Involvement of Nrf2 in proteasome inhibition-mediated induction of ORP150 in thyroid cancer cells.

Oxygen-regulated protein 150 (ORP150) is an inducible ER chaperone by numerous cellular insults and sustains cellular viability. We have previously reported that ORP150 is differentially induced in a panel thyroid cancer cells and represents as an unwanted molecular consequence during exposure to proteasome inhibition. However, the molecular basis for induction of ORP150 by proteasome inhibitors in thyroid cancer cells remains unclear. In the current study, we found that -421/-307 and -243/+53 regions at the ORP150 gene were responsible for its transactivation by MG132 in thyroid cancer cells. Nrf2 directly transactivated the ORP150 gene by direct binding with the -421/-307 region. Nrf2 also indirectly activated OPR150 transcription via facilitating recruitment of ATF4 to the -243/+53 region. Collectively, this study highlights the molecular mechanism by which proteasome inhibition stimulates ORP150 expression via Nrf2 in thyroid cancer cells.