James, J.; Fokin, A. I.; Guschin, D. Y.; Wang, H.; Polesskaya, A.; Rubtsova, S. N.; Le Clainche, C.; Silberzan, P.; Gautreau, A. M.; Romero, S.

Vinculin is a mechanotransducer that reinforces links between cell adhesions and linear arrays of actin filaments upon myosin-mediated contractility. Both adhesions to the substratum and neighboring cells, however, are initiated within membrane protrusions that originate from Arp2/3-nucleated branched actin networks. Vinculin has been reported to interact with Arp2/3, but the role of this interaction is incompletely understood. Here we compared the phenotypes of vinculin knock-out (KO) cells with those of knock-in (KI) cells, where the point mutation P878A that impairs the Arp2/3 interaction is introduced in the two vinculin alleles of MCF10A mammary epithelial cells. The interaction of vinculin with the canonical Arp2/3 complex inhibits actin polymerization at membrane protrusions and decreases migration persistence of single cells. In cell monolayers, vinculin is involved in Arp2/3 recruitment at cell-cell junctions to stabilize them. Through this interaction, vinculin controls the decision to enter a new cell cycle as a function of cell density.