Etk/Bmx mediates expression of stress-induced adaptive genes VEGF, PAI-1, and iNOS via multiple signaling cascades in different cell systems.

We recently showed that Etk/Bmx, a member of the Tec family of nonreceptor protein tyrosine kinases, promotes tight junction formation during chronic hypoxic exposure and augments normoxic VEGF expression via a feedforward mechanism. Here we further characterized Etk's role in potentiating hypoxia-induced gene expression in salivary epithelial Pa-4 cells. Using transient transfection in conditionally activated Etk (ΔEtk:ER) cells, we demonstrated that Etk enhances hypoxia-response element-dependent reporter activation in normoxia and hypoxia. This Etk-driven reporter activation is ameliorated by treatment with wortmannin or LFM-A13. Using lentivirus-mediated gene delivery and small interfering RNA, we provided direct evidence that hypoxia leads to transient Etk and Akt activation and hypoxia-mediated Akt activation is Etk dependent. Northern blot analyses confirmed that Etk activation led to induction of steady-state mRNA levels of endogenous VEGF and plasminogen activator inhibitor (PAI)-1, a hallmark of...