Transmembrane interactions at cell adhesion and invasion sites.

Chicken embryonic fibroblasts transformed by Rous sarcoma virus (RSV-CEF) invade into a film of the extracellular matrix (ECM) by extending membrane protrusions, termed the invadopodia. The invadopodia share similar cytoskeletal components and membrane receptors for ECM components as adhesion sites. However, the organization of these transmembrane components at invadopodia and adhesion sites differs. In addition, degradation of the ECM occurs at sites of the invadopodia, but not at focal adhesions. Thus, the protease and integrin molecules on invadopodia are available for dynamic interactions with the ECM, cleaving established adhesion complexes as well as reconstituting new adhesion sites.