- Authors: Cho, J. H., Kim, Y. W., Choi, B. Y., Keum, Y. S.
- Year: 2014
- Journal: Eur J Pharmacol 741 247-53
- Applications: in vitro / DNA / jetPEI
- Cell type: HEK-293T
Description: Human embryonic kidney Fibroblast
Known as: HEK293T, 293T
Virus production (lentivirus).
Programmed cell death 4 (PDCD4) is a bona fide tumor suppressor protein and plays a critical role in controlling the rate of protein synthesis. Here, we show that TPA selectively activated the S6K1 and ERK1/2 kinases, contributing to PDCD4 proteolysis and Pdcd4 mRNA degradation in HepG2 cells, respectively. In addition, we observed that sulforaphane suppression of TPA-induced S6K1 and ERK1/2 activation played a critical role in attenuating PDCD4 poly-ubiquitination and Pdcd4 mRNA downregulation. Moreover, we observed that silencing Pdcd4 led to not only an increased expression of c-Jun, but also a decreased expression of p21, the latter of which contributed to suppression of Keap1-dependent Nrf2 poly-ubiquitination. Finally, we demonstrate that the expression of PDCD4, p21 and Nrf2 is higher, but that of c-Jun is lower in normal human liver tissues, compared with hepatoma tissues. Collectively, our study illustrates that attenuating the rate of PDCD4 proteolysis and Pdcd4 mRNA degradation serves as a novel anti-inflammatory and cytoprotective mechanism of sulforaphane.