Propagating actomyosin-generated force to intercellular junction

Actomyosin II contractility in epithelial cells plays an essential role in tension-dependent adhesion strengthening. One key unsettling question is how cellular contraction transmits force to nascent cell-cell adhesion when there is no stable attachment between the nascent adhesion complex and actin filament. Here, we showed that application of intercellular tension induces myosin 1c accumulation at the lateral membrane between epithelial cells. We hypothesized that the accumulation of myosin 1c at the cell-cell interface allows coupling of actomyosin contractility to the generation of intercellular tension, thus is essential for tension-induced junction maturation. We showed that myosin 1c KD compromises a-actinin-4 recruitment to cell-cell adhesion during normal junction maturation driven by endogenous actomyosin contractility. However, application of cyclic tension to intercellular junction from outside of the cells rescued tension-dependent a-actinin-4 accumulation, suggesting that myosin-1c KD did not compromise the tension response or disrupt the overall integrity of the junctional complex. Our study identifies myosin-1c as a novel tension-sensitive protein on the lateral membrane and underscores a non-junctional contribution to adhesion strengthening at the epithelial cell-cell adhesion interface.