RhoA modulates functional and physical interaction between ROCK1 and Erk1/2 in selenite-induced apoptosis of leukaemia cells

K J Shi,Y Yang,Q Jiang,H Luo,C M Xu,F Li

doi:10.1038/cddis.2013.243

Abstract

RhoA GTPase dysregulation is frequently reported in various tumours and haematologic malignancies. RhoA, regulating Rho-associated coiled-coil-forming kinase 1 (ROCK1), modulates multiple cell functions, including malignant transformation, metastasis and cell death. Therefore, RhoA/ROCK1 could be an ideal candidate target in cancer treatment. However, the roles of RhoA/ROCK1 axis in apoptosis of leukaemia cells remain elusive. In this study, we explored the effects of RhoA/ROCK1 cascade on selenite-induced apoptosis of leukaemia cells and the underlying mechanism. We found selenite deactivated RhoA/ROCK1 and decreased the association between RhoA and ROCK1 in leukaemia NB4 and Jurkat cells. The inhibited RhoA/ROCK1 signalling enhanced the phosphorylation of Erk1/2 in a Mek1/2-independent manner. Erk1/2 promoted apoptosis of leukaemia cells after it was activated. Intriguingly, it was shown that both RhoA and ROCK1 were present in the multimolecular complex containing Erk1/2. GST pull-down analysis showed ROCK1 had a direct interaction with GST-Erk2. In addition, selenite-induced apoptosis in an NB4 xenograft model was also found to be associated with the RhoA/ROCK1/Erk1/2 pathway. Our data demonstrate that the RhoA/ROCK1 signalling pathway has important roles in the determination of cell fates and the modulation of Erk1/2 activity at the Mek–Erk interplay level.

Highlights

RhoA, the prototype protein of Rho GTPases superfamily, cycles from a GDP-bound inactive state to a GTP-bound active state.[4]
Previous reports have suggested the importance of RhoA/ Rho-associated coiled-coilforming kinase 1 (ROCK1) axis in cell survival
Malignant cells underwent apoptotic cell death when RhoA/ROCK signalling was wrecked in leukaemia cells and xenograft models, indicating the RhoA/ ROCK1 pathway has key roles in the fate determination of haematologic cells

Summary

Introduction

RhoA, the prototype protein of Rho GTPases superfamily, cycles from a GDP-bound inactive state to a GTP-bound active state.[4]. RhoA transmits signals to pleiotropic effectors by binding to its immediate downstream target, Rho-associated coiled-coilforming kinase 1 (ROCK1). Inhibition of RhoA/ROCK1 pathway leads to tumour cell death and reduced metastasis.[9,10] growing investigations have shown that the RhoA/ROCK module interacts with various signalling molecules to affect apoptosis in solid tumours, little is known about the roles of this signalling pathway in leukaemia cell survival and death. The physical interaction between ROCK1 and Erk1/2 was involved in the interplay between RhoA/ROCK1 signalling and Erk1/2. These results indicate that targeting RhoA/ROCK1 axis could be an optional therapeutic strategy for leukaemia

Methods

Results

Conclusion