Sensing Actin Dynamics through Adherens Junctions

Highlights

• Actin bundles connected to adherens junctions consist of a bundle stalk and a tip

• F-actin in the stalk and tip exhibit different organization and dynamics

• F-actin and cadherin turnover rates are interdependent

• Coupling of cadherin and actin dynamics coordinates cells through adherens junctions

Summary

We study punctate adherens junctions (pAJs) to determine how short-lived cadherin clusters and relatively stable actin bundles interact despite differences in dynamics. We show that pAJ-linked bundles consist of two distinct regions—the bundle stalk (AJ-BS) and a tip (AJ-BT) positioned between cadherin clusters and the stalk. The tip differs from the stalk in a number of ways: it is devoid of the actin-bundling protein calponin, and exhibits a much faster F-actin turnover rate. While F-actin in the stalk displays centripetal movement, the F-actin in the tip is immobile. The F-actin turnover in both the tip and stalk is dependent on cadherin cluster stability, which in turn is regulated by F-actin. The close bidirectional coupling between the stability of cadherin and associated F-actin shows how pAJs, and perhaps other AJs, allow cells to sense and coordinate the dynamics of the actin cytoskeleton in neighboring cells—a mechanism we term “dynasensing.”