title: A MAPK-Driven Feedback Loop Suppresses Rac Activity to Promote RhoA-Driven Cancer Cell Invasion.
abstract: Cell migration in 3D microenvironments is fundamental to development, homeostasis and the pathobiology of diseases such as cancer. Rab-coupling protein (RCP) dependent co-trafficking of α5β1 and EGFR1 promotes cancer cell invasion into fibronectin (FN) containing extracellular matrix (ECM), by potentiating EGFR1 signalling at the front of invasive cells. This promotes a switch in RhoGTPase signalling to inhibit Rac1 and activate a RhoA-ROCK-Formin homology domain-containing 3 (FHOD3) pathway and generate filopodial actin-spike protrusions which drive invasion. To further understand the signalling network that drives RCP-driven invasive migration, we generated a Boolean logical model based on existing network pathways/models, where each node can be interrogated by computational simulation. The model predicted an unanticipated feedback loop, whereby Raf/MEK/ERK signalling maintains suppression of Rac1 by inhibiting the Rac-activating Sos1-Eps8-Abi1 complex, allowing RhoA activity to predominate in invasive protrusions. MEK inhibition was sufficient to promote lamellipodia formation and oppose filopodial actin-spike formation, and led to activation of Rac and inactivation of RhoA at the leading edge of cells moving in 3D matrix. Furthermore, MEK inhibition abrogated RCP/α5β1/EGFR1-driven invasive migration. However, upon knockdown of Eps8 (to suppress the Sos1-Abi1-Eps8 complex), MEK inhibition had no effect on RhoGTPase activity and did not oppose invasive migration, suggesting that MEK-ERK signalling suppresses the Rac-activating Sos1-Abi1-Eps8 complex to maintain RhoA activity and promote filopodial actin-spike formation and invasive migration. Our study highlights the predictive potential of mathematical modelling approaches, and demonstrates that a simple intervention (MEK-inhibition) could be of therapeutic benefit in preventing invasive migration and metastasis.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Joseph H R
authors.initials: JH
authors.lastname: Hetmanski
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Egor
authors.initials: E
authors.lastname: Zindy
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Schwartz
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Patrick T
authors.initials: PT
authors.lastname: Caswell
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D019295:Computational Biology; D003198:Computer Simulation; D066246:ErbB Receptors / Q000502:physiology; D025461:Feedback, Physiological; D006801:Humans; D021621:Imaging, Three-Dimensional; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D011554:Pseudopodia / Q000502:physiology; D059016:Tumor Microenvironment / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C489989:EPS8 protein, human; C107953:RAC1 protein, human; C066737:RHOA protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein