β1- and αv-class integrins cooperate to regulate myosin II during rigidity sensing of fibronectin-based microenvironments

How different integrins that bind to the same type of extracellular matrix protein mediate specific functions is unclear. We report the functional analysis of β1- and αv-class integrins expressed in pan-integrin-null fibroblasts seeded on fibronectin. Reconstitution with β1-class integrins promotes myosin-II-independent formation of small peripheral adhesions and cell protrusions, whereas expression of αv-class integrins induces the formation of large focal adhesions. Co-expression of both integrin classes leads to full myosin activation and traction-force development on stiff fibronectin-coated substrates, with αv-class integrins accumulating in adhesion areas exposed to high traction forces. Quantitative proteomics linked αv-class integrins to a GEF-H1–RhoA pathway coupled to the formin mDia1 but not myosin II, and α5β1 integrins to a RhoA–Rock–myosin II pathway. Our study assigns specific functions to distinct fibronectin-binding integrins, demonstrating that α5β1integrins accomplish force generation, whereas αv-class integrins mediate the structural adaptations to forces, which cooperatively enable cells to sense the rigidity of fibronectin-based microenvironments. Faessler and colleagues analyse the distinct properties of β1 and αv integrin subclasses, and provide insight into the different protein compositions, signalling activities and contributions to rigidity sensing of adhesion sites anchored by each integrin subtype.