Nanoscale architecture of integrin-based cell adhesions

Cell adhesions to the extracellular matrix (ECM) are necessary for morphogenesis, immunity and wound healing(1,2). Focal adhesions are multifunctional organelles that mediate cell-ECM adhesion, force transmission, cytoskeletal regulation and signalling(1-3). Focal adhesions consist of a complex network(4) of trans-plasma-membrane integrins and cytoplasmic proteins that form a <200-nm plaque(5,6) linking the ECM to the actin cytoskeleton. The complexity of focal adhesion composition and dynamics implicate an intricate molecular machine(7,8). However, focal adhesion molecular architecture remains unknown. Here we used three-dimensional super-resolution fluorescence microscopy (interferometric photo-activated localization microscopy)(9) to map nanoscale protein organization in focal adhesions. Our results reveal that integrins and actin are vertically separated by a similar to 40-nm focal adhesion core region consisting of multiple protein-specific strata: a membrane-apposed integrin signalling layer containing integrin cytoplasmic tails, focal adhesion kinase and paxillin; an intermediate force-transduction layer containing talin and vinculin; and an uppermost actin-regulatory layer containing zyxin, vasodilator-stimulated phosphoprotein and alpha-actinin. By localizing amino- and carboxyterminally tagged talins, we reveal talin's polarized orientation, indicative of a role in organizing the focal adhesion strata. The composite multilaminar protein architecture provides a molecular blueprint for understanding focal adhesion functions.