Abstract
Actinomyosin activity is an important driver of cell locomotion and has been shown to promote collective cell migration of epithelial sheets as well as single cell migration and tumor cell invasion. However, the molecular mechanisms underlying activation of cortical myosin to stimulate single cell movement, and the relationship between the mechanisms that drive single cell locomotion and those that mediate collective cell migration of epithelial sheets are incompletely understood. Here, we demonstrate that p114RhoGEF, an activator of RhoA that associates with non-muscle myosin IIA, regulates collective cell migration of epithelial sheets and tumor cell invasion. Depletion of p114RhoGEF resulted in specific spatial inhibition of myosin activation at cell-cell contacts in migrating epithelial sheets and the cortex of migrating single cells, but only affected double and not single phosphorylation of myosin light chain. In agreement, overall elasticity and contractility of the cells, processes that rely on persistent and more constant forces, were not affected, suggesting that p114RhoGEF mediates process-specific myosin activation. Locomotion was p114RhoGEF-dependent on Matrigel, which favors more roundish cells and amoeboid-like actinomyosin-driven movement, but not on fibronectin, which stimulates flatter cells and lamellipodia-driven, mesenchymal-like migration. Accordingly, depletion of p114RhoGEF led to reduced RhoA, but increased Rac activity. Invasion of 3D matrices was p114RhoGEF-dependent under conditions that do not require metalloproteinase activity, supporting a role of p114RhoGEF in myosin-dependent, amoeboid-like locomotion. Our data demonstrate that p114RhoGEF drives cortical myosin activation by stimulating myosin light chain double phosphorylation and, thereby, collective cell migration of epithelial sheets and amoeboid-like motility of tumor cells.
Highlights
Locomotion of single and groups of cells underlies dynamic biological processes ranging from development and tissue repair to tumor invasion and metastasis [1,2,3]
Our data indicate that p114RhoGEF drives migration of epithelial sheets, and amoeboid movement and invasion of tumor cells. p114RhoGEF is not required for mesenchymal-like movement, which relies on Rac activation to push cells forward. p114RhoGEF activates cortical myosin by stimulating double phosphorylation of MLC along cell junctions close to leading edges and along the actin cortex of single cells. We propose that this unexpected mechanistic similarity between collective and single cell migration reflects a p114RhoGEFactivated myosin-dependent mechanism that drives cell shape changes and cortical actinomyosin dynamics required for locomotion
Together with our data this indicates that collective cell migration requires careful balancing of inactivation and activation of actinomyosin contractility at cellcell junctions
Summary
Locomotion of single and groups of cells underlies dynamic biological processes ranging from development and tissue repair to tumor invasion and metastasis [1,2,3]. During tumor cell invasion and single cell migration, the importance of the actinomyosin cytoskeleton depends on the mode of migration. Little is known about the RhoA GEFs that stimulate actinomyosin contractility during migration; identification of specific RhoA GEFs that drive tumor cell invasion would be important to design new therapeutic strategies to prevent tumor cell spreading and metastasis. P114RhoGEF activates cortical myosin by stimulating double phosphorylation of MLC along cell junctions close to leading edges and along the actin cortex of single cells. We propose that this unexpected mechanistic similarity between collective and single cell migration reflects a p114RhoGEFactivated myosin-dependent mechanism that drives cell shape changes and cortical actinomyosin dynamics required for locomotion
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