ERK/Ribosomal S6 Kinase (RSK) Signaling Positively Regulates Death Receptor 5 Expression through Co-activation of CHOP and Elk1

You-Take Oh,Xiangguo Liu,Ping Yue,Sumin Kang,Jing Chen,Jack Taunton,Fadlo R Khuri,Shi-Yong Sun

doi:10.1074/jbc.m110.153775

Abstract

Death receptor 5 (DR5) is a death domain-containing transmembrane receptor that triggers apoptosis upon binding to its ligand or when overexpressed. Its expression is induced by certain small molecule drugs, including celecoxib, through mechanisms that have not been fully elucidated. The current study has revealed a novel ERK/ribosomal S6 kinase (RSK)-dependent mechanism that regulates DR5 expression primarily using celecoxib as a DR5 inducer. Both C/EBP homologous protein (CHOP) and Elk1 are required for celecoxib-induced DR5 expression based on promoter deletion and mutation analysis and siRNA-mediated gene silencing results. Co-expression of both CHOP and Elk1 exhibited enhanced effects on increasing DR5 promoter activity and DR5 expression, indicating that CHOP and Elk1 co-operatively regulate DR5 expression. Because Elk1 is an ERK-regulated protein, we accordingly found that celecoxib increased the levels of phosphorylated ERK1/2, RSK2, and Elk1. Inhibition of either ERK signaling with a MEK inhibitor or ERK1/2 siRNA, or RSK2 signaling with an RSK2 inhibitor or RSK2 siRNA abrogated DR5 up-regulation by celecoxib as well as other agents. Moreover, these inhibitions suppressed celecoxib-induced CHOP up-regulation. Thus, ERK/RSK-dependent, CHOP and Elk1-mediated mechanisms are critical for DR5 induction. Additionally, celecoxib increased CHOP promoter activity in an ATF4-dependent manner, and siRNA-mediated blockade of ATF4 abrogated both CHOP induction and DR5 up-regulation, indicating that ATF4 is involved in celecoxib-induced CHOP and DR5 expression. Collectively, we conclude that small molecules such as celecoxib induce DR5 expression through activating ERK/RSK signaling and subsequent Elk1 activation and ATF4-dependent CHOP induction.

Highlights

Death receptor 5 (DR5) is a death domain-containing transmembrane receptor that triggers apoptosis upon binding to its ligand or when overexpressed
We found that the region between Ϫ373 bp and Ϫ240 bp was required for celecoxib to increase DR5 transcription because celecoxib could increase luciferase activity of reporter constructs carrying Ϫ373, Ϫ522, and Ϫ1400 bp DR5 5Ј-flanking regions, but failed to do so in cells transfected with reporter constructs harboring Ϫ240 and Ϫ140 bp DR5 promoter regions (Fig. 2A)
We noted that celecoxib-induced cleavage of caspase-8, caspase-3, and poly(ADP-ribose)polymerase was abolished or attenuated in these cell lines transfected with C/EBP homologous protein (CHOP) Small Interfering RNA (siRNA) compared with control siRNA-transfected cells (Fig. 2C), indicating that CHOP induction is important for celecoxib-induced apoptosis

Summary

Introduction

Death receptor 5 (DR5) is a death domain-containing transmembrane receptor that triggers apoptosis upon binding to its ligand or when overexpressed. Celecoxib increased CHOP promoter activity in an ATF4-dependent manner, and siRNA-mediated blockade of ATF4 abrogated both CHOP induction and DR5 up-regulation, indicating that ATF4 is involved in celecoxib-induced CHOP and DR5 expression. We conclude that small molecules such as celecoxib induce DR5 expression through activating ERK/RSK signaling and subsequent Elk1 activation and ATF4-dependent CHOP induction.

Results

Conclusion