Adhesion-mediated transition to a mesenchymal-like, fan-shaped migration mode in Dictyostelium discoideum
Cells migrate with varying degrees of polarization and directional persistence as exemplified by epithelial, mesenchymal and amoeboid cell types. Depending on the physiological and developmental context, these states are often interchangeable, reflecting the plastic and adaptive nature of the cytoskeleton. However, general principles governing such motility-mode transitions remain poorly established, and it is unclear whether they apply to non-metazoan cells. Here, we report previously overlooked features of the amoebozoan Dictyostelium discoideum, demonstrating that it undergoes pronounced adhesion-dependent changes in both motility and morphology. Unlike the well-known pseudopodia-rich forms observed on weakly adhesive surfaces, cells on highly adhesive substrates adopt fan-shaped morphologies reminiscent of cultured mesenchymal cells. These cells are characterized by lamellipodia-like protrusions enriched in the SCAR/WAVE complex, large focal adhesion-like plaques, F-actin-independent front-rear gradients of Ras/Rap activity. Furthermore, they exhibit a marked increase in cortical stiffness dependent on F-actin, talins, and the RhoA homolog RacE. Their high directional persistence depends on the persistent localization of the SCAR/WAVE complex, talin-mediated substrate anchoring, and RacE-dependent stabilization of the cell rear. We propose that adhesion-engaged remodeling of cell polarity and cortical mechanics is an evolutionarily ancient feature that predates the specialization of adhesion receptors.