Arf1 is involved in Neisseria meningitidis-induced cortical branched F-actin network reorganization.

Cells experience external forces that deform the plasma membrane to which they adapt by reorganizing their actin cytoskeleton. Here, using the extracellular bacterium Neisseria meningitidis as a model system, we explore how this bacterium reorganizes the cortical actin cytoskeleton subsequently to mechanical membrane deformations. Meningococci trigger the formation of tubular cellular plasma membrane protrusions by a previously described adhesion-driven process known as one-dimensional wetting. Cryo-electron tomography reveals that in epithelial cells such a deformation of the plasma membrane leads to the formation of F-actin bundles. In contrast, in endothelial cells a branched F-actin network is formed. By combining high resolution photonic microscopy approaches with genetic and drug perturbations in endothelial cells, we demonstrate that Arp2/3 activity is necessary for forming this branched network. We demonstrate the role of the nucleating-promoting factor N-WASP downstream of Cdc42. Proteomic analyses reveal the contribution of the small GTPase Arf1. Taken together, our results delineate an Arf1-Cdc42-N-WASP-Arp2/3 pathway that links mechanical plasma membrane deformation to the subsequent reorganization of a cortical branched F-actin network in endothelial cells.