EMT induces cell-cycle-dependent changes of Rho GTPases and downstream effectors

Abstract

Epithelial-mesenchymal transition (EMT) is a key cellular transformation for many physiological and pathological processes ranging from cancer over wound healing to embryogenesis. Changes in cell migration, cell morphology and cellular contractility were identified as hallmarks of EMT. These cellular properties are known to be tightly regulated by the actin cytoskeleton. EMT-induced changes of actin-cytoskeletal regulation were demonstrated by previous reports of cell-cycle-dependent changes of actin cortex mechanics in conjunction with characteristic modifications of cortex-associated f-actin and myosin. However, at the current state, the changes of upstream actomyosin signalling that lead to corresponding mechanical and compositional changes of the cortex are not well understood. In this work, we show in breast epithelial cancer cells MCF-7 that EMT results in characteristic changes of the cortical signalling of Rho-GTPases Rac1, RhoA and RhoC and downstream actin regulators cofilin, mDia1 and Arp2/3. In the light of our findings, we propose that cell-cycle-dependent EMT-induced changes in cortical mechanics rely on two hitherto unappreciated signalling paths - i) a cell-cycle-dependent interaction between Rac1 and RhoC and ii) an inhibitory effect of Arp2/3 activity on cortical association of myosin II.