Sensing Actin Dynamics through Adherens Junctions

Abstract

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.” : Indra et al. show that actin bundles at adherens junctions consist of a stalk and a cadherin-interacting tip. F-actin is relatively stable in the stalk, but turns over rapidly in the tip, and turnover rates in both depend on associated cadherin clusters. This bidirectional coupling may allow neighboring cells to coordinate their actin dynamics. Keywords: cadherin, actin, adhesion