Isono 6/3

We have previously shown that the expression of periostin is significantly downregulated in human bladder cancer tissues and that periostin suppresses cell invasiveness and metastasis of cancer cells. To clarify the molecular mechanism of this suppression by periostin, we searched for periostin-binding proteins and identified TAB1, which interacts with and activates TAK1, by mass analysis of proteins co-precipitated with periostin in 293T cells expressing periostin. The association between periostin and TAB1 was confirmed by a pulldown assay in 293T cells co-tranfected with expression plasmids of periostin, TAB1 and TAK1. TAK1 was also co-precipitated with periostin in this assay. Co-transfection experiments in 293T also showed that periostin could activate TAK