Abstract

Integrins control cell adhesion to the extracellular matrix (ECM) by providing an indirect link between the ECM and the actin cytoskeleton. Integrin adhesions are consistently associated with a core of 60 different proteins (integrin associated proteins, IAPs) that coordinate integrin functions. It is unclear why integrin adhesions require so many proteins, but one possibility is that they divide the adhesion into distinct functional layers. Focal adhesions have been shown to be layered, but it is unknown whether similar layers exist in stable integrin adhesions in tissues. We have identified similar layers in the integrin adhesions of Drosophila indirect flight muscles (IFMs). We were struck by the similarity of these adhesions to the structure of a hand and thus termed the layers fingers, palm and wrist. The fingers are similar to layers seen in focal adhesions but the palm and wrist are considerably different. Distinct sets of IAPs are required to build the layers: the fingers are built by FAK , RSU1, tensin and vinculin, while the palm is built by vinculin and filamin.