Abstract
ASK1 (Apoptosis Signal-regulating Kinase 1, also MEKK5) is known to mediate cellular stress signaling pathways through activating p38 kinase. We here observed that ectopically expression of ASK1, but not its kinase-dead mutant, impaired cell proliferation and migration in lung cancer A549 and NCI-H1975 cells. To our surprise, this inhibitory effect of ASK1 is independent on activation of p38 kinase. We further discovered that ASK1 interacts with the WW domain of YAP and TAZ (also WWTR1) that are transcriptional co-activators and the Hippo signaling effectors. Overexpression of wild type ASK1, but not the kinase-dead mutant, in the lung cancer cells down-regulated the expression of the YAP/TAZ target genes CYR61 and CTGF. It seems that ASK1 specifically inactivates TAZ, not YAP, as ASK1 blocked nuclear translocation of TAZ only, while had no effect on YAP. Furthermore, knockdown of TAZ in the lung cancer cells caused the same inhibitory effect on cell proliferation and migration as that of overexpression of ASK1. Thus, our studies have defined a new signaling pathway of ASK1 for regulation of lung cancer cell proliferation and migration via interacting with and inactivating TAZ.