAK1(K298A). In cells infected with Ad-lacZ, TNF caused robust JNK activity, similar to that in noninfected cells. In contrast, Ad-PAK1(K298A) markedly reduced TNF-induced JNK activation. (B) Tyrosine phosphorylation of VE-cadherin and α-catenin was similarly examined in cells infected with Ad-lacZ or AdPAK1(K298A). The PAK1 mutant also reduced tyrosine phosphorylation of VE-cadherin and α-catenin. (C) Histograms illustrate the densitometry values for VE-cadherin (left) and α-catenin (right) phosphorylation. (D) Schematic illustrates the potential signaling pathway linking TNF-induced endothelial oxidant production and junctional phosphorylation.