The activation of INF2 by Piezo1/Ca(2+) is required for mesenchymal-to-amoeboid transition in confined environments.

To invade tissues, cells may undergo a mesenchymal-to-amoeboid transition (MAT). However, the mechanisms regulating this transition are poorly defined. In melanoma cells, we demonstrate that intracellular [Ca(2+)] increases with the degree of confinement in a Piezo1-dependent fashion. Moreover, Piezo1/Ca(2+) is found to drive amoeboid and not mesenchymal migration in confined environments. Consistent with a model in which Piezo1 senses tension at the plasma membrane, the percentage of cells using amoeboid migration is further increased in undulating microchannels. Surprisingly, amoeboid migration was not promoted by myosin light-chain kinase (MLCK), which is sensitive to intracellular [Ca(2+)]. Instead, we report that Piezo1/Ca(2+) activates inverted formin-2 (INF2) to induce widespread actin cytoskeletal remodeling. Strikingly, the activation of INF2 promotes de-adhesion, which in turn facilitates migration across micropatterned surfaces. Thus, we reveal a novel Piezo1/Ca(2+)/INF2 signaling cascade that regulates MAT, enabling cancer cells to adapt their migration mode in response to varying mechanochemical environments.